JP2010215062A - Bumper structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a bumper structure capable of restraining its excessive weight increase, and increasing its bending strength. <P>SOLUTION: The bumper structure 1 in its vertical section with respect to its longitudinal direction includes: a front wall part 11; a pair of vertical wall parts 12, 13 extending rearward from both the ends of the front wall part 11; and a rear wall part 14 which connects the ends in the extending direction of a pair of the vertical wall parts 12, 13, and bends at its central part so as to get close to the front wall part 11. In its vertical section with respect to its longitudinal direction, the vertical wall parts 12, 13 have depressed portions 12a, 13a depressed toward the inside of a bumper in the central portion between the front wall part 11 and the rear wall part 14. In addition, reinforcing plates 21, 22 are disposed along the bottom surfaces of the depressed portions 12a, 13a. In this case, the reinforcing plates 21, 22 are made of an aluminum flat plate which is lighter in specific gravity than the vertical wall parts 12, 13 made of steel. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a bumper structure attached to the body of an automobile.

The role of the bumper beam for automobiles is as follows: (i) It deforms itself when it collides with the collision target and absorbs impact energy at the time of collision. (Ii) The impact load is applied to the left and right side members at the time of the collision. For example, the side member can absorb the energy at the time of collision by transmitting and deforming the side member.
In particular, when a pole-shaped object collides, the bumper beam itself is required to reliably transmit the load to the side member without being greatly deformed. This is because deformation of the cabin of the automobile can be suppressed as designed.
That is, when it is assumed that a pole-shaped object collides at a high speed, the automobile bumper beam is required to have a high bending strength.

On the other hand, it is desired to reduce the weight of the bumper beam from the viewpoint of reducing the weight of the vehicle and improving the controllability of the vehicle.
That is, improvement in fuel efficiency of vehicles is desired due to stricter regulations on exhaust gas, and demands for weight reduction of vehicles are becoming strict. Further, since the bumper beam is mounted at a position far away from the center of gravity of the vehicle body, when the weight of the bumper beam increases, the inertia moment of the vehicle increases, which adversely affects the maneuverability.

  Conventionally, for example, those described in Patent Documents 1 and 2 are known as bumper beams in which the cross-sectional shape is devised from the viewpoint of impact absorption at the time of collision, weight reduction, and the like.

  Patent Document 1 discloses a bumper hose having a substantially B-shaped closed cross section manufactured by a predetermined process using a high-strength steel plate. In this configuration, it is possible to increase the cross-sectional strength as compared with a bumper line hose having a substantially D-shaped closed cross section while suppressing an increase in weight.

  In Patent Document 2, the upper wall and the lower intermediate piece constituting the B-shaped cross section are formed so as to be inclined downward, and the lower wall and the upper intermediate piece are inclined upward. A bumper main beam formed in the above is disclosed. In this configuration, the upper wall and the lower wall of the main beam are buckled in a bellows shape when the vehicle collides. For this reason, the safety of the vehicle occupant who collided and the personnel of the vehicle collided is improved.

JP 2000-334528 A JP 2006-218904 A

However, in the bumper beams described in Patent Documents 1 and 2, since the cross-sectional performance is not sufficiently exhibited due to the compression buckling of the web (wall portion extending in the front-rear direction), the bending strength is limited.
In order to suppress such a buckling of the web, it is effective to increase the thickness of the buckled portion. However, steel bumper beams for automobiles are manufactured by roll forming, so that the entire thickness of the bumper beams including the flanges is uniform. Therefore, if the web thickness is increased, the overall weight of the bumper will increase significantly in proportion to the increase in thickness, and a significant improvement in performance per weight (durability against buckling) can be expected. Absent. In this case, the result is contrary to the request for reducing the weight of the bumper.

  In view of the above circumstances, an object of the present invention is to provide a bumper structure capable of suppressing an excessive weight increase and improving bending strength.

