Thermoplastic support structure, underbody protection device and motor vehicle having underbody protection device

Abstract

The present invention relates to a support structure (2) comprising a for example thermoplastic material or constructed therefrom, for optional arrangement below a traction battery (3) of a motor vehicle (1) and / or optional arrangement above an underbody protection device (4) on an underbody (7) of the motor vehicle (1), said support structure being able to be installed or being installed in a gas conduction system (5) which is closed off from the ambient atmosphere in a sufficiently / largely / substantially / practically air-tight manner, wherein the support structure (2) has such a geometry that it defines / specifies one or more venting cross-sections (6) for hot gas escaping from the traction battery (3) to pass through, wherein the design and material are chosen such that any narrowing of the venting cross-section (6) or the venting cross-sections (6) is counteracted. The invention also relates to an underbody protection device (4) having an underbody protection plate (13) on which such a support structure (2) is arranged and / or secured. The invention furthermore relates to a motor vehicle having a battery (7) the battery housing (10) of which is supplemented by such an underbody protection device (4).

Description

[0001] Thermoplastic support structure, underbody protection device and motor vehicle with underbody protection device

[0002] The present invention relates, inter alia, to a thermoplastic support structure for arrangement in gas guidance systems below a traction battery and above a thermally robust underbody protection device of an at least partially electrically driven motor vehicle and to an underbody protection device for arrangement below a traction battery on the underbody of an at least partially electrically driven motor vehicle as well as to a motor vehicle with such a thermoplastic support structure or such an underbody protection device.

[0003] To protect traction batteries arranged on the underbody of electrically powered motor vehicles, reinforcement structures are generally used today to absorb impacts or stone chips and the like in order to prevent deformation of battery cells placed on the underbody of a motor vehicle and a resulting externally triggered short circuit.

[0004] Such reinforcement structures are known, for example, from the documents DE 10 2021 119 168 A1, JP 2014- 192 052 A, KR 10 2018 006 150 A, US 2013 / 0 059 175 A1, WO 2022 006 894 A1 and DE 10 2021 204 370 A1.

[0005] Furthermore, DE 10 2022 118 977 B3 discloses an underbody protection device for arrangement beneath a traction battery on the underbody of an at least partially electrically driven motor vehicle, comprising an underbody protection plate for protecting the underbody of the motor vehicle, a gas guide structure which can be arranged between the traction battery and the underbody protection plate and is arranged on the underbody protection plate for guiding a gas escaping from the traction battery along the underbody protection plate, wherein the gas guide structure can be arranged on the traction battery in such a way that a gas can be introduced into the gas guide structure via a degassing outlet of the traction battery, wherein the gas guide structure has a plurality of branching points for the branched guidance of the gas escaping from the traction battery along the underbody protection plate,wherein the gas guide structure has at least one gas outlet opening for discharging the gas emerging from the traction battery and guided along the underbody protection plate.,

[0006] DE 10 2021 214245 A1 discloses a cover element for a battery housing of a battery storage device, in particular a high-voltage battery having a plurality of battery cells, of an at least partially electrically powered motor vehicle. The cover element has a sandwich construction with a first cover layer, a second cover layer, and an intermediate layer arranged between the cover layers. When the cover element is mounted on the battery housing, the first cover layer faces the battery storage device and the second cover layer faces away from the battery storage device. The first cover layer is provided with a plurality of bursting sections that are movable relative to the first cover layer depending on a pressure prevailing in the region of a respective bursting section, thereby forming a bursting opening. Furthermore, a battery housing and a motor vehicle are disclosed.

[0007] DE 10 2021 133 796 A1 discloses a fire protection semi-finished product for a plastic component, in particular an underride guard, of an at least partially electrically powered motor vehicle, comprising a fire protection textile layer containing non-combustible mineral fibers as the fire-facing side, and a connecting layer as the component-facing side. The connecting layer is designed such that it can be connected or is connected to the plastic component in a material-locking and / or form-locking manner. Furthermore, methods for producing a plastic component using a fire protection semi-finished product, as well as a motor vehicle, are disclosed.

