Vehicle underbody protection with fusible support structure for traction battery and use of fusible support structure in cavity of vehicle underbody protection

Abstract

In various embodiments, a vehicle underbody protection (1) for a traction battery (2) is provided, comprising a protection plate (11) and a cover (12) resting on the protection plate (11) and defining a cavity (16) together with the protection plate, wherein an inlet opening (13) is arranged in the cover (12); wherein a support structure (14) is arranged in the cavity (16) and made of a material having a melting point selected such that the material melts upon contact with hot gases (23) escaping from a battery cell (21) of the traction battery (2) arranged above the vehicle underbody protection (1) that experiences thermal runaway, thereby increasing the volume of the cavity (16). Furthermore, use of a meltable support structure (14) in a cavity (16) of a vehicle underbody protection (1) is provided.

Description

Technical Field

[0001] This invention relates to a vehicle body underbody protection component with a fusible support structure for a traction battery in an electric vehicle. The invention also relates to the use of the fusible support structure within a cavity of the vehicle body underbody protection component. Background Technology

[0002] In electric vehicles, synchronous or asynchronous motors are used as drive motors instead of internal combustion engines. The energy required for this is provided by traction batteries, which, due to their size and weight, are typically housed in the vehicle floor between the axles. To meet the requirements of the Underbody Protection (UFS), the traction batteries must be physically protected from hazards from below. Simultaneously, under thermal runaway load conditions, the UFS is designed to serve as an exhaust path, regardless of whether it leads to heat propagation. This creates a conflict between objectives in the mechanical design of the UFS: it should be as rigid as possible for underbody load conditions but as flexible as possible for thermal load conditions.

[0003] According to existing technology, UFS is designed as a rigid plate with integrated support components to accommodate load conditions under the vehicle body. Thermal load conditions are not considered in the design of UFS.

[0004] For example, publication DE 10 2022 104 178 A1 discloses a drive battery for a motor vehicle, which has a drive battery housing and a battery cell contact system. The drive battery housing includes a bottom wall and a top wall and houses the battery cells, wherein a support layer for protecting the battery cell layer during a collision with the bottom wall is arranged between the battery cell layer and the bottom wall. Here, the support layer is configured as a carrier for the battery cell contact system.

[0005] Publication DE 10 2021 123 314 A1 discloses an electric vehicle having an electric drive unit, a vehicle bottom battery, a vehicle bottom protection plate (40) disposed on the underside of the battery housing of the vehicle bottom battery, and an exhaust device including at least one exhaust passage. The exhaust passage, capable of fluidly connecting to the interior of the battery housing and to the external environment, is disposed between the bottom of the battery housing and the vehicle bottom protection plate, wherein the exhaust passage is defined by the bottom of the battery housing and the vehicle bottom protection plate. Summary of the Invention

[0006] In view of the above-mentioned prior art, the object of the present invention can be regarded as providing a vehicle body bottom protection component that at least partially solves the above-mentioned conflict of objectives.

[0007] This objective is achieved through the subject matter of the independent claim. Further preferred embodiments can be found in the dependent claims.

[0008] According to the present invention, a vehicle underbody protector for a traction battery is provided, the underbody protector essentially comprising a protective plate and a cover, the cover resting on the protective plate and defining a cavity together with the protective plate, wherein an inlet opening is arranged in the cover. The underbody protector is designed to be disposed in the vehicle floor, wherein the underbody protector is disposed directly below the traction battery. In particular, the underbody protector can abut against the traction battery from below. The cavity referred to herein means a volume formed within a double-walled underbody protector.

[0009] The support structure is arranged within the cavity and is made of a material with a specific melting point, chosen such that the material melts upon contact with hot gases escaping from the thermally runaway battery cells of the traction battery located above the underbody protection member, thereby increasing the volume of the cavity. The hot gases flow through openings in the traction battery housing and subsequently through inlet openings in the cover of the underbody protection member into the underbody protection member. In this respect, the material of the support structure is selected based on its temperature resistance, such that the material melts upon contact with the hot gases, thereby releasing exhaust volumes that were previously inaccessible or spatially occupied by at least one support structure. The material of the support structure may have a melting point of approximately 160°C or lower, preferably 140°C or lower, and more preferably 120°C or lower.

