Vehicular frame

The present invention relates to a vehicular frame disposed in a front portion of a vehicle and extending in a front-rear direction.

Conventional vehicles such as one disclosed in Patent Literature 1 has adopted a structure for protecting an occupant in a front impact of the vehicle, the structure including an axially compressively deformable crash can disposed at a front end of a front side frame made of a high tensile strength steel, and allowing the front side frame to actively deform to bend from an intermediate portion to a rear end thereof.

In such a structure, most of an impact load is absorbed by the bending deformation of the front side frame. Therefore, the energy absorption characteristic of the bending deformation has a greater influence on EA (Energy Absorption) efficiency, i.e. the energy absorption amount per unit mass, than the energy absorption characteristic of the compressive deformation.

Here, it is necessary to further improve the EA efficiency in order to expand design options of a vehicle body and reduce the weight of the vehicle body.

Patent Literature

Patent Literature 1: Japanese Patent Publication No. 5104272

The present invention has an object of providing a vehicular frame capable of improving EA efficiency.

In order to achieve the above-mentioned object, the present invention comprises: a main frame disposed in a front portion of a vehicle and extending in a front-rear direction; and a reinforcing member disposed inside the main frame and extending in the front-rear direction, the reinforcing member defining a plurality of closed cross sections in the main frame by dividing an internal space of the main frame in a vertical direction, wherein: the main frame has a main closed cross section having a substantially rectangular shape and includes, in sectional view, a compression-side wall portion extending in the vertical direction and configured to receive a compressive load in an impact of the vehicle, a tension-side wall portion extending in the vertical direction and facing the compression-side wall portion in a width direction of the vehicle, and configured to receive a tensile load in the impact of the vehicle, a top wall portion linking an upper end of the compression-side wall portion and an upper end of the tension-side wall portion, and a bottom wall portion linking a lower end of the compression-side wall portion and a lower end of the tension-side wall portion; the reinforcing member includes a first compression-side connection portion connected to the compression-side wall portion, a second compression-side connection portion disposed below the first compression-side connection portion and connected to the compression-side wall portion, a first tension-side connection portion disposed below the first compression-side connection portion and above the second compression-side connection portion and connected to the tension-side wall portion, a second tension-side connection portion disposed below the second compression-side connection portion and connected to the tension-side wall portion, a first partition wall portion linking a lower end of the first compression-side connection portion and an upper end of the first tension-side connection portion, a second partition wall portion linking a lower end of the first tension-side connection portion and an upper end of the second compression-side connection portion, and a third partition wall portion linking a lower end of the second compression-side connection portion and an upper end of the second tension-side connection portion; each of the first to third partition wall portions is bended at a plurality of positions between the compression-side wall portion and the tension-side wall portion, and has a compression-side ridge extending in the front-rear direction and a tension-side ridge disposed between the compression-side ridge and the tension-side wall portion and extending in the front-rear direction, the respective compression-side ridges of the first to third partition wall portions facing each other in the vertical direction and the respective tension-side ridges of the first to third partition wall portions facing each other in the vertical direction; and the compression-side ridges and the tension-side ridges are disposed at positions that allow, in a deformation of the partition wall portions, the compression-side ridge of the second partition wall portion to come into contact with the compression-side ridge of the third partition wall portion or the tension-side ridge of the first partition wall portion to come into contact with the tension-side ridge of the second partition wall portion.

In this vehicular frame, each of the partition wall portions has a compression-side ridge and a tension-side ridge. Owing to these ridges, the partition wall portions is strengthened, which makes it possible to suppress a deformation of the partition wall portions and increase the allowable critical load of the vehicular frame.

Further, because a truss structure is formed in the main frame after a buckling of the compression-side wall portion, it is possible to prevent collapse of the cross section of the main frame and a load drop after the buckling. Consequently, the EA efficiency can be improved.

FIG. 1 is a side view of a front side frame according to a first embodiment, as seen from the inside of an engine room.

FIG. 2 is a plan view of a right front side frame.

FIG. 3 is a sectional view taken along the line of FIG. 2 .

FIG. 4 is an exploded perspective view of the right front side frame.

FIG. 5 is a perspective view showing an essential part of a reinforcing member.

FIG. 6 is a schematic view showing a state of the front side frame before receipt of a front impact load.

FIG. 7 is a schematic view showing a state of the front side frame after the receipt of the front impact load.

FIG. 8 is a front view of a modified reinforcing member.

FIG. 9 is a perspective view of an essential part of the modified reinforcing member.

FIG. 10 show perspective views of frame models for analysis, FIG. 10A showing a frame model M 1 according to a prior art, FIG. 10B showing a frame model M 2 according to a prior art, FIG. 10C showing a frame model M 3 according to the modification, and FIG. 10D showing a frame model M 4 according to the first embodiment.

FIG. 11 is a graph showing respective F-S characteristics of the frame models.

FIG. 12 is a front view of the frame model M 3 in a buckled state.

FIG. 13 is a front view of the frame model M 4 in a buckled state.

FIG. 14 is a diagram for explaining an analysis method of a deformation of a frame having a closed cross-section.

FIG. 15 illustrate deformations of the frame having the closed cross-section, FIG. 15A showing a state of the frame before receipt of a load and FIG. 15B showing a state of the frame after the receipt of the load.

FIG. 16 is a diagram for explaining an elastic buckling of a frame having a closed cross-section.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

The following description illustrates an example of application of the present invention to a front side frame of a vehicle, and is not intended to limit the scope, application, and usage of the present invention.

It should be noted that in the drawings, “F” denotes the front side (the front side of a vehicle in a front-rear direction), “L” denotes the left side (the left side as seen from a driver's seat), and “U” denotes the top side. In addition, hereinafter, the width direction of the vehicle will be also referred to as “left-right direction”.

First Embodiment

Hereinafter, a first embodiment of the present invention will be described with reference to FIGS. 1 to 7 .

First, a vehicle body structure of a front portion of a vehicle in which front side frames are installed will be described briefly.

As shown in FIG. 1 , a vehicle V includes: a dash panel 1 extending in a vertical direction and in a vehicle width direction and partitioning an engine room E from a vehicle compartment; front side frames 2 disposed in front of the dash panel 1 and extending in a front-rear direction of the vehicle; suspension towers 3 each disposed laterally adjacent to the front side frame 2 and standing in the form of a tower; an apron 4 extending in the vertical direction and in the vehicle front-rear direction, and connecting the suspension towers 3 and the dash panel 1 ; an apron reinforcing member 5 disposed on an upper end of the apron 4 and extending in the vehicle front-rear direction; and other components. Because a portion around the front side frames 2 has a horizontally symmetrical structure, a right front side frame 2 will be mainly described, and description of a left front side frame 2 will be omitted.

