Suspension arm

Abstract

To provide a suspension arm capable of improving aerodynamic characteristics.SOLUTION: A lower arm 30 includes a bottom wall 31, and a front wall 32A and a rear wall 32B that protrude upward the top of the vehicle from the bottom wall 31 and face each other in a front-rear direction Y. The lower arm 30 includes a rectifying portion 70 having a plate shape extending in a vehicle width direction X. The rectifying portion 70 is cantilevered on the front wall 32A so as to protrude obliquely downward from an upper portion of the front wall 32A toward the front of the vehicle.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a suspension arm. [Background technology]

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

[0003] [Patent Document 1] JP 2016-107838 A Summary of the Invention [Problem to be solved by the invention]

[0004] Here, the suspension arm is provided under the vehicle so as to be exposed to the outside of the vehicle. Therefore, when the vehicle is moving, the suspension arm is exposed to the wind caused by the vehicle moving. When the suspension arm is exposed to the wind caused by the vehicle moving in this way, there is a risk that the aerodynamic characteristics of the vehicle will be deteriorated. [Means for solving the problem]

[0005] A suspension arm for solving the above problem has a bottom wall, and front and rear walls that protrude from the bottom wall above the vehicle and oppose each other in the fore-and-aft direction of the vehicle, and is provided with a straightening portion that is plate-shaped extending in the vehicle width direction and is cantilevered by the front wall so as to protrude diagonally downward from an upper part of the front wall towards the front of the vehicle. [Brief description of the drawings]

[0006] [Figure 1]FIG. 2 is a side end view of a lower arm according to one embodiment of the suspension arm. [Diagram 2] 2 is a schematic diagram showing a suspension system of a vehicle to which the lower arm is applied. FIG. [Diagram 3] FIG. [Figure 4] FIG. 2 is an exploded perspective view showing an arm body and a reinforcing member that constitute the lower arm, separated from each other. [Diagram 5] FIG. [Figure 6] FIG. [Figure 7] 4 is an enlarged cross-sectional side view of a base end portion of the airflow straightening portion of the lower arm and its surrounding area. FIG. [Figure 8] 4 is an enlarged side cross-sectional view of a front wall and an airflow adjustment portion of the lower arm. FIG. [Figure 9] 13 is a graph showing the relationship between the angle θ of the airflow straightening portion, the length ratio R, and the Cd value in the lower arm. [Figure 10] 13 is a graph showing the relationship between the angle θ of the airflow straightening portion, the length ratio R, and the CL value in the lower arm. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0007] Hereinafter, with reference to Figs. 1 to 10, an embodiment in which a suspension arm is embodied as a lower arm of a suspension device will be described. <Suspension device 10> 2, the suspension device 10 is disposed between a vehicle body 100 and a wheel 110, and supports the wheel 110 so as to be able to swing freely relative to the vehicle body 100. The suspension device 10 is configured to absorb shocks transmitted from the road surface to the vehicle body 100 via the wheel 110, and to press the wheel 110 against the road surface.

[0008] 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 and a support member 111 that supports a wheel 110.

[0009] The suspension spring 80 extends in the vehicle up-down direction (hereinafter, referred to as the up-down direction Z). <Lower Arm 30> As shown in Fig. 1 and Fig. 3, the lower arm 30 has a bottom wall 31, a front wall 32A, a rear wall 32B, and an airflow straightening portion 70. The bottom wall 31 extends in the vehicle width direction X and in 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 straightening portion 70 extends from an upper portion of the front wall 32A toward the front of the vehicle. The airflow straightening portion 70 will be described in detail later.

[0010] The lower arm 30 has an arm body 40 , a reinforcing member 50 , and a resin molded portion 60 . <Arm body 40> 1 and 4, the arm body 40 has a body-side bottom wall 41, a body-side front wall 42A, and a body-side rear wall 42B. The body-side bottom wall 41 has an elongated shape extending in the vehicle width direction X. The body-side front wall 42A and the body-side rear wall 42B protrude upward from both end edges of the body-side bottom wall 41 in the front-rear direction Y and face each other. The arm body 40 is open upward.

