structural members

Abstract

A structural member for a vehicle that can reduce air resistance without using additional parts. [Solution] A structural member (100, 100A, 100B) includes an arm portion (10, 10A, 10B). The arm portion (10, 10A, 10B) includes a top plate (11, 11B), a first vertical wall (12, 12A, 12B), and a second vertical wall (13, 13B). The first vertical wall (12, 12A, 12B) extends downward from the top plate (11, 11B) so that its lower end is located forward relative to the top plate (11, 11B). The first vertical wall (12, 12A, 12B) includes a front surface (121), a back surface (122), and a lower end surface (123, 123A, 123B). The lower end surfaces (123, 123A, 123B) include a straight portion (123a) and a curved portion (123b). The straight portion (123a) slopes downward toward the rear surface (122). The curved portion (123b) connects the front surface (121) and the straight portion (123a).

Description

[Technical Field]

[0001] The present disclosure relates to structural members for vehicles. [Background technology]

[0002] Suspension arms (links) are used as a type of structural member in vehicles such as automobiles. For example, Patent Document 1 discloses a lower arm, which is a suspension arm. The lower arm in Patent Document 1 is formed by pressing a metal plate. This lower arm includes a horizontal portion and a vertical portion formed by bending the peripheral edge of the horizontal portion downward. In the lower arm in Patent Document 1, a reverse flange is provided on the lower edge of each vertical portion. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 3725031 Summary of the Invention [Problem to be solved by the invention]

[0004] When a vehicle runs, a large amount of energy (fuel or electricity) is consumed due to air resistance. In particular, in electric vehicles, energy consumption due to air resistance accounts for nearly half of the total energy consumption. In response to this, structural members such as lower arms are sometimes fitted with plastic covers to flatten their undersides and reduce air resistance. However, attaching additional parts such as plastic covers to structural members increases the cost of the vehicle. Furthermore, the use of additional parts increases the volume occupied by the structural members in the vehicle, which may put the structural members at a disadvantage in terms of design space.

[0005] An object of the present disclosure is to provide a structural member for a vehicle that can reduce air resistance without using additional parts. [Means for solving the problem]

[0006] A structural member for a vehicle according to the present disclosure includes an arm portion. The arm portion includes a top plate, a first vertical wall, and a second vertical wall. The first vertical wall is continuous with the top plate. The second vertical wall is continuous with the top plate on the opposite side of the first vertical wall. The first vertical wall is positioned in front of the top plate when the structural member is attached to the vehicle. The first vertical wall extends downward from the top plate so that its lower end is located forward relative to the top plate when viewed in a cross section of the arm portion. The first vertical wall includes a front surface, a back surface, and a lower end surface. The lower end surface connects the front surface and the back surface. The lower end surface includes a straight portion and a curved portion. The straight portion is linear when viewed in a cross section of the arm portion and slopes downward toward the back surface. The curved portion is curved in a convex shape outward from the first vertical wall when viewed in a cross section of the arm portion, and connects the front surface and the straight portion. [Effects of the Invention]

[0007] According to the vehicle structural member of the present disclosure, air resistance can be reduced without using additional parts. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a top view of a structural member according to each embodiment. [Figure 2] FIG. 2 is a cross-sectional view of an arm portion included in the structural member according to the first embodiment. [Figure 3] FIG. 3 is a partially enlarged cross-sectional view of the arm portion shown in FIG. [Figure 4] FIG. 4 is a cross-sectional view of an arm portion included in a structural member according to the second embodiment. [Figure 5] FIG. 5 is a partially enlarged cross-sectional view of the arm portion shown in FIG. [Figure 6] FIG. 6 is a cross-sectional view of an arm portion included in a structural member according to a modified example of each embodiment. [Figure 7] FIG. 7 is a graph showing the resistance of the comparative example, the control example, and the working example. DETAILED DESCRIPTION OF THE INVENTION

[0009] A structural member for a vehicle according to an embodiment includes an arm portion. The arm portion includes a top plate, a first vertical wall, and a second vertical wall. The first vertical wall is continuous with the top plate. The second vertical wall is continuous with the top plate on the opposite side of the first vertical wall. The first vertical wall is positioned in front of the top plate when the structural member is attached to the vehicle. The first vertical wall extends downward from the top plate so that its lower end is located forward relative to the top plate when viewed in a cross section of the arm portion. The first vertical wall includes a front surface, a back surface, and a lower end surface. The lower end surface connects the front surface and the back surface. The lower end surface includes a straight portion and a curved portion. The straight portion is linear when viewed in a cross section of the arm portion and slopes downward toward the back surface. The curved portion is curved and convex outward from the first vertical wall when viewed in a cross section of the arm portion, and connects the front surface and the straight portion (first configuration).