A crash can 6 is disposed on a front end of the front side frame 2 , the crash can 6 being configured to compressively deform (axially compress) to absorb part of an impact energy upon receipt of a front impact load.

An engine mount 7 substantially in the form of a cylinder is disposed in a central portion of the front side frame 2 in the front-rear direction. The engine mount 7 elastically supports a power unit (not shown). In addition, a mount attachment reinforcing member 8 is disposed in a portion inside the front side frame 2 that lies below the engine mount 7 , the mount attachment reinforcing member 8 being provided for increasing the attachment rigidity of the engine mount 7 . A sub-frame attaching bracket 9 is securely connected to a lower surface of a rear portion of the front side frame 2 , the sub-frame attaching bracket 9 being provided for attaching a suspension sub-frame (not shown).

Now, the front side frame 2 will be described in detail.

The front side frame 2 is made of an aluminum alloy material (5000 series).

As shown in FIGS. 2 to 4 , the front side frame 2 comprises a main frame 201 including an outer member 10 having substantially the shape of a hat in cross section and an inner member 20 separate from the outer member 10 and having substantially the shape of a panel, and a plurality of reinforcing members 30 , 40 , 50 disposed inside the main frame 201 .

The main frame 201 extends in the front-rear direction. A cross section of the main frame 201 that perpendicularly intersects the front-rear direction is a closed cross section having a substantially rectangular shape. Hereinafter, this closed cross section of the main frame 201 will be referred to as “main closed-cross section C_m”.

The main closed-cross section C_m has a substantially rectangular shape having a longer dimension in the vertical direction (having a vertical dimension greater than a horizontal dimension).

The front side frame 2 includes the following zones defined by function in the front-rear direction: a front end zone 2 a ; an outward bending zone 2 b joining the rear of the front end zone 2 a and having the reinforcing member 30 ; a mount zone 2 c joining the rear of the outward bending zone 2 b and having the mount attachment reinforcing member 8 ; an inward bending zone 2 d joining the rear of the mount zone 2 c and having the reinforcing member 40 , and an outward bending zone 2 e joining the inward bending zone and having the reinforcing member 50 .

As described, the reinforcing members 30 , 40 , 50 are respectively disposed in the outward bending zones 2 b , 2 e , and the inward bending zone 2 d . Therefore, the vehicular frame according to the present invention is applied to each of the outward bending zones 2 b , 2 e , and the inward bending zone 2 d that respectively include the reinforcing members 30 , 40 , 50 .

The front end zone 2 a , when a front impact occurs, axially compressively deforms to absorb part of an impact load not absorbed by the crash can 6 .

In the front impact, the outward bending zone 2 b deforms to bend in a vehicle width outward direction with a first bead part 12 f shifting in a vehicle width inward direction, the first bead part 12 f being formed in an intermediate part of the outward bending zone 2 b and extending in the vertical direction.

The mount attachment reinforcing member 8 is disposed at an inner side of the mount zone 2 c.

In the front impact, the inward bending zone 2 d deforms to bend in the vehicle with inward direction with a second bead part 24 f shifting in the vehicle width outward direction, the second bead part 24 f formed in an intermediate part of the inward bending zone 2 d and extending in the vertical direction. A rear end of the inward bending zone 2 d supports the sub-frame attaching bracket 9 .

Further, in the front impact, the outward bending zone 2 e deforms to bend outwardly with a third bead part 15 f shifting in the vehicle width inward direction, the third bead part 15 f being formed in an intermediate part of the outward bending zone 2 e and extending in the vertical direction. A rear end of the outward bending zone 2 e is adhered to the dash panel 1 .

The outer member 10 will be described.

The outer member 10 includes a first outer section 11 constituting the right side of the front end zone 2 a , a second outer section 12 constituting the right side of the outward bending zone 2 b , a third outer section 13 constituting the right side of the mount zone 2 c , a fourth outer section 14 constituting the right side of the inward bending zone 2 d , and a fifth outer section 15 constituting the right side of the outward bending zone 2 e , the first to fifth outer sections 12 to 15 being formed in one body.

<First Outer Section>

The first outer section 11 includes a right wall portion 11 a extending along a plane substantially perpendicularly intersecting the left-right direction (extending in the vertical and front-rear directions), an upper end wall portion 11 b extending leftward from an upper end of the right wall portion 11 a , and a lower end wall portion 11 c extending leftward from a lower end of the right wall portion 11 a , the wall portions 11 a to 11 c being formed in one body.

The upper end wall portion 11 b and the lower end wall portion 11 c include an upper flange part 11 d and a lower flange part 11 e , respectively. The upper flange part 11 d extends upwardly at a left end of the upper end wall portion 11 b . The lower flange portion 11 e extends downwardly at a left end of the lower end wall portion 11 c.

<Second Outer Section>

Now, the second outer section 12 will be described.

The second outer section 12 includes a compression-side wall portion 12 a extending along a plane substantially perpendicularly intersecting the left-right direction (extending in the vertical and front-rear directions), an upper end wall portion (top wall portion) 12 b extending leftward from an upper end of the compression-side wall portion 12 a , and a lower end wall portion (bottom wall portion) 12 c extending leftward from a lower end of the compression-side wall portion 12 a , the wall portions 12 a to 12 c being formed in one body.

The compression-side wall portion 12 a includes the first bead part 12 f projecting into the inside of the main closed-cross section C_m. The first bead part 12 f extends in a direction substantially perpendicularly intersecting the front-rear direction over the entirety of the compression-side wall portion 12 a in the vertical direction.

The upper end wall portion 12 b includes an upper flange part 12 d extending upward at a left end thereof and the lower end wall portion 12 c includes a lower flange part 12 e extending downward at a left end thereof.

<Third Outer Section>

The third outer section 13 has substantially the same configuration as the first outer section 11 , and includes a right wall portion 13 a , an upper end wall portion 13 b , a lower end wall portion 13 c , an upper flange part 13 d , and a lower flange part 13 e.

<Fourth Outer Section>

The fourth outer section 14 has substantially the same configuration as the first outer section 11 , and includes a tension-side wall portion 14 a , an upper end wall portion (top wall portion) 14 b , a lower end wall portion (bottom wall portion) 14 c , an upper flange part 14 d , and a lower flange part 14 e.

<Fifth Outer Section>

The fifth outer section 15 has substantially the same configuration as the second outer section 12 , and includes a compression-side wall portion 15 a , an upper end wall portion (top wall portion) 15 b , a lower end wall portion (bottom wall portion) 15 c , an upper flange part 15 d , a lower flange part 15 e , and the third bead part 15 f similarly to the second outer section 12 .

Now, the inner member 20 will be described.

