Welding method and laser apparatus

Abstract

To provide a welding method which eliminates a need of trimming step in which a tip side of a flat wire is flattened in a manufacturing step of a stator, and to provide a laser apparatus.SOLUTION: In a welding method, a first member and a second member, each of whose tip side has a projection shape, are butted and tips are placed facing a laser apparatus to be welded by a laser beam. The welding method includes: a first step in which the laser beam is radiated to a position near a butted surface of the tip of the first member to form a first fusion part; and a second step in which the laser beam is radiated to a position near a butted surface of the tip of the second member to form a second fusion part.SELECTED DRAWING: Figure 3

Description

Technical Field

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

Background Art

[0002] As one of the techniques for performing metal welding, laser welding using a laser beam is utilized. Compared with other welding techniques, 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 rectangular wires, and since the welding surface is as fine as several square millimeters, laser welding is suitable. In the manufacturing process of a stator, first, a rectangular wire is inserted into a slot of the stator. At this time, in order to prevent the tip of the rectangular wire from getting caught, the tip of the rectangular wire is cut into a tapered shape and then inserted. And after inserting and aligning each rectangular wire, a "trimming process" is performed to align the heights of the rectangular wires with each other and flatten the tips in order to stabilize the quality of the subsequent welding process (see Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, the above trimming process requires a large-scale apparatus and affects the tact time of the manufacturing line. In addition, there is a problem that the trimmed end materials are discarded, resulting in a decrease in material utilization rate. Therefore, the present invention has been made in view of the above problems, and an object thereof is to provide a welding method and a laser apparatus that eliminate the need for a trimming process.

Means for Solving the Problems

[0005] In order to solve the above problems, the present invention is a welding method in which a first member and a second member having a convex shape at the tip end side are abutted against each other, and the tip end is opposed to a laser apparatus and welded by laser light, the method including: a first step of irradiating the laser light at a position near the butting surface of the tip end of the first member to form a first molten portion; and a second step of irradiating the laser light at a position near the butting surface of the tip end of the second member to form a second molten portion.

Effects of the Invention

[0006] According to the present invention, since it is possible to weld the first member and the second member having a convex shape at the tip end side, the trimming process in the manufacturing process of the stator becomes unnecessary.

Brief Description of the Drawings

[0007]

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Embodiments for Carrying Out the Invention

[0008] <Summary> A welding method according to one aspect of the present embodiment is a welding method in which a first member and a second member having a convex shape on the tip side are abutted against each other, and the tip is opposed to a laser device and welded by laser light. The method includes a first step of irradiating the laser light at a position near the butting surface of the tip of the first member to form a first molten portion, and a second step of irradiating the laser light at a position near the butting surface of the tip of the second member to form a second molten portion. In the welding method according to another aspect of the present embodiment, the first member and the second member are flat wires constituting a stator coil, and the convex shape on the tip side is a gable roof shape having a first inclined surface formed at the tip of the flat wire and a second inclined surface formed non-parallel to the first inclined surface. The first step and the second step are characterized by irradiating the laser light onto one of the first inclined surface and the second inclined surface, which is located closer to the butting surface.

[0009] In the welding method according to another aspect of the present embodiment, the first step forms the first molten portion by reciprocally irradiating the inclined surface located near the butting surface in the first member in a substantially straight line, and the second step forms the second molten portion by reciprocally irradiating the inclined surface located near the butting surface in the second member in a substantially straight line. In the welding method according to another aspect of the present embodiment, the laser irradiation in the first step and the laser irradiation in the second step are alternately repeated. In the welding method according to another aspect of the present embodiment, the laser irradiation in the first step and the laser irradiation in the second step are alternately repeated until the first molten portion and the second molten portion are joined.

[0010] In the welding method according to another aspect of the present embodiment, the laser irradiation in the first step and the laser irradiation in the second step are alternately repeated until the first molten portion and the second molten portion are joined to form a molten ball of a predetermined size. In the welding method according to another aspect of the present embodiment, there is a gap between the first member and the second member, and the welding method is characterized in that the laser irradiation in the first step and the second step is alternately repeated until the first molten portion and the second molten portion enter the gap. The welding method according to another aspect of the present embodiment further includes a jump step of moving the laser irradiation position to the other flat diagonal line in a state where the laser irradiation is stopped after performing the laser irradiation on one flat diagonal line while alternately repeating the laser irradiation in the first step and the laser irradiation in the second step.