[0010] When the structural member according to the first configuration is mounted on a vehicle, the first vertical wall of the arm portion is positioned in front of the top panel. The lower end surface of the first vertical wall is connected to the front surface of the first vertical wall via a curved portion and includes a straight portion that descends toward the rear surface of the first vertical wall. This lower end surface regulates the airflow below the arm portion as air passes from the front to the rear of the arm portion while the vehicle is traveling. This facilitates reducing the air resistance of the structural member while the vehicle is traveling.

[0011] Therefore, according to the first configuration, air resistance can be reduced by the shape of the structural member itself, without using any additional parts.

[0012] In the structural member according to the first configuration, in a cross section of the arm portion, an angle formed by a normal to the front surface and the longitudinal direction of the vehicle may be equal to or greater than 5° and equal to or less than 20° (second configuration).

[0013] In the structural member according to the first or second configuration, the curved portion in the cross section of the arm portion may have a radius of curvature that is 1 / 5 or more of the plate thickness of the first vertical wall (third configuration).

[0014] In the third configuration, the radius of curvature of the curved portion at the lower end surface of the first vertical wall is ensured to be 1 / 5 or more of the plate thickness of the first vertical wall. In this case, the air flow below the arm portion is more easily regulated, and the air resistance of the structural member is more easily reduced.

[0015] In the structural member according to any one of the first to third configurations, the straight portion may extend along the thickness direction of the first vertical wall in a cross section of the arm portion (fourth configuration).

[0016] In the structural member according to any one of the first to third configurations, the straight portion may be inclined with respect to the thickness direction of the first vertical wall in the cross section of the arm portion (fifth configuration).

[0017] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In these drawings, the same or equivalent components are designated by the same reference numerals, and the same description will not be repeated.

[0018] First Embodiment [Structural Members] FIG. 1 is a top view of a structural member 100 according to an embodiment. The structural member 100 is used in a vehicle such as an automobile. The structural member 100 is typically a suspension arm. In this embodiment, an example will be described in which the structural member 100 is a lower arm (front lower arm), which is a type of suspension arm.

[0019] The structural member 100 is formed, for example, by pressing a metal plate. The metal plate may be a steel plate or a non-ferrous metal plate such as an aluminum alloy plate. The structural member 100 includes arm portions 10 and 20. The arm portion 10 extends substantially or generally in the left-right direction of the vehicle when the structural member 100 is installed in the vehicle. The arm portion 20 is provided continuous with the arm portion 10. When the structural member 100 is installed in the vehicle, the arm portion 20 extends from the arm portion 10 toward the rear of the vehicle.

[0020] The structural member 100 is attached to the vehicle body and wheels. In this embodiment example, the structural member 100 includes mounting portions 30, 40, and 50. The structural member 100 is attached to the vehicle body or wheels at the mounting portions 30, 40, and 50.

[0021] The mounting portion 30 is provided at the outer end of the arm portion 10 in the left-right direction of the vehicle. A ball joint may be attached to the mounting portion 30. The arm portion 10 is attached to a wheel, for example, via the ball joint of the mounting portion 30 and a steering knuckle.

[0022] The mounting portion 40 is provided on the inner end of the arm portion 10 in the left-right direction of the vehicle. The mounting portion 40 may include a cylindrical collar 41. A bushing is press-fitted into the collar 41. The arm portion 10 is attached to the vehicle body via, for example, the bushing and a suspension member.

[0023] The mounting portion 50 is disposed behind the mounting portion 40 when the structural member 100 is installed in the vehicle. In the example of FIG. 1, the mounting portion 50 is a through-hole that passes through the arm portion 20 in the vertical direction. A bushing may be press-fitted into the mounting portion 50. The arm portion 20 is attached to the vehicle body via, for example, a bushing and a suspension member.

[0024] Figure 2 is a cross-sectional view of the arm portion 10 (cross-sectional view taken along line II-II in Figure 1). The cross-section of the arm portion 10 refers to a cross-section of the arm portion 10 taken perpendicularly to a direction corresponding to the left-right direction of the vehicle in which the structural member 100 is incorporated. Hereinafter, in the structural member 100, the direction corresponding to the left-right direction of the vehicle may be simply referred to as the left-right direction. Similarly, in the structural member 100, the directions corresponding to the front-rear and up-down directions of the vehicle may be simply referred to as the front-rear and up-down directions.

