JP2023013373A - bumper reinforcement - Google Patents

Abstract

To provide a bumper reinforcement which can previously buckle and deform a crash box without easily buckling even when a bumper beam is thinned and reduced in the weight.SOLUTION: A bumper reinforcement 1 includes a metal-made bumper beam 2, two crash boxes 4, and a reinforcement part 3 formed of a fiber-reinforced resin for reinforcing the bumper beam, wherein the bumper beam has such a hollow structure as to have a cabin side side wall and a collision surface side side wall extending in a vehicle width direction, an upper wall connecting upper ends of the side walls and a lower wall connecting lower ends thereof, the two crash boxes are provided on the cabin side side wall, the reinforcement part is provided on the upper wall and/or the lower wall of the bumper beam, and is continuous between at least the two crash boxes, and accordingly an impact load can be transmitted and absorbed to the crash boxes even when the bumper beam is thinned.SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD The present invention relates to a bumper reinforcement, and more particularly to a bumper reinforcement in which a metal bumper beam is reinforced with fiber-reinforced resin.

Bumper reinforcement protects occupants from impact loads when other vehicles collide with the front or rear of the vehicle.

This bumper reinforcement is required not only to have the strength to withstand the impact load, but also to be able to absorb the impact load. Absorbs the impact load.

However, in recent years, there has been a demand for lighter vehicles due to the trend toward greater fuel efficiency, and bumper reinforcement is no exception.

Patent Document 1 discloses a metal bumper beam having a side wall extending in the vehicle width direction, two walls erected on the upper and lower sides of the side wall, and having an open side surface on the passenger compartment side, and the bumper beam. A bumper reinforcement is disclosed in which a carbon fiber reinforced resin is adhered to the intermediate portion of the side surface of the vehicle compartment side to connect the upper wall and the lower wall.

This bumper reinforcement has an open side on the passenger compartment side, making it lighter than a cylindrical bumper reinforcement. , discloses that the upper wall and the lower wall do not open at the time of collision and function as ribs to transmit the impact load to the crash box.

JP 2018-65452 A

However, in the bumper reinforcement described in Patent Document 1, if the thickness of the bumper beam wall is reduced for weight reduction, the bumper beam is likely to break in the middle, and the impact load cannot be transmitted to the crash box. , it is difficult to absorb the impact load.

That is, the carbon fiber reinforced resin of Patent Document 1 maintains the shape of the bumper beam so that the upper wall and the lower wall do not open, and does not improve the strength of the bumper beam itself. If the wall thickness of the beam is reduced, the moment of inertia of area decreases and the beam buckles.

SUMMARY OF THE INVENTION The present invention has been made in view of the problems of the prior art. To provide a bumper reinforcement capable of being buckling deformed first.

As a result of intensive studies to achieve the above object, the inventors of the present invention have found that the upper and/or lower walls of a hollow metal bumper beam having a substantially rectangular cross-sectional shape are reinforced with a fiber reinforced resin. We have found that the object can be achieved, and have completed the present invention.

That is, the bumper reinforcement of the present invention includes a metal bumper beam, two crash boxes, and a reinforcing portion made of fiber-reinforced resin that reinforces the bumper beam.
The bumper beam has a hollow structure having a passenger compartment side wall and a collision surface side side wall extending in the vehicle width direction, an upper wall connecting the upper ends of the side walls, and a lower wall connecting the lower ends of the side walls,
The two crash boxes are provided on the side wall of the passenger compartment,
The reinforcing part is provided on the upper wall and/or the lower wall of the bumper beam and is continuous between at least the two crash boxes.

According to the present invention, the surface substantially horizontal in the direction of receiving the impact load, that is, the upper wall and/or the lower wall of the bumper beam is reinforced with fiber-reinforced resin, so that even if the thickness of the bumper beam is reduced, the impact load can be reduced. A bumper reinforcement can be provided that can be transmitted to and absorbed by the box.

It is a top view which shows an example of a bumper reinforcement. 2 is a cross-sectional view taken along line A-A' in FIG. 1; FIG. FIG. 10 is a diagram for explaining the relationship between the geometrical moment of inertia and the shape of the plate when the tip of the plate is pushed with a force of “P”; It is a figure explaining the state which the bumper reinforcement bent in the middle. FIG. 10 is a cross-sectional view showing another example of a bumper reinforcement having an S-shaped cross section on the collision surface side wall; FIG. 10 is a perspective view showing an example of a bumper reinforcement having a reinforcing portion on the side wall on the collision surface side; FIG. 10 is a cross-sectional view showing an example of a bumper reinforcement in which the reinforcing portion of the side wall on the impact surface side has a canopy; FIG. 4 is a plan view showing an example of a bumper reinforcement in which a curved bumper beam is provided with a canopy. 4 is a graph showing the relationship between displacement and reaction force of bumper beams of Examples and Comparative Examples.