[0011] In the welding method according to another aspect of the present embodiment, in the first step, the laser beam is irradiated on the inclined surface of the first member in a substantially straight line for 1.5 reciprocations, and in the second step, the laser beam is irradiated on the inclined surface of the second member in a substantially straight line for 1.5 reciprocations. The welding method according to another aspect of the present embodiment includes an imaging step of imaging the first member and the second member to be welded, and a control step of analyzing the image captured in the imaging step to obtain the position information of the first member and the second member, and determining the irradiation position of the laser beam based on the obtained position information. The welding method according to another aspect of the present embodiment includes an imaging step of imaging the first member and the second member to be welded, and a control step of analyzing the image captured in the imaging step to obtain the height information of the first member and the second member, and determining the midpoint of the heights of the first member and the second member as the focus position based on the obtained height information. In the welding method according to another aspect of the present embodiment, the laser beam is composed of a first laser beam and a second laser beam having different wavelengths from each other.

[0012] In the welding method according to another aspect of the present embodiment, the wavelength of the first laser beam is 300 to 600 nm. In the welding method according to another aspect of the present embodiment, the wavelength of the second laser light is characterized in that it is 780 nm to 1100 nm. In the welding method according to another aspect of the present embodiment, the output powers of the first laser light and the second laser light are characterized in that they are 500 W to 3 kW. In the welding method according to another aspect of the present embodiment, the condensing diameter of the second laser light is smaller than the condensing diameter of the first laser light, and the welding method according to claim 1 is characterized in that. In the welding method according to another aspect of the present embodiment, the condensing diameter of the second laser light is characterized in that it is 1 / 10 or less of the condensing diameter of the first laser light.

[0013] In the welding method according to another aspect of the present embodiment, the condensing diameter of the second laser light is characterized in that it is 10 μm to 100 μm. In the welding method according to another aspect of the present embodiment, nitrogen is blown against the tip portion at a flow rate of 5 L / min to 100 L / min and an inclination angle with respect to the tip portion of 0 to 90° simultaneously with or before the irradiation of the laser light, until the irradiation ends or longer. A laser device according to one aspect of the present embodiment is a laser device that welds the tips by butting a first member and a second member whose tip sides are convex, and includes an oscillator that oscillates laser light, a galvano scanner unit that displaces and irradiates the laser light in an arbitrary direction, and a control unit that controls the oscillator and the galvano scanner unit, and the control unit irradiates the laser light at a position near the butting surface of the tip of the first member to form a first molten portion, and irradiates the laser light at a position near the butting surface of the tip of the second member to form a second molten portion, and is characterized in that it controls the oscillator and the galvano scanner unit.

[0014] A laser device according to another aspect of the present embodiment further includes an image processing unit that images the first member and the second member and detects position information, and the control unit determines the irradiation position of the laser light using the position information detected by the image processing unit. <Embodiment> Here, a laser device 1 according to an embodiment of the present invention will be described in detail with reference to the drawings. The laser device 1 is a welding device that irradiates a workpiece (work) W made of a material with high thermal conductivity with laser light and performs welding of the workpiece W by thermally converting the energy of the laser light. The workpiece W is, for example, a coil for a stator incorporated in an electric vehicle or the like.

[0015] FIG. 1 is a flowchart showing a conventional method for manufacturing a stator coil. In the conventional manufacturing method, before inserting a flat wire into the slots of the stator, in order to prevent the flat wire tip from getting caught, the tip of the flat wire is cut into a tapered shape (step S1). Then, each flat wire is inserted into the corresponding slot (step S2), and after alignment, a trimming process is performed to align the heights of the flat wires with each other and flatten the tips in order to stabilize the quality of the subsequent welding process (step S3). Thereafter, the tips of the corresponding flat wires are laser welded (step S4). On the other hand, FIG. 2 is a flowchart showing a method for manufacturing a stator coil when using the laser device according to the present embodiment. In the present embodiment, first, in order to prevent the flat wire tip from getting caught during slot insertion in the same manner as in the conventional example, the tip of the flat wire is cut into a tapered shape (step S11). Then, each flat wire is inserted into the corresponding slot and aligned (step S12). Subsequently, in the present embodiment, with the tips of the flat wires remaining tapered, the tips of the corresponding flat wires are laser welded (step S13).

