Vehicle framework structure and vehicle rear structure

Abstract

A vehicle framework structure (101) is provided with: a first section (101A) including one end (103); a second section (101B) including the other end (104); an intermediate section (101C); and a flange portion (120). The flange portion (120) includes at least a first flange portion (121) continuously provided from one end (103) to a flange boundary (125) provided in the middle of a second region portion (132), and a second flange portion (122) continuously provided from the flange boundary (125) toward the other end (104). The second flange portion (122) protrudes upward or downward of the vehicle.

Description

Vehicle frame structure and vehicle rear structure

[0001] This application claims priority to Japanese Patent Application No. 2024-061573, filed on April 5, 2024, the contents of which are incorporated herein by reference.

[0002] Conventionally, there have been vehicles that have an energy absorbing section in the front straight section of a vehicle skeletal structure in the front structure of the vehicle, or in the rear straight section of a vehicle skeletal structure in the rear structure of the vehicle, which deforms due to a load input through the bumper during a front or rear collision, and absorbs collision energy (for example, Patent Document 1).

[0003] The vehicle frame structure in the front or rear structure of a vehicle generally has a closed cross-section structure, and the rear rail of Patent Document 1 has a rear straight section, a front straight section whose tube axis position is different from that of the rear straight section, and a bent section located between the rear straight section and the front straight section. Patent Document 1 discloses a technology that can appropriately absorb collision energy in a rear collision by making the product of the material strength and plate thickness at the bent section greater than the product of the material strength and plate thickness of the rear straight section.

[0004] As a deformation mode of the energy absorption section (hereinafter, sometimes referred to as the EA section) for ensuring energy absorption performance, a so-called bellows deformation is preferable, which can ensure a large amount of plastic deformation throughout the entire EA section before fracture of the material forming the EA section progresses. For this reason, Patent Document 1 also employs a structure that promotes bellows deformation by arranging multiple geometric deformation sections 25 along the vertical direction perpendicular to the load input direction on the wall surface corresponding to the EA section.

[0005] Here, if the rigidity of the portion adjacent to the EA section downstream in the load input direction in the rear straight section, i.e., the portion adjacent to the EA section forward, is different, the degree of deformation of that portion will be different during a rear-end collision, and as a result, the deformation pattern of the EA section during a rear-end collision may be different.

[0006] However, in the structure of the straight section at the rear side of the rear rail in Patent Document 1, no special measures are taken in the section adjacent to the front side of the EA section, so that the rigidity of that section is insufficient, and the desired bellows-like deformation may not be obtained in the EA section during a rear-end collision. In other words, when the EA section deforms in a rear-end collision, the section located further forward of the EA section may deform more significantly, and this deformation may hinder the desired deformation of the EA section.

[0007] Japan Special Table No. 2022-547492

[0008] The present invention has been made in consideration of the above circumstances, and an object of the present invention is to provide a vehicle frame structure and a vehicle rear structure that are less likely to be hindered in the bellows-like deformation that is considered preferable when absorbing collision energy, and that can sufficiently ensure energy absorption performance.

[0009] In order to solve the above problems, the present invention employs the following configuration: [1] A hollow tubular vehicle frame structure that can be arranged at a front or rear of a vehicle and has one end and the other end spaced apart along a longitudinal direction, the vehicle frame structure comprising: a first portion that can be arranged closer to the front of the front portion or closer to the rear of the rear portion of the vehicle and includes the one end, a second portion that can be arranged closer to the center of the vehicle, the position of the tube axis being different from that of the first portion and including the other end, an intermediate portion that is arranged between the first and second portions and connects the first and second portions, and a flange portion that is provided along the longitudinal direction of the vehicle frame structure and protrudes in a direction different from the longitudinal direction, the first portion is provided with: a first region that includes the one end, and a second region that is closer to the other end of the vehicle frame structure than the first region, adjacent to the first region, and has an axial strength greater than that of the first region, the flange portion A vehicle skeletal structure comprising at least a first flange portion provided continuously from the one end of the vehicle skeletal structure to a flange boundary provided midway through the second region, and a second flange portion provided continuously from the flange boundary toward the other end of the vehicle skeletal structure, the second flange portion protruding upward or downward from the vehicle. [2] The vehicle skeletal structure according to [1], wherein the first flange portion and the second flange portion protrude in different directions from different positions in a circumferential direction perpendicular to the longitudinal direction of the hollow tubular vehicle skeletal structure. [3] The vehicle skeletal structure according to [1] or [2], wherein the first region is an energy absorbing portion that deforms due to an axial compressive load in the axial direction of the tube to absorb load energy. [4] The vehicle skeletal structure according to any one of [1] to [3], wherein the thickness of the vehicle skeletal structure in the first region is smaller than the thickness of the vehicle skeletal structure in the second region. [5] A vehicle skeletal structure according to any one of [1] to [3], wherein the tensile strength and thickness of the vehicle skeletal structure in the first region are smaller than the tensile strength and thickness of the vehicle skeletal structure in the second region.[6] The vehicle skeleton structure according to any one of [1] to [3], wherein, for each of the first region and the second region, when the difference (Hm-Hs) between the hardness Hm at the center in the thickness direction in a cross section perpendicular to the tube axis direction of the first portion and the hardness Hs at the surface layer in the thickness direction in the cross section is defined as a hardness difference, the hardness difference in the first region is greater than the hardness difference in the second region. [7] The vehicle skeleton structure according to any one of [1] to [6], wherein an opening is formed in the vehicle skeleton structure to enable connection of a hollow cylindrical cross bar extending along the left-right direction of the vehicle, and the opening is formed at a position closer to the other end than the flange boundary. [8] The vehicle skeleton structure according to [7], wherein the opening is in the first portion of the vehicle skeleton structure. [9] A vehicle rear structure including the vehicle skeleton structure according to any one of [1] to [8].