  The first feature of the bumper structure according to the present invention is that, in a cross section perpendicular to the longitudinal direction, a front wall portion, a pair of vertical wall portions extending rearward from both ends of the front wall portion, and the pair of vertical walls And a rear wall portion that is bent so as to approach the front wall portion at an intermediate portion, and in the cross section, the vertical wall portion includes the front wall portion and the rear wall. A plate-like member having a concave portion having a linear bottom surface that is recessed inward at an intermediate portion and having a lighter specific gravity than at least the vertical wall portion is disposed along the bottom surface of the concave portion. It is that you are.

According to this configuration, since the plate-like member is disposed along the vertical wall portion, buckling of the vertical wall portion can be suppressed.
Furthermore, since the plate-like member is disposed in the recessed portion of the vertical wall portion, when the vertical wall portion is about to buckle, the vertical wall portion undergoes buckling deformation between both ends. Has the effect of stretching to prevent it. Thereby, the buckling of a vertical wall part can be suppressed more notably.
Therefore, the bending strength of the bumper structure can be significantly improved.
Moreover, since a specific gravity is lighter than a vertical wall part, a plate-shaped member can suppress an excessive weight increase.

  Moreover, the 2nd characteristic in the bumper structure which concerns on this invention is that the said plate-shaped member is aluminum or aluminum alloy.

  According to this configuration, the manufacturing cost of the bumper structure can be suppressed by using relatively inexpensive aluminum or aluminum alloy as the plate-like member.

  A third feature of the bumper structure according to the present invention is that, in the cross section, the length of the bottom surface of the recessed portion is greater than 60% of the length of the vertical wall portion, and the entire length of the bottom surface of the recessed portion. That is, the plate-like member is disposed.

  According to this configuration, the bending strength of the bumper structure can be effectively increased.

  According to the present invention, it is possible to suppress the excessive weight increase and improve the bending strength.

The perspective view which shows the bumper structure which concerns on embodiment of this invention. FIG. 2 is a cross-sectional view of the bumper structure shown in FIG. The figure which shows the analysis model of bending strength analysis 1. The figure which shows the result of bending strength analysis 1. The figure which shows the result of the bending strength analysis 2. FIG. The figure which shows typically the deformation | transformation state at the time of a collision.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.

  A bumper structure according to an embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a perspective view showing a bumper structure 1 according to an embodiment of the present invention. 2 is a cross-sectional view perpendicular to the longitudinal direction of the bumper structure 1 shown in FIG. 1 (the direction indicated by the arrow X in FIG. 1). 2 corresponds to the position of the arrow AA in FIG.

(Bumper structure)
As shown in FIG. 1, the bumper structure 1 includes a steel bumper body 10 (bumper beam) and a pair of upper and lower aluminum reinforcing plates 21 and 22.

The bumper main body 10 has a curved bow shape when viewed from above, and is formed so that the vertical cross section in the longitudinal direction is substantially B-shaped.
In addition, since the reinforcing plates 21 and 22 are disposed along the bumper body 10, the reinforcing plates 21 and 22 also have a bowed shape that is curved when viewed from above, like the bumper body 2.

  The bumper structure 1 is attached to the front part of the vehicle body. The bumper body 10 is attached to the left and right side members of the vehicle body or the crash box S (beam material extending in the longitudinal direction of the vehicle body) by welding or bolts at two left and right locations. A bumper cover (not shown) made of synthetic resin is attached so as to cover the bumper structure 1.

  In the following description, in the front-rear direction of the vehicle body (the direction indicated by the arrow Y in FIG. 1), the front side is the Y1 side, and the rear side is the Y2 side (see symbols Y1 and Y2 in FIG. 1). The Y2 side corresponds to the side (vehicle body side) approaching the vehicle body in the front-rear direction Y, and the Y1 side corresponds to the side away from the vehicle body in the front-rear direction Y. Further, in the vertical direction Z of the vehicle body (the direction indicated by the arrow Z in the figure), the upper side is the Z1 side, and the lower side is the Z2 side (see symbols Z1 and Z2 in FIG. 1).