As shown in FIGS. 2 to 4 , the inner member 20 includes a first inner section 21 constituting the left side of the front end zone 2 a , a second inner section 22 constituting the left side of the outward bending zone 2 b , a third inner section 23 constituting the left side of the mount zone 2 c , a fourth inner section 24 constituting the left side of the inward bending zone 2 d , and a fifth inner section 25 constituting the left side of the outward bending zone 2 e , the first to fifth inner sections 21 to 25 being formed in one body.

<First Inner Section>

The first inner section 21 includes a left wall portion 21 a extending along a plane substantially perpendicularly intersecting the left-right direction (extending in the vertical and front-rear directions), an upper flange portion 21 d extending upward from an upper end of the left wall portion 21 a , and a lower flange portion 21 e extending downward from a lower end of the left wall portion 21 a , the portions 21 a to 21 e being formed in one body.

<Second Inner Section>

The second inner section 22 has substantially the same configuration as the first inner section 21 . The second inner section 22 includes a tension-side wall portion 22 a extending in the vertical and front-rear directions and facing the compression-side wall portion 12 a of the second outer section 12 in the left-right direction, an upper flange portion 22 d extending upward from an upper end of the tension-side wall portion 22 a , and a lower flange portion 22 e extending downward from a lower end of the tension-side wall portion 22 a , the portions 22 a to 22 e being formed in one body.

<Third Inner Section>

The third inner section 23 has substantially the same configuration as the first inner section 21 , and includes a left wall portion 23 a , an upper flange portion 23 d , and a lower flange portion 23 e that are formed in one body.

<Fourth Inner Section>

The fourth inner section 24 includes a compression-side wall portion 24 a extending along a plane substantially perpendicularly intersecting the left-right direction (extending in the vertical and front-rear directions) and facing the tension-side wall portion 14 a of the fourth outer section 14 in the left-right direction, an upper flange portion 24 d extending upward from an upper end of the compression-side wall portion 24 a , and a lower flange portion 24 e extending downward from a lower end of the compression-side wall portion 24 a.

The compression-side wall portion 24 a includes the second bead part 24 f projecting into the inside of the main closed-cross section C_m. The second bead part 24 f extends in a direction substantially perpendicularly intersecting the front-rear direction over the entirety of the compression-side wall portion 24 a in the vertical direction.

<Fifth Inner Section>

The fifth inner section 25 has substantially the same configuration as the second inner section 22 . The fifth inner section 25 includes a tension-side wall portion 25 a extending in the vertical and front-rear directions and facing the tension-side wall portion 15 a of the fifth outer section 15 in the left-right direction, an upper flange portion 25 d , and a lower flange portion 25 e , the portions 25 a to 25 e being formed in one body.

The upper flange parts 11 d to 15 d of the outer sections 11 to 15 are connected to the upper flange portions 21 d to 25 d of the inner sections 21 to 25 , respectively, and the lower flange parts 11 e to 15 e of the outer sections 11 to 15 are connected to the lower flange portions 21 e to 25 e of the inner sections 21 to 25 , respectively. Consequently, the main closed-cross section C_m extending in the front-rear direction is defined.

Now, the reinforcing member 30 disposed in the outward bending zone 2 b will be described.

It should be noted that the reinforcing member 50 disposed in the outward bending zone 2 e has the same configuration as the reinforcing member 30 with its structure being laterally symmetrical to the reinforcing member 40 disposed in the inward bending zone 2 d . Therefore, only the reinforcing member 30 disposed in the outward bending zone 2 b will be described, and detailed description of the reinforcing members 40 , 50 will be omitted here.

As shown in FIG. 3 , the reinforcing member 30 is disposed in the main closed-cross section C_m, and defines five sub closed-cross sections c in the main frame 201 , i.e. in the main closed-cross section C_m, in cooperation with the main closed-cross section C_m, the sub closed-cross sections c being vertically adjacent to each other.

As shown in FIGS. 3 to 5 , the reinforcing member 30 includes an upper level section 31 , a middle level section 32 , and a lower level section 33 disposed in this order from above.

In the present embodiment, the upper level section 31 , the middle level section 32 , and the lower level section 33 are provided as separate components from each other.

As shown in FIG. 5 , the upper level section 31 includes a first compression-side connection portion 31 a extending along a plane substantially perpendicularly intersecting the left-right direction, a first partition wall portion 31 b joining a lower end of the first compression-side connection portion 31 a and dividing the main closed-cross section C_m in the vertical direction, and a partition wall flange portion 31 c . These portions 31 a to 31 c are formed in one body.

The first compression-side connection portion 31 a extends along the compression-side wall portion 12 a and in the front-rear and the vertical directions. The first compression-side connection portion 31 a is connected to a left surface of the compression side wall portion 12 a by welding.

The first partition wall portion 31 b extends leftward from a lower end of the first compression-side connection portion 31 a . The first partition wall portion 31 b links the lower end of the first compression-side connection portion 31 a and an upper end of a first tension-side connection portion 32 b described later.

The partition wall flange portion 31 c extends upward from a left end of the first partition wall portion 31 b.

The first partition wall portion 31 b is bent at two positions in intermediate parts thereof in the left-right direction. In other words, the first partition wall portion 31 b is bent at two positions between the compression-side wall portion 12 a and the tension-side wall portion 22 a . Consequently, the first partition wall portion 31 b has a first compression-side ridge 31 s lying at an intermediate part thereof in the left-right direction and extending in the front-rear direction, and a first tension-side ridge 31 t lying on the left of the first compression-side ridge 31 s and extending in the front-rear direction.

The first partition wall portion 31 b includes a part extending substantially horizontally from the lower end of the first compression-side connection portion 31 a to the first compression-side ridge 31 s . The first partition wall portion 31 b includes a part sloping downward as progressing leftward from the first compression-side ridge 31 s to the first tension-side ridge 31 t . In other words, a part of the first partition wall portion 31 b that extends from the first compression-side ridge 31 s to the first tension-side ridge 31 t slopes downward to the left. The first partition wall portion 31 b includes a part extending substantially horizontally from the first tension-side ridge 31 t to a lower end of the partition wall flange portion 31 c.

The first compression-side ridge 31 s and the first tension-side ridge 31 t are located at positions sandwiching the neutral axis under a load in front view.

The middle level section 32 includes a second compression-side connection portion 32 a located below the first compression-side connection portion 31 a , the first tension-side connection portion 32 b joining the left end of the first partition wall portion 31 b and extending along a plane substantially perpendicularly intersecting the left-right direction (extending in the vertical and front-rear directions), a second tension-side connection portion 32 c located below the first tension-side connection portion 32 b , a second partition wall portion 32 d linking a lower end of the first tension-side connection portion 32 b and an upper end of the second compression-side connection portion 32 a and dividing the main closed-cross section C_m in the vertical direction, a third partition wall portion 32 e linking a lower end of the second compression-side connection portion 32 a and an upper end of the second tension-side connection portion 32 c and dividing the main closed-cross section C_m in the vertical direction, and connection flange portions 32 f , 32 g . These portions 32 a to 32 g are formed in one body.

