Suspension arm

Abstract

This suspension arm (30) is configured so as to connect a body (100) of a vehicle and a wheel (110). The suspension arm (30) is provided with: a bottom wall (31); a front wall (32A) and a rear wall (32B) which protrude from the bottom wall (31) in a vehicle upward direction and face each other in a vehicle front-rear direction (Y); and a rectification unit (70) which has a plate shape extending in a vehicle width direction (X) and is cantilevered by the front wall (32A) so as to protrude obliquely downward from the upper part of the front wall (32A) in the vehicle front direction.

Description

Suspension arms

[0001] The present disclosure relates to a suspension arm.

[0002] Vehicles such as automobiles are provided with suspension arms that connect the vehicle body to the wheels (see, for example, Patent Document 1). The suspension arm described in Patent Document 1 has two side walls that extend in the vehicle width direction so as to face each other, and a bottom wall that extends so as to connect the lower ends of the two side walls.

[0003] JP 2016-107838 A

[0004] Suspension arms are mounted on the underside of a vehicle so that they are exposed to the outside of the vehicle. Therefore, when the vehicle is moving, the suspension arms are exposed to the wind. This can lead to a deterioration in the aerodynamic characteristics of the suspension arms.

[0005] A suspension arm according to one aspect of the present disclosure is configured to connect a vehicle body and a wheel of a vehicle, and includes a bottom wall, front and rear walls each protruding upward from the bottom wall and facing each other in the longitudinal direction of the vehicle, and a plate-shaped airflow rectifier extending in the vehicle width direction and cantilevered by the front wall so as to protrude diagonally downward from an upper portion of the front wall toward the front of the vehicle.

[0006] 1 is a side end view of a lower arm which is one embodiment of a suspension arm. FIG. 2 is a schematic diagram showing a suspension device of a vehicle to which the lower arm of FIG. 1 is applied. FIG. 3 is a perspective view of the lower arm of FIG. 1. FIG. 4 is an exploded perspective view showing the arm main body and reinforcing member which constitute the lower arm of FIG. 3 separated from each other. FIG. 5 is a plan view of the lower arm of FIG. 1. FIG. 6 is a bottom view of the lower arm of FIG. 1. FIG. 7 is an enlarged side cross-sectional view of a base end portion of the airflow rectifying portion and its surroundings in the lower arm of FIG. 1. FIG. 8 is an enlarged side cross-sectional view of a front wall and airflow rectifying portion in the lower arm of FIG. 1. FIG. 9 is a graph showing the relationship between the angle θ of the airflow rectifying portion, the length ratio R, and the Cd value in the lower arm of FIG. 8. FIG. 10 is a graph showing the relationship between the angle θ of the airflow rectifying portion, the length ratio R, and the CL value in the lower arm of FIG. 8.

[0007] A lower arm of a suspension system, which is one embodiment of a suspension arm, will be described below with reference to Figures 1 to 10. In this specification, the terms "upper," "lower," "front," "rear," and similar terms refer to directions or orientations defined in relation to a vehicle.

[0008] 2, the suspension 10 is disposed between the vehicle body 100 and the wheels 110, and supports the wheels 110 so that they can swing freely relative to the vehicle body 100. The suspension 10 is configured to absorb shocks transmitted from the road surface to the vehicle body 100 via the wheels 110, and to press the wheels 110 against the road surface.

[0009] The suspension system 10 includes an upper arm 20, a lower arm 30, and a suspension spring 80. The upper arm 20 and the lower arm 30 extend in the vehicle width direction X. The upper arm 20 is disposed above the lower arm 30. The upper arm 20 and the lower arm 30 connect a frame 101 of a vehicle body 100 to a support member 111 that supports a wheel 110.

[0010] The suspension spring 80 extends in the vehicle up-down direction (hereinafter referred to as the up-down direction Z). The lower end of the suspension spring 80 is supported by the lower arm 30. <Lower Arm 30> As shown in FIGS. 1 and 3 , the lower arm 30 has a bottom wall 31, a front wall 32A, a rear wall 32B, and an airflow rectifying portion 70. The bottom wall 31 extends in the vehicle width direction X and the vehicle front-rear direction (hereinafter referred to as the front-rear direction Y). The bottom wall 31 has an elongated shape extending in the vehicle width direction X. The front wall 32A and the rear wall 32B protrude upward from both end edges of the bottom wall 31 in the front-rear direction Y and face each other. The airflow rectifying portion 70 extends from an upper portion of the front wall 32A toward the front of the vehicle. This airflow rectifying portion 70 will be described in detail later.

