Laser welding method of electric wires

Abstract

To provide a welding method of electric wires which inhibits a laser beam from entering a space between butted surfaces of a first electric wire and a second electric wire and enables reduction of occurrence of spatter.SOLUTION: A welding method of electric wires includes: a first step of forming a first molten pool 40 by scanning a laser beam LB within an end edge surface of a first electric wire when the laser beam LB is radiated to end edge surfaces 34Uw, 35Uw of end edge parts of the first electric wire 34 and a second electric wire 35; a second step of forming a second molten pool 41 by scanning the laser beam within the end edge surface of the second electric wire after the first step; and a third step of forming a third molten pool 42 by connecting the first molten pool to the second molten pool by scanning the laser beam over the first molten pool and the second molten pool and after the second step.SELECTED DRAWING: Figure 12

Description

[Technical field]

[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. [Background technology]

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

[0003] In order to improve the efficiency of such motors, it is possible to increase the number of segment coils. However, increasing the number of segment coils means that the number of welds on the coil ends also increases, and with current TIG welding, the CT (cycle time) of the welding process is extended, resulting in a decrease in production efficiency and costs. TIG welding has a low energy density, and it takes time to ensure the required amount of penetration (bead volume). In addition, the long welding time also increases the heat-affected area, and in order to avoid damage to the insulating coating, it is necessary to take a long time to peel off the coating.

[0004] In order to compensate for such weaknesses of TIG welding, it has been proposed to weld the end portions of the segment coils together by laser welding. For example, JP 2018-20340 A (Patent Document 1) discloses a laser welding method for rectangular wires in which the end side surfaces of the first and second rectangular wires from which the insulating coating has been peeled off are butted together, and a laser beam is irradiated onto the end surfaces of the first and second rectangular wires to weld the end side surfaces together.

[0005] Patent document 1 shows that when a laser beam is irradiated onto the end faces of the first and second rectangular wires, the steps of scanning the laser beam in a loop-like manner within the end face of the first rectangular 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 rectangular wire until the molten pool reaches the butt face between the end side faces, thereby suppressing the adverse effects caused by the laser beam penetrating into the gap between the butt faces. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2018-20340 A Summary of the Invention [Problem to be solved by the invention]

[0007] In Patent Document 1, the molten pool certainly reaches the gap between the butted surfaces of the end faces of the first and second rectangular wires, so the gap is blocked by molten metal and the laser beam is prevented from penetrating. However, the welding method of Patent Document 1 has a problem that spatter is likely to occur. In Patent Document 1, a single core mode laser beam is used to continuously irradiate the end faces of the first and second rectangular wires with a laser beam to expand the molten area, or the laser beam is branched and simultaneously irradiated to the end faces of the first and second rectangular wires to form a molten area. As a result, the energy density naturally becomes large, and a deep molten pool is formed in a narrow keyhole, making it easy for spatter to occur.

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

[0009] The present invention is characterized in that the laser welding method for electric wires includes bringing side end faces of the first electric wire and the second electric wire along the axis of the first electric wire and the 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 including carrying out the following steps 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 surface of the end face 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 face of the second electric wire to form a second molten pool after the first step; 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. Effect of the Invention

[0010] According to the present invention, it is possible to provide a wire welding method that can prevent a laser beam from entering a gap between the butted surfaces of a first wire and a second wire and also can prevent the generation of spatter. [Brief description of the drawings]

