JP6733560B2 - Body frame structure - Google Patents

Description

The present invention relates to a vehicle body frame structure.

Patent Document 1 discloses a vehicle body frame structure having a front side member extending in the vehicle front-rear direction and a crash box connected to a front end portion of the front side member.

JP, 2005-63243, A

The crash box and the front side member are connected by fastening the plate on the crash box side and the plate on the front side member side with a bolt in the vehicle front-rear direction. The portion where the two plates are connected is unlikely to be deformed when a collision load is applied in the vehicle front-rear direction. In other words, the part where the two plates are connected is a dead space that hardly contributes to the absorption of collision energy. As described above, there is room for improvement in extending the crash stroke at the time of a frontal collision in a vehicle body of a limited size.

In consideration of the above facts, an object of the present invention is to obtain a vehicle body frame structure capable of lengthening a crash stroke at the time of a frontal collision as compared with a structure in which a crash box is fastened to a frame member.

In the vehicle body skeletal structure according to the first aspect of the present invention, the plate thickness is set to the first plate thickness, and the first plate portion that is coupled to the bumper reinforcement and extends in the vehicle front-rear direction, and the plate thickness is The second plate thickness is set to be thicker than the first plate thickness, and a thickness difference is coupled to a rear end of the first plate portion so that a step is formed at a coupling portion with the first plate portion. And a pair of side rails each including a second plate portion that is provided with a bent portion that is bent outward in the vehicle width direction from the front of the vehicle toward the rear of the vehicle, and the pair of side rails. And a pair of cross members bridged over the front portion and the bent portion .

Difference thickness bonding is so-called tailored blank welding, in which a plurality of steel plates having different plate thicknesses or a plurality of steel plates having different plate thicknesses and materials are welded (joined) by laser welding or the like before press forming, It is a steel plate.

In the vehicle body skeletal structure according to the present invention as set forth in claim 1, the collision input by the first plate part having the first plate thickness that is thin and the second plate part having the second plate thickness that is thick The load bearing capacity is different. Therefore, when a collision load is input to the skeleton member in a frontal collision, the first plate portion is compressed and deformed, absorbs collision energy, and the second plate portion resists the collision load. Here, the first plate portion and the second plate portion are directly joined with a different thickness, and other members do not intervene in these joined portions. For this reason, the first plate portion can be deformed up to the connecting portion of the first plate portion and the second plate portion, so that the crash stroke at the time of a frontal collision can be lengthened as compared with the configuration having the crash box. it can.

As described above, according to the vehicle body frame structure of the first aspect, the crash stroke at the time of a frontal collision can be lengthened as compared with the configuration in which the crash box is fastened to the frame member.

1 is a plan view of a skeleton portion of a vehicle to which a vehicle body skeleton structure according to the present embodiment is applied. It is a side view of the body frame structure concerning this embodiment. (A) It is a cross-sectional view (cross section taken along the line AA of FIG. 2) showing a connecting portion between the first plate portion and the second plate portion according to the present embodiment, and (B) the first comparative example. It is a cross-sectional view which shows the connection part of a board part and a 2nd board part. (A) It is a side view of a vehicle body skeletal structure according to a modified example of the present embodiment, and (B) a connecting portion between a front side member and a bracket according to a modified example of the present embodiment (one-dot chain line M in FIG. 4A). FIG. It is a partial side view which shows the joining part of the front side member and the crash box which concern on a 2nd comparative example.

〔overall structure〕
FIG. 1 shows a skeleton portion of a vehicle 10 according to this embodiment. In addition, an arrow FR, which is shown in each drawing as appropriate, indicates the front side (the traveling direction) of the vehicle, an arrow UP indicates the upper side of the vehicle, and OUT indicates the outer side in the vehicle width direction. In the following description, the front-rear direction, the up-down direction, and the left-right direction, unless otherwise specified, indicate the front-rear direction of the vehicle body, the up-down direction of the vehicle body up-down direction, and the left-right direction of the vehicle width when facing the traveling direction. I shall.

