JP2008261493A - Shock absorbing member and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a shock absorbing member having sufficient shock absorbing performance according to the patent invention presented by a patent document 1 while preventing hole formation in the end of a cylinder body or a reduction in the plate thickness thereof even when the plate thickness of the cylinder body as part of a crush box is 1.4 mm or smaller and the cylinder body is arc-welded abutting onto a back plate. <P>SOLUTION: The crush box 1 has the cylinder body 2 as a molded product formed of metal plates 4a, 4b and arranged between a side member and a bumper. On all or peripheral part of the end including one axial end face 2a of the cylinder body 2, a folded portion 6a is formed into such a shape that the metal plates 4a, 4b are folded. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an impact absorbing member and a manufacturing method thereof. Specifically, the present invention includes a cylindrical body that is a molded body of a metal plate for absorbing collision energy by buckling due to an impact load applied in the axial direction when a vehicle such as an automobile collides. For example, the present invention relates to an impact absorbing member such as a crash box and a manufacturing method thereof.

  Vehicles such as automobiles can protect passengers in the cabin by absorbing impact energy by impact absorbing members that are sequentially arranged from the front end to the rear end of the vehicle in the event of a collision such as a forward collision. Designed. An example of such an impact absorbing member is a crash box made of a cylindrical body.

  When an impact load is applied to the crash box in the axial direction (which means the longitudinal direction of the crash box in this specification) at the time of a vehicle collision, priority is given to the side member, which is a strength member of the automobile body, before plastic deformation. Then, by repeatedly buckling in the axial direction and plastically deforming into an accordion shape (accordion shape), the collision energy is absorbed. By installing the crash box at a predetermined position on the vehicle body, (a) Since it is attached to the body shell by welding, it is possible to prevent the side members from being effectively replaced and protect passengers in the cabin. (B) In the case of a collision at low speed, the side member can be prevented from being damaged and repaired by replacing only the bumper and crash box damaged by the collision. Both cost reduction can be achieved.

  For this reason, the shock absorption performance required for a crash box can be broadly classified as follows: (a) When an impact load is applied in the axial direction, it does not fall down or bend, and it buckles stably and repeatedly in the axial direction. It is plastically deformed into a bellows shape, (b) the load drop is small until the second half of the crush box crushing, and (c) the maximum reaction force generated when the crush box is crushed is impacted through this crush box. This is a point that the load is suppressed to a range where other members such as the side member are not destroyed, and as a result, the side member or the like is not damaged until the crush box is completely collapsed.

  Many inventions related to materials and shapes for improving the impact absorbing performance of the crash box have been proposed so far. For example, an invention in which the crash box is repeatedly buckled stably in the axial direction by forming a plurality of beads in the axial direction on the outer wall of the cylindrical body constituting the crash box in the axial direction. Known and already in practical use. However, in the present invention, the crush box is often greatly bent and deformed during repeated buckling in the axial direction. In this case, only a part of the axial direction is plastically deformed in a bellows shape. For this reason, it becomes difficult to stably obtain the targeted bellows-like plastic deformation, and the amount of absorption of impact energy is small.

  In view of this, the applicants described in advance in International Publication No. WO2005-010398 (Japanese Patent Application No. 2005-512120, Japanese Patent No. 3912422), to the inside, on the long side of a polygon having a transverse section. It has a cylindrical body that has a groove that is convex toward the axial direction and that extends in the axial direction, and is repeatedly buckled by an impact load applied in the axial direction, and is plastically deformed into a bellows shape, thereby impact energy. Proposed a patented invention related to a crash box that absorbs water.

According to the patented invention related to this proposal, since the long side of the polygon forming the cross section of the cylindrical body constituting the crash box is formed with a groove that is convex toward the inside and extends in the axial direction. , The rigidity of the part provided with the groove is increased, which prevents the crash box from falling or bending in the middle of repeated buckling due to impact load in the axial direction, and stably repeating in the axial direction It can buckle and plastically deform in a bellows shape. Therefore, the plate thickness of the cylindrical body constituting the crash box can be reduced from about 1.6 mm to about 0.8 to 1.4 mm, and the amount of shock absorption energy per unit mass can be dramatically increased. .
International Publication No. WO2005-010398

  Many crash boxes including the crash box according to this patented invention are usually welded with one end face in the axial direction butt welded to the back plate, and the back plate is fixed to the mounting surface of the automobile bumper reinforcement with bolts and nuts. Alternatively, one end surface in the axial direction is fixed to the mounting surface of the bumper reinforcement of the automobile by butt welding. The crash box has a back plate attached to the other end face by butt welding or the like on the end face of the side member constituting the car body (front end face for the front side member, rear end face for the rear side member). A set plate (or a flange provided at the end of a side member) mounted by welding or the like is overlapped and fastened with a bolt and a nut that are mounted through the plate, so that the set plate is detachably mounted. . As described above, at least one end face of the cylinder constituting the crash box is butt welded (usually arc welding) to the bumper reinforcement or the back plate.

