JP3422605B2 - Hollow profile - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hollow member which is bent so as to be bent at a predetermined bending radius.

[0002]

2. Description of the Related Art Hollow profiles formed by extrusion molding are
2. Description of the Related Art Conventionally, a bent shape material is formed by bending using a press bender so that it can be used for automobile structural members such as bumpers. In the bending process by the press bender, as shown in FIG. 10, the rod-shaped mandrel 52 is inserted into the hollow shape member 51, and the pressing die 54 is circumferentially pressed so as to press the hollow shape member 51 against the bending die 53. Bending is performed by moving in the direction
By moving the mandrel 52 in the direction of the arrow in the drawing in accordance with the processing position, it is possible to prevent the shape from being crushed by the pressing die 54, and to prevent and erase the wrinkles that occur in the bending inner wall portion. It has become.

[0003]

However, the hollow shape member 5 is used.
When bending No. 1 with a small bending radius R, even if the cored bar 52 is inserted into the hollow shape member 51 as in the conventional case described above, wrinkles due to buckling occur in the bending inner side wall portion, and deep wrinkles occur. Therefore, there is a problem that mounting work may become difficult.

Therefore, as measures for preventing the generation of wrinkles, measures for increasing the number of reinforcing intermediate walls provided in the hollow profile, connection between the vertical wall and the horizontal wall of the hollow profile, and connection between the outer wall and the intermediate wall. To reduce the wall width by using a slanted wall, and to incline either the upper wall or the lower wall parallel to the bending direction of the hollow section (Japanese Patent Publication No. 63-39).
No. 146), measures for increasing the ratio (t1 / t2) of the plate pressure t1 on the inner wall of bending to the plate thickness t2 of the reinforcing plate by 1.1 times or more (Japanese Patent Publication No. 7-51738), cryogenic molding, Measures for bending by local heating (Japanese Patent Publication No. 2-62089 and Japanese Patent Laid-Open No. 59-185527) have been proposed and disclosed, but these measures have the following problems.

That is, as a measure for increasing the reinforcing intermediate wall provided in the hollow frame member, the weight of the hollow frame member is significantly increased, which is unsuitable as a structural member for automobiles which needs to be lightened. become. In addition, in the measure to connect the vertical wall and the horizontal wall of the hollow shape member or the outer wall and the intermediate wall with the inclined wall whose wall width is reduced, the wrinkle depth is remarkably increased so that the mounting work becomes difficult. Cannot be reduced. In addition, as a measure to incline either the upper wall or the lower wall parallel to the bending direction of the hollow frame, it is possible to reduce the wrinkles that occur on the upper wall and the lower wall, but the inner wall of the bent portion. It is not possible to reduce the wrinkles that occur in the.
Further, as a measure for increasing the ratio (t1 / t2) of the plate pressure t1 of the bending inner side wall to the plate thickness t2 of the reinforcing plate to 1.1 times or more, when the thickness of the bending inner side wall is thin or the bending radius is small. Moreover, it is not possible to sufficiently prevent the generation of wrinkles. Further, in the measures for bending by cryogenic molding or local heating, it takes a long time for cooling and heating, which increases the production cost and makes mass production difficult.

Therefore, the present invention is intended to provide a hollow profile capable of sufficiently reducing the wrinkles generated in the inner wall portion of the bend even when bent with a small bend radius R.

[0007]

In order to solve the above-mentioned object, the invention of claim 1 is a hollow shape member which is bent so as to be bent at a predetermined bending radius, and is bent by the bending process. The inner wall is characterized in that a recess having a depth that exceeds three times the wall thickness is formed parallel to the bending circumferential direction .

According to the above construction, the recess is formed in the inner wall of the bend, so that a step is formed on the wall surface of the inner wall of the bend. When bending is performed in this state, the recess has a wall thickness of 3 mm. Since the depth is set to more than double , each wall surface divided by the step is bent independently. Therefore, the buckling limit stress of the bending inner side wall during bending is determined by the wall width of each wall surface caused by the step. Since each of these wall surfaces has a smaller wall width than the wall surface of the bent inner side wall where no recess is formed, it has a large buckling limit stress, and as a result, wrinkles due to buckling of the bent inner side wall are generated. It becomes possible to prevent. Further, as described above, when each wall is bent independently, the wall width of each wall determines the pitch of wrinkles,
Since wrinkles occur at a pitch limited by the wall width of each wall surface, it is possible to prevent deep wrinkles from occurring.

