JP2011218935A - Collision energy absorbing structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a collision energy absorbing structure which prevents the structure from getting complicated, and which can be worked by pressing, obtain a stable deformed shape, and keep resistance for load in a deformation process stable at a high level, and the energy absorbing efficiency high.SOLUTION: The collision energy absorbing structure is cylindrical, and displaced in the axial direction to absorb collision energy. The shape of a section perpendicular to the axial direction is a polygonal shape which is symmetrical with respect to the center of the section, and not symmetrical with respect to the center line of the section. When the outline of the section has a rectangular shape, the aspect ratio is less than 1.5, and the ratio of the lengths of the adjacent sides among the sides of the polygonal shape constituting the section is 2.3 or less.

Description

  The present invention relates to a collision energy absorbing structure used for automobiles and the like.

  A vehicle body such as an automobile is provided with a structure that absorbs the collision energy by being deformed during the collision in order to mitigate the collision with the occupant or the vehicle body at the time of the collision. As performance required for such a collision energy absorbing structure, from the viewpoint of reducing the weight of the vehicle body in consideration of recent environmental problems, it is required to increase the energy absorption efficiency and make the cross section compact or thin.

  Such a collision energy absorption structure is required to have high energy absorption efficiency, that is, the deformation resistance load is highly stable even after deformation starts and has high energy absorption ability. Since the collision energy absorbing structure cannot sufficiently absorb the collision energy when the deformation at the time of collision is unstable deformation as shown in FIG. 21 (a), as shown in FIG. 21 (b), large and small concentric circles are formed. It is made of a tubular structure and absorbs collision energy by plastic deformation while the small diameter tube is immersed in the large diameter tube with respect to the collision load in the axial direction (immersion type; for example, Patent Document 1), or FIG. As shown in (c), a structure in which the structure is plastically deformed in an accordion shape with respect to an axial collision load (for example, Patent Documents 2 to 7) is required.

  Of Patent Documents 2 to 7, Patent Document 2 is a polygonal cross section provided with a recess in the cross section of the structure, and Patent Document 3 has a radial intermediate beam connecting each corner from the center of the cross section. Patent Document 4 has an 8-shaped cross-sectional structure, and both increase the cross-sectional line length and the number of ridge lines to obtain a structure with good energy absorption efficiency. . Patent document 5 improves collision absorption performance by providing a filler inside a structure.

  In addition, Patent Documents 6 and 7 are provided with concavities and convexities in the vertical direction with respect to the axial direction mainly subjected to the collision load, and are continuously buckled even when receiving an axial impact including an oblique load. The deformation shape is controlled so that the bellows-like plastic deformation shown in FIG.

JP-A 48-1676 JP 2008-284931 A JP 2001-124128 A JP 2008-296716 A JP 2001-182769 A Japanese Patent Laid-Open No. 2-175252 JP 2002-104107 A

  However, the immersive type as shown in Patent Document 1 has a complicated structure, which causes an increase in the molding process and has problems in cost and productivity.

  The structures shown in Patent Documents 2 to 7 that are plastically deformed in a bellows shape have the following problems.

  The technique of Patent Document 2 is effective as a method for improving energy absorption efficiency while effectively utilizing a limited space, but greatly buckles when subjected to an axial impact including an oblique load, The deformation load may not be stable, and in such a case, energy absorption efficiency is reduced.

  In the techniques disclosed in Patent Documents 3 and 4 above, the cross-sectional shape is extremely complicated, and forging is unavoidable, which not only causes an increase in cost compared to general press processing, but also in terms of production. But it is disadvantageous.

  In the technique disclosed in Patent Document 5, the use of the filler increases the weight and cost of the structure.

  In the techniques disclosed in Patent Documents 6 and 7, the uneven shape is provided perpendicularly to the axial direction to stabilize the deformed shape. However, the deformation is promoted in the uneven portion, so the load is stabilized at a low level. Therefore, it is difficult to obtain a structure having excellent energy absorption efficiency.

  The present invention has been made in view of the above points, the structure is not complicated, press working is possible, lightweight and compact, a stable deformed shape is obtained, and the resistance load in the deformation process It is an object of the present invention to provide a collision energy absorption structure that is highly stable and has high energy absorption efficiency.