  When the plate thickness of the cylinder is reduced to less than 1.4 mm as described above, the end of the cylinder melts when butt welding is performed to the bumper reinforcement or back plate by high heat input welding such as arc welding. Even if the hole is opened or the hole is not opened, the plate thickness at the end portion becomes thin and the strength of the butt welded portion is lowered. For this reason, for example, the shock absorbing performance of the patented invention proposed by Patent Document 1 cannot be sufficiently exhibited.

  The object of the present invention is to provide high heat input welding such as arc welding to a bumper reinforcement or back plate even when the thickness of a cylinder constituting an impact absorbing member such as a crash box is thinner than 1.4 mm. Even if it is butt welded, it is possible to prevent the occurrence of perforations and reduction in plate thickness at the end of the cylinder, and thereby, for example, an impact absorbing member that can sufficiently exhibit the impact absorbing performance of the patented invention proposed by Patent Document 1 and The manufacturing method is provided.

  The present invention is an impact-absorbing member including a cylindrical body, which is a molded body of a metal plate, for absorbing collision energy by buckling due to an impact load applied in the axial direction from one end face in the axial direction. And a shock absorber characterized by having a folded portion formed in a shape in which the metal plate is folded at at least a part of the end portion including at least one end face in the axial direction of the cylindrical body in the circumferential direction. It is a member.

The impact absorbing member according to the present invention preferably includes a plate-like member which is abutted against the end face or inserted into an end including the end face and welded to the end face.
From another point of view, the present invention forms a folded portion by performing hem processing to fold back at least a part of the length direction of at least one of the two opposing edges of the metal plate. The cylindrical body constituting the shock absorbing member according to the present invention described above is formed by forming a metal plate on which the folded portion is formed so that the folded portion thus formed is an end portion including one end face in the axial direction. Is a manufacturing method of an impact-absorbing member.

In the manufacturing method of the impact absorbing member according to the present invention, it is preferable that the cylindrical body and the plate-like member are welded by the folded portion after the cylindrical body is manufactured.
In these inventions, the length of the folded portion in the axial direction is desirably 3 mm or more and 20 mm or less.

  In these present inventions, at least one of the end faces opposite to the one end face has a groove portion that protrudes toward the inside and that extends in the axial direction on the side wall that forms the end portion including the other end face. desirable.

In the present invention, the thickness of the metal plate is desirably 0.8 mm or more and less than 1.4 mm.
Furthermore, it is desirable that the impact absorbing member in the present invention is a crash box used for an automobile body.

  Furthermore, in the present invention, it is desirable that the groove portion is a groove portion having a substantially trapezoidal shape or a substantially V-shaped cross section. Furthermore, in these present inventions, it is desirable that the cylindrical body constituting the impact absorbing member has a closed cross-sectional structure and does not have a flange directed to the outside.

  According to the impact absorbing member and the manufacturing method thereof according to the present invention, for example, even when the plate thickness of the cylinder constituting the impact absorbing member such as a crash box is thinner than 1.4 mm, the bumper reinforcement or the back plate is used. Even when butt welding is performed by high heat input welding such as arc welding, it is possible to prevent the occurrence of perforations and reduction in plate thickness at the end of the cylinder, and thus, for example, the impact absorbing performance of the patented invention proposed in Patent Document 1 Can be fully demonstrated.

(Embodiment 1)
The best mode for carrying out the shock absorbing member and the manufacturing method thereof according to the present invention will be described below in detail with reference to the accompanying drawings. In the following description of the embodiment, the case where the shock absorbing member is a crash box according to the patent invention disclosed in Patent Document 1 is taken as an example, but the shock absorbing member according to the present invention is included in this crash box. It is not limited, and, in short, by disposing one end surface of the member constituted by the cylindrical body so as to face one end surface in the axial direction of the side member constituted by the cylindrical body. A crash box disclosed in Patent Document 1 is a crash box for absorbing impact energy by buckling repeatedly by an impact load applied in a direction substantially parallel to the axial direction and plastically deforming into a bellows shape. The same applies to crash boxes other than boxes.

  Further, in the following description, the case where the first member is a side member constituting the automobile body and the second member is a bumper is taken as an example, but this is merely an example, and other cases are also described. The invention is applicable.

