Side sill structure of automobile

Abstract

A side sill structure 1 according to the present invention has: an impact absorption structure 20 which is disposed in a side sill 10 thereof, has a vehicle interior-side width-directional end 20a connected to a vertical surface 11a of a side sill inner 11, and absorbs an impact applied to the side sill 10 during a lateral collision of a vehicle; and a recess 30 which is provided to the vertical surface 11a of the side sill inner 11 and which restrains the vehicle interior-side end 20a in the vehicle vertical direction. The impact absorption structure 20 is provided with a pair of waveform components 21, 23 that are disposed in the vehicle vertical direction and that have a wave shape in which projections and recesses are continuously alternated in the vehicle longitudinal direction. Recesses 21b of an upper waveform component 21 and recesses 23b of a lower waveform component 23 are arranged facing each other and are joined together such that the facing recesses 21b, 23b are positioned out of alignment with each other in the vehicle longitudinal direction.

Description

Automobile side sill structure

[0001] The present invention relates to a side sill structure for an automobile that improves crashworthiness by absorbing impacts input during a side crash of the vehicle.

[0002] In general, an electric vehicle is equipped with a battery module below a floor panel between the left and right side sills in the vehicle width direction, and the battery module is composed of battery cells (also called a battery pack) and a battery case for storing the battery cells.

[0003] The battery case uses high-rigidity and high-yield-strength materials to protect the battery cells from the impact load applied during a vehicle collision. Additionally, materials are arranged around the battery case to absorb crash energy by deforming due to the impact (load) applied to the vehicle during a collision. In particular, during a side collision, the side sill deforms to absorb the crash energy in response to the load applied from the side of the vehicle, and the remaining load is received by the floor cross member or the battery case side member, thereby protecting the battery cells.

[0004] If the amount of deformation required for the side sill to absorb collision energy during a side collision can be reduced, the portion of the side sill that absorbs collision energy can be reduced, making it possible to create a space-saving side sill structure. In electric vehicles equipped with such a side sill structure, the volume of the battery module can be increased by the amount of the side sill reduction, which increases the amount of battery that can be installed, leading to an increase in cruising range. For these reasons, electric vehicles are required to have a space-saving side sill structure that is excellent at absorbing collision energy during a side collision.

[0005] Several technologies have been proposed to increase the stiffness of side sills and improve their ability to absorb collision energy during a side collision. For example, Patent Document 1 discloses a vehicle body side member structure (side sill) that includes an impact absorbing member that is disposed inside a tubular body that extends in the longitudinal direction of the vehicle body, has a plurality of ridges spaced apart along the vehicle width direction, and has a wave-like shape that rises and falls along the longitudinal direction of the vehicle body.

[0006] Patent Document 2 discloses a side structure (side sill) of a vehicle body that is arranged inside a cylindrical body extending in the longitudinal direction of the vehicle body and has an impact absorbing member having a web that is a corrugated plate that repeatedly bends up and down alternately along the longitudinal direction.

[0007] Patent Documents 3 and 4 disclose a vehicle body structure that includes a reinforcing member that constitutes at least a part of a continuous cylindrical structure formed inside the side sill, and the continuous cylindrical structure has a shape consisting of multiple polygonal closed cross sections connected together when viewed from the vehicle width direction.

[0008] Patent Document 5 discloses a vehicle body structure in which an energy absorbing member, which is a corrugated plate that extends in the vehicle width direction and repeatedly bends or curves up and down, is disposed and fixed within a side sill.

[0009] Japanese Patent Application Laid-Open No. 2021-146973 Japanese Patent No. 7095821 Japanese Patent Application Laid-Open No. 2020-111267 Japanese Patent Application Laid-Open No. 2021-024350 Japanese Patent Application Laid-Open No. 2023-056569

[0010] According to Patent Document 1, even when an impact is applied in a side pole crash, the impact absorbing member as a whole can efficiently absorb locally large impact energy (corresponding to the "collision energy" in this application; the same applies hereinafter). Furthermore, according to Patent Document 2, even when an impact load acts in the vehicle width direction, the impact energy (corresponding to the collision energy in this application) can be efficiently absorbed, and deformation toward the interior of the vehicle can be suppressed, thereby effectively protecting the battery case that houses the battery pack. However, the technologies disclosed in Patent Documents 1 and 2 use a corrugated impact absorbing member made of a single metal plate, which has low rigidity and is prone to deformation in the longitudinal direction of the vehicle due to an impact load, causing the corrugated openings to open. When the corrugated openings open, the crash energy absorption characteristics are reduced.

[0011] According to Patent Document 3, by appropriately arranging a stiffened member inside the side sill, the reaction force of the stiffened member is improved, thereby improving side impact performance. However, because the continuous tubular structure expands and contracts in the fore-and-aft direction of the vehicle body during a side impact, it is deformed by the force that pushes it out in the fore-and-aft direction of the vehicle body, and there is a risk that the originally expected reaction force of the stiffened member will not be secured.

[0012] According to Patent Document 4, by further providing a deformation control component that suppresses deformation of the continuous tubular structure in the fore-and-aft direction of the vehicle body in the vehicle body structure described in Patent Document 3, it is possible to restrict deformation of the continuous tubular structure in the fore-and-aft direction of the vehicle body during a side collision. Furthermore, it is expected that the reaction force of the reinforcing member can be improved, thereby improving collision energy absorption performance. However, the vehicle body structure described in Patent Document 4 increases the number and weight of parts due to the provision of the deformation control component.

[0013] According to Patent Document 5, when a collision load is input during a side collision, the energy absorbing member in the side sill can be easily crushed, thereby effectively absorbing the collision energy. However, when the energy absorbing member is made by bonding two metal plates together, a polygonal portion and the bonded portion are formed, and because these have different rigidities, the collision performance varies depending on the collision position. In order to reduce such differences in collision performance, it is effective to improve the rigidity of the bonded portion, but this requires an increase in plate thickness, which leads to an increase in weight.

[0014] Furthermore, in the technology disclosed in Patent Document 5, when a polygonal shaped portion is produced using an extruded material, a method of gradually changing the cross-sectional area in the collision direction to ensure stable buckling during a collision, or a method of inducing buckling by forming a bead portion perpendicular to the collision direction, is used. However, since the cross section of the extruded material is constant in the extrusion direction, gradually changing the cross-sectional area is extremely difficult, and forming a bead portion increases the number of processes, which leads to increased manufacturing costs.

[0015] The present invention has been made to solve the above-mentioned problems, and its purpose is to provide an automobile side sill structure that improves collision performance in the event of a side collision without increasing weight or manufacturing costs.

[0016] The side sill structure for an automobile according to the present invention comprises a side sill having a side sill inner having a groove shape extending in a vehicle longitudinal direction and opening toward the vehicle exterior side in the vehicle width direction, and a side sill outer having a groove shape extending in the vehicle longitudinal direction and opening toward the vehicle interior side in the vehicle width direction, wherein the side sill inner and the side sill outer are joined together with the opening sides facing each other, and the side sill structure further comprises an impact absorbing structure disposed within the side sill, the end portion on the vehicle interior side in the vehicle width direction being connected to the bottom of the groove shape of the side sill inner and / or the end portion on the vehicle exterior side in the vehicle width direction being connected to the bottom of the groove shape of the side sill outer, and absorbing an impact input to the side sill in the event of a side collision of the vehicle; and a vertical restraint structure provided at the bottom of the side sill inner and restraining the end portion on the vehicle interior side in the vehicle vertical direction in the event of a side collision of the vehicle. The impact absorbing structure has a wave-shaped configuration in which convex and concave shapes alternate in the longitudinal direction of the vehicle in a cross section perpendicular to the vehicle width direction, and is provided with a pair of wave-shaped components arranged in the vertical direction of the vehicle, the pair of wave-shaped components being made of metal plates, and arranged so that the concave shape of the upper wave-shaped component faces the concave shape of the lower wave-shaped component, and the opposing concave shapes are joined together while being offset in the longitudinal direction of the vehicle.

[0017] The upper and lower restraint structure is a recess provided at the bottom of the groove shape in the side sill inner and recessed toward the inside of the vehicle in the vehicle width direction, and the end of the impact absorbing structure on the inside of the vehicle is inserted into the recess.

[0018] Preferably, a leading end of the impact absorbing structure on the vehicle outer side in the vehicle width direction abuts against the bottom of the groove shape of the side sill outer.