[0008] The reinforcement structures serve, among other things, to protect the battery systems from corrosion damage caused by splashing water or road salt. In addition to effectively preventing externally triggered short circuits, increasing driving safety in electric vehicles also requires preventing internally triggered short circuits and minimizing the resulting damage. It has proven effective to quickly and effectively vent the hot battery gases escaping from internal short circuits in motor vehicle battery systems from a battery module or battery system in order to prevent a resulting chain reaction that could lead to a fire or explosion of the entire battery module or battery system.

[0009] For this purpose, it is known to equip traction battery systems of motor vehicles with a gas discharge system for discharging hot battery gases into the ambient atmosphere. These gas discharge systems are guided through the reinforcement structures arranged on the underbody of a motor vehicle. These reinforcement structures can be designed to have gas channels with a large number of branching points in order to force the gas flow into a long guide path to a defined gas outlet opening located at the end of the path, thereby cooling the gas flowing past. Due to the centrifugal forces acting on the gas flow, corner regions in the gas guide structure act as particle traps for the hot or glowing combustion products from the battery cells that are carried along with them, which are thus filtered out of the gas flow.

[0010] In this way, the risk of explosion when the gases escape into the ambient air at the end of the gas guide structure is minimized, since the flammable gas mixed with oxygen has ideally cooled to a temperature below the auto-ignition point and the risk of externally triggered ignition by ejected glowing particles is greatly reduced.

[0011] The gas outlet openings are preferably located at the end of a gas guide structure and dimensioned to handle the sudden gas flow in the event of a thermal runaway and ensure its reliable discharge. The entry of oxygen-containing air from the ambient atmosphere due to pressure differences must be avoided, as otherwise an explosive gas mixture could form and ignite within the gas channels. It has proven advantageous to hermetically seal the gas outlet opening with a membrane and / or a valve. The membrane and / or valve are preferably only permeable to the battery gas above a certain overpressure.

[0012] Due to the effort to equip vehicles with ever larger traction batteries without shifting the vehicle type-specific floor interface downwards, the available height of the underbody protection plate and thus the height of the effective gas duct cross-section is limited and is essentially restricted to the necessary minimum heights resulting from the mechanical load cases. The height of the gas ducts is usually in a range of more than approximately 5 mm but less than approximately 30 mm. The usable gas duct volume is further reduced by the support structures required to support the underbody protection plate on the battery housing above it, which can be rib-like, trapezoidal, column-like or flat in order to rest on the load-bearing zones of the battery housing. These support structures, in turn, consume volume in the degassing chamber, even though they sometimes provide an open channel for the gas discharge system orin turn form the gas conducting structure.

[0013] As a disadvantageous consequence of a gas channel cross-section that is too small, high internal pressures build up in the event of a "thermal runaway", which prevents rapid heat dissipation. This effect can be exacerbated by an increasing channel constriction when the combustion products from the battery cells deposit on the surfaces and particle traps of the gas discharge system. A backflow of hot gases into the cell casings of the traction battery can promote chain reactions within the battery system and / or cause a functional failure of seals, interfaces, adhesive bonds or a structural failure of the battery housing or the gas discharge system, and thus lead to fires and explosions. The object of the present invention is to avoid the disadvantages of the prior art or at least to mitigate them.

[0014] This object is achieved by a thermoplastic support structure for arrangement in gas guidance systems below a traction battery and above a thermally robust underbody protection device of an at least partially electrically driven motor vehicle having the features of independent patent claim 1.

[0015] The present invention therefore relates to a support structure made of a thermoplastic material for placement beneath a traction battery and above an underbody protection device on the underbody of an at least partially electrically powered motor vehicle, which support structure is installed in a gas distribution system that is sufficiently hermetically sealed from the ambient atmosphere. During normal operation, the support structure improves the mechanical function of the underbody protection device and, in the event of a thermal runaway, enables the dissipation of hot battery gases by reducing the component's own volume and thus increasing the volume of the degassing chamber. Due to its inherent material properties, it thus contributes to the effective cooling of the hot gas mixture.