[0011] The lower arm 30 has an arm main body 40, a reinforcing member 50, and a resin molded portion 60. <Arm main body 40> As shown in Figures 1 and 4, the arm main body 40 has a bottom wall main body 41, a front wall main body 42A, and a rear wall main body 42B. The bottom wall main body 41 has an elongated shape extending in the vehicle width direction X. The front wall main body 42A and the rear wall main body 42B protrude upward from both end edges of the bottom wall main body 41 in the front-rear direction Y and face each other. The arm main body 40 is open upward.

[0012] The arm body 40 is formed, for example, by pressing a metal plate. The material of the arm body 40 is a metal material such as high-tensile steel. The middle portion 41a of the bottom wall body 41 in the vehicle width direction X has a larger width in the front-rear direction Y than the other portions of the bottom wall body 41. The width of the middle portion 41a in the front-rear direction Y gradually decreases toward both ends in the vehicle width direction X. The middle portion 41a of the bottom wall body 41 has a spindle shape when viewed from the up-down direction Z.

[0013] The portions of the bottom wall main body 41 adjacent to the middle portion 41a on both sides in the vehicle width direction X extend linearly in the vehicle width direction X. The front wall main body 42A and the rear wall main body 42B are symmetrical in the fore-and-aft direction Y. For this reason, hereinafter, the configuration of the front wall main body 42A will be described, and a description of the configuration of the rear wall main body 42B may be omitted.

[0014] The front wall main body 42A extends over the entire bottom wall main body 41 in the vehicle width direction X. One end of the front wall main body 42A in the vehicle width direction X, which constitutes a first connecting portion 47 described later, protrudes in the vehicle width direction X from the bottom wall main body 41.

[0015] The portion of the front wall main body 42A that protrudes from the intermediate portion 41a has an inclined portion 43 that continues to the bottom wall main body 41 and a straight portion 44 that continues to the inclined portion 43. The inclined portion 43 of the front wall main body 42A is inclined so as to move away from the rear wall main body 42B in the front-rear direction Y as it extends upward.

[0016] The straight portion 44 extends linearly in the up-down direction Z. The straight portion 44 of the front wall main body 42A and the straight portion 44 of the rear wall main body 42B extend parallel to each other. The front wall main body 42A and the rear wall main body 42B each have a first flange 45A and a second flange 45B. The first flange 45A protrudes from the end of the front wall main body 42A opposite the bottom wall main body 41 toward the opposite side from the rear wall main body 42B in the front-to-rear direction Y. The first flange 45A and the second flange 45B protrude opposite each other in the front-to-rear direction Y. The first flange 45A forms the tip portion of the front wall main body 42A in the protruding direction. The first flange 45A extends across the entire front wall main body 42A in the vehicle width direction X.

[0017] 3 and 4, the arm body 40 has a spring accommodating portion 46, a first connecting portion 47, and a second connecting portion 48. The spring accommodating portion 46 forms the center portion of the arm body 40 in the vehicle width direction X. The first connecting portion 47 and the second connecting portion 48 are connected to both ends of the spring accommodating portion 46 in the vehicle width direction X, respectively.

[0018] 1 and 4, the spring accommodating section 46 includes an intermediate section 41a, a front wall main body 42A, and a rear wall main body 42B to define an accommodating space for accommodating the lower end of the suspension spring 80 (see FIG. 2). The front wall main body 42A and the rear wall main body 42B of the spring accommodating section 46 bulge outward in opposite directions in the front-to-rear direction Y. A through-hole 46a that penetrates in the up-down direction Z is provided in the bottom of the spring accommodating section 46, i.e., the intermediate section 41a. The through-hole 46a has a circular shape.

[0019] 3 and 4 , the first connecting portion 47 is a portion of the arm main body 40 that is connected to the vehicle body 100. The front wall main body 42A and the rear wall main body 42B of the first connecting portion 47 extend parallel to each other in the vehicle width direction X. The front wall main body 42A and the rear wall main body 42B of the first connecting portion 47 protrude in the vehicle width direction X beyond the edge of the bottom wall main body 41 in the vehicle width direction X.

[0020] The front wall main body 42A and the rear wall main body 42B of the first connecting portion 47 are each provided with a first connecting hole 47a that penetrates in the fore-and-aft direction Y. The first connecting portion 47 is rotatably connected to the frame 101 of the vehicle body 100 via a rotation shaft (not shown) that is inserted into the first connecting hole 47a.

[0021] <Second Connecting Portion 48> The second connecting portion 48 is a portion of the arm body 40 that is connected to the wheel 110. The front wall main body 42A and the rear wall main body 42B of the second connecting portion 48 extend parallel to each other in the vehicle width direction X.

[0022] The front wall main body 42A and the rear wall main body 42B of the second connecting portion 48 are each provided with a second connecting hole 48a that penetrates in the front-to-rear direction Y. The second connecting portion 48 is rotatably connected to the support member 111 of the wheel 110 via a rotation shaft (not shown) that is inserted into the second connecting hole 48a.