[0011] The arm body 40 is formed, for example, by pressing a metal plate. Examples of the material for the arm body 40 include metal materials such as high tensile steel. An intermediate portion 41a of the main body side bottom wall 41 in the vehicle width direction X has a larger width in the front-rear direction Y than the other portions. The width of the intermediate portion 41a in the front-rear direction Y gradually decreases toward both side portions in the vehicle width direction X. The intermediate portion 41a of the main body side bottom wall 41 has a spindle shape when viewed from the up-down direction Z.

[0012] The portions of the main body side bottom wall 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 main body side front wall 42A and the main body side rear wall 42B are symmetrical in the front-rear direction Y. Therefore, hereinafter, the configuration of the main body side front wall 42A will be described, and a description of the configuration of the main body side rear wall 42B may be omitted.

[0013] The body-side front wall 42A extends over the entire body-side bottom wall 41 in the vehicle width direction X. One end of the body-side front wall 42A in the vehicle width direction X, which constitutes a first connecting portion 47 described later, protrudes in the vehicle width direction X beyond the body-side bottom wall 41.

[0014] The portion of the main body side front wall 42A that protrudes from the intermediate portion 41a has an inclined portion 43 that continues to the main body side bottom wall 41 and a straight portion 44 that continues to the inclined portion 43. The inclined portion 43 is inclined so as to move away from the main body side rear wall 42B in the front-rear direction Y as it goes upward.

[0015] The straight portion 44 extends straight in the up-down direction Z. The straight portion 44 of the main body side front wall 42A and the straight portion 44 of the main body side rear wall 42B extend parallel to each other. The main body side front wall 42A and the main body side rear wall 42B each have a first flange 45A and a second flange 45B. The first flange 45A protrudes from an end of the main body side front wall 42A opposite the main body side bottom wall 41 toward the opposite side of the main body side rear wall 42B in the front-rear direction Y. The first flange 45A and the second flange 45B protrude in opposite directions to each other in the front-rear direction Y. The first flange 45A constitutes a tip portion of the main body side front wall 42A in the protruding direction. The first flange 45A extends over the entire main body side front wall 42A in the vehicle width direction X.

[0016] 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 constitutes a central portion in the vehicle width direction X of the arm body 40. 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.

[0017] <Spring housing part 46> 1 and 4, the spring accommodating portion 46 defines an accommodating space for accommodating the lower end of the suspension spring 80 (see FIG. 2) by the intermediate portion 41a, the main body-side front wall 42A, and the main body-side rear wall 42B. The main body-side front wall 42A and the main body-side rear wall 42B of the spring accommodating portion 46 bulge out in opposite directions in the front-to-rear direction Y. A through hole 46a penetrating in the up-down direction Z is provided in the bottom portion of the spring accommodating portion 46, i.e., the intermediate portion 41a. The through hole 46a is circular.

[0018] <First connection part 47> 3 and 4, the first connecting portion 47 is a portion of the arm body 40 that is connected to the vehicle body 100. The body-side front wall 42A and the body-side rear wall 42B of the first connecting portion 47 extend parallel to each other in the vehicle width direction X. The body-side front wall 42A and the body-side rear wall 42B of the first connecting portion 47 protrude in the vehicle width direction X beyond the edge of the body-side bottom wall 41 in the vehicle width direction X.

[0019] A first connecting hole 47a penetrating in the front-rear direction Y is provided in each of the main body side front wall 42A and the main body side rear wall 42B of the first connecting portion 47. The first connecting portion 47 is rotatably connected to the frame 101 of the vehicle body 100 via a rotating shaft (not shown) inserted into the first connecting hole 47a.

[0020] <Second connection part 48> The second connecting portion 48 is a portion of the arm body 40 that is connected to the wheel 110. The main body side front wall 42A and the main body side rear wall 42B of the second connecting portion 48 extend in parallel in the vehicle width direction X.

