JP4604740B2 - Shock absorbing member - Google Patents

Description

  The present invention relates to an impact absorbing member. Specifically, the present invention relates to an impact absorbing member that can absorb impact energy generated when a vehicle such as an automobile collides.

  As is well known, the body of many current automobiles is constituted by a monocoque body that supports the load by the entire body integrated with the frame in order to achieve both weight reduction and high rigidity. The body of an automobile must have a function of suppressing damage to the functions of the vehicle and protecting the lives of passengers in the cabin in the event of a vehicle collision. In order to reduce the damage to the cabin as much as possible by absorbing the impact energy at the time of vehicle collision and reducing the impact force on the cabin, it is effective to preferentially crush spaces other than the cabin, such as the engine room and trunk room It is.

  Because of these safety requirements, impacts to actively absorb impact energy by collapsing when impact loads are applied to the appropriate parts such as the front, rear, or side of the vehicle body. An absorbent member is provided. Conventionally, as such an impact absorbing member, a front side member, a side sill, a rear side member, and the like are known.

  In recent years, a shock absorbing member called a crash box is attached to the tip of the front side member by an appropriate means such as fastening or welding, for example, to improve the safety of the vehicle body and substantially eliminate the vehicle damage caused by a light collision. It has come to be carried out together with the reduction of the repair cost. A crash box means that impact energy is generated by buckling preferentially in a bellows shape (accordion shape) in the axial direction by an impact load applied in the axial direction (in this specification, the longitudinal direction of the shock absorbing member). It is a member to absorb.

  Specifically, the impact absorbing performance required for this impact absorbing member is that when an impact load is applied in the axial direction, it is repeatedly buckled in the axial direction to be deformed into a bellows shape, The average load is high, and further, the maximum reaction force generated at the time of crushing is suppressed within a range in which other members disposed in the vicinity of the shock absorbing member are not destroyed.

  Many materials and shapes for improving the shock absorbing performance of the shock absorbing member have been developed so far. A shock absorbing member that has been widely used in general is, for example, by spot welding a back plate via a flange provided at the edge of a hat-shaped cross-sectional member as disclosed in Patent Document 1. A box-shaped member having a square cross section is used. In the present specification, the “flange” means a flat plate-like portion protruding outward from the outline in the cross section.

  On the other hand, in Patent Document 2, the cross-sectional shape from one end to the other end is continuously changed from a convex polygon having a quadrangle or more to another convex polygon having more sides than the convex polygon. There has been disclosed an invention relating to an impact absorbing member that has a closed cross-sectional structure that changes, and that has improved impact absorption while reducing the initial load of collision. In the present specification, the term “convex polygon” means a polygon in which all of the line segments obtained by connecting two arbitrary points existing inside are present.

Patent Document 3 discloses an invention relating to an impact absorbing member having a partition inside and having a contour cross-sectional shape that is a convex polygon.
Further, in Patent Document 4, an impact with increased strength is obtained by forming a groove portion having a substantially right isosceles triangle shape toward the inside at four corners including four apexes of a material having a quadrangular cross section. An invention relating to an absorbent member is disclosed.

  Further, in Patent Document 5, a bead extending in the axial direction is formed on a side surface of a front side frame having a hat-shaped cross section having a flange, whereby the front side frame when an impact load is applied is formed. An invention for suppressing bending is disclosed.

JP-A-8-128487 Japanese Patent Laid-Open No. 9-277753 JP 2003-48569 A JP 2002-284033 A JP-A-8-108863

  However, according to any of these conventional inventions, the impact load, in particular, the direction intersecting the axial direction of the impact absorbing member, for example, the direction in which the intersecting angle with the axial direction is included in the range of more than 0 degrees and 15 degrees or less. When an impact load (referred to as “oblique load” in this specification) is input, a predetermined amount of impact energy is absorbed by buckling in an accordion-like manner without causing bending in the axial direction. Therefore, it is not possible to provide an impact absorbing member that can ensure stable and high performance.

  That is, the impact load applied to the impact absorbing member during an actual vehicle collision is more often applied in a direction shifted from the axial direction of the impact absorbing member than in a direction parallel to the axial direction of the impact absorbing member. However, the load direction of the impact load assumed by the inventions described in Patent Documents 1 to 5 described above is a direction parallel to the axial direction of the shock absorbing member. For this reason, when an oblique load is applied to the shock absorbing members disclosed in Patent Documents 1 to 5, bending in the axial direction occurs, and it becomes impossible to stably buckle in the bellows shape in the axial direction. There is a high possibility that the amount of shock energy absorbed cannot be secured.

  In most cases, the cross-sectional shape of the impact absorbing member used in the automobile body is flat. For this reason, it is difficult to use an impact absorbing member having a convex polygonal cross-sectional shape such as a simple regular polygon as disclosed in Patent Document 1 in the first place.

  In the invention disclosed in Patent Document 2, the cross-sectional shape of the shock absorbing member gradually changes over substantially the entire length. For this reason, depending on the position in the axial direction, the cross-sectional shape of the shock absorbing member is inevitably in a shape that is not suitable for stable buckling. Therefore, even when the impact load is applied in a direction parallel to the axial direction, it is difficult for the impact absorbing member to buckle stably and repeatedly in the axial direction and may not be deformed into a bellows shape.

  Further, in the invention disclosed in Patent Document 3, the strength of the portion provided with the partition wall may increase excessively. For this reason, in the present invention, the buckling may become unstable and the amount of absorption of impact energy may be insufficient, and the maximum reaction force generated in the impact absorbing member particularly in the initial stage of crushing is in the vicinity of the impact absorbing member. There is also a possibility that the strength of the other member existing in the above will be exceeded and the other member may be crushed first before the shock absorbing member is crushed. Therefore, even when the impact load is applied in a direction parallel to the axial direction, this impact absorbing member cannot be stably buckled repeatedly in the axial direction and may not be deformed into a bellows shape.

  Moreover, in the invention disclosed by patent document 4, since the notch part was originally processed and provided with a notch part, the intensity | strength of this notch part will rise excessively and it may buckle stably. It may not be possible. Therefore, in this invention, similarly to the invention disclosed in Patent Document 3, there is a possibility that the amount of shock energy absorbed may be insufficient, and other members may be crushed before the shock absorbing member is crushed. Even if the impact load is applied in a direction parallel to the axial direction, it cannot be repeatedly buckled stably in the axial direction and may not be deformed into a bellows shape.

  Furthermore, in the invention disclosed by Patent Document 5, the shock absorbing member has a hat-shaped cross-sectional shape having a flange. For this reason, according to the present invention, it is considered that the bending due to the applied impact load can surely be suppressed. However, depending on the present invention, even when the impact load is applied in parallel to the axial direction, it cannot be repeatedly buckled stably in the axial direction and may not be deformed into a bellows shape.

  Therefore, an object of the present invention is not only when an impact load is applied in the axial direction, but also in a direction intersecting the axial direction, for example, a direction in which the intersecting angle with the axial direction is included in the range of more than 0 degrees to 15 degrees or less. Even when all impact loads are applied, it is possible to secure a predetermined amount of shock energy absorption by stably buckling in the axial direction without causing bending in the axial direction. An object of the present invention is to provide an impact absorbing member capable of exhibiting high performance.

The present inventors have made various studies in view of the problems of the above-described conventional techniques, and as a result, obtained the new and important findings (I) to (V) listed below, thereby completing the present invention.
(I) A multilayer structure including at least a cross-sectional shape of the shock absorbing member, (a) an external member made of a cylindrical body, and a bending rigidity improving member disposed inside the external member to improve the bending rigidity of the external member (B) The outer member has a closed cross section having a plurality of vertices, does not have an outward flange, and has a plurality of vertices. It is a partial area of at least one side of the basic cross section consisting of the largest outline obtained by connecting a part of them with a straight line, and has a groove part recessed inward of this outline at a position excluding the end point of this side. By adopting a shape including the elements (a) and (b), even when an actual shock absorbing member has a flat cross-sectional shape often used, an axial impact load or an oblique load is generated. Load Be stable can be secured predetermined impact absorbing performance by buckling into an accordion shape in the axial direction without causing bending deformation in the axial direction.

(II) In order to bend in the axial direction stably without causing bending deformation in the axial direction, the bending rigidity improving member has a closed cross section in which the cross-sectional shape in the axial direction has a plurality of vertices. It is desirable that the inner member has a shape, and it is further desirable that the distance between the inner member and the outer member is 13 mm or more, and the cross-sectional area of the inner member is 20% or more of the cross-sectional area of the outer member. .
(III) The bending rigidity improving member may be a plate-like member in order to bend in the axial direction stably without causing bending deformation in the axial direction.

(IV) As a result of the FEM analysis, there is a suitable condition to be selected for stabilizing the buckling at the position where the bending rigidity improving member is fixed to the external member, and the condition deviates from this condition. The buckling behavior becomes unstable, and the shock absorption performance may be reduced. (V) As a result of the FEM analysis, there is a preferable condition to be selected for stabilizing the buckling in the shape of the groove portion provided in the external member, and the condition deviates from this condition. The buckling behavior becomes unstable, and the shock absorption performance may be reduced.

