JP2004360746A - Rivet, and junction method using rivet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rivet capable of securing favorable junction reliability. <P>SOLUTION: This rivet comprises an outer circumferential surface 35 on which a resin film 40 including thermosetting resin that foams to harden as a heating process is added is formed. Junction members combined with each other are jointed by the rivet, and the heating process is added to harden the resin film, so that a hardened foam layer is formed between the rivet and a junction part. Otherwise, after the junction members combined with each other are jointed by the rivet, a projection part is fitted into a boundary part between the junction members, and the heating process is added to harden the resin film, so that the hardened foam layer is formed between the rivet and the junction part. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a rivet and a joining method using a rivet.
[0002]
[Prior art]
In a conventional joining method, a rivet is mechanically joined to a superposed work material, for example, a steel plate or an aluminum plate, by driving (pressing) the rivet (see, for example, Patent Document 1).
[0003]
[Patent Document 1]
JP 2000-205213 A
[Problems to be solved by the invention]
However, the joining between the rivet and the material to be joined is based on the plastic deformation caused in the rivet and the joint to be joined, and when a high-strength steel plate or a thick plate is applied as the material to be joined, sufficient pressure is applied to the rivet. Is difficult to do.
[0005]
For this reason, for example, a gap is formed between the rivet and the portion to be joined, plastic deformation of the rivet and the lower plate (material to be joined disposed below) becomes insufficient, and a crack is formed in the rivet or the lower plate. May occur. Therefore, there is a problem that it is difficult to secure the joining reliability such as the joining strength and the rust prevention performance.
[0006]
The present invention has been made in order to solve the problems associated with the above-described conventional technology, and an object of the present invention is to provide a rivet and a joining method using the rivet that can ensure good joining reliability.
[0007]
[Means for Solving the Problems]
The invention according to claim 1 for achieving the above object,
A rivet having an outer peripheral surface on which a resin film containing a thermosetting resin that foams and hardens when subjected to a heat treatment is formed.
[0008]
The invention according to claim 6 for achieving the above object is as follows.
A joining method using the rivet according to any one of claims 1 to 3,
After joining the superposed workpieces with the rivet, a heat treatment is performed, and the resin film is foam-cured, thereby forming a foam hardened layer between the rivet and the workpiece. It is a joining method.
[0009]
The invention according to claim 7 for achieving the above object is as follows.
A joining method using the rivet according to claim 4 or claim 5,
The superimposed materials to be joined are joined by the rivet, and after the protrusion is pressed into the boundary portion of the material to be joined, a heating process is performed, and the resin film is foamed and hardened, thereby joining the rivet to the rivet. A foaming hardened layer is formed between a portion and a boundary portion of the material to be joined.
[0010]
【The invention's effect】
The present invention configured as described above has the following effects.
[0011]
According to the first aspect of the present invention, when a heat treatment is performed after joining the superposed materials to be joined, the resin film formed on the outer peripheral surface of the rivet is foamed and hardened, so that the rivet is joined to the rivet. It is possible to form a foamed hardened layer between the portions.
[0012]
The foam hardened layer eliminates a gap between the rivet and the part to be joined, and reinforces the joining strength between the rivet and the part to be joined, so that good joining reliability can be secured. That is, it is possible to provide a rivet that can ensure good joining reliability.
[0013]
According to the invention as set forth in claim 6, the foamed hardened layer formed between the rivet and the part to be joined by performing the heat treatment eliminates the gap between the rivet and the part to be joined, and the rivet Strengthens the joint strength between the part and the part to be joined. Therefore, good joining reliability is ensured. That is, it is possible to provide a joining method using rivets that can ensure good joining reliability.
[0014]
According to the invention as set forth in claim 7, the foam hardened layer formed between the rivet and the portion to be joined formed by performing the heat treatment eliminates a gap between the rivet and the portion to be joined, In addition, the joining strength between the rivet and the portion to be joined is reinforced. Further, the foamed hardened layer formed at the boundary of the materials to be joined reinforces the bonding strength between the materials to be joined. Therefore, joining reliability is improved. In other words, it is possible to provide a joining method using rivets that can ensure better joining reliability.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0016]
FIG. 1 is a sectional view of a rivet according to Embodiment 1 of the present invention, and FIG. 2 is a sectional view for explaining a method of manufacturing the rivet of FIG.