[10] A rear structure for a vehicle, comprising: a pair of hollow tubular vehicle skeletal structures arranged along the fore-and-aft direction of the vehicle; and a hollow tubular crossbar arranged along the left-and-right direction of the vehicle and connecting the pair of vehicle skeletal structures, wherein the pair of vehicle skeletal structures are the vehicle skeletal structures described in any one of [1] to [8].

[0010] According to the present invention, it is possible to provide a vehicle frame structure and a vehicle rear structure that are less likely to be hindered by the bellows-like deformation that is considered preferable when absorbing collision energy, and that can fully ensure the expected energy absorption performance.

[0011] 7A , 7B, 7C, 7D, 7E, 7F, 7G, 7H ... 6 is a graph showing test results of the vehicle rear structure of the example and the vehicle rear structure of the comparative example.

[0012] Hereinafter, a vehicle frame structure and a vehicle rear structure according to embodiments of the present invention will be described.

[0013] First Embodiment First, a vehicle rear structure 100 according to a first embodiment of the present invention will be described. The vehicle rear structure 100 according to this embodiment, shown in the perspective view of FIG. 1 and the plan view of FIG. 2, includes a pair of hollow tubular vehicle skeletal structures 101 arranged along the longitudinal direction of the vehicle, and a hollow tubular crossbar 102 arranged along the lateral direction of the vehicle and connecting the pair of vehicle skeletal structures 101. The vehicle rear structure 100 shown in FIGS. 1 and 2 may also include a bumper beam 110 joined to one end 103 of the pair of vehicle skeletal structures 101, as shown by the dashed dotted line in FIG. 2. As can be seen from the arrangement of the bumper beam 110, in the vehicle rear structure 100 shown in FIGS. 1 and 2, the one end 103 of the pair of vehicle skeletal structures 101 is located on the rear side of the vehicle, and the other end 104 of the pair of vehicle skeletal structures 101 is located on the central side of the vehicle.

[0014] Figures 3 to 5 show schematic cross-sectional views taken along lines A-A, B-B, and C-C in Figure 2, respectively. As shown in Figures 3 to 5, the pair of vehicle skeletal structures 101 and crossbar 102 are both hollow tubular members with a closed cross-sectional structure. However, at the connection between the vehicle skeletal structure 101 and the crossbar 102, the hollow portion of the vehicle skeletal structure 101 and the hollow portion of the crossbar 102 are configured to communicate with each other. Accordingly, an opening is provided in the vehicle skeletal structure 101 at the connection position with the crossbar 102. The opening will be described later.

[0015] As shown in FIGS. 3 to 5 , the vehicle rear structure 100 of this embodiment is configured by integrally joining an upper member 100A located on the upper side of the vehicle and a lower member 100B located on the lower side of the vehicle. The upper member 100A and the lower member 100B are each formed, for example, by processing a steel plate into a predetermined shape to form a blank, followed by hot stamping. As is apparent from the cross sections taken along lines A-A, B-B, and C-C in FIG. 2 , each of the upper member 100A and the lower member 100B has a cross-sectional shape consisting of web portions 100a, 100b, a vertical wall portion 100c, and a flange portion 100d. The vehicle rear structure 100 of this embodiment is integrated by joining the flange portions 100d of the upper member 100A and the lower member 100B together. Spot welding, for example, can be used as a joining method. Furthermore, spot welding can also be used in combination with a structural adhesive.

[0016] 3 to 5, the upper member 100A is further provided with an upper rail 101U and an upper crossbar 102U. The upper rail 101U constitutes the vehicle frame structure 101 of the vehicle rear structure 100 when the upper member 100A is joined integrally with the lower member 100B from above and below. The upper crossbar 102U constitutes the crossbar 102 of the vehicle rear structure 100.

