JP6934276B2 - Suspension arm and vehicle suspension - Google Patents

Description

The present invention relates to a suspension arm and a vehicle suspension device.

As a vehicle suspension device, there is known a configuration in which a suspension arm that is swingably supported by a vehicle body and supports wheels at a swing end is provided. Patent Document 1 discloses a suspension device provided with a lower arm having a specific shape as a suspension arm of a front suspension.

This lower arm has an almost L-shaped shape in the plan view of the vehicle. A first mounting portion (front pivot support) to be attached to the vehicle body is provided at an intermediate portion that serves as a bending portion of the lower arm. One end of the lower arm is provided with a second mounting portion (rear pivot support) that is mounted on the vehicle body behind the first mounting portion. Each of the first and second mounting portions is mounted on the vehicle body via an elastic body such as a rubber bush. The other end of the lower arm is provided with a third mounting portion that is fixed to the wheel via a ball joint. The third mounting portion is a swinging end portion that swings around a shaft connecting the first mounting portion and the second mounting portion as a swinging shaft.

In such a lower arm, the angle between the first axis connecting the first mounting portion and the second mounting portion and the second axis connecting the first mounting portion and the third mounting portion is generally set to less than 90 °. NS. Further, the position of the second mounting portion in the vehicle width direction is substantially the same as the position of the first mounting portion in the vehicle width direction, or is arranged outside in the vehicle width direction. With this configuration, in the event of a frontal collision of the vehicle, the collision safety performance is satisfied by buckling the middle of the vehicle body side arm (arm base) connecting the first mounting portion and the second mounting portion.

Japanese Unexamined Patent Publication No. 2012-158200

On the other hand, the lower arm having the above configuration has room for further improvement in terms of vehicle steering stability. Especially when braking, the front suspension is fully bumped and the rear suspension is fully rebounded, which tends to cause a nose dive phenomenon. At the time of braking, the first mounting portion is relatively low with respect to the third mounting portion due to the braking load, and is also relatively low with respect to the second mounting portion. At that time, the lower arm behaves so as to rotate about the axis connecting the first mounting portion and the third mounting portion, and the second mounting portion tends to be displaced outward and upward in the vehicle width direction. Such behavior of the lower arm hinders the stability of the wheel during braking.

The present invention has been made in view of the above circumstances, and one of the objects thereof is to provide a suspension arm capable of suppressing a nose dive phenomenon while ensuring collision safety performance.

(1) The suspension arm according to the first aspect of the present invention has a first mounting portion attached to the vehicle body via a first elastic body and a second mounting portion behind the first mounting portion in the vehicle length direction. (Ii) A second mounting portion that is attached to the vehicle body via an elastic body, a third mounting portion that is attached to a wheel via a ball joint outside the first mounting portion in the vehicle width direction, and the first mounting portion. A vehicle body side arm that connects the portion and the second mounting portion, and a wheel side arm that connects the first mounting portion and the third mounting portion are provided. The suspension arm has an angle between the first axis connecting the center of the first elastic body and the center of the second elastic body and the second axis connecting the center of the first elastic body and the center of the ball joint. Is more than 90 °, the distance between the first shear center and the first axis in the cross section of the vehicle body side arm on the first mounting portion side is L1, and the distance between the vehicle body side arm and the second mounting portion side. When the distance between the second shear center and the first axis in the cross section is L2, L1> L2 is satisfied.

(2) The vehicle suspension device according to the first aspect of the present invention includes the suspension arm, and the center of the second elastic body is on the vehicle body inside the center of the first elastic body in the vehicle width direction. It is attached.

The above suspension arm has the following effects.
By making the angle between the first axis and the second axis (hereinafter, sometimes referred to as an arm angle) an obtuse angle, a suspension arm having excellent anti-dive characteristics can be obtained. This is because if the arm angle is an obtuse angle, the second mounting portion can be easily arranged inside the vehicle width direction with respect to the first mounting portion. At the time of braking, the first mounting portion is relatively low with respect to the third mounting portion due to the braking load, and is also relatively low with respect to the second mounting portion. At that time, the lower arm behaves so as to rotate about the second axis connecting the first mounting portion and the third mounting portion. When the arm angle is an obtuse angle, the behavior of the lower arm described above suppresses the second mounting portion from trying to displace outward and upward in the vehicle width direction, and the stability of the wheel during braking can be ensured. ..