The bumper reinforcement of the present invention will be described in detail.
The bumper reinforcement includes a metal bumper beam, at least two crash boxes, and a reinforcing portion made of fiber-reinforced resin that reinforces the bumper beam.

A plan view of the bumper reinforcement is shown in FIG. 1, and a cross-sectional view taken along line AA' in FIG. 1 is shown in FIG.
As shown in FIG. 2, the bumper beam has a hollow cylindrical structure with a substantially rectangular cross-sectional shape. and a lower wall connecting the lower ends thereof.

As shown in FIG. 1, two crash boxes are provided on the side wall of the bumper beam on the passenger compartment side, and reinforcing portions formed of fiber reinforced resin are provided on the upper wall, the lower wall, or both walls of the bumper beam. is provided and is continuous between at least two crash boxes.

Here, the strength of the bumper beam is determined by how much impact load it can withstand without buckling. Therefore, in order to maximize the tensile strength of the steel plate and improve the strength of the bumper beam, it is necessary to prevent the bumper beam from buckling.

This buckling is a phenomenon in which a load much smaller than the strength of the steel plate causes a decrease in yield strength, and is caused by a large deformation of the bumper beam. Improving is important.

The bending rigidity is determined by the Young's modulus and the geometrical moment of inertia. Even high-strength steel sheets have almost the same Young's modulus as ordinary steel sheets. The bending stiffness of the beam is almost unchanged.

Further, for example, the geometric moment of inertia of a plate-shaped wall having a rectangular cross-sectional shape is proportional to the cube of the plate thickness (a) in the direction horizontal to the load direction (P), as shown in FIG. Proportional to the strip width (b) in the direction perpendicular to the load direction.

In other words, if you increase the strength of the metal bumper beam using high-tensile steel and reduce the thickness of the bumper beam to reduce the weight of the bumper beam by increasing the strength, the bending rigidity of the bumper beam will be reduced if the shape is the same. decreases in proportion to the cube of the plate thickness, and buckling is likely to occur, resulting in a decrease in the strength of the bumper beam.

In the present invention, the direction of receiving the impact load is substantially horizontal, and in the case shown in FIG. The hollow cylindrical structure of the bumper beam is less likely to be crushed, and the bending rigidity of the bumper beam is dramatically improved, compared to reinforcing the side wall on the side of the passenger compartment or the side wall on the collision surface that is substantially perpendicular to the rim.

Therefore, even if the impact load (P) is applied between the crash boxes, the bumper beam is less likely to bend in the middle as shown in FIG. The crash box is first to buckle and deform to absorb the impact load.

As shown in FIG. 5, the bumper beam preferably has an S-shaped cross-section on the collision surface side wall. The S-shaped cross section improves the geometrical moment of inertia of the side wall on the collision surface side, and the hollow cylindrical shape of the bumper reinforcement is less likely to collapse, improving the strength of the bumper beam.

The hollow cylindrical bumper beam having the S-shaped cross section can be produced by roll molding.

Roll forming is a forming method in which a steel sheet is bent into a complicated cross-sectional shape using a roll having a desired cross-sectional shape, and the steel sheet is normally sent out from a coil material wound into a cylindrical shape. Therefore, the thickness of the roll-formed bumper beam is constant, and it is not possible to thicken only the upper and lower surfaces of the hollow cylindrical structure.

In the present invention, since the bumper beam is reinforced with the fiber-reinforced resin, it is possible to manufacture the bumper beam using a thin steel plate that easily buckles.

As the thin steel plate, it is preferable to use a high-tensile steel plate having a tensile strength of 780 MPa or more. The thickness of the high-tensile steel plate, that is, the thickness of the walls that make up the bumper beam, depends on the tensile strength of the high-tensile steel plate and the cross-sectional shape of the bumper beam, but is preferably 1.0 mm to 5.0 mm. , 1.0 to 2.0 mm.

Within the above range, the strength and bending rigidity of the bumper beam can be achieved together with the reinforcing portion formed of the fiber-reinforced resin, and the impact load can be absorbed by the bumper beam and transmitted to the crash box.

