JPH043734B2 - - Google Patents

Description

[Detailed Description of the Invention] (Technical Field) The present invention can be used, for example, when a synthetic resin tank for a heater core of an automobile heater and a water pipe for water supply and drainage provided in this tank are joined in a liquid-tight manner. .

(Background Art) As means for liquid-tightly joining synthetic resin parts, methods using screws and O-rings, methods using adhesives, methods using heat welding, and the like are conventionally known. Among these methods, heat welding is a joining method in which a metal is interposed in the joint, the metal is heated by high-frequency induction heating, and the joining surfaces of thermoplastic synthetic resin parts are heated and welded, and the joining surfaces are strongly pressed together. BACKGROUND ART A method of joining synthetic resin parts together using a high frequency induction heating method is known, in which synthetic resin parts are joined together in a liquid-tight manner.

An example of such a joining method is the invention described in US Pat. No. 3,461,014. In this invention, when joining synthetic resin parts made of the same material, an adhesive mixed with ferromagnetic powder such as magnetic iron oxide is applied to the bonding surface, and this ferromagnetic powder is applied to a high-frequency induction heating coil. By generating heat, the joint surfaces of the synthetic resin parts to be joined are melted, and together with the action of the adhesive, the synthetic resin parts are strongly bonded together. However, according to the inventor's experiments, when attempting to generate heat using high-frequency induction heating for adhesives mixed with ferromagnetic powder, ultra-high-frequency induction heating of 2 to 27 MHz, which is popular in the United States, is effective. Although it is possible to generate sufficient heat with a coil, the high frequency induction heating coil of 100 to 450 KHz, which is popular in Japan, does not generate enough heat and cannot perform bonding.

Furthermore, as described in Japanese Patent Application Laid-open No. 48-49828, a wire mesh is interposed between the joint surfaces of synthetic resin parts, and the wire mesh is heated by high-frequency induction heating to melt the synthetic resin at the joint surface. There is a method of bonding by strongly pressing the bonding surfaces together. However,
This type of joining method works well when the joining area is relatively large, but when the joining area is narrow and the shape of the joining surface is relatively complex, such as an annular shape, such as when joining a pipe to a synthetic resin tank, The work of forming the wire mesh into a predetermined shape or properly aligning the wire mesh with the joint surface becomes troublesome. Furthermore, JP-A-53-
As described in Publication No. 58582, a method in which a heating conductor such as an iron wire is interposed at the joining part and the heating conductor is heated by high-frequency induction to melt and join the joining surfaces of synthetic resins, When hot water is repeatedly supplied to a joint such as a radiator or heater core, and the temperature rises and falls rapidly, the joint is likely to crack due to the difference in thermal expansion between the synthetic resin and the heating conductor, resulting in water leakage. This can easily cause a malfunction.

(Objective of the Invention) The present invention eliminates the above-mentioned disadvantages, makes it possible to perform good bonding using high-frequency induction heating coils that are widely used in Japan, and also allows the temperature of the bonded portion to rise and fall rapidly. The object of the present invention is to provide a method for joining synthetic resin parts that is unlikely to cause water leakage failure due to the occurrence of cracks even in such cases.

(Structure of the Invention) The method of joining synthetic resin parts of the present invention is to attach metal joining parts whose surfaces have been polished and cleaned and coated with a hot water-resistant rubber-modified thermosetting resin adhesive to the synthetic resin to be joined. A high-frequency induction coil is placed between the joining surfaces of manufactured parts, and is placed near the joining parts while lightly pressing the parts to be joined together with enough pressure that the joining surfaces and the surfaces of the joining parts come into close contact. energizes the bonding parts to generate high-frequency induction heat. When the resin on the joining surfaces melts due to this heat generation, the parts to be joined are strongly pressed together, the power supply to the high frequency induction coil is stopped, and the molten resin is held as it is until it cools and solidifies. As a result, the synthetic resin parts are firmly joined to each other, so the pressure is then released and the joined synthetic resin parts are taken out.