[0017]
The rivet 10 is a so-called self-piercing rivet, and has a head 20, a cylindrical shaft portion 30 extending from the head 20, and a resin film 40. The material to be joined by the rivet 10 is, for example, a structural panel member such as a center pillar or a front side member of a vehicle.
[0018]
The head 20 has a disk shape whose diameter gradually decreases toward the shaft portion 30. The shaft 30 has a cylindrical hole 31. The distal end side (the distal side with respect to the head 20) of the hole 31 has a tapered surface 32 whose diameter increases toward the distal end. The tapered surface 32 facilitates expansion of the shaft portion 11 when the rivet 10 is driven.
[0019]
The thickness T of the shaft portion 30 (the distance between the outer peripheral surface 35 of the shaft portion 30 and the surface of the hole portion 31) T is set to an appropriate size to prevent buckling when the rivet 10 is driven. .
[0020]
The resin film 40 is formed on the outer peripheral surface 35 of the rivet 10, and includes a thermosetting resin that foams and hardens when subjected to a heat treatment. The thermosetting resin contains, for example, an epoxy resin, and the heat treatment condition is a temperature of 140 to 200 ° C. for 5 to 20 minutes.
[0021]
Therefore, when a heat treatment is performed after joining the superposed materials with the rivet 10, the resin film 40 formed on the outer peripheral surface 35 of the rivet 10 is foamed and hardened, so that the rivet 10 and the portion to be joined are bonded. A foamed hardened layer can be formed between them.
[0022]
The foam hardened layer eliminates a gap between the rivet 10 and the portion to be joined, and reinforces the joining strength between the rivet 10 and the portion to be joined, so that good joining reliability can be secured.
[0023]
The resin film 40 can be formed by, for example, injection molding as shown in FIG. In this case, the rivet 10 is positioned and fixed inside the injection mold 45 having an inner surface shape corresponding to the outer peripheral surface shape.
[0024]
Then, a molten thermosetting resin is injected under pressure into a gap space 46 formed between the outer peripheral surface of the rivet 10 and the inner surface of the injection mold 45. The thermosetting resin filled in the interstitial space 46 solidifies to form the resin film 40. Therefore, the thickness of the gap space 46 is the thickness of the resin film 40.
[0025]
The resin film 40 formed by injection molding is preferable because it has good adhesion to the outer peripheral surface of the rivet 10 and is prevented from falling off when the rivet 10 is driven.
[0026]
As described above, in the first embodiment, it is possible to provide a rivet that can ensure good joining reliability.
[0027]
The material to be joined by the rivets is not limited to the two-ply material, but can be applied to, for example, three-ply material.
[0028]
Next, a joining method using the rivet 10 of FIG. 1 will be described with reference to FIGS. 3 shows a state at the start of rivet driving, FIG. 4 shows a state during rivet driving, FIG. 5 shows a state at the time of rivet driving end, and FIG. 6 shows a state after heat treatment is performed. Is shown.
[0029]
First, after setting the superposed workpieces 50 (51, 52) on the upset die 60, the rivet 10 is placed on the workpiece 51 located on the rivet driving side, and the head 20 of the rivet 10 is placed. The punch 70 is lowered from above (see FIG. 3). The upset die 60 has an annular concave portion 61.
[0030]
The rivet 10 pressed against the workpiece 50 by the punch 70 is driven into the workpiece 51. The leading end of the rivet 10 cuts the workpiece 51, penetrates the workpiece 51, and cuts the workpiece 52 located on the upset die side (see FIG. 4).
[0031]
Then, as the driving of the rivet 10 further proceeds, the workpiece 52 and the shaft 30 of the rivet 10 are deformed in accordance with the shape of the annular concave portion 61. As a result, the shaft portion 30 of the rivet 10 is sufficiently expanded, and the material to be joined 51 and the material to be joined 52 are mechanically joined (see FIG. 5).
