JPH0820297A - Bumper reinforcement - Google Patents

Abstract

PURPOSE:To prevent the damage of a vehicle body and lighten weight through the improvement of collision energy absorbing capacity so as to reduce the quantity of deformation caused by a collision by lowering the flexural strength of plural positions of a straight part so as to increase collision energy absorbing places. CONSTITUTION:A bumper reinforcement has a straight part 1a where bending moment distribution with the maximum value is generated to a center part C at the time of a collision, and collision energy is absorbed by the bending of the straight part 1 at the time of bending moment exceeding flexural strength. Plural positions X1, X2 of the straight part 1a have oblong holes 1d formed to lower flexural strength so that the time of bending moment exceeding flexural strength there is earlier than the center part C.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bumper reinforcement that bends and absorbs collision energy when a bending moment at the time of collision exceeds bending strength.

[0002]

Bumpers mounted on automobiles and vehicles are
For example, it has a bumper body formed of a shock absorbing member such as urethane foam, and a bumper reinforcement that supports this bumper body, and damages the occupant and the vehicle body by reducing the impact at the time of collision with an obstacle. It is designed to be reduced.

The above bumper reinforcement is
Conventionally, it is composed of a straight portion arranged in the vehicle width direction and a pair of slant portions formed at both ends of the straight portion, and the straight portion and the slant portion are the longitudinal direction of the bumper reinforcement. Is formed so as to have a uniform cross section. And
This bumper reinforcement is fixed to a pair of left and right side members, which are vehicle body side members, directly or via a stay (see FIG. 2), and it is considered that the bumper reinforcement is a beam in relation to the side members. , Mechanically it is a support beam at both ends.

[0004]

By the way, in recent years, bumpers are often formed in a curved shape in which the central portion of the bumper body is projected toward the front of the vehicle from the viewpoint of designability. When a bumper formed in a shape collides head-on, an impact load distribution and a bending moment distribution having the maximum values are generated in the central portion in the bumper reinforcement (see FIGS. 3 and 4).

The above bending moment causes the bumper reinforcement to bend when it exceeds the bending strength of the bumper reinforcement, but the bending point is the central portion where the bending moment value is the highest in the bumper reinforcement. Cheap. Therefore, as shown in FIG. 8, the bumper reinforcement is deformed from the central portion to a V shape, and the deformation amount ε at the central portion is particularly increased, which damages the vehicle body protected by the bumper. It is easy to give.

Therefore, conventionally, it has been necessary to increase the bending strength by increasing the strength of the bumper reinforcement by increasing the thickness and increasing the size of the cross section. As a result, the weight and cost of the bumper reinforcement are increased. Is to be increased significantly.

Accordingly, the present invention is intended to provide a bumper reinforcement capable of preventing bending in the central portion without increasing the thickness and increasing the size.

[0008]

In order to solve the above-mentioned problems, a straight portion having a bending moment distribution having a maximum value at the center portion at the time of collision is provided, and when the bending moment exceeds the bending strength, a straight portion is formed. It absorbs the collision energy by bending the curved portion, and has the following features.

That is, bending strength lowering means for lowering the bending strength is formed at a plurality of positions of the straight portion so that the bending moment exceeds the bending strength earlier than in the central portion. There is. Specifically, the reduction rate of the bending strength by the bending strength reducing means is a ratio (Mx) of the bending moment Mx at a plurality of positions and the bending moment Mc at the central portion, which are generated when a load due to a collision is applied to the straight portion.
/ Mc) or less.

[0010]

According to the above structure, at the time of collision, the bending strength lowering means is bent at a plurality of positions, and the collision energy is absorbed at these bending points. In comparison, the absorption capacity is improved by increasing the number of collision energy absorption points. Therefore, the amount of deformation due to a collision is reduced, and it is possible to sufficiently prevent damage to the vehicle body. Moreover, since the amount of deformation due to collision is reduced by reducing the bending strength of the straight portion, it is possible to reduce the amount of deformation by increasing the bending strength by increasing the thickness and increasing the size as in the conventional structure. Therefore, it becomes possible to reduce the weight, and eventually to reduce the cost.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS. The bumper reinforcement according to the present embodiment is used for a bumper 2 of an automobile or a vehicle, as shown in FIG. The bumper 2 includes a bumper reinforcement 1, a bumper body 3 formed of a shock absorbing member such as urethane foam, and a bumper cover 4 that covers an outer surface of the bumper body 3.
The bumper body 3 and the bumper cover 4 are formed in a curved shape with a central portion protruding forward of the vehicle.

