JP2004203211A - Automobile bumper beam - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a bumper beam structure that reduces a maximum load generated at the moment of collision. <P>SOLUTION: The bumper beam has an H-shaped section, which is formed of an upper wall, a bottom wall opposite to the upper wall, a pair of side walls connecting both ends of the upper wall to that of the bottom wall, and a connecting rib, which is formed in the middle between the upper and bottom walls to connect the two side walls. The upper wall is thicker than the bottom wall, and the upper wall, connecting rib, and bottom wall are arranged in this order of increasing or decreasing thickness. Both corners of the upper wall are curved at a radius of curvature R 0.1-0.3 times as long as the length of the upper wall. The bumper beam is made of an aluminum alloy extruded hollow member. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a bumper beam for reinforcing a bumper of an automobile.
[0002]
[Prior art]
2. Description of the Related Art In general, a bumper of an automobile generally includes a bumper beam that is connected to a vehicle body and maintains the strength of the bumper, and a resin skin material that is attached to the bumper beam to adjust the appearance of the vehicle body. The bumper beam has been reduced in weight in order to reduce fuel consumption, and in recent years, the use of light alloys has been increasing. For example, a bumper beam 30 shown as a cross-sectional view in FIG. 5 is an example of a bumper beam extruded from an aluminum alloy material, and has a hollow structure extruded in a “sun-shaped” cross section. That is, the upper wall portion 31 and the bottom wall portion 32 which are parallel to each other, the side wall portions 33 and 34 which are parallel to each other in a direction perpendicular thereto, and the side wall portions 33 and 34 which are parallel to the upper wall portion 31 and the bottom wall portion 32. Is formed by a connecting rib 35 provided at the center so as to divide it into two.
[0003]
The bumper beam 30 is actually attached to the front or rear surface of the vehicle 17 via the side member 16, and in the event of a collision, the side wall 33 on the collision surface side generates an impact force F from the direction of the left arrow in the drawing. It is the face to receive. Therefore, the side wall portion 33 is formed to be the thickest among the members having the "sun-shaped" sectional structure. In the example of FIG. 5, the upper wall 31 and the bottom wall 32 and the connecting rib 35 are formed to have the same thickness, and have a structure in which the impact force from the left side of the figure is equally received and the impact force is softened. ing.
Such a bumper beam is made of a 7000 series high-strength aluminum alloy or the like for the purpose of weight reduction. Usually, a cushioning material made of a foam material or the like is attached to the bumper beam, and the surface is covered with a bumper cover.
[0004]
When a bumper beam receives an external impact due to a collision of a car, etc., it absorbs the impact energy by plastic deformation of the bumper beam material, which is important for avoiding damage to other members and ensuring the safety of the human body. It is a member.
By the way, there are two types of collisions of a vehicle: a wall-shaped obstacle collides with the entire surface of the bumper beam at a relatively high speed, and a columnar obstacle collides with a part of the wall of the bumper beam at a relatively low speed. There is a form.
In the former type of collision, the collision energy due to the collision is often large enough to cause injury to the occupant and buckling damage of the bumper beam mounting member, and the bumper beam gradually deforms and collapses, causing a large amount of collision. It is desired that the material can absorb energy.
On the other hand, in the latter type of collision, there are few cases in which the collision energy is large enough to cause injury to the occupant or damage to the mounting member, and the bumper beam is deformed and collapsed to absorb the collision energy rather than absorbing the collision energy. It is desired that the material has high rigidity that is difficult to deform.
[0005]
For the bumper beam, it is required to increase the bending rigidity of the profile and the amount of energy absorbed when bending, while reducing the weight. A proposal for improving these characteristics by improving the cross-sectional shape has been disclosed (for example, see Patent Information 1).
Here, a bumper beam that is made of an aluminum alloy profile with a rectangular cross section that is uniform in the length direction and that has a wall surface that is perpendicular to the collision direction and that is mounted on the vehicle body at both ends of the wall surface located on the vehicle body side is used. In addition, there is disclosed a bumper beam in which a corner of the aluminum alloy profile located on the vehicle body side is curved with a radius R that is 2.5 times or more the plate thickness.