  FIG. 1 is an explanatory view showing the structure of the crash box 1 of the present embodiment. FIG. 1 (a) is a perspective view showing the entire configuration of the crash box 1, and FIG. 1 (b) is FIG. 1 (a). FIG. 1C is an explanatory view showing a cut surface of the cylindrical body 2 in the longitudinal section P1, and FIG. 1D is a crash box shown in FIG. 1 is a perspective view showing a longitudinal section P2 in FIG. 1, and FIG. 1E is an explanatory view showing a cut surface of the cylindrical body 2 in the longitudinal section P2.

As described above, the crash box 1 of the present embodiment is a crash box disclosed in Patent Document 1, and its features will be briefly described first.
The crash box 1 of the present embodiment includes a cylindrical body 2 that absorbs collision energy by buckling in a bellows shape under an impact load applied in the axial direction (the direction of a double arrow in FIG. 1A).

  The cylindrical body 2 includes, for example, a first metal plate 4a that is press-molded so as to have groove portions 3a and 3b described later, and a second metal plate 4b that is press-molded so as to have grooves 3c and 3d. By overlapping the flat portions (left and right vertical wall surfaces 5a, 5b in FIG. 1 (a)) formed at the respective end portions, and joining by appropriate means (for example, laser welding or spot welding) at this overlapping portion, Assembled. For this reason, the cylindrical body 2 has a closed cross section having a substantially polygonal shape as shown in the figure, and does not include a flange facing the outside of the closed cross section.

  Furthermore, the cross-sectional shape of the cylindrical body 2 is a large number of basic cross-sections having a maximum area among polygons obtained by connecting a part of a plurality of vertices constituting a substantially polygonal shape with a straight line. Grooves 3a, 3b, 3c, and 3d that are convex toward the inside in a part of the sides AB and EF of the square ABCDEFGH and excluding the end points A, B, E, and F of the sides, It has toward the axial direction of the cylinder 2.

  In other words, the crash box 1 has an octagonal shape (an octagon composed of sides AB, BC, CD, DE, EF, FG, GH, and HA) that forms the basic cross section of the cylinder 2 on the side wall. And a cylindrical body 2 formed with grooves 3a to 3d, which are convex toward the top and extend in the axial direction (the direction of the double arrow in FIG. 1A). The cylindrical body 2 is repeatedly buckled by an impact load applied in the axial direction, and finally plastically deforms in a bellows shape, whereby the crash box 1 absorbs impact energy.

  In the present embodiment, the case where the grooves 3a to 3d have a substantially trapezoidal cross-sectional shape is taken as an example. However, the cross-sectional shape of the groove portions 3a to 3d is not limited to a substantially trapezoidal shape, and the same effects can be obtained even when the groove portions 3a to 3d have a shape other than a substantially trapezoidal shape such as a substantially V-shape. .

  Moreover, in this Embodiment, although the case where the groove parts 3a-3d were formed in the whole area of the axial direction of the cylindrical body 3 was taken as an example, it is not necessary to provide the groove parts 3a-3d in the whole area of an axial direction, and it is cylindrical. If it is provided in the entire range of at least 30% of the axial length of the cylindrical body 2 from one end surface on the side member side of the body 3 to the other end surface, the effects of the present invention described later can be obtained. Played.

  As disclosed in Patent Document 1, the crush box 1 is convex toward the inside and extends in the axial direction on the side portions AB and EF of the polygon ABCDEFGH that forms a cross section of the cylindrical body 2. The groove portions 3a to 3d are formed, and the rigidity of the portions provided with the groove portions 3a to 3d is increased, so that an impact load is applied in the axial direction without adding a partition wall or increasing the plate thickness. In the middle of repeated buckling, the cylindrical body 2 is prevented from falling or bending. For this reason, the crash box 1 can be buckled stably and repeatedly in the axial direction without an increase in mass, and finally can be plastically deformed into a bellows shape. Therefore, the amount of impact energy absorbed per unit mass can be dramatically improved.

  As described above, the crash box 1 according to the present embodiment is disposed between the side member as the first member and the bumper as the second member, and is directed from the one end face 2a in the axial direction toward the axial direction. And a cylindrical body that is a molded body of the metal plates 4a and 4b for absorbing the collision energy by buckling due to the impact load applied. The plate | board thickness of the metal plates 4a and 4b in this Embodiment is 0.8 mm or more and less than 1.4 mm.

  And in this Embodiment, as shown to Fig.1 (a)-FIG.1 (c), the edge part containing the end surfaces 2a and 2b of at least one (both in this Embodiment) of the axial direction of the cylinder 1 Folded portions 6a and 6b formed in a shape in which the metal plates 4a and 4b are folded are provided in part or all of the circumferential direction (all in the present embodiment).

