JP2005321018A - Rivet and joining method using rivet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rivet, imparting favorable corrosion resistance to a joining part by a rivet, and a jointing method using the rivet. <P>SOLUTION: In this rivet 1, a film 3 made of resin molten by predetermined heating treatment and hardened at room temperature is formed on the head part 2a. After the superposed members to be joined are joined, heating treatment is performed within a temperature range of 140 to 200°C about 5 to 20 minutes, thereby melting the resin film 3 to flow in between the rivet 1 and a joined material. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a joining technique using a rivet, and can be suitably used for a rivet that can be joined without impairing corrosion resistance at a joint, and a joining method using such a rivet, particularly a vehicle body such as an automobile. The present invention relates to a joining method.

Conventionally, as one of the mechanical joining methods, joining with rivets has been put into practical use and widely applied to steel plates, aluminum plates, and the like (for example, see Patent Document 1).
Japanese National Patent Publication No. 8-5087

  In such rivet joining, for example, when the material of the rivet is carbon steel, there is a fear of electric contact when attempting to join a metal plate other than steel. For this reason, it is necessary to prevent rust by applying electrodeposition coating, but there is a problem that sufficient corrosion resistance cannot be obtained because there is a gap at the interface between the rivet and the material to be joined and the coating film becomes thin. doing. Moreover, the phenomenon that rust is generated from the edge portion of the rivet head is also a problem.

  In the present invention, it is possible to apply coating in a later process from the viewpoint of rust prevention, decoration, or appearance, as in the case of conventional rivet bonding, particularly when the material of the rivet and the material of the material to be joined are different from each other. The present invention has been made in order to solve the above-mentioned problems in rivet joining as required, and the object is to provide a rivet capable of imparting good corrosion resistance without generating a gap in the joining part by the rivet. Another object is to provide a joining method using such rivets.

  In order to achieve the above object, the present inventors have made extensive studies on the coating method and coating composition, and as a result, formed a resin film in advance on the head of the rivet, and performed heat treatment after joining, The present inventors have found that the above-mentioned object can be achieved by melting the glass, and have completed the present invention.

  The present invention is based on the above knowledge, and the rivet of the present invention has a film made of a resin having a property of melting at a predetermined heat treatment and curing at room temperature. It is characterized by.

  Further, in the joining method of the present invention, the stacked materials to be joined are joined to each other using the rivet of the present invention, that is, the rivet having the resin film on the head, and then formed on the head of the rivet by heat treatment. In order to solve the above-mentioned problems in the prior art described above, the resin film is melted and allowed to flow into the gap formed between the rivet and the material to be joined. It is characterized by having made it.

According to the present invention, while being heated and melted at a predetermined processing temperature, a material to be bonded is overlapped and bonded by a rivet formed on the head with a resin film having a property of curing at room temperature, After that, by applying a heat treatment, the resin film formed on the rivet head is melted and flows into the gap between the rivet and the material to be joined. A resin layer can be formed.
When the heat treatment is finished and the temperature drops to room temperature, the resin hardens, there is no gap between the rivet and the material to be joined, and the coating thickness by electrodeposition coating is made uniform, improving the corrosion resistance. Can be made. Further, since the resin contributes to the reinforcement of the joint portion, it is possible to ensure good joint reliability.

  Hereinafter, the joining method using the rivet together with the rivet of the present invention will be described in more detail. In the present specification, “%” means mass percentage unless otherwise specified.

  FIG. 1 shows an example of the shape of a rivet according to the present invention. A rivet 1 shown in the figure is obtained by forming a resin film 3 on a head 2a of a metallic rivet main body 2, for example, FIG. 2, the resin film 3 can be formed by immersing the head 2 a of the rivet body 2 in the molten resin bath B.

The metal material constituting the rivet body 2 is not particularly limited. In addition to iron-based materials such as carbon steel, alloy steel, and stainless steel, a wide range of materials such as copper-based alloys and aluminum-based alloy materials may be used. it can.
In FIG. 1, a self-piercing rivet is shown as the rivet 1 of the present invention. However, the present invention is not limited to the self-piercing rivet. Can be applied.

