JP5158246B2 - Shock absorbing member - Google Patents

Description

  The present invention relates to an impact absorbing member, and more specifically, to an impact absorbing member that is inexpensive, has excellent axial crushing characteristics, and can be reduced in weight without performing overlay welding or quenching.

  As is well known, in order to protect passengers by absorbing the collision energy at the time of a car collision and mitigating the impact force on the cabin, for example, the space other than the cabin such as the engine room and the trunk room is preferentially crushed. It is effective. Therefore, when an impact load at the time of a collision is applied to an appropriate portion such as a front portion, a rear portion, or a side portion of a car body of an automobile, it is crushed in an axial direction (in this specification, the longitudinal direction of the shock absorbing member) Thus, an impact absorbing member for positively absorbing the collision energy is arranged. As such an impact absorbing member, a front side member, a side sill, and a rear side member are known. In recent years, the seat is preferentially seated in an accordion shape in the axial direction due to an impact load applied in the axial direction. A crash box that absorbs collision energy by bending is also adopted.

  An impact absorbing member such as a crash box is required to have high load resistance in order to absorb impact energy at the time of collision. In order to increase the load resistance of the shock absorbing member, the plate thickness may be increased or a high strength material may be used. However, the former causes an increase in the weight of the vehicle body, and the latter causes an increase in manufacturing cost. Both are not suitable as an impact absorbing member for automobiles.

  Therefore, it has been proposed to increase the load resistance by performing build-up welding or induction hardening on a specific part of the shock absorbing member, or by forming the corner portion of the shock absorbing member into a convex shape or a concave shape.

  Patent Document 1 discloses an invention that increases the absorption amount of impact energy at the time of an axial collision by forming, for example, an arc or laser overlay weld in a ridge line of a bending member or a region in the vicinity of the ridge line. Has been.

  Patent Document 2 discloses an invention in which the amount of impact energy absorbed at the time of an axial collision is increased by forming a hardened hardening portion by induction hardening at a specific portion of a press-formed member.

  Further, in Patent Document 3, a corner portion other than a corner portion adjacent to a flange portion of a member obtained by joining a flange and a closing plate in a structural member having a substantially hat-shaped cross section is formed into a concave shape or a convex shape. Thus, an invention for increasing the amount of absorption of impact energy at the time of an axial collision is disclosed.

JP 2004-276031 A Japanese Patent Laid-Open No. 11-152541 JP-A-9-249155

  In order to increase the amount of impact energy absorbed by the impact absorbing member, it is necessary to perform overlay welding in the invention disclosed in Patent Document 1, and in the invention disclosed in Patent Document 2, it is necessary to perform induction hardening, Furthermore, in the invention disclosed in Patent Document 3, it is necessary to perform molding into a concave shape or a convex shape. For this reason, it is difficult to apply the invention as an impact-absorbing member for automobiles, in which any increase in manufacturing cost cannot be denied and low cost is strongly demanded.

  The present invention has been made in view of the problems of such conventional techniques, and since it is not necessary to perform overlay welding or quenching, an increase in manufacturing cost can be suppressed as much as possible, and excellent axial crushing characteristics can be obtained. It is to provide an impact absorbing member that can be reduced in weight.

  In the present invention, if the corner portion of the substantially groove-shaped member constituting the impact absorbing member is configured to be folded three or more times, the impact load can be increased without increasing the thickness of the steel plate which is the material of this member. Based on a very original technical idea that the corner thickness can be strengthened by substantially increasing the thickness of the corner portion that receives high stress when loaded, thereby improving the shock absorbing performance of the shock absorbing member. Is.

  The present invention is obtained by molding a metal plate, and has at least a first member having two side wall portions, a bottom portion, and a corner portion connecting the side wall portions and the bottom portion. An impact absorbing member for absorbing impact energy loaded in an axial direction, wherein at least a part of the corner portion is folded in such a manner that a metal plate is folded three times so as to follow the shape of the corner portion. It is an impact-absorbing member characterized by being an overlapping shape part.

In the present invention, it is desirable that at least a part of the metal plate forming the folded shape portion is overlapped and joined.
In the present invention, it is desirable that the folded-up portion is formed in the vicinity of the corner portion and in a part of the side wall part and / or a part of the bottom part.

In the present invention, it is desirable that the first member has a flange provided on two side wall portions.
In the present invention, it is desirable to further have a second member for forming a closed cross section by being joined to the first member via the flange of the first member.

  It is exemplified that the first member in the impact absorbing member according to the present invention is obtained, for example, by press-molding a metal plate.

  According to the present invention, since it is not necessary to perform overlay welding or quenching, an increase in manufacturing cost can be suppressed as much as possible, and an impact absorbing member having excellent axial crushing characteristics can be provided.

