Suspension element

Abstract

Suspension element (10) with: a rear cross member (16) formed in an open cross-sectional shape whose vehicle body bottom is open, the rear cross member (16) extending in a vehicle width direction and having a pair of secondary side rails (18) extending integrally from both vehicle width direction end portions of the rear cross member (16) in a vehicle body frontward direction, a front cross member (12) formed in a closed cross-sectional shape and extending in the vehicle width direction, a pair of right and left front body brackets (14) each formed in an open cross-sectional shape whose vehicle body bottom is open and connected to both vehicle width direction end portions of the front cross member (12), and a pair of right and left side rails (20, 30) each formed in a closed cross-sectional shape with a higher ductility than a ductility of the front body brackets (14) and the secondary side rails (18), extending in the extending direction of the secondary side rails (18), and covered by and connected to the front body brackets (14) from a vehicle body upper side in a state in which vehicle body rear-side portions of the side rails (20, 30) are covered by and connected to the secondary side rails (18) from their vehicle body upper side, and in which vehicle body front-side portions of the side rails (20, 30) overlap over front end portions of the front body brackets (14) as seen in a plan view, wherein the right and left side rails (20, 30) are continuous over their direction of extension from the vehicle body rear side regions to the vehicle body front side regions.

Description

BACKGROUNDTechnical field

[0001] The present exemplary embodiments relate to a suspension element for a vehicle. Related state of the art

[0002] Conventionally, suspension members have been known in which right and left rear coupler sections and a rear cross member are integrally formed by injection, die casting, or gravity casting, right and left front coupler sections are formed by injection, die casting, or gravity casting, and a front cross member and right and left longitudinal members are formed by extrusion (see, for example, Japanese Patent Application Laid-Open (JP 2005-289115 A).

[0003] However, when the front coupler portions of the suspension member are ultimately broken by an impact load input from the vehicle body front side, such as when the vehicle is involved in a frontal collision, it becomes difficult to transmit the impact load to the longitudinal members (side frames), so there is a concern that the amount of energy absorbed by the longitudinal members will be reduced.

[0004] According to WO 2014 / 063 687 A2, a modular system with rear and front cross elements and a pair of right and left body mounts is known from the prior art, with right and left side rails pointing rearward and being formed in several parts on both sides of the body mounts.

[0005] From US 2006 / 0 001 228 A1 a vehicle end structure is known which can be provided either at the front or rear end of the vehicle.

[0006] US 2007 / 0 138 840 A1, JP 2000- 177 621 A, DE 10 213 223 405 A1, US 6 010 155 A disclose bending sections on side rails.

[0007] Further embodiments according to the state of the art can be found in the documents DE 11 2014 006 012 T5, US 3 860 258 A, JP H08- 108 861 A and US 2003 / 0 075 951 A1. TASK

[0008] The present invention has an object to provide a suspension member that can efficiently absorb a load input from the vehicle body front side. SOLUTION TO THE TASK

[0009] This object is achieved by the subject matter of claim 1. Further developments according to the invention are the subject matter of the dependent claims.

[0010] To achieve this object, a suspension member according to a first aspect of the present invention includes: a rear cross member formed in an open cross-sectional shape whose vehicle body lower side is open, the rear cross member extending in a vehicle width direction and having a pair of secondary side rails integrally extending from both vehicle width direction end portions of the rear cross member in a vehicle body frontward direction; a front cross member formed in a closed cross-sectional shape and extending in the vehicle width direction; a pair of right and left front body brackets each formed in an open cross-sectional shape whose vehicle body lower side is open and connected to both vehicle width direction end portions of the front cross member.are joined together, and a pair of right and left side rails each formed in a closed cross-sectional shape having higher ductility than that of the front body brackets and the secondary side rails, extending in the extending direction of the secondary side rails and covered from their vehicle body upper side by and joined to the front body brackets in a state where their vehicle body rear side portions are covered from their vehicle body upper side by and joined to the secondary side rails and their vehicle body front side portions overlap front end portions of the front body brackets as viewed in a plan view.

[0011] According to the first aspect of the present invention, the vehicle body front portions of the side rails are covered from their vehicle body upper side by and joined to the front body brackets in a state of overlapping the front end portions of the front body brackets as viewed in a plan view.

