Side member for vehicle, crash box, and method for manufacturing same

Abstract

The present invention provides a side member for a vehicle, which increases energy absorption capacity by inducing a stabilized collapse shape and simultaneously has a mass-producible structure, a crash box, and a method for manufacturing same. In an embodiment, a first tubular portion extending in the lengthwise direction and having a hexagonal cross-section and a second tubular portion which is connected to the first tubular portion, extends in the lengthwise direction, and has a hexagonal cross-section are included, wherein the first tubular portion and the second tubular portion are integrally formed by bending a single first plate material, and the first plate material may have a bead portion formed adjacent to one end portion thereof in the lengthwise direction.

Description

Vehicle side member, crash box and method of manufacturing the same

[0001] The present invention relates to a vehicle side member, a crash box, and a method for manufacturing the same, which can be applied to the front or rear of a vehicle body to sufficiently absorb collision energy during a front or rear collision.

[0002] The vehicle's side members play a role in absorbing collision energy as much as possible during a frontal or rear collision to minimize the transfer of collision loads to the passenger compartment or, in the case of electric vehicles, the battery compartment.

[0003] Side members in currently mass-produced electric vehicles utilize extruded aluminum in key areas responsible for absorbing energy during frontal or rear collisions. In this scenario, the entire longitudinal compressive deformation of the member is induced upon impact, allowing this single component to absorb a significant portion of the vehicle's kinetic energy. Furthermore, due to the ample space available at the front of electric vehicles, the structural freedom of side members is greater than that of internal combustion engine vehicles. Consequently, to maximize energy absorption capacity through sufficient compressive deformation along the length, side members can be designed as straight lines without altering their cross-sectional shape. Such members serve to protect the battery and passengers during frontal or rear collisions. To achieve this, there is a growing trend to apply extruded aluminum components, despite the resulting increase in cost, in order to ensure a consistently robust cross-sectional structure along the length and achieve weight reduction.

[0004] To address the issue of rising costs, side members made of steel, which is cheaper than aluminum or aluminum alloys, have been proposed; however, there is a problem in that it is difficult to construct side members with complex cross-sections due to the high density of steel and the complexity of the manufacturing process. Furthermore, steel side members have a limitation in that they absorb only a portion of the impact energy because they absorb it through bending deformation rather than longitudinal crushing deformation during a collision.

[0005] In order to solve these problems, the applicant proposed in Patent Document 1 a side member with an octagonal cross-section that can double energy absorption capacity by inducing a stable crushed shape. However, the side member with an octagonal cross-section has a problem of interference with the mold during the roll forming process in mass production, and if the bending point is lower than 40° to avoid said interference, there is a problem of excessive springback. In addition, the side member undergoes a sizing roll process to ensure dimensional accuracy after the closed cross-section is formed during the roll forming process, but if the bending point is lower than 40°, it is difficult to apply the sizing roll, resulting in a problem of low mass production capability.

[0006] (Patent Document 1) KR 10-2423412 B1

[0007] The present invention aims to solve the above problems by providing a vehicle side member, a crash box, and a method for manufacturing the same, which double the energy absorption capacity by inducing a stable crushed shape and simultaneously have a structure with high mass producibility.

[0008] In addition, the present invention aims to provide a vehicle side member, a crash box, and a method for manufacturing the same, which can also improve interaction with the other vehicle during a collision.

[0009] A vehicle side member according to one embodiment of the present invention comprises: a first tubular upper portion that extends in the longitudinal direction and has a hexagonal cross-sectional shape; and a second tubular upper portion that is connected to the first tubular upper portion, extends in the longitudinal direction, and has a hexagonal cross-sectional shape; wherein the first tubular upper portion and the second tubular upper portion are formed integrally by being bent and formed from a single first plate, and the first plate may have a bead portion formed adjacent to one end in the longitudinal direction.

[0010] In addition, the bead portion may be formed within 100 mm in the longitudinal direction from one end.

[0011] Additionally, when viewed from the longitudinal direction, the first tubular upper portion is composed of first to sixth sides formed by folding in sequence in one direction, and the second tubular upper portion is composed of seventh to eleven sides formed by folding in sequence in the opposite direction to the one direction based on the sixth side, including the sixth side, and the bead portion may be characterized by being formed on at least one of the first to fifth sides and on at least one of the seventh to eleven sides.

[0012] In addition, the first tubular upper part and the second tubular upper part may be characterized by being bent such that the bending angle of each bending point is 40° or more.

[0013] In addition, it may include a welded portion formed on the outer wall of the first tubular upper portion and the second tubular upper portion.

[0014] Additionally, the welded portion may include: a first welded portion formed by welding a first flange, which is bent outward from one end of the first plate member to the outside of the first tubular upper portion, to the outside wall of the second tubular upper portion; and a second welded portion formed by welding a second flange, which is bent outward from the other end of the first plate member to the outside of the second tubular upper portion, to the outside wall of the first tubular upper portion.

[0015] In addition, the first tubular upper part and the second tubular upper part share one side, and the first tubular upper part and the second tubular upper part may have the same cross-sectional shape and size with respect to the side.

[0016] Additionally, when viewed from the longitudinal direction, the first tubular upper portion is composed of first to sixth sides formed by being bent sequentially in one direction, and the second tubular upper portion is composed of seventh to eleven sides formed by being bent sequentially in the opposite direction of the one direction based on the sixth side, including the sixth side, and the first flange is located at the end of the first side, and the second flange may be located at the end of the eleventh side.

[0017] Additionally, the third side of the first tubular upper part and the ninth side and the sixth side of the second tubular upper part are parallel to each other, the first side of the first tubular upper part and the seventh side of the second tubular upper part are parallel, and the first welded part may be formed by welding the first flange located on the first side to the seventh side, the eleventh side of the second tubular upper part and the fifth side of the first tubular upper part are parallel, and the second welded part may be formed by welding the second flange located on the eleventh side to the fifth side.

[0018] In addition, the 6th side can be extended orthogonally to the 1st side and the 11th side.

[0019] In addition, the first plate may be a steel material having a tensile strength of 780 MPa or more.

[0020] In addition, in the hexagonal cross-sectional shape, the radius of curvature (R) at the bending point between one side and an adjacent side and the thickness (t) of the first plate may be a vehicle side member satisfying the following relationship.

[0021] R / t < R / t_p

[0022] Here, R / t_p may be a limit value of the radius of curvature relative to the thickness when the first plate is bent and formed by a press.

[0023] A vehicle crash box according to another embodiment of the present invention comprises: a first tubular upper portion that extends in the longitudinal direction and has a hexagonal cross-sectional shape; a second tubular upper portion that is connected to the first tubular upper portion and extends in the longitudinal direction and has a hexagonal cross-sectional shape; and a mounting plate connected to the longitudinal ends of the first and second tubular upper portions; wherein the first tubular upper portion and the second tubular upper portion are formed integrally by being bent and molded from a single first plate material, and the first plate material may have a bead portion formed adjacent to one end in the longitudinal direction.

[0024] Additionally, the device may further include a weld formed on the outer wall of the first tubular upper section and the second tubular upper section; wherein the weld may include a first weld formed by welding a first flange, which is bent outward from one end of the first plate material to the outside of the first tubular upper section, to the outer wall of the second tubular upper section; and a second weld formed by welding a second flange, which is bent outward from the other end of the first plate material to the outside of the second tubular upper section, to the outer wall of the first tubular upper section.

[0025] Additionally, when viewed from the longitudinal direction, the first tubular upper part is composed of first to sixth sides formed by being bent sequentially in one direction, and the second tubular upper part is composed of seventh to eleven sides formed by being bent sequentially in the opposite direction of the one direction based on the sixth side, including the sixth side, and the third side of the first tubular upper part and the ninth side and the sixth side of the second tubular upper part are parallel to each other, and the first side of the first tubular upper part and the seventh side of the second tubular upper part are parallel, and the first welded part is formed by welding the first flange located on the first side to the seventh side, and the eleventh side of the second tubular upper part and the fifth side of the first tubular upper part are parallel, and the second welded part can be formed by welding the second flange located on the eleventh side to the fifth side.

[0026] In addition, the 6th side can be extended orthogonally to the 1st side and the 11th side.

[0027] In addition, the bead portion may be formed on at least one of the second to fourth sides and on at least one of the eighth to tenth sides.

[0028] A method for manufacturing an energy-absorbing structure for a vehicle according to another embodiment of the present invention may include: a bead portion forming step of forming a bead portion adjacent to one end in the longitudinal direction of a single first plate; a first bending step of forming a first tubular portion by bending the first plate five times in a first direction; and a second bending step of forming a second tubular portion by bending the first plate five times in a second direction opposite to the first direction.

[0029] In addition, the bead portion forming step may be characterized by forming the bead portion within 100 mm in the longitudinal direction from one end.

[0030] In addition, the first bending step and the second bending step may be characterized by bending such that the bending angle of the bending point is 40° or more.

[0031] Additionally, the method may further include a flange forming step performed prior to the welding step, wherein one end of the first plate is bent outward to the outside of the first tubular upper part to form a first flange, and the other end of the first plate is bent outward to the outside of the second tubular upper part to form a second flange; and a closed cross-section forming step wherein the first flange is brought into contact with the outer wall of the second tubular upper part to form a closed cross-section, and the second flange is brought into contact with the outer wall of the first tubular upper part to form a closed cross-section.

[0032] In addition, it may further include a sizing step performed after the closed cross-section forming step but before the welding step, in which the closed cross-section is re-compressed from the outside to have preset dimensions.

[0033] Additionally, the first bending step may bend the first plate in the first direction at the second bending point, the third bending point, the fourth bending point, the fifth bending point, and the sixth bending point in sequence from one end side toward the other end side, and the second bending step may bend the first plate in the second direction opposite to the first direction at the seventh bending point, the eighth bending point, the ninth bending point, the tenth bending point, and the eleventh bending point in sequence.

[0034] A vehicle side member according to another embodiment of the present invention comprises: a first tubular upper portion that extends in the longitudinal direction and has a hexagonal cross-sectional shape; and a second tubular upper portion that is connected to the first tubular upper portion and extends in the longitudinal direction and has a hexagonal cross-sectional shape; wherein the first tubular upper portion and the second tubular upper portion are integrally formed by bending and forming a TWB (Tailor Welded Blank) plate material in which first and second steel materials having different strengths or thicknesses are combined, and a groove portion may be formed at one end of the first and second tubular upper portions.

[0035] In addition, the first and second steel materials may be placed at different positions in the longitudinal direction.

[0036] In addition, it may further include bead portions formed on the sides of the first and second tubular upper portions.

[0037] In addition, the first steel material may have relatively lower strength or thinner thickness compared to the second steel material, and the bead portion and the groove portion may be formed in the first steel material.

[0038] In addition, the first steel member may be positioned far from the center of the vehicle in the longitudinal direction.

[0039] In addition, the groove may be formed at the corner of the hexagonal cross-sectional shape.

[0040] Additionally, when viewed from the longitudinal direction, the first tubular upper portion is composed of first to sixth sides formed by being bent sequentially in one direction, and the second tubular upper portion is composed of seventh to eleven sides formed by being bent sequentially in the opposite direction of the one direction with respect to the sixth side, including the sixth side, and the bead portion and the groove portion may be formed symmetrically with respect to the sixth side in the first tubular upper portion and the second tubular upper portion.

[0041] In addition, the first tubular upper part and the second tubular upper part may be characterized by being bent such that the bending angle of each bending point is 40° or more.

[0042] Additionally, it may include a weld formed on the outer wall of the first tubular upper portion and the second tubular upper portion; wherein the weld may include a first weld formed by welding a first flange, which is bent outward from one end of the TWB plate material to the outer wall of the second tubular upper portion; and a second weld formed by welding a second flange, which is bent outward from the other end of the TWB plate material to the outer wall of the second tubular upper portion.

[0043] Additionally, when viewed from the longitudinal direction, the first tubular upper portion is composed of first to sixth sides formed by being bent sequentially in one direction, and the second tubular upper portion is composed of seventh to eleven sides formed by being bent sequentially in the opposite direction of the one direction based on the sixth side, including the sixth side, and the first flange is located at the end of the first side, and the second flange may be located at the end of the eleventh side.

[0044] Additionally, the third side of the first tubular upper part and the ninth side and the sixth side of the second tubular upper part are parallel to each other, the first side of the first tubular upper part and the seventh side of the second tubular upper part are parallel, and the first welded part may be formed by welding the first flange located on the first side to the seventh side, the eleventh side of the second tubular upper part and the fifth side of the first tubular upper part are parallel, and the second welded part may be formed by welding the second flange located on the eleventh side to the fifth side.

[0045] In addition, the 6th side can be extended orthogonally to the 1st side and the 11th side.

[0046] A vehicle crash box according to another embodiment of the present invention comprises: a first tubular upper portion extending in the longitudinal direction and having a hexagonal cross-sectional shape; a second tubular upper portion connected to the first tubular upper portion and extending in the longitudinal direction and having a hexagonal cross-sectional shape; and a mounting plate connected to the longitudinal ends of the first and second tubular upper portions; wherein the first tubular upper portion and the second tubular upper portion are integrally formed by bending and forming a TWB plate material in which first and second steel materials having different strengths or thicknesses are combined, and the TWB plate material may have a groove formed at one end in the longitudinal direction.

[0047] In addition, the first steel may have relatively lower strength or thinner thickness compared to the second steel, and the first steel may be positioned far from the center of the vehicle in the longitudinal direction.

[0048] In addition, it further includes a bead portion formed on the sides of the first and second tubular upper portions, and the bead portion may be formed in the first steel material together with the groove portion.

