Vehicle undercarriage

Abstract

This vehicle underbody structure not only improves fire resistance and heat insulation performance against combustion beneath the vehicle body, thereby reducing heat input to the battery pack, but also provides a structure that can extinguish combustion beneath the vehicle body. [Solution] The system comprises a battery pack 1, a shear panel 2 positioned below the battery pack 1, and a fire-resistant heat-insulating sheet 3 fixed to the underside of the shear panel 2. The fire-resistant heat-insulating sheet 3 is fixed to the shear panel 2 with a low-melting-point adhesive 5 that melts when the fire-resistant heat-insulating sheet 3 is exposed to flames 6.

Description

Technical Field

[0001] The present invention relates to a vehicle underbody structure including a battery pack.

Background Art

[0002] In electric vehicles and hybrid cars, a battery pack that supplies power to an electric motor as a driving power source is mounted under the vehicle body. In such a vehicle equipped with a battery pack, fireproofing measures are required so that the battery does not thermally runaway when combustion occurs on the road surface under the vehicle body and the lower side of the vehicle body is exposed to flames. Patent Document 1 discloses an in-vehicle battery housing case composed of a laminate including a layer of nonflammable or flame-retardant nonwoven fabric.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The in-vehicle battery housing case disclosed in Patent Document 1 can improve the fireproof performance by including a layer of nonflammable or flame-retardant nonwoven fabric. However, since this in-vehicle battery housing case does not have a function of extinguishing combustion under the vehicle body, the lower side of the vehicle body continues to be exposed to flames until the fire is extinguished, and there is a possibility that the battery cannot withstand the heat input from the flames and thermally runs away.

[0005] Therefore, an object of the present invention is to provide an underbody structure of a vehicle that can not only improve the fireproof heat insulation performance against combustion under the vehicle body and reduce the heat input to the battery pack, but also extinguish the combustion under the vehicle body.

Means for Solving the Problems

[0006] The vehicle understructure according to the present invention comprises a battery pack, a shear panel disposed below the battery pack, and a fire-resistant heat-insulating sheet fixed to the lower side of the shear panel, wherein the fire-resistant heat-insulating sheet is fixed to the shear panel with a low-melting-point adhesive that melts when the fire-resistant heat-insulating sheet is exposed to flames. [Effects of the Invention]

[0007] This invention not only improves the fire-resistant and heat-insulating performance against combustion beneath the vehicle body, thereby reducing heat input to the battery pack, but also provides a vehicle underbody structure that can extinguish combustion beneath the vehicle body. [Brief explanation of the drawing]

[0008] [Figure 1] This figure shows the undercarriage structure of a vehicle according to the first embodiment of the present invention as viewed from the front of the vehicle. [Figure 2] This figure shows the vehicle understructure of a second embodiment of the present invention as viewed from the front of the vehicle. [Figure 3] This figure shows the vehicle understructure of the third embodiment of the present invention as viewed from the front of the vehicle. [Figure 4] This figure shows the undercarriage of a modified example 1 of the present invention as viewed from the front of the vehicle. [Figure 5] This figure shows the undercarriage structure of a modified example 2 related to the present invention, viewed from the front of the vehicle. [Modes for carrying out the invention]

[0009] <First Embodiment> The vehicle understructure 10 of the first embodiment of the present invention will be described below with reference to Figure 1. Figure 1 is a diagram showing the vehicle understructure 10 as viewed from the front of the vehicle. As shown in Figure 1, the vehicle understructure 10 comprises a battery pack 1, a shear panel 2 positioned below the battery pack 1, and a fire-resistant heat-insulating sheet 3 fixed to the underside of the shear panel 2. The battery pack 1 is mounted on the vehicle body 4 as a power source that supplies power to an electric motor (not shown), which is the power source for the vehicle's driving. The shear panel 2 covers the underside of the battery pack 1 to prevent damage to the battery pack 1 due to interference from uneven or bumpy road surfaces. The shear panel 2 may be made of metal, such as aluminum. The fire-resistant heat-insulating sheet 3 may be, for example, a heat-resistant flame-retardant felt made of PBO (poly(p-phenylene benzobis(oxazole)) fibers, or silica cloth. Silica cloth is a woven sheet of inorganic fibers mainly composed of silicon dioxide. The fire-resistant heat-insulating sheet 3 is fixed to the shear panel 2 with adhesive 5 so that it is exposed on the underside of the vehicle body 4. The adhesive 5 is made of a material with a low melting point that melts when the underside of the fire-resistant heat-insulating sheet 3 is exposed to flames 6. The adhesive 5 may be, for example, solder, or an alloy containing tin or bismuth.

