JP2012011836A - Energy absorbing member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lightweight energy absorbing member by increasing the energy absorbing amount per weight.SOLUTION: The energy absorbing member includes a cylindrical body 6 to be deformed by an impact compression load in the axial direction. The cylindrical body 6 is formed with three to ten inward bent parts 7, which are bent inward in the radial direction, with intervals in the circumferential direction, and these inward bent parts 7 are each formed by crossing two sides 9 at 88°-92°, and an interval between each inward bent part 7 is formed by an arc-like wall part 8 protruding outward in the radial direction. When plate thickness is t mm and width of each side 9 of the inward bent part 7 is D mm, the plate thickness and the width of each side are set to satisfy an expression 2.3t-3t+15≤D≤2.3t-3t+16.5.

Description

  The present invention relates to an energy absorbing member that can absorb impact energy generated when a vehicle collides.

In order to protect passengers in the cabin in the event of a vehicle collision, an energy absorbing member is provided on a body frame such as a side member extending in the front-rear direction of the vehicle. The energy absorbing member is set to have a lower deformation load with respect to the impact compression load in the axial direction than the vehicle body frame, and is transmitted to the cabin by being buckled and deformed in a bellows shape by the impact energy generated when the vehicle collides. Impact energy can be reduced and passengers in the cabin can be protected.
Conventionally, for example, Patent Documents 1 to 3 include such energy absorbing members.

  In the energy absorbing member described in Patent Document 1, the cross-sectional shape of the cylindrical body constituting the shock absorbing member is a closed cross section having a plurality of vertices. The basic cross section consisting of the maximum contour obtained by connecting a part of them with a straight line is a convex polygon, and the entire area of at least one side of the convex polygon passes through the inside of the convex polygon. The structure is formed in a straight line. By adopting such a structure, it is possible to secure a long amount of displacement (stroke) until bottoming occurs, thereby stably securing the amount of absorption of impact energy. This energy absorbing member is made of steel.

  The energy absorbing member described in Patent Document 2 has cutout portions at four corners of a basic rectangular cross section, and has a cross-shaped closed cross section as a whole. And, the thickness of the notch at the corner is thicker than the thickness of the portion other than the notch, or the hardness of the notch is harder than the hardness of the portion other than the notch, Thereby, even if the member mass per unit length is the same, the amount of energy absorption can be increased and the bending strength performance can be improved. This energy absorbing member is also made of steel.

  The energy absorbing member described in Patent Document 3 has a substantially cross-shaped closed section (substantially cross-box shape), similar to that described in Patent Document 2. And the length of each side of the roughly rectangular convex part that protrudes in the four directions of up, down, left and right is set to be almost equal, and the angle formed by the corners between each side is also set to be almost right angle Has been. As a result, the section modulus can be increased not only in the vertical direction in the vertical direction but also in the horizontal direction in the vehicle width direction, and the rigidity in the horizontal direction can be increased. For example, when an offset load in the vehicle width direction is applied. However, it is said that it can be prevented from falling and deforming.

Japanese Patent No. 4375239 Japanese Patent No. 3854812 JP 2009-83686 A

  By the way, under the demand for weight reduction, energy saving members are also considered to use light metal such as aluminum alloy instead of steel, and to reduce the wall thickness in order to save space and weight. In addition, even a small weight is required to have a large energy absorption amount. Each energy absorbing member described in each patent document has a limit in weight reduction.

  This invention is made | formed in view of the said situation, and aims at provision of the energy absorption member which can enlarge the energy absorption amount per weight and can aim at weight reduction.

The energy absorbing member of the present invention is an energy absorbing member having a cylindrical body that is deformed by an impact compression load in the axial direction, and the cylindrical body has an inward bent portion that is bent inward in the radial direction in the circumferential direction. 3 to 10 are formed at an interval, and these inwardly bent portions intersect two sides at an angle of 88 ° to 92 °, and each inwardly bent portion is radially outward. If the plate thickness is tmm and the width of each side of the inwardly bent portion is Dmm, the plate thickness and the width of each side are 2.3 t ^2. -3t + 15 ≦ D ≦ 2.3t ² −3t + 16.5 is set.

