JP2021187433A - Automobile structural component, and method for manufacture thereof - Google Patents

Abstract

To provide an automobile structural component which can easily improve collision resistant performance while suppressing weight increase due to reinforcement.SOLUTION: An automobile structural component has a hollow member which constitutes a closed cross-sectional shape in such a manner that opposite flange parts 10C, 11C in two hat cross section members 10, 11 comprising a hat cross-sectional shape, in which side wall parts 10B, 11B and the flange parts are continuous on both sides of top plate parts 10A, 11A respectively. When an opposite direction of two top plate parts is so made as to be a height direction, a position in a height direction of a first mating surface S2 that is a joint area between one flange parts, and a position in a height direction of a second mating surface S1 that is a joint area between the other flange parts are different from each other.SELECTED DRAWING: Figure 2

Description

The present invention relates to a structural member (hollow member) for an automobile in which a closed cross-sectional shape is formed by two hat cross-sectional members having a cross-sectional hat shape in which a side wall portion and a flange portion are continuous on both sides of a top plate portion. .. INDUSTRIAL APPLICABILITY The present invention is a technique for providing a structural member having collision resistance particularly against bending deformation due to a collision load input from a direction along the opposite direction of the two top plates.

In recent years, in the automobile field, stricter collision safety standards have been promoted from the viewpoint of occupant protection, and there is a strong demand for expanding the application of high-strength steel and developing vehicles with excellent collision safety performance.
Here, as the form of collision, there are a collision form in which the shaft is crushed and a collision form in which bending deformation occurs. In the collision mode in which the shaft is crushed, the longitudinal direction of the member coincides with the collision direction and the shaft crush occurs, such as a crash box or a front side member that receives a collision load input from the front surface of the automobile. In the collision mode in which bending deformation occurs, a collision load is applied to the side surface of the structural member and the member bends and deforms, as in the case of the B pillar and the side sill in a side collision. In both forms, the member absorbs collision energy by buckling and deforming, and exhibits collision resistance.

In addition, the collision resistance required for each member differs. For example, the skeletal member around the cabin is required to play a role of suppressing deformation and ensuring safety from the viewpoint of occupant protection. On the other hand, at the front end side and the rear end side away from the cabin, from the viewpoint of energy absorption, the members are actively deformed to efficiently absorb the energy at the time of collision and disperse the load to other structural members. The role of transmitting the load is required.

As one of the techniques for improving the collision resistance performance, a technique for improving the strength of the structural member by attaching a reinforcing component has been proposed. For example, Patent Document 1 describes a technique for suppressing deformation by providing a plurality of bulkheads inside a structural member and providing a reinforcing material between the bulkheads. Further, in Patent Document 2, a reinforcing part having an L-shaped or U-shaped cross section along the shape of the structural member is arranged inside or outside the structural member, so that the bottom plate is centered on the ridgeline of the structural member. Techniques for reinforcing the portion and the side wall portion are mentioned. Further, Patent Documents 3 and 4 describe a technique for suppressing deformation by filling the inside of a structural member with a foam material or arranging a reinforcing part filled with foam at a bent portion that is easily deformed at the time of collision. ..
Further, as another reinforcing method, Patent Document 5 discloses a technique of optimizing the plate thickness and partially thickening the portion including the ridge line portion to increase the member strength and suppress the deformation.

On the other hand, Patent Document 6 is premised on a structure including a closed cross-section structure from a hat cross-section member and a closing plate, and a reinforcing component connecting the left and right side wall portions. Further, in Patent Document 6, by providing partial low-strength portions on the left and right side wall portions of the hat cross-sectional member, the deformation behavior at the time of bending crushing is controlled, the bending in the longitudinal direction of the member is suppressed, and the bending at the time of deformation is suppressed. A technique for suppressing the amount of member intrusion is described.
Further, Patent Document 7 describes a technique for optimizing the arrangement position of a reinforcing component (first connecting portion 30) connecting the left and right side wall portions to restrain cross-sectional deformation at the time of bending crushing and improve collision performance. Is mentioned.