[0021] The second connecting portion 48 has a second connecting hole 48a penetrating in the front-rear direction Y in each of the main body side front wall 42A and the main body side rear wall 42B. The second connecting portion 48 is rotatably connected to the support member 111 of the wheel 110 via a rotating shaft (not shown) inserted into the second connecting hole 48a.

[0022] As shown in Fig. 1 and Fig. 4, the reinforcing member 50 has a flat plate shape. The reinforcing member 50 covers the portion of the spring accommodating portion 46 on the first connecting portion 47 side from above. Examples of materials for the reinforcing member 50 include metal materials 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.

[0023] <Resin molding section 60> 1 and 3 to 5, the resin molded portion 60 is molded by inserting the arm body 40 and the reinforcing member 50. The arm body 40 to which the reinforcing member 50 is joined is placed as an insert part inside a mold device (not shown), and then the inside of the mold device is filled with resin, thereby molding the resin molded portion 60. Examples of materials for the resin molded portion 60 include thermoplastic resin materials.

[0024] 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 main body side front wall 42A facing the front of the vehicle (hereinafter, the front surface). More specifically, the first covering portion 61 covers a portion of the front surface of the main body side front wall 42A excluding the peripheries of the first connecting hole 47a and the second connecting hole 48a. The front surface of the main body side front wall 42A is the surface opposite to the surface of the main body side front wall 42A facing the main body side rear wall 42B, and includes the lower surface of the first flange 45A. In this embodiment, the first covering portion 61 corresponds to the "covering portion."

[0025] The first covering portion 61 has an inclined covering portion 61b that covers the inclined portion 43 of the main body side front wall 42A, and a straight covering portion 61a that covers the straight portion 44 of the main body side front wall 42A. The inclined covering portion 61b extends along the outer surface of the inclined portion 43 of the main body side front wall 42A. The straight covering portion 61a extends along the outer surface of the straight portion 44 of the main body side front wall 42A.

[0026] The first covering portion 61 has two engaging portions 62 which respectively engage with both ends in the vehicle width direction X of the main body-side front wall 42A, and an engaging portion 63 which engages with a tip portion of the first flange 45A.

[0027] Each engagement portion 62 covers one end portion of the main body side front wall 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 engagement portion 62 engages with the one end portion of the main body side front wall 42A over the entirety in the up-down direction Z.

[0028] The engagement 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 engagement portion 63 engages with the tip portion of the first flange 45A over the entirety in the vehicle width direction X.

[0029] In the portion of the spring accommodating portion 46 on the first connecting portion 47 side, the engaging portion 63 covers the joint portion between the first flange 45A and the reinforcing member 50 in addition to the tip portion of the first flange 45A.

[0030] <Second covering portion 64> The second covering portion 64 covers the surface of the main body-side rear wall 42B facing the rear of the vehicle (hereinafter, the rear surface). More specifically, the second covering portion 64 covers a portion of the rear surface of the main body-side rear wall 42B excluding the peripheries of the first connecting hole 47a and the second connecting hole 48a. The rear surface of the main body-side rear wall 42B is the surface opposite to the surface of the main body-side rear wall 42B facing the main body-side front wall 42A, and includes the lower surface of the second flange 45B.

[0031] The second covering portion 64 has an inclined covering portion 64b that covers the inclined portion 43 of the main body side rear wall 42B, and a straight covering portion 64a that covers the straight portion 44 of the main body side rear wall 42B. The inclined covering portion 64b extends along the rear surface of the inclined portion 43 of the main body side rear wall 42B. The straight covering portion 64a extends along the rear surface of the straight portion 44 of the main body side rear wall 42B.

[0032] The second covering portion 64 has two engaging portions 65 which respectively engage with both ends in the vehicle width direction X of the main body side rear wall 42B, and an engaging portion 66 which engages with a tip portion of the second flange 45B.

[0033] Each engagement portion 65 covers one end portion of the main body side rear wall 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 engagement portion 65 engages with the one end portion of the main body side rear wall 42B over the entirety in the up-down direction Z.

[0034] The engagement 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 engagement portion 66 engages with the tip portion of the second flange 45B over the entirety in the vehicle width direction X.

