Side beam structure and vehicle body lower structure of automobile

Abstract

In a closed cross-sectional space (3) in a side member (1), an impact absorbing structure (4) is provided by a vertical partition member (2) that vertically passes through the space. The shock absorbing structure part 4 is configured from a transverse partition member 5 that traverses the closed cross-sectional spaces 3a, 3b on the inside and outside of the vehicle body partitioned by the vertical partition member 2 in the vehicle width direction, and a partition plate 6 that is provided in the upper-side spaces 30a, 30b partitioned by the transverse partition member 5 in the vehicle width direction. A transverse partition member 5 and a bulkhead 6 on the inner and outer sides of the vehicle body are disposed so as to face each other with a vertical partition member 2 interposed therebetween, and a rib is formed on the transverse partition member 5 in the vehicle width direction. According to the side beam structure, expected collision characteristics can be obtained even if the number of partition plates (6) is reduced, and therefore high collision energy absorption characteristics can be obtained with small collision deformation while weight increase caused by structural members is restrained.

Description

Technical Field

[0001] The present invention relates to a side sill structure of a vehicle body side and a vehicle body lower structure including the side sill, and more particularly to a structure suitable for an automobile equipped with a battery assembly below a floor panel between two side sills. Background Art

[0002] Typically, a battery assembly is mounted under the floor of an electric vehicle. The battery assembly consists of internal battery cells and a battery box for housing the battery cells. Typically, the battery box has the function of protecting the battery cells from impact loads, and uses components with high rigidity and high crashworthiness load. Components are arranged around the battery box to absorb energy by deforming the components themselves. In particular, in the event of a side impact, the side beam absorbs the impact load from the side of the vehicle body, and the remaining load is borne by the floor cross member or the battery box longitudinal beam. At this time, if the amount of deformation required for the energy absorption of the side beam is small, the energy absorption part can be reduced, and instead, the volume of the battery assembly can be expanded, thereby increasing the cruising distance. In view of the above circumstances, a side beam structure with excellent energy absorption property and light weight is required.

[0003] In the past, regarding the side member structure and the vehicle body lower structure including the side member structure, for example, the following technology has been disclosed. Patent document 1 discloses a side member structure of a vehicle body having a cylinder extending in the front-rear direction of the vehicle body and an impact absorption member (impact absorption member) arranged inside the cylinder, which has the following structure and function. The impact absorption member has: a web extending in the front-rear direction of the vehicle body and flat in the vehicle width direction; an outer side flange connected to the outer side end of the web and extending in the front-rear direction of the vehicle body; and an inner side flange connected to the inner side end of the web and extending in the front-rear direction of the vehicle body. In addition, the outer side flange and the inner side flange are arranged in a manner of clamping the web from above and below, and have ribs extending in the front-rear direction of the vehicle body, thereby suppressing local deformation while maintaining the impact absorption capacity.

[0004] Patent document 2 discloses a vehicle body lower structure having a side beam extending in the front-rear direction of the vehicle and a stiffener extending in the extension direction of the side beam, which has the following structure and function. The stiffener includes an outer stiffener with a hat-shaped cross-section bulging outward in the width direction of the vehicle body and an inner stiffener with a hat-shaped cross-section bulging inward in the width direction of the vehicle body. The first side surface of the stiffener formed on the inner side of the stiffener is relatively offset upward compared to the second side surface of the stiffener formed on the outer side of the stiffener. A stiffening rib (bead) extending in the width direction of the vehicle body is formed on at least one of the upper and lower surfaces of the outer stiffener. Through the above structure, the collision load input to the side beam is efficiently transferred to the inner side of the width direction of the vehicle body.

[0005] Patent Document 3 discloses a vehicle underbody structure having the following structure and function. The underbody structure includes side members extending in the vehicle's longitudinal direction, and bulkheads positioned within the side members, across from the points where the battery pack is secured, to reinforce the cross-section of the side members from the inside. This structure allows the battery cross member to fully absorb the energy of an impact load from the side of the vehicle body, and stably protect the battery cells within the battery pack.

[0006] Patent Document 4 discloses a vehicle body underbody structure comprising a side member, a first energy-absorbing member, and a second energy-absorbing member. The structure has the following configuration: The first energy-absorbing member is disposed on the inner panel side of a hollow cross-section of the side member, while the second energy-absorbing member is disposed on the outer panel side of the hollow cross-section of the side member, facing the first energy-absorbing member. The first energy-absorbing member is designed to have a greater strength than the second energy-absorbing member. This results in a vehicle body underbody structure that can be mass-produced inexpensively using conventional steel sheets.

[0007] [Prior art literature]

[0008] [Patent Document]

[0009] Patent Document 1: International Publication No. 2021 / 157651

[0010] Patent Document 2: Japanese Patent Application Laid-Open No. 2018-131133

[0011] Patent Document 3: Japanese Patent Application Laid-Open No. 2019-202743

[0012] Patent Document 4: International Publication No. 2020 / 070935 Summary of the Invention

[0013] [Problems to be Solved by the Invention]

[0014] The technology of Patent Document 1 uses a reinforcement member within the side sill with a constant cross-section in the vehicle's longitudinal direction, thus absorbing collision energy regardless of the collision location. However, the presence of reinforcement members in areas not requiring reinforcement can lead to excessive weight. Furthermore, in side sills with partition members, as in the technology of Patent Document 2, sufficient collision energy absorption properties cannot be achieved simply by placing reinforcement members with hat-shaped cross sections on both sides of the partition member (inside and outside the partition member). Furthermore, even when ribs extending in the vehicle body width direction are formed on at least one of the upper and lower surfaces of the reinforcement member, the collision energy absorption properties achieved are still insufficient.

[0015] Furthermore, in side sills having a partition member, as in the technique of Patent Document 3, when a bulkhead is disposed in the closed sectional space between the side sill and the partition member, the bulkhead comes into line contact with the partition member during a collision, resulting in insufficient load transmission efficiency and insufficient collision energy absorption performance. Furthermore, in the technique of Patent Document 4, when a hat-shaped cross-section member is disposed on the inner panel side of the side sill as a first energy absorbing member and a bulkhead is disposed on the outer panel side so as to oppose the first energy absorbing member as a second energy absorbing member, buckling of each energy absorbing member during a collision causes cross-section collapse of the side sill in the vehicle height direction, failing to achieve sufficient collision energy absorption performance.

[0016] The present invention has been developed to address the aforementioned issues, and its object is to provide a vehicle side member structure that achieves high collision energy absorption characteristics with low collision deformation while suppressing weight increases due to structural members. Another object of the present invention is to provide a vehicle body underbody structure including a side member structure having such excellent collision characteristics.

[0017] [Means for solving the problem]

[0018] The present inventors have conducted repeated research to address the aforementioned issues and have discovered that, in order to solve the aforementioned problems, it is effective to utilize a vertical partition member that vertically extends through the closed cross-sectional space within the side sill and to provide an impact-absorbing structural portion comprised of specific structural members within the closed cross-sectional space. Specifically, they have discovered that the aforementioned problems can be solved by providing an impact-absorbing structural portion comprised of a ribbed horizontal partition member and a bulkhead. The horizontal partition member is disposed so as to extend across the closed cross-sectional space on the inside and outside of the vehicle body, separated by the vertical partition member, in the vehicle width direction. The bulkhead is disposed above each horizontal partition member in the closed cross-sectional space along the vehicle width direction. The horizontal partition members and bulkhead on the inside and outside of the vehicle body are disposed opposite each other with the vertical partition member interposed therebetween. Furthermore, they have discovered that by optimizing the structure, arrangement, and connection method of the horizontal partition member and bulkhead that constitute the impact-absorbing structural portion with other members, higher collision energy absorption characteristics can be achieved. The present invention has been developed based on this finding, and its gist is as follows.

[0019] The side member structure of an automobile to which the present invention relates comprises: a side member (1), which is composed of a side member inner member (1a) on the inner side of the vehicle and a side member outer member (1b) on the outer side of the vehicle, forming a closed cross-sectional space (3) inside; and a longitudinal partition member (2), which is sandwiched between the side member inner member (1a) and the side member outer member (1b) of the side member (1), and divides the closed cross-sectional space (3) into a closed cross-sectional space (3a) on the inner side of the vehicle and a closed cross-sectional space (3b) on the outer side of the vehicle by the longitudinal partition member (2), wherein the side member structure of the automobile comprises an impact absorbing structural portion (4) in the closed cross-sectional space (3), and the impact absorbing structural portion (4) is composed of a transverse partition member (5) and a partition (6), wherein the transverse partition member (5) crosses each closed cross-sectional space (3a), (3b) in the vehicle width direction to separate the closed cross-sectional space up and down. Partition, the partition (6) is arranged in the upper side space (30a), (30b) in the space divided by the horizontal partition member (5) in the vehicle width direction, the partition (6) is arranged in the upper side space (30a), (30b) in the vehicle length direction in a manner that the upper side space (30a), (30b) is divided into multiple parts in the vehicle length direction, and a reinforcing rib (7) is formed between the partitions (6) on the horizontal partition member (5) along the vehicle width direction, and the reinforcing rib (7) is arranged in the vehicle length direction. The horizontal partition member (5) and the partition (6) in the closed cross-sectional space (3a) on the inner side of the vehicle and the horizontal partition member (5) and the partition (6) in the closed cross-sectional space (3b) on the outer side of the vehicle are respectively arranged opposite to each other in the vehicle width direction with the longitudinal partition member (2) sandwiched therebetween.

[0020] Alternatively, the transverse partition member (5) in the closed cross-sectional space (3a) on the inner side of the vehicle is joined to the inner side member (1a) of the side beam and the longitudinal partition member (2), and the transverse partition member (5) in the closed cross-sectional space (3b) on the outer side of the vehicle is joined to the outer side member (1b) of the side beam and the longitudinal partition member (2).

[0021] Alternatively, the transverse partition member (5) in the closed cross-sectional space (3a) on the inner side of the vehicle may have a flange portion (50x) on one end side in the vehicle width direction and a flange portion (50y) formed continuously upward and extending along the longitudinal partition member (2) to the upper end portion of the side beam (1) on the other end side, the flange portion (50x) on one end side in the vehicle width direction is joined to the inner surface of the side beam inner member (1a), and the upper end portion of the flange portion (50y) on the other end side is joined to the upper end portion of the side beam inner member (1a) and the upper end portion of the longitudinal partition member (2) in a state of being clamped by the upper end portion of the side beam inner member (1a) and the upper end portion of the longitudinal partition member (2), and the transverse partition member (5) in the closed cross-sectional space (3b) on the outer side of the vehicle may have a flange portion (50y) on one end side in the vehicle width direction. The flange portion (51x) has an edge portion and a flange portion (51y) formed continuously upward and extending along the longitudinal partition member (2) to the upper end portion of the side beam (1). The flange portion (51x) on one end side in the vehicle width direction is joined to the inner surface of the side beam outer member (1b), and the upper end portion of the flange portion (51y) on the other end side is joined to the upper end portion of the side beam outer member (1b) and the upper end portion of the longitudinal partition member (2) in a state of being clamped by the upper end portion of the side beam outer member (1b) and the upper end portion of the longitudinal partition member (2).

