Welding method and laser apparatus

Abstract

To provide a welding method capable of shortening a processing time even while keeping excellent welding quality in the welding method of performing metal welding according to laser welding.SOLUTION: A welding method includes a step of causing end parts of a first member 52 and a second member 52 which are arranged opposite to a laser device 100 to abut each other and a step of welding the arranged end parts to each other by laser beam L1. Therein, the laser beam L1 is turned and applied with a predetermined turning diameter r with respect to end surfaces to which the first member 52 and the second member 52 are abutted, a condensed diameter d1 of the laser beam L1 is the same with the turning diameter r or is larger than the turning diameter r, and an irradiation area of the laser beam L1 according to turning irradiation strides over the first member 52 and the second member 52.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a welding method and a laser device for performing metal welding using laser light.

Background Art

[0002] As one of the technologies for performing metal welding, laser welding using laser light is utilized. Compared with other welding technologies, laser welding can weld a workpiece with energy densified by a condenser lens, has high welding quality, and is suitable for fine welding. In recent years, this laser welding has been utilized in the manufacture of stators (stators) for motors incorporated in hybrid vehicles and electric vehicles. A stator is composed of a stator core and a plurality of segment coils mounted in slots of the stator core, and the ends of corresponding segment coils are joined by laser welding. Usually, individual segment coils use flat conductors instead of round wires. This makes it possible to eliminate the gaps created by round wires and increase the density of the joint, thereby achieving low fuel consumption and miniaturization. Since the welding surface is as fine as several square millimeters, laser welding is suitable. Patent Document 1 discloses a laser welding technique for stator coils. Here, corresponding flat conductors are arranged with a gap and both end faces are laser melted. At this time, it is characterized in that the melt-solidified portion where the melted flat conductor is solidified penetrates under the end face so as to dent both end faces. That is, this technique considers that in the conventional welding method, the swelling of the molten pool on the convex lens and the deepening of the molten pool are one of the factors of spatter, and in order to suppress this, the molten flat conductor during welding sequentially flows into the gap, thereby forming a shallow molten pool at the irradiated point irradiated with the laser light (see paragraph 0045).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

[0004] The above technology makes it possible to suppress spatter generated during welding and maintain consistent welding quality. However, while there is a desire to improve productivity in the stator manufacturing process, the above-mentioned literature does not contain any information on productivity improvements such as shortening processing time. Therefore, the present invention aims to provide a welding method and laser apparatus that can shorten processing time while maintaining good welding quality in a welding method for metal welding using laser welding. [Means for solving the problem]

[0005] To solve the above problems, the present invention provides a welding method for welding a first member and a second member, which are arranged opposite a laser device, by butting their ends together and welding them with laser light, characterized in that the laser light is irradiated in a swirling motion on the butted end faces of the first member and the second member with a predetermined swirling diameter, the focusing diameter of the laser light is the same as or larger than the swirling diameter, and the irradiation area of ​​the laser light due to the swirling irradiation spans both the first member and the second member. [Effects of the Invention]

[0006] According to the present invention, since the focusing diameter of the laser beam is the same as or larger than the swirl diameter, the laser beam is always irradiated to the central part of the welding surface. Therefore, it is possible to supply sufficient energy to the central part of the welding surface, causing melting to begin from the center and gradually melting toward the edges due to heat conduction. In this way, by not overheating the edges of the welding surface and melting from the center, the molten metal does not melt and flow from the edges of the welding surface, making it possible to form a clean molten pool. Furthermore, by swirling the laser beam, heat concentration is suppressed and a swirling flow is created inside the molten pool, thereby stabilizing the molten pool. As a result, spatter generation is suppressed and high welding quality can be achieved. Furthermore, since the above-mentioned prior art documents do not involve a configuration in which laser light is constantly irradiated to the central part of the welding surface, the welding method of the present invention allows for earlier melting of the central part compared to the above-mentioned prior art documents. This promotes the formation of the molten pool, making it possible to melt the workpiece to be welded more quickly. [Brief explanation of the drawing]

[0007] [Figure 1] This is a schematic diagram showing the overall configuration of a laser device 100 according to the first embodiment of the present invention. [Figure 2] This diagram shows the configuration of the galvanometer scanner 8. [Figure 3] (a) A perspective view showing the schematic configuration of the stator. (b) A diagram illustrating the segment coil 52. (c) A diagram illustrating the workpiece W. [Figure 4] This is a diagram illustrating a welding method according to the first embodiment. [Figure 5] This is a schematic diagram showing the overall configuration of a laser device 1 according to a second embodiment of the present invention. [Figure 6] This figure illustrates an example of a welding method according to the second embodiment (in the case of r ≤ d1). [Figure 7] This figure illustrates an example of a welding method according to the second embodiment (in the case of r > d1). [Figure 8] This is a photograph of the workpiece W after processing. [Figure 9] This is a diagram illustrating the welding of segment coils. [Modes for carrying out the invention]

[0008] <Overview> A welding method according to one aspect of the present embodiment is a welding method in which ends of a first member and a second member arranged opposite to a laser device are abutted and welded by laser light. The laser light is swirled and irradiated with a predetermined turning diameter with respect to an end face where the first member and the second member are abutted. The condensing diameter of the laser light is the same as or larger than the turning diameter, and the irradiation region of the laser light by the swirling irradiation straddles the first member and the second member. In the welding method according to another aspect of the present embodiment, the wavelength of the laser light is 300 to 600 μm. In the welding method according to another aspect of the present embodiment, the end face is rectangular. When the length of the short side of the rectangle forming the end face is a, the condensing diameter of the laser light is d1, and the turning diameter is r, r ≦ d1 < a.

