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) is positioned in front of the top plate (11, 11B) and extends downward from the top plate (11, 11B) when viewed in a cross section of the arm portion (10, 10A, 10B). 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 inclined portions (124, 124A) of the lower end surfaces (123, 123A, 123B) are inclined with respect to the thickness direction of the first vertical walls (12, 12A, 12B) so that the rear surface (122) side is positioned lower than the front surface (121) side.

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, and extends downward from the top plate when viewed in 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 an inclined portion. The inclined portion is adjacent to the front surface. The inclined portion is inclined with respect to the thickness direction of the first vertical wall so that the back surface side is positioned lower than the front surface side. [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 partially enlarged cross-sectional view of the arm portion shown in FIG. 2, showing an example of an arm portion different from that shown in FIG. [Figure 5] FIG. 5 is a cross-sectional view of an arm portion included in a structural member according to the second embodiment. [Figure 6] FIG. 6 is a partially enlarged cross-sectional view of the arm portion shown in FIG. [Figure 7] FIG. 7 is a partially enlarged cross-sectional view of the arm portion shown in FIG. 5, showing an example of an arm portion different from that shown in FIG. [Figure 8] FIG. 8 is a cross-sectional view of an arm portion included in a structural member according to a modified example of each embodiment. [Figure 9]FIG. 9 is a graph showing the resistance force of the comparative example and the 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, and extends downward from the top plate when viewed in 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 an inclined portion. The inclined portion is adjacent to the front surface. The inclined portion is inclined with respect to the thickness direction of the first vertical wall so that the back surface side is positioned lower than the front surface side (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 provided with an inclined portion that is inclined in the thickness direction of the first vertical wall so that the rear side is positioned lower than the front side. This inclined portion 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, the inclined portion may include a straight portion that is linear when viewed in cross section of the arm portion and slopes downward toward the rear side (second configuration).

[0013] In the second configuration, the inclined portion includes a straight portion. The straight portion has a shape that slopes downward toward the rear side of the first vertical wall, which can regulate the airflow below the arm portion. This makes it easier to reduce the air resistance of the structural member.

[0014] In the structural member according to the second configuration, the angle that the straight portion makes with respect to the thickness direction of the first vertical wall may be 45° or less (third configuration).

[0015] In the structural member according to the second or third configuration, the inclined portion may further include a curved portion that has a convex curved shape on the outside of the first vertical wall when viewed in cross section of the arm portion, and connects the front surface and the straight portion (fourth configuration).

[0016] In the fourth configuration, the straight portion is connected to the front surface of the first vertical wall via a curved portion, which makes it easier to regulate the airflow below the arm portion and more easily reduces the air resistance of the structural member.

[0017] In the structural member according to the first configuration, the inclined portion may include a curved portion that is continuous with the front surface and has a curved shape that is convex outward from the first vertical wall when viewed in cross section of the arm portion (fifth configuration).

[0018] In the fifth configuration, the inclined portion includes a curved portion that continues to the front surface of the first vertical wall. This curved portion regulates the airflow below the arm portion, thereby further reducing the air resistance of the structural member.

[0019] 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.

[0020] 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.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] 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).

[0033] The vertical wall 12 extends downward from the top plate 11 when viewed in a cross section of the arm unit 10. The vertical wall 12 may be substantially parallel to the vertical direction, or may be inclined relative to the vertical direction. In the example of FIG. 2, the vertical wall 12 extends substantially parallel to the vertical direction when viewed in a cross section of the arm unit 10. The vertical wall 12 includes a front surface 121, a back surface 122, and a bottom surface 123.

[0034] 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. The front surface 121 extends substantially or roughly in the vertical direction when viewed in the cross section of the arm unit 10. In this embodiment, the front surface 121 is substantially parallel to the vertical direction.

[0035] 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 portion 10. When viewed in the cross section of the arm portion 10, the rear surface 122 extends substantially parallel to the front surface 121.

