Lower structure of vehicle

Abstract

In order to prevent the deformation of a vehicle body due to a side collision extending to a battery (2), regardless of battery size, a lower structure of a vehicle comprises: a floor panel (13) constituting a floor surface of a vehicle (1); a pair of side members (14, 14) disposed on the left and right sides of a floor rear surface of the floor panel; the battery (2) disposed between the pair of side members on the floor rear side of the floor panel; and a battery frame (3) that has a pair of left and right first members (31, 31) fixed to the pair of side members, and a pair of front and rear second members (32, 32) connecting the pair of left and right first members, the battery frame supporting the battery. A weakened section (33) is provided to each of the pair of front and rear second members (32, 32).

Description

Vehicle undercarriage

[0001] The present invention relates to a vehicle undercarriage.

[0002] A vehicle body structure surrounding a battery mounted under the floor of a vehicle includes a battery case that houses the battery and a case mounting frame that connects the side sill and the battery case and supports the battery case, and a lower frame that straddles the side sill and the battery case has a weak portion at a first location located below the upper frame (Patent Document 1).With this vehicle body structure, when a side impact load is input to the case mounting frame through the side sill during a side collision, the weak portion is crushed and deformed so as to bend upward in a convex shape, and as a result, the end of the lower frame on the battery case side is prevented from deforming upward and piercing the battery case (see paragraph

[0007] of the same document).

[0003] Japanese Patent Application Laid-Open No. 2022-124191

[0004] The body structure of an automobile must be designed so that deformation of the body in a side collision does not extend to the battery cell. However, in the above-mentioned conventional technology, the battery case is fixed to the body, which limits the battery size in order to ensure the deformation stroke of the body.

[0005] The problem to be solved by the present invention is to provide a vehicle underbody structure that can prevent deformation of the vehicle body due to a side collision from extending to the battery without limiting the battery size.

[0006] The present invention solves the above problem by providing weak portions in a pair of front and rear second members of a battery frame that supports a battery in a vehicle understructure in which a battery is placed on the underside of the vehicle's floor panel.

[0007] According to the present invention, the battery size is not limited, and deformation of the vehicle body due to a side collision can be prevented from extending to the battery.

[0008] 1 is a bottom view of a vehicle showing one embodiment of a vehicle undercarriage structure according to the present invention. FIG. 2 is an exploded perspective view showing the battery and battery frame of FIG. 1. FIG. 3 is a bottom view of a vehicle showing a main part of the vehicle undercarriage structure of FIG. 1. FIG. 4 is a cross-sectional view showing a cross section taken along line IV-IV of FIG. 3 upside down. FIG. 5 is a perspective view showing a second member of FIG. 1. FIG. 6 is a cross-sectional view taken along line VI-VI of FIG. 5. FIG. 7 is a cross-sectional view taken along line VII-VII of FIG. 5. FIG. 8 is a cross-sectional view taken along line VIII-VIII of FIG. 5. FIG. 9 is a cross-sectional view taken along line IX-IX of FIG. 3. FIG. 10 is a cross-sectional view taken along line XX of FIG. 3. FIG. 11 is a front view for explaining the function of a weak portion and a cutout portion according to an embodiment of the present invention. FIG. 12 is a bottom view and a cross-sectional view showing a main part of the vehicle when an input is applied to the vehicle of FIG. 1 in the vehicle width direction. FIG. 13 is a bottom view showing a main part of a vehicle when an input is applied to a vehicle according to a comparative example of the present invention in the vehicle width direction.

[0009] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Fig. 1 is a bottom view of a vehicle showing one embodiment of a vehicle undercarriage according to the present invention. As shown in Fig. 1, the vehicle 1 of this embodiment has an internal combustion engine 11 and a drive motor 12. The type of vehicle 1 of this embodiment is not particularly limited, and may be a hybrid vehicle in which both the internal combustion engine 11 and the drive motor 12 are used as drive sources for driving, or a hybrid vehicle in which only the drive motor 12 is used as a drive source for driving and the internal combustion engine 11 is used as a power source for generating electricity.