By forming the cross-sectional shape of the suspension arm such that the relationship between the distance L1 and the distance L2 is L1> L2, it is possible to realize high fatigue endurance strength while making the arm angle obtuse. When the arm angle is obtuse, the anti-dive characteristics are excellent as described above, but stress is concentrated on the rear side of the first mounting portion during braking. This is because the second mounting portion is twisted with respect to the first axis due to the braking load acting on the third mounting portion. If the cross-sectional shape of the vehicle body side arm satisfies L1> L2, the above-mentioned twisting is unlikely to occur on the second mounting portion side of the vehicle body side arm, and stress concentration is suppressed on the rear side of the first mounting portion. can. Therefore, it is possible to obtain a suspension arm having excellent fatigue durability while making the arm angle obtuse.

Since the distance L1 and the distance L2 are different between the first mounting portion side and the second mounting portion side, a displacement point of the moment of inertia of area is generated in the middle of the vehicle body side arm. Therefore, at the time of a frontal collision of the vehicle, it is easy to buckle the middle of the vehicle body side arm connecting the first mounting portion and the second mounting portion, and the collision safety performance can be satisfied.

By providing the suspension arm described above, the suspension device of the vehicle can be configured with the suspension arm having high fatigue durability while ensuring collision safety performance. In particular, since the center of the second elastic body is attached to the vehicle body inside the vehicle width direction from the center of the first elastic body, the nose dive phenomenon can be effectively suppressed.

It is a schematic block diagram of the suspension system which concerns on embodiment seen from the front of a vehicle. It is the schematic plan view of the suspension arm which concerns on embodiment. It is a schematic side view of the suspension arm which concerns on embodiment. It is a schematic plan view which shows the suspension device which concerns on embodiment. The suspension arm according to the embodiment is shown, and FIGS. (A) to (D) are cross-sectional views taken along the line AA to DD of FIG. The suspension arm according to the embodiment is shown, and FIGS. (E) to (H) are cross-sectional views taken along the line of EE to HH in FIG.

[Embodiment 1]
Details of the embodiments of the present invention will be described with reference to the drawings. Here, a strut type suspension device will be described as an example of the suspension device according to the embodiment, and a case where the suspension arm according to the embodiment is used for the suspension device will be described as an example. This suspension arm is a lower arm used for the front suspension. In FIG. 2, the front of the vehicle is indicated by FR, the rear of the vehicle is indicated by RR, the outside in the vehicle width direction is indicated by OUT, and the inside in the vehicle width direction is indicated by IN.

[Overview]
As shown in FIG. 1, the suspension device according to the embodiment swingably supports the wheels with respect to the vehicle body. The vehicle body includes a side member (not shown) extending in the vehicle length direction and a subframe 20 fixed to the side member. The first mounting portion 11 and the second mounting portion 12 of the lower arm 10 are mounted on the subframe 20. On the other hand, the third attachment portion 13 of the lower arm 10 is attached to the lower part behind the steering knuckle 30 via the ball joint 13B. At the center of the steering knuckle 30, an end of a tie rod 50 that is attached to the wheel 42 of the wheel 40 and slides in the vehicle width direction as the steering is steered is connected. The lower end of the strut 60 provided with the shock absorber is connected to the upper portion of the steering knuckle 30. The upper end of the strut 60 is fixed to the suspension tower 70.

One of the features of the lower arm 10 is that the bending angle of the lower arm 10 bent into an L shape (arm angle θ ₁ described later) is an obtuse angle. Further, one of the other features of the lower arm 10 is that the cross-sectional shape of the lower arm 10 is set so as to satisfy a specific condition on the first mounting portion 11 side and the second mounting portion 12 side. Hereinafter, the configuration of the lower arm 10 will be described in detail.

[Lower arm]
The lower arm 10 includes an arm body 10S made of a press-molded metal plate. The arm body 10S is bent into an L shape in a plan view in a state of being assembled to the vehicle. Further, the arm body 10S is also bent into a predetermined cross-sectional shape, which will be described later.