Specifically, as shown in FIG. 6, the bumper beam 40 is made of an aluminum alloy material provided in the bumper cover, and the wall surface 41 a located on the vehicle body 42 side is connected to the vehicle body 42 via the side member 44. Supported. The above-described aluminum alloy material is formed in a rectangular cross section having a uniform shape in the longitudinal direction, for example, in the shape of a "Japanese character". The pair of horizontal ribs 41b, 41b, and both ends of both horizontal ribs 41b, 41b are provided at both ends. The vertical ribs 41a, 41a are connected, and the reinforcing ribs 41c are connected between the vertical ribs 41a, 41a.
[0006]
The bumper beam 40 is provided such that the vertical ribs 41a, 41a are perpendicular to the collision direction and the horizontal ribs 41b, 41b are parallel to the collision direction. The corners 41d, 41d on the vehicle body 42 side are curved with a radius R of at least 2.5 times the plate thickness in a range of 1/6 or less of the length of the vertical ribs 41a, 41a. On the other hand, the corners 41e, 41e on the collision side of the bumper beam 40 are bent at a substantially right angle with a radius r about the plate thickness. Thereby, at the time of barrier collision, the curved corners 41d, 41d are positioned at the starting point of buckling, thereby promoting buckling while suppressing the generated load and efficiently absorbing the collision energy. Has become. Further, at the time of a pole collision, a large generated load is generated by positioning the curved corners 41d, 41d on the side opposite to the starting point of buckling. The reason that the radius R is limited to 1/6 or less of the length of the vertical ribs 41a, 41a is that if it exceeds 1/6, it becomes difficult to attach the side member 44 and the absorbed energy decreases. It has been.
According to this structure, it is possible to have both a characteristic capable of absorbing a large amount of collision energy by gradually deforming and collapsing and a characteristic of high rigidity that is difficult to be deformed by a collision load, which can cope with the above two collision modes. It is possible.
[0007]
[Patent Document 1]
JP-A-8-80879 (page 5, FIG. 2)
[0008]
[Problems to be solved by the invention]
However, if the bumper beam is too strong, the buckling of the bumper beam and the side member, which is the mounting bracket of the vehicle body, will be damaged.
The side members are damaged by the maximum load that occurs at the moment of the collision.
For example, in the case of a bumper beam whose all corners are bent at right angles as shown in the cross section in FIG. 5, the average load during the plastic deformation of the bumper beam by 3.5 to 4.5 mm due to collision is 50 kN as shown in FIG. On the other hand, the maximum load as much as 250 kN is generated during the plastic deformation of about 0.5 mm before the displacement of the bumper beam reaches 1 mm immediately after the collision, and after the displacement of about 2 mm, the load is almost constant. Deforms with an average crushing load. In this case, the maximum load reaches 5.88 times the average load.
If the maximum load can be reduced, the collision energy can be absorbed only by the deformation and collapse of the bumper beam without damaging the side members.
Conventionally, the relationship between the maximum load and the absorbed energy when the generated load is not accompanied by a large fluctuation during the plastic deformation of the bumper beam of 3.5 to 4.5 mm has been a problem. No attempt was made to lower it.
In order to ensure personal safety, it is important to minimize the peak of the maximum load generated at the moment of a collision as much as possible.
An object of the present invention is to provide a bumper beam structure that can minimize the peak of the maximum load generated at the moment of the collision as much as possible and can prevent damage to a side member that is a mounting bracket for the bumper beam. .
[0009]
[Means for Solving the Problems]
As a result of various examinations of the cross-sectional shape of the bumper beam of an ordinary passenger car to solve the above problem, the side member is damaged only when a high load is instantaneously generated when a load is applied to a bumper beam specimen having a length of 100 mm. Exceeds the load that crushes the vehicle body. By making the maximum load generated at the moment of a collision equal to the load that crushes the vehicle body, it was found that the plastic deformation of the bumper beam could absorb the collision energy without damaging the side members. It was also found that if the maximum load is reduced as in the conventional bumper beam structure, the impact load generated in the latter half of the collision will be too low, and the energy absorption capacity of the bumper beam will be reduced. .
