Resistance welding method

Abstract

To satisfactorily generate nuggets while suppressing occurrence of spatter and burrs in a resistance-welding device for joining a plurality of laminated metal plates.SOLUTION: A resistance-welding device joins a plurality of metal plates by use of a rivet 30. The device comprises an upper electrode 10 which presses the rivet 30 in a lamination direction with respect to the plurality of metal plates, and a lower electrode which presses the plurality of metal plates to the upper electrode 10 side. The device uses, as the rivet 30, a product having: a shade part 31 of which a top face 31a contacts an apical surface 10a of the upper electrode 10; a shank 33 which extends downward from a center of the shade part 31; and an outer peripheral wall part 35 which extends from a peripheral edge part of the shade part 31 in the same direction as the shank 33, and forms a groove 37 between itself and the shank 33. A diameter D1 of a contact surface between the upper electrode 10 and the shade part 31 of the rivet 30 when starting electric conduction is so set as to be larger than an outer diameter D2 on the shade part 31 side in the shank 33, and to be smaller than an inner diameter D3 of the outer peripheral wall part 35.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a method for joining a plurality of stacked metal plates together using rivets. Resistance welding method This is regarding. [Background technology]

[0002] Conventionally, there has been known a method of joining dissimilar metal components by resistance welding using a metal rivet having a disk-shaped cap portion, a shaft portion extending from the center of the cap portion in a direction perpendicular to the cap portion, and an outer peripheral wall portion extending from the peripheral edge of the cap portion in the same direction as the shaft portion so as to form a groove between the shaft portion (see, for example, Patent Document 1).

[0003] When joining an aluminum plate and a steel plate using this dissimilar material joining method, for example, the rivet, aluminum plate, and steel plate are sandwiched between two electrodes in the following order: cap, shank, aluminum plate, and steel plate, and then these are pressurized and electrified to form a nugget between the shank that penetrates the aluminum plate and the steel plate. In this way, by sandwiching an aluminum plate between the iron plate and the cap of a rivet whose shank is welded to the iron plate, it becomes possible to join aluminum plates and steel plates, which are difficult to weld. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2021-137853 A Summary of the Invention [Problem to be solved by the invention]

[0005] Generally known electrodes for use in resistance welding apparatuses are radius electrodes, the tip of which is spherical, and flat electrodes, the tip of which is flat.

[0006] When resistance welding is performed using a radius electrode, the contact area between the tip of the electrode and the cap of the rivet tends to be relatively small due to the spherical tip of the electrode. This causes current to concentrate at the contact point between the electrode and the rivet. Although this is advantageous for producing a nugget, it also causes the problem that excessive heat is generated between the electrode and the rivet, making it more likely for spatter (molten metal to fly out from the metal surface due to high energy) and burrs to occur.

[0007] On the other hand, when resistance welding is performed using a flat electrode, for example a cylindrical electrode with a large diameter is used, the contact area between the flat tip surface of the electrode and the cap of the rivet is relatively large, which makes it possible to suppress the generation of spatter and burrs due to current concentration. However, a large amount of current will flow from the outer wall of the rivet into the metal plate. In other words, the number of current paths that do not contribute to the generation of the nugget increases, which may have a negative effect on the generation of the nugget.

[0008] These problems also apply when, for example, the diameter of the flat electrode is small, resulting in a relatively small contact area between the tip surface of the flat electrode and the cap of the rivet, or when, for example, the cap of the rivet is not flat, resulting in a relatively large contact area between the tip surface of the radius electrode and the cap of the rivet.

[0009] The present invention has been made in view of the above-mentioned points, and an object of the present invention is to provide a method for joining a plurality of laminated metal plates. Resistance welding method The present invention aims to provide a technique capable of satisfactorily forming a nugget while suppressing the generation of spatters and burrs. [Means for solving the problem]

[0010] In order to achieve the above object, the present invention Resistance welding method In the method, the contact surface between the electrode and the rivet is set to an appropriate size so that the current is not too concentrated and is not too dispersed.