[0019] The shift amount W2 in the vehicle longitudinal direction of the opposing concave shapes in the upper and lower corrugated parts is preferably 20% or more and 50% or less of the center-to-center distance W1 between the convex shape and the concave shape adjacent in the vehicle longitudinal direction in the corrugated parts.

[0020] A recess amount D of the recess provided in the side sill inner may be 0.8 to 1.2 times the height h of the shock absorbing structure in the vehicle vertical direction.

[0021] The corrugated part is preferably made of a metal plate having a tensile strength of 590 MPa or more.

[0022] According to the present invention, the buckling resistance against the impact load input to the side sill during a side collision can be increased, and the impact absorption structure can be crushed while maintaining high deformation resistance. Furthermore, the amount of deformation in the vehicle width direction can be reduced, and high impact energy absorption characteristics can be achieved. Furthermore, the concave shape of the upper corrugated part and the concave shape of the lower corrugated part of the impact absorption structure face each other and are joined asymmetrically in the vertical direction while being offset in the vehicle longitudinal direction. This allows the positions of the ridgelines of the convex and concave shapes of each corrugated part to be dispersed in the vehicle longitudinal direction. Furthermore, the buckling load (peak load) during a side collision can be kept low, thereby reducing differences (variations) in impact performance depending on the position where the impact load is input. Furthermore, when applied to electric vehicles, the space required to absorb impact energy can be reduced, allowing the volume of the battery module installed in the electric vehicle to be expanded. Furthermore, because the impact absorption structure of the present invention has high bending rigidity, it is not necessary to increase the plate thickness to improve rigidity, and an increase in vehicle weight can also be suppressed.

[0023] FIG. 1 is a diagram showing an example of the configuration of a side sill structure according to an embodiment of the present invention ((a) cross-sectional view perpendicular to the vehicle longitudinal direction, (b) cross-sectional view perpendicular to the vehicle width direction). FIG. 2 is a diagram illustrating an ideal load-stroke curve of a side sill structure during a side collision of a vehicle (solid line: load-stroke curve of a conventional side sill structure, dashed line: ideal load-stroke curve). FIG. 3 is a development view of an impact absorbing structure of a side sill structure according to an embodiment of the present invention. FIG. 4 is a diagram illustrating the amount of offset W2 in the vehicle longitudinal direction between the corrugated component on the upper side of the vehicle body and the corrugated component on the lower side of the impact absorbing structure in the side sill structure according to an embodiment of the present invention. FIG. 5 is a diagram showing an example of a vehicle side structure including a side sill structure according to an embodiment of the present invention. FIG. 6 is a diagram illustrating a modified vertical restraint structure that restrains the vehicle interior end of the impact absorbing structure in the vertical direction of the vehicle in the side sill structure according to an embodiment of the present invention. FIG. 7 is a diagram illustrating a support structure that supports the impact absorbing structure disposed within the side sill in the side sill structure according to an embodiment of the present invention. FIG. 8 is a diagram illustrating a test specimen analyzed in a crash test simulating a vehicle side collision in Example 1. FIG. 9 is a diagram illustrating a side sill structure tested in a crash test simulating a vehicle side collision in Example 1. FIG. 10 is a diagram illustrating the deformation state of the impact absorption structure in a crash analysis simulating a vehicle side collision in Example 1 ((a) top view of the impact absorption structure, (b) perspective view of the impact absorption structure from the vehicle exterior, (c) cross-sectional view of the side sill structure). FIG. 11 is a diagram illustrating the deformation behavior of the impact absorption structure in a crash analysis simulating a vehicle side collision in Example 1. FIG. 12 is a graph illustrating the relationship between the amount of collision energy absorbed by the side sill structure and the maximum load input to the side sill structure during a side collision in the crash test in Example 1. FIG. 13 is a cross-sectional view of an impact absorption structure tested in a side collision test in Example 2 ((a) Example 3, (b) Comparative Examples 6 and 7, (c) Comparative Example 8).Fig. 14 is a cross-sectional view showing the deformation behavior of the side sill structure during a side collision in Example 2 ((a) side sill structure according to Example 3, (b) side sill structure according to Comparative Example 6). Fig. 15 is a load-stroke curve obtained by crashworthiness analysis for side collision tests of test specimens according to Example 3 and Comparative Example 6 in Example 2. Fig. 16 is a graph showing (a) the load-stroke curve and (b) the transition of crash absorbed energy obtained by crash analysis for side collision tests of test specimens according to Example 3, Comparative Examples 7 and 8 in Example 2.

[0024] <Background to the Invention> The technologies disclosed in Patent Documents 1 to 5 mentioned above all involve disposing, within a side sill, a member having a wave-like shape in which a shape that is bent or curved in the vertical direction of the vehicle is repeated in the longitudinal direction of the vehicle (Patent Documents 1 and 2: impact absorbing member, Patent Documents 3 and 4: reinforcing member, Patent Document 5: energy absorbing member). Hereinafter, a structure in which a wave-shaped member is disposed within a side sill will be referred to as a "conventional side sill structure."

[0025] In general, a side sill structure absorbs the impact load input to the side sill during a side collision by transmitting the load (impact load) to a high-yield strength member, such as a cross member, located on the vehicle interior side. The reaction force from the high-yield strength member causes the side sill structure to collapse, thereby absorbing the collision energy. During the collapse of a conventional side sill structure, the corrugated member disposed within the side sill undergoes bellows-shaped buckling deformation while undulating to form multiple antinodes. In the following description, this lantern-shaped ("bellows-shaped" or "sausage-shaped") buckling deformation is also referred to as the "lantern-shaped buckling mode" or "axial crash mode."

[0026] During a side collision in which an impact object strikes the side of a vehicle equipped with a conventional side sill structure in which a corrugated member is arranged inside the side sill, a load-stroke curve is shown in Figure 2, which schematically shows the relationship between the load input to the side sill and the stroke, which is the amount of penetration of the impact object into the vehicle interior.

[0027] In the graph shown in Figure 2, the load on the vertical axis is the contact reaction force from load-bearing parts such as cross members, and the value obtained by integrating the load with the stroke (the amount of deformation of the side sill structure in the vehicle width direction), i.e., the area surrounded by the load-stroke curve, represents the amount of collision energy absorption.

[0028] In the conventional side sill structure, as shown by the load-stroke curve indicated by the solid line in Figure 2, after elastic deformation, the ridges of the corrugated members undergo lantern-like buckling deformation (lantern buckling mode), and the load continues to increase as the stroke increases.

[0029] Normally, load-bearing parts such as cross members have a set allowable load (buckling strength Fa). Therefore, in order for the battery case to be protected by load-bearing parts during a side collision, the maximum load (Fmax) must be equal to or less than the allowable load (Fa), as shown by the solid line load-stroke curve in Figure 2.

[0030] Therefore, in conventional side sill structures, in order to keep the maximum load (Fmax) below the allowable load (Fa) of the load-bearing component, it was necessary to set the thickness and material (e.g., yield stress) of the metal plates that make up the corrugated members so that the corrugated members would buckle at a buckling load (Fb) that was lower than the maximum load (Fmax). Therefore, in side sill structures with corrugated members, it was necessary to increase the deformation amount of the side sill (S1 in Figure 2) so that the desired amount of collision energy absorption could be obtained during a side collision.

[0031] On the other hand, in electric vehicles, in order to increase the volume of the battery module, it has been necessary to reduce the amount of deformation of the side sill required to absorb a certain amount of collision energy using a side sill structure. Therefore, the inventors thought that in order to reduce the stroke while ensuring the same amount of collision energy absorption as conventional side sill structures, it would be necessary to create a side sill structure that achieves the ideal load-stroke curve shown by the dashed line in Figure 2.

[0032] The ideal load-stroke curve shown in Figure 2 increases the rigidity of the side sill structure to speed up the rise of the load generated on the side sill during a side collision, and while increasing the buckling load to approximately the maximum load (Fmax) of a conventional side sill structure, it suppresses the increase in load during the collision process after buckling deformation and maintains a constant load. With a side sill structure that can achieve this kind of load-stroke curve, it is believed that it will be possible to reduce the amount of deformation of the side sill (S2 in Figure 2) while ensuring the necessary amount of collision energy absorption.