[0010] The vehicle 1 of this embodiment has a vehicle lower structure (also referred to as an automobile underbody structure) that includes a floor panel 13, a pair of side members 14, and a battery 2. The floor panel 13 is a metal plate that forms the floor surface of the passenger compartment. The pair of side members 14 are fixed to the left and right sides of the underside of the floor panel 13 by welding or the like. The side members 14 are formed by bending a metal plate, have high rigidity among the vehicle structures, and form part of the framework of the underside of the vehicle 1. The battery 2 is disposed between the pair of side members 14 on the underside of the floor panel 13. The battery 2 supplies power to the drive motor 12, on-board electrical equipment, and the like.

[0011] The internal combustion engine 11 has an exhaust pipe 15 that guides exhaust gas. The exhaust pipe 15 extends toward the rear of the vehicle, and a portion of it is routed in the space between the battery 2 and the right side member 14. A first silencer 16 and a second silencer 17 are provided midway along the exhaust pipe 15. The first silencer 16 is disposed between the battery 2 and the right side member 14. The first silencer 16 and the second silencer 17 may include a filter portion and a catalyst portion. The second silencer 17 is not necessarily required, and only the first silencer 16 may be disposed. Furthermore, the battery 2 and the first silencer 16 may be disposed in reverse left-right positions.

[0012] 2 is an exploded perspective view showing the battery 2 and battery frame 3 of FIG. 1, FIG. 3 is a bottom view of the vehicle 1 showing the main parts of the undercarriage of the vehicle of FIG. 1, and FIG. 4 is a cross-sectional view showing the cross section along line IV-IV of FIG. 3 upside down.

[0013] As shown in Fig. 4 , the battery 2 of this embodiment includes a battery case 21 and a cell module 22 housed within the battery case 21. The battery case 21 is formed in a substantially rectangular parallelepiped shape and includes a rectangular bottom plate 23, four side walls 24 fixed to each of the four sides of the bottom plate 23, and rectangular covers 25 that cover openings at the upper ends of the four side walls 24. Of the four side walls 24, two that extend in the vehicle width direction and are spaced apart in the front-rear direction of the vehicle 1 are formed in a substantially L-shape as shown in Fig. 2 and include a vertical wall 24a and a flange 24b that extends from the vertical wall 24a in the front-rear direction of the vehicle 1. The battery 2 is fixed to second members 32, 32 of the battery frame 3 (described later) at the flange 24b. The material constituting the battery case 21 is not particularly limited, and for example, the bottom plate portion 23 may be made of a solid metal plate material, the side wall portion 24 may be made of a hollow metal body divided into multiple hollow chambers by ribs, and the cover portion 25 may be made of a solid metal plate material.

[0014] 1 to 4, a vehicle 1 of this embodiment includes a battery frame 3 that supports a battery 2 on the underside of a floor panel 13. The battery frame 3 of this embodiment is fixed to a side member 14, and the battery 2 is not directly fixed to the side member 14 but is fixed to second members 32, 32 of the battery frame 3. Therefore, the battery 2 is indirectly fixed to the side member 14 via the battery frame 3. The battery 2 is fixed to the second members 32, 32 of the battery frame 3 by fixing means such as bolts.

[0015] The battery frame 3 of this embodiment has a pair of left and right first members 31, 31 and a pair of front and rear second members 32, 32, and is formed in a lattice shape as a whole. The pair of left and right first members 31, 31 extend in the front-rear direction of the vehicle 1 and are fixed to the pair of left and right side members 14, respectively. The pair of front and rear second members 32, 32 extend in the vehicle width direction and are fixed to the pair of left and right first members 31, 31. The fixed portions between the side members 14 and the first members 31 are firmly fixed by fastening means such as bolts, and the fixed portions between the first members 31 and the second members 32 are also firmly fixed by fastening means such as bolts. Note that, as shown in FIGS. 4 and 6 , the first members 31 and the second members 32 are basically skeletal members with closed cross sections.