  By adopting such a shape, the cylindrical body has a generally circular or elliptical outer shell as a whole, and these arc-shaped wall portions are subjected to an impact compression load. The drum is deformed into a drum shape with respect to the force to expand the diameter of the wire and exhibits resistance. On the other hand, each inwardly bent portion buckles in a bellows shape when two sides receive an impact compression load. In this case, since the angle formed by each side of the inwardly bent portion is set to 88 ° to 92 °, the bellows-like buckling deformation can be appropriately generated by alternately folding each side. it can.

When the width dimension of both sides exceeds (2.3t ² −3t + 16.5) in relation to the plate thickness, the bellows-like deformation becomes large, and energy absorption becomes intermittent. Further, if the width of the side is large, the weight increases and the weight reduction is impaired. On the other hand, if it is less than (2.3t ² −3t + 15), the side width is too small and the energy absorption becomes insufficient.
The number of inwardly bent parts is set according to the balance between the energy absorption capacity due to the bellows-like deformation and the resistance force due to the drum-like deformation of the arcuate wall part. 10 to 10 is preferable, and 4 to 8 is more preferable.
By setting it as such a shape, use of light metals, such as an aluminum alloy, becomes possible, and weight reduction can be achieved.

In the energy absorbing member of the present invention, the thickness of the cylindrical body is preferably 1.0 mm to 2.0 mm.
For weight reduction, the energy absorption ability by the shape of an inward bending part and an arc-shaped wall part can be effectively exhibited, so that it is formed thinly and becomes thin.

In the energy absorbing member of the present invention, the arc-shaped wall portion may be formed along one circle.
As each arcuate wall, a part of a circle, a part of an ellipse, etc. can be applied, but each arcuate wall is formed along one circle so that the entire cylinder is basically a circle. Then, it has a large resistance against the force that is pushed outward in the radial direction, and the amount of energy absorption can be increased.

  According to the energy absorbing member of the present invention, when receiving an impact compressive load, the inwardly bent portion is buckled and deformed in a bellows shape, and the arc-shaped wall portion is deformed in a drum shape to absorb the impact energy. In this case, by appropriately setting the number and dimensions of the inwardly bent portions, the amount of energy absorbed per weight can be increased, and the weight can be reduced.

It is the perspective view which made the attachment plate of the energy absorption member in one Embodiment of this invention the transparent state. It is an end view of the cylinder of the energy absorption member of FIG. It is a schematic diagram which shows the example of attachment structure to the vehicle body frame of the energy absorption member of FIG. It is the graph which showed the relationship between the ratio of the energy absorption amount per unit weight with respect to a square cylinder, and the width | variety of a side in the Example and comparative example of this invention. In the Example of this invention, it is the graph which showed the relationship between the ratio of the energy absorption amount per unit weight with respect to a square cylinder, and the number of inward bending parts about different board thickness. It is the graph which showed the relationship between the width | variety of the edge | side for every various board thickness, and the energy absorption amount per unit weight among the Examples of this invention. In the Example of this invention, it is the graph which showed the relationship between the plate | board thickness which makes the energy absorption amount per unit weight peak, and the width | variety of a side.

Hereinafter, embodiments of an energy absorbing member according to the present invention will be described with reference to the drawings.
As shown in FIG. 3, the energy absorbing member 1 is provided between the tip of the side member 2 of the vehicle body frame and the bumper reinforcement 3, and between the side members 2 and the mounting plates 4, 5 to the bumper reinforcement 3. A cylindrical body 6 along the axial direction of the side member 2 is integrally provided.
In addition, in the example shown in FIG. 3, since it is attached to the inclined part of the bumper reinforcement 3, one end part of the cylindrical body 6 is formed obliquely, and the attachment plate 5 is also inclined according to the attachment part of the bumper reinforcement 3. Although it is arranged, depending on the attachment position, as shown in FIG. 1, both ends of the cylindrical body 6 may be formed in a direction orthogonal to the axial direction, and the attachment plates 4 and 5 may be provided in parallel to each other. Hereinafter, unless otherwise noted, description will be made assuming that both ends of the cylindrical body 6 are parallel.

