JP3183464B2 - Energy absorbing member - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an energy absorbing member.
For example, the shock absorbing member of a bumper
And a suitable tubular fibrous structure.

[0002]

2. Description of the Related Art In order to protect a vehicle body and a passenger at the time of a collision, an automobile is generally provided with a bumper for absorbing impact energy at the time of a collision in front and rear of the vehicle body. Bumpers need to irreversibly absorb energy in the event of a large load applied when the vehicle collides with an obstacle. In order to increase the absorbed energy, various improvements in the material and structure of the support member for supporting the bumper body have been conventionally made.

[0003] For example, a German patent (3626150) published on February 18, 1988 discloses a structure in which a bumper 22 is attached to a stay 23 of a vehicle body via an elliptical annular damping molded body 21 as shown in FIG. Have been. The damping molded body 21 is formed of FRP (fiber reinforced plastic) in which fibers are arranged in the circumferential direction, and is attached so that the elliptical long sides contact the bumper 22 and the stay 23, respectively.

Japanese Patent Application Laid-Open No. 57-124142 discloses an energy absorbing structural material used for a bumper as shown in FIG.
As shown in FIG. 1, there has been proposed a structural body 25 formed in a cylindrical shape with a network structure composed of strips 24 made of a fiber composite material (for example, an epoxy resin impregnated glass fiber). The structure 25 is used in a state where a compressive load is applied in the axial direction of the cylinder. When an axial load is applied to the structure 25, delamination occurs at the opposing nodes 26 of the network, and the shear yield is caused by the fiber and the matrix. The energy is absorbed stepwise by being generated at the interface. In addition, each node 26
Is formed of about ten layers of fiber composite material strips 24.

[0005]

The above-mentioned German patent discloses the use of an FRP damping molded body 21 in which fibers are arranged in the circumferential direction as an energy absorbing member, but a load is applied to the member. No mention is made of the stress, fluctuations, absorbed energy, etc., which occur when this occurs. As a method for manufacturing an annular structure made of FRP in which long fibers are arranged in a circumferential direction, filament impregnating (adhering) is performed by winding a mandrel (core material) in multiple layers while impregnating (adhering) resin, and then heating and curing the filament winding (FW). The method is generally used. When the structure produced by the FW method is compressed by the load from the side, the stress increases at the same time as the intensive deformation of the curved surface, and when exceeding a certain limit, the fiber delaminates and the stress suddenly increases. To decline. In the initial stage of compression, this severe stress change is repeated and delamination proceeds,
The stress tends to decrease gradually. The deformation is further increased, and the stress is further attenuated when the breaking limit of the fiber is exceeded. The product of the stress and the deformation amount generated in the compression deformation process (specifically, the area between the compression load-displacement amount curve and the axis indicating the displacement amount) is the absorbed energy at that time. For bumper support members, etc.
Since the ability to reduce the stress is also required, the maximum stress
It is necessary to keep the lower level, and when the fluctuation of the stress is severe, the energy absorption as a whole becomes small.
Therefore, reducing the shock, yet to meet the demands of the increasing amount of energy absorption during deformation, compressive load - be kept constant displacement curve at the lowest possible level is an important point.

[0006] An elliptical ring-shaped structure made of FRP having glass fibers arranged in the circumferential direction and having a constant thickness is manufactured in the same manner as that disclosed in the German patent, and compressed by a load from the elliptical longitudinal side surface. When the relationship between the load and the amount of displacement was measured, the result shown in FIG. 10 was obtained. In this case, a sudden change in the load occurs at the point where the peeling starts first, and the change is extremely severe.If the maximum value of the load is suppressed to a low level below a certain level, the amount of energy absorption decreases,
It is insufficient as an energy absorbing member for a bumper.

On the other hand, the cylindrical energy absorbing structural material disclosed in JP-A-57-124142 exhibits its function when a compressive load is applied in the axial direction of the cylinder.
It can hardly cope with a load from an oblique direction.
As described above, in order to increase the absorbed energy, it is important that the load is maintained at a constant level even if the displacement amount increases. Is gradually attenuated, and the amount of energy absorption is hardly increased.

The present invention was made in view of the problems described above, the object does not generate a certain level of stress in the time of collision abrupt change shape, large energy absorbed for a given amount of deformation, In addition, an object of the present invention is to provide an energy absorbing member which has a high impact absorbing ability even with a load from an oblique direction and is lighter in weight than metal.

[0009]

In order to achieve the above object, an energy absorbing member according to the present invention has a structure in which fibers are wound in a circumferential direction so as to form an annular cross section, and
Is formed of a fiber-reinforced composite material bound and hardened with a resin, and has a thickness that varies along the axial direction with the inner diameter .