[0032]
In this case, since the rivet 10 does not penetrate the material 52 to be joined, the sealing properties and appearance of the joint are good. However, if necessary, it can be penetrated.
[0033]
Thereafter, the material to be joined 50 joined by the rivets 10 is subjected to a heat treatment at, for example, a temperature of 140 to 200 ° C. for 5 to 20 minutes. As a result, the resin film 40 formed on the outer peripheral surface 35 of the rivet 10 is foamed and hardened, and a foam hardened layer 44 is formed between the rivet 10 and the portion to be joined (see FIG. 6).
[0034]
The foam hardening layer 44 eliminates a gap between the rivet 10 and the part to be joined, and reinforces the bonding strength between the rivet 10 and the part to be joined. Therefore, good joining reliability is ensured.
[0035]
As described above, in the first embodiment, it is possible to provide a joining method using rivets that can ensure good joining reliability.
[0036]
Note that the heat treatment for forming the foamed hardened layer is not limited to being performed independently. For example, when a material to be joined and an assembly having the material to be joined joined by the rivet 10 are applied in a subsequent process, heat for baking the coating film can be used for heat treatment, and cost can be reduced. Can be reduced.
[0037]
In this case, it is preferable to select the thermosetting resin of the resin film so that the heat treatment conditions for forming the foamed hardened layer substantially match the baking conditions of the coating film.
[0038]
For example, when the material to be joined is a panel member for a structure such as a center pillar or a front side member of a vehicle, after being joined by rivets 10 at the time of assembly after press molding, before assembly of a chassis or the like, Electrodeposition is applied. Therefore, heat for baking and hardening a coating film formed by electrodeposition coating can be used for heat treatment.
[0039]
In addition, for example, when a cationic epoxy-based paint is used for electrodeposition coating, if an epoxy resin is applied as the thermosetting resin for the resin film, the baking conditions of the coating film and the heating for forming the foamed cured layer are performed. This is preferable because the processing conditions substantially match.
[0040]
FIG. 7 is a cross-sectional view of a rivet according to Embodiment 2 of the present invention, and FIG. 8 is a cross-sectional view for explaining a joining method using the rivet of FIG. 7 and shows a state after heat treatment. ing.
[0041]
Embodiment 2 is generally different from Embodiment 1 in that the resin film 140 of the rivet 110 has a protrusion 141 that protrudes in the rivet radial direction.
[0042]
The protruding portion 141 is located away from the rivet head end (the end of the head 120 of the rivet 110) 121 in the distal direction by a distance D substantially equal to the plate thickness of the workpiece 151 positioned on the rivet driving side. I do.
[0043]
Therefore, when joining the joined workpieces 150 (151, 152) with the rivets 110, the protruding portions 141 are pressed into the boundaries of the joined workpieces 150. When the heat treatment is performed, the foam hardened layer 144 is formed between the rivet 110 and the part 150 to be joined and at the boundary part of the material 150 to be joined.
[0044]
The foam hardening layer 144 formed between the rivet 110 and the part 150 to be joined eliminates a gap between the rivet 110 and the part 150 to be joined and reinforces the bonding strength between the rivet 110 and the part 150 to be joined. I do. The foam hardened layer 144A formed at the boundary of the workpieces 150 reinforces the bonding strength between the workpieces. That is, the joining reliability can be improved as compared with the case where the rivet 10 is applied.
[0045]
As described above, in the second embodiment, it is possible to provide a rivet and a joining method using the rivet that can secure better joining reliability than the embodiment.
[0046]
When the protrusion height of the protrusion 141 is 0.5 mm or more, the improvement in bonding strength is remarkable, and when the driving property is considered, the protrusion height is 1.0 mm at the maximum. That is, the protrusion 141 preferably has a protrusion height of 0.5 mm or more and 1.0 mm or less.
[0047]
In addition, the heat treatment according to the second embodiment can also reduce costs by using heat for baking a coating film formed on a material to be joined or an assembly having the material to be joined. .
