WO2023079805A1

WO2023079805A1 - Automobile battery case protection structure and floor crossmember

Info

Publication number: WO2023079805A1
Application number: PCT/JP2022/029955
Authority: WO
Inventors: 和彦樋貝; 毅塩崎
Original assignee: Ｊｆｅスチール株式会社
Priority date: 2021-11-04
Filing date: 2022-08-04
Publication date: 2023-05-11
Also published as: JP2023068736A; JP7264204B1

Abstract

An automobile battery case protection structure 1 according to the present invention comprises a floor 3, a battery case 5, a pair of side sills 7, and a floor crossmember 9 provided on the upper surface of the floor 3 so as to cross over the battery case 5 in the vehicle width direction and protrude out farther than the battery case 5 on both sides in the vehicle width direction, wherein the floor crossmember 9 comprises: a hat cross-section member 13 having a top plate 13a, vertical walls 13b, and flanges 13c; a resin 15 affixed or applied to at least the inner and/or outer surface of the vertical walls 13b of the hat cross-section member 13; and a reinforcing plate 17 laid out to cover the resin 15 and bonded to the resin 15.

Description

Automotive battery case protection structure and floor cross member

The present invention relates to a battery case protection structure for protecting a battery case of an automobile, and a floor cross member used in the battery case protection structure.

A floor cross member, one of the body frame parts of an automobile, extends in the width direction of the vehicle body on the floor (floor panel) to improve the rigidity and strength of the vehicle body. It has Fig. 12 shows the structure around the floor cross member in an internal combustion engine (ICE). Note that FIG. 12 illustrates the left half of the figure in the width direction of the vehicle body. The central part of the floor 3 of the internal combustion locomotive (ICE) is formed to be convex upward in order to pass the exhaust system and power transmission mechanism provided under the floor. A floor tunnel 21 is provided so as to extend in the longitudinal direction of the vehicle body. In the case of the floor 3 provided with the floor tunnel 21, the floor cross member 23 has one end joined to the floor tunnel 21 and the other end connected to the side sill 7 (FIG. It is joined to the constituting side sill inner (only side sill inner 7a is shown).

On the other hand, in the case of an electric vehicle (battery electric vehicle), no exhaust system or change mechanism is provided, so there is no need to provide the floor tunnel 21 described above. Therefore, recently, the floor 3 is often designed to be flat without providing the floor tunnel 21 in order to install a large-capacity battery and secure the space in the cabin. In the case of a floor that does not have a floor tunnel as described above, the floor cross member is provided so as to cross over the battery case mounted under the floor in the width direction of the vehicle body and connect the left and right side sills. By doing so, the floor cross member reduces deformation of the battery case in the event of a side collision, and prevents damage to the battery stored inside the battery case.

As mentioned above, the floor cross member has the function of protecting the battery case from the crash load during a side crash of the car, so it is a part that requires a high level of strength. In order to improve the stiffness of the floor cross member, thickening and ultra-high strength steel exceeding HP1.5GP are progressing, but the accompanying weight increase and manufacturing cost are issues. It's becoming Therefore, there are many technologies related to vehicle structure modification as described below.

For example, in Patent Document 1, "a floor panel of a vehicle, a pair of side members arranged spaced apart from each other in the vehicle width direction below the floor panel and extending in the vehicle front-rear direction, and above the floor panel in the vehicle width direction. and a floor cross member arranged to extend from the side member, wherein the lower part of the floor cross member is positioned above the outer lower part of the side member between the pair of side members. A floor structure of a vehicle body, characterized in that the floor panel has a recess formed along the recess and is provided with a reinforcing member that is detachably connected to the pair of side members. . According to the above technique, a concave portion that is recessed upward is provided in the lower portion of the floor cross member, thereby increasing the space under the floor panel and securing the mounting space for the battery unit. In addition, in a gasoline engine vehicle, by connecting a pair of side members with the reinforcing member (brace), it is possible to ensure strength against side collisions.

Further, Patent Document 2 describes "a floor of a vehicle, a battery pack mounted under the floor, and a cloth provided on the floor extending in the left-right direction of the vehicle so as to traverse above the battery pack. and a member, wherein the cross member has sloping portions on each of the right and left halves that rise toward the center. In Patent Document 2, in the event of a side collision, the inclined portion transmits the collision load to the central portion and pushes up the central portion, bending the cross member upward. It is said that the input of collision load to the pack is suppressed.

In addition, Patent Document 3 discloses that "a pair of lockers are arranged on both sides of a vehicle floor panel in the vehicle width direction and extend along the vehicle front-rear direction, and the vehicle width direction is the longitudinal direction. and a plurality of cross members each having both ends in the longitudinal direction fixed to the pair of rockers respectively, and spaced apart in the vehicle front-rear direction, wherein the distance between adjacent cross members in the vehicle front-rear direction discloses a vehicle side structure in which a bending reaction force of the rocker against an input load applied at the time of a side collision of the vehicle is set to be greater than or equal to the input load. In Patent Document 3, it is possible to secure the necessary bending reaction force N of the side sill (rocker) at the time of a side collision of the vehicle. It is said that it is possible to suppress the intrusion of

Patent Document 4 discloses an automobile floor structure in which a cross member has a front wall and a rear wall and a member made of fiber reinforced resin such as CFRP (carbon fiber reinforced resin) with an open bottom surface is applied.

JP 2018-161934 A JP 2019-151294 A JP 2019-31219 A JP 2014-91422 A

Although the technique of Patent Document 1 described above has a certain effect against side collisions, the increase in the number of parts increases the weight and cost, and complicates the manufacturing of the vehicle body.
In addition, although the technology of Patent Document 2 suppresses deformation of the battery case, the floor cross member is bent upward (toward the inside of the vehicle) so as to project upward, reducing the cabin volume and increasing the degree of freedom in design. decreases significantly.
Further, the technique of Patent Document 3 can secure the necessary bending reaction force of the side sills in the event of a side collision of the vehicle, but the installation position of the floor cross member is limited. Since the floor cross member is also used to fix the seat rails, if the installation position of the floor cross member is limited, the degree of freedom in vehicle design is greatly reduced.

As mentioned above, there are many technical disclosures for improving the function to prevent the large load from the side sills generated in the event of a side collision from entering the battery case. There was a problem of lowering the degree.