As shown in FIG. 5 , the second compression-side connection portion 32 a lies below the first tension-side connection portion 32 b , and extends along the compression-side wall portion 12 a and in the front-rear and vertical directions, the second compression-side connection portion 32 a being connected to the left surface of the compression-side wall portion 12 a by welding.

The first tension-side connection portion 32 b is disposed below the first compression-side connection portion 31 a and above the second compression-side connection portion 32 a . The first tension-side connection portion 32 b extends along the tension-side wall portion 22 a and in the front-rear and vertical directions, the first tension-side connection portion 32 b being connected to a right surface of the tension-side wall portion 22 a by welding.

The connection flange portion 32 f extends upward from an upper end of the first tension-side connection portion 32 b . The connection flange portion 32 f is connected to the partition wall flange portion 31 c by welding.

The second tension-side connection portion 32 c lies below the second compression-side connection portion 32 a , and extends along the tension-side wall portion 22 a and in the front-rear and vertical directions, the second tension-side connection portion 32 c being connected to the right surface of the tension-side wall portion 22 a by welding.

The connection flange portion 32 g extends downward from a lower end of the second tension-side connection portion 32 c.

The second partition wall portion 32 d extends rightward from the lower end of the first tension-side connection portion 32 b . The second partition wall portion 32 d links the lower end of the first tension-side connection portion 32 b and the upper end of the second compression-side connection portion 32 a , and divides the main closed-cross section C_m in the vertical direction.

The connection flange portion 32 f , i.e. one of the flange portions of the middle level section 32 , extends upward from the upper end of the first tension-side connection portion 32 b . The partition wall flange portion 31 c of the upper level section 31 extends along a right surface of the connection flange portion 32 f , and these flanges are connected to each other by welding.

The second partition wall portion 32 d is bent at two positions in intermediate parts thereof in the left-right direction. In other words, the second partition wall portion 32 d is bent at two positions between the compression-side wall portion 12 a and the tension-side wall portion 22 a . Consequently, the second partition wall portion 32 d has a second compression-side ridge 32 s lying at an intermediate part thereof in the left-right direction and extending in the front-rear direction, and a second tension-side ridge 32 t lying on the left of the second compression-side ridge 32 s and extending in the front-rear direction.

The second partition wall portion 32 d includes a part extending substantially horizontally from the upper end of the second compression-side connection portion 32 a to the second compression-side ridge 32 s . The second partition wall portion 32 d includes a part sloping upward as progressing leftward from the second compression-side ridge 32 s to the second tension-side ridge 32 t . In other words, a part of the second partition wall portion 32 d that extends from the second compression-side ridge 32 s to the second tension-side ridge 32 t slopes upward to the left. The second partition wall portion 32 d includes a part extending substantially horizontally from the second tension-side ridge 32 t to the lower end of the first tension-side connection portion 32 b.

The second compression-side ridge 32 s lies directly under and faces the first compression-side ridge 31 s , and extends in the front-rear direction. The second tension-side ridge 32 t lies directly under and faces the first tension-side ridge 31 t , and extends in the front-rear direction.

The first and second tension-side ridges 31 t , 32 t lie below the first compression-side ridge 31 s and above the second compression-side ridge 32 s , respectively. The vertical distance between the first and second tension-side ridges 31 t , 32 t is smaller than the vertical distance between the first and second compression-side ridges 31 s , 32 s.

The third partition wall portion 32 e extends leftward from the lower end of the second compression-side connection portion 32 a . The third partition wall portion 32 e links the lower end of the second compression-side connection portion 32 a and the upper end of the second tension-side connection portion 32 c and divides the main closed-cross section C_m in the vertical direction.

The connection flange portion 32 g , i.e. the other of the flange portions of the middle level section 32 , extends downward from a left end of the third partition wall portion 32 e.

As shown in FIG. 5 , the third partition wall portion 32 e is bent at two positions in intermediate parts thereof in the left-right direction. In other words, the third partition wall portion 32 e is bent at two positions between the compression-side wall portion 12 a and the tension-side wall portion 22 a . Consequently, the third partition wall portion 32 e has a third compression-side ridge 32 u lying at an intermediate part thereof in the left-right direction and extending in the front-rear direction, and a third tension-side ridge 32 v lying on the left of the third compression-side ridge 32 u and extending in the front-rear direction.

The third partition wall portion 32 e includes a part extending substantially horizontally from the lower end of the second compression-side connection portion 32 a to the third compression-side ridge 32 u . The third partition wall portion 32 e includes a part sloping downward as progressing leftward from the third compression-side ridge 32 u to the third tension-side ridge 32 v . In other words, a part of the third partition wall portion 32 e that extends from the third compression-side ridge 32 u to the third tension-side ridge 32 v slopes downward to the left. The third partition wall portion 32 e includes a part extending substantially horizontally from the third tension-side ridge 32 v to the upper end of the second tension-side connection portion 32 c.

The third compression-side ridge 32 u lies directly under and faces the second compression-side ridge 32 s , and extends in the front-rear direction. The third tension-side ridge 32 u lies directly under and faces the second tension-side ridge 32 t , and extends in the front-rear direction.

The second and third compression-side ridges 32 s , 32 u lie below the second tension-side ridge 32 t and above the third tension-side ridge 32 v , respectively. The vertical distance between the second and third compression-side ridges 32 s , 32 u is smaller than the vertical distance between the second and third tension-side ridges 32 t , 32 v.

In the present embodiment, the vertical distance between the second compression-side ridge 32 s and the third compression-side ridge 32 u is greater than the vertical distance between the first tension-side ridge 31 t and the second tension-side ridge 32 t and the vertical distance between the third tension-side ridge 32 v and a fourth tension-side ridge 33 t.

The lower level section 33 includes a third compression-side connection portion 33 a located below the second compression-side connection portion 32 a , a fourth partition wall portion 33 b joining an upper end of the third compression-side connection portion 33 a and dividing the main closed-cross section C_m in the vertical direction, and a partition wall flange portion 33 c . These portions 33 a to 33 c are formed in one body.

The third compression-side connection portion 33 a lies below the second tension-side connection portion 32 c , and extends along the compression-side wall portion 12 a and in the front-rear and vertical directions, the third compression-side connection portion 33 a being connected to the left surface of the compression-side wall portion 12 a by welding.

