JPH07125651A - Strengthening member - Google Patents

Abstract

PURPOSE:To doubly increase a crash load and stabilize a crash mode by applying welding within a range of specified effective width in the width direction of a flange from the center of a corner part adjacent to the flange. CONSTITUTION:A first member 11 has a roughly hut section and flanges 13 are provided on both end parts in the width direction of the first member 11 through corner parts K1. The first member 11 has roughly constant thickness (t) and has the corner parts K1, K2 of n=4 pieces. A second member 12 has a plate shape of the same thickness (t), both of its end parts 12a in the width direction are put against the flanges 13 of the first member 11 and are welded 14 along the longitudinal direction. The welding 14 is wire welding, and it is carried out by radiating a laser beam, etc. Consequently, a strengthening member 30 has a wire welding part N at a position adjacent to the corner part K1 adjoining the flanges 13. The strengthening member 30 has the wire welding part N in a range of effective width (a)=16t<0.46> toward end parts in the width direction of the flanges 13 from the center (head part) of the corner part K1 adjoining the flanges 13.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a strength member such as a front side member which is crushed by receiving a compressive load in the longitudinal direction to absorb collision energy and the like.

[0002]

2. Description of the Related Art As a conventional strength member, there is one as shown in FIG. 24 which is used for the front side member 103 of the automobile 100 shown in FIG.
(See the official gazette).

First, the strength member 10 shown in FIG. 24 (a) projects a first member 11 having a hat cross section having a substantially constant plate thickness t and a second plate member 12 having a plate thickness t and having a substantially plate shape. It is applied and welded to form a closed cross-section structure. That is, the first member 11 has first flanges 13 at both ends in the width direction, and when a corner K1 adjacent to the first flange 13 is added, it has corners K1 and K2 of n = 4. There is. The second member 12 is arranged so as to close the opening of the first member 11, and both end portions 12a are welded 14 to the flange 13 to form a long tubular strength member 10 having a quadrangular cross section. The welding 14 is spot welding or line welding.

The strength member 20 shown in FIG. 24 (b) has n = 4.
A pair of the first members 11 having the individual corners K1 and K2 are provided, and the flanges 13 are welded 14 together to form a long tubular strength member 20 having a substantially quadrangular cross section.

Then, the strength members 10 and 20 are connected to the front side member 103 of the vehicle 100 as shown in FIG.
In this case, the collision energy is absorbed when the vehicle collides. That is, if the collision load F acts on the vehicle 100 from the front and the load is large, the front side member 103 will be
As shown in (3), it is crushed into a bellows shape at a predetermined pitch (hereinafter referred to as “crush pitch”) in the length direction to absorb collision energy.

[0006]

FIG. 26 shows the relationship between the crush load P and the crush stroke S when absorbing collision energy. Usually, the crush load P has the maximum value (P _max ) at the beginning of the collision, and decreases as the crush stroke S increases. At this time, the amount of collision energy absorbed can be obtained as an integrated value of P, and this value is proportional to the average value of the crush load (average crush load) P _ave . Therefore, for the absorption of the collision energy is important to increase the average crush load P _{av e.}

On the other hand, looking at a cross section of the strength member 10 used as the front side member 103 at the time of crushing, FIG.
As shown in FIG. 7, the corners K1 and K2 are plastically deformed so as to extend. It has been clarified that the collision energy is absorbed by this plastic deformation, but most of the energy is absorbed by the plastic deformation of the corners K1 and K2.

However, in the case of a welded structure as shown in FIG.
The location of the weld 14 between the first member 11 and the second member 12 is not optimized for the corner K1, and if the location of the weld 14 is located far from the corner K1, the corner K1 will be Deformation becomes easy, and there is a limit to increase the average crush load P _ave as it is.

Here, if the plate thickness of the member is increased, the rigidity of the corner portion K1 is also increased and the average crush load P _ave is increased accordingly. However, simply increasing the plate thickness causes an increase in weight, which is not a good measure.

Further, as described in Japanese Patent Laid-Open No. 454854/1985, there is a means for providing a reinforcing member at the corner of the member, but this also causes the weight increase and the fixing of the reinforcing member because the reinforcing material is provided. A new process is required to do so, which is still not a good idea.

Further, means for heat treating the member to increase the strength of the material have been studied. However, if the member is entirely heat-treated, the rigidity of the entire member increases, the crushing pitch becomes long, the crushing mode becomes unstable, and it is difficult to set the collision energy absorption.

Therefore, an object of the present invention is to provide a strength member capable of achieving both an increase in a crush load and a stable crush mode by specifying a welding range.

