JPH06328988A - Vehicle bumper beam - Google Patents

Abstract

PURPOSE:To provide a bumper beam of downsized space, of lightweight structure and of high buckling strength. CONSTITUTION:Flanges 22 and 32, and flanges 24 and 34 on each side of a front side member 20 of U-shaped section and a rear side member 30' are overlapped respectively, and arc welding is executed thereto to form a bumper beam body 10'. The upper and lower end of a reinforcing member 8 parallel to a front longitudinal wall 12 and a rear longitudinal wall are abutted on an upper wall 16 and a lower wall 18 on the inner side of the bumper beam body of this box-shaped section, and welded thereto by the fillet welding. Notches 36, 37 having the width where K/H<=0.45 are formed in the rear longitudinal wall 14. This constitution prevents the deformation of the upper wall and the lower wall where the wall is bulged outside when the load is applied thereto even when the walls are made of thin plate, the buckling strength is improved, and the weight is reduced. No peeling or opening are generated because no spot welding is executed, and the ventilating efficiency to the engine room is also improved because no flanges are projected downward.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bumper beam used in a bumper for passenger cars and other vehicles.

[0002]

2. Description of the Related Art A bumper for a vehicle has an outer skin (not shown) formed to match the design of the vehicle body.
A bumper beam 40 for bearing a load and absorbing a shock as shown in FIG. 14 is provided. A conventional bumper beam of this type has a basic cross section as shown in FIG.
, A trapezoidal shape in which the hat-shaped member 41 and the flat plate 42 are combined, or a quadrangular shape in which hat-shaped members 44 and 45 having substantially the same shape as in FIG. It is formed by spot welding at the portions 43 and 46. In FIG. 15, reference numeral 48 is an outer skin.
Since this bumper beam is a large-sized part of the vehicle parts and has a large weight, as shown in FIG. 16, the bumper beam main body 50 is formed of a thin plate material as much as possible, and a reinforcing material 56 is provided in a key portion to increase strength. I am trying to increase.
The reinforcing member 56 extends substantially in the same direction as the load direction indicated by P and is spot-welded to the front and rear vertical wall surfaces 52 and 54.

[0003]

However, in the conventional bumper beam structure described above, although the reinforcing member 56 is provided, when the load in the P direction is applied, the structure shown in FIG.
As shown in FIG. 7, the upper wall 58, the lower wall 60, etc. extending in the same direction as the load bulge outward and finally buckle. For this reason, there is a problem that it is necessary to make the plate thickness of the reinforcing member sufficiently thick, or it is not possible to thoroughly reduce the thickness of the beam main body itself.

Therefore, for example, the weight is 1000 to 2000.
1.6m under the required specifications that the displacement is 30mm or less when the buckling load is 3.5 tons for Kg class passenger cars.
A combination of m and 1.4 mm thick steel plates is often used. Further, since the connection in the flange portion is made by spot welding, when the load is applied, spot peeling or opening between the spots occurs, which makes it difficult to secure the strength and rigidity as designed.

Further, in the above-mentioned conventional structure, since the flanges 43 and 46 extend in the vertical direction, the radiator provided behind the bumper beam and other winds to be introduced into the engine room are projected by the flange so as to be F '. It is deflected to, and smooth ventilation is blocked, which hinders the effective cooling effect. Therefore, in view of the above conventional problems, it is an object of the present invention to provide an improved vehicle bumper beam that is lightweight, does not occupy space, and is easy to secure design strength.

[0006]

Therefore, the present invention provides a vehicle bumper beam having a box-shaped cross section that extends in the lateral direction of the vehicle and has a front vertical wall, a rear vertical wall, an upper wall, and a lower wall. In the box-shaped cross section, a reinforcing member having upper and lower ends connected to the upper wall and the lower wall, respectively, and being substantially parallel to the front vertical wall or the rear vertical wall is provided.

The box-shaped cross section can be formed by welding the front side member and the rear side member, each of which has a U-shaped cross section, to both side flanges of the front side member and the rear side member, or can be formed integrally with the reinforcing member by an extruded material. it can. The relative dimension of the distance d of the reinforcing member from the front vertical wall or the rear vertical wall and the width D of the box-shaped cross section is 0.07 ≦ d / D ≦ 0.
25, and in particular d / D = 0.20. Furthermore, it is possible to form a notch having a width dimension K whose relative dimension to the height H of the box-shaped cross section is K / H = 0.45 or less on the rear vertical wall.

