Vehicle side member, crash box, and method for manufacturing energy-absorbing structure

Abstract

The objective of the present invention is to provide: a method for manufacturing a vehicle side member, which doubles energy-absorbing capacity by inducing a stable crush pattern and of which the structure is highly mass-producible; and the vehicle side member manufactured using same. One embodiment provides the vehicle side member comprising: a first tubular part extending in the longitudinal direction, and having a hexagonal cross-sectional shape; and a second tubular part, which is connected to the first tubular part, extends in the longitudinal direction, and has a hexagonal cross-sectional shape, wherein the first tubular part and the second tubular part are integrally formed by being bent using a single first plate, and a bending angle at each bending point of the first tubular part and the second tubular part is 40° or greater.

Description

Method for manufacturing vehicle side member, crash box, and energy absorption structure

[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, side members made of steel have a limitation in that they absorb only a portion of the impact energy because they absorb collision energy through bending deformation rather than longitudinal crushing deformation.

[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] (Prior Art Literature)

[0007] (Patent Document 1) KR 10-2423412 B1

[0008] 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.

[0009] To achieve the above objectives, the present invention provides the following vehicle side member, crash box, and method for manufacturing the same.

[0010] In one embodiment, the present invention may include a vehicle side member comprising: 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 formed integrally by bending and molding from a single first plate material, and the bending angle at each bending point of the first tubular upper portion and the second tubular upper portion is 40° or more.

[0011] In one embodiment, the first flange of the first tubular upper portion, which is one end of the first plate, is bent inward toward the first tubular upper portion, and the second flange of the second tubular upper portion, which is the other end of the first plate, can be bent inward toward the second tubular upper portion.

[0012] In one embodiment, the welded portion formed on the side where the first flange and the second flange come into contact with either the first tubular upper portion or the second tubular upper portion by bending may be further included.

[0013] In one embodiment, the first tubular upper portion is formed by bending the first plate material in the first direction sequentially from one end side to the other end side at the second bending point, the third bending point, the fourth bending point, the fifth bending point, and the sixth bending point, and the second tubular upper portion can be formed by bending the first plate material in the second direction opposite to the first direction sequentially at the seventh bending point, the eighth bending point, the ninth bending point, the tenth bending point, and the eleventh bending point.

[0014] In one embodiment, when viewed from the longitudinal direction, the ratio of the width to the height of the cross-section may be 1:3 or less.

[0015] In one embodiment, 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] In one embodiment, the first and second flanges are in contact with the side shared by the first and second tubular upper parts, and the weld portion may be formed on the outside of the first and second flanges.

[0017] In one embodiment, the weld may be a spot weld or a fillet weld.

[0018] In one embodiment, 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 on the first tubular upper portion side of the sixth side, and the second flange may be located on the second tubular upper portion side of the sixth side.

[0019] In one embodiment, 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 eleventh side of the second tubular upper part and the fifth side of the first tubular upper part may be parallel.

[0020] In one embodiment, the sixth side may extend orthogonally to the first side and the eleventh side.

[0021] In one embodiment, the first plate may be a steel having a tensile strength of 780 MPa or more.

[0022] In one embodiment, 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.

[0023] R / t < R / t_p

[0024] 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.

[0025] A method for manufacturing a vehicle side member according to one embodiment of the present invention comprises: a first bending step of forming a first tubular upper portion having a hexagonal cross-sectional shape by bending a single first plate five times in a first direction; and a second bending step of forming a second tubular upper portion having a hexagonal cross-sectional shape by bending the first plate five times in a second direction opposite to the first direction; wherein 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.

[0026] In one embodiment, a welding step of welding both ends of the first plate to the portion where they meet by bending the first plate may be further included.

[0027] In one embodiment, the method may further include a flange forming step performed prior to the welding step, wherein one end of the first plate is bent to form a first flange and the other end of the first plate is bent to form a second flange; and a closed cross-section forming step wherein the first flange and the second flange are brought into contact with either the first tubular upper portion or the second tubular upper portion to form a closed cross-section.

[0028] In one embodiment, a sizing step may be further included, which is performed after the closed cross-section forming step but before the welding step, and which re-compresses from the outside so that the closed cross-section has preset dimensions.

[0029] In one embodiment, the first bending step involves bending the first plate in the first direction sequentially from one end side to the other end side at the second bending point, the third bending point, the fourth bending point, the fifth bending point, and the sixth bending point, and the second bending step may continue to 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.

[0030] A vehicle crash box 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; 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; 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 bending and molding a single first plate material, and the bending angle of each bending point of the first tubular upper portion and the second tubular upper portion may be 40° or more.