[0016] In this way, in the present embodiment, trimming processing for cutting the flat wire flat is not performed, and the flat wire with a pointed tip is irradiated with laser light. A laser device and a welding method capable of preventing the occurrence of sputtering and realizing high-quality welding even in such a case will be described in detail below. FIG. 3 is an external view showing the configuration of the laser device 1 according to the present embodiment, and FIG. 4 is a schematic view showing the functional configuration of the laser device 1. As shown in FIGS. 3 and 4, the laser device 1 includes a first oscillator 2 (blue semiconductor laser) that oscillates a first laser beam L1, a second oscillator 3 (IR fiber laser) that oscillates a second laser beam L2, a hybrid galvano scanner 10 that aligns the optical axes of the first laser beam L1 and the second laser beam L2 and displaces the irradiation positions of the first laser beam L1 and the second laser beam L2 with respect to the workpiece W, an image processing unit 9 that captures an image of the workpiece W and analyzes the position information of each straight angle line, a workpiece stage 11 on which the workpiece W is placed and that can move the placed workpiece W in three-dimensional directions (x, y, z) and in the rotational direction (θ) around the z-axis, a fixing jig 15 for fixing the workpiece W to the workpiece stage 11, a control PC (Personal Computer) 12 that controls the entire laser device 1, a PLC (Programmable Logic Controller) 13 that controls each device in cooperation with the control PC 12, a laser controller 14 that controls the operations of the first oscillator 2 and the second oscillator 3, and shield gas nozzles 19a and 19b for supplying a shield gas such as nitrogen to the workpiece W (in FIG. 4, the description of the shield gas nozzles 19a and 19b is omitted).

[0017] Further, the image processing unit 9 includes an illumination device 101, an imaging device 102, and a controller 103, and the controller 103 is built into the control panel 100 in FIG. 1. The control panel 100 has a computer built therein for controlling the laser device 1. Specifically, in addition to the controller 103 of the image processing unit 9, the PLC 13 and the laser controller 14 are built therein. Also, the workpiece stage 11 includes a base 11a, an x-axis stage 11x that is a mechanism for moving the workpiece W in the x-axis direction, a y-axis stage 11y that is a mechanism for moving the workpiece W in the y-axis direction, a θ-axis stage 11θ that is a mechanism for rotating the workpiece W around the z-axis, and a z-axis stage 11z that is a mechanism for relatively moving the workpiece W and the hybrid galvano scanner 10 in the z-axis direction. (2) Regarding the laser beam

[0018] The first laser beam L1 and the second laser beam L2 oscillated from the first oscillator 2 and the second oscillator 3 are respectively transmitted through optical fibers and incident on the hybrid galvano scanner 10. Then, the first laser beam L1 and the second laser beam L2 are overlapped by the hybrid galvano scanner 10 so that their optical axes coincide. The overlapped L1 and L2 are reduced to a predetermined diameter and then irradiated onto the workpiece W facing them. In this way, in the laser device 1, the workpiece W is irradiated with two laser beams L1 and L2 to perform welding. As the first laser beam L1, a blue semiconductor laser connected to a multimode fiber is used. The first laser beam L1 only needs to have a wavelength of 300 to 600 nm, and a green laser may be used instead of the blue laser. Also, the output power of the first laser beam L1 is preferably 500 W to 3 kW, and in this embodiment, it is set to 800 W as an example.

[0019] As the second laser beam L2, a near-infrared single-mode fiber laser with a wavelength of 780 nm to 1100 nm is used. That is, the first laser beam L1 and the second laser beam L2 have different wavelengths from each other, and the wavelength of the first laser beam L1 is shorter than the wavelength of the second laser beam L2. The output power of the second laser beam L2 is preferably 500 W to 3 kW, and in this embodiment, it is set to 2 kW as an example. In this embodiment, the first laser beam L1 is multimode and the second laser beam L2 is single mode. The second laser beam L2 is a spot light with a smaller condensing diameter compared to the first laser beam L1. Therefore, by using a single-mode fiber laser as the second oscillator 3, the second laser beam L2 with a small beam diameter and a high peak energy intensity can be effectively generated.