[0017] Similarly, the lower member 100B is provided with a lower rail 101D and a lower crossbar 102D. The lower rail 101D, together with the upper rail 101U, constitutes the vehicle frame structure 101 of the vehicle rear structure 100. The lower crossbar 102D, together with the upper crossbar 102U, constitutes the crossbar 102 of the vehicle rear structure 100.

[0018] The upper rail 101U and the upper crossbar 102U that make up the upper member 100A are integrally formed by hot stamping. Similarly, the lower rail 101D and the lower crossbar 102D that make up the lower member 100B are integrally formed by hot stamping. The hot stamping method refers to a method in which a steel plate that will become a blank is heated and softened, and the heated blank is formed in a forming die and then heat is removed by the die to process the blank into a desired shape. The heating temperature of the blank is Ac ３ It is recommended to set it to 1 point or more. ３ The temperature at which ferrite disappears from the metal structure of the blank is the temperature at which the metal structure after processing by the hot stamping method becomes a structure mainly composed of martensite.

[0019] The upper member 100A and the lower member 100B may also be formed by hot stamping a so-called tailored blank. A tailored blank is formed by welding together multiple types of steel plates with different tensile strengths and thicknesses. The upper member 100A and the lower member 100B formed from such a tailored blank may have different tensile strengths or thicknesses in parts. For example, the upper rail 101U and the lower rail 101D may each be composed of multiple regions (first and second regions described below) with different tensile strengths or thicknesses, as described below.

[0020] When forming a tailored blank by hot stamping, the tailored blank is ３ By heating to above this point, it is possible to eliminate the heat-affected zone of the weld that remained when the tailored blank was manufactured.

[0021] The pair of vehicle skeletal structures 101 and crossbars 102 of the vehicle rear structure 100 of this embodiment each have upper wall portions 101a, 102a facing the upper side of the vehicle and lower wall portions 101b, 102b facing the lower side of the vehicle. In the vehicle rear structure 100 of this embodiment, the heights of the upper wall portions 101a, 102a are the same and the heights of the lower wall portions 101b, 102b are the same at the connection position between the vehicle skeletal structure 101 and the crossbar 102. Note that, in order to further improve energy absorption performance, the heights of the upper wall portions 101a, 102a may be made different, and the heights of the lower wall portions 101b, 102b may also be made different so that a ridge line is formed at the connection position between the vehicle skeletal structure 101 and the crossbar 102.

[0022] Next, a pair of vehicle skeletal structures 101 that are part of the vehicle rear structure 100 of this embodiment will be described in detail. FIG. 6 shows a schematic plan view of the vehicle skeletal structure 101 of this embodiment. FIG. 7A shows a schematic plan view of the upper surface of a portion of the vehicle skeletal structure 101, and FIG. 7B shows a schematic longitudinal cross-sectional view taken along line D-D in FIG. 7A. FIG. 8A shows a schematic cross-sectional view of a side surface of a portion of the vehicle skeletal structure 101, and FIG. 8B shows a schematic longitudinal cross-sectional view taken along line E-E in FIG. 8A. As described in FIGS. 1 to 5, the vehicle skeletal structure 101 of this embodiment can be disposed in the rear of the vehicle. However, the position of the vehicle skeletal structure 101 of this embodiment is not limited to the rear of the vehicle, and the vehicle skeletal structure 101 can also be disposed in the front of the vehicle.

[0023] 6 , the vehicle skeletal structure 101 of this embodiment is a hollow tubular member having one end 103 and the other end 104 spaced apart along the longitudinal direction, and includes a first portion 101A including the one end 103 of the vehicle skeletal structure 101, a second portion 101B including the other end 104 of the vehicle skeletal structure 101, an intermediate portion 101C disposed between the first portion 101A and the second portion 101B, and a flange portion 120. The flange portion 120 is provided along the longitudinal direction of the vehicle skeletal structure 101 and protrudes in a direction different from the longitudinal direction of the vehicle skeletal structure 101.

[0024] The first portion 101A, the second portion 101B and the intermediate portion 101C are all hollow tubular, and the hollow portions of each are in communication with each other.

[0025] The first portion 101A, the second portion 101B, and the middle portion 101C that constitute the vehicle frame structure 101 each have an upper wall portion 101a disposed on the upper side of the vehicle, a lower wall portion 101b disposed on the lower side of the vehicle, and a side wall portion 101c that connects the upper wall portion 101a and the lower wall portion 101b. The upper wall portion 101a and the lower wall portion 101b correspond to the web portions 100a, 100b of the upper member 100A and the lower member 100B, as shown in Figures 3 to 5. The side wall portion 101c corresponds to the vertical wall portion 100c of the upper member 100A and the lower member 100B.

[0026] As shown in FIGS. 3 to 5, the flange portion 120 is formed by joining the flange portions 100d of the upper member 100A and the lower member 100B together.