[0013]

In order to solve the above problems, the invention of claim 1 has a flange and n corners,
In a long tubular strength member composed of a first member having a plate thickness t and a second member that is abutted against the flange and welded along the longitudinal direction, the corner portion adjacent to the flange Effective width a = 4nt from center to flange width direction
^The welding is performed within the range of ^0.46 .

The invention of claim 2 is the strength member according to claim 1, wherein the corner portion adjacent to the flange has a curvature r, and the effective width a is from the center of the corner portion having the curvature r. It is given as a circumference based on the center of curvature, and the welding is performed at a position of πr / 4 or more from the center of the corner.

A third aspect of the present invention is the strength member according to the first or second aspect, characterized in that a non-welded portion having a predetermined pitch is secured in the welding.

The invention according to claim 4 is the strength member according to claim 3, wherein the non-welded portion is formed by providing beads on the flange at a predetermined pitch.

[0017]

According to the invention of claim 1 of the above-mentioned means, welding is performed along the longitudinal direction within the effective width a = 4nt ^0.46 from the center of the corner adjacent to the flange of the first member in the width direction of the flange. Therefore, the strength of the corner portion adjacent to the flange can be improved by the effective width a. In addition, since the strength of the corner portion is improved by specifying the welding location as the effective width a, it is not necessary to increase the overall strength.

According to the second aspect of the invention, the effective width a is given as the circumference from the center of the corner of the curvature r with the center of curvature as a reference, and the flange welding is performed at a position πr / 4 or more from the center of the corner. Since the welding is performed, the welding is not affected by the curvature r of the corner.

According to the invention of claim 3, in addition to the effect of the invention of claim 1 or 2, the presence of the non-welded portion having a predetermined pitch allows the high strength portion and the relatively low strength portion to have a predetermined pitch. It will be lined up alternately. Therefore, the deformation proceeds with the relatively low strength portion as the antinode.

According to the invention of claim 4, in addition to the effect of the invention of claim 3, since the non-welded portion is formed by the bead, the bead can be integrally formed on the first member, and thereby the non-welded portion can be formed. The welded portion can be easily provided.

[0021]

Embodiments of the present invention will be described below.

FIG. 1 is a perspective view of a strength member 30 as a first embodiment of the present invention. This strength member 30 is shown in FIG.
Similar to the strength member 10 shown in (a), the first member 11
And the second member 12 are welded and joined together to form a long tubular shape having a substantially quadrangular cross section.

The first member 11 has a substantially hat cross section. The first member 11 has flanges 13 at both ends in the width direction via corners K1. Also, the first member 1
1 is a substantially constant plate thickness t, and has n = 4 corner portions K1 and K2.

The second member 12 has a plate shape having the same plate thickness t, and both widthwise end portions 12a are abutted against the flange 13 of the first member 11 and welded along the longitudinal direction.
Has been done. The welding 14 is line welding and is performed by irradiating a laser beam. Therefore, the strength member 30 has the line welded portion N at a position close to the corner K1 adjacent to the flange 13. To further explain, as shown in FIG. 2, the strength member 30 has a line welded portion N within the range of effective width a = 16t ^0.46 from the center (top) of the corner K1 adjacent to the flange 13 toward the end in the width direction of the flange 13.
have.

The basis of the effective width a will be described below.

As described above, when a member having a plurality of corners is crushed by a compressive load in the longitudinal direction, the corners play an important role in energy absorption.

Now, consider a model 1 having a rectangular cross section as shown in FIG. The model 1 has a rectangular tubular cross section having n = 4 corners K and four sides H. Here, the length of the vertical side is d, the length (width) of the horizontal side is b, and the plate thickness is t, and the member length is sufficiently larger than the cross-sectional dimensions b and d.

For this model 1, the stress distribution on the side H on the side of the width b was determined by simulation.
The results shown in FIG. 4 were obtained. According to this result,
In the range from the corner portion K to the effective width a, the stress is substantially equal to or higher than the yield stress σy, and the stress is equal to or lower than the yield stress σy in the other portion (the central portion of the side H).

From this result, "When the model 1 is crushed by the axial collision load, the collision energy is absorbed mainly by the plastic deformation in the range of the effective width a from the top of the corner K. Can be said. The range of the effective width a is a shaded portion of the model 1 shown in FIG. 5, and this portion is a portion that effectively contributes to energy absorption.

Next, let us consider how the cross-sectional dimension b of the model 1 (hereinafter referred to as “cross-sectional width”) and the plate thickness t affect the change in the crush load.

