Underbody structure

Abstract

To provide a vehicle body lower part structure which can efficiently absorb collision energy while preventing damage of a battery mounted theron when a buffer load is input.SOLUTION: A vehicle body lower part structure includes: side frames 50 each connecting a battery pack 20 disposed below a floor part 13 with a side sill 12; and a battery frame 38 supporting a battery 27 in the battery pack 20. A first joint flange 55, which is joined to a case bottom part 41, of the side frame 50 is arranged so that a second joint flange 75, which is joined to the case bottom part 41, of the battery frame 38 overlaps with the upper side of the first joint flange in a vertical direction.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a vehicle underbody structure. [Background technology]

[0002] A known vehicle underbody structure has a battery case housing multiple batteries and is disposed below the floor of the vehicle. A known vehicle underbody structure has both widthwise sides of the battery case suspended from a pair of side sills below the sides of the vehicle. In this type of vehicle, it is important to protect the high-voltage battery in the battery case when a collision load is applied to the vehicle body in order to ensure collision safety performance. Therefore, as a measure to protect the battery, a vehicle lower body structure has been devised in which a crushable portion (a portion that is easily crushed) such as a bead is provided on the cross member connected to the side sill, at a portion located outside the battery case in the vehicle width direction (see, for example, Patent Document 1).

[0003] When a collision load is applied from the side of the vehicle to the side sill inward in the vehicle width direction, the cross member begins to collapse from the easily crushable part, making it possible to absorb the collision energy before the collision load deforms the battery case. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 3132261 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the above-described conventional vehicle body underbody structure, after the easily crushable portion collapses when a collision load is applied, the easily crushable portion displaces toward the battery as a mass. This raises concerns that the load may be transferred from the easily crushable portion to the battery, damaging it. Therefore, there is still room for improvement in terms of collision safety performance.

[0006] The present invention aims to provide an underbody structure that can efficiently absorb collision energy while preventing damage to the battery installed when a collision load is input, thereby improving collision safety performance and contributing to the development of a sustainable transportation system. [Means for solving the problem]

[0007] In order to solve the above problems, the present invention proposes the following means. (1) The vehicle body understructure of the present invention is a vehicle body understructure that includes a side frame (e.g., side frame 50 in the embodiments) that connects a battery pack (e.g., battery pack 20 in the embodiments) arranged below a floor portion (e.g., floor portion 13 in the embodiments) to a side sill (e.g., side sill 12 in the embodiments), and a battery frame (e.g., battery frame 38 in the embodiments) that supports a battery (e.g., battery 27 in the embodiments) inside the battery pack, in which a first joining flange (e.g., first joining flange 55 in the embodiments) that joins to the battery pack of the side frame is arranged so as to overlap above a second joining flange (e.g., second joining flange 75 in the embodiments) that joins to the battery pack of the battery frame in the vertical direction.

[0008] With this configuration, the second joining flange is positioned so as to overlap the first joining flange in the up-down direction. The first joining flange and the second joining flange are formed to allow deformation due to a collision load. Hereinafter, the portion including the first joining flange and the second joining flange may be referred to as the "collision absorbing portion." When a collision load is applied to the first connecting flange of the side frame due to a side collision, such as a side collision with a pole, the first connecting flange is pressed down from above by the second connecting flange. This allows the impact absorption section to deform downward due to the collision load. Hereinafter, a side collision, such as a side collision with a pole, may be simply referred to as a "side collision."

[0009] It is possible to secure a space below the impact absorption section to accommodate the deformation of the impact absorption section. This prevents the impact absorption section from remaining crushed, thereby improving the efficiency of absorbing impact energy. By deforming the impact absorption section downward, it is possible to prevent the impact absorption section from coming into contact with the battery arranged inside the battery pack. This allows the vehicle to efficiently absorb collision energy while preventing damage to the battery when a collision load is applied. Therefore, this vehicle underbody structure can improve collision safety performance and contribute to the development of sustainable transportation systems.

[0010] (2) In the above aspect, the battery frame may have a bent portion (e.g., bent portion 76 in the embodiment) formed at the inner end of the second joining flange in the vehicle width direction, and a convex portion (e.g., convex portion 71 in the embodiment) protruding upward from the bent portion, and the first joining flange may have an edge portion on the battery side (e.g., edge portion 55a in the embodiment) extending to the bent portion side, and the edge portion may have a first joining portion (e.g., first joining portion 55b in the embodiment) joined to the battery pack.

[0011] With this configuration, the edge of the first joint flange extends to the bent portion side of the battery frame (i.e., the inner side of the vehicle width), and the first joint portion of the edge is joined to the battery pack. This allows the collision load to be transmitted to the bent portion of the battery frame. This allows the bent portion to serve as a base point for folding in response to the collision load, and the first joint flange can be more reliably deformed (bent) downward together with the battery frame.

[0012] (3) In the above aspect, the second joint flange may have a second joint portion (e.g., second joint portion 75a in the embodiment) that is joined to the battery pack, and the first joint portion may be positioned closer to the battery than the second joint portion.