[0009] In the welding method according to another aspect of the present embodiment, the condensing area (spot area) of the laser light is 1 percent to 30 percent of the total area of the end face. In the welding method according to another aspect of the present embodiment, the output power of the laser light is 500 W to 2 kW. In the welding method according to another aspect of the present embodiment, the energy intensity distribution of the laser light on the end face is the strongest at the substantially central portion of the irradiation region, becomes weaker in the region other than the substantially central portion of the irradiation region, and is zero outside the irradiation region. The welding method according to another aspect of the present embodiment further swirls and irradiates a second laser light having a wavelength different from that of the laser light with respect to the end face, and the condensing diameter of the second laser light is smaller than the condensing diameter of the laser light.

[0010] In the welding method according to another aspect of the present embodiment, the optical axis of the laser light and the optical axis of the second laser light coincide. In the welding method according to another aspect of the present embodiment, the wavelength of the second laser light is 780 nm to 1100 nm. In the welding method according to another aspect of the present embodiment, the condensing diameter of the second laser beam is 1 / 10 or less of the condensing diameter of the laser beam. In the welding method according to another aspect of the present embodiment, the condensing diameter of the second laser beam is 10 μm to 100 μm. In the welding method according to another aspect of the present embodiment, the laser beam and the second laser beam are rotated at a rotation speed of 100 to 1000 mm / s. In the welding method according to another aspect of the present embodiment, the irradiation time of the laser beam and the second laser beam is 50 msec or more.

[0011] In the welding method according to another aspect of the present embodiment, the first member and the second member are flat conductors with a rectangular cross-section that form a coil for a stator, and the ends of two flat conductors arranged facing the laser device are abutted and welded by the laser beam and the second laser beam to form a molten pool on the end face. In the welding method according to another aspect of the present embodiment, nitrogen is blown onto the end face at a flow rate of 5 L / min to 100 L / min and an inclination angle with respect to the end face of 0 to 90° simultaneously with or before the irradiation of the laser beam and the second laser beam, until the irradiation ends or more. The welding method according to one aspect of the present embodiment is a welding method in which the ends of a first member and a second member arranged facing a laser device are abutted and welded by a laser beam, the laser beam is composed of a first laser beam and a second laser beam having different wavelengths, and the laser beam is rotationally irradiated with a predetermined turning radius with respect to the approximate center of the end face, so that the first laser beam and the second laser beam are annularly irradiated with respect to the end face, and the condensing diameter of the second laser beam is smaller than the condensing diameter of the first laser beam. <000009​A laser device according to one aspect of the present embodiment is a laser device that butt-welds the ends of a first member and a second member, and includes an oscillator that oscillates laser light, and a galvanometer scanner unit that scans and irradiates the laser light around a substantially central portion of the end face with a predetermined turning radius. The condensing diameter of the laser light is the same as or larger than the turning radius, and the irradiation region of the laser light by the turning irradiation straddles the first member and the second member. A laser device according to one aspect of the present embodiment is a laser device that butt-welds the ends of a first member and a second member, and includes a first oscillator that oscillates first laser light, a second oscillator that oscillates second laser light having a different wavelength from the first laser light, a combiner unit that superimposes the first laser light and the second laser light on the same optical axis, and a galvanometer scanner unit that scans and irradiates the first laser light and the second laser light around a substantially central portion of the end face with a predetermined turning radius. The condensing diameter of the first laser light is the same as or larger than the turning radius, and the condensing diameter of the second laser light is smaller than the condensing diameter of the first laser light.

[0013] A laser device according to one aspect of the present embodiment is a laser device that butt-welds the ends of a first member and a second member, and includes a first oscillator that oscillates first laser light, a second oscillator that oscillates second laser light having a different wavelength from the first laser light, and one or more galvanometer scanner units that scan and irradiate the first laser light and the second laser light around a substantially central portion of the end face with a predetermined turning radius. The first laser light and the second laser light are irradiated in an annular shape with respect to the end face, and the condensing diameter of the second laser light is smaller than the condensing diameter of the first laser light. <First Embodiment> Here, the laser device 100 according to the first embodiment of the present invention will be described. The laser device 100 is a device that performs butt welding of a workpiece formed of a material having high thermal conductivity, and performs heat conduction welding by irradiating laser light so that the energy distribution of the laser on the rectangular welding surface is highest at the central portion and zero at the peripheral portion.

