Solid state resistance spot joining apparatus

Abstract

To provide a solid phase resistance spot joining device capable of improving joining quality.SOLUTION: The solid phase resistance spot joining apparatus includes a pressurizing shaft 10 capable of pressurizing materials to be joined to each other in the thickness direction thereof. The pressurizing shaft 10 has a pressurizing part 14 for pressurizing the material to be joined. A length in a first direction orthogonal to a pressurizing direction is longer than a length in a second direction orthogonal to both the pressurizing direction and the first direction in a cross section of the pressurizing part 14 on an orthogonal plane orthogonal to the pressurizing direction of the material to be joined by the pressurizing shaft 10.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a solid resistance spot bonding apparatus. [Background technology]

[0002] WO 2021 / 182444 discloses a solid-state spot joining device including a pair of central pressure shafts and a pair of electrodes. The tip of the central pressure shaft has a flat portion formed in the center, a tapered portion connected to the peripheral portion of the flat portion, a step extending from the peripheral portion of the tapered portion along the axial direction of the central pressure shaft, and a flat portion extending from the base end of the step in a direction perpendicular to the axial direction. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2021 / 182444 Summary of the Invention [Problem to be solved by the invention]

[0004] In solid resistance spot bonding apparatus such as that described in WO 2021 / 182444, it is desirable to improve the bonding quality.

[0005] An object of the present disclosure is to provide a solid resistance spot joining apparatus that can improve joining quality. [Means for solving the problem]

[0006] As a result of extensive research to solve the above-mentioned problems, the inventors discovered that ensuring the circumferential length of the indentation (nugget) increases the joining strength. Specifically, in the case of a solid-state resistance spot, burrs are expelled during joining, and the area of ​​the portion of the joined materials where plastic flow occurs directly contributes to the joining. Therefore, shortening the distance from the pressure point of the pressure shaft to the burr expulsion point of the joined materials (the distance from the pressure point to the outer periphery of the indentation) increases the joining strength. On the other hand, for the same area of ​​the indentation, the periphery of the outer shape is longer when the outer shape of the indentation is rectangular than when it is circular. Therefore, the inventors discovered that by making the outer shape of the indentation rectangular, the burr expulsion distance is shortened, thereby improving the joining strength.

[0007] The present invention has been made based on the above viewpoint. Specifically, a resistance spot welding device according to one aspect of the present disclosure includes a pressure shaft capable of applying pressure to workpieces to be joined in a thickness direction thereof, the pressure shaft having a pressure part that applies pressure to the workpieces, and a length in a first direction orthogonal to the pressure direction in a cross section of the pressure part in an orthogonal plane orthogonal to the direction in which the pressure shaft applies pressure to the workpieces is longer than a length in a second direction orthogonal to both the pressure direction and the first direction. [Effects of the Invention]

[0008] According to the present disclosure, it is possible to provide a solid resistance spot joining apparatus that can improve joining quality. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a cross-sectional view schematically illustrating a solid resistance spot bonding apparatus according to an embodiment of the present disclosure. [Figure 2] FIG. [Figure 3] FIG. 4 is a cross-sectional view of the pressure unit in an orthogonal plane. [Figure 4] FIG. 10 is a diagram schematically showing the direction in which burrs of the workpieces move when pressure is applied; [Figure 5]FIG. 10 is a diagram schematically showing the direction in which burrs of the workpieces move when pressure is applied; [Figure 6] FIG. 10 is a diagram showing a schematic outline of an indentation after pressure is applied. [Figure 7] FIG. 10 is a perspective view schematically showing a modified example of the pressure unit. [Figure 8] FIG. 10 is a cross-sectional view schematically showing a modified example of the pressure unit. [Figure 9] FIG. 10 is a cross-sectional view schematically showing a modified example of the pressure unit. [Figure 10] FIG. 10 is a perspective view schematically showing a modified example of the pressure unit. [Figure 11] FIG. 10 is a cross-sectional view schematically showing a modified example of the pressure unit. [Figure 12] FIG. 10 is a cross-sectional view schematically showing a modified example of the pressure unit. DETAILED DESCRIPTION OF THE INVENTION

[0010] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] The present disclosure will be described with reference to the accompanying drawings, in which the same or corresponding elements are designated by the same reference numerals.