[0020] (3) Regarding the hybrid galvano scanner 10 Next, the details of the hybrid galvano scanner 10 will be described. The hybrid galvano scanner shown in FIGS. 5 to 7 includes a combiner unit 4 that superimposes laser beams L1 and L2 supplied from a first oscillator 2 and a second oscillator 3 on the same optical axis, a focus shifter unit 6 downstream of the combiner unit 4 that adjusts the focal length of the laser beams L1 and L2 superimposed on the same optical axis, and a galvano scanner unit 8 downstream of the focus shifter unit 6 that displaces the direction of the optical axes of the laser beams L1 and L2 toward the workpiece W.

[0021] As shown in FIG. 5, the combiner unit 4 includes, for example, lenses (such as collimation lenses) 31 and 32 that collimate the laser beams L1 and L2 supplied from the first oscillator 2 and the second oscillator 3, respectively, and mirrors (including beam splitters, half mirrors, combiners, etc.) 33 and 34 necessary to align the optical axes of the respective laser beams L1 and L2 that have passed through the lenses 31 and 32. Of course, the combiner unit 4 may have optical elements, optical fibers, or the like other than those described above. Also, in the combiner unit 4, it is possible to superimpose three or more types of laser beams having different wavelengths. As shown in FIG. 6, the focus shifter unit 6 includes a lens (concave lens, particularly a biconcave lens, etc.) 41 that expands the diameters of the laser beams L1 and L2 superimposed in the combiner unit 4, and lenses (a plurality of convex lenses, particularly plano-convex lenses that serve as collimation lenses or condenser lenses, etc.) 42 and 43 that reduce the diameters of the laser beams L1 and L2 that have passed through the lens 41. Of course, the focus shifter unit 6 may have optical elements, optical fibers, or the like other than those described above.

[0022] The focus shifter unit 6 variably adjusts the focal length F of the laser beams L1 and L2 provided by the combiner unit 4. For this purpose, in the example shown in FIG. 6, at least one of the concave lens 41 and the convex lens 42 is supported by a linear motor carriage or other appropriate drive mechanism so that the relative distance D along the optical axes of the laser beams L1 and L2 between the concave lens 41 and the convex lens 42 can be variably adjusted, and is movable forward and backward along the optical axis direction. Incidentally, the final condenser lens 43 does not necessarily need to move forward and backward along the optical axis direction. As shown in Fig. 6(a), the shorter the distance D between the concave lens 41 and the convex lens 42, the longer the focal length F of the laser beams L1 and L2 that have passed through the lenses 41, 42, and 43 of the focus shifter section 6. That is, the foci of the laser beams L1 and L2 move away from the lens 43 at the end of the focus shifter section 6.

[0023] Conversely, as shown in Fig. 6(b), the longer the distance D between the concave lens 41 and the convex lens 42, the shorter the focal length F of the laser beams L1 and L2 that have passed through the lenses 41, 42, and 43 of the focus shifter section 6. That is, the foci of the laser beams L1 and L2 approach the lens 43 at the end of the focus shifter section 6. Note that chromatic aberration inevitably occurs in the lenses 41, 42, and 43 as an inevitable physical law (due to the refractive index of light depending on the wavelength of that light). Therefore, when attempting to irradiate the workpiece W with a superposition of a plurality of laser beams having different wavelengths, the irradiation position of a laser beam of a certain wavelength and the irradiation position of another laser beam that should be superimposed thereon will shift on the workpiece. Due to this shift, there is a concern that the desired laser processing or machining result cannot be obtained. Therefore, in practice, the positions of the lenses 31 and / or the lens 32 through which the laser beams L1 and L2 output from the first oscillator 2 and the second oscillator 3 pass are adjusted so that the foci of the superimposed laser beam L1 and the laser beam L2 are aligned.