(First mounting part)
A first mounting portion 11 to be mounted on the subframe 20 is provided on the outer peripheral edge of the bent portion of the lower arm 10. The first mounting portion 11 has a cylindrical collar 11C welded to a bent portion of the arm body 10S. A first elastic body 11r is arranged inside the collar 11C. As the first elastic body 11r, a rubber bush provided on the outer circumference of the first support shaft 11a can be used. This rubber bush is inserted into the collar 11C so that the collar 11C and the first support shaft 11a are coaxial with each other. Both ends of the first support shaft 11a are supported by the subframe 20 so that the axial direction of the first support shaft 11a is substantially along the vehicle length direction. The center of elastic deformation of the first elastic body 11r is defined as the center C1 of the first elastic body 11r. The welded portion of the collar 11C with the arm body 10S is displaced downward from the center of the first elastic body 11r.

(Second mounting part)
One end of the lower arm 10 is provided with a second mounting portion 12 that is mounted on the subframe 20 behind the first mounting portion 11 of the vehicle. The second mounting portion 12 has a through hole 12h formed at one end of the arm body 10S. As shown by the alternate long and short dash line in FIG. 3, a thin annular member 12c is press-fitted into the through hole 12h. That is, the axial direction of the through hole 12h and the annular member 12c is the direction along the thickness direction of the arm body 10S. A second elastic body 12r is arranged in the annular member 12c. As for the second elastic body 12r, like the first elastic body 11r, a rubber bush provided on the outer circumference of the second support shaft 12a can be used. This rubber bush is inserted into the annular member 12c so that the annular member 12c and the second support shaft 12a are coaxial with each other. Both ends of the second support shaft 12a are supported by the subframe 20 so that the axial direction of the second support shaft 12a is substantially along the height direction of the vehicle. The center of elastic deformation of the second elastic body 12r is defined as the center C2 of the second elastic body 12r. The horizontal piece (described later) of the arm body 10S constituting the second mounting portion 12 is fixed to the annular member 12c so as to be located above the center C2 of the second elastic body 12r. Further, the line segment connecting the center C1 of the first elastic body 11r and the center C2 of the second elastic body 12r is defined as the first axis line a1. As shown in FIG. 3, the first axis line a1 is a line segment substantially along the vicinity of the upper surface of the arm body 10S, and is slightly inclined upward from the first mounting portion 11 toward the second mounting portion 12. ing.

(Third mounting part)
The other end of the lower arm 10 is provided with a third mounting portion 13 fixed to the wheel via a ball joint 13B. The third mounting portion 13 is a swinging end portion that is swung around the first axis line a1 as a swinging axis. The third mounting portion 13 has a through hole 13h formed at the other end of the arm body 10S. A socket for accommodating the ball of the ball joint 13B is supported in the through hole 13h. The center of this ball is defined as the center C3 of the ball joint. The line segment connecting the center C1 of the first elastic body 11r and the center C3 of the ball joint 13B is defined as the second axis a2.

(Body side arm and wheel side arm)
The arm body 10S includes a vehicle body side arm 10B that connects the first mounting portion 11 and the second mounting portion 12, and a wheel side arm 10W that connects the first mounting portion 11 and the third mounting portion 13. The inner edge of the bend of the arm body 10S is a substantially arcuate curve from the vehicle body side arm 10B to the wheel side arm 10W. The outer edge of the vehicle body side arm 10B is an S-shaped curve that once dents outward from the first mounting portion 11 in the vehicle width direction and swells inward in the vehicle width direction from the middle. The outer edge of the wheel-side arm 10W is an arcuate curve that generally bulges toward the front of the vehicle. The width of the vehicle body side arm 10B increases from the first mounting portion 11 side toward the second mounting portion 12 side. By increasing the width of the vehicle body side arm 10B toward the second mounting portion 12 side, the rigidity against twisting on the second mounting portion 12 side can be increased. The vehicle body side arm 10B is provided with a recess in the central portion in the width direction, and the width of the recess is also formed to be wider toward the second mounting portion 12 side. When the vehicle body side arm 10B is viewed in a plan view, the contour of the recess has a shape in which the second mounting portion 12 side is closed and the first mounting portion 11 side is open. On the other hand, the wheel side arm 10W has substantially the same width from the first mounting portion 11 side to the second mounting portion 12 side. The wheel side arm 10W is also provided with a recess in the central portion in the width direction, and the width of the recess is also substantially the same from the first mounting portion 11 side to the second mounting portion 12 side. When the wheel side arm 10W is viewed in a plan view, the contour of the recess has a shape in which the first mounting portion 11 side is closed and the third mounting portion 13 side is open.