As shown in FIGS. 1 and 2, the cylindrical body 6 has a shape in which a plurality of locations along the circumferential direction of the cylinder are bent inward in the radial direction. A plurality of inwardly bent portions 7 are formed at intervals in the circumferential direction, and a space between each inwardly bent portion 7 is an arcuate wall portion 8 constituting a part of a cylinder. The number of inwardly bent portions 7 is preferably 3 to 10. In the illustrated example, eight inwardly bent portions 7 are formed at equal intervals in the circumferential direction, and these are connected by an arcuate wall portion 8 that protrudes outward in the radial direction.
Each arcuate wall 8 is formed to have the same cross-sectional shape by setting the same radius of curvature and width to each other, so that the center of curvature of each arcuate wall 8 coincides with the center C of one circle. Is arranged.
Mounting plates 4 and 5 are provided at both ends of the cylindrical body 6.

  Each inwardly bent portion 7 is formed in a V-shaped cross section in which two sides 9 intersect at an angle θ1 of 88 ° to 92 °. The inwardly bent portions 7 are formed in the same cross-sectional shape, and the two sides 9 constituting each inwardly bent portion 7 are formed in the same width dimension D. Therefore, the angles θ2 formed by the sides 9 of the inward bent portions 7 and the tangent lines of the arcuate wall portion 8 are all the same angle.

Specifically, the cylinder body 6 is made of an aluminum alloy of JIS series 6000 or 7000, the diameter (diameter of a circle formed by continuously connecting the arcuate wall portion 8) is 80 mm to 120 mm, and the plate thickness is 1.0 mm to 2.0 mm. Among these, the width Dmm of each side 9 of the inward bending portion 7 is set to have a relationship of 2.3t ² −3t + 15 ≦ D ≦ 2.3t ² −3t + 16.5 with respect to the plate thickness tmm. . When the plate thickness is in the range of 1.0 mm to 2.0 mm, the width D of each side 9 of the inward bending portion 7 is set in the range of 14.3 mm to 19.7 mm.

  The energy absorbing member 1 having such a shape is fixed between the side member 2 and the bumper reinforcement 3 by the mounting plates 4 and 5 with the axial direction of the cylindrical body 6 aligned with the axial direction of the side member 2. Is done. When an impact compressive load is applied in the axial direction due to the collision of the vehicle, the cylindrical body 6 is buckled and deformed in a bellows shape (accordion shape) in the axial direction, thereby absorbing impact energy and a cabin (not shown). Reduce the impact energy transmitted to the.

At this time, the arc-shaped wall portions 8 of the cylindrical body 6 are arranged at equal intervals in the circumferential direction, and constitute a circular outer shell as a whole, and force to expand the diameter when receiving an impact compression load. It is deformed into a drum shape and shows resistance.
On the other hand, each inwardly bent portion 7 buckles in a bellows shape when the two sides 9 receive an impact compression load. In this case, since the angle θ1 formed by each side 9 of the inward bending portion 7 is set to 88 ° to 92 °, the bellows-like buckling deformation is appropriately folded so as to be alternately folded on each side 9. Can be generated. The angle θ1 formed by both sides 9 is most preferably 90 °.

If the angle θ1 exceeds 92 °, the two sides 9 are too open, and there is a possibility that the two sides 9 may be deformed in the same direction without being folded alternately. When these sides 9 are deformed in the same direction, the deformation period of the bellows increases, and the energy absorption amount changes intermittently correspondingly, and the shock compression load is not absorbed during this time, and the vehicle body frame (side member 2) Will be transmitted. Even when the angle θ1 formed by the two sides 9 is less than 88 °, the two sides 9 approach each other and try to deform in the same direction as almost one sheet. Similarly to the case where the angle θ1 between the two sides 9 is large, Energy absorption is intermittent.
Therefore, by setting the angle θ1 formed by each side 9 to 88 ° to 92 °, the sides 9 are alternately buckled and deformed so as to be alternately folded with respect to the impact compression load, thereby securely absorbing the impact energy. can do. Moreover, if it is in the range of ± 2 °, it is advantageous in terms of tolerance due to aluminum extrusion.