[0022] Alternatively, the transverse partition member (5) in the closed cross-sectional space (3a) on the inner side of the vehicle may have a flange portion (52x) on one end side in the vehicle width direction and a flange portion (52y) on the other end side that is continuously formed downward and extends along the longitudinal partition member (2) to the lower end portion of the side beam (1), the flange portion (52x) on one end side in the vehicle width direction is joined to the inner surface of the side beam inner member (1a), and the lower end portion of the flange portion (52y) on the other end side is clamped by the lower end portion of the side beam inner member (1a) and the lower end portion of the longitudinal partition member (2) and is joined to the lower end portion of the side beam inner member (1a) and the lower end portion of the longitudinal partition member (2). The horizontal partition member (5) in the closed cross-sectional space (3b) on the outside of the vehicle has a flange portion (53x) on one end side in the vehicle width direction and a flange portion (53y) on the other end side that is continuously formed downward and extends along the longitudinal partition member (2) to the lower end portion of the side beam (1), the flange portion (53x) on one end side in the vehicle width direction is joined to the inner surface of the side beam outer member (1b), and the lower end portion of the flange portion (53y) on the other end side is joined to the lower end portion of the side beam outer member (1b) and the lower end portion of the longitudinal partition member (2) in a state of being clamped by the lower end portion of the side beam outer member (1b) and the lower end portion of the longitudinal partition member (2).

[0023] Alternatively, the transverse partition member (5) in the closed cross-sectional space (3a) on the inner side of the vehicle may have flange portions (54) at one end side and the other end side in the vehicle width direction, the flange portion (54) at one end side in the vehicle width direction is joined to the inner surface of the side beam inner part (1a), and the flange portion (54) at the other end side is joined to the vehicle inner surface of the longitudinal partition member (2), and the transverse partition member (5) in the closed cross-sectional space (3b) on the outer side of the vehicle may have flange portions (55) at one end side and the other end side in the vehicle width direction, the flange portion (55) at one end side in the vehicle width direction is joined to the inner surface of the side beam outer part (1b), and the flange portion (55) at the other end side is joined to the vehicle outer surface of the longitudinal partition member (2).

[0024] Alternatively, the partition (6) in the upper side space (30a) on the inner side of the vehicle body is at least respectively joined to the upper transverse surface (101A) of the inner side member (1a) of the side beam and the transverse partition member (5), and the partition (6) in the upper side space (30b) on the outer side of the vehicle body is at least respectively joined to the longitudinal surface (100), the upper transverse surface (101A) and the transverse partition member (5) of the outer side member (1b).

[0025] Alternatively, the partition plate (6) may include a partition plate (6) provided in an area within the width of the floor cross member in the front-rear direction of the vehicle. x ) and a partition (6) provided in an area outside the width of the floor beam y ), in the front-rear direction of the vehicle, partitions (6 x ), and a partition plate (6 y ), when the two adjacent partitions (6 x ) is set to w1 and the partition (6 x ) and the partition (6 x ) adjacent partitions (6 y ) is set to w2, it is set to w1<w2.

[0026] Alternatively, at least a portion of the partition (6 y ) includes a partition group consisting of two or more partitions arranged adjacent to each other.

[0027] Alternatively, the partition plate (6) is joined to the transverse partition member (5) via the flange (60), and the distance between two adjacent reinforcing ribs (7) in the vehicle length direction is set to W. H The width of the flange (60) of the partition (6) is set to W BF When W is satisfied BF ≤W H≤127mm, wherein the distance between two adjacent reinforcing ribs (7) in the vehicle length direction refers to the distance between the edges of the two reinforcing ribs (7).

[0028] The yield strength of the metal sheet constituting the shock absorbing structure (4) may be less than or equal to the yield strength of the metal sheet constituting the floor cross member.

[0029] The metal plate constituting the impact absorbing structure (4) may have a tensile strength of 780 MPa or higher, or a Vickers hardness (HV) of 250 or higher at a position of 1 / 4 of the thickness of the metal plate.

[0030] Alternatively, the metal plate constituting the impact absorbing structure (4) is a steel plate containing, by mass%, C: 0.030% to 0.250%, Si: 0.01% to 2.50%, Mn: 1.00% to less than 3.50%, P: 0.001% to 0.100%, S: 0.0200%, and Al: 0.010% to 2.000%.

[0031] Alternatively, the metal plate constituting the shock absorbing structure (4) may have, at a position 1 / 4 of the thickness of the metal plate, a steel structure comprising ferrite having an area ratio of not less than 0% and not more than 65%, martensite and tempered martensite having an area ratio of not less than 30% and not more than 100%, and residual austenite having an area ratio of not less than 0% and not more than 15%.

[0032] The ultimate deformability of the metal plate constituting the shock absorbing structure (4) in a tensile test may be 0.55 or more.

[0033] Alternatively, the critical curvature radius R (mm) of the metal plate constituting the impact absorbing structure (4) that does not produce cracks when subjected to a 90° V-bending test and the sheet thickness t (mm) of the metal plate satisfy R / t≤7.0.

[0034] A first embodiment of the present invention relates to a lower body structure of an automobile comprising: side beams (1) arranged on both sides of the lower body of the automobile along the longitudinal direction of the vehicle; a floor cross beam (10) arranged on a bottom plate (11) along the width direction of the vehicle and connecting the two side beams (1); and a battery box (12) arranged between the two side beams (1) on the lower side of the floor cross beam (10), wherein the lower body structure of the automobile comprises the side beam structure of the automobile according to the present invention, the battery box longitudinal beam (120) of the battery box (12) and the side beam (1) are adjacent in the width direction of the vehicle and are arranged at a position where at least a portion of them overlap when viewed from the side of the vehicle, and the transverse partition member (5) is arranged so that the battery box longitudinal beam (120) is located on the horizontal extension line of the transverse partition member (5).

[0035] Alternatively, the crashworthiness load of the member constituting the impact absorbing structure (4) may be less than or equal to the crashworthiness load of the floor cross member (10) and the battery box longitudinal member (120).

[0036] A second embodiment of the present invention relates to a lower body structure of an automobile comprising: side members (1) arranged on both sides of the lower body of the automobile along the longitudinal direction of the vehicle; and a floor cross member (10) arranged on a bottom plate (11) along the width direction of the vehicle and connecting the two side members (1), wherein the lower body structure of the automobile comprises the side member structure of the automobile according to the present invention, and a transverse partition member (5) is arranged in such a manner that the floor cross member (10) is located on a horizontal extension line of the transverse partition member (5).

[0037] Alternatively, the endurance of the member constituting the impact absorbing structure (4) may be less than the endurance of the floor cross member (10).

[0038] [Effects of the Invention]

[0039] The side member structure of the automobile of the present invention and the lower body structure including the side member structure utilize a longitudinal partition member 2 that longitudinally passes through the closed cross-sectional space 3 within the side member 1 to provide an impact absorbing structure 4 composed of specific structural members within the closed cross-sectional space 3, thereby achieving high collision energy absorption characteristics with a small collision deformation amount. Therefore, in the case of an automobile such as an electric vehicle equipped with a battery assembly between the two side members, it has the advantages of being able to reduce the space required for energy absorption and to expand the volume of the battery assembly. In addition, the impact absorbing structure 4 can achieve high bending stiffness with the minimum necessary components, thereby also being able to suppress the weight increase of the vehicle body caused by the components. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 The present invention schematically shows an embodiment of a side member structure of an automobile and a vehicle lower structure including the same, and is a longitudinal cross-sectional view of the vehicle lower structure (one of the structures on both sides of the vehicle lower structure) including the side member in the vehicle width direction.

[0041] Figure 2 It is along Figure 1 Cross-sectional view along line II-II.

[0042] Figure 3 It is along Figure 2 A cross-sectional view of the horizontal partition member along line III-III.

[0043] Figure 4 yes Figure 1 Component expansion diagram of the side beam structure in an embodiment.

[0044] Figure 5 The width W of the floor cross member in the vehicle body lower structure used to explain the present invention. F Picture.

[0045] Figure 6 It is an explanatory diagram showing another example of arrangement of bulkheads in the automobile side member structure according to the present invention.

[0046] Figure 7 It is an explanatory diagram showing another example of arrangement of bulkheads in the automobile side member structure according to the present invention.

[0047] Figure 8 The present invention schematically shows another embodiment of the automobile side member structure and the vehicle lower structure including the same, and is a longitudinal cross-sectional view of the vehicle lower structure (one of the structural parts on both sides of the vehicle lower part) including the side member in the vehicle width direction.

[0048] Figure 9 The present invention schematically shows another embodiment of the automobile side member structure and the vehicle lower structure including the same, and is a longitudinal cross-sectional view of the vehicle lower structure (one of the structural parts on both sides of the vehicle lower part) including the side member in the vehicle width direction.

[0049] Figure 10 The present invention schematically shows another embodiment of the automobile side member structure and the vehicle lower structure including the same, and is a longitudinal cross-sectional view of the vehicle lower structure (one of the structural parts on both sides of the vehicle lower part) including the side member in the vehicle width direction.

[0050] Figure 11 It is a diagram for explaining the test conditions of a crash test in the embodiment.

[0051] Figure 12-1 It is an explanatory diagram showing a test body (side member structure) and test conditions of Inventive Example 1 in a collision test of an embodiment.

[0052] Figure 12-2 It is an explanatory diagram showing a test body (side sill structure) and test conditions of Inventive Example 2 in a collision test of an embodiment.

[0053] Figure 12-3 It is an explanatory diagram showing a test body (side sill structure) and test conditions of Comparative Example 1 in the collision test of the embodiment.

[0054] Figure 12-4 It is an explanatory diagram showing a test body (side sill structure) of Comparative Example 2 and test conditions in the collision test of the embodiment.

[0055] Figure 12-5 It is an explanatory diagram showing a test body (side sill structure) and test conditions of Comparative Example 3 in the collision test of the embodiment.

[0056] Figure 12-6 It is an explanatory diagram showing a test body (side sill structure) of Comparative Example 4 and test conditions in the collision test of the embodiment.

[0057] Figure 13-1 This is a graph showing the relationship between the intrusion amount of an impact object (column) and the absorbed energy in the collision test of Examples (Inventive Examples 1 and 2 and Comparative Example 1).

[0058] Figure 13-2 It is a graph showing the relationship between the amount of penetration of the collision body (column) and the absorbed energy in the collision tests of Examples (Comparative Examples 2 to 4).

[0059] Figure 14 This is a graph showing the absorbed energy at the time of maximum penetration of the collision body (column) in the collision tests of Examples (Inventive Examples and Comparative Examples).

[0060] Figure 15 This is a graph showing the maximum penetration amount of the collision body (column) in the collision test of Examples (Invention Examples and Comparative Examples). DETAILED DESCRIPTION

[0061] Figures 1 to 4 An embodiment of the automobile side member structure and the vehicle body lower structure including the same is schematically shown. Figure 1 This is a longitudinal sectional view of the vehicle body lower structure (one of the structural parts on both sides of the vehicle body lower structure) including the side members in the vehicle width direction. Figure 2 It is along Figure 1The cross-sectional view of line II-II, Figure 3 It is along Figure 2 A cross-sectional view of the horizontal partition member along line III-III in FIG. Figure 4 This is a diagram of the components of the side member structure. The side member is a frame structure member arranged along the length of the vehicle on both sides of the lower portion of the vehicle body. The automotive side member structure of the present invention comprises a side member 1 comprising an inner side member 1a on the vehicle's inner side and an outer side member 1b on the vehicle's outer side, and a longitudinal partition member 2 sandwiched between the inner side member 1a and the outer side member 1b of the side member 1 as basic structural components. A closed cross-sectional space 3 is formed within the side member 1. This closed cross-sectional space 3 is divided into a closed cross-sectional space 3a on the vehicle's inner side and a closed cross-sectional space 3b on the vehicle's outer side by the longitudinal partition member 2 extending longitudinally through the space. Details will be described later. The inner side member 1a and the outer side member 1b that constitute the side member 1 each have a cross-sectional groove shape. The side member structure is formed by joining the inner side member 1a and the outer side member 1b together while sandwiching the longitudinal partition member 2.