[0036] 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.

[0037] FIG. 3 is an enlarged view of the lower end surface 123 of the vertical wall 12 and the vicinity thereof in the cross section of the arm portion 10 shown in FIG.

[0038] As shown in FIG. 3, the lower end surface 123 includes an inclined portion 124. The inclined portion 124 is a portion of the lower end surface 123 that is inclined with respect to the thickness direction of the vertical wall 12 so that the back surface 122 side is positioned lower than the front surface 121 side. The thickness direction of the vertical wall 12 refers to a direction perpendicular to the front surface 121 (normal direction). In this embodiment, the thickness direction of the vertical wall 12 substantially coincides with the front-rear direction of the vehicle. However, the thickness direction of the vertical wall 12 does not have to coincide with the front-rear direction of the vehicle.

[0039] The inclined portion 124 includes a straight portion 124a and a curved portion 124b. The straight portion 124a has a substantially straight shape when viewed in a cross section of the arm portion 10. The straight portion 124a is inclined with respect to the thickness direction of the vertical wall 12 in the cross section of the arm portion 10. The straight portion 124a is formed so as to slope downward toward the back surface 122.

[0040] The curved portion 124b 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 124b is disposed between the front surface 121 and the straight portion 124a. The curved portion 124b connects the front surface 121 and the straight portion 124a. It is preferable that the curved portion 124b smoothly connects to the front surface 121 and the straight portion 124a. That is, it is preferable that the front surface 121 and the straight portion 124a contact the curved portion 124b at both ends in the cross section of the arm unit 10. The end (rear end) of the curved portion 124b on the straight portion 124a side is disposed below the end (front end) of the curved portion 124b on the front surface 121 side. The straight portion 124a extends from the rear end of the curved portion 124b to the back surface 122 in the cross section of the arm unit 10.

[0041] The curved portion 124b also inclines relative to the thickness direction of the vertical wall 12 in the cross section of the arm portion 10. Specifically, when a tangent line TL is drawn at the midpoint of the curved portion 124b in the cross section of the arm portion 10, the tangent line TL inclines relative to the thickness direction of the vertical wall 12. The tangent line TL of the curved portion 124b descends toward the back surface 122.

[0042] In the cross section of the arm portion 10, the curved portion 124b 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.

[0043] The thickness t1 of the vertical wall 12 and the radius of curvature R1 of the curved portion 124b 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 located at positions 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 124b is the radius of an approximate circle that is tangent to the plane on which the front surface 121 exists and the plane on which the bottom end surface 123 exists in the cross section of the arm portion 10, and that minimizes the error (root mean square) between the three points in the curved portion 124b. The plane on which the front surface 121 exists is an approximate plane created from a point on the front surface 121 that corresponds 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 on which the bottom end 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 end surface 123, and an intermediate point between these two points.

[0044] The curved portion 124b 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. On the other hand, the straight portion 124a 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. The angle θ1 of the straight portion 124a can be measured in a cross section of the arm portion 10 where the thickness t1 of the vertical wall 12 and the radius of curvature R1 of the curved portion 124b are measured. The angle θ1 is the angle that the straight portion 124a makes with respect to the thickness direction of the vertical wall 12. In this embodiment, the angle θ1 can also be said to be the angle that the straight portion 124a makes with respect to the front-to-rear direction. The angle θ1 is, for example, 45° or less. The angle θ1 is preferably 30° or less. The angle θ1 may be 5° or more, or may be 10° or more.

[0045] 1 and 3, the inclined portion 124 is 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 inclined portion 124 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 inclined portion 124 is provided on the lower end surface 123 of the vertical wall 12 over a range of 100% or less of the length L. The inclined portion 124 may be provided on the lower end surface 123 over the entire length of the vertical wall 12.