[0049] Additionally, it may further include a weld formed on the outer wall of the first tubular upper portion and the second tubular upper portion; wherein the weld may include a first weld formed by welding a first flange, which is bent outward from one end of the TWB plate material to the outer wall of the second tubular upper portion; and a second weld formed by welding a second flange, which is bent outward from the other end of the TWB plate material to the outer wall of the second tubular upper portion.

[0050] Additionally, when viewed from the above length direction, the first tubular upper part is composed of first to sixth sides formed by being bent sequentially in one direction, and the second tubular upper part is composed of seventh to eleven sides formed by being bent sequentially in the opposite direction of the one direction based on the sixth side, including the sixth side, and the third side of the first tubular upper part and the ninth side and the sixth side of the second tubular upper part are parallel to each other, and the first side of the first tubular upper part and the seventh side of the second tubular upper part are parallel, and the first welded part is formed by welding the first flange located on the first side to the seventh side, and the eleventh side of the second tubular upper part and the fifth side of the first tubular upper part are parallel, and the second welded part can be formed by welding the second flange located on the eleventh side to the fifth side.

[0051] A method for manufacturing an energy-absorbing structure for a vehicle according to another embodiment of the present invention may include: a first bending step of forming a first tubular upper portion by bending a TWB plate, in which first and second steel materials having different strengths or thicknesses are combined along the longitudinal direction, five times in a first direction; a second bending step of forming a second tubular upper portion by bending the TWB plate five times in a second direction opposite to the first direction; and a chamfering step of forming a groove at one end of the bent TWB plate.

[0052] In addition, it may further include a bead portion forming step performed before the first bending step and forming a bead portion adjacent to one end of the TWB plate.

[0053] In addition, the first bending step and the second bending step can bend the bend so that the bending angle of the bending point is 40° or more.

[0054] The present invention, through the vehicle side member, crash box, and method for manufacturing the above, can double the energy absorption capacity by inducing a stable crushed shape and simultaneously present a structure with high mass production capability.

[0055] In addition, the present invention can reduce negative interaction with the other vehicle during a collision through the vehicle side member, crash box, and method of manufacturing the same as above.

[0056] FIG. 1 is a perspective view illustrating a side member according to an embodiment of the present invention.

[0057] Figure 2 is a cross-sectional view of Figure 1.

[0058] Figure 3 is a diagram showing the behavioral pattern in the results of performance verification through the analysis of a conventional side member.

[0059] FIG. 4 is a diagram showing the behavioral pattern in the results of performance verification through analysis of a side member according to an embodiment of the present invention.

[0060] FIGS. 5 and 6 are graphs showing a comparison of performance according to the distance of the bead portion in a side member according to an embodiment of the present invention.

[0061] FIGS. 7 and 8 are graphs showing a comparison of performance according to the number of bead portions in a side member according to an embodiment of the present invention.

[0062] Figure 9 is a drawing showing the bending angle in the open cross-section state during the roll forming process of a side member having an octagonal cross-section shape.

[0063] Figure 10 is a drawing showing the bending angle in the open cross-section state during the roll forming process of a side member having a hexagonal cross-section shape.

[0064] FIG. 11 is a flowchart of a method for manufacturing a side member according to an embodiment of the present invention.

[0065] FIG. 12 is a schematic diagram of a forward energy absorption structure including a crash box according to an embodiment of the present invention.

[0066] FIG. 13 is a side view illustrating a side member according to another embodiment of the present invention.

[0067] FIG. 14 is a perspective view illustrating a side member according to another embodiment of the present invention.

[0068] FIG. 15 is a schematic diagram of a forward energy absorption structure including a crash box according to another embodiment of the present invention.

[0069] FIG. 16 is a perspective view illustrating a side member according to an embodiment of the present invention.

[0070] Fig. 17 is a side view of Fig. 16.

[0071] FIG. 18 is a schematic perspective view of the side member of Reference Example 1.

[0072] FIG. 19 is a schematic perspective view of the side member of Reference Example 2.

[0073] FIG. 20 is a schematic perspective view of the side member of Reference Example 3.

[0074] FIGS. 21 to 24 are drawings showing a modified example in which the bead portion of a side member is changed according to an embodiment of the present invention.

[0075] FIG. 25 is a drawing showing the bending angle in the open cross-section state during the roll forming process of a side member having an octagonal cross-section shape.

[0076] FIG. 26 is a drawing showing the bending angle in the open cross-section state during the roll forming process of a side member having a hexagonal cross-section shape.

[0077] FIG. 27 is a flowchart of a method for manufacturing a side member according to an embodiment of the present invention.

[0078] FIG. 28 is a schematic diagram of a forward energy absorption structure including a crash box according to an embodiment of the present invention.

[0079] FIG. 29 is a side view of a vehicle side member according to another embodiment of the present invention.

[0080] FIG. 30 is a perspective view of a vehicle side member according to another embodiment of the present invention.

[0081] FIG. 31 is a schematic diagram of a forward energy absorption structure including a crash box according to another embodiment of the present invention.

[0082] FIG. 32 is a drawing showing a modified example in which a groove portion is deformed in a side member according to another embodiment of the present invention.

[0083] Specific embodiments of the present invention will be described below with reference to the attached drawings. However, the concept of the present invention is not limited to the presented embodiments, and those skilled in the art who understand the concept of the present invention may easily propose other inventions that are inferior or other embodiments included within the scope of the concept of the present invention by adding, changing, or deleting other components within the same scope of the concept, and such are also to be considered to be included within the scope of the concept of the present invention.

[0084] Furthermore, throughout the specification, the statement that one component is 'connected' to another component means that it includes not only cases where these components are 'directly connected,' but also cases where they are 'indirectly connected' with another component in between. Also, the statement that a component 'includes' means that, unless specifically stated otherwise, it does not exclude other components but may include additional components.

[0085] Additionally, components with the same function within the scope of the same concept appearing in the drawings of each embodiment are described using the same reference numeral.

[0086] FIGS. 1 and FIGS. 2 present a side member according to an embodiment of the present invention. More specifically, FIG. 1 is a perspective view illustrating a side member according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view of FIG. 1.

[0087] A vehicle side member includes a front side member and a rear side member, and is positioned on both the left and right sides of the vehicle at the front and rear, and can extend forward or backward. When viewed from above, the side member may have a shape that extends in an almost straight line in the front-rear direction. By doing so, the side member can absorb collision energy to suppress body deformation during a frontal or rear collision. For example, one end of the side member may be connected to a kick-up portion installed at the front end of the vehicle's floor section to extend forward, or one end may be connected to a kick-up portion installed at the rear end of the floor section to extend backward. Assembly of the side member and the vehicle body may be achieved by inserting any connecting member into the side member and bolting it, or by forming a flange at the front or rear end of the side member and joining it using welding or the like using this flange. A more detailed description of such assembly is omitted in this specification.

[0088] In addition, since a pair of side members are arranged symmetrically to each other and have the same actual configuration, one side member will be described below as a representative example. Also, for the convenience of explanation, a side member installed at the front of the vehicle body is used as an example, but it is not limited to this and can be applied to a side member installed at the rear of the vehicle body as well.

[0089] Referring to FIGS. 1 and 2, a side member (100) made of general steel includes a first tubular upper section (110) and a second tubular upper section (120). It can be formed integrally by machining a single first plate (1) of a metal, such as steel, and can be formed by bending or roll forming. At this time, the first tubular upper section (110) and the second tubular upper section (120) may have a hexagonal cross-sectional shape that extends in the X direction, which is the longitudinal direction. More specifically, the side member (100) may be formed by bending a first plate (1) having a predetermined width and length multiple times to form a plurality of closed cross-sections, each having a hexagonal cross-sectional shape.

[0090] For example, a single first plate (1) can be bent in a counterclockwise direction from one end (p1) toward the other end (p2), and for example, a first tubular upper part (110) with a hexagonal cross-section can be formed by bending it five times in the same first direction (e.g., counterclockwise) in the order of the first side (s1), second side (a2), second side (s2), third side (a3), third side (s3), fourth side (a4), fourth side (s4), fifth side (a5), fifth side (s5), sixth side (a6), and sixth side (s6) centered on the first bending point (a1).

[0091] Next, the first plate (1) can be folded five times in the same second direction (e.g., clockwise) in the order of the seventh bend point (a7), the seventh side (s7), the eighth bend point (a8), the eighth side (s8), the ninth bend point (a9), the ninth side (s9), the tenth bend point (a10), the tenth side (s10), the eleventh bend point (a11), the eleventh side (s11), and the twelveth bend point (a12) to form a second tubular upper part (120) with a hexagonal cross-section.

[0092] The side member (100) includes a weld (130) for connecting the first tubular upper part (110) and the second tubular upper part (120). The weld (130) includes a first weld (131) located on one end (p1) and a second weld (132) located on the other end (p2). Both ends (p1, p2) of the first plate (1) may be bent at a predetermined angle to form flanges (f1, f2), and the weld (130) may be located on the side where the flanges (f1, f2) are connected to the first tubular upper part (110) and the second tubular upper part (120).

[0093] In a conventional side member, the flanges (f1, f2) are formed by being bent inward toward the first tubular upper portion (110) and the second tubular upper portion (120). For example, the flanges (f1, f2) are formed by being bent so as to be in contact with the sixth side (s6). That is, in a conventional side member, the first flange (f1) can be connected to the first tubular upper portion (110) of the sixth side (s6) as it is formed by being bent inward toward the first bending point (a1), and the second flange (f2) can be connected to the second tubular upper portion (120) of the sixth side (s6) as it is formed by being bent inward toward the second bending point (a12). Meanwhile, in this specification, being bent inward may mean being bent inwardly to the closed cross-section of the first tubular upper part (110) or the second tubular upper part (120), and being bent outward may mean being bent outwardly to the closed cross-section of the first tubular upper part (110) or the second tubular upper part (120).

[0094] Meanwhile, since the side member made of steel forms a closed cross-section and then performs welding, the conventional side member could perform welding at the first bend point (a1) and the seventh bend point (a7) where the first flange (f1), the first side (s1), and the seventh side (s7) meet, and could perform welding at the sixth bend point (a6) and the twelfth bend point (12) where the second flange (f2), the fifth side (s5), and the eleventh side (s11) meet. In other words, the conventional side member could perform fillet welding, for example, to form a weld at the edge, but this has the problem that the weld (w1, w2) breaks upon a front-to-rear collision.

[0095] Meanwhile, in one embodiment of the present invention, the side member (100) may be formed such that the flanges (f1, f2) are bent outward toward the first tubular upper part (110) and the second tubular upper part (120). For example, the first flange (f1) may be formed by being bent to abut the seventh side (s7) of the second tubular upper part (120), and the second flange (f2) may be formed by being bent to abut the fifth side (s5) of the first tubular upper part (110). That is, the first flange (f1) can be connected to the outer wall of the second tubular upper part (120) by being formed by being bent in the first direction around the first bending point (a1), and the second flange (f2) can be connected to the outer wall of the first tubular upper part (110) by being formed by being bent in the first direction around the twelfth bending point (a12). Furthermore, in the side member (100) according to an embodiment of the present invention, the first tubular upper part (110) and the second tubular upper part (120) share a sixth side (s6), which is a side between the sixth bending point (a6) and the seventh bending point (a7), and the first tubular upper part (110) and the second tubular upper part (120) may have the same cross-sectional shape and size based on the side (s6).

[0096] Accordingly, in a side member (100) according to an embodiment of the present invention, a first weld (131) may be formed on the surface where the first flange (f1) and the seventh side (s7) meet, and a second weld (132) may be formed on the surface where the second flange (f2) and the fifth side (s5) meet. That is, unlike a conventional side member, the side member (100) according to an embodiment of the present invention provides a structure in which the entire surface of the flanges (f1, f2) is weldable, thereby preventing fracture of the welds (131, 132) and increasing crushing stability. At this time, since the entire surface of the flanges (f1, f2) can be weldable, the length (d1) of the weld (130) may correspond to the length of the flanges (f1, f2) and may be approximately 5 mm to 20 mm.

[0097] Furthermore, a side member (100) according to an embodiment of the present invention further includes a bead portion (140). The bead portion (140) may be formed adjacent to one end of the lengthwise direction of the first plate (1), and may be formed on a plurality of surfaces where each side constituting the side member (100) is extended in the lengthwise direction. The bead portion (140) may have a structure that protrudes inwardly from the first tubular upper portion (110) or the second tubular upper portion (120) when viewed from the lengthwise direction, and may be spaced apart by a predetermined distance (d) from one end of the lengthwise direction. The structure of the bead portion (140) will be described later with reference to FIGS. 5 and FIGS. 8.

[0098] FIGS. 3 and 4 illustrate a side member (100) according to an embodiment of the present invention compared with a conventional side member. More specifically, FIG. 3 is a diagram showing the behavioral pattern in the results of performance verification through analysis of a conventional side member, and FIG. 4 is a diagram showing the behavioral pattern in the results of performance verification through analysis of a side member according to an embodiment of the present invention. That is, the conventional side member is a side member that does not include a bead portion, while the side member (100) according to an embodiment of the present invention differs in that it includes a bead portion (140).

[0099] As illustrated in FIG. 3, it can be observed that a conventional side member without a bead section exhibits unstable sequential collapse as crushing deformation proceeds simultaneously in the rear section as well as in the front section where the collision occurs. In other words, the conventional side member has the potential for bending deformation to occur due to initial deformation instability when colliding in the longitudinal direction. On the other hand, as illustrated in FIG. 4, the side member (100) according to an embodiment of the present invention prevents crushing deformation in the rear section due to energy absorption by the bead section (140, see FIG. 2) in the front section where the collision occurs, and can induce sequential crushing deformation starting from the front section. That is, the side member (100) according to an embodiment of the present invention has a larger average load value absorbed in the front section than the conventional side member due to the application of the bead section (140), and the amount of fluctuation required for energy absorption is much smaller, making it easier to absorb energy.