[0016] In particular, this object is achieved by a support structure comprising a thermoplastic material or constructed from it, for optional arrangement below a traction battery of a (preferably land-based) motor vehicle (such as a passenger car or a commercial vehicle) and above an underbody protection device on an underbody of the motor vehicle, which can be installed or is installed in a gas guidance system that is sufficiently / predominantly / substantially / practically hermetically sealed from the ambient atmosphere, wherein the support structure has a geometry such that it defines / fixes one or more degassing cross sections for the passage of hot gas escaping from a battery, wherein a design and material selection are made such that a narrowing of the degassing cross section or the degassing cross sections is counteracted.The present invention further aims to provide an advantageous design and material selection for a support structure that counteracts a narrowing of the degassing cross-section and the associated adverse consequences described in the event of a thermal runaway. At the same time, during normal vehicle operation, it provides a powerful vertical force path through which underbody loads on the underbody protection plate, such as bollard crossings, projectile impacts, and crash events, are specifically directed into the load-bearing zones of the traction battery. This support structure can either fully assume the functions of a gas guide structure or must be partially supplemented by a thermally robust gas guide structure.

[0017] Advantageous embodiments are the subject of the subclaims and are explained in more detail below.

[0018] For the case of normal operation, it has been shown that thermoplastic particle foams have a wide range of positive properties for the described application, such as high structural strength with very low weight, great design freedom, very good energy absorption, high resilience, good sound insulation / sound absorption, economical production and complete recyclability.

[0019] In a preferred embodiment, a support structure is used as a tool-falling molded part made of expanded polypropylene (EPP) and meets all mechanical requirements despite its low density and low overall height.

[0020] In the case of "thermal runaway," it has been shown that thermoplastic particle foams installed in gas ducts melt within a sufficiently short period of time due to the high ambient temperatures encountered, thereby reducing their own volume requirements to a fraction of their original volume. For example, the melted EPP particle foam with a density of 80 g / l occupies only about a tenth of its expanded volume. The volume reduction of the support structures, which are only necessary for mechanical underbody load cases and no longer required in the degassing load case, due to melting is accompanied by an increase in degassing volume for the gas discharge system. The enlarged gas ducts, or rather the increasing volume available for degassing, reduces flow resistance, counteracts clogging of the gas ducts with particles, and promotes the rapid and safe discharge of the hot gases.The increase in volume also leads to a reduction in internal pressure and thus promotes the cooling of the gas mixture.

[0021] Another positive effect is the phase transition of the thermoplastic material and the melting energy (enthalpy of fusion) required for this process, which is extracted from the passing battery gas. This creates an additional cooling effect on the gas flow.

[0022] Since the thermoplastic support structure, unlike the thermally robust underbody protection device, is specifically designed to physically dissolve at high temperatures, it cannot be an integral part of the underbody protection device. It must be manufactured as a separate element and applied in a material-to-material or form-fitting manner above the underbody protection device or above a thermal barrier.

[0023] It can also be inserted as an intermediate layer between a thermally robust protective plate and a thermally robust bonded cover, which together form a sealed chamber, in a material-to-material or form-fitting manner. The protective plate and cover can, for example, be made of thermosetting fiber-reinforced materials or metallic materials and can additionally be thermally reinforced through the use of mica, graphite, ATH or other materials and / or coatings and / or additives. In a preferred embodiment, the thermoplastic support structure is bonded to the lower protective plate and the upper cover only in the form of predetermined breaking points in order to enable the underbody protection plate to expand downwards (bulge) by breaking the predetermined breaking points in the event of increasing internal pressure during "thermal runaway", thereby providing additional degassing cross-section and reducing pressure peaks.

[0024] In addition to the use of molded or milled particle foams based on thermoplastics such as PS, PE, PP, PA, PET, TPU, foams produced by thermoplastic injection molding or thermoplastic extrusion can also be suitable as material for the support structure.

[0025] Furthermore, homogeneously produced molded parts are also conceivable using conventional injection molding processes. In contrast to foams, these parts are equipped with a large number of thin-walled macroscopic cells and thus have comparable weights and properties in relation to the required installation space.

[0026] The invention is explained in more detail below with the help of a drawing.

[0027] They show:

[0028] Fig. 1 shows a motor vehicle with a battery located in a housing below which a support structure according to the invention and an underbody protection device are provided,

[0029] Fig. 2 shows detail II from Fig. 1 in an enlarged view,

[0030] Fig. 3 the intact support structure of Figures 1 and 2,

[0031] Fig. 4 shows the melting support structure during a gas discharge, Fig. 5 shows a first embodiment of the support structure with a foamed cell structure, and

[0032] Fig. 6 shows a second embodiment of the support structure with injection-molded cell structure.