[0048]
FIG. 9 is a chart for explaining a rivet evaluation result according to the embodiment of the present invention.
[0049]
First, conditions for forming a rivet applied to a test piece will be described.
[0050]
The material to be joined was a hot-dip galvanized steel sheet (tensile strength: 270 MPa class) having a thickness of 1.5 mm. The rivets used for joining the materials to be joined are 5 mm long dish rivets having a 5 mm diameter head.
[0051]
The resin film is formed by injection molding using an olefin-modified thermosetting epoxy resin, and the thickness is changed in a range of 0.3 to 2.5 mm. The expansion ratio is changed in the range of 1.2 to 2.0. The protruding height of the test piece having a protruding portion is 0.5 mm.
[0052]
The inner diameter of the annular recess 61 in the upset die 60 for driving a rivet is 9 mm. The pressing force of the punch for pressing the rivet against the material to be joined is about 5000N. The heat treatment condition for forming the foamed hardened layer is 170 ° C. for 20 minutes.
[0053]
Next, evaluation items and evaluation methods will be described.
[0054]
The evaluation items are the moldability of the resin film, the rivet driving property, the appearance after driving, and the bonding strength characteristics.
[0055]
The moldability of the resin film is evaluated based on the uniformity of the thickness of the resin film in injection molding. The symbol ○ indicates a case where sufficient uniformity was shown, and the symbol △ indicates a case where a partially uneven portion was formed.
[0056]
The rivet driving performance was evaluated by the presence or absence of the resin film falling off. The symbol ○ indicates that no dropout occurred, and the symbol △ indicates that the dropout occurred partially.
[0057]
The appearance after the driving was evaluated for the presence or absence of cracks in the rivet and the presence or absence of a gap between the rivet and the portion to be joined. In addition, when the rivet had a crack or a gap, the length was also measured.
[0058]
The joint strength characteristics were evaluated by a shear strength according to a test according to JIS-Z-3136, a cross tensile strength according to a test according to JIS-Z-3137, and a fatigue strength according to a tensile shear fatigue test according to JIS-Z-3138. .
[0059]
Next, evaluation results will be described. Note that the sign "-" indicates that the evaluation was omitted.
[0060]
Regarding the moldability of the resin film, when the thickness of the resin film was 0.3 mm, partially uneven portions were formed, but when the thickness was 0.5 mm or more, good results were shown. In terms of rivet driving properties, good results were obtained up to a thickness of 2.0 mm of the resin film, and when the thickness was 2.5 mm, the resin film partially dropped off. Therefore, the thickness of the resin film is preferably 0.5 mm or more and 2.0 mm or less in consideration of moldability and driveability.
[0061]
In the appearance after the driving, the test piece having a resin film thickness of 0 mm, that is, the resin film is not formed, and in the case of the comparative example having no foam hardened layer, the crack of the rivet and the rivet between the rivet and the joined part A gap has occurred.
[0062]
When the expansion ratio of the resin film was 1.5 to 3.0, good results were obtained. However, when the expansion ratio of the resin film was 1.2, although improved compared to the comparative example, cracks in the rivet and a gap between the rivet and the joined portion occurred.
[0063]
In general, the gap between the rivet and the part to be joined occurs unevenly and may reach up to 2 mm. When the expansion ratio is 3.0 or more, it is not easy to secure the performance. Therefore, the expansion ratio is preferably set to 1.5 or more and 3.0 or less by appropriately selecting the type of the additive.
[0064]
Except for the case where the expansion ratio is low, the bonding strength characteristics are significantly improved as compared with the comparative example having no foam hardened layer. For example, the shear strength increases by about 30 to 100%, the cross tensile strength increases by about 30 to 120%, and the fatigue strength increases by about 30 to 60%. In addition, under the same conditions except for the presence of the protrusion, the bonding strength characteristics are improved by the presence of the protrusion.
[0065]
The bonding strength increases in proportion to the rivet diameter including the foam hardened layer. This is due to the fact that the fracture of the test piece in the joint strength test occurred in the base material around the rivet, and the fracture diameter was increased by the foam hardened layer.
