Filling structure

Abstract

A filling structure 10 is a structure in which a filling material 12 having a higher impact energy absorbing performance is inserted into the inner part of a hollow member 11, and the filling material 12 so inserted is fixed to the hollow member 11 with an adhesive layer 13 resulting when the filling material 12 is heated to expand and is cooled to set thereafter.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a filling structure which is preferable for application to a vehicle body frame, in particular, to a bumper, a front side member and a pillar.

2. Description of the Related Art

In recent years, there have been made attempts to improve the collision energy absorbing performance at the location of a certain vehicle body structural member by filling a material having a superior energy absorbing performance in the inner part of the structural member such as disclosed in JP-A-8-164869

The patent literature of JP-A-8-164869 discloses a technique described in its paragraph [0015] such as to state, “according to an embodiment shown in FIG. 1, an impact absorbing frame member 5 made up of the frame portion 51 constituted by an angular pipe stock and an expanded aluminum 52 filled in the inner part thereof is constructed by adding predetermined amounts of a thickener and an expanding agent to a molten aluminum or molten aluminum alloy to be stirred together, and thus produced mixture is put into the inner part of the frame portion 51 for expansion. ”.

As for a joint condition between the frame portion 51 and the expanded aluminum 52, it depends on the expansion force of the expanded aluminum 52. However, since the expanded aluminum 52 is formed with a porous structure, lots of pores exist in the surface thereof. Therefore, when the force is applied thereto, the surface tends to be damaged, and the joining force is decreased, whereby a gap might be formed between the frame portion 5 and the expanded aluminum 52 after a long time period of use.

Namely, according to the structure thereof, any mechanical bonding of the expanded aluminum 52 to the frame member 51 cannot be secured to be achieved.

In addition, snow-melting salt is distributed as a counter measure against the freezing road surface in cold regions. Under such an environment or a corrosion environment where the water containing the snow-melting salt penetrates between the filling material and the hollow member, there is a possibility that corrosion might occur in the sheet-steel member where said corrosion propagates from the inner part of the member, which ends up being an open hole rust, unless any appropriate corrosion protection treatment, such as formation treatment, or electro-deposition coating, is applied to the sheet steel member, specifically, to the hollow member thereof.

Furthermore, there is also a possibility that a galvanic corrosion might be made due to the contact of a non-treated sheet steel with an aluminum filling material a serious functional deterioration might occur in the aluminum filling material.

SUMMARY OF THE INVENTION

It is an object of this invention to provide a filling structure which allows a filling material such as expanded aluminum to be bonded rigidly to a hollow member whereby secures corrosion resistance thereof.

According to a first aspect of the invention, there is provided a filling structure comprising a hollow member and a filling material filled in the inner part of the hollow member, the filling material having a higher impact energy absorbing performance, wherein the filling material is fixed to the hollow member with an adhesive having a property that the adhesive expands when heated.

When used herein, the adhesive denotes polymer resins having adhesion properties, and among them, an epoxy adhesive and a urethane adhesive are taken for example.

According to a second aspect of the invention, there is provided a filling structure as set forth in the first aspect of the invention, wherein the adhesive has such a property that the adhesive melts and expands by heating for 10 to 30 minutes at a temperature of 140° C. to 190° C., and said adhesive is cured after cooling treatment.

In a case where the heating of the adhesive and the drying of an electro-deposition coating film are carried out simultaneously in parallel, it is insufficient for said coating film to be properly dried in the event that the heating is implemented at a temperature of lower than 140° C. or for a time period being less than 10 minutes. On the other hand, temperature of higher than 190° C. is not preferable since such a higher temperature may change the quality of the coating film. Further more, in the event that a required time for drying becomes longer than 30 minutes, productivity of the film comes to be decreased.

According to a third aspect of the invention, there is provided a filling structure as set forth in the second aspect of the invention, wherein the adhesive has a property that the adhesive expands in volume by at least 10% in the process of melting, expanding and curing.

In the event that the coefficient of volume expansion is less than 10%, a gap becomes too small at a stage where the filling material with the adhesive is inserted into the hollow member, and hence the insertion becomes difficult, decreasing the working efficiency. Then, it becomes important to secure an appropriate amount of gap by increasing the volume expansion coefficient.