[0031] In one embodiment, the first flange of the first tubular upper portion, which is one end of the first plate, is bent inward toward the first tubular upper portion, and the second flange of the second tubular upper portion, which is the other end of the first plate, can be bent inward toward the second tubular upper portion.

[0032] In one embodiment, the first plate may further include a welded portion in which the first and second tubular upper portions are welded on the outside of the first flange and the outside of the second flange.

[0033] In one embodiment, 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 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 eleventh side of the second tubular upper part and the fifth side of the first tubular upper part are parallel, the first flange is located on the first tubular upper part side of the sixth side, and the second flange may be located on the second tubular upper part side of the sixth side.

[0034] 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.

[0035] FIG. 1 is a perspective view illustrating a side member according to an embodiment of the present invention.

[0036] Figure 2 is a cross-sectional view of Figure 1.

[0037] Figure 3 is an image showing the behavioral pattern in the results of verifying performance through analysis of a side member according to an embodiment of the present invention.

[0038] Figure 4 is a graph showing the results of verifying performance through analysis of a side member according to an embodiment of the present invention and the prior art.

[0039] Figure 5 is a diagram 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.

[0040] Figure 6 is a diagram 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.

[0041] FIG. 7 is a flowchart of a method for manufacturing a side member according to an embodiment of the present invention.

[0042] FIG. 8 is a schematic diagram of a forward energy absorption structure including a crash box according to an embodiment of the present invention.

[0043] FIG. 9 is a side view illustrating a side member according to another embodiment of the present invention.

[0044] FIG. 10 is a perspective view illustrating a side member according to another embodiment of the present invention.

[0045] FIG. 11 is a schematic diagram of a forward energy absorption structure including a crash box according to another embodiment of the present invention.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] FIGS. 1 and FIGS. 2 illustrate 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.

[0050] Vehicle side members include front side members and rear side members, and are 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 members may have a shape that extends in an almost straight line in the front-rear direction. By doing so, the side members 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 the flange by welding or the like. A more detailed description of such assembly is omitted in this specification.

[0051] 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.

[0052] Referring to FIGS. 1 and 2, a side member (10) according to an embodiment of the present invention includes a first tubular upper portion (110) and a second tubular upper portion (120). It may be integrally formed by machining a single first plate (1) of a metal, such as steel, and may be formed by bending or roll forming. At this time, the first tubular upper portion (110) and the second tubular upper portion (120) may have a hexagonal cross-sectional shape that extends in the X direction, which is the longitudinal direction. More specifically, the side member (10, 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. In this case, the length direction in the specification of the present invention may refer to the X direction in the drawing, the width direction may refer to the horizontal direction when viewed from the length direction and the Y direction in the drawing, and the height direction may refer to the vertical direction when viewed from the length direction and the direction perpendicular to the length direction and the width direction, i.e., the Z direction in the drawing.

[0053] 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).

[0054] 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.

[0055] A side member (10) according to one embodiment of the present invention includes a weld (w1, w2) for connecting the first tubular upper part (110) and the second tubular upper part (120). The weld (w1, w2) includes a first weld (w1) located on one end (P1) and a second weld (w2) located on the other end (P2), and can be formed on the side where both ends (P1, P2) of the first plate (1) come into contact with either the first tubular upper part (110) or the second tubular upper part (120) by bending. More specifically, as illustrated in FIG. 2, the first weld (w1) may be formed at a side bending point (a6, a12) where the second flange (f2) located at one end (P1) of the first plate (1) is bent inward toward the second tubular upper part (120) and comes into contact with the first tubular upper part (110), and the second weld (w2) may be formed at a side bending point (a1, a7) where the first flange (f1) located at the other end (P2) of the first plate (1) is bent inward toward the first tubular upper part (110) and comes into contact with the second tubular upper part (120). At this time, the first weld (w1) and the second weld (w2) may be formed by joining by spot welding or fillet welding.

[0056] Meanwhile, in one embodiment of the present invention, the side member (10) may have a ratio of the width (W) to the height (H) of the cross section of 1:3 or less when viewed from the longitudinal direction. At this time, the width (W) may refer to the length of both ends of the cross section in the width direction when viewed from the longitudinal direction, and the height (H) may refer to the length of both ends of the cross section in the height direction when viewed from the longitudinal direction. Accordingly, the side member (10) can easily secure stable cross-sectional support rigidity when an impact occurs in the longitudinal direction. However, if the ratio of the width (W) to the height (H) deviates from the 1:3 range, it may induce bending deformation rather than sequential crushing in the longitudinal direction. Furthermore, in one embodiment of the present invention, the side member (10) has the first tubular upper part (110) and the second tubular upper part (120) sharing the sixth side (s6), which is the variable 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).