[0046] The inclined portion 124 of the lower end surface 123 is typically formed before the arm portion 10 is formed. For example, when a blank used to form the arm portion 10 is punched out of a metal strip or metal plate, the blank is punched so that the end surface is oblique to the plate thickness direction, thereby forming the straight portion 124a in the blank before forming. Specifically, before punching the blank, the metal strip or metal plate is pressed to form a predetermined shape at a location that will become the lower end surface 123, and then the metal strip or metal plate is punched out, thereby forming the straight portion 124a in the blank before forming. Alternatively, the curved portion 124b can be formed in the blank before forming by using a die to crush the corner between the portion of the blank that corresponds to the front surface 121 and the end surface that corresponds to the lower end surface 123 before or after punching. Alternatively, the straight portion 124a and the curved portion 124b may be formed in the blank before forming by pressing or cutting the end surface of the blank after punching.

[0047] 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.

[0048] The vertical wall 13 extends downward from the tabletop 11 when viewed in a cross section of the arm portion 10. The vertical walls 12, 13 are connected by the tabletop 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 side opposite the tabletop 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, the vertical wall 13 moves away from the vertical wall 12 as it extends downward from the tabletop 11.

[0049] 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 non-parallel to the vertical direction.

[0050] 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.

[0051] 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).

[0052] [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. A sloped portion 124 is provided on the lower end surface 123 of the vertical wall 12. The sloped portion 124 is inclined relative to the thickness direction of the vertical wall 12 so that the rear surface 122 side of the vertical wall 12 is positioned lower than the front surface 121 side when viewed in cross section of the arm portion 10. In this embodiment, the sloped portion 124 includes a straight portion 124a that descends toward the rear surface 122 side. In this case, when air passes from the front to the rear of the arm portion 10 during vehicle travel, the lower end surface 123 of the vertical wall 12 straightens the air flow below the arm portion 10. This facilitates reduced air resistance of the structural member 100 during vehicle travel. 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.

[0053] In this embodiment, the angle θ1 that the straight line portion 124a makes with respect to the thickness direction of the vertical wall 12 may be 40° or less. This regulates the air flow below the arm portion 10, making it easier to reduce the air resistance of the structural member 100.

[0054] In this embodiment, the inclined portion 124 of the lower end surface 123 of the vertical wall 12 includes a curved portion 124b in addition to a straight portion 124a. The straight portion 124a is connected to the front surface 121 of the vertical wall 12 via the curved portion 124b. 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.

[0055] However, the inclined portion 124 does not have to include the curved portion 124b. That is, as shown in Fig. 4, the straight portion 124a may be directly connected to the front surface 121 of the vertical wall 12. In this case, too, the inclined portion 124 can regulate the air flow below the arm portion 10.

[0056] In the structural member 100 according to this embodiment, the vertical wall 13 is disposed behind the vertical wall 12 that has an inclined portion 124 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, which further reduces the air resistance of the structural member 100 when the vehicle is traveling.

[0057] 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.

[0058] Second Embodiment Fig. 5 is a cross-sectional view of the arm portion 10A of the structural member 100A according to this embodiment. Fig. 5 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). Figs. 6 and 7 are enlarged views of the lower end surface 123A of the vertical wall 12A and its vicinity in the cross-section of the arm portion 10A shown in Fig. 5, and each illustrate an example of the shape of the lower end surface 123A. 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.

[0059] 6 and 7, the vertical wall 12A includes an inclined portion 124A on its lower end surface 123A. The inclined portion 124A includes a curved portion 124b. In this embodiment, the entire inclined portion 124A is composed of the curved portion 124b. As in the first embodiment, the curved portion 124b is continuous with the front surface 121 and has a curved shape that convexly extends outward from the vertical wall 12A when viewed in a cross section of the arm portion 10A.

[0060] In the example of FIG. 6, inclined portion 124A forms the entire lower end surface 123A. More specifically, the entire lower end surface 123A is curved portion 124b. Curved portion 124b extends from front surface 121 to back surface 122 when viewed in a cross section of arm portion 10A. It is preferable that curved portion 124b smoothly continue into front surface 121. In other words, it is preferable that, when viewed in a cross section of arm portion 10A, front surface 121 contacts curved portion 124b at the front end of curved portion 124b.