According to a fourth aspect of the invention, there is provided a filling structure as set forth in the first, second or third aspect of the invention, wherein the adhesive is a sheet-like adhesive.

According to the first aspect of the invention, the filling material is fixed to the hollow member using the adhesive which expands when heated. The adhesive firmly sticks to the surface of the filling material in the process of expansion. Even if there are a number of pores in the surface of the filling material, the adhesive is joined properly to the filling material. Similarly, the adhesive firmly sticks to an inner part surface of the hollow member in the process of expansion. Even if the inner part surface of the hollow member is irregular, the adhesive is joined properly to the hollow member.

As result, the filling material can be fixed rigidly to the hollow member.

According to the second aspect of the invention, since the adhesive is adopted which has the property that the adhesive melts and expands by being heated for 10 to 30 minutes at a temperature of 140° C. to 190° C. and sets when cooled thereafter, the adhesive is allowed to melt, expand and set in the process of drying the coating film in a drying oven after the electro-deposition coating. As a result, there is provided an advantage that the process of the adhesive can be implemented by making use of the existing drying oven without providing an additional heating unit.

According to the third aspect of the invention, since the adhesive is adopted which has the property that the adhesive expands in volume by at least 10%, in a case where an adhesive is additionally provided in a filling material, so that the filling material is then inserted into a hollow member, a gap in a sufficient size can be secured between the hollow member and the filling material. As a result, a treatment liquid is allowed to easily flow between the hollow member and the filling material while a corrosion protection treatment is being carried out so as to ensure the formation of a film to which the corrosion protection treatment has been applied, thereby making it possible to secure the corrosion resistance on the inner part surfaced of the hollow member.

According to the fourth aspect of the invention, since the sheet-like adhesive is adopted, the handling of the adhesive becomes easy, and a required size of adhesive can be affixed to a required location on the filling material in an easy fashion.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a filling structure according to the invention.

FIG. 2 is an enlarged view of a portion indicated by reference numeral 2 in FIG. 1.

FIG. 3 is a flow diagram illustrating the manufacture of the filling structure of the invention.

FIG. 4 is a cross-sectional view of a hollow member after a filling material according to the invention has been inserted thereinto.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, a best mode for carrying out the invention will be described based on the accompanying drawings.

FIG. 1 is a cross-sectional view of a filling structure according to the invention, and a filling structure 10 is a structure in which a filling material 12 having a higher impact energy absorbing performance is inserted into the inner part of a hollow member 11 whose inner part surface is provided with a layer to which a corrosion protection treatment is applied, and the filling material 12 is fixed to the hollow member 11 with an adhesive layer 13 which results when the filling material 12 expands by being heated and sets thereafter.

The hollow member 11 is an extruded material produced by extruding a metallic ingot, a pressed product obtained by applying a plastic working on a sheet metal with a pressing machine, or a tubular member obtained in other manufacturing methods. An aluminum alloy, zinc alloy, iron alloy or other materials can be adopted as a metal for the sheet metal.

An expanded aluminum having a bulk density of in the order of 0.6 g/cm³ is preferred for use for the filling material 12.

FIG. 2 is an enlarged view of a portion indicated by reference numeral 2 in FIG. 1. Since the bulk density of the filling material 12 is in the order of in the order of 0.6 g/cm³, the ratio of void pores 14 is extremely large. Due to this, there exist a number of cavities 15 . . . in the surface of the filling member 12. The adhesive layer 13 enters these cavities 15 via the normal corrosion protection treated layer 11a and is then joined to the filling material 12 rigidly.

In addition, while, in the event that the hollow member is an extruded material, there is provided a high flatness, in the event that the hollow member is produced using the other methods, minute recessed portions 16 are likely to be generated. These recessed portions 16 enter the adhesive layer 13, and the adhesive layer 13 sticks firmly to the hollow member 11.

As a result, the filling material 12 can be fixed to the hollow member 11 rigidly by virtue of the existence of the adhesive layer.

Next, a method for manufacturing the filled structural member that is constructed as has been described heretofore will be described below.

FIG. 3 is a flow diagram illustrating the manufacture of the filled structural member according to the invention.

In FIG. 3A, the hollow member 11 is prepared. The hollow member 11 is, for example, an extruded material of aluminum alloy whose thickness is 1.7 mm (A6063-T5).

