Suspension arm

Abstract

The suspension arm has: a bottom wall (31); a first side wall (32A) and a second side wall (32B) protruding upward from the bottom wall (31) and facing each other; and a rectifying part (70) extending from the first side wall (32A) to the side opposite to the second side wall (32B). The first side wall (32A) has, in a protruding direction from the bottom wall (31), a base end section that is an end section close to the bottom wall (31), and a tip section that is an end section away from the bottom wall (31). The rectifying portion (70) extends from a portion of the first side wall (32A) between the base end portion and the tip end portion.

Description

Technical Field

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

[0002] Conventionally, vehicles such as automobiles include suspension arms that connect wheels to the vehicle body. The suspension arm described in Patent Document 1 includes a main body and a cover bonded to the main body by vulcanization. The main body includes a bottom wall and a pair of side walls, the pair of side walls protrude from the bottom wall and face each other. The cover covers the outer surface of the bottom wall and the outer surfaces of the pair of side walls. A portion of the cover extends from the outer surface of the base end of one side wall to the side opposite to the other side wall. This portion functions as a rectifying member that reduces the air resistance of the traveling wind. Prior art literature Patent Literature

[0003] Patent Document 1: Japanese Patent Application Publication No. 2006-56463 Summary of the invention Problems to be solved by the invention

[0004] However, Patent Document 1 does not specifically mention the effect of the shape of the cover on the aerodynamic characteristics of the suspension arm. Therefore, there is room for improvement in improving the aerodynamic characteristics of the suspension arm. Solutions to Solve Problems

[0005] A suspension arm according to one aspect of the present invention comprises: a bottom wall; a first side wall and a second side wall which protrude upward from the bottom wall and are opposed to each other; and a rectifying portion which extends from the first side wall to a side opposite to the second side wall. The first side wall has a base end portion which is an end portion close to the bottom wall and a terminal end portion which is an end portion away from the bottom wall in a protruding direction from the bottom wall. The rectifying portion extends from a portion of the first side wall between the base end portion and the terminal end portion. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Figure 1 It is a perspective view of a lower arm as one embodiment of a suspension arm. Figure 2 It is indicated that the application Figure 1 Schematic diagram of the lower arm of a vehicle's suspension arrangement. Figure 3 It will constitute Figure 1 An exploded perspective view of the lower arm with the arm body and reinforcement member separated and shown. Figure 4 yes Figure 1 Top view of the lower arm. Figure 5 is along Figure 4 A cross-sectional view of line 5-5. Figure 6 It is a cross-sectional view of the lower arm for explaining the evaluation index of the aerodynamic characteristics in the simulation. Figure 7 It is shown Figure 6 A coordinate diagram showing the relationship between the length ratio of the rectifying portion of the lower arm and the Cd value. Figure 8 It is shown Figure 6 A coordinate diagram showing the relationship between the length ratio of the rectifier section of the lower arm and the Cl value. Fig. 9 It is shown Figure 6 A coordinate diagram showing the relationship between the height ratio of the rectifying portion of the lower arm and the Cd value. Fig.10 It is shown Figure 6 A coordinate diagram showing the relationship between the height ratio of the rectifier section of the lower arm and the Cl value. Fig.11 It is shown Figure 6 A coordinate diagram showing the relationship between the rectifying portion angle of the rectifying portion of the lower arm and the Cd value. Fig.12 It is shown Figure 6 A coordinate diagram showing the relationship between the rectifying portion angle of the rectifying portion of the lower arm and the C1 value. DETAILED DESCRIPTION

[0007] Below, refer to Figures 1 to 12 , an embodiment in which the suspension arm is embodied as a lower arm of a suspension device is described. (Suspension device 10) like Figure 2 As shown, the suspension device 10 is disposed between the vehicle body 100 and the wheel 110, and supports the wheel 110 to swingably on the vehicle body 100. The suspension device 10 is configured to relieve the impact transmitted from the road surface to the vehicle body 100 through the wheel 110, and to press the wheel 110 against the road surface.

[0008] The suspension device 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. The upper arm 20 is disposed above the lower arm 30. The upper arm 20 and the lower arm 30 connect a support member 111 supporting a wheel 110 to a vehicle frame 101 of the vehicle body 100.