[0062] The side beam inner member 1a and the side beam outer member 1b constituting the side beam 1 are formed by forming a metal plate. The side beam inner member 1a and the side beam outer member 1b respectively have a main body portion with a groove-shaped cross section, which includes a longitudinal face portion 100 and transverse faces 101A and 101B continuously formed at the upper and lower ends thereof. A flange portion 102 is continuously formed at the upper and lower ends of the main body portion (the ends of the transverse faces 101A and 101B). The longitudinal face portion 100 may not be vertical, but may have an appropriate inclination or curve. In addition, the transverse faces 101A and 101B may not be horizontal, but may be as follows Figure 1 The vertical partition member 2 is also made of a metal plate, but it may not be a completely flat plate, but may be a member obtained by bending a flat plate (bend forming).

[0063] The side sill inner member 1a and the side sill outer member 1b are joined (typically by spot welding) by overlapping their flange portions 102, thereby forming a side sill 1 with a closed cross-sectional space 3 formed inside. At this time, since a longitudinal partition member 2 is sandwiched between the side sill inner member 1a and the side sill outer member 1b, the flange portions 102 of the side sill inner member 1a and the side sill outer member 1b are joined via the upper and lower ends of the longitudinal partition member 2 sandwiched therebetween. This creates a structure in which the longitudinal partition member 2 longitudinally extends through the closed cross-sectional space 3 within the side sill 1, dividing the closed cross-sectional space 3 into two closed cross-sectional spaces 3a and 3b in the vehicle width direction. In this embodiment, as described later, the upper end portion of the flange portion 50y of the transverse partition member 5 on the vehicle interior is joined to these members, sandwiched between the upper end portion of the longitudinal partition member 2 and the upper flange portion 102 of the side sill inner member 1a. Similarly, the upper end of the flange 51y of the transverse partition member 5 on the vehicle's outer side is joined to these members, sandwiched between the upper end of the longitudinal partition member 2 and the flange 102 of the side sill outer member 1b. Consequently, the upper flanges 102 of the side sill inner member 1a and the side sill outer member 1b are joined via the upper end of the longitudinal partition member 2 and the upper end of the flanges 50y and 51y of the transverse partition member 5, sandwiched therebetween. The longitudinal partition member 2 is sandwiched between the side sill inner member 1a and the side sill outer member 1b, with its upper and lower ends joined to the upper and lower ends of the side sill body (in this embodiment, joined between the flanges 102 of the side sill inner member 1a and the side sill outer member 1b). This provides high resistance, preventing the cross-section of the side sill 1 from collapsing in the vehicle height direction (cross-section collapse) during a side impact, contributing to improved collision performance.

[0064] The automotive side member structure of the present invention includes an impact-absorbing structure 4 comprising specific structural members within the closed cross-sectional space 3 of the side member 1. This impact-absorbing structure 4 is composed of a transverse partition member 5 and a bulkhead 6. The transverse partition member 5 extends across each of the closed cross-sectional spaces 3a and 3b in the vehicle width direction, dividing the closed cross-sectional spaces into upper and lower portions. The bulkhead 6 is provided along the vehicle width direction within the upper side spaces 30a and 30b of the space divided vertically by the transverse partition member 5. Multiple bulkheads 6 are provided at intervals along the vehicle length direction within the upper side spaces 30a and 30b, dividing each upper side space 30a and 30b into multiple portions in the vehicle length direction. Ribs 7 are formed between the bulkheads 6 in the transverse partition member 5 along the vehicle width direction. Multiple ribs 7 are provided at intervals along the vehicle length direction. The transverse partition member 5 and bulkhead 6 within the closed cross-sectional space 3a on the vehicle interior are disposed opposite the transverse partition member 5 and bulkhead 6 within the closed cross-sectional space 3b on the vehicle exterior, with the longitudinal partition member 2 interposed therebetween. This impact-absorbing structure 4 is provided in the portion of the side member 1 that extends at least along the battery box (battery box longitudinal member) in the vehicle longitudinal direction. A side member structure incorporating this impact-absorbing structure 4 achieves the effects (i) to (vii) described below. By combining these effects, high collision energy absorption characteristics can be achieved. In particular, this structure achieves desired collision characteristics even with a reduced number of baffles 6. This provides the advantage of achieving high collision energy absorption characteristics with minimal collision deformation while minimizing the weight increase associated with structural components.

[0065] The following describes the details of the impact absorbing structure 4 of this embodiment. The transverse partition member 5 is arranged along the longitudinal direction of the vehicle body in a manner that horizontally crosses each closed cross-sectional space 3a, 3b, and divides each closed cross-sectional space 3a, 3b into upper side spaces 30a, 30b and lower side spaces 31a, 31b. The transverse partition member 5 is formed by forming a metal plate. The transverse partition member 5 in the closed cross-sectional space 3a on the inner side of the vehicle is joined to the inner side member 1a of the side beam and the longitudinal partition member 2, and the transverse partition member 5 in the closed cross-sectional space 3b on the outer side of the vehicle is joined to the outer side member 1b of the side beam and the longitudinal partition member 2. One of the functions of the transverse partition member 5 is to ensure a load transfer path (load transfer path) for transferring load to the floor cross member or the battery box from the initial stage of the collision by crossing the side beam 1, so it is preferably joined as described above relative to the side beam 1 and the longitudinal partition member 2.

[0066] The mounting / joining structure of the transverse partition member 5 relative to the side sill 1 and the longitudinal partition member 2 is not particularly limited. In this embodiment, each transverse partition member 5 has mounting (joining) flanges at one and the other ends in the vehicle width direction, and is mounted / joined to the side sill 1 and the longitudinal partition member 2 via these flanges. In this embodiment, the transverse partition member 5 within the closed cross-sectional space 3a on the vehicle interior side has a flange 50x formed continuously downward (facing downward) at one end, and a flange 50y formed continuously upward (facing upward) at the other end. The flange 50y extends along the longitudinal partition member 2 to the upper end of the side sill 1. Furthermore, the flange 50x at one end is joined to the inner surface of the side sill inner panel 1a, while the upper end of the flange 50y at the other end is joined to the upper end portion (flange 102) of the side sill inner panel 1a and the upper end portion of the longitudinal partition member 2, while being sandwiched between the upper end portion (flange 102) of the side sill inner panel 1a and the upper end portion of the longitudinal partition member 2.

[0067] In addition, the transverse partition member 5 within the closed cross-sectional space 3b on the outside of the vehicle has a flange portion 51x formed continuously downward (toward the bottom) on one end side in the vehicle width direction, and a flange portion 51y formed continuously upward (toward the top) on the other end side. The flange portion 51y extends along the longitudinal partition member 2 to the upper end portion of the side beam 1. In addition, the flange portion 51x on one end side is joined to the inner surface of the side beam outer member 1b, and the upper end portion of the flange portion 51y on the other end side is joined to the upper end portion (flange portion 102) of the side beam outer member 1b and the upper end portion of the longitudinal partition member 2 in a state of being clamped therebetween. Through holes can also be provided in the flange portions 50x, 50y, 51x, 51y (especially the flange portions 50y, 51y of larger size) to achieve lightweighting. For the same reason, the flanges 50x, 50y, 51x, and 51y may be formed only on a portion of the longitudinal direction of the horizontal partition member 5 (e.g., intermittently at predetermined intervals). The above configuration also applies to the flanges of the horizontal partition member 5 in other embodiments described below.

[0068] By configuring the horizontal partition member 5 to be mounted and joined via these flanges 50x, 50y, 51x, and 51y, the side sill structure can be easily assembled as follows. The horizontal partition member 5 on the vehicle interior side is secured to the side sill interior member 1a by joining flange 50x to the longitudinal surface 100 of the side sill interior member 1a and by joining the upper end of flange 50y to the flange 102 on the upper side of the side sill interior member 1a. Furthermore, the horizontal partition member 5 on the vehicle exterior side is secured to the side sill exterior member 1b by joining flange 51x to the longitudinal surface 100 of the side sill exterior member 1b and by joining the upper end of flange 51y to the flange 102 on the upper side of the side sill exterior member 1b. These three members are then joined, with the longitudinal partition member 2 being sandwiched between the side sill interior member 1a and the side sill exterior member 1b, to which the horizontal partition member 5 is thus secured. As a joining method in this case, for example, with respect to the upper end side of the side sill 1, the flange portion 50y (the upper end portion of the flange portion 50y) of the vehicle-interior transverse partition member 5 joined to the flange portion 102 on the upper side of the side sill inner member 1a, the flange portion 51y (the upper end portion of the flange portion 51y) of the vehicle-outterior transverse partition member 5 joined to the flange portion 102 on the upper side of the side sill outer member 1b, and the upper end portion of the longitudinal partition member 2 may be joined (spot welded). Furthermore, with respect to the lower end side of the side sill 1, the flange portion 102 on the lower side of the side sill inner member 1a, the flange portion 102 on the lower side of the side sill outer member 1b, and the lower end portion of the longitudinal partition member 2 may be joined (spot welded).

[0069] Each transverse partition member 5 is provided with a reinforcing rib 7 along the vehicle width direction, and a plurality of these ribs 7 are provided at intervals in the vehicle length direction. The reinforcing ribs 7 increase the rigidity of the transverse partition member 5 and improve the collision energy absorption characteristics by increasing the maximum collision load (endurance) generated in the initial stage of deformation during a side collision. In addition, by providing a plurality of reinforcing ribs 7 at intervals in the vehicle length direction, it is also possible to achieve the effect of suppressing the propagation of strain in the transverse partition member 5 and suppressing the buckling of the transverse partition member 5 outside the side collision position. The reinforcing ribs 7 are formed in the vehicle length direction at positions where no partitions 6 are provided, that is, positions between the partitions 6. The reinforcing ribs 7 of this embodiment are formed by recessing a portion of the plate material constituting the transverse partition member 5 in a groove-like manner toward the bottom. Conversely, they can also be formed by recessing a portion of the plate material constituting the transverse partition member 5 in a groove-like manner toward the top.

[0070] The spacing between the ribs 7 and the size of the ribs 7 are not particularly limited and can be appropriately determined from the perspective of ensuring the rigidity of the transverse partition member 5 by taking into account the workability, the arrangement of the partition 6, etc. However, it is generally preferred to arrange them under the following conditions. The ribs 7 do not necessarily need to be arranged at equal intervals in the longitudinal direction of the vehicle body, but are generally arranged at equal intervals. The spacing between the ribs 7 (see Figure 2 ), that is, the distance W between two adjacent reinforcing ribs 7 in the longitudinal direction of the vehicle body H (This refers to the distance between the edges of the two reinforcing ribs 7) is preferably set to 127 mm or less. Since the radius of the collision body in the side impact test (side pole impact test specified by Euro NCAP) is 127 mm, if the distance between the reinforcing ribs W is less than 127 mm, H ≤127mm, there must be at least one reinforcing rib 7 within the column radius range (127mm), and the rigidity improvement effect brought by the reinforcing rib 7 can always be properly obtained. H If the distance W between the ribs is less than 63 mm, which is roughly half of 127 mm, then there must be two or more ribs 7 within the column radius (127 mm), and the rigidity improvement effect of the ribs 7 is further enhanced. On the other hand, from the perspective of ensuring the rigidity of the horizontal partition member 5, the distance W between the ribs is H The lower limit of is not particularly limited, but as described later, when the width of the flange portion 60 of the partition plate 6 is set to W BF When the distance between the ribs is preferably W H Set to W BF ≤W H Therefore, the preferred distance between ribs is W. H It is set to be 30 mm or more. In addition, it is preferred that the depth d of the reinforcing rib 7 (see Figure 3 ) is about 3 to 7 mm, and the curvature radius of the rib section R (refer to Figure 3 ) is about 6 to 10 mm. Thus, it is possible to achieve an improvement in rigidity due to the ribs while ensuring workability during rib formation.