Further, the resin film may be formed not only by the immersion method shown in FIG. 2, but also by applying a resin with an appropriate spray device or coater.
The film thickness at this time is preferably applied so as to be in the range of 0.5 to 2.0 mm in a cured state. That is, if the thickness of the resin film is less than 0.5 mm, not only is it difficult to form the resin film uniformly, but the amount of resin flowing between the rivet and the material to be joined is insufficient due to the heat treatment, On the other hand, there is a possibility that the gap cannot be sufficiently filled. On the other hand, when the thickness of the resin film exceeds 2.0 mm, the rivet driving property tends to be impaired.

  As the resin material for forming the resin film, it is desirable to use, for example, a resin material containing an EVA (ethylene-vinyl acetate copolymer) resin, a rubber-based resin, and carbon.

The EVA resin has excellent adhesiveness, heat fluidity, flexibility, low temperature characteristics, and compatibility, and is a component that is a main component of the resin film.
The EVA resin is obtained by polymerization of an ethylene monomer and a vinyl acetate monomer, and examples thereof include polymerization methods such as solution polymerization and radical polymerization. Preferably, it is solution polymerization in which molecular weight control can be easily performed, and conventionally known Can be used. The ratio of the ethylene segment to the vinyl acetate segment in the EVA resin is preferably a charging ratio (blending ratio) at the time of polymerization, and the vinyl acetate monomer is 10 to 30 parts by weight per 100 parts by weight of the ethylene monomer. When the charging ratio of vinyl acetate monomer is 10 parts by weight or more with respect to 100 parts by weight of ethylene monomer, an EVA resin having excellent adhesion and flexibility can be obtained, and the charging ratio of vinyl acetate monomer is 30%. If it is at most parts, an EVA resin having excellent creep resistance and compatibility can be obtained.

  The number average molecular weight of the EVA resin is preferably 5000 to 50000. If the number average molecular weight is 5000 or more, the EVA resin exhibits excellent adhesiveness, and if the number average molecular weight is 50000 or less, EVA The resin exhibits excellent heat fluidity and flexibility. The number average molecular weight of the EVA resin can be easily measured by gel permeation chromatography (GPC).

  The rubber-based resin is added to impart elasticity and tackiness, and examples thereof include styrene-butadiene rubber, styrene-isoprene rubber, and butadiene rubber, and styrene-butadiene rubber is preferable. The addition amount of the rubber-based resin is preferably in the range of 10 to 100 parts by weight with respect to 100 parts by weight of the EVA resin. If the addition amount of the rubber resin is 10 parts by weight or more with respect to 100 parts by weight of the EVA resin, a resin film having excellent adhesiveness can be obtained, and the addition amount of the rubber resin is 100 parts by weight or less. If it is, the resin film which has the outstanding storage stability can be obtained.

The carbon is added in order to impart conductivity to the resin film in order to adhere the coating film during electrodeposition coating in a later step. For example, carbon black or graphite may be used. it can. The amount of carbon added is preferably 5 to 50 parts by weight with respect to 100 parts by weight of the EVA resin. If the amount of carbon added is 5 parts by weight or more with respect to 100 parts by weight of the EVA resin, sufficient conductivity to enable electrodeposition coating can be imparted to the resin film, and the amount of carbon added is If it is 50 parts by weight or less, the resin film exhibits excellent adhesiveness.
In this way, carbon is added in order to impart conductivity to the resin film in consideration of electrodeposition coating. Therefore, coating by methods other than electrodeposition coating, such as spray coating or roll coater coating, is used. When performing the above, it is not always necessary to add carbon to the resin film.

Moreover, as a physical property of the said resin film, about melt viscosity, it is desirable that it is 5000-100000 mPa * s in heat processing temperature, for example, the temperature range of about 140-200 degreeC. That is, by setting the melt viscosity of the resin film within this range, even when the top and bottom are reversed, the molten resin can flow between the rivet and the material to be joined without dripping, and fill the gap. It becomes possible.
In addition, although the said resin film melt | dissolves in the heat processing temperature range as mentioned above, and shows the said viscosity, when the temperature falls to room temperature, ie, 25 degreeC, it is calculated | required that it is hardened | cured. .

