JPS6161965B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for joining resin parts, and particularly to a method for joining two resin parts by welding, which increases the joining strength between the two and does not cause external burrs. The present invention relates to a method for improving the appearance.

Conventionally, various welding methods such as hot air welding, friction welding, and ultrasonic welding have been used to join two resin parts together. A major challenge was how to increase the bonding strength between the two.

In addition, burrs or whiskers that occur during bonding are generally considered unavoidable, and these substances can impair the appearance, adversely affect functionality, etc.
This significantly reduced the commercial value of the finished bonded product.

For example, in FIG. 1, a resin component 4 having an end surface 2 and a resin component 8 having an end surface 6 are friction welded by bringing their end surfaces 2 and 6 into contact with each other as shown in FIG. 2, and sliding them in the longitudinal direction. 3.
As shown in the figure, as the joint surfaces of both are heated and melted, burrs 10 are emitted to both sides, and when the bonding is completed (Figure 4), a large amount of burrs 10 are generated, spoiling the appearance of the product. There are also cases where the product's functionality is affected.

Furthermore, when these two resin parts are made of different materials, the physical properties (melting point, crystallinity, polarity, etc.) of the two parts will inevitably differ, so it is necessary to simultaneously melt and bond their joint surfaces. Therefore, it was necessary to take some measures for bonding.

For example, in JP-A No. 53-86772, when joining two resin parts made of different materials, a first part made of a material that can be ultrasonically welded and a second part made of another material. is placed in the joining position, a third part made of the same material as the first part is placed in engagement with the second part and in contact with the first part; A method has been proposed in which the second part is fixed (joined) to the first part through the third part by ultrasonic welding the part and the third part. .

However, none of the various joining methods that have been proposed to date are yet satisfactory, and in particular when it comes to joining dissimilar materials, it is not possible to directly join those dissimilar materials; Since a joining structure is adopted through a third part, etc., the number of parts is large, the number of man-hours for assembling them is also increased, and the problem of preventing burrs from occurring remains unsolved.

Here, the present invention effectively increases the bonding strength between the two resin parts by a predetermined welding operation, and does not cause external burrs or damage the appearance. To provide a joining method, in particular, to join parts made of different materials without intervening a third part.
The purpose is to provide a method that can be performed directly.

In order to achieve such an object, the present invention provides a method for providing a recess in the joining surface of the first resin part when joining the first resin part and the second resin part by welding. , by providing a protrusion that is inserted into the recess and having its tip abutted against the bottom of the recess on the joint surface of the second resin part, and performing a predetermined welding operation, these two parts can be welded together. The protrusion is held in the recess by softening or melting of the joint surfaces of the resin parts, and the other resin is attached to at least one side of the joint surface of one of the resin parts. This is characterized by the provision of ribs that protrude toward the parts to prevent softened or melted resin from being pushed out laterally at the joint surfaces of the parts.

Thus, according to the present invention, the joint strength between the two parts can be effectively increased by the interlocking of the recess and the protrusion, and the recess and the protrusion can be separated from each other. The ribs prevent burrs generated when welding the joining surfaces of two resin parts together to the outside, so that damage to the appearance caused by burrs can be effectively eliminated. The presence of the rib makes it possible to reliably position the two resin parts. In addition, this configuration fully exhibits its characteristics particularly when joining parts made of different materials.

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

First, in FIG. 5, an oval recess 16 is provided in the longitudinal direction of the joint surface 14 of the lower resin part (first resin part) 12, and an oval recess 16 is provided on both edges in the longitudinal direction. Ribs 18 are erected at predetermined intervals A along each side. On the other hand, a protrusion 26 is provided on the joint surface 24 of the upper resin part (second resin part) 22, and the protrusion 26 is inserted into the recess 16 so that its tip 28 is inserted into the recess 16.
It is adapted to be brought into contact with the bottom part 30 of. (See FIG. 6) The size B of the resin component 22 in the width direction is equal to or slightly smaller than the spacing A. Here, the material of the resin part 22 is, for example, polypropylene (PP), and the material of the other resin part 12 is ABS resin, which has a slightly higher melting point than the PP.

Therefore, when friction joining these two resin parts 12 and 22, the protrusion 26 is inserted into the recess 16, and the tip 28 of the protrusion 26 is inserted into the bottom 30 of the recess 16.
At the same time, with the width B of the resin part 22 fitted within the interval A of the ribs 18 of the resin part 12 (Fig. 6), welding by friction welding is performed by reciprocating the resin part 22 in its longitudinal direction. It will be added. The frictional heat generated by this operation first heats the tip 28 and the bottom 30, and joins the protrusion 26 made of a resin material (PP) with a slightly lower melting point than the recess 16. The surfaces are melted, and a molten material produced by the melting, the so-called burr 32, fills the lower part of the recess 16, and then the joint surfaces 14 and 24 are pressed and rubbed, and the seventh
As shown in the figure, the burr 34 enters the inner cavity, but is blocked by the rib 18 and does not flow out to the outside.