The fourth partition wall portion 33 b extends rightward from the upper end of the third compression-side connection portion 33 a . The fourth partition wall portion 33 b links the upper end of the third compression-side connection portion 33 a and the lower end of the second tension-side connection portion 32 c , and divides the main closed-cross section C_m in the vertical direction.

The fourth partition wall portion 33 b is bent at two positions in intermediate parts thereof in the left-right direction. In other words, the fourth partition wall portion 33 b is bent at two positions between the compression-side wall portion 12 a and the tension-side wall portion 22 a . Consequently, the fourth partition wall portion 33 b has a fourth compression-side ridge 33 s lying at an intermediate part thereof in the left-right direction and extending in the front-rear direction, and the fourth tension-side ridge 33 t lying on the left of the fourth compression-side ridge 33 s and extending in the front-rear direction.

The fourth partition wall portion 33 b includes a part extending substantially horizontally from the upper end of the third compression-side connection portion 33 a to the fourth compression-side ridge 33 s . The fourth partition wall portion 33 b includes a part sloping upward as progressing leftward from the fourth compression-side ridge 33 s to the fourth tension-side ridge 33 t . In other words, a part of the fourth partition wall portion 33 b that extends from the fourth compression-side ridge 33 s to the fourth tension-side ridge 33 t slopes upward to the left. The fourth partition wall portion 33 b includes a part extending substantially horizontally from the fourth tension-side ridge 33 t to an upper end of the partition flange portion 33 c.

The partition wall flange portion 33 c of the lower level section 33 extends downward from a left end of the fourth partition wall portion 33 b . The partition wall flange portion 33 c extends along a right surface of the connection flange portion 32 g constituting the lower portion of the middle level section 32 , the partition wall flange portion 33 c and the connection flange portion 32 g being connected to each other by welding.

The fourth compression-side ridge 33 s lies directly under and faces the third compression-side ridge 32 u , and extends in the front-rear direction. The fourth tension-side ridge 33 t lies directly under and faces the third tension-side ridge 32 v , and extends in the front-rear direction.

The third and fourth tension-side ridges 32 v , 33 t lie under the third compression-side ridge 32 u and above the fourth compression-side ridge 33 s , respectively.

The vertical distance between the third and fourth ridges 32 v , 33 t is smaller than the vertical distance between the third and fourth compression-side ridges 32 u , 33 s.

As described above, in the present embodiment, the main closed-cross section C_m is divided into the five sub closed-cross sections c in the vertical direction by the partition wall portions 31 b , 32 d , 32 e , 33 b.

Here, in the present embodiment, each sub closed-cross section c has a vertical dimension or a height that is smaller than a lateral dimension or a width. Thus, the length-to-width ratio of each sub closed-cross section is 1 or less.

Now, a deformation of the vehicle V upon receipt of a front impact load will be described with reference to FIGS. 6 and 7 . FIGS. 6 and 7 are schematic top views of the periphery of the front side frame.

In the schematic view of FIG. 6 , “F” denotes a front frame unit including the front side frame and the crash can, “D” denotes the dash panel, “M” denotes a linking reinforcing member, “I” denotes an inner load transmission unit including a dash lower cross member and a member provided in a tunnel section, “U” denotes an upper linking member, “Q” (a hatched region) denotes the mount attachment reinforcing member, “R” (a hatched region) denotes the sub-frame attaching bracket, and “T” denotes a front tire.

In addition, a plurality of points P 1 to P 5 are shown in the front frame unit F for sake of convenience so that their relative positions after a deformation can be easily seen.

The first point P 1 denotes a front end position of the crash can 6 , the second point P 2 denotes a front end position of the front side frame 2 , the third point P 3 denotes a position where the first bead part 12 f is formed, the fourth point P 4 denotes a rear end position of the mount attachment reinforcing member 8 , the fifth point P 5 denotes a position where the second bead part 24 f is formed, and the sixth point P 6 denotes a position where the third bead part 15 f is formed.

Upon receipt of a load Z, the front frame unit F actively causes a compressive deformation and a bending deformation in the vehicle width direction to thereby absorb an impact energy.

As shown in FIG. 7 , when a collision object collides with the front frame unit F, an axially compressive deformation occurs in a portion of the front frame unit F that extends from the first point P 1 to a position slightly behind the second point P 2 .

Because the first bead part 12 f is formed near the third point P 3 , a bending deformation in the vehicle width outward direction (outward bending deformation) occurs in such a way that the third point P 3 shifts in the vehicle width inward direction.

Specifically, in a region extending from the third point P 3 to the fourth point P 4 , a deformation is hindered by the mount attachment reinforcing member Q and the like. Consequently, a portion between the second point P 2 and the third point P 3 deforms to bend in the vehicle width inward direction (inwardly bend) and a portion behind the third point P 3 is deformed to bend in the vehicle width outward direction.

Because the second bead part 24 f is formed near the fifth point P 5 , a bending deformation in the vehicle width inward direction (inward bending deformation) occurs in such a way that the fifth point P 5 jumps out in the vehicle width outward direction.

In particular, the sub-frame attaching bracket R for attaching the sub-frame is disposed in a region behind the fifth point P 5 . In addition, the portion behind the fifth point P 5 has a high frame rigidity in order to disperse a load at its rear position. This promotes the bending deformation in the vehicle width inward direction that occurs near the fifth point P 5 .

Because the third bead part 15 f is formed near the sixth point P 6 , a bending deformation in the vehicle width outward direction occurs in such a way that the sixth point P 6 shifts in the vehicle width inward direction.

As described above, the bending deformation in the vehicle width outward direction occurs at the third point P 3 and the sixth point P 6 , and the bending deformation in the vehicle width inward direction occurs at the fifth point P 5 . This allows achievement of sufficiently high EA efficiency.

Now, a modification of the reinforcing member 30 will be described with reference to FIGS. 8 and 9 .

Elements that have configurations identical to those of the first embodiment are denoted by the same reference numerals as in the first embodiment.

As shown in FIGS. 8 and 9 , a reinforcing member 30 A is formed by pressing a single steel plate in such a way as to include an upper level section 31 A, a middle level section 32 A, and a lower level section 33 A in one body.

In the upper level section 31 A, a first compression-side connection portion 31 a , a first partition wall portion 31 b , a first compression-side ridge 31 w , and a first tension-side ridge 31 x are formed.

In the lower level section 33 A, a third compression-side connection portion 33 a , a fourth partition wall portion 33 b , a fourth compression-side ridge 33 w , and a fourth tension-side ridge 33 x are formed.

In the middle level section 32 A, a second compression-side connection portion 32 a , a first tension-side connection portion 32 b , a second tension-side connection portion 32 c , a second partition wall portion 32 d , and a third partition wall portion 32 e are formed.

