Structural member

Abstract

A structural member (100, 100A, 100B) comprises a first attachment portion (11), a second attachment portion (12), a third attachment portion (13), an arm member (20), and a reinforcing member (30). The arm member (20) includes a first vertical wall (221), a second vertical wall (222), a third vertical wall (223), and a top plate (21). The reinforcing member (30) includes a reinforcing member body (31) and a flange (32). The reinforcing member body (31) is joined to the second vertical wall (222) and the third vertical wall (223). The flange (32) is continuous with an end edge (311) of the reinforcing member body (31) on the first attachment portion (11) side and / or an end edge (312) of the reinforcing member body (31) on the third attachment portion (13) side, and is joined to the top plate (21). The end edges (311, 312) of the reinforcing member body (31) and the flange (32) are disposed within an intermediate region (R3) of the arm member (20).

Description

Structural member

[0001] The present disclosure relates to a structural member for a vehicle.

[0002] A plurality of structural members are used in vehicles such as automobiles. External force acts on each structural member during traveling or collision of the vehicle.

[0003] Patent Document 1 discloses a lower arm as an example of a structural member for a vehicle. In Patent Document 1, the lower arm includes an arm member and a reinforcing member. The reinforcing member includes a reinforcing member main body and a flange. The reinforcing member main body faces the top plate of the arm member. The flange protrudes from the reinforcing member main body toward the top plate of the arm member, and is arranged with a gap from the top plate. In Patent Document 1, the reinforcing member main body branches into a first branch portion and a second branch portion, and the flange is arranged along the branch portion of the reinforcing member main body. Patent Document 1 describes that, as a result, when an external force is input to the structural member that is, for example, a lower arm, the shear force acting on the arm member and the reinforcing member main body is easily dispersed to the flange, so that out-of-plane deformation of the arm member and the reinforcing member is less likely to occur.

[0004] Patent Document 2 also discloses a lower arm as an example of a structural member for a vehicle. In Patent Document 2, the lower arm includes an arm member and a reinforcing member. The reinforcing member includes a bottom wall portion facing the top wall portion of the arm member, and a flange portion. The reinforcing member is provided over a wide range of the arm member. In the lower arm of Patent Document 2, the flange portion of the reinforcing member is arranged at a position close to the load input point. For example, the length from the mounting portion of the vehicle body-side component to the flange portion is 83% or more of the length from the mounting portion of the vehicle body-side component to the mounting portion of the wheel-side component that is the load input point. Patent Document 2 describes that, as a result, torsional deformation of the lower arm can be effectively suppressed, and the mass efficiency of deformation strength can be improved.

[0005] JP 2024-126603 A Patent No. 6717445

[0006] Structural components for vehicles are required to have strength (bearing capacity) against external forces applied during driving or collisions. Furthermore, structural components also need to be lightweight from the perspective of improving vehicle fuel efficiency. Therefore, it is preferable for structural components to have a structure that efficiently improves their strength against external forces in terms of weight.

[0007] The object of this disclosure is to provide a structural member for a vehicle that can improve strength against external forces in a weight-efficient manner.

[0008] The structural member for a vehicle according to this disclosure comprises a first mounting portion for attaching the wheels of the vehicle, a second mounting portion and a third mounting portion for attaching the body of the vehicle, an arm member, and a reinforcing member. The arm member includes a first vertical wall, a second vertical wall, a third vertical wall, and a top plate. The first vertical wall extends from the first mounting portion side to the second mounting portion side. The second vertical wall extends from the second mounting portion side to the third mounting portion side. The third vertical wall extends from the first mounting portion side to the third mounting portion side. The top plate is continuous with each of the first vertical wall, the second vertical wall, and the third vertical wall. The reinforcing member includes a reinforcing member body and a flange. The reinforcing member body faces the top plate with a gap between them. The reinforcing member body is joined to each of the second vertical wall and the third vertical wall. The flange is continuous with at least one of the edges of the reinforcing member body on the first mounting portion side and the edge on the third mounting portion side. The flange is joined to the top plate. When the arm member is divided equally into a first region on the first mounting side, a second region on the third mounting side, and an intermediate region located between the first and second regions along the longitudinal direction of the arm member, each of the edges of the reinforcing member body and the flange are positioned within the intermediate region.

[0009] The structural member for vehicles described herein can improve strength against external forces in a weight-efficient manner.

[0010] Figure 1 is a schematic perspective view of a structural member according to the first embodiment. Figure 2 is another schematic perspective view of a structural member according to the first embodiment. Figure 3 is a plan view of a structural member according to the first embodiment. Figure 4 is a cross-sectional view taken along line IV-IV of Figure 3. Figure 5 is a cross-sectional view taken along line V-V of Figure 3. Figure 6 is a plan view of a structural member according to the first embodiment. Figure 7A shows data for a height 30% lower than the limit height obtained in the stretch flange forming test and its approximation line. Figure 7B shows an equation approximating the slope of the approximation line shown in Figure 7A with Vickers hardness. Figure 7C shows an equation approximating the intercept of the approximation line shown in Figure 7A with Vickers hardness. Figure 8 is a plan view of a structural member according to the second embodiment. Figure 9 is a plan view of a structural member according to the third embodiment. Figure 10 is a cross-sectional view of a structural member according to a modified example of each embodiment at the position of the mounting portion on the wheel side. Figure 11 is a graph showing the weight efficiency of the maximum reaction force against the collision load for each example and comparative example.