[0033] The figures are merely schematic and serve only to clarify the invention. The same elements are provided with the same reference numerals. Features of the individual embodiments may be interchangeable or complementary.

[0034] Fig. 1 shows a motor vehicle 1 with a support structure 2 comprising a thermoplastic material or constructed from it, for optional arrangement below a traction battery / battery 3 of a (preferably land-based) motor vehicle 1 (such as a passenger car or a commercial vehicle) and above an underbody protection device 4 on an underbody 7 of the motor vehicle, which can be installed or is installed in a gas guidance system 5 that is sufficiently / predominantly / substantially / practically airtight from the ambient atmosphere, wherein the support structure 2 has a geometry such that it defines / fixes one or more degassing cross sections 6 (see Figs. 2 and 3) for the passage of hot gas escaping from the traction battery / battery 3, wherein a design and material selection are made such that a narrowing of the degassing cross section 6 or the degassing cross sections 6 is counteracted.

[0035] The battery has a plurality of battery cells 8. The gas guidance system 5 is determined by the support structure 2, the underbody protection device 4 with an underbody protection plate 13, and a battery housing / casing 10.

[0036] As can be seen even better in Fig. 2, there is a thermal reinforcement 9 beneath the support structure 2. The battery cells 8 of the battery 3 are arranged in the battery housing / casing 10. A gas inlet opening 12 is provided in a cover 11 on the underside that closes the housing 10. A sealing chamber 15 is provided between the cover 11 and the underbody protection plate 13 of the underbody protection device 4.

[0037] In the “thermal runway” case, hot gas meanders / flows / flows from the gas inlet opening 11 through the sealing chamber 11 past the support structure 2 to a gas outlet opening 16 and leaves the overall structure, which is otherwise sealed from the outside environment, and ultimately also the housing 10. The support structure 2 can be rib-like, have a plurality of ribs and / or have / provide (un)connected segments.

[0038] In Fig. 3, the flow is referenced by reference numeral 17. It can be clearly seen that the support structure 2 is mounted on the underbody protection plate 13 and connected to it. The support structure 2 can encompass the underbody protection plate 13 or be configured separately from it.

[0039] In Fig. 4, the melting of the support structure 2 is indicated when hot gas flows out.

[0040] Figures 5 and 6 indicate that the support structure 2 has a foamed cell structure or an injection-molded cell structure, depending on the manufacturing method.

Claims

AMENDED CLAIMS received by the International Bureau on 17 April 2025 (17.04.2025) 1. Support structure (2) for arrangement below a traction battery (3) of a motor vehicle (1) and / or arrangement above an underbody protection device (4) on an underbody (7) of the motor vehicle (1), which can be installed in a closed gas guidance system (5), wherein the support structure (2) defines one or more degassing cross sections (6) for the passage of hot gas escaping from the traction battery (3), characterized in that the support structure comprises a thermoplastic material and is designed such that the thermoplastic material melts when hot gas flows out in such a way that no constriction of the degassing cross section (6) or the degassing cross sections (6) occurs.

2. Support structure (2) according to claim 1, wherein at least one thermoplastic particle foam is used.

3. Support structure (2) according to claim 1 or 2, wherein at least one component or section of the support structure is constructed from thermoplastic particle foam.

4. Support structure (2) according to one of the preceding claims, wherein the support structure (2) is designed as a tool-falling molded part made of expanded polypropylene (EPP).

5. Support structure (2) according to one of the preceding claims, wherein thermoplastic particle foams are used in gas channels.

6. Support structure (2) according to one of the preceding claims, wherein such a material is used, for example, for a part of the support structure (2) or the entire support structure (2), that the molten material of the part of the support structure (2) or the support structure (2) has only one tenth of the foamed volume.

7. Support structure (2) according to one of the preceding claims, wherein predetermined breaking points are provided and preferably the support structure (2) or part(s) thereof serve as predetermined breaking point(s).

8. Support structure (2) according to one of the preceding claims, wherein particle foams, for example containing / constructed from thermoplastics such as PS, PE, PP, PA, PET and / or TPU, are shaped, milled, injection-molded and / or extruded.

9. Underbody protection device (4) with an underbody protection plate (13) on which a support structure (2) according to one of the preceding claims is arranged and / or fastened.

10. Motor vehicle with a battery (7), the battery housing (10) of which is supplemented with an underbody protection device (4) according to claim 9.

Images