[0023] As shown in FIGS. 1 and 4 , the reinforcing member 50 has a flat plate shape. The reinforcing member 50 covers from above a portion of the spring accommodating portion 46 adjacent to the first connecting portion 47. The reinforcing member 50 is made of a metal material such as high-tensile steel. The reinforcing member 50 is joined to the upper surfaces of the first flange 45A and the second flange 45B by, for example, welding. As shown in FIG. 5 , both end edges of the reinforcing member 50 in the front-rear direction Y are located inside the outer end edges of the first flange 45A and the second flange 45B in the front-rear direction Y.

[0024] <Resin molded portion 60> As shown in Figures 1 and 3 to 5, the resin molded portion 60 is molded by inserting the arm main body 40 and the reinforcing member 50. The resin molded portion 60 is molded by placing the arm main body 40, to which the reinforcing member 50 has been joined, as an insert part inside a mold device (not shown), and then filling the inside of the mold device with resin. The material of the resin molded portion 60 is, for example, a thermoplastic resin material.

[0025] The resin molded portion 60 has a first covering portion 61, a second covering portion 64, and a third covering portion 67. <First covering portion 61> The first covering portion 61 covers the surface of the front wall main body 42A facing the front of the vehicle (hereinafter referred to as the front surface). More specifically, the first covering portion 61 covers a portion of the front surface of the front wall main body 42A excluding the periphery of the first connecting hole 47a and the periphery of the second connecting hole 48a. The front surface of the front wall main body 42A is the surface opposite to the surface of the front wall main body 42A facing the rear wall main body 42B, and includes the underside of the first flange 45A. In this embodiment, the first covering portion 61 corresponds to the "covering portion."

[0026] The first covering portion 61 has an inclined covering portion 61b that covers the inclined portion 43 of the front wall main body 42A and a straight covering portion 61a that covers the straight portion 44 of the front wall main body 42A. The inclined covering portion 61b extends along the front surface of the inclined portion 43 of the front wall main body 42A. The straight covering portion 61a extends along the front surface of the straight portion 44 of the front wall main body 42A.

[0027] The first covering portion 61 has two engaging portions 62 that engage with both end portions of the front wall main body 42A in the vehicle width direction X, and an engaging portion 63 that engages with the tip portion of the first flange 45A.

[0028] Each engaging portion 62 covers one end portion of the front wall main body 42A in the vehicle width direction X from both sides in the front-rear direction Y and from one side in the vehicle width direction X. Each engaging portion 62 engages with the one end portion of the front wall main body 42A over the entire area in the up-down direction Z.

[0029] The engaging portion 63 covers the tip portion of the first flange 45A from both sides in the up-down direction Z and from the front side in the front-rear direction Y. The engaging portion 63 engages with the tip portion of the first flange 45A over the entirety in the vehicle width direction X.

[0030] In the portion of the spring accommodating portion 46 adjacent to the first connecting portion 47, the engaging portion 63 covers not only the tip portion of the first flange 45A but also the joint portion between the first flange 45A and the reinforcing member 50.

[0031] <Second covering portion 64> The second covering portion 64 covers the surface of the rear wall main body 42B facing the vehicle rear (hereinafter referred to as the rear surface). Specifically, the second covering portion 64 covers the rear surface of the rear wall main body 42B except for the areas around the first connecting hole 47a and the second connecting hole 48a. The rear surface of the rear wall main body 42B is the surface of the rear wall main body 42B opposite the surface facing the front wall main body 42A, and includes the underside of the second flange 45B.

[0032] The second covering portion 64 has an inclined covering portion 64b that covers the inclined portion 43 of the rear wall main body 42B and a straight covering portion 64a that covers the straight portion 44 of the rear wall main body 42B. The inclined covering portion 64b extends along the rear surface of the inclined portion 43 of the rear wall main body 42B. The straight covering portion 64a extends along the rear surface of the straight portion 44 of the rear wall main body 42B.

[0033] The second covering portion 64 has two engaging portions 65 that engage with both ends of the rear wall main body 42B in the vehicle width direction X, and an engaging portion 66 that engages with the tip portion of the second flange 45B.

[0034] Each engaging portion 65 covers one end portion of the rear wall main body 42B in the vehicle width direction X from both sides in the front-rear direction Y and from one side in the vehicle width direction X. Each engaging portion 65 engages with the one end portion of the rear wall main body 42B over the entire area in the up-down direction Z.

[0035] The engaging portion 66 covers the tip portion of the second flange 45B from both sides in the up-down direction Z and from the rear side in the front-rear direction Y. The engaging portion 66 engages with the tip portion of the second flange 45B over the entirety in the vehicle width direction X.