The present invention includes at least an external member formed of a cylindrical body and a bending rigidity improving member that is disposed inside the external member and improves the bending rigidity, and the axial direction or the axial direction from one end of the cylindrical body in the axial direction. An impact absorbing member for absorbing impact energy by deforming into an accordion shape by buckling with an impact load applied in a direction crossing the axial direction, and at least a part of the external member in the axial direction The cross-sectional shape of this is a closed cross section having a plurality of vertices, and is not provided with a flange outside the closed cross section, and is composed of a maximum contour obtained by connecting a part of the plurality of vertices with straight lines. region excluding the end points of the part at a by and the sides of at least one side of the cross section, so as to form a groove recessed into the inside of the contour, be formed by bending, grooves I concavely, outer member To the axial direction of It is provided with beauty, and flexural stiffness enhancing member, through an area that does not include a plurality of vertices of the outer member is a shock absorbing member characterized by being fixed to the inner surface of the outer member.

In the impact absorbing member according to the present invention, it is desirable that the bending rigidity improving member is an internal member provided with a closed cross section having a plurality of vertices in the axial cross section and extending in the axial direction . In this case, it is desirable that the distance between the internal member and the external member is 13 mm or more, and the cross-sectional area of the internal member is 20% or more of the cross-sectional area of the external member.

Moreover, in the impact-absorbing member according to the present invention, even if the bending rigidity improving member is not present in a plate shape such as a flat plate or a corrugated plate, the same effect as the above-described internal member can be obtained .

  In these shock absorbing members according to the present invention, it is desirable that the remaining region of the side excluding the partial region of the side having the groove portion provided in the external member is formed linearly or in a curved shape. .

  In the shock absorbing member according to the present invention, the groove provided in the external member is provided on the side where the width of the side having the groove is a, the opening width of one groove is Wi, the plate thickness of the external member is t. When the number of the grooves formed is n and the width of each of the (n + 1) remaining regions divided by the n grooves provided on the side is Xj, the following equation (1) and ( 2) It is desirable to be provided so as to satisfy the equation.

4t <Wi <65t i = 1 to n (1)
4t <Xj <65t j = 1 to (n + 1) (2)
However, ΣWi + ΣXj = a, and ΣWi is the sum of the opening widths Wi of the grooves formed on the side of the width a, and the opening width of the groove is the two intersections of the side of the width a and the outline of the groove ΣXj is the sum of the widths Xj.

  In these shock absorbing members according to the present invention, when the total length in the axial direction of the external member is T, (a) the groove is axially separated from one end (T × 0.3). Or (b) at least one of the ranges up to a position where the cross-sectional area of the external member is separated from one end by a distance (T × 0.3) in the axial direction. It is desirable that each part is smaller than other parts.

  In these shock absorbing members according to the present invention, the internal angle (α) of the intersection of the side of the width a having the groove portion provided in the external member and the outline of the groove portion is equal to or larger than the internal angle (β) of the end point of the side. Is desirable.

  Furthermore, in these shock absorbing members according to the present invention, the cross-sectional shape of the groove provided in the external member is trapezoidal, curved, triangular or square, or a combination of two or more of these shapes. It is desirable to be.

  According to the present invention, an impact load (oblique load) is input not only in a direction parallel to the axial direction but also in a direction intersecting the axial direction, for example, a direction in which the intersecting angle with the axial direction is included in the range of more than 0 degrees to 15 degrees or less. Even if it is a case, it is possible to ensure a predetermined amount of shock absorption by stably buckling in the axial direction without causing bending in the axial direction, and shock absorption that can exhibit stable high performance A member can be provided.

(Embodiment 1)
The best mode for carrying out the shock absorbing member according to the present invention will be described in detail with reference to the accompanying drawings. In this description, the case where the bending rigidity improving member is the internal member 20 having a closed cross section in which the cross-sectional shape in the axial direction has a plurality of apexes is taken as an example.

  FIG. 1 is an explanatory view schematically showing a cross section of the shock absorbing member 1 of the present embodiment. As shown in FIG. 1, since the shock absorbing member 1 includes an external member 10 and an internal member 20 that is a bending rigidity improving member, the external member 10 and the internal member 20 will be sequentially described below. In the description of the first embodiment, the groove portion 14 provided in the external member 10 has, in the cross section, some of the vertices A to P A, B, C, D, I, J, K, A region of at least one side D-I and L-A of the basic cross-section composed of the maximum contour A-B-C-D-I-J-K-LA obtained by connecting L with a straight line And provided at a position excluding the end points D, I, L, A of this side in a shape recessed inward of the maximum contour A-B-C-D-I-J-K-L-A, and For example, the remaining areas D-E, H-I, L-M, and P-A excluding this area are formed in a straight line.

[External member 10]
As shown in FIG. 1, the external member 10 constituting the shock absorbing member 1 of the present embodiment has at least part of the cross-sectional shape in the axial direction having a plurality of vertices A, B, C, D, E, and F. , G, H, I, J, K, L, M, N, O, and P, and a cylindrical body having a shape that does not include a flange toward the outside of the closed section. Furthermore, at least a part of the cross-sectional shape in the axial direction is obtained by connecting a part A, B, C, D, I, J, K, L, and A of the vertices A to P with a straight line. It is a partial area of at least one side D-I, LA of the basic cross section composed of the largest outline A-B-C-D-I-J-K-L-A, and end points D, I of this side , L, and A at a position excluding A, a shape having a groove portion recessed inward of the maximum contour A-B-C-D-I-J-K-LA.

  That is, the cross-sectional shape of the external member 10 is (i) a closed cross-section having a plurality of vertices AP, (ii) not having a flange facing the outside of the closed cross-section, and (iii) Maximum contour A-B-C-D-I-J obtained by connecting a part of a plurality of vertices A to P with straight lines A, B, C, D, I, J, K, L, and A -Maximum contour AB- in a region of a part of at least one side D-I, LA of the basic cross section composed of K-LA and excluding end points D, I, L, A of this side It is a shape provided with all three elements (i) to (iii) that have a groove portion 14 that is recessed inward of C-D-I-J-K-L-A.

  The impact absorbing member 1 according to the present embodiment includes the external member 10 including all the three elements (i) to (iii), so that when an impact load is applied, the shaft is not bent in the axial direction. A predetermined shock absorbing performance is secured by buckling stably in a bellows shape in the direction. Therefore, the principle of the external member 10 of the present embodiment will be described.

  As an object material for explanation, an external member 10 made of a 590 MPa class 1.6 mm thick steel plate and having a length of 200 mm was used. The cross-sectional shape of the external member is (a) a square having a long side length of 80 mm and a short side length of 60 mm, or a regular octagon having a side length of 35 mm, and (b) outward facing. (C) A polygonal shape having a trapezoidal groove portion 14 and (c) an octagonal flatness is changed variously by extending the lengths of two opposing sides thereof, and these external members The effect of the shape of the groove 14 on the buckling stability was investigated by performing FEM numerical analysis on 10. In this specification, “flatness” means the ratio of the length of the long side to the short side of the rectangle with the shortest side length among the rectangles circumscribing the contour of the cross section of the shock absorbing member (long side) Length / short side length).

As a result, knowledge (Knowledge 1) to (Knowledge 3) regarding deformation stabilization of the external member of the present embodiment listed below was obtained.
(Knowledge 1)
For example, an impact load is applied to each of an external member having a flange as a joining margin when two or more members formed by press molding or the like are joined by, for example, spot welding, and the external member not having this flange. The behavior of collapse when loaded was analyzed by FEM numerical analysis.

  FIG. 2 is an explanatory view showing a state of crushing of an external member having a quadrangular cross section by FEM numerical analysis. FIG. 2 (a) shows an impact absorbing member 30 having a flange, and FIG. An impact absorbing member 31 that does not include a flange is shown.

  As shown in FIG. 2A, when the shock absorbing member 30 has a flange, the buckling generated in the shock absorbing member 30 loaded with an impact load becomes extremely unstable, and the shock absorbing member 30 is in the middle of being crushed. Bends in the longitudinal direction. On the other hand, as shown in FIG. 2B, if the shock absorbing member 31 does not have a flange, the shock absorbing member 31 is stably buckled in a bellows shape without being bent in the longitudinal direction.

(Knowledge 2)
FIG. 3 schematically shows a state of crushing a flat octagon in which the length of two sides facing each other from the regular octagon is gradually increased using a shock absorbing member 32 having a regular octagonal cross-sectional shape. When the flatness of the shock absorbing member 32 is increased, the buckling at the time of crushing becomes unstable and becomes a complicated shape, and the buckling at the time of crushing becomes gradually unstable.
(Knowledge 3)
At this time, the buckling of the shock absorbing member 32 can be stabilized by providing the groove on the long side of the flat octagon where the buckling becomes unstable.

