Laser welding method for electric wire

Abstract

Performed in the present invention are: a first step for, when irradiating terminal end faces 34Uw, 35Uw of terminal end sections of a first electric wire 34 and a second electric wire 35 with a laser beam LB, scanning the laser beam and forming a first molten pool 40 in the plane of the terminal end face of the first electric wire; a second step for scanning the laser beam and forming a second molten pool 41 in the plane of the terminal end face of the second electric wire after the first step; and a third step for scanning the laser beam across the first molten pool and the second molten pool to connect the first molten pool and the second molten pool and form a third molten pool 42 after the second step.　Thus, it is possible to suppress entry of the laser beam into a gap between abutment surfaces of the first electric wire and the second electric wire and to suppress the production of spatter.

Description

Laser welding method for electric wires

[0001] The present invention relates to a laser welding method for electric wires, and more particularly to a laser welding method for electric wires in which end faces of two electric wires are laser-welded while the two electric wires are placed close to each other.

[0002] A stator for an electric motor comprises a stator core and a number of segment coils fitted into slots formed on the inner periphery of the stator core. Typically, each segment coil is made of insulating, rectangular wire, and the ends of the segment coils are joined together by welding or other means.

[0003] Increasing the number of segment coils in such electric motors is one way to increase their efficiency. However, increasing the number of segment coils also increases the number of welds at the coil ends, which extends the cycle time (CT) of the welding process with current TIG welding, resulting in reduced production efficiency and costs. TIG welding has a low energy density, and it takes time to achieve the required penetration (bead volume). Furthermore, a long welding time increases the heat-affected area, necessitating a longer coating removal time to avoid damage to the insulating coating.

[0004] To overcome these weaknesses of TIG welding, it has been proposed to weld the end portions of the segment coils together by laser welding. For example, Japanese Patent Application Laid-Open No. 2018-20340 (Patent Document 1) discloses a laser welding method for flat wires in which the end sides of the first and second flat wires, from which the insulating coating has been peeled off, are butted together and a laser beam is irradiated onto the end faces of the first and second flat wires to weld the end sides together.

[0005] Patent document 1 shows that when a laser beam is irradiated onto the end faces of the first and second flat wires, the steps of scanning the laser beam in a loop within the end face of the first flat wire to form a molten pool, and increasing the diameter of the loop-like trajectory along which the laser beam is scanned within the end face of the first flat wire until the molten pool reaches the butting surface between the end side faces, thereby suppressing the adverse effects caused by the laser beam penetrating into the gap between the butting surfaces.

[0006] JP 2018-20340 A

[0007] In Patent Document 1, the molten pool does indeed reach the gap between the butted end faces of the first and second rectangular wires, blocking the gap with molten metal and preventing the laser beam from penetrating. However, the welding method of Patent Document 1 has the problem of prone to spatter. In other words, Patent Document 1 uses a single-core mode laser beam to continuously irradiate the end faces of the first and second rectangular wires to expand the molten pool, or splits the laser beam and simultaneously irradiates the end faces of the first and second rectangular wires to form a molten pool. This naturally increases the energy density, forming a deep molten pool in a narrow keyhole and prone to spatter.

[0008] An object of the present invention is to provide a method for welding electric wires that can prevent a laser beam from penetrating into a gap between the butted surfaces of a first electric wire and a second electric wire, and can also prevent the generation of spatter.

[0009] A feature of the present invention is a laser welding method for electric wires, in which side end surfaces of the first electric wire and the second electric wire along the axis of the first electric wire and the second electric wire are brought close to each other, and a laser beam is irradiated onto end surfaces of the end surfaces of the first electric wire and the second electric wire in a direction transverse to the axis, and the method is characterized in that when the laser beam is irradiated onto the end surfaces of the first electric wire and the second electric wire, the method comprises a first step of scanning the laser beam within the surface of the end surface of the first electric wire to form a first molten pool, a second step of scanning the laser beam within the surface of the end surface of the second electric wire after the first step to form a second molten pool, and a third step of scanning the laser beam across the first and second molten pools to connect the first and second molten pools to form a third molten pool after the second step.

[0010] According to the present invention, it is possible to provide a method for welding electric wires that can prevent a laser beam from penetrating into a gap between the butted surfaces of a first electric wire and a second electric wire, and also can prevent the generation of spatter.

