Arm member

Abstract

To provide an arm member which enables press molding to be applied thereto, yet secure strength and rigidity in a longitudinal direction of the arm member, and can properly reduce torsional rigidity around the longitudinal direction of the arm member with high design flexibility.SOLUTION: In an arm member 1, at intermediate side wall parts 12 and 112 including a center of the arm member 1 in a longitudinal direction, in addition to vertical walls 32 and 132, inclined walls 22 and 122 are provided above the vertical walls 32 and 132, corresponding to the vertical walls 32 and 132. Upper ends of the inclined walls 22 and 122 are connected by a connection wall 210. At extension side wall parts 52, 54, 152, and 154 which are both ends of the arm member 1 in the longitudinal direction, the inclined walls 22 and 122 disappear and upper ends of the vertical walls 32 and 132 are connected by the connection wall 210.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an arm member, and more particularly to an arm member that is used as a component part of a vehicle such as an automobile. [Background technology]

[0002] In recent years, in order to improve the dynamic marketability of vehicles such as automobiles, there has been a demand for further reductions in noise, vibration and harshness (NVH) that occurs during vehicle driving and is transmitted to passengers. There is also a demand for further reductions in NVH transmitted to the vehicle body for the suspension system that suspends the vehicle wheels and connects them to the vehicle body.

[0003] Here, the arm member, which is a component of the suspension system of the vehicle, is a link member that connects the components on the unsprung side of the suspension system to the components on the vehicle body side so as to realize a required geometry. An insulator member such as a bush member attached to such an arm member is typically set with required spring characteristics in the compression direction in the longitudinal direction of the arm member and required spring characteristics in the shear direction in the width direction of the arm member. Therefore, when a displacement in the longitudinal direction or width direction of the arm member is applied to such an insulator member via the arm member, it is possible to make the required positioning performance and required insulation performance exhibited. However, when a displacement in which a displacement in the longitudinal direction and a displacement in the width direction are combined in the arm member, that is, a displacement that twists the insulator member, is applied, it is assumed that such required performance cannot be exhibited.

[0004] Under such circumstances, Patent Document 1 aims to reduce the torsional rigidity of the suspension arm 1 while suppressing a decrease in bending rigidity, and discloses that the suspension arm 1 comprises a tubular arm body 10 extending from the vehicle body side to the wheel side, a first connecting portion 20 joined to the vehicle body side end 14 of the arm body 10, and a second connecting portion 30 joined to the wheel side end 16 of the arm body 10, and that the arm body 10 has a shape in which diameters Rb, Rc of the vehicle body side end 14 and the wheel side end 16 are larger than the diameter Ra of the central portion 12, and the diameter Rb of the vehicle body side end 14 is larger than the diameter Rc of the wheel side end 16. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2015-074319 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, according to the inventors' investigations, the configuration of Patent Document 1 requires that large and small diameter sections with different diameters be formed in the arm main body, which is a tubular object. This makes it difficult to reduce the weight, and also makes it difficult to maintain shape precision by simply performing press processing such as rolling a plate member into a cylindrical shape. In this respect, there is room for improvement.

[0007] Furthermore, through further investigations by the present inventors, it has been found that by adopting a configuration in an arm member such as a suspension arm in which the height and width of the longitudinal cross section of the main part is kept constant while the shape of some of the walls is changed within the range of the maintained height and width to partially reduce the longitudinal cross section, it is possible to apply press molding that is easy for mass production while ensuring sufficient forming accuracy for practical use, and it is possible to appropriately reduce, with a high degree of design freedom, the torsional rigidity when a torsional moment is applied which imparts a twisting displacement around the longitudinal axis of the arm member while ensuring strength such as buckling strength and rigidity such as bending rigidity in the longitudinal direction of the arm member.

[0008] The present invention was made after taking into account the above considerations, and aims to provide an arm member that ensures strength and rigidity in the longitudinal direction of the arm member while allowing the application of press molding, and that can appropriately reduce torsional rigidity around the longitudinal direction of the arm member with a high degree of design freedom. [Means for solving the problem]

[0009] In order to achieve the above object, a first aspect of the present invention is an arm member extending in a longitudinal direction, the arm member having a first side wall, a second side wall opposing the first side wall in a width direction perpendicular to the longitudinal direction, and a connecting wall connecting the first side wall and the second side wall at an upper side in a vertical direction perpendicular to the longitudinal direction and the width direction, the connecting wall including a first inclined wall which is an upper component of the first side wall and a second inclined wall which is a lower component in the vertical ... and a first vertical wall which is the upper component and a second vertical wall which is the lower component are provided as components of the second side wall, and the connecting wall connects the first inclined wall and the second inclined wall at the upper side, and at both ends of the arm member in the longitudinal direction, the first inclined wall disappears from the component of the first side wall, and the second inclined wall disappears from the component of the second side wall, and the first vertical wall and the second vertical wall are connected by the connecting wall.