[0011] [Figure 1] 1 is an external perspective view of a stator of an electric motor to which the present invention is applied, as viewed obliquely from above; [Diagram 2] 13 is an explanatory diagram of the case where the connection portion of the stator segment coil is laser-welded by a galvanometer scanner. FIG. [Diagram 3] 4 is a diagram illustrating the configuration of a connection portion of a segment coil. FIG. [Figure 4] FIG. 2 is an explanatory diagram illustrating the configuration of a multi-core laser beam. [Diagram 5] FIG. 2 is an explanatory diagram illustrating the beam configuration of a multi-core laser beam. [Figure 6] FIG. 2 is an explanatory diagram illustrating a welding state using a multi-core laser beam. [Figure 7] FIG. 2 is an explanatory diagram illustrating the laser absorptance of various lasers to copper. [Figure 8]FIG. 2 is an explanatory diagram illustrating a state when a laser beam is irradiated onto a first rectangular copper wire. [Figure 9] FIG. 4 is an explanatory diagram illustrating a state when a laser beam is irradiated onto a second rectangular copper wire. [Figure 10] 1 is an explanatory diagram illustrating the state when a laser beam is irradiated to a molten pool of a first rectangular copper wire and a molten pool of a second rectangular copper wire. FIG. [Figure 11] 1 is an explanatory diagram showing the state after a laser beam is irradiated onto a molten pool of a first rectangular copper wire and a molten pool of a second rectangular copper wire. FIG. [Figure 12] FIG. 2 is an explanatory diagram illustrating a procedure (step) for laser welding a first rectangular copper wire and a second rectangular copper wire. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, an embodiment of a steering device 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 in the scope of the present invention.

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

[0014] Fig. 1 is a perspective view showing a 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.

[0015] The inner peripheral surface of the stator core 10 is provided with teeth 11 that protrude to the inner peripheral side 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 having a rectangular cross section, i.e., a rectangular wire. Usually, the segment coil 20 is made of pure copper, but it may be made of a metal material having 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 into 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. The joints 25 are portions where the ends of radially adjacent segment coils 20 are welded together. A plurality of joints 25 are arranged in an annular shape in the circumferential direction of the stator core 10. In the example of FIG. 1, 48 joints 25 are arranged in an annular shape. Furthermore, the joints 25 arranged in an annular shape are arranged in four rows in the radial direction.

[0018] Each joint 25 of the segment coil 20 is welded by a laser beam LB emitted in a predetermined order by a galvanometer scanner GS, as shown in Fig. 2. Laser welding devices using the galvanometer scanner 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 rectangular copper wire 30 and the second rectangular copper wire 31 are covered with a first insulating coating 32 and a second insulating coating 33, but the insulating coatings 32 and 33 are removed from the tip sides to be welded. The areas where the insulating coatings 32 and 33 are removed are defined as a first end portion 34 and a second end portion 35.

[0020] When welding, the first flat copper wire 30 is 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 come into contact with each other. At this time, the side end surface 34Sc of the first terminal portion 34 and the side end surface 35Sc of the second terminal portion 35 facing this are also close to each other, but since the insulating coatings 32, 33 have been removed, they are close to each other with a small gap G in the axial direction. The axis P1 and the axis P2 are in a generally parallel positional relationship.

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

[0022] In this embodiment, the first end face 34Uw and the second end face 35Uw are welded together after being overlapped so that the side faces 33Si of the second rectangular copper wire 31 come into contact with each other, but the first end face 34Uw and the second end face 35Uw may be welded together in a state in which the side faces 33Si of the second rectangular copper wire 31 do not come into contact with each other. Also, the first end face 34Uw and the second end face 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 sputtering.

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

[0025] The inner core laser beam LBin and the outer core laser beam LBout pass through the 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 outside of the inner core laser beam LBin, and the outer core laser beam LBout provides preheating, and the inner core laser beam LBin melts the base material.

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

[0027] Therefore, the steam MV, shown by the broken line, generated from the molten metal base material M is discharged without entraining the molten metal. This makes it possible to suppress the generation of spatter. Furthermore, since the output is small, the welding form is a heat conduction type, making it possible to further suppress the generation of spatter.

[0028] In addition, the laser beam used at this time is a visible light laser, and a blue laser or a green laser is particularly suitable. Figure 7 shows the laser absorption rate of copper forming the rectangular copper wire. As can be seen from this figure, the laser absorption rate of blue lasers and green lasers is high, and they are easy to use for a thermal conduction type welding form. Therefore, it is found that it is good to use a multi-core laser beam using a blue laser or a green laser. Although a visible light laser is applied in this embodiment, an infrared laser may also be used.