[0011] FIG. 1 is an external perspective view of a stator of an electric motor to which the present invention is applied, seen from diagonally above. FIG. 2 is an explanatory diagram of laser welding the connection portion of a stator segment coil using a galvanometer scanner. FIG. 3 is a structural diagram illustrating the configuration of the connection portion of a segment coil. FIG. 4 is an explanatory diagram illustrating the configuration of a multi-core laser beam. FIG. 5 is an explanatory diagram illustrating the beam configuration of a multi-core laser beam. FIG. 6 is an explanatory diagram illustrating the welding state using a multi-core laser beam. FIG. 7 is an explanatory diagram illustrating the laser absorptivity of various lasers for copper. FIG. 8 is an explanatory diagram illustrating the state when a laser beam is irradiated onto a first flat copper wire. FIG. 9 is an explanatory diagram illustrating the state when a laser beam is irradiated onto a second flat copper wire. FIG. 10 is an explanatory diagram illustrating the state when a laser beam is irradiated onto a molten pool of the first flat copper wire and a molten pool of the second flat copper wire. FIG. 11 is an explanatory diagram illustrating the state after irradiating the molten pool of the first flat copper wire and a molten pool of the second flat copper wire with a laser beam. FIG. 12 is an explanatory diagram illustrating the procedure (step) when laser welding a first flat copper wire and a second flat copper wire.

[0012] Hereinafter, an embodiment of the laser welding method for electric wires according to the present invention will be described with reference to the drawings. The present invention is not limited to the following embodiment, and various modifications and applications within the technical concept of the present invention are also included within the scope of the present invention.

[0013] First, an example of the configuration of a stator including segment coils welded using the flat wire laser welding method according to this embodiment will be described.

[0014] Fig. 1 is a perspective view showing the schematic configuration of a stator. As shown in Fig. 1, stator 1, which is the stator of an electric motor, has a stator core 10 and a plurality of segment coils 20. Stator core 10 is made by laminating annular electromagnetic steel plates in the axial direction of stator 1 (z-axis direction in Fig. 1), and has a generally cylindrical shape as a whole.

[0015] The inner peripheral surface of the stator core 10 is provided with teeth 11 that protrude inward and extend in the axial direction of the stator 1, and slots 12 that are grooves formed between adjacent teeth 11. A segment coil 20 is attached to each slot 12.

[0016] The segment coil 20 is an electric wire with a rectangular cross section, i.e., a rectangular wire. Typically, the segment coil 20 is made of pure copper, but it may also be made of a metal material with high conductivity, such as aluminum, copper, or an alloy mainly composed of aluminum. Since the segment coil 20 is made of pure copper in this embodiment, it will be described below as a rectangular copper wire.

[0017] Each segment coil 20 is formed in a roughly U-shape. As shown in FIG. 1 , the ends (coil ends) of the segment coils 20 all protrude from the upper end surface of the stator core 10. A joint 25 is a portion where the ends of radially adjacent segment coils 20 are welded together. A plurality of joints 25 are arranged in a circular ring shape in the circumferential direction of the stator core 10. In the example of FIG. 1 , 48 joints 25 are arranged in a circular ring shape. Furthermore, these circularly arranged joints 25 are arranged in four rows in the radial direction.

[0018] The respective joints 25 of the segment coil 20 are welded by laser beams LB emitted in a predetermined order by a galvanometer scanner GS, as shown in Figure 2. Laser welding devices using galvanometer scanners GS are well known, so a detailed description will be omitted.

[0019] Next, the detailed configuration of the joint 25 will be described with reference to Fig. 3. In Fig. 3, the first flat copper wire 30 and the second flat copper wire 31 are coated with a first insulating coating 32 and a second insulating coating 33, respectively, but the insulating coatings 32 and 33 have been removed from the tip ends to be welded. The areas where the insulating coatings 32 and 33 have been removed are defined as a first end portion 34 and a second end portion 35.

[0020] When welding, the first flat copper wire 30 and the second flat copper wire 31 are overlapped so that the side surface 32Si of the first flat copper wire 30 along the axis P1 of the first flat copper wire 30 and the side surface 33Si of the second flat copper wire 31 along the axis P2 of the second flat copper wire 31 are in contact. At this time, the side end surface 34Sc of the first terminal end 34 and the side end surface 35Sc of the second terminal end 35 facing it are also close to each other, but because the insulating coatings 32 and 33 have been removed, there is a slight gap G between them in the axial direction. The axes P1 and P2 are generally parallel to each other.

