Underride guard with thermally optimised reinforcement, underride guard battery module and motor vehicle having improved underbody protection device

Abstract

The present invention relates to an underride guard (1) for attaching under a battery (3) of a motor vehicle, said battery having if possible one battery module (2), said underride guard having a main body (4) which is or can be constructed in a sandwich-like manner, wherein on or at the upper side (5) of the main body (4) facing the battery module, a thermal reinforcement (6) is arranged, wherein the thermal reinforcement (6) has carbon. The invention also relates to an underride guard battery module (7) and a motor vehicle / BEV.

Description

[0001] Underrun protection with thermally optimized reinforcement, underrun protection battery module, and motor vehicle with improved underbody protection device. The present invention relates, among other things, to a thermally optimized reinforcement of an underbody protection device / underbody protection / underrun protection, i.e., an underbody protection device / underbody protection / underrun protection, an underrun protection battery module, and a preferably land-based motor vehicle, such as a passenger car or a commercial vehicle, with an improved underbody protection device / underrun protection. Such motor vehicles / vehicles are typically battery-electric vehicles (BEVs), which use (high-voltage) batteries / traction batteries as their sole or additional energy source. For the protection of traction batteries arranged on the underbody of electrically powered motor vehicles,Today, reinforcement structures are generally used to absorb impacts or stone chips and the like, in order to prevent deformation of battery cells (the traction battery / high-voltage battery) located on the underbody of a motor vehicle and the resulting externally triggered short circuit. Such reinforcement structures are known, for example, from documents DE 102021119168 A1, JP 2014-192052 A, KR 102018006150 A, US 2013 / 0059175 A1, WO 2022006894 A1, and DE 102021204370 A1. Generic prior art is also known from DE 102014004853 A1 and DE 10 2022105 511 B3. Furthermore, DE 102022118977 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 device which can be arranged between the traction battery and the underbody protection plate,a gas guide structure 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,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. Furthermore, DE 102022118978 B3 discloses an underrun protection device and a method for producing an underrun protection device. The reinforcing structures generally serve to protect against corrosion damage to the battery systems caused by splash water or road salt. In addition to effectively preventing externally triggered short circuits, it is also necessary to prevent internally triggered short circuits and minimize the resulting damage in order to increase driving safety in electric vehicles. It has proven effective to quickly and effectively discharge the hot battery gases escaping from internal short circuits in motor vehicle battery systems from a battery module or battery system.To prevent a resulting chain reaction that could lead to a fire or explosion of the entire battery module or the entire battery system. 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 routed 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.to force the gas flow into a long guide path to a defined gas outlet opening at the end of the path, thereby cooling the passing gas. Corner areas in the gas guide structure act as particle traps for the hot or glowing combustion products from the battery cells carried along by the centrifugal forces acting in the gas flow, which are thus filtered out of the gas flow. 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, as the flammable gas mixed with oxygen has ideally cooled to a temperature below its auto-ignition point, and the risk of externally triggered ignition by ejected glowing particles is greatly reduced. The gas outlet openings are preferably located at the end of a gas guide structure and dimensioned so thatthat they can handle the sudden gas flow in the event of a thermal runaway and ensure its reliable removal. 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 ducts. 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. Due to the effort to equip vehicles with ever larger traction batteries without shifting the vehicle's 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 essentially restricted to the necessary minimum heights resulting from the mechanical load cases. The height of the gas ducts is usually in the 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. These support structures can be rib-like, trapezoidal, columnar, or flat in order to adhere to the load-bearing zones of the battery housing. These support structures, in turn, consume volume in the degassing chamber.Although they partially provide an open channel for the gas vent system or, in turn, form the gas vent structure. The adverse consequence of a gas vent 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 the combustion products from the battery cells deposit on the surfaces and particle traps of the gas vent 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 vent system.and thus lead to fires and explosions. In the event of a thermal runaway of the high-voltage battery / HV battery, it is important to prevent the underrun protection from burning through the escaping abrasive gases and to ensure their safe dissipation so that the occupants can exit the vehicle safely. High-voltage batteries for BEVs are often attached to the vehicle's underbody and must therefore be protected from external influences such as dirt, water, and mechanical damage from below during normal operation. In addition, the underrun protection performs load-bearing functions during structural load cases such as fatigue strength over service life, overall vehicle rigidity, and crash load cases. In the event of a fire underneath the vehicle, the underrun protection must protect the HV technology above it.so that it does not pose a danger to the occupants. Suitable systems have become established on the market as a technical solution for these requirements. These systems