The second partition wall portion 32 d is formed with a second compression-side ridge 32 w and a second tension-side ridge 32 x , and the third partition wall portion 32 is formed with a third compression-side ridge 32 y and a third tension-side ridge 32 z.

In this modification, all of the vertical distance between the first tension-side ridge 31 x and the second tension-side ridge 32 x , the vertical distance between the second compression-side ridge 32 w and the third compression-side ridge 32 y , and the vertical distance between the third tension-side ridge 32 z and the fourth tension-side ridge 33 x are equal to each other.

It should be noted that the first compression-side ridge 31 w , the second compression-side ridge 32 w , the third compression-side ridge 32 y , and the fourth compression-side ridge 33 w face each other in the vertical direction, and that the first tension-side ridge 31 x , the second tension-side ridge 32 x , the third tension-side ridge 32 z , and the fourth tension-side ridge 33 x face each other in the vertical direction.

Now, the functions and effects of the vehicular frame according to the present embodiment will be described.

First, FIGS. 10A to 10D show frame models M 1 to M 4 prepared to analyze the correlation (FS characteristic) between the supportable load and the deformation stroke of each of the frame models M 1 to M 4 using a CAE (Computer Aided Engineering).

The frame model M 1 (see FIG. 10A ) consists only of a main frame having a rectangular shape in cross section, and has no reinforcing member.

The frame model M 2 (see FIG. 10B ) includes a main frame and a reinforcing member disposed in the main frame, the reinforcing member having a different structure from that of the present invention. Specifically, the reinforcing member includes a plurality of walls each horizontally extending from one side wall to the other side wall of the main frame in a width direction of the main frame. These walls are arranged in a vertical direction and dividing a main closed cross-section of the main frame into a plurality of sub closed-cross sections in the vertical direction. Further, all of these walls are formed in one body together with portions connected to the side walls of the main frame.

The frame model M 3 (see FIG. 10C ) includes the reinforcing member 30 A of the modification.

The frame model M 4 (see FIG. 10D ) includes the reinforcing member 30 of the first embodiment.

A load was applied to each of the frame models M 1 to M 4 in a direction to bend the respective axis to analyze a displacement of a load point and a reaction force at the load point, the application of the load being performed in a state that opposite ends of the frame models M 1 to M 4 are clamped (see FIGS. 14 and 15 ).

FIG. 11 shows an analysis result provided by the CAE. In the graph of F-S characteristics of FIG. 11 , the vertical axis represents the load (kN) and the horizontal axis represents the stroke (mm).

As shown in FIG. 11 , the frame model M 1 having no reinforcing member was buckled by an allowable critical load lower than those of the frame models M 2 to M 4 , and a load drop immediately after the buckling was significant. Thus, the frame model M 1 was found to have the lowest EA efficiency.

As for the frame model M 2 , the decreasing rate of the load immediately after the buckling was great, and a second load drop occurred soon after the buckling.

In contrast, as for the frame model M 3 , the decreasing rate of the load immediately after the buckling was small compared to those of the frame models M 1 and M 2 , a second load drop occurred later than in the frame model M 2 . Therefore, the frame model M 3 was found to have a higher EA efficiency than the frame models M 1 and M 2 .

This is because, in the reinforcing member 30 A, the ridges 31 w , 31 x , 32 w , 32 x , 32 y , 32 e , 33 w , 33 x are formed in the partition wall portions 31 b , 32 d , 32 e , 33 b , which strengthens each of the partition wall portions 31 b , 32 d , 32 e , 33 b . In addition, in the frame model M 3 , the compression-side ridges 32 w , 32 y come into contact with each other in a deformation of the frame caused upon receipt of a compressive load on the compression-side wall portion, as shown in FIG. 12 . Consequently, as shown by the reference character Ts in FIG. 12 , a truss structure is formed in the main frame by the partition wall portions 32 e , 32 d . This prevents collapse of the main closed cross-section and the sub closed-cross sections. In other words, the partition wall portions 32 d , 32 e come into contact with each other at their respective intermediate parts to thereby form a truss structure in cooperation with the tension-side wall portion and the compression-side wall portion (second compression-side connection portion).

In this manner, the front side frame 2 including the reinforcing member 30 A can have an increased EA efficiency owing to the reinforced partition wall portions 31 b , 32 d , 32 e , 33 b due to the ridges 31 w , 31 x , 32 w , 32 x , 32 y , 32 e , 33 w , 33 x formed in the reinforcing member 30 A, and owing to the truss structures created in the deformation.

The decreasing rate of the load immediately after a buckling of the frame model 4 was smaller than that of the frame model M 3 . Therefore, the frame model M 4 was found to have a higher EA efficiency than the frame model M 3 .

This is because, in the frame model M 4 , truss structures are formed in the main frame sooner than in the frame model M 3 .

Specifically, as described, in the reinforcing member 30 of the frame model M 4 , the vertical distance between the first tension-side ridge 31 t and the second tension-side ridge 32 t and the vertical distance between the third tension-side ridge 32 v and the fourth tension-side ridge 33 t are smaller than the vertical distance between the second compression-side ridge 32 s and the third compression-side ridge 32 u . Therefore, as shown in FIG. 13 , soon after the buckling, the first tension-side ridge 31 t comes into contact with the second tension-side ridge 32 t and the third tension-side ridge 32 v comes into contact with the fourth tension-side ridge 33 t , so that truss structures Ts are created in the main frame.

Further, because such quick creation of the truss structures on the tension-side further prevents collapse of the main closed cross-section and the sub closed-cross sections, a second load drop after the buckling is suppressed.

As described, in the front side frame 2 to which the vehicular frame (vehicular frame including the reinforcing member 30 ) according to the present embodiment is applied, the first to third partition wall portions 31 b , 32 d , 32 e are respectively formed with the first to third compression-side ridges 31 s , 32 s , 32 u that extend in the front-rear direction and face each other, and the first to third tension-side ridges 31 t , 32 t , 32 v that lie closer to the tension side than the first to third compression-side ridges 31 s , 32 s , 32 u , the tension-side ridges 31 t , 32 t , 32 v extending in the front-rear direction and facing each other. This makes it possible to strengthen the first to third partition wall portions 31 b , 32 d , 32 e , and in turn, to prevent an out-of-plane deformation of the first to third partition wall portions 31 b , 32 d , 32 e and increase the allowable critical load of the front side frame 2 . In addition, the fourth partition wall portion 33 b is also formed with the fourth compression-side ridge 33 s and the fourth tension-side ridge 33 t , which further increases the allowable critical load.