[0012] Additionally, the side rails are each formed in a closed cross-sectional shape with higher ductility than the front body mounts and the secondary side rails. Consequently, when a load is applied to the suspension element from the front of the vehicle body, such as when the vehicle is involved in a frontal collision, the load is efficiently and effectively absorbed by the side rails.

[0013] Further, a suspension member according to a second aspect of the present invention is the suspension member according to the first aspect, wherein front end portions of the side rails are placed on the vehicle body front side of the front end portions of the front body brackets.

[0014] According to the second aspect of the present invention, the front end portions of the side rails are positioned on the vehicle body front side of the front end portions of the front body mounts. Consequently, when a load is input to the suspension member from the vehicle body front side, such as when the vehicle is involved in a frontal collision, the load is absorbed by the side rails before being absorbed by the front body mounts. Thus, the occurrence of damage such as fracture in the front body mounts is controlled or restricted.

[0015] Furthermore, a suspension member according to a third aspect of the present invention is the suspension member according to the first or second aspect, wherein the front body mounts have ribs joined to side walls of the side rails.

[0016] According to the third aspect of the present invention, the front body mounts have ribs connected to the side walls of the side rails. Consequently, the connection points between the side rails and the front body mounts are increased compared to a configuration where the front body mounts do not have ribs connected to the side walls of the side rails. Therefore, the connection strength between the side rails and the front body mounts is increased.

[0017] Furthermore, a suspension member according to a fourth aspect of the present invention is the suspension member according to any one of the first to third aspects, wherein the side rails have recessed bead portions along their circumferential direction on the vehicle body front side of the front body mounts, and the side rails have bent portions bent in the vehicle body downward direction on the vehicle body rear side of the front body mounts.

[0018] According to the fourth aspect of the present invention, the side rails have the recessed bead portions along their circumferential direction on the vehicle body front side of the front body mounts, and the side rails on the vehicle body rear side of the front body mounts have the bent portions bent in the vehicle body downward direction.

[0019] Consequently, when a load is input to the suspension member from the vehicle body front, such as when the vehicle is involved in a frontal collision, the load is absorbed as a result of the vehicle body front sides of the side rails being compressively deformed in their axial direction, and the load is absorbed as a result of the flexure portions being bent and deformed downward. That is, the load is absorbed more efficiently by the side rails.

[0020] According to the first aspect of the present invention, a load input from the vehicle body front side can be absorbed efficiently.

[0021] According to the second aspect of the present invention, the occurrence of damage such as breakage in the front body mounts due to load input from the vehicle body front side can be controlled or restrained.

[0022] According to the third aspect of the present invention, the connection strength between the side rails and the front body brackets can be increased.

[0023] According to the fourth aspect of the present invention, a load input from the vehicle body front side can be absorbed more efficiently. SHORT DESCRIPTION OF THE FIGURES

[0024] Exemplary embodiments of the present invention will be described in detail based on the following figures, wherein: Fig. 1 is a perspective view showing a suspension element relating to a first embodiment, Fig. Fig. 2 is an enlarged perspective view showing main portions of the suspension member relating to the first embodiment, Fig. 3 is an enlarged perspective view showing a bottom surface side of the main portions of the suspension member concerning the first embodiment, Fig. 4A and Fig. 4B are perspective views showing exemplary modifications of side rails of the suspension member relating to the first embodiment, and Fig. 5 is a perspective view showing a suspension member relating to a second embodiment. DETAILED DESCRIPTION

[0025] Embodiments relating to the present invention will be described in detail below based on the figures. Note that, for convenience of description, an arrow OB, conveniently shown in the figures, indicates a vehicle body upward direction, an arrow FR indicates a vehicle body forward direction, and an arrow RH indicates a vehicle body rightward direction. Furthermore, in the following description, when the directions of up and down, front and back, and right and left are given without further specification, they are understood to mean up and down in the vehicle body upward and down direction, front and back in the vehicle body forward and back direction, and right and left in the vehicle body rightward and leftward direction (vehicle width direction). < First embodiment >

[0026] First, a suspension element 10 relating to a first embodiment will be described. Fig. The suspension member 10 shown in FIG. 1 is supported on the underside of front portions of a pair of right and left front side members or side members (not shown in the figures) extending along the vehicle body front-and-rear direction, in a state where the suspension member 10 is suspended from these front side members. Here, each of the front side members has a deflection portion for positioning the vehicle body front portion side at a higher position than the vehicle body rear portion side.

