Vehicle lower structure

Abstract

To provide a vehicle lower part structure capable of more surely and inexpensively protecting a protection object component arranged on a lower side of a floor panel.SOLUTION: The vehicle lower structure includes a protection target component 10 disposed below a floor panel 16 of a vehicle, a first impact absorbing member 20 formed of a first plate material 22 that is bent one or more times and has no joint, and a second impact absorbing member 30 disposed adjacent to an outer side of the first impact absorbing member 20 in a vehicle-width direction, wherein the first impact absorbing member 20 includes two or more closed spaces 24U and 24L surrounded by the first plate material 22 and arranged in a vertical direction or a horizontal direction. The protection target component 10 and the vehicle body are fastened to the first shock absorbing member 20.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present specification discloses a vehicle underbody structure having a component to be protected that is disposed below a floor panel of the vehicle, and an impact absorbing member that protects the component to be protected. [Background technology]

[0002] It has been proposed to mount components to be protected under the floor panel of a vehicle. The components to be protected are on-board components that are expected to be protected without being damaged in the event of a vehicle collision. The components to be protected are, for example, a battery, a fuel tank, or a fuel cell. To protect such components to be protected, it has been proposed to place an impact absorbing member.

[0003] For example, Patent Document 1 discloses a structure in which a battery pack is disposed below a floor panel. The peripheral walls at the vehicle widthwise ends of this battery pack have a substantially B-shaped cross section, with closed spaces extending in the vehicle's longitudinal direction lined up one above the other. This peripheral wall functions as an impact absorbing member. According to the technology described in Patent Document 1, the impact of a vehicle side collision is absorbed by the substantially B-shaped cross section of the peripheral wall, thereby providing adequate protection for the battery. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2019-006303 Summary of the Invention [Problem to be solved by the invention]

[0005] The peripheral wall in Patent Document 1 is manufactured by extrusion molding of a light metal (for example, an aluminum alloy). However, such extrusion moldings have the problem of being expensive. Furthermore, in Patent Document 1, the battery pack is fastened to a locker that receives a load in the event of a side collision. In this case, the side collision load could cause the fastening between the battery pack and the locker to be released, causing the battery pack to fall.

[0006] Therefore, this specification discloses a vehicle underbody structure that can more reliably protect parts to be protected that are arranged below the floor panel at low cost. [Means for solving the problem]

[0007] The vehicle undercarriage structure disclosed in this specification comprises a part to be protected that is arranged below the floor panel of the vehicle, a first impact absorbing member that is bent one or more times and is composed of a single seamless first plate material, and a second impact absorbing member that is arranged adjacent to the outside of the first impact absorbing member in the vehicle width direction, wherein the first impact absorbing member is two or more closed spaces surrounded by the first plate material, including two or more closed spaces aligned vertically or horizontally, and the part to be protected and the vehicle body are fastened to the first impact absorbing member.

[0008] In this case, the second impact absorbing member is made of a single piece of seamless second plate material that is bent one or more times, and includes two or more closed spaces that are surrounded by the second plate material and aligned vertically or horizontally, the first impact absorbing member is joined to the second impact absorbing member, and the arrangement direction of the two or more closed spaces of the second impact absorbing member may be the same as the arrangement direction of the two or more closed spaces of the first impact absorbing member.

[0009] Furthermore, the vehicle width direction dimension of the first impact absorbing member and the vehicle width direction dimension of the second impact absorbing member may be different from each other.

[0010] In addition, the first impact absorbing member and the second impact absorbing member each have two or more closed spaces aligned in the vertical direction and penetrating in the fore-and-aft direction of the vehicle, and the vehicle width dimension of the first impact absorbing member may be larger than the vehicle width dimension of the second impact absorbing member.

[0011] Furthermore, the first impact absorbing member has two closed spaces formed by the first plate material bent into an approximately figure-8 shape, the second impact absorbing member has two closed spaces formed by a single seamless second plate material bent into an approximately figure-8 shape, the ends of the first plate material and the ends of the second plate material are welded to the middle part of the first plate material and the middle part of the second plate material, respectively, the part to be protected is a battery unit, and both the first plate material and the second plate material may be made of an iron-based metal. [Effects of the Invention]

