Side sill structure of automobile

Abstract

An impact absorbing structure 2 is disposed within a closed cross-sectional space 3 of a side sill 1. This impact absorbing structure 2 is composed of: a cross-sectional hollow member 4 provided along a vehicle front-rear direction within the closed cross-sectional space 3 so as to vertically partition the closed cross-sectional space 3; and bulk heads 6, which are members for partitioning a closed cross-sectional space 5 of the cross-sectional hollow member 4 by being provided along a vehicle width direction within the closed cross-sectional space 5, and are provided at a plurality of places spaced apart in the vehicle front-rear direction within the closed cross-sectional space 5. Each bulk head 6 is joined to the inner wall of the cross-sectional hollow member 4.

Description

Automobile side sill structure

[0001] The present invention relates to a side sill structure for the side of an automobile body, and particularly to a side sill structure suitable for an automobile equipped with a battery module below a floor panel between both side sills.

[0002] Electric vehicles typically have a battery module mounted under the floor panel. The battery module consists of battery cells (battery packs) and a battery case to house them. The battery case generally protects the battery cells from impact loads and is made of high-rigidity, high-proof stress / high-durability materials. The battery case is surrounded by components that absorb energy by deforming. In particular, in the case of a side collision, the side sill absorbs the impact load from the side of the vehicle, while the remaining load is supported by the floor cross member or battery case side member. If the deformation required for energy absorption by the side sill is small, the energy absorption area can be reduced, allowing the battery module volume to be expanded, thereby increasing the vehicle's driving range. For these reasons, a lightweight side sill structure with excellent collision energy absorption properties is required.

[0003] Conventional techniques for increasing the stiffness of side sills and improving their energy absorption performance during a side collision include, for example, the following: Patent Document 1 discloses a technique for preventing the collapse of the cross-section of a side sill during a side collision by providing a bulkhead along the vehicle width direction inside the closed sectional space of a side sill of a closed cross-section structure that forms the side of an automobile. A flange is formed on the outer periphery of the bulkhead and is welded to a reinforcement within the side sill. Patent Documents 2 and 3 disclose techniques for preventing the collapse of the cross-section of a side sill during a side collision, in which the closed sectional space within the side sill is partitioned into two closed sectional spaces in the vehicle width direction by a partition member / stiffener that runs vertically through the side sill. The combination of the bulkheads and the partition member provides multiple bulkheads along the vehicle width direction within the closed sectional space within the side sill. In these technologies, the partition member is provided to prevent the side sill from opening up and down and collapsing in the cross section during a side collision. In Patent Document 2, the bulkhead is disposed only on one side of the partition member in the closed cross section space within the side sill. On the other hand, in Patent Document 3, the bulkheads are disposed on both sides of the partition member in the closed cross section space within the side sill.

[0004] Patent Document 4 discloses a technology in which a closed cross-sectional space within a side sill is divided into two closed cross-sectional spaces in the vehicle width direction by a partition member that runs vertically through the side sill, and hat-shaped cross-sectional impact absorption members are arranged on both sides of the partition member (inside and outside of the partition member). Patent Document 5 discloses a technology in which an impact absorbing member having a plurality of ridges spaced apart along the vehicle width direction and a wave-shaped member that extends up and down along the vehicle front-rear direction is arranged in the closed cross-sectional space within the side sill, thereby suppressing local deformation while maintaining impact absorption capacity.

[0005] JP 10-59218 A JP 2009-202620 A JP 2013-49378 A JP 2017-226353 A JP 2021-146973 A JP 2023-78067 A

[0006] The technology disclosed in Patent Document 1 has a bulkhead structure that is prone to buckling, which easily occurs during a side collision. Once buckling occurs, the cross-sectional collapse of the side sill occurs. This prevents adequate collision energy absorption. Furthermore, in a side sill having a partition member, as in the technologies disclosed in Patent Documents 2 and 3, even when a bulkhead is disposed in a closed cross-sectional space within the side sill, sufficient collision energy absorption characteristics are not achieved. In particular, in the technology disclosed in Patent Document 2, the bulkhead is disposed only in one closed cross-sectional space sandwiched between the partition member, so it only functions to maintain the cross-sectional shape of that closed cross-sectional space, and therefore sufficient collision energy absorption characteristics are not achieved. Furthermore, even when bulkheads are disposed in both spaces sandwiched between the partition member, as in the technology disclosed in Patent Document 3, the resulting collision energy absorption characteristics are insufficient.

[0007] Furthermore, the technology disclosed in Patent Document 3 requires the creation of slits in the partition member to allow the insertion of the bulkhead. When multiple bulkheads are installed along the longitudinal direction of the side sill, the spacing between the bulkheads cannot be increased to avoid a decrease in the strength of the partition member due to the slits. This results in a problem of increased weight due to the increased number of bulkheads installed. Furthermore, in a side sill having a partition member, simply placing hat-shaped impact absorbing members on both sides of the partition member (inside and outside of the partition member), as in the technology disclosed in Patent Document 4, sufficient collision energy absorption characteristics cannot be achieved. Furthermore, the technology disclosed in Patent Document 5 achieves high collision energy absorption characteristics by distributing and uniformly transmitting the impact load during a side collision across a cross section perpendicular to the vehicle width direction. However, a side sill internal reinforcement member with a constant cross section in the vehicle longitudinal direction may be excessively heavy due to the presence of stiffened members in areas that do not require reinforcement.

[0008] In contrast to the above-described conventional technology, Patent Document 6 discloses a technology for providing a shock absorbing structure of a specific structure within a closed cross-sectional space within a side sill using a partition member that runs vertically through the closed cross-sectional space. This shock absorbing structure is composed of a pair of grooved cross-section members joined to each other on both sides of the partition member, and multiple bulkheads that are installed under predetermined conditions within the two closed cross-sectional spaces formed between the grooved cross-section members and the partition member. This technology enables a side sill structure to achieve high collision energy absorption characteristics with minimal collision deformation. Furthermore, because the shock absorbing structure achieves high bending rigidity with fewer components, it also minimizes the increase in vehicle weight due to the components. However, this side sill structure has been found to have the following issues.

[0009] The outer bulkhead and inner bulkhead are located opposite each other across the vehicle width, sandwiching a partition member between them. The two bulkheads must be precisely aligned, requiring strict assembly precision. This is because even slight misalignment of the two bulkheads in the longitudinal direction of the vehicle during assembly can reduce load transfer and potentially prevent the desired collision energy absorption characteristics from being achieved. This requires labor-intensive assembly, which, combined with the increased assembly man-hours, increases manufacturing costs. Furthermore, because the impact absorption structure is constructed by joining a pair of sectional groove-shaped members (or cross-section grooved members) to sandwich the partition member from both sides, this places restrictions on the shape of the partition member, potentially hindering vehicle weight reduction. For example, while partition members can be drilled to reduce weight if they can withstand tensile loads, drilling holes may not be possible due to the need to join the cross-section grooved members, limiting vehicle weight reduction. Furthermore, since a pair of groove-shaped cross-section members are joined to the partition member via flanges, it is necessary to leave a gap (space) in the vertical direction equal to the width of the flanges. This may result in a reduction in the design freedom of the impact absorption structure, such as shortening the vertical dimension of the vehicle body or restricting its vertical position within the side sill.

[0010] The present invention has been made to solve the above-mentioned problems, and its object is to provide an automobile side sill structure that can obtain high collision energy absorption characteristics with a small amount of collision deformation while suppressing weight increase due to structural members, is easy to assemble with a small number of assembly steps, and is also advantageous in increasing the design freedom of the impact absorbing structure.

