JP2002053076A - Front side member structure of vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a front side member from being deformed when a vehicle comes into collision. SOLUTION: In this front side member structure, a kick part 11 bent diagonally down is formed in the intermediate position of right and left side members 1, a member rear half part 12 behind the kick part 11 is positioned lower than a member front half part 10 ahead the kick part 11, a sub frame 2 is arranged below the member front half part 10, the front end is connected to the front end lower surface side of the member front half part, and the rear end is connected to the front end lower surface side of the member rear half part 12. The level difference X1 between the member front half part 10 and the member rear half part 12 is set smaller than the level difference X2 between the member rear half part 12 and the sub frame 2, and moment in the opposite direction acting on the front end of the member rear half part 12 from the member front half part 10 side and the sub frame 2 side in a collision of the vehicle is made to balance and offset.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a front side member structure of a vehicle, and more particularly, to a front side member structure provided with a subframe below a front half of the member.

[0002]

2. Description of the Related Art FIGS. 5 and 6 show a front side member structure conventionally used in a wagon vehicle or the like. A left and right front side member 1A extending in the vehicle front-rear direction includes a member front half in an engine room. The rear end 10 is bent obliquely downward and rearward from the rear end, and a rear half 12 of the member lower than the front half 10 of the member extends rearward along the lower surface of the passenger compartment floor from the stepped kick portion 11. ing. The front terminals of the left and right front side members 1A are connected by a front cross member 3.

The front side member 1A has an engine, a suspension, etc. (not shown) below the front half 10 of each member.
Is provided. The left and right sub-frames 2 have cross frames 21 and 22 between the front end and the rear end, respectively, and are connected in a grid pattern. The sub-frame 2 has its front end fastened to a mounting portion 13 projecting downward from the lower surface of the front end of the member front half 10 via a mounting member 4, and its rear end connected to the front lower surface of the member rear half 12 via a mounting member 4. Fastened and mounted almost horizontally.

In this type of front side member structure, when a large collision load F is input to the front side member 1A via the front cross member 3 at the time of a vehicle frontal collision, this portion extends from the kick portion 11 to the front end of the rear half portion 12 of the member. Bending deformation that is lifted obliquely rearward and upward (in the direction of arrow Y1) occurs.

Therefore, conventionally, the front side member 1A
7 and 8, the kick portion 1 having a substantially U-shaped cross section, which forms a closed cross section with the floor panel 5, in order to enhance the rigidity of the
A plurality of reinforcements 61, 62, 63, 64, 65 are provided in each of the member 1 and the rear half portion 12, so that the wall surface has a laminated structure or a closed section is divided.

[0006]

However, in such a reinforcing structure, the weight of the front side member 1A increases, and a plurality of reinforcements must be prepared and welded to the front side member 1A. The cost is high. SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to reduce the weight and cost of the front side member and to prevent or minimize the deformation of the front side member at the time of a vehicle collision.

[0007]

According to the present invention, a kick portion is formed at a longitudinally intermediate position between left and right front side members extending in a vehicle front-rear direction and bent obliquely rearward and downward. The rear half of the member at the rear of the kick portion is set at a low position, and a subframe extending in the front-rear direction is disposed below the front half of the member, and the front end is located on the lower surface of the front end of the front half of the member. In a front side member structure in which ends are connected to a front end lower surface of the rear half of the member, a height difference between the front half of the member and the rear half of the member is determined by a height between the rear half of the member and the subframe. Set smaller than the difference.

In the conventional structure shown in FIG. 6, when a collision load F is inputted via the front cross member 3 at the time of a vehicle frontal collision, the collision load F is changed to a load F1 on the member front half 10 side.
And the load F2 on the subframe 2 side, and the load F1
Is applied to the rear half portion 12 of the member via the kick portion 11 and the load F2
Acts on the rear half portion 12 of the member via the connecting portion at the rear end of the subframe 2.

In this case, a moment M1 (= F1 · x1) in the direction of the arrow Y1 is formed in a portion from the kick portion 11 to the front end of the member rear half portion 12 due to a height difference x1 between the member front half portion 10 and the member rear half portion 12. Works. Further, a moment M2 (= F2 · x2) in the direction of the arrow Y2 opposite to the direction of the arrow Y1 acts on the front end of the member rear half 12 due to the height difference x2 between the member rear half 12 and the subframe 2.