The vehicle 10 is configured as a vehicle having a frame structure (frame vehicle), for example. Further, the vehicle body skeleton structure 20 according to the present embodiment is applied to the vehicle 10. The vehicle body frame structure 20 has a pair of side rails 14 as an example of a frame member provided on both sides in the vehicle width direction.

The pair of side rails 14 extend along both sides of the vehicle front portion 12 in the vehicle width direction along the vehicle front-rear direction. Front tires (not shown) are arranged on both sides in the vehicle width direction on the front portion 14A side of the side rails 14. Therefore, on the front portion 14A side of the side rail 14, in consideration of the interference with the front tire, the dimension in the vehicle width direction is shorter than that of the intermediate portion 14B side located at the middle of the side rail 14 in the vehicle longitudinal direction. Is set to. Between the front portion 14A and the middle portion 14B of the side rail 14 in the vehicle front-rear direction, a bent portion 15 that is bent outward in the vehicle width direction from the vehicle front side of the side rail 14 to the vehicle rear side is provided.

Extensions 22 to be described later are formed at the front end portions of the pair of side rails 14. In other words, the extension 22 is a part of the side rail 14. The bumper reinforcement 16 is laid across the front ends 23 of the pair of extensions 22 along the vehicle width direction. A plurality of cross members 18A, 18B, 18C extend in the vehicle width direction between the pair of side rails 14 and on the vehicle rear side of the bumper reinforcement 16. As a result, a ladder-shaped frame is formed on the vehicle front portion 12. The cross member 18A and the cross member 18B are bridged over the front portion 14A of the side rail 14. The cross member 18C is bridged around the bent portion 15.

A suspension mount bracket 19 projecting outward in the vehicle width direction is provided at a portion of the side rail 14 between the cross member 18B and the cross member 18C. A suspension mount (not shown) can be attached to the suspension mount bracket 19. The suspension unit can be connected to the side rails 14 via the suspension mount and the suspension mount bracket 19.

A cab mount bracket 17 is arranged on the rear side of the bent portion 15. The cab mount bracket 17 projects from the bent portion 15 to the outside in the vehicle width direction. A cabin (body) (not shown) can be connected to the side rail 14 via the cab mount bracket 17.

[Structure of essential parts]
Next, the extension 22 will be described.

As shown in FIG. 2, the extension 22 is a portion that extends toward the front of the vehicle body in the front portion of the side rail 14. The extension 22 includes a side rail inner panel 24 and a side rail outer panel (not shown) joined to the side rail inner panel 24 from the outside in the vehicle width direction. Further, the extension 22 has a substantially rectangular closed cross-section structure when viewed from the vehicle front-rear direction.

The side rail inner panel 24 is formed in a hat-shaped cross section that opens outward in the vehicle width direction when viewed from the vehicle front-rear direction. Specifically, the siderail inner panel 24 is provided with a vertical wall 26 that is upright in the vehicle vertical direction and extends in the vehicle front-rear direction, and extends from the upper end and the lower end of the vertical wall 26 toward the vehicle width direction outer side and the vehicle. It has a pair of lateral walls 28 extending in the front-rear direction.

The siderail inner panel 24 is thicker than the first plate portion 32 forming the front end portion, and is joined to the rear end of the first plate portion 32 in the vehicle front-rear direction with a different thickness. And a second plate portion 34. Specifically, the side rail inner panel 24 is formed by press-forming a difference thickness steel plate having a thin steel plate portion and a thick steel plate portion.

Difference thickness bonding is so-called tailored blank welding, and multiple steel plates with different plate thickness (blank material) or multiple steel plates with different plate thickness and material (blank material) are laser welded before press forming. They are welded (joined) to form one steel plate. By joining dissimilar steel plates using the difference thickness bonding, the characteristics of one material can be partially changed. Although the side rail outer panel (not shown) has the first plate portion 32 and the second plate portion 34 similarly to the side rail inner panel 24, the side rail inner panel 24 will be described here, and the description of the side rail outer panel will be omitted. To do.

