JP2002174219A - Self-piercing rivet and fastening method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aluminum alloy self-piercing rivet preventing buckling at driving, and a fastening method using the self-piercing rivet. SOLUTION: This self-piercing rivet 1 is made of an aluminum alloy, and provided with a shaft portion 11 formed with a cutting edge portion 111 having a cutting edge function in a circumferential direction at a tip end, and a head portion 12 having a hole portion (an engaging means) for rotating the rivet 1. The fastening method comprises a first step wherein the rivet 1 is held to a rotating indenter by the hole portion 121, and the rivet 1 is driven in s fastened material while rotating the rivet by the rotating indenter; and a second step wherein the rivet 1 is further driven in the fastened material after stopping the rotations of the rivet 1. Since the first step driving the rivet 1 having the cutting edge function in the circumferential direction into the fastened material while rotating, pressing force added on the rivet 1 at driving can be decreased, so that buckling of the rivet 1 is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a self-piercing rivet made of an aluminum alloy and a fastening method using the self-piercing rivet. The self-piercing rivet and the fastening method of the present invention are particularly suitably used for fastening an aluminum alloy material.

[0002]

2. Description of the Related Art As a self-piercing rivet for fastening members made of an aluminum alloy, it is preferable to use an aluminum alloy self-piercing rivet from the viewpoint of recyclability and prevention of electrochemical corrosion.

[0003]

However, when a self-piercing rivet made of aluminum or the like is used instead of a conventional self-piercing rivet made of iron or the like, the strength of the aluminum alloy is generally lower than that of iron or the like. There is a problem that the part buckles and causes a joint failure. JP-A-9-
Japanese Patent Publication No. 317730 discloses a driving rivet provided with a tapered hole which expands at a shaft end side in a shaft portion of the rivet as one of the problems to be solved to prevent the buckling. But,
Since the prevention of buckling is performed by previously performing a heat treatment or the like on the driving rivet to improve the strength, there are problems such as complicated management of the heat treatment process and an increase in cost.

[0004] It is an object of the present invention to provide a self-piercing rivet made of an aluminum alloy in which buckling during driving is prevented. Another object of the present invention is to provide a fastening method using the above self-piercing rivet.

[0005]

According to the first aspect of the present invention,
A self-piercing rivet made of an aluminum alloy, comprising: a shaft portion having a cutting edge portion having a circumferential cutting edge function formed at a front end; and a head portion having an engagement means for rotating the rivet. It is characterized by the following.

According to a second aspect of the present invention, there is provided a fastening method using the self-piercing rivet according to the first aspect,
A first stage in which the rivet is held by a rotary indenter by the engaging means, and the rivet is driven into the material to be fastened while rotating; and the rotation of the rivet is stopped, and the rivet is further driven into the material to be fastened. And a second step.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to the drawings. The self-piercing rivet of the present invention is shown in FIGS.
As shown in FIG. The self-piercing rivet 1 is made of an aluminum alloy and includes a shaft 11 and a head 12.

The shaft portion 11 is cylindrical and has a tip (FIG. 2).
(Lower side), a sawtooth-shaped cutting portion 111 having a cutting function in the circumferential direction is formed. Each of the blades constituting the cutting blade portion 111 is machined into a shape in which the advancing end when the rivet 1 is rotated counterclockwise becomes a blade edge 111a. Here, the “circumferential cutting blade function” means that when the rivet 1 is rotated with respect to the center of the shaft of the shaft 11, the rotation has a function of cutting a member in contact with the tip of the shaft 11. . The shape of the cutting edge portion 111 is not particularly limited as long as it can exhibit the cutting edge function. For example, the number, size, interval, formation position and shape of the blade edge of the saw-tooth-shaped blade can be appropriately set. Further, in the example shown in FIG. 1, the cutting edge 111 is formed over the entire periphery of the tip of the shaft 11, but the cutting edge 111 may be provided only in a partial range of the tip.

As shown in FIG. 2, the tip of the shaft portion 11 has a tapered shape in which the inner surface of the shaft portion 11 increases in diameter toward the tip. With such a tapered shape, it is easy to expand the shaft portion 11 in a second stage of fastening described later, and a good fastening portion can be formed. The buckling prevention effect of the present invention can be obtained even when the tip of the shaft portion 11 is not tapered.

The head 12 is provided at the upper end of the shaft 11 and has a disk shape whose diameter gradually decreases toward the shaft 11. In the center of the upper surface 12a of the head 12, a one-character groove-shaped hole 121 is formed as an engagement means for rotating the rivet 1 in a first stage of fastening described later. The "engaging means" may be any as long as it can rotate the rivet 1 while holding the rivet 1 by a rotary indenter described later. For example, the shape of the hole 121 may be a cross-shaped groove, a polygon, an ellipse, or the like. Good. Further, instead of providing the hole 121, the engaging means may be constituted by making the outer periphery of the head 11 into a polygonal shape. Alternatively, a screw hole may be provided in the upper surface 12a of the head 12, and the screw hole and the rotary indenter may be screwed together to hold the rivet 1. Of these, it is preferable that the holes 121 of various shapes provided on the upper surface 12a of the head 12 be the engaging means from the viewpoint of workability at the time of driving.