[0036] In the portion of the spring accommodating portion 46 adjacent to the first connecting portion 47, the engaging portion 66 covers not only the tip portion of the second flange 45B but also the joint portion between the second flange 45B and the reinforcing member 50.

[0037] 1, 4, and 6, the third covering portion 67 covers the entire lower surface of the bottom wall main body 41. As shown in Figures 5 and 6, the third covering portion 67 has two engaging portions 68 that engage with both end portions of the bottom wall main body 41 in the vehicle width direction X, and an engaging portion 69 that engages with the periphery of the through-hole 46a.

[0038] 4 to 6 , each engaging portion 68 covers one end portion of the bottom wall main body 41 in the vehicle width direction X from both sides in the up-down direction Z and from one side in the vehicle width direction X. Each engaging portion 68 engages with the one end portion of the bottom wall main body 41 over the entire area in the front-rear direction Y.

[0039] The engaging portion 69 covers the periphery of the through hole 46a from both sides in the vertical direction Z and from the inner surface side of the through hole 46a. The engaging portion 69 engages with the periphery of the through hole 46a over the entire circumferential direction.

[0040] The bottom wall 31 of the lower arm 30 includes a bottom wall main body 41 and a third covering portion 67. The front wall 32A of the lower arm 30 includes a front wall main body 42A and a first covering portion 61. The rear wall 32B of the lower arm 30 includes a rear wall main body 42B and a second covering portion 64.

[0041] 1, 3, and 6, the lower arm 30 has a rectifying portion 70, a protruding wall portion 71, and a rib 72. In this embodiment, the rectifying portion 70, the protruding wall portion 71, and the rib 72 are utilized to rectify the flow of air around the lower arm 30.

[0042] <Airflow rectifying portion 70> The airflow rectifying portion 70 has a plate shape extending in the vehicle width direction X. The airflow rectifying portion 70 has an elongated shape extending in the vehicle width direction X along the front wall 32A. The airflow rectifying portion 70 extends over the entire front wall 32A of the spring accommodating portion 46 in the vehicle width direction X. The airflow rectifying portion 70 extends in a curved manner along the front surface of the front wall 32A of the spring accommodating portion 46. The airflow rectifying portion 70 is provided integrally with the first covering portion 61. The airflow rectifying portion 70 extends toward the front of the vehicle from a portion of the first covering portion 61 that covers the front surface of the front wall main body 42A of the spring accommodating portion 46. The airflow rectifying portion 70 is cantilevered by the front wall 32A so as to protrude obliquely downward toward the front of the vehicle from an upper portion of the front wall 32A, more specifically, from the upper end. An upper portion of the front wall 32A is a portion of the front wall 32A that is continuous with the first flange 45A. The shape of the airflow rectifying portion 70 is the same at any portion in the vehicle width direction X of the airflow rectifying portion 70.

[0043] The flow rectifying portion 70 includes a main body portion 70a and a tip portion 70b. As shown in FIGS. 1, 5, and 7, the main body portion 70a is a portion of the flow rectifying portion 70 that is closer to the front wall 32A than the tip portion 70b. The main body portion 70a extends linearly in the front-rear direction Y. The main body portion 70a is inclined relative to the horizontal direction so that the further away from the front wall 32A in the front-rear direction Y the main body portion 70a is, the lower it becomes. The end of the main body portion 70a opposite the tip portion 70b (hereinafter referred to as the base end portion 70c) extends to a position above the upper end of the front wall 32A. The base end portion 70c is also the end of the flow rectifying portion 70 that is closer to the front wall 32A.

[0044] The tip portion 70b constitutes the tip portion of the airflow rectifying portion 70, i.e., the end portion farther from the front wall 32A. The tip portion 70b extends in the front-rear direction Y so as to curve downward toward the vehicle. <Protruding Wall Portion 71> As shown in FIGS. 5 and 8 , the protruding wall portion 71 is provided at the base end portion 70c of the airflow rectifying portion 70. The protruding wall portion 71 is provided integrally with the airflow rectifying portion 70. The protruding wall portion 71 forms part of the resin molded portion 60. The protruding wall portion 71 has a generally rectangular cross section and forms a protrusion extending in the vehicle width direction X along the front wall 32A. The protruding wall portion 71 protrudes upward from the upper end, i.e., the rear end, of the base end portion 70c. The protruding wall portion 71 extends across the entire spring accommodating portion 46 (more specifically, the front wall main body 42A) in the vehicle width direction X. The protruding wall portion 71 extends in a curved manner along the front surface of the spring accommodating portion 46 .

