Vehicle lower part structure

Abstract

To provide a vehicle lower part structure that can provide enhanced load absorption performance by ensuring a sufficient amount of compressive deformation of vehicle body components at the time of a vehicle side collision.SOLUTION: In a vehicle lower part structure includes: side frames 11 extending along a vehicle body front-rear direction on both sides in a vehicle width direction; a battery pack 2 arranged between the side frames 11; and a battery fastening member 3 having a boss portion 34 that is fastened to the side frames 11 and connecting the side frames 11 to the battery pack 2. The battery fastening member 3 is provided with a weak portion 35 at a position on an inner side in the vehicle width direction of the position of the boss portion 34 fastened to the side frame 11. Thus, at the time of a vehicle side collision, deformation of the weak portion 35 causes the part of the battery fastening member 3 on an outer side in the vehicle width direction of the weak portion 35 and the side frame 11 to move inward in the vehicle width direction, thereby ensuring a sufficient amount of compressive deformation in the direction along the vehicle width direction.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a vehicle underbody structure, and more particularly to an improvement for enhancing load absorption performance in a vehicle side collision. [Background technology]

[0002] Patent Document 1 discloses a conventional vehicle underbody structure for absorbing a side impact load (energy) during a vehicle side impact. The vehicle underbody structure disclosed in Patent Document 1 includes a battery pack disposed below a floor panel between a pair of left and right side sills (framework members) extending in the longitudinal direction of the vehicle body. A recess is formed in the lower part of the side sill, and a hollow reinforcing flange (reinforcing member) is disposed in the recess. The upper surface of the reinforcing flange is fastened to the upper surface of the recess with a bolt, and the inner surface of the reinforcing flange in the vehicle width direction is welded to the battery pack case, thereby connecting the side sill and the battery pack via the reinforcing flange. A deformable portion is provided by bending the lower surface of the reinforcing flange downward, and when a side impact load is input, the deformable portion deforms downward to absorb the side impact load. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-196952 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the vehicle undercarriage structure disclosed in Patent Document 1, the upper surface of the reinforcing flange is bolted to a recess in the side sill, making the upper surface less likely to deform during a side collision. On the other hand, the lower surface of the reinforcing flange is made easily deformable, making the lower surface more likely to deform during a side collision. Therefore, when a side collision load is applied, the reinforcing flange may rotate downward about an axis extending in the fore-and-aft direction of the vehicle. If the reinforcing flange rotates downward, the side sill also rotates downward. Even if an attempt is made to absorb the load by compressively deforming the side sill (deforming in the vehicle width direction), the amount of compressive deformation is insufficient, limiting the improvement of load absorption performance.

[0005] Furthermore, even when the configuration disclosed in Patent Document 1 is applied to a vehicle in which an energy absorbing member is arranged on the vehicle widthwise outer side of a frame member (such as a side frame), the energy absorbing member also rotates as the frame member rotates, making it impossible to ensure a sufficient amount of compressive deformation of the energy absorbing member, and even in this case, there is a limit to how much load absorption performance can be improved.

[0006] The present invention has been made in consideration of the above points, and its object is to provide a vehicle undercarriage structure that can improve load absorption performance by sufficiently ensuring the amount of compressive deformation of vehicle body components (in the above-mentioned examples, frame members or energy absorbing members) during a vehicle side collision. [Means for solving the problem]

[0007] The solution of the present invention for achieving the above object is based on a vehicle understructure including skeletal members extending along the fore-and-aft direction of the vehicle body on both sides in the vehicle width direction, a battery disposed between the skeletal members, and a battery fastening member having a fastening portion fastened to the skeletal members and connecting the skeletal members to the battery. The vehicle understructure is characterized in that the battery fastening member has a weak portion provided at a position more inward in the vehicle width direction than the fastening portion fastened to the skeletal members, and in the event of a vehicle side collision, deformation of the weak portion causes the portion of the battery fastening member more outward in the vehicle width direction than the weak portion and the skeletal member to move inward in the vehicle width direction.