[0011] 1 is a cross-sectional view schematically illustrating a solid-state resistance spot joining apparatus according to an embodiment of the present disclosure. The solid-state resistance spot joining apparatus 1 is an apparatus for joining overlapping workpieces while maintaining the workpieces in a solid state by passing an electric current through the workpieces to form softened regions and plastically deforming the softened regions.

[0012] In this embodiment, the workpieces include a first workpiece W1 and a second workpiece W2. Each of the workpieces W1 and W2 is made of a metal such as iron or aluminum. Each of the workpieces W1 and W2 is formed, for example, in a flat plate shape.

[0013] As shown in FIG. 1, the solid-state resistance spot bonding apparatus 1 includes a pressure shaft 10 and an electrode 20.

[0014] The pressure shaft 10 is capable of applying pressure to the workpieces in their thickness direction. The pressure shaft 10 has a shape that extends long in one direction (the vertical direction in FIG. 1). For example, the pressure shaft 10 may be formed in a cylindrical shape. The pressure shaft 10 is capable of pressing the workpieces so as to plastically deform the workpieces. The pressure shaft 10 is made of, for example, tungsten carbide. The pressure shaft 10 is driven by a drive source (such as a servo press) not shown. As shown in FIG. 1, the solid-state resistance spot bonding apparatus 1 may have a pair of pressure shafts 10 that are capable of applying pressure to the workpieces from both sides in their thickness direction.

[0015] As shown in FIG. 1, the pressure shaft 10 includes a pressure shaft main body 12 having a shape that extends elongated in one direction, and a pressure portion 14.

[0016] The pressure applying part 14 is a part that applies pressure to the workpieces. The pressure applying part 14 is formed at the tip of the pressure applying shaft 10. The pressure applying part 14 is a part that comes into contact with the workpieces and forms an indentation (nugget) in the workpieces.

[0017] Fig. 2 is a perspective view of the pressure applying unit 14. Fig. 3 is a cross section of the pressure applying unit 14 on an orthogonal plane perpendicular to the direction in which the pressure applying shaft 10 applies pressure to the workpieces (the vertical direction in Fig. 1). In this embodiment, the pressure applying direction coincides with the central axis AX of the pressure applying shaft 10.

[0018] 2 and 3, the length of the pressure applying unit 14 in a first direction perpendicular to the pressure applying direction (central axis AX) is longer than the length of the pressure applying unit 14 in a second direction perpendicular to both the pressure applying direction and the first direction. As shown in Fig. 3, the length L1 in the first direction of the cross section of the pressure applying unit 14 on the perpendicular plane is longer than the length L2 in the second direction of the cross section. The length L1 is preferably 1.2 to 7.0 times the length L2, and more preferably 2.0 to 6.0 times the length L2.

[0019] 3, the length in the second direction of the cross section of the pressure applying unit 14 in the orthogonal plane gradually increases with increasing distance from the tip of the pressure applying unit 14. The length in the first direction of the cross section of the pressure applying unit 14 in the orthogonal plane may gradually increase with increasing distance from the tip of the pressure applying unit 14.

[0020] The electrode 20 is disposed around the pressure shaft 10. The electrode 20 can pass electricity through the workpieces while in contact with the workpieces. A voltage is applied to the electrode 20 from a power supply unit (not shown). The electrode 20 contacts a portion of the workpieces surrounding a portion that is pressed by the pressure unit 14. In this embodiment, the electrode 20 is formed in a cylindrical shape that surrounds the pressure shaft 10. A gap is provided between the inner peripheral surface of the electrode 20 and the outer peripheral surface of the pressure shaft 10. The electrode 20 is made of, for example, copper.

[0021] 4 and 5 show schematic diagrams illustrating the movement direction of burrs on the workpieces when pressure is applied. As shown in Fig. 4, when the workpieces are pressed by the pressure unit 14, a portion of the workpieces is ejected mainly in the second direction. Furthermore, as shown in Fig. 5, when the workpieces are pressed by the pressure unit 14, a portion of the workpieces is also ejected in the first direction.