Next, a method of fastening the upper plate 21 and the lower plate 22 of the aluminum alloy material 2 with the self-spring rivet 1 will be described with reference to FIGS. As shown in FIG. 4, an aluminum alloy material 2 as a material to be fastened is set on a die 3. The die 3 has an annular recess 31 for expanding the rivet 1 in the second stage of fastening.
Is provided. Next, the rivet 1 is arranged on the upper plate 21, and the projection 41 of the rotary indenter 4 is fitted into the hole 121 of the rivet 1, and the rivet 1 is held by the rotary indenter 4.

In the first stage of fastening, the rivet 1 is rotated by the rotary indenter 4 and pressed against the aluminum alloy material 2 side, and the rivet 1 is driven until the tip penetrates the upper plate 21 (FIG. 5). Since the cutting in the first stage is performed by cutting the upper plate 21 with the cutting blade 111, it is necessary to apply a large pressing force in the axial direction of the rivet 1, unlike the conventional technique of press-fitting without rotating the rivet. There is no. Then, in the second stage of the fastening, the rotation of the rivet 1 is stopped and the rivet 1 is further driven into the aluminum alloy material 2, whereby the shaft portion 11 is expanded along the shape of the annular concave portion 31, and the upper plate 21 and the lower plate 21 are joined together. The plate 22 is fastened (FIG. 6). For the driving of the second stage, an indenter different from the rotary indenter 4 used in the first stage can be used,
It is preferable that the rotation of the rotary indenter 4 used in the first stage is stopped and the rotary indenter 4 is also used in the second stage.

In the above embodiment, the rivet 1 is fastened so as not to penetrate the lower plate 22 of the aluminum alloy material 2, but the rivet 1 may be penetrated to the back side of the aluminum alloy material 2. As shown in FIG. 6, when the rivet 1 is in a fastening state in which the rivet 1 does not penetrate to the back side, there is an advantage that the sealing performance and appearance of the fastening portion are excellent. In the first stage of driving while rotating the rivet, the depth to which the rivet is driven may be appropriately determined according to the material and strength of the rivet and the material to be fastened, the final fastening state, and the like. Usually, at the end of the first stage, it is preferable that the tip of the rivet reaches a range of not less than 1/3 of the thickness of the upper plate and not more than 2/3 of the thickness of the lower plate. If the degree of driving in the first stage is less than the above range, the buckling preventing effect of the present invention may not be sufficiently exhibited. On the other hand, if the first step is made longer than necessary, the efficiency of the fastening step decreases, so it is preferable to set the first step within the above range.

The self-piercing rivet 1 used in the above embodiment can be manufactured by molding and working an aluminum alloy such as an Al-Zn-Mg alloy (JIS alloy symbol 7075) by a method such as cold forging. it can. Further, the self-piercing rivet 1 does not particularly require heat treatment for improving strength, but may be subjected to a heat treatment such as a solution treatment and a subsequent age hardening treatment.

[0015]

In the self-piercing rivet according to the first aspect of the present invention, since a cutting edge having a circumferential cutting edge function is formed at the tip of the shaft, the rivet is rotated to cut the workpiece. Thus, the rivet can be driven without applying a large pressing force to the shaft. This allows
Buckling of the shaft portion is prevented, and a good fastening portion is obtained. This self-piercing rivet is preferably used in a fastening method in which the rivet is rotated and driven until the tip reaches a predetermined thickness of the material to be fastened, and then the rotation of the rivet is stopped and further driven, as described in claim 2. Used for

[Brief description of the drawings]

FIG. 1 is a perspective view showing a self-piercing rivet of the present invention.

FIG. 2 is a sectional view taken along line II-II of FIG.

FIG. 3 is a view in the direction of arrow III in FIG. 1;

FIG. 4 is a cross-sectional view showing a state at the start of a first stage in the fastening method of the present invention.

FIG. 5 is a cross-sectional view showing a state at the end of the first stage (at the start of the second stage) in the fastening method of the present invention.

FIG. 6 is a cross-sectional view showing a state at the end of the second step in the fastening method of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1: Self-piercing rivet, 11: Shaft part, 111; Cutting blade part, 111a; Cutting edge, 12; Head, 12a;
1; hole (engaging means); 2; aluminum alloy material (fastened material); 21; upper plate, 22; lower plate, 3; die, 31;
Annular concave portion, 4; rotary indenter, 41; convex portion.

Claims (2)

[Claims] 1. A self-piercing rivet made of an aluminum alloy, comprising: a shaft portion having a cutting edge portion having a cutting edge function in a circumferential direction formed at a tip end; and a head having an engagement means for rotating the rivet. A self-piercing rivet, comprising: 2. A fastening method using a self-piercing rivet according to claim 1, wherein the rivet is held by a rotary indenter by the engagement means, and the rivet is driven into a workpiece while rotating the rivet. A fastening method, comprising: a first step; and a second step of stopping rotation of the rivet and further driving the rivet into the workpiece.