[0011] The inventors of the present invention have conducted extensive research to solve the above-mentioned problems and have found that the problem can be solved by providing a shock absorbing structure with a specific structure within the closed cross-sectional space of the side sill without the need for a partition member (a member sandwiched between the side sill outer and inner panels to divide the closed cross-sectional space into an outer and inner side; the same applies hereinafter). Specifically, the inventors have found that providing a shock absorbing structure with an integrated structure comprising a sectional hollow-shaped member (or cross-section hollow member) extending along the vehicle longitudinal direction to divide the closed cross-sectional space of the side sill into upper and lower sections, and multiple bulkheads installed within the closed cross-sectional space of the cross-section hollow member under predetermined conditions, can achieve high energy absorption performance while minimizing the weight increase due to the structural members, and also solve the problems of the prior art (particularly Patent Document 6). The present invention was made based on this finding and is summarized as follows.

[0012] The automobile side sill structure of the present invention is an automobile side sill structure comprising side sills (1) extending along the longitudinal direction of the vehicle on both sides of the lower part of the vehicle, and an impact absorbing structure (2) arranged in a closed cross-sectional space (3) within the side sill (1), the impact absorbing structure (2) having a closed cross-sectional space (5) formed inside thereof, the impact absorbing structure (2) being composed of a hollow cross-sectional member (4) arranged within the closed cross-sectional space (3) along the longitudinal direction of the vehicle so as to divide the closed cross-sectional space (3) into upper and lower parts, and bulkheads (6) arranged at multiple locations spaced apart in the longitudinal direction of the vehicle within the closed cross-sectional space (5) as members that divide the closed cross-sectional space (5) by being arranged within the closed cross-sectional space (5) of the hollow cross-sectional member (4) along the width direction of the vehicle, and each bulkhead (6) being joined to the inner wall of the hollow cross-sectional member (4).

[0013] The bulkhead (6) is preferably joined to at least the inner wall of the vertical surface portion (40) on the vehicle inner side and the inner wall of the upper horizontal surface portion (41A) and / or the lower horizontal surface portion (41B) of the cross-sectional hollow member (4).

[0014] The bulkhead (6) is a bulkhead (6) provided in an area within the width of the floor cross member in the vehicle longitudinal direction. ｘ ) and a bulkhead (6) provided in the area outside the width of the floor cross member ｙ ) and in the vehicle longitudinal direction, bulkheads (6) are provided at two or more locations within the width of the floor cross member. ｘ ) is provided, and a bulkhead (6) is provided at one or more locations in the area outside the width of the floor cross member. ｙ ) are provided, and two adjacent bulkheads (6 ｘ ) spacing is w1, bulkhead (6 ｘ ) and the adjacent bulkhead (6 ｙ ) is w2, it is advisable to make w1 < w2.

[0015] At least some of the bulkheads (6 ｙ ) may comprise a bulkhead set consisting of two or more bulkheads arranged adjacent to each other.

[0016] Preferably, the vertical surface portion (40) of the hollow cross-section member (4) and the opposing vertical surface portion (100) of the side sill (1) are joined together.

[0017] The vertical surface portion (40) of the cross-sectional hollow member (4) and the opposing vertical surface portion (100) of the side sill (1) are in contact with each other or face each other at a predetermined distance, and the cross-sectional hollow member (4) is preferably supported on the side sill (1) via a support member (15).

[0018] Preferably, beads are formed on the lateral faces (41) of the cross-sectional hollow member (4) and / or on the bulkhead (6).

[0019] The metal plate constituting the shock absorbing structure (2) preferably has a tensile strength of 590 MPa or more.

[0020] The automotive side sill structure of the present invention provides high collision energy absorption characteristics with minimal collision deformation by providing an impact absorption structure 2 with a specific structure within the closed cross-sectional space 3 of the side sill 1. Therefore, when applied to a vehicle equipped with a battery module between both side sills, such as an electric vehicle, the space required for energy absorption can be reduced, thereby enabling the volume of the battery module to be increased. Furthermore, the impact absorption structure 2 is provided within the closed cross-sectional space of the side sill without any intervening partition member, achieving high bending rigidity with a minimum number of components, thereby minimizing the increase in vehicle weight due to the components of the side sill structure, including the impact absorption structure 2. Furthermore, the impact absorption structure 2 is provided within the closed cross-sectional space 3 of the side sill 1 without any intervening partition member, and each bulkhead 6 provided within the hollow cross-sectional member 4 is a single member integrated in the vehicle width direction. This ensures reliable load transmission in the vehicle width direction, thereby achieving the desired collision energy absorption characteristics. Furthermore, because the bulkhead 6 is a single member integrated in the vehicle width direction, the impact absorption structure 2 is easily assembled, requiring fewer assembly steps. Furthermore, because the hollow cross-sectional member 4 is installed without a partition member, there is no need to provide upper and lower flanges for joining to the partition member. This eliminates the need to provide gaps (spaces) above and below the hollow cross-sectional member 4 for the flanges, which has the advantage of increasing the degree of freedom in designing the impact absorption structure 2. This makes it possible to increase the vertical dimension of the impact absorption structure 2 on the vehicle body and reduce vertical positional constraints within the side sill 1.

[0021] FIG. 1 is a schematic diagram of an embodiment of a side sill structure for a vehicle according to the present invention, showing a longitudinal cross-section of the side sill in the vehicle width direction. FIG. 2 is a cross-section taken along line II-II in FIG. 1. FIG. 3 is a longitudinal cross-section of a vehicle body side including a side sill in the embodiment of FIG. 1, shown in the vehicle width direction. FIG. 4 is an exploded view of a component of an embodiment of a side sill structure for a vehicle according to the present invention. FIG. 5 is an explanatory diagram showing an exploded view of a floor panel, a floor cross-member, and a battery case disposed between both side sills of the vehicle body. FIG. 6 is an explanatory diagram showing another example of the arrangement of a bulkhead in the side sill structure for a vehicle according to the present invention. FIG. 7 is an explanatory diagram showing another example of the arrangement of a bulkhead in the side sill structure for a vehicle according to the present invention. FIG. 8 is a diagram illustrating the width wa of the floor cross-member according to the present invention. FIG. 9 is a diagram (cross-sectional view of the side sill) illustrating the width We of the impact absorbing structure and the width Ws of the side sill in the vehicle width direction for the embodiment of FIG. 1. FIG. 10 is a schematic diagram of another embodiment of a side sill structure for a vehicle according to the present invention, showing a longitudinal cross-section of the side sill in the vehicle width direction. FIG. 11 is an explanatory diagram showing an example of a support structure for an impact absorption structure in an automobile side sill structure according to the present invention. FIG. 12 is a schematic longitudinal cross-sectional view of another embodiment of an automobile side sill structure according to the present invention, taken in the vehicle width direction. FIG. 13 is an explanatory diagram showing an example of the structure of a hollow cross-section member constituting an impact absorption structure in an automobile side sill structure according to the present invention. FIG. 14 is an explanatory diagram showing, in a horizontal cross-section, the step-by-step deformation state during a side pole crash of an automobile side sill structure according to the present invention. FIG. 15 is a graph showing the relationship between the impact object (pole) penetration amount and absorbed energy when an automobile side sill structure according to the present invention is deformed in a side pole crash. FIG. 16 is an explanatory diagram showing the side sill structures and test conditions of an example and a comparative example in a crash test of an example. FIG. 17-1 is a graph showing the relationship between the impact object (punch) penetration amount, punch reaction force, and absorbed energy in a crash test of an example (example). FIG. 17-2 is a graph showing the relationship between the impact object (punch) penetration amount, punch reaction force, and absorbed energy in a crash test of an example (comparative example).FIG. 18 is a graph showing the absorbed energy at the maximum penetration of the impact body (punch) in the impact test of Examples (inventive examples and comparative examples).

