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EP-3578290-B1 - RIVET-JOINED STRUCTURE

EP3578290B1EP 3578290 B1EP3578290 B1EP 3578290B1EP-3578290-B1

Inventors

  • FUJIWARA JUNJI
  • KAWAMOTO ATSUHIRO
  • NAKAGAWA TATSUYUKI
  • SAKAI TORU

Dates

Publication Date
20260506
Application Date
20180123

Claims (13)

  1. A rivet-joined structure comprising: a first material member (1) and a third material member (3) made of similar metallic materials or a first material member (1) made of a metallic material, a weld zone where the similar metallic materials of the first material member (1) and the third material member (3) or the metallic material of the first material member (1) is melted and joined together; and at least one second material member (2) different in type from the similar metallic materials or from the metallic material and difficult to be welded to the similar metallic materials or to the metallic material, the second material member (2) being sandwiched and fixed between the first material member (1) and the third material member (3) or between a region (1E) and another region of the first material member (1) by lap jointing; characterized in that the first material member (1) and/or the third material member (3) have at least one exhaust groove or at least one exhaust hole (1a, 3a) near the weld zone, the at least one exhaust groove or the at least one exhaust hole (1a, 3a) penetrating a thickness direction of the first material member (1) and/or of the third material member (3).
  2. The rivet-joined structure according to claim 1, wherein the weld zone has a circular or oval ring-shaped pattern, the ring-shaped pattern being a welding pattern to which energy has been applied from a heat source, and the at least one exhaust groove or the at least one exhaust hole is located either inside or outside the ring-shaped pattern.
  3. The rivet-joined structure according to claim 1, wherein the weld zone has a spot or linear pattern, the spot or linear pattern being a welding pattern to which energy has been applied from a heat source, and the at least one exhaust groove or the at least one exhaust hole (1a, 3a) is located outside the spot or linear pattern.
  4. The rivet-joined structure according to any one of claims 1 to 3, wherein the second material member (2) has a through part (2H), and at least one of the first material member (1) and the third material member (3) has a projection (1E, 3E) or the first material member (1) has a projection (1E), wherein the second material member is sandwiched between the first material member (1) and the third material member (3) or between a region (1E) and another region of the first material member (1) respectively, in such a manner that the projection (1E, 3E) is inserted in the through part and that the projection and the through part (2H) are spaced from each other by a predetermined gap (4) in a radial or width direction of the through part (2H), the predetermined gap (4) is provided inside smaller than a diameter or a width of the through part (2H), and the similar metallic materials have been melted or the metallic material has been melted respectively, by energy applied to the projection from a heat source along the thickness of the first material member (1) and the third material member (3) or of the first material member (1) respectively, so that the first material member (1) and the third material member (3) or the first material member (1) respectively, are fixed and joined together with the second material member (2).
  5. The rivet-joined structure according to claim 4, wherein the projection (1E, 3E) has a region to which the energy has been applied from the heat source along the thickness of the first material member (1) and the third material member (3) or of the first material member (1) respectively, the region is configured to be smaller by a predetermined amount than a diameter or a width of the projection (1E, 3E).
  6. The rivet-joined structure according to any one of claims 2 to 5, wherein the heat source is laser.
  7. The rivet-joined structure according to any one of claims 2 to 5, wherein the heat source is arc.
  8. The rivet-joined structure according to any one of claims 2 to 5, wherein the heat source is plasma.
  9. The rivet-joined structure according to claim 4, wherein a surface of the through part has been melted by indirect heat generated when the projection has been welded, the surface has been flowing and is fixed around an outer periphery of the projection of the first material member (1) and the third material member (3) or of the first material member (1) respectively.
  10. The rivet-joined structure according to claim 4 or 9, wherein at least one of the first material member (1) and the third material member (3) has a positioning protrusion (3d, 3e) at an end of the at least one exhaust hole (1a, 3a) or the at least one exhaust groove formed outside the projection (1E, 3E), the positioning protrusion (3d) protruding toward the second material member (2) and positioning the second material member (2).
  11. The rivet-joined structure according to claim 10, wherein the positioning protrusion (3d) is formed at the end of the at least one exhaust hole (1a, 3a) or the at least one exhaust groove formed outside the projection (1E, 3E) of at least one of the first material member (1) and the third material member (3).
  12. The rivet-joined structure according to claim 4, wherein the heat source is an arc, the projection (1E, 3E) has an arc welding opening at an end side of the projection (1E, 3E), the end side of the projection (1E, 3E) is a side to which arc has been applied, and the first material member (1) and the third material member (3) are welded and joined each other by the arc so that the first material member (1) and the third material member (3) or the first material member (1) respectively, are fixed to each other, the second material member (2) is sandwiched between the first material member (1) and the third material member (3) or between the region (1E) and the another region of the first material member (1) respectively, and the arc has been applied along the thickness of the first material member (1) and the third material member (3) or of the first material member (1) respectively.
  13. The rivet-joined structure according to claim 4 or any one of claims 5 to 12 when they depend on claim 4, wherein the first material member (1) and the third material member (3) comprise two opposing similar metallic materials, at least one of the first material member (1) and the third material member (3), comprises: a first exhaust hole or an exhaust groove; and a second exhaust hole or an exhaust groove, the first exhaust hole, the second exhaust hole, and the exhaust groove penetrating along a thickness direction of the one of the first material member (1) and the third material member (3), the first exhaust hole (1a, 3a) or the exhaust groove is disposed at a position corresponding to an outside of the through part (2H) of the second material member (2), and the second exhaust hole (1a, 3a) or the exhaust groove is disposed at another position corresponding to the outside of the through part (2H) of the second material member (2), so that the through part (2H) is disposed between: the first exhaust hole (1a, 3a) or the exhaust groove; and the second exhaust hole (1a, 3a) or the exhaust groove.

