JPH0520616Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an automobile bumper core material made of polyolefin resin foam.

[Prior art]

Conventionally, car bumpers were generally made of metal plates, but in recent years, as automobiles have become lighter, structures in which the back side of a foam core is covered with a metal or resin skin have been introduced. have come to be used. Conventionally, for such automobile bumper core materials, it has been known to use a bumper-shaped foam molded product obtained by filling pre-expanded polyolefin resin particles into a mold of a desired shape and foaming them. There is. In addition, these core materials are
It is usually shaped to match the inner shape of the skin and back beam.

[Problem that the invention attempts to solve]

Although conventional core materials for bumpers are lightweight and have some degree of impact resistance, there are still some areas where they are unsatisfactory in terms of impact resistance.

Conventional core material for bumpers generally has a speed of 2.5 miles/hr.
It is formed to withstand impact of about 5.0 miles/hr, and if you try to make it into a core material with higher energy absorption capacity, for example, that can withstand 10 miles/hr, the weight will increase and the foam The drawback was that it lost its original lightness.

The present invention has been made 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 impair its lightweight properties and has high energy absorption capacity.

[Means for solving problems]

As a result of intensive research by the present inventors to solve the above problems, they discovered that a core material for automobile bumpers, which uses a polyolefin resin foam as a core material and has a filler-mixed synthetic resin structure having a specific density positioned in the recesses of the core material, has high energy absorption capacity without compromising its light weight, and has thus completed the present invention.

That is, according to the present invention, a density of 0.15 with a concave portion
It consists of a resin foam of ~0.01g/cm ³ and a resin structure located in a recess of the foam, and the depth of the recess is
The thickness of the core material in the front-rear direction at the location of the recess
15% or more, and the weight ratio of the resin structure to the resin foam is 1/50 to 5/1, in which the resin foam is a polyolefin resin foam and the resin structure has a density of An automobile bumper core material is provided, which is a resin structure containing a filler of 0.2 to 3.5 g/cm ³ .

The polyolefin resin foam core material of this invention is
It has a recessed portion, and this recessed portion is formed on the front and/or rear surface of the core material. In this case, the shape of the recesses provided on the front and/or rear surfaces of the core material can be various shapes such as circular, elliptical, and square, and the number of recesses is usually 1 to 100, preferably 2.
~50 pieces. Further, the opening area of the single recess is usually 0.5 to 20 cm ² , preferably 1 to 10 cm ² ,
The total opening area of the recesses provided on the front or rear surface is preferably about 15 to 100% of the projected area of the entire core material in the front-rear direction (including the portion where the recesses are present). In this case, the opening area is considered independently of the opening area of the recess provided on the front surface and the opening area of the recess provided on the rear surface, and the total opening area of the opening area provided on the front surface and the opening area provided on the rear surface is within the above range. Bye.
In addition, in the present invention, the maximum depth of one recess is 15% or more of the thickness of the core material in the front-rear direction at that part (thickness with the recess buried), preferably 50 to 95%.
%. In particular, when recesses are provided on both the front and rear surfaces of the core material, the opening area of the recesses on each surface should be within the above range, and the depth of the recesses should be such that the recesses coincide with the front and rear surfaces. If provided, the sum of the maximum depths of both recesses in the portion may be set within the above range.

The polyolefin resin foam used as the core material in this invention has a density of 0.15 to 0.01 g/
cm ³ , preferably 0.1 to 0.015 g/cm ³ , and specific examples of the resin include polypropylene resins such as polypropylene, ethylene-propylene random copolymers, ethylene-propylene block copolymers, etc. Examples include density polyethylene resins or resins obtained by absorbing and polymerizing vinyl aromatic monomers into high-density polyethylene resins, among which polypropylene resins are most preferred.

In the present invention, the density of the filler-containing resin structure located in the recess of the core material is 0.2 to 3.5 g/cm ³ ,
Preferably it is 0.5 to 3.0 g/cm ³ . This structure is
Any shape or size may be used as long as it can be installed in the recess, for example, a columnar body that fills the entire recess, a plate that partially fills the recess, a combination of plates, or a honeycomb structure. It can be of a shape such as. Further, this structure may be independent from the bumper member, or it may be connected in advance to the bumper member, for example, as a skin constituting the bumper or a rib protruding inward from the back beam. good. Further, the skin and back beam having such ribs can be molded as one piece using a filler-containing resin.

The filler-containing resin structure can be foamed or unfoamed, and its resin materials include, for example, polyolefin resins such as polypropylene and polyethylene, polyurethane, polystyrene,
Acrylonitrile-styrene-butadiene copolymers, various nylons, polycarbonates, polyethylene terephthalate, vinyl chloride resins, etc. are used. Even if two or more of these are mixed,
More than one type may be laminated. In addition, examples of fillers to be added to the resin include silica, mica,
Talc, clay, bentonite, graphite,
Examples include carbon black, calcium carbonate, titanium oxide, alumina, iron powder, molybdenum disulfide, vanadium sulfide, polyacrylurea, copper phthalocyanine, asbestos, glass fiber, and glass fiber cloth. The blending amount thereof is 10 to 80 parts by weight, preferably 20 to 70 parts by weight, per 100 parts by weight of the resin. The ratio of the filler-containing resin structure to be installed and positioned in the recess of the foam core material is 1/50 to 5/1, preferably 1/20 in terms of weight ratio to the foam core material.
-1/2 range. Further, when the foam core material has a plurality of recesses, the structure does not necessarily have to be installed in all the recesses.