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

[0030] First, the irradiation form of the laser beam irradiated to the end faces of the two rectangular copper wires executed in this embodiment will be described. The irradiation form of the laser beam is basically executed in the order of "irradiation to the first rectangular copper wire 30" ⇒ "irradiation to the second rectangular copper wire 31" ⇒ "irradiation across the first rectangular copper wire 30 and the second rectangular copper wire 31". However, there are also cases where additional irradiation is performed individually as necessary.

[0031] <Irradiation to No. 1 rectangular copper wire> 8 shows a method of irradiating the first end surface 34Uw of the first end portion 34 of the first rectangular copper wire 30. Note that in this drawing, the laser beam LB is exaggerated for ease of understanding.

[0032] In Fig. 8, the laser beam LB is irradiated in a vertical direction to the first end surface 34Uw of the first rectangular wire 30. Then, the laser beam LB is scanned within the first end surface 34Uw of the first rectangular wire 30 along a loop-shaped scanning trajectory Scn1 shown by a dashed line to form 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 surface 34Uw. This prevents the laser beam LB from being irradiated into the gap G formed between the side end surface 34Sc of the first rectangular copper wire 30 and the side end surface 35Sc of the second terminal end portion 35 ...

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

[0035] Here, since the scanning trajectory Scn1 of the laser beam LB is formed in a loop shape, 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 melt volume of molten metal required for welding can be secured. When the 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 that are attached after welding, thereby making it possible to improve reliability.

[0038] <Irradiation to second rectangular copper wire> When the irradiation of the laser beam LB onto the first end face 34Uw is completed, irradiation of the second end face 35Uw of the second rectangular copper wire 31 is then performed.

[0039] In Fig. 9, the laser beam LB is irradiated in a vertical direction to the second end surface 35Uw of the second rectangular wire 31. Then, within the second end surface 35Uw of the second rectangular wire 31, the laser beam LB is scanned along a loop-shaped scanning trajectory Scn2 shown by a dashed line to form 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 end of the second terminal 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 rectangular copper wire 30 and the side end surface 35Sc of the second terminal portion 35, thereby avoiding laser drop. In addition, the gap G is blocked by the molten metal of the first molten pool 40 formed on the first terminal surface 34Uw of the first rectangular copper wire 30, which also prevents laser drop.

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

[0042] Here, since the scanning locus Scn2 of the laser beam LB is formed in a loop shape, the second molten pool 41 can be grown by scanning the laser beam LB multiple times. This allows a sufficient amount of the 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 melt volume of molten metal required for welding can be secured. When the 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 an insulating cover or the like that is attached after welding, thereby making it possible to increase reliability.

[0044] <Straddle irradiation of the first and second rectangular copper wires> After irradiation of the laser beam LB onto the first end face 34Uw of the first flat rectangular copper wire 31 and irradiation of the second end face 35Uw of the second flat rectangular copper wire 31 are completed, cross-irradiation is then performed onto the first end face 34Uw of the first flat rectangular copper wire 31 and the second end face 35Uw of the second flat rectangular 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 a long and narrow rectangular shape connecting the first terminal surface 34Uw and the second terminal surface 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 ends of the first terminal surface 34Uw and the second terminal surface 35Uw.

[0046] The irradiation of the laser beam LB along this scanning trajectory Scn3 is performed before the first molten pool 40 on the first end face 34Uw cools and solidifies, so that the entire first end face 34Uw and the second end face 35Uw can be efficiently melted and made into a homogeneous state, thereby enabling the 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. In addition, 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, since the laser beam LB is irradiated over the entire first end face 34Uw and the second end face 35Uw along the scanning trajectory Scn3, which spans the entire first end face 34Uw and the second end face 35Uw, heat conduction welding is performed, which also makes it possible to suppress the generation of spatter.

[0050] A specific laser welding method for a rectangular copper wire 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 trajectory Scn1 to 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 may be the number of times required to form the first molten pool 40, and is not particularly limited. 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 a laser beam LB along a loop-shaped scanning trajectory Scn2. In this state, a second molten pool 41 is formed. Again, the number of scanning revolutions may be the number of times required to form the second molten pool 41, and is not particularly limited. 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, a third molten pool 42 is formed. Again, the number of scanning revolutions may be the number of times required to form the third molten pool 42, and is not particularly limited. After step (3) is completed, step (4) is carried out.