In the joining method of the present invention, after joining the joined materials using the rivet of the invention, the resin film formed on the head of the rivet is melted by heat treatment, and the rivet and the joined material are joined. Although it is made to flow in the clearance gap formed in between, as heat-processing conditions at this time, it is desirable to make it heat for about 5 to 20 minutes in the temperature range of 140-200 degreeC.
In addition, a to-be-joined material is not limited only to 2 sheets overlap, It can apply to 3 sheets overlap, 4 sheets overlap, or more lap joints.

  Moreover, about the said heat processing, after joining a to-be-joined material with the said rivet, when the above coating by electrodeposition coating or spraying is given, the heat at the time of the baking process of the said coating film is utilized. In other words, it is efficient to combine the heat treatment for melting the resin film on the rivet head and flowing it into the gap between the rivet and the material to be joined, and the baking treatment for the coating film, which is a manufacturing cost. From the point of view is desirable.

  Hereinafter, the present invention will be specifically described based on examples. In addition, this invention is not limited only to these Examples.

A self-piercing rivet main body 2 (5 mm diameter × 6.5 mm length) as shown in FIG. 2 was formed from a low carbon steel wire (equivalent to SCM435).
As the EVA resin, the charging ratio of the vinyl acetate monomer is 20 parts by weight with respect to 100 parts by weight of the ethylene monomer, and 50 parts by weight of styrene-butadiene rubber is contained as a rubber-based resin with respect to 100 parts by weight of the EVA resin. Further, by immersing the head portion 2a of the rivet body 2 in a molten bath B of resin containing 20 parts by weight of carbon with respect to 100 parts by weight of EVA resin, the resin film 3 is applied to the head portion 2a. Was formed to a thickness of 1.0 mm to obtain a self-piercing rivet 1 as shown in FIG. As a result of separately examining the melt viscosity of the resin, it was 35000 mPa · s at 170 ° C.

Next, two 50 mm × 100 mm × 1.5 mm aluminum alloy sheets made of A2014P defined by JIS H 4000 were prepared and joined in the longitudinal direction using the self-piercing rivet 1.
The obtained rivet joint was electrodeposited using a cationic electrodeposition paint, washed with water and baked at 170 ° C.

  After baking of the coating film, the temperature of the rivet joint is lowered to room temperature, and the periphery of the rivet 1 is visually observed, and the joint is cut along the axis of the rivet 1 to obtain a cross section. As a result of inspection, it was confirmed that the resin film 3 formed on the rivet head 2a melted and flowed into the gap with the specific bonding material. However, it was found that a good painting was made.

It is a longitudinal cross-sectional view which shows an example of the rivet of this invention. It is explanatory drawing which shows an example of the manufacturing method of the rivet of this invention.

Explanation of symbols

1 rivet 2 rivet body 2a head 3 resin coating

Claims (7)

  A rivet characterized in that a resin film having a property of being melted by heat treatment and cured at room temperature is formed on the head.   The rivet according to claim 1, wherein the resin film has a thickness of 0.5 to 2.0 mm.   The rivet according to claim 1 or 2, wherein the resin film includes an EVA resin, a rubber-based resin, and carbon, and is made of a resin having conductivity.   The rivet according to any one of claims 1 to 3, wherein a melt viscosity of the resin film at a heat treatment temperature is 5000 to 100,000 mPa · s.   A joining method using the rivet according to any one of claims 1 to 4, wherein after joining the materials to be joined using the rivet, heat treatment is performed to melt the resin film. Letting it flow between the rivet and the material to be joined.   The bonding method according to claim 5, wherein a temperature of the heat treatment is 140 to 200 ° C.   The joining method according to claim 5 or 6, wherein the heat treatment also serves as a treatment for baking a coating film formed on the material to be joined or a member assembled using the material to be joined. .

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