Hereinafter, the present invention will be described in more detail with reference to the drawings.

Figure 1 shows the shape of the polyolefin resin foam used as the core material, Figure 1a is its oblique view, and Figure 1b is a cross-sectional view taken along plane A-A in Figure 1a. It is. In FIG. 1, 1 is a polyolefin resin foam, and 2 is a recess provided on the rear surface.

FIG. 2 is a perspective view of an example of a filler-containing resin structure installed in the recess 2. FIG.

Figure 3 shows that a second
FIG. 3 is a perspective view of a core material equipped with the resin structure shown in the figure.

FIG. 4 is a perspective view of a filled resin structure (rib) attached in advance to the inner surface of the back beam, where 5 indicates the back beam and 3 indicates the filled resin structure. A back beam with such ribs can be integrally molded using a filled resin.

〔Example〕

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

Example 1 A rectangular parallelepiped 10 having a concave portion 11 shown in ^FIG . /cm ³ ) was made from a resin mixed with glass fiber as a filler. In this case, the dimensions of the rectangular parallelepiped 10 are length e: 200 mm, width f: 100 mm, and height d: 100 mm, and the dimensions of the recess formed in the plane part are length a: 3 mm, width b: 100 mm, and depth c. :80
It was warm in mm. Also, the dimensions of the structure 20 are m: 100
mm, p: 80 mm, l: 3 mm.

Next, the structure shown in Fig. 6 was installed in the recess of the rectangular parallelepiped shown in Fig. 5, and an impact test was performed by dropping a plate-shaped weight over the entire surface at an impact speed of 5 miles/hr. At that time, the strain (%) in the thickness direction and dynamic stress (Kg/cm ² ) that the rectangular parallelepiped received was measured, and the amount of energy absorbed relative to the strain was calculated. The results are shown in graphs in FIGS. 7 and 8.

In addition, the stress-strain curve shown in Fig. 7 and the
The energy absorption efficiency shown in the figure is
Calculated according to the method described in No. 221746.

Energy absorption efficiency (%) = energy absorption amount / stress × strain × 100 Comparative example 1 A bumper core material was produced in the same manner as in Example 1 except that the structure 20 was not attached, and the impact test was conducted. I went. The results are shown in FIGS. 7 and 8.

As a result, at 70% strain, the energy absorption efficiency of Comparative Example 1 was 55.6% [2.14/(5.5×
0.7)], whereas in the case of the present invention it is 72.5%
[3.3/(6.5×0.7)], which means that the distortion is 70%.
The amount of energy absorbed when
This shows an improvement in absorption amount of about 1.5 times compared to that of the previous one.

Comparative Example 2 A bumper core material of Comparative Example 2 was produced in the same manner as in Example 1 except that the density of the plate-shaped body (resin structure) was 0.019 g/cm ³ , and the same was used as in Example 1. A similar impact test was conducted. As a result, at 70% strain, the energy absorption efficiency of the bumper core material of Comparative Example 2 was 58.1% [2.32/(5.7×0.7)], which was significantly inferior to 72.5% of the product of the present invention. It turned out to be.

Comparative Example 3 A bumper core material for Comparative Example 3 was produced in the same manner as in Example 1, except that the density of the plate-like body (resin structure) was 0.36 g/cm ³ in Example 1. A similar impact test was conducted. As a result, at 70% strain, the bumper core material of Comparative Example 3 had an excellent energy absorption efficiency of 86% [4.5/(7.5×0.7)], but the weight of the bumper core material was 105.6g. It was found that this was a considerable weight increase compared to the weight of the invented product, which was 88.4 g.

As can be seen from the results of the impact tests shown above, the core material for automobile bumpers of the present invention clearly has improved impact absorption amount and impact absorption efficiency. There is no particular loss. Therefore, when using the core material for automobile bumpers of the present invention, it is possible to achieve an improvement in impact absorption amount and efficiency when comparing products of the same weight, and when comparing products with the same impact absorption efficiency, the core material is lighter in weight. It is possible to achieve miniaturization and downsizing.

[Brief explanation of drawings]

Figure 1 shows a foam core material having a concave portion, Figure 1a is its perspective view, and Figure 1b is A-
A sectional view is shown. FIG. 2 shows a perspective view showing the shape of the structure attached to the foam recess. FIG. 3 shows a perspective view of the core material of the present invention with a structure attached to the recess. FIG. 4 shows a perspective view of the structure attached to the back beam. FIG. 5 is a perspective view of a foam sample having a recess used in the impact test, and FIG. 6 is a perspective view of a structure sample mounted in the recess. FIG. 7 is a graph showing a dynamic stress-strain curve obtained in the impact test, and FIG. 8 is a graph showing an energy absorption strain curve, respectively. 1... Foam, 2... Recess, 3... Structure, 5
... Back beam, 10 ... Foam sample, 1
1... Concavity of foam sample, 20... Structure sample.

Claims (1)

[Scope of utility model registration request] It consists of a resin foam with a density of 0.15 to 0.01 g/cm ³ having a recess and a resin structure located in the recess of the foam, and the depth of the recess is the thickness of the core material in the front-rear direction at the position of the recess. In a core material for an automobile bumper in which the weight ratio of the resin structure and resin foam is 1/50 to 5/1, the resin foam is a polyolefin resin foam, and the resin structure is An automobile bumper core material characterized by being a filler-containing resin structure having a density of 0.2 to 3.5 g/cm ³ .