  In particular, as shown in FIG. 1 (c), the folded portion 6 a of the metal plate 4 a is folded back toward the outside of the cylinder 2, and the folded portion 6 a of the metal plate 4 b is directed toward the inside of the cylinder 2. Is folded. Thereby, when the metal plate 4a and the metal plate 4b are overlapped with the vertical wall surfaces 5a and 5b, no gap is generated between the metal plates 4a and 4b. As described above, it is desirable that the folding direction of the folded portions 6a and 6b be different between the inner side and the outer side of the cylindrical body 2 so that no gap is generated in the overlapping portions of the metal plates 4a and 4b.

FIG. 2A and FIG. 2B are explanatory diagrams of the folded portion.
As shown in FIG. 2A, it is desirable that the folded portions 6a and 6b have a completely hemmed structure in order to prevent the occurrence of poor welding, but springback in the hemming process is unavoidable. Therefore, it is actually difficult to make the gap d in the folded portions 6a and 6b zero. The gap d is allowed up to about 0.8 mm.

  Further, if the folding range 6 of the folded portions 6a and 6b is too short, it is not possible to prevent the occurrence of poor welding. On the other hand, if it is too long, impact absorption performance and weight increase are caused. Needless to say, considering the workability of the welding operation, the folding range l may be set appropriately depending on the bumper side or the back plate side.

FIGS. 3A to 3D are explanatory views schematically showing a procedure for forming the folded portions 6a and 6b at the end of the metal plate 4a (4b).
As shown in FIG. 3B, the both edges of the blank (flat plate) which is the metal plate 4a (4b) shown in FIG. If the die R at this time is set large, the hem processing shape accuracy may be lowered, so it is better to make it as small as possible. Next, hem processing 1 is performed as shown in FIG. In this step, pre-bending is performed at about 135 ° to facilitate the final hem step. Further, as shown in FIG. 3D, hem processing 2 of 180 ° bending is performed to form folded portions 6a and 6b in the shape shown in FIG. By the blanking process described above, the folded portions 6a and 6b are formed on the metal plate 4a (4b). Note that the first hem and second hem steps are not necessarily separated, and may be performed in one step by weaving a cam mechanism in the mold.

  Thereafter, the metal plate 4a (4b) on which the folded portions 6a and 6b are formed is subjected to, for example, press molding to thereby form the metal plate 4a (having the grooves 3a and 3b (3c and 3d) shown in FIG. 4b).

  FIG. 4 is an explanatory diagram showing a back plate 7 that is a plate-like member that is welded and fixed to the end surfaces formed in the folded portions 6a and 6b, which are components of the crash box 1 of the present embodiment. .

  The folded portion 6a, 6b formed at the end of the metal plate 4a (4b), which constitutes the end surface 2a of the cylindrical body 2 constituting the crash box 1 of the present embodiment, and the back plate 7 are brought into contact with each other. As shown in (a) or FIG. 4 (b), fillet welding is performed to form an arc welded portion, whereby the cylindrical body 2 and the back plate 7 are joined by welding.

  In this arc welding, according to the crash box 1 of the present embodiment, the thickness of the metal plate 4a (4b) forming the cylindrical body 2 constituting the crash box 1 is thinner than 1.4 mm. However, even if the butt welding is performed on the back plate 7 by high heat input welding such as arc welding, folded portions 6a and 6b are formed at the end of the cylindrical body 2, and the thickness of the end is substantially doubled. Therefore, it is possible to prevent the occurrence of perforations and a reduction in the plate thickness at the end, and it is possible to reliably weld the cylindrical body 2 and the back plate 7 without causing poor welding.

  For this reason, according to this Embodiment, the impact absorption performance which the crash box which concerns on the patent invention proposed by patent document 1 has can fully be exhibited, for example.

(Embodiment 2)
Next, a second embodiment will be described. In the following description, portions that are different from the above-described first embodiment will be described, and overlapping descriptions of common portions will be omitted.

  The present embodiment is different from the above-described first embodiment in that the end of the cylinder 2 is inserted into the back plate 7 instead of arc welding by abutting the cylinder 2 against the flat back plate 7. A hole that can be formed is formed by punching, and the end of the cylinder 2 is inserted into the hole, and arc welding between the cylinder 2 and the back plate 7 is performed.