[0008]

[Function] Since the reinforcing member which is connected to the upper wall and the lower wall and is substantially parallel to the front vertical wall or the rear vertical wall is provided, the upper wall and the lower wall which try to expand outward when a load in the front-rear direction is applied. The deformation of the wall is prevented by the reinforcing member, and the buckling strength is improved. In addition, since it has a box-shaped cross section, there is no portion protruding outward, and it is formed in a small size.

The position of the reinforcing member is 0.07≤d /
When D ≦ 0.25, the buckling strength is remarkably improved. Further, especially when d / D = 0.20, the maximum buckling strength is obtained. At this time, when a notch of K / H = 0.45 or less is formed on the rear vertical wall,
Weight is reduced while maintaining high buckling strength.

[0010]

FIG. 1 shows a first embodiment of the present invention. (B) of the figure is an enlarged cross-sectional view of the AA portion in (a). The bumper beam 1 includes a bumper beam body 10 and a reinforcing member 8. The bumper beam main body 10 extending in the lateral width direction of the vehicle includes front members 20 each having a U-shaped cross section.
And a rear member 30. The front member 20 is a front vertical wall 12 with its bottom wall facing the front of the vehicle, and its both side flanges 22 and 24 are rearward, and the rear member 30 is a rear vertical wall 14 with its bottom wall facing the vehicle rear. The flanges 32 and 34 of the front member 20 are superposed on the outside of the flanges 32 and 34 of the rear member 30, with the flanges 32 and 34 facing forward. Then, the front member 20 is joined at the trailing edges of the flanges 22, 24 to the mating flanges 32, 34 that overlap with each other by arc welding W1, whereby the upper wall 16 and the lower wall 18 of the bumper beam body are formed. There is.

A reinforcing member 8 parallel to the front vertical wall 12 and the rear vertical wall 14 is arranged inside the central portion of the bumper beam main body 10 having a box-shaped cross section in this manner, and the reinforcing member 8 has its upper end. The lower end is abutted against the upper wall 16 and the lower wall 18, and they are joined by continuous fillet welding W2 by an arc over the entire length of the reinforcing member in the lateral direction.

Since the bumper beam according to this embodiment is constructed as described above, even if it receives a load in the P direction shown in FIG. 1B, it does not bulge outward as shown in FIG. Reinforcing member 8 parallel to front vertical wall 12 or rear vertical wall 14
Even if the bumper beam body 10 is thinned, it has a high buckling strength.

Next, the measurement results based on this embodiment will be described. For passenger cars, as shown in FIG. 2, 100 mm (H) using a high-strength steel plate of 120 kg / mm ² each having a plate thickness of 1.4 mm as the front member 20 and a plate thickness of 1.2 mm as the rear member 30. A bumper beam body having a length of 1346 mm formed in a rectangular box cross section of × 74 mm (D) and having a plate thickness of 1.2 mm as the reinforcing member 8
The measurement was performed by changing the joining position of the reinforcing member 8 with respect to a joined plate having a length of 400 mm. In addition,
(B) of the figure is an enlarged cross-sectional view of the BB portion in (a).

The measurement is 911 m as shown in FIG.
The load-displacement curve was obtained by supporting at points separated by m and applying a load to the intermediate point of the load element S including the load cell Sa. The joint position of the reinforcing member from the front vertical wall is d =
Load-displacement curves when 3, 5, 12, 14, 17, and 27 mm are shown in FIGS. 4 to 9. From these, each displacement and buckling load are summarized as shown in FIG. The displacement amount of the bumper beam, which is allowed to be structurally attached to the vehicle body, is limited to about 50 mm, and beyond that, the bumper beam will not be displaced due to interference with other structures. Therefore, when considering the absorbed energy of the bumper beam, it is necessary to consider the displacement up to 50 mm.
In 0, the amount of energy in this range is also shown.

As the required strength, if the displacement at a buckling load of 3.5 tons is 30 mm or less, the positional specification of the reinforcing member that satisfies this is d = 5 to 17
mm, that is, the width of the box-shaped cross section of the bumper beam body, that is, the relative dimension d / D with respect to the width D (= 74 mm) of the upper and lower walls 16 and 18 is obtained as 0.07 ≦ d / D ≦ 0.25. As a result, the plate thickness of the constituent members is thinner than the conventional one and the required specifications are satisfied. Therefore, the measured product is 4.4 Kg, which is 24% of the conventional structure of 5.8 Kg.
It was made lighter.