[0027] Here, when external stress is input due to a collision, the vehicle skeletal structure 101 of this embodiment is intended to absorb the collision energy by deforming a part of the first portion 101A, i.e., a portion of the first portion 101A near one end 103, into an accordion-like shape while leaving the second portion 101B and the intermediate portion 101C unchanged. More specifically, a region of the first portion 101A near the one end 103 of the vehicle skeletal structure 101 (a first region described later) is deformed into an accordion-like shape to absorb the collision energy, while a region of the first portion 101A near the other end 104 of the vehicle skeletal structure 101 (a second region described later) is not deformed. In this way, deformation due to the collision is prevented from occurring in the intended connection position between the vehicle skeletal structure 101 and the crossbar 102 and in the intermediate portion 101C, which is located closer to the center of the vehicle than the first portion 101A. The first portion 101A, the second portion 101B, the intermediate portion 101C, and the flange portion 120 will be described below.

[0028] The first portion 101A can be disposed toward the front of the vehicle or toward the rear of the vehicle, and includes one end 103 of the vehicle frame structure 101. When the bumper beam 110 is attached to the vehicle frame structure 101, it is attached to this first portion 101A. The tube axis of the first portion 101A is substantially linear.

[0029] A crossbar 102 can be connected to the first portion 101A. The vehicle skeletal structure 101 of this embodiment has a closed cross-sectional structure as a whole, but when the crossbar 102 is connected to the vehicle skeletal structure 101, an opening 150 is provided in the side wall portion 101c of the vehicle skeletal structure 101 at the connection position, as shown in Fig. 8A. A hollow portion of the vehicle skeletal structure 101 and a hollow portion of the crossbar 102 are configured to communicate with each other via the opening 150.

[0030] The second portion 101B can be disposed closer to the center of the vehicle, and the position of its tube axis is different from the position of the tube axis of the first portion 101A. The second portion 101B is a portion that includes the other end 104 of the vehicle skeleton structure 101. The other end 104 of the vehicle skeleton structure 101 can be joined to another structure that constitutes the cabin of the vehicle.

[0031] The intermediate portion 101C is disposed between the first portion 101A and the second portion 101B and is provided to connect the first portion 101A and the second portion 101B. If the first portion 101A and the second portion 101B were disposed in a straight line without the intermediate portion 101C, the first portion 101A might interfere with the wheel wells that house the front or rear wheels of the vehicle, the engine, the battery, the axles, etc. Therefore, the intermediate portion 101C serves to position the tube axis of the first portion 101A at a position different from that of the second portion 101B.

[0032] As shown in FIGS. 6 and 7A , the first portion 101A is divided into a first region 131 located on the one end 103 side of the vehicle skeletal structure 101, and a second region 132. The second region 132 is located closer to the other end 104 than the first region 131 and adjacent to the first region 131, and has a greater axial strength than the first region 131. The vehicle skeletal structure 101 also has a third region 133 located closer to the other end 104 of the vehicle skeletal structure 101 than the second region 132. The third region 133 includes an intermediate portion 101C and a second portion 101B. As shown in FIGS. 6 , 7A , and 8A , the first region 131 occupies a region of the first portion 101A that includes the one end 103 of the vehicle skeletal structure 101. The second region 132 is adjacent to the first region 131 and also adjacent to the middle portion 101C, and further occupies a region including the position where the crossbar 102 is to be formed.

[0033] The first region 131, the second region 132, and the third region 133 are joined to one another, for example, via welds. The first region 131, the second region 132, and the third region 133 are provided, for example, by manufacturing the upper member 100A and the lower member 100B using a tailored blank as a material, as described above.

[0034] When providing the first region 131 and the second region 132 in the first portion 101A, the thicknesses of the upper wall portion 101a, the lower wall portion 101b, and the side wall portion 101c constituting the first region 131 are preferably made smaller than the respective thicknesses of the second region 132. This results in a greater axial strength of the second region 132 than the axial strength of the first region 131. Therefore, when impact energy is input to the first portion 101A, the second region 132 is not deformed, and the first region 131 is preferentially deformed into an accordion-like shape. In this way, the first region 131 functions as an energy absorbing portion that deforms due to an axial compressive load in the pipe axis direction and absorbs the load energy. The thickness of the first region 131 is constant and does not vary locally. Similarly, the thickness of the second region 132 is constant and does not vary locally.

[0035] Furthermore, when providing the first region 131 and the second region 132 in the first portion 101A, the tensile strength and thickness of the upper wall portion 101a, the lower wall portion 101b, and the side wall portion 101c constituting the first region 131 may be smaller than the tensile strength and thickness of the second region 132, respectively. This results in a greater axial strength of the second region 132 than the axial strength of the first region 131. Therefore, when impact energy is input to the first portion 101A, the second region 132 is not deformed, and the first region 131 is preferentially deformed into an accordion-like shape. The tensile strength and thickness of the first region 131 are constant and do not vary locally. Similarly, the tensile strength and thickness of the second region 132 are constant and do not vary locally.

