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

Abstract

The present invention relates to a support structure (2) comprising, for example, a thermoplastic material or constructed from it, 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), which support structure 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) for the passage of hot gas escaping from the traction 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.The invention also relates to an underbody protection device (4) with an underbody protection plate (13) on which such a support structure (2) is arranged and / or fastened. The invention also relates to a motor vehicle with a battery (7), the battery housing (10) of which is supplemented with such an underbody protection device (4).

Description

[0001] 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 and to a motor vehicle with such a thermoplastic support structure or such an underbody protection device.

[0002] 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.

[0003] 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 175A1, WO 2022 006 894 A1 and DE 10 2021 204 370 A1.

[0004] Furthermore, DE 10 2022 118 977 B3 discloses an underbody protection device for arrangement below 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 escaping from the traction battery and guided along the underbody protection plate.,

[0005] 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 fire or explosion of the entire battery module or battery system.

[0006] 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 in such a way that they 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 assume the function of 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.

[0007] 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.

[0008] 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, whereby the membrane and / or valve is preferably only permeable to the battery gas above a certain overpressure.

[0009] 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, columnar or flat in order to be aligned with 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.

[0010] The adverse consequence of a gas channel cross-section that is too small is that high internal pressures build up in the event of thermal runaway, preventing rapid heat dissipation. This effect can be exacerbated by increasing channel constriction as 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 functional failure of seals, interfaces, adhesives, or structural failure of the battery enclosure or gas discharge system, thus leading to fires and explosions.

[0011] It is the object of the present invention to avoid or at least mitigate the disadvantages of the prior art.

[0012] 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 with the features of independent patent claim 1.

[0013] The present invention therefore relates to a support structure made of a thermoplastic material for placement below 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 material-imminent properties, it thus contributes to the effective cooling of the hot gas mixture.

[0014] 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 / establishes 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.

[0015] 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 load events on the underbody protection plate, such as bollard crossings, shelling, 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.

[0016] Advantageous embodiments are the subject of the subclaims and are explained in more detail below.

[0017] 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.

[0018] 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.

[0019] 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 occurring and thus reduce their own space requirement to a fraction of their initial volume.

[0020] For example, the melt of EPP particle foam with a density of 80g / l occupies only about a tenth of its expanded volume. The volume reduction of the support structures, which are only necessary for mechanical underbody loads and no longer required for degassing loads, through melting is accompanied by an increase in degassing volume for the gas discharge system. The enlarged gas channels, or the increasing volume available for degassing, reduces flow resistance, counteracts clogging of the gas channels with particles, and promotes the rapid and safe discharge of hot gases. The increased 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 have the property of physically disintegrating 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, either by a material fit or a form fit. The protective plate and cover can be made of thermosetting fiber-reinforced materials or metallic materials, for example, and can be additionally thermally reinforced using mica, graphite, ATH, or other materials and / or coatings and / or additives.

[0024] 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 inflate 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.

[0025] In addition to the use of molded or milled thermoplastic particle foams such as EPS, EPE, EPP, foams produced by thermoplastic injection molding can also be suitable as a material for the support structure.

[0026] 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.

[0027] The invention is explained in more detail below with the help of a drawing.

[0028] They show: Fig. 1 a motor vehicle, with a battery which is located in a housing below which a support structure according to the invention and an underbody protection device are present, Fig. 2 the detail II from Fig. 1 in enlarged view, Fig. 3 the intact support structure of the Fig. 1 and Fig. 2, Fig. 4 the melting support structure during a Gaussian explosion, Fig. 5 a first embodiment of the support structure with foamed cell structure, and Fig. 6 a second embodiment of the support structure with injection-molded cell structure.

[0029] The figures are merely schematic and serve only to facilitate understanding of the invention. The same elements are provided with the same reference numerals. Features of the individual embodiments may be interchangeable or complementary.

[0030] 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 such a geometry that it has one or more degassing cross sections 6 (see Fig. 2 and Fig. 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 constriction of the degassing cross section 6 or the degassing cross sections 6 is counteracted.

[0031] The battery has a plurality of battery cells 8. The gas guidance system 5 is defined by the support structure 2, the underbody protection device 4 with an underbody protection plate 13, and a battery housing / casing 10.

[0032] How even better in Fig. 2, there is a thermal reinforcement 9 below the support structure 2. The battery cells 8 of the battery 3 are arranged in the battery housing / casing 10. In a cover 11 on the underside closing the housing 10, there is a gas inlet opening 12. A sealing chamber 15 is present between the cover 11 and the underbody protection plate 13 of the underbody protection device 4.

[0033] 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.

[0034] In Fig. In Figure 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.

[0035] In the Fig. 4 shows the melting of the support structure 2 when hot gas flows out.

[0036] In the Fig. 5 and Fig.6 indicates that the support structure 2 has a foamed cell structure or an injection-molded cell structure, depending on the manufacturing method. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2021 119 168 A1

[0003] JP 2014-192 052 A

[0003] KR 10 2018 006 150 A

[0003] US 2013 / 0 059 175A1

[0003] WO 2022 006 894 A1

[0003] DE 10 2021 204 370 A1

[0003] DE 10 2022 118 977 B3

[0004]

Claims

[1] Support structure (2) comprising, for example, a thermoplastic material or constructed from it, 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), 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) for the passage of hot gas escaping from the traction 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. [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 installed in gas channels are used. [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 thermoplastic particle foams, for example containing / constructed of EPS, EPE and / or EPP, are shaped, milled and / or injection-molded. [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.

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