[0010] In the prior art, it is known that underbody protection components include an arrangement of fiber-reinforced plastic (FRP) with a foam core, such as polyurethane, arranged between these fiber-reinforced plastics. This arrangement typically has a thickness between 9 mm and 20.5 mm, with each of the top and bottom layers being 1 mm thick.

[0011] In the context of this invention, the foam core providing the integrated support structure is omitted from the FRP interlayer according to the prior art. According to the invention, the support structure is replaced by a thermally unstable but mechanically effective support structure. Under mechanical load conditions (body underside load conditions), the force is absorbed and dissipated by the support structure. Under thermal load conditions, the support structure melts and releases exhaust volume. By using a support structure inside the body underside protection component, the conflicting objectives described in the introduction can be resolved using only one component, thereby satisfying the requirements of both load conditions.

[0012] In another embodiment of the underbody protection according to the invention, the cover can be hermetically joined to the protective plate at its edge. Therefore, the cavity (outside the inlet opening) can be made hermetically tight relative to its environment. The joining can be achieved by means of adhesives or welds.

[0013] In another embodiment of the vehicle body underbody protection according to the invention, the protection plate may be constructed in a basin shape. In other words, the sidewalls of the protection plate may be curved upward at their edges and form edges that rise relative to the bottom of the protection plate.

[0014] In another embodiment of the vehicle body underbody protection component according to the invention, the support structure can be formed as a circumferentially closed structure surrounding the inlet opening. Therefore, each support structure can define a small cavity within itself relative to the remaining cavities.

[0015] In another embodiment of the vehicle body underbody protection component according to the present invention, the support structure may include or be composed of plastic foam, preferably expanded polypropylene.

[0016] According to the present invention, an electric vehicle is also provided, the electric vehicle comprising: a traction battery including a battery housing in which a plurality of battery cells are arranged, wherein an exhaust opening is disposed in the bottom of the battery housing; and a vehicle body underbody protection member according to any one of the preceding claims. An inlet opening disposed in a cover is connected to the exhaust opening of the battery housing. Therefore, hot gases escaping from battery cells experiencing thermal runaway during a thermal event can flow from the battery housing into the vehicle body underbody protection member through the inlet opening.

[0017] The support structure can be located within the underbody protection of the vehicle body, below the battery cell. For relatively large battery cells, the base area of ​​the support structure in the plan view can be the same as or larger than the base area of ​​the battery cell.

[0018] According to the present invention, a fusible support structure is provided for use in a cavity between a protective plate and a cover of a vehicle body underbody protection component for a traction battery, wherein the support structure is formed of a material having a melting point selected such that the material melts upon contact with hot gases escaping from a battery cell undergoing thermal runaway, thereby increasing the volume of the cavity.

[0019] Without departing from the scope of the invention, the above features and the features to be explained below can be used not only in the separately specified combinations, but also in other combinations or individually. Attached Figure Description

[0020] Additional advantages and construction options of the present invention will become apparent from the following description and accompanying drawings of exemplary embodiments.

[0021] Figure 1A An exemplary embodiment of the vehicle body underrun protection according to the invention is shown in the first stage of a thermal load condition.

[0022] Figure 1BAn exemplary embodiment of the vehicle body underrun protection according to the invention is shown in the second stage of a thermal load condition.

[0023] Figure 2 Another exemplary embodiment of the vehicle body underbody protection component according to the present invention is shown. Detailed Implementation

[0024] exist Figure 1A The diagram illustrates an exemplary embodiment of a vehicle body underbody protection member 1 for a traction battery 2 according to the present invention. The vehicle body underbody protection member 1 is shown here together with the traction battery 2, which is implemented by a housing in which battery cells 21 are arranged (in... Figure 1A (Only one is shown in the image). The casing of the traction battery 2 is attached to the underbody protection component 1.

[0025] The vehicle underbody protection component 1 includes a protective plate 11 and a cover 12, the cover resting on the protective plate 11 and defining a cavity 16 together with the protective plate. The protective plate 11 represents the lower portion of the vehicle underbody protection component 1 facing the road in its installed state, while the cover 12, which is hermetically bonded to the protective plate 11 at its edges, corresponds to the upper portion of the housing facing the traction battery 2. In the example shown, the cover 12 is bonded to the protective plate 11 by means of an adhesive layer 15. An inlet opening 13 is provided in the cover 12 (only one inlet opening 13 is shown in Figure 1). A support structure 14 is arranged in the cavity 16 formed between the cover 12 and the protective plate 11, which increases the mechanical stability of the vehicle underbody protection component 1. The support structure 14 can also be fixed to the inside of the protective plate 11 using the adhesive layer 15.