[0027] Accordingly, a pair of right and left front body mounts 14 of the suspension member 10 (described later) are attached to the front end portions of the front side members on the vehicle body front side of the deflection portions, and a pair of right and left mounting portions 16A of a rear cross member 16 (described later) of the suspension member 10 are attached to the lower end portions of the deflection portions. A front shock absorber upper reinforcement (not shown in the figures) extending in the vehicle width direction bridges the front end portions of the pair of right and left front side members.

[0028] The suspension member 10 is provided with: a front cross member 12 extending on the vehicle body front side in the vehicle width direction, a pair of right and left front body brackets 14 connected to both vehicle width direction end portions of the front cross member 12, a rear cross member 16 extending on the vehicle body rear side in the vehicle width direction and having a pair of right and left secondary side rails 18 integrally connected to the vehicle body rear side.integrally extending from both vehicle-width-direction end portions of the rear cross member 16 in the vehicle-body frontward-and-outward direction, and a pair of right and left side rails 20 extending in the extending direction of the secondary side rails 18, wherein portions (parts of later-described projecting portions 24) of the side rails 20 on the vehicle-body front side of later-described bending portions 22 are joined to the front body brackets 14, and wherein portions (rear end portions) of the side rails 20 on the vehicle-body rear side of the bending portions 22 are joined to the secondary side rails 18.

[0029] As in Fig. 1 to Fig. 3, the front cross member 12 and the side rails 20 are each formed in a substantially constant rectangular closed cross-sectional shape by, for example, extruding a light metal such as an aluminum alloy. Consequently, as described later, the front cross member 12 and the side rails 20 have higher ductility compared to that of the front body mounts 14 and the rear cross member 16, which are formed by, for example, die-casting a light metal such as an aluminum alloy. Therefore, the side rails 20 are more easily plastically deformed than the front body mounts 14 and the secondary side rails 18 when an impact load is input from the extending direction of the secondary side rails 18 (the vehicle body front side).

[0030] The side rails 20 have, on the vehicle body rear side, bending portions 22 of rear end portions 14B of the front body brackets 14, which are bent in the vehicle body downward direction (bent downward), as viewed from a side view in the vehicle width direction. The side rails 20 further have, on the vehicle body front side, protruding portions 24 of front end portions 14A of the front body bracket 14, which extend in the extension direction of the secondary side rails 18.

[0031] That is, the front portion sides of the side rails 20 protrude a predetermined length—specifically, a length where the front portion sides of the side rails 20 can function as crash boxes (shock absorbers)—in the vehicle body frontward direction beyond the front end portions 14A of the front body mounts 14, and these protruding parts are the protruding portions 24. A front bumper lower reinforcement (not shown in the figures) extending in the vehicle width direction bridges the front end portions 24A of the protruding portions 24. Those areas covered by the front body mounts 14 on the vehicle body front side of the bending portions 22 are also parts of the protruding portions 24.

[0032] As in Fig. 4A, a plurality of recessed bead portions 26 may be formed along the circumferential direction of the protruding portions 24A adjacent to each other in the vehicle body front-and-rear direction in only the upper wall and the lower wall of the protruding portions 24, which protrude beyond the front end portions 14A of the front body brackets 14 in the vehicle body front-and-rear direction, so as to support compressive deformation of the protruding portions 24 in their axial direction. The recessed bead portions 26 may also be formed in only both side walls of the protruding portions 24, or, as shown in Fig. 4B, along the entire circumferential direction (the top wall, the bottom wall and both side walls) of the protruding portions 24.

[0033] As in Fig. 1 to Fig. 3, the front body brackets 14 are each formed into an open cross-sectional shape with the vehicle body bottom open, for example, by die-casting a light metal such as an aluminum alloy, and the front body brackets 14 are held at the front end portions of the front side members. The rear cross member 16 is each formed into an open cross-sectional shape with the vehicle body bottom open, for example, by die-casting a light metal such as an aluminum alloy, and the secondary side rails 18 are each also each formed into an open cross-sectional shape (a substantially inverted U-shape in cross-section) with the vehicle body bottom open.