The above problems are solved by the following inventions (1) to (6).
(1) A collision energy absorbing structure that is cylindrical and deforms in the axial direction to absorb collision energy,
The cross-sectional shape of the cross section perpendicular to the axial direction is a polygon that is point-symmetric and non-symmetric with respect to the center of the cross-section, and the aspect ratio when the outer shape of the cross-section is a rectangle is less than 1.5. A collision energy absorbing structure characterized in that a ratio of lengths of adjacent sides among polygon sides constituting a cross section is 2.3 or less.
(2) The collision energy absorbing structure according to (1), which is tapered in the axial direction.
(3) The collision energy absorbing structure according to (1) or (2), wherein the tip has a recess that is recessed in the axial direction.
(4) The collision energy absorbing structure according to any one of (1) to (3), wherein the collision energy absorbing structure is formed of a press-molded material formed by pressing a metal plate.
(5) The collision energy absorbing structure according to (4), wherein at least two of the press-molded materials are joined.
(6) The collision energy absorbing structure according to (4) or (5), wherein the metal plate constituting the press-formed material is a steel plate having a tensile strength of 270 to 1500 MPa.

  According to the present invention, the cross-sectional shape of the cross section perpendicular to the axial direction is point symmetric with respect to the center of the cross section and non-axisymmetric, and the aspect ratio is less than 1.5 when the outer shape of the cross section is rectangular. In addition, since the ratio of the lengths of adjacent sides among the sides of the polygon forming the cross section is 2.3 or less, a stable deformed shape can be obtained. Therefore, a collision energy absorption structure having high energy absorption efficiency can be obtained by pressing without impairing productivity, and the structure can be made compact and lightweight.

It is the perspective view and sectional drawing which show the collision energy absorption structure which concerns on one Embodiment of this invention. It is a perspective view which shows the collision energy absorption structure which concerns on other embodiment of this invention. It is a perspective view which shows the collision energy absorption structure which concerns on other embodiment of this invention. It is a figure for demonstrating an example of the manufacturing method of the collision energy absorption structure of FIG. It is a figure for demonstrating the other example of the manufacturing method of the collision energy absorption structure of FIG. It is a figure which shows the cross-sectional shape of the structure of the example 1 of this invention, the shape before and behind a collision, and a load-stroke curve. It is a figure which shows the cross-sectional shape of the structure of the example 2 of this invention, the shape before and behind a collision, and a load-stroke curve. It is a figure which shows the cross-sectional shape of the structure of the example 3 of this invention, the shape before and behind a collision, and a load-stroke curve. It is a figure which shows the cross-sectional shape of the structure of the example 4 of this invention, the shape before and behind a collision, and a load-stroke curve. It is a figure which shows the cross-sectional shape of the structure of the example 5 of this invention, the shape before and behind a collision, and a load-stroke curve. It is a figure which shows the cross-sectional shape of the structure of the example 6 of this invention, the shape before and behind a collision, and a load-stroke curve. It is a figure which shows the cross-sectional shape of the structure of the example 7 of this invention, the shape before and behind a collision, and a load-stroke curve. It is a figure which shows the cross-sectional shape of the structure of the comparative example 1, the shape before and behind a collision, and a load-stroke curve. It is a figure which shows the cross-sectional shape of the structure of the comparative example 2, the shape before and behind a collision, and a load-stroke curve. It is a figure which shows the cross-sectional shape of the structure of the comparative example 3, the shape before and behind a collision, and a load-stroke curve. It is a figure which shows the cross-sectional shape of the structure of the comparative example 4, the shape before and behind a collision, and a load-stroke curve. It is a figure which shows the cross-sectional shape of the structure of the comparative example 5, the shape before and behind a collision, and a load-stroke curve. It is a figure which shows the cross-sectional shape of the structure of the comparative example 6, the shape before and behind a collision, and a load-stroke curve. It is a figure which shows the cross-sectional shape of the structure of the comparative example 7, the shape before and behind a collision, and a load-stroke curve. It is a figure which shows the cross-sectional shape of the structure of the comparative example 8, the shape before and behind a collision, and a load-stroke curve. It is a figure for demonstrating the deformation | transformation form of a collision energy absorption structure.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

<Shape of structure>
FIG. 1 shows a collision energy absorbing structure according to an embodiment of the present invention, in which (a) is a perspective view and (b) is a cross-sectional view.

  As shown in FIG. 1A, the collision energy absorbing structure according to the present embodiment is basically formed of a cylindrical body, and one end (for example, the upper end) is a collision tip, and collides with the collision tip. When an object collides, it is deformed in the direction of the axis L to absorb collision energy.

