JP7207452B2 - Automobile structural member and manufacturing method thereof - Google Patents

Description

The present invention relates to a structural member (hollow member) for an automobile, which comprises two hat-shaped cross-sectional members each having a hat-shaped cross section in which a side wall portion and a flange portion are connected to both sides of a top plate portion, respectively, to form a closed cross-sectional shape. . The present invention is a technique for providing a structural member that has particularly good collision resistance against bending deformation due to a collision load input from a direction along the direction in which two top plate portions face each other.

In recent years, in the automobile field, collision safety standards have been tightened from the viewpoint of passenger protection, and there is a strong demand for the expansion of the application of high-strength steel and the development of vehicles with excellent collision safety performance.
Here, as the form of collision, there are a collision form of axial crushing and a collision form of bending deformation. In a collision mode that causes axial crushing, axial crushing occurs when the longitudinal direction of a member coincides with the direction of collision, such as a crash box or a front side member that receives a collision load input from the front of an automobile. In a collision mode in which bending deformation occurs, a collision load is applied to the side surface of a structural member such as a B-pillar or a side sill in a side collision, and the member bends and deforms. In both forms, the member undergoes buckling deformation to absorb the collision energy and exhibits anti-collision performance.

In addition, the collision resistance required differs depending on the member. For example, frame members around the cabin are required to play a role of suppressing deformation and ensuring safety from the viewpoint of passenger protection. On the other hand, from the perspective of energy absorption, the front end and rear end parts away from the cabin are actively deformed to efficiently absorb the collision energy and distribute the load to other structural members. It is required to play the role of transmitting the load while

As one technique for improving collision resistance, a technique for improving the strength of structural members by attaching reinforcing parts has been proposed. For example, Patent Literature 1 discloses a technique for suppressing deformation by providing a plurality of bulkheads inside a structural member and providing reinforcing members between the bulkheads. Further, in Patent Document 2, a reinforcing part having an L-shaped or U-shaped cross section that conforms to the shape of the structural member is arranged inside or outside the structural member, so that the bottom plate is bent around the ridge line of the structural member. Techniques to reinforce the part and the side wall part are mentioned. Furthermore, Patent Literatures 3 and 4 disclose techniques for suppressing deformation by filling the inside of a structural member with a foam material, or by arranging a reinforcing part filled with foam in a bending portion that is likely to deform during a collision. .
As another reinforcing method, Patent Literature 5 discloses a technique of optimizing the plate thickness and partially thickening portions including ridges to increase member strength and suppress deformation.

On the other hand, Patent Literature 6 assumes a structure including a hat cross-section member and a closing plate to form a closed cross-section structure, and reinforcing parts connecting left and right side wall portions. Patent Document 6 discloses that the left and right side walls of the hat section member are provided with partial low-strength portions, respectively, to control the deformation behavior during bending crushing, suppress bending in the longitudinal direction of the member, and prevent deformation during deformation. A technique for suppressing the amount of member intrusion is described.
In addition, Patent Document 7 discloses a technique for improving collision performance by optimizing the placement position of a reinforcing part (first connecting part 30) that connects left and right side walls to restrain cross-sectional deformation during bending and crushing. are mentioned.

JP-A-9-20267 WO2017-030191 JP-A-2002-36413 JP 2017-159896 A Japanese Patent Application Laid-Open No. 2009-173110 WO2018-207668 JP 2012-236525 A

However, these patent documents do not disclose a technique for controlling the deformation of members and efficiently absorbing energy at the time of collision without providing reinforcing parts.
For example, the techniques of Patent Documents 1 to 5 are techniques for increasing the load at the time of collision by increasing the deformation resistance with reinforcing parts and fillers.
However, simply attaching reinforcing parts to structural members improves crash resistance, but increases the number of parts, resulting in an unnecessarily large weight increase, as well as an increase in the number of molds. There is a surface issue.
Moreover, there is concern that the reinforcement with foamed fillers will complicate the production process, and there is also a problem from the viewpoint of recyclability. Also, when partially attaching a foam filling member, adhesive is used to attach the member, but there are issues with adhesion such as peeling during deformation and aging deterioration, and it is difficult to ensure stable collision resistance performance. Conceivable.

Furthermore, when adopting the reinforcing method of partially increasing the plate thickness, a steel plate with a different thickness is required. In this case, for example, techniques such as tailored blanks are required, and there are problems in welding and forming, or in terms of production.
Furthermore, the methods described in these patent documents are techniques for improving collision resistance by increasing rigidity and increasing deformation resistance. It is not a technique for maintaining high deformation resistance even in the process of progressing. As described above, the collision resistance required differs depending on the member, but it is difficult to say that the methods described in each patent document are suitable for absorbing energy by squeezing.