[0011] The structural member for a vehicle according to this embodiment includes a first mounting portion for attaching the vehicle's wheels, a second mounting portion and a third mounting portion for attaching the vehicle's body, respectively, an arm member, and a reinforcing member. The arm member includes a first vertical wall, a second vertical wall, a third vertical wall, and a top plate. The first vertical wall extends from the first mounting portion side to the second mounting portion side. The second vertical wall extends from the second mounting portion side to the third mounting portion side. The third vertical wall extends from the first mounting portion side to the third mounting portion side. The top plate is continuous with each of the first, second, and third vertical walls. The reinforcing member includes a reinforcing member body and a flange. The reinforcing member body faces the top plate with a gap between them. The reinforcing member body is joined to each of the second and third vertical walls. The flange is continuous with at least one of the edges of the reinforcing member body on the first mounting portion side and the edge on the third mounting portion side. The flange is joined to the top plate. When the arm member is divided equally into a first region on the first mounting side, a second region on the third mounting side, and an intermediate region located between the first and second regions along the longitudinal direction of the arm member, each of the edges of the reinforcing member body and the flange are arranged within the intermediate region (first configuration).

[0012] When a structural member comprising a first mounting portion on the wheel side and second and third mounting portions on the vehicle body side is incorporated into a vehicle, the longitudinal load of the vehicle is likely to be applied to the first mounting portion of the structural member during vehicle travel or collision. When the third mounting portion is located behind the second mounting portion, buckling is likely to occur in the intermediate region of the arm member when a load directed towards the rear is applied to the first mounting portion. In contrast, in the structural member according to the first configuration, a reinforcing member is positioned to target the intermediate region of the arm member where buckling is likely to occur. That is, when the arm member is divided equally into a first region on the first mounting portion side, a second region on the third mounting portion side, and an intermediate region between these, the flange of the reinforcing member is positioned within the intermediate region where buckling is likely to occur. The flange of the reinforcing member is joined to the top plate of the arm member in the intermediate region, suppressing out-of-plane deformation of the top plate. Therefore, when a longitudinal load is applied to the first mounting portion, buckling of the arm member is less likely to occur.

[0013] In addition, in the structural member relating to the first configuration, the reinforcing member is provided in a relatively narrow area on the arm member. More specifically, the first mounting portion side and the end edge of the third mounting portion of the reinforcing member body, and a flange continuous with at least one of these, are positioned within the intermediate region of the arm member. In this case, the reinforcing member does not become large, and the increase in the weight of the structural member due to the reinforcing member can be suppressed.

[0014] Thus, with the structural member according to the first configuration, buckling of the arm member can be made less likely without significantly increasing the weight of the structural member. Therefore, the structural member according to the first configuration can improve the strength against external forces in a weight-efficient manner.

[0015] In the structural member relating to the first configuration, flanges may be provided on each of the edges of the reinforcing member body (second configuration).

[0016] In the second configuration, flanges are provided on both the edge of the reinforcing member body on the first mounting side and the edge on the third mounting side, and these flanges are joined to the top plate of the arm member. Therefore, out-of-plane deformation of the arm member is more easily suppressed, and the strength of the structural member against external forces is further improved.

[0017] In the structural member relating to the first or second configuration, the reinforcing member body may be further joined to the first vertical wall (third configuration).

[0018] A structural member relating to any of the first to third configurations may further include a first auxiliary reinforcing member. The first auxiliary reinforcing member is positioned, for example, on the first mounting portion side with respect to the reinforcing member. The first auxiliary reinforcing member is joined to the arm member (fourth configuration).

[0019] A structural member relating to any of the first to fourth configurations may further include a second auxiliary reinforcing member. The second auxiliary reinforcing member is positioned, for example, on the third mounting portion side with respect to the reinforcing member. The second auxiliary reinforcing member is joined to the arm member (fifth configuration).

[0020] In the structural member relating to the fourth or fifth configuration, the arm member is further reinforced by an auxiliary reinforcing member. This makes it easier to further improve the strength of the structural member against external forces.

[0021] In the structural member relating to any of the first to fifth configurations, the top plate may have a Vickers hardness of 184 HV or more. The second vertical wall may include a curved portion. The curved portion is concave inward of the arm member in a plan view of the structural member and has a radius of curvature of, for example, 10 mm to 60 mm (sixth configuration).

[0022] In a structural member relating to any of the first to fifth configurations, the second vertical wall may include a curved portion. The curved portion curves concavely inward towards the arm member in a plan view of the structural member. The surface cross-sectional hardness of the second vertical wall in the curved portion may be 1.13 times or more the surface cross-sectional hardness of the top plate (seventh configuration).

[0023] In the structural member relating to the sixth or seventh configuration, the thickness of the plate at the end of the second vertical wall in the curved portion opposite to the top plate may be smaller than the thickness of the top plate obtained at the maximum test force in the tensile test of the top plate (eighth configuration).

[0024] In a structural member relating to any of the sixth to eighth configurations, when the height of the second vertical wall in the curved portion is H [mm], the radius of curvature of the curved portion in a plan view of the structural member is R [mm], and the Vickers hardness of the top plate is Hv [HV], the height H, radius of curvature R, and Vickers hardness Hv may satisfy the following equation (ninth configuration): 10 ≤ (-0.000007Hv) ２ +0.002Hv+0.3495)R+(0.0002Hv ２ -0.0929Hv+12.799)≦H≦60

[0025] Embodiments of this disclosure will be described below with reference to the drawings. In these drawings, the same or equivalent components are denoted by the same reference numerals, and the same description will not be repeated.

[0026] <First Embodiment> [Structural Member Configuration] Figures 1 and 2 are schematic perspective views showing the structural member 100 according to this embodiment. The structural member 100 is used in vehicles such as automobiles. The structural member 100 is, for example, a chassis component of an automobile. Chassis components include suspension arms such as lower arms and upper arms. In this embodiment, an example in which the structural member 100 is a front lower arm will be described.