  FIG. 4 is an explanatory diagram showing a situation in which a trapezoidal groove portion 14 is provided in a part of the long side portion 12 of the external member 10 having a flat octagonal cross section of the shock absorbing member 1. In this example, two groove portions 14 are provided at symmetrical positions with dimensions of width W and depth d.

  The cross-sectional shape of the external member 10 of the shock absorbing member 1 of the present embodiment is the shape shown in FIG. 4, specifically (i) a closed cross-section having a plurality of vertices AP, (ii) ) Do not have a flange facing the outside of the closed cross section, and (iii) A part of the vertices A to P A, B, C, D, I, J, K, L, and A in a straight line A groove 14 that is recessed inward of a basic cross section (the figure A-B-C-D-I-J-K-L-A in FIG. 4) having the maximum contour obtained by connecting the basic cross section A-B. −C−D−I−J−K−L−A, which is a partial area of each of the side 12 (A−L) and the side 12 (D−I) and constituting the vertices A, D, I, and L By having a shape with all three elements (i) to (iii) of having one at a position that does not contain any of Stable occur buckling, outer member 10 buckles into a bellows shape. That is, the external member 10 is buckled in a bellows shape by being deformed by receiving the impact load and by alternately deforming the groove portion 14 and the remaining straight portion divided by the groove portion 14.

  The mechanism by which the shock absorbing member 1 of the present embodiment including the external member 10 exhibits such excellent operational effects is considered as follows when comprehensively determined in consideration of the results of the FEM numerical analysis described above. It is done.

  The groove portion 14 provided on the side 12 is recessed inward of the basic cross section described above (figure A-B-C-D-I-J-K-L-A in FIG. 4). For this reason, when an impact load is applied, the displacement of the vertices E, F, G, H, M, N, O, and P constituting the groove portions 14 and 14 is represented by a graphic ABCDJIJ. The direction is directed to the inside of -KLA.

  On the other hand, the displacement of the vertices A, B, C, D, I, J, K, and L constituting the basic cross section (figure A-B-C-D-I-J-K-L-A) A-B-C-D-I-J-K-L-A is directed to the outside.

  For this reason, the displacement directions of the vertices E, F, G, H, M, N, O, and P are opposite to the displacement directions of the vertices A, B, C, D, I, J, K, and L. , The respective displacements cancel each other.

  For this reason, it is hard to produce the big collapse that the external member 10 bends in one direction in the middle of buckling. Furthermore, the time when buckling occurs at the vertices E, F, G, H, M, N, O and P constituting the groove portion 14 and the basic cross section (figure A-B-C-D-I-J-K- The timing at which buckling occurs at vertices A, B, C, D, I, J, K, and L constituting LA) is different. For this reason, the buckling behavior is stabilized.

  And the suitable conditions about the range in which this groove part 14 is formed were investigated by FEM analysis. In this investigation, FEM analysis at the time of crushing of regular tetragon, regular hexagon, regular octagon, and regular decagon was performed, and a suitable range of the length of the side constituting each polygon was examined.

  The results of the FEM analysis are shown graphically in FIG. The horizontal axis in the graph of FIG. 5 indicates l (the length of the side of the external member 10) / t (the thickness of the external member 10), and the vertical axis S indicates the average load per unit cross-sectional circumference at 70% collapse ( kN / mm).

  As shown in the graph of FIG. 5, if the length l of one side of the external member 10 satisfies the range of 4 <(l / t) <65 with respect to the plate thickness t, the number of corners of the polygon Stable deformation can be obtained regardless of, and the shock absorbing performance can be secured stably. That is, in the graph shown in FIG. 5, if (l / t) is 3.6, which is slightly less than 4, the external member 10 is bent without being buckled in a bellows shape, and the absorbed energy cannot be secured. is there. On the other hand, when (l / t) is 4.7, which is slightly higher than 4, the outer member 10 can be bent in a desired shape without bending, and sufficient absorbed energy can be secured.

  On the other hand, in the graph shown in the figure, when (1 / t) is 64, which is slightly less than 65, bellows-like buckling is obtained, and sufficient absorbed energy can be secured. On the other hand, if (l / t) is 65 or more, the entire external member 10 is bent, and the amount of absorbed energy decreases.

  From the above results, the groove 14 provided in the external member 10 has a width of the side having the groove 14 as a, an opening width of one groove 14 as Wi, a plate thickness of the external member 10 as t, When the number of the grooves 14 provided is n and the width of one of the remaining (n + 1) remaining areas divided by the n grooves 14 is Xj, the following ( It is desirable to be provided so as to satisfy the formulas (1) and (2).

4t <Wi <65t i = 1 to n (1)
4t <Xj <65t j = 1 to n + 1 (2)
However, ΣWi + ΣXj = a, and ΣWi is the sum of the opening widths Wi of the grooves formed on the side of the width a, and the opening width of the groove is the two intersections of the side of the width a and the outline of the groove ΣXj is the sum of the widths Xj.

More preferably, in the graph of FIG.
4t <Wi <35t i = 1 to n (1a)
4t <Xj <35t j = 1 to n + 1 (2a)
It is.

  If the depth d of the groove portion 14 is too small, less than 0.3 of the opening width Wi of the groove portion 14, the strength of the groove portion 14 becomes weaker than the strength of other vertices that do not constitute the groove portion 14, Buckling tends to be unstable. For this reason, it is desirable that the depth d of the groove 14 is 0.3 times or more the opening width Wi of the groove 14.

  That is, the opening width Wi of one groove portion 14 satisfies 4t <Wi <65t, where t is the thickness of the external member 10. When Wi is 4 t or less, the strength against buckling of the groove 14 is excessively higher than the other apexes A, B, C, D, I, J, K, and L forming the polygon, and the crushing is in progress. May cause buckling instability such as bending. On the other hand, when Wi is 65 t or more, the effect of providing the groove 14 may be weakened. Such a relationship is satisfied for any of n.

  Moreover, the groove part 14 in this Embodiment may be provided in any side of a polygon, and the number of the groove parts 14 may be two or more in one side. However, when the groove portion 14 is provided at a position including any one of the vertices A, B, C, D, I, J, K, and L of the basic cross section, as in the invention described in Patent Document 4 described above, Vertex strength increases excessively. For this reason, buckling may become unstable, and the amount of shock absorption may be insufficient. In addition, the maximum reaction force generated in the external member 10 particularly in the initial stage of crushing exceeds the strength of other members, and other members There is also a risk of damage.

Next, the remaining area excluding a part of the area where the groove 14 is formed will be described.
In FIG. 4, when n grooves 14 are provided on the side 12, the side is divided into (n + 1) new straight line portions by the groove 14. At this time, when the width of each of the (n + 1) divided linear portions is Xj, the expression (2) is satisfied.

4t <Xj <65t j = 1 to n + 1 (2)
When the width Xj is 4 t or less or 65 t or more, sufficient absorbed energy cannot be obtained.

  These relationships are specifically shown in FIG. FIG. 6 shows a case where three grooves 14 are provided on the side 12 having the width a. Each of the opening widths W1, W2, and W3 of each groove portion 14 is larger than 4 times the plate thickness t of the external member 10 and smaller than 65 times the plate thickness t. At the same time, the widths X1, X2, X3, and X4 of the four straight portions remaining after the side 12 of the width a is divided are both larger than four times the plate thickness t and smaller than 65 times the plate thickness t.

  In the above description, an example in which the cross-sectional shape of the groove 14 is a trapezoid is taken as an example. However, the present invention is not limited to this form. In addition to this form, the cross-sectional shape of the groove may be a curved shape, a triangular shape or a quadrangular shape, or a shape obtained by combining two or more of these shapes.

  Further, the shape of the bottom of the groove 14 need not be a flat surface. Several examples of the cross-sectional shape of the groove 14 are collectively shown in FIGS. 7 (a) to 7 (d). FIG. 7 (a) shows a case where it is formed in a shape having an arc, FIG. 7 (b) shows a case where it is formed in a quadrangular shape, FIG. 7 (c) shows a case where it is formed in a triangular shape, Further, FIG. 7D shows a case where a part of a triangle and a shape having an arc are combined.

FIG. 8 is a drawing similar to FIG. 4, and the same reference numerals denote the same members.
In the present embodiment, as shown in FIG. 8, the internal angle α of the intersection M between the contour line of the groove 14 and the side is not less than the internal angle β of the end point L of the side, that is, α ≧ β in FIG. It is preferable. If α is less than β, the strength of the groove portion 14 exceeds the strength of the vertices A, D, I, and L of the basic cross section, and the buckling tends to be unstable.