[0010]

[Action] energy absorption member of the present invention is attached from the side of the cylindrical portion to receive a compressive load. The deformation that occurs in the energy absorbing member due to the compressive load is compressed on the inner layer side,
It is elongated on the outer layer side, and the amount of deformation increases as the distance from the neutral layer increases. Since delamination is more likely to occur in a portion having a larger deformation amount, delamination occurs gradually from a thicker portion, and the deformation stress is not changed drastically, but is smoothly deformed with a relatively small stress to absorb a large amount of energy.

[0011]

【Example】

(Embodiment 1) Hereinafter, a first embodiment of the present invention will be described with reference to FIGS. As shown in FIG. 1, the energy absorbing member 1 is formed in a cylindrical shape having a constant outer diameter, and is formed such that its thickness gradually changes from a central portion in the axial direction toward both ends.

The energy absorbing member 1 is formed of FRP in which synthetic resin is reinforced with endless long fibers (filaments), and is formed in a state where the filaments are wound in the circumferential direction. In this embodiment, a glass fiber is used as a filament and an epoxy resin is used as a synthetic resin. The manufacturing method used was a filament winding (FW) method in which the resin was wound on a mandrel while adhering the resin to the glass fiber, and then the resin was cured by heating. In order to allow the mandrel to be separated from the energy absorbing member 1 after heat curing, a mandrel that can be divided in the axial direction from the center was used.

FIG. 2 shows the result of measuring the relationship between the load and the displacement when a compressive load is applied to the energy absorbing member 1 configured as described above from the side surface.
As is clear from the figure, the maximum load is smaller than the case where the wall thickness is uniform as shown in FIG. 10, but the sudden change in the load in the initial stage of compression is significantly reduced, and the load in the latter half of the plastic deformation is reduced. The drop is also small. this is,
When the wall thickness is uniform, the amount of deformation due to the compressive load becomes constant in the axial direction, and when the compressive energy is stored and exceeds a certain limit, delamination occurs at once. It is considered that the thickness changes from the central portion in the axial direction toward both ends, so that delamination occurs sequentially from the thick central portion. That is, in the thick portion, the inner layer of the cylindrical portion has a smaller fiber winding amount and a larger deformation amount, so that delamination occurs sequentially from the portion. Therefore, the energy absorbing member 1 has a small load variation and a large ratio between the energy absorption amount and the maximum load as compared with the conventional one, and is thus preferable as an energy absorbing member for a bumper. The material of the energy absorbing member 1 has a specific gravity of about 2
Since it is a nearby FRP, it is much smaller than that of metal and can be reduced in weight.

(Embodiment 2) Next, a second embodiment will be described with reference to FIGS.
It will be described according to. Energy absorbing member 1 of this embodiment
The second embodiment is different from the first embodiment in that the cross section is formed in a substantially elliptical cylindrical shape and the inner diameter is changed stepwise. When the energy absorbing member 1 of this embodiment is formed by the FW method, the use of a metal mandrel makes it difficult to remove the mandrel after heating and curing the resin. Therefore, in this example, the mandrel was made of foamed polypropylene, and was left in the formed energy absorbing member 1. The mandrel made of expanded polypropylene may be destroyed and removed without remaining. When a mandrel made of expanded polypropylene is left, when a compressive load is applied to the energy absorbing member 1, the expanded polypropylene is also deformed, thereby contributing to improvement in the amount of absorbed energy and mitigation of load fluctuation.

FIG. 4 shows the result of measuring the relationship between the load and the amount of displacement when a compressive load is applied from the side to the energy absorbing member 1 in which the mandrel made of expanded polypropylene is left. Also in this case, the sudden change of the load is remarkably reduced, and the reduction of the load in the latter half of the plastic deformation is also small. (Embodiment 3) Next, a third embodiment will be described with reference to FIGS. The energy absorbing member 1 of this embodiment is formed in a cylindrical shape having a constant outer diameter, a thin portion exists at both ends, and a thick portion exists at an axial center portion. Is formed in a shape that changes smoothly. When manufacturing this energy absorbing member 1,
As in the first embodiment, a mandrel that can be divided axially from the center is used. FIG. 6 shows the result of measuring the relationship between the load and the amount of displacement when a compressive load is applied to the energy absorbing member 1 from the side. In this case as well, the sudden change of the load decreases, and the decrease of the load in the latter half of the plastic deformation is also small.