[0021] The first end face 34Uw is formed in a direction transverse to the axis P1 of the first end portion 34, in this case, a direction perpendicular to the axis P1. Similarly, the second end face 35Uw is formed in a direction transverse to the axis P2 of the second end portion 35, in this case, a direction perpendicular to the axis P2. The first end face 34Uw and the second end face 35Uw are determined to be at the same height in the axial direction, or "flush." ​​In this state, a laser beam is irradiated onto the first end face 34Uw and the second end face 35Uw, and the first end portion 34 and the second end face 35 are joined by welding.

[0022] In this embodiment, the side surface 32Si of the first flat copper wire 30 and the side surface 33Si of the second flat copper wire 31 are overlapped so that they come into contact with each other, and then joined by welding, but they may also be joined by welding in a state where they are arranged so that they do not come into contact with the side surface 33Si of the second flat copper wire 31. Furthermore, the first end surface 34Uw and the second end surface 35Uw do not have to be at the same height when viewed in the axial direction.

[0023] Next, the configuration of the laser beam used in this embodiment will be described with reference to Figures 4 to 6. In this embodiment, a multi-core laser beam is used to further reduce the occurrence of spatter.

[0024] As shown in Fig. 4, the emitted multi-core laser beam LB is separated into an inner core laser beam LBin and an outer core laser beam LBout by a variable beam switch VBS. In this case, the inner core laser beam LBin has a larger output than the outer core laser beam LBout.

[0025] The inner core laser beam LBin and the outer core laser beam LBout pass through a condenser lens CL and are incident on the 2-in-1 fiber FB. The cross-sectional shape of the laser beam LB generated at this time is as shown in Figure 5. As shown in Figure 5, the outer core laser beam LBout is formed around the outer periphery of the inner core laser beam LBin, and preheating is performed by the outer core laser beam LBout, and the base material is melted by the inner core laser beam LBin.

[0026] 6 shows a state in which a base material is melted by a multi-core laser beam. When an inner core laser beam LBin and an outer core laser beam LBout are irradiated onto a metal base material M, the base material M is preheated by the outer core laser beam LBout in the traveling direction. At this time, a keyhole KH is formed by the inner core laser beam LBin, and an opening OP of the keyhole KH is formed large by the outer core laser beam LBout.

[0027] Therefore, the vapor MV (shown by the broken line) generated from the molten metal base material M is discharged without entraining the molten metal. This suppresses the generation of spatter. Furthermore, because the output is small, the welding is of a heat conduction type, which further suppresses the generation of spatter.

[0028] In addition, the laser beam used in this case is a visible light laser, with blue or green lasers being particularly suitable. Figure 7 shows the laser absorption rate of the copper that forms the rectangular copper wire. As can be seen from this figure, blue or green lasers have a high laser absorption rate and are easy to use in a thermal conduction welding form. Therefore, it is clear that it is best to use a multi-core laser beam from a blue or green laser. Note that although a visible light laser was used in this example, an infrared laser may also be used.

[0029] Next, the present embodiment in which the flat copper wire described above is laser-welded by a multi-core laser beam will be described.

[0030] First, the irradiation pattern of the laser beam applied to the end faces of the two flat copper wires in this embodiment will be described. The laser beam is basically applied in the following order: "irradiation onto the first flat copper wire 30" ⇒ "irradiation onto the second flat copper wire 31" ⇒ "irradiation across the first flat copper wire 30 and the second flat copper wire 31." However, additional irradiation may be performed individually if necessary.

[0031] <Irradiation onto the first flat copper wire> Fig. 8 shows a method of irradiating the first end surface 34Uw of the first end portion 34 of the first flat copper wire 30. Note that in this figure, the laser beam LB is exaggerated for ease of understanding.

[0032] 8, the laser beam LB is irradiated perpendicularly to the first end surface 34Uw of the first rectangular wire 30. Then, the laser beam LB scans the first end surface 34Uw of the first rectangular wire 30 along a loop-shaped scanning trajectory Scn1 indicated by a dashed line, thereby forming a first molten pool 40 (see FIG. 9).