[0035] In the portion of the spring accommodating portion 46 on the first connecting portion 47 side, the engaging portion 66 covers the joint portion between the second flange 45B and the reinforcing member 50 in addition to the tip portion of the second flange 45B.

[0036] <Third covering part 67> 1, 4 and 6, the third covering portion 67 covers the entire lower surface of the main body side bottom wall 41. As shown in Figures 5 and 6, the third covering portion 67 has two engaging portions 68 which respectively engage with both ends of the main body side bottom wall 41 in the vehicle width direction X, and an engaging portion 69 which engages with the periphery of the through hole 46a.

[0037] 4 to 6, each engagement portion 68 covers one end portion of the main body side bottom wall 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 engagement portion 68 engages with the one end portion of the main body side bottom wall 41 over the entirety in the front-rear direction Y.

[0038] The engaging portion 69 covers the periphery of the through hole 46a from both sides in the up-down 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.

[0039] The bottom wall 31 of the lower arm 30 includes a main body side bottom wall 41 and a third covering portion 67. The front wall 32A of the lower arm 30 includes a main body side front wall 42A and a first covering portion 61. The rear wall 32B of the lower arm 30 includes a main body side rear wall 42B and a second covering portion 64.

[0040] 1, 3, and 6, the lower arm 30 has a straightening portion 70, a protruding wall portion 71, and a rib 72. In this embodiment, the straightening portion 70, the protruding wall portion 71, and the rib 72 are used to straighten the air flow around the lower arm 30.

[0041] <Rectifier section 70> The rectifying portion 70 has a plate shape extending in the vehicle width direction X. The rectifying portion 70 has an elongated shape extending in the vehicle width direction X along the front wall 32A. The rectifying portion 70 extends over the entire front wall 32A in the spring accommodating portion 46 in the vehicle width direction X. The rectifying portion 70 extends in a curved manner along the front surface of the front wall 32A in the spring accommodating portion 46. The rectifying portion 70 is provided integrally with the first covering portion 61. The 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 main body side front wall 42A in the spring accommodating portion 46. The rectifying portion 70 is cantilevered by the front wall 32A so as to protrude obliquely downward from an upper portion of the front wall 32A, more specifically, from an upper end thereof toward the front of the vehicle. The upper portion of the front wall 32A is a portion of the front wall 32A that is continuous with the first flange 45A. Each portion of the airflow straightening portion 70 in the vehicle width direction X has the same shape.

[0042] The flow rectifying portion 70 is composed of a main body portion 70a and a tip portion 70b. 1, 5 and 7, the main body 70a constitutes a portion of the flow straightening section 70 on the front wall 32A side. The main body 70a extends linearly in the front-rear direction Y. The main body 70a is inclined with respect to the horizontal direction so as to be positioned lower the further away from the front wall 32A in the front-rear direction Y. An end portion of the main body 70a on the front wall 32A side (hereinafter, base end portion 70c) extends to a position above the vehicle beyond the upper end of the front wall 32A.

[0043] The tip portion 70b constitutes the tip portion of the airflow straightening portion 70, that is, the end portion on the side farther from the front wall 32A. The tip portion 70b extends in the front-rear direction Y so as to curve toward the bottom of the vehicle. <Protruding wall part 71> As shown in FIG. 5 and FIG. 8, the protruding wall portion 71 is provided at the base end portion 70c of the flow straightening portion 70. The protruding wall portion 71 is provided integrally with the flow straightening portion 70. The protruding wall portion 71 forms a 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 is an upper end of the base end portion 70c and protrudes from the rear end of the base end portion 70c toward the upper side of the vehicle. The protruding wall portion 71 extends over the entire spring accommodating portion 46 (more specifically, the main body side front wall 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.

[0044] <Rib 72> 3, 6, and 8, the rib 72 is composed of a first rib 72a and a second rib 72b. The rib 72 forms a part of the resin molded portion 60.