[0014] Figure 1 shows a schematic configuration of the laser device 100. As shown in the figure, the laser device 100 consists of a first oscillator 2 that emits a first laser beam L1, a transmission fiber 21 which is an optical fiber that transmits the first laser beam L1, a collimating lens 22 that converts the first laser beam L1 into parallel light, a focusing lens 6 that reduces the focusing diameter of the first laser beam L1, protective glass 7 for protecting the focusing lens 6, a galvanometer scanner 8 that two-dimensionally displaces the irradiation position of the first laser beam L1 on the workpiece W, and shielding nozzles 9a and 9b for supplying shielding gas to the workpiece W. In addition to the above components, the laser device 100 may also include other optical systems, optical fibers, etc. In this embodiment, a blue semiconductor laser connected to a multimode fiber is used as the first laser beam L1. The first laser beam L1 can have a wavelength of 300 to 600 nm, and a green laser may be used instead of a blue laser. The output power of the first laser beam L1 is preferably 500 W to 2 kW.

[0015] Next, the galvanometer scanner 8 will be described. Figure 2 is a schematic diagram showing the configuration of the galvanometer scanner 8. As shown in the figure, the galvanometer scanner 8 consists of an X-axis galvanometer mirror 81, an X-axis galvanometer motor 82 that rotates the X-axis galvanometer mirror 81, a Y-axis galvanometer mirror 83, and a Y-axis galvanometer motor 84 that rotates the Y-axis galvanometer mirror 83. In other words, the galvanometer scanner 8 has the function of deflecting the first laser beam L1 in any direction in two dimensions. Stepping motors, servo motors, etc. can be used as the X-axis galvanometer motor 42 and the Y-axis galvanometer motor 44.

[0016] The galvanometer scanner 8 is connected to a control unit (not shown) and controls the irradiation position of the first laser beam L1 on the workpiece W in two dimensions by driving motors 82 and 84 based on control commands transmitted from the control unit. More specifically, it controls the first laser beam L1 to rotate on the two-dimensional plane of the workpiece W. The workpiece W to be welded will be explained using Figure 3. Figure 3(a) is a perspective view showing the schematic configuration of a stator 50, which is the stator of a motor such as an electric vehicle. As shown in the figure, the stator 50 has a roughly cylindrical stator core 51 and a plurality of segment coils 52. The segment coils 52 are electric wires with a rectangular cross-section, i.e., flat rectangular conductors. Usually, segment coils 52 are made of pure copper, but they may also be made of a metal material with high conductivity, such as an alloy mainly composed of copper, or an alloy made of copper and aluminum. The ends of each segment coil 52 protrude from the upper end of the stator core 51, and the laser device 100 laser-welds the ends of two segment coils (flat rectangular conductors) 52 that are adjacent in the radial direction of the stator core 51.

[0017] First, as shown in Figure 3(b), the butt surfaces 52b of the segment coils (flat rectangular conductors) 52 from which the insulating coating has been removed are brought together. At this time, a jig (not shown) may be used to bring the segment coils 52 together. As shown in Figure 3(c), the end faces 52a of the two butted segment coils 52 become the welding surface, i.e., the workpiece W in this embodiment. Here, a gap in the welding surface can cause welding defects. To suppress welding defects, it is preferable to bring the two segment coils 52 together so that their end faces 52a are flush. The laser device 100 rotates the first laser beam L1 onto the butted end faces 52a of the two adjacent segment coils 52 to weld the two adjacent segment coils 52 together.

[0018] Next, the welding method using the laser device 100 will be described in detail with reference to Figure 4. Figure 4(a) schematically shows the irradiation area of ​​the first laser beam L1 on the workpiece W when the galvanometer scanner 8 is stopped. As described above, the workpiece W is rectangular in shape with the ends of two segment coils 52 joined together, and its size is arbitrary. If the length of the short side is a and the length of the long side is b, then for a typical stator segment coil, the values ​​are approximately 2.5 mm ≤ a ≤ 4.0 mm and 3.0 mm ≤ b ≤ 5.0 mm. In that case, the total area (a × b) of the workpiece W is 7.5 mm².2 ≦(a × b) ≦ 20.0 mm 2 It becomes such a degree. In this embodiment, as an example, let a = 2.8 mm and b = 3.2 mm. As shown in Fig. 4(a), with the condensing diameter of the first laser beam L1 being d1, the first laser beam L1 is rotated around the center O of the workpiece W with a turning radius r as indicated by the arrow. At this time, r ≦ d1 < a. Preferably, r < d1 < a. Also, the condensing diameter d1 may be determined such that the condensing area of the first laser beam L1 (the gray area in Fig. 4(a)) is 1% to 30% of the total area of the workpiece W. Here, as an example, let the turning radius r be 800 μm and the condensing diameter d1 be 1050 μm.