[0024] As shown in FIGS. 5 and 7, the galvanometer scanner unit 8 is a known device that rotates mirrors 81 and 83, which reflect the laser beams L1 and L2 provided by the focus shifter unit 6, via a drive mechanism such as servo motors, stepping motors, etc. 82 and 84. In short, the galvanometer scanner unit 8 can displace the directions of the optical axes of the laser beams L1 and L2 reflected by the mirrors 81 and 83. The galvanometer scanner unit 8 in the present embodiment includes an x-axis galvanometer scanner 83 and 84 that change the optical axes of the laser beams L1 and L2 heading toward the workpiece W along the x-axis direction on the workpiece W, and a y-axis galvanometer scanner 81 and 82 that change the optical axes of the laser beams L1 and L2 along the y-axis direction on the workpiece W. The laser beams L1 and L2 are scanned in the xy two-dimensional direction with respect to the workpiece W, so that the irradiation positions of the laser beams L1 and L2 on the workpiece W can be controlled two-dimensionally.

[0025] A feature of the hybrid galvanometer scanner 10 of the present embodiment is that the adjustment of the focal length F by the focus shifter unit 6 and the displacement of the direction of the optical axis by the galvanometer scanner unit 8 are synchronized. The closer the angle θ of the optical axes of the laser beams L1 and L2 passing through the mirrors 81 and 83 of the galvanometer scanner unit 8 with respect to the workpiece W is to perpendicular, the shorter the optical path length from the mirror 83 to the workpiece W becomes. Therefore, as the angle θ of the laser beams L1 and L2 axes with respect to the workpiece W approaches perpendicular (90°), the focus shifter unit 6 and the galvanometer scanner unit 8 are synchronously controlled so as to shorten the focal length F realized by the focus shifter unit 6.

[0026] Conversely, the more the angle θ of the optical axes of the laser beams L1 and L2 passing through the mirrors 81 and 83 of the galvanometer scanner unit 8 with respect to the workpiece W is inclined from perpendicular, the longer the optical path length from the mirror 83 to the workpiece W becomes. Therefore, as the angle θ of the laser beams L1 and L2 axes with respect to the workpiece W inclines (moves away from 90°), the focus shifter unit 6 and the galvanometer scanner unit 8 are synchronously controlled so as to increase the focal length F realized by the focus shifter unit 6. Through the synchronization control of the lenses 41 and 42 of the focus shifter unit 6 and the mirrors 81 and 83 of the galvanometer scanner unit 8 described above, the laser beams L1 and L2 can be irradiated to any location on the workpiece W, and moreover, the foci of the laser beams L1 and L2 can be accurately aligned with the desired processing target surface of the workpiece W.

[0027] It is desirable that there is no lens (such as an fθ lens) that allows the laser beams L1 and L2 to pass between the mirrors 81 and 83 of the galvanometer scanner unit 8 and the workpiece W. This can reliably avoid the problem of chromatic aberration that occurs when the laser beams L1 and L2 whose optical axis directions are manipulated by the galvanometer scanner unit 8 pass through the lens. That is, there is no shift between the position where the laser beam L1 of a certain wavelength hits the workpiece W and the position where the laser beam L2 superimposed thereon hits the workpiece W. Therefore, the desired laser treatment or processing result can be obtained. However, if chromatic aberration occurs only to the extent that the shift in the irradiation positions of the laser beams L1 and L2 can be ignored, there is no obstruction to interposing some lens that transmits the laser beams L1 and L2 between the mirrors 81 and 83 of the galvanometer scanner unit 8 and the workpiece W.

[0028] Note that the hybrid galvanometer scanner used in this embodiment is not limited to the configuration as described above. Although the biconcave lens 41, the collimation lens 42, and the condenser lens 43, which are elements of the focus shifter unit 6, are all located downstream of the mirrors 33 and 34, which are elements of the combiner unit 4, the arrangement of these optical elements 33, 34, 41, 42, and 43 is not limited to that shown in FIG. 5. (4) Regarding the image processing unit 9 In the welding of the stator coil, in order to appropriately irradiate a flat wire of several millimeters with a laser, it is preferable to accurately measure the position of the flat wire. Therefore, in the laser device 1, the central position and height with respect to the tips of a plurality of flat wires 52 are measured by image analysis by the image processing unit 9. As shown in FIG. 8, the image processing unit 9 includes an illumination device 101 that applies illumination light to the workpiece W, an imaging device 102 that images the workpiece W illuminated by the illumination device 101, and a controller 103 that measures the center position and height of each flat angle line 52 included in the workpiece W using the image data imaged by the imaging device 102.