[0071] The bulkhead 6 is formed by forming a metal plate. Multiple bulkheads 6 are provided at intervals along the vehicle length within the upper side spaces 30a, 30b, dividing the upper side spaces 30a, 30b on the inside and outside of the vehicle body into multiple spaces in the vehicle length direction. Each bulkhead 6 is arranged along the vehicle width direction with its plate surface perpendicular to the transverse partition member 5. The bulkhead 6 is preferably provided so as to partition the entire cross-section of the upper side spaces 30a, 30b in the vehicle width direction. Each bulkhead 6 is preferably joined to the members surrounding the upper side spaces 30a, 30b at multiple locations along its outer periphery. However, to achieve minimum collision energy absorption characteristics, it is preferably joined to at least the surrounding members as follows. Specifically, to form a load transfer path during a side collision and prevent the bulkhead from shifting, at least the upper and lower portions of the bulkhead 6 on the inside of the vehicle body are preferably joined to the upper transverse surface 101A of the side sill inner member 1a and the transverse partition member 5, respectively. It is particularly preferred to further join both sides of the bulkhead 6 to the longitudinal surface 100 of the side sill inner member 1a and the flange 50y of the transverse partition member 5, that is, to join the upper, lower, and both sides of the bulkhead 6 to the surrounding components. Furthermore, to prevent positional displacement during a side collision, it is preferred that at least the upper and lower portions of the bulkhead 6 on the vehicle body's exterior be joined to the upper transverse surface 101A of the side sill outer member 1b and the transverse partition member 5, respectively. Furthermore, since the portion of the bulkhead 6 on the vehicle body's exterior that contacts the longitudinal surface 100 of the side sill outer member 1b will significantly deform during a side collision, it is preferred that its side portions be joined to the longitudinal surface 100 of the side sill outer member 1b. Furthermore, it is particularly preferred to further join the other side of the bulkhead 6 to the flange 51y of the transverse partition member 5, that is, to join the upper, lower, and both sides of the bulkhead 6 to the surrounding components. Typically, the bulkhead 6 is joined to the surrounding components by spot welding.

[0072] The partition 6 of this embodiment has a flange portion 60 on the outer periphery of its main body portion (partition wall portion), and is joined to the surrounding components via the flange portion 60 as described above (usually by spot welding). The flange portion 60 may be formed only (for example, intermittently formed at a predetermined interval) on a portion of the outer periphery of the main body portion (partition wall portion). The partition 6 may also be arranged at equal intervals along the length direction of the vehicle in the upper side spaces 30a, 30b of the side beam 1, for example, it may be arranged to alternate wide intervals with narrow intervals. In addition, as described later, it may also be arranged at different intervals in each area in the front-rear direction of the vehicle. As described above, the partition 6 is joined to other components such as the transverse partition member 5 via the flange portion 60, but the flange width W is preferably BF Distance W between ribs H Satisfy W BF ≤W HThis is because, if Figure 2 As shown, the partition plate 6 needs to be arranged on the surface of the horizontal partition member where the reinforcement rib 7 is not formed.

[0073] When the partitions 6 are arranged at intervals along the longitudinal direction of the vehicle, in order to improve the crash worthiness of the shock absorbing structure 4, as shown in FIG. Figure 2 As shown, the width W of the floor beam 10 is F In the area within the 10, the partition plate 6 can be set at two or more locations. F By providing partitions 6 at two or more locations in the area within the vehicle body and reducing the distance between the partitions 6, the collision characteristics can be improved. F It may be set as the width of the portion between the two side walls in the width direction of the floor beam. Figure 5 The width direction cross section of a typical floor beam 10 is schematically shown. Figure 5 In the case of a floor cross member 10 having flanges at both edges as shown, the width W of the floor cross member 10 is F It is preferably set as the width of the portion of both edges excluding the flange portion in the width direction of the floor cross member (the width of the main portion functioning as a frame member), that is, the width between the locations where the rounded portion of the flange portion begins.

[0074] The width W of the floor beam 10 F When partitions 6 are arranged at multiple locations within the interior, if the distance W between two adjacent partitions 6 is B ( Figure 2 If the distance between the main parts of the partitions 6 shown in FIG. 1 is too small, the width W of the floor beam 10 will be increased. F The effect of the collision characteristics inside the vehicle is reduced or the number of partitions 6 is unnecessarily increased, which is not preferable. F The partitions 6 at two or more locations in the inner region are preferably arranged so that the interval W between the partitions 6 is B The width W of the floor beam 10 F Ratio W B / W F The width W of the floor beam 10 is not less than 0.5 and not more than 1.0. F The inner arrangement of the bulkhead 6 means that the main body (partition wall) of the bulkhead 6 is located within the width W of the floor cross member 10 in the vehicle longitudinal direction. F Inside.

[0075] In the impact absorbing structure 4, the transverse partition member 5 is a member extending in the longitudinal direction of the vehicle, and a plurality of reinforcing ribs 7 are provided on the surface of the transverse partition member at intervals in the longitudinal direction of the vehicle. Therefore, the impact absorbing structure 4 functions as an impact absorbing member regardless of the position of the side collision. Therefore, even if the number of partitions 6 is reduced, sufficient collision energy absorption characteristics can be obtained by the impact absorbing structure 4. For example, Figure 2 As shown, the width W of the floor beam 10 is F When partitions 6 are provided at two or more locations in the area within the width of the floor cross member 10 and at one or more locations in the area outside the width of the floor cross member 10 (a location on the surface of the horizontal partition member where the ribs 7 are not formed), the partitions 6 can be aligned with the width W of the floor cross member 10. F The interval between the partitions 6 is configured to be greater than the width W of the floor cross member 10. F The spacing between the partitions 6 is wide (for example, see the following Figure 6 Thus, the collision characteristics of the area outside the width of the floor cross member 10 can be improved while suppressing the number of bulkheads 6 installed and achieving weight reduction.

[0076] The transverse partition member 5 and the partition plate 6 in the closed cross-sectional space 3a on the inside of the vehicle are arranged opposite to the transverse partition member 5 and the partition plate 6 in the closed cross-sectional space 3b on the outside of the vehicle in the vehicle width direction (i.e., at the same position in the vehicle length direction) in a manner that clamps the longitudinal partition member 2. As a result, the transverse partition members 5 and the partition plates 6 on the inside and outside of the vehicle function as a whole by clamping the longitudinal partition member 2, thereby achieving high collision energy absorption characteristics as described later. On the other hand, since the longitudinal partition member 2 is configured to separate the impact absorbing structure 4 on the inside and outside of the vehicle body, the buckling wavelength (wavelength of buckling) of the impact absorbing structure 4 (transverse partition member 5, partition plate 6) in the vehicle width direction is shortened, and the buckling resistance (buckling strength) is improved, which is also the main reason for the improved collision energy absorption characteristics.

[0077] The following describes the preferred material of the metal plate (usually a "steel plate") constituting the impact absorbing structure 4 (the transverse partition member 5 and the partition plate 6). The tensile strength of the metal plate constituting the impact absorbing structure 4 (the transverse partition member 5 and the partition plate 6) is preferably 780 MPa or higher. As the collision characteristics of the impact absorbing structure 4, the higher the load (hereinafter referred to as "endurance") when the impact absorbing structure 4 transforms from elastic deformation (elastic deformation) after the initial deformation to plastic deformation (plastic deformation) during a side collision, the less likely deformation occurs during a collision, and the better the collision characteristics. As for endurance, the higher the yield strength of the metal plate used in the impact absorbing structure 4, the higher the endurance, so it is preferably set to a metal plate with a tensile strength of 780 MPa or higher, which has a yield strength higher than that of plain carbon steel. In addition, from the same point of view, it is more preferable to set it to a metal plate with a tensile strength of 1180 MPa or higher, and it is particularly preferable to set it to a metal plate with a tensile strength of 1470 MPa or higher. It is known that approximately 1 / 3 of the tensile strength corresponds to the Vickers hardness HV (for example, JIS Handbook (1) Steel I, Japanese Standards Association, SAE-J-417 Hardness Conversion Table). Therefore, the metal plate constituting the shock absorbing structure 4 preferably has a Vickers hardness HV of 250 or higher at a position 1 / 4 of the plate thickness, more preferably 310 or higher, and particularly preferably 440 or higher.

[0078] The metal sheet constituting the impact-absorbing structure 4 is preferably a steel sheet containing, by mass%, C: 0.030% to 0.250%, Si: 0.01% to 2.50%, Mn: 1.00% to 3.50%, P: 0.001% to 0.100%, S: 0.0200%, and Al: 0.010% to 2.000%. A C content of less than 0.030% generally makes it difficult to increase the tensile strength of the metal sheet (e.g., 780 MPa or higher). Low tensile strength makes it difficult to ensure the resistance of the impact-absorbing structure 4 during a side collision, resulting in reduced collision performance. On the other hand, a C content exceeding 0.250% causes martensite, a hard phase described later, to become brittle, reducing ductility. Consequently, bending properties are likely to be reduced, and the metal sheet is more likely to fracture when the impact-absorbing structure 4 is crushed. Therefore, the C content is preferably 0.030% to 0.250%. From the above viewpoint, the C content is more preferably 0.100% to 0.250%, and even more preferably 0.150% to 0.250%.

[0079] Si is an element effective for improving the balance of tensile strength and elongation (elongation) (ductility) by solid-solution strengthening of steel to generate retained austenite described later. In order to obtain such an effect, it is preferred that the Si amount is set to more than 0.01%. On the other hand, if the Si amount exceeds 2.50%, the reduction in ductility caused by embrittlement easily leads to a reduction in bending characteristics, and the fracture of the metal plate is easily produced when the impact absorbing structure 4 is crushed. Therefore, it is preferred that the Si amount is more than 0.01% and less than 2.50%. Mn is effective for the strengthening of steel and is an element that promotes the generation of martensite as a hard phase. In order to obtain such an effect, it is preferred that the Mn amount is set to more than 1.00%. If the Mn amount is less than 1.00%, it is impossible to promote the generation of martensite, and it is usually difficult to improve the tensile strength (for example, more than 780MPa level) of the metal plate. On the other hand, if the Mn content exceeds 3.50%, the bending properties tend to deteriorate due to reduced ductility, and the metal plate tends to break when local deformation occurs in the shock absorbing structure 4. Therefore, the Mn content is preferably 1.00% to 3.50%.