Furthermore, the technology of Patent Document 4 is such that even if fiber reinforced resin such as CFRP (carbon fiber reinforced resin), which is stronger, more rigid and lighter than steel materials, is applied to the floor cross member, the fiber reinforced resin breaks. Low elongation. For this reason, the technique of Patent Document 4 has a problem in that deformation of the battery case of an automobile in which the battery case is mounted cannot be sufficiently suppressed in the event of a side collision.

The present invention was made to solve such problems, and suppresses the deformation of the battery case in the event of a side collision, enables weight reduction of the automotive body, and provides vibration-damping properties. To provide an automotive battery case protection structure and a floor cross member used in the battery case protection structure, without reducing the cabin volume or reducing the freedom of vehicle design. and

A battery case protection structure for an automobile according to the present invention comprises: a floor that constitutes at least a part of a floor portion of a vehicle body that constitutes an automobile; a battery case that is mounted under the floor and stores a battery; a pair of side sills provided at both ends of the vehicle body and extending in the longitudinal direction of the vehicle body; A battery case protection structure for protecting the battery case in a vehicle body structure of an automobile comprising a floor cross member which is provided in a pair of side sills and has both ends in contact with the side surfaces of the pair of side sills, wherein the floor cross member is , a hat-shaped section part having a top portion, a side wall portion and a flange portion; and an inner surface of at least said vertical wall portion of said hat-shaped section part and/or a resin attached or applied to the outer surface, and a reinforcing plate (reinforcement) disposed so as to cover the resin and adhered to the resin.

Further, it is preferable that the resin is disposed with a constant thickness only in the range of the floor cross member that protrudes from the battery case in the vehicle width direction.

Further, it is preferable that the resin is disposed with a constant thickness only in the area of the floor cross member located above the battery case.

The resin is disposed over the entire length of the floor cross member, and the thickness of the resin is constant in the range above the battery case, and extends outward in the vehicle width direction in other ranges. It is preferable that the thickness is gradually reduced.

Further, it is preferable that the resin has a thickness of 0.1 to 5 mm and the reinforcing plate has a thickness of 0.15 to 1 mm.

A floor cross member according to the present invention comprises a floor constituting at least a part of a floor portion of a vehicle body of an automobile, a battery case mounted under the floor for storing a battery, and both ends of the floor in the width direction of the vehicle body. and a pair of side sills extending in the longitudinal direction of the vehicle body. A floor cross member provided on the upper surface of the floor so as to protrude on both sides in the vehicle width direction and having both end portions in contact with the side surfaces of the pair of side sills, the hat section having a top plate portion, a vertical wall portion and a flange portion. a member, a resin attached or applied to at least the inner surface and/or the outer surface of the vertical wall portion of the hat section member, and a reinforcing plate disposed so as to cover the resin and adhered to the resin.

Further, it is preferable that the resin is disposed with a constant thickness only in a range that protrudes in the vehicle width direction from the battery case in the attached state.

Further, it is preferable that the resin is arranged with a constant thickness only in a range located above the battery case in the attached state.

In addition, the resin is arranged over the entire length in the longitudinal direction, and the thickness of the resin is constant in the range located above the battery case in the attached state, and in the other range outward in the vehicle width direction. It is preferable that it gradually becomes thinner toward

In the present invention, a hat cross-sectional member having a top plate portion, a vertical wall portion and a flange portion, a resin attached or applied to at least the inner surface and / or the outer surface of the vertical wall portion of the hat cross-sectional member, and so as to cover the resin A floor cross member is provided and comprises a resin and a bonded reinforcing plate. As a result, the stiffness of the floor cross member is improved to suppress the deformation of the battery case in the event of a side collision, and the weight of the floor cross member can be reduced and the damping performance can be improved. In addition, since the installation position of the floor cross member is not limited, the flexibility of vehicle design is not reduced. Furthermore, since there is no need to change the shape of the conventional floor cross member significantly, the cabin volume is not reduced.

1A and 1B are diagrams for explaining a battery case protection structure according to an embodiment of the present invention, FIG. 1A being an exploded perspective view, and FIG. It is a diagram. FIG. 2 is a diagram for explaining a resin pasting (applying) range in the longitudinal direction of the floor cross member in the battery case protection structure shown in FIG. FIG. 3 is a cross-sectional view of a conventional floor cross member as a comparative example of the floor cross member of FIG. Fig. 4 shows a model (invention model) for evaluating the plane stiffness of the vertical wall portion of the floor cross member in Fig. 1 and the conventional model in Fig. 3 for evaluating the plane stiffness of the vertical wall portion of the floor cross member. It is a figure explaining the model (conventional model) for doing. FIG. 5 is a graph showing the results of evaluating the surface rigidity of the conventional model and the invention model of FIG. FIG. 6 is a diagram for explaining the deformation state of the floor cross member at the time of a side collision. FIG. 7 is a diagram illustrating another aspect of the resin pasting (applying) range in the longitudinal direction of the floor cross member (No. 1). FIG. 8 is a diagram illustrating another aspect of the resin pasting (applying) range in the longitudinal direction of the floor cross member (No. 2). FIG. 9 is a diagram illustrating another aspect of the resin pasting (applying) range in the circumferential direction of the floor cross member. 10A and 10B are diagrams showing the application (sticking) range of the resin in the circumferential direction of the test body according to Example 1, FIG. 9A and FIG. 9B are examples of the invention, and FIG. For example. FIG. 11 is a diagram showing load-stroke curves during collision tests of Invention Example 1 and Comparative Example 1 according to Example 1. FIG. FIG. 12 is a diagram illustrating a configuration around a floor cross member on the floor of an internal combustion engine (ICE).

An automobile battery case protection structure 1 (hereinafter simply referred to as "battery case protection structure 1") according to an embodiment of the present invention will be described with reference to FIGS. 1 and 2. FIG. FIG. 1 is a schematic diagram showing a battery case protective structure 1 of this embodiment. The direction of the arrow FR in the drawing indicates the front of the vehicle body, and the direction of the arrow UP indicates the upper direction of the vehicle body. FIG. 2 is a schematic diagram showing a part of the vehicle width direction in a vertical cross section of the battery case protection structure 1 of FIG.

The battery case protection structure 1, as shown in FIG. It protects the battery case 5 from the load caused by The floor 3 is the floor of the electric vehicle, and the battery case 5 is mounted under the floor 3. A pair of side sills 7 (only a portion of the side sill inner 7a constituting the side sills 7 is shown in FIG. 1) are provided at both ends of the floor 3 in the vehicle width direction, and the floor cross members 9 extend in the vehicle width direction. It is provided on the upper surface of the floor 3 . Each configuration will be described in detail below.