[0100] FIGS. 5 and 6 are graphs showing a comparison of performance according to the distance of the bead portion in a side member according to an embodiment of the present invention, and FIGS. 7 and 8 are graphs showing a comparison of performance according to the number of bead portions in a side member according to an embodiment of the present invention. Hereinafter, the structure of the bead portion (140) according to an embodiment of the present invention will be described with reference to FIGS. 5 to 8, and will be described with reference to FIGS. 1 and 2 together.

[0101] As described above, in one embodiment of the present invention, the bead portion (140) of the side member (100) may be spaced apart from one end in the longitudinal direction of the side member (100) by a predetermined distance (d) in the longitudinal direction.

[0102] FIGS. 5 and 6 are drawings comparing energy absorption performance through analysis by varying the spacing distance (d) of the bead portion (140) to d1, d2, d3, and d4, respectively, under the same conditions. In FIG. 6, the X-axis represents the deformation length of the member for energy absorption, and the Y-axis represents the load applied to the member. At this time, as shown in FIG. 6, when the bead portion (140) is spaced by d1, the deformation length of the member for energy absorption is 518.2 mm; when the bead portion (140) is spaced by d2, the deformation length of the member is 515.4 mm; when the bead portion (140) is spaced by d3, the deformation length of the member is 513.8 mm; and when the bead portion (140) is spaced by d4, the deformation length of the member is 519.8 mm. That is, in the side member (100) according to one embodiment of the present invention, even if the separation distance (d) is changed to d1 to d4 within 100 mm, it can be confirmed that there is no significant difference in deformation mode and deformation length and that the energy absorption capacity is similar. Accordingly, in the side member (100) according to one embodiment of the present invention, the bead portion (140) can be formed within 100 mm in the longitudinal direction from one end.

[0103] FIGS. 7 and FIGS. 8 are drawings comparing energy absorption performance through analysis with different numbers of bead portions (140) under the same conditions, where the X-axis of FIG. 7 represents the deformation length of the member for energy absorption and the Y-axis represents the load applied to the member. At this time, FIG. 7(a) represents a case where the bead portion (140) is formed on only one side of each of the first tubular upper portion (110) and the second tubular upper portion (120); FIG. 7(b) represents a case where the bead portion (140) is formed on three sides of each of the first tubular upper portion (110) and the second tubular upper portion (120); FIG. 7(c) represents a case where the bead portion (140) is formed on four sides of each of the first tubular upper portion (110) and the second tubular upper portion (120); FIG. 7(d) represents a case where the bead portion (140) is formed on all sides except for one side (s6) shared by the first tubular upper portion (110) and the second tubular upper portion (120). At this time, as illustrated in FIG. 8, (a) to (d) can induce sequential crushing deformation in the longitudinal direction regardless of the number of beads, and since the deformation mode and deformation length are similar, it can be confirmed that the energy absorption capacity is similar. Accordingly, when viewed from the longitudinal direction, the bead portion (140) of the side member (100) according to an embodiment of the present invention may be formed on any one of the first to fifth sides (s1, s2, s3, s4, s5) and may be formed on any one of the seventh to eleventh sides (s7, s8, s9, s10, s11). By doing so, the side member (100) according to an embodiment of the present invention can minimize the number of the bead portion (140) while having the same energy absorption effect.

[0104] FIGS. 9 and 10 are drawings showing the bending angle according to the cross-sectional shape of a side member during a roll forming process. More specifically, FIG. 9 shows the bending angle in an open cross-section state during the roll forming process of a side member having an octagonal cross-section shape, and FIG. 10 shows the bending angle in an open cross-section state during the roll forming process of a side member having a hexagonal cross-section shape. The following description will be explained with reference to FIGS. 9 and 10.

[0105] The roll forming process is known as a process for producing a beam with a uniform cross-section by introducing a coil or a long plate into a continuous arrangement of upper and lower forming roll sets and sequentially bending and forming it. A side member using steel (P) is produced by bending and forming a single piece of steel (P), and the bending and forming is performed by compression of the upper and lower dies. For example, as shown in FIG. 9, the steel (P) is sequentially bent to a first bend point (a1), a second bend point (a2), a third bend point (a3), a fourth bend point (a4), a fifth bend point (a5), a sixth bend point (a6), a seventh bend point (a7), and an eighth bend point (a8) to form a closed cross-section. At this time, the steel (P) can be bent by compression of the upper die (UD1, UD2) and lower die (LD1, LD2) before the closed cross-section is formed, that is, in an open state. Since compression is possible only on the outer side of the closed cross-section after the closed cross-section is formed, the steel (P) undergoes a sizing process using a sizing roll on the outer side of the closed cross-section to have a target bending angle and cross-sectional shape.

[0106] Meanwhile, when the steel (P) is in an open cross-section state before a closed cross-section is formed, and is pressed by the mold (UD1, UD2, LD1, LD2), the bending angle at each bending point (e.g., the first to eighth bending points) must be at least 40° to ensure dimensional accuracy by the sizing roll. If the bending angle in the open cross-section state is lower than 40°, during the sizing roll process, the bending angle at each bending point may not bend to the target angle, but rather bend at an unexpected point, or problems such as springback may occur, making it difficult to secure the target dimensional accuracy. Therefore, for mass production, it is important to ensure that the bending angle at the bending point is at least 40° when forming the side member using the steel (P).

[0107] As shown in FIG. 9, since the side member with an octagonal cross-section has seven bending points in a single closed cross-section, the bending angle must be formed in a limited manner to avoid interference between the steel (P) and the die during the roll forming process. For example, if the bending angle at the second to fifth bending points (a2, a3, a4, a5) is secured to 40°, interference may occur between the first lower die (LD1) and the first flange (f1) as shown in part B, and as a result, the bending angle at the sixth and seventh bending points (a6, a7) becomes smaller than 40°. Additionally, for the side member with an octagonal cross-section, compression must be performed between the first lower die (LD1) and the first upper die (UD1) to form the sixth bending point (a6). However, if the size of the first lower die (LD1) is reduced due to interference with the first flange (f1), a problem arises in which the first lower die (LD1) cannot be matched to the first upper die (UD1).

[0108] As illustrated in FIG. 10, the side member with a hexagonal cross-section can be formed by bending such that the bending angle at the bending point is greater than at least 40° during the roll forming process. For example, the side member with a hexagonal cross-section can provide a structure in which interference between the first lower die (LD1) and the first flange (f1) does not occur even if the bending angle at the second to fifth bending points (a2, a3, a4, a5) is greater than 40°. Furthermore, since the first upper die (UD1) and the first lower die (LD1) can be precisely matched, the side member with a hexagonal cross-section can be mass-produced while maintaining a bending angle of 40° or more at the bending point.

[0109] Accordingly, the method for manufacturing a side member according to one embodiment of the present invention recognizes the above problems and can provide a method for manufacturing a side member having a hexagonal cross-sectional shape as a structure with high mass production capability, while doubling the energy absorption capacity by inducing a stable crushed shape.

[0110] FIG. 11 is a flowchart of a method for manufacturing a side member according to an embodiment of the present invention. A method for manufacturing a side member according to an embodiment of the present invention will be described with reference to FIG. 11. Since the side member (100) according to an embodiment of the present invention is manufactured by the method for manufacturing a side member according to an embodiment of the present invention, FIG. 1 and FIG. 2 will be described together.

[0111] A method for manufacturing a side member according to an embodiment of the present invention includes a bead portion forming step (S205), a first bending step (S210), a second bending step (S220), a flange forming step (S230), a closed cross-section forming step (S240), a sizing step (S250), and a welding step (S260). The bead portion forming step (S205) may form a bead portion (140) at one end in the longitudinal direction of a single first plate (1). At this time, in the bead portion forming step (S205), the bead portion (140) may be formed within 100 mm in the longitudinal direction from one end. The first bending step (S210) may form a first tubular portion (110) by bending the first plate (1) five times in a first direction (e.g., counterclockwise). The second bending step (S220) can form a second tubular upper part (120) by bending the first plate (1) five times in a second direction opposite to the first direction (e.g., clockwise). For example, as illustrated in FIG. 2, the first bending step (S210) bends the first plate (1) in the first direction at the second bending point (a2), the third bending point (a3), the fourth bending point (a4), the fifth bending point (a5), and the sixth bending point (a6) in sequence from the end (p1) side toward the other end (p2), and the second bending step (S220) can continue to bend the first plate (1) in the second direction opposite to the first direction at the seventh bending point (a7), the eighth bending point (a8), the ninth bending point (a9), the tenth bending point (a10), and the eleventh bending point (a11) in sequence.

[0112] At this time, the method for manufacturing a side member according to an embodiment of the present invention may bend the bending point so that the bending angle is 40° or more during the first bending step (S210) and the second bending step (S220). According to the above-described problem, if the bending angle of the bending point becomes smaller than 40° in the open cross-section state, a problem arises in which it becomes difficult to secure the target dimensional accuracy due to the bending occurring at an unexpected point other than the bending point during the sizing step (S250) described later, or due to springback. Therefore, the method for manufacturing a side member according to an embodiment of the present invention may bend the bending point so that the bending angle is 40° or more during the first bending step (S210) and the second bending step (S220). Furthermore, since five bending points are formed in the first bending step (S210) and the second bending step (S220), even if the bending angle of the bending points is maintained at 40° or more, there is no interference problem with the flanges (f1, f2) described later, so mass production is ensured.

[0113] The above flange forming step (S230) may be performed prior to the welding step (S260), and a first flange (f1) may be formed by bending one end of the first plate (1) outwardly toward the first tubular upper part (110), and a second flange (f2) may be formed by bending the other end of the first plate (1) outwardly toward the second tubular upper part (120). Meanwhile, although not shown in the drawing, the flange forming step (S230) may be performed before the first bending step (S210) and the second bending step (S220); for example, the first bending step (S210) may be performed after the first flange (f1) is formed first. That is, if the flange forming step (S230) is performed before the welding step (S260), the order of the first bending step (S210) and the second bending step (S220) is not limited by the flowchart (see FIG. 11).

[0114] The above closed cross-section forming step (S240) may form a closed cross-section by bringing the first flange (f1) into contact with the outer wall of the second tubular upper part (120), and may form a closed cross-section by bringing the second flange (f2) into contact with the outer wall of the first tubular upper part (110). More specifically, as shown in FIG. 4, the first flange (f1) may be brought into contact with the seventh side (s7) to form a closed cross-section with a hexagonal cross-section inside the first tubular upper part (110), and the second flange (f2) may be brought into contact with the fifth side (s5) to form a closed cross-section with a hexagonal cross-section inside the second tubular upper part (120).

[0115] The sizing step (S250) is performed after the closed cross-section forming step (S240) but before the welding step (S260), and the closed cross-section can be re-compressed from the outside to have preset dimensions. The sizing step (S250) can be re-compressed by a sizing roll (not shown) to have a preset curvature of the bending point or a bending angle of the final closed cross-section. For example, the first plate (1) can be pre-bent at the first bending step (S210) or the second bending step (S220) so that one bending point has a bending angle of 55°, and then in the sizing step (S250), the bending point can be bent so that it has a bending angle of 60°. Accordingly, the first plate (1) can be formed into a closed cross-section with a hexagonal cross-section shape.

[0116] Accordingly, according to the method for manufacturing a side member according to one embodiment of the present invention, by forming a bead portion (140), longitudinal crushing can be induced from the front end where the collision is first transmitted, thereby effectively absorbing collision energy and preventing deformation at the rear end, thereby preventing overall bending deformation.

[0117] Meanwhile, FIG. 12 illustrates a front collision absorption structure of a vehicle including a crash box according to an embodiment of the present invention.

[0118] As shown in FIG. 12, the front energy absorption structure includes a bumper (300), a crash box (200) connected to the bumper, and a front side member (400) connected to the crash box (200).

[0119] In this embodiment, the crash box (200) may include the same structure as the side member of FIG. 1. Specifically, the crash box (200) includes a first tubular upper part (210) that extends in the longitudinal direction and has a hexagonal cross-sectional shape; and a second tubular upper part (220) that is connected to the first tubular upper part (210), extends in the longitudinal direction, and has a hexagonal cross-sectional shape; wherein the first tubular upper part (210) and the second tubular upper part (220) are formed integrally by being bent and molded from a single first plate, and a bead portion (240) is formed adjacent to one end of the longitudinal direction of the first plate.

[0120] Additionally, the crash box (200) includes mounting plates (250, 260) connected to the first and second tubular upper portions (210, 220) at both longitudinal ends so as to be connected to the bumper (300) or the side member (400). The mounting plates (250, 260) can be bolted to the bumper-side mounting plate and the side member-side mounting plate.

[0121] In this embodiment, the box portion of the crash box (200), excluding the mounting plates (250, 260), may have the same structure as the side member described above. That is, two first and second tubular portions (210, 220) having a hexagonal cross-sectional shape are formed from a single plate, and a weld portion (230) is included in which a bead portion (240) and the end of the plate are welded to the first and second tubular portions (210, 220).

[0122] The above welded portion (230) may include a first welded portion formed by a first flange, which is bent outward from the first tubular upper portion (210) at one end of the first plate material, being welded to the outer wall of the second tubular upper portion, and a second welded portion formed by a second flange, which is bent outward from the second tubular upper portion (220) at the other end of the first plate material, being welded to the outer wall of the first tubular upper portion (210). Since this is identical to the structure of the side member (100) shown in FIG. 1, a detailed description is omitted.