[0045] 3, 6, and 8, the rib 72 is made up of a first rib 72a and a second rib 72b. The rib 72 forms a part of the resin molded portion 60.

[0046] The first rib 72a is provided on the lower surface of the airflow rectifying portion 70. The first rib 72a extends in the front-rear direction Y and the up-down direction Z. A plurality of first ribs 72a are provided so as to extend parallel to one another at intervals in the vehicle width direction X. Each first rib 72a is provided so as to connect the lower surface of the airflow rectifying portion 70 to the front surface of the front wall 32A in a portion sandwiched between the lower surface of the airflow rectifying portion 70 and the front surface of the front wall 32A. The lower end surface of each first rib 72a extends in a curved shape convex upward in the vehicle direction as viewed in the vehicle width direction X. In this embodiment, each first rib 72a divides the portion sandwiched between the lower surface of the airflow rectifying portion 70 and the front surface of the front wall 32A into a right portion and a left portion in the vehicle width direction X.

[0047] The second rib 72b extends across the lower front surface of the front wall 32A, the lower surface of the bottom wall 31, and the lower rear surface of the rear wall 32B. Specifically, the second rib 72b extends in the front-rear direction Y on the outer surfaces of the inclined covering portion 61b, the third covering portion 67, and the inclined covering portion 64b.

[0048] The second rib 72b extends on the outer surface of the lower arm 30 so as to be continuous with the first rib 72a. More specifically, the second rib 72b has a generally rectangular cross section and forms a protrusion extending in the front-to-rear direction Y along the outer surface of the lower arm 30. A plurality of second ribs 72b are provided so as to extend parallel to each other at intervals in the vehicle width direction X. When wind flows below the lower arm 30 during vehicle travel, the air is rectified by the second ribs 72b.

[0049] According to this embodiment, the airflow from the front of the vehicle toward the front wall 32A of the lower arm 30 is blocked and deflected by the airflow straightening portion 70, so that the airflow can be directed upward and to the side of the vehicle without hitting the front wall 32A. This reduces the drag generated on the lower arm 30.

[0050] 8 , the length of the airflow rectifying portion 70, specifically the length of the main body 70a thereof in the direction of protrusion from the front wall 32A, is referred to as the "length L of the airflow rectifying portion 70." The height from the lower surface of the bottom wall main body 41 to the upper surface of the front wall main body 42A is referred to as the "height H of the arm main body 40." The ratio of the length L of the airflow rectifying portion 70 to the height H of the arm main body 40 is referred to as the "length ratio R (= L / H)." When the airflow rectifying portion 70 is viewed from the vehicle width direction X, the angle formed between an imaginary axis V extending in the front-rear direction Y and the main body 70a of the airflow rectifying portion 70 is referred to as the "angle θ of the airflow rectifying portion 70."

[0051] As is clear from Figure 8, in the lower arm 30 of this embodiment, if the length L of the airflow straightening portion 70 is excessively short, the front wall 32A is more likely to be hit by the wind when the vehicle is traveling. This increases the drag acting on the lower arm 30. If the length L of the airflow straightening portion 70 is excessively long, the area of ​​the portion of the airflow straightening portion 70 that is hit by the wind when the vehicle is traveling increases. This increases the drag acting on the airflow straightening portion 70, and therefore the drag acting on the lower arm 30.

[0052] In light of this, in this embodiment, the shape of each part of the lower arm 30 is set based on the results of simulations performed by the inventors, etc., so that the length L of the airflow rectifying portion 70 is an appropriate length. Specifically, the shape of each part of the lower arm 30 is set so that the length ratio R is 0.62.

[0053] As is clear from Figure 8, in the lower arm 30 of this embodiment, the closer the angle θ of the airflow straightening portion 70 is to "0 degrees," the more likely it is that the traveling wind will hit the front wall 32A. Therefore, the drag acting on the lower arm 30 increases. On the other hand, the closer the angle θ of the airflow straightening portion 70 is to "90 degrees," the closer the angle θ at which the traveling wind hits the airflow straightening portion 70 becomes to a right angle. Therefore, the drag acting on the airflow straightening portion 70, and ultimately the drag acting on the lower arm 30, increases.

[0054] Taking this into consideration, in this embodiment, based on the results of simulations by the inventors, the shape of each part of the lower arm 30 is set so that the angle θ of the straightening section 70 is an appropriate angle, specifically "35 degrees."

[0055] <Simulation Results> Below, the aerodynamic characteristics of the lower arm 30 when the length L of the airflow straightening portion 70, the height H of the arm main body 40, and the angle θ of the airflow straightening portion 70 are changed will be described using the results of a simulation conducted by the inventors.