The invention of claim 2 is characterized in that the wall width of the bent inner side wall of claim 1 is equally divided by the recess. According to this structure, since the wall width is half the wall surface of the bent inner side wall in which the recess is not formed, the wrinkle pitch is halved, and the wrinkle depth can be reduced by 50% or more.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described with reference to FIGS. The hollow profile according to the present embodiment is used for, for example, bumper reinforcement of an automobile bumper device after being bent to be a bent profile. This hollow shape member has a cross-sectional shape in which a concave portion is formed in a bending inner side wall of a day shape member, and as shown in FIG. 1, a bending inner side wall 2 against which a bending die is abutted during bending, Bending outside wall 3 arranged in parallel to bending inside wall 2
An upper surface wall 4 and a lower surface wall 5 provided so as to connect both ends of the bending inner side wall 2 and the bending outer side wall 3, and an upper surface wall 4
And an intermediate wall 6 provided between the lower surface walls 5.

The bending inner side wall 2 has a recess 7 formed in the center thereof so as to be recessed toward the bending outer side wall 3.
The concave portion 7 forms a wall surface portion 2a, 2b, 2c, 2d by forming a step on the wall surface of the bent inner side wall 2, and these wall surface portions 2a, 2b, 2c, 2d are separated by the intermediate wall 6. It has a wall width b obtained by equally dividing the wall surface of the bent inner side wall 2. Further, the recess 7 has a depth that is a step amount of the bending inner side wall 3 set to be three times or more the wall thickness of the bending inner side wall 2, and when the hollow profile 1 is bent, each wall surface portion is bent. 2a ・ 2b
・ By bending 2c and 2d independently,
The large buckling limit stress determined by the wall width b of each wall surface 2a, 2b, 2c, 2d prevents the occurrence of wrinkles.

The hollow profile 1 in the present embodiment has a cross-sectional shape in which a recess is formed in a day profile that is frequently used for automobile structural members, but the invention is not limited to this.
For example, it may have a cross-sectional shape in which a concave portion is formed in a mouth-shaped material, an eye-shaped material, a rice-shaped material, or the like.

The operation of bending the hollow frame member 1 having the above structure will be described. The hollow profile 1 is attached to a press bender (not shown), the rod-shaped core of the press bender is inserted into the hollow profile 1, and then the pressing die is pressed in the circumferential direction so as to press the hollow profile 1 against the bending die. The bending process is started by moving to.

When the bending process is started, compressive stress is applied to the bending inner side wall 2 of the hollow frame 1.
At this time, the bent inner side wall 2 has wall surfaces 2a, 2b,
2c and 2d, and the depth of the recess 7 is 3 of the wall thickness.
It is set to more than double. Therefore, the wall surfaces 2a, 2b, 2c, 2d of the bending inner side wall 2 are independently bent,
Since each of the wall surface portions 2a, 2b, 2c, 2d has a large buckling limit stress due to the wall width b, generation of wrinkles is prevented.

That is, the stress when the plate buckles (σcr)
Is generally expressed by the following equation.

Σcr = [KπE / 12 (1-ν ² )] × (t / b) ² (1)

Here, K is a load, a coefficient determined by a supporting condition (for example, K = 4.0 when the periphery of the rectangular cross section is simply supported), E is an elastic coefficient, ν is a Poisson's ratio, and t.
Is the wall thickness and b is the wall width.

Considering that the bending inner side wall 2 which receives a compressive stress in the bending process is a single plate supported by the outer wall (upper surface wall 4 / lower surface wall 5) and the intermediate wall 6, the hollow shape member of the present embodiment. 1, the inner wall 2 of the bend is formed by the recess 7 to form the wall surface 2a.
Since the wall width b of 2b, 2c, and 2d is set, the wall width b of the first formula is shorter than that of the hollow frame member 1 having the rectangular cross section of the "day" cross section in FIG. Become. This allows
Since the width-thickness ratio (t / b) is increased, the buckling limit stress (σcr) in the first equation is improved, and buckling is less likely to occur, so that the occurrence of wrinkles is prevented.