[0123] Although the forward energy absorption structure was described in FIG. 12, it is obvious that the crash box according to this embodiment can be applied to a rear energy absorption structure rather than a forward energy absorption structure.

[0124] In addition, although the front side member (400) in the front energy absorption structure shown in FIG. 12 is depicted as having a square cross-section, the present invention also allows the side member (100) shown in FIG. 1 to be applied as the front side member (400) of FIG. 12. That is, it is also possible for the side member having the first and second tubular upper parts (110, 120) of FIG. 1 to be connected through a mounting plate (260) to the rear of the crash box (200) having the first and second tubular upper parts (210, 220) having a hexagonal cross-section.

[0125] Meanwhile, FIGS. 13 and 14 illustrate a side member according to another embodiment of the present invention. Specifically, FIG. 13 illustrates a side view of a side member according to another embodiment of the present invention, and FIG. 14 illustrates a schematic perspective view of the side member of FIG. 13.

[0126] The side member (100) of this embodiment can be formed by roll forming a single sheet metal, similar to the previous embodiment.

[0127] In this embodiment, the side member (100) includes a first tubular upper section (110) and a second tubular upper section (120), and the first tubular upper section (110) and the second tubular upper section (120) can be formed by forming a plate of high-strength steel, for example, steel having a tensile strength of 780 MPa or more, in different directions by machining, for example, roll forming or bending. Accordingly, each side is welded only on one side with respect to a shared side, and the rest are continuously connected.

[0128] Each side is formed around a bending point. In the first tubular upper section (110), the first to fifth sides (s1 to s5) are formed by bending at multiple bending points (a2 to a6) in a clockwise direction around the shared sixth side (s6), and in the second tubular upper section (110), the seventh to eleventh sides (s7 to s11) are formed by bending at multiple bending points (a7 to a11) in a counterclockwise direction around the sixth side (s6). The first and second tubular upper sections (110, 120) have a hexagonal cross-sectional shape and include the third side (s3) parallel to the shared sixth side (s6), and the ninth side (s9), and the first and eleventh sides (s1, s11) in a direction orthogonal to the extension direction of the sixth side (s6) when viewed from a cross-section perpendicular to the length direction.

[0129] The first tubular upper section (110) has a first side (s1) that extends in the Z direction perpendicular to the Y direction, which is the extension direction of the sixth side (s6), when viewed from the X direction, which is the length direction, and a flange (f1) that forms a first weld (131) is disposed at the edge. The first side (s1) and the flange (f1) are continuous without bending. The second side (s2) is configured to connect the first side (s1) with the third side (s3) which is parallel to the sixth side (s6), and is formed by bending at the second bending point (a2) opposite the flange (f1) of the first side (s1). The second side (s2) is formed at an angle with respect to the Y direction or the Z direction.

[0130] The third side (s3) is parallel to the sixth side (s6), is bent at the third bend point (a3) ​​to connect to the second side (s2), and is bent at the fourth bend point (a4) to connect to the fourth side (s4). The fourth side (s4) is connected to the third side (s3) and is formed to have the same angle with respect to the second side (s2) with respect to the Z direction, but inclined in opposite directions. The fifth side (s5) is parallel to the first side (s1), is connected to the fourth side (s4) through the fifth bend point (a5), and is connected to the sixth side (s6) through the sixth bend point (a6). At the 6th bending point (a6), the 5th side (s5) and the 6th side (s6) are connected by bending at 90°, so they can be bent with a larger radius of curvature than the 2nd to 5th bending points (a2~a5), but are not limited thereto.

[0131] The sixth side (s6) is used to form the closed cross-section of the first tubular upper part (110) and the closed cross-section of the second tubular upper part (120), so it can be said to be a side shared by the first and second tubular upper parts (110, 120).

[0132] The 7th to 11th sides (s7~s11) are symmetrical with respect to the 1st to 5th sides (s1~s5) from the center of the 6th side (s6). The 7th to 11th sides (s7~s11) are formed by bending from the 6th side (s6). Specifically, the 7th side (s7) is connected to the 6th side (s6) through the 7th bend point (a7), the 8th side (s8) is connected to the 7th side (s7) through the 8th bend point (a8), the 9th side (s9) is connected to the 8th side (s8) through the 9th bend point (a9), the 10th side (s10) is connected to the 9th side (s9) through the 10th bend point (a10), and the 11th side (s10) is connected to the 10th side (s10) through the 11th bend point (a11).

[0133] The 7th side (s7) and the 11th side (s11) are parallel to the Z direction. That is, the 1st side (s1) and the 5th side (s5) of the 1st tubular upper part (110) and the 7th side (s7) and the 11th side (s11) of the 2nd tubular upper part (120) are parallel to the Z direction. These parallel sides not only facilitate the formation of the 1st and 2nd welded parts (131, 132), but also facilitate the attachment of other configurations to the 1st, 5th, 7th, and 11th sides (s1, s5, s7, s11), making it advantageous to attach other configurations to the side member (100).

[0134] The ninth side (s9) is parallel to the sixth side (s6) as with the third side (s3), and the eighth and tenth sides (s8, s10) are positioned at an angle with respect to the Z direction or the Y direction. The angle of inclination of the eighth and tenth sides (s8, s10) with respect to the Z direction may correspond to the second and fourth sides (s2, s4).

[0135] The first side (s1) faces the fifth side (s5), and the length of the first side (s1) in the Z direction is longer than the length of the fifth side (s5) in the Z direction. The first side (s1) is formed to pass through the seventh bending point (a7) and overlap with the seventh side (s7). The portion where the seventh side (s7) and the first side (s1) overlap acts as the first flange (f1), and at this portion, the seventh side (s7) and the first side (s1) are welded to form the first weld portion (131).

[0136] The first weld (131) is structured such that the entire surface of the first flange (f1) of the first side (s1) is welded to the seventh side (s7), thereby preventing the first weld (131) from breaking upon impact in the X direction and increasing crush stability. At this time, the front surface of the first flange (f1) may be weldable, and the length of the first weld (131) may be the length of the first flange (f1) and may be in the range of about 5 to 20 mm.

[0137] Likewise, the eleventh side (s11) faces the seventh side (s7), and the length of the eleventh side (s11) in the Z direction is formed to be longer than the length of the seventh side (s7) in the Z direction. Accordingly, the eleventh side (s11) can pass through the sixth bend point (a6) and overlap with the fifth side (s5), and the part where the eleventh side (s11) and the fifth side (s5) overlap acts as the second flange (f2), and the eleventh side (s11) and the fifth side (s5) are welded at this part to form the second weld (132).

[0138] The second weld (132) is structured such that the entire surface of the second flange (f2) of the eleventh side (s11) is welded to the fifth side (s5), thereby preventing the second weld (132) from breaking upon impact in the X direction and increasing crush stability. At this time, the front surface of the second flange (f2) may be weldable, and the length of the second weld (132) may be the length of the second flange (f2) and may be in the range of approximately 5 to 20 mm, which is the same as the length of the first weld (131).

[0139] A side member (100) according to another embodiment of the present invention also further includes a bead portion (140). The bead portion (140) may be formed on the second, third, fourth, eighth, ninth, and tenth sides (s2, s3, s4, s8, s9, s10). The bead portion (140) may be formed adjacent to one end in the longitudinal direction of the side member (100), and may be formed on a plurality of surfaces formed by each side constituting the side member (100) extending in the longitudinal direction. The bead portion (140) may have a structure formed to protrude inwardly from the first tubular upper portion (110) or the second tubular upper portion (120) when viewed from the longitudinal direction, and may be spaced apart by a predetermined distance (d) from one end in the longitudinal direction.

[0140] In this embodiment, the length of the weld section (130) is secured in the same way as in the previous embodiment to increase crushing stability, while also ensuring formability. Additionally, by including a side parallel to the Z or Y direction, the ease of joining with surrounding components is improved when installed in a vehicle. Furthermore, by including a bead section (140), crushing deformation in the rear section is prevented due to energy absorption by the bead section (140) in the front section, and sequential crushing deformation can be induced starting from the front section. That is, the side member (100) according to one embodiment of the present invention has a larger average load value absorbed in the front section than a conventional side member due to the application of the bead section (140), and the amount of fluctuation required for energy absorption is much smaller, making it easier to absorb energy.

[0141] As mentioned above, in this embodiment as well, since the side member (100) is formed by roll forming, it can be formed to have a radius of curvature for thickness smaller than the radius of curvature for thickness (R / t_p), which is the bending forming limit by press. That is, as the side member (100) is sequentially bent by roll forming, the radius of curvature for thickness (R / t) at each bending point (a2~a11) can be formed to be smaller than the radius of curvature for thickness limit value (R / t_p) by press.

[0142] FIG. 15 illustrates a front collision absorption structure of a vehicle including a crash box according to another embodiment of the present invention. As shown in FIG. 15, the front energy absorption structure includes a bumper (300), a crash box (200) connected to the bumper, and a front side member (400) connected to the crash box (200).

[0143] In this embodiment, the crash box (200) may include the same structure as the side member of FIG. 13. Specifically, the crash box (200) includes a first tubular upper part (210) that extends in the longitudinal direction and has a hexagonal cross-sectional shape; and a second tubular upper part (220) that is connected to the first tubular upper part (210), extends in the longitudinal direction, and has a hexagonal cross-sectional shape; wherein the first tubular upper part (210) and the second tubular upper part (220) are formed integrally by being bent and molded from a single first plate, and a bead portion (240) is formed adjacent to one end of the longitudinal direction of the first plate.

[0144] Additionally, the crash box (200) includes mounting plates (250, 260) connected to the first and second tubular upper portions (210, 220) at both longitudinal ends so as to be connected to the bumper (300) or the side member (400). The mounting plates (250, 260) can be bolted to the bumper-side mounting plate and the side member-side mounting plate.

[0145] In this embodiment, the box portion of the crash box (200), excluding the mounting plates (250, 260), may have the same structure as the side member described above. That is, two first and second tubular portions (210, 220) having a hexagonal cross-sectional shape are formed from a single plate, and a weld portion (230) is included in which a bead portion (240) and the end of the plate are welded to the first and second tubular portions (210, 220).

[0146] FIGS. 16 and FIGS. 17 present a side member according to an embodiment of the present invention. More specifically, FIG. 16 is a perspective view illustrating a side member according to an embodiment of the present invention, and FIG. 17 is a view of FIG. 16 seen from one side.

[0147] A vehicle side member includes a front side member and a rear side member, and is positioned on both the left and right sides of the vehicle at the front and rear, and can extend forward or backward. When viewed from above, the side member may have a shape that extends in an almost straight line in the front-rear direction. By doing so, the side member can absorb collision energy to suppress body deformation during a frontal or rear collision. For example, one end of the side member may be connected to a kick-up portion installed at the front end of the vehicle's floor section to extend forward, or one end may be connected to a kick-up portion installed at the rear end of the floor section to extend backward. Assembly of the side member and the vehicle body may be achieved by inserting any connecting member into the side member and bolting it, or by forming a flange at the front or rear end of the side member and joining it using welding or the like using this flange. A more detailed description of such assembly is omitted in this specification.

[0148] In addition, since a pair of side members are arranged symmetrically to each other and have the same actual configuration, one side member will be described below as a representative example. Also, for the convenience of explanation, a side member installed at the front of the vehicle body is used as an example, but it is not limited to this and can be applied to a side member installed at the rear of the vehicle body as well.

[0149] Referring to FIGS. 16 and 17, a side member (100) made of general steel includes a first tubular upper section (110) and a second tubular upper section (120). The first and second tubular upper sections (110, 120) can be integrally formed by processing a Tailor Welded Blank (TWB) plate (TP) in which the first and second steel materials (10, 20) are combined, and can be formed by bending or roll forming, etc. Here, the TWB plate refers to a plate manufactured by the TWB method. The first and second steel materials (10, 20) may be different steel grades with different thicknesses or different strengths from the same material, and various combinations of steel grades and thicknesses are possible to achieve a stable crushing mode through a relatively low-strength material by configuring them to have different strengths.

[0150] The first and second steel members (10, 20) are positioned at different locations along the longitudinal direction of the side member. That is, the weld line where the first and second steel members (10, 20) are welded is orthogonal to the longitudinal direction. Although the longitudinal lengths (l10, l20) of the first and second steel members (10, 20) can be varied, in this embodiment, the length (l10) of the first steel member (20), which is a relatively low-strength material, is configured to be shorter than the length (l20) of the second steel member (20), which is a relatively high-strength material.

[0151] In addition, among the first and second steel materials (10, 20), the first steel material (10), which has relatively low strength, is positioned far from the center of the vehicle. That is, as shown in FIG. 16, in the case of a front side member (100), the first steel material (10) is positioned in front of the second steel material (20), and in the case of a rear side member, the first steel material (10) is positioned behind the first steel material (20). The second steel material (10) deforms first upon vehicle collision, thereby inducing crushing.

[0152] At this time, the first tubular upper part (110) and the second tubular upper part (120) may have a shape in which a hexagonal cross-sectional shape is extended in the X direction, which is the length direction. More specifically, the side member (100) may be formed by folding a TWB plate (TP) having a predetermined width and length multiple times to form a plurality of closed cross-sections, each having a hexagonal cross-sectional shape.