[0013] With this configuration, the second joint portion of the second joint flange is joined to the battery pack, and the first joint portion is positioned closer to the battery (i.e., closer to the inside of the vehicle width) than the second joint portion. The second joint flange is positioned above the battery pack, and the first joint flange is positioned below the battery pack. This prevents the first joint flange from directly contacting the battery.

[0014] Specifically, for example, when an excessive collision load is applied to the first joint flange of the side frame due to a side collision, the first joint flange may deform upward. Even in this case, the edge (i.e., the first joint) is in contact with the battery frame. Therefore, the battery frame can prevent the first joint flange from deforming significantly upward. This allows the battery frame to protect the battery.

[0015] (4) In the above aspect, the battery frame may form a hollow cross section together with the battery pack at the convex portion, and the battery may be fastened to an inner end of the convex portion of the battery frame in the vehicle width direction.

[0016] With this configuration, the battery is fastened to the inside of the convex portion in the vehicle width direction. Therefore, in the event of a side collision, the portion of the convex portion from the center of the vehicle width direction to the outside of the vehicle width direction can be bent in a mountain fold. As a result, when the first joining flange deforms downward and the edge portion is bent in a valley fold, the convex portion can be bent in a mountain fold in cooperation with the valley fold of the edge. In other words, downward deformation by the outer portion of the battery of the battery pack (i.e., the collision absorption portion) can be suitably induced. This increases the efficiency with which the collision energy is absorbed by the collision absorption portion, and suitably prevents the collision absorption portion from coming into contact with the battery.

[0017] (5) In the above aspect, the protrusion of the battery frame may have a plurality of recesses (for example, recesses 81 in the embodiment) joined to the battery pack along the vehicle longitudinal direction.

[0018] With this configuration, the protrusion is provided with a recess that joins with the battery pack, and the recess can be positioned toward the center of the protrusion in the width direction. This allows the rigidity of the center of the protrusion in the width direction to be higher than that of the recess, creating a difference in strength compared to the outer portion in the width direction (i.e., the portion on the bent portion side). This makes it possible to more reliably use the bent portion as a folding base point, and more reliably deform (bend) the first joining flange downward.

[0019] (6) In the above aspect, the battery frame may have a plurality of outer surface portions of the convex portion on the outer side in the vehicle width direction (e.g., outer surface portion 73 in the embodiment) and a plurality of ridge lines (e.g., ridge line 85 in the embodiment) extending in the vehicle width direction continuous with the second joining flange, spaced apart in the fore-and-aft direction of the vehicle.

[0020] With this configuration, the battery frame has a ridge line formed continuously on the outer surface of the convex portion and the second connecting flange, with multiple ridge lines spaced apart in the vehicle longitudinal direction. This increases the rigidity of the second connecting flange against the impact load input in a side impact, thereby increasing the amount of impact energy absorbed by the impact absorption section including the second connecting flange.

[0021] (7) In the above aspect, the side frame may include a horizontal portion (e.g., horizontal portion 53 in the embodiment) fixed to the lower portion of the side sill (e.g., lower portion 12a of the side sill in the embodiment) and a vertical portion (e.g., vertical portion 54 in the embodiment) connecting the horizontal portion and the first joining flange, the horizontal portion and the vertical portion being formed into a hollow portion (e.g., hollow portion 52 in the embodiment) having an approximately L-shaped cross section that includes a plurality of hollow cells (e.g., hollow cell 61 in the embodiment), and the second joining flange of the battery frame may be positioned at a distance inward in the vehicle width direction from the vertical portion.

[0022] With this configuration, the horizontal and vertical portions of the side frame form a hollow portion with a substantially L-shaped cross section, and the hollow portion contains multiple hollow cells. The hollow portion is formed to have high rigidity against a collision load input in a side collision. Therefore, by separating the second joining flange of the battery frame from the vertical portion (i.e., the hollow portion) toward the inside in the vehicle width direction, a gap can be created between the battery frame and the hollow portion. This ensures an appropriate deformation margin for the collision absorption portion against a collision load input in a side collision, further increasing the amount of collision energy absorption.

[0023] (8) In the above aspect, the lower surface of the horizontal portion (e.g., lower surface portion 66 in the embodiment) may be formed such that the thickness (e.g., thickness T1 in the embodiment) of the inner portion (e.g., inner portion 66a in the embodiment) formed on the vertical portion side is thinner than the outer portion (e.g., outer portion 66b in the embodiment) formed on the outer side in the vehicle width direction.

[0024] With this configuration, when a collision load is applied in a side collision, the collision load actively deforms the inner portion of the lower surface of the horizontal portion on the vertical portion side. This allows the boundary between the vertical portion and the first connecting flange to deform upward due to the collision load. This allows the side frame to deform favorably, further increasing the amount of collision energy absorbed.

[0025] (9) In the above aspect, the lower surface of the horizontal portion may be positioned lower than the lower surface of the battery pack (e.g., case bottom 41 in the embodiment), and the lower surface of the vertical portion (e.g., lower surface portion 67 in the embodiment) may be formed in an inclined shape that slopes upward from the lower surface of the horizontal portion toward the first connecting flange, and the lower surface of the vertical portion may connect the lower surface of the horizontal portion to the first connecting flange.