[0008] Due to this feature, when a side impact load is input to the battery fastening member during a vehicle side impact, the weak portion provided in the battery fastening member deforms due to the side impact load, causing the portion of the battery fastening member that is outboard of the weak portion in the vehicle width direction and the skeletal member to move inward in the vehicle width direction. In other words, if the portion of the battery fastening member that is inboard in the vehicle width direction of the fastening portion with the skeletal member is less likely to deform, there is a risk that the battery fastening member and the skeletal member will rotate around an axis extending in the fore-and-aft direction of the vehicle body. However, in this solution, the weak portion is provided in a position inboard in the vehicle width direction of the fastening portion with the skeletal member, and deformation of this weak portion causes the battery fastening member and the skeletal member to move inward in the vehicle width direction while being prevented from rotating around an axis extending in the fore-and-aft direction of the vehicle body. This ensures a sufficient amount of compressive deformation in the vehicle width direction, thereby enabling high load absorption performance.

[0009] Another solution to achieve the above object of the present invention is a vehicle underbody structure including skeletal members extending along the front-rear direction of the vehicle body on both sides in the vehicle width direction, a battery disposed between the skeletal members, and a battery fastening member having a fastening portion fastened to the skeletal members and connecting the skeletal members to the battery. This vehicle underbody structure is characterized in that the battery fastening member has a vertical wall portion located between the battery and the skeletal members and extending in the up-down direction, and has a weakened portion in a region between the fastening portion and the vertical wall portion.

[0010] Even with this feature, when a side impact load is input to the battery fastening member, the weak portion deforms due to the side impact load, causing the portion of the battery fastening member that is outboard of the weak portion in the vehicle width direction and the skeletal member to move inward in the vehicle width direction. In other words, the skeletal member moves toward the vertical wall portion of the battery fastening member. When the skeletal member abuts against the vertical wall portion of the battery fastening member, a wide range of reaction force is ensured in the vertical direction of the vehicle body in response to the input of the side impact load. Due to this movement, the skeletal member fastened to the battery fastening member moves inward in the vehicle width direction while being restricted from rotating about an axis extending in the fore-and-aft direction of the vehicle body. This ensures a sufficient amount of compressive deformation in the vehicle width direction, thereby enabling high load absorption performance.

[0011] The weakened portion is located below the skeletal member.

[0012] With this configuration, the distance (distance in the vehicle width direction) between the skeletal member and the battery can be made shorter than in a configuration in which the fragile portion is located at a position more inward in the vehicle width direction than the skeletal member, and it is possible to prevent a situation in which the skeletal member is more likely to rotate around an axis extending in the fore-and-aft direction of the vehicle body during a side collision due to this long distance. In other words, by appropriately setting the location of the fragile portion, it is possible to ensure a sufficient amount of compressive deformation in the direction along the vehicle width direction, thereby contributing to the demonstration of high load absorption performance.

[0013] In addition, an energy absorbing member that can be compressed and deformed when subjected to a side impact load is arranged on the outer side of the skeletal member in the vehicle width direction, and the energy absorbing member is arranged in a position where, when viewed from the vehicle width direction, at least a portion of the energy absorbing member overlaps with each of the weak portions of the skeletal member and the battery fastening member.

[0014] According to this, when a side impact load is input to the energy absorbing member during a vehicle side impact, the side impact load is input to each of the weak portions of the skeletal member and the battery fastening member via the energy absorbing member. In other words, an equal side impact load is input to each of the weak portions of the skeletal member and the battery fastening member. This ensures that the portions of the battery fastening member that are outward in the vehicle width direction from the weak portion and the skeletal member move inward in the vehicle width direction due to deformation of the weak portion, and accordingly, the energy absorbing member can also move inward in the vehicle width direction. As a result, the energy absorbing member moves inward in the vehicle width direction while rotation about an axis extending in the fore-and-aft direction of the vehicle body is suppressed, so that a sufficient amount of compressive deformation in the vehicle width direction is ensured, allowing high load absorption performance to be exhibited.

[0015] The specific configuration of the weakened portion is a bent portion that is convex in either the up or down direction.