[0033] Here, the scanning locus Scn1 of the laser beam LB is determined so that the outer edge of the outer core laser beam LBout does not extend beyond the outer peripheral edge of the first terminal end face 34Uw. This prevents the laser beam LB from being irradiated into the gap G formed between the side end face 34Sc of the first flat rectangular copper wire 30 and the side end face 35Sc of the second terminal end portion 35. This prevents so-called laser dropout.

[0034] In this embodiment, the scanning locus Scn1 is set to an ellipse because the shape of the first end face 34Uw of the first flat rectangular copper wire 30 is rectangular, but if the shape of the first end face 34Uw is square, it will be set to a circle. Also, although the scanning locus Scn1 is a closed loop locus, it may be, for example, an open spiral locus.

[0035] Here, the scanning locus Scn1 of the laser beam LB is formed in a loop shape, so the first molten pool 40 can be grown by scanning the laser beam LB multiple times. This allows a sufficient amount of the first molten pool 40 to be formed over the entire first terminal end surface 34Uw of the first rectangular copper wire 30. In other words, a sufficient molten volume of molten metal required for welding can be secured. When irradiation of the laser beam LB is completed, the first molten pool 40 is formed in the form shown in FIG. 9.

[0036] Furthermore, when the first molten pool 40 is formed over the entire surface in this manner, the molten metal (copper) of the first molten pool 40 flows into the gap G formed between the side end surface 34Sc and the side end surface 35Sc, and the gap G is blocked by the molten metal, thereby preventing the laser beam LB in the next process from penetrating into the gap G.

[0037] Furthermore, since the first molten pool 40 is formed over almost the entire area, it is possible to eliminate corner residues that could cause damage to insulating covers and other parts attached after welding, thereby improving reliability.

[0038] <Irradiation of Second Flat Rectangular Copper Wire> After the irradiation of the first end surface 34Uw with the laser beam LB is completed, irradiation of the second end surface 35Uw of the second flat rectangular copper wire 31 is then performed.

[0039] 9, the laser beam LB is irradiated perpendicularly to the second end surface 35Uw of the second rectangular wire 31. Then, the laser beam LB is scanned within the second end surface 35Uw of the second rectangular wire 31 along a loop-shaped scanning trajectory Scn2 indicated by the dashed line, thereby forming a second molten pool 41 (see FIG. 10).

[0040] Here, the scanning locus Scn2 of the laser beam LB is determined so that the outer edge of the outer core laser beam LBout does not extend beyond the outer peripheral edge of the second terminal end surface 35Uw. This prevents the laser beam LB from being irradiated into the gap G formed between the side end surface 34Sc of the first flat copper wire 30 and the side end surface 35Sc of the second terminal end portion 35, thereby avoiding laser dropout. In addition, the gap G is blocked by the molten metal of the first molten pool 40 formed on the first terminal end surface 34Uw of the first flat copper wire 30, which also prevents laser dropout.

[0041] As with the first flat copper wire, the second end surface 35Uw of the second flat copper wire 31 has a rectangular shape, so the scanning locus Scn2 is set to an elliptical shape. If the first end surface 34Uw has a square shape, the scanning locus Scn2 is set to a circular shape. While the scanning locus Scn2 is a closed loop locus, it may also be, for example, an open spiral locus.

[0042] Here, the scanning locus Scn2 of the laser beam LB is formed in a loop shape, so that the second molten pool 41 can be grown by scanning the laser beam LB multiple times. This allows a sufficient amount of second molten pool 41 to be formed over almost the entire second terminal end surface 35Uw of the second rectangular copper wire 31. In other words, a sufficient molten volume of molten metal required for welding can be secured. When irradiation of the laser beam LB is completed, the second molten pool 41 is formed in the form shown in FIG. 10.

[0043] Furthermore, since the second molten pool 41 is formed over the entire area, it is possible to eliminate corner residues that could cause damage to insulating covers and other parts attached after welding, thereby improving reliability.

[0044] <Cross-irradiation of the first flat copper wire and the second flat copper wire> After the irradiation of the laser beam LB to the first end face 34Uw of the first flat copper wire 31 and the irradiation to the second end face 35Uw of the second flat copper wire 31 are completed, cross-irradiation is then carried out to the first end face 34Uw of the first flat copper wire 31 and the second end face 35Uw of the second flat copper wire 31.