  Although the shock absorbing member 1 of the present embodiment including the external member 10 can secure sufficient absorbed energy, the initial load at the start of crushing becomes high and may cause a problem. For this reason, depending on the relationship with other members, the other members may be damaged by a high initial maximum load. Therefore, in this embodiment, in order to reduce the initial maximum load, the position where the cross-sectional area of the external member 10 is separated by a distance (T × 0.3), where T is the total axial length of the external member 10. It is provided so as to be smaller than other parts in the range up to For example, in at least a part of the range from the one end to the position separated in the axial direction by the distance (T × 0.3), the position away from the distance (T × 0.3) to the one end 15. It is provided so that the cross-sectional area gradually decreases as it goes.

Next, the relationship between the axial length that reduces the cross-sectional area and the effect of reducing the initial maximum load will be described.
FIG. 9 is an explanatory view showing the external member 10 constituting the shock absorbing member 1 of the present embodiment. As shown in the figure, an impact-absorbing member was obtained by providing a groove 14 having an opening width W of 37.5 t in a cylinder having an octagonal cross section having a flatness of 2.0 and a total length of T. In this example, the cross-sectional area at one end 15 to which an impact load is applied is 60% of the cross-sectional area at the other end 16. Then, this cross-sectional area is gradually increased from one end 15 within a range of (T × 0.3) or less, and the cross-sectional area at a position outside this range is set as the cross-sectional area at the other end 16. And the same. Then, the analysis was performed under the condition of crushing 70% of the member length in the axial direction, and the magnitude of the initial maximum load was examined.

  The examination results are shown graphically in FIG. The horizontal axis U in the graph of FIG. 10 indicates the length of the portion where the cross-sectional area of the external member 10 is reduced / the length T of the external member 10. The left vertical axis V indicates the initial maximum load ratio (when the cross-sectional area is not reduced is 1), and the right vertical axis Z is the absorbed energy ratio at the time of 70% collapse (when the cross-sectional area is not reduced). Is 1). In the graph of FIG. 10, the black square mark indicates the initial maximum load ratio, and the black circle mark indicates the absorbed energy ratio.

  As shown in the graph of FIG. 10, when compared with the case where the cross-sectional area of one end 15 is not reduced, at least a range from the one end 15 to a position away from the end 15 in the axial direction (T × 0.3). In some cases, by gradually reducing the cross-sectional area from the predetermined position toward one end, an effect of reducing the initial maximum load can be obtained, and a significant reduction in the impact energy absorption amount can be suppressed.

  Further, unlike the example shown in FIG. 9, as shown in FIG. 11, in this range, at least a part of the range from one end portion 15 to a position away in the axial direction (T × 0.3) is provided. The groove 14 may not be provided.

  As described above, in this embodiment, in order to reduce the initial maximum load and to suppress a significant decrease in the amount of shock energy absorption, the distance from the one end portion 15 in the axial direction (T × 0.3) is increased. In all or part of the range up to the position, (1) as shown in FIG. 9, the cross-sectional area of one end 15 is set to 60% of the cross-sectional area of the other end 16, and from one end 15 ( Gradually increase this cross-sectional area over a range of length equal to or less than (T × 0.3) and make the cross-sectional area at a position out of this range the same as the cross-sectional area at the other end 16 or (2 11) As shown in FIG. 11, by not providing the groove portion 14 for stable buckling, the initial maximum load can be reduced by either destabilizing the external member 10 in this range as unstable buckling. While reducing the load, A significant decrease in attack energy absorption can be suppressed.

In FIG. 9, the cross-sectional area in the range exceeding the distance (T × 0.3) is the same as the cross-sectional area at the other end, but it does not necessarily have a constant cross-sectional area.
If the means of (1) or (2) is applied to a range exceeding 30% of the member length T, it affects the buckling after the initial buckling, and stable buckling cannot be obtained. In other words, it is desirable that the groove portion 14 defined in the present invention is provided over a region of 70% or more in the axial direction from the other end portion 16 opposite to the one end portion 15 where the impact load acts on the external member 10. .

  In the example shown in FIGS. 9 and 11, the groove portion 14 is continuously provided in the entire region of 70% or more in the axial direction from the other end portion 16, but the groove portion 14 is continuously provided in the entire region. It is not necessary and may be provided intermittently in this region.

  As shown in FIG. 9, the means (1) shown in FIG. 9 is such that the cross-sectional area of the external member 10 is a distance (T × 0.3) when the total axial length of the external member 10 is T. As long as it is smaller than other parts in at least a part of the range up to a distant position, the cross-sectional area may be reduced rapidly or gradually. In addition to the means (1) or (2), a bead that is a starting point of crushing is formed at least partially in a range up to a position separated by a distance (T × 0.3). May be.

  The external member 10 in the present embodiment may be manufactured by well-known and appropriate means, and is not limited to a specific manufacturing method. For example, one or more processes such as extrusion, hydroforming (liquid seal molding) or roll forming are performed on the hollow material, or press bending, drawing, winding or roll forming is performed on a steel sheet having a predetermined thickness. It is good also as a closed cross-sectional shape by joining a part suitably after making it a cylinder which has a polygonal cross-sectional shape by performing any one or more. As a joining method at this time, for example, intermittent joining such as spot, caulking or spot friction stir welding, or continuous joining such as arc (plasma), laser or friction stir welding may be used.

  Further, post-treatment such as induction quenching, laser quenching, carburizing, and nitriding is preferably performed on the molded external member 10 because the strength of the external member 10 can be further increased. In addition, if the external member 10 of this example is comprised using materials other than a tailored blank and also a thin steel plate, an aluminum alloy, etc. for weight reduction, high load can also be achieved.

  In addition, it is illustrated that the flatness of this external member 10 is 1.0 or more and 3.5 or less. If the flatness exceeds 3.5, buckling may become unstable and the amount of shock absorption may be insufficient, and the maximum reaction force generated in the cylindrical body at the initial stage of crushing exceeds the strength of other members. Other members may be damaged.

Next, a modified example 10-1 of the external member 10 will be described.
This modification 10-1 is the above-mentioned in that it has a groove portion recessed inwardly at the position which is a partial region of at least one side of the basic cross section having the maximum contour and does not include the end point of this side. The external member 10 is common.

  However, in the modified example 10-1, the remaining area excluding the partial area is not formed linearly like the external member 10, but is a curve that protrudes outside the outline, or the inside of the outline. The external member 10 is further developed and improved by forming a shape having a concave curve.

Therefore, in the following description, the differences from the above-described external member 10 will be mainly described, and overlapping descriptions will be appropriately omitted for the common parts.
In general, the impact performance of the shock absorbing member is governed by a load (buckling load) at which the shock absorbing member buckles. This buckling load is substantially governed by the load when the apex having high rigidity in the cross section of the shock absorbing member undergoes buckling deformation.

  On the other hand, when the load increases, compressive strain is accumulated at the apex, and compressive deformation proceeds at the apex before buckling. Thereafter, when this apex buckling occurs, the load decreases rapidly. In order to suppress this decrease in load, it is necessary to limit the buckling of the apex to a more locally small area, and to generate and grow the buckling wrinkle on the surface portion formed between the apexes. It is both important to increase the deformation stress of the bending deformation that occurs.

  Therefore, in order to increase the load at the time of buckling, it is necessary to enlarge the area where the compressive deformation occurs by making the surface portion other than the apex a shape that can easily compress the deformation without buckling. desirable. In order to increase the deformation stress at the time of bending deformation, if work hardening is generated on the surface where buckling wrinkles are generated and grow, the compressive deformation is accelerated before the buckling starts to increase the deformation stress at the time of bending deformation. This can suppress the rapid decrease in load described above during buckling.

  In other words, the reason why the remaining region of the external member 10 described above is formed in a shape that is convex outside the contour or a shape that is concave inside the contour is to increase the rigidity of the surface portion and That is, compressive strain is accumulated in the surface portion. As a result, by increasing the buckling load and accumulating compressive strain (work hardening), it is possible to increase the generation of buckling wrinkles and the deformation resistance during growth, and to suppress a decrease in load during buckling.

  However, depending on the cross-sectional shape of the external member 10, by forming the remaining region in a curved shape, the rigidity of the surface portion is increased, thereby breaking the rigidity balance between the surface portion and the vertex and causing the buckling of the vertex to occur. May become unstable. Therefore, when a curved shape is formed in the remaining region to increase the rigidity of the surface portion, it is desirable to apply to the external member 10 having a cross-sectional shape that originally has a high rigidity at the apex.

FIG. 12 is an explanatory view showing a cross section of a modified external member 10-1.
As shown in FIG. 12, in the modified external member 10-1, grooves 14 and 14 are provided in order to achieve high performance and stable buckling between the vertices (AL, DI), and surface portions ( D-E1, H1-E2, H2-I, L-M1, P1-M2, P2-A) FEM analysis is performed on the external member 10-1 having a cross-sectional shape obtained by adding curved shapes having various curvatures ρ. went.