[0036] Furthermore, when providing the first region 131 and the second region 132 in the first portion 101A, it is preferable to adjust the hardness difference in the thickness direction of the upper wall portion 101a, the lower wall portion 101b, and the side wall portion 101c. Specifically, it is preferable to make the hardness difference in the first region 131 larger than the hardness difference in the second region 132. Note that the hardness difference in the first region 131 is constant and does not vary partially. Similarly, the hardness difference in the second region 132 is constant and does not vary partially.

[0037] The hardness difference refers to the difference (Hm-Hs) between the hardness Hm at the center of the thickness direction in a cross section perpendicular to the tube axis of the first portion 101A in the upper wall portion 101a, the lower wall portion 101b, and the side wall portion 101c, and the hardness Hs at the surface layer in the thickness direction in the same cross section. The surface layer in the thickness direction refers to the region extending from the surface to a depth of (1 / 8)t, where t is the thickness of the upper wall portion 101a, the lower wall portion 101b, and the side wall portion 101c. The hardness Hs and Hm may be Vickers hardness measured under the same conditions.

[0038] By making the hardness difference in the first region 131 greater than the hardness difference in the second region 132, when collision energy is input to the first portion 101A and the first region 131 is deformed, the surface layers of the upper wall portion 101a, the lower wall portion 101b and the side wall portion 101c of the first region 131 undergo plastic deformation, making it less likely for cracks to occur.This makes it possible to prevent the first portion 101A from breaking and to maintain the energy absorption capacity of the vehicle skeletal structure 101 until the collision energy disappears.

[0039] The thickness, tensile strength, and hardness difference of the third region 133 are not particularly limited and may be, for example, the same as the thickness, tensile strength, and hardness difference of the first region 131. Moreover, the thickness, tensile strength, and hardness difference of the third region 133 are each constant and do not vary partially.

[0040] In addition, it is preferable that the welded portion joining the first region 131, the second region 132, and the third region 133 does not have a heat-affected zone. ３ By heating to a temperature above this point, the heat-affected zone disappears in the welded portion joining the first region 131, the second region 132, and the third region 133 together.

[0041] Next, the flange portion 120 will be described. As shown in Figures 2, 6, and 7A, the vehicle skeleton structure 101 of this embodiment is provided with the flange portion 120. The flange portion 120 of the vehicle skeleton structure 101 includes a first flange portion 121, a second flange portion 122, a third flange portion 123, and a fourth flange portion 124. The upper member 100A and the lower member 100B that constitute the vehicle skeleton structure 101 are joined at these first flange portion 121, second flange portion 122, third flange portion 123, and fourth flange portion 124, thereby forming the hollow tubular vehicle skeleton structure 101 as described above.

[0042] The first flange portion 121 is located in a part of the first portion 101A of the vehicle skeletal structure 101 and protrudes toward one side of the vehicle skeletal structure 101 (outside in the vehicle width direction). The protruding direction of the first flange portion 121 is substantially constant along the longitudinal direction of the first flange portion 121. More specifically, the first flange portion 121 is located on the one end 103 side of the first portion 101A of the vehicle skeletal structure 101. As described above, the first portion 101A is composed of a first region 131 including the one end 103 and a second region 132. The first flange portion 121 is continuous from the one end 103 of the first region 131 to a position midway through the second region 132. In this embodiment, the position where the first flange portion 121 ends midway through the second region 132 is referred to as a flange boundary 125. The first flange portion 121 extends from one end 103 to a flange boundary 125 midway through the second region portion 132 , and is not interrupted at the boundary between the first region portion 131 and the second region portion 132 .

[0043] Of the first flange portion 121, the portion 121A protruding from the first region 131 is formed from the material that constitutes the first region 131. Furthermore, the portion 121B protruding from the second region 132 is formed from the material that constitutes the second region 132. In other words, the first flange portion 121 is formed from materials that differ in one or more of thickness, hardness, and hardness difference. The portion 121A protruding from the first region 131 and the portion 121B protruding from the second region 132 are joined by welding.

[0044] The flange boundary 125 may be located anywhere in the longitudinal direction of the second region 132. More preferably, the flange boundary 125 is located closer to the other end 104 than the boundary between the first region 131 and the second region 132, and closer to the one end 103 than the side wall of the crossbar 102. However, the flange boundary 125 does not overlap the boundary between the first region 131 and the second region 132. In Figures 7A and 8A, the range in which the flange boundary 125 can be located is indicated by a double-headed arrow marked F. In other words, the position of the flange boundary 125 is not limited to the position shown in Figure 7A, and may be located anywhere within the range marked F. Because flange boundary 125 is located closer to other end 104 than the boundary between first region 131 and second region 132, there is no risk of first portion 101A being damaged at the boundary between first region 131 and second region 132 when collision energy is input. In addition, because flange boundary 125 is located closer to one end 103 than the position of the side wall portion of crossbar 102, the range of deformation during a collision is limited, reducing the risk of deformation affecting intermediate portion 101C or crossbar 102.