[0019] When the first laser beam L1 is rotated from this state, as shown in Fig. 4(b), the irradiation area S of the first laser beam L1 (the light gray area in Fig. 4(b)) becomes circular, and its diameter is d1 + r. Here, in order to form a beautiful molten ball on the workpiece W, it is desirable that the distance a' from the outer peripheral edge of the irradiation area S of the first laser beam L1 to the edge portion of the workpiece W is at least 0.2 mm or more apart. If the distance a' from the outer peripheral edge of the irradiation area S to the edge portion of the workpiece W is too short, sputtering may occur or the molten metal may flow away. As shown in Fig. 4(b), the first laser beam L1 is constantly irradiated on a circular area s (the dark gray area in Fig. 4(b)) with a diameter of d1 - r in the central portion of the workpiece W. That is, the energy distribution of the first laser beam L1 is the highest in the circular area s which is the central portion of the workpiece W, and is constant and lower than that in the central portion in other areas. Since the first laser beam L1 is not irradiated outside the irradiation area S, the energy distribution becomes zero. The laser device 100 rotates the first laser beam L1 at a rotation speed of 500 mm / s. Also, the irradiation time of the first laser beam L1 is 50 msec or more.

[0020] Thus, in the laser device 100, the first laser beam L1 is always irradiated onto the central part of the workpiece W, making it possible to irradiate the central part of the workpiece W with the first laser beam L1 at a sufficient energy density. As a result, the central part starts to melt quickly, and the workpiece W gradually melts from the center toward the edges due to heat conduction. Here, although the workpiece W is copper, which has a very high thermal conductivity, there is no place for heat to escape around the edges of the workpiece W, so if too much heat is applied to the edges of the workpiece W, the molten metal will melt and flow, making it impossible to form a clean molten ball. Therefore, in this embodiment, the laser device 100 does not irradiate the edges of the workpiece W with laser beam, and gradually melts the workpiece W from the center toward the edges, thereby making it possible to form a clean molten ball. Furthermore, by rotating the first laser beam L1, it becomes possible to supply the necessary energy to the workpiece W without using a laser light source with a large focal diameter and high output.

[0021] The laser device 100 sprays nitrogen, which is a shielding gas, onto the welding surface at a rate of 5 L / min to 100 L / min from before or simultaneously with the irradiation of the first laser beam L1 until the irradiation is completed or longer. More preferably, it is sprayed at a rate of 10 L / min to 40 L / min. As shown in Figure 1, in this embodiment, nitrogen is sprayed from the left and right using two shielding nozzles 9a and 9b. The angle of each shielding nozzle 9a and 9b with respect to the workpiece W is, for example, 30 degrees. The diameter of the tip opening of the shielding nozzles 9a and 9b (nozzle tip diameter) is preferably about 1 to 10 mm. The working distance, which is the distance from the tip opening of the shielding nozzles 9a and 9b to the workpiece W, is preferably about 5 to 15 mm. By supplying nitrogen to the workpiece W through shield nozzles 9a and 9b, the laser device 100 performs welding of the workpiece W in a nitrogen atmosphere. The shielding gas prevents oxidation of the weld surface, thereby suppressing the reduction in weld strength and the occurrence of porosity caused by oxidation of the weld surface. Furthermore, by suitably selecting conditions such as the flow rate of the shielding gas, the nozzle tip diameter, and the working distance, it is possible to suppress fluctuations in the molten ball and form a clean molten ball. In particular, by blowing nitrogen from both sides, a clean, symmetrical molten ball is formed. This improves the welding quality.

[0022] <Second Embodiment> Next, a second embodiment of the present invention will be described. The second embodiment is a welding method that can perform the welding process at an even higher speed by further irradiating the first laser beam L1 with a second laser beam L2. Figure 5 is a diagram showing the schematic configuration of the laser device 1 according to the second embodiment. As shown in the figure, the laser device 1 consists of a first oscillator 2 that emits a first laser beam L1, a second oscillator 3 that emits a second laser beam L2, a transmission fiber 21 which is an optical fiber that transmits the first laser beam L1, a transmission fiber 31 which is an optical fiber that transmits the second laser beam L2, a collimating lens 22 that converts the first laser beam L1 into parallel light, a collimating lens 32 that converts the second laser beam L2 into parallel light, mirrors 4 and 5 for aligning the optical axes of the first laser beam L1 and the second laser beam L2, a focusing lens 6 that reduces the focusing diameter of the first laser beam L1 and the second laser beam L2, protective glass 7 for protecting the focusing lens 6, a galvanometer scanner 8 that displaces the irradiation position of the first laser beam L1 and the second laser beam L2 on the workpiece W, and shielding nozzles 9a and 9b for supplying shielding gas to the workpiece W.