[0056] Fig. 9 is a graph showing the relationship between the Cd value (hereinafter simply referred to as the Cd value), which is the drag coefficient of the lower arm 30, and the length ratio R when the angle θ of the airflow rectifying unit 70 is set to "10 degrees," "35 degrees," and "60 degrees." The dashed-dotted line in Fig. 9 is a graph when the angle θ of the airflow rectifying unit 70 is set to "10 degrees," the solid line in Fig. 9 is a graph when the angle θ of the airflow rectifying unit 70 is set to "35 degrees," and the dashed line in Fig. 9 is a graph when the angle θ of the airflow rectifying unit 70 is set to "60 degrees."

[0057] 9, it was confirmed that when the angle θ of the rectifying section 70 was 10 degrees and the length ratio R was in the range of 0.95 to 1.10, the Cd value was suitably reduced. In this simulation, when the angle θ of the rectifying section 70 was 10 degrees and the length ratio R was 1.05, the Cd value was smallest.

[0058] 9, it was confirmed that when the angle θ of the rectifying section 70 was "35 degrees," the Cd value was suitably reduced when the length ratio R was in the range of "0.60 to 0.90." In this simulation, when the angle θ of the rectifying section 70 was "35 degrees," the Cd value was smallest when the length ratio R was "0.73."

[0059] 9, it was confirmed that when the angle θ of the rectifying section 70 was "60 degrees," the Cd value was suitably reduced when the length ratio R was in the range of "0.60 to 0.70." In this simulation, when the angle θ of the rectifying section 70 was "60 degrees," the Cd value was smallest when the length ratio R was "0.62."

[0060] Fig. 10 is a graph showing the relationship between the CL value (hereinafter simply referred to as the CL value), which is the lift coefficient of the lower arm 30, and the length ratio R when the angle θ of the airflow rectifying section 70 is set to "10 degrees," "35 degrees," and "60 degrees." The dashed-dotted line in Fig. 10 is a graph when the angle θ of the airflow rectifying section 70 is set to "10 degrees," the solid line in Fig. 10 is a graph when the angle θ of the airflow rectifying section 70 is set to "35 degrees," and the dashed line in Fig. 10 is a graph when the angle θ of the airflow rectifying section 70 is set to "60 degrees."

[0061] As shown in Figure 10, it was confirmed that the CL value was reduced as the length ratio R increased, i.e., as the length L of the rectification section 70 increased, regardless of whether the angle θ of the rectification section 70 was 10 degrees, 35 degrees, or 60 degrees.

[0062] As shown by the dotted line in FIG. 10 , when the angle θ of the rectifying section 70 is “10 degrees,” if the length ratio R is set to “1.05,” it has been confirmed that although the Cd value can be reduced as described above, the CL value becomes a value deviated from “0,” specifically, a negative value.

[0063] Here, the smaller the CL value, the more the lift acting on the lower arm 30 is suppressed. However, if the CL value is an excessively large negative value, it will cause an increase in the rolling resistance of the vehicle. Therefore, it is preferable that the CL value is approximately "0." In this regard, it has been confirmed that when the angle θ of the airflow rectifying portion 70 is set to "10 degrees" and the length ratio R is set to "1.05," the CL value becomes an excessively large negative value, thereby increasing the rolling resistance of the vehicle.

[0064] As shown by the solid line in Figure 10, when the angle θ of the airflow straightening portion 70 is "35 degrees," it was confirmed that the CL value becomes approximately "0" when the length ratio R is in the range of "0.60 to 0.70." As shown by the dashed line in Figure 10, it was confirmed that even when the angle θ of the airflow straightening portion 70 is "60 degrees," the CL value becomes approximately "0" when the length ratio R is in the range of "0.60 to 0.70." In either case, it was confirmed that the Cd value is reduced and the CL value becomes approximately "0," thereby suppressing an increase in the rolling resistance of the vehicle.

[0065] From the above, it can be seen that the aerodynamic characteristics of the lower arm 30 can be effectively improved by setting the angle θ of the airflow control portion 70 to "35 degrees" and the length ratio R to "0.62".

[0066] <Operations and Effects> The operations and effects of this embodiment will be described. (1) The lower arm 30 has a bottom wall 31, and a front wall 32A and a rear wall 32B that each protrude from the bottom wall 31 in an upward direction of the vehicle and face each other in the front-to-rear direction Y. The lower arm 30 has a plate-shaped airflow straightening portion 70 that extends in the vehicle width direction X. The airflow straightening portion 70 is cantilevered by the front wall 32A so as to protrude obliquely downward from an upper portion of the front wall 32A in a forward direction of the vehicle.