Therefore, in the crushing displacement-crushing load curve shown in FIG. 7, if only the maximum peak is lowered to make the waveform closer to a rectangular waveform, the collision energy can be absorbed by plastic deformation of the bumper beam without damaging the side members. It is considered that a bumper beam having stable performance as an energy absorbing material can be obtained. Therefore, as a result of various examinations of the cross-sectional shape of the bumper beam, the thickness of the member on the impacted surface was increased, the thickness of the member perpendicular to the impacted surface was changed, and both ends of the impacted member surface were changed. It has been found that the above object can be achieved by giving a specific radius of curvature, and the present invention has been accomplished.
[0010]
That is, in the bumper beam of the present invention, the cross-sectional shape is an upper wall portion, a bottom wall portion facing the upper wall portion, a pair of side wall portions connecting both ends of the upper wall portion and the bottom wall portion, and A connection rib provided between the wall portion and the bottom wall portion for connecting the two side wall portions, and the thickness of the side wall portion on the collision surface side is the thickness of the side wall portion on the vehicle body mounting surface side. The upper wall portion, the connecting ribs, and the bottom wall portion are configured such that the thicknesses thereof gradually increase or decrease in this order, and both corners of the side wall portion on the collision surface side are on the collision surface side. The bumper beam was made of an extruded hollow member made of an aluminum alloy and curved with a radius of curvature R of 0.05 to 0.3 times the length of the side wall portion.
[0011]
It is preferable that the thickness of the upper wall be 0.8 times or more and less than 0.9 times the thickness of the bottom wall. Further, it is preferable that the thickness of the connecting rib is 0.9 times or more and less than 1.0 times the thickness of the bottom wall portion.
By configuring the connecting ribs in this way, it is possible to have a high rigidity and dramatically reduce the maximum peak load generated at the time of a collision, and to reduce the collision energy without damaging the side members. It is absorbed by the bumper beam, and the damage to the occupant can be drastically reduced.
[0012]
In the present invention, the attachment position of the connecting rib may be provided closer to the bottom wall than the center of the side wall, or may be provided closer to the upper wall than the center of the side wall.
By shifting the position of the connecting rib in this way, the center line of the bumper beam does not match the center line of the side member due to the design of the vehicle, and the center line of the bumper beam is higher or lower than the center line of the side member. In this case, the bottom of the cross section of the bumper beam which receives strong impact energy can be strengthened.
When the attachment position of the connecting rib is provided closer to the bottom wall than the center of the side wall, the thickness of the upper wall, the connecting rib, and the bottom wall is gradually increased in this order.
Conversely, when the connecting rib is mounted closer to the upper wall than the center of the side wall, the thickness of the upper wall, the connecting rib, and the bottom wall is gradually reduced in this order. .
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, the present invention will be specifically described with reference to the drawings. In the following drawings, the scale of each part is not necessarily drawn accurately for easy understanding.
(1st Embodiment)
FIG. 1 is a sectional view showing a first embodiment of the bumper beam of the present invention. As shown in the figure, a bumper beam 10 of the present invention connects an upper wall 1 with a cross-sectional shape, a bottom wall 2 facing the upper wall 1, and both ends of the upper wall 1 and the bottom wall 2. A pair of side walls 3 and 4 and a connection rib 5 provided at the center of the top wall 1 and the bottom wall 2 and connecting these two parts are configured to exhibit a “sun” shape. The rigidity is ensured. In the bumper beam 10, the side wall 3 on the left side of the drawing is the side wall on the collision surface side, and an impact force at the time of collision indicated by arrow F is applied. The side wall 4 on the right side of the drawing is the side wall on the vehicle body mounting surface side, and is mounted on the vehicle body 7 via the side member 6.
[0014]
In the bumper beam of the present invention, the thickness t3 of the side wall portion 3 on the collision surface side is larger than the thickness t4 of the side wall portion 4 on the vehicle body mounting surface side, and the upper wall portion 1, the connecting rib 5, and the bottom wall portion 2 are provided. Are configured such that the thicknesses t1, t5, and t2 of the first layer gradually increase in this order. That is, in FIG. 1, t4 <t3 and t1 <t5 <t2.
In this case, based on the thickness t2 of the bottom wall 2, the thickness t1 of the upper wall 1 is 0.80 times or more and less than 0.9 times the thickness t2 of the bottom wall 2, and the thickness of the connecting rib 5 t5 is preferably set to 0.90 or more and less than 1.0 times the thickness t2 of the bottom wall portion 2. That is,
0.8 × t2 ≦ t1 <0.9 × t2 (1)
0.9 × t2 ≦ t5 <1.0 × t2 (2)
It is preferable to set the degree.