[0009] The suspension spring 80 extends in the up-down direction. The lower end portion of the suspension spring 80 is supported by the lower arm 30 . (Lower arm 30) like Figure 1As shown, the lower arm 30 includes a bottom wall 31, a first side wall 32A, a second side wall 32B, and a rectifying portion 70. The bottom wall 31 is in a strip shape extending in the vehicle width direction. The first side wall 32A and the second side wall 32B protrude upward from both end edges of the bottom wall 31 and are opposed to each other. The first side wall 32A and the second side wall 32B each have a base end portion as an end portion close to the bottom wall 31 and a terminal end portion as an end portion away from the bottom wall 31 in a protruding direction from the bottom wall 31. The rectifying portion 70 extends from the first side wall 32A to the side opposite to the second side wall 32B.

[0010] The lower arm 30 is disposed so that the second side wall 32B and the first side wall 32A are located at the front and rear of the vehicle, respectively. Therefore, the airflow rectifying portion 70 extends from the first side wall 32A to the rear of the vehicle.

[0011] Hereinafter, the direction in which the bottom wall 31 extends is referred to as the X-axis direction. In addition, the direction in which the first side wall 32A and the second side wall 32B are opposite to each other is referred to as the Y-axis direction. In addition, the direction which is orthogonal to both the X-axis direction and the Y-axis direction and in which the first side wall 32A and the second side wall 32B protrude is referred to as the Z-axis direction. The X-axis direction is a direction consistent with the vehicle width direction, and is equivalent to the "third direction". The Y-axis direction is a direction consistent with the front-rear direction of the vehicle, and is equivalent to the "first direction". The Z-axis direction is a direction consistent with the up-down direction, and is equivalent to the "second direction".

[0012] The lower arm 30 includes an arm body 40 , a reinforcement member 50 , and a resin molded portion 60 . (Arm body 40) like Figure 3 As shown, the arm body 40 has a body side bottom wall 41, a body side first side wall 42A, and a body side second side wall 42B. The body side bottom wall 41 is in the shape of a strip extending in the X-axis direction. The body side first side wall 42A and the body side second side wall 42B protrude upward from both end edges of the body side bottom wall 41 in the Y-axis direction and are opposed to each other. The arm body 40 is open at the top.

[0013] The arm body 40 is formed by, for example, pressing a metal plate. The material of the arm body 40 is, for example, a metal material such as high-strength steel. The width of the middle portion 41a in the X-axis direction of the main body side bottom wall 41 in the Y-axis direction is larger than that of other portions. The width of the middle portion 41a in the Y-axis direction gradually decreases toward both sides in the X-axis direction. When viewed from the Z-axis direction, the middle portion 41a of the main body side bottom wall 41 is spindle-shaped.

[0014] Portions of the main body-side bottom wall 41 adjacent to the intermediate portion 41 a on both sides in the X-axis direction extend linearly in the X-axis direction. The first body side wall 42A and the second body side wall 42B are symmetrical in the Y-axis direction. Therefore, the structure of the first body side wall 42A will be described below, and the description of the structure of the second body side wall 42B may be omitted.

[0015] The first body side side wall 42A extends over the entire body side bottom wall 41 in the X-axis direction. A portion of the first body side side wall 42A at one end in the X-axis direction and constituting a first connecting portion 47 described later protrudes further than the body side bottom wall 41 in the X-axis direction.

[0016] like Figure 5 As shown, the portion of the main body side first side wall 42A that protrudes upward from the intermediate portion 41 a has an inclined portion 43 connected to the main body side bottom wall 41 and a straight portion 44 connected to the inclined portion 43 .

[0017] The inclined portion 43 is inclined so as to be separated from the second main body side side wall 42B in the Y-axis direction as it goes upward. The inclined portion 43 includes a base end portion in the protruding direction of the first main body side side wall 42A.

[0018] The straight portion 44 extends straight in the Z-axis direction. The straight portion 44 of the first main body side wall 42A and the straight portion 44 of the second main body side wall 42B extend parallel to each other. like Figure 3 As shown, the first side wall 42A on the main body side and the second side wall 42B on the main body side have a first flange 45A and a second flange 45B, respectively. The first flange 45A protrudes from the end of the first side wall 42A on the side opposite to the main body side bottom wall 41 to the side opposite to the second side wall 42B on the main body side in the Y-axis direction. The first flange 45A and the second flange 45B protrude to opposite sides in the Y-axis direction. The first flange 45A constitutes the terminal end of the first side wall 42A on the main body side in the protruding direction. The first flange 45A extends over the entire first side wall 42A on the main body side in the X-axis direction.

[0019] The arm body 40 has a spring housing portion 46, a first connection portion 47, and a second connection portion 48. The spring housing portion 46 constitutes the center portion in the X-axis direction of the arm body 40. The first connection portion 47 and the second connection portion 48 are provided on both sides of the spring housing portion 46 in the X-axis direction.