However, the load F1 on the front half portion 10 of the member to which the collision load F directly acts is larger than the load F2 on the subframe 2 side. Moreover, conventionally, the height difference x1> x2
, The moment M1> M2.
Therefore, when the collision load F is large and the moment M1-M2 exceeds the proof stress of the front side member 1A, the bending deformation occurs from the kick portion 11 to the rear half portion 12 of the member.

The present invention has been made by paying attention to this fact, and the above-mentioned bending deformation is prevented by balancing and canceling moments M1 and M2 for setting the height difference x2> x1 and reversing the directions. is there. Therefore, it is not necessary to attach a large number of reinforcing members to the front side member as in the conventional structure.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. 1, a pair of left and right front side members 1 (only one of them is shown in the figure) extending in the front-rear direction of a vehicle includes a member front half 10 in an engine room and a vehicle. It is connected to a rear half member 12 extending rearward along the lower surface of the room floor. The connecting portion between the member front half 10 and the member rear half 12 forms a kick portion 11 that is bent stepwise obliquely downward and rearward from the rear end of the member front half 10, and the member rear half 12 is connected to the member front half 10. Is low.

At the front end of the front side member 1, a rectangular tubular crash box 15 is provided at the front end of the front half portion 10 of the member. In the event of a light frontal collision of the vehicle, the crash box 15 is compressed and deformed in the axial direction to collide. It is designed to absorb the load. The front end surfaces of the crash boxes 15 of the left and right front side members 1 are connected by a front cross member 3 extending in the vehicle width direction.

At a position below the front side member 1,
A sub-frame 2 is provided extending in the front-rear direction from the lower front end of the member front half 10 to the lower front end of the member rear half 12. The sub-frame 2 has a rectangular closed cross-section structure, extends obliquely downward and rearward from the front end, further extends rearward linearly, and has a rear end slightly higher than the linear portion. A pair of left and right sub-frames 2 are provided below the left and right front side members 1 (only one of them is shown in the figure). The left and right sub-frames 2 have cross-frames (not shown) between front ends and rear ends. And are connected in a girder shape.

The sub-frame 2 has its front end fixed to the lower surface of a box-shaped mounting portion 13 projecting downward from the lower surface of the front end of the member front half portion 10 via a mounting member 4 with bolts. The rear end is bolted and fixed via a mounting member 4 to the lower surface of a box-shaped mounting portion 14 projecting downward from the lower surface of the front end of the rear half portion 12 of the member. The straight part of the subframe 2 is the first half of the member
It is almost parallel to 0.

[0016] Front side member 1 and subframe 2
Is a height difference x1 between the center axis of the member front half 10 and the center axis of the member rear half 12, and the height difference between the center axis of the member rear half 12 and the center axis of the linear portion of the subframe 2. x
2 (x1 <x
2). In practice, the member first half 10 and the subframe 2
Is approximately the same size as that of the conventional structure,
The height difference x1 is made smaller than that of the related art, and as a result of the height of the rear half portion 12 of the member being increased, the mounting portion 14 is provided to increase the height difference x2. For example, the height difference x1 is about 127 mm, and the height difference x2 is about 234 mm.

As shown in FIG. 2, the front half member 10 of the front side member 1 comprises an inner panel 1a having a substantially U-shaped cross section and an outer panel 1b having a substantially flat plate-like shape. With the combined closed cross section structure,
Inside the front half 10 of the member, there is a reinforcement 6 having a substantially U-shaped cross section along the inner surface of the inner panel 1a.
0 is overlapped and reinforced.

As shown in FIG. 1, the kick portion 11 is formed by fitting and welding a front end of a rear half portion 12 of the member bent obliquely forward and upward to a rear end of a front half portion 10 of the member bent obliquely rearward and downward. I have. The rear half 12 of the member is made of a steel material 1c having a substantially U-shaped cross section. As shown in FIG. 3, in the kick portion 11, the reinforcement 6 having a substantially U-shaped cross section along the inner surface of the bottom wall and the inner surfaces of the left and right side walls of the steel material 1c.
1 is provided, and the left and right upper edge flanges of the steel material 1c are welded to the lower surface of the floor panel 5 of the passenger compartment to form a closed cross section.
A reinforcement 63 is provided between the upper ends of the left and right side walls of FIG.