[0022] 1 to 3 are schematic diagrams illustrating an embodiment of a side sill structure for an automobile according to the present invention. FIG. 1 is a longitudinal cross-sectional view of the side sill structure in the vehicle width direction, FIG. 2 is a cross-sectional view taken along line II-II in FIG. 1, and FIG. 3 is a longitudinal cross-sectional view of a vehicle body side structure including a side sill in the vehicle width direction. Also, FIG. 4 is an exploded view of one embodiment of the side sill structure for an automobile according to the present invention, and FIG. 5 is an explanatory view showing an exploded view of a floor panel, a floor cross member, and a battery case disposed between both side sills. The side sill structure for an automobile according to the present invention will be described below using the embodiment shown in FIGS. 1 to 3 as an example.

[0023] <Basic Structure of Side Sill and Its Surrounding Area> The side sill 1 is constructed by joining a side sill outer 1a and a side sill inner 1b, each of which has a groove-shaped cross section, and a closed cross-sectional space 3 is formed within the side sill 1. Details of this side sill structure will be described later. The vehicle underbody structure including the side sill will be described with reference to FIG. 3 . The side sill 1 is a frame structure member disposed on both sides of the vehicle's lower body. A floor panel 7 is disposed between the side sills 1, and this floor panel 7 is joined to both side sills 1 (in FIG. 3, the upper part of the vertical surface portion 100 of the side sill inner 1b) via its two flange portions 70. Furthermore, a floor cross member 8, a frame structure member extending along the vehicle width direction, is disposed on the floor panel 7, and both ends of the floor cross member 8 are joined to both side sills 1 (in FIG. 3, the upper part of the vertical surface portion 100 of the side sill inner 1b) via the floor panel 7 (flange portion 70). The floor cross members 8 are provided at multiple locations at predetermined intervals (e.g., approximately 300 mm) in the vehicle's fore-and-aft direction. The joining of the floor panel 7 and floor cross member 8 to the side sill 1 is usually performed by spot welding.

[0024] A battery case 9 containing a battery pack 10 is disposed below the floor panel 7. The side of the battery case 9 (battery case side member 90) faces the lower part of the side sill 1 (the lower part of the vertical surface 100 of the side sill inner panel 1b) at a predetermined distance. A mounting flange 92 is connected to the bottom of the battery case 9 (battery case bottom plate 91) so as to protrude toward the side sill. The battery case 9 is held to the side sill 1 by fastening this mounting flange 92 to the lower end of the side sill 1 (the lower horizontal surface 101B of the side sill inner panel 1b) with fixing bolts 11. With this structure, the load input to the side sill 1 during a side collision is input to both the floor cross member 8 and the battery case 9, allowing the load to be borne over a wide area. Furthermore, the load during a side collision is input to the floor cross member 8 before the battery case 9, thereby reducing the load input to the battery case 9.

[0025] The side sill outer 1a and side sill inner 1b that make up the side sill 1 are formed by molding metal plates. These components 1a and 1b each include a main body portion with a groove-shaped cross section, consisting of a vertical surface portion 100 and horizontal surfaces 101A and 101B connected to the upper and lower ends thereof, and flange portions 102 connected to both ends (the ends of the horizontal surfaces 101A and 101B). The vertical surface portion 100 does not have to be vertical and may have a suitable inclination or curved surface. Furthermore, the horizontal surfaces 101A and 101B do not have to be horizontal and may have a suitable inclination or curved surface. The side sill outer 1a and the side sill inner 1b are joined (usually by spot welding) with their flange portions 102 overlapping each other to form the side sill 1, which defines a closed cross-sectional space 3 therein.

[0026] <Impact Absorption Structure 2 in Side Sill Structure> The side sill structure described above is characterized in that the present invention provides an impact absorption structure 2 with a specific structure within the closed cross-sectional space 3 within the side sill 1. Specifically, the impact absorption structure 2 is provided within the closed cross-sectional space 3 of the side sill 1. The impact absorption structure 2 is comprised of a hollow cross-sectional member 4 arranged along the vehicle longitudinal direction to divide the closed cross-sectional space 3 into upper and lower sections, and multiple bulkheads 6 with a specific structure and arrangement arranged within the closed cross-sectional space 5 of the hollow cross-sectional member 4, and is structurally integrated into the closed cross-sectional space 5. This allows the side sill structure to achieve high impact energy absorption characteristics with minimal impact deformation. Furthermore, the impact absorption structure 2 is provided within the closed cross-sectional space 3 of the side sill 1 without any intervening partition member, achieving high bending rigidity with the minimum necessary components (especially the minimum number of bulkheads). This also minimizes the increase in vehicle weight due to the components of the side sill structure, including the impact absorption structure 2. The impact absorption structure 2 is provided in a portion of the side sill along at least the battery case side member 90 in the vehicle longitudinal direction.

[0027] The hollow cross-section member 4 defines a closed cross-section space 5 therein and is arranged along the vehicle longitudinal direction (longitudinal direction of the side sill) within the closed cross-section space 3 of the side sill 1 so as to divide the closed cross-section space 3 into upper and lower sections. In this embodiment, the hollow cross-section member 4 is composed of a grooved cross-section member 4a that opens downward and a plate-shaped lid structure 4b that closes the downward opening (open side) of the grooved cross-section member 4a. The members that make up the hollow cross-section member 4 (the grooved cross-section member 4a and the lid structure 4b) are formed by bending a metal plate. Joining flanges 42 are formed on both widthwise ends of the lid structure 4b. The lid structure 4b is fitted into the opening of the grooved cross-section member 4a so that both flanges 42 are in close contact with the inside of the opening (i.e., the inside of the tip ends of both flanges of the grooved cross-section member 4a), and both flanges 42 are joined to the grooved cross-section member 4a. This joining is usually achieved by spot welding. The flange portion 42 may be formed only on a portion of the cover member 4b in the longitudinal direction (for example, formed intermittently at predetermined intervals).

[0028] The hollow cross-section member 4 configured as described above is a member having a substantially horizontally elongated rectangular cross section in the vehicle width direction, which includes upper and lower horizontal surface portions 41A, 41B and both vehicle outer and vehicle inner vertical surface portions 40, and the interior of the member defines a closed cross-section space 5. That is, in this substantially horizontally elongated rectangular cross-section member, the upper and lower horizontal surface portions 41A, 41B are the upper and lower surfaces, respectively, and the vehicle outer and vehicle inner vertical surface portions 40 are the side surfaces. Because the hollow cross-section member 4 has a substantially horizontally elongated rectangular cross section in the vehicle width direction as described above, the load during a side collision is efficiently transmitted to the floor cross member 8 and the battery case 9. The hollow cross-section member 4 is disposed at a vertically intermediate position within the closed cross-section space 3 of the side sill 1 so as to separate the closed cross-section space 3 into upper and lower portions. As shown in Figure 3, the hollow cross-sectional member 4 is preferably disposed so that the height position of the vertical surface portion 40 of the hollow cross-sectional member 4 overlaps with at least one (preferably both) of the floor cross-member 8 and the battery case 9. In this case, it is preferable to adjust the height overlap between the vertical surface portion 40 and the floor cross-member 8 and the battery case 9 so that the load input to the floor cross-member 8 and the battery case 9 is appropriately balanced. In addition, it is also preferable to adjust the distance (space) between the upper and lower horizontal surface portions 41A, 41B of the hollow cross-sectional member 4 and the side sills (the upper and lower horizontal surface portions 101A, 101B of the side sill outer 1a and the side sill inner 1b) from the same perspective.