[0010] For example, if a traffic accident causes flammable liquids such as gasoline or other flammable materials to spread on the road surface and ignite, resulting in combustion below the vehicle body 4, the underside of the fire-resistant heat-insulating sheet 3 may be exposed to flames 6, as shown in Figure 1. In the vehicle understructure 10, when the underside of the fire-resistant heat-insulating sheet 3 is exposed to flames 6 in this way, the fire-resistant heat-insulating sheet 3 reduces the heat input to the battery pack 1. Furthermore, as the combustion continues and the adhesive 5 begins to melt, the vehicle understructure 10 reduces the heat input to the battery pack 1 due to the heat of fusion of the adhesive 5, and also reduces the heat input to the battery pack 1 due to the increased thermal resistance caused by the formation of a gap between the share panel 2 and the fire-resistant heat-insulating sheet 3. If the combustion continues further, the adhesive 5 will completely melt, causing the fire-resistant heat-insulating sheet 3 to fall to the road surface, covering the flames 6 and preventing oxygen supply, thereby extinguishing the combustion below the vehicle body 4. In this way, the vehicle's understructure 10, by being equipped with a fire-resistant and heat-insulating sheet 3, not only improves its fire-resistant and heat-insulating performance and reduces the heat input to the battery pack 1, but also extinguishes the fire below the vehicle body 4 by melting the adhesive 5 and causing the fire-resistant and heat-insulating sheet 3 to fall off.

[0011] <Second Embodiment> Next, the vehicle understructure 20 of the second embodiment will be described with reference to Figure 2. The vehicle understructure 20 of the second embodiment has the same configuration as the vehicle understructure 10 of the first embodiment, except that the fire-resistant heat-insulating sheet 3a is a thermally expandable fire-resistant heat-insulating sheet that expands when exposed to flames 6. Therefore, parts common to the vehicle understructure 10 of the first embodiment are denoted by the same reference numerals and their descriptions are omitted.

[0012] Figure 2 shows the vehicle understructure 20 as viewed from the front of the vehicle. As shown in Figure 2, the vehicle understructure 20 includes a battery pack 1 and a shear panel 2 positioned below the battery pack 1, similar to the vehicle understructure 10 of the first embodiment. The vehicle understructure 20 also includes a heat-expandable fire-resistant heat-insulating sheet 3a fixed to the underside of the shear panel 2. The fire-resistant heat-insulating sheet 3a of the vehicle understructure 20 is fixed to the shear panel 2 so as to be exposed on the underside of the vehicle body 4, similar to the fire-resistant heat-insulating sheet 3 of the vehicle understructure 10.

[0013] As shown in Figure 2, when combustion occurs beneath the vehicle body 4 and the underside of the fire-resistant heat-insulating sheet 3a of the vehicle understructure 20 is exposed to flames 6, the sheet expands and increases in thickness, further improving its heat-insulating performance compared to before expansion. In this way, when exposed to flames 6, the fire-resistant heat-insulating sheet 3a of the vehicle understructure 20 expands and increases in thickness, thereby reducing the heat input to the battery pack 1.

[0014] <Third Embodiment> Next, the vehicle understructure 30 of the third embodiment will be described with reference to Figure 3. The vehicle understructure 30 of the third embodiment has the same configuration as the vehicle understructure 10 of the first embodiment, except that a gap 7 is formed between the shear panel 2 and the fire-resistant heat-insulating sheet 3. Therefore, parts common to the vehicle understructure 10 of the first embodiment are denoted by the same reference numerals and their descriptions are omitted.

[0015] Figure 3 shows the vehicle understructure 30 as viewed from the front of the vehicle. As shown in Figure 3, the vehicle understructure 30, like the vehicle understructure 10 of the first embodiment, includes a battery pack 1, a shear panel 2 positioned below the battery pack 1, and a fire-resistant heat-insulating sheet 3 fixed to the underside of the shear panel 2. The fire-resistant heat-insulating sheet 3 of the vehicle understructure 30 is fixed to the shear panel 2 with adhesive 5 such that a plurality of gaps 7 are formed between it and the shear panel 2.

[0016] Because the vehicle understructure 30 has a gap 7 formed between the shear panel 2 and the fire-resistant heat-insulating sheet 3, it can improve the heat insulation performance compared to the vehicle understructure 10, which does not have a gap 7. Therefore, as shown in Figure 3, when combustion occurs below the vehicle body 4 and the lower surface of the fire-resistant heat-insulating sheet 3 is exposed to flames 6, the vehicle understructure 30 can reduce the heat input to the battery pack 1 more than the vehicle understructure 10, which does not have a gap 7 formed between the shear panel 2 and the fire-resistant heat-insulating sheet 3.

[0017] The vehicle underbody structures of the first to third embodiments of the present invention have been described so far. Hereinafter, vehicle underbody structures of Modification Examples 1 and 2 related to the present invention, which are different from the present invention, will be described.

[0018] <Modification Example 1 Related to the Present Invention> Hereinafter, with reference to FIG. 4, the vehicle underbody structure 40 of Modification Example 1 related to the present invention will be described. FIG. 4 is a view showing the vehicle underbody structure 40 as viewed from the front of the vehicle. As shown in FIG. 4, the vehicle underbody structure 40 includes a battery pack 1, a shared panel 2 disposed below the battery pack 1, and a fireproof heat insulation sheet 3 fixed to the upper side of the shared panel 2. In the vehicle underbody structure 40, unlike the vehicle underbody structure 10 of the first embodiment of the present invention, the fireproof heat insulation sheet 3 is fixed to the upper side of the shared panel 2. The shared panel 2 may be made of a metal such as aluminum, for example. The fireproof heat insulation sheet 3 may be, for example, a heat-resistant flame-retardant felt using PBO fibers or a silica cloth.