Japanese Unexamined Patent Publication No. 9-20267 WO2017-03091 Gazette Japanese Unexamined Patent Publication No. 2002-36413 Japanese Unexamined Patent Publication No. 2017-159896 Japanese Unexamined Patent Publication No. 2009-173110 WO2018-207668A Japanese Unexamined Patent Publication No. 2012-236525

However, these patent documents do not disclose a technique for controlling the deformation of a member and efficiently absorbing energy at the time of a collision without providing a reinforcing component.
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 by using reinforcing parts and fillers.
However, if a reinforcing component is simply attached to a structural member, the collision resistance is improved, but the number of components increases, the weight increases more than necessary, and the mold increases, resulting in cost. There are face issues.
In addition, reinforcement with a foam filler has a problem from the viewpoint of recyclability because there is a concern that the production process will be complicated. In addition, when partially attaching the foam filling member, adhesion is used to attach the member, but there are problems with adhesion such as peeling and deterioration over time during deformation, and it is difficult to secure stable collision resistance. Conceivable.

Further, when a reinforcing method for partially increasing the plate thickness is adopted, a differential thickness steel plate is required. In this case, for example, a technique such as a tailored blank is required, and there are problems in welding, molding, or production.
Furthermore, the methods described in these patent documents are techniques for improving collision resistance by increasing rigidity and deformation resistance, in order to deform members and efficiently increase energy absorption, that is, deformation. It is not a technique for maintaining high deformation resistance even in the process of progress. As described above, the collision resistance required for each member differs, but it cannot be said that the method described in each patent document is suitable for absorbing energy by crushing it.

Further, the techniques of Patent Documents 6 and 7 are collision performance improving techniques for controlling the deformation behavior of parts in the collision process, but since it is premised that reinforcing parts are provided for the closed cross-sectional structure, the same as the above findings. There are issues in terms of weight and cost.
Further, the technique of Patent Document 6 is a technique for controlling the amount of member intrusion due to bending, and is different from the technique for efficiently absorbing an impact. In the technique of Patent Document 6, it is necessary to utilize techniques such as local heat treatment and tailored blank for controlling the strength of members, and there are also problems in terms of production such as an increase in the number of processes and material variation.
The technique of Patent Document 7 is to improve the collision performance by controlling the cross-sectional deformation as in the present disclosure. However, the technique of Patent Document 7 is a suitable arrangement of reinforcing parts for the purpose of improving the maximum load at the time of a collision due to the restraint of cross-sectional deformation, and while controlling the balance of cross-sectional deformation, it is easy and efficient without utilizing the reinforcing parts. It is not a cross-sectional deformation control technique for maintaining high deformation resistance even in the process of deformation to increase energy absorption.

The present invention has been made focusing on the above points, and an object of the present invention is to provide a structural member for an automobile capable of easily improving collision resistance while suppressing an increase in weight due to reinforcement. do.

In order to solve the above problems, the present inventor positively deforms the member to efficiently enhance the collision energy absorption, suppresses the increase in the number of reinforcing parts due to press working, suppresses the increase in weight, and suppresses the increase in weight. We have diligently studied the shape of the structural member that easily improves the collision resistance. As a result of the examination, it was 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 the reinforcing parts. Obtained. The present invention has been made based on such findings.

In order to solve the problem, one aspect of the present invention is to join the opposing flange portions of two hat cross-sectional members having a cross-sectional hat shape in which the side wall portion and the flange portion are continuous on both sides of the top plate portion. When a hollow member constituting a closed cross-sectional shape is provided and the opposite direction of the two top plate portions is the height direction, the position in the height direction of the first mating surface which is the joint surface between the flange portions. The gist is that the position in the height direction of the second mating surface, which is the joint surface between the other flange portions, is different.

Another aspect of the present invention is a method for manufacturing a structural member for an automobile having a closed cross-sectional shape, which has two cross-sections having a cross-sectional hat shape in which a side wall portion and a flange portion are continuous on both left and right sides of the top plate portion, respectively. The gist is to form a hollow member having a closed cross-sectional shape by joining the flange portions facing each other in the member, and to use members having different heights of the left and right side wall portions as the two hat cross-sectional members. ..

According to an aspect of the present invention, there is provided a structural member for an automobile that can easily improve collision resistance while suppressing an increase in weight due to the fact that it is not always necessary to provide a reinforcing component for a closed cross-sectional structure. Is possible.
That is, in the aspect of the present invention, the heights of the first mating surface and the second mating surface, which are the left and right mating surfaces (joining planes) of the two hat cross-sectional members, from one of the top plates as a reference are set. Arrange differently. Thereby, according to the aspect of the present invention, the member is deformed by distributing the load applied when the member cross-sectional deformation at the time of bending deformation is applied to the collision load in the direction along the opposite direction of the two top plate portions. It is possible to efficiently absorb the collision energy while making the collision energy.