[0029] In this embodiment, the two vertical surfaces 40 of the hollow cross-section member 4 face the two vertical surfaces 100 of the side sill 1 at a predetermined distance. Therefore, the hollow cross-section member 4 is supported on the side sill 1 by a separately installed support member (not shown). This structure will be described in detail later. The vehicle outer vertical surface 40 of the hollow cross-section member 4 constitutes a pressure-receiving surface portion that receives a side impact load, and the upper and lower lateral surfaces 41A, 41B constitute energy-absorbing surface portions that deform due to the side impact load to absorb the impact energy. Because the hollow cross-section member 4 is installed without a partition member, there is no need to provide upper and lower flanges for joining to the partition member. This eliminates the need for gaps (spaces) above and below the hollow cross-section member 4 for the flanges, resulting in advantages such as increased vertical dimensions of the impact absorbing structure 2 and reduced vertical positioning constraints within the side sill 1.

[0030] The bulkheads 6 are members disposed within the closed cross-sectional space 5 of the hollow cross-sectional member 4 along the vehicle width direction to partition the closed cross-sectional space 5, and are disposed at multiple locations within the closed cross-sectional space 5 at intervals in the vehicle longitudinal direction. The bulkheads 6 are preferably disposed so as to partition the entire cross section of the closed cross-sectional space 5 in the vehicle width direction. The bulkheads 6 suppress cross-sectional collapse of the hollow cross-sectional member 4 and absorb collision energy by buckling and undergoing bending collapse. In the impact absorption structure 2 of the present invention, the bulkheads 6 disposed within the closed cross-sectional space 5 along the vehicle width direction are a single member integral with the vehicle width direction, ensuring reliable load transmission in the vehicle width direction and achieving the desired impact energy absorption characteristics. Furthermore, because the bulkheads 6 are a single member integral with the vehicle width direction, assembly of the impact absorption structure 2 is facilitated and requires fewer assembly steps.

[0031] Each bulkhead 6 is formed from a metal plate, and its outer peripheral edge is joined to the inner wall of the hollow cross-sectional member 4 (the peripheral wall of the closed cross-sectional space 5). Of the inner walls of the hollow cross-sectional member 4 that form the closed cross-sectional space 5, each bulkhead 6 is preferably joined to at least the inner wall of the vehicle-inner-side vertical surface 40, which is subject to significant deformation due to a side collision load, and at least one of the inner walls of the upper horizontal surface 41A and the lower horizontal surface 41B. In this case, it is more preferable that each bulkhead 6 be joined to the inner walls of both the upper horizontal surface 41A and the lower horizontal surface 41B. Furthermore, each bulkhead 6 may also be joined to the vehicle-outer-side vertical surface 40, so that each bulkhead 6 is joined to all four inner walls of the hollow cross-sectional member 4. In this embodiment, a flange 61 is formed on the outer peripheral edge of the bulkhead 6's main body (partition wall) (see FIG. 4 ), and the bulkhead 6 is joined to the inner wall of the hollow cross-sectional member 4 via this flange 61. This joining is typically achieved by spot welding. The flange portion 61 may be formed only on a portion of the outer peripheral edge of the main body (partition portion) that is joined to the inner wall of the hollow cross-sectional member 4. The bulkheads 6 may be provided at equal intervals in the vehicle longitudinal direction within the closed cross-sectional space 5, or, for example, may be provided so that wide intervals and narrow intervals alternate as shown in Figure 2, or may be provided at different intervals in different regions in the vehicle longitudinal direction, as will be described later.

[0032] As described above, the impact absorption structure 2 is comprised of the hollow cross-sectional member 4, which is provided in the closed cross-sectional space 3 of the side sill 1 along the vehicle longitudinal direction so as to divide the closed cross-sectional space 3 into upper and lower sections, and a plurality of bulkheads 6 of a specific structure and arrangement provided in the closed cross-sectional space 5 of this hollow cross-sectional member 4, and these are structurally integrated. In other words, the hollow cross-sectional member 4 contains the bulkheads 6 of a specific structure that are arranged at intervals in the vehicle longitudinal direction, forming an integrated structure. This results in high impact energy absorption characteristics as described below.

[0033] The yield strength of the metal plates constituting the impact absorption structure 2 (the hollow cross-section member 4 and the bulkhead 6) is preferably equal to or lower than the yield strength of the metal plates constituting the floor cross-member 8. This is to ensure that, during a side collision, the impact absorption structure 2 deforms before the floor cross-member 8 to absorb the impact energy, thereby suppressing deformation of the floor cross-member 8. For this reason, if the yield strength of the metal plates of the impact absorption structure 2 is equivalent to the yield strength of the metal plates of the floor cross-member 8, it is preferable to provide a crash bead in a portion of the impact absorption structure 2 so that its buckling strength (the load at which the member itself begins to buckle; the same applies below) is lower than that of the floor cross-member 8. Specifically, it is preferable to provide a bead 60 (crash bead) or the like, as shown in FIG. 12( b ), to the lateral surface portions 41 (41A, 41B) of the bulkhead 6 and / or hollow cross-section member 4 constituting the impact absorption structure 2.

[0034] Furthermore, the metal plates used for the impact absorption structure 2 (the hollow cross-section member 4 and the bulkhead 6) preferably have a tensile strength of 590 MPa or higher. Regarding the impact absorption structure 2's collision characteristics, the higher the load (hereinafter referred to as "yield strength") at which the impact absorption structure 2 changes from elastic deformation immediately after deformation begins to plastic deformation during a side collision, the less likely it is to deform during a collision, resulting in better impact characteristics. Since the higher the tensile strength of the metal plates used for the impact absorption structure 2, the higher the yield strength is. Therefore, metal plates with a tensile strength of 590 MPa or higher, which is higher than that of ordinary steel, are preferred. Furthermore, if high-tensile steel sheets are used as the metal plates (material) for the impact absorption structure 2, the impact absorption structure 2 disposed inside the side sill 1 also functions as a reinforcement for the side sill. Therefore, it is particularly preferred that the metal plates used for the impact absorption structure 2 be high-tensile steel sheets with a tensile strength of 1180 MPa or higher.

[0035] <Functions, Effects, and Effects of Impact Absorption Structure 2> The impact absorption structure 2 included in the automotive side sill structure according to the present invention has an integrated structure comprising a hollow cross-section member 4 that is provided under predetermined conditions within the closed cross-sectional space 3 of the side sill 1 and a plurality of bulkheads 6 that are provided under predetermined conditions within the closed cross-sectional space 5 of the hollow cross-section member 4. In other words, the hollow cross-section member 4 contains the bulkheads 6 that are arranged at intervals in the fore-and-aft direction of the vehicle, and these are integrated into one structure. Due to this structure, the entire impact absorption structure 2 has high bending stiffness (bending deformation resistance against a side collision load). This suppresses local deformation around the input point of the side collision load, and by deforming the entire impact absorption structure 2 during a side collision, impact energy absorption (EA) can be improved.

[0036] During a side collision, the vertical surface 40 (pressure-receiving surface) on the vehicle outer side of the hollow cross-section member 4 receives the collision load through the side sill outer panel 1a, and the upper and lower horizontal surfaces 41A, 41B (energy-absorbing surfaces) bend and collapse, absorbing the collision energy. At this time, the bulkhead 6 integrated with the hollow cross-section member 4 prevents the cross-sectional collapse of the hollow cross-section member 4, and the bulkhead 6 itself buckles (axially collapses) to absorb the collision energy. In this case, because the bulkhead 6, which is provided along the vehicle width direction within the closed cross-section space 5, is a single member integrated in the vehicle width direction, load transmission in the vehicle width direction is ensured, and the impact absorption structure 2 collapses under reaction forces from the floor cross-member 8 and the battery case 9, thereby appropriately achieving the desired collision energy absorption characteristics.