[0045] The second flange portion 122 is located in a part of the first portion 101A where the first flange portion 121 is not formed, in the intermediate portion 101C, and in the second portion 101B. The second flange portion 122 protrudes toward the upper side of the vehicle skeletal structure 101 (the upper side of the vehicle). The protruding direction of the second flange portion 122 relative to the vehicle skeletal structure 101 is substantially constant along the longitudinal direction of the second flange portion 122. More specifically, the second flange portion 122 extends from the middle of the first portion 101A of the vehicle skeletal structure 101, in other words, from a flange boundary 125 of the second region portion 132, toward the other end 104, through the intermediate portion 101C and the second portion 101B, and to the other end 104. In this embodiment, the second flange portion 122 is continuous without interruption at the boundary between the second region 132 of the first portion 101A and the intermediate portion 101C, and at the boundary between the intermediate portion 101C and the second portion 101B, but is not limited to this configuration, and the second flange portion 122 may be interrupted along the way. Furthermore, the second flange portion 122 may protrude toward the lower side of the vehicle frame structure 101 (the lower side of the vehicle).

[0046] The first flange portion 121 and the second flange portion 122 each protrude from different positions in the circumferential direction perpendicular to the longitudinal direction of the hollow tubular vehicle skeleton structure 101. That is, as shown in Fig. 4, the first flange portion 121 protrudes from the side wall portion 101c of the vehicle skeleton structure 101. On the other hand, as shown in Fig. 3, the second flange portion 122 protrudes from the connection portion between the upper wall portion 101a and the side wall portion 101c of the vehicle skeleton structure 101, and protrudes in a direction different from that of the first flange portion 121.

[0047] The third flange portion 123 and the fourth flange portion 124 are located on the opposite side of the first flange portion 121 across the pipe axis direction of the vehicle skeleton structure 101. The third flange portion 123 is located closer to the one end 103 than the cross bar 102 and protrudes toward the other side of the vehicle skeleton structure 101 (inner in the vehicle width direction). The fourth flange portion 124 is located closer to the other end 104 than the cross bar 102 and protrudes toward the other side of the vehicle skeleton structure 101 (inner in the vehicle width direction). In addition, the third flange portion 123 and the fourth flange portion 124 are connected to the flange portion 100d of the cross bar 102.

[0048] According to the vehicle frame structure 101 of this embodiment, the axial strength of the first region 131 is smaller than the axial strength of the second region 132. Therefore, when collision energy is input along the axial direction of the first portion 101A, buckling deformation occurs in the first region 131, and preferably the first region 131 deforms in an accordion-like manner to absorb the collision energy. Here, as described above, the first flange portion 121 extends from the one end 103 to the flange boundary 125 without being interrupted at the boundary between the first region 131 and the second region 132, i.e., the boundary where the material properties change. Therefore, when collision energy is input along the axial direction of the first portion 101A, there is no risk of breakage occurring at the boundary between the first region 131 and the second region 132, and the first region 131 can be deformed in an accordion-like manner to sufficiently absorb the collision energy. Furthermore, since the boundary (flange boundary 125) between the first flange portion 121 and the second flange portion 122 is located closer to one end 103 than the position of the side wall portion of the crossbar 102, there is less risk of deformation during a collision affecting the intermediate portion 101C or the crossbar 102.

[0049] Therefore, according to this embodiment, it is possible to provide a vehicle skeletal structure 101 and a vehicle rear structure 100 that are less likely to be hindered by the bellows-like deformation that is desirable when absorbing collision energy, and that can sufficiently ensure energy absorption performance.

[0050] Furthermore, since the second flange portion 122 is provided continuously from the flange boundary 125 to the other end 104, the rigidity of the intermediate portion 101C and the second portion 101B can be increased.

[0051] Furthermore, when the vehicle skeletal structure 101 of this embodiment is applied to a vehicle, parts such as a wheel house may be joined to the intermediate portion 101C, but the second flange portion 122 of the vehicle skeletal structure 101 protrudes upward from the vehicle, and the second flange portion 122 protrudes in a direction different from the protruding direction of the first flange portion 121, so there is no risk of the second flange portion 122 interfering when attaching the wheel house to the vehicle skeletal structure 101.

[0052] In addition, the vehicle skeletal structure 101 of this embodiment may have an opening 150 formed therein to enable connection of the crossbar 102. In this case, the opening 150 is formed closer to the other end 104 than the flange boundary 125. Therefore, even if there is a concern that the presence of the opening 150 will reduce the rigidity of the vehicle skeletal structure 101, the first flange portion 121 maximizes the amount of collision energy absorbed, thereby suppressing deformation at the intended connection position with the crossbar 102.

[0053] Furthermore, in the vehicle skeletal structure 101 of this embodiment, the thickness of the vehicle skeletal structure 101 in the first region 131 is smaller than the thickness of the vehicle skeletal structure 101 in the second region 132, so that in the event of a collision, the second region 132 is less likely to deform, while the first region 131 is more likely to deform, and the collision energy can be absorbed in the first region 131.