(Embodiment 4) Next, a fourth embodiment will be described with reference to FIGS.
It will be described according to. Energy absorbing member 1 of this embodiment
Is greatly different from the above embodiments in that it has a structure in which a plurality of annular tubular portions are combined. The energy absorbing member 1 has two cylindrical portions 2 having the same shape as that of the first embodiment arranged in parallel at an interval, and an elliptical cylindrical portion 3 is integrated outside the two cylindrical portions 2 in a state of circumscribing the two cylindrical portions 2. Is formed. In this energy absorbing member 1, first, a cylinder corresponding to the cylindrical portion 2 is manufactured by the FW method, and then two cylinders are arranged in parallel at an interval, and glass fibers having resin adhered to the outer peripheral portion thereof are formed by the FW method. It is produced by winding and heating and curing the resin.

FIG. 8 shows the result of measuring the relationship between the load and the amount of displacement when a compressive load is applied to the energy absorbing member 1 from the side. As the sudden change of the load decreases, the load becomes substantially constant until the latter half of the plastic deformation, and the ratio between the energy absorption amount and the maximum load becomes larger than that of each of the above embodiments. This is presumably because load averaging is performed due to the presence of a plurality of cylindrical portions 2.

The present invention is not limited to the above-described embodiment. For example, the cross-sectional shape of the cylindrical portion of the energy absorbing member 1 is not limited to a circle or an ellipse but may be substantially a combination of arcs having different curvatures. It may be an annular shape. Further, the resin constituting the material FRP is not limited to the epoxy resin, a phenol resin, a thermosetting resin such as unsaturated polyester, or a high elasticity such as carbon fiber, aramid fiber instead of glass fiber as the reinforcing fiber, Various functional fibers having high-strength physical properties are used, but in the case of a bumper for an automobile, glass fibers are preferable in terms of heat resistance and the like in terms of cost. In the case of a structure in which a plurality of cylindrical portions are combined as in the fourth embodiment, the number of cylindrical portions may be increased or the diameter of the cylindrical portion may be changed.

[0019]

As described above in detail, according to the present invention, since the energy absorbing member is formed in an annular cross section and is used in a state of receiving a compressive load from the side surface thereof, it can withstand a load in an oblique direction. It also has high shock absorption capacity. In addition, the thickness of the cylindrical energy absorbing member is the same as its inner diameter.
To change along the axial direction, delamination due to compressive deformation is gradually generated from a large part of the thickness not occur sudden stress change can be either tooth absorb large energy.

[Brief description of the drawings]

FIG. 1 shows an energy absorbing member of a first embodiment,
(A) is a sectional view taken along line AA of (b), and (b) is a side view.

FIG. 2 shows a compressive load of the energy absorbing member of the first embodiment.
It is a displacement amount curve.

FIG. 3 shows an energy absorbing member of a second embodiment,
(A) is a sectional view taken along line BB of (b), and (b) is a side view.

FIG. 4 shows a compressive load of the energy absorbing member of the second embodiment.
It is a displacement amount curve.

FIG. 5 shows an energy absorbing member of a third embodiment,
(A) is a sectional view taken along line CC of (b), and (b) is a side view.

FIG. 6 shows a compressive load of the energy absorbing member of the third embodiment.
It is a displacement amount curve.

FIG. 7 is a schematic perspective view of an energy absorbing member according to a fourth embodiment.

FIG. 8 shows a compressive load of the energy absorbing member of the fourth embodiment.
It is a displacement amount curve.

FIG. 9 is a schematic plan view showing a bumper supporting state by a conventional bumper supporting member.

FIG. 10 is a compression load-displacement amount curve of a conventional bumper support member.

FIG. 11 is a schematic perspective view showing a conventional energy absorbing structural material.

[Explanation of symbols]

 1 ... energy absorbing member, 2 ... cylindrical part.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hiroshi Omori 2-1-1, Toyota-cho, Kariya-shi, Aichi Pref. Inside the Toyota Industries Corporation (72) Inventor Yoshiharu Yasui 2-1-1, Toyota-cho, Kariya-shi, Aichi Pref. Inside Toyota Industries Corporation (72) Inventor Yasumi Miyashita 2-1-1 Toyota-cho, Kariya-shi, Aichi Co., Ltd. Inside Toyota Industries Corporation (72) Inventor Toshiro Kondo 2-1-1 Toyota-cho, Kariya-shi, Aichi Japan Toyoda Auto Corporation Loom Works (72) Inventor Naohiro Tada 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Corporation (56) References JP-A-54-124168 (JP, A) (58) . ^7, DB name) B60R 19/34 B60R 19/30

Claims (1)

(57) [Claims] 1. A fiber is wound in a circumferential direction so as to form an annular cross section, and the fiber is formed into a tubular shape from a fiber-reinforced composite material which is bound and cured by a resin , and has a wall thickness.
An energy absorbing member that changes along the axial direction with the inner diameter .