<First plate part>
A front end surface of the first plate portion 32 in the vehicle front-rear direction shown in FIG. 2 is fastened to a rear end of a part of the bumper reinforcement 16 with a bolt 35. The first plate portion 32 extends from the rear end position of the bumper reinforcement 16 toward the vehicle rear side with a length L1 in the vehicle front-rear direction. Further, a bead 33 that is recessed inward is formed on the first plate portion 32 so as to open toward the outer side in the vehicle width direction.

Since the bead 33 induces deformation (bending) of the extension 22 (side rail 14) at the time of a frontal collision of the vehicle 10, the strength of the bead 33 against the load in the vehicle front-rear direction is lower than that of other portions of the first plate portion 32. It is formed as a fragile part. As shown in FIG. 3A, the plate thickness of the first plate portion 32 is set to the first plate thickness d1. Moreover, the 1st board part 32 is comprised by the soft steel plate as an example. As described above, the first plate portion 32 is made of a soft steel plate, and the first plate thickness d1 is set so that the proof stress against a collision load input at the time of a frontal collision of the vehicle 10 becomes low.

<Second plate part>
The front end face in the vehicle front-rear direction of the second plate portion 34 shown in FIG. 2 is joined to the rear end of the first plate portion 32 by the above-described difference thickness joining. Then, the second plate portion 34 extends from the rear end position of the first plate portion 32 toward the vehicle rear side with a length L2 (>L1) in the vehicle front-rear direction. The second plate portion 34 is made of a steel plate that is harder (harder) than the first plate portion 32.

As shown in FIG. 3A, the second plate portion 34 is set to have a second plate thickness d2 that is thicker than the first plate thickness d1 of the first plate portion 32. As a result, a step 38, which will be described later, is formed in the joint portion 36 (boundary portion) formed by the difference thickness joint between the first plate portion 32 and the second plate portion 34. In the present embodiment, as an example, when the joint portion 36 is viewed from the vehicle width direction, the joint portion 36 is formed in a straight line along the vehicle vertical direction. Here, the side of the closed cross-section space of the side rail 14 is called the back side, and the outside is called the front side. As an example, the side surface 32A on the front side (inside the vehicle width direction) of the first plate portion 32 and the side surface 34A on the front side (inside the vehicle width direction) of the second plate portion 34 are arranged on the same plane. That is, the side surface 32A and the side surface 34A are aligned in the vehicle front-rear direction.

On the other hand, the side surface 32B on the back side (outer side in the vehicle width direction) of the first plate portion 32 and the side surface 34B on the back side (outer side in the vehicle width direction) of the second plate portion 34 are arranged displaced in the vehicle width direction. That is, a step 38 corresponding to a width of d2-d1 in the vehicle width direction is formed between the side surface 32B of the first plate portion 32 and the side surface 34B of the second plate portion 34. Thus, the second plate portion 34 is made of a steel plate that is harder than the first plate portion 32, and the second plate thickness d2 is thicker than the first plate thickness d1. For this reason, the proof stress against the collision load input at the time of a frontal collision of the vehicle 10 is set to be higher in the second plate portion 34 than in the first plate portion 32.

The weld bead 42 formed by joining the first plate portion 32 and the second plate portion 34 is formed so as to cover the step 38. That is, the welding bead 42 is formed on the back side (closed cross section space side) with respect to the first plate portion 32 and the second plate portion 34. Therefore, when the joint portion 36 of the first plate portion 32 and the second plate portion 34 is viewed from the vehicle width direction, the welding bead 42 is not visible (hidden).

<First Comparative Example>
FIG. 3(B) shows a vehicle body skeletal structure 200 of a first comparative example with respect to the present embodiment, in which a joint between the first plate portion 32 and the second plate portion 34 is formed by arc welding. .. In the vehicle body frame structure 200, the rear end of the first plate portion 32 and the front end of the second plate portion 34 are overlapped (wrapped) in the vehicle front-rear direction. The lap cost in the vehicle front-rear direction is W1. Therefore, an extra material for the portion corresponding to the wrap margin W1 is required, and it is difficult to reduce the weight. Further, in the vehicle body frame structure 200, the beads 202 formed by arc welding are formed on the front side (outside) of the joint portion. For this reason, there is a possibility that interference occurs between the attachment parts arranged around the extension 22 and the beads formed by arc welding.