[0034] Consequently, the substantially upper halves (top surfaces) of the rear end portions of the side rails 20 on the vehicle body rear side of the bent portions 22 are covered by the secondary side rails 18, and the lower end portions 18A and the front end portions 18B of the secondary side rails 18 are joined linearly to the side walls and top walls of the side rails 20 by arc welding. Therefore, the substantially lower halves (bottom surfaces) of the rear end portions of the side rails 20 on the vehicle body rear side of the bent portions 22 are not covered by the secondary side rails 18 but are left exposed to the outside.

[0035] The substantially upper halves (top surfaces) of parts of the projecting portions 24 of the side rails 20 on the vehicle body front side of the bending portions 22 are covered by the front body brackets 14, and the lower end portions (lower end portions 46A and 48A of ribs 46 and 48 described later), the front end portions 14A and the rear end portions 14B of the front body brackets 14 are joined or joined by arc welding in a linear manner to the side walls and the top walls of the side rails 20. Therefore, the substantially lower halves (bottom surfaces) of parts of the projecting portions 24 of the side rails 20 on the vehicle body front side of the bending portions 22 are not covered by the front body brackets 14, but are left exposed to the outside (see Fig. 3).

[0036] The substantially upper halves of both vehicle width direction end portions of the front cross member 12 are covered by the front body brackets 14, and the lower end portions (the lower end portions of the front walls 44A described later and the lower end portions of the connecting walls 45 described later) and the vehicle width direction inner end portions of the front body brackets 14 are joined or joined to the side walls and the top wall of the front cross member 12 in a linear manner by arc welding. Therefore, the substantially lower halves (bottom sides) of both vehicle width direction end portions of the front cross member 12 are not covered by the front body brackets 14, but are left exposed to the outside (see Fig. 3).

[0037] Here, the structure by which the side rails 20 and the front cross member 12 are connected to the front body mounts 14 will be described in more detail.

[0038] As in Fig. 2 and Fig. 3, the front body mounts 14 each include a substantially flat, plate-shaped top wall 42 and a peripheral wall 44 extending upright in the vehicle body downstream direction from the peripheral edge portion of the top wall 42. The peripheral wall 44 is configured to include a front wall 44A facing the vehicle body downstream direction, an outer wall 44B facing outward in the vehicle width direction, and an inner wall 44C facing inward in the vehicle width direction. The front end portion of the top wall 42 and the front end portions of ribs 46 and 48 described later at a rectangular recessed portion formed in the front wall 44A function as the front end portion 14A of the front body mount 14.

[0039] The front end portions 24A of the protruding portions 24 of the side rails 20 are positioned on the vehicle body front side of the front end portions 14A of the front body brackets 14. That is, the areas (parts of the protruding portions 24) of the side rails 20 on the vehicle body front side of the bent portions 22 overlap the front end portions 14A of the front body brackets 14, as viewed in a plan view, and in this state, the parts of the protruding portions 24 of the side rails 20 are covered from their vehicle body top side by and joined to the front body brackets 14.

[0040] More specifically, a pair of vertical wall-like ribs 46 and 48 extending along the extending direction of the side rails 20 (the substantially vehicle body front-and-rear direction) are integrally arranged upright and opposite to each other in the vehicle width direction on the lower surface of the upper wall 42 of each of the front body brackets 14, and the distance between the ribs 46 and 48 is the same as the vehicle width direction length of each of the side rails 20. Thus, the side rails 20 are inserted and placed between the ribs 46 and 48, and lower end portions 46A and 48A of the ribs 46 and 48 are joined to the side walls of the side rails 20 in a linear manner by arc welding.

[0041] The height of the ribs 46 and 48 is the same as the height of the peripheral wall 44, and the front end portion and the rear end portion of the rib 46 formed on the vehicle width direction outer side are integrally connected to the front wall 44A and the outer wall 44B, respectively. A round tubular boss portion 40 for inserting a bolt (not shown in the figures) for fastening to the front side member is integrally formed between the rib 46 and the outer wall 44B on the top wall 42. A part of the outer peripheral surface of the boss portion 40 is integrally connected to the wall surface of the rib 46 facing outward in the vehicle width direction (see Fig. 3).