(Bumper body)
As shown in FIG. 2, the bumper body 10 is formed by rolling a steel plate so as to have a vertically symmetrical shape, and is bent with a front wall portion 11 and a pair of vertical wall portions 12 and 13. And a rear wall portion 14. The bumper body 10 forms a closed region with the front wall portion 11, the pair of vertical wall portions 12 and 13, and the bent rear wall portion 14 in the vertical cross section in the longitudinal direction. Hereinafter, the inside of the closed region is referred to as a bumper inside, and the outside of the closed region is referred to as a bumper outside.

  In the present embodiment, the bumper body 10 is formed using a steel plate having a thickness of 1.4 mm. The length L1 in the front-rear direction of the bumper body 10 is 65 mm, and the length L2 in the vertical direction. Is 150 mm. Further, the steel material constituting the bumper body 10 has a Young's modulus of 21000 MPa, a yield point (YP) of 1200 MPa, and a density of 7874 kg / m 3.

  As shown in FIG. 2, the bumper body 10 is configured as follows in a cross section perpendicular to the longitudinal direction of the bumper body 10.

  The front wall portion 11 extends linearly in the vertical direction. It is curved in the longitudinal direction (see FIG. 1).

The vertical wall portion 12 located on the upper side extends rearwardly (Y2 side) substantially perpendicularly to the front wall portion 11 as a whole while partially bending from the upper end of the front wall portion 11. The vertical wall portion 12 has a recessed portion 12a that is recessed inside the bumper so that the bottom surface is a flat surface in the center portion in the front-rear direction.
In the present embodiment, the length La of the bottom surface (planar portion) of the recess 12a in the front-rear direction is formed to be about 2/3 of the length L1 of the bumper body 10 in the front-rear direction. Yes.

Further, the vertical wall portion 13 located on the lower side is vertically symmetric with the vertical wall portion 12. In other words, the bumper body 10 is formed symmetrically with the vertical wall portion 12 with respect to a surface passing through the center in the vertical direction.
Specifically, the vertical wall portion 13 extends backward (Y2 side) substantially perpendicularly to the front wall portion 11 as a whole while partially bending from the lower end of the front wall portion 11. At the center of the direction, there is a recess 13a that is recessed inward of the bumper so that the bottom surface is a flat surface.

The rear wall portion 14 is a wall portion that connects the rear end portions of the pair of vertical wall portions 12 and 13. The rear wall portion 14 is bent so as to approach the front wall portion 11 at the central portion in the vertical direction.
Specifically, the rear wall portion 14 includes a first rear wall 14a, a second rear wall 14b, a third rear wall 14c, a fourth rear wall 14d, and a fifth rear wall 14e.

The first rear wall 14 a linearly extends downward (Z2 side) substantially perpendicularly to the vertical wall portion 12 from the rear end portion of the vertical wall portion 12.
The fifth rear wall 14e extends linearly from the rear end of the vertical wall portion 13 upward (Z1 side) substantially perpendicular to the vertical wall portion 13.
The second rear wall 14b extends linearly from the lower end of the first rear wall 14a to the front (Y1 side) substantially perpendicular to the first rear wall 14a.
The fourth rear wall 14d extends linearly from the upper end of the fifth rear wall 14e to the front (Y1 side) substantially perpendicularly to the fifth rear wall 14e.
The third rear wall 14c is a wall that connects the front end portion of the second rear wall 14b and the front end portion of the fourth rear wall 14d, and extends linearly in parallel with the front wall portion 11.

  In addition, the connection part between the front wall part 11, the vertical wall parts 12 and 13, and the 1st rear wall 14a-the 5th rear wall 14e becomes circular arc shape of a predetermined radius.

  In the present embodiment, the length (L3, L4 in FIG. 2) of the first rear wall 14a and the fifth rear wall 14e in the vertical direction Z is 52 mm, respectively, and the vertical direction of the third rear wall 14c. The length in Z (L5 in FIG. 2) is 46 mm.