On the other hand, the resin part 12 made of ABS resin material whose melting point is slightly higher than that of PP is melted or softened later than the resin part 22. Due to the action of the pressing force and the sliding action, the recess 16 is deformed into a shape with a bulge that widens inward as shown in FIG. 8, and the protrusion 26 is similarly deformed.
meshes with the swelling part 36 of both resin parts 12,
22 will be firmly integrated.

Therefore, according to such a joining method, the protrusion 26 of the resin part 22 enters the recess 16 of the resin part 12, melts and deforms each other, cools and solidifies, and the so-called anchor effect causes the two to be joined together. Since the bonding strength between the parts can be significantly increased, the bonding surfaces 14, 2 are flat.
Even if there is no welding action between the two parts, it is possible to reliably join them together.

In addition, the existence of the ribs 18 on both sides can completely prevent burrs generated from the welded portion from coming out, so there is no risk of damaging the appearance of the product, and the design can be improved. Furthermore,
The presence of the ribs 18 also provides the effect of accurately positioning the two parts when they are joined.

In particular, such a joining method has the great advantage that direct joining between resin parts made of different materials can be reliably and easily made.

In addition, in the above-mentioned embodiment, both resin parts 1
Although only an example in which the width dimensions of resin parts 2 and 22 are different is shown, the present invention is not limited to this in any way, and as shown in FIG. It is. In this case, in the resin part 40 in the upper part of FIG. 9, a notch 44 that is approximately the same in shape as the rib 42 is provided at a position corresponding to the rib 42, and the rib 42 is accommodated in this notch 44 when welding is completed. It is desirable to avoid creating gaps.

Also, as in the previous example, there is a protrusion on the upper resin part,
Although it is preferable that the lower plastic part is provided with a recess, this is not necessarily important and as shown in FIG. 10, the upper plastic part 50
The present invention can also be applied to a type of joint in which a recess 52 is provided on the lower resin part 54 and a protrusion 56 and a rib 58 are provided on the lower resin part 54.

Furthermore, in the example, the rib 18 is connected to the resin part 12.
Although an example in which the ribs according to the present invention are provided on both sides of the joint surface 14 of the resin component 22 is shown, the ribs according to the present invention may be provided on both sides of the joint surface 24 of the resin component 22, or on either side of the joint surface 24 of the resin component 22. It may be provided only on the side of the.

In addition to the case where the resin part 12 is made of ABS resin and the resin part 22 is made of PP, the former is made of PP.
Therefore, the latter can be made of ABS resin, and there is no problem even if both are made of the same material, and the fitting shape of the two is also an oval recess 16, In addition to the combination of the protrusions 26, any combination of rectangular or other shaped recesses and protrusions may be used. Further, as the welding method, in addition to friction welding, methods such as hot air welding and ultrasonic welding can also be adopted.

It goes without saying that various modifications and improvements can be made to the present invention based on the knowledge of those skilled in the art without departing from the spirit of the present invention.

[Brief explanation of the drawing]

FIG. 1 is an explanatory view (perspective view) showing a conventional joining method for resin parts, and FIGS. 2 to 4 are cross-sectional explanatory views showing the joining process according to the joining method. FIG. 5 is a perspective view showing a combined state of two resin parts to which the method of the present invention is applied;
8 to 8 are cross-sectional explanatory diagrams showing the joining process according to each joining method. FIGS. 9 and 10 are cross-sectional views of two resin parts before being joined, illustrating different embodiments of the method of the present invention. 12,50: Resin part (first resin part), 1
4, 24: Joint surface, 16, 52: Recess, 18, 4
2, 58: rib, 22, 40, 54: resin part (second resin part), 26, 56: protrusion, 28: tip, 30: bottom.

Claims (1)

[Claims] 1. When joining a first resin part and a second resin part by welding, a recess is provided in the joint surface of the first resin part, and a recess is inserted into the recess. By providing a protrusion whose tip comes into contact with the bottom of the recess on the joint surface of the second resin part and performing a predetermined welding operation, the joint surface of the two resin parts is softened. or, the protrusion is held in the recess by melting, and a rib protrudes toward at least one side of the joint surface of one of the resin parts toward the other resin part. 1. A method for joining resin parts, characterized in that softened or melted resin is prevented from being extruded laterally at the joint surfaces thereof. 2. The two resin parts are each made of different resin materials, and the resin material forming the first resin part in which the recess is provided has a melting point lower than that of the resin material forming the second resin part. A method according to claim 1, wherein the method is high. 3. The method according to claim 1 or 2, wherein the welding operation is friction welding.