  FIG. 5 (a) is an explanatory view showing an arc welded portion obtained by penetrating the cylindrical body 2 through the back plate 7 in which this hole is formed and performing arc welding using a welding wire, and FIG. It is explanatory drawing which shows the other arc welding part obtained by making the cylinder 2 penetrate the back plate 7 which formed this hole, and performing arc welding using a welding wire, FIG.5 (c) forms this hole It is explanatory drawing which shows the arc welding part obtained by making the cylindrical body 2 penetrate the back plate 7 and performing arc welding without using a welding wire, and FIG.5 (d) is also the back plate which formed this hole. It is explanatory drawing which shows the arc welding part obtained by making the cylinder 2 penetrate to 7 and performing arc welding without using a welding wire. FIG. 5B and FIG. 5D are obtained by adjusting the insertion position of the cylinder so that the welded portion does not protrude from the upper surface of the back plate.

Further, FIGS. 6A to 6D are explanatory views showing enlarged views of FIGS. 5A to 5D, respectively.
In any of the methods, it is possible to reliably arc weld the cylinder 2 and the back plate 7.

(Embodiment 3)
Next, a third embodiment will be described.

  In the description of the first and second embodiments described above, the case where the shock absorbing member is the crash box 1 according to the patented invention disclosed in Patent Document 1 is taken as an example, but the shock absorbing member according to the present invention is the same. The crash box 10 is not limited to the crash box 1 and may be, for example, the crash box 10 having the cross-sectional shape shown in FIG.

  As shown in FIG. 7, the crash box 10 of the present embodiment is arranged orthogonal to a pair of corner portions 11, 12 arranged opposite to each other and a line connecting the pair of corner portions 11, 12. It comprises a metal cylinder 15 having a pair of other corner portions 13 and 14 and having a rectangular cross section defined by the corner portions 11 to 14 and having no flange on the outside.

  The crash box 10 of the present embodiment is configured by a metal cylinder 15 having a rectangular cross section defined by the corner portions 11 to 14 and having no flange on the outside. You may make it comprise a crash box with the cylinder which has a flange on the outer side.

  As described above, the crash box 10 is a corner that is a ridge line portion having a high rigidity that forms an outline of a cross-sectional shape in the vehicle width direction (for example, the horizontal direction in FIG. 7) or the vehicle height direction (for example, the vertical direction in FIG. 7). It has a square cross-sectional shape in which the portions 11 to 14 are arranged.

  The cross-sectional shape of the crash box 10 is symmetric with respect to a virtual line L that passes through the pair of corner portions 11 and 12. Furthermore, it is desirable that the shape be symmetrical with respect to a temporary line M passing through the other pair of corner portions 13 and 14. This is because the higher the symmetry, the higher the performance against oblique loads from various input directions.

  In the case of an offset collision, an oblique load in the vehicle width direction or the vertical direction is input, so that a bending moment is generated in the crash box 10. In order for the crash box 10 to stably generate plastic buckling deformation even when the load is input from such an oblique direction, the entire bending deformation (bending) caused by the bending moment is suppressed and the input is performed. It is important that the generated impact load causes continuous plastic buckling deformation with a short buckling wavelength similar to that when the impact load is input in the axial direction of the cylindrical body 15. This is because when the bending deformation occurs in the entire cylindrical body 15, the deformation has a long buckling wavelength. Therefore, the corner portions 13 and 14 having high rigidity are arranged at positions corresponding to the outer edge where the load acts. For this reason, in this crash box 10, as shown in FIG. 7, the corner parts 11-15 are arrange | positioned on the straight line which passes along the cross-sectional center.

In the crash box 10, the internal angles θ ₁ and θ ₂ formed by the pair of corner portions 11 and 12 are set to 90 ° or more and 150 ° or less (both 120 ° in the present embodiment), and another pair The internal angles θ ₃ and θ ₄ formed by the corner portions 13 and 14 are set to 30 ° or more and 90 ° or less (both 60 ° in the present embodiment). The reason for this will be explained.

The rigidity of the corner portions 11 to 14 which are ridge line portions is determined by the arc length existing in the ridge line portion, and when the corner portions 11 to 14 are set with a specific radius of curvature, the arc length is equal to the corner portions 11 to 15. Varies depending on the interior angle. Therefore, in order to cause plastic buckling deformation by the impact load without causing the entire bending of the crash box 10 with respect to the bending moment generated by the impact load input from an oblique direction, the pair of corner portions 11, The internal angles θ ₁ and θ ₂ formed by 12 are set to 90 ° to 150 °. When θ ₁ and θ ₂ exceed 150 °, the corner portion has a practical radius of curvature (about 1.5 to 10.0 mm) determined in a range that takes into account the manufacturing and design space of the crash box. The arc lengths 13 and 14 become too short to secure desired rigidity, and the targeted plastic buckling deformation cannot be generated.