[0033] Next, the inventors investigated specific configurations for a side sill structure that can achieve the ideal load-stroke curve shown in Figure 2. The rigidity and buckling load of the side sill structure can be adjusted by appropriately selecting the thickness and material of the corrugated members disposed within the side sill, but it was not possible to suppress the increase in load during a collision after buckling deformation and maintain it constant simply by selecting the thickness and material.

[0034] The inventor therefore conducted extensive research to solve this problem. In this research, the inventor focused on the cause of the gradual increase in load after the initial buckling deformation in conventional side sill structures. As a result, the inventor inferred that in conventional side sill structures, as a collision object penetrates into the vehicle interior, an initial buckling deformation occurs at the outer end of a corrugated member disposed within the side sill, and then a series of accordion-like buckling deformations occur, undulating from the outer side to the inner side of the vehicle, forming multiple antinodes, resulting in an increase in load.

[0035] Therefore, in order to achieve the ideal load-stroke curve shown in Figure 2, we came up with the idea of ​​suppressing the buckling deformation that occurs continuously in a bellows-like wavy shape with multiple antinodes after the initial buckling deformation occurs in the corrugated member arranged inside the side sill.

[0036] They then discovered that by joining the corrugated members inside the side sill in an asymmetrical manner, offset in the longitudinal direction of the vehicle, it is possible to suppress the buckling deformation that occurs continuously in an accordion-like manner, undulating with multiple antinodes, after the initial buckling deformation occurs in the corrugated member, and to make it possible to transition the buckling deformation at a constant load.

[0037] In this way, it was discovered that, compared to conventional side sill structures, the maximum load can be increased by appropriately selecting the plate thickness and material, thereby increasing rigidity, and by keeping the load after buckling constant, it is possible to reduce the amount of deformation while ensuring the necessary amount of collision energy, thereby realizing a compact side sill structure. The present invention was made based on the above findings, and its configuration will be described below.

[0038] <Automobile Side Sill Structure> As shown as an example in Fig. 1 , a side sill structure 1 according to an embodiment of the present invention includes a side sill 10 having a side sill inner 11 and a side sill outer 13, an impact absorbing structure 20, and a recess 30. Each component of the side sill structure 1 will be described below. In this application, terms relating to directions such as "vehicle longitudinal direction," "vehicle width direction," and "vehicle vertical direction," and terms relating to positions such as "vehicle exterior side," "vehicle interior side," "vehicle upper side," and "vehicle lower side," represent directions and positions when the side sill structure 1 is actually installed on a vehicle.

[0039] <Side Sill> As shown in FIG. 1 , the side sill 10 is formed by joining a side sill inner 11 and a side sill outer 13 together.

[0040] The side sill inner panel 11 has a vertical surface 11a that is substantially parallel to the vehicle up-down direction and a pair of horizontal surfaces 11b that extend from the upper and lower ends of the vertical surface 11a toward the vehicle exterior. The vertical surface 11a and the pair of horizontal surfaces 11b form a groove shape in the side sill inner panel 11, with the vertical surface 11a corresponding to the bottom of the groove. Furthermore, the side sill inner panel 11 has flanges 11c that extend upward and downward from the respective ends of the horizontal surfaces 11b on the upper and lower sides of the vehicle.

[0041] The side sill outer 13 has a vertical surface 13a that is substantially parallel to the vehicle up-down direction and a pair of horizontal surface 13b that continue from the upper and lower ends of the vertical surface 13a toward the vehicle interior. The vertical surface 13a and the pair of horizontal surface 13b form a groove shape in the side sill outer 13, and the vertical surface 13a corresponds to the bottom of the groove shape. Furthermore, the side sill outer 13 has flanges 13c that extend upward and downward from the respective ends of the horizontal surface 13b on the upper and lower sides of the vehicle.

[0042] The flange portions 11c and 13c of the side sill inner 11 and the side sill outer 13 are joined (for example, by spot welding) with the opening sides of their grooves facing each other, thereby forming the side sill 10 having a closed cross-sectional space 10a therein.

[0043] The vertical surface portion 11a of the side sill inner 11 and the vertical surface portion 13a of the side sill outer 13 do not have to have a planar shape parallel to the vehicle vertical direction, but may be inclined or curved relative to the vehicle vertical direction. Similarly, the horizontal surface portion 11b of the side sill inner 11 and the horizontal surface portion 13b of the side sill outer 13 do not have to have a planar shape parallel to the horizontal plane, but may be inclined or curved relative to the horizontal plane.

[0044] Impact Absorption Structure The impact absorption structure 20 has an inboard end 20a in the vehicle width direction connected to a vertical surface 11a, which is the bottom of the groove shape of the side sill inner panel 11, and absorbs impact input to the side sill 10 during a side collision of the vehicle. As shown in FIGS. 1 and 3 , the impact absorption structure 20 has a wave shape in which convex shapes and concave shapes alternately continue in the vehicle longitudinal direction in a cross section perpendicular to the vehicle width direction, and includes a pair of corrugated elements 21, 23 arranged in the vehicle vertical direction. The upper corrugated element 21 has a wave shape in which convex shapes 21a and concave shapes 21b alternately continue in the vehicle longitudinal direction in a cross section perpendicular to the vehicle width direction. Similarly, the lower corrugated element 23 has a wave shape in which convex shapes 23a and concave shapes 23b alternately continue in the vehicle longitudinal direction in a cross section perpendicular to the vehicle width direction. In the upper corrugated part 21 and the lower corrugated part 23, the convex shapes 21a, 23a are formed by a top surface and a pair of wall surfaces continuing from both ends thereof, and the concave shapes 21b, 23b are formed by a bottom surface and a pair of wall surfaces continuing from both ends thereof.

[0045] The pair of corrugated parts 21, 23 are made of metal plates. In the impact absorption structure 20, the upper corrugated part 21 and the lower corrugated part 23 are arranged so that the concave shape 21b of the upper corrugated part 21 faces the concave shape 23b of the lower corrugated part. Furthermore, the bottom surfaces of the concave shapes 21b and 23b facing each other are joined with the concave shapes 21b and 23b offset in the vehicle longitudinal direction. "Arranged so that the concave shape 21b of the upper corrugated part 21 faces the concave shape 23b of the lower corrugated part" means that the upper corrugated part 21 and the lower corrugated part 23 are arranged upside down.

[0046] In the impact absorption structure 20, the state in which the recessed shapes 21b and 23b are misaligned in the vehicle longitudinal direction refers to a state in which the centers of the bottom surfaces of the recessed shapes 21b and 23b are misaligned in the vehicle longitudinal direction by a predetermined amount W2, as shown in Figure 4. The bottom surfaces of the recessed shapes 21b and 23b may be joined by, for example, spot welding. As a result, the impact absorption structure 20 is disposed within the side sill 10 and has a structure in which the pair of upper and lower corrugated parts 21 and 23 are integrated.

[0047] Furthermore, in this embodiment, the tip of the impact absorption structure 20 on the vehicle exterior side in the vehicle width direction abuts against the vertical surface portion 13a, which is the bottom portion of the groove shape of the side sill outer panel 13. The tip of the impact absorption structure 20 on the vehicle exterior side refers to the end face of the metal plate used for the corrugated parts 21, 23.

[0048] 5, the impact absorbing structure 20 is preferably disposed within the side sill 10 so as to overlap at least the floor cross member 103 in the vertical direction of the vehicle. This allows the impact input to the side sill 10 during a side collision to be absorbed, and the load to be transmitted to the floor cross member 103, resulting in the reaction force efficiently crushing the impact absorbing structure 20, thereby increasing the amount of collision energy absorption.

[0049] <<Recess>> The recess 30 is provided in the longitudinal surface portion 11a, which is the bottom of the groove shape of the side sill inner panel 11, as a vertical restraint structure that restrains the vehicle interior side end portion 20a of the impact absorption structure 20 in the vehicle vertical direction. The vehicle interior side end portion 20a of the impact absorption structure 20 is inserted into the recess 30, and by pressing down on the end portion 20a from the vehicle vertical direction during a side collision, it resists displacement of the end portion 20a in the vehicle vertical direction. The vehicle interior side end portion 20a of the impact absorption structure 20 inserted into the recess 30 is joined to the bottom 31 of the recess 30.

[0050] An example of a method for joining the end 20a of the shock absorbing structure 20 on the vehicle interior side to the vertical surface 11a of the side sill inner panel 11 will be described with reference to FIG. 1(a) and FIG.