[0029] The illumination device 101 and the imaging device 102 are an illumination device and a 3D camera suitable for the pattern projection method. The illumination device 101 projects a plurality of stripe patterns (striped patterns) onto the workpiece W from a plurality of different directions, and the imaging device 102 receives the reflected light with an image sensor such as a CMOS. The controller 103 generates a 3D image by analyzing the change in the pattern between the projected light and the reflected light. As shown in FIG. 8, the controller 103 includes a memory 104 and a processor 105. A measurement program 111 is stored in the memory 104 in advance. By executing the measurement program 111, the processor 105 measures the center position and height of all the flat angle lines 52 included in the workpiece W, and generates a coordinate table 112 (CSV data) that describes the measurement results for each pair to be welded. The processor 105 stores the generated coordinate table 112 in the memory 104.

[0030] (5) Regarding the control PC12 As shown in FIG. 9, the control PC12 is composed of a control unit 201, a storage unit 202, an input unit 203, a communication unit 204, and a display unit 205. Specifically, the control PC12 is a computer system equipped with hardware resources such as a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), an HDD (Hard Disk Drive), an SSD (Solid State Drive), a display unit, a communication interface, and input devices such as a keyboard and a mouse. In welding processing using a galvanometer scanner, the control PC is sometimes referred to as a "galvano PC".

[0031] The control unit 201 is composed of a CPU 211, a RAM 212 which is a working memory, and the like. The storage unit 202 is a so-called auxiliary storage device, and is composed of a non-volatile memory such as an HDD, an SSD, a ROM (Read Only Memory), or a flash memory. The storage unit 202 stores various data such as a computer program for controlling the laser device 1, various laser parameters input via the input unit 203, and processing graphic data used in welding. The CPU 211 of the control unit 201 loads the computer program stored in the storage unit 202 into the RAM 212 which is a working memory and executes it, thereby controlling the first oscillator 2, the second oscillator 3, the hybrid galvano scanner 10, the PLC 13, the laser controller 14, etc., to perform welding processing on the workpiece W. Note that the laser parameters stored in the storage unit 202 are the laser output used in the first oscillator 2 and the second oscillator 3, the processing rate (laser irradiation time), the mark speed, the slow-up time, the slow-down time, etc.

[0032] The input unit 203 includes an input device that accepts user operations such as a keyboard, a mouse, and various switches, and also includes those that input data by connecting a removable recording medium such as a USB memory or an SD memory card. The data input via the input unit 203 is stored in the storage unit 202. The communication unit 204 performs information communication with external devices (image processing unit 9, hybrid galvano scanner 10, PLC 13, laser controller 14, etc.) connected by wireless or wired means. The display unit 205 includes a display unit, a video codec, a GPU (Graphics Processing Unit), a memory for screen data, etc., generates a UI screen, etc., and displays it on the display unit. The user may input various parameters for instructing the laser controller 14 via the input unit 203 while the UI screen is being displayed on the display unit 205.

[0033] (6) Description of the workpiece W Next, the workpiece W to be welded will be described with reference to FIGS. 10 and 11. FIG. 10 is a perspective view showing a schematic configuration of a stator 50 which is a stator of a motor for an electric vehicle or the like. As shown in the figure, the stator 50 has a substantially cylindrical stator core 51 and a plurality of rectangular wires (segment coils) 52 inserted into a plurality of slots provided in the stator core 51. The rectangular wire 52 is a conductor (electric wire) having a rectangular cross section. Usually, the rectangular wire 52 is made of pure copper, but it may be made of a metal material having high conductivity, such as an alloy mainly composed of copper, an alloy composed of copper and aluminum, etc. The end portions of each rectangular wire 52 protrude from the upper end portion of the stator core 51, and the laser device 1 laser-welds the tip portions of two rectangular wires 52 adjacent to each other in the radial direction of the stator core 51.