[0011] Specifically, the present invention relates to a method for joining a plurality of stacked metal plates together using a rivet. Resistance welding method The following are the targets:

[0012] And this Resistance welding method a first electrode that presses the rivet against the plurality of metal plates in a stacking direction, and a second electrode that is disposed opposite the first electrode across the plurality of metal plates and presses the plurality of metal plates toward the first electrode in the stacking direction. Resistance welding equipment is used, The rivet contacts the tip surface of the first electrode. Has a flat surface a substantially disk-shaped cap portion, a shaft portion extending from a center of the cap portion toward the second electrode side in a stacking direction, and an outer peripheral wall portion extending from a peripheral edge of the cap portion in the same direction as the shaft portion and forming a groove between the shaft portion and the outer peripheral wall portion, In addition, the relationship between the first electrode and the rivet is as follows: The diameter of the contact surface between the first electrode and the cap of the rivet at the start of energization is set to be larger than the outer diameter of the cap side of the shank of the rivet and smaller than the inner diameter of the outer peripheral wall of the rivet. and further using, as the first electrode, an electrode having a flat electrode portion, the tip of which is flat as a surface that comes into contact with the cap portion of the rivet, and a spherical radius electrode portion provided around the outer periphery of the flat electrode portion, the rivet and the multiple metal plates are sandwiched between the first electrode and the second electrode, and current is applied while pressure is applied to the rivet and the multiple metal plates by the first electrode and the second electrode, thereby joining the multiple metal plates. It is characterized by the above.

[0013] In the present invention, "the outer diameter of the shaft portion on the cap side" means that even when the outer diameter of the shaft portion is not constant but changes in the axial direction, the outer diameter of the base part of the shaft portion (the base end part connected to the cap portion) is used as the outer diameter of the shaft portion.

[0014] In addition, the limitation "at the start of current flow" is added because, in the case of a radius electrode, as the current flow progresses, the cap portion softens and the contact surface between the electrode and the cap portion expands, and this is to clarify the definition of "diameter of the contact surface."

[0015] With this configuration, the diameter of the contact surface between the first electrode and the cap of the rivet at the start of current flow is set larger than the outer diameter of the cap side of the rivet shank, so that the current does not concentrate too much on the shank and excessive heat generation between the electrode and the rivet is prevented, thereby suppressing the occurrence of spatter and burrs.

[0016] In addition, since the diameter of the contact surface between the first electrode and the cap of the rivet at the start of current flow is set smaller than the inner diameter of the outer wall of the rivet, excessive current does not flow from the outer wall of the rivet to the metal plate, and current dispersion is suppressed, resulting in a good production of a nugget. Effect of the Invention

[0019] As described above, the present invention Resistance welding method According to the method, it is possible to satisfactorily form a nugget while suppressing the generation of spatters and burrs. [Brief description of the drawings]

[0020] [Figure 1] 1 is a diagram showing a schematic view of a main part of a resistance welding device according to an embodiment of the present invention; [Diagram 2] FIG. 2 is an enlarged view of an electrode of the resistance welding apparatus of FIG. [Diagram 3] 1A to 1C are diagrams illustrating variations of electrodes. [Figure 4] 1A to 1C are diagrams illustrating variations of electrodes. [Diagram 5] FIG. 1 is a diagram showing a schematic view of a main part of a conventional resistance welding device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0022] -Overall configuration of resistance welding equipment- Fig. 1 is a diagram showing a schematic view of a main part of a resistance welding device 1 according to the present embodiment. In Fig. 1 to Fig. 5, a rivet 30, an aluminum plate 40, and an iron plate 50 are shown in cross section for ease of viewing.

[0023] This resistance welding apparatus 1 uses a rivet 30 to join an aluminum plate 40 and an iron plate 50 that are stacked one above the other. As shown in Fig. 1, the resistance welding apparatus 1 includes an upper electrode 10, a lower electrode 20, an upper shank 3 for attaching the upper electrode 10 to an upper electrode holder (not shown), and a lower shank 5 for attaching the lower electrode 20 to a lower electrode holder (not shown). Note that, although an aluminum plate 40 and an iron plate 50 are exemplified as "plurality of metal plates" in this embodiment, the material types of the respective metal plates are not limited to aluminum and iron.

[0024] The upper electrode (first electrode) 10 is formed in a cylindrical shape and configured as a flat electrode with a flat tip surface 10a. As shown in Fig. 1, this upper electrode 10 presses the rivet 30 downward (in the stacking direction) against the laminated aluminum plate 40 and iron plate 50.

[0025] The lower electrode (second electrode) 20 is formed in a substantially cylindrical shape and is configured as a radius electrode with a spherical tip surface. As shown in Fig. 1, the lower electrode 20 is disposed so as to face the upper electrode 10 across the aluminum plate 40 and iron plate 50 stacked vertically, and presses the aluminum plate 40 and iron plate 50 upward (towards the upper electrode 10 in the stacking direction).