[0020] (Spring housing portion 46) The spring housing portion 46 includes the middle portion 41a, a portion of the first body side wall 42A protruding from the middle portion 41a, and a portion of the second body side wall 42B protruding from the middle portion 41a. The spring housing portion 46 forms a housing space in which the lower end of the suspension spring 80 is housed.

[0021] Parts of the first main body side side wall 42A and the second main body side side wall 42B constituting the spring housing portion 46 bulge toward opposite sides in the Y-axis direction. A through hole 46a penetrating in the Z-axis direction is provided in the bottom portion of the spring housing portion 46, that is, in the middle portion 41a. The through hole 46a has a circular shape.

[0022] (First connecting portion 47) The first connection portion 47 is a portion of the arm body 40 connected to the vehicle body 100. The first connection portion 47 includes a portion of the first side wall 42A on the main body side that protrudes in the X-axis direction from the bottom wall 41 on the main body side, and a portion of the second side wall 42B on the main body side that protrudes in the X-axis direction from the bottom wall 41 on the main body side. The portions of the first side wall 42A on the main body side and the second side wall 42B on the main body side that constitute the first connection portion 47 extend parallel to each other in the X-axis direction. The portions of the first side wall 42A on the main body side and the second side wall 42B on the main body side that constitute the first connection portion 47 protrude in the X-axis direction from the end edge of the bottom wall 41 on the main body side in the X-axis direction.

[0023] First connection holes 47a extending in the Y-axis direction are respectively provided in the first body side wall 42A and the second body side wall 42B constituting the first connection portion 47. The first connection portion 47 is rotatably connected to the frame 101 of the vehicle body 100 via a rotation shaft (not shown) inserted into the first connection hole 47a.

[0024] (Second connecting portion 48) The second connection portion 48 is a portion of the arm body 40 that is connected to the wheel 110. The portions of the main body side first side wall 42A and the main body side second side wall 42B that constitute the second connection portion 48 extend in parallel in the X-axis direction.

[0025] Second connection holes 48a extending in the Y-axis direction are respectively provided in the first body side wall 42A and the second body side wall 42B constituting the second connection portion 48. The second connection portion 48 is rotatably connected to the support member 111 of the wheel 110 via a rotation shaft (not shown) inserted into the second connection hole 48a.

[0026] (Reinforcement member 50) The reinforcing member 50 is in the shape of a flat plate. The reinforcing member 50 covers the spring housing portion 46 from above. The reinforcing member 50 is in the shape of a spindle when viewed from the Z-axis direction.

[0027] The material of the reinforcing member 50 is, for example, a metal material such as high-strength steel. The reinforcing member 50 is joined to the upper surfaces of the first flange 45A and the second flange 45B of the spring housing portion 46 by welding, for example.

[0028] like Figure 4As shown, both end edges of the reinforcing member 50 in the Y-axis direction are located inside the end edges of the first flange 45A and the second flange 45B of the spring housing portion 46 in the Y-axis direction.

[0029] The reinforcing member 50 is provided with an insertion hole 50a into which the suspension spring 80 is inserted. The insertion hole 50a communicates with the storage space of the spring storage portion 46. (Resin molding portion 60) like Figure 1 and Figure 4 As shown, the resin molding part 60 injection molds the arm body 40 and the reinforcement member 50 as an insert. Specifically, the insert resin molding part 60 is formed by placing the arm body 40 joined with the reinforcement member 50 as an insert inside a mold device (not shown) and then filling the mold device with resin.

[0030] The material of the resin molded portion 60 is, for example, a thermoplastic resin material. The resin molded portion 60 includes a first covering portion 61 , a second covering portion 64 , and a third covering portion 67 .

[0031] (First covering portion 61) like Figure 5 As shown in FIG. 1 , the first covering portion 61 covers the outer surface of the first side wall 42A on the main body side. More specifically, the first covering portion 61 covers the portion of the outer surface of the first side wall 42A on the main body side except for the first connecting hole 47a and the second connecting hole 48a. The outer surface of the first side wall 42A on the main body side is the surface of the first side wall 42A on the main body side that is opposite to the surface of the second side wall 42B on the main body side. The first covering portion 61 is equivalent to the "covering portion".

[0032] The first covering portion 61 includes an inclined covering portion 61a and a linear covering portion 61b, wherein the inclined covering portion 61a covers the inclined portion 43 of the first main body side wall 42A, and the linear covering portion 61b covers the linear portion 44 of the first main body side wall 42A. The inclined covering portion 61a extends along the outer surface of the inclined portion 43 of the first main body side wall 42A. The linear covering portion 61b extends along the outer surface of the linear portion 44 of the first main body side wall 42A.