[0080] P is an element effective for strengthening steel. In order to obtain such an effect, it is preferable to set the P content to 0.001% or more. On the other hand, if the P content exceeds 0.100%, the steel becomes brittle due to grain boundary segregation, and the impact resistance characteristics are easily reduced. Therefore, it is preferable that the P content is 0.001% or more and 0.100% or less. S exists as inclusions such as MnS and deteriorates the impact resistance and weldability, so it is preferable to reduce its content as much as possible, but considering the manufacturing cost, it is preferable to set the S content to 0.0200% or less. Al is an element effective for generating ferrite to improve the TS-El balance. In order to obtain such an effect, it is preferable to set the Al content to 0.010% or more. On the other hand, if the Al content exceeds 2.000%, there is a risk of cracking of the slab during continuous casting. Therefore, the Al content is preferably set to 0.010% or more and 2.000% or less.

[0081] The steel plate may further contain, in mass%, an element selected from the group consisting of N: 0.0100% or less, Nb: 0.200% or less, Ti: 0.200% or less, V: 0.200% or less, B: 0.0100% or less, Cr: 1.000% or less, Ni: 1.000% or less, Mo: 1.000% or less, Sb: 0.200% or less, Sn: 0.200% or less, Cu: 1.000% or less, Ta: 0.100% or less, W: 0.500% or less, Mg: 0.0200% or less, Zn: At least one element selected from the group consisting of Fe: 0.0200% or less, Co: 0.0200% or less, Zr: 0.1000% or less, Ca: 0.0200% or less, Se: 0.0200% or less, Te: 0.0200% or less, Ge: 0.0200% or less, As: 0.0500% or less, Sr: 0.0200% or less, Cs: 0.0200% or less, Hf: 0.0200% or less, Pb: 0.0200% or less, Bi: 0.0200% or less, and REM: 0.0200% or less. The remainder of the steel composition is Fe and unavoidable impurities.

[0082] The metal plate constituting the impact absorbing structure 4 preferably has a steel structure containing ferrite with an area ratio of 0% to 65% at a position 1 / 4 of the thickness of the metal plate, martensite and tempered martensite with a total area ratio of 30% to 100%, and retained austenite with an area ratio of 0% to 15%. Ferrite, as a soft phase, can be appropriately contained to improve the ductility of the metal plate (steel plate), but if its area ratio exceeds 65%, it is generally difficult to improve the tensile strength of the metal plate (for example, 780 MPa or above). Therefore, it is preferred that the area ratio of ferrite is set to 0% to 65%. Martensite and tempered martensite contribute to the strengthening of the metal plate (steel plate) and are necessary structures from the perspective of obtaining high tensile strength (for example, 780 MPa or above). In order to obtain such an effect, the area ratio of martensite and tempered martensite is preferably 30% to 100% in total. Retained austenite may be contained to improve ductility, but if the area ratio exceeds 15%, it transforms into hard martensite after press forming, resulting in a decrease in ductility (bending properties), and the fracture resistance at bending (collision properties) of the shock absorbing structure 4 during local deformation is likely to be reduced. Therefore, the area ratio of retained austenite is preferably set to 0% or more and 15% or less.

[0083] In order to obtain such a steel structure, for example, it is effective to perform hot rolling and cold rolling on the slab having the above-mentioned composition to produce a cold-rolled steel sheet, and then anneal the cold-rolled steel sheet under appropriate annealing conditions. As annealing conditions, the cold-rolled steel sheet is heated to a temperature range above the Ac3 transformation point, maintained as needed to cause austenite transformation, and then cooled to a temperature range below the temperature at which the transformation from austenite to martensite begins (Ms point), forming a structure of martensite, untransformed austenite, and ferrite. Afterwards, it is heated to a temperature range above the Ms point and less than the Ac1 transformation point and maintained as needed. Thus, martensite becomes tempered martensite, and untransformed austenite becomes martensite or retained austenite.

[0084] Furthermore, when a collision load is input from the side of the side member structure of the present invention, causing the impact absorbing structure 4 to exceed its buckling resistance and collapse, the impact absorbing structure 4 (transverse partition member 5, partition 6) absorbs the collision energy by repeatedly buckling and deforming in a corrugated manner. During this process, the impact absorbing structure 4 is most likely to absorb the collision energy if it buckles without breaking. To achieve this effect, the metal plate of the impact absorbing structure 4 preferably has a strain at break in a tensile test, i.e., the ultimate deformation energy ε. l 0.55 or more. Therefore, even in the face of severe local deformation caused by crushing, it is not easy to break, fully ensuring the strength of the side beam structure as a whole, and achieving high collision energy absorption performance. Taking into account the difference in material, the ultimate deformation energy of the metal plate ε l It is more preferably 0.75 or more, and particularly preferably 0.88 or more.

[0085] Ultimate deformation energy ε l The calculation is as follows: a room temperature tensile test is performed according to JIS Z2241, and the plate width W and plate thickness T at the fracture surface of the tensile test piece after the tensile test are measured. The ultimate deformation energy ε is calculated using the following formula (1) together with the plate width W0 and plate thickness T0 of the tensile test piece before the tensile test. l .

[0086] ε l =-{ln(W / W0)+ln(T / T0)}…(1)

[0087] Where, w: Plate width at the fracture surface of the tensile test piece after the tensile test (mm)

[0088] W0: Width of the tensile test piece before the tensile test (mm)

[0089] T: Plate thickness at the fracture surface of the tensile test piece after the tensile test (mm)

[0090] T0: Thickness of the tensile test piece before the tensile test (mm)

[0091] In order to increase the ultimate deformation energy ε of the metal plate l For example, it is effective to adjust the cooling conditions during annealing (temperature to interrupt cooling, cooling rate), reheating conditions (reheat temperature, holding time), etc., so as to achieve an appropriate balance between the tempered martensite as the second phase and the area ratio of martensite, which is effective in improving the ultimate deformation energy of the metal plate and achieving high strength.

[0092] In addition, the corrugated curved portion produced by the corrugated buckling deformation of the impact absorbing structure 4 is prone to cracking due to stress concentration on the outer surface of the bend. Therefore, it is preferred that the metal plate of the impact absorbing structure 4 be a member with excellent bendability. Specifically, it is preferred to use a metal plate with excellent bendability as follows: in a 90° V-bending test based on the V-block method of JIS Z2248, the ratio R / t of the limit bending radius R (i.e., the minimum radius R of the tip of the V-punch that does not produce cracks (fractures)) (mm) to the plate thickness t (mm) is 7.0 or less. In addition, taking into account the difference in material quality, a metal plate with an R / t of 3.5 or less is more preferred, and a metal plate with an R / t of 2.0 or less is particularly preferred. In order to improve the bendability of the metal plate and obtain the above-mentioned R / t, it is effective to adjust the cooling conditions (cooling stop temperature, cooling rate) and reheating conditions (reheating temperature, holding time) during annealing so that the area ratio of retained austenite is appropriate. Furthermore, the yield strength (proof strength) of the metal plates forming the impact-absorbing structure 4 (transverse partition 5, bulkhead 6) is preferably less than or equal to the yield strength of the metal plates forming the floor cross member. This is to ensure that, in the event of a side collision, the impact-absorbing structure 4 reliably deforms before the floor cross member, absorbing the collision energy and thereby suppressing deformation of the floor cross member.

[0093] In the side sill structure including the impact-absorbing structural portion 4 described above, high collision energy absorption characteristics are achieved by combining the following effects (i) to (vii). In particular, this structure achieves desired collision characteristics even with a reduced number of bulkheads 6. This provides the advantage of achieving high collision energy absorption characteristics with minimal collision deformation while suppressing the increase in weight associated with the structural components.

[0094] (i) The impact-absorbing structure 4 is composed of a transverse partition member 5 that crosses the closed cross-sectional spaces 3a and 3b in the vehicle body width direction, and a plurality of partitions 6 arranged within the upper side space 30a defined by the transverse partition member 5. The transverse partition members 5 and partitions 6 on the inside and outside of the vehicle are arranged opposite each other in the vehicle width direction, sandwiching the longitudinal partition member 2. This provides high bending rigidity (bending deformation resistance against side impact loads). This suppresses local deformation around the input point of the side impact load, allowing the impact-absorbing structure 4 to deform as a whole during a side impact, thereby improving collision energy absorption (EA). Furthermore, during a side impact, the impact-absorbing structure 4 suppresses cross-sectional collapse of the side member 1 through the coordinated action of the transverse partition member 5 and partitions 6. Furthermore, the partitions 6 themselves flex and collapse to absorb collision energy, effectively absorbing collision energy with minimal collision deformation.

[0095] (ii) The inner and outer transverse partition members 5, which cross the closed cross-sectional spaces 3a and 3b in the vehicle body width direction and are disposed opposite each other with the longitudinal partition member 2 interposed therebetween, ensure a load transmission path that transmits the load to the floor cross member and the battery box (battery box longitudinal member) from the initial stage of the collision. As a result, the reaction force from the floor cross member and the battery box causes the side members and the impact absorbing structure 4 to collapse, effectively absorbing the collision energy.

[0096] (iii) The transverse partition member 5 is a member that horizontally crosses the closed cross-sectional space 3a, 3b along the width direction of the vehicle body and extends along the length direction of the vehicle, and a plurality of reinforcing ribs 7 are arranged at intervals on the surface of the transverse partition member in the length direction of the vehicle. Therefore, it can withstand the circumferential collision load of the collision body (column) at any position in the length direction of the vehicle and can effectively absorb the collision energy.

[0097] (iv) The impact-absorbing structure 4 and the surrounding members (the longitudinal partition member 2 and the side member 1) function as a single unit during a side collision. This allows the impact load to be distributed over a wide area in the longitudinal direction of the vehicle to the floor cross member and the battery box. This reduces the impact load transferred to the battery pack.

[0098] (v) The transverse partition members 5 and bulkhead 6 on the inside and outside of the vehicle body that constitute the impact-absorbing structure 4 are arranged in opposing relation, sandwiching the longitudinal partition member 2 that vertically extends through the closed cross-sectional space 3. This creates a structure in which the longitudinal partition member 2 divides the transverse partition member 5 and bulkhead 6 in the vehicle width direction. Consequently, the buckling wavelength of the impact-absorbing structure 4 (transverse partition member 5 and bulkhead 6) in the vehicle width direction is shortened, improving the buckling resistance of the impact-absorbing structure 4 and enhancing its collision energy absorption characteristics.

[0099] (vi) The ribs 7 formed on the transverse partition member 5 increase the rigidity of the transverse partition member 5, thereby enhancing collision energy absorption by increasing the maximum collision load (resistance) generated during the initial deformation phase of a side collision. Furthermore, by providing multiple ribs 7 spaced apart along the vehicle's longitudinal direction on the surface of the transverse partition member, strain propagation in the transverse partition member 5 outside the side collision location can be suppressed, thereby inhibiting buckling of the transverse partition member 5. Consequently, localized deformation of the impact-absorbing structure 4 can be reduced, enhancing collision energy absorption.

[0100] (vii) The horizontal partition member 5 that constitutes the impact-absorbing structure 4 extends along the vehicle's longitudinal direction, and multiple reinforcement ribs 7 are provided at intervals along the vehicle's longitudinal direction. Therefore, the impact-absorbing structure 4 functions as an impact-absorbing member regardless of its position in the vehicle's longitudinal direction. Furthermore, as described above, the impact-absorbing structure 4 and the surrounding members (the vertical partition member 2 and the side sill 1) function as a single unit during a side collision. Therefore, even with a small number of partitions 6, high impact energy absorption characteristics can be achieved, and the weight increase associated with the structural components can be suppressed accordingly.