[0022] Fig. 6 shows a schematic outline of the indentation after pressure is applied. As shown in Fig. 6, the outline t2 of the indentation after pressure is applied by the pressure applying unit 14 is approximately rectangular. The perimeter of this indentation is longer than the perimeter of a circular indentation having the same area as the indentation. In Fig. 6, the outline t1 of the indentation at the initial stage of contact by the pressure applying unit 14 is shown by a dashed line.

[0023] As described above, in the solid-state resistance spot welding apparatus 1 of this embodiment, the length L1 in the first direction of the cross section of the pressing unit 14 in the orthogonal plane is longer than the length L2 in the second direction, so the outer shape of the indentation is approximately rectangular, ensuring a long perimeter of the indentation. In other words, the distance over which burrs are removed from the workpieces during welding is shortened, improving the welding strength of the workpieces.

[0024] In the above embodiment, an example of joining a first workpiece W1 and a second workpiece W2 to each other is shown, but the solid resistance spot joining apparatus 1 can also be applied to the case of joining three or more workpieces to each other.

[0025] As shown in FIGS. 7 to 9, the cross section of the pressure member 14 in a plane perpendicular to the first direction may be formed in a downwardly convex arc shape.

[0026] As shown in Figures 10 to 12, the cross section of the pressure applying portion 14 in a plane perpendicular to the first direction may have a tip pressure applying portion 14a formed in an arc shape that is convex downward, and a tapered portion 14b whose length in the second direction gradually increases as it moves away from the tip pressure applying portion 14a.

[0027] It will be appreciated by those skilled in the art that the exemplary embodiments described above are examples of the following aspects.

[0028] [Aspect 1] a pressure shaft capable of applying pressure to the workpieces to be joined in the thickness direction thereof; the pressure shaft has a pressure portion that applies pressure to the workpieces, a cross section of the pressing portion in an orthogonal plane perpendicular to the pressing direction of the workpieces by the pressing axis, the cross section having a length in a first direction perpendicular to the pressing direction that is longer than a length in a second direction perpendicular to both the pressing direction and the first direction.

[0029] In this resistance spot welding device, the length in the first direction of the cross section of the pressurizing part in the orthogonal plane is longer than the length in the second direction, so the outer shape of the indentation is approximately rectangular, ensuring a long perimeter, thereby improving the welding strength of the workpieces.

[0030] [Aspect 2] 2. The solid-state resistance spot joining apparatus according to claim 1, wherein the length of the first direction in the cross section of the pressure applying portion in the orthogonal plane is 1.2 to 7.0 times the length of the second direction in the cross section.

[0031] [Aspect 3] 3. The solid-state resistance spot joining apparatus according to claim 1, wherein a length of the pressure applying portion in the second direction in the cross section of the orthogonal plane gradually increases with increasing distance from the tip of the pressure applying portion.

[0032] In this embodiment, when the workpieces are pressed by the pressing shaft, burrs are discharged from the tip of the pressing part in the second direction, that is, in the relatively short direction, thereby shortening the distance over which the burrs are discharged.

[0033] It should be noted that the embodiments disclosed herein are illustrative in all respects and should not be considered limiting. The scope of the present invention is defined by the claims, not by the description of the above embodiments, and further includes all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0034] 1 solid resistance spot joining device, 10 pressure shaft, 12 pressure shaft body, 14 pressure part, 20 electrode, W1 first workpiece, W2 second workpiece.

Claims

1. a pressure shaft capable of applying pressure to the workpieces to be joined in the thickness direction thereof; the pressure shaft has a pressure portion that applies pressure to the workpieces, a cross section of the pressing portion in an orthogonal plane perpendicular to the pressing direction of the workpieces by the pressing axis, the cross section having a length in a first direction perpendicular to the pressing direction that is longer than a length in a second direction perpendicular to both the pressing direction and the first direction.

2. 2. The solid-state resistance spot joining device according to claim 1, wherein a length in the first direction of the cross section of the pressure applying part on the orthogonal plane is 1.2 times or more and 7.0 times or less a length in the second direction of the cross section.

3. 3. The solid-state resistance spot joining device according to claim 1, wherein a length in the second direction of the cross section of the pressure applying portion in the orthogonal plane gradually increases with increasing distance from the tip of the pressure applying portion.

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