[0042] The front end portion and the rear end portion of the rib 48 formed on the vehicle width direction inner side are equally integrally connected to the front wall 44A and the inner wall 44C, respectively, and the front end portion of the inner wall 44C and the rib 48 are integrally connected to each other by means of a connecting wall 45 arranged upright on the lower surface of the upper wall 42 and parallel to the front wall 44A. An insertion portion 50 (see Fig. 3) for inserting the vehicle width direction outer side end portion of the front cross member 12 is formed by the front wall 44A, the connecting wall 45 and the upper wall 42.

[0043] Thus, the lower end portions of the front wall 44A and the connecting wall 45 are linearly joined to the side walls of the vehicle width direction outer side end portion of the front cross member 12 inserted into the insertion portion 50 by arc welding. The end surface of the vehicle width direction outer side end portion of the front cross member 12 is in abutting contact with the wall surface of the rib 48 facing inward in the vehicle width direction and is linearly joined to this wall surface by arc welding in a substantially U-shape.

[0044] As in Fig. 1 and Fig. 2, the secondary side rails 18 are each formed in a substantially hat-shaped cross-section, the plate thickness of which is thicker than that of the side rails 20. That is, ribs 28 projecting outward in the vehicle width direction and inward in the vehicle width direction are integrally formed at lower end portions 18A of the secondary side rails 18. Therefore, the strength and rigidity of the secondary side rails 18 are further increased.

[0045] As in Fig. 1, there are cases where the upper portions of the side walls on the vehicle width direction inner sides of the side rails 20 are configured as slant walls 20A that are inclined upward and outward in the vehicle width direction (downward and inward in the vehicle width direction) as viewed in a front cross-sectional view from the vehicle body front-and-rear direction in order to avoid interference (contact) with a power plant, etc. described later. In this case, the lower end portions 18A of the side walls on the vehicle width direction inner sides of the secondary side rails 18 extend beyond the slant walls in the vehicle body lower direction.

[0046] A power unit (not shown in the figures) including an engine and a transmission is arranged on the vehicle body front side of the suspension member 10. For this reason, an engine mount (not shown in the figures) for supporting the power unit from below is arranged at the substantially vehicle width direction center portion of the front cross member 12 of the suspension member 10.

[0047] As in Fig. As shown in Figure 1, attachment portions 16A for attachment to the lower end portions of the deflection portions of the front side members are formed in both vehicle width direction end portions of the rear cross member 16. Lower arm attachment portions 16B for attaching lower arms (not shown in the figures) constituting suspensions (not shown in the figures) are also formed in both vehicle width direction end portions of the rear cross member 16.

[0048] Next, the operation of the suspension member 10 having the above configuration will be described.

[0049] As described above, the front bumper lower reinforcement, which extends in the vehicle width direction, bridges the front end portions 24A of the protruding portions 24 of the side rails 20, which are located on the vehicle body front side of the front end portions 14A of the front body brackets 14 (overlapping the front end portions 14A of the front body brackets 14 as viewed in a plan view). Consequently, when the vehicle is involved in a frontal collision, the impact load is input from the front bumper lower reinforcement (the vehicle body front side) in the axial direction of the protruding portions 24 to the side rails.

[0050] Here, the protruding portions 24 of the side rails 20, which protrude beyond the front end portions 14A of the front body brackets 14 in the vehicle body frontward direction, are configured to function as crash boxes (the recessed bead portions 26 along the circumferential direction of the protruding portions 24 are formed in the protruding portions 24). Consequently, when an impact load is input to the protruding portions 24 of the side rails 20 in their axial direction, the protruding portions 24 of the side rails 20 are compressively deformed in their axial direction and absorb some of the input impact load.

[0051] That is, when the vehicle is involved in a frontal collision, some of the impact load can be absorbed by the protruding portions 24 of the side rails 20 before being absorbed by the front body mounts 14. Consequently, the occurrence of damage such as breakage in the front body mounts 14 can be controlled. Some of the remaining impact load that was not completely absorbed by the compressive deformation of the protruding portions 24 in their axial direction is transmitted to the side rails 20 located on the vehicle body rear side of the front end portions 14A of the front body mounts 14.

[0052] The engine mount, which supports the power unit from below, is disposed at the substantially vehicle-width-direction center portion of the front cross member 12. Consequently, when the vehicle is involved in a frontal collision, some of the impact load is also input to the front cross member 12 of the suspension member 10 via the engine mount.