Further, because the truss structure Ts is created by the contact between the first and second tension-side ridges 31 t , 32 t after a buckling of the compression-side wall portion 11 a , it is possible to prevent collapse of the cross section of the front side frame 2 . Therefore, it is possible to prevent a load drop after the buckling and increase the EA efficiency. Similarly, the truss structure Ts is created by the contact between the fourth tension-side ridge 33 t and the third tension-side ridge 32 v . Therefore, it is possible to further prevent collapse of the cross section of the front side frame 2 .

Here, a configuration for preventing collapse of the cross-section is considered in which respective intermediate parts of the partition wall portions are connected to each other by separately provided wall members in advance, for example. In this case, however, the structure would be complex. Further, because the partition wall portions have to be secured to the wall members by welding in the frame, the number of welding positions would increase, which would deteriorate the productivity. In contrast, in the present embodiment, the respective intermediate parts of the partition wall portions are configured to come into contact with each other in a deformation, instead of being connected to each other in advance. This makes it possible to simplify the structure and reduce the number of welding portions, so that collapse of the cross-section can be prevented while improving the productivity.

In particular, in the present embodiment, the first and second tension-side ridges 31 t , 32 t are disposed vertically between the first and second compression-side ridges 31 s , 32 s , and the second and third compression-side ridges 32 s , 32 u are disposed vertically between the second and third tension-side ridges 32 t , 32 v.

Therefore, it is possible to reliably cause the first and second tension-side ridges 31 t , 32 t to come into contact with each other to thereby create the truss structure in a deformation of the first and second partition wall portions 31 b , 32 d.

The vertical distance between the first and second tension-side ridges 31 t , 32 t is smaller than the vertical distance between the second and third compression-side ridges 32 s , 32 u.

This makes it possible to more reliably cause the contact between the first and second tension-side ridges 31 t , 32 t supported by the tension-side wall portion 22 a to thereby create the truss structure, and in turn, to further improve the effect of preventing collapse of the cross-section.

Similarly, the vertical distance between the third and fourth tension-side ridges 32 v , 33 t is smaller than the vertical distance between the second and third compression-side ridges 32 s , 32 u . Therefore, it is possible to more reliably cause the contact between these tension-side ridges 32 v , 33 t to thereby create the truss structure, and in turn, to further improve the effect of preventing collapse of the cross-section.

The first partition wall portion 31 b and the second partition wall portion 32 d are configured as separate components, and the connection flange portion 32 f extending upward from the upper end of the first tension-side connection portion 32 b and the partition wall flange portion 31 c extending upward from the tension-side end of the first partition wall portion 31 b are connected to each other.

Therefore, it is possible to set the vertical distance between the first and second tension-side ridges 31 t , 32 t to any value.

Similarly, because the third partition wall portion 32 e and the fourth partition wall portion 33 b are configured as separate components, it is possible to set the vertical distance between the third and fourth tension-side ridges 32 v , 33 t to any value.

Further, in the present embodiment, the sub closed-cross section c has a height (vertical dimension) smaller than a width (lateral dimension), and thus has the length-to-width ratio of 1 or less. This makes it possible to increase the allowable critical load of the front side frame 2 and maintain it for a certain stroke.

A specific explanation is given below.

In order to study buckling of a frame having a vertically long rectangular shape in cross section, the present inventors performed an analysis of the mechanism of deformation of the frame, using the CAE (Computer Aided Engineering).

First, the basic idea of the analysis will be explained.

As shown in FIG. 14 , there were prepared a frame model M made of a steel plate and having a longer dimension and a closed cross-section, and a load application means T configured to bend an axis of the frame model M in a state of clamping opposite ends of the frame model M. Using these components, a displacement of a load point P and a reaction force at the load point P were analyzed.

As shown in FIGS. 14, 15A and 15B , the load application means T includes a support section Ta pivotable about a pivot shaft R, and a support section Tb having the load point P at which a load is applied, the support section Tb being pivotable to move toward the support section Ta. The straight line connecting the pivot shaft R and the load point P is offset from the axis of the frame model M by 50 mm. Wall portions constituting the frame model M include a compression-side wall portion Ma on which a compressive load acts, a tension-side wall portion Mb on which a tensile load acts, and an upper end wall portion Mc and a lower end wall portion Md connecting respective upper ends of the wall portions Ma and Mb and respective lower ends of the wall portions Ma and Mb, respectively.

Now, an analysis result will be described.

As shown in FIG. 16 , the mechanism to cause a buckling of a frame having a rectangular cross-section can be reasoned as follows.

Upon receipt of a load exceeding an allowable limit of elastic deformation, a surface deformation W occurs at an interval in the compression-side wall portion Ma. Each surface deformation W spreads to the upper end wall portion Mc and the lower end wall portion Md. Consequently, an out-of-plane deformation occurs in a bulge region n of each of the upper end wall portion Mc and the lower end wall portion Md, the bulge region n corresponding to a depression region m formed due to the surface deformation W in the compression-side wall portion Ma. This brings the frame into a fully buckled state with each of the upper end wall portion Mc and the lower end wall portion Md bulging out in an out-of-plane direction, and the compression-side wall portion Ma being folded in half.

Therefore, if the periodic surface deformations W are prevented from spreading to the upper end wall portion Mc and the lower end wall portion Md, it will be possible to increase the load that brings the frame into the fully buckled state. In other words, it will be possible to increase the amount of energy absorption before the full buckling, and in turn, to improve the EA efficiency.

In contrast, in the present embodiment, the lateral dimension of the sub closed-cross section c is greater than its vertical dimension. This makes it possible to prevent periodic surface deformations W from spreading to the upper end wall portion and the lower end wall portion. Accordingly, it is possible to increase the allowable limit load that causes a buckling of the front side frame and maintain it for a certain stroke.

Now, partial modifications of the above-described embodiment will be described.

[1] The above-described embodiment illustrates the case of the front side frame. However, the present invention can be applied to any vehicular frame on which a compressive load and a tensile load act, such as a rear side frame, a suspension cross member, a bumper beam, a center pillar, and an impact bar.

[2] In the above-described embodiment, 5000 series aluminum alloy is used as the material. However, the advantageous effects of the present invention can be achieved even when an ordinary steel plate or high tensile strength steel plate is used. Further, an aluminum alloy material may be selected from the 1000 series, 3000 series, 4000 series that are of non-heat-treated type, and the 2000 series, 6000 series, and 7000 series that are of heat-treated type, depending on design requirements.

[3] In the above-described embodiment, the case of including four partition wall portions is illustrated in the light of EA efficiency. However, the advantageous effects of the present invention can be achieved by including at least three partition wall portions. Further, five or more partition wall portions may be used for design purpose.