[0016] This makes it possible to specifically specify the shape of the weak portion for deforming the weak portion so as to exhibit the high load absorption performance described above. [Effects of the Invention]

[0017] In the present invention, a weak portion is provided in the battery fastening member that connects the frame member and the battery, and in the event of a vehicle side collision, deformation of this weak portion causes the portion of the battery fastening member that is on the outer side of the weak portion in the vehicle width direction and the frame member to move inward in the vehicle width direction. This ensures a sufficient amount of compressive deformation in the direction along the vehicle width during a vehicle side collision, thereby enabling high load absorption performance to be achieved. [Brief explanation of the drawings]

[0018] [Figure 1] FIG. 1 is a plan view schematically showing a framework of a frame vehicle according to an embodiment. [Figure 2] FIG. 2 is a cross-sectional view taken along line II-II in FIG. [Figure 3] 2 and illustrates an example of a state at the time when a weak portion is deformed in a vehicle side collision. [Figure 4] 2 and illustrates an example of a state when an energy absorbing member is compressed and deformed during a vehicle side collision. [Figure 5] 10A to 10C are cross-sectional views showing a number of modified examples of the fragile portion. DETAILED DESCRIPTION OF THE INVENTION

[0019] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In this embodiment, the present invention will be described as being applied to an electric frame vehicle (a vehicle having a so-called ladder frame) equipped with a driving battery.

[0020] -Outline of the frame structure of a frame vehicle- FIG. 1 is a plan view that schematically shows the skeleton of a frame vehicle according to this embodiment. FIG. 1 shows a battery pack (battery) 2 mounted on a body frame 1 that constitutes the skeleton of the frame vehicle. While FIG. 1 shows a configuration in which one large battery pack 2 is mounted, a configuration in which multiple battery packs 2 are mounted may also be used. FIG. 2 is a cross-sectional view taken along line II-II in FIG. 1. In these figures, arrow Fw indicates the front direction of the vehicle body, arrow Up indicates the upward direction, and arrow Lf indicates the left direction in the vehicle width direction. Note that while FIG. 2 only shows a side frame (framework member) 11 and its surrounding area on the left side in the vehicle width direction, the side frame 11 and its surrounding area on the right side in the vehicle width direction also have a similar configuration (a configuration symmetrical to that in FIG. 2).

[0021] 1, the body frame 1 includes a pair of left and right side frames 11, 11 extending along the front-to-rear direction of the vehicle on both sides in the vehicle width direction. The side frames 11, 11 have a closed cross-sectional structure and include intermediate portions 11a, 11a, front kick portions 11b, 11b, front portions 11c, 11c, rear kick portions 11d, 11d, and rear portions 11e.

[0022] The middle portion 11a extends horizontally along the fore-and-aft direction of the vehicle body in a predetermined range between the positions of the front wheels (not shown) and the rear wheels (not shown). The front kick portion 11b continues from the front end of the middle portion 11a and curves upward as it approaches the front of the vehicle body. The front portion 11c continues from the front end of the front kick portion 11b and extends toward the front of the vehicle body. The rear kick portion 11d continues from the rear end of the middle portion 11a and curves upward as it approaches the rear of the vehicle body. The rear portion 11e continues from the rear end of the rear kick portion 11d and extends toward the rear of the vehicle body.

[0023] 2 (cross section at intermediate portion 11a), the side frame 11 is specifically configured by integrally joining an outer frame member 12, an inner frame member 13, and a reinforcing frame member 14. The outer frame member 12 and the inner frame member 13 each include vertical portions 12a, 13a extending vertically, upper plate portions 12b, 13b extending horizontally from the upper ends of the vertical portions 12a, 13a, and lower plate portions 12c, 13c extending horizontally from the lower ends of the vertical portions 12a, 13a, and the upper plate portions 12b, 13b and the lower plate portions 12c, 13c are butt-welded to each other to form a closed cross-sectional structure (note that FIG. 2 shows the cross section at a portion different from the butt-welded portion between the lower plate portions 12c, 13c). The reinforcing frame material 14 is disposed so as to extend horizontally inside the closed cross-sectional structure of the side frame 11, and the flange portions 14a, 14a are welded to the inner surfaces of the vertical portions 12a, 13a of the frame materials 12, 13, thereby increasing the rigidity of the entire side frame 11. The side frame 11 is not limited to the configuration described above.

[0024] As shown in FIG. 1, a plurality of cross members 15a to 15f extend between the side frames 11, 11 in the vehicle width direction.

[0025] Between the middle portions 11a, 11a of the side frames 11, 11, a battery pack 2 is disposed for storing electric power to be supplied to an electric motor (not shown) that serves as a driving force source for the vehicle.