[0034] Each rectangular wire 52 is cut in advance so that its tip is tapered in order to prevent it from getting caught when inserted into the slot 53. An example of the shape of the rectangular wire 52 is shown in FIG. 11. As shown in FIG. 11(b), the rectangular wire 52 is composed of a base portion 52d and a neck portion 52e having a width in the y-axis direction narrower than that of the base portion 52d. The neck portion 52e has a gabled roof shape having two inclined surfaces 52a and 52b as shown in FIG. 11(a). In the tip welding process of the rectangular wire 52, the insulating coating portion on the tip side is peeled off, the tip portions of the corresponding two rectangular wires are butted against each other, and the butted tip portions are opposed to the laser device 1 and irradiated with laser light. As described above, in this embodiment, since the tip side of the rectangular wire 52 has a gabled roof shape, if welding is performed without considering this shape, a large amount of spatter may occur. Therefore, the laser device 1 focuses the laser light on the inclined surface 52b near the butting surface 52c of the corresponding two rectangular wires 52 and irradiates the laser. Note that due to variations in the processing accuracy of each rectangular wire 52, the mechanical accuracy of the fixing jig 15, the insertion condition into the slot 53, etc., a gap (gap, void) or a step may occur when the tip portions of the two rectangular wires 52 are butted against each other.

[0035] (7) Operation of the welding process by the laser device 1 Next, the operation of the laser device 1 will be described with reference to FIGS. 12 and 13. First, the workpiece W is set on the work set stage 11 (step S101). The control PC 12 sets laser parameters (laser output, ramp-up time, ramp-down time, etc.) for each oscillator 2, 3 via the laser controller 14 (step S102). The user operates the input unit 203 of the control PC 12 to input the machining graphic data used by the hybrid galvano scanner 10 during the laser irradiation in the first step and the second step, and the control PC 12 registers the machining graphic data in the storage unit 202 (step S103). In the present embodiment, machining graphic data representing a "straight line" locus is registered. The processes of step S101, step S102, and step S103 do not necessarily have to be performed in this order.

[0036] Subsequently, the work set stage 11 on which the workpiece W is placed is moved to position the workpiece W directly below the image processing unit 9. Next, the position measurement of each flat angle line 52 is performed by the image processing unit 9 (step S104). Specifically, the illumination device 101 projects a plurality of stripe patterns (striped patterns) from a plurality of different directions onto the workpiece W by the pattern projection method, each image is captured by the imaging device 102, and the controller 103 synthesizes the captured images to calculate a 3D shape. From this 3D shape, the controller 103 of the image processing unit 9 measures the center position and height of each flat angle line 52 and generates CSV data (coordinate table 112) describing the measurement results. The image processing unit 9 transmits the CSV data (coordinate table 112) on which the measurement results are described to the control PC 12. At this time, the transmission of the CSV data from the image processing unit 9 to the control PC 12 may be transmitted via a wireless or wired network, or may be transmitted via a portable recording medium such as a USB memory or an SD memory card.

[0037] Subsequently, the laser device 1 performs laser processing. In this embodiment, it is assumed that the scanning range of the hybrid galvanometer scanner 10 covers the entire size of the workpiece W. However, when performing welding on a motor larger than the scanning range of the galvanometer scanner, the laser device 1 may perform welding while rotating the workpiece W by the θ-axis stage 11θ of the work set stage 11. Depending on the size of the motor, welding may be performed while rotating by one-fourth, or welding may be performed while rotating by one-eighth. The laser device 1 repeats the processes from step S105 to step S115 for each pair of flat angle lines 52 to be welded. The control unit 201 of the control PC 12 refers to the coordinate table 112 to acquire the position information of the pair being processed (step S106). The position information acquired here includes at least the center coordinates and height information of each of the two flat angle lines.

[0038] The control unit 201 determines the laser irradiation positions in the first and second steps described later at positions closer to the inside of each flat angle line 52 (step S107). The position closer to the inside means, referring to FIG. 11(a), on the inclined surface 52b close to the butting surface 52c of each flat angle line 52. Also, the control unit 201 determines the midpoint of the heights of the two flat angle lines 52 as the focus position (step S108). If there is no step between the two flat angle lines 52, the foci of the first laser beam L1 and the second laser beam L2 are aligned at the JF (just focus) position shown in FIG. 14(a). If there is a step between the two flat angle lines 52, the foci of the first laser beam L1 and the second laser beam L2 are aligned at the JF position shown in FIG. 14(b). The laser device 1 of this embodiment can perform processing with sufficiently high welding quality even if there is a step of about 2 mm.