Therefore, here, the change in the crush load was examined when the cross-sectional width b of the model 1 was changed or the plate thickness t was changed. In addition, the maximum stress σmax
The effective width a was also examined.

The results are shown in FIGS. 6 and 7. 6 shows the results when the cross-sectional width was changed, and FIG. 7 shows the results when the plate thickness was changed. From this result, it was found that the average crush load P _ave and the effective width a depend on the plate thickness t, but hardly depend on the sectional width b.

From these _facts , the relationship between the effective width a and the average crush load P _ave can be defined by the following equation.

P _ave = 8at σmax ... “8at” in this equation substantially corresponds to the cross-sectional area shown by the diagonal lines in FIG. This formula is based on the cross-sectional area x maximum stress (σmax) = average crush load.

On the other hand, from the result of FIG. 7, the average crush load P
It can be seen that a certain function holds between _ave and the plate thickness t. When this function is obtained, P _ave = 128t ^1.46 σmax.

Therefore, a = 16t ^0.46 ... Is obtained from the above two equations. As described above, since “8” in the equation is a value in the case of a quadrangle, a = 4nt ^0.46 ... Is obtained by generalizing the equation for polygons other than the quadrangle.

That is, it can be said that most of the collision energy is absorbed by the plastic deformation of the material within the effective width a.

Next, in order to demonstrate the effective width a, the model 1
The effective width “a” of the corner portion was examined for stress during crushing with and without heat treatment, and the results shown in FIG. 8 were obtained. The heat treatment reinforces the effective width a.
When the heat treatment was not performed, the yield stress σy of the material itself was uniform as shown in FIG. 8A, and the region of the effective width a was equal to or higher than the yield stress, and the crushing proceeded. On the other hand, when the heat treatment is performed in the range of the effective width a, the yield stress σy ′ in that region locally increases as shown in FIG. 8 (b). Then, as the yield stress of the effective width a increased, the stress during crushing increased overall. That is, the average crush load P _ave increased.

Next, in order to support the above theory, the model 1
Was used to examine the change in the average crush load P _ave when the effective width a of the heat treatment was changed.

FIG. 9A shows the model 1. Here, the plate thickness t = 2.0 mm, and the length of each side H is 100
mm, the effective width a of the heat treatment was changed between 0 mm and 50 mm, and the change of the average crush load P _ave was examined.
Got the result. Note that 0 mm indicates no heat treatment, and 50 mm indicates whole surface heat treatment.

From the results shown in FIG. 9 (b), the average crush load P _ave increased as the effective width a of the heat treatment was increased from 0 mm, and P _ave became constant at a certain width. This "certain width" corresponds to the above-mentioned effective width a.
Therefore, if the range of the effective width a is heat-treated, the average crush load can be effectively increased.

Incidentally, when the thickness t = 2.0 mm, a = 16t ^0.46 = 22 mm according to the above theory.
It was confirmed that the results agree well with those in (b).

Next, the crushing pitch will be examined. The crushing pitch of the model 1 changes as shown in FIG. 10 depending on the ratio between the strength of the corner K and the strength of the center of the side H. Therefore, it was confirmed that the crushing pitch was smaller when the strength of the corner portion K was higher than the strength of the center of the side H. Therefore, the corner K
The crushing pitch of the model 1 can be reduced by the reinforcement of the chisel.

Based on the above, the first shown in FIG.
Consider the member 11 of FIG.

In this case as well, since the corner portion K1 plays the same important role in absorbing the collision energy, it is natural to apply the idea of the effective width a to the first member 11. . Therefore, it can be said that the shaded area is a large portion that absorbs the collision energy.

Here, as shown in FIG. 12, this first member 1
Consider the case where the plate-shaped second member 12 is welded to 1.

12A and 12B show a strength member 30 in which the plate-shaped second member 12 is line-welded to the first member 11.
A and 30B are shown respectively. In the strength member 30A of FIG. 10A, the position U of the line welding is outside the effective width a,
In the strength member 30B shown in FIG. 7B, the position U of line welding is inside the effective width a. Comparing the two, the strength member 30
In A, the meaning of reinforcement of the effective width a is small, and the reinforcement effect of the corner portion K1 is weak. The strength member 30B has a high effect of reinforcing the effective width a. Therefore, as shown in FIG. 13A, the corner portion K1 of the strength member 30A is easily deformed during crushing, and the crushing load is relatively low. On the other hand, the strength member 30B of FIG.
And the crushing load is relatively high.