[0026] FIG. 2 shows a portion of the battery pack 2 (a portion on the outer side in the vehicle width direction). As shown in FIG. 2, the battery pack 2 is configured such that a battery module 22 (shown by a two-dot chain line in FIG. 2) is housed in a battery case 21. The battery case 21 includes a case upper 23, a case lower 24, and a case inner 25. Flanges 23a, 24a provided on the outer edges of the case upper 23 and the case lower 24, respectively, are joined together to form a housing space for the battery module 22. The case inner 25 is welded to the case lower 24 at multiple locations and supports the battery module 22. The battery pack 2 also includes a base plate 26 that is fastened to a battery fastening member 3 (described later). The fastening structure between the battery fastening member 3 and the base plate 26 will be described later. The battery pack 2 is not limited to the configuration described above.

[0027] The battery pack 2 is supported on the side frame 11 by the battery fastening member 3. That is, the battery fastening member 3 is fastened to both the battery pack 2 and the side frame 11, thereby connecting the battery pack 2 and the side frame 11. The battery fastening member 3 will be described below.

[0028] The battery fastening member 3 is made of metal and includes a vertical wall portion 31 extending in the up-down direction and a horizontal portion 32 extending outward in the vehicle width direction, continuing from the lower end of the vertical wall portion 31. The battery fastening member 3 is disposed on the outer side in the vehicle width direction at the middle portions 11a, 11a of the side frames 11, 11.

[0029] The vertical wall portion 31 is located between the battery pack 2 and the side frame 11 and includes an outer plate portion 31a and an inner plate portion 31b, which are arranged perpendicular to the vehicle width direction and spaced a predetermined distance apart in the vehicle width direction. The outer plate portion 31a and the inner plate portion 31b are connected by multiple connecting plates 31c, 31c, ... extending horizontally. As a result, the vertical wall portion 31 is made of a member with a closed cross-section structure having multiple internal spaces, ensuring high rigidity while reducing weight. The inner plate portion 31b is superimposed on the outer surface of the vertical wall portion 24b of the case lower 24. The inner plate portion 31b of the battery fastening member 3 and the vertical wall portion 24b of the case lower 24 each have a bolt insertion hole (not shown in the figure). Nuts N1 are welded to the inner plate portion 31b of the battery fastening member 3 in correspondence with the bolt insertion hole provided in the inner plate portion 31b. With these bolt insertion holes aligned, bolts B1 are inserted into the respective bolt insertion holes and then screwed into nuts N1, thereby integrally fastening the case lower 24 and the vertical wall portion 31. Although not shown, the battery case 21 is provided with an opening or the like for inserting a tool for performing this bolt fastening work. The configuration for fastening the case lower 24 and the vertical wall portion 31 is not limited to this, and the outer surface of the vertical wall portion 24b of the case lower 24 and the upper surface of the vertical wall portion 31 may be connected via a bracket.

[0030] The horizontal portion 32 includes an upper plate portion 32a and a lower plate portion 32b that extend horizontally (in the vehicle width direction) and are spaced a predetermined distance apart in the vertical direction. The inner portion of the upper plate portion 32a in the vehicle width direction is continuous with the lower end of the outer plate portion 31a of the vertical wall portion 31. The inner portion of the lower plate portion 32b in the vehicle width direction is continuous with the lower end of the inner plate portion 31b of the vertical wall portion 31. The upper plate portion 32a and the lower plate portion 32b are connected by multiple connecting plate portions 32c, 32c that extend vertically. This structure allows the horizontal portion 32 to be made of a member with a closed cross-section structure that has multiple internal spaces, ensuring high rigidity while reducing weight. The lower plate portion 32b is located above the outer portion of the base plate 26 of the battery pack 2 in the vehicle width direction. The lower plate portion 32b and the base plate 26 each have a bolt insertion hole (not shown). Nuts N2 are welded to correspond to the bolt insertion holes provided in the lower plate portion 32b. Then, with these bolt insertion holes aligned, bolts B2 are inserted into each bolt insertion hole and the bolts B2 are screwed into the nuts N2, thereby integrally fastening the base plate 26 and the horizontal portion 32. Note that a spacer 33 is interposed between the lower plate portion 32b and the base plate 26 as needed. The fastening structure between the battery fastening member 3 and the battery case 21 is not limited to the configuration described above.