[0025] 2 shows a cross section of the arm unit 10 at the midpoint in the left-right direction between the center positions of the mounting unit 30 and the mounting unit 40. In this embodiment, the center position of the mounting unit 30 is the center position of the ball joint attached to the mounting unit 30. The center position of the mounting unit 40 is the position of the central axis (fastening point) of the bushing attached to the mounting unit 40.

[0026] Referring to FIG. 2, arm portion 10 of structural member 100 includes a top plate 11 and vertical walls 12 and 13. As shown in FIG.

[0027] The top plate 11 is disposed so as to intersect with the vertical direction of the vehicle. The top plate 11 may be disposed substantially perpendicular to the vertical direction of the vehicle, or may be tilted with respect to the direction perpendicular to the vertical direction. In the example of this embodiment, the top plate 11 is tilted with respect to the direction perpendicular to the vertical direction so that the rear end side is positioned higher than the front end side.

[0028] In this embodiment, the table top 11 includes table top bodies 111, 112 and a groove portion 113. The groove portion 113 is a portion of the table top 11 that has a recessed shape downward relative to the table top bodies 111, 112. In a cross-sectional view of the arm portion 10, the groove portion 113 is disposed between the table top bodies 111 and 112. The table top body 111 is disposed in front of the groove portion 113. The table top body 112 is disposed behind the groove portion 113.

[0029] In the example of FIG. 2, the table top body 111 has an upwardly convex curved shape as a whole in a cross-sectional view of the arm section 10. On the other hand, the table top body 112 includes a portion that is substantially straight in a cross-sectional view of the arm section 10. However, the shapes of the table top bodies 111 and 112 are not limited to the example of this embodiment. The table top body 111 may include a straight portion in a cross-sectional view of the arm section 10, or the table top body 112 may have an overall curved shape in a cross-sectional view of the arm section 10. Furthermore, the table top 11 does not have to be provided with a groove portion 113.

[0030] The vertical wall 12 is positioned in front of the top plate 11 when the structural member 100 is installed in the vehicle. The vertical wall 12 is continuous with the top plate 11 in front of the top plate 11. In this embodiment, the vertical wall 12 is provided continuous with the top plate main body 111 of the top plate 11. When the structural member 100 is installed in the vehicle, the vertical wall 12 extends substantially or approximately in the left-right direction of the vehicle (the depth direction of the paper in FIG. 2). The vertical wall 12 may extend from the wheel-side mounting portion 30 (FIG. 1) to the vehicle body-side mounting portion 40 (FIG. 1).

[0031] The vertical wall 12 extends downward from the tabletop 11 so that its lower end is located forward relative to the tabletop 11 when viewed in cross section of the arm portion 10. That is, the vertical wall 12 is inclined in the vertical direction. The vertical wall 12 is inclined in the vertical direction so that it moves away from the vertical wall 13 as it extends downward from the tabletop 11. The vertical wall 12 includes a front surface 121, a back surface 122, and a bottom surface 123.

[0032] The front surface 121 is a surface that faces the front of the vehicle when the structural member 100 is installed in the vehicle. The front surface 121 may have a substantially linear shape in a cross section of the arm unit 10. When viewed in the cross section of the arm unit 10, the front surface 121 is inclined in the vertical direction so that its lower end is located forward of its upper end.

[0033] The rear surface 122 is a surface that faces the rear of the vehicle when the structural member 100 is installed in the vehicle. The rear surface 122 is positioned rearward relative to the front surface 121. The rear surface 122 may have a substantially linear shape in a cross section of the arm unit 10. When viewed in the cross section of the arm unit 10, the rear surface 122 extends substantially parallel to the front surface 121. In other words, when viewed in the cross section of the arm unit 10, the rear surface 122, like the front surface 121, is inclined in the up-down direction so that its lower end is located forward relative to its upper end.

[0034] The lower end surface 123 is positioned below the top plate 11 when the structural member 100 is installed in a vehicle. The lower end surface 123 is the end surface on the free end side of the vertical wall 12. The lower end surface 123 connects the front surface 121 and the rear surface 122.

[0035] Fig. 3 is an enlarged view of the lower end surface 123 of the vertical wall 12 and its vicinity in the cross section of the arm portion 10 shown in Fig. 2. As shown in Fig. 3, the lower end surface 123 includes a straight portion 123a and a curved portion 123b.