[0037] <Other Embodiments of the Impact Absorption Structure 2> Figure 6 shows other examples of the arrangement of the bulkheads 6 in the vehicle longitudinal direction, in which the bulkheads 6 are provided at different intervals in each region in the vehicle longitudinal direction. The bulkheads 6 in these arrangements are the bulkheads 6 provided in the region within the width wa of the floor cross member 8 in the vehicle longitudinal direction. ｘ and the bulkhead 6 provided in the other area (area outside the width of the floor cross member 8). ｙIn the vehicle longitudinal direction, the bulkhead 6 is provided at two or more locations (two locations in the embodiment of FIG. 6) within the width wa of the floor cross member 8. ｘ and a bulkhead 6 is provided at one or more locations in the area outside the width of the floor cross member 8. ｙ Furthermore, two adjacent bulkheads 6 ｘ The distance between them is w1, and the bulkhead is 6. ｘ and the adjacent bulkhead 6 ｙ When the distance between the floor cross member 8 and the floor cross member 8 is w2, the relationship w1 < w2 is established. The reason for arranging the bulkheads 6 in this manner is as follows. In other words, in the area within the width wa of the floor cross member 8, the bulkheads 6 are located in two or more places. ｘ Bulkhead 6 ｘ By reducing the gap between the two, the collision characteristics are improved. On the other hand, the bulkhead 6 in the other area ｙ and Bulkhead 6 ｘ By increasing the distance between the floor cross member 8 and the bulkhead 6, the number of bulkheads 6 installed can be reduced, thereby reducing the weight. ｙ When two adjacent bulkheads 6 are provided, ｙ It is also preferable that the interval w3 between them satisfies w1<w3.

[0038] The width wa of the floor cross member 8 may be the width of the portion between both side walls in the width direction of the floor cross member. Figure 8 shows a schematic cross section of a typical floor cross member 8 in the width direction, which has flange portions on both edges. In this case, the width wa of the floor cross member 8 may be the width of the portion in the width direction of the floor cross member excluding the flange portions on both edges (the width of the main portion that functions as a framework member), i.e., the width between the points where the R of the flange portions begins. Bulkheads 6 are provided at multiple points within the width wa of the floor cross member 8. ｘ When arranging two adjacent bulkheads 6 ｘ If the distance w1 between the bulkheads 6 is too small, the effect of improving the collision characteristics within the width wa of the floor cross member 8 is reduced. ｘThis will lead to an unnecessary increase in the number of installations. ｘ It is preferable that the widths w1 and w1 of the floor cross member 8 are arranged so that the ratio w1 / wa of the width w1 and w1 of the floor cross member 8 is 0.4 or more and 1.0 or less.

[0039] On the other hand, adjacent bulkhead 6 ｘ and Bulkhead 6 ｙ Distance w2 and bulkhead 6 ｙ The distance w3 between them is preferably 254 mm or less to ensure the bending rigidity of the impact absorption structure 2 in the event of a side collision. This 254 mm is the diameter of the impact body (pole) used in a side impact test (a side pole crash test specified by Euro NCAP). By making the distances w2 and w3 equal to or less than the diameter of the impact body (pole) used in this test, the bending rigidity of the impact absorption structure 2 in the event of a side collision can be more appropriately ensured. Also, from the same viewpoint, the distance between adjacent bulkheads 6 ｘ and Bulkhead 6 ｙ Distance w2 and bulkhead 6 ｙ The spacing w3 between them is preferably about 1 / 4 to 1 / 2 of the installation spacing of the floor cross members 8 (the spacing wb between adjacent floor cross members 8).

[0040] In the arrangement shown in FIG. 6( a ), the bulkhead 6 is provided at one location in an area between adjacent floor cross members 8 and outside the width of the floor cross members 8 . ｙ This is an example where a bulkhead 6 ｘ , 6 ｙ 6(b) and 6(c) are provided under the condition that w1<w2 is satisfied. In addition, in the arrangement form of FIG. 6(b) and 6(c), the bulkheads 6 are provided at two or three places in the area between the adjacent floor cross members 8 and outside the width of the floor cross members 8. ｙ This is an example where a bulkhead 6 ｘ , 6 ｙ are set under the condition that w1<w2 and w1<w3 are satisfied.

[0041] 7 shows another example of the arrangement of the bulkheads 6 in the longitudinal direction of the vehicle. In this arrangement, the bulkheads 6 are provided at different intervals in each region in the longitudinal direction of the vehicle, as in the embodiment of FIG. 6. However, in order to further increase the bending rigidity of the impact absorbing structure 2 between the floor cross members 8, the bulkheads 6 are arranged at different intervals. ｙ That is, the bulkhead 6 is provided in an area outside the width of the floor cross member 8. ｙ 7 is configured as a bulkhead set consisting of two or more adjacent bulkheads (two bulkheads in the embodiment of FIG. 7). ｙ The bulkhead 6 is made up of two bulkheads as a set. The size of the interval w4 between the bulkheads that make up this bulkhead set is arbitrary, but it is basically determined from the same perspective as the interval w1, so it should be set under the same conditions as the interval w1 described above. ｙ A bulkhead set consisting of two or more bulkheads is ｙ It may be targeted at some bulkheads 6 ｙ It may also be possible to target only

[0042] In the arrangement shown in FIG. 7( a ), the bulkhead 6 is provided at one location in an area between adjacent floor cross members 8 and outside the width of the floor cross members 8 . ｙ This is an example of a bulkhead set (a set of two bulkheads). ｘ , 6 ｙ 7(b) and 7(c) are provided under the condition that w1<w2 is satisfied. In addition, in the arrangement form of FIG. 7(b) and 7(c), the bulkheads 6 are provided at two or three places in the area between the adjacent floor cross members 8 and outside the width of the floor cross members 8. ｙ This is an example of a bulkhead set (a set of two bulkheads). ｘ , 6 ｙ are set under the condition that w1<w2 and w1<w3 are satisfied.

[0043] In the automotive side sill structure according to the present invention, the impact absorption structure 2 (hollow cross-section member 4) may have an appropriate gap (space) between the side sill outer 1a and the side sill inner 1b (their respective longitudinal surface portions 100) as shown in FIG. 1 (Mode 1). Alternatively, the impact absorption structure 2 (hollow cross-section member 4) may abut or be joined to the inner surfaces of the side sill outer 1a and the side sill inner 1b (their respective longitudinal surface portions 100) primarily to prevent vibration (Mode 2). In the case of Mode 1, if the gap between the impact absorption structure 2 (hollow cross-section member 4) and the side sill outer 1a and the side sill inner 1b is too narrow, the two components may come into contact with each other due to vibrations during driving, resulting in noise and further vibration problems. For this reason, it is preferable that the two components face each other with a gap that prevents contact due to vibrations during driving. Meanwhile, since impact absorption performance is improved by transmitting side impact loads to the floor cross member from the initial stage of a collision, the impact absorption performance is structurally higher the closer the width of the impact absorption structure 2 is to the full width of the side sill. For this reason, the width We of the impact absorption structure 2 (hollow cross-section member 4) in the vehicle width direction is preferably 60% or more of the width Ws of the side sill 1 (the distance between the vertical surface portions 100 of the side sill outer 1a and side sill inner 1b). Figure 9 shows the width We of the impact absorption structure 2 and the width Ws of the side sill 1. If the width We of the impact absorption structure 2 and the width Ws of the side sill 1 vary depending on the position in the vehicle height direction, the widths at the widest height positions are taken as Ws and We.