[0016] 5 is a perspective view showing the second member 32 of FIG. 1, FIG. 6 is a cross-sectional view taken along line VI-VI of FIG. 5, FIG. 7 is a cross-sectional view taken along line VII-VII of FIG. 5, FIG. 8 is a cross-sectional view taken along line VIII-VIII of FIG. 5, FIG. 9 is a cross-sectional view taken along line IX-IX of FIG. 3, FIG. 10 is a cross-sectional view taken along line XX of FIG. 3, and FIG. 11 is a front view for explaining the function of the fragile portion 33 and the cutout portion 34 according to an embodiment of the present invention.

[0017] The battery frame 3 of this embodiment is provided with a pair of front and rear second members 32, 32 each having a weak portion 33. The weak portion 33 of this embodiment refers to a portion that collapses in the direction of an input when the vehicle 1 receives an input from the vehicle width direction, such as in a side collision. In particular, the weak portion 33 of this embodiment refers to a portion that collapses so as to move the battery 2 relative to the vehicle 1 in the direction of the input when the vehicle 1 receives an input from the vehicle width direction, such as in a side collision, against the side of the vehicle 1 closer to the battery 2 (from the left side in the case of the vehicle 1 shown in FIG. 1 ).

[0018] The configuration of the fragile portion 33 of the present invention is not particularly limited, and may be any configuration that collapses in the vehicle width direction, particularly in a manner that causes the battery 2 to move relatively when an input is applied to the side of the vehicle 1 closest to the battery 2. For example, the fragile portion 33 in the embodiment shown in Figures 4 and 5 is formed by a recess provided in each of the pair of front and rear second members 32, 32. If the pair of front and rear second members 32, 32 each have a fragile portion 33 formed by a recess, as shown in Figure 7, the cross-sectional area of ​​the fragile portion 33 will be smaller than the cross-sectional area of ​​the general portion shown in Figure 6, and therefore the strength against an input in the vehicle width direction will be smaller than that of the general portion.

[0019] 2 and 4, the fragile portions 33 of this embodiment are provided on the upper surfaces of the pair of front and rear second members 32, 32, at positions closer to the first silencer 16 than the battery 2. That is, the fragile portions 33 of this embodiment are formed in the space between the battery 2 and the right side member 14 shown in Fig. 4. As a result, in the event of an input to the vehicle 1 from the vehicle width direction, such as a side collision, the second members 32 can be crushed around the fragile portions 33 in the space between the battery 2 and the right side member 14 shown in Fig. 4, and as a result, interference between the left side member 14 and the battery 2 or damage to the battery 2 by the left side member 14 can be suppressed.

[0020] In this embodiment, the fragile portions 33 are provided on each of the pair of front and rear second members 32, 32 as shown in Fig. 2, and these pair of fragile portions 33, 33 are provided at the same position in the vehicle width direction. As a result, when the vehicle 1 receives an input from the vehicle width direction, such as in a side collision, the pair of front and rear second members 32, 32 can be crushed at the same position in the vehicle width direction in the space between the battery 2 and the left side member 14 as shown in Fig. 4. As a result, the battery 2 moves along the vehicle width direction, preventing the battery 2 from rotating and interfering with surrounding components.

[0021] 5 to 8 , each of the pair of front and rear second members 32, 32 in this embodiment is a skeletal member with a closed cross section, having an upper surface (first surface) provided with a recess that constitutes the fragile portion 33, and a lower surface (second surface) facing the upper surface (first surface). As shown in FIGS. 5 and 8 , a cutout portion 34 is provided on the lower surface (second surface) of the second member 32 at a position shifted from the position where the fragile portion 33 consisting of the recess faces. In this embodiment, the cutout portions 34 are a pair of semicircular cutout portions 34, 34 extending from an edge of the lower surface of the second member 32 toward the center. However, the cutout portions 34 of the present invention are not particularly limited to this structure, and may have any structure as long as the strength of the lower surface is smaller than the strength of the upper surface.