[0027] Referring to Figures 1 and 2, the structural member 100 comprises mounting parts 11, 12, and 13, an arm member 20, and a reinforcing member 30.

[0028] The mounting portion 11 is provided on the structural member 100 for attaching the vehicle's wheels. When the structural member 100 is assembled into the vehicle, the mounting portion 11 is positioned outward in the vehicle width direction (left-right direction) relative to the mounting portions 12 and 13. The mounting portion 11 is provided with, for example, a ball joint. The structural member 100 is attached to the wheels via, for example, the ball joint and steering knuckle.

[0029] The mounting portion 12 is provided on the structural member 100 for attaching the vehicle body. The mounting portion 12 is positioned inward in the vehicle width direction relative to the mounting portion 11 when the structural member 100 is assembled into the vehicle. For example, a cylindrical collar 40 is provided on the mounting portion 12. The structural member 100 is attached to the vehicle body via, for example, a bush and a suspension member that are press-fitted into the collar 40.

[0030] The mounting portion 13 is provided on the structural member 100 for attaching the vehicle body. When the structural member 100 is assembled into the vehicle, the mounting portion 13 is positioned inward in the vehicle width direction relative to the mounting portion 11. When the structural member 100 is assembled into the vehicle, the mounting portion 13 is positioned behind the mounting portion 12. For example, a bushing is provided on the mounting portion 13. The structural member 100 is attached to the vehicle body, for example, via the bushing and suspension member.

[0031] The arm member 20 has an overall curved shape when viewed in plan of the structural member 100. A plan view of the structural member 100 refers to viewing the structural member 100 along the direction corresponding to the vertical direction of the vehicle into which the structural member 100 is incorporated. Hereinafter, with respect to the structural member 100, the direction corresponding to the vertical direction of the vehicle will simply be referred to as the vertical direction.

[0032] The arm member 20 is typically made of a metal plate. The arm member 20 may also be made of a steel plate. The arm member 20 includes a top plate 21 and vertical walls 221, 222, and 223.

[0033] The top plate 21 is provided on the arm member 20 so as to intersect in the vertical direction when the structural member 100 is assembled to the vehicle. In this embodiment, the wheel-side mounting portion 11 and the vehicle body-side mounting portion 13 are provided on the top plate 21. More specifically, the mounting portion 11 may include a recess 111 provided on the end face of the top plate 21. The mounting portion 13 may include a through hole 131 that penetrates the top plate 21 in the thickness direction. For example, a ball joint is mounted in the recess 111. For example, a bush is press-fitted into the through hole 131.

[0034] The top plate 21 is provided with through holes 23. The through holes 23 are located near the mounting portion 12 and penetrate the top plate 21 in the thickness direction. The through holes 23 are used, for example, to pass tools through when assembling the structural member 100 to the vehicle.

[0035] The top plate 21 is continuous with each of the vertical walls 221, 222, and 223. The vertical walls 221, 222, and 223 are connected by the top plate 21. In the curved arm member 20 in plan view, the vertical walls 221 and 222 are positioned on the outside of the curve relative to the vertical wall 223.

[0036] Vertical wall 221 extends from the mounting portion 11 side to the mounting portion 12 side. Vertical wall 222 extends from the mounting portion 12 side to the mounting portion 13 side. Vertical wall 223 extends from the mounting portion 11 side to the mounting portion 13 side. The vertical wall 223 on the inside of the curve extends from the mounting portion 11 side to the mounting portion 13 side so as to face the vertical walls 221 and 222 on the outside of the curve.

[0037] The arm member 20 preferably has a Vickers hardness of 184 HV or higher. More specifically, the top plate 21 preferably has a Vickers hardness of 184 HV or higher. The Vickers hardness of the top plate 21 may be 244 HV or higher, 306 HV or higher, or 369 HV or higher. The arm member 20 may have a plate thickness of, for example, 0.4 mm or more. The plate thickness of the arm member 20 may be 1.0 mm or more. The plate thickness of the arm member 20 may be 6.0 mm or less, or 4.0 mm or less.

[0038] The reinforcing member 30 is attached to the arm member 20. The reinforcing member 30 is typically made of a metal plate. The reinforcing member 30 may also be made of a steel plate. The thickness of the reinforcing member 30 may be the same as or different from the thickness of the arm member 20. The tensile strength of the reinforcing member 30 may be the same as or different from the tensile strength of the arm member 20.

[0039] The reinforcing member 30 includes a reinforcing member body 31 and at least one flange 32.

[0040] The reinforcement member main body 31 is provided on the reinforcement member 30 so as to intersect the vertical direction in a state where the structural member 100 is assembled to a vehicle. The reinforcement member main body 31 faces the top plate 21 of the arm member 20. A through hole 33 may be formed in the reinforcement member main body 31. The flange 32 is provided continuously to the reinforcement member main body 31.

[0041] Hereinafter, the configuration of the structural member 100 will be described in more detail with reference to FIGS. 3 to 6. FIGS. 3 and 6 are plan views of the structural member 100. FIG. 3 shows a view of the structural member 100 as viewed along the vertical direction from the reinforcement member 30 side. FIG. 4 is a sectional view taken along line IV-IV in FIG. 3. FIG. 5 is a sectional view taken along line V-V in FIG. 3. FIG. 6 shows a view of the structural member 100 as viewed along the vertical direction from the top plate 21 side of the arm member 20.