In FIG. 3B, the filling material 12 is prepared.

In FIG. 3C, sheet-like adhesives 17 . . . are affixed to the filling material 12.

The sheet-like adhesive 17 is such as to have a property that the adhesive melts and expands when heated for 10 to 30 minutes at 140° C. to 190° C. and sets when cooled thereafter, and the High-modulus Melt Seal Tape No. 5231 (a trade name) can be adopted therefor.

In FIG. 3D, the filling material 12 with the sheet-like adhesive 17 is inserted into the hollow member 11. A cross-sectional view will be shown next of the hollow member 11 resulting after the filling material 12 with the sheet-like adhesives 17 has been inserted thereinto.

FIG. 4 is a cross-sectional view of the hollow member after the filling material has been inserted thereinto, and while there has been provided no description of this, cross-sectional dimensions of the hollow member 11 and the filling material 12 and the thickness of the sheet-like adhesive 17 are determined such that a gap 18 is allowed to exist between the sheet-like adhesives 17 and the inner part surface of the hollow member 11.

It can be said that since the gap 18 so exists, the easy insertion of the filling material 12 with the sheet-like adhesives 17 into the hollow member was attained.

Note that it is desirable to temporarily fasten the filling material 12 with temporal fastening bolts 19, 19 in order to maintain the gap 18.

Although not shown, the hollow member 11 and the like in this state are then loaded in the corrosion protection treatment process for application of a corrosion protection treatment thereto. As this occurs, since a corrosion protection fluid passes through the gap 18, a corrosion protection treatment can be applied uniformly to the exterior and inner part surfaces of the hollow member 11.

If needed, coating (in the event that the electrode position coating was effected as a prime coating, then for an intermediate coating and/or a finish coating) is applied to the hollow member 11.

Then, the hollow member 11 is put in the drying oven so as to be heated for 10 to 30 minutes at the temperature of 140° C. to 190° C. By this heating, the coating film is dried to set and the sheet-like adhesive 17 melts and expands, and the sheet-like adhesive 17 is then allowed to set when cooled thereafter. The volume of the sheet-like adhesive 17 expands by 10% or more so as to fill the gap 18.

The filling structure 10 shown in FIG. 1 can be obtained by removing the temporal fastening bolts 19, 19 after the cooling has been completed.

Note that while the filling structure according to the invention is preferred for application to vehicle body frames such as vehicular bumpers, front side beams, pillars and the like, the application thereof is not limited thereto.

In addition, according to the first aspect of the invention, the type of the adhesive (melting temperature, expansion coefficient, liquid/sheet) can be set arbitrarily.

According to the second embodiment, the adhesive may be in the form of liquid or solid, and in the event of solid, the adhesive may be in the form of sheet or powder.

The filling structure according to the invention is preferred for application to the body frames of the vehicle.

Claims

1. A filling structure comprising a hollow member and a filling material filled in the inner part of the hollow member, the filling material having a higher impact energy absorbing performance, wherein the filling material is fixed to the hollow member with an adhesive having a property that the adhesive expands when heated.

2. A filling structure as set forth in claim 1, wherein the adhesive has a property such that the adhesive melts and expands by being heated for 10 to 30 minutes at a temperature of 140° C. to 190° C., and cured after cooling.

3. A filling structure as set forth in claim 2, wherein the adhesive has a property that the adhesive expands in volume by at least 10% in the process of melting, expanding and curing.

4. A filling structure as set forth in claim 1, wherein the adhesive is a sheet-like adhesive.

5. A filling structure as set forth in claim 1, wherein the heating of the adhesive is attained using drying heat applied after electro-deposition coating.

6. A filling structure as set forth in claim 2, wherein the adhesive is a sheet-like adhesive.

7. A filling structure as set forth in claim 2, wherein the heating of the adhesive is attained using drying heat applied after electro-deposition coating.

8. A filling structure as set forth in claim 3, wherein the adhesive is a sheet-like adhesive.

9. A filling structure as set forth in claim 3, wherein the heating of the adhesive is attained using drying heat applied after electro-deposition coating.

10. A filling structure as set forth in claim 4, wherein the heating of the adhesive is attained using drying heat applied after electro-deposition coating.