[0101] Figure 6 This figure shows another example of the arrangement of the bulkhead 6 in the vehicle front-to-back direction, in which the bulkhead 6 is arranged at different intervals in each region in the vehicle front-to-back direction. In this arrangement, the bulkhead 6 arranged at multiple locations spaced apart in the vehicle front-to-back direction includes the bulkhead 6 provided at a width wa (= 1 / 2 of the width wa) of the floor cross member 10 in the vehicle front-to-back direction. Figure 2 Width W F ) in the area of ​​the partition 6 x and the partition 6 provided in the area outside this area (the area outside the width of the floor cross member 10) y Furthermore, in the vehicle front-rear direction, at least two locations (in the region of the width wa of the floor cross member 10) are provided. Figure 6 In the embodiment of the present invention, there are two locations) provided with a partition 6 x , and a partition 6 is provided at one or more locations outside the width of the floor cross member 10. yIn addition, when the two adjacent partitions 6 x The distance between them is set to w1 and the partition 6 x and the adjacent partition 6 y When the interval between is w2, w1<w2. The above arrangement of the partition 6 is to provide the partition 6 at two or more locations in the area within the width wa of the floor cross member 10. x To reduce the partition 6 x The collision characteristics are improved by increasing the spacing between the partitions 6 in the area outside the area. y With partition 6 x The space between the partitions 6 is reduced, thereby reducing the number of partitions 6 and achieving weight reduction. The partitions 6 are provided at two or more locations outside the width of the floor cross member 10. y In the case of the two adjacent partitions 6 y The interval w3 between them is also set to w1<w3.

[0102] On the other hand, the adjacent partition 6 x With partition 6 y The interval w2, partition 6 y The spacing w3 between each other is preferably as wide as possible from the perspective of lightweighting the impact absorbing structure 4, but in order to ensure the bending rigidity of the impact absorbing structure 4 during a side collision, it is preferably set to 254 mm or less. This 254 mm is the diameter of the collision body (column) used in the side collision test (side column impact test specified by Euro NCAP). By setting the spacing w2 and w3 to be less than the diameter of the collision body (column) of the test, the bending rigidity of the impact absorbing structure 4 during a side collision can be more appropriately ensured. In addition, from the same perspective, it is preferred that the adjacent partitions 6 x With partition 6 y The interval w2, partition 6 y The interval w3 is set to approximately 1 / 4 to 1 / 2 of the spacing between the floor cross members 10 (the spacing wb between adjacent floor cross members 10). For example, if the spacing wb between the floor cross members 10 is 260 mm, the intervals w2 and w3 are preferably set to approximately 65 mm to 130 mm. Furthermore, to reduce the weight of the impact absorbing structure 4, the intervals w2 and w3 are preferably set to 50 mm or greater.

[0103] Figure 6 The configuration of (a) is to provide a partition 6 between adjacent floor beams 10, that is, in a region outside the width of the floor beam 10. y Example, separator 6 x , 6 y To meet the condition of w1<w2. In addition, Figure 6 The configurations (b) and (c) are such that partition plates 6 are provided at two to three locations between adjacent floor cross members 10, that is, in the area outside the width of the floor cross members 10. y Example, separator 6 x , 6 y Set to meet the conditions of w1<w2, w1<w3.

[0104] Figure 7 1 is a diagram showing another example of arrangement of the partition 6 in the vehicle front-rear direction. Figure 6 In the embodiment of FIG, the partitions 6 are provided at different intervals in each area in the vehicle front-rear direction. In this embodiment, in order to further improve the bending rigidity of the impact absorbing structure 4 between the floor cross members 10, the partitions 6 provided in the area outside the width of the floor cross member 10 are arranged at different intervals. y By comprising two or more partitions arranged adjacent to each other (in Figure 7 In the embodiment of the present invention, the separator is composed of two separators. Figure 7 Each partition plate 6 of the embodiment y The spacer group is composed of two spacers. The size of the interval w4 between the spacers constituting the spacer group is arbitrary, but is basically determined from the same point of view as the interval w1, so it can be set to the same conditions as the above-mentioned interval w1. y By configuring a partition group including two or more partitions, all the partitions 6 can be y As an object, only a part of the partition 6 may be y As an object.

[0105] Figure 7 The configuration of (a) is to provide a partition 6 in a portion adjacent to the floor cross member 10, that is, in an area outside the width of the floor cross member 10. y (An example of a partition plate group in which two partition plates are set as one group). In this configuration, the partition plate 6 x , 6 y To meet the condition of w1<w2. In addition, Figure 7 The configurations (b) and (c) are such that partition plates 6 are provided at two to three locations between adjacent floor cross members 10, that is, in the area outside the width of the floor cross members 10. y (An example of a partition plate group in which two partition plates are set as one group). In this configuration, the partition plate 6 x , 6 y Set to meet the conditions of w1<w2, w1<w3.

[0106] Typically, the horizontal partition member 5 has a flange portion for installation, such as Figure 1As shown, the flange portion is attached to or joined to other members via the flange portion. However, the configuration of the flange portion in this case (for example, the arrangement form and the arrangement direction of the flange portion) is not particularly limited. Figure 8 and Figure 9 Other embodiments in which the mounting and joining structures of the horizontal partition member 5 are different are shown. Figure 8 The side member structure of the present invention and other embodiments of the vehicle lower structure including the side member structure are schematically shown, and are longitudinal cross-sectional views of the vehicle lower structure (one of the structural portions on both sides of the vehicle lower portion) including the side member in the vehicle width direction. In this embodiment, the transverse partition member 5 within the closed cross-sectional space 3a on the vehicle inner side has a flange portion 52x formed continuously downward (toward downward) at one end side in the vehicle width direction, and has a flange portion 52y formed continuously downward (toward downward) at the other end side. The flange portion 52y extends along the longitudinal partition member 2 to the lower end portion of the side member 1. Furthermore, the flange portion 52x on one end side is joined to the inner surface of the side member inner member 1a, and the lower end portion of the flange portion 52y on the other end side is joined to the lower end portion (flange portion 102) of the side member inner member 1a and the lower end portion of the longitudinal partition member 2 in a state of being clamped therebetween.

[0107] In addition, the transverse partition member 5 in the closed cross-sectional space 3b on the outside of the vehicle has a flange portion 53x formed continuously downward (toward the bottom) on one end side in the vehicle width direction, and has a flange portion 53y formed continuously downward (toward the bottom) on the other end side. The flange portion 53y extends along the longitudinal partition member 2 to the lower end portion of the side beam 1. Moreover, the flange portion 53x on one end side is joined to the inner surface of the side beam outer member 1b, and the lower end portion of the flange portion 53y on the other end side is joined to them in a state of being clamped by the lower end portion (flange portion 102) of the side beam outer member 1b and the lower end portion of the longitudinal partition member 2. Other configurations of this embodiment are similar to Figure 1 The embodiments are the same, so the same figure marks are given and detailed descriptions are omitted.

[0108] By configuring the horizontal partition member 5 to be mounted and joined via these flanges 52x, 52y, 53x, and 53y, the side sill structure can be easily assembled as follows. The horizontal partition member 5 on the vehicle interior side is secured to the side sill inner member 1a by joining flange 52x to the longitudinal surface 100 of the side sill inner member 1a and by joining the lower end of flange 52y to the flange 102 on the lower side of the side sill inner member 1a. Furthermore, the horizontal partition member 5 on the vehicle exterior side is secured to the side sill outer member 1b by joining flange 53x to the longitudinal surface 100 of the side sill outer member 1b and by joining the lower end of flange 53y to the flange 102 on the lower side of the side sill outer member 1b. The three members are then joined, with the longitudinal partition member 2 sandwiched between the side sill inner member 1a and the side sill outer member 1b, to which the horizontal partition member 5 is thus secured. As a joining method in this case, for example, with respect to the lower end side of the side sill 1, the flange portion 52y (the lower end portion of the flange portion 52y) of the vehicle-interior transverse partition member 5 joined to the flange portion 102 on the lower side of the side sill inner member 1a, the flange portion 53y (the lower end portion of the flange portion 53y) of the vehicle-outterior transverse partition member 5 joined to the flange portion 102 on the lower side of the side sill outer member 1b, and the lower end portion of the longitudinal partition member 2 may be joined (spot welded). Furthermore, with respect to the upper end side of the side sill 1, the flange portion 102 on the upper side of the side sill inner member 1a, the flange portion 102 on the upper side of the side sill outer member 1b, and the upper end portion of the longitudinal partition member 2 may be joined (spot welded).

[0109] Figure 9 The side member structure of the present invention and other embodiments of the vehicle body lower structure including the same are schematically shown, and are longitudinal cross-sectional views of the vehicle body lower structure (one of the structural parts on both sides of the vehicle body lower part) including the side member in the vehicle width direction. In this embodiment, the transverse partition member 5 in the closed cross-sectional space 3a on the inner side of the vehicle has a flange portion 54 formed continuously downward (toward downward) at one end side and the other end side in the vehicle width direction. In addition, the flange portion 54 on one end side is joined to the inner surface of the side member inner part 1a, and the flange portion 54 on the other end side is joined to the vehicle inner side surface of the longitudinal partition member 2. In addition, the transverse partition member 5 in the closed cross-sectional space 3b on the outer side of the vehicle has a flange portion 55 formed continuously downward (toward downward) at one end side and the other end side in the vehicle width direction. In addition, the flange portion 55 on one end side is joined to the inner surface of the side member outer part 1b, and the flange portion 55 on the other end side is joined to the vehicle outer side surface of the longitudinal partition member 2. Other configurations of this embodiment and Figure 1 The embodiments are the same, so the same figure marks are given and detailed descriptions are omitted.

[0110] Should Figure 9The assembly of the side beam structure of the embodiment is compared with the previous two examples ( Figure 1 、 Figure 8 Although it takes a little effort for the embodiment (of the embodiment), it can be carried out as follows. The horizontal partition member 5 on the inside of the vehicle is fixed to the side sill inner member 1a by joining the flange portion 54 on one side to the longitudinal surface 100 of the side sill inner member 1a. Next, the vertical partition member 2 is arranged on the side sill inner member 1a in a state where the components are assembled. In addition, the flange portion 55 on one side of the horizontal partition member 5 on the outside of the vehicle is arranged to face the flange portion 54 on the other side of the horizontal partition member 5 on the inside of the vehicle while sandwiching the longitudinal partition member 2, and the three components are joined. Next, the side sill outer member 1b is arranged on the side sill inner member 1a and the longitudinal partition member 2 in a state where the components are assembled, and the flange portion 55 on the other side of the horizontal partition member 5 on the outside of the vehicle is joined to the longitudinal surface 100 of the side sill outer member 1b. And, in this way, the three components are joined while the longitudinal partition member 2 is sandwiched between the side sill inner member 1a and the side sill outer member 1b to which the horizontal partition member 5 is respectively joined. In this case, the upper end of the side sill 1 can be joined (spot welded) by the upper flange portion 102 of the side sill inner member 1a, the upper flange portion 102 of the side sill outer member 1b, and the upper end portion of the vertical partition member 2. Furthermore, the lower end of the side sill 1 can be joined (spot welded) by the lower flange portion 102 of the side sill inner member 1a, the lower flange portion 102 of the side sill outer member 1b, and the lower end portion of the vertical partition member 2.