  As shown in FIG. 1B, the shape of the cross section perpendicular to the direction of the axis L is a polygon that is point-symmetric and non-axisymmetric with respect to the center O of the cross section. The figure shows a case where the cross-sectional shape is a hexagon including a recess.

  By making the shape of the cross section perpendicular to the axis L into a polygon like this, it can be produced by press working and the cross section line length can be made long, so that the collision performance is improved in a limited space. be able to.

  In addition, the load at the time of collision is not limited to being input in the axial direction, for example, and it is assumed that an oblique load having an angle with respect to the axial direction is received. In this case, if the deformation of the member becomes unstable due to large buckling or local bending, the deformation load is reduced and the energy absorption ability is remarkably reduced, but the cross section perpendicular to the axis L of the cylindrical body By making the shape of the point symmetrical and non-linearly symmetric, it is possible to stabilize the deformation mode at the time of crushing including such an oblique load and obtain a stable collision performance. This is considered to be because point buckling and non-linear symmetry cause deviation in the progress of buckling on opposite sides, and it is difficult for large deformations such as buckling, lying down, and folding with a large period to occur.

  A rectangle R forming a polygonal outline constituting the cross section has an aspect ratio of less than 1.5. Here, the aspect ratio is a value of long side / short side (a / b in the example in the figure). When the rectangle R is a square (a = b), the aspect ratio is 1, and the aspect ratio is always 1 or more.

  The reason why the aspect ratio of the polygon that forms the outline of the polygon that forms the cross section is specified to be less than 1.5 is to obtain a stable deformation. It is because it becomes easy to generate | occur | produce.

  Moreover, the ratio of the lengths of adjacent sides among the sides of the polygon forming the cross section is 2.3 or less. Here, the ratio of the lengths of adjacent sides is the value of the longer side / shorter side. When the lengths of two adjacent sides are the same, the ratio of the lengths of the adjacent sides is 1, and the ratio of the lengths of the adjacent sides is always 1 or more. In the example in the figure, the combination having the maximum ratio of the lengths of adjacent sides is a combination of the side L1 and the side L2 (L1> L2), and L1 / L2 ≦ 2.3.

  The reason why the ratio of the lengths of adjacent sides among the sides of the polygon constituting the cross section is set to 2.3 or less is that the deformation form is thereby stabilized. This is probably because large deformation is likely to occur in the longer side of the adjacent sides, and in order to suppress such large deformation, the side of the shorter side of the adjacent sides This is probably because the length is important and there is an optimal ratio between these adjacent sides.

  From the viewpoint of stabilizing the deformed form, it is preferable that the collision energy absorbing structure is tapered in the axial direction as shown in FIG. The taper in this case is preferably formed so as to spread from the front end (collision front end) to the rear end, as shown in the figure. This is considered to be because it is possible to specify the part where the deformation starts by attaching a taper, and the deformation starts stably.

  As shown in FIG. 3, it is also possible to specify a part where deformation starts similarly by forming a notched shape N such as a notch at the tip (collision tip), and stably start the deformation. be able to.

  A concave shape N as shown in FIG. 3 may be added to the tapered structure as shown in FIG.

<Applicable materials for structures>
The collision energy absorbing structure of the present embodiment is preferably configured by press-molding a metal plate. Examples of the metal plate to be applied include a hot-rolled steel plate, a cold-rolled steel plate, a plated steel plate obtained by subjecting the steel plate to electroplating such as electrogalvanizing or hot-dip galvanizing, and further a stainless steel plate (SUS). In the case of a hot dip galvanized steel sheet, an alloying treatment may be performed. The plated steel sheet may be further subjected to an organic film treatment after plating. A steel plate having a tensile strength of 270 to 1500 MPa is preferable. Moreover, as a metal plate, other metal materials, such as aluminum, magnesium, and these alloys other than a steel plate, can also be used.