Further, as shown in FIG. 3, when the relationship between the wrinkle pitch L generated when the wall surface is buckled and the wall width b of the wall surface is obtained, the wrinkle pitch L undergoes compression. It was found that it was about 0.7 times the wall width b in proportion to the wall width b of the member. As a result, as shown in FIGS. 4 (a) and 4 (b), when the hollow profiles are equally compressed, the smaller the wrinkle pitch (L1> L2), the more the wrinkle increases,
Since the wrinkles become shallow (W1> W2), when a step is formed in the inner wall 2 of the bend by the recess 7 as in the present embodiment,
Since wrinkles are generated at a pitch limited by the wall width b of each wall surface portion 2a, 2b, 2c, 2d, it is possible to prevent the generation of deep wrinkles.

Further, the wall width b set by the wall surface portions 2a, 2b, 2c, 2d is a length obtained by equally dividing the wall width of the bent inner side wall 2 divided by the intermediate wall 6, and is the date pattern of FIG. Since it is half the pitch of the profile, it is possible to reduce the wrinkle depth by 50% or more.

Next, as shown in FIGS.
5 (a) day shape, 5 (b) eye shape, FIG.
Three cross-sectional shapes (outer dimensions: width 60 mm x height 10) composed of the dated profile (c) that has the recess of (c).
An aluminum profile having 0 mm x wall thickness of 2.0 mm) was prepared. Then, bend these aluminum profiles to an inner radius of 200
The wrinkle generation state was investigated by performing a bending process of 30 ° in mm. The test results are shown in Table 1.

[0022]

[Table 1]

As a result, the depth of wrinkles generated in the day shape member was 2.42 mm and the depth of the eye shape member was 1.09 mm, whereas wrinkles were found in the recessed day shape member. I couldn't do it. Therefore, it was confirmed that it is possible to sufficiently reduce the wrinkle generation amount and the depth by forming the cross-sectional shape having the concave portion as in the present embodiment.

Further, it was also confirmed that it is possible to reduce the wrinkle depth from 2.42 to 1.09 by increasing the intermediate wall from the day shape to the eye shape. However, the eye-shaped profile, in which an intermediate wall is added to the daily profile, is expected to increase the weight by about 1.15 times that of the daily profile due to the intermediate wall. On the other hand, in the case of the cross-section shaped material in which the concave portion is formed in the day shape shaped material as in the present embodiment, the weight increase is suppressed to a minimum of about 1.02 times that of the day shape shaped material, and the structure for automobiles is increased. It was also confirmed that it can be suitably used as a member.

Next, FEM analysis was performed using the depth of the recess formed on the inner wall of the bend as a parameter. In particular,
As shown in FIG. 6, a profile having a normal cross-sectional shape (outer dimension 100 × 60 mm, plate thickness 2 mm) having no recess,
As shown in FIG. 7, a profile with a recess having a depth of 6 mm (three times the plate thickness) and a depth of 10 mm as shown in FIG.
The FEM analysis was performed to predict the state when a core metal was used and a bending process was performed at 30 ° with a bending inner radius of 200 mm for a shape member having a recess (5 times the plate thickness).

As a result, it was confirmed that wrinkles having a depth of about 2.5 mm were formed on the inner wall of the bent piece in the case of the ordinary day shape shown in FIG. Further, in the case of the dated shape member having a concave portion having a thickness three times as large as that shown in FIG. 7, the bending inner wall has a depth of 1.8 mm.
It was confirmed that a certain amount of wrinkles were generated, and it was confirmed that by forming a recess in the inner wall of the bend, it is possible to reduce the wrinkle depth as compared with a normal day shape member having no recess. Furthermore, it was confirmed that wrinkles were hardly generated in the case of the day shape member having a recess having a thickness 5 times that of FIG.