[0031] Furthermore, the central portion of the horizontal portion 32 in the vehicle width direction is integrally fastened to the lower portion of the side frame 11. This fastening structure will be described below.

[0032] The horizontal portion 32 is provided with a boss portion (fastening portion) 34 having a bolt insertion hole 34a penetrating in the vertical direction. The boss portion 34 is disposed from the upper plate portion 32a to the lower plate portion 32b of the horizontal portion 32 and has, for example, a cylindrical shape. Alternatively, the boss portion 34 may have a rectangular tubular shape. Meanwhile, an auxiliary plate 16 is joined to the lower side of the side frame 11. The auxiliary plate 16 has a horizontal portion 16a and flange portions 16b, 16b extending upward from both sides of the horizontal portion 16a in the vehicle width direction. Each of the flange portions 16b, 16b is welded to the outer surfaces of the vertical portions 12a, 13a of each frame member 12, 13. A bolt insertion hole 16c is formed in the center of the horizontal portion 16a of the auxiliary plate 16. A nut insertion hole 11f is formed in the center of the lower portion of the side frame 11. The nut insertion hole 11f is formed at a position opposite the bolt insertion hole 16c of the auxiliary plate 16. Nuts N3 are welded to the auxiliary plate 16 in correspondence with the bolt insertion holes 16c. A portion of the nut N3 is also inserted into the nut insertion hole 11f of the side frame 11. With the bolt insertion holes 34a, 16c aligned, bolts B3 are inserted into the bolt insertion holes 34a, 16c, and the bolts B3 are screwed into the nuts N3, thereby fastening the central portion of the horizontal portion 32 in the vehicle width direction integrally to the lower portion of the side frame 11. The configuration for fastening the horizontal portion 32 to the side frame 11 is not limited to the one described above.

[0033] An energy absorbing member 4 is disposed on the outer side of the side frame 11 in the vehicle width direction. This energy absorbing member 4 is a member that absorbs the side impact load (energy) by compressively deforming when subjected to the side impact load during a vehicle side collision. The energy absorbing member 4 includes a plurality of vertical plate portions 41, 41, ... disposed at predetermined intervals in the vehicle width direction, and a plurality of horizontal plate portions 42, 42, ... disposed at predetermined intervals in the up-down direction. As shown in FIG. 1, the energy absorbing member 4 is disposed on the outer side of the intermediate portions 11a, 11a of the side frames 11, 11.

[0034] The vertical portion 12a of the outer frame member 12 of the side frame 11 and the upper surface of the energy absorbing member 4 are connected by an L-shaped connecting bracket 43. Specifically, the vertical portion 43a of the connecting bracket 43 is welded to the outer surface of the vertical portion 12a of the outer frame member 12, and the horizontal portion 43b of the connecting bracket 43 is bolted to the upper surface of the energy absorbing member 4.

[0035] In this state where the energy absorbing member 4 is disposed on the outer side of the side frame 11 in the vehicle width direction, the energy absorbing member 4 is disposed in a position that overlaps with the lower portion of the side frame 11 and the battery fastening member 3 when viewed from the vehicle width direction. In other words, when a side collision load is input to the energy absorbing member 4, this side collision load is input (input toward the inside in the vehicle width direction) to each of the side frame 11 and the battery fastening member 3 (particularly the horizontal portion 32) via the energy absorbing member 4. In other words, an equal side collision load is input to each of the side frame 11 and the battery fastening member 3.

[0036] A feature of this embodiment is that a weak portion 35 is provided in the horizontal portion 32 of the battery fastening member 3. The weak portion 35 is disposed in a position that is further inward in the vehicle width direction than the position where the battery fastening member 3 is fastened to the side frame 11 (the position of the boss portion 34), and is also located below the side frame 11 (a position that overlaps with the side frame 11 in the up-down direction).