The bumper body 3 is supported by the bumper reinforcement 1. The bumper reinforcement 1 is fixedly mounted on the pair of left and right side members 5, 5, and as shown in FIG. 1, a straight portion 1a arranged in the vehicle width direction and both ends of the straight portion 1a. It is composed of a pair of slanted portions 1b and 1b formed. The straight portions 1a and the slanted portions 1b and 1b are made of an extruded or extruded shape member made of aluminum or the like, a press-worked material of a steel plate or a welded assembly material, or a composite material of these members to form a single piece in the longitudinal direction. The cross-section is shaped like a "day". The cross-sectional shape is
The shape is not limited to the "Sun" shape, and other shapes may be used.

Further, the connecting hole 1 is provided between the straight portion 1a of the bumper reinforcement 1 and the inclined portions 1b and 1b.
c are formed respectively, and these coupling holes 1c ...
Is a bumper reinforcement 1 and side members 5
・ It is designed to be used for fixing with 5. In addition, the position X1 of a predetermined distance L from the central portion C of the straight portion 1a.
In the X2, upper and lower elongated holes 1d and 1d (bending strength reducing means) are formed symmetrically with respect to the central portion C. These elongated holes 1d and 1d are located at the position X where the elongated holes 1d and 1d exist by causing a cross-section defect in the straight portion 1a.
The bending strength of the straight portion 1a in 1 · X2 is reduced, and the rate of decrease of the bending strength due to the elongated holes 1d · 1d is as follows when the bending moment distribution of FIG. 3 occurs at the time of collision. The time when the bending strength is exceeded is set to be earlier than the central portion C.

Specifically, when the same load is applied to the entire straight portion 1a, the position X where the long holes 1d and 1d exist.
If the bending moment Mx is generated at 1 · X2 and the bending moment Mc is generated at the central portion C, the bending strength by the slotted holes 1d · 1d is set so as to be equal to or less than the ratio (Mx / Mc) of both moments Mx · Mc. The rate of decrease is set.

The operation of the bumper reinforcement 1 having the above structure will be described. As shown in FIG. 2, since the bumper reinforcement 1 is fixed to the pair of left and right side members 5, 5, considering the bumper reinforcement 1 as a beam in relation to the side members 5, 5. , Mechanically it is a support beam at both ends.

Therefore, for example, when the vehicle collides head-on with another vehicle 6, the straight portion 1a of the bumper reinforcement 1 is subjected to a distributed impact load having a maximum value in the central portion C as shown in FIG. Will be. This allows
As shown in FIG. 4, the position X where the long holes 1d and 1d are formed
A bending moment Mx is generated at 1.multidot.X2 and a maximum bending moment Mc is generated at the central portion C, which is a distributed bending moment.

At this time, the elongated holes 1d and 1d are designed to reduce the bending strength in the straight portion 1a due to the lack of cross section. The rate of decrease in the bending strength due to the elongated holes 1d and 1d is the bending moment at the time of collision. Is set to be earlier than the central portion C when the bending strength exceeds the bending strength. That is, the rate of decrease in bending strength is such that when the straight portion 1a is applied with a distributed collision load having a maximum value in the central portion, the bending moment Mx is present at the positions X1 and X2 where the long holes 1d and 1d exist. If a bending moment Mc is generated in the central portion C, the ratio of both moments Mx · Mc (Mx / M
c) It is set as follows. Therefore, due to the following reason, at the time when the bending moment exceeds the bending strength at the time of collision, the positions X1 and X2 where the elongated holes 1d and 1d are formed are earlier than the central portion C.

That is, as shown in FIG. 7 (a), as the load increases due to the collision, the central bending moment Mc also increases, as shown in FIG. 7 (b), and the bending strength of the profile is increased. It approaches Mcr. Then, when Mc = Mcr, the bumper reinforcement 1 is bent. However, as shown in FIG. 7 (c), when a strength-reduced portion due to a section defect is provided and the strength reduction rate is set to Mx / Mc or less, the bending strength of the defect portion is Mcr ^(X) ≤Mcr · Mx / Mc = Mx becomes, and the bending strength Mcr ^(X) of the profile becomes smaller than the bending moment Mx that acts. As a result, the portion X is bent before the central portion.

Therefore, the bumper reinforcement 1
As shown in Fig. 5, the bending energy is bent at two positions X1 and X2 where the long holes 1d and 1d are formed, and the collision energy is absorbed at these bending positions. Accordingly, in the bumper reinforcement 1 after the collision, since the absorption capacity is improved due to the increase in the collision energy absorption location, the deformation amount ε can be reduced to half, for example, as compared with the case of bending at one location in the central portion C. As a result, it is possible to sufficiently reduce the damage to the vehicle body as a result.

In this embodiment, as shown in FIG. 1, elongated holes 1d and 1d (bending strength reducing means) are formed at two positions X1 and X2 which are symmetrical with respect to the central portion C. However, the present invention is not limited to this, and it may be formed at arbitrary plural positions. However, it is desirable that the long holes 1d and 1d (bending strength reducing means) are formed at the positions X1 and X2 where the largest stress is generated under the bending load. Specifically, the tension side flange portion and the compression side are formed. A side flange part can be mentioned.