Description

TECHNICAL FIELD The present disclosure relates to a rivet-joined structure including similar metallic materials and at least one material that is different in type from the similar metallic materials and that is sandwiched between the similar metallic materials. These materials are joined together with rivets by using laser, arc, or plasma as the heat source (see, e.g. US 2016/167158 A1 or US 2009/278371 A1, both disclosing the preamble of claim 1). BACKGROUND ART The recent worldwide increase in the production of automobiles and other transportation vehicles has created a growing demand for reducing the total cost for each vehicle as well as for reducing the production time so as to increase vehicle production. Furthermore, there is a growing global demand for reducing CO2 emissions to prevent global warming. This demand has been answered by the transportation vehicle industry, which has been making increasing efforts to improve the fuel efficiency of vehicles. One of the efforts is to reduce the vehicle weights by, for example, increasing the proportion of light-weight materials in the vehicles. With such a background, spot welding has been often used in this industry. This welding is a kind of resistance welding in which the materials to be welded are pressurized by upper and lower electrodes until no gap remains between the materials, and then the electrodes are energized. For this reason, spot welding is not suitable for one side welding. In other words, spot welding imposes limitations on the product shape because the parts to be welded are sandwiched from above and below. Another disadvantage of this welding is that pressurizing the parts to be welded needs a space into which the welding gun having the upper and lower electrodes is inserted above and below the materials to be welded. Still another disadvantage is that beside welding time, spot welding takes additional time, such as the time to carry the heavy gun to the parts to be welded, the time to pressurize the materials after the gun reaches the parts to be welded, and the time to cool the welded parts. Meanwhile, the industry has been trying to reduce the weight of materials of some automobile parts by replacing steel with light metal such as aluminum. This trend has created a growing demand for techniques and structures that allow the joining of light metal and steel. Different types of materials have conventionally been joined together by using, for example, rivets for spot welding or adhesives for bonding purposes. Patent Literature 1 discloses a joined structure in which rivets and a material of the same type as the rivets sandwich a different type of material. To be more specific, Patent Literature 1 discloses the following techniques: a method for pressing the above-mentioned different type of material between the rivets and the material of the same type as the rivets; the shape of rivets capable of absorbing the plastic flow of the different type of material caused by welding heat; and methods of crimping and spot welding capable of the absorption. These methods ensure the space into which the deformed part of the different type of material is moved during the crimping and spot welding. The methods also prevent depression of the different type of material due, for example, to misalignment of the electrodes during spot welding, thereby maintaining the joining strength. Citation List Patent Literature PTL 1: Japanese Unexamined Patent Application Publication No.2015-42417 SUMMARY The conventional joining of different types of materials needs rivets with a complicated-shaped part, such as a radius-chamfered part or an annular groove. These rivets provide a space to accommodate the deformed part of the different type of material during crimping and spot welding. These rivets also prevent depression of the different type of material caused by the misalignment of the electrodes during spot welding, thereby maintaining the joining strength between the joined materials. These rivets with such a complicated-shaped part are fabricated by high precision processing technology, thus increasing the production cost. Furthermore, resistance spot welding involves time-consuming steps such as pressurization, energization, cooling, and transfer. Moreover, a set of materials to be joined together is sandwiched from both sides, which indicates a low degree of design freedom. In addition, adjacent rivets too close to each other can cause current diversion during spot welding. This would result in insufficient formation of a nugget, which is a part welded and solidified in the resistance welding. A desired nugget without current diversion can be formed by setting the pitch between adjacent rivets at not less than the minimum pitch. Arranging rivets at a pitch not less than the minimum pitch cannot improve joining stiffness at required positions. When a surface-treated material such as a zinc-plated steel sheet is resistance spot welded, the molten material of