This is because the center line of the bumper beam does not always coincide with the center line of the side member due to the design of the vehicle, and the center line of the bumper beam is often located higher than the center line of the side member. In such a case, since the impact energy is stronger at the bottom of the cross section of the bumper beam, it is effective to strengthen the bottom.
[0015]
Further, both corners of the side wall 3 on the collision surface side are curved with a radius of curvature R of 0.05 to 0.3 times the length L1 of the side wall 3 on the collision surface side. That is,
R = (0.05-0.3) × L1 (3)
And
The radius of curvature r at both corners of the side wall portion 4 on the vehicle body mounting surface side is set to be equal to the thickness of the side wall portion 4. What is necessary is just to give a slightly small radius of curvature r. That is,
r = (0.2-0.4) × t4 (4)
It is good if you put it.
[0016]
If the bumper beam is configured as described above, the peak of the maximum load generated at the moment of a collision can be effectively reduced, and the collision energy is absorbed by the bumper beam without damaging the side members and given to the occupant. Damage can be drastically reduced.
[0017]
FIG. 2 schematically shows the relationship between the displacement of the bumper beam and the crushing load in a bumper-beam collision experiment having the cross-sectional shape shown in FIG. As shown in the figure, the maximum load is generated before the displacement immediately after the collision reaches 1 mm, and thereafter, it deforms with a substantially constant crushing load. Similar to FIG. 7, the curve j indicated by the bold line in FIG. 2 is a displacement amount curve when the radius of curvature R at both ends of the side wall on the collision surface side of the “sun-shaped” bumper beam is set to 0 (no radius of curvature). The maximum load of 250 kN is generated when the displacement is about 0.5 mm. On the other hand, a curve a according to the present invention shown by a thin line is a case where the radius of curvature R is 10 mm, and when the displacement amount is about 1 mm, the maximum load is significantly reduced to about 150 kN, and the curve a is generated. Is closer to a square wave.
In this way, by giving the radius of curvature R to both ends of the side wall on the collision surface side of the "sun-shaped" bumper beam, the maximum load generated at the time of collision can be greatly reduced, and the side member is not damaged. The collision energy can be effectively absorbed by the bumper beam, which is extremely effective for ensuring the safety of the occupants.
[0018]
(Second embodiment)
Next, an example in which the center line of the bumper beam does not coincide with the center line of the side member as the second embodiment, and the center line of the bumper beam is lower than the center line of the side member is shown in FIG. Shown in
In this case, the thickness t3 of the side wall portion 3 on the collision surface side is larger than the thickness t4 of the side wall portion 4 on the vehicle body mounting surface side, and the thickness of the upper wall portion 1, the connecting rib 5, and the bottom wall portion 2 The thicknesses t1, t5, and t2 are configured to become gradually thinner in this order. That is, in FIG. 3, t4 <t3 and t2 <t5 <t1. The thickness t5 of the intermediate rib 5 is 0.9 times or more and less than 1.0 times the thickness t1 of the reference upper wall 1, and the thickness t2 of the bottom wall 2 is the thickness of the reference upper wall 1. It is preferable that t1 is 0.8 times or more and less than 0.9 times.
That is,
0.9 × t1 ≦ t5 <1.0 × t1 (5)
0.8 × t1 ≦ t2 <0.9 × t1 (6)
As in the case of the first embodiment, both corners of the side wall on the collision side have a curvature of 0.05 to 0.3 times the length L1 of the side wall 3 on the collision side. Curved with radius R. Further, both corners of the side wall portion 4 on the vehicle body mounting surface side are preferably curved with a radius of curvature r of 0.2 to 0.4 times the thickness t4 of the side wall portion 4 on the vehicle body mounting surface side. preferable.
By configuring the bumper beam as described above, the maximum load generated at the time of collision can be significantly reduced due to the effect of the radius of curvature R provided at both corners of the side wall on the collision side of the bumper beam.