[0010] In addition, in the arm member of a second aspect of the present invention, in addition to the first aspect, a first transitional portion is provided in which the first inclined wall becomes smaller and disappears from the component of the first side wall as the R-shaped portion connecting the first inclined wall and the first vertical wall shifts upward from the intermediate portion toward the two end portions, and a second transitional portion is provided in which the second inclined wall becomes smaller and disappears from the component of the second side wall as the R-shaped portion connecting the second inclined wall and the second vertical wall shifts upward from the intermediate portion toward the two end portions.

[0011] Furthermore, in an arm member in a third aspect of the present invention, in addition to the first or second aspects, in the intermediate portion, the length of the first inclined wall in the vertical direction is set longer than the length of the first vertical wall in the vertical direction, and in the intermediate portion, the length of the second inclined wall in the vertical direction is set longer than the length of the second vertical wall in the vertical direction.

[0012] A fourth aspect of the present invention is, in addition to any one of the first to third aspects, that in the intermediate portion, a distance between the first vertical wall and the second vertical wall in the width direction is set longer than a length of the arm member in the up-down direction, the lower end of the first vertical wall and the lower end of the second vertical wall have corresponding first folded walls and second folded walls facing each other, and in the intermediate portion, a distance between the facing ends of the first folded wall and the second folded wall in the width direction is set longer than a width of the connecting wall in the width direction. Effect of the Invention

[0013] According to the configuration of the first aspect of the present invention, in the intermediate portion including the center of the arm member in the longitudinal direction, the first side wall has a first inclined wall which is an upper component and a first vertical wall which is a lower component in the up-down direction as components of the first side wall, and the second side wall has a second inclined wall which is an upper component and a second vertical wall which is a lower component as components of the second side wall, and the connecting wall connects the first inclined wall and the second inclined wall at the upper side, and at both ends of the arm member in the longitudinal direction, the first inclined wall disappears from the component of the first side wall and the second inclined wall disappears from the component of the second side wall, and the first vertical wall and the second vertical wall are connected by the connecting wall, so that press molding can be applied, and the torsional rigidity around the longitudinal direction of the arm member can be appropriately reduced with a high degree of design freedom while ensuring the strength and rigidity of the arm member in the longitudinal direction.

[0014] According to the configuration of the second aspect of the present invention, as the R-shaped portion connecting the first inclined wall and the first vertical wall deviates upward from the middle portion toward both ends, a first transitional portion is provided in which the first inclined wall becomes smaller and disappears from the component of the first side wall, and as the R-shaped portion connecting the second inclined wall and the second vertical wall deviates upward from the middle portion toward both ends, a second transitional portion is provided in which the second inclined wall becomes smaller and disappears from the component of the second side wall.Therefore, the torsional rigidity around the longitudinal axis of the arm member can be appropriately reduced with high design freedom while suppressing the occurrence of unnecessary stress concentration.

[0015] According to the configuration of the third aspect of the present invention, in the intermediate portion, the length of the first inclined wall in the up-down direction is set longer than the length of the first vertical wall in the up-down direction, and in the intermediate portion, the length of the second inclined wall in the up-down direction is set longer than the length of the second vertical wall in the up-down direction. Therefore, the torsional rigidity around the longitudinal axis of the arm member can be appropriately reduced with high design freedom while increasing the existence area of ​​the first inclined wall and the second inclined wall, which have a high contribution to the torsional rigidity around the longitudinal axis of the arm member.

[0016] According to the configuration of the fourth aspect of the present invention, in the intermediate portion, the distance between the first vertical wall and the second vertical wall in the width direction is set to be longer than the length of the arm member in the up-down direction, and the lower end of the first vertical wall and the lower end of the second vertical wall have the first folded wall and the second folded wall facing each other, respectively. In the intermediate portion, the distance between the facing ends of the first folded wall and the second folded wall in the width direction is set to be longer than the width of the connecting wall in the width direction. Therefore, during press molding, the punch that presses the connecting wall can be moved toward the connecting wall while passing between the relatively wide opposing ends of the first folded wall and the second folded wall, and the punch can be secured to have a required size, i.e., a required strength, and the overall formability of the connecting wall and therefore the arm member can be improved, thereby improving the molding precision. [Brief description of the drawings]