[0067] With this configuration, the airflow straightening portion 70 blocks and deflects the traveling wind that flows from the front of the vehicle toward the front wall 32A of the lower arm 30, allowing the wind to escape toward the top and sides of the vehicle without hitting the front wall 32A. This reduces the drag generated on the lower arm 30. The traveling wind collides with the front surface of the airflow straightening portion 70, i.e., the inclined surface that slopes diagonally upward when viewed from the front of the vehicle. This collision generates a force that presses the airflow straightening portion 70 downward. This pressing force reduces the lift acting on the lower arm 30. According to this embodiment, the aerodynamic characteristics of the lower arm 30 can be improved in this way.

[0068] (2) The lower surface of the airflow rectifying portion 70 is provided with a first rib 72a extending in the longitudinal direction Y. This configuration allows an air flow to flow in the longitudinal direction Y along the first rib 72a in the portion (hereinafter referred to as the specific portion) sandwiched between the lower surface of the airflow rectifying portion 70 and the front surface of the front wall 32A. This prevents the air flow from stagnating in the specific portion. Each first rib 72a divides the specific portion into a right portion and a left portion in the vehicle width direction X. This makes it difficult for air to flow in the vehicle width direction X in the specific portion. This prevents air from flowing around the specific portion from both sides of the airflow rectifying portion 70 in the vehicle width direction X. Therefore, the above configuration reduces the drag generated in the lower arm 30.

[0069] In this embodiment, the following has been confirmed from the results of simulations performed by the inventors. When the angle θ of the airflow rectifying portion 70 is set to 35 degrees and the length ratio R is set to 0.62, it has been confirmed that providing the first rib 72a reduces the Cd value compared to when the first rib 72a is not provided. When the angle θ of the airflow rectifying portion 70 is set to 35 degrees and the length ratio R is set to 0.62, it has been confirmed that even when the first rib 72a is provided, the CL value remains approximately 0 and hardly changes compared to when the first rib 72a is not provided.

[0070] (3) The tip 70b of the airflow straightening portion 70 extends in a curved manner downward relative to the vehicle. This configuration can prevent the traveling wind that passes through the tip 70b of the airflow straightening portion 70 from flowing rearward of the airflow straightening portion 70, i.e., around the specific portion, compared to when the tip of the airflow straightening portion 70 is not curved or when the tip extends in a curved manner upward relative to the vehicle. This can reduce the drag generated on the lower arm 30.

[0071] (4) The base end portion 70c of the airflow rectifying portion 70 extends to a position above the upper end of the front wall 32A. In this embodiment, a portion of the traveling wind flows obliquely upward toward the rear of the vehicle along the front surface of the airflow rectifying portion 70. According to the above configuration, since the base end portion 70c of the airflow rectifying portion 70 extends to a position above the upper end of the front wall 32A, the flow of traveling wind that passes above the base end portion 70c can be separated from the upper opening of the lower arm 30, specifically the upper opening of the spring accommodating portion 46. This prevents the flow of traveling wind that passes above the base end portion 70c from entering the interior of the lower arm 30. This reduces the drag generated on the lower arm 30.

[0072] (5) A protruding wall portion 71 that protrudes upward in the vehicle direction and extends in the vehicle width direction X is provided at the rear end, which is the upper end, of the base end portion 70c of the airflow straightening portion 70. In this embodiment, a portion of the traveling wind flows obliquely upward toward the rear of the vehicle along the front surface of the airflow straightening portion 70. With the above configuration, the protruding wall portion 71 can change the flow direction of the traveling wind to a direction away from the upper opening of the lower arm 30, specifically, upward. This makes it possible to prevent the traveling wind from entering the interior of the lower arm 30 after passing above the airflow straightening portion 70.

[0073] (6) The lower arm 30 includes an arm main body 40 and a resin molded portion 60 that is molded by inserting the arm main body 40. The arm main body 40 includes a bottom wall main body 41 and a front wall main body 42A and a rear wall main body 42B that each protrude upward from the bottom wall main body 41 and face each other in the longitudinal direction Y. The resin molded portion 60 includes a first covering portion 61 that covers the front surface of the front wall main body 42A. The bottom wall 31 includes the bottom wall main body 41, the front wall 32A includes the front wall main body 42A and the first covering portion 61, and the rear wall 32B includes the rear wall main body 42B. The flow straightening portion 70 is provided integrally with the first covering portion 61.

[0074] According to this configuration, the rectifying section 70 can be molded as part of the resin molded section 60 that is molded by inserting the arm main body 40. This makes it possible to suppress an increase in the number of parts of the lower arm 30 and an increase in the number of assembly steps compared to when the rectifying section 70, which is separate from the arm main body 40, is later attached to the arm main body 40. Also, alignment of the arm main body 40 and the rectifying section 70 is not required.

[0075] <Modifications> This embodiment can be modified as follows: This embodiment and the following modifications can be combined and implemented within the scope of technical compatibility.