[0153] For example, a single TWB plate (TP) can be bent in a counterclockwise direction from one end (P1) toward the other end (P2), and for example, a first tubular upper part (110) with a hexagonal cross-section can be formed by bending it five times in the same first direction (e.g., counterclockwise) in the order of the first side (s1), second side (a2), second side (s2), third side (a3), third side (s3), fourth side (a4), fourth side (s4), fifth side (a5), fifth side (s5), sixth side (a6), and sixth side (s6) centered on the first bending point (a1).

[0154] Next, the TWB plate (TP) can be folded five times in the same second direction (e.g., clockwise) in the order of the 7th bend point (a7), the 7th side (s7), the 8th bend point (a8), the 8th side (s8), the 9th bend point (a9), the 9th side (s9), the 10th bend point (a10), the 10th side (s10), the 11th bend point (a11), the 11th side (s11), and the 12th bend point (a12) to form a second tubular upper part (120) with a hexagonal cross-section.

[0155] The side member (100) includes a weld (130) for connecting the first tubular upper part (110) and the second tubular upper part (120). The weld (130) includes a first weld (131) located on one end (P1) and a second weld (132) located on the other end (P2). Both ends (P1, P2) of the TWB plate (TP) may be bent at a predetermined angle to form flanges (f1, f2), and the weld (130) may be located on the side where the flanges (f1, f2) are connected to the first tubular upper part (110) and the second tubular upper part (120).

[0156] In a conventional side member, the flanges (f1, f2) are formed by being bent inward toward the first tubular upper portion (110) and the second tubular upper portion (120). For example, the flanges (f1, f2) are formed by being bent so as to be in contact with the sixth side (s6). That is, in a conventional side member, the first flange (f1) can be connected to the first tubular upper portion (110) of the sixth side (s6) as it is formed by being bent inward toward the first bending point (a1), and the second flange (f2) can be connected to the second tubular upper portion (120) of the sixth side (s6) as it is formed by being bent inward toward the second bending point (a12). Meanwhile, in this specification, being bent inward may mean being bent inwardly to the closed cross-section of the first tubular upper part (110) or the second tubular upper part (120), and being bent outward may mean being bent outwardly to the closed cross-section of the first tubular upper part (110) or the second tubular upper part (120).

[0157] Meanwhile, since the side member made of steel forms a closed cross-section and then performs welding, the conventional side member could perform welding at the first bend point (a1) and the seventh bend point (a7) where the first flange (f1), the first side (s1), and the seventh side (s7) meet, and could also perform welding at the sixth bend point (a6) and the twelfth bend point (a12) where the second flange (f2), the fifth side (s5), and the eleventh side (s11) meet. In other words, the conventional side member could perform fillet welding, for example, to form a weld at the edge, but this has the problem that the weld fractures upon a front-to-rear collision.

[0158] Meanwhile, in one embodiment of the present invention, the side member (100) may be formed such that the flanges (f1, f2) are bent outward toward the first tubular upper part (110) and the second tubular upper part (120). For example, the first flange (f1) may be formed by being bent to abut the seventh side (s7) of the second tubular upper part (120), and the second flange (f2) may be formed by being bent to abut the fifth side (s5) of the first tubular upper part (110). That is, the first flange (f1) can be connected to the outer wall of the second tubular upper part (120) by being formed by being bent in the first direction around the first bending point (a1), and the second flange (f2) can be connected to the outer wall of the first tubular upper part (110) by being formed by being bent in the first direction around the twelfth bending point (a12). Furthermore, in the side member (100) according to an embodiment of the present invention, the first tubular upper part (110) and the second tubular upper part (120) share a sixth side (s6), which is a side between the sixth bending point (a6) and the seventh bending point (a7), and the first tubular upper part (110) and the second tubular upper part (120) may have the same cross-sectional shape and size based on the side (s6).

[0159] Accordingly, in a side member (100) according to an embodiment of the present invention, a first weld (131) may be formed on the surface where the first flange (f1) and the seventh side (s7) meet, and a second weld (132) may be formed on the surface where the second flange (f2) and the fifth side (s5) meet. That is, unlike a conventional side member, the side member (100) according to an embodiment of the present invention provides a structure in which the entire surface of the flanges (f1, f2) is weldable, thereby preventing fracture of the welds (131, 132) and increasing crushing stability. At this time, since the entire surface of the flanges (f1, f2) can be weldable, the length (d1) of the weld (130) may correspond to the length of the flanges (f1, f2) and may be approximately 5 mm to 20 mm.

[0160] Furthermore, a side member (100) according to an embodiment of the present invention further includes a bead portion (140). The bead portion (140) is formed adjacent to one end of the first steel member (10) in the longitudinal direction and may be formed on a plurality of surfaces where each side constituting the side member (100) is extended in the longitudinal direction. The bead portion (140) may have a structure that protrudes inwardly from the first tubular upper portion (110) or the second tubular upper portion (120) when viewed from the longitudinal direction, and may be spaced apart by a predetermined distance (d) from one end of the longitudinal direction. In this embodiment, the bead portion (140) is formed on the first steel member (10), which can reduce the maximum support load and induce deformation quickly. However, if necessary, it is also possible for the bead portion (140) to be formed on the second steel member (20). The structure of the above bead portion (140) will be further explained with reference to FIGS. 21 and FIGS. 24.

[0161] Meanwhile, the ratio of the width of the first tubular upper part (110) or the second tubular upper part (120) in the side member (100) to the height of the first and second tubular upper parts (110, 120) may be less than 1:4 and may be 1:3 or less.

[0162] A side member (100) according to one embodiment of the present invention includes a groove (150) formed inwardly from the end surface (160) at one end where a bead portion (140) is formed. The groove (150) can be placed in a first steel material (10) which has relatively low strength, such as the bead portion (140). In an embodiment, the groove portion (150) includes a first groove (151) that spans the edge between the first side (s1) and the second side (s2), a second groove (152) that spans the edge between the second side (s2) and the third side (s3), a third groove (153) that spans the edge between the third side (s3) and the fourth side (s4), a fourth groove (154) that spans the edge between the fourth side (s4) and the fifth side (s5), a fifth groove (155) that spans the edge between the seventh side (s7) and the eighth side (s8), a sixth groove (156) that spans the edge between the eighth side (s8) and the ninth side (s9), a seventh groove (151) that spans the edge between the ninth side (s9) and the tenth side (s10), and an eighth groove (158) that spans the edge between the tenth side (s10) and the eleventh side (s11). The first to fourth grooves (151 to 154) are formed in the first tubular upper section (110), and the fifth to eighth grooves (155 to 158) are formed in the second tubular upper section (120). Each groove (151 to 158) is formed with a shape symmetrical on both sides with respect to the corner, and an end surface (160) extending in the longitudinal direction is located between the grooves (151 to 158). The end surface (160) is located on each side (s1 to s11).

[0163] The groove (150) can be formed using a laser cutter while the first and second tubular upper parts (110, 120) are manufactured, and performs the role of reducing the initial support load at the location where the groove (150) is formed.

[0164] In the embodiments of FIG. 16-2, the groove portion (150) is formed at the corner, but the present invention is not limited thereto, and the location of the groove portion (150) may be formed on a side other than the corner. For example, the groove portion (150) includes a first groove (151) formed at the center of the end of the second side (s2), a second groove (152) formed at the center of the end of the third side (s3), a third groove (153) formed at the center of the end of the fourth side (s4), a fourth groove (154) formed at the center of the end of the eighth side (s8), a fifth groove (155) formed at the center of the end of the ninth side (s9), and a sixth groove (156) formed at the center of the end of the tenth side (s10). In this case, the end surface (160) may be formed centered on the corner. Even when formed in this way, it can help to reduce the maximum support load.

[0165] With reference to FIGS. 18 to 5 and Table 1, an embodiment of the present invention and a reference side member will be described in comparison. FIG. 18 shows a perspective view of a reference side member of Reference Example 1, FIG. 19 shows a perspective view of a reference side member of Reference Example 2, FIG. 20 shows a perspective view of a reference side member of Reference Example 3, and Table 1 shows a table comparing Reference Examples 1 to 3 with the embodiment of FIG. 16.

[0166] The side member (100) of the reference example in FIGS. 18 to 20 commonly includes a first tubular upper part (110) and a second tubular upper part (120), and the first and second tubular upper parts (110, 120) are configured to have a hexagonal cross-sectional shape by bending a plate material and are welded through a weld part (130), and includes a bead part (140) adjacent to one end.

[0167] In the case of Reference Example 1, only the common features described above are present, in the case of Reference Example 2, in addition to the common configuration, the groove portion (150) is formed in the same manner as the embodiment of FIG. 16, and in the case of Reference Example 3, in addition to the common configuration, the plate is formed as a TWB plate (TP). That is, Reference Example 2 is not formed using a TWB plate, so the side member (100) is not composed of the first and second steel materials (10, 20), and Reference Example 3 does not include the groove portion (150).

[0168] [Table 1] shows the analysis results of the reference side members (Reference Examples 1 to 3) described above and the side member (100; Example) according to an embodiment of the present invention. The analysis was performed using the same load and the same boundary conditions.

[0169] Reference Example 1 Reference Example 2 Reference Example 3 Example Material 980 DP-H 980 DP-H Steel 1 - 780 DP Steel 2 - 980 DP-H Steel 1 - 780 DP Steel 2 - 980 DP-H Yield Strength (MPa) 872 872 872 872 Thickness 1.0t 1.0t 1.0t 1.0t Weight (kg) 2.6 12.5 92.6 12.6 Energy Absorption (kJ) 58.4 58.9 58.8 58.8 Maximum Support Load (kN) 400.8 324.4 317.4 246.0 Support Load Magnitude Standard Deviation 26.1 22.8 21.0 20.7 Deformation Mode Stability Stability Stability Stability

[0170] As shown in Table 1 above, the embodiment showed improved effects in terms of maximum support load and standard deviation of support load magnitude compared to Reference Examples 1 to 3 in the analysis results. The side member (100) according to one embodiment absorbed more energy and had a lower maximum support load. That is, it was confirmed that deformation occurred at a relatively small load in the embodiment, and the standard deviation was also stable. In particular, in the Mobile Progressive Deformable Barrier (MPDB) front collision test of a vehicle, the degree of injury to the opposing vehicle is also observed along with the injury value to the vehicle's protected target after the collision. Therefore, if the initial support load is high from the perspective of the front or rear side member, there is a concern that it may cause significant damage to the opposing vehicle. However, in the embodiment of the present invention, by lowering the maximum support load without lowering the energy absorption capacity, damage to the opposing vehicle as well as the vehicle's protected target can be reduced.

[0171] In particular, considering only the maximum load support improvement rate, the embodiment formed a bead portion (140) and a groove portion (150) on the first steel material (10) of the TWB plate (TP), thereby reducing the maximum load support rate to approximately 61% of the maximum load support rate of Reference Example 1, which only has a bead portion (140). This is a combined ratio (81% * 79% = 64%) of the improved ratio of Reference Example 1 (81% of Reference Example 1) in Reference Example 2, which formed a groove portion (150) in Reference Example 1, and the improved ratio of Reference Example 3, which used a TWB plate (TP) in Reference Example 1 (79% of Reference Example 1). It can be confirmed that there is a significant relationship between the formation of the groove portion (150) and the composition of the TWB plate (TP).

[0172] FIGS. 21 to 24 illustrate a modified example in which the bead portion of a side member is changed according to an embodiment of the present invention.

[0173] In FIGS. 21 to 24, a side member (100) includes a first tubular upper portion (110) and a second tubular upper portion (120), and the first tubular upper portion (110) and the second tubular upper portion (120) have a groove portion (150) formed together with a bead portion (140), and are formed by molding a TWB plate (TP). Since the structure of the first tubular upper portion (110), the second tubular upper portion (120), the groove portion (150), and the TWB plate (TP) in FIGS. 21 to 24 is identical to the structure of the side member (100) described in FIGS. 16 and 2, a detailed description is omitted, and the explanation will focus on the differences.

[0174] In FIG. 21, the bead portion (140) is formed on the third side (s3) of the first tubular upper portion (110) and the ninth side (s9) of the second tubular upper portion (120), respectively, corresponding to the upper and lower surfaces of the side member (100). The bead portion (140) is formed to protrude inwardly from the tubular upper portions (110, 120). In FIG. 22, the bead portion (140) is formed on the first, second, fourth, and fifth sides (s1, s2, s4, s5) and the seventh, eighth, tenth, and eleventh sides (s7, 8, 10, 11), respectively, corresponding to the sides of the side member (100). In FIG. 23, the bead portions (140) of FIG. 21 and FIG. 22 are formed simultaneously, with bead portions (140) formed on the first to fifth sides (s1 to s5) and the seventh to eleventh sides (s7 to s11), respectively. In FIG. 24, the bead portions (140) are formed on all sides, specifically the first to eleventh sides (s1 to s11). On the sixth side (s6), the bead portion is formed to protrude inwardly from the first tubular upper portion (110).

[0175] FIGS. 25 and 26 are drawings showing the bending angle according to the cross-sectional shape of a side member during a roll forming process. More specifically, FIG. 25 shows the bending angle in an open cross-section state during the roll forming process of a side member having an octagonal cross-section shape, and FIG. 26 shows the bending angle in an open cross-section state during the roll forming process of a side member having a hexagonal cross-section shape. The following description will be explained with reference to FIGS. 25 and 26.

[0176] The roll forming process involves introducing a TWB plate (TP), in which the first and second steel materials (10, 20) are alternately arranged and welded, into a continuous upper and lower forming roll set and sequentially bending and forming it to produce a beam having a constant cross-section. Although the first and second steel materials are alternately arranged in the case of the TWB plate (TP), they behave in the same way as a continuous plate, so they can be formed in the same way as a single plate.