[0017] [Figure 1] FIG. 1 is a side view showing a lower arm in an embodiment of the present invention. [Diagram 2] FIG. 2 is a view taken along the Z1 arrow in FIG. 1, and is a plan view of the lower arm in this embodiment. [Diagram 3] 3 is a view taken along the Z2 arrow in FIG. 1, and is a bottom view of the lower arm in this embodiment. [Figure 4] FIG. 4 is a view taken along the X arrow in FIG. 1, and is a front view of the lower arm in this embodiment. [Diagram 5] FIG. 5 is a vertical cross-sectional view taken along line AA in FIG. [Figure 6] FIG. 6 is a vertical cross-sectional view taken along line BB of FIG. [Figure 7] FIG. 7 is a vertical cross-sectional view taken along line CC in FIG. [Figure 8] FIG. 8 is a longitudinal sectional view taken along line DD of FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] Hereinafter, with reference to Figures 1 to 8 as appropriate, an arm member according to an embodiment of the present invention will be described in detail using a lower arm, which is a component part of a suspension system of a vehicle such as an automobile, as an example. In the drawings, the x-axis, y-axis, and z-axis form a three-axis orthogonal coordinate system. The direction of the x-axis may be called the longitudinal direction, the direction of the y-axis the width direction, and the direction of the z-axis the up-down direction.

[0019] Fig. 1 is a side view showing a lower arm in this embodiment. Figs. 2 to 4 correspond in order to each other, being a view seen from an arrow Z1 in Fig. 1, which is a plan view of the lower arm in this embodiment, a view seen from an arrow Z2 in Fig. 1, which is a bottom view of the lower arm in this embodiment, and a view seen from an arrow X in Fig. 1, which is a front view of the lower arm in this embodiment. Figs. 5 to 8 correspond in order to each other, being a vertical sectional view taken along lines AA to DD in Fig. 1. In the drawings, the reference characters of components located symmetrically to the components shown in the drawings may be written in parentheses.

[0020] First, as shown in FIG. 1 to FIG. 8, the lower arm 1 is an arm member made of a metal such as iron, which typically has a U-shape that opens mainly toward the negative direction of the z-axis in a vertical cross section cut along a plane parallel to the yz plane, and extends in the direction of the x-axis as the longitudinal direction. The lower arm 1 typically has a shape that is plane-symmetrical with respect to a plane that is parallel to the yz plane and passes through the center position of the lower arm 1 in the longitudinal direction, and is plane-symmetrical with respect to a plane that is parallel to the xz plane and passes through the center position in the y-axis direction as the width direction perpendicular to the longitudinal direction of the lower arm 1. The lower arm 1 can be manufactured by press molding using a steel plate material or the like. Note that the lower arm 1 may have an asymmetrical shape instead of such a symmetrical shape when there is anisotropy in the directionality of the required strength and rigidity.

[0021] Specifically, the lower arm 1 mainly comprises a first side wall 10 located on the negative side of the y-axis, a second side wall 110 located on the positive side of the y-axis and facing the first side wall 10, and a connecting wall 210 located on the positive side of the z-axis and connecting the first side wall 10 and the second side wall 110 at their ends (upper ends) on the positive side of the z-axis.

[0022] In detail, the first side wall 10 includes an intermediate side wall portion 12, a transitional side wall portion 42 that is connected to the end portion of the intermediate side wall portion 12 on the negative side of the x-axis with respect to the intermediate side wall portion 12 in the negative direction of the x-axis, a transitional side wall portion 44 that is connected to the end portion of the intermediate side wall portion 12 on the positive side of the x-axis with respect to the intermediate side wall portion 12 in the positive direction of the x-axis, and a transitional side wall portion 44 that is connected to the end portion of the transitional side wall portion 42 on the negative side of the x-axis with respect to the transitional side wall portion 42 and is a vertical length (in the z-axis direction) of the intermediate side wall portion 12. The first side wall 10 integrally includes an extended side wall portion 52 having a vertical length larger than the vertical length of the intermediate side wall portion 12 and the vertical length of the transitional side wall portion 42, an extended side wall portion 54 that is connected to the end of the transitional side wall portion 44 on the positive side of the x-axis of the transitional side wall portion 44 on the positive side of the x-axis and has a vertical length larger than the vertical length of the intermediate side wall portion 12 and the vertical length of the transitional side wall portion 44, and a bent wall 80 that is bent from the end (lower end) of the first side wall 10 on the negative side of the z-axis to the positive side of the y-axis. Note that when it is not necessary to increase the vertical length of the extended side wall portions 52 and 54 due to requirements such as the layout of the components of the lower arm 1, the vertical length of the extended side wall portions 52 and 54 may be set to be equal to or shorter than the vertical length of each of the intermediate side wall portion 12 and the transitional side wall portions 42 and 44. When the intermediate side wall portion 12 and the extended side wall portions 52 and 54 can be smoothly connected, the transitional side wall portions 42 and 44 may be omitted. Also, when the requirement for strength and rigidity of the lower arm 1 is not large, the bent wall 80 may be omitted.