<floor>
The floor 3 is a member (panel) that constitutes at least a part of the floor portion of the vehicle body that constitutes the electric vehicle. Since the floor 3 is not provided with a floor tunnel 21 (see FIG. 12) like the floor of an internal combustion engine (ICE), it has a shape that facilitates securing a space for the battery case 5 and a cabin space.

<Battery case>
The battery case 5 stores the battery of the electric vehicle, and is composed of a battery case lower 5a, a battery case upper 5b, and a battery case cross 5c. It is configured. The battery case lower 5a is made of a bottomed frame that stores the battery, and the battery case upper 5b is a lid that covers the battery case lower 5a. The battery case cross 5c is a stiffening member that improves the rigidity of the battery case 5 itself, and is provided inside the battery case lower 5a so as to extend in the vehicle width direction. Suppress deformation.

<Side sill>
The side sills 7 are arranged so as to extend in the longitudinal direction of the vehicle body and are joined to both outer sides of the floor 3 in the vehicle width direction. The side sill 7 is composed of a side sill inner 7a arranged inside the vehicle body and a side sill outer 7b arranged outside the vehicle body (see FIG. 2). As shown in FIG. 2, a horizontal portion of a fixing component 11 having an L-shaped cross section is joined to the lower portion of the side sill inner 7a. is joined to the side wall portion of the lower battery case 5a. As described above, the battery case 5 is fixed to the side sill 7 via the fixing parts 11 .

<Floor cross member>
The floor cross member 9 is a hat-shaped cross-sectional part, as shown in FIG. 1(b). Further, as shown in FIG. 2, the floor cross member 9 is provided on the upper surface of the floor 3 so as to cross the upper side of the battery case 5 in the vehicle width direction. It protrudes on both sides in the width direction and is joined to the side sill inner 7a.

As described above, the floor cross member 9 is provided above the battery case 5 so as to protrude to both sides of the battery case 5 in the vehicle width direction. As a result, the load at the time of side collision is input to the floor cross member 9 before the battery case 5, and the load input to the battery case 5 is reduced.

As shown in FIG. 1(b), the floor cross member 9 includes a hat section member 13, a resin 15 attached or applied to the inner surface of the hat section member 13, and a reinforcing plate 17 provided so as to cover the resin 15. and

The hat cross-sectional member 13 is a hat cross-sectional metal (for example, steel sheet) member having a top plate portion 13a, a vertical wall portion 13b, and a flange portion 13c. The flange portion 13c of the hat cross-section member 13 is joined to the upper surface of the floor 3, and the vertical wall flange portions 13d formed at both ends of the vertical wall portion 13b in the vehicle width direction are connected to the side sill inner 7a. is joined to As a material for the hat cross-section member 13, a high strength steel sheet of, for example, 980 MPa (MPa-class) or more is used in order to increase strength and rigidity.

A resin 15 is patched or coated on the inner surface of the vertical wall portion 13b of the hat cross-section member 13 with a predetermined adhesive strength. The resin 15 may be pre-molded (injection-molded resin part) and attached to the hat cross-section member 13, or the pre-molded resin may be applied to the hat cross-section member 13 and baked ( baking).

The lower limit of the thickness of the resin 15 in the case of forming the resin 15 by applying the resin to the hat cross-section member 13 before molding and baking it is about 0.1 mm, which allows uniform application. The lower limit of the thickness of the resin 15 when the film-like resin 15 is attached to the hat cross-section member 13 is about 20 μm. Also, the upper limit of the thickness of the resin 15 is preferably about 5 mm from the viewpoint of cost.

Furthermore, a reinforcing plate 17 is provided so as to cover the resin 15 . The reinforcing plate 17 prevents the peeling of the resin 15 from the vertical wall portion 13b of the hat cross-section member 13, and cooperates with the resin 15 to improve the surface rigidity of the vertical wall portion 13b as described later. It improves the rigidity of the member 9 . The reinforcing plate 17 is fixed to the vertical wall portion 13b of the hat section member 13 by spot welding. Further, the reinforcing plate 17 and the resin 15 are adhered with a predetermined strength. The effect of improving the surface rigidity of the vertical wall portion 13b in the present embodiment does not greatly depend on the tensile strength of the material of the reinforcing plate 17, as will be described later. Therefore, the tensile strength of the material of the reinforcing plate 17 may be lower than the tensile strength of the material of the hat section member 13, and from the viewpoint of manufacturing cost reduction, the tensile strength may be 270 MPa class to 590 MPa class. Further, since the reinforcing plate 17 only needs to prevent the resin 15 from peeling off from the vertical wall portion 13b of the hat cross-section member 13, the thickness of the reinforcing plate 17 is thinner than the thickness of the material of the hat cross-section member 13. good. A specific thickness of the reinforcing plate 17 may be 0.15 to 1 mm from the viewpoint of weight reduction and manufacturing cost reduction. The tensile strength of the 270 MPa grade to 590 MPa grade is set because the 270 MPa grade has the lowest tensile strength among steel sheets that are normally used, and if the tensile strength exceeds the 590 MPa grade, the cost increases significantly. Within this range, the 270 MPa grade (so-called mild steel), which is a grade of inexpensive general cold rolled steel sheet called common steel such as JIS standard SPCC, is used. It is preferable from the viewpoint of cost. The reason why the plate thickness is set to 0.15 to 1 mm is that if the thickness is less than 0.15 mm, the manufacturing cost rises, and if it exceeds 1 mm, the effect of weight reduction decreases.

A conventional general floor cross member 23 was composed only of a metal hat cross-section member 13, as shown in FIG. In this case, in order to increase the strength and rigidity of the floor cross member 23, it is necessary to increase the plate thickness of the hat section member 13, which increases the weight.

In this regard, in the floor cross member 9 of the present embodiment, the hat section member 13 is provided with the resin 15 and the reinforcing plate 17, and the apparent plate thickness of the resin 15 and the reinforcing plate 17 is increased. The weight is less likely to increase compared to the case where the plate thickness of the hat cross-section member 13 itself is increased as in the related art. This is because the floor cross member 9 is made of resin 15 having a density lower than that of metal.