[4] In the above-described embodiment, the front side frame 2 includes the two outward bending deformation zones and the one inward bending deformation zone, and the reinforcing members provided in all of these deformation zones. Alternatively, a reinforcing member may be provided in at least one of the deformation zones of the front side frame 2 . Further, the front side frame 2 may alternatively be made to include one outward bending deformation zone or one inward bending deformation zone.

[5] Persons skilled in the art may make other various modifications to the above-described embodiment without departing the spirit of the present invention, and the present invention includes such modifications.

The present invention is summarized as follows.

The present invention defines a vehicular frame, comprising: a main frame disposed in a front portion of a vehicle and extending in a front-rear direction; and a reinforcing member disposed inside the main frame and extending in the front-rear direction, the reinforcing member defining a plurality of closed cross sections in the main frame by dividing an internal space of the main frame in a vertical direction, wherein: the main frame has a main closed cross section having a substantially rectangular shape and includes, in sectional view, a compression-side wall portion extending in the vertical direction and configured to receive a compressive load in an impact of the vehicle, a tension-side wall portion extending in the vertical direction and facing the compression-side wall portion in a width direction of the vehicle, and configured to receive a tensile load in the impact of the vehicle, a top wall portion linking an upper end of the compression-side wall portion and an upper end of the tension-side wall portion, and a bottom wall portion linking a lower end of the compression-side wall portion and a lower end of the tension-side wall portion; the reinforcing member includes a first compression-side connection portion connected to the compression-side wall portion, a second compression-side connection portion disposed below the first compression-side connection portion and connected to the compression-side wall portion, a first tension-side connection portion disposed below the first compression-side connection portion and above the second compression-side connection portion and connected to the tension-side wall portion, a second tension-side connection portion disposed below the second compression-side connection portion and connected to the tension-side wall portion, a first partition wall portion linking a lower end of the first compression-side connection portion and an upper end of the first tension-side connection portion, a second partition wall portion linking a lower end of the first tension-side connection portion and an upper end of the second compression-side connection portion, and a third partition wall portion linking a lower end of the second compression-side connection portion and an upper end of the second tension-side connection portion; each of the first to third partition wall portions is bended at a plurality of positions between the compression-side wall portion and the tension-side wall portion, and has a compression-side ridge extending in the front-rear direction and a tension-side ridge disposed between the compression-side ridge and the tension-side wall portion and extending in the front-rear direction, the respective compression-side ridges of the first to third partition wall portions facing each other in the vertical direction and the respective tension-side ridges of the first to third partition wall portions facing each other in the vertical direction; and the compression-side ridges and the tension-side ridges are disposed at positions that allow, in a deformation of the partition wall portions, the compression-side ridge of the second partition wall portion to come into contact with the compression-side ridge of the third partition wall portion or the tension-side ridge of the first partition wall portion to come into contact with the tension-side ridge of the second partition wall portion.

According to this configuration, it is possible to strengthen the first to third partition wall portions by reinforcing them by the ridges, to thereby prevent an out-of-plane deformation of the first to third partition wall portions. Therefore, it is possible to increase the allowable critical load of the vehicular frame.

Furthermore, it is possible to form truss structures in the main frame by bringing the second and third compression-side ridges into contact with each other or the first and second tension-side ridges into contact with each other in a deformation of the vehicular frame, which makes it possible to prevent collapse of the cross-section of the vehicular frame. Consequently, it is possible to prevent a load drop after the buckling and, in turn, to increase the EA efficiency.

In addition, in this vehicular frame, the structure is simplified with a reduced number of welding positions, and the sub closed-cross section has a vertical dimension smaller than its lateral dimension (the length-to-width ratio being adjusted to be 1 or less, which makes it possible to increase the allowable critical load and maintain it for a certain stroke.

In the present invention, it is preferred that the tension-side ridge of the first partition wall portion and the tension-side ridge of the second partition wall portion are disposed below the compression-side ridge of the first partition wall portion and above the compression-side ridge of the second partition wall portion, respectively, and the compression-side ridge of the second partition wall portion and the compression-side ridge of the third partition wall portion are disposed below the tension-side ridge of the second partition wall portion and above the tension-side ridge of the third partition wall portion, respectively.

According to this configuration, it is possible to more reliably create the truss structures by more reliably bringing the second or third compression-side ridges into contact with each other and the first and second tension-side ridges into contact with each other.

Further, in the present invention, it is preferred that the vertical distance between the tension-side ridge of the first partition wall portion and the tension-side ridge of the second partition wall portion is smaller than the vertical distance between the compression-side ridge of the second partition wall portion and the compression-side ridge of the third partition wall portion.

According to this configuration, it is possible to create the truss structures in the main frame by bringing the first and second tension-side ridges lying close to the tension-side wall portion into contact with each other more quickly. Therefore, it is possible to more effectively suppress collapse of the cross section of the main frame.

Further, in the present invention, it is preferred that the first partition wall portion and the second partition wall portion are configured as separate components.

This configuration makes it possible to set the vertical distance between the first and second tension-side ridges to any value. In other words, it is possible to shorten the vertical distance between the first and second tension-side ridges to bring them into contact with each other more quickly.

Further, this configuration may further be made to comprise a connection flange portion extending upward from an upper end of the first tension-side connection portion; and a partition wall flange portion extending upward from one end of the first partition wall portion that is closer to the tension side wall portion than the other end in the vehicle width direction, wherein: the first partition wall portion and the partition wall flange portion are formed in one body; the second partition wall portion, the first tension-side connection portion, and the connection flange portion are formed in one body; and the connection flange portion and the partition wall flange portion are connected to each other.

According to this configuration, the first partition wall portion and the second partition wall portion are configured as separate components, and the connection flange portion and the partition wall flange portion are connected to each other, which makes it possible to easily secure these components to the main frame.

V: vehicle

C_m: main closed-cross section

c: sub closed-cross section

2 : front side frame

11 : first outer section

12 a : compression-side wall portion

12 b : upper end wall portion (top wall portion)

12 c : lower end wall portion (bottom wall portion)

14 b : upper end wall portion (top wall portion)

14 c : lower end wall portion (bottom wall portion)

15 b : upper end wall portion (top wall portion)

15 c : lower end wall portion (bottom wall portion)

21 : first inner section

22 a : tension-side wall portion

30 : reinforcing member

31 a : first compression-side connection portion

31 b : first partition wall portion

31 c : partition wall flange portion

31 s : first compression-side ridge

31 t : first tension-side ridge

32 a : second compression-side connection portion

32 b : first tension-side connection portion

32 c : second tension-side connection portion

32 d : second partition wall portion

32 e : third partition wall portion

32 f : connection flange portion

32 s : second compression-side ridge

32 t : second tension-side ridge

32 u : third compression-side ridge

32 v : third tension-side ridge

201 : main frame