[0023] The intermediate side wall portion 12 is a plate-like side wall portion having a constant vertical length H1, and includes the center position in the longitudinal direction of the lower arm 1 and extends over the longitudinal direction of the lower arm 1, i.e., on both the positive and negative sides of the x-axis. The intermediate side wall portion 12 has an inclined wall 22 provided on the upper side (the positive side of the z-axis) and a vertical wall 32 provided on the lower side (the negative side of the z-axis). The inclined wall 22 is a flat inclined side wall portion that intersects with a plane parallel to the xz plane at a constant angle that inclines toward the positive side of the y-axis as it goes from the lower side to the upper side, and its upper end portion is connected to the connecting wall 210 via the upper R-shaped portion R1. The vertical wall 32 is a flat inclined side wall portion that is parallel to the xz plane, and its lower end portion is connected to the bent wall 80. The lower end portion of the inclined wall 22 and the upper end portion of the vertical wall 32 are connected to each other via the lower R-shaped portion R2. The vertical length H1 of the intermediate side wall portion 12 means the distance in the z-axis direction between the end portion of the intermediate side wall portion 12 on the positive side of the z-axis and the end portion of the intermediate side wall portion 12 on the negative side of the z-axis, but for convenience, it will be treated as the distance in the z-axis direction between the part of the connecting wall 21 that communicates with the intermediate side wall portion 12 and the part of the folded wall 80 that communicates with the intermediate side wall portion 12. The vertical length is defined in the same way for the transitional side wall portions 42 and 44 and the extended side wall portions 52 and 54.

[0024] The upper R-shaped portion R1 is defined by an upper R-end line L1 and a lower R-end line L2, each of which extends in the longitudinal direction of the lower arm 1, and is typically connected by a single R-shaped arc that is convex on the negative y-axis side and the positive z-axis side. The upper R-end line L1 connects to the end (left end) of the connecting wall 210 on the negative y-axis side, and the lower R-end line L2 connects to the upper end of the inclined wall 22. The lower R-shaped portion R2 is defined by an upper R-end line L3 and a lower R-end line L4, each of which extends in the longitudinal direction of the lower arm 1, and is typically connected by a single R-shaped arc that is convex on the negative y-axis side and the positive z-axis side. The upper R-end line L3 connects to the lower end of the inclined wall 22, and the lower R-end line L2 connects to the upper end of the vertical wall 32. In the drawings, for convenience, the vertical length H1 of the intermediate side wall portion 12 is shown by a dimension line between the outside of the plate, and the vertical length H2 of the inclined wall 22 and the vertical length H3 of the vertical wall 32 are shown by dimension lines that omit the upper R-shaped portion R1 and the lower R-shaped portion R2, etc., but the vertical length H2 will be treated as the distance in the z-axis direction between the lower R end line L2 and the upper R end line L3, and the vertical length H3 will be treated as the distance in the z-axis direction between the lower R end line L4 and the end portion of the intermediate side wall portion 12 on the negative side of the z-axis (the portion that connects to the intermediate side wall portion 12 of the folded wall 80).

[0025] The transitional sidewall portion 42 is a plate-shaped sidewall portion whose vertical length gradually increases from the vertical length H1 of the intermediate sidewall portion 12 as it moves toward the negative side of the x-axis, and extends from the intermediate sidewall portion 12 toward the negative side of the x-axis. The transitional sidewall portion 42 has an inclined wall 22, a vertical wall 32, a bent wall 80, an upper R-shaped portion R1, and a lower R-shaped portion R2, each of which is continuous with the intermediate sidewall portion 12. However, compared to the intermediate sidewall portion 12, in the transitional sidewall portion 42, the position of the lower R-shaped portion R2 is shifted upward as it moves from the intermediate sidewall portion 12 toward the negative side of the x-axis, and therefore the vertical length of the inclined wall 22 in the transitional sidewall portion 42 is shorter than the vertical length H2 of the inclined wall 22 in the intermediate sidewall portion 12. At the most negative position of the x-axis in the transitional sidewall portion 42, the vertical length of the inclined wall 22 becomes zero, and the inclined wall 22 itself disappears.

[0026] The transitional sidewall portion 44, like the transitional sidewall portion 42, is a plate-like sidewall portion whose vertical length gradually increases in the positive direction of the x-axis compared to the vertical length H1 of the intermediate sidewall portion 12, and extends from the intermediate sidewall portion 12 to the positive direction of the x-axis. The transitional sidewall portion 44 has an inclined wall 22, a vertical wall 32, a folded wall 80, an upper R-shaped portion R1, and a lower R-shaped portion R2, each of which is continuous with the intermediate sidewall portion 12. However, compared to the intermediate side wall portion 12, in the transitional side wall portion 44, the position of the lower R-shaped portion R2 shifts upward as one moves from the intermediate side wall portion 12 toward the positive side of the x-axis, and as a result, the vertical length of the inclined wall 22 in the transitional side wall portion 42 is shorter than the vertical length H2 of the inclined wall 22 at the intermediate side wall portion 12.At the position most positive on the x-axis in the transitional side wall portion 42, the vertical length of the inclined wall 22 becomes zero, and the inclined wall 22 itself disappears.