In addition, the techniques of Patent Documents 6 and 7 are collision performance improvement techniques that control the deformation behavior of parts in the collision process. Problems in terms of weight and cost can be mentioned.
Moreover, the technique of Patent Document 6 is a technique for controlling the amount of member penetration due to bending, and is different from a technique for efficiently absorbing impact. In the technique of Patent Document 6, it is necessary to utilize techniques such as local heat treatment and tailored blanks to control member strength, and there are also production issues such as an increase in the number of processes and material variations.
The technology of Patent Document 7 is, like the present disclosure, improved collision performance by cross-sectional deformation control. However, the technique of Patent Document 7 is a suitable arrangement of reinforcing parts for the purpose of increasing the maximum load at the time of collision by restraining cross-sectional deformation, and while controlling the balance of cross-sectional deformation, it is possible to simply and efficiently without using reinforcing parts. It is not a cross-sectional deformation control technique to maintain high deformation resistance even in the process of deformation to enhance energy absorption.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a structural member for automobiles capable of easily improving crash resistance performance while suppressing an increase in weight due to reinforcement. do.

In order to solve the above-described problems, the inventors of the present invention actively deform members to efficiently enhance collision energy absorption, while suppressing an increase in the number of reinforcing parts due to press working to suppress weight increase, and Intensive research was conducted on the shape of structural members that can easily improve crash resistance. As a result of this study, we found that by devising the joining position of the closed cross-sectional shape of the member, it is possible to easily improve the collision resistance performance while suppressing the increase in weight by not necessarily requiring reinforcement parts. Obtained. The present invention is made based on such findings.

In order to solve the problem, one aspect of the present invention provides two hat cross-sectional members having a hat-shaped cross section in which side wall portions and flange portions are continuous on both sides of a top plate portion. It has a hollow member that forms a closed cross-sectional shape, and when the direction in which the two top plate parts face each other is taken as the height direction, the position in the height direction of the first mating surface that is the joint surface between the flange parts on one side , and the position in the height direction of the second mating surface, which is the joint surface between the other flange portions.

Another aspect of the present invention is a method for manufacturing a structural member for a vehicle having a closed cross-section, comprising two hat-shaped cross-sections in which a side wall portion and a flange portion are continuous on both left and right sides of a top plate portion. A hollow member having a closed cross section is produced by joining opposing flange portions of a member to each other, and members having left and right side wall portions with different heights are used as the two hat cross section members. .

According to an aspect of the present invention, there is provided an automotive structural member that can easily improve crash resistance performance while suppressing an increase in weight due to the fact that reinforcing parts are not necessarily required for a closed cross-section structure. becomes possible.
That is, in the aspect of the present invention, the first mating surface and the second mating surface, which are the left and right mating surfaces (bonding surfaces) of the two hat cross-section members, are set so that the mutual height from one top plate portion as a reference is Arrange differently. Thus, according to the aspect of the present invention, the member is deformed by dispersing the load applied when the member cross-sectionally deforms during bending deformation with respect to the collision load in the direction along the direction in which the two top plate portions face each other. It is possible to efficiently absorb the collision energy while

In addition, according to the aspect of the present invention, since it is not necessary to use reinforcing parts or foam materials, there is no need to increase the weight due to an increase in the number of parts, increase the cost due to an increase in molds, or hinder recycling and productivity. The anti-collision performance can be easily improved without
Here, examples of the reinforcing component include reinforcing components as described in each patent document. The reinforcing part may be, for example, a reinforcing part that connects the left and right side walls constituting the hat section member, for example, a reinforcing part that is arranged in the closed cross section and extends in the left and right direction, and whose ends are connected to the left and right side walls, respectively. and a reinforcing component extending across the top plate portion in the width direction thereof and having ends connected to the outer surfaces of the left and right side wall portions, respectively.

1 is a perspective view of a hollow member according to an embodiment of the invention; FIG. 1 is a cross-sectional view of a hollow member according to an embodiment of the invention; FIG. It is a side view explaining three-point bending analysis conditions in an example. It is a perspective view explaining three-point bending analysis conditions in an example. It is a figure which shows the behavior at the time of applying load in the direction which goes to a lower top plate part from an upper top plate part. It is a figure which shows an example of the relationship between the stroke (push amount) of load application, and load. It is a figure which shows the relationship between an average load and the height between mating surfaces.