are often designed as plate-shaped sandwich constructions using continuous fiber-reinforced cover layers, thus providing maximum shock absorption capacity and functional reliability, while simultaneously offering a good compromise in terms of weight and cost-effectiveness. However, the known designs have so far only inadequately addressed the possibility of thermal runaway and are often not robust enough to meet the increasingly stringent legislative, regulatory, and safety requirements. Thermal runaway is particularly critical in battery architectures with downward-facing battery burst vents.Because the underrun protection is exposed to the concentrated escaping gas jet at a few exposed points over a short distance, it must withstand this for several minutes in the event of "thermal propagation" (i.e., the transfer of temperature from one cell of the high-voltage battery to another cell of the high-voltage battery). Particularly with lithium batteries, temperatures of up to approximately 1200°C can occur in a highly exothermic reaction (caused by cell combustion or cell combustion products). This, combined with the projectile-like escape of particles, has a destructive thermal and abrasive effect on the underrun protection. Even under these conditions, the affected area must still have sufficient tightness and structural strength to prevent the hot, flammable gases (primarily methane, ethane, ethene, or hydrogen) and glowing particles from escaping into the ambient atmosphere.This would otherwise lead to immediate ignition under the influence of atmospheric oxygen, which is to be avoided. Even the thermally robust solutions currently used, made of steel and / or mica, have significant disadvantages. Such common solutions are often heavy, complex, and expensive. For example, the sheet steel variant, with the disadvantage of poor weight performance, and the mica variant, with its questionable conditions during mining and production, are worth highlighting. In light of new legislation, its use is increasingly risky and uneconomical. The object of the present invention is to avoid or at least mitigate the disadvantages of the prior art. This object is achieved by the subject matter of claim 1.Namely, by an underrun protection device for mounting beneath a high-voltage battery / traction battery, preferably with a battery module, for a preferably (exclusively) battery-powered (land-based) motor vehicle, with a main body that can be constructed or is constructed in a sandwich-like manner or can be constructed or is constructed monolithically, with a thermal reinforcement arranged on or at the upper side of the main body facing the battery module, the thermal reinforcement comprising carbon. This provides a thermally robust solution that is lightweight, easy to install, inexpensive, and cost-optimized. As a result, a material is used that offers such high temperature resistance,that it does not lose structural strength prematurely and which simultaneously possesses sufficient mechanical resistance against the effects of particle impact / thermal runway impact. To determine the performance of various material alternatives, their barrier effect against hole penetration is classified in a suitable substitute test using stage fountains. Advantageous embodiments are the subject of the dependent claims and are explained in more detail below. Thus, an advantageous embodiment is characterized bythat the main body comprises a sandwich core and a cover layer laminate (constructed from one or more layers) arranged on the battery side. The thermal reinforcement is arranged between the cover layer laminate and outgassing openings in a battery module / battery. As an alternative to the sandwich construction associated with the sandwich core, the underrun protection can be constructed monolithically. This means that the underrun protection can preferably be designed as a three-dimensionally shaped thermal reinforcement element, for example made of graphite. As an alternative to the sandwich construction, the thermal reinforcement can be integrally integrated into a composite component. This enables advantageous thermal reinforcement of the component. In addition, an advantageous reduction in thickness can be achieved. The thickness of the thermal reinforcement, i.e. preferably a thermal reinforcement layer,is preferably reducible to a quarter of the total thickness compared to the sandwich structure. This means that the required installation space / occupied by the thermal reinforcement is advantageously reduced. Furthermore, it is advantageous if the thermal reinforcement is designed as a local reinforcement or as a layer. It has proven useful if the thermal reinforcement runs essentially, i.e. partially, or completely in a (straight / flat) plane. Planarly arranged layers or reinforcement plies are advantageous, for example. Furthermore, it is conceivable that the base area of ​​the thermal reinforcement, preferably of a thermal reinforcement element, runs in one plane and / or the thermal reinforcement preferably extends from a first plane into a second plane, which is preferably arranged parallel to the first plane. This also means in particular,that contours modeled on the underrun protection are conceivable. Furthermore, the underrun protection can be designed with three-dimensional reinforcement elements, such as molded parts. If the thermal reinforcement consists of pure carbon, is composed of carbon, or at least comprises carbon, particularly good protection against burn-off is achieved. It is also advantageous if the thermal reinforcement is constructed (only / also) as graphite foil and / or as a graphite-containing filler and / or as a graphite layer and / or from carbon fiber fabric and / or from carbon fiber laminate(s). It is advantageous if the thermal reinforcement is made of expanded natural graphite. The graphite foil, in its natural graphite form, is advantageously inexpensive to manufacture or acquire and is also easy to process. Alternatively, the thermal reinforcement can be designed as a composite variant with functional reinforcement layers.such as a stainless steel sheet. The design of the graphite foil advantageously increases resistance to particle bombardment, i.e., particularly bombardment