[0026] This configuration positions the lower surface of the horizontal portion below the lower surface of the battery pack, preventing the hollow portion of the side frame from collapsing toward the interior (i.e., toward the inside of the vehicle width direction) due to the impact load applied during a side collision. This allows the first joining flange of the side frame to be deformed downward more reliably.

[0027] (10) In the above aspect, the battery may be formed in a rectangular shape in a plan view and may be disposed inside the battery pack with its long side facing the front-rear direction of the vehicle.

[0028] With this configuration, the battery is placed inside the battery pack with its long side facing the vehicle's front-to-rear direction. This allows the battery's widthwise dimension to be kept smaller than, for example, when the same number of batteries of the same size are placed with their long sides facing the vehicle's width. In other words, the battery's widthwise dimension can be reduced without compromising the battery's capacity. This allows for a long deformation stroke of the impact absorbing section located between the battery and the hollow section of the side frame.Furthermore, by keeping the battery support member small in the vehicle width direction, the vehicle weight can be reduced, and by ensuring the battery capacity, the vehicle's cruising range can be ensured. [Effects of the Invention]

[0029] According to the present invention, when a collision load is input, collision energy can be efficiently absorbed while preventing damage to the onboard battery, thereby improving collision safety performance and contributing to the development of sustainable transportation systems. [Brief explanation of the drawings]

[0030] [Figure 1] 1 is a schematic diagram of a battery pack-equipped vehicle equipped with a vehicle underbody structure according to an embodiment of the present invention, viewed from the left side; [Figure 2] FIG. 2 is a cross-sectional view taken along line II-II in FIG. [Figure 3] 1 is a perspective view showing a state in which a case cover is disassembled from a battery pack according to an embodiment of the present invention. [Figure 4] FIG. 4 is a perspective view cut along line IV-IV in FIG. [Figure 5] 2 is an exploded perspective view of a battery case, a lower cross member, a battery frame, and a side frame according to an embodiment of the present invention. FIG. [Figure 6] 6 is a cross-sectional view taken along the arrow VI in FIG. 4. [Figure 7] 1 is a perspective view including a partial cross section illustrating a state in which a collision load is input to a vehicle underbody structure in an embodiment of the present invention due to a side collision. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0031] A battery pack-equipped vehicle having an underbody structure according to one embodiment of the present invention will be described below with reference to the drawings. In the drawings, arrow FR indicates the front of the vehicle, arrow UP indicates the upper side of the vehicle, and arrow LH indicates the left side of the vehicle. The battery pack-equipped vehicle has a generally symmetrical configuration. Therefore, the following description will be given with the same reference numerals assigned to left and right components.

[0032] Fig. 1 is a schematic diagram of a battery pack-equipped vehicle Ve having a vehicle body underbody structure as seen from the left side, and Fig. 2 is a cross-sectional view taken along line II-II in Fig. 1. 1 and 2, the battery pack-equipped vehicle Ve includes a vehicle body 10, a battery pack 20 disposed in the lower center of the vehicle body 10, and a left side frame 50 and a right side frame 50 that connect the battery pack 20 to the vehicle body 10. Hereinafter, the battery pack-equipped vehicle Ve may be abbreviated as "vehicle Ve."

[0033] <Body> The vehicle body 10 includes a left side sill (side sill) 12, a right side sill (side sill) (not shown), and a floor portion 13. The left side sill 12 and the right side sill (not shown) are generally symmetrical in configuration. Therefore, in the following description, the left side sill 12 will be abbreviated as "side sill 12," and a description of the right side sill (not shown) will be omitted.

[0034] The side sill 12 is formed by overlapping the open sides of an inner panel 15 and an outer panel 16, which are C-shaped when viewed from the front-rear direction of the vehicle, with the open sides overlapping. The inner panel 15 is disposed on the inner side in the vehicle width direction, and the outer panel 16 is disposed on the left outer side in the vehicle width direction. The side sill 12 is a highly rigid member that forms part of the skeleton of the vehicle body 10. The side sill 12 is provided on the left outer side in the vehicle width direction (outside in the vehicle width direction) of the battery pack 20. The side sill 12 extends in the front-rear direction of the vehicle along the left outer side in the vehicle width direction of the floor portion 13. The floor portion 13 has a left outer portion 13a provided on the side sill 12. The floor portion 13 forms the floor portion of the vehicle body 10. A battery pack 20 is fixed to the side sill 12, the floor portion 13, etc. The side sill 12, the floor portion 13, the battery pack 20, etc. constitute a vehicle lower body structure.

[0035] <Battery pack> FIG. 3 is a perspective view showing the battery pack 20 with the case cover 32 disassembled therefrom. 2 and 3, the battery pack 20 is disposed below the floor portion 13 (i.e., under the floor of the vehicle Ve shown in FIG. 1). The battery pack 20 includes a battery case 22 and a battery module 24.