  The best mode for carrying out the impact absorbing member according to the present invention will be described below with reference to the accompanying drawings. The shock absorbing member according to the present invention is equally applicable as long as it is a member that undergoes axial crushing deformation at the time of collision deformation of an automobile, such as a crash box, a side sill, a cross member, or a side member.

Since the impact absorbing member of the present embodiment has a first member and a second member, these will be described.
[First member]
The shock absorbing member of the present embodiment has a substantially groove-shaped first member. When the impact energy is loaded in the axial direction of the first member, the impact absorbing member buckles preferentially in an accordion shape in the axial direction to absorb the impact energy. It is a member.

  In the present embodiment, a steel plate made of ordinary steel is used as the material for the first member. The first member is formed as a substantially groove-shaped member having two side wall portions, a bottom portion, and a curved corner portion connecting the side wall portion and the bottom portion by press forming the steel plate by a well-known and conventional means. Molded.

In the present embodiment, a part of this press forming process is provided with a process in which at least the corner part becomes a folded shape part obtained by folding the steel plate.
Fig.1 (a)-FIG.1 (d) are explanatory drawings which show typically an example of the process for forming a folding shape part in the corner part of a 1st member.

  As shown in FIG. 1A, a flat blank 1 is used to secure the extra length of the folded shape portion, and the first mold 5 including the blank holder 2, the punch 3 and the die 4 is used. The concave portion 1a is formed by drawing the portion corresponding to the bottom. At this time, it is desirable to dispose the blank holder 2 and the punch 3 in the upper die as shown in FIG.

  Next, as shown in FIG. 1 (b), in the state where the concave portion 1a is pressed with the pad 7 by the second mold 10 constituted by the die 6, the pad 7, the holder 8 and the punch 9, Bending is performed to form a hat shape.

  Next, as shown in FIG. 1 (c), the third mold 14 constituted by the die 11, the holder 12, and the punch 13 is used to move the concave extra wire length 1 b to the periphery of the shoulder of the punch 13. Is preformed. In order to facilitate folding, it is effective that the tip of the punch 13 has a substantially convex shape. Further, it is effective to provide a stepped return 11a on the die 11 in order to prevent the folded portion from moving.

And as shown in FIG.1 (d), as a last process, it shape | molds to the predetermined folding shape part 1c with the 4th metal mold | die 18 comprised with the die | dye 15, the holder 16, and the punch 17. FIG.
Thereby, at least a part of at least the corner portion of the first member constituting the crash box of the present embodiment becomes a folded shape portion in which the steel plate is folded. Further, in the present embodiment, as shown in FIG. 1 (d), the folded shape portion 1c is not only the corner portion of the first member, but also in the vicinity of the corner portion and a part of the side wall portion, and It is formed up to one or both of a part of the bottom.

  The range in which the part of the side wall part and the part of the bottom part also become the folded shape part is preferably adjacent to the corner part and within about five times the corner R from the corner. This is because if it exceeds this range, it may be difficult to improve the amount of energy absorption per unit mass.

  In the present embodiment, the case where the first member is formed by press molding has been taken as an example. However, the present invention is not limited to press molding, and may be formed by roll forming, for example.

  In the present embodiment, the reason why the shock absorbing performance is improved by forming the corner portion, and also the vicinity of the corner portion and a part of the side wall part and / or a part of the bottom part as a folded shape part will be described. To do.

  A groove-type impact absorbing member having two side walls, a curved corner connected to one end of the side walls, and a bottom connected to one end of the corner is provided with a shaft When an impact load is applied in the direction, high stress is generated in the corner portion and the vicinity thereof. For this reason, the impact-absorbing performance of the impact-absorbing member can be improved by strengthening the corner portion that receives high stress. Reinforcement of the corner can be easily achieved by increasing the strength of the material and the thickness of the material as described above, but this leads to an increase in weight and cost and cannot ensure the characteristics required as a shock absorbing member. .

  Therefore, in the present embodiment, by forming the corner portion in the folded shape portion, it is possible to substantially increase the plate thickness of the corner portion without increasing the plate thickness of the steel plate as the material, Thereby, since the corner part which receives high stress when an impact load is loaded can be strengthened, the impact absorbing performance of the impact absorbing member can be improved.

  Furthermore, not only the corner part, but also a part including the part of the bottom part in the vicinity of the corner part or the part of the side wall of the substantially groove-shaped cross section is formed into a folded shape part, thereby the corner part and the vicinity region thereof. The plate thickness can be substantially increased, and the impact absorbing performance can be further improved.

  The folded shape portion in the present embodiment only needs to be in a state where the folded steel plates overlap each other, and the folded steel plates are not necessarily in contact with each other. The gap between the folded portions may be about 5 times or less of the plate thickness. It is further desirable to set the thickness to about the plate thickness or less.