[0045] The first rib 72a is provided on the lower surface of the straightening portion 70. The first rib 72a extends in the front-rear direction Y so as to extend in the front-rear direction Y and the up-down direction Z. A plurality of the first ribs 72a are provided so as to extend parallel to each other at intervals in the vehicle width direction X. Each of the first ribs 72a is installed so as to connect the lower surface of the straightening portion 70 and the front surface of the front wall 32A in a portion sandwiched between the lower surface of the straightening portion 70 and the front surface of the front wall 32A. The lower end surface of each of the first ribs 72a extends in a curved manner so as to form a convex shape toward the upper side of the vehicle when viewed from the vehicle width direction X. In this embodiment, each of the first ribs 72a divides the portion sandwiched between the lower surface of the straightening 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.

[0046] 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.

[0047] 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-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 the wind flows below the lower arm 30, the air is rectified by the second rib 72b.

[0048] According to this embodiment, the traveling wind from the front of the vehicle toward the front wall 32A of the lower arm 30 can be blocked and deflected by the straightening portion 70, so that the wind can escape to the upper part or the side of the vehicle without hitting the front wall 32A. This can reduce the drag generated on the lower arm 30.

[0049] 8, the length of the flow straightening portion 70, specifically, the length of the main body portion 70a thereof in the protruding direction from the front wall 32A is referred to as the "length L of the flow straightening portion 70." The height from the lower surface of the main body side bottom wall 41 to the upper surface of the main body side front wall 42A is referred to as the "height H of the arm main body 40." The ratio of the height H of the arm main body 40 to the length L of the flow straightening portion 70 is referred to as the "length ratio R (=L / H)." When the flow straightening portion 70 is viewed from the vehicle width direction X, the angle formed between the imaginary axis V extending in the front-rear direction Y and the main body portion 70a of the flow straightening portion 70 is referred to as the "angle θ of the flow straightening portion 70."

[0050] 8, in the lower arm 30 of this embodiment, if the length L of the airflow straightening portion 70 is excessively short, the traveling wind is more likely to hit the front wall 32A, and the drag acting on the lower arm 30 becomes large. Also, 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 traveling wind becomes large, and the drag acting on the airflow straightening portion 70 and, ultimately, the drag acting on the lower arm 30 becomes large.

[0051] Taking this into consideration, in this embodiment, based on the results of simulations performed by the inventors, the shape of each part of the lower arm 30 is set so that the length L of the straightening section 70 is an appropriate length, specifically, so that the above-mentioned length ratio R is "0.62".

[0052] 8, in the lower arm 30 of this embodiment, as the angle θ of the airflow straightening portion 70 approaches "0 degrees," the traveling wind hits the front wall 32A more easily, and the drag acting on the lower arm 30 becomes larger. On the other hand, as the angle θ of the airflow straightening portion 70 approaches "90 degrees," the angle θ at which the traveling wind hits the airflow straightening portion 70 becomes closer to a right angle, and the drag acting on the airflow straightening portion 70 and, ultimately, the drag acting on the lower arm 30 becomes larger.

[0053] Taking this into consideration, in this embodiment, based on the results of simulations performed 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."

[0054] <Simulation results> Hereinafter, the aerodynamic characteristics of the lower arm 30 when the length L of the airflow straightening portion 70, the height H of the arm body 40, and the angle θ of the airflow straightening portion 70 are changed will be described using the results of a simulation performed by the inventors.

[0055] 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 straightening portion 70 is set to "10 degrees," "35 degrees," and "60 degrees." The dashed and dotted line in Fig. 9 is a graph when the angle θ of the airflow straightening portion 70 is set to "10 degrees," the solid line in Fig. 9 is a graph when the angle θ of the airflow straightening portion 70 is set to "35 degrees," and the dashed line in Fig. 9 is a graph when the angle θ of the airflow straightening portion 70 is set to "60 degrees."

[0056] 9, it was confirmed that when the angle θ of the rectifying section 70 is "10 degrees" and the length ratio R is in the range of "0.95 to 1.10", the Cd value is suitably reduced. In this simulation, when the angle θ of the rectifying section 70 is "10 degrees", the Cd value was smallest when the length ratio R was "1.05".