[0061] In the example of FIG. 7, the inclined portion 124A forms a part of the lower end surface 123A. More specifically, a part of the lower end surface 123A is a curved portion 124b. In the example of FIG. 7, the lower end surface 123A includes a parallel portion 125 in addition to the inclined portion 124A. The parallel portion 125 has a substantially linear shape in the cross section of the arm portion 10A. The parallel portion 125 is substantially parallel to the thickness direction of the vertical wall 12A. The parallel portion 125 is, for example, a shear surface formed when punching out the blank.

[0062] In the vertical wall 12A, the parallel portion 125 is disposed between the inclined portion 124A and the back surface 122. The parallel portion 125 connects the inclined portion 124A and the back surface 122. In this embodiment, the parallel portion 125 connects the curved portion 124b of the inclined portion 124A and the back surface 122. It is preferable that the curved portion 124b smoothly connects to the parallel portion 125 in addition to the front surface 121. That is, it is preferable that the front surface 121 and the parallel portion 125 contact the curved portion 124b at both ends thereof when viewed in a cross section of the arm portion 10. The parallel portion 125 extends from the rear end of the curved portion 124b to the back surface 122 in the cross section of the arm portion 10. However, in addition to or instead of the parallel portion 125, a fracture surface (not shown) having an uneven surface may be provided on the lower end surface 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 123A.

[0063] In this embodiment, the curvature radius R1 of the curved portion 124b in the cross-sectional view of the arm portion 10A is, for example, 1 / 5 or more of the thickness t1 of the vertical wall 12A. The curvature radius R1 may be 1 / 3 or more of the thickness t1 of the vertical wall 12A. The curvature radius R1 is 2.0 times or less of the thickness t1. The curvature radius R1 may be 1.7 times or less of the thickness t1 of the vertical wall 12A, or may be less than the thickness t1. The curvature radius R1 of the curved portion 124b and the thickness t1 of the vertical wall 12A can be measured by the method described in the first embodiment.

[0064] In the structural member 100A according to this embodiment, the vertical wall 12A also includes an inclined portion 124A on its lower end surface 123A. The inclined portion 124A is inclined with respect to the thickness direction of the vertical wall 12A so that the back surface 122 side is positioned lower than the front surface 121 side when viewed in a cross section of the arm portion 10A. More specifically, when a tangent line TL is drawn at the midpoint of the curved portion 124b included in the inclined portion 124A in the cross section of the arm portion 10A, the tangent line TL is inclined with respect to the thickness direction of the vertical wall 12A. Therefore, the structural member 100A according to this embodiment can achieve the same effects as the structural member 100 according to the first embodiment.

[0065] In the structural member 100A according to this embodiment, in the cross section of the arm portion 10A shown in FIG. 6 or 7, the entire or a part of the lower end surface 123A of the vertical wall 12A is an inclined portion 124A. Similarly, in the structural member 100 according to the first embodiment, in the cross section of the arm portion 10 shown in FIG. 3 or 4, the entire lower end surface 123 of the vertical wall 12 may be an inclined portion 124, or only a part of the lower end surface 123 may be an inclined portion 124. When only a part of the lower end surface 123 is an inclined portion 124, the lower end surface 123 may further include a parallel portion 125 ( FIG. 7 ). In this case, the parallel portion 125 is located between the inclined portion 124 and the back surface 122 of the vertical wall 12. Alternatively, in addition to or instead of the parallel portion 125, a fractured surface (not shown) may be provided on the lower end surface 123 of the vertical wall 12. The fractured surface is located at a position adjacent to the back surface 122 on the lower end surface 123.

[0066] 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.

[0067] 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 include 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 include an arm portion that has an attachment portion on the vehicle body side and an attachment portion on the wheel side.