[0057] FIGS. 3 and 4 are drawings showing the analysis results of a side member following a collision. The applicant performed a performance analysis of the side member of the present invention through simulation. More specifically, FIG. 3 is an image showing the behavioral pattern in the results of performance verification through analysis of a side member according to an embodiment of the present invention, and FIG. 4 is a graph showing a comparison of the results of performance verification through analysis of the side member according to an embodiment of the present invention and the prior art. Hereinafter, the effects of the side member according to an embodiment of the present invention will be described with reference to FIGS. 3 and 4, while also referring to the configuration illustrated in FIGS. 1 and 2.

[0058] While side members using conventional aluminum extrusion structures have the advantages of a robust cross-sectional configuration and being lighter than steel, aluminum members have the limitation of absorbing only a portion of the energy that the member can absorb through bending deformation rather than sufficient crushing deformation in the longitudinal direction upon impact. In contrast, side members using steel have the advantage of being able to have a polygonal cross-section to facilitate efficient absorption of impact energy and connection with other parts before and after, particularly face-to-face contact. In particular, as shown in FIG. 3, the side member (10) according to an embodiment of the present invention can maximize energy absorption capacity by inducing sequential crushing deformation in the longitudinal direction without bending deformation.

[0059] Figure 4 shows a comparison of the energy absorption capacity of a side member according to an embodiment of the present invention and a side member with a conventional aluminum extrusion structure. The X-axis represents the deformation length of the member for energy absorption, and the Y-axis represents the load applied to the member. This graph is the result of an analysis conducted through simulations performed under the same load and boundary conditions.

[0060] As shown in FIG. 4, the side member (10) according to one embodiment of the present invention withstands an average higher level of impact load than the side member with an aluminum extrusion structure, and it can be seen that the length change required for energy absorption is approximately 494.4 mm, which is shorter than the aluminum member with a length of approximately 586.2 mm. That is, it can be confirmed that the side member (10) according to one embodiment of the present invention can absorb greater energy even with small deformation, as the average load transmitted is measured to be higher than that of the conventional side member with an aluminum extrusion structure. In other words, the side member (10) according to one embodiment of the present invention has a greater energy absorption capacity at a limited amount of deformation.

[0061] FIGS. 5 and 6 are drawings showing the bending angle according to the cross-sectional shape of a side member during a roll forming process. More specifically, FIG. 5 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. 6 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. 5 and 6.

[0062] 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. 5, 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.

[0063] 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).

[0064] As shown in FIG. 5, 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).

[0065] As illustrated in FIG. 6, 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.

[0066] Accordingly, the side member (10) according to one embodiment of the present invention recognizes the above problems and can provide 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.

[0067] FIG. 7 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. 7. Since the side member 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, the description will be made with reference to FIG. 1 and FIG. 2 together.

[0068] A method for manufacturing a side member according to an embodiment of the present invention includes 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 first bending step (S210) may form a first tubular upper part (110) by bending a single first plate (1) five times in a first direction (e.g., counterclockwise). The second bending step (S220) may form a second tubular upper part (120) by bending the first plate (1) five times in a second direction (e.g., clockwise), which is opposite to the first direction. For example, as illustrated in FIG. 4, 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) side, 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.

[0069] 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.

[0070] The flange forming step (S230) can be performed prior to the welding step (S260), and a first flange (f1) can be formed by bending one end of the first plate (1), and a second flange (f2) can be formed by bending the other end of the first plate (1). Meanwhile, although not shown in the drawing, the flange forming step (S230) can be performed prior to the first bending step (S210) and the second bending step (S220), for example, the first bending step (S210) can be performed after the first flange (f1) is formed first. That is, if the flange forming step (S230) is performed prior to 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. 7).

[0071] The above closed cross-section forming step (S240) may form a closed cross-section by bringing the first flange (f1) and the second flange (f2) into contact with either the first tubular upper part (110) or the second tubular upper part (120). For example, in the above closed cross-section forming step (S240), the first flange (f1) may be brought into contact with the inner wall of the first tubular upper part (110) to form a closed cross-section, and the second flange (f2) may be brought into contact with the inner wall of the second tubular upper part (120) to form a closed cross-section. More specifically, as illustrated in FIG. 2, the first flange (f1) may be made to be in contact with the side surface of the first tubular upper part (110) of the sixth side (s6) 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 made to be in contact with the side surface of the second tubular upper part (120) of the sixth side (s6) to form a closed cross-section with a hexagonal cross-section inside the second tubular upper part (120).