It is desirable that the steel sheet in the folded portion is folded in triplicate from the viewpoint of improvement of the obtained impact absorbing performance and manufacturing cost.
Further, it is desirable that at least a part of the steel sheet forming the folded shape portion is overlap-joined. In this way, when the steel plates formed in the folded shape portion are overlapped and joined, the deformation of the steel plates formed in the folded shape portion is restrained by the joining, so that the plate thickness is substantially larger than in the case of not joining. This is because the shock absorption performance is further improved.

Further, for this overlap joining, welding such as laser welding, resistance spot welding or plasma welding, brazing, mechanical joining, or structural bonding is exemplified.
In addition, when joining the 2nd member mentioned later, the outward flange is provided, for example in the edge part of the side wall part of a 1st member, and a 2nd member is joined via this outward flange. It is desirable. However, it goes without saying that the end of the side wall portion of the first member may be abutted against the joining partner material depending on the form and means to be joined.

The first member is configured as described above.
[Second member]
The crash box of the present embodiment has a second member. The second member is used to form a closed cross section by joining, for example, by welding, to the two side walls of the first member, preferably through flanges provided on the two side walls. It is a member.

  In this embodiment, a flat plate is used as the second member. However, the present invention is not limited to this, and the second member is closed by being joined to the two side wall portions of the first member. Any member that can form a cross section may be used.

  For example, press-molded members having the same shape as the first member are provided in opposite directions by overlapping the flanges, or press-formed members having side wall portions different in height from the first member are overlapped with the flanges. May be provided in the same direction.

The first member and the second member are welded, but the welding method is not particularly limited. For example, laser welding, resistance welding, or plasma welding can be used.
When the shock absorbing member of the present embodiment is a crash box, the second member is used. However, when the shock absorbing member is a member such as a front side member, the second member is not used. One member may be directly welded to a component (for example, a hood ridge) of an automobile body.

The second member is configured as described above.
The shock absorbing member of the present embodiment is configured as described above.
Thus, according to the present embodiment, the corner portion of the first member obtained by press-molding the steel plate and having two side wall portions, a bottom portion, and a corner portion connecting these side wall portions and the bottom portion. Is formed as a folded shape portion, so that it is possible to substantially increase the thickness of the corner portion without increasing the thickness of the steel plate, which is a material, and this is high when an impact load is applied. The corner part which receives stress can be strengthened. Therefore, since it is not necessary to perform overlay welding or quenching on the corner portion, it is possible to provide an impact absorbing member that is inexpensive and has excellent axial crushing characteristics.

The present invention will be described more specifically with reference to examples.
The effect of the present invention was examined by numerical analysis.
2 (a) to 2 (e) and FIGS. 3 (a) to 3 (d) are explanatory views partially showing the cross-sectional shape of the shock absorbing member 20 numerically analyzed in this embodiment.

  In each of FIGS. 2A to 2E, the first member 21 and the second member 22 both have a so-called hat-shaped cross section, and both are overlapped and joined by a flange. FIG. 3 (a) and FIG. 3 (b) show the case where the first member 21 has a hat-shaped cross section. And the second member 23 is a flat back plate, and shows a case where the cross section is closed by overlapping and joining with the flange of the first member 21 (hereinafter simply referred to as “one-hat”), Further, in both FIG. 3C and FIG. 3D, the first member 21 has a hat-shaped cross section, and the second member 23 is different in size from the first member 21. Cross-section with a hat-shaped cross-section, closed by overlapping the two with a flange If you want to (hereinafter, simply referred to as "double-open hat") shows the.

  In addition, the joining of the flange of the first member 21 and the second members 22 to 24 is performed by resistance spot welding at a position of 10 mm from the end in the flange width direction and a region at a position of 15 mm from both ends in the axial direction at intervals of 30 mm. This was done by spot joining.

  In the present embodiment, the shape of the folded shape portion of the corner portion 21a of the first member 21 and the fixing condition thereof are changed as listed below in the cross-sectional shapes of both hats, single hats, and double hats. Then, numerical analysis was performed.

[Cross-sectional shape / dimensions of members, shape / dimensions of fold-shaped parts, welding (fixing) conditions]
Member length: 300mm
Cross-sectional shape: both hats (FIGS. 2A to 2E), single hat (FIGS. 3A and 3B), double open hat (FIGS. 3C and 3D) )

Shape of folded shape part: 4 types of M1, M2, M4, and M5 M1: A corner is formed in a triple folded shape part, and the opening of the folded shape part is on the bottom side
(Fig. 2 (b)).
M2: A corner is formed in a triple folded shape portion, and the opening of the folded shape portion is on the side wall side.
(Fig. 2 (c)).
M4: A three-fold shape portion of the corner and the vicinity of the corner (a range twice as large as the corner R)
The structure in which the opening of the folded portion is arranged on the bottom side (FIG. 2D)
And FIG. 3 (b) and FIG. 3 (d)).
M5: Triple folded shape portion of corner and corner vicinity (range of corner R twice)
A structure in which the opening of the folded shape portion is arranged on the side wall side (FIG. 2E).