[0051] The shock absorbing structure 20 has an end 20a on the vehicle interior side in the vehicle width direction inserted into a recess 30 provided in the vertical surface 11a of the side sill inner panel 11. The end 20a is joined (by spot welding or the like) to a bottom 31 of the recess 30 via a flange portion 25 provided at the tip of the end 20a. The flange portion 25 may be provided over the entire length of the vehicle in the longitudinal direction, or may be provided intermittently in the longitudinal direction of the vehicle.

[0052] The effects of the side sill structure 1 according to the embodiment of the present invention will be described below based on the vehicle side structure 100 shown in FIG.

[0053] <Vehicle Side Structure> The floor cross member 103 is a body frame structural member disposed above the floor panel 101 and extending in the vehicle width direction, with each end 103a in the vehicle width direction joined (e.g., by spot welding) to the vertical surface portion 11a, which is the bottom of the groove shape of the side sill inner 11. Multiple floor cross members 103 are provided at predetermined intervals (e.g., about 300 mm) in the vehicle longitudinal direction.

[0054] The battery case 105 is disposed below the floor panel 101 and houses a battery pack 107 inside. Each side surface 105a of the battery case 105 in the vehicle width direction faces the side sill inner 11 at a predetermined distance. In the vehicle side structure 100, the side surface 105a of the battery case 105 faces the lower part of the vertical surface 11a of the side sill inner 11.

[0055] A mounting flange 105c is connected to the bottom plate 105b, which is the bottom portion of the battery case 105, so as to protrude toward the side sill 10. The mounting flange 105c and the lower lateral surface 11b of the side sill inner panel 11 are fastened together with fixing bolts 109, thereby holding the battery case 105 to the side sill 10.

[0056] The impact absorbing structure 20 disposed inside the side sill structure 1 is disposed so as to overlap with the floor cross member 103 in the vehicle height direction when viewed from the side in the vehicle width direction.

[0057] <<Function and effect of side sill structure 1>> In the side sill structure 1 according to this embodiment, the shock absorbing structure 20 arranged within the side sill 10 has the bottom surfaces joined together in a state in which the concave shape 21 b of the upper corrugated part 21 and the concave shape 23 b of the lower corrugated part 23 are offset in the longitudinal direction of the vehicle and face each other asymmetrically in the vertical direction.

[0058] In the cross-sectional view of the impact absorption structure 20 perpendicular to the vehicle width direction shown in Figure 1(b), the ridgelines (corners) of the convex shapes 21a, 23a and the concave shapes 21b, 23b have high deformation resistance against a collision load from the vehicle exterior in the vehicle width direction. The top surface (indicated by the dashed ellipse in Figure 1(b)) sandwiched between the ridgelines of the convex shapes 21a, 23a and having a long gap between the ridgelines has relatively low deformation resistance compared to the wall surfaces (indicated by the solid ellipse in Figure 1(b)) having a short gap between the ridgelines. The upper corrugated part 21 and the lower corrugated part 23 of the impact absorption structure 20 are joined while being offset from each other in the vehicle longitudinal direction. As a result, as shown in Figure 1 (b), in a cross section perpendicular to the vehicle width direction, areas with relatively high deformation resistance (solid ellipses) and areas with relatively low deformation resistance (dashed ellipses) face each other above and below in the vehicle longitudinal direction, and areas where the deformation resistance of the upper corrugated part 21 and the lower corrugated part 23 differs between the top and bottom are intermittently created in the vehicle longitudinal direction.

[0059] Therefore, in a side collision of a vehicle equipped with the side sill structure 1, as shown in FIG. 10( c), a rotational moment is generated around the longitudinal axis of the vehicle due to the difference in deformation resistance between the upper corrugated element 21 and the lower corrugated element 23 at the longitudinal position of the vehicle where the impact body strikes the vehicle, resulting in initial buckling deformation at both ends of the vehicle, bending out of the plane in the rotational direction. Because the impact absorption structure 20 is inclined with respect to the horizontal plane in the vehicle width direction, after the initial buckling deformation, the corrugated elements 21, 23 do not undergo bellows-like buckling, but instead continue to bend. Thus, the side sill structure 1 according to this embodiment can suppress the increase in load associated with an increase in stroke (deformation amount) as shown in FIG. 2 and maintain a load substantially equal to the maximum load.

[0060] The impact absorption structure 20 is disposed within the side sill 10 and has a structure in which the corrugated part 21 and the corrugated part 23 are integrated. Therefore, in the impact absorption structure 20, closed cross-sectional spaces formed by the convex shapes 21a of the upper corrugated part 21 and the convex shapes 23a of the lower corrugated part 23 are continuously arranged at regular intervals in the vehicle longitudinal direction. Therefore, the entire impact absorption structure 20 has high bending rigidity (resistance to bending deformation against a side collision load). This suppresses local deformation of the impact absorption structure 20 around the portion of the side sill where the impact load is input, and also allows buckling deformation around the portion where the collision load is input, thereby increasing the amount of collision energy absorption.

[0061] Furthermore, in the side sill structure 1, a recess 30 is provided in the vertical surface portion 11a, which is the bottom portion of the groove shape of the side sill inner panel 11, and the vehicle-interior end portion 20a of the impact absorption structure 20 is inserted into the recess 30 to restrain it in the vertical direction of the vehicle. This prevents the vehicle-interior end portion 20a of the impact absorption structure 20 from shifting in the vehicle-interior direction, causing the impact absorption structure 20 to tip over, or the end portion 20a from undergoing significant out-of-plane deformation, during a side collision of the vehicle. As a result, it is possible to prevent the impact absorption structure 20 from tipping over or the end portion 20a from undergoing significant out-of-plane deformation.

[0062] The impact absorption structure 20 is disposed so as to overlap the floor cross member 103 in the vehicle height direction in a side view from the vehicle width direction. As a result, a collision load input from the side sill outer 13 from outside the vehicle is transmitted to rigid parts such as the floor cross member via the impact absorption structure 20, and the reaction force from the rigid parts is transmitted to the impact absorption structure 20 via the side sill inner 11. This allows the impact absorption structure 20 to be efficiently crushed, making it possible to improve collision energy absorption performance.

[0063] As described above, the side sill structure 1 according to this embodiment increases the buckling resistance against the impact load input to the side sill 10 during a side collision, and can crush the impact absorption structure 20 while maintaining a state of high deformation resistance, thereby achieving high collision energy absorption performance.

[0064] Furthermore, the concave shapes 21b of the upper corrugated part 21 and the concave shapes 23b of the lower corrugated part 23 in the shock absorbing structure 20 are arranged to face each other, and the facing concave shapes 21b and 23b are joined while being offset in the vehicle longitudinal direction. This distributes the positions of the ridge lines of the convex shapes 21a, 23a and the ridge lines of the concave shapes 21b, 23b in the vehicle longitudinal direction, making it less likely that differences (variations) in collision performance will occur depending on the position where the impact load is input.

[0065] Furthermore, when the side sill structure 1 is applied to an electric vehicle, it is possible to reduce the space required to absorb collision energy in the side sill structure 1. This also makes it possible to increase the volume of the battery module disposed between the side sills 10 on both sides in the vehicle width direction.

[0066] Furthermore, in the side sill structure 1 according to this embodiment, the impact absorbing structure 20 has high bending stiffness, so there is no need to increase the thickness of the metal plate used in the side sill structure 1 in order to improve the stiffness, and the increase in the weight of the vehicle body can also be suppressed.

[0067] The side sill structure 1 of this embodiment has a recess 30 provided in the vertical surface portion 11a of the side sill inner 11 as a vertical restraint structure that restrains the vehicle-interior end portion 20a of the impact absorbing structure 20 in the vertical direction of the vehicle.

[0068] However, in the present invention, the upper and lower restraint structures are not limited to the recesses 30. Fig. 6 shows a modified example of the upper and lower restraint structures. The side sill structure 1 shown in Fig. 6 has L-shaped brackets 35 provided on both the upper and lower sides of the vehicle-interior end 20a of the impact absorbing structure 20 as the upper and lower restraint structures. The upper L-shaped bracket 35 is joined to the top surface of the upper corrugated part 21 and the vertical surface 11a of the side sill inner panel 11, and the lower L-shaped bracket 35 is joined to the lower surface of the lower corrugated part 23 and the vertical surface 11a of the side sill inner panel 11. The L-shaped brackets 35 may be joined to the corrugated parts 21, 23, and the vertical surface 11a by spot welding or the like.