[0072] 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.

[0073] Accordingly, according to the method for manufacturing a side member according to one embodiment of the present invention, it is possible to manufacture a side member having a double hexagonal cross-section shape that has energy absorption capacity similar to that of an octagonal cross-section side member and doubles energy absorption capacity through the induction of a stable crushed shape, and at the same time is more efficient for mass production than an octagonal cross-section side member.

[0074] FIG. 8 shows a schematic diagram of a forward energy absorption structure including a crash box according to an embodiment of the present invention.

[0075] As shown in FIG. 8, 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).

[0076] 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 material, and the bending angle of each bending point of the first tubular upper part and the second tubular upper part is formed to be 40° or more.

[0077] 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.

[0078] 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 welded portion (w1) is welded to the first and second tubular portions (210, 220).

[0079] In this embodiment, the first and second tubular upper sections are welded to form a weld (w1) on the outside of the flange where one end of the first plate is bent inward toward the first tubular upper section (210). Although not shown in FIG. 8, as in FIG. 2, a weld is also formed on the outside of the flange where one end of the first plate is bent inward toward the second tubular upper section (220). Since this is identical to the structure of the side member (100) shown in FIG. 1, a detailed description is omitted.

[0080] Although the forward energy absorption structure was described in Fig. 8, 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.

[0081] In addition, although the front side member (400) in the front energy absorption structure illustrated in FIG. 8 is depicted as having a square cross-section, the present invention also allows the side member (100) illustrated in FIG. 1 to be applied as the front side member (400) of FIG. 8. That is, it is also possible for a 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 a crash box (200) having the first and second tubular upper parts (210, 220) having a hexagonal cross-section.

[0082] Meanwhile, FIGS. 9 and FIGS. 10 illustrate a side member according to another embodiment of the present invention. Specifically, FIG. 9 illustrates a side view of a side member according to another embodiment of the present invention, and FIG. 10 illustrates a schematic perspective view of the side member of FIG. 9.

[0083] The side member (100) of this embodiment can be formed by roll forming a single sheet metal, similar to the previous embodiment.

[0084] 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.

[0085] 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.

[0086] 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 first flange (f1) is placed at the edge. The first flange (f1) is bent inward toward the first tubular upper section (110) to contact the first tubular upper section (110) side surface of the sixth side (s6), and a first weld (w1) is welded on the outside of the first flange (f1). 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.

[0087] 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 being bent at 90°, so they can be bent with a radius of curvature equal to or greater than that of the 2nd to 5th bending points (a2~a5), but are not limited thereto.

[0088] 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).

[0089] 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).

[0090] 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, making it easy to combine other configurations on the 1st, 5th, 7th, and 11th sides (s1, s5, s7, s11), which is advantageous for combining other configurations on the side member (100).

[0091] 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).

[0092] The first side (s1) faces the fifth side (s5), and the first side (s1) is formed by being bent from the first flange (f1) at the first bending point (a1). Similarly, the second flange (f2) is formed by being bent from the eleventh side (s11) at the twelfth bending point (a12). A first weld (w1) is formed at the side bending point (a1) where the first flange (f1) is bent inward toward the first tubular upper part (110) and contacts the second tubular upper part (120), and a second weld (w2) is formed at the side bending point (a12) where the second flange (f2) is bent inward toward the second tubular upper part (120) and contacts the first tubular upper part (110). At this time, the first weld (w1) and the second weld (w2) may be formed by joining using spot welding or fillet welding. The first and second welds (w1, w2) prevent the first weld (131) from breaking upon impact in the X direction and can increase crush stability.

[0093] In this embodiment, as in the previous embodiment, crush stability can be increased while also ensuring moldability. Additionally, by including a side parallel to the Z or Y direction, ease of connection with surrounding components is improved when installed in a vehicle.

[0094] 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.

[0095] FIG. 11 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. 11, 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).

[0096] In this embodiment, the crash box (200) may include the same structure as the side member of FIG. 9. 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.

[0097] 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.

[0098] 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 the ends of the plate are welded to the first and second tubular portions (210, 220) to form a welded portion (w1).

[0099] 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.

