Suspension arm

Abstract

A suspension arm has an elongated shape. The suspension arm is shaped such that a line defining an outer shape of the suspension arm does not coincide with a line of force transmission, but a line extending through a shearing center point of each of a plurality of cross sections of the suspension arm coincides with the line of force transmission.

Claims

1. A suspension arm comprising: an elongate-shaped suspension arm, the suspension arm being shaped such that a line defining an outer shape of the suspension arm does not coincide with a line of force transmission, and a line extending through a shearing center point of each of a plurality of cross-sections of the suspension arm each coincide with the line of force transmission.

2. The suspension arm according to claim 1, further comprising: a pair of flanges each extending in a longitudinal direction of the suspension arm; and a connector connecting the pair of flanges to each other, wherein: the suspension arm is bent with respect to the longitudinal direction, and the connector is offset towards one of opposite sides of a center point of the pair of flanges with respect to the center point of the pair of flanges in a widthwise direction of the pair of flanges, the one of the opposites sides being nearer to the line of force transmission than another one of the opposite sides.

3. The suspension arm according to claim 2, wherein: the line defining the outer shape of the suspension arm is a line extending through the center point of the pair of flanges in the widthwise direction, and the connector is offset towards any one of opposite sides of the pair of flanges in the widthwise direction, with respect to the line defining the outer shape.

4. The suspension arm according to claim 2, wherein: the line defining the outer shape of the suspension arm is the line extending through the center point of the pair of flanges in the widthwise direction, and the line extending through a shearing center point of each of a plurality of cross-sections of the suspension arm is located on any one of opposite sides of the line defining the outer shape.

5. The suspension arm according to claim 2, wherein: the line defining the outer shape of the suspension arm is the line extending through the center point of the pair of flanges in the widthwise direction, the line of force transmission and the line defining the outer shape intersect each other, and the line extending through the shearing center point of each of a plurality of cross-sections of the suspension arm and the line defining the outer shape intersect each other.

6. The suspension arm according to claim 2, wherein the suspension arm has a crank shape curved when viewed in the longitudinal direction.

7. The suspension arm according to claim 2, wherein the suspension arm has an S-shape curved when viewed in the longitudinal direction.

8. The suspension arm according to claim 2, wherein the suspension arm has an I-shape.

9. The suspension arm according to claim 2, wherein the suspension arm is shaped such that a distance between: (i) the line extending through centroids on a plurality of cross-sections of the suspension arm, and (ii) the line of force transmission, is less than a distance between (a) the line extending through a center point of the suspension arm in the widthwise direction of the suspension arm and (b) the line of form transmission.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The objects, features, advantages, and technical and industrial significance of the present disclosure will be better understood by reading the following detailed description of the embodiment, when considered in connection with the accompanying drawings, in which:

(2) FIG. 1 is a front elevational view of a suspension arm according to one embodiment;

(3) FIG. 2A is a plan view of the suspension arm, FIG. 2B is a cross-sectional view taken along line IIB-IIB in FIG. 2A, FIG. 2C is a cross-sectional view taken along line IIC-IIC in FIG. 2A, and FIG. 2D is a cross-sectional view taken along line IID-IID in FIG. 2A;

(4) FIG. 3 is a view for explaining a shearing center point and a centroid of each of a plurality of cross sections of the suspension arm;

(5) FIG. 4A is a view illustrating one example of a state in which the suspension arm is mounted on a vehicle, FIG. 4B is a cross-sectional view taken along line IVB-IVB in FIG. 4A, FIG. 4C is a cross-sectional view taken along line IVC-IVC in FIG. 4A, and FIG. 4D is a cross-sectional view taken along line IVD-IVD in FIG. 4A; and

(6) FIG. 5A is a view illustrating an up/down directional force, a moment, and a shearing force acting on the suspension arm, and FIG. 5B is a view illustrating a compressive force acting on the suspension arm.

DETAILED DESCRIPTION OF THE EMBODIMENT

(7) Hereinafter, there will be described a suspension arm according to one embodiment by reference to the drawings. It is to be understood that the following embodiment are described only by way of example, and the disclosure may be otherwise embodied with various modifications without departing from the scope and spirit of the disclosure.

(8) As illustrated in FIGS. 1 and 2A, a suspension arm 10 according to the present embodiment is elongated in its longitudinal direction and includes: an arm body 12, a mount portion 15 provided at one end portion of the arm body 12, and a mount portion 18 provided at the other end portion of the arm body 12. The mount portion 15 has a through hole 14, and the mount portion 18 has two through holes 16, 17. As illustrated in FIGS. 2B-2D, the arm body 12 has an I-shape in cross section and includes: a pair of flanges 20, 22 each extending in the longitudinal direction; and a connector 24 connecting the pair of flanges 20, 22 to each other. This connector 24 may be referred to as “vertical web”.

(9) In FIGS. 1-2D, the longitudinal direction of the suspension arm 10 is defined as an x direction. The height direction of the suspension arm 10 (i.e., a direction in which the connector 24 extends) is defined as a z direction. A direction perpendicular to the x direction and the z direction is defined as a y direction.