[0069] In this way, even in the event of a side collision of the side sill structure 1 provided with the L-shaped bracket 35 as a vertical restraint structure, the end 20a on the vehicle interior side of the impact absorbing structure 20 can be restrained in the vertical direction of the vehicle.

[0070] The L-shaped bracket 35 does not have to be installed over the entire length of the vehicle in the longitudinal direction, as long as it is capable of restraining the end 20a on the inside of the vehicle in the vertical direction of the vehicle during a side collision, but may also be installed intermittently in the longitudinal direction of the vehicle.

[0071] 1 or 6, the present invention is not limited to a structure in which the vehicle interior end 20a of the impact absorbing structure 20 is joined to the vertical surface 11a of the side sill inner 11. In other words, the present invention does not necessarily require a flange portion to be provided at the vehicle interior end of the impact absorbing structure, and the vehicle interior tip may be the end face of a metal plate constituting a corrugated part, and may abut against the vertical surface of the side sill inner.

[0072] However, as shown in FIG. 1, the end portion 20a of the impact absorption structure 20 on the vehicle interior side is connected to the vertical surface portion 11a of the side sill inner panel 11, which is preferable because it provides good collision energy absorption performance in the event of a side collision.

[0073] Furthermore, in the present invention, the vehicle-exterior end portion 20b of the impact absorption structure 20 may be connected to the vertical surface portion 13a of the side sill outer 13. As an example of a mode in which the vehicle-exterior end portion 20b of the impact absorption structure 20 is connected to the vertical surface portion 13a of the side sill outer 13, a flange portion bent from the tip of the vehicle-exterior end portion may be provided and joined (by spot welding or the like) to the vertical surface portion of the side sill outer.

[0074] However, if the outer end of the impact absorption structure is connected to the side sill outer by a flange portion that connects via a bent portion that bends in the vehicle vertical direction with a predetermined curvature radius, the rigidity against the load input during a side collision may be reduced. For this reason, as shown in FIG. 1 , it is preferable that the outer end of the impact absorption structure 20 is not provided with a flange, and that the outer end of the impact absorption structure 20 abuts against the vertical surface 13a of the side sill outer 13. This allows the impact absorption structure 20 to withstand the load input to the side sill 10 without reducing its rigidity, thereby accelerating the load buildup in the initial stage of a collision and increasing the amount of collision energy absorption.

[0075] The shock absorbing structure 20 may be such that both the upper corrugated part 21 and the lower corrugated part 23, or either the upper or lower corrugated part 21 or 23, abuts against the vertical surface portion 11a of the side sill inner 11 and / or the vertical surface portion 13a of the side sill outer 13.

[0076] The present invention does not exclude a case where a gap is provided between the outer-vehicle end 20b of the impact absorbing structure 20 and the side sill outer 13, or a case where a gap is provided between the inner-vehicle end 20a and the side sill inner 11. In other words, it is sufficient that the impact absorbing structure 20 is supported within the side sill 10 by connecting the inner-vehicle end 20a to the vertical surface 11a of the side sill inner 11, or by connecting the outer-vehicle end 20b to the vertical surface 13a of the side sill outer 13.

[0077] In the side sill structure 1 according to this embodiment, as described above, the upper corrugated part 21 and the lower corrugated part 23 are joined at their bottom surfaces with the opposing recessed shapes 21 b and 23 b offset in the vehicle longitudinal direction. The amount of offset between the recessed shapes 21 b and 23 b in the vehicle longitudinal direction may be determined so that the bottom surfaces can be joined.

[0078] Figure 4 shows the offset between the concave shape 21b of the upper corrugated part and the concave shape 23b of the lower corrugated part 23. In the corrugated part 21, the center-to-center distance between the adjacent convex shape 21a and concave shape 21b in the vehicle longitudinal direction (the distance between the dashed lines passing through the black dots in Figure 4) is defined as W1. When the offset between the concave shape 21b of the upper corrugated part 21 and the concave shape 23b of the lower corrugated part 23 (the center-to-center distance between the concave shapes) is defined as W2, it is preferable that the offset W2 be 20% or more and 50% or less of W1 (0.2 x W1 ≤ W2 ≤ 0.5 x W1).

[0079] If the offset W2 is less than 20% of W1 (W2 < 0.2 × W1), buckling deformation occurs almost simultaneously at the ridges of the upper corrugated part 21 and the lower corrugated part 23, resulting in an axial crushing mode in which accordion-like buckling deformation occurs in the corrugated parts 21 and 23, and the effect of suppressing the increase in load during the collision process after buckling deformation is small. Also, if the offset W2 is more than 50% of W1 (W1 > 0.5 × W1), the area where the bottom surfaces of the concave shapes 21b and 23b overlap is narrow, making joining by spot welding or the like difficult.

[0080] The recess 30 has the function of suppressing displacement of the vehicle interior end 20a in the vehicle vertical direction during the deformation process of the impact absorption structure 20 in the event of a side collision. Therefore, the amount of recess D of the recess 30 toward the vehicle interior should be set so that this function can be exerted. Therefore, it is preferable that the amount of recess D of the recess 30 be 0.8 to 1.2 times the vehicle vertical height h of the impact absorption structure 20. The vehicle vertical height h of the impact absorption structure 20 is the height of the pair of corrugated components 21, 23 arranged side by side in the vehicle vertical direction.

[0081] If the recess amount D of the recess 30 is less than 0.8 times the height h of the impact absorption structure 20, the recess 30 will deform and open up and down as the cross-section of the side sill 10 opens up and down and collapses during a side collision, causing the interior end 20a of the impact absorption structure 20 to come out of the recess 30. Furthermore, if the recess amount D of the recess 30 exceeds 1.2 times the height h, the recess 30 will interfere with the floor cross member, battery pack, etc. that are located further interior than the side sill inner 11, which may require significant changes to the structure of the floor cross member or battery pack.

[0082] Furthermore, when a flange portion 25 is provided at the end portion 20a on the vehicle interior side of the impact absorption structure 20 and the flange portion 25 is spot welded to the bottom portion 31 of the recessed portion 30, the height of the recessed portion 30 in the vehicle vertical direction should be set to an extent that ensures a working space for welding the flange portion 25. For the above reasons, the height H of the recessed portion 30 in the vehicle vertical direction is preferably set to 1.3 to 1.4 times the height h of the impact absorption structure 20 (see FIG. 1(a)).

[0083] The metal plate used in the impact absorption structure 20 preferably has a tensile strength of 590 MPa or higher. In terms of crash worthiness of the impact absorption structure 20, the higher the load (buckling strength) when the impact absorption structure 20 changes from elastic deformation immediately after the start of deformation to plastic deformation during a side collision, the less likely buckling deformation will occur and the better the crash worthiness will be. The buckling strength increases as the tensile strength (yield strength) of the metal plate used in the impact absorption structure 20 increases, so it is preferable to use a metal plate with a tensile strength of 590 MNPa or higher, which is higher than that of common steel.

[0084] Furthermore, if a high-tensile steel sheet is used for the impact absorption structure 20, the impact absorption structure 20 disposed within the side sill 10 also functions as a reinforcement for the side sill 10. Therefore, it is particularly preferable that the metal plate used for the impact absorption structure 20 be a high-tensile steel sheet of 980 MPa class or higher.

[0085] Furthermore, it is preferable that the yield strength of the metal plates used for the corrugated parts 21, 23 of the impact absorption structure 20 is equal to or less than the yield strength of the metal plates used for the floor cross member 103 (FIG. 5). This is to ensure that, in the event of a side collision, the impact absorption structure 20 buckles and deforms before the floor cross member 103, sufficiently absorbing the collision energy and suppressing deformation of the floor cross member 103.

[0086] If the yield strength of the metal plates that make up the impact absorption structure 20 is similar to the yield strength of the metal plates that make up the floor cross member 103, it is preferable to add beads (crash beats) or the like to the corrugated parts that make up the impact absorption structure 20, making buckling deformation possible starting from the beads, thereby making the buckling strength of the impact absorption structure 20 (= the load at which the member itself begins to buckle) lower than the buckling strength of the floor cross member 103.