Further, in this embodiment, the long holes 1d.1
Although d is the bending strength reducing means, the invention is not limited to this, and as shown in FIG. 6, the round holes 1e ... Alternatively, a groove for making the thickness and cross-sectional area of the straight portion 1a smaller than those of other portions may be used as the bending strength lowering means.

Thus, as shown in FIG. 1, the bumper reinforcement 1 of the present embodiment has the straight portion 1a in which the bending moment distribution having the maximum value is generated in the central portion C at the time of collision, and the bending moment is increased. Bending strength of the straight portion 1a when the bending strength exceeds the bending strength, the collision energy is absorbed, and the bending strength is reduced so that the bending moment exceeds the bending strength earlier than the central portion C. The lowering means (long hole 1d, round hole 10, groove) is formed at a plurality of positions (positions X1 and X2) of the straight portion 1a.

That is, the bending strength lowering means has a bending moment Mx at a plurality of positions (positions X1 and X2) and a central portion where the bending strength lowering means is formed when a load due to a collision is applied to the straight portion 1a. The rate of decrease in bending strength by the bending strength reducing means is set so as to be equal to or less than the ratio (Mx / Mc) of C to the bending moment Mc.

As a result, as shown in FIG. 5, the bumper reinforcement 1 has a bending strength reducing means (elongated hole 1).
d. 1d) is bent at a plurality of positions (positions X1 and X2), and the collision energy is absorbed at these bent portions, so that the collision energy of The absorption capacity is improved by increasing the number of absorption points. Therefore, since the deformation amount ε due to the collision is reduced, it is possible to sufficiently prevent damage to the vehicle body.

Bumper reinforcement 1
Is the deformation amount ε due to collision by reducing the bending strength of the straight portion 1a at a plurality of positions by the bending strength lowering means.
Is decreasing. Therefore, it is possible to reduce the weight as compared with the conventional configuration in which the bending strength is increased and the deformation amount ε is decreased by increasing the thickness and increasing the size,
As a result, it is possible to reduce costs.

[0026]

As described above, according to the present invention, the bending strength lowering means for lowering the bending strength is formed at a plurality of positions of the straight portion so that the bending moment exceeds the bending strength earlier than the central portion. Since the structure is designed to absorb collision energy at a plurality of bending points, the absorption capacity is improved by increasing the number of collision energy absorbing points as compared with the case of bending at one central point. Become. Therefore, the amount of deformation due to a collision is reduced, and it is possible to sufficiently prevent damage to the vehicle body. Further, since the bending strength at a plurality of positions of the straight portion is lowered by the bending strength lowering means, the deformation amount due to the collision is reduced. Therefore, the bending strength can be increased by increasing the thickness or increasing the size as in the conventional case. It is possible to reduce the weight and to reduce the cost as compared with the configuration in which the amount of deformation is reduced.

[Brief description of drawings]

FIG. 1 is a perspective view of a bumper reinforcement according to the present embodiment.

FIG. 2 is an explanatory view showing a state in which a bumper reinforcement is fixed to a side member.

FIG. 3 is an explanatory diagram showing a collision load distribution.

FIG. 4 is an explanatory diagram showing a bending moment distribution.

FIG. 5 is an explanatory diagram showing a state where the bumper reinforcement is bent.

FIG. 6 is a perspective view of a bumper reinforcement.

7A and 7B are explanatory diagrams showing a distribution state when a load is increased due to a collision, FIG. 7A is an acting load distribution, FIG. 7B is a generated bending moment distribution, and FIG. 7C is a bending strength distribution.

FIG. 8 shows a conventional example and is an explanatory view showing a state where the bumper reinforcement is bent.

[Explanation of symbols]

 1 Bumper Reinforcement 1a Straight part 1b Slanted part 1c Coupling hole 1d Long hole 1e Round hole 2 Bumper 3 Bumper body 4 Bumper cover 5 Side member 6 Vehicle

Claims (2)

[Claims] 1. A bumper having a straight portion in which a bending moment distribution having a maximum value is generated in a central portion at the time of collision, and the collision energy is absorbed by bending of the straight portion when the bending moment exceeds bending strength. In the reinforcement, bending strength lowering means for lowering the bending strength is formed at a plurality of positions of the straight portion so that the bending moment exceeds the bending strength earlier than in the central portion. Bumper reinforcement to be. 2. The rate of decrease in bending strength by the bending strength reducing means is a ratio of the bending moment Mx at the plurality of positions and the bending moment Mc at the central portion when a load due to a collision is applied to the straight portion ( The bumper reinforcement according to claim 1, wherein the bumper reinforcement is set to be Mx / Mc) or less.