<Second Comparative Example>
FIG. 5 shows a vehicle body frame structure 210 of a second comparative example with respect to the present embodiment, which includes a front side member 212 extending in the vehicle front-rear direction and a crash box 214 coupled to a front end portion of the front side member 212. The joint is shown. In the vehicle body frame structure 210, a flange 212A projecting in the vehicle width direction at the front end of the front side member 212 and a flange 214A projecting in the vehicle width direction at the rear end of the crash box 214 overlap in the vehicle front-rear direction. Are fastened with bolts 216. Further, a part of the flange 212A and a part of the flange 214A are joined by welding in the vehicle front-rear direction.

The total length of the two welding beads A and B in the vehicle front-rear direction is La+Lb, and the total length of the flange 212A and the flange 214A in the vehicle front-rear direction is Lc+Ld. Here, in the vehicle body frame structure 210, when a collision load is input to the crash box 214 during a frontal collision, a range corresponding to the total length La+Lb+Lc+Ld is a range that does not function as a crash stroke. In other words, in the vehicle body frame structure 210, the range corresponding to the total length La+Lb+Lc+Ld is the dead space, and it is difficult to effectively use the limited space.

[Action and effect]
Next, the operation and effect of the vehicle body frame structure 20 of this embodiment will be described.

In the vehicle body skeletal structure 20 shown in FIG. 3(A), the first plate portion 32 having the first plate thickness d1 having a small plate thickness and the second plate portion 34 having the second plate thickness d2 having a large plate thickness are input. The resistance to collision load is different. In other words, the collision performance is controlled by providing a difference in proof strength between the front portion and the rear portion of the extension 22. Therefore, at the time of a frontal collision of the vehicle 10 shown in FIG. 2, when the collision load is input to the front portion of the side rail 14, the first plate portion 32 having a low proof stress precedes the second plate portion 34. The second plate portion 34 having a high proof stress resists the collision load while being compressed and deformed and absorbing the collision energy.

Here, in the vehicle body skeleton structure 20, the first plate portion 32 and the second plate portion 34 are directly coupled, and no other member is interposed in the coupling portion 36. In other words, since the connecting portion between the crash box 214 and the front side member 212 in the above-described second comparative example (see FIG. 5) is abolished, the dead space that is difficult to deform is reduced as compared to the second comparative example. There is. Therefore, when the collision load is input, the first plate portion 32 can be deformed up to the joint portion 36. As a result, in the vehicle body frame structure 20, the crash stroke (deformation length) at the time of a frontal collision can be made longer than in the second comparative example described above in which the crash box is fastened to the frame member. In other words, the limited space of the vehicle 10 can be effectively utilized. Further, since the joint portion 36 has no bolts and nuts, the collision performance does not depend on the fastening performance of the bolts and nuts.

Further, in the vehicle body frame structure 20, the plate, bolts and nuts for connection are eliminated by eliminating the connecting portion between the crash box 214 and the front side member 212 in the second comparative example (see FIG. 5) described above. It becomes unnecessary. As a result, the vehicle 10 can be made lighter than the second comparative example. Further, since the bolts and nuts are unnecessary, the number of parts can be reduced.

Further, in the vehicle body frame structure 20, the lap allowance W1 of the above-described first comparative example (see FIG. 3B) is unnecessary. Therefore, it is possible to reduce the weight of the portion corresponding to the lap margin W1 and reduce the dead space of the crash stroke. Further, since the rear end portion of the first plate portion 32 and the front end portion of the second plate portion 34 are not wrapped in the vehicle front-rear direction, rust is less likely to occur than in the first comparative example.