[0053] Here, the rear cross member 18 including the secondary side rails 18 is manufactured by die-casting a light metal such as an aluminum alloy, and the secondary side rails 18 are each formed into a substantially hat-shaped cross-section whose plate thickness is thicker than that of the side rails 20. That is, the ribs 28 projecting outward in the vehicle width direction and inward in the vehicle width direction are integrally formed at the lower end portions 18A of the secondary side rails 18, and the strength and rigidity of the secondary side rails 18 are increased.

[0054] Furthermore, the substantially lower halves of the rear end portions of the side rails 20 on the vehicle body rear side of the bent portions 22 are not covered by the secondary side rails 18, but are left exposed to the outside. Therefore, there is no concern that the bending deformation of the bent portions 22 of the side rails 20 (the absorption of energy by plastic deformation of the undersurface sides undergoing tensile deformation) will be hindered by the secondary side rails 18.

[0055] In addition, the side rails 20 are made by extruding a light metal such as an aluminum alloy and have higher ductility compared to that of the secondary side rails 18 of the rear cross member 16 formed by injection, compression, or die casting. For this reason, the side rails 20 are more easily plastically deformed than the secondary side rails 18 when an impact load is input from the extending direction of the secondary side rails 18 (the vehicle body front side).

[0056] Consequently, when some of the impact load is transmitted via the projecting portions 24 and the front cross member 12 to the side rails 20 on the vehicle body rear side of the front end portions 14A of the front body mounts 14, deformation of the front end portions 18B of the secondary side rails 18 in the vehicle body up-and-back direction is controlled, and the sides of the projecting portion 24 of the side rails 20 are bent and deformed such that the bending portions 22 deflect in the vehicle body up-and-back direction (the bending portions 22 are bent and deformed downward), and absorb some of the transmitted impact load.

[0057] That is, the side rails 20 in the present embodiment can be plastically deformed continuously from the protruding portions 24 to the bent portions 22, regardless of whether damage such as fracture occurs in the front body mounts 14, and can stably and efficiently absorb some of the impact load. Thus, when the vehicle is involved in a frontal collision, the energy absorption characteristics of the suspension member 10 can be improved.

[0058] The substantially lower halves of the areas (parts of the protruding portions 24) of the side rails 20 on the vehicle body front side of the bending portions 22 are also not covered by the front body mounts 14, but are left exposed to the outside. For this reason, there is also no concern that the bending deformation of the bending portions 22 of the side rails 20 (the absorption of energy due to the plastic deformation of the undersurface sides undergoing tensile deformation) will be hindered by the front body mounts 14.

[0059] Consequently, when some of the impact load is transmitted to the side rails 20 on the vehicle body rear side of the front end portions 14A of the front body brackets 14, the bending deformation of the bending portions 22 of the side rails (the plastic deformation on the under surface side) can be assisted and some of the impact load can be absorbed more efficiently by the side rails 20.

[0060] The ribs 46 and 48 extending in the extending direction of the side rails 20 (the substantially vehicle body front-and-rear direction) are arranged upright on the bottom surfaces of the upper walls 42 of the front body mounts 14, and the rigidity (bending rigidity) of the front body mounts 14 with respect to bending deformation in the vehicle body up-and-rear direction is increased. Consequently, deformation of the upper walls 42 of the front body mounts 14 in the vehicle body up-and-rear direction accompanied by the deformation of the sides of the projecting portion 24 of the side rails 20 in the vehicle body up-and-rear direction can be controlled or restrained. That is, the occurrence of damage such as breakage in the front body mounts 14 can be effectively restrained.

[0061] Furthermore, the lower end portions 46A and 48A of the ribs 46 and 48 are linearly connected to the side walls of the side rails 20, so that the connection points between the side rails 20 and the front body brackets 14 can be increased. That is, according to this configuration, the connection strength between the side rails 20 and the front body brackets 14 can be increased.

[0062] Further, in the suspension member 10 concerning the present embodiment, the protruding portions 24 where the side rails 20 are extended in the vehicle body frontward direction function as crash boxes, so that the number of parts can be reduced compared with a configuration where, for example, crash boxes (not shown in the figures) are attached to the front end portions of the front body brackets 14 and the front shock absorber lower reinforcement bridges the front end portions of the crash boxes.