[0087] In the side sill structure 1 shown in Fig. 1 , the impact absorbing structure 20 is supported within the side sill 10 by having the vehicle-interior end portion 20a joined (by welding or adhesive) to the bottom portion 31 of the recessed portion 30 in the vertical surface portion 11a of the side sill inner panel 11. However, the impact absorbing structure 20 may also be supported within the side sill 10 via a structure for support 37, as shown in Fig. 7 .

[0088] In FIG. 7( a ), the upper end of the support structure 37 is joined to the underside of the shock absorbing structure 20, and the lower end is joined to the flange portions 11 c, 13 c of the side sill 10. In FIG. 7( b ), one end of the support structure 37 is joined to the underside of the shock absorbing structure 20, and the other end is joined to the vertical surface portion 13 a of the side sill outer 13. In FIG. 7( c ), the shock absorbing structure 20 is supported by support structures 37 arranged both above and below the shock absorbing structure 20. The manner in which the shock absorbing structure 20 is supported by the support structures 37 is not limited to FIGS. 7( a ) to 7 ( c ). For example, in the side sill structure 1 shown in FIG. 7( c ), the shock absorbing structure 20 may be supported only by the support structure 37 arranged above the shock absorbing structure 20.

[0089] The support structure 37 may be joined to the shock absorbing structure 20 and the side sill 10 by at least one of welding such as spot welding, mechanical fastening using bolts or rivets, or adhesive bonding.

[0090] The corrugated components 21, 23 of the side sill structure 1 according to the present embodiment have the same corrugated shape in a cross section perpendicular to the vehicle width direction, except that they are arranged upside down. The convex shapes 21a, 23a and concave shapes 21b, 23b of each corrugated component 21, 23 preferably have a height or depth of 15 mm to 100 mm, a width between the top surface of the convex shape 21a and the bottom surface of the concave shape 21b of 15 mm to 150 mm, and an inclination angle (the acute angle between the wall and a vertical line horizontal to the vehicle's vertical direction) of 1° to 30°. This allows the bottom surfaces of the concave shapes to be joined with offset, and the ridges of the convex and concave shapes to crush during a side collision, improving collision performance.

[0091] Furthermore, the convex and concave shapes of the corrugated parts do not necessarily have to be identical in cross section perpendicular to the vehicle width direction, but may be different. For example, in a pair of corrugated parts, the width of the bottom surface of the concave shape may be wider than the width of the top surface of the convex shape in order to facilitate joining of the bottom surfaces of the opposing concave shapes.

[0092] An analysis was conducted to verify the effects of the automobile side sill structure according to the present invention, and this will be described below.

[0093] In Example 1, the purpose was to evaluate the collision characteristics of the side sill structure during a side collision of a vehicle, and a collision analysis was performed on a collision test in which a collision body 210 was collided with the side of a side sill 10 in a test body 200 equipped with a side sill structure 1, as shown in FIG. 8 .

[0094] The test specimen 200 simulates the vehicle side structure 100 described above, and includes, on the side of the side sill 10 opposite the collision body 210, a floor cross member simulation portion 201 corresponding to the floor cross member 103, a battery case wall portion 203 corresponding to the side portion 105a of the battery case 105, and a battery case bottom plate portion (not shown) corresponding to the bottom plate 105b of the battery case 105. In the test specimen 200, the battery case bottom plate portion is fixed to the side sill inner panel 11 by fixing bolts. The length of the floor cross member simulation portion 201 in the vehicle longitudinal direction was 160 mm.

[0095] In the collision analysis, as shown in Fig. 8, a collision object 210 was collided with a test specimen 200 in the vehicle width direction. The collision object 210 was a rigid pole with a radius R of 127 mm (equivalent to a diameter of 254 mm), an initial velocity of 35.0 km / h, and a maximum intrusion amount of 80 mm. The load capacity (allowable load) of the floor cross member simulation portion 201 was set to 500 kN or less, and the target value for the amount of collision energy absorption by the side sill structure was set to 27 kJ (equivalent to 90% of the collision energy by the collision object 210).

[0096] In the collision analysis, as shown in Fig. 8, the deformation behavior of the side sill 10 was determined during the collision process in which a collision object 210 that collided with the side surface of the side sill 10 penetrated into the side sill 10. Then, from the deformation behavior of the side sill 10, the relationship between the load and stroke input to the side sill 10, and the amount of collision energy absorption from the start of the collision to the maximum penetration amount were determined. The load input to the test specimen 200 was the load transmitted to the rigid jig used to fix the test specimen 200.

[0097] Figure 9 shows the side sill structures tested in the examples. In Figure 9, (a) and (b) show side sill structures 1 according to the present invention (Examples 1 and 2), and (c) to (g) show side sill structures 3 used for comparison (Comparative Examples 1 to 3). In each of Figures 9(a) to 9(g), the left-hand side view is a cross-sectional view of the side sill 10 perpendicular to the vehicle longitudinal direction, and the right-hand side view is a cross-sectional view of the impact absorbing structure 20 within the side sill 10 perpendicular to the vehicle width direction.

[0098] 9(a) shows a side sill structure 1 according to Example 1 of the invention, in which the concave shape 21b of the upper corrugated part 21 and the concave shape 23b of the lower corrugated part are arranged opposite each other as a shock absorbing structure 20 within a side sill 10, and the bottom surfaces of the two corrugated parts are joined together with a displacement in the vehicle longitudinal direction. In the side sill structure 1, the displacement amount between the concave shapes 21b and 23b is W2 = 0.5 × W1 (the center-to-center distance between the concave shapes 21b and 23b), and the recess amount D of the recess 30 provided in the side sill inner 11 is 35 mm (1.0 times the height h of the shock absorbing structure 20).

[0099] In the side sill structure 1 according to Example 2 of the invention shown in FIG. 9B, the offset amount between the recessed shape 21b and the recessed shape 23b in Example 1 of the invention is changed to W2=0.2×W1.

[0100] The side sill structure 3 according to Comparative Example 1 shown in Figure 9(c) includes a side sill 40 in which the recess 30 of the side sill inner panel 11 in Example 1 is removed to form a side sill inner panel 41 with a flattened vertical surface portion 41a. Similarly to Example 1, the impact absorbing structure 20 has a shift amount W2 between the recessed shape 21b and the recessed shape 23b of W2 = 0.5 x W1. Note that because the vertical surface portion 41a of the side sill inner panel 41 of the impact absorbing structure 20 is flattened, the length in the vehicle width direction is shorter than that of Example 1.

[0101] The side sill structure 3 according to Comparative Example 2 shown in Figure 9(d) is similar to Comparative Example 1 in that the recess 30 of the side sill inner panel 11 of Example 2 is removed to create a side sill inner panel 41 with a flattened vertical surface portion 41a. Furthermore, the offset W2 between the recessed shape 21b and the recessed shape 23b in the impact absorbing structure 20 is W2 = 0.0 x W1, meaning that the bottom surfaces of the recessed shapes 21b and 23b are joined together without being offset in the vehicle longitudinal direction. Because the vertical surface portion 41a of the side sill inner panel 41 of the impact absorbing structure 20 is flattened, the vehicle width direction length is shorter than that of Example 2.

[0102] The side sill structures 3 according to Comparative Example 3 shown in Figure 9(e) and Comparative Example 4 shown in Figure 9(f) have an impact absorbing structure 50, which is obtained by removing the lower corrugated part 23 from the impact absorbing structure 20 of Comparative Example 2, and which is disposed within the side sill 40. Comparative Example 3 and Comparative Example 4 differ in the thickness of the metal plate used as the material for the impact absorbing structure 50, with Comparative Example 3 having a thickness of 2.2 mm, the same as Invention Examples 1 and 2 and Comparative Examples 1 and 2, and Comparative Example 4 having a thickness of 3.2 mm, which is thicker than Comparative Example 3.

[0103] The side sill structure 3 according to the comparative example 5 shown in FIG. 9( g ) does not include a shock absorbing structure within the side sill 40 , and only the side sill 40 is provided.

[0104] Table 1 summarizes the tensile strength and thickness of the metal plate used in the side sill 10 in Examples 1 and 2 and Comparative Examples 1 to 5, the material (tensile strength), thickness, and number of corrugated parts that make up the impact absorbing structures 20 and 50, the coefficient α that determines the amount of shift W2 of the concave shape, and the amount of concavity D of the recess 30 provided in the vertical surface portion 11a of the side sill inner 11.