[0036] <Battery case> The battery case 22 includes a case body 31 and a box-shaped case cover 32 that is open on the side of the case body 31 and fits over the case body 31. The case body 31 includes a case section 34 provided below the battery modules 24, a lower cross member 35 provided in the case section 34, an upper cross member 36 disposed above the lower cross member 35, a plurality of connecting sections 37 that connect the upper cross members 36 disposed above the lower cross member 35, and a plurality of battery frames 38 that support the battery modules 24.

[0037] The case section 34 has a case bottom 41 and a case peripheral wall 42. The case bottom 41 is disposed below the battery module 24. The case bottom 41 is formed in a generally rectangular shape in a plan view. The case bottom 41 forms the bottom of the battery case 22. The case peripheral wall 42 is formed along the outer periphery of the case bottom 41. A flange portion 42a is integrally formed with the case peripheral wall 42 so as to protrude outward. The flange portion 32a of the case cover 32 is disposed so as to overlap this flange portion 42a. The lower cross member 35, the upper cross member 36, the plurality of connecting portions 37, and the plurality of battery frames 38 are provided inside the battery pack 20.

[0038] Fig. 4 is a perspective view cut along line IV-IV in Fig. 1. Fig. 5 is a perspective view in which the lower cross member 35, the battery frame 38, and the side frame 50 are disassembled from the battery case 22. As shown in Figures 4 and 5, the lower cross member 35 is provided in the case portion 34 (particularly, the case bottom portion 41). The lower cross member 35 is disposed in the center of the case portion 34 in the vehicle longitudinal direction and extends in the vehicle width direction. For example, the right end portion 35a of the lower cross member 35 is in contact with the right wall of the case peripheral wall 42. For example, the left end portion 35b (see Figure 3) of the lower cross member 35 is in contact with the left wall of the case peripheral wall 42. A plurality of battery frames 38 are provided in the case bottom portion 41 at the front and rear of the lower cross member 35.

[0039] The upper cross member 36 is disposed above the lower cross member 35 and is provided along the lower cross member 35. A plurality of connecting portions 37 are interposed between the upper cross member 36 and the lower cross member 35 at intervals in the vehicle width direction. The multiple connecting portions 37 are members that connect the lower cross member 35 and the upper cross member 36 in the up-down direction. Of the multiple connecting portions 37, only the connecting portion 37 on the left outer side in the vehicle width direction is shown in the figure.

[0040] The upper cross member 36, the multiple connecting portions 37, and the lower cross member 35 are connected by mounting bolts (not shown) that pass through the upper cross member 36, the multiple connecting portions 37, and the lower cross member 35. In this state, the upper cross member 36 secures the battery module 24 from above. The lower cross member 35, the multiple connecting portions 37, and the upper cross member 36 are connected in the vertical direction to the floor portion 13 (see FIG. 2) and a floor frame (not shown) with fastening members 45 (see FIG. 6) such as bolts and nuts. The floor frame (not shown) is a highly rigid member joined to the upper surface of the floor portion 13. The battery frame 38 will be described later.

[0041] <Side frame> As shown in Figures 2 and 3, the left side frame 50 connects the battery pack 20 to the left side sill 12, allowing the battery pack 20 to be positioned at a distance from the side sill 12 toward the inside in the vehicle width direction. The right side frame 50 connects the battery pack 20 to the right side sill (not shown), allowing the battery pack 20 to be positioned at a distance from the side sill 12 toward the inside in the vehicle width direction. The left side frame 50 and the right side frame 50 are configured roughly symmetrically. For this reason, hereinafter, the left side frame 50 will be referred to simply as "side frame 50," and a description of the right side frame 50 will be omitted.

[0042] 2, 4, and 5, the side frame 50 is disposed on the left side of the vehicle width direction with a gap therebetween from the left side edge 24a of the battery module 24 (the left outer side edge of a battery 27, which will be described later). The side frame 50 extends in the front-to-rear direction of the vehicle along the side sill 12 and the battery pack 20. The side frame 50 has a horizontal portion 53 fixed to the lower portion 12a of the side sill 12 (specifically, the lower portion of the inner panel 15), a vertical portion 54 fixed to the battery pack 20, and a first joining flange 55 joined to the battery pack 20.

[0043] The horizontal portion 53 has an outer portion fixed to the lower portion 12a of the inner panel 15 with fastening members 58 such as bolts and nuts. The vertical portion 54 is integrally formed on the inner portion of the horizontal portion 53 and stands upward. The horizontal portion 53 and the vertical portion 54 form a hollow portion 52 with a substantially L-shaped cross section that includes a plurality of hollow cells 61. For this reason, the hollow portion 52 is formed with high rigidity. The flange portion 42a of the case body 31 and the flange portion 32a of the case cover 32 are fixed to the top portion 62 of the vertical portion 54 with fastening members 64 such as bolts and nuts. The vertical portion 54 is interposed between the horizontal portion 53 and the first joining flange 55 in the vehicle width direction, and connects the horizontal portion 53 and the first joining flange 55.