Next, embodiments of the present invention will be described with reference to the drawings.
(Constitution)
In the present embodiment, two hat cross-sectional members 10 each having a hat-shaped cross section in which side wall portions 10B and 11B and flange portions 10C and 11C are continuous on both sides of top plate portions 10A and 11A as shown in FIGS. Regarding 11, the left and right facing flange portions 10C and 11C are joined together to create a closed cross-sectional shape to form a hollow member. Let the hollow member be a structural member 1 for automobiles to be reinforced (hereinafter also simply referred to as structural member 1). The joining of the flange portions 10C and 11C is performed by spot welding, for example.

Here, the joint surface between the flange portions 10C and 11C facing each other on the right side is referred to as a first mating surface S2, and the joint surface between the flange portions 10C and 11C facing each other on the left side is referred to as a second mating surface S1.
In this specification, as shown in FIGS. 1 and 2, the posture in which the top plate portions 10A and 11A of the two hat cross-section members 10 and 11 are vertically opposed to each other will be described. In this embodiment, it is assumed that an impact from the side of the structural member 1 is likely to be input to the top plate portion 10A on the side of the hat cross-section member 10 on the upper side.

Also, in this specification, the direction in which the two top plate portions 10A and 11A face each other is referred to as the height direction.
In the present embodiment, the position in the height direction of the height L2 of the first mating surface S2 on the right side from the top plate portion 10A, which is one of the two top plate portions 10A and 11A, and the second The position in the height direction of the height L1 of the mating surface S1 is set to be different.
One of the top plate portions is, for example, the upper top plate portion 10A to which impact is likely to be input.

Let H be the distance between the two opposing top plate portions 10A and 11A, and h be the difference between the height L2 of the first mating surface S2 and the height L1 of the second mating surface S1 (=|L1−L2| ), it is preferable to satisfy the following formula (1).
0 < h/H ≤ 0.55 (1)
More preferably, it is "0.05 ≤ h/H ≤ 0.5".
Here, if the height difference h between the first mating surface S2 and the second mating surface S1 is greater than 0.55 times the height H between the top plate portions, the collision load is applied. If this happens, the balance of deformation in the collision process will be greatly disrupted, and the cross section will be bent in one direction (like a crushed parallelogram), so the deformation resistance will be greatly reduced.
Moreover, it is preferable that the difference h in the height direction between the right and left mating surfaces is larger than 2 mm, for example. Moreover, the difference h in the height direction between the right and left mating surfaces is preferably 0.05H or more, for example.

However, as the height difference h between the first mating surface S2 and the second mating surface S1 increases, deformation in the direction in which the closed cross-sectional shape is twisted is more likely to be applied to an axial load or the like. Therefore, the smaller the difference h, the better. From this point of view, a more preferable upper limit of the difference h is 0.55H or less.

In this embodiment, members having the same cross-sectional shape are employed as the two hat cross-sectional members 10 and 11, and one of the two hat cross-sectional members 10 and 11 is joined upside down to achieve a closed cross-sectional shape. A hollow member is used. Therefore, the height of the right first mating surface S2 with respect to the proximal top plate portion 10A is equal to the height of the left second mating surface S1 with respect to the proximal top plate portion 11A.
Further, the heights a and b of the left and right mating surfaces S1 and S2 with respect to the central position in the height direction of the hollow member are equal. These values may be different for left and right. However, adopting members having the same cross-sectional shape as the two hat cross-sectional members 10 and 11 is advantageous in terms of processing costs and the like. The cross-sectional shapes of the two hat cross-sectional members 10 and 11 may be slightly different. For example, one of the two hat cross-section members at the midpoint position SP between the height direction position of the first mating surface S2 and the height direction position of the second mating surface S1 along the height direction. The distance ((L1+L2)/2) from the top plate is set to 0.4H or more and 0.6H or less. If the midpoint position is located at or near the center in the height direction, it is possible to prevent the left-right balance from being greatly disturbed while imparting a left-right difference to the closed cross-section structure.

However, the two hat profile members 10, 11 need not have the same dimensions. For example, the height of the hat section member 11 on the lower side may be lower than the height of the hat section member 10 on the upper side. The height of the hat cross-section members 10 and 11 is the height at the average value position of the heights of the left and right flange portions with respect to the top plate portion. The height ratio of the two hat cross-section members 10 and 11 is, for example, the height ratio between the hat cross-section members 10 and 11 having the larger height and the hat cross-section members 10 and 11 having the lower height, 1: 1 to 1: 0.5.