(Embodiments of the Invention) Next, the present invention will be explained in more detail by explaining the illustrated embodiments.

The illustrated embodiment shows a state in which a tank 1 made of a thermoplastic synthetic resin such as nylon and a liquid passage pipe 2 made of the same type of synthetic resin are bonded by the bonding method of the present invention. A cylindrical portion 4 that can be fitted into the liquid passage pipe 2 is formed at the peripheral edge of the through hole 3 that opens on the side surface (or the top and bottom surfaces) of the tank 1. An annular joining part 6 made of metal and having a surface coated with a hot water-resistant rubber-modified thermosetting resin adhesive is inserted into the annular groove 5 formed in the annular groove 5 .

The main metal material of the joining parts may be any metal that generates heat by high-frequency induction heating, and aluminum, copper, etc. can also be used, but iron is most preferable from the viewpoint of efficiency. Prior to applying the above-mentioned resin adhesive to the surface of the metal material, the surface of the metal material is polished and cleaned. For polishing, for example, alumina particles with a particle size of about 150 to 600 mesh are shot-peened. This can be easily done by tapping it on the surface of the metal material. Further, as a cleaning means, cleaning can be efficiently performed by immersing the roughened metal material in an organic solvent such as triclene solvent and applying ultrasonic vibration.
In this way, by polishing and cleaning the metal material, the oxide film and oil film on the surface of the metal material are removed, and when a resin adhesive is applied to the surface, the resin adhesive and the surface of the metal material become more compatible. and the bond strength increases. Examples of hot water-resistant rubber-modified thermosetting resin adhesives to be applied to the surface of metal materials include acrylonitrile rubber-modified phenolic resin adhesives (manufactured by Bostik Japan Co., Ltd., product names 1755 and 2300S).
etc.) can be used. After this adhesive is applied to the surface of the metal material, it is left to dry in an uncured state.

The joining part 6, whose surface has been treated in this manner and coated with a hot water-resistant rubber-modified thermosetting resin adhesive, is inserted into the groove 5 on the side of the tank as shown in the figure. The joining component 6 is primarily pressurized with a relatively light force between the bottom surface of the groove 5 and the end surface of the liquid passage tube 2 fitted onto the cylindrical portion 4 . The appropriate pressure during this primary pressurization is 0.5 to 5 Kg/cm ² , and this primary pressurization ensures that the surface of the joining component 6, the bottom of the groove 5, and the end surface of the liquid passage tube 2 are in good condition. When the joining component 6 generates heat due to high-frequency induction heating, this heat is well transmitted to the bottom surface of the groove 5 and the end surface of the liquid passage tube 2.

Next, with this primary pressure applied, a high frequency induction coil 7 provided near the joining parts 6 is energized,
By inducing a high-frequency induced current in this joining component 6, this component 6 is heated, and the bottom surface of the concave groove 5 in contact with the joining component 6 and the liquid passage pipe 2 are heated.
Melt the resin with the end face. The time for energizing the high-frequency induction coil 7 varies depending on various conditions such as the size of the parts to be joined, but for example, when joining a synthetic resin liquid passage pipe to a synthetic resin tank of an automobile heater core, it is 4 to 10 seconds. It is enough to turn on the electricity to a certain extent.

When the synthetic resin at the joint is melted by applying electricity to the high-frequency induction coil 7, secondary pressurization is performed to press the tank 1 and the liquid passage pipe 2 together with strong force, and after the electricity to the high-frequency induction coil 7 is stopped, , the molten resin remains in that state until it cools and solidifies. The holding time varies depending on various conditions such as the size of the parts to be joined, but when the above-mentioned automotive heater core is joined and allowed to cool naturally, 30 to 60 seconds is sufficient, and forced cooling methods such as cold air blowing are sufficient. If adopted, this retention time can also be shortened.

The appropriate pressure during secondary pressurization is 180 to 250 kg/ ^cm2 , but this secondary pressurization will
As the molten resins mix with each other, the resin adhesive on the surface of the joining part 6 strongly adheres to the metal material that makes up the main part of the joining part and the synthetic resin of the parts to be joined, and the molten resin cools and solidifies. After that, the tank 1 and the liquid passage pipe 2 are firmly joined.