[0026] FIG. 2 is an enlarged view of the upper electrode 10 of the resistance welding apparatus 1 of FIG. 1. In this embodiment, as shown in FIG. 2, a rivet 30 made of iron is used, which has a substantially disk-shaped cap portion 31, a shaft portion 33 extending downward (toward the lower electrode 20 in the stacking direction) from the center of the cap portion 31, and an outer peripheral wall portion 35 extending in the same direction as the shaft portion 33 from the periphery of the cap portion 31 to form a groove 37 between the shaft portion 33. As shown in FIG. 1, the shaft portion 33 is formed in a substantially cylindrical shape, and the tip portion is in the shape of a truncated cone tapering downward, but FIG. 2 shows only the cylindrical portion (the portion of the shaft portion 33 on the cap portion 31 side). As shown in FIG. 1 and FIG. 2, the rivet 30 is set in the resistance welding apparatus 1 so that the upper surface 31a of the cap portion 31 is perpendicular to the stacking direction, in other words, so that the upper surface 31a of the cap portion 31 is in contact with the flat tip surface 10a of the upper electrode 10.

[0027] When using the resistance welding apparatus 1 configured as above to join aluminum plate 40 and iron plate 50, which are dissimilar metal materials, the rivet 30, aluminum plate 40, and iron plate 50 are sandwiched between the upper electrode 10 and the lower electrode 20 so that the cap portion 31, shaft portion 33, aluminum plate 40, and iron plate 50 are arranged from top to bottom in this order. Then, a current is applied to the rivet 30, aluminum plate 40, and iron plate 50 while pressure is applied by the upper electrode 10 and lower electrode 20.

[0028] More specifically, in the early stage of current flow, pressure is applied while, for example, a high current is applied, causing the shank 33 of the rivet 30 to penetrate the aluminum plate 40. Then, from the middle stage of current flow onwards, pressure is applied while, for example, a low current is applied, causing a nugget 60, as shown by the two-dot chain line in Fig. 1, to form between the shank 33 that has penetrated the aluminum plate 40 and the iron plate 50.

[0029] In this way, by welding the shaft 33 of the iron rivet 30 to the iron plate 50 and sandwiching the aluminum plate 40 between the cap 31 of the rivet 30 and the iron plate 50, it is possible to join the aluminum plate 40 and the iron plate 50, which are difficult to weld.

[0030] - Conventional resistance welding equipment - Here, in order to facilitate understanding of this embodiment, a conventional resistance welding device will be described. Fig. 5 is a diagram showing a schematic view of the main part of a conventional resistance welding device. In Fig. 5, reference numeral 103 indicates an upper shank, reference numeral 105 indicates a lower shank, and reference numeral 120 indicates a lower electrode. In the conventional resistance welding device, as in the resistance welding device 1 of this embodiment, a rivet 30 is used to join an aluminum plate 40 and an iron plate 50 that are stacked one on the other.

[0031] Generally, electrodes in a resistance welding device are a radius electrode such as the lower electrode 20 of this embodiment and a flat electrode such as the upper electrode 10, but as shown in Fig. 5(a), when resistance welding is performed using a radius electrode 110, the contact area between the tip surface of the radius electrode 110 and the cap portion 31 of the rivet 30 tends to be relatively small because the tip surface of the radius electrode 110 is spherical, so that the current concentrates at the contact portion CP between the radius electrode 110 and the rivet 30. Therefore, as shown by the dashed line in Fig. 5(a), the current flows intensively through the shank portion 33, which is advantageous for generating the nugget 60, but there is a problem that the heat generated between the radius electrode 110 and the rivet 30 becomes too large, making it easy for spatters S and burrs to occur.

[0032] On the other hand, as shown in Figure 5(b), when resistance welding is performed using a flat electrode 111, if a cylindrical flat electrode 111 with a large diameter is used, the contact area between the tip surface of the flat electrode 111 and the cap portion 31 of the rivet 30 becomes relatively large, so that the generation of spatter S and burrs can be suppressed. However, as shown by the dashed line in Figure 5(b), a large amount of current flows from the outer wall portion 35 of the rivet 30 to the aluminum sheet 40 and the iron sheet 50. In other words, the number of current paths that do not contribute to the generation of the nugget 60 increases, which has a negative effect on the generation of the nugget 60.

[0033] The problem of spatters S and burrs being easily generated as shown in FIG. 5(a) also applies when the diameter of the flat electrode 112 is small and the contact portion CP between the tip surface of the flat electrode 112 and the cap portion 31 of the rivet 30 is relatively small as shown in FIG. 5(c).