[0177] A side member using a TWB plate (TP) is manufactured by bending the TWB plate (TP), wherein the bending is performed by compression of the upper and lower dies. For example, as shown in FIG. 24, the plate (TP) is sequentially bent to a first bend point (a1), a second bend point (a2), a third bend point (a3), a fourth bend point (a4), a fifth bend point (a5), a sixth bend point (a6), a seventh bend point (a7), and an eighth bend point (a8) to form a closed cross section. At this time, the TWB plate (TP) may be bent by compression of the upper die (UD1, UD2) and lower die (LD1, LD2) before the closed cross section is formed, that is, in an open state. Since compression is possible only from the outer side of the closed section after the closed section is formed, the TWB plate (TP) is subjected to a sizing process using a sizing roll on the outer side of the closed section to have a target bending angle and cross-sectional shape.

[0178] Meanwhile, when the above TWB sheet (TP) is in an open cross-section state before a closed cross-section is formed, and is pressed by the mold (UD1, UD2, LD1, LD2), the bending angle at each bending point (e.g., the first to eighth bending points) must be at least 40° to ensure dimensional accuracy by the sizing roll. If the bending angle in the open cross-section state is lower than 40°, during the sizing roll process, the bending angle at each bending point may not bend to the target angle but instead bend at an unexpected point, or problems such as springback may occur, making it difficult to secure the target dimensional accuracy. Therefore, for mass production of side members using the TWB sheet (TP), it is important to ensure that the bending angle at the bending point is at least 40° during bending forming.

[0179] As illustrated in FIG. 25, since the side member with an octagonal cross-section has seven bending points in a single closed cross-section, the bending angle must be formed in a limited manner to avoid interference between the plate (TP) and the die during the roll forming process. For example, if the bending angle at the second to fifth bending points (a2, a3, a4, a5) is secured to 40°, interference may occur between the first lower die (LD1) and the first flange (f1) as illustrated in part B, and as a result, the bending angle at the sixth and seventh bending points (a6, a7) becomes smaller than 40°. Additionally, for the side member with an octagonal cross-section, compression must be performed between the first lower die (LD1) and the first upper die (UD1) to form the sixth bending point (a6). However, if the size of the first lower die (LD1) is reduced due to interference with the first flange (f1), a problem arises in which the first lower die (LD1) cannot be matched to the first upper die (UD1).

[0180] As illustrated in FIG. 26, the side member with a hexagonal cross-section can be formed by bending such that the bending angle at the bending point is greater than at least 40° during the roll forming process. For example, the side member with a hexagonal cross-section can provide a structure in which interference between the first lower die (LD1) and the first flange (f1) does not occur even if the bending angle at the second to fifth bending points (a2, a3, a4, a5) is greater than 40°. Furthermore, since the first upper die (UD1) and the first lower die (LD1) can be precisely matched, the side member with a hexagonal cross-section can be mass-produced while maintaining a bending angle of 40° or more at the bending point.

[0181] Accordingly, the method for manufacturing a side member according to one embodiment of the present invention recognizes the above problems and can provide a method for manufacturing a side member having a hexagonal cross-sectional shape as a structure with high mass production capability, while doubling the energy absorption capacity by inducing a stable crushed shape.

[0182] FIG. 27 is a flowchart of a method for manufacturing a side member according to an embodiment of the present invention. A method for manufacturing a side member according to an embodiment of the present invention will be described with reference to FIG. 27. Since the side member (100) according to an embodiment of the present invention is manufactured by the method for manufacturing a side member according to an embodiment of the present invention, FIG. 16 and FIG. 17 will be described together.

[0183] A method for manufacturing a side member according to an embodiment of the present invention comprises a TWB plate manufacturing step (S201), a bead portion forming step (S205), a first bending step (S210), a second bending step (S220), a flange forming step (S230), a closed section forming step (S240), a sizing step (S250), a welding step (S260), and a chamfering step (S270).

[0184] The TWB plate manufacturing step (S201) involves manufacturing a TWB plate (TP; see FIG. 26) by alternately arranging first and second steel materials (10, 20) having different strengths, and includes the step of cutting the first steel material (10) and the second steel material (20) to a preset length, and the step of joining the cut steel materials into a single plate through welding, for example, laser welding, after arranging them. The TWB plate manufacturing step (S201) may be performed during the manufacturing method, but it can also be replaced by using a TWB plate that has already been manufactured.

[0185] The bead portion forming step (S205) can form a bead portion (140) at one end in the longitudinal direction of the first steel material (10) of a single TWB plate (TP). At this time, in the bead portion forming step (S205), the bead portion (140) can be formed within 100 mm in the longitudinal direction from one end. The first bending step (S210) can form a first tubular portion (110) by bending the TWB plate (TP) five times in a first direction (e.g., counterclockwise). The second bending step (S220) can form a second tubular portion (120) by bending the TWB plate (TP) five times in a second direction (e.g., clockwise), which is opposite to the first direction. For example, as illustrated in FIG. 17, the first bending step (S210) bends the TWB plate (TP) in the first direction at the second bending point (a2), the third bending point (a3), the fourth bending point (a4), the fifth bending point (a5), and the sixth bending point (a6) in sequence from the end (P1) side toward the other end (P2) side, and the second bending step (S220) can continue to bend the TWB plate (TP) in the second direction opposite to the first direction at the seventh bending point (a7), the eighth bending point (a8), the ninth bending point (a9), the tenth bending point (a10), and the eleventh bending point (a11) in sequence.

[0186] At this time, the method for manufacturing a side member according to an embodiment of the present invention may bend the bending point so that the bending angle is 40° or more during the first bending step (S210) and the second bending step (S220). According to the above-described problem, if the bending angle of the bending point becomes smaller than 40° in the open cross-section state, a problem arises in which it becomes difficult to secure the target dimensional accuracy due to the bending occurring at an unexpected point other than the bending point during the sizing step (S250) described later, or due to springback. Therefore, the method for manufacturing a side member according to an embodiment of the present invention may bend the bending point so that the bending angle is 40° or more during the first bending step (S210) and the second bending step (S220). Furthermore, since five bending points are formed in the first bending step (S210) and the second bending step (S220), even if the bending angle of the bending points is maintained at 40° or more, there is no interference problem with the flanges (f1, f2) described later, so mass production is ensured.

[0187] The above flange forming step (S230) may be performed prior to the welding step (S260), and one end of the TWB plate (TP) may be bent outward toward the first tubular upper part (110) to form a first flange (f1), and the other end of the TWB plate (TP) may be bent outward toward the second tubular upper part (120) to form a second flange (f2). Meanwhile, although not shown in the drawing, the flange forming step (S230) may be performed before the first bending step (S210) and the second bending step (S220); for example, the first bending step (S210) may be performed after the first flange (f1) is formed first. That is, if the flange forming step (S230) is performed before the welding step (S260), the order of the first bending step (S210) and the second bending step (S220) is not limited by the flowchart (see FIG. 27).

[0188] The above closed cross-section forming step (S240) may form a closed cross-section by bringing the first flange (f1) into contact with the outer wall of the second tubular upper part (120), and may form a closed cross-section by bringing the second flange (f2) into contact with the outer wall of the first tubular upper part (110). More specifically, as shown in FIG. 19, the first flange (f1) may be brought into contact with the seventh side (s7) to form a closed cross-section with a hexagonal cross-section inside the first tubular upper part (110), and the second flange (f2) may be brought into contact with the fifth side (s5) to form a closed cross-section with a hexagonal cross-section inside the second tubular upper part (120).

[0189] The sizing step (S250) is performed after the closed cross-section forming step (S240) but before the welding step (S260), and the closed cross-section can be re-compressed from the outside to have preset dimensions. The sizing step (S250) can be re-compressed by a sizing roll (not shown) to have a preset curvature of the bending point or a bending angle of the final closed cross-section. For example, the TWB plate (TP) may be pre-bent at the first bending step (S210) or the second bending step (S220) so that one bending point has a bending angle of 55°, and then in the sizing step (S250), the bending point may be bent so that it has a bending angle of 60°. Accordingly, the TWB plate (TP) can be formed into a closed cross-section with a hexagonal cross-section shape.

[0190] The welding step (S260) is a step of welding the flanges (f1, f2) to the 7th and 5th sides (s7, s5) so as to maintain the formed closed section.

[0191] After the welding step (S260) is completed, a chamfering step (S270) is performed. The chamfering step (S270) is a step of forming a groove (150) at the ends of the first and second tubular upper parts (110, 120), and using a laser cutter, first to eighth grooves (151 to 158) are formed symmetrically on adjacent sides centered on the corner of one end formed of the second steel material (20).

[0192] Accordingly, according to the method for manufacturing a side member according to one embodiment of the present invention, a bead portion (140) and a groove portion (150) are formed in a first steel material (20) of relatively weak strength, thereby inducing longitudinal crushing from the front shear where the collision is transmitted first, so that collision energy can be effectively absorbed and deformation at the rear end can be prevented, thereby preventing overall bending deformation.

[0193] Meanwhile, FIG. 28 illustrates a front collision absorption structure of a vehicle including a crash box according to an embodiment of the present invention.

[0194] As shown in FIG. 28, the front energy absorption structure includes a bumper (300), a crash box (200) connected to the bumper, and a front side member (400) connected to the crash box (200).

[0195] In this embodiment, the crash box (200) may include the same structure as the side member of FIG. 16. Specifically, the crash box (200) includes a first tubular upper part (210) that extends in the longitudinal direction and has a hexagonal cross-sectional shape; and a second tubular upper part (220) that is connected to the first tubular upper part (210), extends in the longitudinal direction, and has a hexagonal cross-sectional shape; wherein the first tubular upper part (210) and the second tubular upper part (220) are integrally formed by bending and forming a TWB plate material in which a first steel material (10) and a second steel material (20) are combined, and a bead portion (240) and a groove portion (270) are formed adjacent to one end in the longitudinal direction on the first steel material (10) of the TWB plate material (TP).

[0196] Additionally, the crash box (200) includes mounting plates (250, 260) connected to the first and second tubular upper sections (210, 220) at both longitudinal ends so as to be connected to the bumper (300) or the side member (400). The bumper-side mounting plate (250) is welded to the end surface (280) between the groove (270) in the first and second tubular upper sections (210, 220), and the mounting plates (250, 260) can be bolted to the bumper-side mounting plate and the side member-side mounting plate.

[0197] In this embodiment, the box portion of the crash box (200), excluding the mounting plates (250, 260), may have the same structure as the side member described above. That is, two first and second tubular portions (210, 220) having a hexagonal cross-sectional shape are formed by a TWB plate (TP), and a weld portion (230) is included in which a bead portion (240) and the end of the plate are welded to the first and second tubular portions (210, 220).

[0198] The above welded portion (230) may include a first welded portion formed by a first flange, which is bent outward from the first tubular upper portion (210) at one end of the TWB plate, being welded to the outer wall of the second tubular upper portion, and a second welded portion formed by a second flange, which is bent outward from the second tubular upper portion (220) at the other end of the TWB plate, being welded to the outer wall of the first tubular upper portion (210). Since this is identical to the structure of the side member (100) shown in FIG. 16, a detailed description will be omitted.

[0199] Although the forward energy absorption structure was described in FIG. 28, it is obvious that the crash box according to this embodiment can be applied to a rear energy absorption structure rather than a forward energy absorption structure.

[0200] Additionally, although the front side member (400) in the front energy absorption structure illustrated in FIG. 28 is depicted as having a square cross-section, the present invention also allows the side member (100) illustrated in FIG. 16 to be applied as the front side member (400) of FIG. 28. That is, it is also possible for a side member having the first and second tubular upper parts (110, 120) of FIG. 16 to be connected to the rear of a crash box (200) having the first and second tubular upper parts (210, 220) having a hexagonal cross-section shape through a mounting plate (260).

[0201] Meanwhile, FIGS. 29 and FIGS. 30 illustrate a side member according to another embodiment of the present invention. Specifically, FIG. 29 illustrates a side view of a side member according to another embodiment of the present invention, and FIG. 30 illustrates a schematic perspective view of the side member of FIG. 29.

[0202] In this embodiment, the side member (100) includes a first tubular upper section (110) and a second tubular upper section (120). The first and second tubular upper sections (110, 120) can be integrally formed by processing a Tailor Welded Blank (TWB) plate (TP) in which the first and second steel materials (10, 20) are combined, and can be formed by bending or roll forming, etc.

[0203] The first and second steel materials (10, 20) may be different steel types with different thicknesses or strengths from the same material, and may be configured to have different strengths so that various combinations of steel types and thicknesses are possible to achieve a stable crushing mode through a relatively low-strength material.

[0204] The first and second steel members (10, 20) are positioned at different locations along the longitudinal direction of the side member. That is, the weld line where the first and second steel members (10, 20) are welded is orthogonal to the longitudinal direction. Although the longitudinal lengths (l10, l20) of the first and second steel members (10, 20) can be varied, in this embodiment, the length (l10) of the first steel member (10), which is a relatively low-strength material, is configured to be shorter than the length (l20) of the second steel member (20), which is a relatively high-strength material.

[0205] In addition, among the first and second steel materials (10, 20), the first steel material (10), which has relatively lower strength, is positioned far from the center of the vehicle. That is, as shown in FIG. 29, in the case of a front side member (100), the first steel material (10) is positioned in front of the second steel material (20), and in the case of a rear side member, the first steel material (10) is positioned behind the second steel material (20). The first steel material (10) deforms first upon a vehicle collision, thereby inducing crushing.

[0206] At this time, the first tubular upper part (110) and the second tubular upper part (120) may have a shape in which a hexagonal cross-sectional shape is extended in the X direction, which is the length direction. More specifically, the side member (100) may be formed by folding a TWB plate (TP) having a predetermined width and length multiple times to form a plurality of closed cross-sections, each having a hexagonal cross-sectional shape.