  In this FEM analysis, the material of the external member 10-1 was a 590 MPa class 1.0 mm-thick steel plate, and the strain rate dependency was taken into account according to the Cowper-Symmonds law. Further, the conditions for giving the curvature are as follows. Surface portions (D-E1, H1-E2, H2-I, L-M1, P1) having a width of 28 mm between the vertices (AL, D-I) in the target portion shown in FIG. -M2, P2-A) is given a curvature so as to form a curved shape having a height h of 0.5 to 15.0 mm toward the outside or the inside, and the surface portion (D-E1, H1-E2). H2-I, L-M1, P1-M2, and P2-A) were analyzed for collision performance when formed in a straight line.

  The performance was compared by the ratio of absorbed energy up to 70% collapse displacement of the member length with respect to the unit weight of the member. The member length T used for the analysis is 200 mm. Comparison between the conditions was performed relative to the case where the surface portions (D-E1, H1-E2, H2-I, L-M1, P1-M2, and P2-A) were formed in a straight line. The results are summarized in a graph in FIG.

  In the graph of FIG. 13, the horizontal axis represents h / X, the vertical axis Y represents the collision performance (%) per unit weight, and is 100% when the surface portion is formed in a straight line. In this graph, a black circle indicates a case where a convex shape is provided toward the outside of the surface portion, and a white circle indicates that a concave shape is provided toward the inside of the surface portion.

  As can be understood from the graph of FIG. 13, in the region where (h / X) is 0.075 or less, a concave shape (concave shape) is provided, and (h / X) is 0.075 to 0.375. By providing a convex shape (convex shape) on the outer side in the region, and further providing a concave shape on the inner side in the region where (h / X) is 0.26 or more, the collision performance per unit weight can be improved.

Thus, the collision performance can be further improved by providing the curvature to the surface portions (D-E1, H1-E2, H2-I, L-M1, P1-M2, P2-A).
FIG. 14 is an explanatory view schematically showing a state of bending due to elastic buckling of the apex and the surface when the curvature is given to the surface of the external member 10-1 having the groove 14, and FIG. FIG. 14B shows a case where a convex curvature is given to the inside.

  As shown in FIG. 14 (a), when a curvature that is convex outward is applied, if the applied curvature is small, the spread of the cross section at the initial stage of the collision becomes large. For this reason, when compared with the case where the surface portions (D-E1, H1-E2, H2-I, L-M1, P1-M2, P2-A) are straight, the cross section causes elastic buckling to spread outward and the apex. In (A to P2), the amount of compressive strain acting in the axial direction is reduced, and the buckling load is reduced.

  However, when the curvature applied to the surface portions (D-E1, H1-E2, H2-I, L-M1, P1-M2, P2-A) increases to some extent, the surface portions (D-E1, H1-E2, H2-I). , L-M1, P1-M2, P2-A) itself is increased in rigidity, and compression distortion is also caused in the surface portions (D-E1, H1-E2, H2-I, L-M1, P1-M2, P2-A). Increases and the buckling load increases. Moreover, the height of the convex imparted to the surface portions (D-E1, H1-E2, H2-I, L-M1, P1-M2, P2-A) is about 0.075 to 0.375 in h / X. Since the plastic deformation of the face portions (D-E1, H1-E2, H2-I, L-M1, P1-M2, and P2-A) is promoted by increasing the size, the deformation resistance during the growth of buckling wrinkles Is increased, and a decrease in load after occurrence of buckling is suppressed. Thereby, collision performance improves rather than the case where a surface part (D-E1, H1-E2, H2-I, L-M1, P1-M2, P2-A) is a straight line.

  On the other hand, as shown in FIG. 14B, when a concave curvature is applied to the inside, if the applied curvature is small, the apex (A to P2) and the surface portion (D-E1, H1-E2, H2-I, L-M1, P1-M2, and P2-A) have different directions of elastic buckling. Thereby, the spread of the vertices (A to P2) is suppressed, and a larger compression strain is accumulated. As a result, the buckling load is increased and the collision performance is improved as compared with the case where the surface portions (D-E1, H1-E2, H2-I, L-M1, P1-M2, and P2-A) are straight lines.

  However, when the curvature to be applied is further increased, the buckling mode repeatedly generated in the entire external member 10-1 becomes unstable, and the collision performance is deteriorated. This is because the height of the recesses imparted to the apex (A to P2) and the surface (D-E1, H1-E2, H2-I, L-M1, P1-M2, P2-A) is 0 in h / X. By increasing it to about .075 to 0.26, it becomes a form in which buckling wrinkles that grow are involved and the buckling proceeds, so that the repeatedly generated buckling becomes unstable, and the entire external member 10-1 This will cause the collision performance to deteriorate.

  However, when the height of the concave portion to be applied is further increased to about 0.26 to 0.55 in h / X, the surface portion (D-E1, H1) is provided in the same manner as in the case of giving a convex curvature toward the outside. -E2, H2-I, L-M1, P1-M2, and P2-A) are promoted to increase the buckling load until buckling occurs and also increase the deformation resistance during the growth of buckling wrinkles. Therefore, load reduction after occurrence of buckling can be suppressed, and collision performance is improved as compared with the case where the surface portions (D-E1, H1-E2, H2-I, L-M1, P1-M2, P2-A) are straight lines. To do.

  As in the present embodiment, the buckling strength of the apex (A to P2) is controlled and the surface portions (D-E1, H1-E2, H2-I, L-M1, P1-M2, P2-A) are controlled. However, the collision performance can be further improved by providing an appropriate curvature.

  In addition, the optimal value of the curvature given to the surface portions (D-E1, H1-E2, H2-I, L-M1, P1-M2, P2-A) is the overall cross-sectional rigidity of the external member 10-1, and the surface portion. (D-E1, H1-E2, H2-I, L-M1, P1-M2, P2-A), that is, the surface (D-E1, H1-E2, H2-I, L-M1, P1-M2) , P2-A) is considered to change.

  On the other hand, the impact absorbing member for a vehicle body of an automobile provided with the external member 10-1 has an upper limit in the applicable cross-sectional area because of the dimensional relationship with other members. In addition, it is necessary to consider forming a reference plane for joining other members.

For this reason, the height h is desirably 50 mm or less.
As described above, the external member 10-1 according to the modified example also accumulates the compressive strain in the axial direction and buckles at the surface portion which is a portion other than the apex in the axial crushing process at the time of collision. By increasing both the deformation stress at the time of forming, an excellent shock absorbing performance is obtained. For this purpose, it is desirable to impart a shape (curvature) also to the surface portion and improve the rigidity of the surface portion.
Thus, since the impact absorbing member 1 of the present embodiment includes the external member 10 or 10-1, a stable crushing behavior can be realized when an impact load is applied in the axial direction.

[Internal member 20]
As shown in FIG. 1, the impact absorbing member 1 of the present embodiment includes an internal member 20 inside the external member 10 described above. The cross-sectional shape of the internal member 20 in the axial direction is a closed cross section having a plurality of vertices.

As described above, the internal member 20 is disposed inside the external member 10 described above and functions as a bending rigidity improving member for improving the bending rigidity of the shock absorbing member 1.
That is, the shock absorbing member 1 of the present embodiment increases the bending rigidity of the external member 10 by including the internal member 20, whereby not only the direction parallel to the axial direction but also the direction intersecting the axial direction, For example, even when an impact load (diagonal load) is input in a direction in which the angle of intersection with the axial direction is greater than 0 ° and not more than 15 °, the axial direction is stable without causing bending in the axial direction. A predetermined amount of shock absorption can be ensured by plastic buckling in a bellows shape, and excellent shock absorption performance can be exhibited. The knowledge about the deformation stabilization of the internal member 20 will be described below.

(Knowledge 4)
As shown in FIG. 1, the shock absorbing member 1 of the present embodiment has an internal member 20 disposed inside an external member 10. That is, in the present embodiment, the external member 10 (A-B-C-D-E-F-G-H-I-J-K-LM-N-OP) is disposed inside the external member 10. An internal member 20 having a similarity ratio of 0.65 to 10 is arranged. The internal member 20 is joined to the external member 10 by the joining member 21 via the sides FG and ON of the external member 10.

  Thus, when the internal member 20 is arranged inside the external member 10, the bending rigidity of the cross section of the shock absorbing member 1 is increased, so that the crossing angle with the axial direction, for example, the crossing angle with the axial direction is more than 0 degree 15 Stable crushing deformation is exhibited without causing bending deformation with respect to impact loads in all directions included below the degree.

  In general, when an oblique load is input to the impact absorbing member, a load that induces a collapse acts on the impact absorbing member on the collision end side (the oblique load input side). At this time, when the structure has only the external member 10 and does not have the internal member 20, the bending rigidity of the cross section of the shock absorbing member is low, so that it falls in the longitudinal direction due to the applied load (bending deformation). Is induced, and the compressive strain necessary to generate the buckling deformation in the axial direction does not accumulate. For this reason, bending deformation occurs in the entire shock absorbing member without showing stable buckling deformation, and the amount of shock energy absorbed does not reach a desired value.