[0111] Next, the vehicle body lower structure of the side beam structure of the automobile to which the present invention is applied is described. The vehicle body lower structure of the side beam structure of the automobile to which the present invention is applied comprises: side beams 1 (side beam structure) arranged on both sides of the lower portion of the vehicle body along the longitudinal direction of the vehicle; a floor cross member 10 arranged on the floor plate 11 along the width direction of the vehicle and connecting the two side beams 1 (directly or via a portion of the floor plate, etc.); and a battery box 12, etc. arranged between the two side beams 1 on the lower side of the floor cross member 10. The floor plate 11 is arranged between the two side beams 1 arranged on both sides of the lower portion of the vehicle body along the longitudinal direction of the vehicle. The floor plate 11 is connected to the two side beams 1 (at Figure 1 In addition, a floor cross member 10 is arranged on the floor panel 11 as a frame structure member along the vehicle width direction. The floor cross member 10 is connected (fixed) to the two side members 1 (at the top of the longitudinal surface 100 of the side member inner member 1a) via the flange portion 110 of the floor panel 11 at both ends. Figure 1The two side sills 1 are connected by a joint (in the middle, the upper portion of the longitudinal surface 100 of the side sill inner member 1a). The floor cross members 10 are provided at multiple locations spaced at predetermined intervals (e.g., approximately 300 mm) in the vehicle longitudinal direction. It should be noted that the floor panel 11 or floor cross member 10 is typically joined (fixed) to the side sills 1 by spot welding.

[0112] A battery box 12 housing a battery pack 13 is located below the floor panel 11 and floor cross member 10. The side of the battery box 12 (the battery box longitudinal beam 120) faces the lower portion of the side sill 1 (the lower portion of the longitudinal surface 100 of the side sill inner member 1a) at a predetermined distance. A mounting flange 122 is continuously provided on the bottom of the battery box 12 (the battery box floor 121) so as to protrude toward the side sill. This mounting flange 122 is fastened to the lower end of the side sill 1 (the lower transverse surface 101B of the side sill inner member 1a) with fixing bolts 14, thereby securing the battery box 12 to the side sill 1.

[0113] The floor cross member 10 and the battery box longitudinal member 120 are used to transfer loads. When these components buckle, their effectiveness is significantly reduced. Therefore, the transferred load needs to be adjusted to be below the buckling resistance of the components. The amount of load transferred to these components varies depending on the overlap of the impact absorbing components and can be adjusted by the height position of the horizontal partition member 5. For example, if the buckling resistance of the battery box 12 is low and it is not desirable to transfer the collision load, the height position of the horizontal partition member 5 can be raised, as described later. Figure 10 As in the embodiment of FIG, the horizontal partition member 5 may be arranged so that the floor cross member 10 is located on the horizontal extension line of the horizontal partition member 5. This can reduce the load transmitted to the battery box 12. Figure 1 In the embodiment, the battery box longitudinal beam 120 and the side beam 1 adjacent in the vehicle width direction are arranged at a position where at least a portion overlaps when viewed from the side of the vehicle, and the transverse partition member 5 is arranged so that the battery box longitudinal beam 120 is located on the horizontal extension line of the transverse partition member 5.

[0114] In such a vehicle body lower structure, the collision load input to the side member 1 during a side collision is input to both the floor cross member 10 and the battery box 12 (battery box longitudinal member 120). As a result, the load can be borne over a wide range, and the collision load is input to the floor cross member 10 connected (fixed) to the side member 1 before being input to the battery box 12, which can reduce the load input to the battery box 12. In this case, it is preferred that the endurance of the components constituting the impact absorbing structure 4 is less than the endurance of the floor cross member 10 and the battery box longitudinal member 120. This is to ensure that the impact absorbing structure 4 can reliably deform before the floor cross member 10 and the battery box longitudinal member 120 to absorb the collision energy during a side collision. As a result, the deformation of the floor cross member 10 and the battery box longitudinal member 120 is suppressed.

[0115] Another embodiment of the automobile side member structure and the vehicle body lower structure including the same according to the present invention is a longitudinal cross-sectional view of the vehicle body lower structure (one of the structural parts on both sides of the vehicle body lower structure) including the side member in the vehicle width direction. Figure 10 The lower structure of the vehicle body is shown with Figure 1 Different embodiments. As shown in this embodiment, the transverse partition member 5 can be arranged in such a manner that the floor cross member 10 is located on the horizontal extension line of the transverse partition member 5. As described above, in a case where the battery box 12 has a low flexural strength and does not want to transfer the collision load, if the height position of the transverse partition member 5 is raised, the load transferred to the battery box 12 can be reduced. In this case, it is preferred that the endurance of the member constituting the impact absorbing structure 4 is less than the endurance of the floor cross member 10. This is to enable the impact absorbing structure 4 to reliably deform before the floor cross member 10 to absorb the collision energy during a side collision, thereby suppressing the deformation of the floor cross member 10. Other configurations of this embodiment are different from Figure 1 The embodiments are the same, so the same figure marks are given and detailed descriptions are omitted.

[0116] Example

[0117] To verify the effectiveness of the automotive side sill structure of the present invention, the following crash tests were conducted using FEM analysis (finite element method analysis). In these crash tests, the side sill structures of the inventive example and the comparative example were used as test specimens to evaluate their deformation patterns and collision energy absorption characteristics. Furthermore, a rigid body jig, designed to secure the test specimens, was used to correspond to the floor cross member and battery box longitudinal member adjacent to the side sill. The load transmitted to the rigid body jig was evaluated using contact reaction forces. Figure 11 The test conditions for the collision test of the invention example are schematically shown. Figure 11(a) is a top view, Figure 11 (b) is along Figure 11 Cross-sectional view along line bb in (a).

[0118] like Figure 11 As shown in the figure, in the collision test, a collision body 17 (column) with a radius of 127 mm was made to collide perpendicularly with the longitudinal direction of the test body 16 at an initial velocity of 30.9 km / h and a maximum penetration of 100 mm. The collision energy at this time was 32 kJ. The fixing fixture 18 of the side member on the opposite side of the collision body 17 was fixed by Figure 11 The floor beam simulation portion 180 shown (equivalent to Figure 1 Floor beam 10), battery box longitudinal beam simulation part 181 (equivalent to Figure 1 The battery box longitudinal beam 120) and the mounting flange simulation portion 182 (equivalent to Figure 1 The mounting flange 122 is formed, and the mounting flange simulation part 182 is connected to the inner side member of the side member by bolts (equivalent to Figure 1 It should be noted that the width W of the floor cross member simulation portion 180 in the vehicle front-rear direction is F The collision body 17 is collided in such a way that the collision position when viewed from the side is the floor beam portion. Figure 11 The collision test was carried out under the test conditions.

[0119] Table 1 shows the strength grades and plate thicknesses of the steel plates used for the various components of the test bodies of the inventive examples and the comparative examples.

[0120] [Table 1]

[0121] Table 1

[0122] member Strength level Plate thickness Side beam 1 1470MPa grade 1.6mm Partition 6 1470MPa grade 1.6mm Horizontal partition member 5 1470MPa grade 1.6mm Longitudinal partition member 2 1470MPa grade 0.8mm

[0123] FIG12(a) to (f) show the test bodies and test conditions of the invention example and the comparative example. In each of FIG12(a) to (f), the schematic diagram on the left is a cross-sectional view of the side beam in the vehicle width direction, and the schematic diagram on the right is a horizontal cross-sectional view of the side beam, showing the collision position of the collision body (column) and the position of the floor cross beam relative to the side beam. The invention example 1 shown in FIG12(a) is designed so that, in the impact absorbing structure 4, partitions 6 are provided at two locations in the area within the width of the floor cross beam simulation part 180, and the interval W between the above-mentioned partitions 6 is set. B (= Figure 6 The interval w1) is set to 40mm. B The width W of the floor cross member simulation portion 180 F (= Figure 6 The ratio of the width wa)B / W F In addition, a partition plate 6 is provided at two locations in the area outside the width of the floor cross member simulation part 180 in front and behind. The partition plate 6 and the width W of the floor cross member simulation part 180 are equal. F The spacing between the inner partitions 6 (= Figure 6 The interval w2) is larger than the interval w1 and is less than 254 mm, and is set to about 1 / 2 of the assumed floor cross member installation interval (the interval between adjacent floor cross members) of 280 mm, that is, 139 mm. In addition, the interval between the partitions 6 outside the width of the floor cross member simulation part 180 (= Figure 6 The spacing w3) is set to 40mm, the same as the spacing w1. In addition, the size of the reinforcement rib 7 formed on each horizontal partition member 5 on the inside and outside of the vehicle is Figure 3 The depth d shown is set to 7 mm and the curvature radius R of the rib cross section is set to 10 mm. BF When the distance between the ribs is 20 mm, H The radius of the collision body (column) is set to be less than 1 / 2 of 127 mm, that is, 41 mm.

[0124] Inventive Example 2 shown in FIG12(b) is obtained by removing the partition 6 in the area outside the width of the floor cross member simulation portion 180 of Inventive Example 1. Comparative Example 1 shown in FIG12(c) is obtained by removing the reinforcing rib 7 of the transverse partition member 5 of Inventive Example 2. Comparative Example 2 shown in FIG12(d) is obtained by removing the partition 6 from the impact absorbing structure portion 4 of Inventive Example 2. Comparative Example 3 shown in FIG12(e) is an example in which a longitudinal partition member and a partition are arranged inside the side member, and partitions are arranged at two locations in the area within the width of the floor cross member simulation portion. Comparative Example 4 shown in FIG12(f) is an example of a test body in which no partition member or impact absorbing member is arranged inside the side member, and only the side member is provided.

[0125] Figures 13 (a) to (e) show the relationship between the amount of intrusion of the impactor (column) into the side sill during the collision test and the absorbed energy (the change in absorbed energy relative to the amount of intrusion of the impactor) for the invention examples and comparative examples. It should be noted that the absorbed energy is calculated by subtracting the kinetic energy calculated based on the velocity of the impactor from the collision energy (32 kJ). When the maximum stroke of the impactor is set to 100 mm, the impactor stops at 77 mm before reaching the maximum intrusion of 100 mm, and the absorbed energy is 32.0 kJ. In addition, the impactor stops at 95 mm before reaching the maximum intrusion of 100 mm, and the absorbed energy is 32.0 kJ for the invention example 1 shown in Figure 13 (a). In contrast, the impactor stops at 95 mm before reaching the maximum intrusion of 100 mm, and the absorbed energy is 32.0 kJ for the invention example 2 shown in Figure 13 (b) to (e). In contrast, the comparative examples 1 to 4 shown in Figure 13 (b) to (e) all reach the maximum stroke of the impactor of 100 mm before reaching the absorbed energy of 32.0 kJ (the absorbed energy of the invention examples).

[0126] exist Figure 14 In the embodiment of the present invention and the comparative example, the absorption energy of the collision body at the time of maximum penetration is shown in a comparative manner. Figure 15 , the maximum penetration amount of the collision body is shown in comparison with the invention example and the comparative example.

[0127] Industrial applicability

[0128] According to the present invention, it is possible to provide a side member structure for an automobile that can achieve high collision energy absorption characteristics with low collision deformation while suppressing the increase in weight caused by structural members. Furthermore, according to the present invention, it is possible to provide a vehicle body lower structure including a side member structure having such excellent collision characteristics.