[0033] like Figure 1 As shown, the first covering portion 61 has two engaging portions 62 and an engaging portion 63. The two engaging portions 62 engage with both ends of the first side wall 42A on the main body side in the X-axis direction, respectively, and the engaging portion 63 engages with the terminal end of the first flange 45A. The engaging portion 63 is equivalent to the "engaging portion".

[0034] The engagement portion 62 covers the corresponding ends of the first body side wall 42A in the X-axis direction from both sides in the Y-axis direction and the corresponding sides in the X-axis direction. The engagement portion 62 engages with the corresponding ends of the first body side wall 42A over the entire Z-axis direction.

[0035] like Figure 5 As shown, the engagement portion 63 covers the distal end of the first flange 45A from both sides in the Z-axis direction and the first side in the Y-axis direction. The engagement portion 63 is engaged with the distal end of the first flange 45A over the entire X-axis direction.

[0036] In the spring housing portion 46 , the engagement portion 63 covers the junction portion between the first flange 45A and the reinforcing member 50 , except for the distal end portion of the first flange 45A. (Second covering portion 64) like Figure 5 As shown in FIG. 1 , the second covering portion 64 covers the outer surface of the second side wall 42B on the main body side. More specifically, the second covering portion 64 covers the portion of the outer surface of the second side wall 42B on the main body side excluding the first connection hole 47a and the second connection hole 48a. The outer surface of the second side wall 42B on the main body side is the surface of the second side wall 42B on the main body side that is opposite to the surface facing the first side wall 42A on the main body side.

[0037] The second covering portion 64 includes an inclined covering portion 64a and a linear covering portion 64b, wherein the inclined covering portion 64a covers the inclined portion 43 of the second side wall 42B on the main body side, and the linear covering portion 64b covers the linear portion 44 of the second side wall 42B on the main body side. The inclined covering portion 64a extends along the outer surface of the inclined portion 43 of the second side wall 42B on the main body side. The linear covering portion 64b extends along the outer surface of the linear portion 44 of the second side wall 42B on the main body side.

[0038] like Figure 1 As shown, the second covering portion 64 has two engaging portions 65 and an engaging portion 66. The two engaging portions 65 engage with both ends of the second main body side wall 42B in the X-axis direction, respectively, and the engaging portion 66 engages with the distal end of the second flange 45B.

[0039] The engagement portion 65 covers the corresponding ends of the second body side wall 42B in the X-axis direction from both sides in the Y-axis direction and the corresponding sides in the X-axis direction. The engagement portion 65 engages with the corresponding ends of the second body side wall 42B over the entire Z-axis direction.

[0040] like Figure 5 As shown, the engagement portion 66 covers the tip of the second flange 45B from both sides in the Z-axis direction and from the second side opposite to the first side in the Y-axis direction. The engagement portion 66 engages with the tip of the second flange 45B over the entire X-axis direction.

[0041] In the spring housing portion 46 , the engagement portion 66 covers the joint portion between the second flange 45B and the reinforcing member 50 , in addition to the distal end portion of the second flange 45B. (Third covering portion 67) like Figure 5 As shown, the third covering portion 67 covers the entire outer surface of the main body side bottom wall 41. The outer surface of the main body side bottom wall 41 is the lower surface of the main body side bottom wall 41.

[0042] like Figure 4 As shown, the third covering portion 67 includes two engaging portions 68 and an engaging portion 69. The two engaging portions 68 engage with both ends of the body-side bottom wall 41 in the X-axis direction, respectively, and the engaging portion 69 engages with the peripheral edge of the through hole 46a.

[0043] The engagement portion 68 covers the corresponding ends of the body side bottom wall 41 in the X-axis direction from both sides in the Z-axis direction and the corresponding sides in the X-axis direction. The engagement portion 68 engages with the corresponding ends of the body side bottom wall 41 over the entire Y-axis direction.

[0044] like Figure 5 As shown in FIG. 1 , the engagement portion 69 covers the peripheral edge of the through hole 46a from both sides in the Z-axis direction and the inner surface side of the through hole 46a. The engagement portion 69 is engaged with the peripheral edge of the through hole 46a over the entire circumferential direction.

[0045] The bottom wall 31 of the lower arm 30 includes the body-side bottom wall 41 and the third covering portion 67. The first side wall 32A of the lower arm 30 includes the body-side first side wall 42A and the first covering portion 61. The second side wall 32B of the lower arm 30 includes the body-side second side wall 42B and the second covering portion 64.