  Therefore, in the present embodiment, as described above, the internal member 20 is disposed inside the external member 10 to increase the bending rigidity of the cross section of the shock absorbing member 1 particularly on the collision end side (oblique load input side). . As a result, the external member 10 and the internal member 20 come to bear an oblique load that is input as a unit, and the rigidity at the support point for fixing the shock absorbing member 1 is improved, and the external at the input end side of the oblique load A load that induces the collapse of the member 10 (moment for bending and deforming the external member 10) can be reduced. For this reason, it is possible to generate a stable crushing deformation (buckling deformation) even with a load in an oblique direction, and to obtain a high impact energy absorption amount with respect to the oblique load. Can be reliably induced, the rigidity on the anti-collision end side can be increased, and the shock absorbing member 1 can be prevented from falling from the position where the shock absorbing member 1 is supported (the position where the shock absorbing member 1 is coupled). It becomes like this.

  Next, it will be specifically described with reference to the FEM analysis result that by providing the internal member 20, it is possible to realize stable deformation characteristics even when an oblique load is applied.

FIG. 15 is a graph showing the result of FEM analysis of load characteristics at the time of collision deformation for an impact absorbing member having the internal member 20 and an impact absorbing member not having the internal member 20.
Condition 1 in the graph of FIG. 15 is that load characteristics (displacement) when an impact load is input in a direction substantially parallel to the axial direction of the impact absorbing member including only the external member 10 without the internal member 20 (load input A). Condition 3 shows a case where an oblique load Fa is inputted to the same shock absorbing member as the shock absorbing member of Condition 1 from a direction of 10 ° with respect to the axial direction (load input B). The load characteristics are shown. On the other hand, the conditions 2 and 4 are the load characteristics when the impact load is input to the impact absorbing member 1 shown in FIG. 1 described above from the direction parallel to the axial direction and the oblique 10 ° direction (load inputs A and B). Are shown respectively.

  The material characteristics of the external member 10 and the internal member 20 of the shock absorbing member 1 used in this FEM analysis are 590 MPa class high-tensile steel plates with a plate thickness of 1.0 mm. Further, in order to reduce the initial load at the time of the collision, the external member 10 is directed in the longitudinal direction with respect to the apex portions of the E-F-G-H and M-N-O-P on the impact load input side. A notch was provided in a range of 15 mm in length. Similarly, the inner member 20 was provided with a notch.

  As shown in the graph of FIG. 15, in conditions 1 and 3 where the internal member 20 is not provided, the load input A shows stable load characteristics up to a deformation displacement of 110 mm, whereas the load input B Shows a tendency for the load to rapidly decrease after displacement 30 mm. However, the conditions 2 and 4 in which the internal member 20 is provided are satisfactory because the load inputs A and B both show stable load characteristics.

  That is, when the internal member 20 is not provided, stable load characteristics are exhibited with respect to an axial load, but when an oblique load is applied, a collapse occurs, and the entire shock absorbing member is bent, resulting in a deformation load. Decreases. However, when the internal member 20 is provided, even if an oblique load is applied as well as an axial load, the entire shock absorbing member does not bend, and a stable buckling deformation occurs and a good collision performance is obtained. be able to.

  The cause of the rapid drop of the deformation load and the large load fluctuation in the condition 3 in the graph of FIG. 15 is that the external member 10 falls when an oblique load is applied. For this reason, as in Condition 4, the internal member 20 is arranged inside the external member 10 to increase the rigidity in the cross section of the shock absorbing member 1, thereby causing the external member 10 due to an oblique load being applied. Can be suppressed, whereby stable buckling deformation can be generated without causing bending of the entire shock absorbing member, and good collision performance can be obtained.

  From this result, by providing the internal member 20 inside the external member 10, even when an impact load is input not only from the axial direction but also from the direction intersecting the axial direction, stable performance is obtained and desired high performance is achieved. It can be seen that it is possible to realize a large absorbed energy.

Next, the internal member 20 will be described more specifically.
The maximum size of the inner diameter member 20 is determined by the size of wrinkles generated when crushing (buckling). That is, in order to prevent the buckling wrinkles generated by the buckling of the outer member 10 and the inner member 20 from interfering with each other, the inner member 20 It is desirable to arrange the outer member 10 with a distance of 13 mm or more from the entire circumference.

  The size of the wrinkle generated during crushing deformation depends on the length of the side, and a large buckling wrinkle is generated on the long side. Therefore, as described above, the interference between wrinkles between the external member 10 and the internal member 20 is an important distance between the long sides of the external member 10 and the internal member 20 (distance SP in FIG. 22 to be described later). In this part, the deformation behavior of the member is largely governed when it is 13 mm or more.

  Further, as described above, in order for the internal member 20 to bear an oblique load that is input integrally with the external member 10, the cross-sectional area of the internal member 20 is 20% or more of the cross-sectional area of the external member 10. It is also desirable to be.

  Further, the internal member 20 is to reduce the oblique load borne by the external member 10 to prevent the internal member 20 from falling down, and to suppress bending in the longitudinal direction due to the rigidity improvement of the plane portion between the ridge lines of the external member 10. The shape and arrangement of the internal member 20 do not require any particular limitation. For example, the inner member 20 may be configured to be similar or non-similar to the outer member 10, and the inner member 20 is symmetric with respect to a symmetry line (straight lines 1 and m in FIG. 1) of the outer member 10. You may provide in the position used as or asymmetrical position.

  In the present embodiment, the joining member 21 that supports the internal member 20 is fixed to the inner surfaces of the sides FG and ON of the external member 10. However, as a result of FEM analysis, when the joining member 20 is joined to a position including the inner surfaces of the vertices A to P of the external member 10, the rigidity of the joined vertices A to P increases. There is a risk that the shock absorption performance will be deteriorated due to the unstable behavior. For this reason, in order not to impede the absorption of impact energy by buckling and deforming into a bellows shape due to the applied impact load, the internal member 20 that is a bending rigidity improving member has each apex A of the external member 10. It is fixed to the inner surface of the external member 10 through a straight line portion (each side) formed between the adjacent apexes AP of the external member 10, specifically, an area not including P. ,desirable.

  In this way, the dimensions of the internal member 20 may be adjusted as appropriate in accordance with the direction in which the impact load is input. In the present embodiment, for example, as shown in FIG. As a result, the internal member 20 is arranged via the joining member 21 so as to connect the side FG of the external member 10 and the side ON. The size of the cross section of the internal member 20 is about 80% of the size of the cross section of the external member 10.

  Further, when the shock absorbing member 1 of the present embodiment is mounted as a crash box at the front end of a front side member of an automobile body by appropriate means such as fastening or welding, a tie-down hook is mounted inside the internal member 20. It is conceivable to incorporate a nut. In this case, the inner diameter member 20 needs to have an area necessary for incorporating the nut, but the area may be appropriately determined in consideration of the dimension of the incorporated nut. For example, securing an area of 40 mm or more is exemplified. If the internal member 20 cannot secure this area, the mounting position of the nut for attaching the tie-down hook may be changed to a position other than the inside of the internal member 20.

  Similar to the external member 10, the internal member 20 may be manufactured by well-known and appropriate means, and is not limited to a specific manufacturing method. For example, one of extrusion, hydrofoam (liquid seal molding), roll forming, etc., or a combination of these may be performed on a hollow material, or press bending, drawing, winding, or rolling on a steel plate of a predetermined thickness By performing any one or a plurality of processes such as forming, a closed cross-sectional shape is obtained by forming a cylindrical body having a polygonal cross-sectional shape and then joining the appropriate portions. Examples of the joining method in this case include intermittent joining such as spot, caulking or spot friction stir welding, and continuous joining such as arc (plasma), laser or friction stir welding.

Moreover, what is necessary is just to assemble using welding, such as a spot and an arc, also when joining the internal member 20 to the external member 10 via the joining member 21. FIG.
Furthermore, it is effective to perform post-treatment such as induction hardening, laser hardening, carburizing, and nitriding on the internal member 20 in order to further improve the performance. Further, as the material of the internal member 20, a tailored blank, and a material other than a thin steel plate and an aluminum alloy can be used for weight reduction.

  Since the shock absorbing member 1 of the present embodiment includes the external member 10 and the internal member 20 disposed inside the external member 10, only the direction parallel to the axial direction is provided from one end in the axial direction. In addition, even if an impact load is applied in a direction crossing the axial direction, for example, in any direction in which the crossing angle with the axial direction is included in the range of more than 0 degrees to 15 degrees or less, it is surely buckled and deformed into a bellows shape. Thus, it is possible to sufficiently absorb the impact energy and to secure a predetermined impact absorption performance. For this reason, if the shock absorbing member 1 is applied to the above-described crash box and attached to the front end of the front side member by appropriate means such as fastening or welding, the safety of the vehicle body is improved and the vehicle body caused by a light collision is obtained. The repair cost can be reduced by substantially eliminating the damage.

  In this way, according to the present embodiment, even when an oblique load is input, a predetermined shock absorption is achieved by buckling in the axial direction stably without causing bending in the axial direction. It was possible to provide an impact-absorbing member capable of securing the amount and exhibiting stable high performance.