[0068] For example, a structural member 100B that is a lateral link or a toe control link can have a cross section shown in FIG. 8. FIG. 8 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. 8, the arm portion 10B can include a top panel 11B and front and rear vertical walls 12B, 13B, similar to the above-described embodiment. In this case, the lower end surface 123B of the vertical wall 12B can also include an inclined portion 124 (FIG. 3 or 4) or 124A (FIG. 6 or 7), similar to the above-described embodiment. [Example]

[0069] 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.

[0070] 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.

[0071] The conditions and evaluation results of the comparative example and the example are shown in Table 1 and FIG.

[0072] [Table 1]

[0073] The comparative examples and examples in Table 1 all used the same material for the structural members. The arm section 10 or 10A (vertical wall 12 or 12A) also had a common plate thickness t1 of 3.5 mm. In Examples 1 to 9, similar to the first or second embodiment, the arm section 10 or 10A had an inclined portion 124 or 124A on the lower end surface 123 or 123A of the front vertical wall 12 or 12A. In Examples 1 to 4, the entire lower end surface 123 was formed as the inclined portion 124, and the entire inclined portion 124 was formed as a straight portion 124a (FIG. 4). In Examples 1 to 4, the angle θ1 of the straight portion 124a was different from one another. In Examples 5 and 9, the lower end surface 123A was formed by the inclined portion 124A and the parallel portion 125, and the entire inclined portion 124A was formed as a curved portion 124b (FIG. 7). In Examples 5 and 9, the angle φ of the vertical wall 12A was different. In Example 6, the entire lower end surface 123A was made into an inclined portion 124A, and the entire inclined portion 124A was made into a curved portion 124b (FIG. 6). In Examples 7 and 8, the entire lower end surface 123 was made into an inclined portion 124, and the inclined portion 124 was provided with both a straight portion 124a and a curved portion 124b (FIG. 3). In Examples 7 and 8, the angle θ1 of the straight portion 124a was different. In the comparative example, no inclined portion was provided on the lower end surface of the front vertical wall. In the comparative example, the entire lower end surface was parallel to the thickness direction of the vertical wall.

[0074] The angle φ in Table 1 is the angle that the normal to the front surface 121 of the vertical wall 12 or 12A makes with the longitudinal direction of the vehicle. When the angle φ=0°, this means that the front surface 121 is parallel to the vertical direction of the vehicle. On the other hand, when the angle φ>0°, this means that the front surface 121 is inclined with respect to the vertical direction of the vehicle so that the lower end is positioned further forward than the upper end.

[0075] In this analysis, the resistance force of the structural member after 0.3 seconds was evaluated as a ratio to that of the comparative example. As shown in Table 1 and Fig. 9, it was confirmed that the resistance force received by the structural member in Examples 1 to 9 was reduced compared to that of the comparative example. Therefore, by providing the inclined portion 124 inclined with respect to the thickness direction of the vertical wall 12 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]

[0076] 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 124,124A: Inclined part 124a: Straight section 124b: Curved part 13, 13B: Vertical wall (second vertical 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 when viewed in a cross section of the arm portion; 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 lower end surface including an inclined portion adjacent to the front surface and inclined with respect to a thickness direction of the first vertical wall so that the back surface side is positioned lower than the front surface side;

2. 10. The structural member of claim 1, A structural member, wherein the inclined portion has a linear shape when viewed in cross section of the arm portion and includes a linear portion that descends toward the rear side.

3. 3. The structural member of claim 2, A structural member, wherein the angle formed by the linear portion with respect to the thickness direction is 45° or less.

4. 4. A structural member according to claim 2 or 3, The inclined portion further includes 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 that connects the front surface and the straight portion.

5. 10. The structural member of claim 1, The inclined portion is continuous with the front surface and includes a curved portion having a convex curved shape outward from the first vertical wall when viewed in a cross section of the arm portion.

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