[0207] In this embodiment, the side member (100) includes a first tubular upper section (110) and a second tubular upper section (120), and the first tubular upper section (110) and the second tubular upper section (120) can be formed by forming TWB plates (TP), which include high-strength steel plates, for example, steel plates having a tensile strength of 780 MPa or more, in different directions by machining, for example, roll forming or bending. Accordingly, each tubular upper section is welded only on one side around a shared side, and the rest are continuously connected.

[0208] Each side is formed around a bending point. In the first tubular upper section (110), the first to fifth sides (s1 to s5) are formed by bending at multiple bending points (a2 to a6) in a clockwise direction around the shared sixth side (s6), and in the second tubular upper section (110), the seventh to eleventh sides (s7 to s11) are formed by bending at multiple bending points (a7 to a11) in a counterclockwise direction around the sixth side (s6). The first and second tubular upper sections (110, 120) have a hexagonal cross-sectional shape and include the third side (s3) parallel to the shared sixth side (s6), and the ninth side (s9), and the first and eleventh sides (s1, s11) in a direction orthogonal to the extension direction of the sixth side (s6) when viewed from a cross-section perpendicular to the length direction.

[0209] The first tubular upper section (110) has a first side (s1) that extends in the Z direction perpendicular to the Y direction, which is the extension direction of the sixth side (s6), when viewed from the X direction, which is the length direction, and a flange (f1) that forms a first weld (131) is disposed at the edge. The first side (s1) and the flange (f1) are continuous without bending. The second side (s2) is configured to connect the first side (s1) with the third side (s3) which is parallel to the sixth side (s6), and is formed by bending at the second bending point (a2) opposite the flange (f1) of the first side (s1). The second side (s2) is formed at an angle with respect to the Y direction or the Z direction.

[0210] The third side (s3) is parallel to the sixth side (s6), is bent at the third bend point (a3) ​​to connect to the second side (s2), and is bent at the fourth bend point (a4) to connect to the fourth side (s4). The fourth side (s4) is connected to the third side (s3) and is formed to have the same angle with respect to the second side (s2) with respect to the Z direction, but inclined in opposite directions. The fifth side (s5) is parallel to the first side (s1), is connected to the fourth side (s4) through the fifth bend point (a5), and is connected to the sixth side (s6) through the sixth bend point (a6). At the 6th bending point (a6), the 5th side (s5) and the 6th side (s6) are connected by bending at 90°, so they can be bent with a larger radius of curvature than the 2nd to 5th bending points (a2~a5), but are not limited thereto.

[0211] The sixth side (s6) is used to form the closed cross-section of the first tubular upper part (110) and the closed cross-section of the second tubular upper part (120), so it can be said to be a side shared by the first and second tubular upper parts (110, 120).

[0212] The 7th to 11th sides (s7~s11) are symmetrical with respect to the 1st to 5th sides (s1~s5) from the center of the 6th side (s6). The 7th to 11th sides (s7~s11) are formed by bending from the 6th side (s6). Specifically, the 7th side (s7) is connected to the 6th side (s6) through the 7th bend point (a7), the 8th side (s8) is connected to the 7th side (s7) through the 8th bend point (a8), the 9th side (s9) is connected to the 8th side (s8) through the 9th bend point (a9), the 10th side (s10) is connected to the 9th side (s9) through the 10th bend point (a10), and the 11th side (s10) is connected to the 10th side (s10) through the 11th bend point (a11).

[0213] The 7th side (s7) and the 11th side (s11) are parallel to the Z direction. That is, the 1st side (s1) and the 5th side (s5) of the 1st tubular upper part (110) and the 7th side (s7) and the 11th side (s11) of the 2nd tubular upper part (120) are parallel to the Z direction. These parallel sides not only facilitate the formation of the 1st and 2nd welded parts (131, 132), but also facilitate the attachment of other configurations to the 1st, 5th, 7th, and 11th sides (s1, s5, s7, s11), making it advantageous to attach other configurations to the side member (100).

[0214] The ninth side (s9) is parallel to the sixth side (s6) as with the third side (s3), and the eighth and tenth sides (s8, s10) are positioned at an angle with respect to the Z direction or the Y direction. The angle of inclination of the eighth and tenth sides (s8, s10) with respect to the Z direction may correspond to the second and fourth sides (s2, s4).

[0215] The first side (s1) faces the fifth side (s5), and the length of the first side (s1) in the Z direction is longer than the length of the fifth side (s5) in the Z direction. The first side (s1) is formed to pass through the seventh bending point (a7) and overlap with the seventh side (s7). The portion where the seventh side (s7) and the first side (s1) overlap acts as the first flange (f1), and at this portion, the seventh side (s7) and the first side (s1) are welded to form the first weld (131).

[0216] The first weld (131) is structured such that the entire surface of the first flange (f1) of the first side (s1) is welded to the seventh side (s7), thereby preventing the first weld (131) from breaking upon impact in the X direction and increasing crush stability. At this time, the front surface of the first flange (f1) may be weldable, and the length of the first weld (131) may be the length of the first flange (f1) and may be in the range of about 5 to 20 mm.

[0217] Likewise, the eleventh side (s11) faces the seventh side (s7), and the length of the eleventh side (s11) in the Z direction is formed to be longer than the length of the seventh side (s7) in the Z direction. Accordingly, the eleventh side (s11) can pass through the sixth bend point (a6) and overlap with the fifth side (s5), and the part where the eleventh side (s11) and the fifth side (s5) overlap acts as the second flange (f2), and the eleventh side (s11) and the fifth side (s5) are welded at this part to form the second weld (132).

[0218] The second weld (132) is structured such that the entire surface of the second flange (f2) of the eleventh side (s11) is welded to the fifth side (s5), thereby preventing the second weld (132) from breaking upon impact in the X direction and increasing crush stability. At this time, the front surface of the second flange (f2) may be weldable, and the length of the second weld (132) may be the length of the second flange (f2) and may be in the range of approximately 5 to 20 mm, which is the same as the length of the first weld (131).

[0219] A side member (100) according to another embodiment of the present invention also further includes a bead portion (140). The bead portion (140) may be formed on the second, third, fourth, eighth, ninth, and tenth sides (s2, s3, s4, s8, s9, s10). The bead portion (140) may be formed adjacent to one end in the longitudinal direction of the side member (100), and may be formed on a plurality of surfaces formed by each side constituting the side member (100) extending in the longitudinal direction. The bead portion (140) may have a structure formed to protrude inwardly from the first tubular upper portion (110) or the second tubular upper portion (120) when viewed from the longitudinal direction, and may be spaced apart by a predetermined distance (d) from one end in the longitudinal direction.

[0220] The side member (100) according to this embodiment includes a groove (150) formed inwardly from the end surface (160) at one end of the first steel member (10) where the bead portion (140) is formed. In this embodiment, the groove portion (150) includes a first groove (151) that spans the edge between the first side (s1) and the second side (s2), a second groove (152) that spans the edge between the second side (s2) and the third side (s3), a third groove (153) that spans the edge between the third side (s3) and the fourth side (s4), a fourth groove (154) that spans the edge between the fourth side (s4) and the fifth side (s5), a fifth groove (155) that spans the edge between the seventh side (s7) and the eighth side (s8), a sixth groove (156) that spans the edge between the eighth side (s8) and the ninth side (s9), a seventh groove (151) that spans the edge between the ninth side (s9) and the tenth side (s10), and an eighth groove (158) that spans the edge between the tenth side (s10) and the eleventh side (s11). The first to fourth grooves (151 to 154) are formed in the first tubular upper section (110), and the fifth to eighth grooves (155 to 158) are formed in the second tubular upper section (120). Each groove (151 to 158) is formed with a shape symmetrical on both sides with respect to the corner, and an end surface (160) extending in the longitudinal direction is located between the grooves (151 to 158). The end surface (160) is located on each side (s1 to s11).

[0221] The groove (150) can be formed using a laser cutter while the first and second tubular upper parts (110, 120) are manufactured, and performs the role of reducing the initial support load at the location where the groove (150) is formed.

[0222] In this embodiment, the length of the weld section (130) is secured in the same way as in the previous embodiment to increase crushing stability, while also ensuring formability. Additionally, by including a side parallel to the Z or Y direction, the ease of joining with surrounding components is improved when installed in a vehicle. Furthermore, by including a bead section (140) and a groove section (150), crushing deformation in the rear section is prevented due to energy absorption by the bead section (140) and the groove section (150) in the front section, and sequential crushing deformation can be induced starting from the front section. That is, the side member (100) according to one embodiment of the present invention has a larger average load value absorbed in the front section than a conventional side member due to the application of the bead section (140) and the groove section (150), and the amount of fluctuation required for energy absorption is much smaller, making it easier to absorb energy.

[0223] In particular, in this embodiment, a bead portion (140) and a groove portion (150) are formed in the first steel material (10) which has relatively low strength, and a weld portion (130) is formed in the flange (f1, f2). Due to the groove portion (150) and the bead portion (140), deformation can be initiated at a relatively small load without the problem of the weld portion (130) bursting, thereby enabling stable energy absorption. Additionally, deformation starts from the bead portion (140) of the first steel material (10), inducing sequential crushing deformation in the first steel material (10) and the second steel material (20), allowing for the absorption of a large load without causing deformation in the central part where the user is located.

[0224] As mentioned above, in this embodiment as well, since the side member (100) is formed by roll forming of a TWB plate (TP), it can be formed to have a radius of curvature for thickness (R / t_p) smaller than the radius of curvature for thickness, which is the bending forming limit of individual steel by press. That is, as the side member (100) is sequentially bent by roll forming, the radius of curvature for thickness (R / t) at each bending point (a2~a11) can be formed to be smaller than the radius of curvature for thickness limit value (R / t_p) by press.

[0225] FIG. 31 illustrates a front collision absorption structure of a vehicle including a crash box according to another embodiment of the present invention. As shown in FIG. 31, the front energy absorption structure includes a bumper (300), a crash box (200) connected to the bumper, and a front side member (400) connected to the crash box (200).

[0226] In this embodiment, the crash box (200) may include the same structure as the side member of FIG. 29. Specifically, the crash box (200) includes a first tubular upper part (210) that extends in the longitudinal direction and has a hexagonal cross-sectional shape; and a second tubular upper part (220) that is connected to the first tubular upper part (210), extends in the longitudinal direction, and has a hexagonal cross-sectional shape; wherein the first tubular upper part (210) and the second tubular upper part (220) are integrally formed by bending and forming a TWB plate (TP) in which a first steel material (10) which is relatively low-strength steel and a second steel material (20) which is relatively high-strength steel are welded in the longitudinal direction, and a bead part (240) and a groove part (270) are formed adjacent to one end in the longitudinal direction of the first steel material (10) in the TWB plate (TP).

[0227] Additionally, the crash box (200) includes mounting plates (250, 260) connected to the first and second tubular upper sections (210, 220) at both longitudinal ends so as to be connected to the bumper (300) or the side member (400). The bumper-side mounting plate (250) is welded to the end surface (280) between the groove (270) in the first and second tubular upper sections (210, 220), and the mounting plates (250, 260) can be bolted to the bumper-side mounting plate and the side member-side mounting plate.

[0228] In this embodiment, the box portion of the crash box (200), excluding the mounting plates (250, 260), may have the same structure as the side member described above. That is, two first and second tubular portions (210, 220) having a hexagonal cross-sectional shape are formed by a TWB plate (TP), and a weld portion (230) is included in which a bead portion (240) and the end of the TWB plate are welded to the first and second tubular portions (210, 220).

[0229] FIG. 32 illustrates a modified example in which the groove portion of a side member according to another embodiment of the present invention is modified. Since the basic shape of the first and second tubular upper portions (110, 120) of the side member (100) of the embodiment of FIG. 32 is the same as that of the side member (100) shown in FIG. 29 and FIG. 15, a detailed description is omitted. In the embodiment of FIG. 32, the groove portion (150) includes a first groove (151) formed at the center of the end of the second side (s2), a second groove (152) formed at the center of the end of the third side (s3), a third groove (153) formed at the center of the end of the fourth side (s4), a fourth groove (154) formed at the center of the end of the eighth side (s8), a fifth groove (155) formed at the center of the end of the ninth side (s9), and a sixth groove (156) formed at the center of the end of the tenth side (s10). At this time, the end surface (160) is formed around the corner. In this embodiment, the groove (150) is formed on the side where the bead portion (140) is formed, and can help reduce the maximum support load.

[0230] Although the present invention has been described above with reference to embodiments, the present invention is not limited to the embodiments described above, and it is understood that it can be modified and implemented by those skilled in the art without changing the technical concept of the present invention as claimed in the claims.

[0231] Although the present invention has been described above with reference to embodiments, the present invention is not limited to the embodiments described above, and it is understood that it can be modified and implemented by those skilled in the art without changing the technical concept of the present invention as claimed in the claims.