(Embodiment 2)
Further, the present invention will be described in detail with reference to another embodiment. In the following description of the second to fourth embodiments, portions that are different from the above-described first embodiment will be described, and overlapping portions will be omitted by appropriately attaching the same reference numerals in the drawings. .

FIG. 16 is an explanatory diagram schematically showing a cross section of the shock absorbing member 1-1 according to the second embodiment. In addition, the triangle mark in FIG. 16 shows a spot weld part.
The shock absorbing member 1-1 according to the present embodiment is different from the shock absorbing member 1 according to the first embodiment in the cross-sectional shape of the internal member 20-1.

  The internal member 20-1 in the shock absorbing member 1-1 of the present embodiment is assembled in a drum shape by overlapping two hat channel members 20-1a and 20-1b, and each hat channel member 20-1a and 20-1b. Each of the end portions is bent in a crank shape to integrally form the joining member 21-1.

  Also in this example, the inner member 20 was arranged at a distance of 13 mm or more from the outer member 10 on the entire circumference, and the cross-sectional area of the inner member 20 was set to 45% of the cross-sectional area of the outer member 10.

  According to the shock absorbing member 1-1 of the present example, the external member 10 and the internal member 20-1 disposed inside the external member 10 are provided in the same manner as the shock absorbing member 1 of the first embodiment. Even if an impact load is applied from one end in the axial direction not only in this axial direction but in any direction that intersects with this axial direction, the impact energy can be reduced by reliably buckling and deforming into a bellows shape. It is possible to sufficiently absorb and secure a predetermined shock absorbing performance. For this reason, if this shock absorbing member 1-1 is applied to the above-mentioned crash box and attached to the front end of the front side member by an appropriate means such as fastening or welding, the safety of the vehicle body can be improved and light collision can be achieved. It is possible to reduce the repair cost by substantially eliminating the damage to the vehicle body caused by.

Moreover, since the impact-absorbing member 1-1 of this example has a simpler structure than the impact-absorbing member 1 of Embodiment 1 regarding an internal member, it can be manufactured at low cost.
In this way, according to the present embodiment, even when an oblique load is input, a predetermined shock absorption is achieved by buckling in the axial direction stably without causing bending in the axial direction. The impact absorbing member that can secure the amount and can exhibit stable high performance can be provided at a lower cost than the first embodiment.

(Embodiment 3)
FIG. 17 is an explanatory diagram schematically showing a cross section of the shock absorbing member 1-2 according to the third embodiment. In addition, the triangle mark in FIG. 17 shows a spot weld part.

The point that the shock absorbing member 1-2 of the present embodiment is different from the shock absorbing members 1, 1-1 according to the first and second embodiments is also the cross-sectional shape of the internal member 20-2.
The internal member 20-2 in the shock absorbing member 1-1 of the present embodiment is formed by joining a hat-shaped channel member 20-2a and a bottom plate 20-2b, and a hat-shaped channel member 20-2a. The end portions of the base plate 20-2b and the bottom plate 20-2b are bent in a crank shape, and the joining member 21-2 is integrally formed and arranged at an asymmetrical position offset to the left from the symmetry line m of the external member member 10. Is.

  Also in this example, the inner member 20-2 is arranged at a distance of 13 mm or more from the outer member 10 on the entire circumference, and the cross-sectional area of the inner member 20-2 is set to 25% of the cross-sectional area of the outer member 10. did.

  Depending on the components of the automobile body, the input direction of the assumed impact load may be specified in one direction from the requirements on the shape and the connection with other members. When the present invention is applied to such a member, as shown in FIG. 17, the internal member 20-2 having a large number of vertices is arranged in an offset manner only in an area where the rigidity needs to be improved. Thus, it is possible to sufficiently absorb the impact energy by reliably buckling and deforming into a bellows shape, ensuring a predetermined shock absorption performance, and reducing the weight of the entire shock absorbing member 1-2. Can do.

  As described above, according to the present invention, by appropriately adjusting the shape and arrangement of the internal member 20 in accordance with the assumed shock load input conditions, the desired shock absorption performance can be suppressed while minimizing the increase in weight. ,Obtainable.

(Embodiment 4)
FIG. 18 is an explanatory view schematically showing a cross section of the shock absorbing member 1-3 of the present embodiment. As shown in the figure, in the impact absorbing member 1-3 of the present embodiment, the internal member 20 used in the first embodiment, the inner member 20-1 used in the second embodiment, Furthermore, it replaced with the internal member 20-2 used in Embodiment 3, and used the flat partition plate 40. FIG.

  As shown in FIG. 18, the partition plate 40 is formed by bending two edges of a flat plate material in opposite directions to form two flange portions 40a and 40b. In this example, assuming that the load Fa is inputted, the partition plate 40 is inserted into the external member 40 and temporarily fixed, and joining such as spot welding is performed at the position of the triangle mark shown in FIG. Thus, the side FG of the external member 10 is connected to the side ON via the flange portions 40a and 40b.

  What is necessary is just to determine arrangement | positioning of the partition plate 40 corresponding to the input direction of the assumed load. That is, as described above, in this example, since it is assumed that the load Fa is input, the partition plate 40 is disposed so as to connect the side FG and the side ON of the external member 10, but the load Fa When assuming a load Fb input from a direction 90 ° different from the direction, the partition plate 40 may be disposed so as to connect the side BC and the side KJ of the external member 10.

  FIG. 19 is an explanatory view showing another installation method of the partition plate 40. As shown in FIG. 19, a first external member 10a having a closed cross-sectional shape provided with a portion 40 ′ corresponding to the partition plate 40 and a second external member 10b having an open cross-sectional shape are manufactured. As shown in the figure, it is exemplified that joining is carried out by an appropriate joining means such as spot welding at the position of a triangle mark in the figure. Note that the structure, manufacturing method, and the like of the external member 10 are the same as those in the first embodiment described above, and thus the description thereof is omitted.

  Since the shock absorbing member 1-3 of the present embodiment includes the external member 10 and the partition plate 40 arranged as a bending rigidity improving member of the external member 10 inside the external member 10, one of the axial members is arranged in the axial direction. Even if an impact load is applied not only in a direction parallel to the axial direction but also in a direction crossing the axial direction from the end, for example, in any direction where the crossing angle with the axial direction is included in the range of more than 0 degrees to 15 degrees or less By reliably buckling and deforming into a bellows shape, it is possible to sufficiently absorb the impact energy and to secure a predetermined shock absorption performance.

  FIG. 20 intersects the displacement-load diagram when the impact load is applied to the impact absorbing member 1-3 having the cross-sectional shape shown in FIG. 18 from the axial direction (condition 5) and the axial direction by 10 degrees. It is a graph which shows collectively the displacement-load diagram in the case where an impact load is applied from the direction (condition 6).

  As shown in the graph of FIG. 20, the shock absorbing member 1-3 of the present embodiment is similar to the shock absorbing members 1, 1-1, 1-2 of the first to third embodiments described above. Therefore, when an impact load is applied in the axial direction, it can be stably buckled and deformed in a bellows shape, and the impact energy can be sufficiently absorbed.

  Further, as shown in the graph of FIG. 20, the shock absorbing member 1-3 of the present embodiment is crossed because the partition plate 40 is disposed as the bending rigidity improving member of the external member 10 inside the external member 10. Since the bending rigidity of the surface is enhanced, even if an oblique load is input, the impact absorbing member 1-3 is prevented from falling at the initial time of the input, and the buckling is stably buckled in the axial direction. As a result, a predetermined amount of shock absorption can be secured, and stable shock absorption performance is exhibited.

  As described above, the shock absorbing member 1-3 of the present embodiment is also provided with a bending rigidity inside the external member 10 in the same manner as the shock absorbing members 1, 1-1, 1-2 of the first to third embodiments. Since the improvement member is included, not only the direction parallel to the axial direction but also the direction intersecting the axial direction from the one end in the axial direction, for example, the crossing angle with the axial direction is included within 0 degree or more and 15 degrees or less Even if an impact load is applied in the direction, it is possible to sufficiently absorb the impact energy by reliably buckling and deforming into a bellows shape, thereby ensuring a predetermined impact absorption performance. For this reason, if this shock absorbing member 1-3 is applied to the above-mentioned crash box and attached to the front end of the front side member by appropriate means such as fastening or welding, the safety of the vehicle body can be improved and light collision can be achieved. It is possible to reduce the repair cost by substantially eliminating the damage to the vehicle body caused by.

  Further, when the present embodiment is compared with the first embodiment described above, the only difference is the cross-sectional shape of the bending rigidity improving members 40 and 20. That is, the load acting on the shock absorbing member is larger in the shock absorbing member 1 of the first embodiment. However, in terms of the simple structure and the light weight, the load of the shock absorbing member 1-3 of the present embodiment is the same. Is more advantageous. For this reason, what is necessary is just to determine suitably whether the partition plate 40 is used as a bending rigidity improvement member, or the internal member 20 according to the specification separately request | required of an impact-absorbing member.