[0100] (Explanation of symbols)

[0101] 1: Plate, 10, 100: Side member

[0102] 110: 1st tubular upper part 120: 2nd tubular upper part

[0103] a1, a2, a3, a4, a5, a6, a7, a8, a9, a10, a11, a12: 1st to 12th bending points

[0104] f1, f2: 1st and 2nd flanges

[0105] s1, s2, s3, s4, s5, s6, s7, s8, s9, s10, s11, s12: 1st to 12th variables

[0106] w1, w2: First and second welds

[0107] 200: Crash Box 300: Bumper

Claims

1. A first tubular upper portion extending in the longitudinal direction and having a hexagonal cross-sectional shape; and A second tubular upper portion connected to the first tubular upper portion, 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 bending and molding a single first plate material, A vehicle side member characterized in that the bending angle at each bending point of the first tubular upper part and the second tubular upper part is 40° or more.

2. In Paragraph 1, The first flange of the first tubular upper portion, which is one end of the first plate, is bent inward toward the first tubular upper portion, and A vehicle side member in which the second flange of the second tubular upper portion, which is the other end of the first plate, is bent inward toward the second tubular upper portion.

3. In Paragraph 2, A welded portion formed on the side where the first flange and the second flange come into contact with either the first tubular upper portion or the second tubular upper portion by bending; A vehicle side member including additional 4. In Paragraph 3, The above-mentioned first tubular upper part is, The above-mentioned first plate is formed by bending 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 tubular upper part is, A vehicle side member formed by continuously bending the above-mentioned first plate material in sequence at the 7th bend point, 8th bend point, 9th bend point, 10th bend point, and 11th bend point in a second direction opposite to the first direction.

5. In Paragraph 1, A vehicle side member characterized by the ratio of the width to the height of the cross-section being 1:3 or less when viewed from the above-mentioned longitudinal direction.

6. In Paragraph 3, The first tubular upper part and the second tubular upper part share one side, and The above-mentioned first tubular upper part and the above-mentioned second tubular upper part are vehicle side members having the same cross-sectional shape and size based on the side.

7. In Paragraph 6, A vehicle side member in which the first and second flanges are in contact with the side shared by the first and second tubular upper parts, and the welded portion is formed on the outside of the first and second flanges.

8. In Paragraph 7, The above weld is a spot weld or fillet weld for a vehicle side member.

9. In Paragraph 3, 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 on the upper tubular surface of the sixth side, and The second flange is a vehicle side member located on the second tubular upper surface of the sixth side.

10. In Paragraph 9, 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 11th side of the second tubular upper part and the 5th side of the first tubular upper part are parallel vehicle side members.

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

12. In Paragraph 3, The above-mentioned first plate is a steel material having a tensile strength of 780 MPa or more, and is a vehicle side member.

13. In Paragraph 12, 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.

14. A first bending step of forming a first tubular upper portion having a hexagonal cross-sectional shape by bending a single first plate five times in a first direction; and A second bending step of forming a second tubular upper portion having a hexagonal cross-sectional shape by bending the first plate five times in a second direction opposite to the first direction; Includes, The above first bending step and second bending step are, A method for manufacturing a vehicle side member characterized by bending so that the bending angle at the bending point is 40° or more.

15. In Paragraph 14, A welding step of welding the two ends of the first plate to the portion where they meet by bending the first plate; A method for manufacturing a vehicle side member further comprising 16. In Paragraph 15, A flange forming step performed prior to the welding step, wherein one end of the first plate is bent to form a first flange and the other end of the first plate is bent to form a second flange; and A closed cross-section forming step in which the first flange and the second flange are brought into contact with either the first tubular upper portion or the second tubular upper portion to form a closed cross-section; A method for manufacturing a vehicle side member further comprising 17. In Paragraph 16, 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 a vehicle side member further comprising 18. In Paragraph 17, 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 side member by continuously bending the above-mentioned first plate 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.

19. 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; is included, A vehicle crash box in which the first tubular upper part and the second tubular upper part are formed integrally by bending and molding from a single first plate, wherein the bending angle at each bending point of the first tubular upper part and the second tubular upper part is 40° or more.

20. In Paragraph 19, The first flange of the first tubular upper portion, which is one end of the first plate, is bent inward toward the first tubular upper portion, and The second flange of the second tubular upper portion, which is the other end of the first plate, is bent inward toward the second tubular upper portion. Vehicle crash box.

21. In Paragraph 20, A vehicle crash box further comprising a welded portion in which the first and second tubular upper portions are welded on the outside of the first flange and the outside of the second flange of the first plate.

22. In Paragraph 20, 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 11th side of the second tubular upper part and the 5th side of the first tubular upper part are parallel, The first flange is located on the upper tubular surface of the sixth side, and The above second flange is a vehicle crash box located on the second tubular upper surface of the above sixth side.

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