[0022] The second member 32 has a weakened portion 33 formed as a recess on its upper surface, and a cutout portion 34 formed on its underside that is offset from the position of the underside that the weakened portion 33 faces. This allows the weakened portion 33 to collapse downward in the event of an input to the vehicle 1 from the vehicle width direction, such as in a side collision, while the portion with the cutout portion 34 collapses upward in the event of an input to the vehicle 1 from the vehicle width direction, as shown in the right diagram of FIG. 11 . Therefore, the deformation is closer to axial collapse than the collapsed state of the second member 32 without the cutout portion 34, as shown in the left diagram of FIG. 11 . In the vehicle undercarriage structure of this embodiment, the second member 32 is provided with the cutout portion 34, but the cutout portion 34 need not be provided if necessary.

[0023] 3, in the pair of left and right side members 14, 14 of this embodiment, the strength of a portion R2 of the pair of side members 14, 14 excluding the portion R1 between the pair of front and rear second members 32, 32 is set lower than the strength of a portion R1 of the pair of side members 14, 14 between the pair of front and rear second members 32, 32. Specifically, the cross-sectional shape of the portion R1 of the pair of side members 14, 14 between the pair of front and rear second members 32, 32 is a closed cross-section as shown in Fig. 9, whereas the cross-sectional shape of the portion R2 of the pair of side members 14, 14 excluding the portion R1 between the pair of front and rear second members 32, 32 is a C-shaped cross-section with no plate material on the underside.

[0024] If the strength of the portion R2 of the pair of side members 14, 14 excluding the portion R1 between the pair of front and rear second members 32, 32 is set lower than the strength of the portion R1 between the second members 32, 32, when the vehicle 1 receives an input from the vehicle width direction, such as in a side collision, the deformation of the side members 14 will be able to more easily follow the deformation of the vehicle body, and large shear forces can be prevented from acting on the bolts securing the side members 14 to the battery frame 3.

[0025] Next, the operation will be described. Figure 12 is a bottom view and a cross-sectional view showing the main parts of the vehicle 1 of Figure 1 when an input is applied from the vehicle width direction, and Figure 13 is a bottom view showing the main parts of the vehicle according to a comparative example of the present invention when an input is applied from the vehicle width direction, and the operation will be described when an object 4 collides with the left side of the vehicle 1 with a corresponding impact force.

[0026] First, when an impact is applied from the left side of the vehicle width direction to a vehicle according to a comparative example of the present invention, in which the second member 32 does not have a weak portion 33, the floor panel 13 bends and compresses from the left side of the vehicle toward the center in the vehicle width direction, as shown in FIG. 13 . The left side member 14 also bends and moves from the left side of the vehicle toward the center in the vehicle width direction. The impact from the object 4 is transmitted through the left side member 14 and the left first member 31 to the pair of front and rear second members 32, 32 and the right first member 31 of the battery frame 3. However, because the pair of front and rear second members 32, 32 and the right first member 31 have sufficient strength against the impact in the vehicle width direction, the pair of front and rear second members 32, 32 and the right first member 31 hardly deform, and only the left side member 14 deforms significantly. As a result, the left side member 14 may interfere with the battery 2, or, as shown in FIG. 13 , the deformation of the left side member 14 may extend to the battery 2 if the impact is large.

[0027] In contrast, in the vehicle undercarriage of this embodiment, as shown in Figure 12, when an impact is applied to the vehicle 1 from the left side in the vehicle width direction, the floor panel 13 bends and compresses from the left side of the vehicle toward the center in the vehicle width direction. The left side member 14 also moves while bending from the left side of the vehicle toward the center in the vehicle width direction. As the side member 14 moves toward the center in the vehicle width direction, as shown in the figure, the deformed left side member 14 attempts to abut against the side wall portion 24 of the battery case 21. At the same time, the impact input from the left side in the vehicle width direction is applied from the left side member 14 through the first member 31 to the pair of front and rear second members 32, 32, and the pair of front and rear second members 32, 32 are subjected to a compressive force in the vehicle width direction.