  As the bending rigidity improving member, the internal member 20 in the first embodiment, the internal member 20-1 in the second embodiment, the internal member 20-2 in the third embodiment, and a partition in the fourth embodiment. Each of the plates 40 is illustrated. However, it goes without saying that the bending rigidity improving member in the impact absorbing member according to the present invention is not limited to these four examples, and is arranged inside the external member so that the external member has a bellows-like buckling deformation. Any member that can increase the bending rigidity of the external member without hindering the above is applicable equally without being affected by the shape, material, and the like.

Next, the present invention will be described more specifically with reference to examples.
The outer member 10 made of a cylindrical body having a cross-sectional shape shown in FIG. 21 is formed by bending a 590 MPa class high-tensile steel plate having a thickness of 1.0 mm to form a polygonal cross section and welding the butt surfaces. Configured. The external member 10 has one groove portion 14 introduced into a flat octagon, and dimensions of each shape are as follows: W = 60 mm, depth d = 11.5 mm, side X5 = 35 mm, X6 = 35 mm, inner angle α = 100 °, β = 106 °. The member length is 180 mm.

  Furthermore, as shown in FIG. 22, the internal member 20 manufactured so that the cross-sectional area is 80% of the cross-sectional area of the external member 10 is arranged inside the external member 10, and the side 14 is interposed via the joining member 21. The impact absorbing member 1 of this example was manufactured by performing spot welding and joining to the external member 10 in FIG.

The material used for manufacturing the internal member 20 is a high-tensile steel plate of 590 MPa class having a thickness of 1.0 mm, similar to the external member 10.
In addition, the triangle mark in FIG. 19 shows a spot weld part. Further, in this example, the distance between the external member 10 and the internal member 20 is ensured to be 13 mm on the entire circumference of the external member 10. Also, Table 1 shows the external member 10 and the internal member 20 respectively. The dimension specification of the shape of is shown.

  Then, as shown in FIG. 23, in order to realize load input from an oblique direction, the manufactured shock absorbing member 1 is mounted and fixed on a table 40 tilted by 10 °, and then a weight having a weight of 200 kgf. The body 41 was allowed to freely fall from a height of 11.9 m to be collided at a speed of 55 km / h in the axial direction on the collision end side of the shock absorbing member 1.

  And the deformation resistance at the time of crushing of the impact-absorbing member 1 was measured with the piezoelectric load cell. In addition, all member length T was 180 mm, and the absorbed energy until 130 mm collapse was measured. Table 2 shows the initial maximum load and the absorbed energy at 70% collapse. For comparison, Table 2 also shows the measured values of the impact absorbing member in which the internal member 20 is not provided.

  From the results shown in Table 2, it was confirmed that by providing the internal member 20, good absorption energy was exhibited even when an oblique load was applied.

  A shock absorbing member 1-3 having a cross-sectional shape shown in FIG. 18 is manufactured by bending a 590 MPa class high-tensile steel plate with a thickness of 1.6 mm into a polygonal cross section and welding the butted surfaces. did. For comparison, an impact absorbing member not provided with the partition plate 40 shown in FIG. 18 was also manufactured.

  Then, after each of these shock absorbing members is installed on a table 40 inclined at 10 ° in the test apparatus shown in FIG. 23, a weight body 41 having a weight of 200 kgf is moved from the height of 11.9 m to these shock absorbing members. The impact-absorbing member was allowed to fall freely at a speed of 55 km / h in the axial direction, and the deformation resistance when the impact-absorbing member was crushed was measured with a piezoelectric load cell. In addition, all the length T of the impact absorbing member was 180 mm, and the amount of impact energy absorbed until the collapse of 130 mm was compared. Table 3 shows the initial maximum load and the amount of shock energy absorbed at 70% collapse (70 (%) collapse absorption energy).

  From the results shown in Table 3, by providing the partition plate 40, an impact load is applied in a direction intersecting the axial direction, for example, in any direction in which the intersecting angle with the axial direction is included in the range of more than 0 degrees to 15 degrees or less. However, it can be seen that, by buckling reliably and deforming into a bellows shape, the impact energy can be sufficiently absorbed to ensure a predetermined impact absorption performance.

FIG. 3 is an explanatory diagram schematically showing a cross section of the shock absorbing member according to Embodiment 1. It is explanatory drawing which shows the mode of the crushing of the external member which has a square cross section by FEM numerical analysis, Fig.2 (a) shows the impact-absorbing member which comprises a flange, FIG.2 (b) shows the impact which does not comprise a flange. An absorbent member is shown. It is explanatory drawing which shows typically the mode of the crushing of the external member which has a flat octagonal cross-sectional shape. It is explanatory drawing which shows the condition which provided the groove part in the trapezoid shape in a part of long side part of the external member which has a flat octagonal cross section. It is a graph which shows the result of having performed the FEM analysis on the suitable conditions about the range in which a groove part is formed. It is explanatory drawing which shows the cross section of an example of an external member. It is explanatory drawing which shows the example of a groove | channel. It is explanatory drawing which shows the cross section of an example of an external member. It is explanatory drawing which shows the input end side of an external member. It is a graph which shows the relationship between the length of the site | part which reduces the cross-sectional area of an external member / the length of an external member, and the initial maximum load ratio or the absorbed energy ratio at the time of 70% collapse. It is explanatory drawing which shows the input end side of an external member. It is explanatory drawing which shows the cross section of an example of an external member. It is a graph which shows the relationship between ratio (h / X) and the impact performance (%) per unit weight. It is explanatory drawing which shows typically the condition of the bending | flexion by the elastic buckling of the vertex and surface part at the time of giving a curvature to the surface part of the external member which has a groove part, Fig.14 (a) provided the curvature which becomes convex outward. FIG. 14B shows a case where a concave curvature is given to the inside. It is a graph which shows the test result about the effect of an internal member. It is explanatory drawing which shows the cross section of the impact-absorbing member of Embodiment 2 typically. It is explanatory drawing which shows the cross section of the impact-absorbing member of Embodiment 3 typically. It is explanatory drawing which shows the cross section of the impact-absorbing member of Embodiment 4 typically. It is explanatory drawing which shows another installation method of a partition plate. FIG. 18 schematically shows a displacement-load diagram when an impact load is applied from the axial direction to the impact absorbing member having a cross section schematically shown in FIG. 18 and the impact load from the direction intersecting the axial direction by 10 degrees. It is a graph which shows collectively the displacement-load diagram in the case of being loaded (condition t6). It is explanatory drawing which shows the cross-sectional shape of the external member in an Example. It is explanatory drawing which shows the cross-sectional shape of the impact-absorbing member in an Example. It is explanatory drawing which shows the structure of a test apparatus typically.

Explanation of symbols

1 Shock absorbing member 10 External member 20 Internal member 40 Partition plate

Claims (6)

An external member made of a cylindrical body, and a bending rigidity improving member arranged at the inside of the external member to improve the bending rigidity, the axial direction or the axial direction from one axial end of the cylindrical body An impact absorbing member for absorbing impact energy by deforming into an accordion shape by buckling with an impact load applied in a direction intersecting with
The cross-sectional shape of at least a part of the external member in the axial direction is a closed cross section having a plurality of vertices, and has no flange outside the closed cross section, and a part of the plurality of vertices is a straight line. The region that is a part of at least one side of the basic cross-section consisting of the maximum contour obtained by connecting and excluding the end point of the side is bent so as to form a groove portion recessed inward of the contour. Formed ,
The recessed groove is provided extending in the axial direction of the external member ; and
The impact absorbing member, wherein the bending rigidity improving member is fixed to an inner surface of the external member through a region not including the plurality of apexes of the external member.   2. The impact absorbing member according to claim 1, wherein the bending rigidity improving member is an internal member provided so as to have a closed cross section having a plurality of apexes in a cross section in the axial direction and to extend in the axial direction.   The impact absorbing member according to claim 2, wherein a distance between the internal member and the external member is 13 mm or more, and a cross-sectional area of the internal member is 20% or more of a cross-sectional area of the external member.   The impact absorbing member according to claim 1, wherein the bending rigidity improving member is a plate-like member. The width of the side having the groove is a, the opening width of one groove is Wi, the thickness of the external member is t, and the number of the grooves provided on the side is n. The following equations (1) and (2) are satisfied, where Xj is the width of each of the (n + 1) remaining regions divided and left by the n groove portions provided on the side. The shock absorbing member according to any one of claims 1 to 4 , which is provided as described above.
4t <Wi <65t i = 1 to n (1)
4t <Xj <65t j = 1 to n + 1 (2)
However, ΣWi + ΣXj = a, and ΣWi is the sum of the opening widths Wi of the grooves formed on the side of the width a, and the opening width of the groove is the two intersections of the side of the width a and the outline of the groove ΣXj is the sum of the widths Xj. The impact absorbing member according to any one of claims 1 to 5, wherein the impact absorbing member is a crash box.

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