In addition, a large through hole 10h1 is formed at the connecting portion between the vehicle body side arm 10B and the wheel side arm 10W. The through hole 10h1 is a hole for passing a tool when attaching the lower arm 10 to the subframe 20 and for reducing the weight. Further, drain holes 10h2 are formed on each of the second mounting portion 12 side of the vehicle body side arm 10B and the third mounting portion 13 side of the wheel side arm 10W.

(Arm angle)
_{The arm angle θ 1} between the vehicle body side arm 10B and the wheel side arm 10W, that is, the angle between the first axis a1 and the second axis a2 is more than 90 °. By setting the arm angle θ ₁ to an obtuse angle, the second mounting portion 12 can be easily arranged inside the first mounting portion 11 in the vehicle width direction. The upper limit of the arm angle is about 135 °. A more preferable _{upper limit of the arm angle θ 1} is 120 ° or less, particularly 100 ° or less. In this example, the arm angle θ ₁ is 95 ° or more and 100 ° or less.

_{(Displacement angle θ 2} between the center of the first elastic body and the center of the second elastic body)
In the plan view of the lower arm 10 assembled to the vehicle body, the center C2 of the second elastic body 12r is located inside the center C1 of the first elastic body 11r in the vehicle width direction. As shown in FIG. 4, when the line in the vehicle length direction passing through the center C1 of the first elastic body 11r is defined as the axis b, the first axis a1 forms an angle of _{displacement angle θ 2 with respect to the axis b.} The displacement angle θ ₂ is preferably more than 0 ° and 3.0 ° or less, more preferably 0.5 ° or more and 2.0 ° or less, and particularly preferably 0.8 ° or more and 1.2 ° or less. By setting the displacement angle θ ₂ , the anti-dive characteristics can be improved.

_{(Displacement angle θ 3} between the center of the first elastic body and the center of the ball joint)
In the plan view of the lower arm 10 assembling to the vehicle body, the center C3 of the ball joint is located in front of the center C1 of the first elastic body 11r in the vehicle length direction. As shown in FIG. 4, when the line in the vehicle width direction passing through the center C1 of the first elastic body 11r is defined as the axis c, the second axis a2 forms an angle of the _{displacement angle θ 3 with respect to the axis c.} The displacement angle θ ₃ is preferably 2.0 ° or more and 6.0 ° or less, more preferably 3.0 ° or more and 5.5 ° or less, and particularly preferably 4.0 ° or more and 5.0 ° or less. By satisfying the upper limit value of the displacement angle θ ₃ , it is easy to suppress the twist of the second mounting portion 12 with respect to the first axis a1.

(Relationship between the plane composed of each center and the arm body)
When the lower arm 10 is viewed in a plane, most of the arm body 10S is from the above plane with respect to the plane connecting the center C1 of the first elastic body 11r, the center C2 of the second elastic body 12r, and the center C3 of the ball joint 13B. Is also located above. In particular, the vehicle body side arm 10B is located above the plane except for the lower portion of the first horizontal piece 111 and the vertical piece 120, which will be described later. That is, the second horizontal piece 113, which will be described later, is located above the plane. Even with these positional relationships, it is easy to suppress the twist of the second mounting portion 12 with respect to the first axis a1.

(Cross section shape)
On the other hand, the vehicle body side arm 10B has a cross-sectional shape that satisfies the following specific conditions. The condition is that the distance between the first shear center and the first axis a1 in the cross section of the vehicle body side arm 10B on the first mounting portion 11 side is L1, and the cross section of the vehicle body side arm 10B on the second mounting portion 12 side. When the distance between the second shear center and the first axis a1 is L2, L1> L2 is satisfied. In other words, in the cross section of the vehicle body side arm 10B, it can be said that the section coefficient is larger on the second mounting portion 12 side than on the first mounting portion 11 side. Regarding the relationship between the distance L1 and the distance L2, it is preferable that the distance L2 becomes smaller toward the second mounting portion 12 side. However, in the middle of the vehicle body side arm 10B, there may be a place where the distance L2 is not as small as the second mounting portion 12 side.