[0042] With reference to FIG. 3, the vertical wall 222 of the arm member 20 includes a curved portion 242. The curved portion 242 is a portion of the vertical wall 222 that curves concavely toward the inner side of the arm member 20 in a plan view of the structural member 100. The curved portion 242 is disposed adjacent to the mounting portion 12. More specifically, the curved portion 242 is disposed adjacent to the collar 40 provided on the mounting portion 12.

[0043] The vertical wall 223 of the arm member 20 includes a curved portion 243. The curved portion 243 is a portion of the vertical wall 223 that curves concavely toward the inner side of the arm member 20 in a plan view of the structural member 100.

[0044] FIG. 4 shows a cross section of the structural member 100 when cut along the vertical direction at the center position of the through hole 23 so as to pass through the curved portions 242, 243 of the vertical walls 222, 223 of the arm member 20.

[0045] As shown in FIG. 4, the vertical wall 222 includes a vertical wall main body 222a and a ridge portion 222b. In the arm member 20, the ridge portion 222b is a corner portion between the top plate 21 and the vertical wall main body 222a. That is, the ridge portion 222b is disposed between the top plate 21 and the vertical wall main body 222a, and is continuous with both the top plate 21 and the vertical wall main body 222a. The ridge portion 222b may have a substantially arcuate shape in its cross-sectional view.

[0046] The vertical wall main body 222a extends substantially or generally in the vertical direction in the cross section shown in Figure 4. The vertical wall main body 222a may have a substantially linear shape when viewed in cross section. In the example of Figure 4, the end of the vertical wall main body 222a on the side opposite to the top plate 21 is a free end. However, a flange portion (not shown) may be continuously provided at the end of the vertical wall main body 222a on the side opposite to the top plate 21.

[0047] The vertical wall 222 has a height H at the curved portion 242. The height H is the distance in the vertical direction from the R stop on the top plate 21 side of the ridge line portion 222b on the outer surface of the arm member 20 to the free end of the vertical wall main body 222a or the flange portion, in the cross section of the curved portion 242 along the plate thickness direction of the vertical wall 222. The height H is, for example, 10 mm or more, preferably 15 mm or more. The height H is, for example, 60 mm or less.

[0048] The plate thickness of the end portion of the vertical wall 222 at the curved portion 242 may be smaller than the plate thickness of the top plate 21 obtained at the maximum test force in the tensile test of the top plate 21. More specifically, the plate thickness of the end portion of the vertical wall 222 at the curved portion 242 may be smaller than the plate thickness of the top plate 21 (test piece) measured at the maximum test force in the tensile test of the top plate 21 conforming to JIS Z 2241:2022. The end portion here is the end portion of the vertical wall 222 on the side opposite to the top plate 21. The plate thickness of the end portion of the vertical wall 222 at the curved portion 242 is measured, for example, at a position within 1.0 mm from the free end or the flange portion of the vertical wall 222 toward the top plate 21 side.

[0049] The surface cross-sectional hardness of the vertical wall 222 in the curved section 242 may be 1.13 times or more the surface cross-sectional hardness of the top plate 21. The surface cross-sectional hardness of the vertical wall 222 can be measured by cutting a test piece having a cross-section along the thickness direction of the vertical wall 222 from the curved section 242 and performing a Vickers hardness test in accordance with JIS Z 2244-1:2024 using this test piece. Similarly, the surface cross-sectional hardness of the top plate 21 can be measured by cutting a test piece having a cross-section along the thickness direction of the top plate 21 from the top plate 21 and performing a Vickers hardness test in accordance with JIS Z 2244-1:2024 using this test piece. In the Vickers hardness test, the Vickers hardness (HV) is measured by applying a test force of 100 gf (0.98 N) at a position 0.1 mm from the surface toward the center of the plate thickness in the cross-section of the vertical wall 222 or the top plate 21. The obtained Vickers hardness represents the surface cross-sectional hardness of the vertical wall 222 and the surface cross-sectional hardness of the top plate 21 in the curved section 242.

[0050] The vertical wall 223 includes a vertical wall body 223a and a ridge portion 223b. In the arm member 20, the ridge portion 223b is the corner portion between the top plate 21 and the vertical wall body 223a. That is, the ridge portion 223b is positioned between the top plate 21 and the vertical wall body 223a and is continuous with both the top plate 21 and the vertical wall body 223a. The ridge portion 223b may have a substantially arc shape in cross-sectional view.

[0051] The vertical wall body 223a extends substantially or generally in the vertical direction in the cross-section shown in Figure 4. The vertical wall body 223a may have a substantially straight shape in its cross-sectional view. In the cross-section shown in Figure 4, the vertical wall body 223a may be parallel to or disparallel to the vertical wall body 222a. In the example in Figure 4, the end of the vertical wall body 223a opposite to the top plate 21 is a free end. However, a flange portion (not shown) may be continuously provided at the end of the vertical wall body 223a opposite to the top plate 21.

[0052] In the top plate 21 of the arm member 20, a cylindrical peripheral wall 25 may be provided around the through hole 23 for the tool. The through hole 23 and the peripheral wall 25 can be formed by burring the top plate 21. The peripheral wall 25 rises from the periphery of the through hole 23 towards the reinforcing member body 31.

[0053] The reinforcing member body 31 is separated vertically from the top plate 21 of the arm member 20. The reinforcing member body 31 is joined to the vertical walls 222 and 223 of the arm member 20. More specifically, the reinforcing member body 31 is joined to the curved portion 242 of the vertical wall 222 and the curved portion 243 of the vertical wall 223, respectively. The reinforcing member body 31 is joined to the vertical walls 222 and 223, for example, by welding.