[0036] The straight portion 123a has a substantially straight shape when viewed in a cross section of the arm portion 10. The straight portion 123a is a portion of the lower end surface 123 that extends with a radius of curvature that is 10.0 times or more the thickness t1 of the vertical wall 12. In the example of FIG. 3, the straight portion 123a extends along the thickness direction of the vertical wall 12 in the cross section of the arm portion 10. The thickness direction of the vertical wall 12 refers to a direction perpendicular to the front surface 121 (normal direction). The straight portion 123a is substantially parallel to the thickness direction of the vertical wall 12 in the cross section of the arm portion 10. However, because the vertical wall 12 is inclined with respect to the up-down direction, the straight portion 123a is inclined with respect to the front-to-back direction in the cross section of the arm portion 10. More specifically, the straight portion 123a descends toward the back surface 122. That is, the end (rear end) of the straight portion 123a on the rear surface 122 side is disposed below the end (front end) of the straight portion 123a on the front surface 121 side.

[0037] The curved portion 123b has a curved shape that convexly extends outward from the vertical wall 12 when viewed in a cross section of the arm unit 10. The curved portion 123b is a portion of the lower end surface 123 that extends with a radius of curvature that is 2.0 times or less the thickness t1 of the vertical wall 12. The curved portion 123b is disposed between the front surface 121 and the straight portion 123a. The curved portion 123b connects the front surface 121 and the straight portion 123a. It is preferable that the curved portion 123b smoothly connects to the front surface 121 and the straight portion 123a. That is, it is preferable that the front surface 121 and the straight portion 123a contact the curved portion 123b at both ends when viewed in a cross section of the arm unit 10. The end (rear end) of the curved portion 123b on the straight portion 123a side is disposed below the end (front end) of the curved portion 123b on the front surface 121 side. The straight portion 123a extends from the rear end of the curved portion 123b to the back surface 122 in the cross section of the arm portion 10.

[0038] In the cross section of the arm unit 10, when the angle φ formed by the normal line L1 of the front surface 121 of the vertical wall 12 with respect to the front-rear direction is defined as φ, the angle φ may be 5° or more and 20° or less. The angle φ may be 10° or more. In the cross section of the arm unit 10, when the angle θ1 formed by the straight line portion 123a of the lower end surface 123 with respect to the front-rear direction is defined as θ1, the angle θ1 is the sum of the angle φ and the angle formed by the straight line portion 123a with respect to the normal line L1 of the front surface 121. In this embodiment, since the straight line portion 123a is substantially parallel to the normal direction of the front surface 121, the angle θ1 of the straight line portion 123a coincides with the angle φ of the front surface 121. The angle φ of the front surface 121 can be measured in the cross section of the arm unit 10 at the midpoint in the left-right direction between the center position of the mounting portion 30 (FIG. 1) and the center position of the mounting portion 40 (FIG. 1). The angle φ can be measured with the structural member 100 attached to the vehicle. Alternatively, after the direction corresponding to the front-to-rear direction is identified with the structural member 100 attached to the vehicle, the structural member 100 can be removed from the vehicle and the angle φ measured.

[0039] In the cross section of the arm portion 10, the curved portion 123b has a radius of curvature R1. The radius of curvature R1 is, for example, 1 / 5 or more of the thickness t1 of the vertical wall 12. The radius of curvature R1 may be 1 / 3 or more of the thickness t1 of the vertical wall 12. The radius of curvature R1 is 2.0 times or less of the thickness t1, preferably 1.7 times or less of the thickness t1, and more preferably less than the thickness t1. Although not particularly limited, the thickness t1 of the vertical wall 12 may be 1.4 mm or more and 4.5 mm or less.

[0040] The thickness t1 of the vertical wall 12 and the radius of curvature R1 of the curved portion 123b can be measured in a cross section of the arm portion 10 taken between the center positions of the mounting portion 30 (FIG. 1) and the mounting portion 40 (FIG. 1). In other words, it is sufficient that a cross section of the arm portion 10 that satisfies the relationship between the thickness t1 and the radius of curvature R1 described above exists between the center positions of the mounting portion 30 and the mounting portion 40. The thickness t1 is determined as the average value of thicknesses measured at three locations in the cross section of the arm portion 10, within a range of 17 mm to 22 mm upward along the back surface 122 from the lower end of the back surface 122, and corresponding to the front surface 121. The thickness t1 is the distance between the front surface 121 and the back surface 122 in the normal direction of the front surface 121. The radius of curvature R1 of the curved portion 123b is the radius of an approximate circle that is tangent to the plane where the front surface 121 exists and the plane where the bottom surface 123 exists in the cross section of the arm portion 10, and that minimizes the error (root mean square) between the curved portion 123b and three points within the curved portion 123b. The plane where the front surface 121 exists is an approximate plane created from a point on the front surface 121 corresponding to a point 17 mm upward along the back surface 122 from the bottom end of the back surface 122, a point 5 mm upward along the front surface 121 from that point, and an intermediate point between these two points. The plane where the bottom surface 123 exists is an approximate plane created from the bottom end of the back surface 122, a point t1 / 2 forward from the bottom end of the back surface 122 along the bottom surface 123, and an intermediate point between these two points. The angle θ1 of the straight portion 123a can be measured in the cross section of the arm portion 10 where the plate thickness t1 and the radius of curvature R1 are measured.