(Reinforcement plate)
The reinforcing plates 21 and 22 are flat plates made of aluminum, and are attached to the surfaces of the vertical wall portions 12 and 13 facing the outside of the bumper, respectively. The reinforcing plates 21 and 22 are provided so as to overlap the bottom surfaces of the recessed portions 12a and 13a of the vertical wall portions 12 and 13 so as to extend over the entire lengthwise direction of the bumper body 10, respectively. The reinforcing plates 21 and 22 are attached to the vertical wall portions 12 and 13 by bonding.

  In the present embodiment, the plate thickness of the reinforcing plates 21 and 22 is 2.0 mm, which is larger than the plate thickness of the bumper body 10. Further, the Young's modulus of aluminum constituting the reinforcing plates 21 and 22 is 6900 MPa, the yield point (YP) is 310 MPa, and the density is 2700 kg / m 3.

As shown in FIG. 2, the reinforcing plates 21 and 22 are configured as follows in a cross section perpendicular to the longitudinal direction of the bumper body 10.
The reinforcing plates 21 and 22 are formed so that the length in the front-rear direction is substantially equal to the length La of the bottom surface of the recesses 12a and 13a in the front-rear direction.
Further, the thickness of the reinforcing plate 21 is thinner than the depth of the recess 12a. That is, the concave portion 12a has a bottom surface that is at least the thickness of the reinforcing plate 21 at least more than the thickness of the reinforcing plate 21 than the uppermost portion of the vertical wall portion 12 (the tip of the convex portion positioned before and after the concave portion 12a). It is formed by bending the vertical wall portion 12 so as to be located at the position. Therefore, the surface (upper surface) facing the bumper outside of the reinforcing plate 21 is positioned below the upper end of the bumper body 10. Similarly, the surface (lower surface) of the reinforcing plate 22 facing the bumper outside is located above the lower end of the bumper body 10. That is, the reinforcing plates 21 and 22 are provided at positions that are hidden behind the bumper body 10 and cannot be seen when the bumper structure 1 is viewed from the front.

(Bending strength analysis 1)
Next, the evaluation result of the bending strength in the bumper structure will be described. Here, the bending strength of the bumper structure was calculated using four types of bumper structures 100. Specifically, as shown in FIG. 3 (a), while supporting both longitudinal ends of the bumper structure 100 from the rear side (Y2 side) with columnar supports S1 and S2 extending in the vertical direction Z, The bending strength of the bumper structure 100 is determined by a three-point bending analysis in which the central portion in the longitudinal direction of the bumper structure is pressed from the front side (Y1 side) to the rear side (Y2 side) with a cylindrical indenter P extending in the vertical direction Z. Calculated.

The analysis models used as the bumper structure 100 are the following four types (1) to (4).
(1) ... Bumper structure corresponding to the bumper structure 1 of the present embodiment (however, a structure that is not curved in the longitudinal direction but extends linearly)
(2) In the model of (1), the reinforcing plates 21 and 22 are made of steel (the same material as the bumper body 10) (3) In the model of (1), the dents 12a, 13a is eliminated, the vertical wall portions 12 and 13 are flattened, and the reinforcing plates 21 and 22 are removed (see FIG. 3B).
(4) ... In the model of (3), the thickness of the steel forming the bumper body is changed to 2.0 mm

Table 1 shows the thickness of the bumper body (steel plate), the material of the reinforcing plate, the thickness of the reinforcing plate, the weight ratio of the bumper structure, and the maximum bending moment ratio obtained by the analysis. The weight ratio and the maximum bending moment ratio of the bumper structure indicate the ratio when the weight and the maximum bending moment of the model shown in the above (3) are used as the reference (1.0). FIG. 4 is a graph showing the relationship between the weight ratio shown in Table 1 and the maximum bending moment ratio.
In addition, the code | symbol (1)-(4) in Table 1 and FIG. 4 respond | corresponds to (1)-(4) of the said model.

