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EP-4140631-B1 - DISSIMILAR MATERIAL JOINT STRUCTURE AND METHOD FOR JOINING DISSIMILAR MATERIALS

EP4140631B1EP 4140631 B1EP4140631 B1EP 4140631B1EP-4140631-B1

Inventors

  • MIURA, MASAAKI
  • MIURA, SEIJI
  • SAKOTA, KOUJI

Dates

Publication Date
20260506
Application Date
20201102

Claims (6)

  1. A dissimilar material joint structure (1), comprising: a plate member (20); a first tightening member (10, 50) on a front surface (21) of the plate member, the first tightening member being one of a nut or a bolt; and a washer (30) on a back surface (22) of the plate member, the washer being weldable to the first tightening member, the first tightening member and the plate member being made of dissimilar materials different from each other, at least one of the first tightening member or the washer including a projection (12, 35, 52) on a bearing surface (11, 34, 51) thereof, the first tightening member being configured to correspond to a second tightening member (40, 60) which is the other of the nut or the bolt, the plate member having: a bolt through-hole (23) located on a center axis (X) of the first tightening member, for passing therethrough that one of the first tightening member or the second tightening member which is the bolt, and a projection through-hole (24) located on a periphery of the bolt through-hole, the projection through-hole being penetrable by the projection, and the first tightening member being not directly welded to the plate member but joined to the plate member by being welded to the washer via the projection penetrating the projection through-hole; characterized in that each of the projection (12) and the projection through-hole (24) are longer in a radial direction (R) than in a circumferential direction ( θ ) about the center axis (X).
  2. The dissimilar material joint structure (1) of claim 1, wherein the washer (30) is fitted in a recess (22a) on the back surface (22) of the plate member (20).
  3. The dissimilar material joint structure (1) of claim 2, wherein the washer (30) and the recess (22a) are polygonal in transverse cross-section, correspondingly to each other.
  4. The dissimilar material joint structure (1) of any of claims 1 to 3, wherein the first tightening member (10, 50) is a nut.
  5. The dissimilar material joint structure (1) of any of claims 1 to 4, wherein the projection (12, 35, 52) is located on the bearing surface (11, 34, 51) of the first tightening member (10, 50).
  6. A dissimilar material joining method of joining a first tightening member (10, 50) to a plate member (20) made of a material different from the first tightening member, the first tightening member being one of a nut or a bolt, the dissimilar material joining method comprising: arranging the first tightening member on a front surface (21) of the plate member, and a washer (30) on a back surface (22) of the plate member, the washer being weldable to the first tightening member; and joining the first tightening member to the plate member, at least one of the first tightening member or the washer including a projection on a bearing surface (11, 34, 51) thereof, the first tightening member being configured to correspond to a second tightening member (40, 60) which is the other of the nut or the bolt, the plate member having: a bolt through-hole (23) for passing therethrough that one of the first tightening member or the second tightening member which is the bolt; and a projection through-hole (24) on a periphery of the bolt through-hole, the projection through-hole being penetrable by the projection, and the joining including joining the first tightening member to the plate member by welding the first tightening member to the washer via the projection penetrating the projection through-hole; characterized in that each of the projection (12) and the projection through-hole (24) are longer in a radial direction (R) than in a circumferential direction ( θ ) about the center axis (X).

Description

TECHNICAL FIELD The present invention relates to a dissimilar material joint structure and a dissimilar material joining method. BACKGROUND ART Spot welding is often used for welding steel materials. In recent years, it has been attempted to join two members of different materials by spot welding, so that a lightweight material, such as aluminum can be utilized in view of reducing the weights of machines and instruments. For example, Patent Document 1 discloses a plate lamination structure (joint structure) including a first plate member, and second and third plate members provided respectively on either surface of the first plate member, where the second and third plate members are spot-weldable to each other. The first plate member is made of a material different from the second and third plate members and has a positioning hole. The first plate member is not welded to the second and the third plate members. The second plate member has a positioning projection corresponding to the positioning hole of the first plate member. The positioning projection is fitted in the positioning hole of the first plate member. The second and third plate members are then spot-welded with each other at the positioning projection fitted in the positioning hole of the first plate member. In this configuration, the second and third plate members are welded to each other via the positioning hole of the first plate member at a welding point, and because no first plate member of the different material is present at the welding point, a high weld strength can be attained. This makes it possible to joint these three plate members firmly. Further, Patent Document 2 discloses an intermediate link for workpieces to be joined by projection welding. CITATION LIST PATENT DOCUMENT Patent Document 1: Japanese Unexamined Patent Publication No. 2010-240678Patent Document 2: German Patent Applicaiton Publication No. DE1055717B SUMMARY OF THE INVENTION TECHNICAL PROBLEM In case of assembling a component (i.e., a workpiece) to a plate member with a bolt and a nut, there is such a case that the plate member includes a tightening member, for example, a weld nut (i.e., a projection nut) with a projection, the tightening member being spot-welded to the plate member in advance. Here, if the weld nut and the plate member are made of dissimilar materials different from each other, it is difficult to secure a sufficient joint strength (i.e., weld strength) between the weld nut and the plate member. To address the problem, it is conceivable to adopt the joint structure according to Patent Document 1. That is, the plate member may be modified to have a hole for letting the projection of the weld nut penetrate therethrough. A component weldable to the weld nut is additionally provided. The projection penetrating the hole is welded to the weldable component so as to join the weld nut to the plate member. This joint structure, however, requires a dedicated member additionally provided only for joining the weld nut to the plate member, undesirably in view of simplification, and weight and cost reductions of machines and instruments. The same applies to a configuration in which a weld bolt, instead of the weld nut, is joined to the plate member. The present invention was made in view of the problems. It is a main object of the present invention to eliminate the need for a member only for joining a tightening member and a plate member, which are made of different materials. SOLUTION TO THE PROBLEM A dissimilar material joint structure is provided according to claim 1. According to this configuration, the first tightening member is not directly welded to the front surface of the plate member but welded to the washer on the back surface of the plate member, with the projection penetrating the projection through-hole. That is, the first tightening member is welded to the washer with the plate member interposed therebetween via the projection through-hole (the projection) so as to be joined to the front surface of the plate material. This allows joining of even the first tightening member and the plate member made of different materials that are difficult to weld. When assembling a component (i.e., a workpiece) to the back surface of the plate material with a bolt and a nut, the second tightening member is screwed down to the first tightening member with one of the first and second tightening members, which is the bolt, passing through the bolt through-holes of the washer and the plate member. The tightening torque for screwing the second tightening member down to the first tightening member biases the first tightening member to rotate with respect to the plate member. Here, the first tightening member and the washer are welded with the plate member interposed therebetween via the projection through-hole (the projection), whereby the first fastening member and the washer are joined to the either surfaces of the plate material as if being pseudo-pressure-bonded the