Further, by adopting a sandwich structure in which resin is sandwiched between the metal hat cross-section member 13 and the reinforcing plate 17, the surface rigidity of the vertical wall portion 13b can be improved. Here, the surface rigidity of the vertical wall portion refers to the rigidity (bending rigidity) before buckling deformation starts when a load is input from the end of the vertical wall portion in the in-plane direction of the vertical wall portion. stiffness)). This point will be described with reference to FIGS. 4 and 5. FIG.

Figure 4 shows the conventional model and the invention model. The conventional model is a model for evaluating the surface rigidity of the vertical wall portion 13b of the conventional floor cross member 23 (see FIG. 3), and is composed only of a steel plate (hat section member 13). The invention model is a model for evaluating the surface rigidity of the vertical wall portion 13b of the floor cross member 9 (see FIG. 1(b)) of the present embodiment, and the sandwich structure (three-layer laminated structure) described above is used. have. In FIG. 4, parts corresponding to those in FIGS. 1 and 3 are denoted by the same reference numerals.

　The surface stiffness of the conventional model, which is composed only of steel plates, is generally given by the product EI of the material's Young's modulus E and the geometrical moment of inertia I. On the other hand, the surface rigidity EI in the case of a sandwich structure like the invention model can be obtained using the following formula (1).

In the above formula (1), L is the width of the laminated body, i is a subscript to identify the material, n is the number of layers, Ei is the Young's modulus of material i, hi is from the material with i = 1 Thickness to layer of material i, λ is the distance from the surface of the material with i=1 to the neutral plane of the laminate.

FIG. 5 shows the results of comparing the difference in surface stiffness EI when the weight of the conventional model and the invention model shown in FIG. 4 is substantially the same. In FIG. 5, the thickness of the hat section member 13 of the conventional model is 1.2t (total thickness of 1.2t), the thickness of the hat section member 13 of the model of the present invention is 0.6t, the thickness of the resin 15 is 1.5t, and the thickness of the reinforcing plate 17 is 1.5t. With a thickness of 0.3t (total thickness of 2.4t), each surface stiffness EI was calculated using the formula (1). The weight ratio of the two models in FIG. 5 was 0.97 for the invention model when the weight of the conventional model was taken as the standard (1.00). As shown in FIG. 5, the surface rigidity of the invention model (1.65×10 ⁻⁷ GPa·m ⁴ ) is 5.3 times higher than that of the conventional model (0.31×10 ⁻⁷ GPa·m ⁴ ). In this way, the plate thickness of the hat cross-section member 13 (made of metal) of the invention model is made thinner than that of the conventional model, and the resin 15, which has a lower density and a lower Young's modulus than the metal, is replaced with the reinforcing plate 17. The total thickness of the sandwich structure is made thicker than that of the conventional model. As a result, the invention model can significantly increase the surface rigidity compared to the conventional model even if the weight is approximately the same as that of the conventional model.

Next, the reason why the resin 15 and the reinforcing plate 17 are provided on the vertical wall portion 13b of the hat cross-section member 13 will be described with reference to FIG. 6 is a plan view schematically showing how the floor cross member 9 deforms when the side of the vehicle body collides with the pole 19. FIG. FIG. 6(a) shows the state before the collision, and FIG. 6(b) shows the state after the collision. When the pole 19 is in the position shown in FIG. 6(a), when the vehicle body moves in the direction of the black arrow in FIG. The deformation of the floor cross member 9 is often in a bending mode in which it bends toward the colliding part.

At the time of deformation in the folding mode as shown in FIG. 6(b), the top plate portion 13a undergoes in-plane deformation, while the vertical wall portion 13b undergoes out-of-plane deformation. Therefore, the vertical wall portion 13b is more easily deformed than the top plate portion 13a. Therefore, by providing the vertical wall portion 13b with the resin 15 and the reinforcing plate 17 to increase the surface rigidity of the vertical wall portion 13b, the resistance to the bending mode of the floor cross member 9 is effectively improved.

In addition, since the hat section member 13, the resin 15, and the reinforcing plate 17 are united to receive the load, the surface rigidity is effectively improved. must be glued together. This point will be described with a specific example.

For example, if the thickness of the hat section member 13 is 1.0 mm, the thickness of the resin 15 is 1.0 mm, and the thickness of the reinforcing plate 17 (made of iron) is 0.6 mm, the hat section member 13 and the resin 15, and the resin 15 and the reinforcing plate 17 are adhered to each other, the surface rigidity EI is 271.5 GPa·mm ⁴ (Young's modulus of iron is 206 GPa, and Young's modulus of resin is 2 GPa). Here, when the resin 15 and the reinforcing plate 17 are not bonded, the surface rigidity EI of the bonded hat section member 13 and the resin 15 is 19.3 GPa·mm ⁴ , and the surface rigidity EI of the reinforcing plate 17 alone is 3.7. Since it is GPa·mm ⁴ , the total is 23 GPa·mm ⁴ , and the surface rigidity as a whole is remarkably lowered. Therefore, the hat cross-section member 13 and the resin 15 are bonded with sufficient strength so that the hat cross-section member 13, the resin 15 and the reinforcing plate 17 can receive the load together, and the resin 15 and the reinforcing plate 17 are bonded with sufficient strength. It is important that they are glued together.

The adhesive strength is preferably 5 MPa or more, for example. In bending mode deformation as shown in FIG. 6, if the adhesive strength is 5 MPa or more, the adhesive does not separate from the steel plate in bending deformation up to about 90°. Regarding the end of the floor cross member 9, there is a case where an axial crush occurs at the initial stage of the collision, causing a bellows-shaped buckling deformation (see FIG. 6(b)). The amount of deformation is greater than If the resin 15 is peeled off at the initial stage of deformation, the yield strength at the time of subsequent (bellows) deformation is reduced. Therefore, it is more preferable to set the adhesive strength to 10 MPa or more for portions where large deformation such as axial crushing is expected. Also, when the pole 19 collides between two floor cross members 9 as shown in FIG. 6, the deformation of the floor cross member 9 is in the folding mode. On the other hand, when the pole 19 collides with one floor cross member 9 in the axial direction, the amount of deformation of the floor cross member 9 is even greater than in the bending mode of FIG. 6(b). Even when the pole 19 collides with one floor cross member 9 in the axial direction, if the adhesive strength is set to 10 MPa or more, peeling of the resin can be prevented.