[0023] In addition to these components, the laser device 1 may also include other optical systems, optical fibers, etc. The first laser beam L1 and the second laser beam L2 emitted from the first oscillator 2 and the second oscillator 3 are made into parallel beams by collimating lenses 22 and 32, respectively. The first laser beam L1 and the second laser beam L2 that have passed through collimating lenses 22 and 32 are superimposed by mirrors 4 and 5 so that their optical axes coincide. Then the optical axis is changed toward the focusing lens 6 and reduced to a predetermined diameter by the focusing lens 6. Finally, the beams are rotated and irradiated onto the opposing workpiece W by the galvanoscanner 8. Mirror 5 is a dichroic mirror that reflects the wavelength of the first laser beam L1 and transmits the wavelength of the second laser beam L2. In this way, the laser device 1 performs welding by irradiating the workpiece W with two laser beams L1 and L2.

[0024] The first laser beam L1 is basically the same as in the first embodiment. That is, the output power of the first laser beam L1 is preferably 500W to 2kW, and in this embodiment, it is 600W as an example. The output power of the second laser beam L2 is preferably 500W to 2kW, and in this embodiment, it is 900W as an example. Furthermore, the wavelength of the first laser beam L1 is 300 nm to 600 nm, and the wavelength of the second laser beam L2 is 780 nm to 1100 nm. In other words, the wavelengths of the first laser beam L1 and the second laser beam L2 are different, with the wavelength of the first laser beam L1 being shorter than the wavelength of the second laser beam L2. While it is possible to use either multimode or single-mode beam modes, in this embodiment, the first laser beam L1 is multimode and the second laser beam L2 is single-mode. As will be described later, the second laser beam L2 is a spot beam with a smaller focal diameter compared to the first laser beam L1. Therefore, by using a single-mode fiber laser as the second oscillator 3, it is possible to effectively generate the second laser beam L2, which has a small beam diameter and a high peak energy intensity.

[0025] Next, the details of the welding method by the laser device 1 will be described using FIGS. 6 and 7. In the above-described first embodiment, the condensing diameter d1 of the first laser beam L1 satisfies r ≦ d1 < a, the condensing diameter d1 is larger than the turning diameter r, and the first laser beam L1 is always irradiated to the center of the workpiece W. On the other hand, in the second embodiment, the condensing diameter d1 of the first laser beam L1 may be larger, smaller, or the same size as compared with the turning diameter r. FIG. 6 shows an example of a welding method when the condensing diameter d1 of the first laser beam L1 satisfies r ≦ d1 as in the first embodiment. FIG. 7 shows an example of a welding method when the condensing diameter d1 of the first laser beam L1 satisfies r > d1. First, an example of r ≦ d1 will be described. FIG. 6(a) is a diagram schematically showing the irradiation regions of the first laser beam L1 and the second laser beam L2 on the workpiece W in a state where the galvanometer scanner 8 is stopped. The workpiece W is as described in the first embodiment, and in this embodiment, the size of the workpiece W is, for example, a = 2.8 mm and b = 3.2 mm as an example.

[0026] As shown in FIG. 6(a), the first laser beam L1 and the second laser beam L2 are circular beams having the same optical axis and condensing diameters d1 and d2, respectively. The first laser beam L1 and the second laser beam L2 are rotated around the center O of the workpiece W with a turning diameter r as indicated by the arrows. Here, as an example, the condensing diameter d1 of the first laser beam L1 is 1050 μm, and the turning diameter r is 800 μm. Further, the condensing diameter d2 of the second laser beam L2 is smaller than the condensing diameter d1 of the first laser beam L1. For example, d2 is 1 / 10 or less of d1. Here, as an example, d2 is 40 μm. Also, similar to the first embodiment, the condensing diameter d1 may be determined such that the condensing area of the first laser beam L1 (the gray region in FIG. 6(a)) is 1% to 30% of the total area of the workpiece W.

[0027] When the first laser beam L1 and the second laser beam L2 are rotated from this state, the irradiation area S of the first laser beam L1 (the light gray area in Figure 6(b)) becomes circular, as shown in Figure 6(b), and its diameter is d1+r. In order to form a clean molten ball on the workpiece W, it is desirable that the distance a' from the outer edge of the irradiation area S of the first laser beam L1 to the edge of the workpiece W is at least 0.2 mm. If the distance a' from the outer edge of the irradiation area S to the edge of the workpiece W is too short, spatter may occur or the molten metal may melt and flow. As shown in Figure 6(b), the first laser beam L1 is constantly irradiated into the circular region s (the dark gray region in Figure 6(b)) at the center of the workpiece W, where the diameter is d1-r. That is, the energy distribution of the first laser beam L1 is highest in the circular region s at the center of the workpiece W, and is lower and constant in other regions. Since the first laser beam L1 is not irradiated outside the irradiation region S, the energy distribution is zero outside that region.