The cross section of the first mounting portion 11 side and the second mounting portion 12 side is taken at a position equidistant from each of the center C1 of the first elastic body 11r and the center C2 of the second elastic body 12r. It is preferable to compare the relationship between the distance L1 and the distance L2 in each cross section. In particular, it is preferable that L1> L2 is satisfied in the vicinity of the first mounting portion and the vicinity of the second mounting portion. The first mounting portion 11 side is the range from the center of the first mounting portion 11 and the second mounting portion 12 to the first mounting portion 11, and the second mounting portion 12 side is the first mounting portion 11 and the first mounting portion 11. (Ii) The range is from the center of the mounting portion 12 to the second mounting portion 12. Although it depends on the shape and dimensions of the lower arm, the distance L2 may be about 1/8 or more to 1/12 or less, particularly about 1/10 of the distance L1. That is, about 0.125L1 ≦ L2 ≦ 0.083L1 may be satisfied.

The cross-sectional shape of each part of the lower arm 10 will be specifically described with reference to FIGS. 5 and 6. In both figures, S is the center of gravity of the cross-sectional shape of the lower arm 10 and is indicated by a white circle, and M is the shear center of the cross-sectional shape and is indicated by a black circle. Further, in FIG. 2, the black circle is the shear center of the cross-sectional shape of the lower arm 10. In particular, the shear center M near the second mounting portion 12 in FIG. 5 (A) is the second shear center, and the shear center M near the first mounting portion 11 in FIG. 5 (E) is the first shear center.

First, as shown in FIG. 5A, the cross-sectional shape of the portion of the vehicle body side arm 10B closest to the second mounting portion 12 is an inverted U having vertical pieces 120 extending downward from both sides of the horizontal piece 110. It is in the shape of a letter. The shear center M having this cross-sectional shape is located directly above the horizontal piece 110 and substantially directly above the first axis a1 (see also FIG. 2). The center of gravity S is located directly below the center of the horizontal piece 110 in the width direction. That is, the shear center M is located substantially directly above the center of gravity S, and the distance from the center of gravity S is also quite close.

Next, in the vehicle body side arm 10B, the cross-sectional shape of the portion second closest to the second mounting portion 12 is M-shaped as shown in FIG. 5 (B). The center of the vehicle body side arm 10B in the width direction is recessed, and the first horizontal piece 111 is provided at the bottom of the recess. At both ends of the first horizontal piece 111, inclined pieces 112 that incline upward toward both ends in the width direction are provided. Further, a second horizontal piece 113 is provided at both ends of the inclined piece 112 in the width direction. A vertical piece 120 extending downward from both ends in the width direction of the second horizontal piece 113 is provided. In this cross-sectional shape, the shear center M is located above the first lateral piece 111 and at substantially the same height as the second lateral piece 113. Further, as shown in FIG. 2, the shear center M is located slightly inside the first axis a1 in the vehicle width direction. The center of gravity S is located at a position substantially overlapping the upper surface of the first horizontal piece 111 and at the center in the width direction. Therefore, the shear center M is located substantially directly above the center of gravity S, and the distance from the center of gravity S is as close as in the case of the cross-sectional shape of FIG. 5 (A).

Next, the cross-sectional shape of the vehicle body side arm 10B at a position approximately in the center in the longitudinal direction, that is, at a position third from the second mounting portion 12 and third from the first mounting portion 11, is shown in FIG. 5 (C). As you can see, it is M-shaped. Similar to the cross-sectional shape of FIG. 5B, this cross-sectional shape also includes a first horizontal piece 111, an inclined piece 112, a second horizontal piece 113, and a vertical piece 120. However, one end side of the vehicle body side arm 10B in the width direction, that is, the lower end of the vertical piece 120 on the inner edge side of the bent shape of the lower arm 10 is provided with an inner flange 121 that bends and extends toward the opposite vertical piece 120. In this case, the center of gravity S is located at a position substantially overlapping the upper surface of the first horizontal piece 111 and at the center in the width direction, and is not significantly different from the case of FIG. 5 (B). On the other hand, the shear center M is closer to the inner edge side of the lower arm 10 than the center in the width direction of the lower arm 10, and is also separated from the first axis a1 as shown in FIG. Further, the distance between the center of gravity S and the shear center M is wider than in the case of FIG. 5 (B).