[0012] According to the vehicle undercarriage structure disclosed in this specification, the first impact absorbing member is constructed from a single first plate material, which allows the use of inexpensive materials such as iron-based metals. As a result, costs can be reduced compared to conventional impact absorbing members. Furthermore, because both the vehicle body and the protected component are fastened to the first impact absorbing member, which is located inward in the vehicle width direction from the second impact absorbing member, the protected component can be effectively prevented from falling off due to the impact during a side collision. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 2 is a schematic cross-sectional view of the lower part of the vehicle. [Figure 2] FIG. 10 is a schematic cross-sectional view of another example of a vehicle lower portion. [Figure 3] 5A and 5B are schematic diagrams showing how the impact absorbing member is molded. [Figure 4] 5A and 5B are schematic diagrams showing deformation of an impact absorbing member during a side collision; [Figure 5] 10 is a diagram showing the relationship between the movement stroke of an obstacle and the load absorbed by the impact absorbing member. FIG. [Figure 6]FIG. 10 is a schematic diagram showing another example of a vehicle underbody structure. DETAILED DESCRIPTION OF THE INVENTION

[0014] The vehicle underbody structure will be described below with reference to the drawings. Fig. 1 is a schematic cross-sectional view of the vehicle underbody. In each drawing, Fr, Up, and Out indicate the front, top, and outward directions of the vehicle, respectively.

[0015] This vehicle is a vehicle having a large battery unit 12, such as an electric vehicle (e.g., a battery electric vehicle or a battery hybrid vehicle) that uses a motor as one of its driving power sources. The battery unit 12 is a unit in which a rechargeable secondary battery is housed in a case. For example, the battery unit 12 has a flat shape with a thickness dimension smaller than its planar size. The battery unit 12 has a base plate 14 on its bottom surface. The base plate 14 extends in a flange-like shape beyond the main body of the battery unit 12 to the outside in the vehicle width direction. The battery unit 12 is fastened to other components at this flange-like portion. Because the battery unit 12 is a high-voltage component, it is required to be protected from damage even in the event of a vehicle collision. This specification describes a structure for protecting this battery unit 12 as a protected component 10.

[0016] Side frames 18, which constitute the vehicle body, are arranged on both the left and right sides of the battery unit 12. The side frames 18 are skeletal members of the vehicle and extend in the front-to-rear direction of the vehicle. The side frames 18 are, for example, rectangular tubular members with a rectangular cross section. Further outboard in the vehicle width direction from the side frames 18, skeletal members called rockers (not shown) are arranged. The floor panel 16 is located above the side frames 18 and the battery unit 12. Both ends of the side frames 18 in the vehicle width direction are joined to the floor panel 16, for example.

[0017] Here, in order to prevent impact input to the battery unit 12 when an obstacle collides with the side of the vehicle, impact absorbing members 20, 30 are arranged on the outer side of the battery unit 12 in the vehicle width direction. Note that hereinafter, the "impact absorbing members" will be referred to as "EA members."

[0018] The EA members 20, 30 are members that actively collapse when collision energy is input, thereby consuming the collision energy and protecting the protected component 10. The first EA member 20 is disposed on the outer side of the battery unit 12 in the vehicle width direction, and the second EA member 30 is disposed on the outer side of the first EA member 20 in the vehicle width direction. The first EA member 20 and the second EA member 30 each have two closed spaces 24U, 24L, 34U, and 34L arranged vertically. During a vehicle collision, these multiple closed spaces 24U, 24L, 34U, and 34L collapse, absorbing impact energy.

[0019] The first EA member 20 and the second EA member 30 have substantially the same configuration, but the second EA member 30, i.e., the EA member located on the outer side in the vehicle width direction, has a smaller vehicle width dimension than the first EA member 20. The side frame 18 and the battery unit 12 are fastened to the first EA member 20 with bolts 46. The first EA member 20 and the second EA member 30 are joined to each other by welding. The black ovals in FIG. 1 indicate the welded locations of the first EA member 20 and the second EA member 30.

[0020] 1, each of the two EA members 20 and 30 has closed spaces 24U, 24L, 34U, and 34L arranged vertically. However, as shown in FIG. 2, each of the two EA members 20 and 30 may have closed spaces 24I, 24O, 34I, and 34O arranged horizontally. In the following description, when the position of the closed spaces is not to be distinguished, the subscripts U, L, I, and O are omitted and the closed spaces are referred to as "closed spaces 24" or "closed spaces 34."

[0021] As is clear from FIGS. 1 and 2, the first EA member 20 is made up of a first plate material 22 without joints, and the second EA member 30 is made up of a second plate material 32 without joints. The first plate member 22 and the second plate member 32 are both made of an iron-based metal.