As shown in FIG. 4, a general portion of the rear half portion 12 of the member is formed by connecting upper left and right upper flanges of the steel member 1c to a lower surface of the floor panel 5 integrally with a reinforcement 65 extending in the width direction therebetween. To form a closed section.

At the time of a frontal collision of the vehicle, a large collision load F is applied to the front side member 1 via the front cross member 3.
Is input, the load that could not be absorbed by the compression deformation of the crash box 15 becomes the load F1 on the member front half 10 side.
And the load F2 on the sub-frame 2 side input to the sub-frame 2 via the mounting portion 13, the load F1 is applied to the rear half portion 12 of the member via the kick portion 11, and the load F2 is applied via the mounting portion 14. Acts on the rear half 12 of the member. In this case, the load F1 on the member front half 10 on which the collision load acts directly is larger than the load F2 on the subframe 2 side which acts indirectly (F1> F2).

An arrow Y represented by the product of the load F1 and the height difference x1 between the member front half 10 and the member rear half 12 is provided between the kick portion 11 and the front end of the member rear half 12.
Moment M1 in one direction (= F1 · x1) acts.
Further, at the front end of the rear half portion 12 of the member, a moment M2 (= F2) in the direction of the arrow Y2 opposite to the moment M1 is represented by the product of the load F2 and the height difference x2 between the rear half portion 12 of the member and the subframe 2. X2) acts.

In the front side member 1, the height difference x1 between the member front half 10 and the member rear half 12 is relatively smaller than the height difference x2 between the member rear half 12 and the subframe 2, so that the moment M1, The size of M2 can be approximated. As a result, the moments M1, acting in opposite directions to the front end of the member rear end 12
Since M2 cancels each other, bending deformation of the front end of the rear end portion 12 of the member is prevented. Therefore, the front side member 1 does not need to provide a large number of reinforcements in the kick part 11 and the rear half part 12 of the member as in the conventional structure (FIGS. 6 and 7) to enhance the rigidity against bending deformation. Only by providing the minimum necessary reinforcements 61, 63, 65 shown in FIG. 4, sufficient rigidity can be secured, and the weight and cost of the front side member 1 can be reduced.

[0023]

According to the front side member structure of the present invention, opposing moments acting on the front end of the rear half of the member from the front half of the member and from the subframe during a vehicle collision are balanced. ,
Bending deformation of the portion from the kick portion to the front end of the rear half of the member can be effectively prevented with a smaller number of reinforcing members as compared with the conventional structure.

[Brief description of the drawings]

FIG. 1 is a side view of a main part of a front side member structure of a vehicle according to the present invention.

FIG. 2 is a sectional view taken along a line II-II in FIG.

FIG. 3 is a sectional view taken along a line III-III in FIG. 1;

FIG. 4 is a sectional view taken along a line IV-IV in FIG. 1;

FIG. 5 is a schematic view showing a skeletal structure of a front part of a vehicle body of the wagon vehicle.

FIG. 6 is a side view of a main part of a front side member structure of a conventional vehicle.

FIG. 7 is a sectional view taken along a line VII-VII in FIG. 6;

8 is a cross-sectional view taken along a line VIII-VIII in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Front side member 10 Member front half 11 Kick part 12 Member rear half 13, 14 Mounting part 2 Subframe F Impact load F1 Member front half side load F2 Subframe side load x1 Height of member front half and member rear half Difference x2 Height difference between the second half of the member and the subframe

Claims (1)

[Claims] 1. A kick portion which bends obliquely downward and rearward at an intermediate position in the longitudinal direction between left and right front side members extending in the vehicle front-rear direction, and a member at the rear of the kick portion relative to a front half of the member at the front of the kick portion. A rear frame is provided at a lower position, and a sub-frame extending in the front-rear direction is disposed below the front half of the member. The front end of the sub-frame is located at the front lower surface of the front half of the member, and the rear end is the front end of the rear half of the member. In the front side member structure respectively connected to the lower side,
A front side member structure for a vehicle in which a height difference between the member front half and the member rear half is set smaller than a height difference between the member rear half and the subframe.