From the above, the fact that the strength member 30 has the line welded portion N within the effective width a from the center of the corner K1 as shown in FIGS. 1 and 2 increases the average crush load P _ave . It will make a big contribution. Of course, even within the effective width a, the corner K
If line welding is performed at a position close to the center of 1, the strength will be further increased.

As described above, when the strength member 30 shown in FIG. 1 is used as a front side member, for example, the corner portions K1 and K2 can effectively work due to the crushing and can sufficiently absorb energy. Further, since the line-welded portion N on the flange 13 is merely within the effective width a, the weight increase can be restricted.
Further, since the strength member 30 is not entirely heat-treated, the crushing pitch is short and the crushing mode is stable, and the absorbed energy can be easily set.

Next, a second embodiment will be described.

FIG. 14 shows the essential parts of the strength member 40 of the second embodiment. In this second embodiment, the corner K1 has a curvature r. In this embodiment, the effective width a is set to the corner K1.
It is given as a perimeter from the center K1C with the center of curvature O as the reference. The line welded portion N has a peripheral length from the center K1C of the corner portion K1 of πr / 4 or more and a range of the effective width a, that is, FIG.
It is provided in the range of b. In addition, δ is a gap between the flange 13 and the edge portion 12a. The reason for specifying such a range is as follows.

That is, when the corner portion K1 has the curvature r, the first member 11 and the second member 12 at the corner portion K1.
The reason is that the gap δ between and becomes large, and the welding strength due to laser beam irradiation and the like decreases. However, if the welding is performed in the above range b, the welding strength can be maintained at the maximum.

FIG. 15 shows the result of examining the difference in member strength depending on the position of the line welded portion N. Center K1 of corner K1
It was confirmed that the strength is low when the line welded portion N is within the distance πr / 4 from C, the maximum strength is exhibited when the wire welded portion N is in the range of b, and the strength is reduced again when the effective width a is exceeded.

Therefore, in the case of such a strength member 40 of the second embodiment, it is possible to perform energy absorption and the like when crushing as in the first embodiment, and to increase energy absorption more accurately. it can.

Next, a third embodiment will be described.

When the corner K1 of the first member 11 has a curvature r as in the second embodiment, the line welded portion N
Position is regulated by the curvature r, and the center K1 of the corner K1
There is a limit to how close to C side. Then, the third of FIG.
In the strength member 50 of the embodiment, the width direction central portion 12b of the second member 12 is projected to the inside of the strength member 50, and the second member 12 is shaped along the corner K1. That is, as shown in FIGS. 17 and 18, a curved surface 12c having a curvature r ₂ slightly larger than the curvature r ₁ of the corner K1 of the first member 11 is set in the second member 12 and reaches the center K1C of the corner K1. Until then, the gap between the first member 11 and the second member 12 is prevented from widening. In this case, the line welded portion N is provided at the center K1C of the corner portion K1 as shown in FIG.

Therefore, in this third embodiment, in addition to the same effects as in the second embodiment, since the line welded portion N is present in the center K1C of the corner portion K1, the peripheral strength of the corner portion K1 is further improved, and the average strength is improved. The crush load P _ave can be further increased.

Next, a fourth embodiment will be described.

FIG. 19 shows a perspective view of the strength member 60 of the fourth embodiment. In this embodiment, the non-welded portions M which are not welded to the line welded portions N are provided at a predetermined pitch. This predetermined pitch is a crushing pitch λ and is obtained by experiments, numerical analysis, or the like. In the strength member 60, the non-welded portions M are provided at a pitch of ½λ from the one end 60a in the length direction, which is the front end side, and then λ.

Therefore, in this embodiment, in addition to the same effects as the first embodiment, the strength member 60 has the non-welded portion M of low strength as the antinode, and as shown in FIG. 20, at a substantially ideal crush pitch. It will be crushed. Therefore, the crushing mode is stable, and it is extremely easy to set the absorbed collision energy.

Next, a fifth embodiment will be described.

FIG. 21 is a perspective view showing the main part of the strength member 70 according to the fifth embodiment. Also in this embodiment, the non-welded portions M are provided in the line welded portion N at a predetermined pitch. In this embodiment, the beads 13 are provided on the flange 13 on the first member 11 side at a predetermined pitch, and the bead 71 is used to form the second member 1.
A gap 72 is formed between the second end 12a. When line welding is performed by laser beam irradiation or the like, the portion of the bead 71 is not welded and remains as the non-welded portion M.

Therefore, in this embodiment as well, substantially the same operation and effect as in the fourth embodiment can be obtained, and the workability is improved because the non-welded portion M is formed even if the laser beam is continuously irradiated.