[0105]

[0106] Figure 10 shows modified forms of the impact absorption structure 20 in a crash test of a test body 200 having the side sill structure 1 according to Example 1. Figure 10(a) is a perspective view of the impact absorption structure 20 in the side sill 10 as seen from above, Figure 10(b) is a perspective view of the impact absorption structure 20, and Figure 10(c) is a cross-sectional view in the vehicle up-down direction passing through the center line of a collision body 210.

[0107] In a collision test in which a collision object 210 is collided with the side surface of a test specimen 200, the collision object 210 collides with the shock absorbing structure 20 at a position where the center line of the collision object 210 intersects with the shock absorbing structure 20, as shown in FIG. 10( a). As shown in FIG. 10( a), the center line of the collision object 210 intersects with the top surface of the convex shape 23 a of the lower corrugated part 23, and with the upper corrugated part 21, it intersects with the bottom surface of the concave shape 21 b sandwiched between the joint with the lower corrugated part 23 (marked with a black circle in FIG. 10( a)) and the ridge line of the convex shape 21 a of the upper corrugated part 21. The bottom surface of the concave shape 23 b of the lower corrugated part 23 has low deformation resistance, while the bottom surface of the concave shape 21 b of the upper corrugated part 21 has relatively high deformation resistance. Therefore, in the shock absorbing structure 20, the convex shape 23 a of the lower corrugated part 23 undergoes large out-of-plane deformation.

[0108] 10(c), in the impact absorption structure 20, a rotational moment is generated that rotates the outer end 20b downward and the inner end 20a upward about the longitudinal axis of the vehicle due to the difference in deformation resistance between the upper corrugated part 21 and the lower corrugated part 23. Then, in each of the corrugated parts 21, 23 around the impact position of the collision body 210, buckling deformation occurs such that both the inner and outer end portions are bent out of the plane in the rotational direction, causing the impact absorption structure 20 to tilt with respect to the horizontal plane along the vehicle width direction.

[0109] As a result, in the impact absorption structure 20, after the initial buckling deformation, accordion-like buckling deformation does not occur, and the buckled and deformed portions at both ends of the corrugated parts 21, 23 continue to bend. As a result, the side sill structure 1 according to Example 1 of the invention can suppress load fluctuations after the impact absorption structure 20 buckles during the collision process, and can achieve the ideal load-stroke curve shown in Figure 2.

[0110] Fig. 11 shows the deformation behavior of the impact absorption structure 20 in a collision test of a test body 200 having the side sill structure 1 according to Example 1. Fig. 11 is a contour diagram showing the distribution of equivalent plastic strain in the impact absorption structure from the start of collision of the colliding body, where t is the elapsed time (s) from the start of the collision.

[0111] Immediately after the start of a collision, the outer end 20b of the impact absorption structure 20, which is the side that the collision body 210 hits (the collision end side), and the R portion (bent portion) of the flange that joins to the side sill outer 13, deform (t ~ 0.002 sec).

[0112] As the deformation progresses, the tip on the collision end side deforms to conform to the shape of the collision body 210, but at the end 20a on the side of the side sill inner 11 opposite the collision end, the strain expands in the longitudinal direction of the vehicle, and deformation occurs over an area larger than the diameter of the collision body (t ~ 0.006 sec).

[0113] Thereafter, the lateral surface 11b of the side sill inner 11 and the convex ridge of the shock absorbing structure 20 buckle, causing strain to concentrate at the buckled points, and new buckled points propagate in the longitudinal direction of the vehicle.

[0114] Table 1 above compares the amount of collision energy absorbed at the maximum penetration of the impactor 210 in Examples 1 and 2 and Comparative Examples 1 to 5. The maximum penetration of the impactor 210 was 79.9 mm in Example 1, and 80 mm in Example 2 and Comparative Examples 1 to 5.

[0115] The maximum loads (maximum contact reaction force) in Examples 1 and 2 were 465kN and 469kN, respectively, both of which were less than the 500kN allowable load of the floor cross member, which is a load-bearing part. Furthermore, the collision energy absorption amounts were 30.0kN and 27.9kN, respectively, which exceeded the target collision energy absorption amount (=27.0kN).

[0116] In contrast, in Comparative Example 1, in which the recess 30 was removed from the side sill structure 1 of Example 1, the vehicle-interior end 20a of the impact absorption structure 20 was significantly displaced upward toward the vehicle during the collapse of the side sill structure 3, and the collapse of the impact absorption structure 20 did not progress sufficiently. As a result, the maximum load was 403 kN, which was lower than the maximum load (465 kN) of Example 1. Furthermore, the amount of absorbed energy in a collision at the maximum stroke of 80 mm was 403 kN, which was 13% lower than the amount of absorbed energy in Example 1 (465 kJ).

[0117] In Comparative Example 2, in which the bottom surfaces of the concave portions 21b of the upper corrugated part 21 and the concave portions 23b of the lower corrugated part 23 are joined together without being shifted in the vehicle longitudinal direction, the ridges of the upper and lower corrugated parts 21, 23 are concentrated in the vehicle longitudinal direction. As a result, the maximum load in Comparative Example 2 was higher than in Comparative Example 1, reaching 514 kN, exceeding the load capacity (500 kN) of the floor cross member. Furthermore, although the collision energy absorption amount was increased to 25.8 kJ compared to Comparative Example 1 due to the higher maximum load, the target collision energy amount (27.0 kJ) could not be achieved.

[0118] In Comparative Example 3, in which an impact absorption structure 50 was provided in which the lower corrugated part was removed from the impact absorption structure 20 in Comparative Example 2, the maximum load was 348 kN, which was significantly lower than in Invention Examples 1 and 2. Furthermore, as the maximum load decreased, the amount of collision energy absorption also decreased to 17.4 kJ, which was significantly lower than the target amount of collision energy absorption.

[0119] In Comparative Example 4, the plate thickness of the impact absorption structure 50 of Comparative Example 3 was increased (from 2.2 mm to 3.2 mm), resulting in a collision energy absorption amount of 29.3 kJ, achieving the target collision energy absorption amount. However, the maximum load was 526 kN, which significantly exceeded the load capacity of the floor cross member, which was 500 kN.

[0120] The results of Comparative Example 5 show the collision characteristics of the side sill 40 itself, with the amount of collision energy absorption remaining at 1.3 kJ.

[0121] Figure 12 shows the relationship between the amount of collision energy absorbed by the side sill structure and the maximum load input to the side sill structure during a side collision in the collision test for Example 1. As shown in Figure 12, Examples 1 and 2 of the present invention achieved a higher amount of collision energy absorption than Comparative Examples 1 to 5, and furthermore, were able to keep the maximum load during a side collision lower than the allowable load of the load-bearing components.

[0122] In Example 2, the effect on the amount of collision energy absorption during a side collision of an impact absorbing structure arranged within a side sill due to differences in the amount of offset between the concave shape of the upper corrugated part and the concave shape of the lower corrugated part was examined.

[0123] In Example 2, similar to Example 1 described above, a collision analysis was performed on a collision test in which a collision object 210 collided with the side surface of the side sill 10 of a test specimen 200 equipped with the side sill structure 1 shown in FIG. 8 . As in Example 1 described above, in the collision analysis, the collision object 210 collided with the test specimen 200 in a direction perpendicular to the vehicle longitudinal direction at an initial velocity of 35.0 km / h and a maximum penetration of 80 mm, as shown in FIG. 8 . The collision object 210 was a rigid pole with a radius R of 127 mm (equivalent to a diameter of 254 mm). The load capacity of the floor cross member simulation portion 201 was set to 500 kN or less, and the target value for the amount of collision energy absorption by the side sill structure 1 was set to 27 kJ (equivalent to 90% of the collision energy of the collision object 210).

[0124] In Example 2, a test specimen 200 in which the impact absorption structure 20 shown in Figure 13(a) was disposed within the side sill 10 was used as Example 3. In the impact absorption structure 20 according to Example 3, the offset amount W2 between the concave shape 21b of the upper corrugated part 21 and the concave shape 23b of the lower corrugated part 23 was set to 50% (50% offset) of the center-to-center distance W1 between the adjacent convex shape 21a and concave shape 21b.

[0125] In addition, in Example 2, as comparison objects, a test specimen 200 in which the shock absorbing structure 20 shown in Figure 13(b) was arranged in the side sill 10 was used as Comparative Example 6, and a test specimen in which the shock absorbing structure 50 shown in Figure 13(c) was arranged inside the side sill was used as Comparative Example 7.