[0046] (Rectification Unit 70) The rectifying portion 70 extends from the portion of the first covering portion 61 that covers the outer surface of the portion of the first side wall 42A on the main body side that constitutes the spring housing portion 46 to the side opposite to the second side wall 32B. The rectifying portion 70 is provided integrally with the first covering portion 61. That is, the rectifying portion 70 is a portion that is continuous with the first covering portion 61 without interruption.

[0047] The rectifying portion 70 is in the shape of a thin plate and extends from a portion between a base end portion and a terminal end portion of the first side wall 32A in the protruding direction. The base end portion of the first side wall 32A is a portion of the first side wall 32A that is connected to the bottom wall 31 .

[0048] The rectifying portion 70 extends from, for example, a portion of the first covering portion 61 connected to the inclined covering portion 61a at the lower end of the linear covering portion 61b. The rectifying portion 70 is inclined relative to the horizontal direction so as to be located downward as it moves away from the first side wall 32A in the Y-axis direction.

[0049] like Figure 4 As shown in FIG. 1 , the flow rectifying portion 70 is in an elongated shape extending in the X-axis direction along the first side wall 32A. The flow rectifying portion 70 extends over the entire first side wall 32A of the spring housing portion 46 in the X-axis direction.

[0050] The curved portions 71 are provided at both ends of the rectifying portion 70 in the X-axis direction. The curved portions 71 are curved in such a manner that the length from the first side wall 32A gradually decreases as the length in the X-axis direction becomes farther away from the center of the rectifying portion 70. The ends of each curved portion 71 in the X-axis direction are connected to the outer surface of the first covering portion 61 without any step.

[0051] A portion of the rectifying portion 70 excluding the bent portion 71 is bent along the outer surface of the first side wall 32A of the spring housing portion 46 . like Figure 6 As shown, the length of the rectifying portion 70 from the first side wall 32A, i.e., the rectifying portion length 1, is smaller than the side wall width a, which is the distance between the outer surface of the first side wall 32A and the outer surface of the second side wall 32B. The side wall width a is the distance between the lower end of the linear covering portion 61b of the first covering portion 61 and the lower end of the linear covering portion 64b of the second covering portion 64.

[0052] The ratio of the length 1 of the rectifying portion to the side wall width a is set, for example, in the range of 30% to 60% in the portion other than the two ends of the rectifying portion 70 in the X-axis direction. The ratio of the length 1 of the rectifying portion to the side wall width a gradually increases from the central portion in the X-axis direction of the rectifying portion 70 toward the curved portion 71. In the central portion in the X-axis direction of the rectifying portion 70, the ratio of the length 1 of the rectifying portion to the side wall width a is set, for example, to about 30%. In the portion of the rectifying portion 70 where the ratio of the length 1 of the rectifying portion to the side wall width a is in the range of 30% to 60%, the length in the X-axis direction is, for example, more than half of the length of the first side wall 32A in the X-axis direction.

[0053] (Simulation results) The aerodynamic characteristics of the lower arm 30 when the straightening portion length l, the straightening portion height h, and the straightening portion angle θ of the straightening portion 70 are changed will be described using simulation results.

[0054] like Figure 6As shown, the rectifying portion length l in this simulation is the length of the portion extending from the center of the first side wall 32A in the rectifying portion 70 in the X-axis direction. The rectifying portion height h is the height from the lower surface of the bottom wall 31 to the base end of the rectifying portion 70. The rectifying portion angle θ is the angle between the imaginary axis V extending in the Y-axis direction and the rectifying portion 70 when the rectifying portion 70 is viewed from the X-axis direction. In the case where the rectifying portion 70 extends obliquely upward, the rectifying portion angle θ is a positive value. In the case where the rectifying portion 70 extends obliquely downward, the rectifying portion angle θ is a negative value.

[0055] In this simulation, the length ratio R1 and the height ratio R2 are used as indicators for evaluating the aerodynamic characteristics of the lower arm 30 when the rectifying portion length 1 and the rectifying portion height h are changed. The length ratio R1 is the ratio of the rectifying portion length 1 to the side wall width a (1 / a). The height ratio R2 is the ratio of the rectifying portion height h to the height b of the lower arm 30 (h / b). The height b of the lower arm 30 is the height from the lower surface of the bottom wall 31 to the upper surface of the first side wall 32A and the second side wall 32B.