[0034] In addition, the problem of adversely affecting the formation of the nugget 60 as shown in Figure 5(b) also applies when, for example, the cap portion 31 of the rivet 30 is not flat, and so the contact area between the tip surface of the radius electrode 113 and the cap portion 31 of the rivet 30 is relatively large, as shown in Figure 5(d).

[0035] - Setting the size of the contact surface between the electrode and the rivet - Therefore, in the resistance welding apparatus 1 according to this embodiment, the contact surface between the upper electrode 10 and the rivet 30 is set to an appropriate size so that the current is not too concentrated and is not too dispersed.

[0036] Specifically, in the resistance welding apparatus 1, as shown in FIG. 2, the diameter D1 of the contact surface between the tip surface 10a of the upper electrode 10 and the upper surface 31a of the cap portion 31 of the rivet 30 at the start of current flow is set to be larger than the outer diameter D2 of the shank portion 33 of the rivet 30 on the cap portion 31 side and smaller than the inner diameter D3 of the outer wall portion 35 of the rivet 30.

[0037] In this embodiment, since the upper electrode 10 is a cylindrical flat electrode and the outer diameter of the upper electrode 10 is smaller than the outer diameter of the cap portion 31, the outer diameter of the upper electrode 10 is the "diameter D1 of the contact surface". As described above, the tip of the shaft portion 33 is in the shape of a truncated cone, but the base end side is formed in a cylindrical shape, so in this embodiment, the outer diameter D2 of the cylinder is the "outer diameter of the shaft portion 33 on the cap portion 31 side". Furthermore, the limitation "at the start of energization" is added because, in the case of a radius electrode, as the energization progresses, the upper surface 31a of the cap portion 31 softens and the contact surface between the upper electrode 10 and the cap portion 31 expands, and therefore the definition of the "diameter of the contact surface" is avoided from becoming ambiguous.

[0038] In the resistance welding apparatus 1 configured in this manner, the diameter D1 of the contact surface between the upper electrode 10 and the cap portion 31 of the rivet 30 at the start of current flow is set to be larger than the outer diameter D2 of the cap portion 31 side of the shank 33 of the rivet 30. This prevents the current from concentrating too much on the shank 33, and prevents excessive heat generation between the upper electrode 10 and the rivet 30, thereby suppressing the occurrence of spatter S and burrs.

[0039] Furthermore, since the diameter D1 of the contact surface between the upper electrode 10 and the cap portion 31 of the rivet 30 at the start of current flow is set to be smaller than the inner diameter D3 of the outer wall portion 35 of the rivet 30, excessive current does not flow from the outer wall portion 35 of the rivet 30 to the aluminum plate 40 and the iron plate 50; in other words, the number of current paths that do not contribute to the generation of the nugget 60 is not excessively increased, and current dispersion is suppressed, so that the nugget 60 can be generated well.

[0040] -Variation 1- Fig. 3 is a diagram showing a schematic diagram of a variation of the electrode. In the above embodiment, as shown in Fig. 3(a), the upper electrode 10 is configured as a flat electrode, and the flat tip surface 10a is made to contact the flat upper surface 31a of the cap portion 31 of the rivet 30. However, the upper electrode may be of any type as long as the diameter of the contact surface between the upper electrode and the cap portion 31 of the rivet 30 at the start of energization is set to be larger than the outer diameter D2 of the shank portion 33 of the rivet 30 on the cap portion 31 side and smaller than the inner diameter D3 of the outer peripheral wall portion 35 of the rivet 30.

[0041] For example, as shown in Fig. 3(b), the upper electrode 11 may be a radius electrode with a spherical tip surface 11a. In this case, it is preferable to use a rivet 30 in which a spherical recess 31b corresponding to the tip surface 11a of the upper electrode 11 is formed on the upper surface 31a of the cap portion 31 (the surface opposite to the shank portion 33). In this way, it is possible to set the diameter of the contact surface between the upper electrode 11 and the cap portion 31 of the rivet 30 to be larger than the outer diameter D2 of the cap portion 31 side of the shank portion 33 of the rivet 30 and smaller than the inner diameter D3 of the outer peripheral wall portion 35 of the rivet 30 from the stage at which current begins to flow.