[0027] The extended side wall portion 52 is a flat side wall portion whose vertical length gradually increases toward the negative side of the x-axis as compared to the vertical length of the transitional side wall portion 42, and whose end portion on the negative side of the x-axis terminates in a semicircular shape convex toward the negative direction of the x-axis when viewed from the side in the y-axis direction. The extended side wall portion 52 has a burring hole portion 62 penetrating the extended side wall portion 52 in the y-axis direction, and the burring hole portion 62 has a cylindrical side wall-shaped flange 64 that is erected from the extended side wall portion 52 in the positive direction of the y-axis while boring into the extended side wall portion 52 in the y-axis direction, and a through hole 66 defined on the inside of the flange 64 in the radial direction.

[0028] The extended side wall portion 54, like the extended side wall portion 52, is a flat side wall portion whose vertical length gradually increases toward the positive side of the x-axis compared to the vertical length of the transitional side wall portion 44, and whose end portion on the positive side of the x-axis terminates in a semicircular shape convex toward the positive direction of the x-axis in a side view seen in the y-axis direction. The extended side wall portion 54, like the extended side wall portion 52, has a burring hole portion 72 penetrating the extended side wall portion 54 in the y-axis direction, and the burring hole portion 72 has a cylindrical side wall-shaped flange 74 that is provided upright from the extended side wall portion 54 in the positive direction of the y-axis while boring through the extended side wall portion 54 in the y-axis direction, and a through hole 76 defined on the inside of the flange 74 in the radial direction.

[0029] Furthermore, since the vertical lengths of the extended side wall portions 52 and 54 are set to be longer than the vertical length H of the intermediate side wall portion 12 and the vertical lengths of the transitional side wall portions 42 and 44, it is possible to increase the diameters of the burring hole portions 62 and 72, making it possible to accommodate insulator members of large capacity.

[0030] The folded wall 80 comprises an intermediate folded wall portion 82 folded from the negative end of the intermediate side wall portion 12 on the z-axis toward the positive side of the y-axis, an inclined folded wall portion 84 connected to the intermediate folded wall portion 82 and folded from the negative end of the transitional side wall portion 42 and the extended side wall portion 52 on the z-axis toward the positive side of the y-axis, and an inclined folded wall portion 86 connected to the intermediate folded wall portion 82 and folded from the negative end of the transitional side wall portion 44 and the extended side wall portion 54 on the z-axis toward the positive side of the y-axis.

[0031] In the transitional side wall portions 42 and 44, the vertical length gradually increases from the vertical length H1 of the intermediate side wall portion 12 as it approaches the negative and positive sides of the x-axis, so that the bent walls 80 of the inclined bent wall portions 84 and 86 of the transitional side wall portions 42 and 44 also extend downwards in the negative and positive directions of the x-axis. In the extensional side wall portions 52 and 54, the vertical length gradually increases from the vertical length of the transitional side wall portions 42 and 44 as it approaches the positive side of the x-axis, so that the bent walls 80 of the inclined bent wall portions 84 and 86 of the extensional side wall portions 52 and 54 also extend downwards in the negative and positive directions of the x-axis. The bent walls 80 of the intermediate bent wall portion 82 extend parallel to the x-axis.

[0032] The second side wall 110 has components, which correspond to the respective components of the first side wall 10, namely the intermediate side wall portion 112, the transitional side wall portions 142 and 144, the extended side wall portions 152 and 154, the flange 164 and through hole 166 of the burring hole portion 162, the flange 174 and through hole 176 of the burring hole portion 172, and the intermediate folded wall portion 182 and the inclined folded wall portions 184 and 186 of the folded wall 180, facing each other on the positive side of the y-axis. Incidentally, only one of the pair of burring holes 62 and 162 and the pair of burring holes 72 and 172 may be provided as necessary.

[0033] In other words, in the second side wall 110, the inclined wall 122 intersects with a plane parallel to the xz plane at a constant angle that inclines toward the negative side of the y-axis as it goes from the bottom to the top, and the intermediate folded wall portion 182, the inclined folded wall portion 184 and the inclined folded wall portion 186 in the folded wall 180 are folded corresponding to the negative side of the y-axis from the ends on the negative side of the z-axis of the intermediate side wall portion 112, the transitional side wall portion 142, the transitional side wall portion 144, the extended side wall portion 152 and the extended side wall portion 154.