[0057] 9, it was confirmed that when the angle θ of the rectifying section 70 is "35 degrees" and the length ratio R is in the range of "0.60 to 0.90", the Cd value is suitably reduced. In this simulation, when the angle θ of the rectifying section 70 is "35 degrees", the Cd value was smallest when the length ratio R was "0.73".

[0058] 9, it was confirmed that when the angle θ of the rectifying section 70 is "60 degrees", the Cd value is suitably reduced when the length ratio R is in the range of "0.60 to 0.70". In this simulation, when the angle θ of the rectifying section 70 is "60 degrees", the Cd value was smallest when the length ratio R was "0.62".

[0059] 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 straightening section 70 is set to "10 degrees," "35 degrees," and "60 degrees." The dashed and dotted line in Fig. 10 is a graph when the angle θ of the airflow straightening section 70 is set to "10 degrees," the solid line in Fig. 10 is a graph when the angle θ of the airflow straightening section 70 is set to "35 degrees," and the dashed line in Fig. 9 is a graph when the angle θ of the airflow straightening section 70 is set to "60 degrees."

[0060] As shown in FIG. 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.

[0061] As shown by the dotted line in FIG. 10, when the angle θ of the straightening section 70 is "10 degrees," if the length ratio R is set to "1.05," it has been confirmed that the Cd value can be reduced as described above, but the CL value becomes a value deviated from "0," specifically, a negative value.

[0062] Here, the smaller the CL value, the more the lift force acting on the lower arm 30 is suppressed. However, if the CL value is an excessively negative value, this 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 straightening portion 70 is set to "10 degrees" and the length ratio R is set to "1.05," the CL value becomes an excessively negative value, and the rolling resistance of the vehicle increases.

[0063] As shown by the solid line in Fig. 10, when the angle θ of the airflow straightening section 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". Also, as shown by the dashed line in Fig. 10, when the angle θ of the airflow straightening section 70 is "60 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". 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.

[0064] From the above, it can be seen that by setting the angle θ of the airflow control portion 70 to "35 degrees" and the length ratio R to "0.62", the aerodynamic characteristics of the lower arm 30 can be effectively improved.

[0065] <Action and effect> The operation 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 protrude from the bottom wall 31 toward the upper side of the vehicle and face each other in the front-to-rear direction Y. The lower arm 30 has a plate-shaped straightening portion 70 that extends in the vehicle width direction X. The 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 toward the front of the vehicle.

[0066] According to this configuration, the traveling wind 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 traveling wind can be guided upward or to the side of the vehicle without hitting the front wall 32A. This can reduce the drag generated in the lower arm 30. In addition, the traveling wind hits the front surface of the airflow straightening portion 70, that is, the inclined surface that is inclined diagonally upward when viewed from the front of the vehicle. Due to this collision, a force is generated in the airflow straightening portion 70 that presses the airflow straightening portion 70 downward. This pressing force can suppress 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.

[0067] (2) The lower surface of the straightening portion 70 is provided with a first rib 72a extending in the front-rear direction Y. With this configuration, an air flow that flows in the front-rear direction Y along the first rib 72a can be formed in a portion (hereinafter, referred to as the specific portion) sandwiched between the lower surface of the straightening portion 70 and the front surface of the front wall 32A. This prevents the air flow from stagnating in the specific portion. Moreover, the first ribs 72a divide the specific portion into a right portion and a left portion in the vehicle width direction X. As a result, air is less likely to flow in the vehicle width direction X in the specific portion, so that it is possible to prevent air from flowing around the specific portion from both sides of the straightening portion 70 in the vehicle width direction X. Therefore, with the above configuration, it is possible to reduce the drag generated in the lower arm 30.

[0068] In this embodiment, the inventors have confirmed the following from the results of simulations. That is, it has been confirmed that the Cd value is reduced by providing the first rib 72a when the angle θ of the flow straightening section 70 is set to "35 degrees" and the length ratio R is set to "0.62" compared to when the first rib 72a is not provided. It has also been confirmed that the CL value remains at approximately "0" and hardly changes even when the first rib 72a is provided in a flow straightening section 70 with the angle θ set to "35 degrees" and the length ratio R set to "0.62".