[0028] In the second embodiment, the irradiation of the second laser beam L2 is added, causing the irradiation area R of the second laser beam L2 to become annular, as shown in Figure 6(b). Here, the second laser beam L2 is additionally irradiated to supply energy, i.e., the heat necessary for melting, to the workpiece W, and is not intended to form a keyhole in the workpiece W. Therefore, the laser apparatus 1 in this embodiment may or may not form a keyhole by irradiation with the second laser beam L2. Thus, when r ≤ d1, the first laser beam L1 is always irradiated onto the central part of the workpiece W, making it possible to irradiate the central part of the workpiece W with the first laser beam L1 at a sufficient energy density. As a result, the most heat is accumulated in the central part, the temperature rises the most at the joint surface of the two segment coils 52, and a deep molten pool is formed at the butt surface 52b. Then, due to heat conduction, it gradually melts toward the edges of the workpiece W. In other words, the laser device 1 of this embodiment performs heat conduction welding in the same way as the laser device 100 of the first embodiment. The laser device 1 further irradiates the workpiece W, which has a high heat absorption rate due to irradiation with the first laser beam L1, with the second laser beam L2. This accelerates the melting of the workpiece, enabling faster welding.

[0029] Next, we will explain an example where r > d1. Figure 7(a) schematically shows the irradiation areas of the first laser beam L1 and the second laser beam L2 on the workpiece W when the galvanometer scanner 8 is stopped. When the first laser beam L1 and the second laser beam L2 are rotated from this state, as shown in Figure 7(b), the central part of the workpiece W is not irradiated by the first laser beam L1, and the irradiation area S of the first laser beam L1 (the gray area in Figure 7(b)) becomes annular. The outer diameter of the irradiation area S is d1 + r, and the inner diameter is r - d1. It is desirable that the distance a' from the outer edge of the irradiation area S to the edge of the workpiece W is at least 0.2 mm. Also, the irradiation area R of the second laser beam L2 becomes annular as shown in Figure 7(b). Thus, even if the central part of the workpiece W is not irradiated with the first laser beam L1, the addition of the second laser beam L2 causes the workpiece W to start melting from the area irradiated with the second laser beam L2 immediately after irradiation begins. However, heat propagates to the central part of the workpiece W, and the most energy is accumulated in the central part. As a result, the temperature rises the most at the joint surface of the two segment coils 52, and a deep molten pool is formed at the butt surface 52b. Furthermore, the irradiation of the second laser beam L2 accelerates the melting of the workpiece, enabling faster welding. In addition, since the edges of the workpiece W are not irradiated with laser beam, the workpiece W melts gradually from the center toward the edges, forming a clean molten ball.

[0030] The laser device 1 rotates the first laser beam L1 and the second laser beam L2 at a rotation speed of 500 mm / s. The irradiation time of the first laser beam L1 and the second laser beam L2 is set to 50 msec or more. In addition, the laser device 1 performs welding of the workpiece W in a nitrogen atmosphere while supplying nitrogen to the workpiece W through shield nozzles 9a and 9b, similar to the first embodiment. The flow rate of the shielding gas and the nozzle conditions are the same as in the first embodiment. <Effects of the Embodiment> The laser device 100 forms a molten pool on the workpiece W by irradiating it with a first laser beam L1 having a wavelength of 300 nm to 600 nm and a high light absorption rate for copper in a swirling motion. The laser device 100 irradiates the center of the irradiation surface with high energy, while not irradiating the periphery of the irradiation surface with laser light. By irradiating with the first laser beam L1 with this energy distribution, it is possible to form a clean molten ball on a workpiece with high thermal conductivity.

[0031] If the first laser beam L1 is to be directed to a fixed point rather than rotating, a high-power blue laser light source would be required, but high-power blue laser light sources are still difficult to obtain and expensive. Furthermore, if the first laser beam L1 is directed to a fixed point, a large amount of sputtering may be generated. Laser device 1 forms a molten pool in the workpiece W by irradiating it with a first laser beam L1 having a wavelength of 300 nm to 600 nm and a high light absorption rate for copper in a swirling motion. Then, by irradiating the inside of the formed molten pool with a second laser beam L2 having a small focal diameter and high energy density while swirling at high speed, it achieves a locally deep penetration depth inside the molten pool and promotes the formation of the molten pool. Furthermore, compared to conventional welding equipment, laser devices 1 and 100 use a first laser beam L1 with a larger focusing diameter for welding. By further rotating the first laser beam L1, laser devices 1 and 100 can effectively heat and melt the workpiece W.

[0032] Furthermore, laser devices 1 and 100 create a flow in the molten pool by rotating the first laser beam L1 and the second laser beam L2 instead of irradiating them at a fixed point. This expels bubbles generated from the molten pool, which has reached a high temperature, to the outside. This suppresses porosity. In addition, it prevents localized heat concentration in the molten pool, stabilizes the molten pool, and reduces spatter. Since porosity and spatter are causes of welding defects such as poor joints, laser devices 1 and 100, and welding methods using these devices, can suppress the occurrence of welding defects. Figure 8 shows the result of welding the segment coil 52 of the stator 50 using the laser device 1 of the second embodiment. As can be seen in the figure, a glossy, symmetrical, and beautiful molten ball has been formed. Furthermore, since the galvanometer scanner 8 allows for two-dimensional displacement of the optical axis of each laser beam in laser devices 1 and 100, the processing time required for welding the stator segment coils at each stage can be reduced compared to laser devices that do not have a galvanometer scanner 8.