In addition, in the vehicle body frame structure 20, since the weld bead formed by welding at the joint portion 36 does not float to the front side, interference between the attachment component arranged around the extension 22 in the vehicle 10 and the weld bead is suppressed. You can

(Modification)
The present invention is not limited to the above embodiment.

FIG. 4A shows a vehicle body frame structure 20 in which a cab mount bracket 52 is welded to an extension 22 as a modified example of this embodiment. The cab mount bracket 52 is overlapped and welded to the extension 22 from above in the vehicle vertical direction so as to cover the upper surface of the coupling portion 36 of the extension 22. The crash stroke in the vehicle front-rear direction in this configuration is a length L3 from the front end of the first plate portion 32 to the front end of the welding portion of the cab mount bracket 52.

In the vehicle body frame structure 20 of the modified example shown in FIG. 4B, the welding bead 54 is formed by welding the cab mount bracket 52 to the extension 22. Here, a portion having a length L4 from the front end of the cab mount bracket 52 to the front end of the welding bead 54 is a portion that is difficult to function as a crash stroke. However, the length L4 is shorter than the total length La+Lb+Lc+Ld (see FIG. 5) of the second comparative example described above. Therefore, also in the vehicle body frame structure 20 of the modified example, the crash stroke (deformation length) at the time of a frontal collision can be made longer than in the second comparative example.

(Other modifications)
The first plate portion 32 and the second plate portion 34 may have different plate thicknesses in the vehicle width direction in the vehicle front-rear direction as long as the second plate thickness d2 is greater than the first plate thickness d1. Good. Further, the first plate portion 32 and the second plate portion 34 are not limited to being harder than the first plate portion 32, and the second plate portion 34 may be formed of the same material. Further, the connecting portion 36 between the first plate portion 32 and the second plate portion 34 is not limited to being formed on the siderail inner panel 24, but may be formed on the siderail outer panel.

When viewed from the vehicle width direction, the coupling portion 36 is not limited to a linear portion along the vehicle up-down direction, but the upper portion extends along the inclination direction in which the upper portion is located on the front side or the rear side in the vehicle front-rear direction with respect to the lower portion. It may be a linear portion. Further, the connecting portion 36 is not limited to a linear shape, and may be formed in an arc shape or a step shape. Further, the joint portion 36 is not limited to a linear portion along the vehicle width direction when viewed from the vehicle vertical direction, and the left end portion is located on the front side or the rear side in the vehicle front-rear direction with respect to the right end portion. It may be a linear portion along the inclination direction.

The vehicle to which the vehicle body skeleton structure is applied is not limited to the frame vehicle such as the vehicle 10, but may be a vehicle having a monocoque structure (monocoque vehicle) in which the cabin and the skeleton member are integrated. In the monocoque vehicle, the side rails 14 described above replace the front side members. That is, the front side member of the monocoque vehicle may be used as an example of the skeletal member, and the differential thickness connection may be applied to the front side member.

Although the vehicle body skeleton structure according to the embodiment and the modified example of the present invention has been described above, the embodiment and the modified example may be appropriately combined and used, and various modes are possible without departing from the scope of the present invention. Of course, it can be implemented in.

14 Side rail (an example of skeleton member)
16 Bumper reinforcement 20 Body frame structure 32 First plate portion 34 Second plate portion 38 Step d1 First plate thickness d2 Second plate thickness

Claims (1)

The plate thickness is set to the first plate thickness, the first plate portion is connected to the bumper reinforcement and extends in the vehicle front-rear direction, and the plate thickness is set to the second plate thickness which is thicker than the first plate thickness. Rutotomoni are extended in different thickness coupled vehicle longitudinal direction at the rear end of the first plate portion as a step in the binding site is formed between the first plate portion, toward the vehicle front to the vehicle rear A pair of side rails each including a second plate portion provided with a bent portion that is bent outward in the vehicle width direction ;
A pair of cross members bridged over the front portions and the bent portions of the pair of side rails;
Car body skeletal structure having.