Further, the width dimension D of these both sides 9 is set to satisfy 2.3t ² −3t + 15 ≦ D ≦ 2.3t ² −3t + 16.5 in relation to the plate thickness t. When the width dimension D exceeds (2.3t ² -3t + 16.5), bellows-like deformation becomes large, and energy absorption becomes intermittent. Further, if the width D of the side 9 is large, the weight increases and the weight reduction is impaired. Therefore, a smaller width D of the side 9 is advantageous for weight reduction, and bellows-like deformation is continuously generated and the energy absorption capacity is increased, but it is less than (2.3t ² −3t + 15). Then, the width D of the side 9 is too small and the energy absorption is insufficient.
The number of inwardly bent portions 7 is set by the balance between the energy absorption capability due to the bellows-like deformation and the resistance force due to the drum-like deformation of the arcuate wall portion 8, and in order to efficiently exhibit both functions, 3 to 10 is preferable, and 4 to 8 is more preferable.
By adopting such a shape, even if a light metal such as an aluminum alloy is used and the plate thickness is as thin as 1.0 mm to 2.0 mm, the amount of energy absorbed with respect to the weight is large, and the weight can be reduced.

Next, examples of the present invention will be described.
The material is 6063-T5 aluminum, the thickness of the plate is 1.5 mm, the diameter (outer diameter) is 100 mm, the length is 115 mm, the cylindrical body without the inward bending portion, and the inward bending portion. Example cylinders having different numbers and widths of two sides were produced. The angle of the inward bending portion was 90 °. These cylinders are pressed in the axial direction at a speed of 50 mm / min and compressed by 80 mm, the amount of crushing energy at that time is measured, and the amount of energy absorbed per unit weight obtained by dividing this by the weight of the cylinder is obtained. It was.
Further, as a comparative example, in addition to a cylindrical tube having no inwardly bent portion, a 115 mm long corner having the same material, the same plate thickness, and an outer shell having a square cross section with a side of 100 mm. A cylindrical body and a cylindrical body having a cross-sectional cross shape as shown in Patent Document 3 with the four corners bent to the inside at 90 °, with the width of the bent portion changed, are similarly produced. The amount of energy absorbed per hit was determined.

The results are shown in FIG. In FIG. 4, the energy absorption amount per unit weight in the rectangular tube body having no bent portion in the comparative example is set to 1, and the ratio to this is shown. In the figure, 4, 6, 8, and 10 indicate the number of inwardly bent portions in the cylindrical body of the embodiment. In the cylindrical tube body and the rectangular tube body having no inward bent portion, the number of inward bent portions is zero.
As can be seen from FIG. 4, the amount of energy absorption per unit weight is larger in the cylindrical type than in the square cylindrical type, and is larger than in the case where the inwardly bent portion is not provided. This is presumably because the arc-shaped wall portion between the inwardly bent portions has a large resistance when attempting to expand the diameter like a drum.

  Moreover, in the cylindrical tube body, any of the four to ten inwardly bent portions has a large energy absorption amount per unit weight. In particular, the inwardly bent portions having 8 and 10 have a side with a width of about 15 mm and a peak amount of energy absorption, indicating that they have extremely high energy absorption capability. It is considered that the amount of energy absorption increases when both sides of the inwardly bent portion are appropriately buckled and deformed. However, it can be seen that when the width of the side of the inwardly bent portion is increased more than necessary, the amount of energy absorbed per unit weight tends to decrease. Since the width of both sides increases and the weight increases, it is considered that the amount of energy absorbed per unit weight is reduced.

  However, in the case of a cylinder with 4 to 8 inwardly bent portions, the change in energy absorption with respect to the width of the side is relatively small between about 12 mm and about 20 mm. In the case of a cylinder with 10 bent parts, the energy absorption amount varies greatly depending on the width of the side, and the peak is when the side width is 15 mm. Has fallen significantly.