Next, the cross-sectional shape of the vehicle body side arm 10B at the position second closest to the first mounting portion 11 is a deformed C-shape as shown in FIG. 5 (D). This cross-sectional shape includes a horizontal piece 110, a vertical piece 120 extending downward from both sides thereof, and an inner flange 121 bent from the lower end of one vertical piece 120 toward the other vertical piece 120 facing the other. One vertical piece 120 is a vertical piece 120 on the inner edge side of the lower arm 10. The inner flange 121 is longer than the inner flange 121 shown in FIG. 5C. However, the central portion of the horizontal piece 110 in the width direction is slightly recessed as compared with both end portions. In this case, the shear center M is located above the horizontal piece 110 and in the vicinity of the vertical piece 120 on the inner edge side of the lower arm 10. As shown in FIG. 2, the position of the shear center M is far from the first axis a1. On the other hand, the center of gravity S is substantially at the center of the horizontal piece 110 in the width direction and directly below the lower surface of the horizontal piece 110. However, the distance between the center of gravity S and the shear center M is further wider than in the case of FIG. 5C.

Next, the cross-sectional shape of the vehicle body side arm 10B at the position closest to the first mounting portion 11 is C-shaped as shown in FIG. 6 (E). This cross-sectional shape includes a horizontal piece 110, a vertical piece 120 extending downward from both sides thereof, and an inner flange 121 bent from the lower end of one vertical piece 120 toward the other vertical piece 120 facing the other. The horizontal piece 110 has no dent and is substantially linear as compared with the horizontal piece 110 of FIG. 5 (D). In this case, the shear center M is located above the horizontal piece 110 and in the vicinity of the vertical piece 120 on the inner edge side of the lower arm 10. As shown in FIG. 2, the position of the shear center M is the largest in the entire cross section from the first axis a1. It is substantially at the center of the horizontal piece 110 in the width direction and below the lower surface of the horizontal piece 110. The distance between the center of gravity S and the center of shear M is as wide as in the case of FIG. 5 (D).

Further, the cross-sectional shape of the wheel side arm 10W will also be described. Of the wheel-side arm 10W, the cross-sectional shape at the position closest to the first mounting portion 11 is a flat M-shape as shown in FIG. 6 (F). Similar to the cross-sectional shape of FIG. 5B, this cross-sectional shape also includes a first horizontal piece 111, an inclined piece 112, a second horizontal piece 113, and a vertical piece 120. However, the first horizontal piece 111 is longer than the second horizontal piece 113, and the entire cross-sectional shape is flat. Further, as in the case of FIG. 5D, an inner flange 121 is provided below the vertical piece 120 on the inner edge side of the lower arm 10. In this case, the shear center M overlaps the upper end portion of the inclined piece 112 on the inner edge side of the lower arm 10. As shown in FIG. 2, the distance from the first axis a1 to the shear center M is as wide as in the case of FIG. 5 (C). The center of gravity S overlaps the central portion of the first horizontal piece 111 in the width direction. The distance between the center of gravity S and the shear center M is slightly closer than in the case of FIG. 5 (E).

Next, the cross-sectional shape of the wheel-side arm 10W at a position slightly closer to the third mounting portion 13 side is a flat M-shape as shown in FIG. 6 (G). This cross-sectional shape also includes a first horizontal piece 111, an inclined piece 112, a second horizontal piece 113, and a vertical piece 120, as in the case of FIG. 6F. However, the inclined piece 112 on the inner edge side of the lower arm 10 is longer and the first horizontal piece 111 is shorter than in the case of FIG. 6 (H). In this case, the shear center M is located above the lower end of the inclined piece 112 on the inner edge side of the lower arm 10, and is located on the inner edge side of the lower arm 10 from the first axis a1. On the other hand, the center of gravity S is substantially at the center of the first horizontal piece 111 in the width direction and overlaps with the first horizontal piece 111. The distance between the center of gravity S and the shear center M is slightly closer than in the case of FIG. 6 (F).