[0232] (Explanation of symbols)

[0233] 10, 20: 1st and 2nd steel members 100: Side member

[0234] 110: 1st tubular upper part 120: 2nd tubular upper part

[0235] 130: Weld 130a, 130b, 130c: Weld line

[0236] 131, 132: 1st and 2nd welds 140: Bead

[0237] 150: Groove 151~158: 1st to 8th grooves

[0238] a1, a2, a3, a4, a5, a6, a7, a8, a9, a10, a11, a12: 1st to 12th bending points

[0239] f1, f2: 1st and 2nd flanges

[0240] s1, s2, s3, s4, s5, s6, s7, s8, s9, s10, s11: 1st to 11th variables

[0241] w1, w2: First and second welds

[0242] 200: Crash Box 300: Bumper

[0243] TP: TWB board

Claims

1. A first tubular upper portion extending in the longitudinal direction and having a hexagonal cross-sectional shape; and A second tubular upper part connected to the first tubular upper part, extending in the longitudinal direction and having a hexagonal cross-sectional shape; Includes, The first tubular upper part and the second tubular upper part are formed integrally by folding and molding a single first plate material, and The above-mentioned first plate is a vehicle side member having a bead portion formed adjacent to one end in the longitudinal direction.

2. In Paragraph 1, The above bead portion is, A vehicle side member formed within 100mm in the longitudinal direction from one end.

3. In Paragraph 1, When viewed from the longitudinal direction, the first tubular upper portion is composed of first to sixth sides formed by being folded sequentially in one direction, and the second tubular upper portion is composed of seventh to eleven sides formed by being folded sequentially in the opposite direction of the one direction with respect to the sixth side, including the sixth side. The above bead portion is, A vehicle side member characterized by being formed on at least one of the first to fifth sides and formed on at least one of the seventh to eleven sides.

4. In Paragraph 1, The above-mentioned first tubular upper part and second tubular upper part are, A vehicle side member characterized by being bent such that the bending angle at each bending point is 40° or more.

5. In Paragraph 4, A welded portion formed on the outer wall of the first tubular upper portion and the second tubular upper portion; A vehicle side member including 6. In Paragraph 5, The above welded part is, A first welded portion formed by welding a first flange, one end of the first plate member bent outward toward the first tubular upper portion, to abut the outer wall of the second tubular upper portion; and A second welded portion formed by welding a second flange, which is bent outwardly toward the outer side of the second tubular upper portion at the other end of the first plate, to the outer wall of the first tubular upper portion; A vehicle side member including 7. In Paragraph 6, The first tubular upper part and the second tubular upper part share one side, and A vehicle side member having the same cross-sectional shape and size with respect to the side, wherein the first tubular upper portion and the second tubular upper portion are the same.

8. In Paragraph 6, When viewed from the longitudinal direction, the first tubular upper portion is composed of first to sixth sides formed by being folded sequentially in one direction, and the second tubular upper portion is composed of seventh to eleven sides formed by being folded sequentially in the opposite direction of the one direction with respect to the sixth side, including the sixth side. The first flange is located at the end of the first side, and The above second flange is a vehicle side member located at the end of the above eleventh side.

9. In Paragraph 8, The third side of the first tubular upper part, the ninth side of the second tubular upper part, and the sixth side are parallel to each other, The first side of the first tubular upper part and the seventh side of the second tubular upper part are parallel, The first weld is formed by welding the first flange located on the first side to the seventh side, and The 11th side of the second tubular upper part and the 5th side of the first tubular upper part are parallel, The above second weld is a vehicle side member formed by welding the second flange located on the 11th side to the 5th side.

10. In Paragraph 9, The above-mentioned sixth side is a vehicle side member extending orthogonally to the above-mentioned first side and the above-mentioned eleventh side.

11. In Paragraph 2, The above-mentioned first plate is a steel material having a tensile strength of 780 MPa or more, and is a vehicle side member.

12. In Paragraph 11, A vehicle side member having the following relationship between the radius of curvature (R) at the bending point between one side and an adjacent side in the above hexagonal cross-sectional shape and the thickness (t) of the first plate. R / t < R / t_p Here, R / t_p is the limit value of the radius of curvature with respect to the thickness when the first plate is bent and formed by a press.

13. A first tubular upper portion extending in the longitudinal direction and having a hexagonal cross-sectional shape; A second tubular upper portion connected to the first tubular upper portion, extending in the longitudinal direction and having a hexagonal cross-sectional shape; and A mounting plate connected to the longitudinal ends of the first and second tubular upper portions; Includes, The first tubular upper part and the second tubular upper part are formed integrally by folding and molding a single first plate material, and The above first plate is a vehicle crash box in which a bead portion is formed adjacent to one end in the longitudinal direction.

14. In Paragraph 13, It further includes a welded portion formed on the outer wall of the first tubular upper portion and the second tubular upper portion; The above welded portion comprises: a first welded portion formed by welding a first flange, which is bent outward from one end of the first plate member to the outer side of the first tubular upper portion, to abut the outer wall of the second tubular upper portion; and a second welded portion formed by welding a second flange, which is bent outward from the other end of the first plate member to the outer side of the second tubular upper portion, to abut the outer wall of the first tubular upper portion. Vehicle crash box.

15. In Paragraph 14, When viewed from the longitudinal direction, the first tubular upper portion is composed of first to sixth sides formed by being folded sequentially in one direction, and the second tubular upper portion is composed of seventh to eleven sides formed by being folded sequentially in the opposite direction of the one direction with respect to the sixth side, including the sixth side. The third side of the first tubular upper part, the ninth side of the second tubular upper part, and the sixth side are parallel to each other, The first side of the first tubular upper part and the seventh side of the second tubular upper part are parallel, The first weld is formed by welding the first flange located on the first side to the seventh side, and The 11th side of the second tubular upper part and the 5th side of the first tubular upper part are parallel, The above second weld is a vehicle crash box formed by welding the second flange located on the 11th side to the 5th side.

16. In Paragraph 15, The above-mentioned 6th side is a vehicle crash box that extends orthogonally to the above-mentioned 1st side and the above-mentioned 11th side.

17. In Paragraph 15, The above bead portion is, A vehicle crash box formed on at least one of the second to fourth sides and formed on at least one of the eighth to tenth sides.

18. A bead portion forming step of forming a bead portion adjacent to one end in the longitudinal direction of a single first plate; A first bending step of forming a first tubular upper portion by bending the first plate five times in a first direction; and A second bending step of forming a second tubular upper portion by bending the first plate five times in a second direction opposite to the first direction; A method for manufacturing an energy-absorbing structure for vehicles including 19. In Paragraph 18, The above bead formation step is, A method for manufacturing an energy-absorbing structure for a vehicle, characterized by forming the above-mentioned bead portion within 100mm in the longitudinal direction from one end.

20. In Paragraph 18, The above first bending step and second bending step are, A method for manufacturing an energy-absorbing structure for a vehicle, characterized by bending the bending point such that the bending angle is 40° or more.

21. In Paragraph 20, A flange forming step performed prior to the welding step, wherein one end of the first plate is bent outwardly toward the first tubular upper portion to form a first flange, and the other end of the first plate is bent outwardly toward the second tubular upper portion to form a second flange; and A closed cross-section forming step in which the first flange is brought into contact with the outer wall of the second tubular upper portion to form a closed cross-section, and the second flange is brought into contact with the outer wall of the first tubular upper portion to form a closed cross-section; A method for manufacturing an energy-absorbing structure for vehicles, further comprising 22. In Paragraph 21, A sizing step performed after the above-mentioned closed cross-section forming step but before the above-mentioned welding step, wherein the closed cross-section is re-compressed from the outside to have preset dimensions; A method for manufacturing an energy-absorbing structure for vehicles, further comprising 23. In Paragraph 22, The above first bending step is, The above-mentioned first plate is bent in the first direction at the second bend point, third bend point, fourth bend point, fifth bend point, and sixth bend point in sequence from one end side toward the other end side, and The above second bending step is, A method for manufacturing a vehicle impact energy structure by continuously bending the above-mentioned first plate material in sequence at the 7th bending point, 8th bending point, 9th bending point, 10th bending point, and 11th bending point in a second direction opposite to the first direction.

24. A first tubular upper portion extending in the longitudinal direction and having a hexagonal cross-sectional shape; and A second tubular upper part connected to the first tubular upper part, extending in the longitudinal direction and having a hexagonal cross-sectional shape; Includes, The first tubular upper part and the second tubular upper part are integrally formed by folding and forming a TWB (Tailor Welded Blank) plate material in which first and second steel materials having different strengths or thicknesses are combined. A vehicle side member having a groove formed at one end of the first and second tubular upper portions.

25. In Paragraph 24, The first and second steel members are vehicle side members positioned at different locations in the longitudinal direction.

26. In Paragraph 25, A vehicle side member further comprising bead portions formed on the sides of the first and second tubular upper portions.

27. In Paragraph 26, The first steel material has relatively lower strength or thinner thickness compared to the second steel material, The above bead portion and the above groove portion are formed in the first steel material for a vehicle side member.

28. In Paragraph 27, A vehicle side member in which the first steel member is positioned at a location far from the center of the vehicle in the longitudinal direction.

29. In Paragraph 28, The above-mentioned groove is a vehicle side member formed at the corner of the hexagonal cross-sectional shape.

30. In Paragraph 26, When viewed from the above longitudinal direction, the first tubular upper portion is composed of first to sixth sides formed by being folded sequentially in one direction, and the second tubular upper portion is composed of seventh to eleven sides formed by being folded sequentially in the opposite direction of the one direction with respect to the sixth side, including the sixth side. The above bead portion and the above groove portion are A vehicle side member formed symmetrically around the sixth side in the first tubular upper portion and the second tubular upper portion.

31. In Paragraph 24, The above-mentioned first tubular upper part and second tubular upper part are, A vehicle side member characterized by being bent such that the bending angle at each bending point is 40° or more.

32. In Paragraph 31, A welded portion formed on the outer wall of the first tubular upper portion and the second tubular upper portion; Includes, The above welded part is, A first welded portion formed by welding a first flange, one end of the TWB plate and bent outward toward the first tubular upper portion, to abut the outer wall of the second tubular upper portion; and A second welded portion formed by welding a second flange, which is bent outward from the other end of the TWB plate to the outer side of the second tubular upper portion, to the outer wall of the first tubular upper portion; A vehicle side member including 33. In Paragraph 32, When viewed from the above longitudinal direction, the first tubular upper portion is composed of first to sixth sides formed by being folded sequentially in one direction, and the second tubular upper portion is composed of seventh to eleven sides formed by being folded sequentially in the opposite direction of the one direction with respect to the sixth side, including the sixth side. The first flange is located at the end of the first side, and The above second flange is a vehicle side member located at the end of the above eleventh side.

34. In Paragraph 33, The third side of the first tubular upper part, the ninth side of the second tubular upper part, and the sixth side are parallel to each other, The first side of the first tubular upper part and the seventh side of the second tubular upper part are parallel, The first weld is formed by welding the first flange located on the first side to the seventh side, and The 11th side of the second tubular upper part and the 5th side of the first tubular upper part are parallel, The above second weld is a vehicle side member formed by welding the second flange located on the 11th side to the 5th side.

35. In Paragraph 34, The above-mentioned sixth side is a vehicle side member extending orthogonally to the above-mentioned first side and the above-mentioned eleventh side.

36. A first tubular upper portion extending in the longitudinal direction and having a hexagonal cross-sectional shape; A second tubular upper part connected to the first tubular upper part, extending in the longitudinal direction and having a hexagonal cross-sectional shape; and A mounting plate connected to the longitudinal ends of the first and second tubular upper portions; Includes, The first tubular upper part and the second tubular upper part are integrally formed by bending and forming a TWB plate material in which first and second steel materials having different strengths or thicknesses are combined. The above TWB plate is a vehicle crash box with a groove formed at one end in the longitudinal direction.

37. In Paragraph 36, A crash box in which the first steel material has relatively lower strength or thinner thickness compared to the second steel material, and the first steel material is positioned far from the center of the vehicle in the longitudinal direction.

38. In Paragraph 37, It further includes bead portions formed on the sides of the first and second tubular upper portions, The above bead portion is a crash box formed in the first steel material together with the above groove portion.

39. In Paragraph 38, It further includes a welded portion formed on the outer wall of the first tubular upper portion and the second tubular upper portion; The above welded portion comprises: a first welded portion formed by welding a first flange, which is bent outward from one end of the TWB plate to the outer side of the first tubular upper portion, to abut the outer wall of the second tubular upper portion; and a second welded portion formed by welding a second flange, which is bent outward from the other end of the TWB plate to the outer side of the second tubular upper portion, to abut the outer wall of the first tubular upper portion. Vehicle crash box.

40. In Paragraph 39, When viewed from the above longitudinal direction, the first tubular upper portion is composed of first to sixth sides formed by being folded sequentially in one direction, and the second tubular upper portion is composed of seventh to eleven sides formed by being folded sequentially in the opposite direction of the one direction with respect to the sixth side, including the sixth side. The third side of the first tubular upper part, the ninth side of the second tubular upper part, and the sixth side are parallel to each other, The first side of the first tubular upper part and the seventh side of the second tubular upper part are parallel, The first weld is formed by welding the first flange located on the first side to the seventh side, and The 11th side of the second tubular upper part and the 5th side of the first tubular upper part are parallel, The above second weld is a vehicle crash box formed by welding the second flange located on the 11th side to the 5th side.

41. A first bending step of forming a first tubular upper portion by bending a TWB plate, in which first and second steel materials having different strengths or thicknesses are combined along the longitudinal direction, five times in the first direction; A second bending step of forming a second tubular upper portion by bending the above TWB plate five times in a second direction opposite to the first direction; and A method for manufacturing an energy-absorbing structure for a vehicle, comprising: a chamfering step of forming a groove on one end of the bent TWB plate.

42. In Paragraph 41, A method for manufacturing an energy-absorbing structure, further comprising a bead-forming step performed before the first bending step and forming a bead portion adjacent to one end of the TWB plate.

43. In Paragraph 42, The above first bending step and second bending step are, A method for manufacturing an energy-absorbing structure by bending the bending point so that the bending angle is 40° or more.

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