[0037] Specifically, the fragile portion 35 has a cross-sectional shape in which both the upper plate portion 32a and the lower plate portion 32b are slightly bent downward (a cross-sectional shape that is convex downward). That is, as shown in the dashed-dotted circle in FIG. 1 , the fragile portion 35 includes first inclined portions 35a, 35a that are inclined downward toward the outside in the vehicle width direction, horizontal portions 35b, 35b that extend horizontally from the outside portions of the first inclined portions 35a, 35a toward the outside in the vehicle width direction, and second inclined portions 35c, 35c that are inclined upward toward the outside in the vehicle width direction from the outside portions of the horizontal portions 35b, 35b. The fragile portion 35 is provided over the entire horizontal portion 32 of the battery fastening member 3 in the front-to-rear direction of the vehicle body. The configuration of the fragile portion 35 is not limited thereto, and it may have a cross-sectional shape that is curved downward. It may also have a cross-sectional shape that is curved upward or upward. By providing such a weak portion 35, when a horizontal load (side impact load) is input to the horizontal portion 32 of the battery fastening member 3, the weak portion 35 (the bending portion of each of the upper plate portion 32a and the lower plate portion 32b) deforms by bending downward (see the state in Figure 3), and the portion of the horizontal portion 32 of the battery fastening member 3 that is outer in the vehicle width direction than the weak portion 35 moves approximately horizontally toward the inside in the vehicle width direction.

[0038] -When a vehicle crashes into a side vehicle- Next, the deformation state of the vehicle underbody structure configured as described above during a vehicle side collision will be described. Fig. 3 is a view equivalent to Fig. 2, showing an example of the state at the time when the weak portion 35 is deformed during a vehicle side collision. Fig. 4 is a view equivalent to Fig. 2, showing an example of the state at the time when the energy absorbing member 4 is compressively deformed during a vehicle side collision. Note that Fig. 3 shows a state in which the weak portion 35 is deformed by the side collision load but the energy absorbing member 4 is not yet deformed. However, there are cases in which the energy absorbing member 4 also starts to deform when the weak portion 35 starts to deform.

[0039] When a side impact load F is input to the horizontal portion 32 of the battery fastening member 3 via the energy absorbing member 4 during a vehicle side impact, the weak portion 35 provided on the horizontal portion 32 is deformed by the side impact load F and bent downward. Furthermore, as described above, the side impact load is input to each of the side frame 11 and the weak portion 35 of the battery fastening member 3 via the energy absorbing member 4, and therefore an equal side impact load is input to each of the side frame 11 and the weak portion 35 of the battery fastening member 3. As a result, a portion of the horizontal portion 32 of the battery fastening member 3 that is more outer in the vehicle width direction than the weak portion 35 moves substantially horizontally toward the inside in the vehicle width direction. Furthermore, because the side frame 11 is fastened to a portion of the horizontal portion 32 of the battery fastening member 3 that is more outer in the vehicle width direction than the weak portion 35, the side frame 11 also moves substantially horizontally toward the inside in the vehicle width direction. Furthermore, because the energy absorbing member 4 is connected to the outer portion of the side frame 11 in the vehicle width direction, the energy absorbing member 4 also moves substantially horizontally toward the inside in the vehicle width direction.

[0040] In this way, deformation of the fragile portion 35 causes both the side frame 11 and the energy absorbing member 4 to move substantially horizontally toward the inside in the vehicle width direction. That is, the side frame 11 and the energy absorbing member 4 move while being prevented from rotating around an axis extending in the fore-and-aft direction of the vehicle body. That is, in the prior art, if a portion of the battery fastening member that is more inward in the vehicle width direction than the position of the fastening portion with the side frame (the boss portion 34 in the present embodiment) is less likely to deform, there is a risk that the battery fastening member and the side frame will rotate around an axis extending in the fore-and-aft direction of the vehicle body. However, in this embodiment, the fragile portion 35 is provided in a position more inward in the vehicle width direction than the position of the boss portion 34, which is the fastening portion with the side frame 11 of the battery fastening member 3. Deformation of this fragile portion 35 causes the battery fastening member 3 and the side frame 11 to move toward the inside in the vehicle width direction while being prevented from rotating around an axis extending in the fore-and-aft direction of the vehicle body.

[0041] When a side impact load F is further input from the state shown in Fig. 3, the energy absorbing member 4 undergoes compressive deformation along the vehicle width direction to absorb the side impact load (energy absorption) as shown in Fig. 4. As described above, the energy absorbing member 4 undergoes compressive deformation while being prevented from rotating about an axis extending in the fore-and-aft direction of the vehicle body, so that a sufficient amount of compressive deformation in the direction along the vehicle width direction is ensured, thereby demonstrating high load absorption performance. Even if the side frame 11 is deformed by the side impact load F, the side frame 11 undergoes compressive deformation while being prevented from rotating about an axis extending in the fore-and-aft direction of the vehicle body, so this also results in high load absorption performance.