In addition, as shown in FIG. 5, the bumper beam preferably has a middle wall between the upper wall and the lower wall that connects the side wall on the passenger compartment side and the side wall on the collision surface side. By having this middle wall, the surface which is substantially horizontal in the direction of receiving the impact load is increased, and the moment of inertia of the area of the bumper beam is improved.

A bumper beam having a middle wall can be manufactured by stacking a plurality of cylinders having a substantially rectangular cross section and welding the cylinders together.

The crash boxes are provided at intervals in the vehicle width direction on the vehicle compartment side wall.
The attachment positions of the crash boxes may be even positions in the vertical direction of the bumper beam, or positions offset downward or upward from the center in the vertical direction.

Since the portion of the bumper beam that is likely to buckle changes depending on the mounting position of the crash box, it is preferable to provide the reinforcing portion according to the mounting position of the crash box.

When the crash box is installed in the center of the bumper beam in the vertical direction, the impact load is evenly applied to the upper and lower parts of the bumper beam. preferably the same.

Also, if the crash box is offset downward from the center of the bumper beam in the vertical direction, the impact load will be greater in the upper part of the bumper beam than in the lower part, so the upper part of the bumper beam will be more reinforced. The resistance to buckling must be balanced between the upper and lower portions.

Specifically, the reinforcing portion is provided only on the upper wall of the bumper beam, or the reinforcing portion is provided on both the upper wall and the lower wall, and the thickness of the reinforcing portion of the upper wall is thicker than that of the lower wall. It is possible to balance the difficulty of buckling by

If the crash box is offset upward from the center of the bumper beam in the vertical direction, the bumper beam may be provided with a reinforcing section only on the lower wall, or both the upper and lower walls may be provided with a reinforcing section. The resistance to buckling can be balanced by making the thickness of the reinforcing portion of the wall thinner than that of the reinforcing portion of the lower wall.

As shown in FIG. 6, the bumper beam of the present invention preferably has a reinforcing portion on the side wall facing the crash box, in addition to the upper wall and the lower wall.

The mounting portion of the crash box receives a large reaction force from the crash box when it receives an impact load, and the bumper beam tends to buckle at the mounting portion of the crash box.

Reinforcement of the crash box attachment prevents the bumper beam from buckling before the crash box, maximizing impact load absorption.

As shown in FIG. 7, it is preferable that the reinforcing portion of the side wall on the collision surface side has a canopy.
By providing the eaves projecting from the reinforcing portion in the direction of receiving the impact load, it is possible to reduce the reaction force that the metal bumper beam receives from the crash box.

When the bumper beam is curved like a bow and has a convex shape on the collision surface side, as shown in FIG. It is preferable that the tip is receded from the vertex of the curved convex shape.

With such an eaves shape, a large impact load is not applied only to the longitudinal center of the bumper beam at the time of a flat collision, and the impact load is also applied to the eaves, so that the impact load can be dispersed.

Furthermore, as shown in Fig. 8, the tip of the eaves is recessed from the vertex of the bumper beam toward the passenger compartment, so that the bumper beam bends and absorbs the impact load within the range of elastic deformation of the bumper beam. However, if the load is greater than that, the eaves will also receive the impact load, so that the bumper beam can absorb the impact load while preventing its buckling.

In addition, the influence of the curvature of the bumper beam on the vehicle design is reduced, and the design of the vehicle is improved.

It is preferable that the reinforcing portion of the impact surface side sidewall has a plurality of eaves in the vertical direction.
By having a plurality of eaves, the eaves can receive the impact load even when the impact load is applied from a direction that is offset upward or downward. Buckling can be prevented.

The reinforcing portions of the upper and lower walls of the bumper beam and the reinforcing portion of the side wall on the collision surface side can be produced by applying an injection material containing reinforcing fibers to a metal bumper beam by injection molding.

The reinforced parts of the upper and lower walls and the reinforced part of the side wall on the impact side are integrated and continuous by injection molding, so there are no parts that receive local stress and the amount of impact load absorption is maximized. be able to.

Further, it is preferable that the reinforcing fibers of the upper wall and the lower wall are oriented from the collision surface side toward the passenger compartment side. Since the reinforcing fibers are oriented in the direction in which the impact load is received, the strength of the reinforcing portion itself against the impact load is improved, so the thickness of the reinforcing portion can be reduced, and further weight reduction can be achieved.

EXAMPLES The present invention will be described in detail below with reference to examples, but the present invention is not limited to the following examples.