Also, the two opposing top plate portions 10A and 11A may not be parallel to each other, and one top plate portion may be inclined with respect to the other top plate portion.
One or two or more beads extending in the longitudinal direction may be formed on each of the top plate portions 10A and 11A and the side wall portions 10B and 11B. By providing the beads extending in the longitudinal direction, the automotive structural member 1 has improved strength against load input in the direction along the longitudinal direction of the hollow member.
In addition, FIG. 1 and other drawings also show the dimensions of the members in the embodiment, but these dimensions do not limit the present invention.

(effect)
The present embodiment has the following effects.
(1) In the present embodiment, in two hat-shaped cross-sectional members having a hat-shaped cross section in which the side wall portion and the flange portion are continuous on both sides of the top plate portion, the opposing flange portions are joined to form a closed cross-sectional shape. When the direction in which the two top plate portions face each other is defined as the height direction, the position in the height direction of the first mating surface S2, which is the joint surface between the flange portions on one side, and the above-mentioned position on the left side The position in the height direction of the second mating surface S1, which is the joint surface between the flange portions, is different.
According to this configuration, it is possible to improve the collision resistance performance of the structural member 1 in a collision mode in which bending deformation occurs without separately providing a reinforcing part that suppresses the opening of the left and right side walls in the hollow member. Become. That is, according to the present embodiment, it is possible to provide an automotive structural member capable of easily improving crash resistance performance while suppressing an increase in weight due to reinforcement.

That is, according to the present embodiment, the first mating surface S2 and the second mating surface S1, which are the left and right mating surfaces (bonding surfaces) of the two hat cross-section members, are connected to each other from one top plate portion 10A as a reference. The heights L1 and L2 of are arranged differently. As a result, in this embodiment, with respect to the collision load in the direction along the direction in which the two top plate portions face each other, the load applied to the cross-sectional deformation of the member during bending deformation is dispersed, thereby efficiently deforming the member. It is possible to absorb collision energy.
Further, according to the present embodiment, since reinforcing parts and foaming materials are not used, the weight can be easily increased without hindering productivity, such as an increase in weight due to an increase in the number of parts, an increase in cost due to an increase in molds, or recycling. Crash performance can be improved.

(2) Neither of the above two hat cross-section members has a reinforcing part that constitutes the hat cross-section member.
(3) The distance between the two opposing top plate portions is H, and the position in the height direction of the first mating surface and the position in the height direction of the second mating surface along the height direction. The distance of the midpoint position from the top plate portion of either one of the two hat cross-section members is 0.4H or more and 0.6H or less.
(4) Both of the two hat cross-section members have the same cross-sectional shape.

(5) When the distance between the two opposing top plate portions 10A and 11A is H, and the difference between the height of the first mating surface S2 and the height of the second mating surface S1 is h, the following (1) satisfies the formula
0 < h/H ≤ 0.55 (1)
According to this configuration, it is possible to achieve the above effects more reliably.

(6) The automobile structural member of the present embodiment is an automobile structural member capable of bearing a collision load input from a direction along the opposing direction of the two top plate portions facing each other.
By using the automotive structural member of the present embodiment at a position of the vehicle where there is a possibility of bending deformation collision, it is possible to improve the collision resistance performance in a bending deformation collision type without increasing the weight of the automobile. Become.

(7) A method for manufacturing a closed cross-sectional automobile structural member of the present disclosure, in which two hat-shaped cross-sectional members having a hat-shaped cross section in which side wall portions and flange portions are continuous on both left and right sides of a top plate portion are opposed A hollow member having a closed cross-section is produced by joining the flange portions to each other, and members having left and right side wall portions with different heights are used as the two hat cross-section members.

By FEM analysis, the inventors analyzed in detail the part deformation behavior in a three-point bending test using a hollow member composed of a combined hat cross-sectional member having a shape as shown in FIGS. 1 and 2 . 3 and 4 show the three-point bending test conditions. That is, the analysis condition for three-point bending is that two points on the lower surface of the structural member 1 separated in the longitudinal direction are supported by the supporting member 31 and a load is applied from above to the central portion in the longitudinal direction by the punch 30 .
A steel plate having a thickness of 1.2 mm and a tensile strength of 1180 MPa was used as the upper and lower hat section members 10 and 11 .