[0044] The first joining flange 55 is integrally formed with the inner portion 67a at the lower surface portion (lower face) 67 of the vertical portion 54. The first joining flange 55 extends inward in the vehicle width direction from the inner portion 67a. The first joining flange 55 is joined to the case bottom 41 of the battery pack 20 (i.e., the lower face of the battery pack 20) ​​from below. Specifically, the first joint flange 55 has an edge 55a on the battery module 24 side (i.e., on the inner side in the vehicle width direction). The edge 55a is provided with a first joint 55b that is joined to the lower surface 41a of the case bottom 41. The first joint 55b is joined to the lower surface 41a of the case bottom 41 from below by MIG welding, laser welding, or the like. That is, the first joint flange 55 is disposed below the case bottom 41. Therefore, the battery pack 20 and the side sill 12 are connected by the side frame 50.

[0045] FIG. 6 is a cross-sectional view taken along the direction of an arrow VI in FIG. 2 and 6, the horizontal portion 53 has a lower surface portion (lower surface) 66 formed flat on the lower side of the hollow cell 61. The lower surface portion 66 has an inner portion 66a formed on the vertical portion 54 side and an outer portion 66b formed on the outer side in the vehicle width direction. The inner portion 66a is formed so that the thickness T1 is thinner than the thickness T2 of the outer portion 66b. Furthermore, the horizontal portion 53 has a lower surface 66 disposed below the case bottom 41. The vertical portion 54 has a lower surface 67 formed to be inclined upward from the lower surface 66 of the horizontal portion 53 toward the first joining flange 55. Therefore, the lower surface 66 of the horizontal portion 53 and the first joining flange 55 are connected by the inclined lower surface 67. The reasons why the thickness T1 of the inner portion 66a is made thinner than the thickness T2 of the outer portion 66b and why the lower surface 66 of the horizontal portion 53 is disposed below the case bottom 41 will be explained in detail later.

[0046] <Battery module> 3 and 4, the battery module 24 includes a plurality of front batteries (batteries) 27 arranged in front of the vehicle body of a lower cross member 35 extending in the vehicle width direction, and a plurality of rear batteries (batteries) 27 arranged in rear of the vehicle body of the lower cross member 35. In other words, the lower cross member 35 extending in the vehicle width direction is arranged between the front batteries 27 and the rear batteries 27.

[0047] The front battery 27 and the rear battery 27 are rectangular in plan view and are arranged inside the battery pack 20 with their long sides facing the front-to-rear direction of the vehicle. A plurality of the front batteries 27 and the rear batteries 27 are arranged in a row in the vehicle width direction. The plurality of front batteries 27 and the plurality of rear batteries 27 form, for example, a drive battery module 24. A lower cross member 35, a plurality of connecting portions 37, and an upper cross member 36 are arranged between the front battery 27 and the rear battery 27. Hereinafter, the front battery 27 and the rear battery 27 may be abbreviated as "battery 27."

[0048] <Battery frame> The battery frame 38 of the case body 31 and the first joining flange 55 of the side frame 50 will be described below with reference to FIGS. 4 to 6, the battery frame 38 connects the batteries 27 of the battery pack 20 and extends in the front-to-rear direction of the vehicle. The battery frame 38 has a protrusion 71 that protrudes upward from the case bottom 41, a second joint flange 75 that protrudes from the outer lower end of the protrusion 71, a bent portion 76 formed at the inner end of the second joint flange 75 in the vehicle width direction, and a third joint flange 77 that protrudes from the inner lower end of the protrusion 71.

[0049] The protrusion 71 has an apex 72 disposed above and spaced apart from the case bottom 41, an outer surface portion 73 bent downward from the outer edge of the apex 72, and an inner surface portion 74 bent downward from the inner edge of the apex 72. The outer surface portion 73 is a portion that forms the side surface of the protrusion 71 on the outer side in the vehicle width direction. The inner surface portion 74 is a portion that forms the side surface of the protrusion 71 on the inner side in the vehicle width direction. The apex 72, the outer surface portion 73, and the inner surface portion 74 form a U-shaped cross section of the protrusion 71.

[0050] The second joining flange 75 extends from the lower edge of the outer side surface portion 73 outward in the vehicle width direction along the upper surface 41b of the case bottom 41. The second joining flange 75 is joined to the upper surface 41b of the case bottom 41. Therefore, the second joining flange 75 is disposed above the case bottom 41. The second joining flange 75 is disposed in a wrap-like manner so as to overlap the upper side of the first joining flange 55 of the side frame 50 with the case bottom 41 interposed therebetween in the up-down direction.

[0051] The first portion where the first joining flange 55, the case bottom 41, and the second joining flange 75 overlap is formed to allow deformation due to a collision load. The second portion where the first joining flange 55 and the case bottom 41 overlap is also formed to allow deformation due to a collision load. Hereinafter, the portion including the first portion and the second portion may be referred to as the "collision absorbing portion 78." The second joining flange 75 is disposed at a position spaced a distance L1 inward in the vehicle width direction from the vertical portion 54 (i.e., the hollow portion 52) of the side frame 50. A specific example of joining the second joining flange 75 to the upper surface 41b of the case bottom 41 will be described in detail later.