Finally, the cross-sectional shape of the wheel side arm 10W at the position closest to the third mounting portion 13 includes the horizontal piece 110, and one end side of the horizontal piece 110 is L-shaped, as shown in FIG. 6 (H). Shape, the other end side is J-shaped. The horizontal piece 110 is longer than the first horizontal piece 111 in FIGS. 6 (F) and 6 (G). One end side of the horizontal piece 110 is the outer edge side of the lower arm 10, and the other end side is the inner edge side of the lower arm 10. The vertical piece 120 on one end side of the horizontal piece 110 is shorter than the vertical piece 120 of FIG. 6 (F). The other end side of the horizontal piece 110 has a vertical piece 120 that once rises upward and then extends downward, and the lower end of the vertical piece 120 has an inner flange 121 that extends toward the opposing vertical piece 120. In this case, the shear center M is located directly above the center of the horizontal piece 110 in the width direction and slightly closer to the other end. On the other hand, the center of gravity S is located slightly closer to the other end from the center of the first horizontal piece 111 in the width direction and overlaps with the first horizontal piece 111. The distance between the center of gravity S and the shear center M is even closer than in the case of FIG. 6 (G).

As described above, in order to secure the section modulus of the vehicle body side arm 10B, it is preferable to secure a large number of cross sections perpendicular to the axial direction in the cross section. More specifically, a cross-sectional shape having many bending points is preferable. For example, a cross-sectional shape having two or more bending points, three or more points, four points or more, five points or more, or six points or more can be mentioned.

[Action effect]
The suspension arm and suspension device according to the above embodiment can exert the following effects.

(1) By _{setting the arm angle θ 1} to an obtuse angle, a suspension arm having excellent anti-dive characteristics can be obtained. This is because if the arm angle θ ₁ is an obtuse angle, the second mounting portion 12 can be easily arranged inside the first mounting portion 11 in the vehicle width direction. At the time of braking, the first mounting portion 11 is relatively low with respect to the third mounting portion 13 due to the braking load, and is also relatively low with respect to the second mounting portion 12. At that time, the lower arm 10 behaves so as to rotate about the second axis a2 connecting the center of the first elastic body 11r and the center C3 of the ball joint 13B. However, if the arm angle θ ₁ is an obtuse angle and the center C2 of the second elastic body 12r is arranged inside the center C1 of the first elastic body 11r in the vehicle width direction, the second mounting portion is substantially along the vehicle length direction. It either tries to displace upwards or behaves to displace inward and upwards in the vehicle width direction. Due to the behavior of the lower arm 10, the second mounting portion 12 is prevented from being displaced outward and upward in the vehicle width direction, and the stability of the wheels during braking can be ensured.

(2) By adopting a cross-sectional shape of the suspension arm such that the relationship between the distance L1 and the distance L2 is L1> L2, it is possible to realize high fatigue endurance strength while making _{the arm angle θ 1 an obtuse angle.} can. When the arm angle θ ₁ is an obtuse angle, the anti-dive characteristics are excellent as described above, but stress is concentrated on the rear side of the first mounting portion 11 especially during braking. This is because the second mounting portion 12 is twisted with respect to the first axis a1 due to the braking load acting on the third mounting portion 13. If the cross-sectional shape of the vehicle body side arm 10B is a shape satisfying L1> L2, the above-mentioned twist is unlikely to occur on the second mounting portion 12 side of the vehicle body side arm 10B, and stress is concentrated on the rear side of the first mounting portion 11. Can be suppressed. Therefore, it is possible to obtain a suspension arm having excellent fatigue endurance strength while making the arm angle θ _{1 an obtuse angle.}

(3) Since the distance L1 and the distance L2 are different between the first mounting portion 11 side and the second mounting portion 12 side, a displacement point of the section modulus occurs in the middle of the vehicle body side arm 10B. Therefore, at the time of a frontal collision of the vehicle, the vehicle body side arm 10B connecting the first mounting portion 11 and the second mounting portion 12 can be easily buckled in the middle, and the collision safety performance can be satisfied.