[0033] When welding segment coils with a laser device that does not have a galvanometer scanner, as shown in Figure 9(a), first, the irradiation positions of the laser beams L1 and L2 are aligned with the workpiece W1, and then the laser is irradiated. Next, in order to weld workpiece W2, the laser device 1 is transported by a transport means (not shown) to face the workpiece W2, the irradiation positions of the laser beams L1 and L2 are aligned with the workpiece W2, and then the laser is irradiated. Similarly, for workpieces W3 and W4, it is necessary to repeat the transport, positioning, and laser irradiation of the laser device. On the other hand, using laser devices 1 and 100 equipped with a galvanometer scanner 8, as shown in Figure 9(b), the galvanometer scanner 8 is used to align the irradiation positions of laser beams L1 and L2 onto workpiece W1, and then the laser is irradiated. Next, to weld workpiece W2, the galvanometer scanner 8 is used to align the irradiation positions of laser beams L1 and L2 onto workpiece W2, and then the laser is irradiated. In other words, with laser devices 1 and 100, by using the galvanometer scanner 8, the transport of the laser device becomes unnecessary. Similarly, for workpieces W3 and W4, there is no need to transport the laser device each time welding is performed on each workpiece, and positioning and laser irradiation can be repeated.

[0034] In this way, the laser device 1 and laser device 100 eliminate the need for transporting the laser devices, making it possible to shorten the processing time. <Variation> Although the laser device 1 and laser device 100 have been described above as one embodiment of the present invention, the present invention is not limited to the laser device 1, laser device 100 and the welding method using these devices as described above, and the above embodiment can also be modified as follows. Here, we will describe some modifications of the above embodiment. The above embodiment and the modifications described below can be combined in any way.

[0035] (1) In the second embodiment, the laser device 1 superimposes laser beams L1 and L2 with different wavelengths. Here, the refractive index of light depends on the wavelength of the light, and when multiple laser beams with different wavelengths are superimposed and passed through a lens or the like, the irradiation position of the first laser beam L1 and the irradiation position of the second laser beam L2 on the workpiece W may be misaligned. To suppress this, the laser device 1 may be equipped with an fθ lens, or a 3D galvanometer scanner may be used instead of the galvanometer scanner 8. Furthermore, other optical systems, optical fibers, etc. may also be provided. (2) In the first and second embodiments, the focusing diameter d1 of the first laser beam L1 is not limited to 1050 μm. As described above, it is possible to select the focusing diameter d1 such that the area of ​​the irradiation region of the first laser beam L1 (focusing area, spot area) is 1 percent to 30 percent of the total area of ​​the workpiece W. Furthermore, in the second embodiment, the focusing diameter d2 of the second laser beam L2 is not limited to 40 μm. The focusing diameter d2 of the second laser beam L2 can be approximately 10 to 100 μm, and it is preferable to set it to one-tenth or less of the focusing diameter d1 of the first laser beam L1.

[0036] The focusing diameter of each laser beam depends on the core diameter of the transmission fiber, the focal length of the collimating lens, and the focal length of the focusing lens, and can be calculated as follows: Focusing diameter = core diameter of transmission fiber × (focal length of focusing lens / focal length of collimating lens). Therefore, it is possible to change the focusing diameter of each laser beam by adjusting these optical systems. (3) In the first and second embodiments described above, the rotation speed of the first laser beam L1 and the second laser beam L2 was set to 500 mm / s. However, the rotation speed of the first laser beam L1 and the second laser beam L2 is not limited to this and may be in the range of 100 to 1000 mm / s. (4) In the second embodiment described above, the first laser beam L1 is multimode and the second laser beam L2 is singlemode, but this is just an example and the beam modes of each laser beam are not limited.

[0037] (5) In the first and second embodiments described above, side-nozzle type shield nozzles 9a and 9b were used to avoid interference with the operation of the galvanometer scanner 8 and to effectively supply nitrogen, but of course the shield nozzle is not limited to the side-nozzle type. The shield nozzle should be capable of blowing nitrogen at an inclination angle of 0 to 90° with respect to the welding surface and welding in a nitrogen atmosphere. (6) In the first and second embodiments described above, the first laser beam L1 and the second laser beam L2 are focused on the workpiece W (welding surface). However, in the present invention, both the first laser beam L1 and the second laser beam L2 may be focused at a position within ±2 mm vertically from the welding surface. (7) In the first and second embodiments described above, the first laser beam L1 and the second laser beam L2 were circular beams, but the beam shapes of the first laser beam L1 and the second laser beam L2 are not limited thereto. For example, elliptical or rectangular beams may be used. In this case, it is preferable that the longitudinal direction of the rectangular welding surface is the major axis.