FIG. 4A to FIG. 4H are explanatory views showing the presence / absence of overlap welding and the welding position in the folded shape portions M1, M2, M4, and M5 of the members subjected to the analysis.
4 (a) to 4 (d) show the fold-shaped portions M1, M2, M4, and M5 that are not subjected to lap welding, and FIGS. 4 (e) to 4 (h) show the fold-over. An example in which overlap welding is performed at the circled portions in the shape portions M1, M2, M4, and M5 is shown.

And it analyzed in the following ways including handling of joining.
A general-purpose dynamic explicit finite element analysis code was used for the analysis. The material was a 590 MPa class high-tensile steel plate with a plate thickness of 1.0 mm. For the deformation characteristics of the material, the strain rate dependence of the Cowper-Symmonds type was considered.

  In the analysis of axial crushing, a rigid wall was defined at the upper end of the shock absorbing member, a forced displacement of 64 km / h was given, and a forced displacement amount of 200 mm was given. At this time, the absorbed energy up to 200 mm (shaft crushing load × displacement) was calculated, and the amount of absorbed energy per unit weight obtained by dividing it by the member weight was obtained, and further standardized by the absorbed energy per unit weight of the base shape. The value was taken as the evaluation value.

  The resistance spot welded portion is a beam element that simulates spot welding and has a nugget diameter of 5.5 mm, and the positions of both contacts corresponding to the spot joint portion are coupled. At this time, the deformation characteristic of the beam element was an elastic perfect plastic body with a yield stress of 1200 MPa. Further, in joining the folded portions, both contact points of the joined portions are rigidly fastened, and this fastening is performed in the entire region in the longitudinal direction of the member.

  The analysis results are shown in Tables 1 and 2. In Tables 1 and 2, “EA @ 200” indicates the absorbed energy (kJ) up to the crush amount of 200 mm, “Pave” indicates the average value (kN) of the axial crush load up to the crush amount of 200 mm, and “M”. Indicates member mass (g).

  As shown in Tables 1 and 2, energy absorption per unit mass in both hats, single hats, and double open hats compared to the respective base materials (conventional examples in which no folded-shaped portions exist) It can be seen that the amount (EA / M) is improved.

  Further, it is understood that the energy absorption amount per unit mass (EA / M) is further improved by performing overlap bonding in the folded shape portion in both hats, single hats, and double open hats.

Fig.1 (a)-FIG.1 (d) are explanatory drawings which show typically an example of the process for forming a folding shape part in the corner part of a 1st member. Fig.2 (a)-FIG.2 (e) are explanatory drawings which partially show the cross-sectional shape of the impact-absorbing member numerically analyzed in the Example. FIG. 3A to FIG. 3D are explanatory views partially showing the cross-sectional shape of the shock absorbing member numerically analyzed in the example. FIG. 4A to FIG. 4H are explanatory diagrams showing the presence / absence of overlap welding and the welding position in the folded shape portions M1, M2, M4, and M5 of the shock absorbing member used for the analysis.

DESCRIPTION OF SYMBOLS 1 Blank 1a Concave shape part 1c Folding shape part 2 Blank holder 3 Punch 4 Die 5 1st metal mold 6 Die 7 Pad 8 Holder 9 Punch 10 2nd metal mold 11 Die 11a Returning 12 Holder 13 Punch 14 3rd Mold 15 Die 16 Holder 17 Punch 18 Fourth mold 20 Shock absorbing member 21 First member 22 to 24 Second member

Claims (5)

  It is obtained by molding a metal plate, and has at least a first member having two side walls, a bottom, and a corner connecting the side walls and the bottom, and the axial direction of the first member An impact absorbing member for absorbing impact energy loaded toward the corner, wherein at least a part of the corner portion is curved and folded in triple so that the metal plate follows the shape of the corner portion. An impact-absorbing member, wherein the impact-absorbing member is a folded portion.   The impact-absorbing member according to claim 1, wherein at least a part of the metal plate forming the folded shape portion is overlap-joined. The impact absorbing member according to claim 1 or 2 , wherein the first member has a flange provided on the two side wall portions. Furthermore, it has a 2nd member for forming the closed cross section by joining to the said 1st member via the said flange, The any one of Claim 1 to 3 characterized by the above-mentioned. The impact absorbing member described in the item. The impact absorbing member according to any one of claims 1 to 4, wherein the impact absorbing member is a crash box.

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