[0041] 1 and 3, the straight line portion 123a and the curved line portion 123b are provided on the lower end surface 123 of the vertical wall 12 over a range of, for example, 70% or more of the length L. The length L of the vertical wall 12 is the distance in the left-right direction from the center position of the mounting portion 30 on the wheel side of the arm portion 10 to the center position of the mounting portion 40 on the vehicle body side. The straight line portion 123a and the curved line portion 123b may be formed on the lower end surface 123 over a range of 75% or more of the length L, or may be formed on the lower end surface 123 over a range of 80% or more of the length L. The straight line portion 123a and the curved line portion 123b are provided on the lower end surface 123 of the vertical wall 12 over a range of 100% or less of the length L. The straight line portion 123a and the curved line portion 123b may be provided on the lower end surface 123 over the entire length of the vertical wall 12.

[0042] The straight portion 123a and the curved portion 123b are typically formed before the arm portion 10 is formed. For example, the straight portion 123a can be formed in the blank before forming by punching the blank used to form the arm portion 10 from a metal strip or metal plate in the plate thickness direction. Alternatively, the curved portion 123b can be formed in the blank before forming by using a die to crush the corner portion between the portion of the blank corresponding to the front surface 121 and the end surface corresponding to the lower end surface 123 before or after punching. Alternatively, before punching the blank, the portion of the metal strip or metal plate that will become the lower end surface 123 can be pressed to form a predetermined shape, and then the metal strip or metal plate can be punched to form the straight portion 123a and the curved portion 123b in the blank before forming. After punching the blank, the end surfaces of the blank can be pressed, cut, or the like to form the straight portion 123a and the curved portion 123b in the blank before forming.

[0043] Returning to FIG. 2, the vertical wall 13 is positioned behind the top plate 11 when the structural member 100 is installed in the vehicle. The vertical wall 13 is continuous with the top plate 11 on the side opposite to the vertical wall 12. In this embodiment, the vertical wall 13 is provided continuous with the top plate main body 112 of the top plate 11. At least a portion of the vertical wall 13 extends substantially or approximately in the left-right direction of the vehicle (the depth direction of the paper in FIG. 2) when the structural member 100 is installed in the vehicle. The vertical wall 13 extends from the mounting portion 30 (FIG. 1) on the wheel side toward the mounting portion 40 (FIG. 1) on the vehicle body side. However, the vertical wall 13 does not have to reach the mounting portion 40.

[0044] The vertical wall 13 extends downward from the top plate 11 when viewed in a cross section of the arm portion 10. The vertical walls 12, 13 are connected by the top plate 11 at their upper ends but are separated at their lower ends. Therefore, the cross section of the arm portion 10 has an open cross section that opens on the opposite side of the top plate 11. The vertical wall 13 may be substantially parallel to the vertical wall 12 when viewed in a cross section of the arm portion 10, but may also be non-parallel. In this embodiment, from the viewpoint of production of the structural member 100, the vertical walls 12, 13 are spaced apart as they extend downward from the top plate 11. For example, the vertical wall 12 may be inclined relative to the vertical direction, while the vertical wall 13 may be substantially parallel to the vertical direction. However, the vertical wall 13 may also be inclined relative to the vertical direction.

[0045] The vertical wall 13 includes a front surface 131, a back surface 132, and a lower end surface 133. The front surface 131 is a surface that faces the front of the vehicle when the structural member 100 is assembled to the vehicle. The front surface 131 faces the back surface 122 of the vertical wall 12. The front surface 131 of the vertical wall 13 and the back surface 122 of the vertical wall 12 are included in the inner surface of the arm portion 10. The front surface 131 may have a substantially linear shape in a cross section of the arm portion 10. The front surface 131 extends substantially or roughly in the vertical direction when viewed in the cross section of the arm portion 10. In the example of this embodiment, the front surface 131 is substantially parallel to the vertical direction.

