JPH0355466Y2 - - Google Patents

Description

[Detailed explanation of the idea] [Industrial application field] The present invention relates to an automobile bumper core material.

[Conventional technology]

BACKGROUND ART In recent years, there has been a demand for lighter automobiles in order to save on gasoline fuel consumption, and accordingly bumpers have been made lighter. Synthetic resin foam is used as the core material of these bumpers, and polyolefin resin is used as the synthetic resin. By selecting the density of the foam or the resin, bumpers with cushioning capacity and lightness can be achieved. A core material has been developed.

The core material is formed by foam-molding synthetic resin into a bumper shape, and is used by being attached to the skin material.

[Problem that the invention attempts to solve]

Conventional core materials for bumpers are lightweight and have a certain degree of impact resistance, but there are still some unsatisfactory areas in terms of impact resistance.

Conventional core material for bumpers is generally 4.0Km/hr−8.0
It is formed to withstand shocks of about Km/hr, and if we try to make it into a core material with higher energy absorption capacity, for example, that can withstand 16.1 Km/hr, the weight will increase, and the foam itself There was a problem in which the lightweight nature of the product was lost.

The present invention was devised in view of the above-mentioned drawbacks of the prior art, and an object of the present invention is to provide a core material for a bumper that does not lose weight and has high energy absorption ability.

[Means for solving problems]

As a result of intensive research to solve the above problems, the inventors of the present invention have found an automobile bumper core material made by embedding a synthetic resin molded body having a specific density inside a foam layer at a specific weight ratio to the foam layer. However, they discovered that it has a high energy absorption capacity without losing its lightness, and completed the present invention.

That is, the present invention is an automobile bumper core material made of polyolefin resin foam, in which a synthetic resin molded body with a density of 0.2 to 1.5 g/cm ³ is embedded inside the foam layer, and The gist of the present invention is an automobile bumper core material characterized in that the ratio of the weight of the layer to the weight of the synthetic resin molded product is 50/1 to 1/1.

[Embodiments] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIGS. 1 and 2 show an embodiment of the automobile bumper core material of the present invention, and numeral 1 in the figures indicates the automobile bumper core material. The core material 1 is composed of a foam layer 2 and a synthetic resin molded body 3 embedded within the foam layer 2 as shown in FIG.

In the present invention, polyolefin resin is used as the resin forming the foam layer 2, for example,
Polypropylene resins such as polypropylene, ethylene-propylene random copolymers, ethylene-propylene block copolymers, high-density polyethylene resins, or resins obtained by absorbing vinyl aromatic monomers into high-density polyethylene resins and polymerizing them are used. Of these, polypropylene resin is the most preferred.

The density of the foam layer 2 is 0.01 to 0.15 g/cm ³ , preferably 0.015 to 0.1 g/cm ³ .

In the present invention, the material of the molded body embedded in the foam layer can be the same as the resin forming the foam layer, and even if the molded body is a foamed body, it can be a non-foamed one. However, the density must be between 0.2 and 1.5 g/cm ³ .

Further, in the present invention, the ratio of the weight of the foam layer to the weight of the molded product is 50/1 to 1/1, preferably
Must be between 20/1 and 2/1. Even if the density of the molded product is within the above range, if the ratio of the weight of the foam layer to the weight of the molded product is less than 1/1, the weight will be heavy;
If the above ratio exceeds 50/1, energy absorption is poor. Conversely, even if the ratio of the weight of the foam layer to the weight of the molded product is within the above range, the density of the molded product may be
If it is less than 0.2 g/cm ³ , the energy absorption property will be poor, and even if the ratio of the weight of the foam layer to the weight of the molded product is within the above range, if the density of the molded product exceeds 1.5 g/cm ³ , the core will deteriorate. The overall weight of the material becomes heavy, making it impossible to achieve the purpose of the present invention.