[0042] 3(c), the upper electrode 12 may be configured as a combination of a flat electrode and a radius electrode. Specifically, the surface 12a of the upper electrode 12 that contacts the upper surface 31a of the cap portion 31 may be configured as a flat surface, and the surface 12b around the surface 12a may be configured as a spherical surface.

[0043] -Variation 2- 4 is a diagram showing a schematic diagram of a variation of the electrode. As long as the upper electrode has a tip surface such that the diameter of the contact surface with the cap portion 31 of the rivet 30 at the start of energization is larger than the outer diameter D2 of the shank portion 33 of the rivet 30 on the cap portion 31 side and smaller than the inner diameter D3 of the outer peripheral wall portion 35 of the rivet 30, the shape of the base end side (upper side) of the tip surface of the upper electrode may be configured in any manner.

[0044] For example, as shown in FIG. 4(a), the upper electrode 13 may be longer in the vertical direction (stacking direction) than the upper electrode 10. Also, as shown in FIG. 4(b), the upper electrode 14 may be formed in the shape of a truncated cone whose tip tapers downward. Alternatively, as shown in FIG. 4(c), the upper electrode 15 may be formed in a shape that combines two truncated cones, one above the other, whose generatrix has different inclination angles.

[0045] (Other embodiments) The present invention is not limited to the embodiments, and can be embodied in various other forms without departing from the spirit or main characteristics thereof.

[0046] In the above embodiment, two metal plates (an aluminum plate 40 and an iron plate 50) are joined together, but this is not limited thereto, and three or more metal plates, such as one aluminum plate 40 and two iron plates 50, may be joined together.

[0047] In addition, in the above embodiment, metal plates made of two types of metal materials (aluminum plate 40 and iron plate 50) are joined, but this is not limiting, and metal plates made of three or more types of metal materials may be joined.

[0048] Furthermore, in the above embodiment, the lower electrode 20 is configured as a radius electrode, but this is not limiting, and the lower electrode 20 may be configured as a flat electrode.

[0049] In addition, in the above embodiment, the stacking direction and pressing direction of the metal plates are made to coincide with the vertical direction, but this is not limited to the above, and the stacking direction and pressing direction may be made to coincide with, for example, a direction inclined from the vertical direction or the horizontal direction.

[0050] As such, the above-described embodiment is merely illustrative in all respects and should not be construed as limiting. Furthermore, all modifications and variations within the scope of the claims are within the scope of the present invention. [Industrial Applicability]

[0051] According to the present invention, a nugget can be formed satisfactorily while suppressing the generation of spatters and burrs, and therefore it is possible to join a plurality of stacked metal plates using a rivet. Resistance welding method It is extremely useful when applied to [Explanation of symbols]

[0052] 1 Resistance welding equipment 10 Upper electrode (first electrode) 10a Tip surface 20 Lower electrode (second electrode) 30 Rivet 31 Kasabe 31a Top surface (opposite side to the shaft) 31b Recess 33 Shaft 37 Groove 35 Outer wall 40 Aluminum plate (metal plate) 50 Iron plate (metal plate) D1 Contact surface diameter D2 Outer diameter of the shaft on the cap side D3 Inner diameter of outer wall

Claims

[Claim 1] A resistance welding method for joining a plurality of stacked metal plates using a rivet, comprising the steps of: a resistance welding device including a first electrode that presses the rivet against the plurality of metal plates in a stacking direction, and a second electrode that is disposed opposite the first electrode across the plurality of metal plates and presses the plurality of metal plates toward the first electrode in the stacking direction; The rivet used has a substantially disk-shaped cap portion having a flat surface that contacts the tip surface of the first electrode, a shaft portion extending from a center of the cap portion toward the second electrode side in the stacking direction, and an outer peripheral wall portion extending from a peripheral edge of the cap portion in the same direction as the shaft portion and forming a groove between the shaft portion and the outer peripheral wall portion, In addition, the relationship between the first electrode and the rivet is set such that the diameter of the contact surface between the first electrode and the cap portion of the rivet at the start of current flow is larger than the outer diameter of the cap portion side of the shank of the rivet and smaller than the inner diameter of the outer peripheral wall portion of the rivet, Furthermore, the first electrode is provided with a flat electrode portion having a flat tip portion that contacts the cap portion of the rivet, and a spherical radius electrode portion provided around the outer periphery of the flat electrode portion, a resistance welding method for joining the multiple metal plates by sandwiching the rivet and the multiple metal plates between the first electrode and the second electrode and applying a current while applying pressure to the rivet and the multiple metal plates with the first electrode and the second electrode.

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