  From the graph of FIG. 4, compared to the bumper structure (2) in which the bumper body is reinforced with steel or the bumper structure (4) in which the thickness of the bumper body is increased, the bumper corresponding to this embodiment reinforced with an aluminum material. It can be seen that the structure (1) has a larger increase in the maximum bending moment relative to the weight increase from the reference bumper structure (3).

(Bending strength analysis 2)
Next, the result of analyzing the influence of the length of the bottom of the recesses 12a and 13a on the bending strength will be described. Here, the bending strength of the bumper structure was calculated in the same manner as in the bending strength analysis 1 using three types of bumper structures having different bottom lengths La of the recesses 12a and 13a.

The analysis models used as the bumper structure 100 are the following three types (1a) to (3a).
(1a): A bumper structure corresponding to the bumper structure 1 of the present embodiment (the same as (1) in the model of the bending strength analysis 1). In this configuration, the value of “the length La of the bottom of the recesses 12a and 13a / the length L1 in the front-rear direction of the bumper body 10” (hereinafter referred to as “La / L1” at the end) is about 0. .62.
(2a) ... In the model (1a), La / L1 is about 0.54. (3a) ... In the model (1a), La / L1 is about 0.46.

  In both models (2a) and (3a), the length of the reinforcing plate is the same as the length La of the bottom surface of the recess in the longitudinal vertical cross section, as in the model (1a). Moreover, a dent part is located in the center of the front-back direction in a vertical wall part.

Moreover, the plot points on the alternate long and short dash line shown by reference numerals (1a) to (3a) in FIG. 5 correspond to the models (1a) to (3a), respectively. Moreover, the plot points in the black triangles in FIG. 5 indicate the values of the maximum bending moment ratio (left vertical axis) of the models (1a) to (3a), and the plot points in the white triangles are The La / L1 values (right vertical axis) of the models (1a) to (3a) are shown.
5 is a straight line connecting the plot points of the analysis results (maximum bending moment ratio) of the models (3) and (4) in FIG. 4 (above bending strength analysis 1). That is, the straight line B in FIG. 5 shows the characteristic (maximum bending moment ratio) when the thickness of the steel plate is changed in the bumper structure (see FIG. 3B) formed of only steel.
As with the analysis result graph shown in FIG. 4, the weight ratio (horizontal axis) and the maximum bending moment ratio (vertical axis) of the bumper structure shown in FIG. The ratio when the weight and the maximum bending moment of the base are taken as the standard (1.0).

  From the graph of FIG. 5, in the analysis of the above models (1a) to (3a), the maximum bending moment ratio for the bumper structures (2a) and (3a) in which the value of La / L1 is smaller than 0.60 is It is almost equivalent to a bumper structure made of steel only (compared with the same weight). And about the bumper structure (1a) whose value of La / L1 is larger than 0.60, the largest bending moment ratio becomes larger than the bumper structure formed only with steel materials (it compares with the same weight).

  Further, the amount of increase in the maximum bending moment with respect to the increase in unit weight (the slope of the graph) is such that the value of La / L1 is 0 as compared with the case where the value of La / L1 is in the range of about 0.46 to 0.54. It is significantly larger when it is in the range of .54 to 0.62. In any range, the inclination of the graph is larger than the inclination of the straight line B indicating the characteristics of the bumper structure made of only steel.

(Effect of this embodiment)
(1)
As described above, the bumper structure 1 includes, in a cross section perpendicular to the longitudinal direction, the front wall portion 11, the pair of vertical wall portions 12, 13 extending rearward from both ends of the front wall portion 11, and the pair of vertical walls. A rear wall portion that connects end portions in the extending direction of the wall portions 12 and 13 and bends so as to approach the front wall portion 11 at the center portion.
And in the cross section perpendicular | vertical with respect to a longitudinal direction, the vertical wall parts 12 and 13 have the recessed parts 12a and 13a dented inside a bumper in the center part of the front wall part 11 and the rear wall part 14. FIG. Yes.
Further, reinforcing plates 21 and 22 (plate-like members) made of flat aluminum plates having a lighter specific gravity than the vertical wall portions 12 and 13 made of steel are arranged along the bottom surfaces of the recessed portions 12a and 13a.