Further, the angles θ ₃ and θ ₄ of the inner angles formed by the other pair of corner portions 13 and 14 are interlocked with the angles θ ₁ and θ ₂ of the inner angles formed by the pair of corner portions 11 and 12, so the angles θ ₁ and θ _{With 2} being 90 ° or more and 150 ° or less, 30 ° or more and 90 ° or less.

When the bending rigidity of the other pair of corner portions 13 and 14 is required to be higher than that of the pair of corner portions 11 and 12, the angles θ ₁ and θ ₂ formed by the pair of corner portions 11 and 12 are different from each other. It is desirable that the angle is greater than the angles θ ₃ and θ ₄ formed by the pair of corner portions 13 and 14.

  The crash box 10 has a shape capable of increasing the degree of load of the oblique load at the corner portions 11 to 14 that are ridge portions having high rigidity, that is, the corner portions 11 to 14 are arranged with respect to the input direction of the oblique load. The cross-sectional shape is as follows. By setting it as such a cross-sectional shape, the out-of-plane deformation | transformation which arises with respect to the load input from the diagonal direction can be made small, and the compressive distortion with respect to the corner parts 11-14 can be raised.

  Further, the crash box 10 is provided on all of the two sides (16, 17) and (18, 19) forming two pairs arranged symmetrically with a virtual straight line L passing through the pair of corner portions 11 and 12. , One or more that extend in the longitudinal direction and protrude toward the inside at a position excluding the pair of corner portions 11 and 12 and the other pair of corner portions 13 and 14 (FIG. 7 shows one case) Grooves 20-23.

  Each of these grooves 20 to 23 has a plate thickness t (mm) and a length W (mm) on each of the sides 16 to 19 and the number N of grooves 20 to 23 (1 in the case of FIG. 7). ), And the average value Wc (mm) of the opening widths of the N grooves preferably satisfies the relationship of the following equation (1), and more preferably satisfies the relationship of the following equation (1 ′).

5 <(W−N × Wc) / (N + 1) / t <50 (1)
5 <(W−N × Wc) / (N + 1) / t <30 (1 ′)
Thus, the crash box 10 can be plastic buckled and deformed in a bellows shape with a short buckling wavelength, and high shock absorption energy absorption performance can be obtained. The reason for this will be explained.

  From the occurrence of buckling to the next occurrence of buckling, the crash box 10 undergoes continuous plastic buckling (progressive buckling), and in order to increase the amount of shock absorbed energy determined by the load history caused by the deformation. It is effective to suppress the load fluctuation of the material, that is, to shorten the buckling wavelength. This buckling wavelength is closely related to the out-of-plane deformation (displacement) caused by the impact load in the cross section of the crash box 10, and if the amount of this out-of-plane deformation is large, the buckling wavelength becomes long. If is small, the buckling wavelength is short. Therefore, in order to reduce the out-of-plane deformation occurring in the cross section of the crash box 10, the length of the sides 16 to 19 constituting the cross section, that is, the distance between the adjacent corner portions 11 to 14 may be reduced.

  Specifically, the distance between the corner portions 11 to 14 is set to be less than 50 times the plate thickness t of the cylindrical body 15. That is, as shown in FIG. 7, by providing grooves 20 to 23 on the sides 16 to 19 where the distance between the corner portions 11 to 14 is 50 times or more the plate thickness t, the sides 16 to 19 are formed. Divide. In addition, even if the distance (11-14, 14-12, 12-13, 13-11) between the corner portions is less than 50 times the plate thickness, the grooves 20 to 23 are provided on the sides 16 to 19. The sides 16 to 19 may be further finely divided.

  The grooves 20 to 23 are desirably provided at positions that do not include the corner portions 11 to 14 that serve as starting points of plastic buckling deformation due to the load while suppressing the overall bending deformation when an oblique load is applied.

  Thus, the crush box 10 is provided with grooves 20-23 on the sides 16-19 in order to obtain a short buckling wavelength when the length W of the sides 16-19 is large. A new ridge line portion is formed by 20 to 23, and the lengths of the sides 16 to 19 are controlled within a range in which a short buckling wavelength can be obtained.

In addition, when the depth of the grooves 20 to 23 is too shallow, the above-described effect of dividing the sides 16 to 19 is weakened. Therefore, the depth of the grooves 20 to 23 is desirably more than 10 mm.
In the crash box 10, the radius of curvature R of all the corner portions 11 to 15 is greater than the radius of curvature Rc of each of the corner portions 20a to 20d, 21a to 21d, 22a to 22d, and 23a to 23d constituting the grooves 20 to 23. Larger is desirable. The reason for this will be explained.