[0042] -Effects of the embodiment- As described above, in this embodiment, the battery fastening member 3 that connects the side frame 11 and the battery pack 2 is provided with the weak portion 35, and in the event of a vehicle side collision, deformation of this weak portion 35 causes the portion of the battery fastening member 3 that is outward in the vehicle width direction from the weak portion 35 (the boss portion 34 and its surrounding area), the side frame 11, and the energy absorbing member 4 to move inward in the vehicle width direction. This ensures a sufficient amount of compressive deformation in the direction along the vehicle width during a vehicle side collision, enabling high load absorption performance to be exhibited.

[0043] Furthermore, in this embodiment, the weak portion 35 of the battery fastening member 3 is located below the side frame 11. Therefore, compared to a configuration in which the weak portion 35 is located inward in the vehicle width direction from the side frame 11, the distance (distance in the vehicle width direction) between the side frame 11 and the battery pack 2 can be made shorter, thereby preventing a situation in which the side frame 11 tends to rotate around an axis extending in the fore-and-aft direction of the vehicle body due to a long distance. For example, in the configuration disclosed in JP 2014-80116 A, the long distance between the side frame and the battery pack makes the side frame prone to rotate around an axis extending in the fore-and-aft direction of the vehicle body during a side collision. However, in this embodiment, the distance between the side frame 11 and the battery pack 2 can be made shorter, thereby preventing the side frame 11 from easily rotating around an axis extending in the fore-and-aft direction of the vehicle body. This contributes to achieving high load absorption performance by ensuring a sufficient amount of compressive deformation in the vehicle width direction.

[0044] -Variations- Next, a modified example will be described. In this modified example, the configuration of the fragile portion 35 differs from that of the previously described embodiment. The other configurations and operations during a vehicle side collision (such as the movement of the side frame 11 and the energy absorbing member 4) are the same as those of the previously described embodiment, so only the configuration of the fragile portion 35 will be described here.

[0045] Fig. 5 is a cross-sectional view showing several modified examples of the fragile portion 35. Fig. 5 shows only the fragile portion 35 and its surrounding area in the battery fastening member 3 in an enlarged manner.

[0046] 5(a) shows a weakened portion 35 formed by providing thin-walled portions 35d, 35d in a portion of each of the upper plate portion 32a and the lower plate portion 32b of the horizontal portion 32 of the battery fastening member 3. The cross-sectional shapes of the thin-walled portions 35d, 35d match, so that the amounts of deformation (amount of deformation in the direction along the vehicle width) of the upper plate portion 32a and the lower plate portion 32b when a side collision load is input are approximately the same.

[0047] 5(b) shows a weakened portion 35 in which openings 35e, 35e penetrating in the vertical direction are provided in a portion of each of the upper plate portion 32a and the lower plate portion 32b of the horizontal portion 32 of the battery fastening member 3. The opening areas of the openings 35e, 35e are the same, so that the amounts of deformation (amount of deformation in the direction along the vehicle width) of the upper plate portion 32a and the lower plate portion 32b when a side collision load is input are approximately the same.

[0048] 5(c) shows a weak portion 35 formed by forming a portion of each of the upper plate portion 32a and the lower plate portion 32b of the horizontal portion 32 of the battery fastening member 3 into a bellows shape. The bellows shapes are approximately the same, so that the deformation amounts (deformation amounts in the direction along the vehicle width) of the upper plate portion 32a and the lower plate portion 32b when a side collision load is input are approximately the same.

[0049] The configurations of the fragile portion 35 in the above-described embodiment and modified examples can be combined with each other. For example, the configuration of the fragile portion 35 in the above-described embodiment may be thinned as shown in Fig. 5(a), or the configuration of the fragile portion 35 in the above-described embodiment may be provided with an opening 35e as shown in Fig. 5(b).

[0050] In these modified examples, as in the case of the above-described embodiment, the weak portion 35 deforms during a vehicle side collision, thereby ensuring a sufficient amount of compressive deformation in the direction along the vehicle width, thereby enabling the vehicle to exhibit high load absorption performance.

[0051] -Other embodiments- The present invention is not limited to the above-described embodiment and modified examples, and all modifications and applications that fall within the scope of the claims and equivalents thereto are possible.