[0054] In the example shown in Figure 4, the reinforcing member body 31 is joined to the inner surfaces of the vertical walls 222 and 223. That is, the reinforcing member body 31 is joined to the vertical walls 222 and 223 on the side of the top plate 21, rather than at the free ends or flange portions of the vertical walls 222 and 223. In the cross-section shown in Figure 4, both end faces of the reinforcing member body 31 are joined to the inner surfaces of the vertical walls 222 and 223 in a butt-to-butt position. However, the reinforcing member body 31 may also be joined to the inner surfaces of the vertical walls 222 and 223 with both ends bent upward or downward.

[0055] In the reinforcing member body 31, the through hole 33 is provided corresponding to the through hole 23 of the arm member 20. The through hole 33 penetrates the reinforcing member body 31 in the thickness direction. As shown in Figure 4, at least at the locations of the through holes 23, 33, the cross-section of the structural member 100 formed by the reinforcing member body 31 and the arm member 20 is an open cross-section.

[0056] Figure 5 shows a cross-section of the structural member 100 when it is cut vertically along the center of the through holes 23 and 33 so as to pass through the flange 32 (Figure 2) of the reinforcing member 30.

[0057] In this embodiment, the reinforcing member 30 is provided so as to straddle the through hole 23 of the arm member 20. In the cross-section shown in Figure 5, the flanges 32 of the reinforcing member 30 are positioned on both sides of the through hole 23. Each of the flanges 32 protrudes from the reinforcing member body 31 toward the top plate 21 of the arm member 20.

[0058] Each of the flanges 32 may include a flange body 321 and a ridge portion 322. In the reinforcing member 30, the ridge portion 322 is the corner portion between the reinforcing member body 31 and the flange body 321. That is, the ridge portion 322 is positioned between the reinforcing member body 31 and the flange body 321 and is continuous with both the reinforcing member body 31 and the flange body 321. The ridge portion 322 may have a substantially arc shape in its cross-sectional view. The flange body 321 may have a substantially straight shape in its cross-sectional view. In the cross-section shown in Figure 5, the flange body 321 extends substantially or generally in the vertical direction. In its cross-sectional view, the flange body 321 may extend parallel to the vertical direction or may be inclined with respect to the vertical direction.

[0059] Each of the flanges 32 is joined to the top plate 21 of the arm member 20. Each flange 32 is joined to the top plate 21, for example, by welding. In the example in Figure 5, the flanges 32 are joined to the top plate 21 with the end face of the flange body 321 abutting against the inner surface of the top plate 21. However, the flanges 32 may also be joined to the inner surface of the top plate 21 with the end of the flange body 321 bent.

[0060] Referring to Figures 5 and 6, in this embodiment, the flanges 32 are provided on the end edge 311 on the mounting portion 11 side and the end edge 312 on the mounting portion 13 side of the reinforcing member body 31. The flanges 32 are continuous with the end edges 311 and 312 of the reinforcing member body 31. As shown in Figure 6, when the arm member 20 is divided equally along its longitudinal direction into a region R1 on the mounting portion 11 side, a region R2 on the mounting portion 13 side, and an intermediate region R3 located between regions R1 and R2, each of the end edges 311 and 312 of the reinforcing member body 31 and each flange 32 are arranged within the intermediate region R3.

[0061] Referring to Figure 6, the longitudinal direction of the arm member 20 refers to the direction in which the vertical wall 223 extends in a plan view of the structural member 100. By dividing the arm member 20 with imaginary lines (dotted lines in Figure 6) that extend along the normal direction of the vertical wall 223 so as to divide the vertical wall 223 into three equal parts in a plan view of the structural member 100, regions R1, R2, and R3 can be identified. In the example in Figure 6, the edges 311 and 312 of the reinforcing member body 31 are arranged to intersect the longitudinal direction of the arm member 20 in a plan view of the structural member 100.

[0062] In this embodiment, in a plan view of the structural member 100, the entire reinforcing member 30 is positioned within the intermediate region R3 of the arm member 20. The reinforcing member body 31 is joined to the vertical walls 222 and 223 of the arm member 20 within the intermediate region R3. The reinforcing member body 31 is joined to the curved portion 242 of the vertical wall 222 and the curved portion 243 of the vertical wall 223 of the arm member 20 within the intermediate region R3. The reinforcing member body 31 may also be joined to the vertical wall 221 of the arm member 20. The reinforcing member body 31 is joined to the vertical wall 221, for example, by welding. However, the reinforcing member body 31 does not have to be joined to the vertical wall 221.

[0063] The curved portion 242 of the vertical wall 222 is located within the intermediate region R3 of the arm member 20. At least a portion of the curved portion 243 of the vertical wall 223 is located within the intermediate region R3 of the arm member 20. The reinforcing member body 31 is joined to the curved portions 242 and 243. The radius of curvature of the curved portion 242 may be smaller than the radius of curvature of the curved portion 243. In a plan view of the structural member 100, the curved portion 242 extends from the mounting portion 12 side to the mounting portion 13 side with a radius of curvature of, for example, 10 mm or more and 60 mm or less. In a plan view of the structural member 100, the curved portion 242 may have a radius of curvature of 15 mm or more, or a radius of curvature of 20 mm or more. On the other hand, in a plan view of the structural member 100, the curved portion 243 extends from the mounting portion 11 side to the mounting portion 13 side with a radius of curvature of 100 mm or more and 600 mm or less.