[0052] The bent portion 76 is located at the intersection of the second joint flange 75 and the outer surface portion 73 of the protruding portion 71. In other words, the protruding portion 71 protrudes upward from the bent portion 76. An edge portion 55a of the first joint flange 55 is disposed below the bent portion 76. The edge portion 55a of the first joint flange 55 on the battery module 24 (battery 27) side extends to the bent portion 76 side. The first joint portion 55b of the edge portion 55a is joined to the lower surface 41a of the case bottom 41 from below.

[0053] The third joining flange 77 extends inward in the vehicle width direction from the lower side of the inner side surface portion 74 along the upper surface 41b of the case bottom 41. The third joining flange 77 is joined to the upper surface 41b of the case bottom 41. The battery frame 38 is formed with a hat-shaped cross section by the protrusion 71, the second joining flange 75, and the third joining flange 77.

[0054] The battery frame 38 is fixed to the upper surface 41b of the case bottom 41 by joining the second joining flange 75 and the third joining flange 77 to the upper surface 41b of the case bottom 41. In this state, the protrusion 71 forms a hollow cross section (hollow closed cross section) together with the case bottom 41. Therefore, the rigidity of the protrusion 71 is increased. The protrusion 71 has a plurality of recesses 81 along the longitudinal direction of the vehicle. The recesses 81 are formed so as to be recessed downward from the apex 72 of the protrusion 71. The recesses 81 are arranged at intervals in the longitudinal direction of the vehicle. The apex 72 is located at the center of the protrusion 71 in the vehicle width direction. Therefore, the rigidity of the central portion of the protrusion 71 in the width direction is increased. The recesses 81 are joined from above to a raised portion 83 of the case bottom 41 by spot welding or the like.

[0055] Here, the hollow portion 52 of the side frame 50 is formed to have high rigidity. That is, the protrusion 71 and the hollow portion 52 are formed to have higher rigidity than the impact absorbing portion 78 between the protrusion 71 and the hollow portion 52 in the vehicle width direction. The impact absorbing portion 78 is a portion that allows deformation due to a collision load input, for example, due to a side collision. Therefore, when a collision load is input to the side frame 50, the impact absorbing portion 78 interposed between the highly rigid hollow portion 52 and the highly rigid protrusion 71 can be suitably deformed by the collision load.

[0056] The battery module 24 (battery 27) is fastened to an inner end portion 72a in the vehicle width direction (i.e., an inner end portion 72a in the vehicle width direction of the protrusion 71) at the top 72 of the protrusion 71. That is, the battery module 24 is disposed inside the battery pack 20 in a state where it is supported by the inner end portion 72a in the vehicle width direction of the protrusion 71.

[0057] The battery frame 38 has a plurality of ridge lines 85 spaced apart in the vehicle longitudinal direction, extending in the vehicle width direction and continuing from the outer side surface portion 73 and the second joining flange 75. The plurality of ridge lines 85 are formed in a bead-like shape that protrudes (projects) from the outer side surface portion 73 and the second joining flange 75 to the opposite side of the case bottom 41. The second joint flange 75 has second joint portions 75a between adjacent ridge lines 85 in the vehicle longitudinal direction. The multiple second joint portions 75a are arranged in contact with the upper surface 41b of the case bottom 41. The multiple second joint portions 75a are joined to the upper surface 41b of the case bottom 41 by spot welding or the like. Here, the first joint portion 55b of the first joint flange 55 is arranged closer to the battery module 24 (battery 27) than the second joint portion 75a of the second joint flange 75 by a distance L2.

[0058] The operation and effects of the vehicle underbody structure according to the embodiment described above will now be described. FIG. 7 is a perspective view including a partial cross section illustrating a state in which a collision load F is input to the vehicle body underbody structure due to a side collision. As shown in Figures 4 and 7, when a collision load F is input to the side sill 12 (see Figure 2) due to a side collision such as a side collision with a pole, the input collision load F is transmitted to the side frame 50. The collision load F transmitted to the side frame 50 is transmitted to the first joining flange 55 via the hollow portion 52. Hereinafter, a side collision such as a side collision with a pole may be abbreviated as simply "side collision."

[0059] When the collision load F is transmitted to the first joining flange 55, the collision load F is transmitted to the collision absorbing portion 78. The collision absorbing portion 78 is a portion that allows deformation due to the collision load F. Here, the second joining flange 75 of the battery frame 38 is disposed so as to overlap the upper side of the first joining flange 55 in the vertical direction. Therefore, when the collision load F is input to the first joining flange 55, the first joining flange 55 can be pressed down from above by the second joining flange 75. This allows the collision absorbing portion 78 to deform downward.