[0054] In step (4), the laser beam LB is irradiated so as to span both the first molten pool 40 and the second molten pool 41, forming the third molten pool 42 as described in Fig. 11. In this state, as shown by the scanning trajectory Scn4, the laser beam LB is again irradiated to the area corresponding to the second molten pool 42. 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 carried out.

[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 manner, in this embodiment, the first rectangular copper wire is welded in the following order: ⇒ the second rectangular copper wire ⇒ the first rectangular copper wire and the second rectangular copper wire ⇒ the second rectangular copper wire ⇒ the first rectangular copper wire and the second rectangular copper wire. Before the first rectangular copper wire cools completely, the laser beam is irradiated across the first and second rectangular copper wires, so compared to the method of applying the laser beam from a completely cooled state, the desired molten volume can be obtained more quickly, and the welding time can be shortened.

[0057] When step (5) is completed, the state of step (6) is reached and the laser welding is completed. 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, and a good quality weld surface can be formed.

[0058] As described above, the present invention is a laser welding method for electric wires, in which side end faces of the first and second electric wires along the axes of the first and second electric wires are brought close to each other, and a laser beam is irradiated to an end face of the end face of the first and second electric wires in a direction transverse to the axis, and the method includes the following steps when irradiating the end faces of the first and second electric wires 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; 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 after the first step; 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.

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

[0060] The present invention is not limited to the above-described embodiments, but includes various modified examples. The above-described embodiments have been described in detail to clearly explain the present invention, and are not necessarily limited to those having all of the configurations described. In addition, it is possible to replace a 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. [Explanation of symbols]

[0061] 25...connection portion, 30...first rectangular copper wire, 31...second rectangular 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 laser welding method for electric wires, comprising: bringing side end surfaces of the first electric wire and the second electric wire along an axis of the first electric wire and the second electric wire close to each other; and irradiating a laser beam onto an end surface of the end portion of the first electric wire and the second electric wire in a direction transverse to the axis, thereby welding the end portions of the first electric wire and the second electric wire, When the laser beam is irradiated onto the end surfaces of the first electric wire and the second electric wire, a first step of scanning the laser beam within the terminal end surface of the first electric wire to form a first molten pool; a second step of scanning the laser beam within the terminal end surface of the second electric wire to form a second molten pool after the first step; a third step of scanning the laser beam across the first molten pool and the second molten pool after the second step to connect the first molten pool and the second molten pool to form a third molten pool; 1. A method for laser welding an electric wire, comprising:

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

1. A method for laser welding an electric wire comprising the steps of:

3. The method for laser welding electric wires according to claim 2, The first and second steps form a molten pool on the entire end surfaces of the first and second rectangular wires.

1. A method for laser welding an electric wire comprising the steps of:

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

1. A method for laser welding an electric wire comprising the steps of:

5. The method for laser welding electric wires according to claim 1, The third step is to scan the laser beam in a loop shape a plurality of times across the first molten pool and the second molten pool.

1. A method for laser welding an electric wire comprising the steps of:

6. The method for laser welding electric wires according to claim 1, After the third step, the laser beam is scanned within the surface 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.

1. A method for laser welding an electric wire comprising the steps of:

7. The method for laser welding electric wires according to claim 1, The laser beam 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 periphery of the center core and having a lower energy density than the center laser beam.

1. A method for laser welding an electric wire comprising the steps of:

8. The method for laser welding electric wires according to claim 7, At least in the first step, the sub-laser beam is irradiated in an area not exceeding the boundary of the end surface of the first electric wire.

1. A method for laser welding an electric wire comprising the steps of:

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

1. A method for laser welding an electric wire comprising the steps of:

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

1. A method for laser welding an electric wire comprising the steps of:

11. The method for laser welding electric wires according to claim 1, The laser beam is irradiated onto the end faces of the first electric wire and the second electric wire using a galvanometer scanner.

1. A method for laser welding an electric wire comprising the steps of:

Images