[0034] Also, in the second side wall 110, the flange 164 of the burring hole portion 162 and the flange 174 of the burring hole portion 172 are erected toward the negative direction of the y axis, and the intermediate bent wall portion 182 and the inclined bent wall portions 184 and 186 of the bent wall 180 are bent toward the negative side of the y axis, which is different from that in the first side wall 10. In other words, the flange 64 of the burring hole portion 62 and the flange 164 of the burring hole portion 162 face each other on the inner side in the width direction of the lower arm 1, and the flange 74 of the burring hole portion 72 and the flange 174 of the burring hole portion 172 face each other on the inner side in the width direction of the lower arm 1. Further, the intermediate bent wall portion 82 and the inclined bent wall portions 84 and 86 of the bent wall 80 and the intermediate bent wall portion 182 and the inclined bent wall portions 184 and 186 of the bent wall 180 face each other on the inner side in the width direction of the lower arm 1. Further, the through hole 66 of the burring hole portion 62 and the through hole 166 of the burring hole portion 162 have a coaxial central axis which is the C1 axis parallel to the y-axis direction, and the through hole 76 of the burring hole portion 72 and the through hole 176 of the burring hole portion 172 have a coaxial central axis which is the C2 axis parallel to the y-axis direction, and typically, outer tubular portions of the insulator bushing member are inserted into the through holes 66 and 166 and the through holes 76 and 176, respectively. In addition, when only one of the pairs of burring hole portions 62 and 162 and the pair of burring hole portions 72 and 172 is provided, a through hole may be provided at the location where the other pair should be provided, and a separate collar member may be attached around the through hole by welding or the like.

[0035] The connecting wall 210 consists of an intermediate connecting wall portion 212 that is parallel to the xy plane, an inclined connecting wall portion 214 that is connected to the intermediate connecting wall portion 212 and that is inclined so as to rise as it approaches the negative side of the x-axis relative to the intermediate connecting wall portion 212, and an inclined connecting wall portion 216 that is connected to the intermediate connecting wall portion 212 and that is inclined so as to rise as it approaches the positive side of the x-axis relative to the intermediate connecting wall portion 212.

[0036] The intermediate connecting wall portion 212 is an upper wall portion parallel to the xy plane that connects the ends of the intermediate side walls 12 and 112 on the positive side of the z axis via the upper R-shaped portion R1.

[0037] The inclined connecting wall portion 214 is an upper wall portion that connects the ends of the transitional side wall portions 42 and 142 and the extended side wall portions 52 and 152 on the positive side of the z-axis via upper R-shaped portions R1 and R11, and may have a convex-shaped portion 222 that is a protrusion that protrudes toward the negative direction of the x-axis at a part of the end on the negative side of the x-axis (the middle part in the width direction).

[0038] Similar to the inclined connecting wall portion 214, the inclined connecting wall portion 216 is an upper wall portion that connects the ends of the transitional side wall portions 44 and 144 and the extended side wall portions 54 and 154 on the positive side of the z-axis via upper R-shaped portions R1 and R11, and a portion of the end on the positive side of the x-axis (the middle portion in the width direction) may have a convex-shaped portion 224 which is a protrusion that juts out toward the positive direction of the x-axis.

[0039] In the transitional sidewall portions 42, 44, 142, and 144, the vertical length gradually increases from the vertical length H1 of the intermediate sidewall portions 12 and 112 as it approaches the negative and positive sides of the x-axis, so that the bent walls 80 of the inclined connecting walls 214 and 216 of the transitional sidewall portions 42, 44, 142, and 144 also rise correspondingly and extend in the negative and positive directions of the x-axis. Also, in the extensional sidewall portions 52, 54, 152, and 154, the vertical length gradually increases from the vertical length of the transitional sidewall portions 42, 44, 142, and 142 as it approaches the positive side of the x-axis, so that the bent walls 80 of the inclined connecting walls 214 and 216 of the extensional sidewall portions 52, 54, 152, and 154 also rise correspondingly and extend in the negative and positive directions of the x-axis.

[0040] Here, in the above configuration, in the intermediate side wall portions 12 and 112, in addition to the vertical walls 32 and 132, inclined walls 22 and 122 are provided correspondingly on the upper side thereof, and such inclined walls 22 and 122 are inclined at a constant angle of the same magnitude so as to approach each other as they move upward from the corresponding vertical walls 32 and 132. By adjusting the magnitude of the inclination angle of such intermediate side wall portions 12 and 112 at the time of design, it is possible to adjust so as to appropriately reduce the rigidity (torsional rigidity) when a torsional moment about the x-axis is applied to the lower arm 1 while maintaining the required strength and rigidity in the x-axis direction of the lower arm 1. In this case, the inclined walls 22 and 122 need to disappear by the time they reach the extended side wall portions 52, 54, 152 and 154, which are on the intermediate side wall portions 12 and 112 side of the burring holes 62, 72, 162 and 172, so as not to interfere with the burring hole portions 62, 72, 162 and 172 of the extended side wall portions 52, 54, 152 and 154. As a result, at least in the extended side wall portions 52, 54, 152 and 154, there will be portions where only the vertical walls 32 and 132 are provided.