[0056] Figure 7 It is a graph showing changes in the drag coefficient, ie, Cd value (hereinafter referred to as Cd value) of the lower arm 30 when the length ratio R1 is changed from 0.06 to 0.4 when the straightening portion angle θ is 0°. Figure 7 The solid line is the coordinate diagram when the height ratio R2 is 0.2. Figure 7 The double-dashed line is a coordinate diagram when the height ratio R2 is 0.3.

[0057] like Figure 7 As shown, it can be confirmed that when the height ratio R2 is 0.2 and when the height ratio R2 is 0.3, the larger the length ratio R1 is, that is, the longer the rectifying portion length l is, the smaller the Cd value is. In this simulation, when the length ratio R1 is 0.4, the Cd value is the smallest. When the length ratio R1 is 0.4, the Cd value when the height ratio R2 is 0.2 is smaller than the Cd value when the height ratio R2 is 0.3.

[0058] Figure 8 It is a graph showing changes in the lift coefficient of the lower arm 30 , namely, Cl value (hereinafter referred to as Cl value) when the length ratio R1 is changed from 0.06 to 0.4 when the straightening portion angle θ is 0°. Figure 8 The solid line is the coordinate diagram when the height ratio R2 is 0.2. Figure 8 The double-dashed line is a coordinate diagram when the height ratio R2 is 0.3.

[0059] like Figure 8As shown, it can be confirmed that when the height ratio R2 is 0.2 and when the height ratio R2 is 0.3, the larger the length ratio R1 is, that is, the longer the rectifying portion length l is, the smaller the Cl value is. In this simulation, when the length ratio R1 is 0.4, the Cl value is the smallest. When the length ratio R1 is 0.4, the Cl value when the height ratio R2 is 0.2 is smaller than the Cl value when the height ratio R2 is 0.3.

[0060] Fig. 9 It is a graph showing the change of the Cd value when the height ratio R2 is changed from 0 to 0.3 when the rectifying portion angle θ is 0°. Fig. 9 The solid line is the coordinate diagram when the length ratio R1 is 0.2. Fig. 9 The double-dashed line is a coordinate diagram when the length ratio R1 is 0.4.

[0061] like Fig. 9 As shown, it can be confirmed that when the length ratio R1 is 0.2 and when the length ratio R1 is 0.4, the closer the height ratio R2 is from 0 to 0.2, the smaller the Cd value is, and the larger the height ratio R2 is compared with 0.2, the larger the Cd value is. In this simulation, when the height ratio R2 is 0.2, the Cd value is the smallest. When the height ratio R2 is 0.2, the Cd value when the length ratio R1 is 0.4 is smaller than the Cd value when the length ratio R1 is 0.2. In addition, when the height ratio R2 is 0.2, the rectifying portion 70 extends from the inclined covering portion 61a. When the height ratio R2 is 0.3, the rectifying portion 70 extends from the straight covering portion 61b.

[0062] Fig.10 It is a graph showing changes in the Cl value when the height ratio R2 is changed from 0 to 0.3 when the rectifying portion angle θ is 0°. Fig.10 The solid line is the coordinate diagram when the length ratio R1 is 0.2. Fig.10 The double-dashed line is a coordinate diagram when the length ratio R1 is 0.4.

[0063] like Fig.10 As shown, it can be confirmed that when the length ratio R1 is 0.2 and when the length ratio R1 is 0.4, the closer the height ratio R2 is from 0 to 0.2, the smaller the C1 value is, and the larger the height ratio R2 is compared with 0.2, the larger the Cl value is. In this simulation, when the height ratio R2 is 0.2, the Cl value is the smallest. When the height ratio R2 is 0.2, the Cl value when the length ratio R1 is 0.4 is smaller than the Cl value when the length ratio R1 is 0.2.

[0064] When the height ratio R2 is 0, the rectifying portion 70 extends from the base end portion in the protruding direction of the first side wall 32A. Fig. 9 and Fig.10As shown, it was confirmed that when the height ratio R2 is greater than 0, that is, when the airflow rectifying portion 70 extends from a portion between the base end portion and the tip end portion in the protruding direction of the first side wall 32A, the aerodynamic characteristics of the lower arm 30 are improved.

[0065] Fig.11 This is a graph showing changes in the Cd value when the straightening portion angle θ is changed from -20° to 20° when the length ratio R1 is 0.4. Fig.11 The solid line is the coordinate diagram when the height ratio R2 is 0.2. Fig.11 The double-dashed line is a coordinate diagram when the height ratio R2 is 0.3.