[0063] Furthermore, the front body mounts 14 and the rear cross member 16 are each manufactured by die-casting a light metal such as an aluminum alloy, so that seats and bosses for attaching other parts can be easily formed therein. That is, the front body mounts 14 and the rear cross member 16 have high rigidity and a high degree of freedom in their shape, allowing the number of parts to be reduced. Consequently, the weight of the suspension member 10 can be reduced.

[0064] Furthermore, the front cross member 12 itself and the side rails 20 themselves are made by extruding a light metal such as an aluminum alloy, so that they have a high degree of freedom in their shape, like the front body mounts 14 and the rear cross member 16. Consequently, they can be adapted to a variety of vehicle types and designs by appropriately tuning their shapes, sharing peripheral parts.

[0065] Furthermore, the side rails 20 and the secondary side rails 18 are joined together in a linear manner by arc welding, so they can be strongly connected to each other and the ingress of foreign matter between them can be limited or prevented. Consequently, the occurrence of galvanic corrosion between them can also be limited or prevented. The same applies to the linear connection resulting from the arc welding of the side rails 20 and the front body mounts 14.

[0066] Furthermore, the lower arms are attached directly to the rear cross member 16, so that the supporting rigidity of the suspension member 10 with respect to the lower arms can be increased. Consequently, noise caused by vibration input from the front wheels (not shown in the figures) and the powertrain can be controlled or limited.

[0067] Furthermore, the front body mounts 14 and the rear cross member 16 are each formed in an open cross-sectional shape whose vehicle body bottom is open, making it easy to attach them to the front cross member 12 and the side rails 20. Consequently, the assembly process of the suspension member 10 can be simplified. < Second embodiment >

[0068] Next, a suspension member 10 relating to a second embodiment will be described. Parts that are the same as those of the suspension member 10 relating to the first embodiment will be assigned the same reference numerals, and a detailed description of those same parts (including a common function) will be conveniently omitted.

[0069] As in Fig. 5, the suspension element 10 relating to the second embodiment differs from the suspension element 10 relating to the first embodiment only in that it has side rails 30 which are each formed by a cross-sectionally substantially hat-shaped upper panel 36 and a cross-sectionally substantially hat-shaped lower panel 38.

[0070] That is, the side rails 30 are each formed in a rectangular closed cross-sectional shape as a result of joining flange portions 36A of the upper panel 36 and flange portions 38A of the lower panel 38, for example, by spot welding. The side rails 30, like the side rails 20 in the first embodiment, each have a bending portion 32 that is bent downward and a protruding portion 34 to which the front body mounts 14 are joined and which protrudes beyond the front end portions 14A of the front body mounts 14 in the vehicle body frontward direction.

[0071] Consequently, when an impact load is input from the vehicle body front side to the front end portions 34A of the protruding portions 34 of the side rails 30, such as when the vehicle is involved in a frontal collision, the protruding portions 34 are compressively deformed in their axial direction and can absorb some of the impact load. Furthermore, the side rails 30 are bent and deformed (plastically deformed) by the bending portions 32 such that the sides of the protruding portion 34 deflect in the vehicle body up-and-back direction, so that some of the remaining impact load can be absorbed. In this way, even in the suspension member 10 concerning the second embodiment, some of the impact load can be efficiently absorbed by the side rails 30.

[0072] The suspension member 10 relating to the embodiments has been described above based on the figures, but the suspension member 10 relating to the embodiments is not limited to what is shown in the figures, and its design can be appropriately changed without departing from the spirit of the present invention. For example, the secondary side rails 18 are not limited to being formed in a substantially hat-shaped cross-section (with the ribs 28 formed thereon).

[0073] Furthermore, the bottom walls of the vehicle width direction outer end portions of the front cross member 12, which is in Fig.3, the front cross member 12 is inclined obliquely upward and outward in the vehicle width direction (downward and inward in the vehicle width direction) as viewed in a front view from the vehicle body front-and-rear direction, but the front cross member 12 is not limited to this and may also be configured to have a constant cross-sectional shape up to its vehicle width direction outer side end portions.

[0074] Furthermore, the recessed bead portions 26 need not be formed in the protruding portions 24 of the side rails 20, provided that the protruding portions 24 are configured to be efficiently compressively deformable in their axial direction. Furthermore, the welding that linearly connects the secondary side rails 18 and the front body mounts 14 to the side rails 20 is not limited to arc welding and may also be, for example, laser welding.