[0041] In addition, in order to eliminate the inclined walls 22 and 122 by a smooth change in shape so as not to cause unnecessary stress concentration when the inclined walls 22 and 122 are eliminated, it is preferable to provide the transitional sidewall portions 42, 44, 142 and 144. Specifically, in the transitional sidewall portions 42, 44, 142 and 144, the vertical lengths of the inclined walls 22 and 122 are gradually shortened from the vertical length H2 of the inclined walls 22 and 122 at the intermediate sidewall portions 12 and 112 as they move away from the intermediate sidewall portions 12 and 112 in the x-axis direction, coupled with the position of the lower R-shaped portions R2 and R12 being shifted upward, and at the position of the transitional sidewall portions 42, 44, 142 and 144 farthest from the intermediate sidewall portion 12 in the x-axis direction, the vertical lengths of the inclined walls 22 and 122 are preferably zero, and the inclined walls 22 and 122 themselves are preferably eliminated.

[0042] When eliminating the inclined walls 22 and 122 in this manner, from the viewpoint of avoiding unnecessary stress concentration, it is preferable that the magnitude of R of each of the lower R-shaped portions R2 and R12 is gradually changed so as to increase in one or more steps as it moves away from the intermediate side wall portions 12 and 112 in the direction of the x-axis, and that the corresponding upper R end lines L3 and L13 and lower R end lines L4 and L14 are displaced upward, while the distance between the upper R end lines L3 and L13 and the lower R end lines L4 and L14 is also increased. Similarly, although the positions of the upper R-shaped portions R1 and R11 change depending on the position (height) of the connecting wall 210 in the z-axis direction, from the viewpoint of preventing unnecessary stress concentration, it is preferable that the magnitude of R of each of the upper R-shaped portions R1 and R11 is gradually changed so as to increase in one or more steps as it moves away from the intermediate side wall portions 12 and 112 in the x-axis direction, and the distance between the upper R end lines L1 and L11 and the lower R end lines L2 and L12 is increased. In this case, for example, the upper R end lines L1 and L11 are displaced upward depending on the position (height) of the connecting wall 210 in the z-axis direction, while the lower R end lines L2 and L12 extend parallel to the longitudinal direction. However, taking into consideration that the rigidity of the upper R-shaped portions R1 and R11 is higher than the rigidity of the lower R-shaped portions R2 and R12 when the transitional side wall portions 42, 44, 142 and 144 reach the position where the inclined walls 22 and 122 disappear, it is preferable that the upper R-shaped portions L3 and L13 and the lower R-shaped portions L4 and L14 disappear at a position where they are connected to the lower R-shaped portions L2 and L12 while keeping a distance from each other, so that the lower R-shaped portions R2 and R12 merge with and are absorbed into the upper R-shaped portions R1 and R11, and the magnitude of R of each of the upper R-shaped portions R1 and R11 is gradually changed to increase in one or more steps, thereby displacing the lower R-shaped portions L2 and L12 downward. In addition, from the viewpoint of avoiding unnecessary stress concentration, it is preferable that at the positions where the inclined walls 22 and 122 disappear at the transitional side wall portions 42, 44, 142 and 144, the magnitude of R of each of the lower R-shaped portions R2 and R12 is set larger than the magnitude of R of each of the upper R-shaped portions R1 and R11.Additionally, in order to avoid unnecessary stress concentration at the positions where the inclined walls 22 and 122 disappear, it is preferable that the vertical length of the transitional sidewall portions 42, 44, 142 and 144 is set to be longer than the vertical length H1 of the intermediate sidewall portions 12 and 122. Note that, in the portions further away from the intermediate sidewall portions 12 and 112 in the x-axis direction than the portions where the inclined walls 22 and 122 disappear, it is sufficient to complete the gradual change in the magnitude of R of each of the upper R-shaped portions R1 and R11 and make them constant R-shaped portions.

[0043] In addition, from the viewpoint of increasing the contribution of the inclined walls 22 and 122 to reducing the torsional rigidity, it is preferable that, typically in the intermediate side wall portions 12 and 112, the vertical length H2 of the inclined walls 22 and 122 is set longer than the vertical length H3 of the vertical walls 32 and 132.