Further, according to the aspect of the present invention, since it is not always necessary to use reinforcing parts, foaming materials, etc., the weight increase due to the increase in the number of parts, the cost increase due to the increase in the mold, the recycling, and the productivity are hindered. The collision resistance can be easily improved without any problem.
Here, as the above-mentioned reinforcing parts, for example, there are reinforcing parts as described in each patent document. As the reinforcing component, for example, a reinforcing component connecting the left and right side wall portions constituting the hat cross-section member, for example, a reinforcing component arranged in a closed cross section and extending in the left-right direction, and connecting the end portions to the left and right side wall portions, respectively. Examples thereof include the reinforcing parts provided, and the reinforcing parts extending so as to straddle the top plate portion in the width direction of the top plate portion and connecting the end portions to the outer surfaces of the left and right side wall portions, respectively.

It is a perspective view which shows the hollow member which concerns on embodiment based on this invention. It is sectional drawing of the hollow member which concerns on embodiment based on this invention. It is a side view explaining the three-point bending analysis condition in an Example. It is a perspective view explaining the three-point bending analysis condition in an Example. It is a figure which shows the behavior when a load is applied in the direction from the upper top plate part to the lower top plate part. It is a figure which shows an example of the relationship between a stroke (pushing amount) of a load, and a load. It is a figure which shows the relationship between the average load and the height between mating surfaces.

Next, an embodiment of the present invention will be described with reference to the drawings.
(composition)
In the present embodiment, the two hat cross-sectional members 10 having a cross-sectional hat shape in which the side wall portions 10B and 11B and the flange portions 10C and 11C are continuous on both sides of the top plate portions 10A and 11A as shown in FIGS. 1 and 2, respectively. With respect to 11, the left and right facing flange portions 10C and 11C are joined to each other to form a closed cross-sectional shape to form a hollow member. The hollow member is referred to as an automobile structural member 1 to be reinforced (hereinafter, also simply referred to as structural member 1). The flange portions 10C and 11C are joined to each other by, for example, spot welding.

Here, the joining surface between the flange portions 10C and 11C corresponding to each other on the right side is referred to as a first mating surface S2, and the joining 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 the present 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 the present embodiment, it is assumed that an impact from the side of the structural member 1 is easily input to the top plate portion 10A on the upper side of the hat cross-section member 10.

Further, in the present specification, the opposite directions of the two top plate portions 10A and 11A are referred to as height directions.
Then, in the present embodiment, the position in the height direction of the height L2 of the first mating surface S2 on the right side and the second on the left side from the top plate portion 10A of the two top plate portions 10A and 11A. The height of the mating surface S1 is set so as to be different from the position of the height L1 in the height direction.
One top plate portion is, for example, an upper top plate portion 10A on which an impact can be easily input.

The distance between the two facing top plate portions 10A and 11A is H, and the difference between the height L2 of the first mating surface S2 and the height L1 of the second mating surface S1 is h (= | L1-L2 | ), It is preferable to satisfy the following equation (1).
0 <h / H ≤ 0.55 ・ ・ ・ (1)
More preferably, it is "0.05 ≤ h / H ≤ 0.5".
Here, when the height difference h between the first mating surface S2 and the second mating surface S1 is larger than 0.55 times the height H between the top plates, a collision load is applied. As the result, the balance of deformation in the collision process is greatly lost, and the cross section bends in one direction on the left and right (image of crushing a parallelogram), so it is thought that the deformation resistance is greatly reduced.
Further, the difference h in the height direction of the left and right mating surfaces is preferably larger than, for example, 2 mm. Further, the difference h in the height direction of the left and right mating surfaces is preferably 0.05 H or more, for example.

However, the larger the height difference h between the first mating surface S2 and the second mating surface S1, the more easily the deformation in the direction in which the closed cross-sectional shape is twisted is applied to the load in the axial direction or the like. Therefore, it is preferable that the difference h is small. From this point of view, the more preferable upper limit value of the difference h is set to 0.55H or less.