[0022] More specifically, the first EA member 20 is formed by bending a first plate material 22 into the shape of a figure eight. In the example of FIG. 1 , the first plate material 22 moves clockwise from the starting point SE and returns to the starting point SE to form a first loop surrounding the upper closed space 24U, and then moves counterclockwise to form a second loop surrounding the lower closed space 24L. The middle portion of the first plate material 22 becomes a partition wall 26 that separates the upper closed space 24U and the lower closed space 24L. The second EA member 30 is similarly formed by bending a second plate material 32 into the shape of a figure eight.

[0023] The first EA member 20 and the second EA member 30 are manufactured by rolling. FIG. 3 is a schematic diagram showing the rolling process. Rolling is a process in which a plate material is bent in stages using a tool called a roll (not shown). In this example, the first plate material 22 constituting the first EA member 20 is provided to the rolling process in the form of a completely flat plate, as shown in step S1 of FIG. 3. In the rolling process, this flat plate is gradually bent as shown in steps S2 to S5. Finally, the first plate material 22 becomes approximately an eight shape with two closed spaces 24 arranged side by side. Once this state is reached, the starting end SE and the ending end EE of the first plate material 22 are welded to the middle portion of the adjacent first plate material 22, respectively. The black triangles in FIG. 3 indicate the welding locations. Note that while the first EA member 20 has been described as an example here, the second EA member 30 is also manufactured using a similar procedure.

[0024] Conventionally, these EA components have often been manufactured by extrusion using light metals (e.g., aluminum). Extrusion produces EA components with multiple seamlessly connected closed spaces. However, these light metal extrusion parts are expensive, which increases the price of the vehicle.

[0025] On the other hand, in this example, as described above, the EA members 20, 30 are manufactured by rolling the plates 22, 32 made of inexpensive iron-based metal, which allows for a significant reduction in component costs compared to using extruded light metal components.

[0026] Furthermore, in this example, the first EA member 20 is formed from a single seamless first plate member 22. This makes it less likely for the first EA member 20 to break even when subjected to a collision load. That is, when the first EA member 20 is formed from multiple plate members, the strength of the joints between the two plate members is likely to decrease, and breakage is likely to occur at the joints when subjected to a collision load. If the first EA member 20 breaks, the collision load cannot be sufficiently absorbed. Furthermore, depending on the location of the break, the battery unit 12 may be separated from the side frame 18 and fall off the vehicle. On the other hand, if the first EA member 20 is formed from a single seamless first plate member 22, breakage of the first EA member 20 can be prevented, allowing for sufficient absorption of the collision load and preventing the battery unit 12 from falling off. Furthermore, the second EA member 30 is also formed from a single seamless second plate member 32, allowing for sufficient absorption of the collision load while preventing breakage of the second EA member 30.

[0027] In this example, both the battery unit 12 and the side frame 18 are fastened to the first EA member 20. This configuration effectively prevents the battery unit 12 from falling off. That is, the first EA member 20 is located more inward in the vehicle width direction than the second EA member 30. In this case, a large collision load is absorbed by the second EA member 30, so the collision load input to the first EA member 20 is small. As a result, deformation of the first EA member 20 is suppressed, and the fastening between the first EA member 20 and the side frame 18 and the fastening between the first EA member 20 and the battery unit 12 are maintained without being released. As a result, the battery unit 12 does not fall off the vehicle.

[0028] Furthermore, the first EA member 20 and the second EA member 30 are both constructed by bending a single plate 22, 32 into an eight-shaped configuration. This reduces the overlap between the plates. That is, when constructing an EA member from a single plate, it is possible to fold the plate so that it passes through the same edge twice, as in the structure 52 shown in Figure 6 . However, in this case, overlapping and non-overlapping portions of the plate occur, resulting in significant variations in strength within a single EA member 20, 30. As a result, when subjected to a collision load, the closed spaces 24, 34 collapse non-uniformly, complicating control of the collision energy absorption mode. In contrast, in this example, the overlap between the plate members 22, 32 is limited to the starting ends SE and end ends EE of the plate members 22, 32, and the plate members 22, 32 do not overlap in most areas. As a result, the variations in strength within a single EA member 20, 30 can be minimized, and the closed spaces 24, 34 can collapse more uniformly. This allows for better control of the collision energy absorption mode.