[0044] Various embodiments can also be employed in the case of the above-described second embodiment. FIG. 10 is a schematic diagram illustrating one such embodiment, showing a longitudinal cross-section of a side sill in the vehicle width direction. FIG. 10( a) shows an example in which the vertical surface portions 40 of the hollow cross-section member 4 are joined to the inner surfaces of the vertical surface portions 100 of the side sill outer 1a and the side sill inner 1b by welding (usually spot welding) (in the figure, reference numeral 12 denotes a joint). In the embodiment shown in FIG. 10( a), the vertical surface portions 40 may simply abut the vertical surface portions 100 rather than being joined to them. FIG. 10( b) shows an example in which the vertical surface portions 40 of the hollow cross-section member 4 are joined to the inner surfaces of the vertical surface portions 100 of the side sill outer 1a and the side sill inner 1b with an adhesive 13 (adhesive layer). When using adhesive 13 for bonding, the adhesive may be applied only to a portion of the joining surface. This adhesive 13 (adhesive layer) may also function as a vibration-damping member that damps vibrations.

[0045] As shown in FIG. 1 , when the impact absorption structure 2 (hollow cross-section member 4) is not joined to the side sill outer 1 a and side sill inner 1 b (their respective vertical surface portions 100), the impact absorption structure 2 is supported on the side sill 1 by a separately provided support structure. FIGS. 11( a) to 11(c) are explanatory diagrams showing examples of support structures for the impact absorption structure 2 (hollow cross-section member 4) using such support members 15. FIG. 11(a) shows an example in which the support member 15 is made of an L-shaped angle bar (a member with a mountain-shaped cross section). The L-shaped angle bar constituting the support member 15 is joined to the side sill 1 with the widthwise end of its wide side portion 150 sandwiched between the lower flange portions 102 of the side sill outer 1 a and side sill inner 1 b. The narrow side portion 151 of the L-shaped angle iron abuts against and is joined to the lower lateral surface portion 41B of the hollow cross-section member 4, thereby supporting the impact absorption structure 2 (hollow cross-section member 4) on the side sill 1 via the support member 15. Figure 11(b) shows an example in which a support member 15 made of a grooved cross-section member is used. One inclined surface portion 152 of the grooved cross-section member constituting the support member 15 abuts against and is joined to the inner surface of the lower part of the side sill outer panel 1a. The other inclined surface portion 152 of the grooved cross-section member abuts against and is joined to the lower lateral surface portion 41B of the hollow cross-section member 4, thereby supporting the impact absorption structure 2 (hollow cross-section member 4) on the side sill 1 via the support member 15.

[0046] 11(c) shows an example in which the shock absorbing structure 2 (hollow cross-section member 4) is supported by two support members 15A, 15B sandwiched from above and below using the same support member 15 made of L-shaped angle bars as in FIG. 11(a). The L-shaped angle bar constituting the upper support member 15A has its wide side portion 150 sandwiched between the upper flange portions 102 of the side sill outer member 1a and the side sill inner member 1b and joined to the side sill 1. The narrow side portion 151 of the L-shaped angle bar abuts and is joined to the upper lateral surface 41A of the hollow cross-section member 4. The L-shaped angle bar constituting the lower support member 15B has its wide side portion 150 sandwiched between the lower flange portions 102 of the side sill outer member 1a and the side sill inner member 1b and joined to the side sill 1. The narrow side portion 151 of the L-shaped angle member is abutted against and joined to the lower lateral surface portion 41A of the hollow cross-section member 4. As a result, the impact absorption structure 2 (hollow cross-section member 4) is supported on the side sill 1 via the two upper and lower support members 15A, 15B. The support members 15 in each of the embodiments shown in Figure 11 described above are formed by bending a metal plate.

[0047] As another example of a support structure for the impact absorption structure 2, a structure in which the impact absorption structure 2 (hollow cross-section member 4) is supported only by the upper support member 15A shown in FIG. 11( c) can be used. The support member 15 can be joined to the impact absorption structure 2 (hollow cross-section member 4) or the side sill 1 by at least one of welding (usually spot welding), mechanical fastening using bolts or rivets, or adhesive bonding. The support members 15 can be provided along the vehicle longitudinal direction to support the impact absorption structure 2 over its entire length, or can be provided intermittently in the vehicle longitudinal direction to support the impact absorption structure 2 at intervals in the longitudinal direction. Even when the impact absorption structure 2 (hollow cross-section member 4) is joined to the side sill outer member 1 a and the side sill inner member 1 b (their respective longitudinal surface portions 100) as shown in FIG. 10, a support structure using support members 15 as shown in FIG. 11 can also be used for reinforcement or other purposes.

[0048] Furthermore, beads may be provided on the bulkhead 6 and / or the bulkhead body (partition wall portion in the case of the bulkhead) on the lateral surface 41 (41A, 41B) of the hollow cross-section member 4 to increase or decrease their buckling strength (rigidity). Figure 12 is a longitudinal cross-sectional view of a side sill in the vehicle width direction, schematically illustrating an embodiment in which a bead is provided on the bulkhead 6. Figure 12(a) shows a side sill with a bead 60 extending along the vehicle width direction on the bulkhead body (partition wall portion) to increase the buckling strength. Figure 12(b) shows a side sill with a bead 60 extending along the vehicle width direction on the bulkhead body (partition wall portion) to decrease the buckling strength. The reason for providing the bead 60 as shown in Figure 12(b) has been explained above. In addition, beads similar to those shown in Figures 12(a) and (b) can be provided on the lateral surface 41 (lateral surface 41A and / or lateral surface 41B) of the cross-sectional hollow member 4 for the same purpose as above.

[0049] The structure of the hollow cross-sectional member 4 constituting the impact absorption structure 2 is not limited to the embodiment shown in FIGS. 1 to 3 , and various embodiments such as those shown in FIG. 13 are possible. FIGS. 13( a) to 13(f) are explanatory diagrams showing structural examples of the hollow cross-sectional member 4 constituting the impact absorption structure 2. FIG. 13(a) shows the hollow cross-sectional member 4 of the embodiment shown in FIGS. 1 to 3 . FIGS. 13(b) and 13(e) show a hollow cross-sectional member 4 having a substantially horizontally elongated rectangular cross section in the vehicle width direction, constructed by combining two angle-shaped cross-sectional members 4c (L-shaped angle members). A joining flange 42 is formed on the end of the wide side 43 of each angle-shaped cross-sectional member 4c, and this flange 42 abuts against and is joined to the inner surface of the end of the narrow side 44 of the mating angle-shaped cross-sectional member 4c. 13(c) shows a hollow cross-section member 4 having a substantially horizontally elongated rectangular cross section in the vehicle width direction, which is configured by a grooved cross-section member 4d that opens (opens) laterally toward the vehicle inner side and a plate-like lid member 4e that closes the lateral opening (opening) of the grooved cross-section member 4d. Joining flanges 42 are formed on the tips of both flanges that form the opening (opening) of the grooved cross-section member 4d, facing outward, and these flanges 42 are joined by abutting on the surfaces on both widthwise end sides of the lid member 4e.