As the strength member, it is possible to apply it to a structure in which the first members are welded to each other as shown in FIG. 24 (b).

[0065]

As is apparent from the above, according to the invention of claim 1, the strength of the corner portion can be increased only by specifying the welding range, and a large energy absorption is achieved by increasing the average crush load. be able to. Moreover, the entire surface is not heat-treated to improve the rigidity, and the crushing mode is stable and the absorbed energy can be easily set.

According to the invention of claim 2, in addition to the effect of claim 1, even if the corner portion has the curvature r, the strength of the corner portion can be maximized, and the average crush load is increased. As a result, a large collision energy can be reliably absorbed.

According to the invention of claim 3, in addition to the effect of claim 1, crushing can be advanced at a predetermined pitch, and the crushing mode can be stabilized. Therefore, it becomes extremely easy to set the absorbed energy during crushing.

According to the invention of claim 4, in addition to the effect of claim 3, the non-welded portion is automatically secured at a predetermined pitch only by performing ordinary wire welding by the action of the bead, which makes the manufacturing extremely easy. Become.

[Brief description of drawings]

FIG. 1 is a perspective view of a first embodiment of the present invention.

FIG. 2 is a front view of the first embodiment.

FIG. 3 is a perspective view showing a model of a member used for explaining the operation.

FIG. 4 is a graph showing a stress distribution on a side of the model.

FIG. 5 is a cross-sectional view illustrating the concept of effective width in the model.

6A and 6B show the results of examining the change in crush load when the cross-sectional width of the model is changed, where FIG. 6A is a table and FIG. 6B is a graph.

7A and 7B show the results of examining the change in crush load when the plate thickness of the model is changed, and FIG. 7A is a table and FIG. 7B is a graph.

FIG. 8 is a diagram showing a comparison of stress distributions of the same model,
(A) is a diagram showing a stress distribution without heat treatment, (b)
[Fig. 3] is a diagram showing a stress distribution when heat-treated.

9A and 9B show the results of examining changes in the average crush load when the heat treatment width is changed. FIG. 9A is a perspective view showing a model, and FIG. 9B shows the relationship between the heat treatment width and the average crush load. It is a graph.

FIG. 10 is a graph showing the relationship between crushing pitch and strength.

FIG. 11 is a cross-sectional view showing a first member.

12A and 12B are cross-sectional views showing a welding position, where FIG. 12A shows a welding position outside the effective width a, and FIG. 12B shows a welding position inside the effective width a.

FIG. 13 shows a cross-sectional deformation during crushing, where (a) is an effective width a.
When there is a welding position outside, (b) is a diagram showing a case where the welding position is within the effective width a.

FIG. 14 is an enlarged view of a main part of the second embodiment.

FIG. 15 is a characteristic diagram showing the effect of the second embodiment.

FIG. 16 is a perspective view of a third embodiment.

FIG. 17 is an enlarged view of a main part of the third embodiment.

FIG. 18 is an enlarged schematic view of the main part.

FIG. 19 is a perspective view of a fourth embodiment.

FIG. 20 is a side view showing a state when the same is crushed.

FIG. 21 is a perspective view of a main part of the fifth embodiment.

FIG. 22 is a side view of the relevant part.

FIG. 23 is a schematic front perspective view of a vehicle showing front side members.

FIG. 24 is a perspective view showing an example of a strength member.

FIG. 25 is a perspective view showing a crushed state of the strength member.

FIG. 26 is a graph showing a relationship between a crush load and a crush stroke.

FIG. 27 is a schematic view showing a cross-sectional change at the time of crushing.

[Explanation of symbols]

 11 1st member 12 2nd member 13 Flange 30, 40, 50, 60, 70 Strength member 71 Bead K1, K2 Corner part K1C Center part of corner part N line welding part (welding) M Non-welding part

Claims (4)

[Claims] 1. A plate thickness t having a flange and n corners.
A long member having a first member and a second member that is abutted against the flange and welded in the longitudinal direction, the flange being located from the center of the corner adjacent to the flange. The strength member is characterized in that the welding is applied within the effective width a = 4 nt ^0.46 in the width direction. 2. The strength member according to claim 1, wherein a corner portion adjacent to the flange has a curvature r, and the effective width a is based on a center of curvature from a center of the corner portion having the curvature r. The strength member is characterized in that the welding is applied at a position of πr / 4 or more from the center of the corner portion. 3. The strength member according to claim 1 or 2, wherein a non-welded portion having a predetermined pitch is secured in the welding. 4. The strength member according to claim 3, wherein the non-welded portion is formed by providing beads on the flange at a predetermined pitch.