with / deposition of hot combustion products, such as hot particles. Alternatively, the thermal reinforcement can be implemented as a graphite semi-finished product, preferably in plate form. The graphite semi-finished product can be produced in various thicknesses and densities. The graphite semi-finished product can be machined. This means that the graphite semi-finished product can be manufactured and / or processed by two-dimensional shaping, such as punching, or three-dimensional shaping, such as contour milling. Furthermore, pressing of graphite semi-finished products, i.e., molded parts, is also conceivable. In this way, for example, aerodynamically shaped deflector plates can be produced. The deflector plates are preferably arranged in the area of / below the outgassing openings.in order to advantageously ensure a thermal reinforcement function. Alternatively, the thermal reinforcement can be designed as a fibrous semi-finished product with a graphite content, i.e., as a fleece or a felt with a graphite content. The fibrous semi-finished product can be designed in a rigid or flexible form. The fibrous semi-finished product designed in this way can also be designed as a doubled plate or as a protective layer (sacrificial layer) that is integrated into a fiber composite matrix. Alternatively, the thermal reinforcement can be designed as a fiber composite component with graphite powder or graphite-containing powder integrated into the matrix. The graphite in powder form is advantageously added to a carrier material, such as the matrix of a fiber composite component.admixed. In this way, an advantageous thermal reinforcement of the underbody protection can be achieved. Alternatively, the thermal reinforcement can be designed as a carbon-based filler such as graphitized microballoons, which are part of a carrier material. The graphitized microballoons can advantageously be admixed with a carrier material, such as the matrix of a fiber composite component. In this way, an advantageous thermal reinforcement of the underbody protection can be achieved. Alternatively, the thermal reinforcement can be designed as a composite material with carbon fibers embedded in a pure graphite matrix. This embodiment of the composite material advantageously consists entirely of carbon. In other words, the thermal reinforcement can be designed as carbon fiber reinforced carbon (carbon fiber carbon composite,CFC materials / composite materials). By implementing the thermal reinforcement as a CFC material, an advantageously high temperature resistance can be achieved. In addition, increased mechanical stability can be achieved compared to pure, unreinforced graphite. This means that an improvement in the material properties can be achieved compared to the material properties, in particular the brittle material behavior of pure, unreinforced graphite. Alternatively, the thermal reinforcement can be implemented as a coating based on graphite paints or pastes. In other words, the graphite foil can be implemented as a coating material. It is expedientif the thermal reinforcement covers the main body completely or in sections. The thermal reinforcement can also be partially formed on the upper side of the underrun protection or on the battery side of the underrun protection. For example, the thermal reinforcement can preferably be arranged in the area of ​​outgassing openings. The thermal reinforcement can preferably also be designed with recesses, for example in the area of ​​embossments or impressions. This means that the preferably flat thermal reinforcement can be partially or completely doubled on the battery side or can cover the battery-side underbody protection. For the covering, the thermal reinforcement can be connected or bonded to the upper side of the underrun protection in a form-fitting or material-fitting manner. The form-fitting or material-fitting connection can be achieved, for example, by pressing,Pressing or gluing. A further advantageous embodiment is characterized in that the thermal reinforcement is designed as a preferably doubled (thin) layer of graphite foil or as a molded part or as a composite component or as a GRP / CFRP laminate, or is integrated / installed in one piece as a carbon fiber layer in an upper or lower cover layer laminate of the main body. The invention also relates to an underrun protection battery module, with an underrun protection according to one of the preceding claims, which is arranged below a battery module / fastened thereto. It is advantageous if the battery module has a housing for accommodating battery cells of the (high-voltage) battery, and at least one outgassing opening is present in the housing, wherein the thermal reinforcement in the direction of the discharge of hot gases in the event of a "thermal runaway" of the (high-voltage) battery from the housing, as a gas-retaining,diverting or at least conductive barrier is arranged and formed. The invention also relates to a motor vehicle with an underrun protection battery module of the type according to the invention. It has been found that the object is best achieved by using materials made of pure carbon with its advantageous properties such as high temperature resistance and low density. High-purity carbon is readily available in the form of graphite foil made of expanded natural graphite for sealing applications, for example. Alternatively, the use of common carbon fiber fabric for processing in the form of laminates is suitable. It has been proven that the use of graphite foil and carbon fiber laminates in the above-mentioned test method exceeds the resistance of conventional materials such as steel and mica by several times for the same weight. This means,that these materials offer a superior combination of thermal and mechanical resistance. In a preferred embodiment, the underrun protection is designed as a GRP fiber composite component with a PU sandwich core. This means that the underrun protection is constructed with a foam core, particularly for mechanical enhancement. The underrun protection can also be constructed monolithically from another material, such as long-fiber-reinforced thermosetting semi-finished products (Sheet Molding Compound, SMC), fiber-reinforced thermoplastics, or metal. Alternatively, the