[0129] Description of Reference Signs

[0130] 1 side member

[0131] 1a Side member inner part

[0132] 1b Side member outer part

[0133] 2 longitudinal partition members

[0134] 3 Closed cross-sectional space

[0135] 3a, 3b Closed cross-sectional space

[0136] 4 Shock absorbing structure

[0137] 5 horizontal partition members

[0138] 6, 6x, 6y spacers

[0139] 7 Reinforcement

[0140] 10 Floor beams

[0141] 11 bottom plate

[0142] 12 Battery Box

[0143] 13 battery pack

[0144] 14 Fixing bolts

[0145] 16 Test Subjects

[0146] 17 Collider

[0147] 18 Fixing fixture

[0148] 30a, 30b upper side space

[0149] 31a, 31b lower side space

[0150] 50x, 50y, 51x, 51y flange

[0151] 52x, 52y, 53x, 53y flange

[0152] 54, 55 flange

[0153] 60 flange

[0154] 100 vertical faces

[0155] 101A, 101B Horizontal face

[0156] 102 flange

[0157] 110 flange

[0158] 120 Battery box longitudinal beam

[0159] 121 Battery box bottom plate

[0160] 122 Mounting flange

[0161] 180 Floor beam simulation unit

[0162] 181 Battery box longitudinal beam simulation part

[0163] 182 Mounting flange simulation part

Claims

1. The side member structure of an automobile, which has: A side beam (1) is composed of a side beam inner member (1a) on the inner side of a vehicle and a side beam outer member (1b) on the outer side of the vehicle, forming a closed cross-sectional space (3) inside; and a longitudinal partition member (2) is sandwiched between the side beam inner member (1a) and the side beam outer member (1b) of the side beam (1), and the closed cross-sectional space (3) is divided into a closed cross-sectional space (3a) on the inner side of the vehicle and a closed cross-sectional space (3b) on the outer side of the vehicle by the longitudinal partition member (2), wherein: The side member structure of the automobile is provided with a shock absorbing structure (4) in a closed cross-sectional space (3). The impact absorbing structure (4) is composed of a transverse partition member (5) and a partition plate (6), wherein the transverse partition member (5) crosses each closed cross-sectional space (3a), (3b) in the vehicle width direction to divide the closed cross-sectional space into upper and lower parts, and the partition plate (6) is provided in the upper side spaces (30a), (30b) of the space divided up and down by the transverse partition member (5) along the vehicle width direction. A plurality of partitions (6) are provided in the upper side spaces (30a) and (30b) at intervals along the vehicle length direction in such a manner as to divide the upper side spaces (30a) and (30b) into a plurality of partitions in the vehicle length direction. A reinforcing rib (7) is formed between the partitions (6) on the transverse partition member (5) along the vehicle width direction, and a plurality of the reinforcing ribs (7) are arranged at intervals in the vehicle length direction. The transverse partition member (5) and the partition plate (6) in the closed cross-sectional space (3a) inside the vehicle and the transverse partition member (5) and the partition plate (6) in the closed cross-sectional space (3b) outside the vehicle are respectively arranged opposite to each other in the vehicle width direction with the longitudinal partition member (2) sandwiched therebetween.

2. The automobile side member structure according to claim 1, wherein: The horizontal partition member (5) in the closed cross-sectional space (3a) inside the vehicle is connected to the side beam inner member (1a) and the vertical partition member (2). A transverse partition member (5) in a closed cross-sectional space (3b) on the outside of the vehicle is joined to a side beam outer member (1b) and a longitudinal partition member (2).

3. The automobile side member structure according to claim 2, wherein: The transverse partition member (5) in the closed cross-sectional space (3a) on the inner side of the vehicle has a flange portion (50x) on one end side in the vehicle width direction and a flange portion (50y) formed continuously upward and extending along the longitudinal partition member (2) to the upper end portion of the side beam (1) on the other end side. The flange portion (50x) on one end side in the vehicle width direction is joined to the inner surface of the side beam inner member (1a), and the upper end portion of the flange portion (50y) on the other end side is joined to the upper end portion of the side beam inner member (1a) and the upper end portion of the longitudinal partition member (2) in a state of being clamped by the upper end portion of the side beam inner member (1a) and the upper end portion of the longitudinal partition member (2). A transverse partition member (5) in a closed cross-sectional space (3b) on the outside of a vehicle has a flange portion (51x) on one end side in the vehicle width direction and a flange portion (51y) on the other end side that is continuously formed upward and extends along the longitudinal partition member (2) to the upper end portion of the side beam (1). The flange portion (51x) on one end side in the vehicle width direction is joined to the inner surface of the side beam outer member (1b), and the upper end portion of the flange portion (51y) on the other end side is joined to the upper end portion of the side beam outer member (1b) and the upper end portion of the longitudinal partition member (2) in a state of being clamped by the upper end portion of the side beam outer member (1b) and the upper end portion of the longitudinal partition member (2).

4. The automobile side member structure according to claim 2, wherein: The transverse partition member (5) in the closed cross-sectional space (3a) on the inner side of the vehicle has a flange portion (52x) on one end side in the vehicle width direction and a flange portion (52y) on the other end side that is continuously formed downward and extends along the longitudinal partition member (2) to the lower end portion of the side beam (1). The flange portion (52x) on one end side in the vehicle width direction is joined to the inner surface of the side beam inner member (1a), and the lower end portion of the flange portion (52y) on the other end side is joined to the lower end portion of the side beam inner member (1a) and the lower end portion of the longitudinal partition member (2) in a state of being clamped by the lower end portion of the side beam inner member (1a) and the lower end portion of the longitudinal partition member (2). A transverse partition member (5) in a closed cross-sectional space (3b) on the outside of a vehicle has a flange portion (53x) on one end side in the vehicle width direction and a flange portion (53y) on the other end side that is continuously formed downward and extends along the longitudinal partition member (2) to the lower end portion of the side beam (1). The flange portion (53x) on one end side in the vehicle width direction is joined to the inner surface of the side beam outer member (1b), and the lower end portion of the flange portion (53y) on the other end side is joined to the lower end portion of the side beam outer member (1b) and the lower end portion of the longitudinal partition member (2) in a state of being clamped by the lower end portion of the side beam outer member (1b) and the lower end portion of the longitudinal partition member (2).

5. The automobile side member structure according to claim 2, wherein: A transverse partition member (5) in a closed cross-sectional space (3a) on the inner side of a vehicle has flange portions (54) at one end side and the other end side in the vehicle width direction, respectively. The flange portion (54) on the one end side in the vehicle width direction is joined to the inner surface of the side member inner side member (1a), and the flange portion (54) on the other end side is joined to the vehicle inner side surface of the longitudinal partition member (2). A transverse partition member (5) in a closed cross-sectional space (3b) on the outside of a vehicle has flange portions (55) at one end and the other end in the vehicle width direction, respectively. The flange portion (55) on one end in the vehicle width direction is joined to the inner surface of the side member outer member (1b), and the flange portion (55) on the other end is joined to the vehicle outer side surface of the longitudinal partition member (2).

6. The automobile side member structure according to claim 1, wherein: The partition plate (6) in the upper side space (30a) inside the vehicle body is connected to at least the upper side transverse surface (101A) of the side beam inner member (1a) and the transverse partition member (5). The partition plate (6) in the upper side space (30b) outside the vehicle body is respectively connected to at least the longitudinal surface (100) of the side beam outer member (1b), the upper transverse surface (101A) and the transverse partition member (5).

7. The automobile side member structure according to claim 1, wherein: The partition plate (6) includes a partition plate (6) provided in a region within the width of the floor cross member in the front-rear direction of the vehicle. x ) and a partition (6) provided in an area outside the width of the floor beam y ), In the front-to-back direction of the vehicle, Install partitions (6) at two or more locations within the width of the floor beam. x ), and a partition plate (6 y ), When the two adjacent partitions (6 x ) is set to w1 and the partition (6 x ) and the partition (6 x ) adjacent partitions (6 y ) is set to w2, it is set to w1<w2.

8. The automobile side member structure according to claim 7, wherein: At least a portion of the partition (6 y ) includes a partition group consisting of two or more partitions arranged adjacent to each other.

9. The side member structure of an automobile according to claim 1, wherein: The partition plate (6) is connected to the horizontal partition member (5) via the flange (60). The distance between two adjacent reinforcing ribs (7) in the vehicle length direction is set as W H The width of the flange (60) of the partition (6) is set to W BF When W is satisfied BF ≤W H ≤127mm, wherein the distance between two adjacent reinforcing ribs (7) in the vehicle length direction refers to the distance between the edges of the two reinforcing ribs (7).

10. The automobile side member structure according to claim 1, wherein: The yield strength of the metal plate constituting the impact absorbing structure (4) is less than the yield strength of the metal plate constituting the floor cross member.

11. The automobile side member structure according to claim 1, wherein: The tensile strength of the metal plate constituting the impact absorbing structure (4) is 780 MPa or higher, or the Vickers hardness (HV) at a position of 1 / 4 of the plate thickness of the metal plate is 250 or higher.

12. The side member structure of an automobile according to claim 1, wherein: The metal plate constituting the impact absorbing structure (4) is a steel plate containing, by mass%, C: 0.030% to 0.250%, Si: 0.01% to 2.50%, Mn: 1.00% to 3.50%, P: 0.001% to 0.100%, S: 0.0200%, and Al: 0.010% to 2.000%.

13. The side member structure of an automobile according to claim 1, wherein: The metal plate constituting the impact absorbing structure (4) has a steel structure comprising ferrite with an area ratio of not less than 0% and not more than 65%, martensite and tempered martensite with an area ratio of not less than 30% and not more than 100%, and retained austenite with an area ratio of not less than 0% and not more than 15%, at a position of 1 / 4 of the thickness of the metal plate.

14. The side member structure of an automobile according to claim 1, wherein: The ultimate deformation energy of the metal plate constituting the impact absorbing structural portion (4) in a tensile test is 0.55 or more.

15. The side member structure of an automobile according to claim 1, wherein: The metal plate constituting the impact absorbing structure (4) has a limit bending radius R (mm) at which no cracks are generated when a 90° V-bending test is performed, and the plate thickness t (mm) of the metal plate satisfies R / t≤7.

0.

16. An automobile substructure having: A side member (1) is arranged on both sides of the lower part of the vehicle body along the vehicle length direction; a floor cross member (10) is arranged on a bottom plate (11) along the vehicle width direction and connects the two side members (1); and a battery box (12) is arranged between the two side members (1) on the lower side of the floor cross member (10), wherein: The vehicle body lower structure includes the vehicle side member structure according to any one of claims 1 to 15. The battery box longitudinal beam (120) and the side beam (1) of the battery box (12) are adjacent to each other in the vehicle width direction and are arranged at a position where at least a portion of them overlap when viewed from the side of the vehicle. The transverse partition member (5) is arranged in such a manner that the battery box longitudinal beam (120) is located on a horizontal extension line of the transverse partition member (5).

17. The vehicle body lower structure according to claim 16, wherein: The endurance of the components constituting the impact absorbing structure (4) is less than the endurance of the floor cross member (10) and the battery box longitudinal member (120).

18. An automobile substructure having: A side member (1) is arranged on both sides of the lower part of the vehicle body along the vehicle length direction; and a floor cross member (10) is arranged on the bottom plate (11) along the vehicle width direction and connects the two side members (1), characterized in that: The vehicle body lower structure includes the vehicle side member structure according to any one of claims 1 to 15. The transverse partition member (5) is arranged in such a manner that the floor crossbeam (10) is located on a horizontal extension line of the transverse partition member (5).

19. The vehicle body lower structure according to claim 18, wherein: The endurance of the components constituting the impact absorbing structural portion (4) is less than the endurance of the floor cross member (10).

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