According to this configuration, since the reinforcing plates 21 and 22 are disposed along the vertical wall portions 12 and 13, buckling of the vertical wall portions 12 and 13 can be suppressed. Thereby, the bending strength of the bumper structure 1 can be improved.
Further, when the bumper body 10 is deformed by a collision load acting on the front wall portion 11 of the bumper structure 1, as shown in FIG. 6, the reinforcing plates 21 and 22 are longitudinal walls so as to suppress deformation. Since both end portions of the portions 12 and 13 are stretched substantially parallel to the collision direction, the buckling of the vertical wall portions 12 and 13 can be more significantly suppressed. Thereby, the bending strength of the bumper structure 1 can be remarkably improved.
Moreover, since the specific gravity of the reinforcement plates 21 and 22 (aluminum) is lighter than the bumper main body 10 (steel), an excessive weight increase can be suppressed.
Further, since the reinforcing plates 21 and 22 are provided on the surface of the bumper body 10 on the outer side of the bumper, they are less difficult to manufacture than the case where the reinforcing member is provided on the inner side of the bumper, and can be easily installed.

(2)
In the bumper structure 1, the vertical wall portions 12 and 13 are made of steel, and the reinforcing plates 21 and 22 are made of aluminum.

  According to this configuration, the manufacturing cost of the bumper structure 1 can be suppressed by using relatively inexpensive aluminum as the reinforcing plates 21 and 22. Even if an aluminum alloy is used as the reinforcing plate, the same effect can be obtained.

(3)
In addition, in the cross section perpendicular to the longitudinal direction, the length of the bottom surfaces of the recessed portions 12a and 13a is about 2/3 of the length of the vertical wall portions 12 and 13, and the bottom surface of the recessed portions 12a and 13a is The reinforcing plates 21 and 22 are arranged over the entire length.

  Here, as shown in FIG. 5, the bending strength is effectively increased by making the length of the reinforcing plates 21 and 22 in the front-rear direction larger than 60% of the length of the vertical wall portions 12 and 13 in the front-rear direction. However, according to the configuration of the bumper structure 1, the length of the reinforcing plates 21 and 22 in the front-rear direction is larger than 60% of the length of the vertical wall portions 12 and 13 in the front-rear direction. The bending strength can be significantly improved.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made as long as they are described in the claims.

(Modification)
(1) The reinforcing plates 21 and 22 are not limited to those made of aluminum or aluminum alloy, and may be formed of other metal materials.

(2) The reinforcing plates 21 and 22 are not limited to being attached to the bumper body 10 by bonding, and may be attached using welding, rivets, or bolts.

  The present invention can be used as a bumper structure attached to the body of an automobile.

DESCRIPTION OF SYMBOLS 1 Bumper structure 11 Front wall part 12,13 Vertical wall part 12a, 13a Recessed part 14 Rear wall part 21,22 Reinforcement board (plate-shaped member)

Claims (3)

In the cross section perpendicular to the longitudinal direction, the front wall portion, the pair of vertical wall portions extending rearward from both ends of the front wall portion, and the extending direction end portions of the pair of vertical wall portions are coupled to the intermediate portion. And a rear wall portion bent so as to approach the front wall portion,
In the cross section, the vertical wall portion has a concave portion having a linear bottom surface that is recessed inward at an intermediate portion between the front wall portion and the rear wall portion, and extends along the bottom surface of the concave portion. A bumper structure in which a plate-like member having a lighter specific gravity than at least the vertical wall portion is disposed. The bumper structure according to claim 1, wherein the plate-shaped member is aluminum or an aluminum alloy. In the cross section, the length of the bottom surface of the recessed portion is larger than 60% of the length of the vertical wall portion, and the plate-like member is disposed over the entire length of the bottom surface of the recessed portion. The bumper structure described in 1.

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