[0064] The radius of curvature of the curved sections 242 and 243 can be determined, for example, as follows. That is, in a plan view of the structural member 100, evaluation points can be placed at intervals of, for example, 5.0 mm on the R-end of the ridge section 222b on the top plate 21 side, and the radius of curvature of the arc passing through three consecutive evaluation points can be taken as the radius of curvature of the vertical wall 222 at the positions of these evaluation points. Similarly, in a plan view of the structural member 100, evaluation points can be placed at intervals of, for example, 5.0 mm on the R-end of the ridge section 223b on the top plate 21 side, and the radius of curvature of the arc passing through three consecutive evaluation points can be taken as the radius of curvature of the vertical wall 223 at the positions of these evaluation points. For example, in the vertical wall 222, the range in which evaluation points with a radius of curvature of 10 mm or more and 60 mm or less are consecutive is the curved section 242. For example, in the vertical wall 223, the range in which evaluation points with a radius of curvature of 100 mm or more and 600 mm or less are consecutive is the curved section 243.

[0065] The flange 32 of the reinforcing member 30 is joined to the top plate 21 of the arm member 20 within the intermediate region R3. One flange 32 is continuous with the end edge 311 on the mounting portion 11 side of the reinforcing member body 31 between the vertical wall 223 and vertical wall 221 or 222 of the arm member 20. This flange 32 may extend along the end edge 311 of the reinforcing member body 31 to reach one or more of the vertical walls 221, 222, and 223, or it may not reach the vertical walls 221, 222, and 223.

[0066] The other flange 32 is continuous with the end edge 312 on the mounting portion 13 side of the reinforcing member body 31 between the vertical walls 222 and 223 of the arm member 20. This flange 32 may extend along the end edge 312 of the reinforcing member body 31 so as to reach at least one of the vertical walls 222 and 223, or it may not reach the vertical walls 222 and 223.

[0067] In the structural member 100 according to this embodiment, the height H [mm] of the vertical wall 222 in the curved portion 242, the radius of curvature R [mm] of the curved portion 242, and the Vickers hardness Hv [HV] of the top plate 21 (arm member 20) can satisfy the following equation (1): 10 ≤ (-0.000007Hv ２ +0.002Hv+0.3495)R+(0.0002Hv ２ -0.0929Hv+12.799)≦H≦60 (1)

[0068] The Vickers hardness Hv of the top plate 21 used in formula (1) can be measured as follows. Specifically, a test piece having a cross-section along the thickness direction of the top plate 21 is cut from the flat part of the top plate 21, and a Vickers hardness test is performed using this test piece in accordance with JIS Z 2244-1:2024. In the Vickers hardness test, the Vickers hardness is measured with a test force of 100 gf (0.98 N) at a position 1 / 4 of the thickness from the surface of the top plate 21 (test piece) in the cross-section. The obtained Vickers hardness is the Vickers hardness Hv of the top plate 21.

[0069] Equation (1) was derived based on the results of a test (stretch flange forming test) in which a saddle-shaped molded product simulating the shape of the curved portion 242, which is the stretch flange portion, was obtained by press forming. Specifically, the stretch flange forming test was conducted while changing the radius of curvature R in a top view of the stretch flange portion corresponding to the curved portion 242, and the limit height at which the stretch flange end could be formed without fracture was investigated for multiple Vickers hardnesses Hv. Then, for heights H 30% lower than the limit height, an approximate formula using the radius of curvature R was derived for each Vickers hardness Hv. The data for heights 30% lower than the limit height obtained in the stretch flange forming test and their approximate lines are shown in Figure 7A.

[0070] Furthermore, as shown in Figure 7B, an approximation formula using Vickers hardness Hv was created for the slope of the approximation line (approximation formula) shown in Figure 7A. Also, as shown in Figure 7C, an approximation formula using Vickers hardness Hv was created for the intercept of the approximation line (approximation formula) shown in Figure 7A. Then, by using the approximation formula shown in Figure 7B as the coefficient of the radius of curvature R and the approximation formula shown in Figure 7C as the intercept, the above equation (1) was obtained.

[0071] [Effect] When a vehicle incorporating the structural member 100 is in motion or in the event of a collision, a load (backward force) in the longitudinal direction may be applied to the mounting portion 11 on the wheel side. In this case, the arm member 20 is prone to buckling in its intermediate region R3. In contrast, in the structural member 100 according to this embodiment, a reinforcing member 30 is placed in the intermediate region R3 of the arm member 20, and the intermediate region R3 is reinforced by the reinforcing member 30. More specifically, the flange 32 of the reinforcing member 30 is joined to the top plate 21 of the arm member 20 in the intermediate region R3. As a result, when a load in the longitudinal direction is applied to the mounting portion 11, out-of-plane deformation of the top plate 21 is suppressed, and buckling of the arm member 20 is less likely to occur.

[0072] In the structural member 100 according to this embodiment, the reinforcing member 30 is provided in a relatively narrow area on the arm member 20. More specifically, the end edges 311 and 312 of the reinforcing member body 31 and the flange 32 continuous with the end edges 311 and 312 are arranged in the intermediate region R3 of the arm member 20, where buckling is particularly likely to occur. As a result, the reinforcing member 30 does not become large, and the weight of the structural member 100 does not increase significantly due to the reinforcing member 30. Thus, out-of-plane deformation of the top plate 21 and buckling of the arm member 20 can be suppressed without significantly increasing the weight of the structural member 100. Therefore, the structural member 100 according to this embodiment can improve the strength against external forces in a weight-efficient manner.

[0073] In the structural member 100 according to this embodiment, flanges 32 are continuous to both end edges 311 and 312 of the reinforcing member body 31, and each flange 32 is joined to the top plate 21 of the arm member 20. As a result, out-of-plane deformation of the top plate 21 of the arm member 20 is more easily suppressed. However, the flange 32 may be continuously provided on only one of the end edges 311 and 312 of the reinforcing member body 31.