[0054] Furthermore, in the vehicle skeletal structure 101 of this embodiment, the tensile strength and thickness of the vehicle skeletal structure 101 in the first region 131 are smaller than the tensile strength and thickness of the vehicle skeletal structure 101 in the second region 132, so that in the event of a collision, the second region 132 is less likely to deform, while the first region 131 is more likely to deform, and the collision energy can be absorbed in the first region 131.

[0055] Furthermore, in the vehicle skeletal structure 101 of this embodiment, the hardness difference in the first region 131 is greater than the hardness difference in the second region 132, so that in the event of a collision, the surface layers of the upper wall portion 101a, lower wall portion 101b and side wall portion 101c that constitute the first region 131 are less likely to crack, and the collision energy can be sufficiently absorbed in the first region 131, thereby preventing deformation of the second region 132.

[0056] The vehicle rear structure 100 of this embodiment is equipped with a pair of vehicle skeletal structures 101, and this vehicle skeletal structure 101 is the vehicle skeletal structure 101 of this embodiment provided with a first flange portion 121, and when collision energy is input along the pipe axis direction of the first part 101A, buckling deformation occurs in the first region 131 while damage is prevented at the boundary between the first region 131 and the second region 132, so that the amount of collision energy absorbed can be maximized and the propagation of deformation toward the center of the vehicle can be suppressed.

[0057] In addition, the vehicle rear structure 100 of this embodiment comprises a pair of vehicle skeletal structures 101 and a crossbar 102, and this vehicle skeletal structure 101 is the vehicle skeletal structure 101 of this embodiment provided with a first flange portion 121, and when collision energy is input along the pipe axis direction of the first part 101A, buckling deformation occurs in the first region 131 while damage is prevented at the boundary between the first region 131 and the second region 132.As a result, the connection portion between the vehicle skeletal structure 101 and the crossbar 102 does not deform during a collision, so the range of deformation can be reduced and the propagation of deformation toward the center of the vehicle can be suppressed.

[0058] While the present invention has been described above as being an embodiment, it is not limited to the above embodiment and can be modified without departing from the spirit and scope of the present invention. For example, in the above embodiment, the first region 131, the second region 132, and the third region 133 are provided by manufacturing the upper member 100A and the lower member 100B using a tailored blank as a material. However, the first region 131 and the second region 132 are not limited to being joined in advance at the tailored blank stage, and the first region 131 may be joined later by welding or the like.

[0059] Fig. 9 shows an enlarged cross-sectional view of the first portion. As shown in Fig. 9, the first region 131 may be joined by lap welding. The overlap portion K generated by lap welding may be included in the second region 132.

[0060] Furthermore, although each of the pair of vehicle skeletal structures 101 in the vehicle rear structure 100 of this embodiment has an opening 150, openings are not essential in the pair of vehicle skeletal structures 101 and may be omitted. If no openings are provided in the pair of vehicle skeletal structures 101, the vehicle rear structure may be constructed by joining flanges at the ends of the crossbars 102 to the pair of vehicle skeletal structures by welding.

[0061] An upper member and a lower member were manufactured by forming a tailored blank using a hot stamping method, and the upper member and the lower member were joined by spot welding to manufacture a vehicle rear structure according to the embodiment shown in FIGS. 1 and 2 . A bumper beam was joined to one end of the vehicle skeletal structure. The vehicle skeletal structure constituting the vehicle rear structure had a first region, a second region, and a third region. The flange portions included a first flange portion extending continuously from one end of the vehicle skeletal structure to a flange boundary provided midway through the second region, and a second flange portion extending continuously from the flange boundary to the other end of the vehicle skeletal structure. The first region was constructed from steel having a plate thickness of 1.0 mm and a tensile strength of 1000 MPa. The second region was constructed from steel having a plate thickness of 1.4 mm and a tensile strength of 2000 MPa.

[0062] In addition, as a comparative example, a vehicle rear structure of the comparative example was manufactured in the same manner as the example, except that a first flange portion was formed that continued from one end of the vehicle skeletal structure to the boundary between the first and second region portions, and a second flange portion was formed that continued from the boundary between the first and second region portions to the other end of the vehicle skeletal structure.

[0063] A CAE analysis was carried out by crashing the vehicle rear structures of the example and comparative example into the bumper beams under the following test specifications. The change over time in the reaction force applied to the barrier was then measured. The results are shown in Figure 10. In Figure 10, the "offset structure" is the example, and the "matched structure" is the comparative example.