[0066] like Fig.11 As shown, it can be confirmed that when the height ratio R2 is 0.2, the closer the rectifying portion angle θ is from -20° to 0°, the smaller the Cd value is, and the larger the rectifying portion angle θ is compared with 0°, the larger the Cd value is. When the height ratio R2 is 0.3, the closer the rectifying portion angle θ is from -20° to -10°, the smaller the Cd value is, and the larger the rectifying portion angle θ is compared with -10°, the larger the Cd value is.

[0067] Fig.12 It is a graph showing changes in the Cl value when the angle θ of the rectifying portion is changed from -20° to 20° when the length ratio R1 is 0.4. Fig.12 The solid line is the coordinate diagram when the height ratio R2 is 0.2. Fig.12 The double-dashed line is a coordinate diagram when the height ratio R2 is 0.3.

[0068] like Fig.12 As shown, it can be confirmed that when the height ratio R2 is 0.2, the closer the rectifying portion angle θ is from -20° to 0°, the smaller the Cl value is, and the larger the rectifying portion angle θ is compared with 0°, the larger the Cl value is. It can be confirmed that when the height ratio R2 is 0.3, the closer the rectifying portion angle θ is from -20° to -5°, the smaller the Cl value is, and the larger the rectifying portion angle θ is compared with -5°, the larger the Cl value is.

[0069] When the Cl value becomes excessively negative, it becomes a major factor that increases the rolling resistance of the vehicle, so it is preferable that the Cl value is approximately 0. When the height ratio R2 is 0.2, when the straightening portion angle θ is 0°, the Cl value is approximately 0. When the height ratio R2 is 0.3, when the straightening portion angle θ is -10° to 0°, the Cl value is approximately 0.

[0070] It can be seen from this that the aerodynamic characteristics of the lower arm 30 can be effectively improved by setting the length ratio R1 to 0.4, the height ratio R2 to 0.2, and the straightening portion angle θ to -10° to 0°.

[0071] The function and effect of this embodiment will be described. (1) The lower arm 30 includes: a bottom wall 31; a first side wall 32A and a second side wall 32B that protrude upward from the bottom wall 31 and are opposed to each other; and a flow straightening portion 70 that extends from the first side wall 32A to the side opposite to the second side wall 32B. The first side wall 32 has a base end portion that is an end portion close to the bottom wall 31 and a terminal end portion that is an end portion away from the bottom wall 31 in the protruding direction from the bottom wall 31. The flow straightening portion 70 extends from a portion between the base end portion and the terminal end portion in the protruding direction of the first side wall 32A.

[0072] According to such a configuration, when the air flows from the second side wall 32B toward the first side wall 32A, the air is rectified by the rectifying portion 70 , so that the resistance generated in the lower arm 30 can be reduced.

[0073] In addition, compared with the case where the rectifying portion 70 extends from the base end portion of the first side wall 32A to the side opposite to the second side wall 32B, the difference in the flow velocity of the air in the spaces located on opposite sides of the rectifying portion 70 becomes larger. In more detail, the flow velocity in the upper space surrounded by the rectifying portion 70 and the first side wall 32A above the rectifying portion 70 is slower than the flow velocity in the lower space surrounded by the rectifying portion 70 and the first side wall 32A below the rectifying portion 70. Therefore, the pressure of the air in the upper space is higher than the pressure of the air in the lower space. By such a pressure difference, the increase in the lift generated in the lower arm 30 can be suppressed. As a result, the aerodynamic characteristics of the lower arm 30 can be improved.

[0074] (2) The lower arm 30 includes an arm body 40 and a resin molded portion 60 that is injection molded with the arm body 40 as an insert. The arm body 40 includes a body side bottom wall 41 and a body side first side wall 42A and a body side second side wall 42B that protrude upward from the body side bottom wall 41 and are opposed to each other. The resin molded portion 60 includes a first covering portion 61 that covers the outer surface of the body side first side wall 42A. The rectifying portion 70 is a portion that is continuous with the first covering portion 61.

[0075] According to such a structure, the rectifying portion 70 can be formed as a part of the resin molded portion 60 that is injection molded with the arm body 40 as an insert. As a result, compared with the case where the rectifying portion 70 is a separate body from the arm body 40 and then mounted on the arm body 40, an increase in the number of parts of the lower arm 30 and an increase in the number of assembly man-hours can be suppressed. In addition, the arm body 40 and the rectifying portion 70 do not need to be aligned.

[0076] (3) The first covering portion 61 includes the engaging portion 63 that engages with the first flange 45A, which is the distal end portion of the first main body-side side wall 42A in the protruding direction. According to such a structure, the engagement portion 63 engages with the first flange 45A, thereby suppressing the displacement between the first body-side side wall 42A and the first covering portion 61, and further suppressing the displacement between the arm body 40 and the straightening portion 70. Therefore, the straightening portion 70 can easily exert the effect of improving aerodynamic characteristics.