[0046] The back surface 132 is a surface that faces the rear of the vehicle when the structural member 100 is installed in the vehicle. The back surface 132 is positioned rearward of the front surface 131 when the structural member 100 is installed in the vehicle. The back surface 132 of the vertical wall 13 and the front surface 121 of the vertical wall 12 are included in the outer surface of the arm portion 10. The back surface 132 may have a substantially linear shape in a cross section of the arm portion 10. When viewed in the cross section of the arm portion 10, the back surface 132 extends substantially parallel to the front surface 131.

[0047] The lower end surface 133 is positioned lower than the top plate 11 when the structural member 100 is installed in a vehicle. The lower end surface 133 is the end surface on the free end side of the vertical wall 13. The lower end surface 133 connects the front surface 131 and the back surface 132. In the example of Figure 2, the lower end surface 133 extends along the thickness direction of the vertical wall 13 in a cross-sectional view of the arm portion 10. However, at least a portion of the lower end surface 133 may be inclined with respect to the thickness direction of the vertical wall 13. The lower end surface 133 may be formed in the same shape as the lower end surface 123 of the vertical wall 12. The thickness direction of the vertical wall 13 refers to the direction perpendicular to the front surface 131 (normal direction).

[0048] [effect] When the structural member 100 according to this embodiment is attached to a vehicle, the vertical wall 12 of the arm portion 10 is positioned in front of the top panel 11. The lower end surface 123 of the vertical wall 12 includes a straight portion 123a that descends toward the rear surface 122 when viewed in a cross section of the arm portion 10. The straight portion 123a is connected to the front surface 121 of the vertical wall 12 via a curved portion 123b. In this case, when air passes from the front to the rear of the arm portion 10 while the vehicle is traveling, the lower end surface 123 of the vertical wall 12 regulates the air flow below the arm portion 10. This tends to reduce the air resistance of the structural member 100 while the vehicle is traveling. Therefore, the structural member 100 according to this embodiment can reduce air resistance by its own shape, without using additional parts such as a resin cover.

[0049] In this embodiment, the vertical wall 12 extends downward from the top plate 11 so that its lower end is located forward relative to the top plate 11 when viewed in a cross section of the arm unit 10. A normal line L1 to the front surface 121 of the vertical wall 12 is inclined at an angle φ of, for example, 5° to 20° with respect to the longitudinal direction of the vehicle. In this case, even if the straight portion 123a of the lower end surface 123 is substantially parallel to the thickness direction of the vertical wall 12, when the structural member 100 is attached to the vehicle, the straight portion 123a descends as it approaches the back surface 122. Therefore, the lower end surface 123 of the vertical wall 12 can regulate the airflow below the arm unit 10.

[0050] In this embodiment, the lower end surface 123 of the vertical wall 12 includes a curved portion 123b in addition to a straight portion 123a. The curved portion 123b can have a radius of curvature R1 that is, for example, 1 / 5 or more of the thickness t1 of the vertical wall 12. In this case, the air flow below the arm portion 10 is more easily regulated, and the air resistance of the structural member 100 is more easily reduced.

[0051] In the structural member 100 according to this embodiment, the vertical wall 13 is disposed rearward of the vertical wall 12, which has a straight portion 123a and a curved portion 123b on its lower end surface 123. In a cross-sectional view of the arm portion 10, it is preferable that the rear vertical wall 13 does not protrude downward relative to the lower end surface 123 of the front vertical wall 12. This prevents the vertical wall 13 from obstructing the flow of air, and makes it easier to reduce the air resistance of the structural member 100 when the vehicle is traveling.

[0052] In this embodiment, there is no need to attach additional parts such as a resin cover to the structural member 100 in order to reduce air resistance. Therefore, it is possible to avoid an increase in cost due to additional parts in a vehicle to which the structural member 100 is applied. Furthermore, because the volume occupied by the structural member 100 is not increased by additional parts such as a resin cover, the structural member 100 according to this embodiment is advantageous in terms of design space compared to conventional lower arms that require a resin cover.

[0053] Second Embodiment Fig. 4 is a cross-sectional view of the arm portion 10A of the structural member 100A according to this embodiment. Fig. 4 shows the cross-section of the arm portion 10A at the midpoint in the left-right direction between the center position of the mounting portion 30 (Fig. 1) and the center position of the mounting portion 40 (Fig. 1). Fig. 5 is an enlarged view of the cross-section of the arm portion 10A shown in Fig. 4, showing the lower end surface 123A of the vertical wall 12A and its vicinity. The structural member 100A according to this embodiment differs from the structural member 100 according to the first embodiment in the shape of the lower end surface 123A.