[0064] <Test specifications> ・Regulatory test: Complies with US FMVSS 301 ・Barrier type: Deformable aluminum honeycomb barrier ・Collision speed: 80 km / h ・Barrier weight: 1,360 kg ・Lapping ratio: 70% ・Steel type: Tensile strength 1 GPa to 2 GPa-class hot-stamped steel material ・Steel material making up the first region: 1 GPa-class hot-stamped steel plate, thickness t1.0 mm ・Steel material making up the second and third regions: 2 GPa-class hot-stamped steel plate, thickness t1.4 mm ・Steel material making up the crossbar: 1.5 GPa-class hot-stamped steel plate, thickness t1.0 mm

[0065] As shown in Figure 10, the reaction force after 0.01 seconds did not decrease in the vehicle rear structure of the example compared to the vehicle rear structure of the comparative example. In the vehicle rear structure of the example, the first region deformed bellows-like, allowing the impact energy to be sufficiently absorbed. On the other hand, in the vehicle rear structure of the comparative example, damage occurred at the boundary between the first region and the second region, and the impact energy was not sufficiently absorbed. It is believed that this difference is reflected in the graph of Figure 10.

[0066] The present invention has industrial applicability because it can provide a vehicle frame structure and a vehicle rear structure that are less likely to be hindered by the bellows-like deformation that is considered preferable when absorbing collision energy and can fully ensure the expected energy absorption performance.

[0067] DESCRIPTION OF SYMBOLS 100...Vehicle rear structure 100A...Upper member 100B...Lower member 101...Vehicle skeleton structure 101a...Upper wall portion 101b...Lower wall portion 101c...Side wall portion 101A...First portion 101B...Second portion 101C...Middle portion 101U...Upper rail 101D...Lower rail 102...Crossbar 102U...Upper crossbar 102D...Lower crossbar 103...One end of vehicle skeleton structure 104...Other end of vehicle skeleton structure 110...Bumper beam 120...Flange portion 121...First flange portion 122...Second flange portion 125...Flange boundary 131...First region portion 132...Second region portion 133...Third region portion 150...Opening

Claims

1. A hollow tubular vehicle frame structure that can be arranged at the front or rear of a vehicle and has one end and the other end spaced apart along the longitudinal direction, the vehicle frame structure comprising: a first portion that can be arranged towards the front of the front portion or towards the rear of the rear portion of the vehicle and includes the one end; a second portion that can be arranged towards the center of the vehicle, the position of the tube axis being different from that of the first portion and including the other end; an intermediate portion that is arranged between the first and second portions and connects the first and second portions; and a flange portion that is provided along the longitudinal direction of the vehicle frame structure and protrudes in a direction different from the longitudinal direction, the first portion having: a first region that includes the one end; and a second region that is closer to the other end of the vehicle frame structure than the first region, adjacent to the first region, and has an axial strength greater than that of the first region, the flange portion A vehicle skeletal structure having at least a first flange portion provided continuously from the one end of the vehicle skeletal structure to a flange boundary provided midway through the second region portion, and a second flange portion provided continuously from the flange boundary toward the other end of the vehicle skeletal structure, wherein the second flange portion protrudes upward or downward from the vehicle.

2. A vehicle frame structure as described in claim 1, wherein the first flange portion and the second flange portion each protrude in different directions from different positions in a circumferential direction perpendicular to the longitudinal direction of the hollow tubular vehicle frame structure.

3. A vehicle frame structure according to claim 1, wherein the first region is an energy absorbing portion that deforms due to an axial compressive load in the pipe axis direction to absorb the load energy.

4. A vehicle frame structure according to claim 1, wherein the thickness of the vehicle frame structure in the first region is smaller than the thickness of the vehicle frame structure in the second region.

5. A vehicle skeletal structure as described in claim 1, wherein the tensile strength and thickness of the vehicle skeletal structure in the first region are smaller than the tensile strength and thickness of the vehicle skeletal structure in the second region.

6. A vehicle frame structure as set forth in claim 1, wherein, for each of said first region and said second region, when the difference (Hm-Hs) between the hardness Hm at the center in the thickness direction in a cross section perpendicular to the tube axis of said first portion and the hardness Hs at the surface layer in the thickness direction in said cross section is defined as the hardness difference, the hardness difference in said first region is greater than the hardness difference in said second region.

7. A vehicle skeletal structure as described in claim 1, wherein an opening is formed in the vehicle skeletal structure to enable connection of a hollow cylindrical crossbar extending along the left-right direction of the vehicle, and the opening is formed at a position closer to the other end than the flange boundary.

8. The vehicle frame structure of claim 7, wherein the opening is in the first portion of the vehicle frame structure.

9. A rear structure for a vehicle comprising the vehicle frame structure according to any one of claims 1 to 8.

10. A rear structure for a vehicle comprising: a pair of hollow tubular vehicle skeletal structures arranged along the longitudinal direction of the vehicle; and a hollow tubular crossbar arranged along the lateral direction of the vehicle and connecting the pair of vehicle skeletal structures, wherein the pair of vehicle skeletal structures are the vehicle skeletal structures described in any one of claims 1 to 8.

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