[0029] As mentioned above, the multiple closed spaces 24, 34 may be arranged vertically as shown in FIG. 1, or horizontally as shown in FIG. 2. However, the mode of collision energy absorption differs depending on the direction in which the closed spaces 24, 34 are arranged. Therefore, the arrangement of the closed spaces may be selected depending on the required absorption mode. This will be explained with reference to FIGS. 4 and 5. FIG. 4 is a schematic diagram showing the deformation of the EA members 20, 30 during a side collision. Also, FIG. 5 is a diagram showing the relationship between the movement stroke of the obstacle 100 and the load absorbed by the EA members 20, 30.

[0030] In FIG. 4, the left column shows a case where the closed spaces 24, 34 are arranged vertically (hereinafter referred to as the "vertical arrangement"), and the right column shows a case where the closed spaces 24, 34 are arranged horizontally (hereinafter referred to as the "horizontal arrangement"). In FIG. 4, time progresses from top to bottom. As shown in the left column of FIG. 4, in the vertical arrangement, three horizontally extending walls (i.e., the top and bottom walls of the closed spaces 24, 34) are arranged vertically. Therefore, the vertical arrangement exhibits high resistance to horizontal loads. Furthermore, in the vertical arrangement, the load is easily transmitted to all of the closed spaces 24, 34. As a result, a large load can be absorbed immediately after the obstacle 100 collides. The solid line L1 in FIG. 5 shows the load absorption behavior of this vertical arrangement. As shown in FIG. 5, the vertical arrangement can absorb a large load with a small stroke, effectively preventing the load from being input to the battery unit 12 and more reliably protecting the battery unit 12.

[0031] In the case of the side-by-side type, as shown in the right column of Figure 4, there are only two horizontally extending walls, one above the other. Therefore, in the case of the side-by-side type, the load is less likely to be transmitted to the inside of the vehicle width direction than in the case of the vertically arranged type. The load rises more slowly in the side-by-side type than in the vertically arranged type. The dashed line L2 in Figure 5 shows the load absorption behavior of the side-by-side type. As shown in Figure 5, in the case of the side-by-side type, the load rises more gradually. Such a side-by-side type is suitable for, for example, lightweight vehicles. If a lightweight vehicle receives a large load instantaneously, the entire vehicle may not be able to absorb the load, and the vehicle may tip over. Therefore, in the case of a lightweight vehicle, side-by-side EA members 20, 30 may be used to absorb the load over a long stroke instead of suppressing the instantaneous load.

[0032] Furthermore, in the horizontally arranged EA members 20, 30, as shown in Figure 4, one closed space 24, 34 is almost completely crushed before the next closed space 24, 34 is crushed. In other words, in the horizontally arranged type, the multiple closed spaces 24, 34 are crushed in a regular order, in sequence, compared to the vertically arranged type. Therefore, it is easier to grasp the mode of collision energy absorption. As a result, in the horizontally arranged type, it is easier to control the progression of destruction of the EA members 20, 30 during a side collision.

[0033] As is clear from the above description, in this example, the EA members 20, 30 that protect the battery unit 12 from collision loads are configured from single plates 22, 32 made of iron-based metal. This configuration allows for significant cost reduction while maintaining the performance of the EA members 20, 30. In addition, both the battery unit 12 and the side frame 18 are fastened to the first EA member 20, which is located on the inner side in the vehicle width direction. This effectively prevents the battery unit 12 from separating from the side frame 18 and, ultimately, from falling off the vehicle.

[0034] The configuration described above is merely an example, and other configurations may be modified as appropriate as long as the configuration described in claim 1 is included. For example, in the above description, the vehicle width direction dimension of the first EA member 20 located on the inner side in the vehicle width direction is larger than the vehicle width direction dimension of the second EA member 30. However, these dimensions may be modified as appropriate. For example, the vehicle width direction dimensions of the first EA member 20 and the second EA member 30 may be the same. Furthermore, as in the structure 50 shown in FIG. 6, the second EA member 30 located on the outer side in the vehicle width direction may be wider than the first EA member 20. Note that a narrower EA member will have a faster load rise than a wider EA member. For example, in the case of the structure 50, the relationship between load and stroke is as shown by the dashed line L3 in FIG. 5.