  The cross-sectional secondary moment of the thin-walled ring is governed by the diameter and the wall thickness, and the cross-sectional secondary moment increases as the diameter increases, and the section modulus that affects the bending strength also increases as the diameter increases. That is, in order to suppress bending deformation against a bending moment generated when a load is applied to the crash box 10 from an oblique direction, the corner portions 11 to 11 that support an input load positioned on the outline of the cross section. It is effective to increase the cross sectional second moment of 14. Moreover, when the curvature radius of corner | angular part 20a-20d, 21a-21d, 22a-22d, 23a-23d which comprises the groove | channels 20-23 is enlarged, the deformation resistance in the groove | channels 20-23 will increase too much, and in this part Plastic buckling deformation hardly occurs.

  For the reasons described above, in the present invention, the curvature radii R of all the corner portions 11 to 14 that dominate the overall bending strength of the crash box 10 are set to the corner portions 20a to 20d and 21a to 21d constituting the grooves 20 to 23. , 22a to 22d and 23a to 23d are desirably larger than the curvature radius Rc.

As described above, the crash box 10 of the present embodiment has the corner portions 11 to 14 arranged in the vehicle width direction or the vehicle height direction, and the inner angles θ ₁ to θ ₄ forming the corner portions 11 to 14 are in an optimum range. And the corners 11 on all of the two pairs (16, 17), (18, 19) forming a pair symmetrically arranged on a virtual straight line L passing through the pair of corners 11 and 12. In addition to improving the bending strength when an oblique load is input, by providing one or a plurality of grooves that extend in the longitudinal direction to positions other than ˜14, are convex toward the inside, and satisfy Expression (1). This impact load causes plastic buckling deformation.

  Furthermore, the cylindrical body 15 of the crash box 10 is configured by joining two constituent members 15a and 15b divided along the axial direction so that the respective edge portions are overlapped, and the corner portions 13 and 14 are joined. A region including the notch 24 is formed by being cut out in a planar shape. And the notch part 24 has comprised the overlap joining part of several structural members. As a result, the rigidity of the notch 24 is enhanced, and the structure is such that it is less likely to bend and deform due to the axial collapse.

  For this reason, the crash box 10 can suppress the occurrence of bending deformation as a whole even with an impact load applied in an oblique direction with respect to the axial direction, and can be plastically buckled and deformed in a bellows shape. it can.

  Although not shown, also in the present embodiment, a folded portion is formed at least in the circumferential direction at the end portion including at least one end face in the axial direction of the cylindrical body 15 constituting the crash box 10. It is arc welded to the back plate 7 through the folded portion. Thereby, the same effect as Embodiment 1 is acquired.

  In the present embodiment, similarly to the second embodiment, a hole into which the end of the cylinder 15 can be inserted is formed in the back plate 7 by punching, and the hole of the cylinder 15 is formed in this hole. You may make it arc-weld with the cylinder 15 and the backplate 7 by inserting an edge part.

(Deformation)
In the first to third embodiments, the crush boxes 1 and 10 having a cross-sectional shape having no outward flange have been described as an example. However, the present invention is not limited to this embodiment. For example, FIG. ) Shown in FIG. 8B, and a crush box 40 having a so-called cross-sectional shape of both hats shown in FIG. 8B. Even if it has a crash box, the same applies.

  Further, the present invention will be described more specifically with reference to examples.

  As shown in FIG. 4 (a), it is a crash box disclosed in Patent Document 1, and is an axial direction of a cylindrical body constituted by metal plates 4a and 4b having a plate thickness of 0.8 mm or 1.0 mm. The end surfaces of the present invention examples (A2, B2) in which folded portions are provided in the range of the axial length of 5 mm at both ends and the comparative examples (A1, B1) in which folded portions are not provided have a plate thickness of 2.9 mm. A fillet weld was performed on the flat plate-shaped back plate, and the weldability was evaluated.

At this time, the welding between the back plate and the cylinder is MAG welding, the gas condition during welding is (Ar + 10% by volume CO ₂ ), the welding speed is 60 cm / min, the welding current is 80 A, and the welding voltage is 18V. The welding wire diameter was 0.9 mm, and the material of the welding wire was JIS YGW-15 equivalent.

Then, the weldability was evaluated by making a circle that did not cause poor welding such as a hole in the cylindrical body 2 during arc welding, and a circle that did not occur as x.
Next, using a general dynamic explicit method software, a rigid wall is applied to the analytical model in which the end face of the present invention example (A2, B2) and the comparative example (A1, B1) are abutted with a flat plate back plate from above. The average load at the time of axial crushing when the crushing stroke of the crush box was 0 mm to 120 mm was measured by colliding at a constant speed of h.