The present invention does not limit the range of application (or application) of the resin 15 in the longitudinal direction of the floor cross member 9 . The resin 15 may be provided only in the range in which the rigidity of is desired to be improved. Therefore, for example, as shown in FIG. 2, the resin 15 may be attached (or applied) with a constant thickness only to the area of the floor cross member 9 that protrudes from the battery case 5 in the vehicle width direction. The example in FIG. 2 assumes that the side sill 7 alone is designed to absorb the crash energy, and the floor cross member 9 is likely to break (bending deformation) and buckling deformation. It is intended to improve the surface rigidity of the vertical wall portion 13b in the range (see FIG. 6(b)). In this example, the amount of the resin 15 used is the minimum required, so the weight of the parts can be reduced and the manufacturing cost can be suppressed.

As another aspect, as shown in FIG. 7, the resin may be provided with a constant thickness only in the area of the floor cross member 9 located above the battery case 5 . Here, "above the battery case 5" should include at least above the portion of the battery case 5 that stores the battery. Therefore, as in the example of FIG. 7, it is located above the portion between one side wall portion 5d of the battery case 5 (specifically, the side wall portion of the lower battery case 5a) and the other side wall portion (not shown). The resin 15 may be provided in the range.

In the example of FIG. 7, since the surface rigidity of the vertical wall portion 13b is low only at the end portion of the floor cross member 9, bending deformation and buckling deformation are likely to occur only at that portion. As a result, the end portion of the floor cross member 9 is deformed together with the side sill 7 in the event of a side collision, thereby improving crash energy absorbing properties. In addition, since the resin 15 is disposed on most of the battery case 5 except for the portion protruding outward from the battery case 5, the effect of suppressing deformation of the battery case and the effect of weight reduction equivalent to those obtained when the resin 15 is disposed over the entire length in the longitudinal direction can be obtained. be able to.

　In the examples of Figs. 2 and 7, the resin 15 is provided with a constant thickness, but the thickness of the resin 15 may not necessarily be constant, and may vary partially. For example, when the resin 15 is arranged over the entire length of the floor cross member 9 as shown in FIG. You may make it become thin gradually toward the outer side of .

With this arrangement, the surface rigidity of the vertical wall portion 13b of the portion of the floor cross member 9 protruding from the battery case 5 decreases toward the outside. Deformation starts from the end side with low . Since the deformation can be controlled so as to start from the portion apart from the battery case 5 in this way, the effect of suppressing the deformation of the battery case 5 is improved as compared with the example of FIG.

In the above description, the resin 15 and the reinforcing plate 17 are provided only on the vertical wall portion 13b of the hat section member 13 (see FIG. 1(b)). and a reinforcing plate 17 may be provided. Therefore, as shown in FIG. 9, resin 15 and reinforcing plate 17 may be provided on vertical wall portion 13b and top plate portion 13a.

<Method for determining resin thickness>
As described above, the present invention does not limit the thickness of the resin 15 of the floor cross member 9, but if the resin 15 is too thin, the effect of improving the surface rigidity of the vertical wall portion 13b will be reduced, and if it is too thick, the weight will be reduced. may be less effective. Therefore, it is preferable to determine the resin thickness in consideration of the balance between the two. An example of such a resin thickness determination method will be described below.

First, a hat cross-sectional member 13 is prepared as a basis for examination, and the weight and surface rigidity of the vertical wall portion 13b are obtained. Here, a hat cross-sectional member 13 made of steel plate having a thickness of 1.6 mm was prepared, and the weight (including the weight of the floor) and surface rigidity of the vertical wall portion 13b were determined (see <<base>> in Table 1 below).

Next, as the hat cross-section member 13 constituting the floor cross member 9 according to the present embodiment, a hat cross-section member 13 having a thickness smaller than that of the hat cross-section member 13 serving as the base is prepared. Here, three types of hat cross-sectional members 13 with plate thicknesses of 0.8 mm <<No.1>>, 1.0 mm <<No.2>>, and 1.2 mm <<No.3>> were prepared. The reinforcing plate 17 is made of a steel plate having a thickness of 0.4 mm (same for <<No.1>> to <<No.3>>).

When constructing the floor cross member 9 as shown in FIG. The resin thickness was obtained when the surface rigidity was adjusted to be approximately the same as the surface rigidity of (A). Also, the resin thickness was obtained when the weight of the floor cross member 9 was adjusted to be approximately the same as the weight of the <<base>> (B). Table 1 shows the results. The weight in Table 1 includes the weight of the floor (0.9kg common). Also, the surface rigidity is assumed to be that of the vertical wall portion.

A of <<No.1>> to <<No.3>> shown in Table 1 makes the plate thickness of the hat cross-section member 13 thinner than the <<base>>, provides a resin 15 having a lower Young's modulus than the steel plate, and provides a reinforcing plate. The total thickness of the sandwich structure with 17 is made thicker than the plate thickness of the <<base>>. As a result, while maintaining the same level of surface rigidity as the <<base>> surface rigidity (70GPa・mm ⁴ ), the use of a resin with a lower density than the steel plate maximizes the effect of weight reduction. . The weight reduction rate is 21% for <<No.1>>, 12% for <<No.2>>, and 4% for <<No.3>>.

On the other hand, for ≪No.1≫ to ≪No.3≫ B, the resin thickness is thickened until it reaches the same weight as the ≪base≫ (3.59 kg), and the total thickness of the sandwich structure is thicker than A. This is intended to maximize the effect of improving the surface rigidity. The surface rigidity improvement rate is 1599% for <<No.1>>, 796% for <<No.2>>, and 171% for <<No.3>>.

Based on the results in Table 1, the lower limit is the resin thickness in the case of A, which allows the maximum weight reduction without lowering the surface rigidity than the <<base>>, and the maximum surface rigidity without increasing the weight over the <<base>>. The resin thickness is determined with the upper limit of the resin thickness in the case of B that can improve the . Therefore, in the case of <<No. 1>> (thickness hc of the hat section member = 0.8 mm, thickness of the reinforcing plate hp = 0.4 mm), the resin thickness should be set within the range of 0.45 mm to 4.0 mm. Similarly, in the case of <<No.2>> (hat cross section member thickness hc=1.0mm, reinforcing plate thickness hp=0.4mm), within the range of 0.25mm to 2.5mm, <<No.3>> (hat If the thickness of the cross section member hc=1.2mm and the thickness of the reinforcing plate hp=0.4mm), the resin thickness should be set within the range of 0.02mm to 0.8mm. By doing so, the thickness of the resin 15 can be determined in consideration of the balance between weight reduction and improvement in surface rigidity (flexural rigidity).