[0074] <Second Embodiment> Figure 8 is a plan view of the structural member 100A according to this embodiment. The structural member 100A differs from the structural member 100 according to the first embodiment in that it further comprises an auxiliary reinforcing member 50.

[0075] The auxiliary reinforcing member 50 is positioned on the mounting portion 11 side relative to the reinforcing member 30. At least a portion of the auxiliary reinforcing member 50 may be positioned in the region R1 on the mounting portion 11 side of the arm member 20.

[0076] The auxiliary reinforcing member 50 is joined to the arm member 20. The auxiliary reinforcing member 50 is joined to the reinforcing member 30 on the mounting portion 11 side, for example, to the inner curved vertical wall 223 of the arm member 20. In the example in Figure 8, the auxiliary reinforcing member 50 is separated from the outer curved vertical wall 221 of the arm member 20. However, the auxiliary reinforcing member 50 may be joined to the outer curved vertical wall 221 instead of or in addition to the vertical wall 223. The auxiliary reinforcing member 50 is also joined to the top plate 21 of the arm member 20 on the mounting portion 11 side of the reinforcing member 30. The auxiliary reinforcing member 50 is joined to the arm member 20, for example, by welding.

[0077] In the example shown in Figure 8, the auxiliary reinforcing member 50 is provided integrally with the reinforcing member 30. The auxiliary reinforcing member 50 is continuous with respect to the reinforcing member 30 on the vertical wall 223 side of the arm member 20 and extends to the mounting portion 11. However, the configuration of the auxiliary reinforcing member 50 is not limited to this. The auxiliary reinforcing member 50 may be a separate component from the reinforcing member 30. That is, the auxiliary reinforcing member 50 may be separated from the reinforcing member 30 and positioned on the mounting portion 11 side of the reinforcing member 30. Furthermore, the auxiliary reinforcing member 50 does not necessarily have to extend to the mounting portion 11.

[0078] In the structural member 100A according to this embodiment, the arm member 20 is reinforced by an auxiliary reinforcing member 50 in addition to the reinforcing member 30. In this case, when a load in the longitudinal direction is applied to the mounting portion 11 during vehicle travel or collision, buckling of the arm member 20 becomes less likely. Therefore, the strength of the structural member 100A against external forces is further improved.

[0079] <Third Embodiment> Figure 9 is a plan view of the structural member 100B according to this embodiment. The structural member 100B differs from the structural member 100A according to the second embodiment in that it further comprises an auxiliary reinforcing member 60.

[0080] The auxiliary reinforcing member 60 is positioned on the mounting portion 13 side relative to the reinforcing member 30. For example, the auxiliary reinforcing member 60 is positioned within the region R2 on the mounting portion 13 side of the arm member 20.

[0081] The auxiliary reinforcing member 60 is joined to the arm member 20. The auxiliary reinforcing member 60 is joined to the reinforcing member 30 on the mounting portion 13 side, for example, to the outer curved vertical wall 222 of the arm member 20. In the example in Figure 9, the auxiliary reinforcing member 60 is separated from the inner curved vertical wall 223 of the arm member 20. However, the auxiliary reinforcing member 60 may be joined to the inner curved vertical wall 223 instead of or in addition to the vertical wall 222. The auxiliary reinforcing member 60 is also joined to the top plate 21 of the arm member 20 on the mounting portion 13 side of the reinforcing member 30. The auxiliary reinforcing member 60 is joined to the arm member 20, for example, by welding.

[0082] In the example shown in Figure 9, the auxiliary reinforcing member 60 is provided separately from the reinforcing member 30. That is, the auxiliary reinforcing member 60 is separated from the reinforcing member 30 and positioned on the mounting portion 13 side relative to the reinforcing member 30. Preferably, the auxiliary reinforcing member 60 is joined to the arm member 20 near the mounting portion 13. However, the auxiliary reinforcing member 60 may be provided continuously with the reinforcing member 30.

[0083] In the structural member 100B according to this embodiment, the arm member 20 is reinforced by an auxiliary reinforcing member 60 in addition to the reinforcing member 30 and the auxiliary reinforcing member 50. In this case, when a load in the longitudinal direction is applied to the mounting portion 11 during vehicle travel or collision, buckling of the arm member 20 becomes less likely. Therefore, the strength of the structural member 100B against external forces is further improved.

[0084] The structural member 100B according to this embodiment includes auxiliary reinforcing members 50 and 60. However, the structural member 100B does not necessarily have to include the auxiliary reinforcing member 50 on the mounting portion 11 side. In other words, the structural member 100 according to the first embodiment can also be fitted with only the auxiliary reinforcing member 60 of this embodiment.

[0085] In each embodiment, the wheel-side mounting portion 11 includes a recess 111 provided on the end face of the top plate 21. However, as shown in Figure 10, the mounting portion 11 may include a burring portion 112 instead of the recess 111. The burring portion 112 is formed in the top plate 21. In the mounting portion 11, the ball joint 70 is inserted into the burring portion 112.

[0086] While embodiments relating to this disclosure have been described above, this disclosure is not limited to the embodiments described above, and various modifications are possible as long as they do not deviate from its spirit.

[0087] The present disclosure will be further described below with reference to examples. However, the present disclosure is not limited to the following examples.