[Trial calculation example]
A stress analysis model of the lower arm according to the embodiment and the lower arm according to the comparative example was set, and the stress distribution and the displacement of the shape generated in the lower arm at rest and the lower arm in the vibration fatigue state were analyzed using simulation software. Test Example 1 is a model of the lower arm according to the first embodiment. This model has an angle (arm angle θ ₁ ) between the first axis and the second axis of about 96 °, has a cross-sectional shape shown in FIGS. 3 and 4, and satisfies the distance L1> distance L2. Test Example 2 has the same arm angle θ _{1 as} the model of Test Example 1, but differs from Test Example 1 in that the cross-sectional shape of each part and substantially satisfying the above distance L1 = distance L2. The basic configuration such as the material and the dimensions between the mounting portions is the same as that of Test Example 1. Test Example 3 is _{different from Test Example 1 in that the arm angle θ 1} is about 89 ° and substantially satisfies the above distance L1 = distance L2. The basic configuration such as the material and the dimensions between the mounting portions is the same as that of Test Example 1.

As a result, it was found that in each model, a certain amount of stress is likely to be concentrated in the region on the rear side of the vehicle among the joints between the first mounting portion and the arm body. However, it was found that the stress concentration was most relaxed in Test Example 1. In both Test Example 2 and Test Example 3, it was found that a stress larger than that in Test Example 1 was generated at the joint between the first mounting portion and the arm body.

The present invention is not limited to these examples, and is indicated by the scope of claims, and is intended to include all modifications within the meaning and scope equivalent to the scope of claims.

The suspension arm and the vehicle suspension device according to the embodiment of the present invention can be suitably used as, for example, the lower arm of the front suspension of the vehicle.

10 Lower arm 10S Arm body 10B Body side arm 10W Wheel side arm 10h1 Through hole 10h2 Drainage hole 11 First mounting part 11C Color 11r First elastic body 11a First support shaft 12 Second mounting part 12h Through hole 12c Circular member 12r First (Ii) Elastic body 12a Second support shaft 13 Third mounting part 13B Ball joint 13h Through hole 20 Subframe 30 Steering knuckle 40 Wheel 42 Wheel 50 Tie rod 60 Strut 70 Suspension tower 110 Horizontal piece 111 First horizontal piece 112 Inclined piece 113 Second Horizontal piece 120 Vertical piece 121 Inner flange a1 First axis a2 Second axis b, c Axis θ ₁ Arm angle θ ₂ , θ ₃ Displacement angle C1 Center of first elastic body C2 Center of second elastic body C3 Center of ball joint

Claims (2)

The first mounting part, which is mounted to the vehicle body via the first elastic body,
A second mounting portion that is mounted on the vehicle body via a second elastic body behind the first mounting portion in the vehicle length direction.
A third mounting portion that is mounted on the wheel via a ball joint outside the vehicle width direction from the first mounting portion.
A vehicle body side arm connecting the first mounting portion and the second mounting portion,
A wheel-side arm that connects the first mounting portion and the third mounting portion is provided.
The angle between the first axis connecting the center of the first elastic body and the center of the second elastic body and the second axis connecting the center of the first elastic body and the center of the ball joint is more than 90 °. can be,
The distance between the first shear center and the first axis in the first cross section of the vehicle body side arm on the first mounting portion side is L1, and in the second cross section of the vehicle body side arm on the second mounting portion side. when the distance between the second shear center and said first axis and L2, meets the L1> L2,
The first shear center is located outside the center of gravity of the cross-sectional shape of the first cross section in the vehicle width direction.
The distance between the center of gravity of the cross-sectional shape in the first cross section and the center of the first shear in the vehicle width direction is defined as X1, and the direction of the width of the center of the cross section in the second cross section and the center of the second shear in the vehicle width. A suspension arm that satisfies X1> X2, where X2 is the distance between. The suspension arm according to claim 1 is provided.
The center of the second elastic body is a vehicle suspension device attached to the vehicle body inside the vehicle width direction from the center of the first elastic body.

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