[0126] The shock absorbing structures 20 according to Comparative Examples 6 and 7 have their bottom surfaces joined together without any shift in the vehicle longitudinal direction between the centers of the concave shapes 21b of the upper corrugated part 21 and the concave shapes 23b of the lower corrugated part 23 (0% shift). The shock absorbing structure 50 according to Comparative Example 8 is constructed by removing the lower corrugated part 23 from the shock absorbing structure 20 according to Comparative Example 2 and using only the upper corrugated part 21 (one corrugated part).

[0127] Inventive Example 3, Comparative Example 7, and Comparative Example 8, metal plates having the thickness and tensile strength shown in Table 1 were used so that the maximum load during a side collision would be equal to or less than the allowable load of 500 kN. Comparative Example 6 was produced by changing the shift amount W2 of Inventive Example 3 from 50% to 0%, and was produced using metal plates having the same thickness and tensile strength as Inventive Example 3.

[0128] Figure 14 shows cross-sectional views of a side sill structure 1 illustrating the deformation process of the impact absorption structure 20 disposed within the side sill 10. Figure 14(a) is a cross-sectional view of a side sill structure according to Example 3, and Figure 14(b) is a cross-sectional view of a side sill structure 1 according to Comparative Example 6. In Example 3, the concave shape of the upper corrugated part and the concave shape of the lower corrugated part of the impact absorption structure face each other and are joined in an asymmetrical manner, with a displacement in the longitudinal direction of the vehicle. This generates a rotational moment that rotates around the axis in the longitudinal direction of the vehicle, causing buckling deformation in which the inboard and outboard ends are bent out of plane in the rotational direction.

[0129] On the other hand, in Comparative Example 6, after the initial buckling deformation occurred at the end on the vehicle exterior side, buckling deformation occurred successively in a bellows-like shape, undulating from the vehicle exterior side to the vehicle interior side, with multiple antinodes.

[0130] 15 shows load-stroke curves obtained by crash analysis for side crash tests of specimens 200 according to Example 3 and Comparative Example 6. In Example 3, load fluctuations were suppressed after the initial buckling deformation, and a constant load below the withstand load (allowable load = 500 kN) was maintained. In contrast, in Comparative Example 6, the load continued to increase after the initial buckling deformation, reaching a maximum load (= 624 kN > 500 kN) that exceeded the withstand load.

[0131] 16 shows (a) the load-stroke curve and (b) the transition of the collision energy absorption amount, which were obtained by collision analysis for side collision tests of the test specimens 200 according to Example 3, Comparative Example 7, and Comparative Example 8. Table 2 also shows the collision energy absorption amount, maximum load, and maximum penetration amount of the colliding object at a stroke amount of 80 mm, which were obtained by collision analysis for each of Example 3, Comparative Example 7, and Comparative Example 8.

[0132]

[0133] In Example 3, as shown in Figure 16(a), the load rise (rigidity) was fast at the beginning of the collision, and the load fluctuation after buckling was suppressed, maintaining a constant load. As shown in Figure 16(b), the target amount of absorbed energy in the collision of 30 kJ was reached at a stroke of 80 mm.

[0134] In contrast, in Comparative Example 7, as shown in Figure 16(a), the load rise (rigidity) was slow at the beginning of the collision, and the load continued to increase even after buckling occurred. The maximum load at a stroke of 80 mm or less was 475 kN, a lower value than that of Example 6. Therefore, as shown in Figure 16(b), the collision energy absorption amount during the collision process remained lower than that of Example 3, and the collision energy amount at a stroke of 80 mm was 26.7 kJ. The maximum penetration amount of the impacting object required to achieve the target collision energy absorption amount of 30 kJ was 87.3 mm, which was greater than that of Example 3.

[0135] In Comparative Example 8, as shown in Figure 16(a), the load rise (rigidity) at the initial stage of collision was slower than in Comparative Example 7, and the load continued to increase even after buckling occurred. Furthermore, although the maximum load at strokes of 80 mm or less was 479 kN, similar to that of Comparative Example 7, the collision energy absorption amount during the collision process remained lower than in Comparative Example 6, and the collision energy amount at a stroke of 80 mm was 24.2 kJ. Furthermore, the maximum penetration amount of the impacting object required to achieve the target collision energy absorption amount of 30 kJ was 93.2 mm, which was greater than that of Comparative Example 7.

[0136] According to the present invention, it is possible to provide a side sill structure for an automobile that improves crash performance in the event of a side collision without increasing weight or manufacturing costs.

[0137] DESCRIPTION OF SYMBOLS 1 Side sill structure (invention example) 3 Side sill structure (comparison example) 10 Side sill 11 Side sill inner 11a Vertical surface portion 11b Horizontal surface portion 11c Flange portion 13 Side sill outer 13a Vertical surface portion 13b Horizontal surface portion 13c Flange portion 20 Impact absorbing structure 20a Vehicle interior end portion 20b Vehicle exterior end portion 21 Upper corrugated part 21a Convex shape 21b Concave shape 23 Lower corrugated part 23a Convex shape 23b Concave shape 25 Flange portion 30 Concave portion 31 Bottom portion 33 Wall portion 35 L-shaped bracket 37 Support structure 40 Side sill 41 Side sill inner 41a Vertical surface portion 50 Impact absorbing structure 100 Vehicle side structure 101 Floor panel REFERENCE SIGNS LIST 101a Flange portion 103 Floor cross member 103a End portion in vehicle width direction 105 Battery case 105a Side portion 105b Bottom plate 105c Mounting flange 107 Battery pack 109 Fixing bolt 200 Test body 201 Floor cross member simulation portion 203 Battery case wall portion 210 Collision body

Claims

1. A side sill structure for an automobile comprising a side sill having a side sill inner having a groove shape extending in the vehicle longitudinal direction and opening towards the vehicle exterior side in the vehicle width direction, and a side sill outer having a groove shape extending in the vehicle longitudinal direction and opening towards the vehicle interior side in the vehicle width direction, the side sill inner and the side sill outer being joined together with the opening sides facing each other, the side sill structure comprising: a shock absorbing structure disposed within the side sill, the end portion on the vehicle interior side in the vehicle width direction being connected to the bottom of the groove shape of the side sill inner and / or the end portion on the vehicle exterior side in the vehicle width direction being connected to the bottom of the groove shape of the side sill outer, absorbing shock input to the side sill in the event of a side collision of the vehicle; and a vertical restraining structure provided at the bottom of the side sill inner for restraining the end portion on the vehicle interior side in the vehicle vertical direction in the event of a side collision of the vehicle, the shock absorbing structure being: A side sill structure for an automobile comprising a pair of corrugated parts arranged in the vertical direction of the vehicle, the pair of corrugated parts having a corrugated shape in which convex shapes and concave shapes are alternately continuous in the longitudinal direction of the vehicle in a cross section perpendicular to the vehicle width direction, the pair of corrugated parts being made of metal plates, the concave shape of the upper corrugated part being arranged opposite the concave shape of the lower corrugated part, and the opposing concave shapes being joined in a state of being offset in the longitudinal direction of the vehicle.

2. A side sill structure for an automobile as described in claim 1, wherein the upper and lower restraint structure is a recess provided at the bottom of the groove shape in the side sill inner and recessed toward the inside of the vehicle in the vehicle width direction, and the inside end of the shock absorbing structure is inserted into the recess.

3. A side sill structure for an automobile as described in claim 1 or 2, wherein the outer end of the shock absorbing structure in the vehicle width direction is in contact with the bottom of the groove shape in the side sill outer.

4. A side sill structure for an automobile as described in any one of claims 1 to 3, wherein the amount of shift W2 in the longitudinal direction of the vehicle of the opposing concave shapes in the upper and lower corrugated parts is 20% to 50% of the center-to-center distance W1 between the convex shape and the concave shape adjacent in the longitudinal direction of the vehicle in the corrugated part.

5. A side sill structure for an automobile as described in claim 2, wherein the recess amount D of the recess provided in the side sill inner panel is 0.8 to 1.2 times the height h of the shock absorbing structure in the vertical direction of the vehicle.

6. The automobile side sill structure according to any one of claims 1 to 5, wherein the corrugated part is made of a metal plate having a tensile strength of 590 MPa or more.

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