The reason why strong pressure is not applied from the beginning during the bonding work is divided into primary pressurization using relatively weak pressure and secondary pressurization using strong pressure. That is, when the tank 1 and the liquid passage pipe 2 are pressed with strong pressure from the beginning, the molten resin is forcefully pushed out of the groove 5 as the joining part 6 generates heat, and the molten resin spreads over the entire joint surface. Water leakage may occur at the joints more frequently. On the other hand, if the joining parts 6 are made to generate heat under a weak primary pressure as in the present invention, the molten resin generated by this heating will spread evenly over the entire joining surface, and then Even when strong secondary pressure is applied, the molten resin does not disappear from a part of the joint surface, making it difficult for water to leak from the joint.

When synthetic resin parts are joined together in this manner, the joining parts, which are mainly made of metal, remain built into the joining part. Although the thermal expansion coefficients differ between the metal-based joining parts and the synthetic resin parts (tank 1, liquid passage pipe 2), there is a resin adhesive with rubber elasticity between the metal and the synthetic resin. Therefore, even if the temperature of the joining part changes significantly, the deviation between the joining surfaces of the metal and synthetic resin due to the difference in thermal expansion is absorbed by the rubber elasticity, and the gap between the joining parts and the synthetic resin is absorbed. There will be no peeling due to differences in thermal expansion, and no cracks will occur in the joints. Therefore, the joints between synthetic resin parts obtained by the method of the present invention have excellent durability and are resistant to breakage even during thermal cycles.

Next, experiments conducted by the present inventor to confirm the effects of the present invention will be described.

The experiment was conducted using a simple iron ring as a joining part (Comparative Example 1), and a case in which a hot water-resistant rubber modified thermosetting material was polished on the surface of the iron ring as a joining part without cleaning. A case where one coated with a resin adhesive was used (Comparative Example 2), and a case where the surface of the iron ring was polished and cleaned as a joining part, and a hot water-resistant rubber-modified thermosetting resin adhesive was used. The strength of the joint and the airtightness after thermal cycling were compared between the two cases (product of the present invention).

When we compared the bonding strength of the three above, we found that all of them had more than twice the strength (bending strength) of conventional products that bonded synthetic resin parts together using screws, which was sufficient. I understood something.

Next, when comparing the airtightness after applying a heat cycle, Comparative Example 1 was found to have insufficient airtightness. In addition, in the case of Comparative Example 2, Comparative Example 1
Although the airtightness was improved compared to the above, some specimens had poor airtightness due to repeated thermal cycles. In contrast, in the case of the products of the present invention, all test pieces exhibited sufficient airtightness even after repeated thermal cycles.

(Effects of the Invention) As described above, the method of joining synthetic resin parts of the present invention can easily and firmly join synthetic resin parts, and the synthetic resin products can be manufactured with excellent durability. can be obtained.

[Brief explanation of drawings]

The drawings are longitudinal sectional views showing embodiments of the present invention. 1: tank, 2: liquid passage pipe, 3: through hole, 4: cylindrical part, 5: groove, 6: joining parts, 7: high frequency induction coil.

Claims (1)

[Claims] 1 Metal joining parts whose surfaces have been polished and cleaned and coated with a hot water-resistant rubber-modified thermosetting resin adhesive are
A high-frequency induction device installed near the joining parts is clamped between the joint surfaces of the synthetic resin parts to be joined, and is primarily pressurized with such pressure that the joining surfaces and the surfaces of the joining parts are brought into close contact with each other. By energizing the coil, the joining parts are heated, and the synthetic resin parts on the joining surfaces of the synthetic resin parts in contact with the joining parts are molten, and the synthetic resin parts are subjected to secondary pressure with strong pressure. A method for joining synthetic resin parts in which the secondary pressure is released after the molten resin cools and solidifies after the high-frequency induction coil is stopped energizing.