In the present embodiment, members having the same cross-sectional shape are adopted as the two hat cross-sectional members 10 and 11, and one of the two hat cross-sectional members 10 and 11 is joined by reversing the top and bottom to form a closed cross-sectional shape. It is a hollow member. Therefore, the height of the first mating surface S2 on the right side with respect to the proximal top plate portion 10A is equal to the height of the second mating surface S1 on the left side 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 center position in the height direction of the hollow member are equal. These values may be different on the left and right. However, it is advantageous in terms of processing cost and the like to adopt members having the same cross-sectional shape as the two hat cross-sectional members 10 and 11. 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-sectional members of the midpoint position SP of the position in the height direction of the first mating surface S2 and the position in the height direction of the second mating surface S1 along the height direction. The distance from the top plate ((L1 + L2) / 2) shall be 0.4H or more and 0.6H or less. When the midpoint position is in the center or near the center in the height direction, it is possible to prevent the left-right balance from being greatly lost while giving a left-right difference to the closed cross-sectional structure.

However, the two hat cross-section members 10 and 11 do not have to have the same dimensions. For example, the height of the lower hat cross-section member 11 may be lower than the height of the upper hat cross-section member 10. The heights of the hat cross-sectional members 10 and 11 are the heights at the average value positions 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 ratio of the heights of the hat cross-section members 10 and 11 having the higher height to the hat cross-section members 10 and 11 having the lower height. It is set to 1 to 1: 0.5.

Further, the two facing top plate portions 10A and 11A may not be parallel to each other, and the other top plate portion may be inclined with respect to one top plate portion.
In addition, 1 or 2 or more beads extending in the longitudinal direction may be formed on the top plate portions 10A, 11A and the side wall portions 10B, 11B. By providing the bead extending in the longitudinal direction, the structural member 1 for an automobile has improved strength against a load input in the direction along the longitudinal direction of the hollow member.
Further, although the dimensions of the members in the embodiment are also shown in FIGS. 1 and other drawings, these dimensions do not limit the present invention in any way.

(effect)
In this embodiment, the following effects are obtained.
(1) In the present embodiment, in two hat cross-sectional members having a cross-sectional hat shape 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 each other to form a closed cross-sectional shape. When the two top plate portions face each other in the height direction, the position in the height direction of the first mating surface S2, which is the joint surface between the flange portions, and the above on the left side. The position of the second mating surface S1, which is the joint surface between the flange portions, in the height direction is different from that of the second mating surface S1.
According to this configuration, it is possible to improve the collision resistance performance of the structural member 1 in a collision form in which bending deformation is performed, without necessarily providing a reinforcing component for suppressing the opening of the left and right side wall portions in the hollow member. Become. That is, according to the present embodiment, it is possible to provide a structural member for an automobile capable of easily improving the collision 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 (joining surfaces) of the two hat cross-sectional members, are mutually from one of the top plate portions 10A as a reference. The heights L1 and L2 are arranged differently. As a result, in the present embodiment, the load applied to the member cross-sectional deformation at the time of bending deformation is dispersed with respect to the collision load in the direction along the opposite direction of the two top plates, thereby efficiently deforming the member. It becomes possible to absorb the collision energy.
Further, according to the present embodiment, since no reinforcing parts or foaming materials are used, it is easy to withstand an increase in weight due to an increase in the number of parts, an increase in cost due to an increase in molds, recycling, and productivity. Collision performance can be improved.

(2) Neither of the above two hat cross-section members has a reinforcing component constituting the hat cross-section member.
(3) Let H be the distance between the two facing top plates, and the position of the first mating surface in the height direction and the position of the second mating surface in the height direction along the height direction. The distance from the top plate portion of either of the above two hat cross-sectional members at the midpoint position is 0.4H or more and 0.6H or less.
(4) The above two hat cross-sectional members are both members having the same cross-sectional shape.

(5) When the distance between the two facing 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) Satisfy the formula.
0 <h / H ≤ 0.55 ・ ・ ・ (1)
According to this configuration, it is possible to more reliably achieve the above effect.

(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 opposite direction of two facing top plates.
By using the structural member for an automobile of the present embodiment at a position of an automobile having a possibility of a bending deformation collision form, it is possible to improve the collision resistance performance in the bending deformation collision form without increasing the weight of the automobile. Become.

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

The inventors analyzed in detail the deformation behavior of the parts in the three-point bending test by FEM analysis using a hollow member made of a cross-section member of a mating hat having a shape as shown in FIGS. 1 and 2. The three-point bending test conditions are shown in FIGS. 3 and 4. That is, the analysis condition of the three-point bending is a condition that two points on the lower surface of the structural member 1 separated in the longitudinal direction are supported by the support member 31, and a load is applied to the central portion in the longitudinal direction from the upper side by the punch 30.
As the upper and lower hat cross-section members 10 and 11, steel plates having a thickness of 1.2 mm and a tensile strength of 1180 MPa were used.