(10) The suspension arm 10 does not extend in a straight line in the longitudinal direction but is curved in a crank shape in the present embodiment. It is apparent that a line defining an outer shape of the suspension arm 10, e.g., a line La connecting center points (points R in FIGS. 2B-2D) of the flange 20 or the flange 22 in its widthwise direction) does not extend in a straight line on the xy plane but is curved in a crank shape. It is noted that the line La may be hereinafter referred to as “the line defining the outer shape”. It is also apparent that the line La defining the outer shape does not coincide with a line Lb of force transmission which will be described below. It is noted that the line defining the outer shape may be replaced with lines La′, La″ extending along an outer edge of the suspension arm 10.

(11) The arm body 12 has a shape in which a position on the connector 24 relative to the pair of flanges 20, 22 in a widthwise direction of the suspension arm 10 (i.e., a connecting position) changes with a position on the connector 24 in the longitudinal direction. As illustrated in FIGS. 2B-2D, a shearing center point S changes in the y direction with change in the connecting position on the connector 24. In the present embodiment, the position on the connector 24 relative to the pair of flanges 20, 22 on each cross section is designed such that the shearing center point S is aligned with a point. P of force action (i.e., a point of action of force). It is noted that each cross section is a plane perpendicular to the line La defining the outer shape.

(12) The shearing center point S on each cross section is determined based on the shape of the cross section. In the case where, in an I-shape cross section of a pair of flanges K and a connector J, as illustrated in FIG. 3, the width of each flange K is defined as “b”, the length of the connector J is defined as “h”, and the connector J is located at a distance of the length b1 from one end of the flange K (i.e., Y0 in FIG. 3), a distance e between the shearing center point S and the connector J is expressed by the following equation:
e=3b(b.sub.1−b.sub.2)/(6b+h)
Since the sum of the lengths b.sub.1, b.sub.2 is equal to the length b of the flange K (b.sub.1+b.sub.2=b), the equation can be also expressed by the following equation:
e=3b(2b.sub.1−b)/(6b+h)

(13) The point P of force action on each cross section is located on the line Lb of force transmission in the suspension arm 10. In the present embodiment, the line Lb of force transmission is a line that connects points of force input in the suspension arm 10. The suspension arm 10 is mounted on a vehicle-body-side component at the mount portion 15 and mounted on a wheel-side component at the mount portion 18. Thus, as illustrated in FIG. 2A, each of a center point A of the through hole 14 and a center point B located between center points B1, B2 of the respective through holes 16, 17 corresponds to the point of force input. A straight line connecting these input points (i.e., the center points A, B) corresponds to the line Lb of force transmission.

(14) Determination of the line Lb of force transmission determines a position of a point P of action (e.g., a length yP from the one end Y0) on each cross section. Thus, the length b1 can be determined such that the shearing center point S is aligned with the point P of force action (y.sub.P=e+b.sub.1) on each cross section of the suspension arm 10. As a result, the position of the connector J with respect to the pair of flanges K can be determined.

(15) The cross-sectional shape illustrated in FIG. 3 differs from the cross-sectional shape of the actual suspension arm 10. Thus, the position of the shearing center point S of the actual suspension arm 10 is not always determined by the above-described equations. In the actual suspension arm 10, however, the position of the connector 24 with respect to the pair of flanges 20, 22 can be determined in the same manner such that the shearing center point S and the point P of force action are aligned with each other on each of the plurality of cross sections.

(16) Each of the black triangles in FIGS. 2A-2D indicates the shearing center point S on each cross section of the actual suspension arm 10 according to the present embodiment. As apparent from FIG. 2A, a line Lc extending through the shearing center point S on each cross section substantially coincides with the line Lb of force transmission.

(17) In the I-shape cross section illustrated in FIG. 3, a distance yG between a centroid G and the one end Y0 is expressed by the following equation:
y.sub.G=(b/2)−{h(b−2b.sub.1)/2(2b+h)}
As apparent from this equation, when the length b1 is greater than the length b/2, the distance yG is greater than the length b/2, and when the length b1 is less than the length b/2, the distance yG is less than the length b/2. In other words, in the case where the connector 24 is offset to one side with respect to the center point R of the flanges 20, 22, the centroid G is also offset to the same side.

(18) Each of the white circles in FIG. 2A indicates the centroid G on each cross sections of the actual suspension arm 10 according to the present embodiment. As apparent from FIG. 2A, a distance dg between the centroid G and the point of force action (i.e., the point on the line Lb of force transmission) is less than a distance da between the center point R (i.e., the point on the line La defining the outer shape) in the widthwise direction of the suspension arm 10 and the point of force action (dg<da).

(19) The position of the connector 24 of the suspension arm with respect to the flanges 20, 22 is designed as described above. Since the suspension arm 10 according to the present embodiment is curved in the crank shape with respect to the longitudinal direction, the line Lb of force transmission and the line La defining the outer shape (which extends through the center point R in the widthwise direction) intersect each other, and the line Le extending through the shearing center point S and the line La defining the outer shape intersect each other. Thus, the connector 24 is offset, with respect to the line La defining the outer shape, to one or the other side in the widthwise direction. The shearing center point S is also located on one or the other side of the line La defining the outer shape.