Next, the same 6063-T5 material, diameter (outer diameter) of 100 mm, and length of 115 mm cylindrical cylinders were produced with plate thicknesses of 1.5 mm and 2.0 mm, respectively. The relationship between the number and energy absorption was investigated. The width of the side of the inward bending portion was 15 mm for a cylinder with a plate thickness of 1.5 mm, and 18 mm for a cylinder with a plate thickness of 2.0 mm.
In FIG. 5, the vertical axis represents the ratio when the energy absorption amount of the rectangular tube body having no inward bent portion described above is 1. In any case, when the amount of energy absorption is larger than that of the rectangular cylinder and the number of inwardly bent portions is up to about 8, the amount of energy absorption increases as the number increases. When the value is increased, the amount of energy absorption does not increase even if it is further increased, but a tendency to decrease is seen.
Considering together from the results of FIG. 5 and FIG. 4 described above, it can be said that the number of inwardly bent portions is 3 to 10 and more preferably 4 to 8.

  Next, a plurality of eight inwardly bent portions were formed by changing the width of the sides of a cylindrical body having the same material 6063-T5, a diameter (outer diameter) of 100 mm, and a length of 115 mm. The plate thickness was also changed from 1.0 mm to 2.2 mm. These cylinders were pressed in the axial direction at a speed of 50 mm / min and compressed 80 mm, the amount of crushing energy at that time was measured, and the amount of energy absorbed per unit weight obtained by dividing this by the weight of the cylinder was determined.

  The result is shown in FIG. As shown in FIG. 6, as the thickness t increases, the amount of energy absorption increases, but the thickness does not change much when comparing 2.0 mm and 2.2 mm. Accordingly, it can be said that a thickness of up to 2.0 mm is preferable. Further, it can be seen that in any case of the plate thickness, the width of the side of the inwardly bent portion is particularly remarkable when the width is a specific dimension.

Accordingly, FIG. 7 shows the relationship between the width of the side where the energy absorption amount reaches a peak and the plate thickness in these cylinders. As shown in FIG. 7, it can be seen that there is a specific relationship between the plate thickness t and the side width D, and this can be expressed by an approximate expression: D = 2.3t ² −3t + 15.7. It becomes. By combining this approximate expression and the result of FIG. 6, the width dimension D of both sides is set to satisfy 2.3t ² −3t + 15 ≦ D ≦ 2.3t ² −3t + 16.5 in relation to the plate thickness t. Then, the amount of energy absorbed per unit weight can be increased most efficiently.

When the above experiments are combined, as the energy absorbing member, the thickness of the cylindrical body is 1.0 mm to 2.0 mm, the number of inwardly bent portions is 3 to 10, and the angle formed by the sides of each inwardly bent portion is 88. When the relationship between the plate thickness tmm and the width Dmm of each side of the inward bent portion is set to satisfy 2.3t ² −3t + 15 ≦ D ≦ 2.3t ² −3t + 16.5, the unit weight The amount of energy absorption per unit is large, and it is recognized that it is the most effective for weight reduction.

In addition, this invention is not limited to the said embodiment, A various change can be added in the range which does not deviate from the meaning of this invention.
For example, the thickness of the cylindrical body and the dimensions of the inwardly bent portion may be equal to each other, or may be partially changed within the numerical range described above.

DESCRIPTION OF SYMBOLS 1 Energy absorption member 2 Side member 3 Bumper reinforcement 4,5 Mounting plate 6 Cylindrical body 7 Inward bending part 8 Arc-shaped wall part 9 Side

Claims (3)

An energy absorbing member having a cylindrical body that is deformed by an impact compressive load in an axial direction, wherein the cylindrical body has three to ten inwardly bent portions that are bent inward in the radial direction with an interval in the circumferential direction. These inwardly bent portions are formed in an arc shape in which two sides intersect at an angle of 88 ° to 92 °, and the inwardly bent portions are convex outward in the radial direction. When the plate thickness is tmm and the width of each side of the inward bent portion is Dmm, the plate thickness and the width of each side are 2.3t ² −3t + 15 ≦ D ≦ 2.3t. It is set so that it may become ² <-3t + 16.5>, The energy absorption member characterized by the above-mentioned.   The energy absorbing member according to claim 1, wherein the cylindrical body has a thickness of 1.0 mm to 2.0 mm.   The energy absorbing member according to claim 1 or 2, wherein the arc-shaped wall portion is formed along one circle.

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