[0028] When the impact force of the object 4 is large and the compressive force input from the left side member 14 to the second member 32 exceeds the crush threshold of the weak portion 33, the weak portion 33 begins to crush. Then, when the side member 14 attempts to move further toward the center in the vehicle width direction, the weak portions 33 of the pair of front and rear second members 32, 32 are crushed, and the pair of front and rear second members 32, 32 move in the direction of the impact input (to the right in the vehicle width direction) together with the battery 2. This makes it possible to prevent interference between the left side member 14 and the battery 2 or deformation of the left side member 14 from extending to the battery 2.

[0029] Although not shown, a case will be described in which an object 4 collides with the vehicle 1 from the right side in the vehicle width direction with a corresponding impact force. When an impact is input to the vehicle 1 from the right side in the vehicle width direction, the floor panel 13 bends so as to compress from the right side of the vehicle 1 toward the center in the vehicle width direction. The right side member 14 also moves from the right side of the vehicle 1 toward the center in the vehicle width direction. As the right side member 14 moves toward the center in the vehicle width direction, it abuts against the first silencer 16. At the same time, the impact input from the right side in the vehicle width direction is input from the right side member 14 through the first member 31 to the pair of front and rear second members 32, 32, and the pair of front and rear second members 32, 32 are subjected to a compressive force in the vehicle width direction.

[0030] When the impact force of the object 4 is large and the compressive force input from the right side member 14 to the second member 32 exceeds the crush threshold of the weak portion 33, the weak portion 33 begins to crush. Then, while the weak portions 33 of the pair of front and rear second members 32, 32 are crushed, the right side member 14 moves further toward the center in the vehicle width direction, and the first silencer 16 is sandwiched between the battery 2 and the right side member 14 and crushed. This makes it possible to absorb the impact input from the right side of the vehicle and suppress damage to the battery 2.

[0031] As described above, the vehicle understructure of this embodiment includes the floor panel 13 constituting the floor surface of the vehicle 1, a pair of side members 14, 14 arranged on the left and right sides of the underside of the floor panel 13, the battery 2 arranged between the pair of side members 14, 14 on the underside of the floor panel 13, and the battery frame 3 having a pair of left and right first members 31, 31 fixed to the pair of side members 14, 14, and a pair of front and rear second members 32, 32 connecting the pair of left and right first members 31, 31, and supporting the battery 2. In this vehicle understructure, the pair of front and rear second members 32, 32 are provided with weak portions 33, so that when an impact is applied to the vehicle 1 in the vehicle width direction, the weak portions 33 are crushed as the side members 14 deform, and the battery 2 moves in the direction of the impact as the second members 32 move. As a result, the amount of vehicle body deformation can be secured without limiting the battery size, and the amount of impact energy absorption can be increased, while at the same time, the extension of vehicle body deformation due to a side collision to the battery 2 can be suppressed.

[0032] Furthermore, in the vehicle undercarriage structure of this embodiment, when the vehicle 1 is subjected to an input from the vehicle width direction, the fragile portion 33 collapses so as to move the battery 2 relative to the vehicle 1 in the direction of the input. This ensures a certain amount of deformation of the vehicle body without restricting the battery size, allowing for a larger amount of impact energy to be absorbed, while also preventing deformation of the vehicle body due to a side collision from extending to the battery 2.

[0033] Furthermore, the vehicle undercarriage structure of this embodiment further includes a first silencer 16 on the side of the battery 2, and the fragile portion 33 is provided in a position closer to the first silencer 16 than the battery 2. This allows the fragile portion 33 to have a larger deformation amount, which increases the amount of impact energy absorption and also prevents deformation of the vehicle body due to a side collision from extending to the battery 2. Impact energy can also be absorbed by the first silencer 16.