[0019] Since the fireproof heat insulation sheet 3 is fixed to the upper side of the shared panel 2 in the vehicle underbody structure 40, when combustion occurs below the vehicle body 4 as shown in FIG. 4 and the lower surface of the shared panel 2 is exposed to the flame 6, unlike the vehicle underbody structure 10 of the first embodiment of the present invention, the fireproof heat insulation sheet 3 cannot be dropped. However, even when the shared panel 2 exposed to the flame 6 melts and forms a hole, the vehicle underbody structure 40 can suppress the heat input to the battery pack 1 by the fireproof heat insulation sheet 3. Further, in the vehicle underbody structure 40, since the fireproof heat insulation sheet 3 is fixed to the upper side of the shared panel 2 and is not exposed to the lower side of the vehicle body 4, the fireproof heat insulation sheet 3 is not scraped or torn due to road surface interference and is not damaged, so that the fireproof heat insulation effect can be stably exhibited for long-term use.

[0020] <Modification Example 2 Related to the Present Invention> Next, while referring to FIG. 5, the vehicle underbody structure 50 of Modification 2 related to the present invention will be described. FIG. 5 is a view showing the vehicle underbody structure 50 as seen from the front of the vehicle. As shown in FIG. 5, the vehicle underbody structure 50 includes a battery pack 1, a shared panel 2 disposed below the battery pack 1, and a fireproof heat insulation sheet 3 fixed to the upper side of the shared panel 2. The shared panel 2 may be made of a metal such as aluminum, for example. The fireproof heat insulation sheet 3 may be, for example, a heat-resistant and flame-retardant felt using PBO fibers or a silica cloth. And in the vehicle underbody structure 50, unlike the vehicle underbody structure 40 of Modification 1 related to the present invention, a space is formed between the shared panel 2 and the fireproof heat insulation sheet 3, and this space is filled with a fire extinguishing agent 8. That is, the fire extinguishing agent 8 is held between the shared panel 2 and the fireproof heat insulation sheet 3. The fire extinguishing agent 8 may be, for example, a powder ABC fire extinguishing agent. The powder ABC fire extinguishing agent is a powdery fire extinguishing agent that can be used for any of Class A fires (fires of ordinary combustibles), Class B fires (oil fires), and Class C fires (fires of electrical equipment).

[0021] Since the fire extinguishing agent 8 is filled between the shared panel 2 and the fireproof heat insulation sheet 3 in this way, when combustion occurs below the vehicle body 4 as shown in FIG. 5 and the lower surface of the shared panel 2 is exposed to the flame 6, the shared panel 2 exposed to the flame 6 melts and forms a hole, and the fire extinguishing agent 8 flows out from the hole, so that the combustion below the vehicle body 4 can be extinguished.

Description of Reference Numerals

[0022] 1 Battery pack, 2 Shared panel, 3, 3a Fireproof heat insulation sheet, 4 Vehicle body, 5 Adhesive, 6 Flame, 7 Gap, 8 Fire extinguishing agent, 10, 20, 30, 40, 50 Vehicle underbody structure.

[0023] [Configuration of the Present Invention] [Configuration 1] A battery pack, a shared panel disposed below the battery pack, and a fireproof heat insulation sheet fixed to the lower side of the shared panel, A vehicle understructure characterized in that the fire-resistant heat-insulating sheet expands and increases in thickness when exposed to flames, thereby further improving the heat insulation performance of the fire-resistant heat-insulating sheet. [Configuration 2] The device comprises a battery pack, a shear panel positioned below the battery pack, and a fire-resistant heat-insulating sheet fixed to the underside of the shear panel. A vehicle understructure characterized in that a gap is formed between the share panel and the fire-resistant heat-insulating sheet.

[0024] [Modified configuration of a modified example related to the present invention] [Configuration 3] A vehicle understructure characterized by comprising a battery pack, a share panel positioned below the battery pack, and a fire-resistant and heat-insulating sheet fixed to the upper side of the share panel. [Structure 4] The system comprises a battery pack, a shear panel positioned below the battery pack, and a fire-resistant and heat-insulating sheet fixed to the upper side of the shear panel. A vehicle understructure characterized by holding a fire extinguishing agent between the aforementioned share panel and the aforementioned fire-resistant heat-insulating sheet.

Claims

[Claim 1] The system comprises a battery pack, a shear panel positioned below the battery pack, and a fire-resistant heat-insulating sheet fixed to the underside of the shear panel. A vehicle understructure characterized in that the fire-resistant heat-insulating sheet is fixed to the shear panel with a low-melting-point adhesive that melts when exposed to flames.

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