In the present invention, various shapes are possible for the formed body, such as a honeycomb structure as shown in Fig. 3, or a plate-shaped body with recesses as shown in Fig. 4. These may be buried along the longitudinal direction of the foam layer 2 as shown in FIG. 1, or they may be partially buried in areas with weak strength, for example, corner portions 4, 4 as shown in FIG. However, in order not to lose the cushioning properties of the foam layer 2, as shown in FIG.
It is preferable to embed the molded body 3 in a position where the distance a from the frontmost part of the foam layer 2 to the frontmost part of the foam layer 2 is larger than 1/4 of the width L of the foam layer 2 in the front-rear direction.

Further, as shown in FIGS. 3 and 4, a plurality of through holes 5, 5... can be provided in the molded body 3 as necessary, and the foam layer 2 can be bonded in the through holes 5, 5... , the bond between the foam layer 2 and the molded body 3 becomes stronger.

In forming the automobile bumper core material configured as described above, a normal method for forming a bead foam molded product can be applied. For example, after placing the molded product in a predetermined position in a mold, , filled with pre-expanded particles, and foamed to form the particles.

At this time, when the formed body 3 has a honeycomb structure as shown in FIG. 3, it is preferable to form projections 6, 6, . . . as necessary when forming the bumper core material. That is, when the mold is moved after the mold is inserted into the mold with the protruding portion facing forward to form a foam layer, it is possible to prevent the molded product from moving in the direction of movement of the mold.

The invented automobile bumper core material has extremely high energy absorption efficiency;
It has a high energy absorption capacity of over 70%. As described above, the core material of the present invention has a high energy absorption efficiency of 70% or more, so it has the advantage of being able to sufficiently withstand impacts, especially those with high impact speeds, while maintaining its light weight.

In this invention, the energy absorption efficiency is calculated from the stress-strain curve shown in Figure 6 when the sample is impacted at a sample temperature of 20°C and an impact speed of 16.1 km/hr, using the following formula: Energy absorption efficiency = (OAB area/OABC (area).

Hereinafter, the present invention will be explained in more detail with reference to specific examples.

Example After placing a molded body with a density of 0.9 g/cm ³ in the shape shown in Fig. 3 in a mold for forming a core material for a bumper at a predetermined position, a preliminary molding using an ethylene-propylene random copolymer as the base resin was prepared. After pressurizing the foamed particles with air to apply internal pressure, the voids in the mold were filled, and the pre-expanded particles were expanded by heating with water vapor to obtain a core material conforming to the mold.

The energy absorption efficiency of the obtained core material was measured and was 73%. In addition, when the weight of the obtained core material was measured, it was 1.2 times that of a comparative example core material described later.

Comparative Example A core material was obtained in the same manner as in the example except that no molded body was installed.

The energy absorption efficiency of the obtained core material was measured and was 50%. This is inferior to the energy absorption efficiency of 73% of the core material obtained in the above example. The shock absorbing ability of the comparative example is inferior to that of the example.

[Effect of idea]

As explained above, the automobile bumper core material of the present invention is an automobile bumper core material made of a polyolefin resin foam, and has a synthetic resin molded body with a density of 0.2 to 1.5 g/cm ³ inside the foam layer. is embedded therein, and the ratio of the weight of the foam layer to the weight of the synthetic resin molded body is 50/1 to 1/1, so it is a core material with extremely good energy absorption efficiency, Moreover, it is an extremely good core material for a bumper that does not lose its light weight and has high energy absorption efficiency.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention; FIG. 1 is a perspective view showing an embodiment of the automobile bumper core material of the present invention; FIG. 2 is a vertical sectional view taken along the line of FIG. 1;
Figures 3 and 4 are perspective views of essential parts showing an example of a synthetic resin molded body, Figure 5 is a plan view showing a synthetic resin molded body provided at a corner, and Figure 6 is a stress-strain curve. This is a graph showing. 1... Car bumper core material, 2... Foam layer, 3... Synthetic resin molded body.

Claims (1)

[Scope of utility model registration request] An automobile bumper core material made of polyolefin resin foam, with a density inside the foam layer.
It is made by embedding a synthetic resin molded body of 0.2 to 1.5 g/ ^cm3 ,
A bumper core material for an automobile, characterized in that the ratio of the weight of the foam layer to the weight of the synthetic resin molding is 50/1 to 1/1.