[0045] 10, the laser beam LB is irradiated in the vertical direction so as to straddle both the first molten pool 40 and the second molten pool 41. The irradiation form at this time is a loop-shaped scanning locus Scn3 along the elongated rectangular shape connecting the first end face 34Uw and the second end face 35Uw. Here, too, the scanning locus Scn3 of the laser beam LB is determined so that the outer edge of the outer core laser beam LBout does not extend beyond the outer peripheral edges of the first end face 34Uw and the second end face 35Uw.

[0046] The irradiation of the laser beam LB along this scanning trajectory Scn3 is carried out before the first molten pool 40 on the first end face 34Uw cools and solidifies, so the entire first end face 34Uw and the second end face 35Uw can be efficiently melted and made homogeneous, allowing welding to be completed effectively and saving time.

[0047] When the irradiation of the laser beam LB is completed, a third molten pool 42 is formed as shown in Fig. 11. The third molten pool 42 is a molten pool based on the first molten pool 40 and the second molten pool 41, and is a molten pool that entirely covers the first terminal surface 34 and the second terminal surface 35.

[0048] By executing this scanning trajectory Scn3, it is possible to ensure a sufficient melt volume of the molten metal in the first molten pool 40 and the second molten pool 41. Furthermore, since the laser beam LB is irradiated onto the entire first molten pool 40 and the second molten pool 41, it becomes easier to discharge the vapor of the molten metal, and the occurrence of spatter can be suppressed.

[0049] In addition, the laser beam LB is irradiated over the entire surface along the scanning trajectory Scn3 that spans the entire first end face 34Uw and the second end face 35Uw, resulting in heat conduction welding, which also makes it possible to suppress the occurrence of spatter.

[0050] A specific laser welding method for flat copper wires based on the above-described irradiation method of the laser beam LB will be described with reference to FIG.

[0051] In step (1), as described in Fig. 8, a laser beam LB is irradiated along a loop-shaped scanning path Scn1 onto the first terminal end surface 34Uw of the first rectangular copper wire 30. In this state, a first molten pool 40 is formed. The number of scanning revolutions is not particularly limited and may be any number sufficient to form the necessary first molten pool 40. After step (1) is completed, step (2) is performed.

[0052] In step (2), as described in Fig. 9, the second terminal end surface 35Uw of the second rectangular copper wire 31 is irradiated with the laser beam LB along the loop-shaped scanning path Scn2. In this state, the second molten pool 41 is formed. Here, too, the number of scanning revolutions is not particularly limited and may be the number of times required to form the necessary second molten pool 41. After step (2) is completed, step (3) is performed.

[0053] In step (3), as explained in Fig. 10, the laser beam LB is irradiated so as to span both the first molten pool 40 and the second molten pool 41. In this state, the third molten pool 42 is formed. Here, too, the number of scanning revolutions is not particularly limited and may be the number of revolutions required to form the necessary third molten pool 42. After step (3) is completed, step (4) is carried out.

[0054] In step (4), the laser beam LB is irradiated so as to straddle both the first molten pool 40 and the second molten pool 41, forming the third molten pool 42 as described in Figure 11. In this state, the laser beam LB is again irradiated onto the area corresponding to the second molten pool 42, as shown by the scanning trajectory Scn4. Here again, the number of scanning revolutions may be any number considered necessary, and is not particularly limited. After step (4) is completed, step (5) is executed.

[0055] In step (5), the laser beam LB is irradiated onto the third molten pool (corresponding to both the first molten pool 40 and the second molten pool 41) as shown by the scanning trajectory Scn5. Here, too, the number of scanning revolutions may be any number considered necessary, and is not particularly limited.

[0056] In this way, in this embodiment, the welding is performed in the following order: first flat copper wire ⇒ second flat copper wire ⇒ first flat copper wire and second flat copper wire ⇒ second flat copper wire ⇒ first flat copper wire and second flat copper wire. Because the laser beam is irradiated across the first and second flat copper wires before the first flat copper wire cools completely, the desired molten volume can be obtained more quickly than in the case of applying the laser beam from a completely cooled state, thereby shortening the welding time.

[0057] After step (5), the laser welding is completed in step (6). In step (6), a molten pool is formed over almost the entire surface of the first end surface 34Uw of the first rectangular copper wire 30 and the second end surface 35Uw of the second rectangular copper wire 31, resulting in the formation of a high-quality weld surface.