[0035] Furthermore, the configuration of the EA members 20, 30 may be modified as appropriate as long as they have two or more closed spaces 24, 34 aligned vertically or horizontally. For example, as in structure 52 of FIG. 6, the plate members 22, 32 may be bent into a shape other than a figure-eight. Furthermore, as in structure 54 of FIG. 6, one EA member 20, 30 may have three or more closed spaces 24, 34. In structure 54, the plate members 22, 32 pass through one edge more than twice. Therefore, in structure 54, the edges that form the multiple closed spaces 24, 34 include a mixture of edges formed by a single plate and edges formed by two overlapping plates. In this case, strength variations will occur depending on the location of the EA members 20, 30. However, if the benefits of increasing the number of closed spaces 24, 34 outweigh the disadvantages of such strength variations, structure 54 can be considered sufficiently useful. Furthermore, the disadvantage of variations in strength can be alleviated by arranging two or more EA members 20, 30 in 180-degree symmetrical positions.

[0036] Although the closed spaces 24, 34 have been illustrated as being substantially rectangular in shape in the above examples, the shapes of the closed spaces 24, 34 may be modified as appropriate. For example, as shown in structure 56 in FIG. 6, the EA members 20, 30 may be configured such that substantially triangular closed spaces 24, 34 are arranged in succession. In this case, the plate members 22, 32 move clockwise (or counterclockwise) to form one triangle, and then move counterclockwise (or clockwise) to form another triangle. That is, the plate members 22, 32 reverse their direction of movement each time a triangle is completed, thereby continuously forming multiple triangles. This configuration allows the formation of three or more closed spaces 24, 34 while avoiding overlapping of the plate members 22, 32.

[0037] Furthermore, the multiple closed spaces 24, 34 may be arranged in an array in two directions, vertically and horizontally, rather than in one direction. For example, as shown in structure 58 in FIG. 6 , multiple closed spaces 24, 34 may be arranged in both the vertical and horizontal directions. In the above description, both the first EA member 20 and the second EA member 30 are roll-formed products made of iron-based metal. However, as long as at least the first EA member 20 is formed by bending a single seamless plate material 22, the second EA member 30 may be an extrusion-formed product or may be formed by joining multiple components. In the above description, the component to be protected 10 protected by the EA members 20, 30 is the battery unit 12. However, the component to be protected 10 may be any other component located below the vehicle floor panel 16. For example, the component to be protected 10 may be a fuel tank or a fuel cell. [Explanation of symbols]

[0038] 10 Protected part, 12 Battery unit, 14 Base plate, 16 Floor panel, 18 Side frame, 20 First EA member, 22 First plate member, 24, 34 Enclosed space, 26 Partition wall, 30 Second EA member, 32 Second plate member, 46 Bolt, 50, 52, 54, 56, 58 Structure, 100 Obstacle, EE End, SE Start.

Claims

1. a part to be protected that is disposed under a floor panel of a vehicle; a first shock absorbing member that can be bent one or more times and is made up of a single seamless first plate material; a second impact absorbing member disposed adjacent to the first impact absorbing member on the outer side in the vehicle width direction; Equipped with The first impact absorbing member includes two or more closed spaces surrounded by the first plate member, the two or more closed spaces being arranged in a vertical direction or a horizontal direction, The first impact absorbing member is fastened to the protected part and the vehicle body. A vehicle undercarriage characterized by:

2. The vehicle underbody structure according to claim 1, the second impact absorbing member is formed of a single seamless second plate material that is bent one or more times, and includes two or more closed spaces that are surrounded by the second plate material and aligned in the vertical or horizontal direction, the first impact absorbing member is joined to the second impact absorbing member, The arrangement direction of the two or more closed spaces of the second impact absorbing member is the same as the arrangement direction of the two or more closed spaces of the first impact absorbing member. A vehicle undercarriage characterized by:

3. The vehicle underbody structure according to claim 2, A vehicle underbody structure, wherein a vehicle width direction dimension of the first impact absorbing member and a vehicle width direction dimension of the second impact absorbing member are different from each other.

4. The vehicle underbody structure according to claim 3, the first impact absorbing member and the second impact absorbing member each have two or more closed spaces that are aligned in the vertical direction and penetrate in the vehicle front-rear direction, The vehicle width direction dimension of the first impact absorbing member is larger than the vehicle width direction dimension of the second impact absorbing member. A vehicle undercarriage characterized by:

5. The vehicle underbody structure according to claim 1, the first impact absorbing member has two closed spaces formed by the first plate member bent into a substantial figure-8 shape, the second impact absorbing member is bent into a substantially figure-8 shape and has two closed spaces formed by a single seamless second plate member, an end portion of the first plate member and an end portion of the second plate member are welded to a middle portion of the first plate member and a middle portion of the second plate member, respectively; the component to be protected is a battery unit, The first plate material and the second plate material are both made of an iron-based metal. A vehicle undercarriage characterized by:

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