(20) As illustrated in FIG. 4, the suspension arm 10 according to the present embodiment may be used as a leading arm of a rigid suspension, for example. The suspension arm 10 is provided between an axle housing 52 as a wheel-side component and a frame 54 as a vehicle-body-side component. The axle housing 52 is rotatable relative to and movable integrally with a wheel 50. The suspension arm 10 is provided in a state in which its longitudinal direction generally coincides with a front and rear direction of a vehicle, its widthwise direction with a widthwise direction of the vehicle, and its height direction with an up and down direction of the vehicle.

(21) One end portion of the suspension arm 10 is mounted at the mount portion 15 on the frame 54 by a bolt 58 and a nut 59 via a rubber bushing 56 fitted in the through hole 14, such that the suspension arm 10 is pivotable about an axis extending substantially in the widthwise direction of the vehicle. As illustrated in FIG. 4D, the center point A of the mount portion 15 is located on the central axis of the bolt 58. Likewise, the other end portion of the suspension arm 10 is mounted at the mount portion 18 on the axle housing 52 by bolts 64, 65 and respective nuts 66, 67 via rubber bushings 62, 63 fitted in the respective through holes 16, 17, such that the suspension arm 10 is pivotable about an axis extending substantially in the widthwise direction. The center point B of the mount portion 18 is located at a center point between the center points B1, B2 (illustrated in FIGS. 4B and 4C) located on the central axes of the respective bolts 64, 65.

(22) For example, in the case where an external force in the up and down direction is applied to the wheel 50 due to, e.g., road input, as illustrated in FIG. 5A, a force Fa in the up and down direction is applied to the suspension arm 10, whereby a bending moment M is generated, and a shearing force V is applied to the suspension arm 10. In the suspension arm 10 according to the present embodiment, the line Lc extending through the shearing center point S in each cross section substantially coincides with the line Lb of force transmission. Accordingly, the shearing force V makes it difficult to cause torsion, so that torsional deformation is suppressed even though bending is allowed.

(23) In some case, as illustrated in FIG. 5B, a force is applied to the wheel 50 in the front and rear direction, which applies a compressive force Fb to the suspension arm 10 in the longitudinal direction. In the suspension arm 10 according to the present embodiment, the centroid G is offset to one of opposite sides which is nearer to the line Lb of force transmission. Accordingly, it is possible to reduce a bending moment due to a compressive force and increase a buckling strength when compared with the case where the connector 24 is provided on the center point of the flanges 20, 22.

(24) In some case, limitations on, e.g., a space for mounting of the suspension arm and a mounting position (or orientation) of the suspension arm require the suspension arm to be bent with respect to the longitudinal direction and inhibit increase in size of the suspension arm in the widthwise direction. In the case where the suspension arm is bent with respect to the longitudinal direction, a flexural strength and the buckling strength may lower. In this case, the lowering of the flexural strength and the buckling strength is prevented by, e.g., increasing the thickness of the suspension arm in most cases. This increase in thickness, however, causes another problem of increase in weight of the suspension arm. In contrast, the present suspension arm 10 has the cross-sectional shape designed such that the shearing center point S is located on the line Lb of force transmission on each cross section without increase in size of the suspension arm 10 in the widthwise direction. This construction makes it possible to suppress the torsional deformation and reduce the lowering of the buckling strength without increase in weight of the suspension arm 10 and size thereof in the widthwise direction. Also, since the suspension arm 10 is bent with respect to the longitudinal direction, the point of force action may be located off the outer edge of the suspension arm 10. Even in this case, however, the design of the cross-sectional shape of the suspension arm 10 can bring the shearing center point S closer to the line Lb of force transmission outside the outer edge of the suspension arm 10, thereby suppressing the torsional deformation without increase in size of the suspension arm 10 in the widthwise direction.

(25) It is noted that the shape of the present suspension arm 10 in the longitudinal direction and the cross-sectional shape of the present suspension arm 10 are not limited to those in the above-described embodiment. For example, the present suspension arm 10 may be shaped so as to extend in a straight line, be bent, or extend in an arc shape with respect to the longitudinal direction. The present suspension arm 10 may have an L-shape, a C-shape, or a T-shape as the cross-sectional shape, for example.

(26) The present suspension arm 10 may be mounted in any orientation. For example, the present suspension arm 10 may be mounted pivotably about an axis extending generally in the front and rear direction of the vehicle, may be mounted pivotably about an axis extending generally in the up and down direction, and may be mounted pivotably about an axis inclined with respect to the widthwise direction, the front and rear direction, and the up and down direction. Even in the case where the present suspension arm 10 is mounted in any orientation, the present suspension arm 10 can suppress torsional deformation due to a force acting in a direction perpendicular to the line Lb of force transmission and reduce lowering of a buckling strength against a compressive force in the longitudinal direction.

(27) Also in the case where the present suspension arm 10 is mounted not via the rubber bushings but via bearings and ball joints, the suspension arm 10 can suppress the torsional deformation and reduce lowering of the buckling strength. Also, the mount portion to be mounted on the wheel-side component may have a single through hole.