underrun protection can also be constructed from a glass-fiber-reinforced plastic (GRP) or carbon-fiber-reinforced plastic (CFRP) laminate. The monolithic design of the underrun protection advantageously achieves the lowest possible utilization of the available installation space. This means,The installation space required by the thermal reinforcement / underrun protection design is advantageously reduced. The core / foam core in the underrun protection can alternatively be made of thermoplastic PET foam. The PET foam design advantageously allows for thin underrun protection thicknesses of approximately 1 mm or more. If the reinforcement layer is combined with a monolithic structure, the thermal reinforcement layer thickness is likely to be significantly more than one-quarter of the total structure. Values ​​of one-third to even one-half are likely realistic. In the example shown, the battery above has vents located in the center of the vehicle.which are sealed with rupture discs. In the event of a thermal runaway, these rupture due to the resulting high internal pressure, allowing the battery to vent downward onto the underrun protection. The most heavily stressed area (first impact zone) is now additionally reinforced with a thermal barrier made of one of the carbon materials presented above to prevent the underrun protection from burning through. The reinforcement can be implemented either as a doubled thin layer of graphite foil or a GRP / CFRP laminate.or directly integrated as a carbon fiber layer into the upper or lower cover layer laminate. Alternatively, instead of local reinforcement, the entire cover layer can be reinforced with carbon fiber. The invention is explained in more detail below with the aid of a drawing. The application of the invention is illustrated below on an exemplary vehicle architecture with a high-voltage vehicle battery and (seen in the direction of gravity) an underrun protection device located underneath. These show: Figure 1 is a perspective exploded view of an underrun protection device according to the invention with thermal reinforcement according to a first preferred embodiment, Figure 2 is a cross-section through the three components from Figure 1, Figure 3 is an enlargement of area III from Figure 2, Figure 4 is an underrun protection device according to Figure 3 in a second embodiment with thermal reinforcement in a monolithic structure,Figure 5 shows an underrun protection device according to Figure 3 in a third embodiment with thermal reinforcement as an intermediate layer in a composite component structure, and Figure 6 shows an underrun protection device according to Figure 3 in a fourth embodiment with thermal reinforcement as an aerodynamically shaped deflector plate. The figures are merely schematic in nature and serve only to understand the invention. The same elements are provided with the same reference numerals. Features of individual embodiments can be interchanged or complement each other. Figure 1 shows an underrun protection device 1 for attachment beneath a high-voltage battery 3 of a motor vehicle, preferably having a battery module 2, with a main body 4 that can be constructed or is constructed in a sandwich-like manner, with a thermal reinforcement 6 being arranged on or at the upper side 5 of the main body 4 facing the battery module 2.wherein the thermal reinforcement 6 comprises carbon. An underrun protection battery module 7 comprises a housing 8 of the battery module 3, the main body 4, and the thermal reinforcement 6. The housing 8 is prepared to accommodate battery cells 9. There are (see Figure 3) a plurality of outgassing openings 10 in the housing 8, each of which can be closed with a rupture disc (not shown). A fastening means, such as a rivet, a screw, or a crimp element,is referenced in Figure 2 with the reference numeral 11. Figure 3 shows an underrun protection device 1 in a first embodiment with a thermal reinforcement 6 in a sandwich structure. The sandwich structure doubles the thermal reinforcement 6. The preferably planar thermal reinforcement 6 is applied entirely to a cover layer laminate on a side of the underrun protection device 1 facing the battery module 2. A sandwich core is formed between the cover layer laminate and the upper side of the underrun protection device 1. The thermal reinforcement 6 is connected to an upper side 5 of the underrun protection device 1 or applied to the underrun protection device 1. The connection can be positively or materially connected. Figure 4 shows an underrun protection device 1 according to Figure 3 in a second embodiment with a thermal reinforcement 6 in a monolithic structure. The thermal reinforcement 6 can, for example, be a shaped graphite layer,as a foil or as a graphite semi-finished product in plate form. The shape of the thermal reinforcement 6 is adapted to the contour of the upper side 5 of the underrun protection 1. The thermal reinforcement 6 has a three-dimensional shape. The thermal reinforcement 6 can also be provided in the area of ​​embossings, i.e., impressions.be cut out. Figure 5 shows an underrun protection device 1 according to Figure 3 in a third embodiment with a thermal reinforcement 6 as an intermediate layer in a composite component structure. The thermal reinforcement 6 is integrally integrated as an intermediate layer or intermediate layer into a composite component constituting the underrun protection device 1. The thermal reinforcement 6 designed as an intermediate layer is preferably integrally integrated into the composite component. The thermal reinforcement 6 preferably provides for the thermal upgrading of the composite component. The thickness of the thermal reinforcement 6 can, for example, be only a quarter of the total thickness of the composite component constituting the underrun protection device 1. Figure 6 shows an underrun protection device 1 according to Figure 3 in a fourth embodiment with a thermal reinforcement 6 as a streamlined deflector plate. The deflector plate is preferably produced using a forming, in particular pressing, process.The aerodynamically shaped deflector plate is positioned directly beneath a gas vent 10. Two deflector plates are shown. Each of the two deflector plates is positioned directly beneath a gas vent.