[0054] As in the first embodiment, the vertical wall 12A includes a straight portion 123a and a curved portion 123b on its lower end surface 123A. However, in this embodiment, the straight portion 123a is inclined with respect to the thickness direction of the vertical wall 12 in the cross section of the arm portion 10A. Even such a straight portion 123a can be formed before the arm portion 10 is formed. For example, when a blank used to form the arm portion 10 is punched from a metal strip or metal plate, the blank can be formed by punching the end surface at an angle with respect to the plate thickness direction, thereby forming the straight portion 123a in the blank before forming. Specifically, before punching the blank, a portion of the metal strip or metal plate that will become the lower end surface 123 is press-formed into a predetermined shape, and then the metal strip or metal plate is punched, thereby forming the straight portion 123a in the blank before forming. Alternatively, after punching the blank, the straight portion 123a can be formed in the blank before forming by pressing or cutting the end surface of the blank. As described in the first embodiment, the curved portion 123b can be formed on the blank by processing before or after punching.

[0055] In the cross section of the arm unit 10A, the straight line portion 123a forms an angle of more than 90° with the front surface 121 of the vertical wall 12A. In other words, when the angle α1 formed by the straight line portion 123a with respect to the normal line L1 of the front surface 121 in the cross section of the arm unit 10A is defined as α1, the angle α1 is more than 0°. On the other hand, when the angle formed by the straight line portion 123a with the front surface 121 of the vertical wall 12A is substantially 90° as in the first embodiment, the angle α1 is substantially 0°. The sum of the angle φ formed by the front surface 121 with respect to the normal line L1 and the angle α1 formed by the straight line portion 123a with respect to the normal line L1 of the front surface 121 is the angle θ1 of the straight line portion 123a with respect to the front-to-rear direction. As in the first embodiment, the angles α1, θ1, and φ can be measured in a cross section of the arm unit 10 taken between the center position of the mounting portion 30 (FIG. 1) and the center position of the mounting portion 40 (FIG. 1).

[0056] In this embodiment, the vertical wall 12A also includes a straight portion 123a and a curved portion 123b on its lower end surface 123A. The straight portion 123a is connected to the front surface 121 of the vertical wall 12A via the curved portion 123b, and descends toward the back surface 122 of the vertical wall 12A. Therefore, the structural member 100A according to this embodiment can also achieve the same effects as the structural member 100 according to the first embodiment.

[0057] Although the embodiments of the present disclosure have been described above, the present disclosure is not limited to the above-described embodiments, and various modifications are possible without departing from the spirit of the present disclosure.

[0058] In the first embodiment, in the cross section of the arm portion 10 shown in FIG. 3, the lower end surface 123 of the vertical wall 12 is composed of a straight portion 123a and a curved portion 123b. Similarly, in the second embodiment, in the cross section of the arm portion 10A shown in FIG. 4, the lower end surface 123A of the vertical wall 12A is composed of a straight portion 123a and a curved portion 123b. However, a portion of the lower end surface 123 or 123A may be composed of a straight portion 123a and a curved portion 123b. For example, the lower end surface 123 or 123A may include a parallel portion in addition to the straight portion 123a and the curved portion 123b. The parallel portion 125 is, for example, a shear surface formed when punching the blank. The parallel portion may be located between the straight portion 123a and the back surface 122. The parallel portion may have a linear shape that is substantially parallel to the longitudinal direction of the vehicle when viewed in the cross section of the arm portion 10. In addition to or instead of the parallel portion, a fracture surface (not shown) having irregularities may be provided on the lower end surface 123 or 123A of the vertical wall 12. The fracture surface is formed when the blank is punched. The fracture surface is located at a position adjacent to the back surface 122 on the lower end surface 123 or 123A.

[0059] In the above embodiment, an example has been described in which the structural member 100, 100A is a lower arm. However, the structural member 100, 100A may be a structural member other than a lower arm. The configuration of the structural member 100 or 100A according to the above embodiment can also be applied to other structural members that have an arm portion extending in the left-right direction of the vehicle. For example, the configuration of the structural member 100 or 100A according to the above embodiment can also be applied to a lateral link or toe control link included in a multi-link rear suspension. Both the lateral link and the toe control link have an arm portion that has an attachment portion on the vehicle body side and an attachment portion on the wheel side.