[0058] As described above, the present invention is a laser welding method for electric wires, in which side end surfaces of the first electric wire and the second electric wire along the axis of the first electric wire and the second electric wire are brought close to each other, and a laser beam is irradiated onto the end surfaces of the end surfaces of the first electric wire and the second electric wire in a direction transverse to the axis, and the method includes the following steps when irradiating the end surfaces of the first electric wire and the second electric wire with the laser beam: a first step of scanning the laser beam within the surface of the end surface of the first electric wire to form a first molten pool; a second step after the first step of scanning the laser beam within the surface of the end surface of the second electric wire to form a second molten pool; and a third step after the second step of scanning the laser beam across the first and second molten pools to connect the first and second molten pools to form a third molten pool.

[0059] This makes it possible to provide a wire welding method that can prevent the laser beam from penetrating into the gap between the butted surfaces of the first and second wires and also suppress the generation of spatter.

[0060] It should be noted that the present invention is not limited to the above-described embodiments and includes various modifications. The above-described embodiments have been described in detail to clearly explain the present invention, and the present invention is not necessarily limited to those including all of the described configurations. Furthermore, it is possible to replace part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. It is also possible to add, delete, or replace other configurations with respect to the configuration of each embodiment.

[0061] 25...Connection portion, 30...First flat copper wire, 31...Second flat copper wire, 32...First insulating coating, 33...Second insulating coating, 34...First termination portion, 34Sc...Side end face, 34Uw...First termination face, 35...Second termination portion, 35Sc...Side end face, 35Uw...Second termination face, 40...First molten pool, 41...Second molten pool, 42...Third molten pool, LB...Laser beam, LBin...Inner core laser beam, LBout...Outer core laser beam.

Claims

1. A method for laser welding electric wires, comprising bringing side end faces of a first electric wire and a second electric wire along an axis of the first electric wire and a second electric wire close to each other, and irradiating an end face of the end face of the first electric wire and the second electric wire in a direction transverse to the axis with a laser beam, the method comprising the steps of: when irradiating the end faces of the first electric wire and the second electric wire with the laser beam, a first step of scanning the laser beam within the plane of the end face of the first electric wire to form a first molten pool; after the first step, a second step of scanning the laser beam within the plane of the end face of the second electric wire to form a second molten pool; and after the second step, a third step of scanning the laser beam across the first molten pool and the second molten pool to connect the first molten pool and the second molten pool to form a third molten pool.

2. The method for laser welding electric wires described in claim 1, wherein the first electric wire and the second electric wire are a first rectangular wire and a second rectangular wire covered with an insulating coating, and the side end faces of the first rectangular wire and the second rectangular wire from which the insulating coating has been peeled off are butted together, and the laser beam is irradiated to the end faces of the first rectangular wire and the second rectangular wire in the order of the first process, the second process, and the third process to weld the end portions of the first rectangular wire and the second rectangular wire.

3. The method for laser welding an electric wire as described in claim 2, characterized in that a molten pool is formed over the entire end faces of the first rectangular wire and the second rectangular wire by the first process and the second process.

4. The method for laser welding electric wires according to claim 2, wherein the first rectangular wire and the second rectangular wire are coils used in a stator coil of an electric motor.

5. The method for laser welding an electric wire as described in claim 1, characterized in that the third step comprises scanning the laser beam in a loop shape a plurality of times across the first molten pool and the second molten pool.

6. A method for laser welding an electric wire as claimed in claim 1, characterized in that, after the third step, the laser beam is scanned within the plane of the end face of the second electric wire, and after this scanning, the laser beam is scanned across the first molten pool and the second molten pool.

7. A method for laser welding an electric wire as described in claim 1, characterized in that the laser beam used is a multi-core laser beam having a center laser beam emitted from a center core and sub-laser beams emitted from sub-cores on the outer periphery of the center core and having a lower energy density than the center laser beam.

8. A method for laser welding an electric wire as set forth in claim 7, characterized in that, at least in the first step, the sub-laser beam is irradiated within an area not exceeding the boundary of the end surface of the first electric wire.

9. The method for laser welding electric wires according to claim 8, characterized in that the laser beam is a visible light laser beam.

10. The method for laser welding electric wires according to claim 9, wherein the visible light laser beam is a blue laser beam or a green laser beam.

11. A method for laser welding electric wires as claimed in claim 1, characterized in that the laser beam is irradiated onto the end faces of the first electric wire and the second electric wire using a galvanometer scanner.

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