As described above, according to the present embodiment, the resin 15 attached or applied to at least the inner surface of the vertical wall portion 13b of the hat cross-section member 13 and the reinforcing plate disposed and adhered so as to cover the resin 15 17. As a result, the rigidity of the floor cross member 9 is improved, the deformation of the battery case 5 in the event of a side collision is suppressed more than before, and the weight of the floor cross member 9 can be reduced. Further, since the installation position of the floor cross member 9 is not limited, the degree of freedom in vehicle design is not reduced, and the cabin volume is not reduced.
It should be noted that this embodiment can also improve damping properties. This point will be specifically described in the examples below.

In the above embodiment, the resin 15 and the reinforcing plate 17 are provided on the inner surface of the hat section member 13 of the floor cross member 9, but the present invention is not limited to this. The resin 15 and the reinforcing plate 17 may be provided on the substrate. Further, the inner surface and the outer surface of the hat section member may be provided with the resin 15 and the reinforcing plate 17, respectively.

Furthermore, although the above describes an embodiment of the battery case protection structure for an automobile, the present invention is characterized by the configuration of the floor cross member, which is a part of the battery case protection structure. Therefore, the present application also includes the invention as a single floor cross member. Since the embodiment of the floor cross member is the same as the above description, the description is omitted.

Specific experiments were conducted to evaluate the effects of the present invention, and the results are described below. In this example, a cylindrical specimen (length 200 mm) consisting of a hat cross-sectional part corresponding to the floor cross member and a flat plate corresponding to the floor panel was prepared, and crash worthiness was evaluated. An impact test to evaluate vibration characteristics and an impact vibration test to evaluate vibration characteristics were conducted.

As an example of the invention, the above-mentioned specimens have resin 15 and reinforcing plate 17 provided on top plate portion 13a and vertical wall portion 13b of hat cross-section member 13 as shown in FIG. As shown in FIG. 1, a hat cross-section member 13 having only the vertical wall portion 13b provided with the resin 15 and the reinforcing plate 17 was prepared. Also, as a comparative example, as shown in FIG. I used something else. A steel plate was used for the hat section member 13 of the test body, and a steel plate having a thickness of 1.0 mm and a pressure of 440 MPa was used for each of the flat plates. In FIG. 10, parts corresponding to those in FIGS. 1 and 9 are denoted by the same reference numerals.

In the impact test, a load was applied in the axial direction (longitudinal direction) of the test piece with an impact punch at a test speed of 8.9m/s, and the test piece was deformed 20mm in the axial direction from 200mm to 180mm. At that time, the load generated on the supporting part of the test piece and the stroke of the impact punch (amount of axial crush deformation) were measured to obtain a load-stroke curve, and the load- The maximum load (kN) of the stroke curve was taken as the yield strength of the specimen against collision (referred to as crash yield strength). The maximum value of impact resistance indicates the load that changes from elastic deformation immediately after the start of axial crushing deformation to plastic deformation. The higher this value, the more deformation occurs during collision. It can be said that the collision characteristics are good.

In the impact vibration test, an acceleration sensor was attached near the edge of the top plate portion 13a of the suspended test body, and an impact hammer was used to apply impact vibration to the vertical wall portion 13b of the test body. do. Then, the impact force obtained from the impact hammer and the acceleration measured by the test body were input to the FFT analyzer, and the frequency response function of Accelerance (m/s ² /N) was calculated. Here, the frequency response function was obtained by averaging the results of five impact tests.

Tables 2 to 6 show the details of the invention examples and comparative examples (the tensile strength and plate thickness of the hat cross-section member and the reinforcing plate, and the resin thickness of the steel plate of the hat cross-section member and the resin thickness) and the results of the above tests. FIG. 11 shows the load-stroke curves of Invention Example 1 and Comparative Example 1 as an example of the load-stroke curves obtained in the collision test. The test results of this example were evaluated from five points of view, which will be described in detail below. In each table, the "whole circumference" described in the "bonding position of the resin/reinforcement plate in the cross-sectional direction" refers to the top plate portion 13a and the vertical wall portion 13b of the hat cross-section member 13 as shown in FIG. 10(a). shows that the resin 15 and the reinforcing plate 17 are provided. In addition, the "face stiffness" in each table was calculated based on the formula described above.

<Evaluation of Invention Examples for Improving Surface Rigidity and Collision Resistance>
Based on the experimental results shown in Table 2 below, the effect of improving the surface rigidity and impact resistance of the present invention was evaluated.

Comparative Example 1 is an example composed only of the hat cross-section member 13 as shown in FIG. This is an example in which a resin 15 and a reinforcing plate 17 are provided on 13b. As shown in Table 2, the surface rigidity of Inventive Examples 1 to 3 is higher than that of Comparative Example 1 in all cases.

The impact strength, which indicates the impact characteristics, corresponds to the maximum load in the load-stroke curve (see Fig. 11) obtained by the impact test, and was 310 kN for Comparative Example 1 and 600 kN for Invention Example 1. Although the weight of Invention Example 1 is greater than that of Comparative Example 1, the crash resistance is 1.9 times or more that of Comparative Example 1, which is a significant improvement. In invention examples 2 and 3, which were adjusted to have a weight similar to that of comparative example 1, the impact resistance was improved as compared to comparative example 1.

In addition, "vibration damping", which indicates vibration characteristics, is the value of acceleration at a frequency of 200 Hz obtained by an impact vibration test. Suppressed.

As described above, it was shown that invention examples 1 to 3 can improve surface rigidity, impact resistance, and damping performance with a weight comparable to that of comparative example 1.

<Evaluation of Invention Examples for Weight Reduction>
Based on the experimental results shown in Table 3 below, the effect of weight reduction in the present invention was evaluated.

Invention Examples 4 to 6 in Table 3 are examples adjusted to achieve weight reduction while maintaining surface rigidity, impact strength, and vibration damping properties equal to or higher than those of Comparative Example 1 described above. In invention examples 4 to 6, similar to invention examples 1 to 3, resin 15 and reinforcing plate 17 are provided on top plate portion 13a and vertical wall portion 13b over the entire length in the longitudinal direction of hat cross-section member 13 (FIG. 10). (a)). Inventive Examples 4 to 6 all have surface rigidity and impact strength equal to or higher than those of Comparative Example 1, and achieve weight reductions of 10%, 12%, and 21%, respectively, compared to Comparative Example 1. In addition, the damping property was greatly improved in all cases of Inventive Examples 4 to 6.