Further, within the above range, d = 14 mm,
That is, up to d / D = 0.20, the larger the d / D value, the greater the impact absorption energy, and as can be seen from the rising angle of the load-displacement curve, the smaller the d / D value, the higher the rigidity. You can see. Therefore, depending on the vehicle type characteristics of the vehicle in which the bumper beam is mounted,
When the emphasis is placed on shock absorption performance, the d / D value is set to a large value so that it is closer to the middle between the front vertical wall and the rear vertical wall, and when the emphasis is on rigidity, the d / D value is set smaller and the front vertical wall is set. It can be arbitrarily decided to lean.

Next, FIG. 11 shows a second embodiment in which the weight is further reduced based on the first embodiment. Figure (b)
[Fig. 3] is an enlarged cross-sectional view of a CC portion in (a). As is clear from FIG. 10 above, the withstand load (buckling load) is d =
When it is 14 mm, that is, when d / D = 0.20, the maximum value of 4.25 tons is obtained, and when d = 14 mm, the maximum energy absorption amount of 160.5 Kgm is obtained.

In the bumper beam 1'of the present embodiment, the joining position of the reinforcing member has a relationship of obtaining the maximum value of the withstand load and the energy absorption amount, that is, the relative dimension d / D = about 0.
20 and the cutout 3 in the rear member 30 '.
6, 37 are provided. The notch 36 is formed over the entire length between the mounting portions of the bumper beam main body 10 'except the mounting portion to the vehicle body, and the notch 37 is formed on the left and right outside of the mounting portion. Notch width K of notch 36
Is 45 mm in the cross section of FIG. That is, the relative dimension is K / H = 0.45. Other configurations are the same as those in the previous embodiment.

12 and 13, the joining position of the reinforcing member is d = 14 mm, and the notch width K is 0,45 m.
The measurement data when m and 50 mm are shown. According to this, even when the notch width K is 45 mm, a load capacity of 4.1 tons and an energy absorption amount of 154.7 Kgm are obtained, and 4.25 tons when the notches are not provided, 160 With respect to 0.5 Kgm, there is a very slight decrease and a sufficient value is maintained. The conditions for measurement are the same as those described in the first embodiment. The bumper beam 1'provided with the notch of K = 45 mm was reduced in weight ratio to 89% with respect to the bumper beam without the notch. On the other hand, when K exceeds 45 mm, the withstand load drops sharply, and at 50 mm, for example, it is not expected that the required specifications that the displacement is 30 mm or less when the load is 3.5 tons are stably cleared. Therefore, it is preferable to appropriately select the notch width while maximizing the dimension of 45 mm while considering the relationship between the material used and the plate thickness.

In each of the illustrated embodiments, the reinforcing member 8 is provided near the front vertical wall 12 of the bumper beam bodies 10, 10 ', but the present invention is not limited to this, and the rear vertical wall 14 is symmetrical. It can also be leaned, in which case d /
The rear vertical wall 14 is also a reference for the D value. As a result, for a vehicle equipped with an airbag in the passenger compartment, for example, the airbag absorbs a considerable part of impact absorption, and the bumper beam tends to have a relatively high rigidity in order to improve the sensitivity of the collision sensor. Things are easily realized.

The embodiment further includes a bumper beam body 1
Since the joining at 0 and 10 'and the joining of the reinforcing member 8 to the bumper beam main body are performed by arc welding W1 or W2, there is no fear of peeling or opening and the strength as designed is stably secured. Has the advantage. Also,
In the formation of the bumper beam main body, the front member 20 and the rear members 30, 30 'are joined by arc welding at the overlapping edge portion of the flange extending in the front-rear direction. The wind from the front is smoothly guided to the engine room like F, and the ventilation efficiency is also improved.

The material of the bumper beam body and the reinforcing member is a high-tensile steel plate, but other materials such as an aluminum plate or an aluminum extruded material can be appropriately selected and used. Further, although the reinforcing member is parallel to the front vertical wall and the rear vertical wall in the embodiment, it is not necessary to be strictly parallel, and if it is substantially parallel to either the front vertical wall or the rear vertical wall, It is possible to prevent the wall from bulging and obtain the effect of improving the buckling strength. In addition to arc welding,
Laser welding (T-joint penetration welding) or the like can also be used.