[0044] In addition, during press molding, it is possible to pass a punch that presses the connecting wall 210 between the opposing ends of the folded walls 80 and 180, which have a relatively wide gap between them, and move toward the connecting wall 210 to press it, thereby giving the punch the required size, i.e., the required strength. From the viewpoint of improving the overall formability of the connecting wall 210 and therefore the lower arm 1 and improving its molding accuracy, typically, in the intermediate side wall portions 12 and 112, it is preferable that the distance W1 between the vertical walls 32 and 132 in the width direction of the lower arm 1 is set longer than the up-down length H1 of the intermediate side wall portions 12 and 122, so that the vertical cross section of the lower arm 1 in the intermediate side wall portions 12 and 112 is flattened, and it is preferable that the distance W3 between the opposing ends of the folded walls 80 and 180 in the width direction of the lower arm 1 is set longer than the width of the connecting wall 210 (W2: more specifically, the distance in the width direction between the upper R end lines L1 and L11). From the standpoint of increasing the strength and rigidity of the lower arm 1, it is also preferable that the bent walls 80 and 180 are inclined so as to rise toward the inside in the width direction of the lower arm 1.

[0045] In addition, the present invention is not limited to the above-described embodiment in terms of the type, shape, arrangement, number, etc. of the components, and it goes without saying that the components can be appropriately modified within the scope of the gist of the invention, such as by appropriately replacing them with components that achieve the same functional effects. [Industrial Applicability]

[0046] As described above, the present invention makes it possible to provide an arm member that ensures strength and rigidity in the longitudinal direction of the arm member while enabling the use of press molding, and that can appropriately reduce torsional rigidity around the longitudinal direction of the arm member with a high degree of design freedom. Because of its versatile and universal nature, it is expected that the arm member can be widely applied to the field of strength parts for vehicles, etc. [Explanation of symbols]

[0047] 1. Lower arm 10…First side wall 12...Intermediate side wall 22…Slanted wall 32...Vertical wall 42, 44...Transient side wall part 52, 54...Extended side wall 62, 72... Burring hole 64, 74...Flange 66, 76...Through holes 80…Bent wall 82...Intermediate folded wall section 84...Inclined bent wall 86...Inclined bent wall 110…Second side wall 112...Intermediate side wall 122…Slanted wall 132...Vertical wall part 142, 144...Transient side wall part 152, 154...Extended side wall portion 162, 172... Burring hole section 164, 174...Flanges 166, 176...Through holes 180…Bent wall 182...Intermediate folded wall section 184...Inclined bent wall 186...Inclined bent wall 210…Connecting wall 212...Intermediate connecting wall 214...Slanted connecting wall section 216…Slanted connecting wall section 222, 224...Convex shaped part R1, R11...Top R shape part R2, R12…lower R shape part L1, L3, L11, L13...Upper R stop lines L2, L4, L12, L14...Lower R end line

Claims

1. A longitudinally extending arm member, A first side wall; a second side wall opposed to the first side wall in a width direction perpendicular to the longitudinal direction; a connecting wall that connects the first side wall and the second side wall to each other on an upper side in a vertical direction perpendicular to the longitudinal direction and the width direction, In an intermediate portion including a center of the arm member in the longitudinal direction, a first inclined wall which is an upper component and a first vertical wall which is a lower component in the up-down direction are provided as components of the first side wall, and a second inclined wall which is an upper component and a second vertical wall which is a lower component are provided as components of the second side wall, and the connecting wall connects the first inclined wall and the second inclined wall at the upper side, An arm member in which, at both ends of the arm member in the longitudinal direction, the first inclined wall disappears from the component of the first side wall, and the second inclined wall disappears from the component of the second side wall, and the first vertical wall and the second vertical wall are connected by the connecting wall.

2. a first transition portion is provided in which the first inclined wall becomes smaller and disappears from the components of the first side wall as the R-shaped portion connecting the first inclined wall and the first vertical wall is displaced upward from the intermediate portion toward the both end portions, 2. The arm member according to claim 1, further comprising a second transition portion in which the second inclined wall becomes smaller and disappears from the components of the second side wall as the R-shaped portion connecting the second inclined wall and the second vertical wall shifts upward from the intermediate portion toward both ends.

3. In the intermediate portion, a length of the first inclined wall in the up-down direction is set to be longer than a length of the first vertical wall in the up-down direction, The arm member according to claim 1 or 2, wherein, in the intermediate portion, a length of the second inclined wall in the up-down direction is set to be longer than a length of the second vertical wall in the up-down direction.

4. In the intermediate portion, a distance between the first vertical wall and the second vertical wall in the width direction is set to be longer than a length of the arm member in the up-down direction, The lower end of the first vertical wall and the lower end of the second vertical wall have a first folded wall and a second folded wall facing each other, 3. The arm member according to claim 1, wherein in the intermediate portion, a distance between opposing ends of the first folded wall and the second folded wall in the width direction is set to be longer than a width of the connecting wall in the width direction.

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