[0034] Furthermore, in the vehicle undercarriage structure of this embodiment, the fragile portions 33 are formed as recesses provided in each of the pair of front and rear second members 32, 32, and therefore the battery 2 can be moved relative to the vehicle 1 in the direction of impact input with a simple structure. As a result, the shear force acting on the bolts and the like that secure the battery case 21 and the second members 32 can be reduced, thereby reducing the risk of the bolts and the like breaking.

[0035] Furthermore, in the vehicle undercarriage structure of this embodiment, each of the pair of front and rear second members 32, 32 has a first surface on which the recess is provided and a second surface facing the first surface, and a cutout portion 34 is provided on the second surface at a position shifted from the position where the recess faces.Therefore, when an input is applied to the vehicle 1 from the vehicle width direction, one of the weak portion 33 and the cutout portion 34 can be crushed in a mountain fold, and the other of the weak portion 33 and the cutout portion 34 can be crushed in a valley fold, which is closer to axial crushing with less impact on the surrounding area.

[0036] Furthermore, in the vehicle undercarriage structure of this embodiment, the weakened portions 33 provided on each of the pair of front and rear second members 32, 32 are provided at the same position in the vehicle width direction, so that when an input is applied to the vehicle 1 from the vehicle width direction, the pair of front and rear second members 32, 32 can be crushed at the same position in the vehicle width direction in the space between the battery 2 and the right side member 14 shown in Figure 4. As a result, the battery 2 moves along the vehicle width direction, and therefore, it is possible to prevent the battery 2 from rotating and interfering with surrounding components.

[0037] Furthermore, in the vehicle lower structure of this embodiment, the strength of the portion R2 of the pair of side members 14, 14 excluding the portion R1 between the pair of front and rear second members 32, 32 is set lower than the strength of the portion R1 between the pair of front and rear second members 32, 32 of the pair of side members 14, 14. Therefore, when an input is applied to the vehicle 1 from the vehicle width direction, the deformation of the side members 14 is more likely to follow the deformation of the vehicle body, and large shear forces can be prevented from acting on the bolts securing the side members 14 to the battery frame 3.

[0038] REFERENCE SIGNS LIST 1 vehicle 11 internal combustion engine 12 driving motor 13 floor panel 14 side member 15 exhaust pipe 16 first silencer 17 second silencer 2 battery 21 battery case 22 cell module 23 bottom plate portion 24 side wall portion 24a vertical wall portion 24b flange portion 25 cover portion 3 battery frame 31 first member 32 second member 33 fragile portion 34 notch portion 4 object

Claims

1. A vehicle understructure comprising: a floor panel that forms the floor surface of a vehicle; a pair of side members arranged on the left and right sides of the underside of the floor panel; a battery arranged between the pair of side members on the underside of the floor panel; and a battery frame that supports the battery and has a pair of left and right first members fixed to the pair of side members and a pair of front and rear second members connecting the pair of left and right first members, wherein a weak part is provided in the pair of front and rear second members.

2. A vehicle undercarriage structure as described in claim 1, wherein the weakened portion collapses when the vehicle is subjected to an input from the vehicle width direction, causing the battery to move relative to the vehicle in the direction of the input.

3. The vehicle undercarriage structure according to claim 2, further comprising a silencer on the side of the battery, wherein the weakened portion is provided at a position closer to the silencer than the battery.

4. The vehicle undercarriage structure according to claim 3, wherein the weakened portion is a recess provided in each of the pair of front and rear second members.

5. A vehicle undercarriage structure as described in claim 4, wherein each of the pair of front and rear second members has a first surface on which the recess is provided and a second surface facing the first surface, and a notch is provided on the second surface at a position offset from the position facing the recess.

6. The vehicle undercarriage structure according to claim 5, wherein the weakened portions provided on the pair of front and rear second members are provided at the same positions in the vehicle width direction.

7. A vehicle undercarriage structure as claimed in any one of claims 1 to 6, wherein the strength of the portion of the pair of side members excluding the portion between the pair of front and rear second members is set lower than the strength of the portion of the pair of side members between the pair of front and rear second members.

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