[0002] List of reference symbolsUnderrun protectionBattery moduleBattery / high-voltage batteryMain body Oberseite thermal reinforcement underrun protection battery module Gehäuse Battery cell exhaust vent fastening material

Claims

20 AMENDED CLAIMS received by the International Bureau on 28 April 2025 (28.04.2025) 1. Underrun protection (1) for attachment beneath a battery (3) of a motor vehicle, which battery preferably has a battery module (2), having a main body (4) which can be constructed or is constructed in a sandwich-like manner or can be constructed or is constructed monolithically, wherein a reinforcement (6) is provided which comprises carbon, characterized in that the reinforcement (6) is a thermal reinforcement (6) which is arranged on or at the upper side (5) of the main body (4) facing the battery module (2).

2. Underrun protection (1 ) according to claim 1 , wherein the thermal Reinforcement (6) is designed as local reinforcement or as a layer.

3. Underrun protection (1) according to one of the preceding claims, wherein the thermal reinforcement extends substantially or partially in one plane.

4. Underrun protection (1) according to one of the preceding claims, wherein the thermal reinforcement (6) consists of pure carbon, is constructed of carbon or at least comprises carbon.

5. Underrun protection (1) according to one of the preceding claims, wherein the thermal reinforcement (6) is formed as a graphite foil and / or as a graphite-containing filler and / or as a graphite layer and / or from carbon fiber fabric and / or from carbon fiber laminate.

6. Underrun protection (1) according to one of the preceding claims, wherein the thermal reinforcement (6) covers the main body (4) completely or in sections. AMENDED SHEET (ARTICLE 19) 21 7. Underrun protection (1) according to one of the preceding claims, wherein the thermal reinforcement (6) is designed as a doubled layer of graphite foil or as a molded part or as a composite component or GRP / CFRP laminate, or directly as a carbon fiber layer in an upper cover layer laminate or a lower cover layer laminate of the main body is integrated or installed in one piece.

8. Underrun protection battery module (7), with an underrun protection (1) according to one of the preceding claims, which is arranged under a battery module (2).

9. Underrun protection battery module (7) according to claim 8, wherein the battery module (7) has a housing (8) for receiving battery cells (9) of the battery (3), and at least one outgassing opening (10) is present in the housing (8), wherein the thermal reinforcement (6) is arranged and designed as a barrier (3) that stops, redirects or at least conducts the gases in the event of a "thermal runaway" of the battery (3) from the housing (8).

10. Motor vehicle with an underrun protection battery module (7) according to claim 8 or 9. AMENDED SHEET (ARTICLE 19)

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