Joining structure of resin parts

Details Joining structure of resin parts Joining structure of resin parts

2002-03-21

2004-03-16

Thomas, Alexander S. (Department: 1772)

Stock material or miscellaneous articles

Sheets or webs edge spliced or joined

Sheets or webs coplanar

C428S058000

Reexamination Certificate

active

06706357

ABSTRACT:

INCORPORATION BY REFERENCE
The disclosure of Japanese Patent Application No. 2001-088919 filed on Mar. 26, 2001 including the specification, drawings and abstract is incorporated herein by reference in its entirety.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates generally to a joining structure in which two or more resin parts are joined together to form an integral resin product or article, and more particularly to a joining structure of resin parts which are joined together by friction welding, such as orbital welding, that utilizes heat generated by friction between joining members (i.e., the resin parts). In particular, the invention is concerned with a technique for preventing fragments of the resin parts dispersed or scattered during frictional movements thereof from entering the inside of the resulting resin product.
2. Description of Related Art
In these days, various types of resin parts have been used in a wide range of industrial or technical fields. Some of the resin parts have a final shape or configuration that is too complicated to be achieved only solely by molding. In other cases in which another member or component is mounted within a resin structure, for example, a plurality of sections to be finally integrated into a single resin structure are formed by molding, and are then joined together into the final structure.
Various methods of integrating resin parts have been proposed and actually practiced. These methods can be systematically classified into some groups as shown in FIG.
6
. More specifically, resin joining methods are roughly classified into “bonding”, “mechanical fastening or clamping”, “welding”, and “insert”. A technology for joining two members by use of friction, to which the invention pertains, belongs to the “welding” category, and more particularly to “thermal welding”. The “thermal welding” is classified into “external heating” and “internal heating”. The technology to which the invention relates belongs to “internal heating”, and more particularly to “friction welding”, such as “ultrasonic welding”, “vibration welding”, “orbital welding” and “spin welding”, with which parts are joined into a product or an article by utilizing frictional heat.
Among various parts of a fuel supply system of a vehicle engine, for example, certain products, such as a fuel pump and a fuel filter, are more likely to be mounted within a fuel tank so as to satisfy fuel vapor gas regulations in recent years, though they were conventionally mounted outside the tank. Upon final assembling of these parts, the above-indicated products may be subjected to a drying process after mounted within the tank, and therefore the products are required to be highly resistant to heat having a temperature that is much higher than that required in the case where the products are mounted outside the tank. To meet this requirement, the products need be made of materials having high heat resistance, including, for example, reinforced resins, such as PA resin, into which glass fibers, or the like, are mixed. In addition to the products or parts located inside the tank, products or parts located outside the tank are also desired to be made of materials having higher heat resistance, in order to achieve improved durability of the fuel supply system.
Among various friction welding technologies as described above, orbital welding, in particular, is suitably employed for joining parts made of resin having high heat resistance. The basic principle of the orbital welding for joining two parts is illustrated in
FIGS. 7A
,
7
B and
7
C. More specifically, one of the two parts undergoes minute circular vibratory motions in a horizontal plane (i.e., in a plane of abutting surfaces of the two parts) while the one part is pressed against the other part, so that the two parts are welded to each other with fused resin between their abutting surfaces. As shown in
FIG. 7A
, a member A is placed on a member B that is held stationary. Then, the member A is subjected to minute circular vibrations while being pressed against the member B, as shown in FIG.
7
B. At this time, the vibrations occur in a plane (i.e., a plane of the abutting surfaces), causing friction of a constant velocity at the abutting surfaces, thus permitting uniform welding. As a result, heat generated by the friction normally fuses the abutting surfaces of the parts in several seconds, and the parts are automatically positioned at their positions where the vibrations stopped. After holding the parts under pressure for one to two seconds, during which resin solidifies, the welding process is finished. In this manner, a welded product as shown in
FIG. 7C
is completed.
The orbital welding is carried out in the manner as described above, and is particularly advantageous in the following six points:
1. The orbital welding enables joining of parts having various shapes, allowing an increased freedom in the shape or design of the parts.
2. The abutting surfaces of the parts are uniformly welded.
3. The resin part to be welded may include a flange having a small width, permitting a burr to be uniformly formed upon welding.
4. The strength of the welded portion is stable.
5. An acceleration G that appears during welding due to constant-velocity motion of the resin part is 10G or smaller, causing almost no stress to the base on which the parts are mounted.
6. The orbital welding can be employed for a wide range of materials, including those having high heat resistance.
Thus, the orbital welding is suitably employed for joining two members when producing various parts to be installed on vehicles as described above.
FIGS. 8A-8C
illustrate a typical example in which two parts are joined together by orbital welding. More specifically, a lower member
30
has a flange
31
that is formed with an upper protrusion
32
to be welded, and an inside projecting wall
33
and an outside projecting wall
34
are formed on the opposite sides of the upper protrusion
32
to thus form an inside groove
35
and an outside groove
36
. On the other hand, an upper member
37
to be welded and fixed onto the first member
30
has a flange
38
that is formed with a lower protrusion
39
to be welded. As shown in
FIG. 8A
, the first member
30
and the second member
37
are assembled together such that the lower protrusion
39
of the second member
37
abuts on the upper protrusion
32
of the first member
30
.
Next, according to the orbital welding method as shown in
FIGS. 7A
,
7
B and
7
C, the upper member
37
is subjected to minute circular vibrations while being pressed against the lower member
30
. At this time, minute fragments of the resin parts are produced at abutting portions of the upper protrusion
32
and the lower protrusion
39
where frictional vibrations occur. The properties of the fragments vary depending upon the material of the parts to be welded, degree of frictional vibrations, pressing force, and so forth. In any event, the size of the fragments decreases as the heat resistance and rigidity of the welded material increases. In particular, a large number of fragments are likely to be produced when a reinforced resin, such as PA resin, containing glass fibers is used. As shown in
FIG. 8B
, many of the fragments
40
produced due to the vibrations fall into the inside groove
35
and the outside groove
36
formed on the opposite side of the upper protrusion
32
, but part of the fragments
40
pop out of the inside groove
35
and the outside groove
36
, overpassing the inside projecting wall
33
and the outside projecting wall
34
, respectively. If the product in question is in the form of a container, fragments that pass the inside projecting wall
33
enter the interior of the container.
Upon completion of the welding process in which minute circular vibrations are applied as described above, a welded product as shown in
FIG. 8C
is provided. When this product is moved or in use, the fragments
40
accumulated in the bottoms of the inside groove
35
and the outside groove
36
may fall out

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