[0060] A space 90 can be secured below the collision absorbing portion 78 to accommodate deformation of the collision absorbing portion 78. This prevents the collision absorbing portion 78 from remaining uncrushed, thereby improving the efficiency of absorbing collision energy. Furthermore, by deforming the collision absorbing portion 78 downward, it is possible to prevent the collision absorbing portion 78 from coming into contact with the battery 27 disposed inside the battery pack 20 (i.e., above the case bottom 41). As a result, when a collision load F is input, the collision energy can be efficiently absorbed while preventing damage to the mounted battery 27. Therefore, this vehicle underbody structure can improve collision safety performance and contribute to the development of a sustainable transportation system.

[0061] 6 and 7, the edge 55a of the first joint flange 55 extends to the bent portion 76 side of the battery frame 38 (i.e., toward the inside of the vehicle width). The first joint portion 55b (see also FIG. 4) of the edge 55a is joined to the underside 41a of the case bottom 41. This allows the collision load F to be transmitted to the case bottom 41 and the bent portion 76 of the battery frame 38. This allows the bent portion 76 to serve as a base point for breaking in response to the collision load F. The first joining flange 55 can be more reliably deformed (bent) downward together with the case bottom 41 and the battery frame 38 (particularly the second joining flange 75).

[0062] The second joint portion 75a (see also FIG. 4) of the second joint flange 75 is joined to the upper surface 41b of the case bottom 41. The first joint portion 55b is positioned closer to the battery 27 (i.e., on the inner side of the vehicle width) than the second joint portion 75a. The second joint flange 75 is positioned above the case bottom 41, and the first joint flange 55 is positioned below the case bottom 41. This prevents the first joint flange 55 and the case bottom 41 from coming into direct contact with the battery 27.

[0063] Specifically, for example, when an excessive collision load is input to the first joint flange 55 of the side frame 50 due to a side collision, the first joint flange 55 may be deformed upward. Even in this case, the edge 55a (i.e., the first joint portion 55b) contacts the battery frame 38 via the case bottom 41. Therefore, the battery frame 38 can prevent the first joint flange 55 from deforming upward significantly. This allows the battery frame 38 to protect the battery 27.

[0064] In addition, the battery 27 is fastened to the inside of the protrusion 71 in the vehicle width direction. Therefore, in the event of a side collision, the portion 79 of the protrusion 71 on the outer side in the vehicle width direction from the center side in the vehicle width direction can be bent in a mountain fold. As a result, when the first joining flange 55 deforms downward and the edge portion 55a is bent in a valley fold, the protrusion 71 can be bent in a mountain fold in cooperation with the valley fold of the edge portion 55a. In other words, downward deformation by the portion of the case bottom 41 on the outer side of the battery 27 (i.e., the collision absorbing portion 78) can be suitably induced. This increases the efficiency with which the collision energy is absorbed by the collision absorbing portion 78, and suitably prevents the collision absorbing portion 78 from coming into contact with the battery 27.

[0065] By providing a recess 81 at the top 72 of the protrusion 71 that joins with the raised portion 83 of the case bottom 41, it is possible to position the recess 81 at the widthwise center of the protrusion 71. This makes it possible to increase the rigidity of the widthwise center of the protrusion 71 by increasing the rigidity of the recess 81, thereby creating a difference in strength compared to the portion on the widthwise outer side (i.e., the portion on the bent portion 76 side). This makes it possible to more reliably use the bent portion 76 as the folding base point, and more reliably deform (bend) the first joining flange 55 downward.

[0066] As shown in Figures 4 and 7, the battery frame 38 has ridge lines 85 formed continuously on the outer surface portion 73 of the protrusion 71 and the second connecting flange 75. A plurality of ridge lines 85 are arranged at intervals in the longitudinal direction of the vehicle. Therefore, the plurality of ridge lines 85 can increase the rigidity of the second connecting flange 75 against the collision load F input in a side collision. This increases the amount of collision energy absorbed by the collision absorption section 78 equipped with the second connecting flange 75.

[0067] As shown in Figures 6 and 7, the horizontal portion 53 and the vertical portion 54 of the side frame 50 are formed into a hollow portion 52 with a substantially L-shaped cross section. The hollow portion 52 contains a plurality of hollow cells 61. The hollow portion 52 is formed to have high rigidity against a collision load F input during a side collision. Therefore, by separating the second joining flange 75 of the battery frame 38 from the vertical portion 54 (i.e., the hollow portion 52) by a distance L1 toward the inside in the vehicle width direction, the battery frame 38 and the hollow portion 52 can be spaced apart. This ensures an appropriate deformation margin for the collision absorption portion 78 against the collision load F input during a side collision, further increasing the amount of collision energy absorption.

[0068] Furthermore, the thickness T1 of the inner portion 66a is formed thinner than the thickness T2 of the outer portion 66b. Therefore, when a collision load F is applied due to a side collision, the collision load F can actively deform the inner portion 66a on the vertical portion 54 side of the undersurface 66 of the horizontal portion 53. Therefore, the collision load F can deform the boundary portion 56 between the vertical portion 54 and the first joining flange 55 upward as shown by arrow A. The boundary portion 56 is a portion that roughly corresponds to the inner portion 67a of the undersurface portion 67 of the vertical portion 54. In this way, by deforming the boundary portion 56 upward as indicated by the arrow A due to the collision load F, the side frame 50 can be deformed appropriately, and the amount of collision energy absorbed can be further increased.