[0069] (3) The tip 70b of the airflow straightening portion 70 extends in a curved manner toward the bottom of the vehicle. With this configuration, compared to when the tip of the airflow straightening portion 70 is not curved or when it extends in a curved manner toward the top of the vehicle, it is possible to prevent the traveling wind that has passed the tip 70b of the airflow straightening portion 70 from flowing around the vehicle rear side of the airflow straightening portion 70, i.e., the specific portion. This makes it possible to reduce the drag generated in the lower arm 30.

[0070] (4) The base end portion 70c of the airflow straightening portion 70 extends to a position above the vehicle beyond the upper end of the front wall 32A. In this embodiment, a part of the traveling wind flows obliquely upward toward the rear of the vehicle along the front surface of the straightening portion 70. According to the above configuration, the base end portion 70c of the straightening portion 70 extends to a position above the vehicle beyond the upper end of the front wall 32A, so that the flow of the traveling wind that has passed through the base end portion 70c can be separated from the upper opening of the lower arm 30, more specifically, from the upper opening of the spring accommodating portion 46. This makes it possible to prevent the flow of the traveling wind that has passed through the base end portion 70c from entering the inside of the lower arm 30. Therefore, the drag generated in the lower arm 30 can be reduced.

[0071] (5) The protruding wall portion 71 that protrudes toward the top of the vehicle and extends in the vehicle width direction X is provided at the upper and rear end of the base end portion 70c of the airflow straightening portion 70. In this embodiment, a part of the traveling wind flows obliquely upward toward the rear of the vehicle along the front surface of the airflow straightening portion 70. According to the above configuration, the direction of the flow of this traveling wind can be changed by the protruding wall portion 71 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 inside of the lower arm 30 after passing through the airflow straightening portion 70.

[0072] (6) The lower arm 30 includes an arm body 40 and a resin molded portion 60 that is molded by inserting the arm body 40. The arm body 40 has a body-side bottom wall 41, and a body-side front wall 42A and a body-side rear wall 42B that protrude from the body-side bottom wall 41 toward the upper side of the vehicle and face each other in the front-rear direction Y. The resin molded portion 60 has a first covering portion 61 that covers the front surface of the body-side front wall 42A. The bottom wall 31 includes the body-side bottom wall 41, the front wall 32A includes the body-side front wall 42A and the first covering portion 61, and the rear wall 32B includes the body-side rear wall 42B. The straightening portion 70 is provided integrally with the first covering portion 61.

[0073] According to this configuration, the rectifying portion 70 can be molded as a part of the resin molded portion 60 that is molded by inserting the arm 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 a case in which the rectifying portion 70, which is separate from the arm body 40, is later attached to the arm body 40. Also, alignment between the arm body 40 and the rectifying portion 70 is not required.

[0074] <Example of change> This embodiment can be modified as follows: This embodiment and the following modifications can be combined with each other to the extent that they are not technically inconsistent.

[0075] 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.

[0076] The shape of the tip portion 70b of the flow rectifying portion 70 can be changed as desired. For example, the tip portion 70b of the flow rectifying portion 70 can be shaped to extend linearly. The length L of each portion of the airflow straightening portion 70 may be constant in the vehicle width direction X, or may be different in the vehicle width direction X.

[0077] 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.

[0078] The protruding wall portion 71 may be omitted from the lower arm 30. Instead of having the base end portion 70c of the straightening section 70 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.

[0079] 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. Alternatively, the flow rectifying portion 70 may be formed separately from the resin molded portion 60 and fixed to the resin molded portion 60.

[0080] The resin molded portion 60 may be omitted from the lower arm 30. In this case, the flow straightening portion 70 may be fixed to the main body side front wall 42A by welding or the like, or may be configured to be detachable from the main body side front wall 42A. The flow straightening portion 70 may be made of a metal material.

[0081] <Additional Notes> The above embodiment includes the configurations described in the following supplementary notes. [Appendix 1] A suspension arm having a bottom wall, and a front wall and a rear wall protruding from the bottom wall toward an upper side of a vehicle and facing each other in a longitudinal direction of the vehicle, A suspension arm having a plate shape extending in a vehicle width direction and including a straightening portion that is 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.