[0026] The battery cell 21 shown in the housing of the traction battery 2 is a damaged battery cell 21 affected by a thermal event (represented by a lightning bolt symbol). Hot gas 23 is discharged from the battery cell 21, diffuses within the battery housing, and also flows through an exhaust opening 22 disposed at the bottom of the housing. An inlet opening 13 disposed in the cover 12 is disposed directly below the exhaust opening 22 of the battery housing, allowing the hot gas 23 to flow into the cavity 16. In the first stage of the thermal load condition, in the exemplary embodiment shown, the hot gas 23 is initially contained in a reduced volume within the cavity 16, which is partially defined by the support structure 14.

[0027] The support structure 14 is made of a material with a specific melting point, chosen such that the material melts upon contact with hot gases 23 escaping from the traction battery 21, which has experienced thermal runaway, located above the underbody protection 11, thereby increasing the volume of the cavity 16. This second stage of the thermal load condition occurs in... Figure 1BAs shown, the traction battery 2 attached from above has been omitted here. Here, the support structure 14 has melted due to contact with the hot gas 23, so that the volume initially occupied by the support structure has been released and can be occupied by the hot gas 23. Simultaneously, in the illustrated exemplary embodiment, the hot gas 23 can flow into an additional exhaust volume 17, which was unavailable before the support structure 14 melted. For this purpose, the support structure 14 can divide the cavity 16 into mutually airtight sub-regions. Due to the intentionally selected low-temperature resistance of the material of the support structure 14 relative to other components of the vehicle underbody protection 1, these support structures are at least partially "decomposed" under thermal load conditions, and the vehicle underbody protection 1 can be said to dynamically adapt to optimal handling under thermal load conditions.

[0028] Figure 2 Another exemplary embodiment of the vehicle body underbody protection component according to the present invention is shown. A specific design example is shown in an open state without a cover, allowing the interior of the protective panel 11 to be seen. The support structure 14 is designed in an elongated form.

Claims

1. A vehicle body underbody protection member (1) for a traction battery (2), the vehicle body underbody protection member comprising: Protection board (11); and A cover (12) rests on the protective plate (11) and together with the protective plate defines a cavity (16), wherein an inlet opening (13) is arranged in the cover (12); The support structure (14) is arranged in the cavity (16) and is made of a material with a certain melting point, which is selected such that the material melts when it comes into contact with hot gas (23) escaping from the thermally runaway battery cell (21) of the traction battery (2) arranged above the underbody protection (1), thereby increasing the volume of the cavity (16).

2. The underbody protection member (1) according to claim 1, wherein the cover (12) is hermetically joined to the protection plate (11) at the edge.

3. The vehicle body bottom protection member (1) according to claim 1 or 2, wherein the protection plate (11) is constructed in a basin shape.

4. The vehicle body bottom protection member (1) according to any one of claims 1 to 3, wherein the support structure (14) is formed as a circumferentially closed structure around the inlet opening (13).

5. The vehicle body underbody protection component (1) according to any one of claims 1 to 4, wherein the support structure (14) comprises or is composed of plastic foam, wherein the plastic foam is preferably expanded polypropylene.

6. An electric vehicle, the electric vehicle comprising: The traction battery (2) includes a battery housing in which a plurality of battery cells (21) are arranged, wherein an exhaust opening (22) is arranged in the bottom of the battery housing; and a vehicle bottom protector (1) according to any one of the preceding claims, wherein the inlet opening (13) arranged in the cover (12) is connected to the exhaust opening (22) of the battery housing.

7. Use of a fusible support structure (14) in a cavity (16) between a protective plate (11) and a cover (12) of a vehicle body underbody protection member (1) for a traction battery (2), wherein the support structure (14) is formed of a material having a certain melting point, the melting point being selected such that the material melts upon contact with hot gas (23) escaping from the thermally runaway battery cell (21) of the traction battery (2), thereby increasing the volume of the cavity (16).

Images