[0066]
Next, the corrosion resistance of the rivet according to the embodiment of the present invention was evaluated. In addition, the test piece was created according to the tensile shear test of JIS-Z-3136, the thickness of the resin film was 1 mm, and the expansion ratio was 2.0. In addition, the test piece joined by rivets is subjected to electrodeposition coating after performing a pretreatment such as a chemical conversion treatment, and the foam hardening layer is for baking and curing the coating film formed by the electrodeposition coating. It is formed using heat (baking conditions at 170 ° C. for 20 minutes).
[0067]
Evaluation items were: 200 test cycles consisting of salt spray (4 hours at 35 ° C.), drying (2 hours at 60 ° C. at 25% RH), and wet (2 hours at 50 ° C. at 95% RH) It is a rust generation situation in.
[0068]
As a result of observing the appearance and the cross-section obtained by cutting the joint, no rust was observed, and it was confirmed that the rust-preventing performance was good.
[Brief description of the drawings]
FIG. 1 is a sectional view of a rivet according to Embodiment 1 of the present invention.
FIG. 2 is a cross-sectional view for explaining a method of manufacturing the rivet of FIG.
FIG. 3 is a cross-sectional view for explaining a joining method using the rivet of FIG. 1, and shows a state at the time of starting driving of the rivet.
FIG. 4 is a cross-sectional view for explaining a joining method using the rivet of FIG. 1, showing a state in which the rivet is being driven.
FIG. 5 is a cross-sectional view for explaining a joining method using the rivet of FIG. 1, and shows a state at the time of completion of driving of the rivet.
FIG. 6 is a cross-sectional view for explaining a bonding method using the rivet of FIG. 1 and shows a state after heat treatment is performed.
FIG. 7 is a cross-sectional view of a rivet according to Embodiment 2 of the present invention.
8 is a cross-sectional view for explaining a bonding method using the rivet of FIG. 7, and shows a state after heat treatment is performed.
FIG. 9 is a chart for explaining rivet evaluation results according to the embodiment of the present invention.
[Explanation of symbols]
10 ... rivets,
20 ... Head,
30 ... Shaft,
31 ... hole,
32 ... tapered surface,
35 ... outer peripheral surface,
40 ... resin film,
41 ... projecting part,
44 ... foam hardened layer,
45… Injection mold,
46 ... clearance space,
50 (51, 52) ... material to be joined,
60 ... Upset die,
61 ... annular concave portion,
70 ... punch,
110 ... rivet,
120 ... head,
121 ... rivet head end,
140 ... resin film,
141 ... projecting part,
144, 144A: foamed hardened layer,
150 (151, 152) ... material to be joined,
D ... distance,
T: thickness.

Claims (8)

A rivet having an outer peripheral surface on which a resin film containing a thermosetting resin that foams and hardens when subjected to a heat treatment is formed. The rivet according to claim 1, wherein the resin film has a thickness of 0.5 mm or more and 2.0 mm or less. The rivet according to claim 1, wherein a foaming ratio of the resin film is 1.5 or more and 3.0 or less. The resin film has a protruding portion that protrudes in a rivet radial direction. The rivet according to any one of claims 1 to 3, wherein the rivet is located apart. The rivet according to claim 4, wherein the protrusion has a protrusion height of 0.5 mm or more and 1.0 mm or less. A joining method using the rivet according to any one of claims 1 to 3,
After joining the superimposed joined materials with the rivet, a heat treatment is performed, and the resin film is foamed and cured, so that a foamed hardened layer is formed between the rivet and the joined portion. And joining method. A joining method using the rivet according to claim 4 or claim 5,
The superimposed materials to be joined are joined by the rivet, and after the protrusion is pressed into the boundary of the material to be joined, a heat treatment is performed, and the resin film is foamed and hardened, thereby joining the rivet to the rivet. A foaming hardened layer is formed between a portion and a boundary portion of the material to be joined. 8. The bonding method according to claim 6, wherein the heat treatment utilizes heat for baking a coating film formed on the material to be joined or an assembly having the material to be joined. .

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