<Comparison example>
As a comparative component, a hollow member having the same height of the left and right side wall portions of the two hat cross-sectional members and having a zero height difference h between the left and right mating surfaces S1 and S2 was used. The height, length, and plate thickness of the hollow member were set to the same values as those in the invention.
Looking at the behavior of this comparative component 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 portion in the longitudinal direction of the member, starts to deform, and the collision load increases. do. Since the comparative parts have a symmetrical cross section, the left and right ridges (the connection portion between the top plate portion and the side wall portion) are evenly loaded, and the cross section is deformed as the load increases. When the maximum load is exceeded, the buckling of the cross section becomes remarkable, and the cross section widely spreads laterally.

<Invention Example>
As a component of the invention, a hollow member in which the arrangement of the mating surfaces S1 and S2 of the left and right flange portions is vertically offset (offset amount m = 40 mm) is used.
As shown in FIG. 2, the invention component has a left-right asymmetric structure. Therefore, in the invention component, as shown on the right side of FIG. 5, first, the load on one of the left and right ridges (the connection portion between the top plate and the side wall) becomes large, and then the other. It was found that the load on the ridgeline of the ridge increased. That is, it is considered that in the invention part, the timing of the resistance applied to the left and right ridges is different, so that the load does not decrease immediately after the initial deformation occurs, and the deformation resistance is maintained longer than that of the comparative part. ..
In the invention part, the buckling of the cross section is suppressed and the opening of the vertical wall is smaller than that of the comparative part. It is thought to work, and as the deformation progresses, it is also considered to have the effect of suppressing a sharp drop in load due to buckling.

FIG. 6 shows the relationship between the load and the stroke in the above comparative example and the invention example.
As can be seen from FIG. 6, in the invention 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 to the subsequent load input is compared with the comparative example. It turns out that it can be maintained longer than.
Further, Table 1 shows the results of evaluation by changing the above difference h.
Here, the stroke was set to 100 mm.
In Table 1, the average load is the average value of the load in all strokes and corresponds to the energy absorption capacity. Further, the "height between the mating surfaces" represents the ratio (h / H) of the difference h to the height H of the parts.

Further, 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 larger than 0 and 0.55 H or less, the invention example can maintain the deformation resistance for a long period of time as compared with the comparative example, and the average load ( It was found that the value proportional to the total energy up to a stroke of 100 mm) was also larger than that of the comparative example.

1 Automotive structural members 10, 11 Hat cross-section members 10A, 11A Top plate parts 10B, 11B Side wall parts 10C, 11C Flange parts S1 Second mating surface S2 First mating surface h Difference between mating surfaces H Height between top plates SP midpoint position

Claims (7)

Two hat cross-sectional members having a cross-sectional hat shape in which the side wall portion and the flange portion are continuous on both sides of the top plate portion have hollow members that form a closed cross-sectional shape by joining the opposing flange portions to each other. When the opposite direction of the two top plates is the height direction,
The feature is that the position in the height direction of the first mating surface, which is the joining surface between the flange portions, and the position in the height direction of the second mating surface, which is the joining surface between the other flange portions, are different. Structural members for automobiles. Neither of the above two hat cross-section members has a reinforcing component constituting the hat cross-section member.
The structural member for an automobile according to claim 1. Let H be the distance between the two facing top plates.
The sky of one of the two hat cross-sectional members at the midpoint position between 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 structural member for an automobile according to claim 1 or 2, wherein the distance from the plate portion is 0.4H or more and 0.6H or less. The structural member for an automobile according to claim 3, wherein the two hat cross-sectional members are both members having the same cross-sectional shape. When the distance between the two facing top plates is H and the difference between the height of the first mating surface and the height of the second mating surface is h, the following equation (1) is satisfied. The structural member for an automobile according to any one of claims 1 to 4.
0 <h / H ≤ 0.55 ・ ・ ・ (1) The automobile structural member according to any one of claims 1 to 5, wherein the automobile structure can bear a collision load input from a direction along the opposite direction of the two facing top plates. Element. The method for manufacturing an automobile structural member according to any one of claims 1 to 6.
In two hat cross-sectional members having a cross-sectional hat shape in which the side wall portion and the flange portion are continuous on the left and right sides of the top plate portion, the opposing flange portions are joined to each other to produce a hollow member having a closed cross-sectional shape.
A method for manufacturing a structural member for an automobile, characterized in that members having different heights of the left and right side wall portions are used as the two hat cross-sectional members.

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