[0023]

As described above, according to the present invention, since the upper end and the lower end are connected to the upper wall and the lower wall, respectively, in the box-shaped cross section, the reinforcing member substantially parallel to the front vertical wall or the rear vertical wall is provided, The reinforcing member prevents the upper wall and the lower wall from being deformed to expand outward when a load is applied in the front-rear direction, and the buckling strength is improved and the weight is reduced even if the thin plate is used and the wall is thin. Then, the relative dimension of the distance of the reinforcing member from the front vertical wall or the rear vertical wall and the width of the box-shaped cross section is 0.07 ≦ d /
When D ≦ 0.25, the buckling strength is remarkably improved, and especially when d / D = 0.20, the maximum value and the maximum energy absorption amount are obtained.

Further, d / D is set to about 0.20, and the relative dimension to the height of the box-shaped section on the rear vertical wall is K / H = 0.
Forming the notch having a width dimension of 45 or less has the effect of reducing the weight while maintaining high buckling strength. In addition, because of the box-shaped cross section, there is no flange protruding downward as in the past, and it is formed in a small size,
There is an advantage that ventilation efficiency to the engine room is also improved.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of the present invention.

FIG. 2 is a diagram showing dimensions of a measured product based on an example.

FIG. 3 is an explanatory diagram showing a measuring method.

FIG. 4 is a load-displacement curve diagram showing measurement results.

FIG. 5 is a load-displacement curve diagram showing measurement results.

FIG. 6 is a load-displacement curve diagram showing measurement results.

FIG. 7 is a load-displacement curve diagram showing measurement results.

FIG. 8 is a load-displacement curve diagram showing the measurement results.

FIG. 9 is a load-displacement curve diagram showing the measurement results.

FIG. 10 is a diagram showing a displacement based on a load-displacement curve diagram, a buckling load, and an energy absorption amount.

FIG. 11 is a diagram showing a second embodiment.

FIG. 12 is a load-displacement curve diagram when the notch width is changed.

FIG. 13 is a diagram showing measurement data of a relationship between a notch width and a withstand load and an energy absorption amount.

FIG. 14 is a perspective view showing a conventional example.

FIG. 15 is a sectional view of a portion EE in FIG.

FIG. 16 is a cross-sectional view showing a reinforcing structure in a conventional example.

FIG. 17 is an explanatory diagram showing a buckling phenomenon.

[Explanation of symbols]

 1, 1'Bumper beam 8 Reinforcing member 10, 10 'Bumper beam main body 12 Front vertical wall 14 Rear vertical wall 16 Upper wall 18 Lower wall 20 Front side member 22, 24, 32, 34 Flange 30, 30' Rear side member 36, 37 Notch 40 Bumper beam 41, 44, 45 Hat type member 42 Flat plate 43, 46 Flange portion 48 Outer skin 50 Bumper beam body 52, 54 Vertical wall surface 56 Reinforcement material 58 Upper wall 60 Lower wall

Claims (6)

[Claims] 1. A bumper beam for a vehicle, which has a box-shaped cross section that extends in the widthwise direction of the vehicle and comprises a front vertical wall, a rear vertical wall, an upper wall, and a lower wall, the upper and lower ends of which are within the box-shaped cross section. A bumper beam for a vehicle, comprising reinforcing members which are respectively connected to the upper wall and the lower wall and are substantially parallel to the front vertical wall or the rear vertical wall. 2. The box-shaped cross section is formed by a bumper beam main body formed by welding front side members and rear side members each having a U-shaped cross section to respective side flanges, and the reinforcing member includes the upper end and the upper end. The bumper beam for a vehicle according to claim 1, wherein the lower end is welded by abutting against the upper wall and the lower wall. 3. The vehicle according to claim 1, wherein the front vertical wall, the rear vertical wall, the upper wall and the lower wall of the box-shaped cross section and the reinforcing member are integrally formed of an extruded material. Bumper beam for. 4. The relative dimension between the distance d of the reinforcing member from the front vertical wall or the rear vertical wall and the width D of the box-shaped cross section is 0.0.
7. The vehicle bumper beam according to claim 1, wherein 2 ≦ d / D ≦ 0.25. 5. The relative dimension of the distance d of the reinforcing member from the front vertical wall or the rear vertical wall and the width D of the box-shaped cross section is d / D.
= About 0.20, The bumper beam for vehicles according to claim 1, 2 or 3 characterized by things. 6. The rear vertical wall is formed with a notch having a width dimension K whose relative dimension to the height H of the box-shaped cross section is K / H = 0.45 or less. Item 5. A vehicle bumper beam according to item 5.