As a result, it was found that it is possible to reduce the depth and the amount of wrinkles by forming the recess on the inner wall of the bend, and when the depth of the recess is three times the plate thickness, It has been found that the wrinkle depth cannot be reduced sufficiently. The reason for this is that when the depth of the recess is set to be three times the plate thickness, buckling occurs in the vertical wall of the recess, and as in the case of a normal day shape member in which no recess is formed, It is considered that this is because it deforms as a single plate supported by the outer wall and the intermediate wall.

Next, the following test was conducted in order to confirm that the relationship between the depth of the recess and the plate thickness affects the depth of the wrinkle, as obtained from the above-mentioned prediction result of the FEM analysis.
That is, the ratio between the depth of the recess and the plate thickness is "0", "0.
5 ”,“ 1 ”,“ 2 ”,“ 3 ”,“ 3.5 ”,“ 4 ”,
"5" day shape material was prepared. Then, the presence or absence of wrinkles and the depth were measured by bending these day shape members. As a result, as shown in FIG. 9, it was confirmed that the wrinkle depth gradually decreased in the range of the depth to plate thickness ratio of "0" to "3". It was confirmed that when the ratio with the plate thickness exceeds "3", the wrinkle depth sharply decreases, and wrinkles do not occur after "3.5".

[0029]

As described above, according to the first aspect of the present invention, in the hollow shape member bent so as to be bent at a predetermined bending radius, the bending inner wall bent by the bending work has a wall thickness. The concave part set to a depth of more than 3 times the bending circumference
It is a structure formed parallel to the direction .

As a result, since the respective wall surfaces sectioned by the step of the recess are independently bent, the wall width becomes smaller than the wall surface of the bent inner side wall where the recess is not formed, and a large buckling limit stress is generated. Since it has, it is possible to prevent the generation of wrinkles due to the buckling of the inner wall of the bend.
Also, by bending each wall independently,
Since the wall width of each wall surface determines the wrinkle pitch and wrinkles are generated at a pitch limited by the wall width of each wall surface, it is possible to prevent the occurrence of deep wrinkles.

The invention of claim 2 is as described above.
The wall width of the bent inner side wall of claim 1 is equally divided by the recess. As a result, the wall width is half that of the inner wall surface of the bent inner wall where no recess is formed, so the wrinkle pitch is halved, and the wrinkle depth can be reduced by 50% or more.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a hollow frame member.

FIG. 2 is a cross-sectional view of a hollow frame member.

FIG. 3 is a graph showing the relationship between pitch and wall width.

4A and 4B are explanatory diagrams showing a relationship between a wrinkle depth and a pitch, where FIG. 4A is an explanatory diagram when the pitch is large, and FIG. 4B is an explanatory diagram when the pitch is small.

5A and 5B are cross-sectional views of a hollow shape member, in which FIG. 5A is a cross-sectional view of a day shape member, FIG. 5B is a cross-sectional view of an eye shape member, and FIG. FIG.

FIG. 6 is an explanatory view showing a state where the hollow shape member is bent.

FIG. 7 is an explanatory view showing a state where the hollow shape member is bent.

FIG. 8 is an explanatory view showing a state where the hollow shape member is bent.

FIG. 9 is a graph showing the relationship between wrinkle depth and recess depth / plate thickness.

FIG. 10 is an explanatory view showing a bending process.

[Explanation of symbols]

1 Hollow frame 2 Bent inner wall 3 Bending outer wall 4 Top wall 5 Lower wall 6 Middle wall 7 recess

Continuation of front page (56) Reference JP-A-7-96338 (JP, A) JP-A-57-1532 (JP, A) JP-A-60-33176 (JP, A) JP-A-2-30328 (JP , A) JP-A-8-187519 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) B21D 7/024 B21D 53/88 B21D 51/00

Claims (2)

(57) [Claims] 1. A hollow shape member which is bent so as to be bent with a predetermined bending radius, and a bending inner wall which is bent by the bending work is set to have a depth exceeding three times the wall thickness. The recess is in the bending circumferential direction
Hollow shaped material characterized by being formed in parallel with each other. 2. The hollow profile member according to claim 1, wherein the wall width of the bent inner side wall is equally divided by the recess.