[0050] Figure 13(d) shows a hollow cross-section member 4 having a substantially horizontally elongated rectangular cross-section in the vehicle width direction, which is formed by a channel cross-section member 4a that opens (opens) upward and a plate-shaped cover member 4b that closes the upward opening (opening) of the channel cross-section member 4a. Joining flange portions 42 are formed continuously at both widthwise ends of the cover member 4b. The cover member 4b is fitted into the opening of the channel cross-section member 4a so that both flange portions 42 are in close contact with the inside of the opening (i.e., the inside of the flange tips of the channel cross-section member 4a), and both flange portions 42 are joined to the channel cross-section member 4a. Figure 13(f) shows a hollow cross-section member 4 having a substantially horizontally elongated rectangular cross-section in the vehicle width direction, which is formed by a channel cross-section member 4d that opens (opens) laterally toward the vehicle outer side and a plate-shaped cover member 4e that closes the horizontal opening (opening) of the channel cross-section member 4d. As in Figure 13(c), the tips of both flanges constituting the opening (opening) of the groove-shaped cross-section member 4d are joined with outward-facing flanges 42, which abut and are joined to the surfaces of both widthwise ends of the cover member 4e. In each of the embodiments shown in Figure 13 described above, each member constituting the hollow cross-section member 4 is formed by bending a metal plate. Furthermore, the members constituting the hollow cross-section member 4 are usually joined together by spot welding. Furthermore, the flanges 42 may be formed only on a portion of the longitudinal direction of each member (for example, intermittently at a predetermined interval).

[0051] <Crash Deformation of Side Sill Structure During Side Collision> The crash deformation of the automobile side sill structure according to the present invention during a side collision will be described with reference to FIG. 14 . FIG. 14 shows the stage-by-stage deformation of the automobile side sill structure according to the present invention during a side pole collision in a horizontal cross section (cross section taken along line II-II in FIG. 1 ), where t indicates the time (in seconds) from the start of the collision. First, the cross-sectional deformation of the side sill 1 itself will be described. First, the upper and lower lateral surfaces 101A and 101B (energy absorption portions) of the side sill outer panel 1a bend and collapse outward, absorbing the collision energy (from 0.002 seconds onward). During this process of the side sill outer panel 1a collapsing, the lateral surfaces 101A and 101B (energy absorption portions) of the side sill outer panel 1a continue to bend and deform until 0.014 seconds later, absorbing the collision energy until they are completely collapsed. As the side sill outer 1a undergoes crushing and deformation as described above, the collision load is transmitted to the side sill inner 1b via the flange 102 of the side sill 1. Then, after 0.004 seconds, the flange sides of the lateral surfaces 101A, 101B (energy absorption portions) of the side sill inner 1b are bent in a convex shape toward the inside of the closed cross section of the side sill 1 and crushed.

[0052] As the cross-sectional deformation of the side sill 1 itself progresses, the impact absorption structure 2 also undergoes cross-sectional deformation as follows. The crushed side sill outer panel 1a comes into contact with the vehicle-outer-side vertical surface 40 of the hollow cross-section member 4, transmitting the collision load to the impact absorption structure 2. Crushing (axial crush) begins (from 0.002 seconds), in which the upper and lower horizontal surfaces 41A, 41B (energy absorption surfaces) of the hollow cross-section member 4 and the bulkhead 6 bend and deform into a bellows shape. The impact absorption structure 2, which extends along the vehicle's fore-and-aft direction, is pressed as a whole against the floor cross member 8 and battery case 9 via the side sill inner panel 1b. Therefore, the collision load transmitted to the impact absorption structure 2 is distributed and transmitted to the floor cross member 8 and battery case 9. The reaction force from the floor cross member 8 and battery case 9 is then transmitted to the impact absorption structure 2 (lateral surface portions 41A, 41B and bulkhead 6) at a position adjacent in the longitudinal direction of the vehicle to the side pole impact position (0.004 to 0.006 seconds). After that, deformation of the impact absorption structure 2 at the side pole impact position is accelerated, and bending deformation of the lateral surface portions 41A, 41B (energy absorption surfaces) adjacent in the longitudinal direction of the vehicle is also accelerated (0.008 to 0.012 seconds). Furthermore, the bulkhead 6 adjacent to the side pole impact position also bends (0.012 seconds or more).

[0053] FIG. 15 shows the relationship between the amount of penetration of the impacting object and the absorbed energy when the impactor is deformed during a side pole collision.

[0054] Collision object: rigid pole with radius 127 mm (equivalent to a diameter of 254 mm) Collision speed: 30.9 km / h Collision energy: 25 kJ

[0055] This test shows that the impact absorption structure 2 is mainly deformed, and is therefore capable of absorbing impact energy of 25 kJ when the impact object penetration amount is within 100 mm.

[0056] In the cross-sectional deformation of the side sill structure during a side collision as described above, the impact absorbing structure 2, which is installed within the side sill 1 and has a structure in which the hollow cross-section member 4 and the bulkhead 6 are integrated, has high deformation resistance. Therefore, the impact absorbing structure 2 does not deform locally in response to the input load (e.g., does not deform in a bending manner from the impact area), but deforms as a whole, thereby effectively and appropriately absorbing the collision energy. Therefore, the automotive side sill structure according to the present invention functions as follows in an automobile (particularly an electric automobile) equipped with a battery module below the floor panel 7 between both side sills 1 as shown in FIG. 3 . That is, the impact absorbing structure 2 collapses under the load input from the vehicle width direction during a side collision to absorb the energy, while transferring the load to the floor cross member 8 and the battery case 9, thereby preventing the load from being transferred to the battery pack 10 and providing protection from the impact of the collision.

[0057] To confirm the effectiveness of the side sill structure according to the present invention, a crash test was conducted using the following finite element analysis (FEM) analysis. Figures 16(a) through 16(e) show the test specimens and test conditions for the inventive and comparative examples. In each of Figures 16(a) through 16(e), the left-hand side is a cross-sectional view of the side sill in the vehicle width direction, and the right-hand side is a horizontal cross-sectional view of the side sill, showing the impact position of the impact body (pole) against the side sill and the position of the floor cross-member. In this crash test, the side sill and the impact absorbing member (impact absorbing structure 2 in the inventive example) of the vehicle side structure were used as test specimens, and the crash energy absorption characteristics were evaluated. In addition, the floor cross-member and battery case side member adjacent to the side sill were used as rigid jigs for fixing the test specimens, and the load transmitted to the jigs was evaluated using contact reaction force.

[0058] In the collision test, as shown in Figure 16, a collision object (pole) with a curvature radius of 127 mm was collided perpendicular to the longitudinal direction of the test specimen at an initial velocity of 30.9 km / h with a maximum penetration of 100 mm. The collision energy was 25 kJ. The fixing jig for the side sill on the opposite side of the collision object consisted of a floor cross member simulation section (corresponding to floor cross member 8), a battery case wall section (corresponding to battery case side member 90), and a battery case lower section (corresponding to battery case bottom plate 91 and mounting flange 92) that simulated the vehicle body side structure shown in Figure 3. The battery case lower section was fixed to the side sill inner panel with fixing bolts (corresponding to fixing bolts 11). The width (wa) of the floor cross member simulation section in the vehicle longitudinal direction was 80 mm. Table 1 shows the strength levels and thicknesses of the steel plates used for each component of the test specimens for the invention example and comparative example.

[0059]

[0060] In the test specimen of Example 1 shown in FIG. 16(a), the impact absorbing structure 2 has bulkheads 6 at two locations within the width of the floor cross member simulation part (corresponding to the floor cross member 8). ｘ In the area outside the width of the floor cross member simulation part on both sides, there is provided a bulkhead 6 consisting of a bulkhead set consisting of two adjacent bulkheads. ｙ The two adjacent bulkheads 6 ｘ The spacing w1 between them is 35 mm, and the ratio w1 / wa of the spacing w1 to the width wa of the floor cross member is 0.44. ｘ and the adjacent bulkhead 6 ｙ The distance w2 between the floor cross members is larger than w1 and is 254 mm or less, and is set to 125 mm, which is about half of the assumed installation distance of the floor cross members (the distance wb between adjacent floor cross members) of 260 mm. ｙ The distance w4 between the bulkheads constituting the bulkhead set was set to 35 mm, the same as the distance w1.