[0075] Furthermore, it is sufficient for the present invention to have a configuration in which the protruding portions 24 of the side rails 20 overlap the front end portions 14A of the front body mounts 14 as viewed in a plan view. Therefore, the present invention also encompasses a configuration in which the front end portions 24A of the protruding portions 24 of the side rails 20 are flush with (occupying the same position in the vehicle body front-and-rear direction as) the front end portions 14A of the front body mounts 14.

[0076] Furthermore, the suspension member 10 is not limited to being made of an aluminum alloy, and may also be made of, for example, a magnesium alloy. Furthermore, the front body mounts 14 and the rear cross member 16 may be made of an aluminum alloy, and the front cross member 12 and the side rails 20 may be made of steel. In this case, it is sufficient for the front cross member 12 and the side rails 20 to be connected to the front body mounts 14 and the rear cross member 16, for example, by riveting.

[0077] A suspension member thus comprises: a rear cross member having a pair of secondary side rails, a front cross member, a pair of right and left front body brackets and a pair of right and left side rails, each formed in a closed cross-sectional shape having a ductility higher than a ductility of the front body brackets and the secondary side rails, extending in the extending direction of the secondary side rails and covered from the vehicle body upper side by and connected to the front body brackets in a state in which vehicle body rear side portions of the side rails are covered from their vehicle body upper side by and connected to the secondary side rails and vehicle body front side portions of the side rails overlap front end portions of the front body brackets as viewed in a plan view.

Claims

[1] Suspension element (10) with: a rear cross member (16) formed in an open cross-sectional shape whose vehicle body bottom is open, the rear cross member (16) extending in a vehicle width direction and having a pair of secondary side rails (18) extending integrally from both vehicle width direction end portions of the rear cross member (16) in a vehicle body frontward direction, a front cross member (12) formed in a closed cross-sectional shape and extending in the vehicle width direction, a pair of right and left front body brackets (14) each formed in an open cross-sectional shape whose vehicle body bottom is open and connected to both vehicle width direction end portions of the front cross member (12), and a pair of right and left side rails (20, 30) each formed in a closed cross-sectional shape with a higher ductility than a ductility of the front body brackets (14) and the secondary side rails (18), extending in the extending direction of the secondary side rails (18), and covered by and connected to the front body brackets (14) from a vehicle body upper side in a state in which vehicle body rear-side portions of the side rails (20, 30) are covered by and connected to the secondary side rails (18) from their vehicle body upper side, and in which vehicle body front-side portions of the side rails (20, 30) overlap over front end portions of the front body brackets (14) as seen in a plan view, wherein the right and left side rails (20, 30) are continuous over their direction of extension from the vehicle body rear side regions to the vehicle body front side regions. [2] A suspension member according to claim 1, wherein front end portions of the side rails (20) are placed on the vehicle body front side of the front end portions of the front body brackets (14). [3] A suspension element according to claim 1 or claim 2, wherein the front body mounts (14) have ribs connected to side walls of the side rails (20). [4] Suspension element according to one of claim 1 to claim 3, wherein: the side rails (20) have recessed bead sections (26) along their circumferential direction on the vehicle body front side of the front body mounts (14), and the side rails on the vehicle body rear side of the front body brackets have bending portions (22) which are bent in the vehicle body downward direction. [5] Suspension element according to claim 1, wherein: the side rails (20) on the vehicle body rear side of the rear end portions of the front body brackets (14) have bending portions (22) which are bent in the vehicle body downward direction as seen in a side view viewed from the vehicle width direction, and the side rails (20) on the vehicle body front side of the front end portions of the front body brackets have projecting portions (24) which extend in the extension direction of the secondary side rails (18). [6] Suspension element according to claim 1, wherein the side rails (30) each have a cross-sectionally substantially hat-shaped upper panel (36) and a cross-sectionally substantially hat-shaped lower panel (38). [7] Suspension element according to claim 6, wherein: the side rails (30) on the vehicle body rear side of the rear end portions of the front body brackets have bending portions (32) which are bent in the vehicle body downward direction as seen in a side view viewed from the vehicle width direction, and the side rails (30) on the vehicle body front side of the front end portions of the front body brackets have projecting portions (34) which extend in the extension direction of the secondary side rails (18).

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