[0052] For example, in the above-described embodiment and modified example, the present invention has been described as being applied to a frame vehicle. However, the present invention is not limited to this and can also be applied to a monocoque vehicle. In this case, the rocker serves as the component equivalent to the side frame (framework component) 11. Since no energy-absorbing member is disposed on the vehicle widthwise outer side of the rocker, a side impact load is directly input to the rocker during a vehicle side impact. However, even in this case, the rocker moves substantially horizontally toward the vehicle widthwise inner side during a vehicle side impact, and undergoes compressive deformation while being prevented from rotating around an axis extending in the fore-and-aft direction of the vehicle body. This ensures a sufficient amount of compressive deformation, thereby achieving high load absorption performance. Furthermore, in a configuration in which an energy-absorbing member is housed inside the rocker, the amount of compressive deformation of the energy-absorbing member is sufficiently ensured, thereby also achieving high load absorption performance.

[0053] Furthermore, in the above embodiment, the fragile portions 35 were provided over the entire longitudinal direction of the vehicle on the horizontal portion 32 of the battery fastening member 3. However, the present invention is not limited to this, and the fragile portions 35 may be provided intermittently (at predetermined intervals) on the horizontal portion 32 of the battery fastening member 3 in the longitudinal direction of the vehicle. In this case, it is preferable that the input position of the side collision load in the event of a vehicle side collision and the arrangement position of the fragile portions 35 face each other in the vehicle width direction, and therefore it is preferable that the intervals at which the fragile portions 35 are arranged in the longitudinal direction of the vehicle are short.

[0054] In the above embodiment and modified example, the range in which the battery pack 2 and the battery fastening member 3 are disposed is set to a position corresponding to the middle portions 11a, 11a of the side frames 11, 11. In other words, the battery pack 2 is disposed on the inner side in the vehicle width direction corresponding to the middle portions 11a, 11a, and the battery fastening member 3 is disposed on the outer side in the vehicle width direction corresponding to the middle portions 11a, 11a. The present invention is not limited to this, and the battery pack 2 and the battery fastening member 3 may be disposed so as to correspond to other portions of the side frames 11, 11. [Industrial Applicability]

[0055] The present invention is applicable to a vehicle underbody structure for improving the ability to absorb a side impact load during a vehicle side impact. [Explanation of symbols]

[0056] 11 Side frame (framework) 2 Battery pack (battery) 3 Battery fastening member 31 Vertical wall section 34 Boss part (fastening part) 35 Weakened part 4 Energy absorption member

Claims

1. a frame member extending along a front-rear direction of the vehicle body on both sides in the vehicle width direction; a battery disposed between the respective skeletal members; a battery fastening member having a fastening portion fastened to the frame member and connecting the frame member and the battery, the battery fastening member is provided with a weakened portion at a position more inward in a vehicle width direction than a position of the fastening portion at which the battery fastening member is fastened to the frame member, A vehicle undercarriage structure characterized in that, in the event of a side collision of the vehicle, deformation of the weak portion causes the portion of the battery fastening member that is located outside the weak portion in the vehicle width direction and the skeletal member to move toward the inside in the vehicle width direction.

2. a frame member extending along a front-rear direction of the vehicle body on both sides in the vehicle width direction; a battery disposed between the respective skeletal members; a battery fastening member having a fastening portion fastened to the frame member and connecting the frame member and the battery, a battery fastening member having a vertical wall portion positioned between the battery and the skeletal member and extending in the vertical direction, and a weak portion in the region between the fastening portion and the vertical wall portion.

3. The vehicle underbody structure according to claim 1 or 2, The vehicle undercarriage structure, wherein the weak portion is located below the frame member.

4. The vehicle underbody structure according to claim 1 or 2, an energy absorbing member that is compressively deformable when subjected to a side collision load is disposed on the outer side of the frame member in the vehicle width direction; A vehicle undercarriage structure characterized in that the energy absorption member is arranged in a position where, when viewed from the vehicle width direction, at least a portion of the energy absorption member overlaps with each of the weak portions of the skeletal member and the battery fastening member.

5. The vehicle underbody structure according to claim 1 or 2, The vehicle undercarriage structure, wherein the weakened portion is a bent portion that is convex in either the up or down direction.

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