[0077] (4) The rectifying portion 70 has a strip shape extending in the X-axis direction along the first side wall 32A. According to such a configuration, the range in which the effect of improving the aerodynamic characteristics of the airflow straightening portion 70 is exerted can be expanded in the X-axis direction.

[0078] In addition, the ratio of the two ends of the rectifying portion 70 in the X-axis direction to the entire rectifying portion 70 becomes smaller. As a result, the influence of the resistance generated in the rectifying portion 70 by the vortex of the air flowing from the lower surface to the upper surface of the two ends of the rectifying portion 70 in the X-axis direction can be reduced. Therefore, the aerodynamic characteristics of the lower arm 30 can be improved.

[0079] (5) The bent portions 71 are provided at both ends of the rectifying portion 70 in the X-axis direction. The bent portions 71 are bent so that the length from the first side wall 32A gradually decreases as the length increases away from the center of the rectifying portion 70 in the X-axis direction.

[0080] According to such a configuration, the generation of eddy currents flowing from the lower surface to the upper surface at both ends of the rectifying portion 70 in the X-axis direction can be easily suppressed, so that the resistance at the both ends can be reduced. Therefore, the aerodynamic characteristics of the lower arm 30 can be improved.

[0081] <Modification> This embodiment can be implemented as the following modifications. This embodiment and the following modifications can be implemented in combination with each other within the range that there is no technical contradiction.

[0082] The bent portion 71 may be omitted from the rectifying portion 70. In this case, both ends of the rectifying portion 70 in the X-axis direction may be connected to the outer surface of the first covering portion 61 via a step. The rectifying portion length 1 may be constant in the X-axis direction.

[0083] When viewed from the Z-axis direction, the rectifying portion 70 may be in a strip shape that is long in the Y-axis direction. At least one of the engaging portions 62 , 63 , 65 , 66 , 68 , and 69 may be omitted from the resin molded portion 60 .

[0084] The reinforcing member 50 may be omitted from the lower arm 30. In this case, the first main body side wall 42A and the second main body side wall 42B may not have the first flange 45A and the second flange 45B, respectively. In this case, the engaging portion 63 and the engaging portion 66 are preferably engaged with the distal end of the first main body side wall 42A and the distal end of the second main body side wall 42B.

[0085] The rectifying portion 70 may be configured to be attachable to and detachable from the resin molded portion 60 . The resin molded portion 60 may be omitted from the lower arm 30. In this case, the flow rectifying portion 70 may be fixed to the first main body side wall 42A by welding or the like, or may be configured to be attachable to and detachable from the first main body side wall 42A.

[0086] The lower arm 30 may also be applied to the upper arm 20 of the suspension device 10 .

Claims

1. A suspension arm having: bottom wall; a first side wall and a second side wall protruding upward from the bottom wall and facing each other; and a rectifying portion extending from the first side wall to a side opposite to the second side wall, The first side wall has a base end portion as an end portion close to the bottom wall and a terminal end portion as an end portion away from the bottom wall in a protruding direction from the bottom wall. The flow-rectifying portion extends from a portion of the first side wall between the base end portion and the terminal end portion.

2. The suspension arm according to claim 1, wherein: The suspension arm includes an arm body and a resin molded portion formed by injection molding the arm body as an insert. The arm body has a body side bottom wall and a body side first side wall and a body side second side wall that protrude upward from the body side bottom wall and are opposed to each other. The resin molded portion includes a covering portion that covers an outer surface of the first side wall on the main body side. The bottom wall includes the main body side bottom wall, The first side wall includes the main body side first side wall and the covering portion, The second side wall includes the second side wall on the main body side, The rectifying portion is a portion that is continuously connected to the covering portion.

3. The suspension arm according to claim 2, wherein: The covering portion includes an engaging portion that engages with the distal end portion of the main body-side first side wall.

4. The suspension arm according to any one of claims 1 to 3, wherein: The direction in which the first side wall and the second side wall are opposite to each other is a first direction, the direction in which the first side wall protrudes is a second direction, and the direction orthogonal to both the first direction and the second direction is a third direction. The first side wall extends along the third direction, The rectifying portion has a strip shape extending in the third direction along the first side wall.

5. The suspension arm according to claim 4, wherein: Bend portions are provided at both ends of the rectifying portion in the third direction, and the bent portions are bent so that the lengths thereof from the first side wall gradually decrease as they are farther away from a center portion of the rectifying portion in the third direction.

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