[0088] To confirm the effects of this disclosure, structural members 100, 100A, and 100B having the shapes described in the above embodiments were analyzed using commercially available structural analysis software (Abaqs, manufactured by Dassault Systèmes) (Examples 1 to 3). More specifically, structural analysis was performed assuming an input (collision) of a load (backward force) directed from the front to the rear of the vehicle, and the reaction force to the collision load was investigated. For comparison, the same structural analysis was performed on the arm member 20 that was not reinforced by the reinforcing member 30 and the auxiliary reinforcing members 50 and 60, and the reaction force to the collision load was investigated (Comparative Example).

[0089] In this analysis, the material of the arm member 20 was assumed to be a steel plate with a tensile strength of 980 MPa and a plate thickness of 2.6 mm. The material of the reinforcing member 30 and the auxiliary reinforcing members 50 and 60 was assumed to be a steel plate with a tensile strength of 980 MPa and a plate thickness of 2.3 mm. Figure 11 shows the weight efficiency of the maximum reaction force against the impact load for each example and comparative example. The weight efficiency is the value obtained by dividing the maximum reaction force [kN] by the weight of the structural member [kg].

[0090] Example 1 corresponds to the structural member 100 (Figure 3) according to the first embodiment. Examples 2 and 3 correspond to the structural member 100A (Figure 8) according to the second embodiment and the structural member 100B (Figure 9) according to the third embodiment, respectively. As shown in Figure 11, in Example 1, in which the arm member 20 is reinforced with the reinforcing member 30, the weight efficiency was significantly increased compared to the comparative example in which the arm member 20 is not reinforced. In Example 2, in which the arm member 20 is reinforced with the reinforcing member 30 and the auxiliary reinforcing member 50, the weight efficiency was greater than that of Example 1. In Example 3, in which the arm member 20 is reinforced with the reinforcing member 30 and the auxiliary reinforcing members 50 and 60, the weight efficiency was greater than that of Example 2.

[0091] This analysis confirmed that even without extensively providing the reinforcing member 30 on the arm member 20, the weight efficiency of the maximum reaction force during a vehicle collision increases, and the strength against external forces is improved in a weight-efficient manner. More specifically, even when only the intermediate region R3 of the arm member 20 is reinforced with the reinforcing member 30, as in Example 1, the weight efficiency increases significantly. By providing an auxiliary reinforcing member 50 or 60 in addition to the reinforcing member 30, the weight efficiency can be further increased.

[0092] 100, 100A, 100B: Structural members 11: Mounting part (first mounting part) 12: Mounting part (second mounting part) 13: Mounting part (third mounting part) 20: Arm member 21: Top plate 221: Vertical wall (first vertical wall) 222: Vertical wall (second vertical wall) 223: Vertical wall (third vertical wall) 30: Reinforcement member 31: Reinforcement member body 311, 312: Edge 32: Flange 50: Auxiliary reinforcement member (first auxiliary reinforcement member) 60: Auxiliary reinforcement member (second auxiliary reinforcement member) 242, 243: Curved part R1: Region (first region) R2: Region (second region) R3: Intermediate region

Claims

1. A structural member for a vehicle, comprising: a first mounting portion for attaching the wheels of the vehicle; a second mounting portion and a third mounting portion for attaching the body of the vehicle, respectively; an arm member including a first vertical wall extending from the first mounting portion side to the second mounting portion side; a second vertical wall extending from the second mounting portion side to the third mounting portion side; a third vertical wall extending from the first mounting portion side to the third mounting portion side; and a top plate continuous with each of the first, second, and third vertical walls; a reinforcing member body facing the top plate with a gap between them and joined to each of the second and third vertical walls; and a reinforcing member including a flange continuous with at least one of the end edge of the reinforcing member body on the first mounting portion side and the end edge on the third mounting portion side, and joined to the top plate; A structural member in which, when the arm member is divided equally along the longitudinal direction of the arm member into a first region on the side of the first mounting portion, a second region on the side of the third mounting portion, and an intermediate region located between the first region and the second region, each of the edges of the reinforcing member body and the flange are arranged within the intermediate region.

2. A structural member according to claim 1, wherein the flange is provided on each of the edges of the reinforcing member body.

3. A structural member according to claim 1, wherein the reinforcing member body is further joined to the first vertical wall.

4. A structural member according to claim 1, further comprising: a first auxiliary reinforcing member disposed on the first mounting portion side with respect to the reinforcing member and joined to the arm member.

5. A structural member according to claim 1, further comprising: a second auxiliary reinforcing member disposed on the third mounting portion side with respect to the reinforcing member and joined to the arm member.

6. A structural member according to claim 1, wherein the top plate has a Vickers hardness of 184 HV or more, and the second vertical wall includes a curved portion that curves concavely inward from the arm member in a plan view of the structural member and has a radius of curvature of 10 mm or more and 60 mm or less.

7. A structural member according to claim 1, wherein the second vertical wall includes a curved portion that curves concavely inward of the arm member in a plan view of the structural member, and the surface cross-sectional hardness of the second vertical wall in the curved portion is 1.13 times or more the surface cross-sectional hardness of the top plate.

8. A structural member according to claim 6 or 7, wherein the thickness of the second vertical wall in the curved portion opposite to the top plate is smaller than the thickness of the top plate obtained at the maximum test force in a tensile test of the top plate.

9. A structural member according to claim 6 or 7, wherein when the height of the second vertical wall in the curved portion is H [mm], the radius of curvature of the curved portion in a plan view of the structural member is R [mm], and the Vickers hardness of the top plate is Hv [HV], the height H, the radius of curvature R, and the Vickers hardness Hv satisfy the following equation: 10 ≤ (-0.000007Hv ２ +0.002Hv+0.3495)R+(0.0002Hv ２ -0.0929Hv+12.799)≦H≦60

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