[0082] [Appendix 2] A suspension arm as described in [Appendix 1], wherein a rib extending in the fore-and-aft direction of the vehicle is provided on the underside of the straightening portion. [Appendix 3] A suspension arm as described in [Appendix 1] or [Appendix 2], wherein a tip portion of the straightening portion extends in a curved manner toward the bottom of the vehicle.

[0083] [Appendix 4] A suspension arm described in any one of [Appendix 1] to [Appendix 3], wherein the end portion of the airflow straightening portion on the front wall side extends to a position above the vehicle beyond the upper end of the front wall.

[0084] [Appendix 5] A suspension arm as described in [Appendix 4], having a protruding wall portion provided at the end portion on the front wall side of the straightening portion, protruding from the end portion toward the top of the vehicle and extending in the vehicle width direction.

[0085] [Appendix 6] A suspension arm described in any one of [Appendix 1] to [Appendix 5], comprising: an arm body having a body-side bottom wall, and a body-side front wall and a body-side rear wall which protrude from the body-side bottom wall towards the top of the vehicle and which oppose each other in the vehicle fore-and-aft direction; and a resin molded portion molded by inserting the arm body, wherein the resin molded portion has a covering portion which covers a surface of the body-side front wall on the vehicle front side, the bottom wall includes the body-side bottom wall, the front wall includes the body-side front wall and the covering portion, the rear wall includes the body-side rear wall, and the straightening portion is provided integrally with the covering portion. [Explanation of symbols]

[0086] 10…Suspension device 20…Upper arm 30…Lower arm 31…Bottom wall 32A…Front wall 32B…Back wall 40…Arm body 41…Bottom wall of main body 41a...middle part 42A…Main body front wall 42B…Body side rear wall 43…Slope part 44…Straight section 45A…First flange 45B…Second flange 46…Spring housing 46a...Through hole 47...1st connection part 47a...1st connection hole 48…Second connection part 48a…Second connection hole 50…Reinforcing member 60…Resin molding part 61...First covering part 61a, 64a...Straight coated section 61b,64b...Slanted covering part 62, 63, 65, 66, 68, 69 ... Engagement parts 64…Second coating part 67…Third covering part 70... Rectifier 70a…Main body 70b…Tip 70c...Proximal part 71...Protruding wall part 72…Rib 72a…First Rib 72b…2nd Rib 80…Suspension spring 100…Body 101...Frame 110...Wheel 111...Support member

Claims

1. A suspension arm having a bottom wall, and a front wall and a rear wall protruding from the bottom wall toward an upper side of a vehicle and facing each other in a front-rear direction of the vehicle, A suspension arm having a plate shape extending in a vehicle width direction and including a straightening portion that is 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.

2. A rib extending in the front-rear direction of the vehicle is provided on the lower surface of the airflow straightening portion.

2. The suspension arm according to claim 1.

3. The tip portion of the airflow straightening portion is curved and extends toward the bottom of the vehicle.

3. A suspension arm according to claim 1 or 2.

4. An end portion of the airflow straightening portion on the front wall side extends to a position above the vehicle beyond an upper end of the front wall.

3. A suspension arm according to claim 1 or 2.

5. a protruding wall portion provided at an end portion of the straightening portion on the front wall side, protruding from the end portion toward the upper side of the vehicle and extending in a vehicle width direction; 5. A suspension arm according to claim 4.

6. an arm body having a body side bottom wall, and a body side front wall and a body side rear wall protruding from the body side bottom wall toward the upper side of the vehicle and facing each other in the front-rear direction of the vehicle; a resin molded portion molded by inserting the arm body, the resin molding portion has a covering portion that covers a surface of the main body front wall on a vehicle front side, the bottom wall includes the body-side bottom wall, the front wall includes the body-side front wall and the covering portion, and the rear wall includes the body-side rear wall, The rectifying portion is integrally provided with the covering portion.

3. A suspension arm according to claim 1 or 2.

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