[Comparative Example 1]
A high-strength steel plate having a thickness of 1.0 mm was roll-formed to produce a hollow cylindrical metal bumper beam having a substantially square cross-sectional shape.

[Comparative Example 2]
The metal bumper beam of Comparative Example 1 is placed in a mold, the mold is closed, an injection material containing carbon fibers with an average fiber length of 0.5 mm is injected, and a reinforcing portion is formed only on the entire surface of the side wall on the passenger compartment side. was provided to obtain a bumper beam.

[Example 1]
A bumper beam was obtained in the same manner as in Comparative Example 2, except that reinforcing portions were provided on the entire surfaces of the upper and lower walls, and no reinforcing portion was provided on the side wall on the passenger compartment side.

FIG. 9 shows the relationship between the displacement amount and the reaction force of the bumper beams of Comparative Examples 1 and 2 and Example 1. In FIG.
As can be seen from FIG. 9, the bumper beam of Example 1 has a large inclination at the initial stage of collision and high bending rigidity. It was also confirmed that the crash box can be buckled first, and the bumper beam can be thinned and lightened because the peak of the reaction force is high and it is difficult to buckle.

In Comparative Example 2, the reinforcing effect appeared after the hollow cylindrical structure was crushed, but the peak of the reaction force was almost the same as in Comparative Example 1. Therefore, the reinforcing portion of the side wall on the passenger compartment side was the reinforcement of the hollow cylindrical structure. It can be seen that if the thickness of the bumper beam is reduced, the bumper beam tends to buckle before the crash box.

1 Bumper Reinforcement 2 Bumper Beam 21 Cabin Side Side Wall 22 Collision Surface Side Side Wall 23 Upper Wall 24 Lower Wall 25 Middle Wall 3 Reinforcement Part 31 Collision Surface Side Side Wall Reinforcement Part 32 Eaves 4 Crash Box T Vertex

Claims (10)

metal bumper beams,
at least two crash boxes;
and a reinforcing portion formed of a fiber reinforced resin that reinforces the bumper beam,
The bumper beam has a hollow structure having a passenger compartment side wall and a collision surface side side wall extending in the vehicle width direction, an upper wall connecting the upper ends of the side walls and a lower wall connecting the lower ends thereof,
The two crash boxes are provided on the side wall of the passenger compartment,
A bumper reinforcement according to claim 1, characterized in that the reinforcing part is provided on the upper wall and/or the lower wall of the bumper beam and is continuous between at least the two crash boxes. 2. A bumper reinforcement according to claim 1, wherein said metallic bumper beam is made of steel and has a constant thickness. The crash boxes are provided at equal positions in the vertical direction of the bumper beam,
3. A bumper reinforcement according to claim 1, wherein said reinforcing portion is provided on an upper wall and a lower wall of said bumper beam and has the same thickness. The crash box is offset downward in the bumper beam,
3. The reinforcing portion is provided only on the upper wall of the bumper beam, or is provided on both the upper and lower walls of the bumper beam, and the reinforcing portion on the upper wall is thicker than the reinforcing portion on the lower wall. 3. The bumper reinforcement according to 1 or 2. The crash box is offset upwardly of the bumper beam,
2. The reinforcing portion is provided only on the lower wall of the bumper beam, or is provided on both the upper and lower walls of the bumper beam, and the reinforcing portion on the upper wall is thinner than the reinforcing portion on the lower surface. 2. The bumper reinforcement according to 2. Furthermore, a reinforcing portion is provided on the side wall on the collision surface side,
6. The bumper rain according to any one of claims 1 to 5, wherein the reinforcing portion of the side wall on the collision surface side is provided in each of the portions facing the mounting portions of the two crash boxes. force. 7. The bumper reinforcement according to claim 6, wherein the reinforcing portion of the side wall on the collision surface side has a canopy. The bumper beam has a convex curved shape on the collision surface side,
8. The bumper reinforcement according to claim 7, wherein the eaves have a shape that protrudes greatly on both end sides of the bumper beam and slightly on the center side, and the tip of the eaves recedes from the vertex of the curved shape. 9. The bumper reinforcement according to claim 8, wherein each of the two reinforcing portions of the side wall on the impact surface side has a plurality of eaves in the vertical direction. 10. The reinforcing portion of the impact surface side sidewall and the reinforcing portion provided on the upper surface and/or the lower surface of the bumper beam are integrated as one body according to any one of claims 6 to 9. bumper reinforcement.

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