[0060] For example, a structural member 100B that is a lateral link or a toe control link can have a cross section shown in FIG. 6. FIG. 6 shows an example of a cross section of the structural member 100B at the position of an arm portion 10B extending in the left-right direction of the vehicle. As shown in FIG. 6, the arm portion 10B can include a top panel 11B and front and rear vertical walls 12B, 13B, similar to the above embodiment. In this case, the lower end surface 123B of the vertical wall 12B can also include a straight portion 123a and a curved portion 123b (FIG. 3 or 4) similar to the above embodiment. [Example]

[0061] The present disclosure will be described in more detail below with reference to examples, although the present disclosure is not limited to the following examples.

[0062] Using commercially available software (STAR-CCM+, manufactured by Siemens), a fluid analysis (3D unsteady analysis) was performed on a simplified model of a front lower arm (structural member) with air flowing from the front to the rear of the simplified model at a speed of 100 km / h, assuming driving at a speed of 100 km / h. The simplified model is a model (half model) that mimics the arm portion of the front lower arm that extends in the left-right direction of the vehicle, and has a constant cross-sectional shape along its entire length in the left-right direction.

[0063] The conditions and evaluation results of the comparative example, control example, and example are shown in Table 1 and FIG.

[0064] [Table 1]

[0065] The comparative example, control example, and example in Table 1 all share the same structural member material. The plate thickness t1 of the arm portion 10 or 10A (vertical wall 12 or 12A) was also common, at 3.5 mm. In the example, similar to the first embodiment, the front vertical wall 12 of the arm portion 10 is inclined with respect to the vertical direction of the vehicle (φ>0), and a straight portion 123a and a curved portion 123b are provided on the lower end surface 123 of the vertical wall 12. On the other hand, in the comparative example, the vertical wall 12 is parallel to the vertical direction of the vehicle (φ=0), and the lower end surface 123 of the vertical wall 12 is composed of only the straight portion 123a. In the example and comparative example, the straight portion 123a is parallel to the thickness direction of the vertical wall 12.

[0066] Control Examples 1 and 2 differ from the Examples in that the vertical wall 12 is parallel to the up-down direction of the vehicle (φ=0). Control Example 1 also differs from the Examples in that the straight portion 123a is inclined with respect to the thickness direction of the vertical wall 12 (α1>0). Control Example 3 differs from the Examples in that the curved portion 123b is not provided on the lower end surface 123 of the vertical wall 12.

[0067] In this analysis, the resistance force of the structural member after 0.3 seconds had elapsed was evaluated as a ratio to that of the comparative example. As shown in Table 1 and FIG. 7, it was confirmed that the resistance force received by the structural member in the example was reduced compared to the comparative example. The resistance force received by the structural member in the example was also reduced compared to control examples 1 to 3. Therefore, by tilting the vertical wall 12 with respect to the up-down direction of the vehicle and providing a straight portion 123a and a curved portion 123b on the lower end surface 123 of the vertical wall 12, it is possible to reduce the air resistance of the structural member. [Explanation of symbols]

[0068] 100, 100A, 100B: Structural members 10, 10A, 10B: Arm section 11, 11B: Top plate 12, 12A, 12B: Vertical wall (first vertical wall) 121:Front 122: Back 123,123A,123B: Bottom end surface 123a: Straight section 123b: Curved section 13,13B: Wall (2nd wall)

Claims

1. A structural member for a vehicle, an arm portion including a top plate, a first vertical wall continuous with the top plate, and a second vertical wall continuous with the top plate on the opposite side of the first vertical wall; the first vertical wall is positioned in front of the top plate when the structural member is attached to the vehicle, and extends downward from the top plate so that a lower end side of the arm portion is positioned forward relative to the top plate when viewed in cross section, the first vertical wall includes a front surface, a rear surface, and a lower end surface connecting the front surface and the rear surface, a structural member, wherein the lower end surface has a linear shape when viewed in a cross section of the arm portion and includes a linear portion that descends toward the back surface side, and a curved portion that has a convex curved shape outward from the first vertical wall when viewed in a cross section of the arm portion and connects the front surface and the linear portion.

2. 10. The structural member of claim 1, A structural member, wherein in a cross section of the arm portion, an angle formed by a normal to the front surface and the fore-and-aft direction of the vehicle is greater than or equal to 5° and less than or equal to 20°.

3. 10. The structural member of claim 1, A structural member, wherein in a cross section of the arm portion, the curved portion has a radius of curvature that is 1 / 5 or more of the plate thickness of the first vertical wall.

4. 10. The structural member of claim 1, In a cross section of the arm portion, the straight portion extends along a thickness direction of the first vertical wall.

5. 10. The structural member of claim 1, In a cross section of the arm portion, the straight portion is inclined with respect to a thickness direction of the first vertical wall.

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