As described above, it was shown that invention examples 4 to 6 are capable of weight reduction while ensuring surface rigidity, impact resistance, and damping performance equivalent to or greater than those of comparative example 1.

<Evaluation of Invention Examples Aimed at Both Improvement of Surface Rigidity and Impact Resistance and Weight Reduction>
Based on the experimental results shown in Table 4 below, the effect of realizing both improvement in surface rigidity/impact resistance and weight reduction in the present invention was evaluated.

Invention Examples 7 to 9 in Table 4 are examples in which surface rigidity and impact strength are improved compared to Comparative Example 1 described above, and adjustments are made so as to achieve weight reduction. In invention examples 7 to 9, similar to invention examples 1 to 6, resin 15 and reinforcing plate 17 are provided on top plate portion 13a and vertical wall portion 13b over the entire length in the longitudinal direction of hat cross-section member 13 (FIG. 10). (a)).

Invention Example 7 was 3% (0.09 kg) lighter than Comparative Example 1, while improving crash resistance by 11% (35 kN). Inventive Example 8 was 7% (0.27 kg) lighter than Comparative Example 1, while improving crash strength by 6.4% (20 kN). Inventive example 9 is an example with the thinnest resin thickness among the inventive examples, and even in this case, the weight was reduced by 4% (0.13 kg), while the crash strength was improved by 3% (10 kN). In addition, the damping property was greatly improved in all cases of Inventive Examples 7 to 9.

As described above, invention examples 7 to 9 were shown to be lighter than comparative example 1 while improving surface rigidity and impact strength.

<Evaluation of presence or absence of adhesion and influence of adhesion strength>
As described in the embodiment, in order to properly exhibit the effect of improving the surface rigidity in the present invention, the hat cross-section member 13 and the resin 15 and the resin 15 and the reinforcing plate 17 are adhered to each other so that the portion concerned is It is necessary to be able to receive the load as one unit. In addition, it is preferable to bond with a sufficient bonding strength of, for example, 10 MPa or more so that a part of the bonding does not delaminate due to axial crushing and the impact strength does not decrease.

Therefore, based on the experimental results shown in Table 5 below, we evaluated how much surface rigidity and impact resistance are affected by the presence or absence of adhesion.

The four examples in Table 5, except for Comparative Example 1, all use the steel plate hat cross-section member 13 having the same tensile strength as Comparative Example 1, and are constructed in the same manner except for the adhesive strength. In invention examples 10 and 11, which had an adhesive strength of 10 MPa or more, both had improved surface rigidity and improved impact strength by 6.4% (20 kN) compared to comparative example 1. In addition, damping performance has been greatly improved, and vibration has been greatly suppressed.

In Comparative Example 2, the adhesive strength is 0 MPa, that is, neither the hat cross-section member 13 and the resin 15 nor the resin 15 and the reinforcing plate 17 are bonded, so the surface rigidity cannot be calculated from the formula (1). Instead, it is the total value of the surface stiffness EI of the hat section member 13, the resin 15, and the reinforcing plate 17. As a result, the surface rigidity of Comparative Example 3 was lower than that of Comparative Example 1 by 45%, and the impact resistance was also lower than that of Comparative Example 1 by 6.5% (20 kN). Moreover, the damping property was the same as that of Comparative Example 1, and no improvement was observed.

From the above, the effectiveness of bonding the hat cross-section member 13 and the resin 15, and the resin 15 and the reinforcing plate 17, has been demonstrated.

<Evaluation of resin sticking (coating) range>
Based on the experimental results shown in Table 6 below, evaluation was made on the case where the position (range) where the resin 15 and the reinforcing plate 17 were adhered to the hat section member 13 was changed.

The four examples in Table 6, except for Comparative Example 1, all use the steel plate hat cross-section member 13 having the same tensile strength as Comparative Example 1, and are all the same except for the affixing positions of the resin 15 and the reinforcing plate 17. It is configured. In invention example 8 (same as Table 4), resin 15 and reinforcing plate 17 are attached to "vertical wall portion 13b and top plate portion 13a" over the "full length" of hat cross-section member 13 in the longitudinal direction ( (See FIG. 10(a)). As described above, the experimental result was that the weight was reduced by 7% (0.27 kg) compared to Comparative Example 1, while the crash resistance was improved by 6.4% (20 kN). Vibration damping is also greatly improved.

In Invention Example 12, a resin 15 and a reinforcing plate 17 are attached "only to the vertical wall portion 13b" over the "full length" of the hat cross-section member 13 in the longitudinal direction (see FIG. 10(b)), which is a comparative example. 9% (0.32kg) lighter than 1. Compared with Example 8 of the invention, the effect of reducing the weight is great because the resin 15 and the reinforcing plate 17 are not provided on the top plate portion 13a. Although the crash resistance is slightly lower than that of Invention Example 8, it is better than that of Comparative Example 1. Vibration damping is also greatly improved.

In Comparative Example 3, a resin 15 and a reinforcing plate 17 are attached to "only the top plate portion 13a" over the "full length" of the hat cross-section member 13 (see FIG. 10(c)). 10% (0.37kg) lighter than 1. This is probably because the hat section member 13 has two vertical wall portions 13b but only one top plate portion 13a, thereby further reducing the weight. The damping property was also improved compared to Comparative Example 1. On the other hand, the effect of improving crash resistance was smaller than that of Invention Examples 8 and 12. In the collision test of this example, the load was input in the axial direction of the specimen. In the case of modal deformation, it can be expected that the difference in yield strength against deformation will become even more pronounced. It should be noted that the fact that the provision of the resin 15 and the reinforcing plate 17 on the vertical wall portion 13b is effective for deformation in the bending mode will be described in a second embodiment described later.

In invention example 13, resin 15 and reinforcing plate 17 are pasted on "vertical wall portion 13b and top plate portion 13a" only in the range of "40%" in the longitudinal direction from the tip of hat cross-section member 13 ( (See FIG. 10(a)), while the weight is reduced by 20% (0.72 kg) compared to Comparative Example 1, the crash resistance is improved by 6% (20 kN). Vibration damping is also greatly improved.

As described above, in the cross-sectional direction of the hat cross-sectional member 13, by providing the resin 15 and the reinforcing plate 17 in a range including at least the vertical wall portion 13b, the surface rigidity and impact strength can be effectively improved. In addition, it is shown that the hat section member 13 does not necessarily have to be provided over the entire length in the longitudinal direction, and a certain effect can be obtained even when the resin 15 and the reinforcing plate 17 are provided in a part of the longitudinal direction. rice field.