[0076] At least one of the engaging portions 62, 63, 65, 66, 68, and 69 may be omitted from the resin molded portion 60. The reinforcing member 50 may be omitted from the lower arm 30.

[0077] The shape of the tip end 70b of the airflow rectifying portion 70 may be changed as desired. For example, the tip end 70b of the airflow rectifying portion 70 may be shaped to extend linearly. The length L of the airflow rectifying portion 70 may vary from portion to portion in the vehicle width direction X.

[0078] The extension range of the airflow straightening portion 70 and the protruding wall portion 71 in the vehicle width direction X can be changed as desired. For example, the airflow straightening portion 70 and the protruding wall portion 71 may be provided so as to extend over the entire lower arm 30 in the vehicle width direction X.

[0079] The protruding wall portion 71 may be omitted from the lower arm 30. Instead of shaping the base end portion 70c of the airflow rectifying portion 70 to extend to a position above the upper end of the front wall 32A, the base end portion 70c may be shaped to extend to the upper end of the front wall 32A or to a position below the upper end of the front wall 32A.

[0080] At least one of the first rib 72a and the second rib 72b may be omitted. At least one of the second covering portion 64 and the third covering portion 67 may be omitted. The flow rectifying portion 70 may be configured to be detachable from the resin molded portion 60. The flow rectifying portion 70 may be formed separately from the resin molded portion 60, and the flow rectifying portion 70 may be fixed to the resin molded portion 60.

[0081] The resin molded portion 60 may be omitted from the lower arm 30. In this case, the airflow rectifying portion 70 may be fixed to the front wall main body 42A by welding or the like, or may be configured to be detachable from the front wall main body 42A. The airflow rectifying portion 70 may be made of a metal material.

Claims

1. A suspension arm configured to connect a vehicle body and a wheel, comprising: a bottom wall; a front wall and a rear wall each protruding in an upward direction of the vehicle from the bottom wall and opposing each other in the fore-and-aft direction of the vehicle; and a plate-shaped straightening portion extending in the vehicle width direction and supported in a cantilever manner by the front wall so as to protrude diagonally downward from an upper portion of the front wall towards the front of the vehicle.

2. The suspension arm according to claim 1, further comprising a rib provided on a lower surface of the airflow straightening portion and extending in the front-rear direction of the vehicle.

3. A suspension arm as set forth in claim 1 or 2, wherein a tip portion of the airflow straightening portion extends in a curved manner toward the bottom of the vehicle.

4. A suspension arm according to any one of claims 1 to 3, wherein an end of said airflow control portion closer to said front wall extends to a position higher than an upper end of said front wall.

5. A suspension arm according to claim 4, wherein the airflow adjustment portion has a protruding wall portion that protrudes upward from the end portion closer to the front wall and extends in the vehicle width direction.

6. A suspension arm as claimed in any one of claims 1 to 5, comprising: an arm body having a bottom wall body, and a front wall body and a rear wall body which each protrude from the bottom wall body in a direction upwardly of the vehicle and which face each other in the fore-and-aft direction of the vehicle; and a resin molded portion which is molded by inserting the arm body, wherein the front wall body has a front surface facing towards the front of the vehicle, the resin molded portion has a covering portion which covers the front surface of the front wall body, the bottom wall includes the bottom wall body, the front wall includes the front wall body and the covering portion, and the rear wall includes the rear wall body, and the straightening portion is provided integrally with the covering portion.

7. A suspension arm configured to connect a vehicle body and wheels, comprising: a bottom wall; and a front wall and a rear wall each protruding from the bottom wall in an upward direction of the vehicle and opposing each other in the longitudinal direction of the vehicle, wherein the front wall has a front wall main body extending in the vertical direction of the vehicle and a flange extending in the forward direction of the vehicle from an upper end of the front wall main body in the vertical direction of the vehicle, and is provided with a plate-like straightening portion extending in the width direction of the vehicle and cantilevered by the flange so as to protrude diagonally downward from a front end portion of the flange in the forward direction of the vehicle.

8. A suspension arm as described in claim 7, comprising: a bottom wall body, an arm body having the front wall body and the rear wall body which each protrude from the bottom wall body in a direction upwardly of the vehicle and which face each other in the fore-and-aft direction of the vehicle, and the flange, and a resin molded portion which is molded by inserting the arm body, wherein the front wall body has a front surface facing toward the front of the vehicle, and the flange has a lower surface facing toward the bottom of the vehicle, the resin molded portion has a covering portion which covers the front surface of the front wall body and the lower surface of the flange, the bottom wall includes the bottom wall body, the front wall includes the front wall body, the flange and the covering portion, and the rear wall includes the rear wall body, and the straightening portion is provided integrally with the covering portion.

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