[0019]
(Third embodiment)
Next, as a third embodiment, an example in which the center line of the bumper beam does not match the center line of the side member, and the center line of the bumper beam is located higher than the center line of the side member is shown in FIG. Shown in As a countermeasure to strengthen the bottom of the cross section of the bumper beam, as shown in FIG. 4, the connecting position of the connecting rib is set closer to the bottom wall than the center of the opposing side wall on the collision side and the side wall on the vehicle body mounting side. Provide. Considering the amount of misalignment between the center line of the bumper beam and the center line of the side member, and the strength of the bumper beam, the mounting position of the connecting rib is three-thirds below the side wall on the collision side and the side wall on the vehicle body mounting side. Use around one.
Also in this case, similarly to the first and second embodiments, the thickness t3 of the side wall portion 3 on the collision surface side is larger than the thickness t4 of the side wall portion 4 on the vehicle body mounting surface side, and The thicknesses t1, t5, and t2 of the wall portion 1, the connection rib 5, and the bottom wall portion 2 are configured to gradually increase in this order. The corners at both ends of the side wall on the collision side are curved with a radius of curvature R of 0.05 to 0.3 times the length L1 of the side wall 3 on the collision side. Further, both corners of the side wall portion 4 on the vehicle body mounting surface side are preferably curved with a radius of curvature r of 0.2 to 0.4 times the thickness t4 of the side wall portion 4 on the vehicle body mounting surface side. preferable.
By configuring the bumper beam as described above, the maximum load generated at the time of collision can be significantly reduced due to the effect of the radius of curvature R provided at both corners of the side wall on the collision side of the bumper beam.
[0020]
【The invention's effect】
According to the present invention, as a result of examining the cross-sectional shape of the bumper beam in detail, as a result of increasing the thickness of the impact-receiving surface to increase rigidity, the impact-receiving surface is formed to have a radius of curvature R at both ends of the impact-receiving surface. In addition, the maximum load generated immediately after the deformation of the bumper beam in the event of a collision is reduced, so that physical damage to the occupant can be reduced.
A vehicle equipped with the bumper beam of the present invention can be said to be a vehicle with higher safety.
[Brief description of the drawings]
FIG. 1 is a diagram showing a cross-sectional shape of a first embodiment of an automobile bumper beam of the present invention.
FIG. 2 is a diagram schematically illustrating a relationship between a displacement amount and a crushing load of the bumper beam for an automobile according to the present invention.
FIG. 3 is a view showing a cross-sectional shape of a second embodiment of the automotive bumper beam of the present invention.
FIG. 4 is a view showing a sectional shape of a third embodiment of the bumper beam for an automobile of the present invention.
FIG. 5 is a diagram showing an example of a cross-sectional shape of a conventional bumper beam for an automobile.
FIG. 6 is a view showing another example of a cross-sectional shape of a conventional bumper beam for an automobile.
FIG. 7 is a diagram showing a relationship between a displacement amount and a load of a conventional bumper beam for an automobile.
[Explanation of symbols]
1 ... top wall, 2 ... bottom wall, 3 ... side wall on collision side, 4 ... side wall on vehicle mounting side 5, connecting ribs, 10, 11, 30, 40 ... bumper beam

Claims (3)

The cross-sectional shape is an upper wall portion, a bottom wall portion facing the upper wall portion, a pair of side wall portions connecting both ends of the upper wall portion and the bottom wall portion, and an intermediate portion between the upper wall portion and the bottom wall portion. And a connecting rib for connecting the two side walls. The side wall on the collision surface side is thicker than the side wall on the vehicle body mounting surface side. The thickness of the connecting rib and the bottom wall is gradually increased or decreased in this order, and both corners of the side wall on the collision surface side have a length of 0. A bumper beam for an automobile, comprising an extruded hollow member made of an aluminum alloy and having a curvature radius R having a length of 0.5 to 0.3 times. The thickness of the top wall is 0.8 times or more and less than 0.9 times the thickness of the bottom wall, and the thickness of the connecting rib is 0.9 times or more the thickness of the bottom wall. 2. The automotive bumper beam according to claim 1, wherein the ratio is less than 1.0. The thickness of the bottom wall is 0.8 times or more and less than 0.9 times the thickness of the upper wall, and the thickness of the connection rib is 0.9 times or more the thickness of the upper wall. 2. The automotive bumper beam according to claim 1, wherein the ratio is less than 1.0.

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