In this embodiment, a CAE analysis simulating the side impact of the pole shown in FIG. In the CAE calculation, the length of the two floor crossmembers 9 in FIG. , and a load of 200 kN was input to the side sill 7. Since the above CAE calculation was performed while changing the configuration of the floor cross member 9, Table 7 shows the configuration of the floor cross member 9 and the calculation results in each calculation. In Table 7, "side sill side" of "resin/reinforcement plate pasting position in part longitudinal direction" indicates the mode in FIG. In addition, "battery case upper part" shows the aspect of FIG. 7, and "full length * sill side thin gauge" shows the aspect of FIG.

Comparative example a is an example of a floor cross member 9 composed only of a hat cross-section member 13 similar to the conventional example (see FIG. 3). Inventive Examples A to F and Comparative Example b are examples in which the resin 15 and the reinforcing plate 17 are provided on the hat cross-sectional member 13, and all configurations except for the bonding positions of the resin 15 and the reinforcing plate 17 are the same. All adhesive strengths were set to 11 MPa.

In the evaluation of the presence or absence of deformation of the floor cross member 9 and the battery case 5, if there is no deformation, ◯ is given, and if there is deformation, x is given if it is the same as Comparative Example a (conventional example). The case where the degree of deformation was small was rated as Δ. Also, △ indicates the degree of deformation (small, medium).

In Comparative Example a (conventional example), as shown in Table 7, the floor cross member 9 buckled at the tip and a large break (bending deformation) occurred, and the battery case 5 was also greatly deformed.

On the other hand, in invention examples A to C, both the floor cross member 9 and the battery case 5 were not deformed, and good results were obtained.

In Invention Example D, although very slight buckling deformation was observed at the tip of the floor cross member 9 on the pole collision side, there was no large deformation such as bending (bending deformation), and the battery case 5 was not deformed. . Similarly, in invention examples A' and invention examples E, although very slight buckling deformation was observed at the tip of the floor cross member 9 on the pole impact side, there was no large deformation such as bending. There was no deformation.

In Example F, slight buckling deformation was observed at the tip of the floor cross member 9 on the pole collision side, but there was no large deformation such as bending (bending deformation), and the battery case 5 was not deformed.

In Comparative Example b, buckling and breakage (bending deformation) occurred at the tip of the floor cross member 9, and slight deformation was observed in the battery case 5 as well.

As described above, deformation of the battery case 5 was observed in Comparative Examples a and b, whereas deformation of the battery case 5 was not observed in Invention Examples A to F. As a result, it was verified that the present invention can improve the effect of protecting the battery case with a weight equal to or less than that of the conventional example.

According to the present invention, the deformation of the battery case in the event of a side collision can be suppressed, the weight can be reduced, the damping performance is excellent, the cabin volume can be reduced, and the degree of freedom in vehicle design can be reduced. Therefore, it is possible to provide a battery case protection structure for an automobile and a floor cross member used in the battery case protection structure.

1 Automotive Battery Case Protective Structure 3 Floor 5 Battery Case 5a Battery Case Lower 5b Battery Case Upper 5c Battery Case Cloth 5d Side Wall Part 7 Side Sill 7a Side Sill Inner 7b Side Sill Outer 9 Floor Cross Member 11 Fixing Part 13 Hat Sectional Member 13a Top Plate 13b vertical wall portion 13c flange portion 13d vertical wall flange portion 15 resin 17 reinforcing plate 19 pole 21 floor tunnel 23 floor cross member (conventional example)

Claims

a floor that constitutes at least a part of a floor portion of a vehicle body that constitutes an automobile;
a battery case mounted under the floor for storing the battery;
a pair of side sills provided at both ends of the floor in the width direction of the vehicle body and extending in the longitudinal direction of the vehicle body;
a floor cross member provided on the upper surface of the floor so as to traverse above the battery case in the vehicle width direction and protrude to both sides in the vehicle width direction beyond the battery case, and have both ends thereof in contact with side surfaces of the pair of side sills; A battery case protection structure for protecting the battery case in an automobile body structure configured with
The floor cross member is
a hat cross-sectional member having a top plate portion, a vertical wall portion and a flange portion;
a resin attached or applied to at least the inner surface and/or the outer surface of the vertical wall portion of the hat cross-section member;
A battery case protection structure for an automobile, comprising: a reinforcing plate disposed so as to cover the resin and adhered to the resin.
2. The battery case protective structure for an automobile according to claim 1, wherein the resin is provided with a constant thickness only in a range of the floor cross member that protrudes in the vehicle width direction from the battery case.
The battery case protective structure for an automobile according to claim 1, wherein the resin is provided with a constant thickness only in the area of the floor cross member located above the battery case.
The resin is disposed over the entire length of the floor cross member, and the thickness of the resin is constant in the range above the battery case, and gradually decreases outward in the vehicle width direction in other ranges. The automotive battery case protection structure according to claim 1, wherein:
The automotive battery case protection structure according to any one of claims 1 to 4, wherein the resin has a thickness of 0.1 to 5 mm, and the reinforcing plate has a thickness of 0.15 to 1 mm.
a floor that constitutes at least a part of the floor portion of the vehicle body of the automobile;
a battery case mounted under the floor for storing the battery;
A pair of side sills provided at both ends of the floor in the width direction of the vehicle body and extending in the longitudinal direction of the vehicle body. A floor cross member provided on the upper surface of the floor so as to traverse in the width direction and protrude to both sides in the vehicle width direction beyond the battery case, and has both ends thereof in contact with the side surfaces of the pair of side sills,
a hat cross-sectional member having a top plate portion, a vertical wall portion and a flange portion;
a resin attached or applied to at least the inner surface and/or the outer surface of the vertical wall portion of the hat cross-section member;
A floor cross member comprising a reinforcing plate disposed so as to cover the resin and adhered to the resin.
The floor cross member according to claim 6, wherein the resin is provided with a constant thickness only in a range that protrudes in the vehicle width direction from the battery case in the attached state.
The floor cross member according to claim 6, wherein the resin is provided with a constant thickness only in a range located above the battery case in the attached state.
The resin is arranged over the entire length in the longitudinal direction,
7. The floor cloth according to claim 6, wherein the thickness of said resin is constant in a range located above said battery case in an attached state, and gradually decreases outward in the vehicle width direction in other ranges. member.