[0061] The specimen of the invention example 2 shown in FIG. 16(b) is the same as the bulkhead 6 of the invention example 1.ｙ In this example, the bulkheads 6 were removed from the impact absorbing structure 2, and the bulkheads 6 were provided only in two locations within the width of the floor cross member simulated section (corresponding to the floor cross member 8). The test specimen of Comparative Example 1 shown in Figure 16(c) is the impact absorbing structure 2 of Example 2, with the bulkheads 6 removed. The test specimen of Comparative Example 2 shown in Figure 16(d) is the side sill test specimen with only bulkheads provided. The bulkheads were provided in two locations within the width of the floor cross member simulated section. Furthermore, a bulkhead set consisting of two adjacent bulkheads was provided in the areas outside the width of the floor cross member simulated section on both sides. The test specimen of Comparative Example 3 shown in Figure 16(e) is the side sill test specimen with no impact absorbing member provided within the side sill.

[0062] Figures 17(a) to 17(e) show the relationship between the impact force (punch reaction force) and the impact force (punch penetration force) on the side sill during a collision test for the above-mentioned example and comparative examples, as well as the change in absorbed energy versus impact force (punch penetration). Absorbed energy was calculated by subtracting the kinetic energy calculated from the impact force's speed from the collision energy (25 kJ). The maximum stroke of the impact force was 100 mm. For example 1 shown in Figure 17(a), the impact force stopped 99 mm before reaching the maximum impact force of 100 mm. The absorbed energy of the side sill structure of example 1 was 25.0 kJ. In contrast, example 2 and comparative examples 1 to 3 shown in Figures 17(b) to 17(e) all reached the maximum impact force stroke of 100 mm before reaching the absorbed energy of 25.0 kJ (the absorbed energy of example 1).

[0063] Figure 18 compares the absorbed energy at maximum penetration of the impacting object between the above-mentioned invention example and comparative examples. The maximum penetration was 99 mm for invention example 1, and 100 mm (maximum penetration of the impacting object) for invention example 2 and comparative examples 1 to 3. The absorbed energy of invention example 1 was 5.8 times that of comparative example 3, which had only a side sill, and 2.6 times that of comparative example 1 without a bulkhead and comparative example 2, which had only a bulkhead. It was also approximately 1.3 times the combined total of 19.0 kJ for comparative examples 1 and 2. Furthermore, because invention example 2 had fewer bulkheads installed in the longitudinal direction of the vehicle than invention example 1, its absorbed energy was 17% lower than that of invention example 1, but it was 4.8 times that of comparative example 3 and 2.2 times that of comparative examples 1 and 2. It was also approximately 1.1 times the combined total of comparative examples 1 and 2.

[0064] From the results of the above-mentioned examples and comparative examples, it was confirmed that the automobile side sill structure according to the present invention provides extremely excellent collision characteristics that exceed the effect of simply adding up the collision energy absorption performance of comparative example 1 (a side sill structure in which only a hollow cross-section member is provided within the side sill) and comparative example 2 (a side sill structure in which only a bulkhead is provided within the side sill). Furthermore, from the results of examples 1 and 2, it was confirmed that the collision characteristics can be further improved by arranging multiple bulkheads not only in the area within the width of the floor crossmember but also in other areas in the fore-and-aft direction of the vehicle.

[0065] According to the present invention, it is possible to provide an automobile side sill structure that can achieve high collision energy absorption characteristics with a small amount of collision deformation while suppressing weight increase due to structural members, is easy to assemble with a small number of assembly steps, and is also advantageous in terms of increasing the design freedom of the impact absorbing structure.

[0066] REFERENCE SIGNS LIST 1 Side sill 1a Side sill outer 1b Side sill inner 2 Impact absorbing structure 3 Closed cross-sectional space 4 Cross-sectional hollow member 4a Cross-sectional groove member 4b Lid member 4c Cross-sectional angle member 4d Cross-sectional groove member 4e Lid member 5 Closed cross-sectional space 6, 6 ｘ , 6 ｙBulkhead 7 Floor panel 8 Floor cross member 9 Battery case 10 Battery pack 11 Fixing bolt 12 Joint 13 Adhesive 15, 15A, 15B Support member 40 Vertical surface 41, 41A, 41B Horizontal surface 42 Flange 43 Wide side 44 Narrow side 60 Bead 61 Flange 70 Flange 90 Battery case side member 91 Battery case bottom plate 92 Mounting flange 100 Vertical surface 101A, 101B Horizontal surface 102 Flange 150 Wide side 151 Narrow side 152 Inclined surface

Claims

1. A side sill structure for an automobile comprising side sills (1) extending along the longitudinal direction of the vehicle on both sides of the lower part of the vehicle, and a shock absorbing structure (2) arranged in a closed cross-sectional space (3) within the side sill (1), wherein the shock absorbing structure (2) comprises: a hollow cross-sectional member (4) arranged within the closed cross-sectional space (3) along the longitudinal direction of the vehicle so as to form a closed cross-sectional space (5) inside and to divide the closed cross-sectional space (3) into upper and lower parts; and bulkheads (6) arranged at a plurality of locations spaced apart in the longitudinal direction of the vehicle within the closed cross-sectional space (5) as members for dividing the closed cross-sectional space (5) by being arranged within the closed cross-sectional space (5) of the hollow cross-sectional member (4) along the width direction of the vehicle, and each bulkhead (6) is joined to the inner wall of the hollow cross-sectional member (4).

2. A side sill structure for an automobile as described in claim 1, wherein the bulkhead (6) is joined to at least the inner wall of the vertical surface portion (40) on the vehicle inner side and the inner wall of the upper horizontal surface portion (41A) and / or the lower horizontal surface portion (41B) of the inner wall of the cross-sectional hollow member (4).

3. The bulkhead (6) is a bulkhead (6) provided in an area within the width of the floor cross member in the vehicle longitudinal direction. ｘ ) and a bulkhead (6) provided in the area outside the width of the floor cross member ｙ ) and in the vehicle front-rear direction, there are bulkheads (6) at two or more points in the area within the width of the floor cross member. ｘ ) is provided, and a bulkhead (6 ｙ ) are provided, and two adjacent bulkheads (6 ｘ ) spacing is w1, bulkhead (6 ｘ ) and the adjacent bulkhead (6 ｙ 3. The automobile side sill structure according to claim 1, wherein, when a distance between the side sill and the rear end of the vehicle is w2, w1 < w2.

4. At least some of the bulkheads (6 ｙ 4. The side sill structure of an automobile according to claim 3, wherein the first bulkhead comprises a bulk head set consisting of two or more adjacent bulkheads.

5. A side sill structure for an automobile according to any one of claims 1 to 4, wherein a vertical surface portion (40) of the hollow cross-sectional member (4) and an opposing vertical surface portion (100) of the side sill (1) are joined.

6. A side sill structure for an automobile according to any one of claims 1 to 4, wherein the vertical surface portion (40) of the hollow cross-section member (4) and the opposing vertical surface portion (100) of the side sill (1) abut against each other or face each other with a specified gap therebetween, and the hollow cross-section member (4) is supported by the side sill (1) via a support member (15).

7. A side sill structure for an automobile according to any one of claims 1 to 6, wherein a bead is formed on the lateral surface portion (41) of the hollow cross-sectional member (4) and / or the bulkhead (6).

8. A side sill structure for an automobile according to any one of claims 1 to 7, wherein the tensile strength of the metal plate constituting the shock absorbing structure (2) is 590 MPa class or higher.

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