  The analysis results of the average load are shown together with the analysis conditions in Table 1, and the relationship between the crush stroke (mm) from 0 to 120 mm and the load is shown in a graph in FIG.

  When comparing A1 and A2 and B1 and B2 in Table 1, there is no difference in average load and weldability is improved. According to the present invention, there is a difference in the collision characteristics with the comparative example in which no folded portion is provided. It can be seen that the weldability could be remarkably improved.

1A is a perspective view showing the overall configuration of the crash box, FIG. 1B is a perspective view showing a longitudinal section P1 of the crash box shown in FIG. 1A, and FIG. 1C is a longitudinal section P2. FIG. 1D is a perspective view showing a longitudinal section C in the crush box shown in FIG. 1A, and FIG. 1E is a sectional view of the cylinder in the longitudinal section C. FIG. It is explanatory drawing which shows. FIG. 2A and FIG. 2B are explanatory diagrams of the folded portion. FIG. 3A to FIG. 3D are explanatory views schematically showing a procedure for forming a folded portion at an end portion of the metal plate. It is explanatory drawing which shows the backplate which is a plate-shaped member which is a component of the crush box of embodiment, and is welded and fixed to the end surface formed in a folding part. FIG. 5A is an explanatory view showing an arc welded portion obtained by penetrating a cylindrical body through a back plate in which a hole is formed and performing arc welding using a welding wire, and FIG. It is explanatory drawing which shows the other arc welding part obtained by penetrating a cylinder to the backplate which was made, and performing arc welding using a welding wire, FIG.5 (c) is a cylinder in the backplate which formed the hole. It is explanatory drawing which shows the arc welding part obtained by making it penetrate and arc-welding without using a welding wire, and also FIG.5 (d) penetrates a cylinder body in the backplate in which the hole was formed, and a welding wire is used. It is explanatory drawing which shows the arc welding part obtained by performing arc welding without using. 6 (a) to 6 (d) are explanatory views showing enlarged views of FIGS. 5 (a) to 5 (d), respectively. It is explanatory drawing which shows the cross-sectional shape of the crush box used in Embodiment 3. It is explanatory drawing which shows the cross-sectional shape of the crush box of a deformation | transformation form. It is a graph which shows the result of an Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Crash box 2 Cylindrical body 3a-3d Groove part 4a, 4b Metal plate 5a, 5b Vertical wall surface 6a, 6b Folding part 7 Backplate 8 Arc welding part 10 Crash box 11, 12 A pair of corner parts 13, 14 Other pairs Corner portion 15 Cylindrical body 16-19 Side 20-23 Grooves 20a-20d, 21a-21d, 22a-22d, 23a-23d Corner portion 24 Notch portion 30 Crash box 40 having a cross-sectional shape of one hat Crossing of both hats Crash box with surface shape

Claims (8)

  An impact-absorbing member comprising a cylindrical body, which is a molded body of a metal plate, for absorbing collision energy by buckling due to an impact load applied in the axial direction from one end face in the axial direction, An impact-absorbing member comprising: a folded portion formed in a shape in which the metal plate is folded at least in a circumferential direction at an end portion including at least one end surface in the axial direction of the body.   The impact-absorbing member according to claim 1, further comprising a plate-like member that is abutted against the end face or inserted into an end portion including the end face and welded to the end face.   The impact absorbing member according to claim 1 or 2, wherein a length of the folded portion in the axial direction is 3 mm or more and 20 mm or less.   The cylindrical body has a groove portion that protrudes toward the inside and extends in the axial direction on a side wall that forms an end portion including the other end surface opposite to at least one of the end surfaces. The impact-absorbing member according to any one of claims 1 to 3.   The thickness of the said metal plate is 0.8 mm or more and less than 1.4 mm, The impact-absorbing member described in any one of Claim 1- Claim 4.   The impact absorbing member according to any one of claims 1 to 5, wherein the impact absorbing member is a crash box used for an automobile body.   A folded portion is formed by performing hem processing for folding at least a part of the length direction of at least one of the two opposing edges of the metal plate, and the formed folded portion is one of the axial directions. A manufacturing method of an impact-absorbing member according to claim 1, wherein the cylindrical body according to claim 1 is manufactured by forming the metal plate on which the folded portion is formed so as to be an end portion including the end face of .   The method for manufacturing an impact absorbing member according to claim 7, wherein after the cylindrical body is manufactured, the cylindrical body and the plate-like member are welded by the folded portion.

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