[0038] (8) In the first and second embodiments described above, a stator coil was used as an example of a workpiece. However, it goes without saying that the welding method and the laser apparatus 1 and laser apparatus 100 described above are not limited to use in welding a stator coil. (9) In the second embodiment, the optical axis of the first laser beam L1 and the optical axis of the second laser beam L2 are aligned and rotated by the galvanoscanner 8. However, the present invention is not limited to this, and the optical axes of the first laser beam L1 and the optical axis of the second laser beam L2 may not be aligned, and each can be rotated by a separate laser scanning optical system (galvanoscanner). That is, the present invention also includes a configuration in which the laser device 100 is equipped with two galvanoscanners, one galvanoscanner rotates the first laser beam L1 and the other galvanoscanner rotates the second laser beam L2. [Explanation of symbols]

[0039] 1.100 Laser Device 2. First Oscillator 3. Second Oscillator 4, 5 Mirror (Combiner section) 6. Focusing lens 7. Protective Glass 8 Galvanometer Scanner 9a, 9b Shield nozzle 21, 31 Transmission Fiber 21, 32 Collimating lenses 52 Segment coil (first component, second component) 52a End face

Claims

1. A welding method in which the ends of a first member and a second member, which are positioned opposite a laser device, are butted together and welded with laser light, The laser beam is irradiated onto the end faces of the first and second members joined together, rotating at a predetermined rotational diameter. The focusing diameter of the laser beam is the same as or larger than the rotation diameter, and the irradiation area of ​​the laser beam due to rotational irradiation spans both the first member and the second member. A welding method characterized by the following features.

2. The wavelength of the laser light is 300 to 600 μm. The welding method according to feature 1.

3. The end face is rectangular, If the length of the shorter side of the rectangle forming the end face is a, the focusing diameter of the laser beam is d1, and the rotation diameter is r, r ≤ d1 < a The welding method according to feature 2.

4. The focusing area of ​​the laser beam is 1 percent to 30 percent of the total area of ​​the end face. The welding method according to feature 3.

5. The output power of the laser beam is 500W to 2kW. The welding method according to feature 4.

6. The energy intensity distribution of the laser light at the end face is strongest in the approximate center of the irradiation region, weaker in regions other than the approximate center of the irradiation region, and zero outside the irradiation region. A welding method according to any one of claims 1 to 5, characterized by the present invention.

7. The welding method further includes, A second laser beam, having a different wavelength from the aforementioned laser beam, is irradiated onto the end face in a swirling motion. The focusing diameter of the second laser beam is smaller than the focusing diameter of the first laser beam. The welding method according to feature 1.

8. The optical axis of the first laser beam and the optical axis of the second laser beam coincide. The welding method according to feature 7.

9. The wavelength of the second laser beam is 780 nm to 1100 nm. The welding method according to feature 8.

10. The focusing diameter of the second laser beam is one-tenth or less of the focusing diameter of the first laser beam. The welding method according to feature 9.

11. The focusing diameter of the second laser beam is 10 μm to 100 μm. The welding method according to feature 9.

12. The aforementioned laser beam and the second laser beam are rotated at a rotational speed of 100 to 1000 mm / s. The welding method according to any one of claims 7 to 11, characterized by...

13. The irradiation time for the aforementioned laser light and the second laser light is 50 msec or longer. The welding method according to any one of claims 7 to 12, characterized by...

14. The first member and the second member are rectangular conductors with a rectangular cross-section that constitute a coil for a stator, A molten ball is formed on the end surface by welding the ends of two rectangular conductors, which are positioned opposite the laser device, together with the laser beam and the second laser beam. A welding method according to any one of claims 7 to 13, characterized by the present invention.

15. Simultaneously with or before the irradiation of the first laser beam and the second laser beam, nitrogen is blown onto the end face at a flow rate of 5 L / min to 100 L / min and an inclination angle of 0 to 90° relative to the end face until the irradiation is completed or longer thereafter. A welding method according to any one of claims 7 to 14, characterized by the present invention.

16. A laser device for butt welding the ends of a first member and a second member, An oscillator that emits laser light, The system includes a galvanometer scanner unit that rotates and irradiates the laser beam with a predetermined rotational diameter to approximately the center of the end faces where the ends of the first and second members meet. The focusing diameter of the laser beam is the same as or greater than the rotation diameter. The irradiation area of ​​the laser beam due to the swirling irradiation spans both the first member and the second member. A laser device characterized by the following features.

17. A laser device for butt welding the ends of a first member and a second member, A first oscillator that emits a first laser beam, A second oscillator that emits a second laser beam having a different wavelength from the first laser beam, A combiner unit that superimposes the first laser beam and the second laser beam on the same optical axis, The system includes a galvanometer scanner unit that rotates and irradiates the first laser beam and the second laser beam with a predetermined rotational diameter to approximately the center of the end faces where the ends of the first member and the second member meet, The focusing diameter of the first laser beam is the same as or greater than the swivel diameter. The focusing diameter of the second laser beam is smaller than the focusing diameter of the first laser beam. A laser device characterized by the following features.

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