<Comparative example>
As a comparison part, a hollow member was used in which the left and right side wall portions of the two hat section members had the same height and the height difference h between the left and right mating surfaces S1 and S2 was zero. The height, length, and plate thickness of the hollow member were set to values equal to those of the invention example.
Looking at the behavior of this comparison part at the time of collision, as shown on the left side of Fig. 5, as the stroke increases, the punch contact portion, which is the central part in the longitudinal direction of the member, begins to deform, and the collision load increases. do. Since the comparative part has a symmetrical cross section, the deformation of the cross section progresses as the load increases while the load is evenly applied to the left and right ridges (the connection between the top plate and the side wall). When the maximum load is exceeded, buckling of the cross section becomes remarkable, and the cross section widens greatly.

<Invention example>
As the inventive component, a hollow member was used in which the joint surfaces S1 and S2 of the left and right flange portions were vertically offset (offset amount m=40 mm).
As shown in FIG. 2, the inventive part has a bilaterally asymmetrical structure. For this reason, in the inventive part, as shown on the right side of FIG. It was found that the load on the ridgeline of the In other words, in the invention part, the timing of the resistance applied to the left and right ridges is different, so the load does not decrease immediately after the initial deformation occurs, and it is thought that the deformation resistance is maintained longer than the comparative part. .
In addition, in the invented parts, buckling of the cross section is suppressed and the opening of the vertical wall is smaller than that of the comparative parts. It is thought that it also has the effect of suppressing a sudden drop in the load due to buckling as the deformation progresses.

FIG. 6 shows the relationship between the load and the stroke in the comparative example and the invention example.
As can be seen from FIG. 6, in the invention example, compared with the comparative example, the deformation resistance at the initial stage of the collision is reduced to alleviate the sudden impact on the occupant at the initial stage of the collision, and the deformation resistance against the subsequent load input is reduced in the comparative example. I have found that I can keep it longer.
Furthermore, Table 1 shows the results of evaluation by changing the difference h.
Here, the stroke was made up to 100 mm.
In Table 1, the average load is the average value of the load over the entire stroke and corresponds to the energy absorption capacity. Also, the "height between mating surfaces" represents the ratio of the difference h to the height H of the part (h/H).

FIG. 7 shows the relationship between the "height between mating surfaces" and the average load.
As can be seen from Table 1 and FIG. 7, by setting the difference h to be greater than 0 and 0.55H or less, the invention example can maintain deformation resistance over a long period of time compared to the comparative example, and the average load ( A value proportional to the total energy up to a stroke of 100 mm) was also found to be larger than in the comparative example.

1 automotive structural members 10, 11 hat cross-section member 10A, 11A top plate portion 10B, 11B side wall portion 10C, 11C flange portion S1 second mating surface S2 first mating surface h difference between mating surfaces H height between top plate portions S SP Middle point position

Claims (6)

2. A hollow member having a closed cross-sectional shape formed by joining opposing flange portions of two hat-shaped cross-sectional members having a hat-shaped cross section in which a side wall portion and a flange portion are continuous on both sides of a top plate portion; When the two top plate parts face each other as the height direction,
The position in the height direction of the first mating surface that is the joint surface between the flange portions on one side and the position in the height direction of the second mating surface that is the joint surface between the flange portions on the other side are different,
The hollow member does not have a reinforcing part that reinforces the hollow member in the closed cross section formed by the two hat cross-section members,
The two hat cross-sectional members are members with the same cross-sectional shape,
A structural member for an automobile, characterized by: Both of the two hat cross-section members do not have a reinforcing part that constitutes the hat cross-section member,
The structural member for automobiles according to claim 1, characterized in that: Let H be the distance between the two opposing top plate parts,
The top of either one of the two hat cross-section members at the midpoint position between the height direction position of the first mating surface and the height direction position of the second mating surface along the height direction. 3. The automotive structural member according to claim 1, wherein the distance from the plate portion is 0.4H or more and 0.6H or less. It satisfies the following formula (1), where H is the distance between the two opposing top plate portions, and h is the difference between the height of the first mating surface and the height of the second mating surface. The automotive structural member according to any one of claims 1 to 3 .
0 < h/H ≤ 0.55 (1) The automotive structural member according to any one of claims 1 to 4, wherein the automotive structure is capable of bearing a collision load input from a direction along the opposing direction of two opposing top plate portions. Element. A method for manufacturing an automotive structural member according to any one of claims 1 to 5 ,
A hollow member having a closed cross-sectional shape is produced by joining the opposing flange portions of two hat-shaped cross-sectional members each having a hat-shaped cross section in which the side wall portion and the flange portion are continuous on both left and right sides of the top plate portion,
1. A method of manufacturing a structural member for an automobile, characterized in that members having left and right side wall portions with different heights are used as the two hat cross-section members.

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