[0069] In addition, the lower surface portion 66 of the horizontal portion 53 is positioned lower than the case bottom portion 41. This prevents the hollow portion 52 of the side frame 50 from collapsing toward the interior (i.e., toward the inside in the vehicle width direction) due to the collision load F input during a side collision. This allows the first joining flange 55 of the side frame 50 to be deformed downward more reliably.

[0070] 3, 6, and 7, the battery 27 is disposed inside the battery pack 20 with its long side facing the vehicle longitudinal direction. Therefore, the vehicle width dimension of the battery 27 can be reduced compared to, for example, a case in which the same number of batteries of the same size are disposed with their long sides facing the vehicle width direction. In other words, the vehicle width dimension of the battery 27 can be reduced without compromising the battery capacity of the battery 27. This ensures a long deformation stroke of the impact absorbing portion 78 located between the battery 27 and the hollow portion 52 of the side frame 50. Furthermore, by keeping the support member for the battery 27 small in the vehicle width direction, the weight of the vehicle Ve (see FIG. 1) can be reduced, and by ensuring the battery capacity of the battery 27, a sufficient cruising range of the vehicle Ve can be ensured.

[0071] The technical scope of the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention.

[0072] In addition, within the scope of the spirit of the present invention, the components in the above-described embodiments may be replaced with well-known components as appropriate, and the above-described modifications may be combined as appropriate. [Explanation of symbols]

[0073] Ve…Vehicle equipped with a battery pack (vehicle) 10...Body 12...Side sill 12a…Lower side sill 13...Floor section 20...Battery pack 27...Battery 38...Battery frame 41...Case bottom (bottom of battery pack) 50...Side frame 52...Hollow part 53…Horizontal part 54…Vertical part 55...First connecting flange 55a...Edge 55b...1st joint 61...Hollow cell 66...Underside of horizontal part (underside of horizontal part) 66a…Inner part 66b…Outer part 67...Underside of vertical part (underside of vertical part) 71...Convex part 73…Outer surface part 75...Second connecting flange 75a…Second joint part 76...Bend 81...recess 85...Ridge T1: Thickness of inner part T2: Thickness of outer part

Claims

1. a side frame that connects a battery pack disposed below the floor portion to the side sill; a battery frame supporting a battery inside the battery pack, a first joining flange of the side frame joined to the battery pack is disposed so as to overlap a second joining flange of the battery frame joined to the battery pack in the up-down direction; The battery frame has a bent portion formed at the inner end of the second joining flange in the vehicle width direction, and is provided with a convex portion protruding upward from the bent portion.

2. The first joining flange has an edge portion on the battery side extending to the bent portion side, The vehicle underbody structure according to claim 1 , wherein the edge portion includes a first joining portion joined to the battery pack.

3. the second joining flange includes a second joining portion joined to the battery pack, The vehicle underbody structure according to claim 2, wherein the first joint portion is disposed closer to the battery than the second joint portion.

4. the battery frame forms a hollow cross section together with the battery pack at the protrusion, 3. The vehicle underbody structure according to claim 2, wherein the battery is fastened to an inner end portion of the protrusion of the battery frame in the vehicle width direction.

5. 5. The vehicle underbody structure according to claim 4, wherein the protruding portion of the battery frame has a plurality of recesses along the vehicle longitudinal direction that are joined to the battery pack.

6. The battery frame includes a plurality of ridge lines extending in the vehicle width direction and continuing from the outer surface portion of the convex portion on the outer side in the vehicle width direction and the second joining flange, the ridge lines being spaced apart in the vehicle front-rear direction, The vehicle underbody structure according to claim 2 , wherein the ridge line is formed in a bead shape protruding from the outer side surface portion and the second joining flange.

7. The side frame is a horizontal portion fixed to a lower portion of the side sill; and a vertical portion connecting the horizontal portion and the first joining flange, the horizontal portion and the vertical portion are formed in a hollow portion having a substantially L-shaped cross section including a plurality of hollow cells, The vehicle underbody structure according to claim 1, wherein the second joining flange of the battery frame is disposed at a position spaced apart from the vertical portion toward the inside in the vehicle width direction.

8. 8. The vehicle underbody structure according to claim 7, wherein the thickness of the inner portion of the lower surface of the horizontal portion formed on the vertical portion side is thinner than the thickness of the outer portion formed on the outer side in the vehicle width direction.

9. a lower surface of the horizontal portion is disposed below a lower surface of the battery pack, The lower surface of the vertical portion is formed in an inclined shape that slopes upward from the lower surface of the horizontal portion toward the first joining flange, 8. The vehicle underbody structure according to claim 7, wherein a lower surface of the vertical portion connects a lower surface of the horizontal portion and the first joining flange.

10. 2. The vehicle underbody structure according to claim 1, wherein the battery is formed in a rectangular shape in a plan view and is disposed inside the battery pack with a long side facing in the longitudinal direction of the vehicle.

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