<Manufacturing method>
Next, an example of a method for manufacturing such a collision energy absorbing structure will be described.
Here, the case where a collision energy absorber is manufactured by press molding is shown. In the example of FIG. 4, two metal plates are prepared as shown in (a), these are formed as shown in (b) using a die and a die, and as shown in (c). Further, by joining the end faces of the obtained molded product, the structure shown in (d) is obtained. Specifically, in order to manufacture the structure of FIG. 1, a molded product having the same shape is manufactured by press molding from two metal plates, and these are joined. In the example of FIG. 5, the single metal plate shown in (a) is formed as shown in (b) using a die and a die, and this is closed to form a closed cross section by bending. Are joined to obtain the structure shown in (c). The mold (die and punch) used for press molding is the above cross-sectional shape (a point-symmetrical and non-axisymmetric polygon with respect to the center of the cross-section, and the aspect ratio when the outer shape of the cross-section is a rectangle) Is less than 1.5, and the ratio of the lengths of adjacent sides among the sides of the polygon forming the cross section is 2.3 or less).

  In the example of FIGS. 4 and 5, the case where a structure is manufactured by manufacturing and bonding a molded part having a predetermined cross-sectional shape from one or two metal plates has been described. However, three or more metal plates are used. It is also possible to form the respective parts by using and to manufacture the structure by joining them. As methods for joining the end faces, various methods such as spot welding, laser welding, arc welding, caulking, rivet joining, and application of an adhesive can be employed.

Here, the characteristics of various types of collision energy absorbing structures were grasped by simulation.
For the simulation, general-purpose dynamic explicit software LS-DYNA ver. 971 was used. The applied material was a steel plate having a tensile strength of 440 MPa and a plate thickness of 1.6 mm. With respect to the structures of Invention Examples 1 to 7 having shapes within the scope of the present invention and the structures of Comparative Examples 1 to 8 that deviate from the scope of the present invention, a flat indenter without curvature was caused to collide at a speed of 15 km / h. The crushing performance of time was simulated. In order to evaluate the crushing performance by the deformation resistance load after the start of deformation, the average load was obtained from a load-stroke curve when the crushing distance was 20 mm to 70 mm, and the average load per unit weight and the shape after deformation were evaluated. The results are summarized in Table 1, and the cross-sectional shape of the structures of Invention Examples 1-7, the shape before and after the collision, and the load-stroke curve are shown in FIGS. 6-12, and the cross-sectional shape of the structures of Comparative Examples 1-8. The shape before and after the collision and the load-stroke curve are shown in FIGS. In Table 1, in the column of deformed shape, ◯ is continuously deformed into a bellows shape, and X is bent or a buckle with a large period occurs. Moreover, in FIGS. 6-20, (a) is a cross-sectional shape, (b) is the shape before and behind a collision, (c) is a load-stroke curve. As shown in these figures, Examples 1 to 7 of the present invention within the scope of the present invention are plastically deformed in a stable and bellows continuously during crushing, and the average load per unit weight during crushing is It was confirmed that the absorbed energy efficiency was high. On the other hand, in Comparative Examples 1 to 8 that deviate from the scope of the present invention, it was confirmed that bending in the axial direction and large period buckling occurred, the deformed shape was unstable, and the average load per unit weight was low. It was done.

  From the above, when the cross-sectional shape of the cross section perpendicular to the axial direction is a point-symmetrical and non-axisymmetric polygon with respect to the center of the cross-section as in the present invention, and the outline of the cross-section is a rectangle When the aspect ratio is less than 1.5 and the ratio of the lengths of adjacent sides among the polygon sides constituting the cross section is 2.3 or less, a stable deformed shape can be obtained, and the resistance load It has been confirmed that a collision energy absorption structure with high energy absorption efficiency and high energy absorption efficiency can be obtained.

Claims (6)

A collision energy absorbing structure that is cylindrical and deforms in the axial direction to absorb collision energy,
The cross-sectional shape of the cross section perpendicular to the axial direction is a polygon that is point-symmetric and non-symmetric with respect to the center of the cross-section, and the aspect ratio when the outer shape of the cross-section is a rectangle is less than 1.5. A collision energy absorbing structure characterized in that a ratio of lengths of adjacent sides among polygon sides constituting a cross section is 2.3 or less.   The collision energy absorption structure according to claim 1, wherein the collision energy absorption structure is tapered in the axial direction.   The collision energy absorption structure according to claim 1 or 2, wherein the tip end portion has a recess portion that is recessed in the axial direction.   The collision energy absorption structure according to any one of claims 1 to 3, wherein the collision energy absorption structure is formed of a press-molded material formed by pressing a metal plate.   The collision energy absorbing structure according to claim 4, wherein at least two of the press molding materials are joined.   The collision energy absorbing structure according to claim 4 or 5, wherein the metal plate constituting the press-formed material is a steel plate having a tensile strength of 270 to 1500 MPa.