[0039] Next, the laser device 1 performs laser irradiation in the first step (step S109). FIG. 15(a) shows the irradiation locus l1 of the first laser beam L1 and the second laser beam L2 in the first step. In the first step, the first laser beam L1 and the second laser beam L2 are irradiated reciprocally 1.5 times at a speed of 500 mm / s in a substantially straight line in the y-axis direction on the inclined surface 52b of one flat angle line 52. Here, as shown in FIG. 15(a), the condensing diameter of the first laser beam L1 is larger than the condensing diameter of the second laser beam L2. As an example, in this embodiment, the condensing diameter of the first laser beam is 1050 μm, and the condensing diameter of the second laser beam L2 is 40 μm. Also, the size of the flat angle line 52 used in this embodiment is approximately 2.0 mm × 3.0 mm. When the irradiation in the first step is completed, the laser device 1 stops the laser output and jumps to the other flat angle line 52 (moves the laser irradiation position) (step S110). In the case of fillet welding of flat angle lines, there are slightly gaps caused by the thickness of the insulating coating between the flat angle lines. The size of the gap is generally about 0.4 mm to 1. mm. If the laser passes through this gap, it will damage the lower part of the flat angle line. Therefore, when moving the laser irradiation position from one flat angle line to the other flat angle line, the laser output is stopped. This prevents the laser from passing through the gap.

[0040] Subsequently, the laser device 1 performs laser irradiation in the second step (step S111). FIG. 15(b) shows the irradiation locus l2 of the first laser beam L1 and the second laser beam L2 in the second step. In the second step, the first laser beam L1 and the second laser beam L2 are irradiated reciprocally 1.5 times at a speed of 500 mm / s in a substantially straight line in the y-axis direction on the inclined surface 52b of the other flat angle line 52. Even when the irradiation in the second step is completed, if a molten pool of the desired size is not formed at the tip of the two flat angle lines (N in step S112), the laser output is stopped and the laser device jumps to the other flat angle line 52 (step S113). Then, the irradiation in the first step is repeated. When the irradiation in the second step is completed and a molten pool of the desired size is formed at the tip of the two flat angle lines (Y in step S112), the laser irradiation position is moved to the next pair of flat angle lines (step 114), and the process returns to step 106.

[0041] Before or simultaneously with the irradiation of the first laser beam L1 and the second laser beam L2, the laser device 1 sprays nitrogen, which is a shielding gas, onto the welding surface of the flat angle line 52 at a rate of 5 L / min to 100 L / min until the irradiation ends or for a longer time. More preferably, the spraying is performed at a rate of 10 L / min to 40 L / min. By performing the welding of the flat angle line 52 in a nitrogen atmosphere, the laser device 1 can prevent the oxidation of the welding surface, thereby suppressing a decrease in welding strength and the occurrence of porosity caused by the oxidation of the welding surface. In the present embodiment, two shielding nozzles 19a and 19b are used to spray nitrogen from the left and right, and the angle of each shielding nozzle 19a and 19b with respect to the workpiece W is 30 degrees as an example. The diameter of the tip opening (nozzle tip diameter) of the shielding nozzles 19a and 19b is preferably about 1 to 10 mm. Further, the working distance, which is the distance from the tip opening of the shielding nozzles 19a and 19b to the workpiece W, is preferably about 5 to 15 mm. By appropriately selecting conditions such as the flow rate of the shielding gas, the nozzle tip diameter, and the working distance in this way, it is possible to suppress the sway of the molten pool and form a beautiful molten pool.

[0042] As described above, by repeating the irradiation in the first step and the irradiation in the second step by the laser device 1, the angle of the flat angle line end face is gradually melted and rounded, and a first melting part and a second melting part are formed on the tip side of each flat angle line 52. By these melting parts entering the gap and joining, one melting part straddling the two flat angle lines 52 is formed. After that, the irradiation in the first step and the irradiation in the second step are repeated until a molten pool of a desired size is formed. Incidentally, it is difficult to measure the size of the molten pool during welding, and the time until a molten pool of a desired size is formed at the tip of the flat straight line 52 varies depending on the size of the flat straight line 52 and laser conditions, etc. Therefore, it is preferable to perform test processing in advance. Perform test processing on the target flat straight line 52 and measure the laser irradiation time until a molten pool of a desired size is formed. Then, if the laser irradiation time obtained as a result of the test processing is input to the control PC 12 and set as laser parameters for each oscillator 2, 3 via the laser controller 14, in step S112, it is possible to determine whether or not a molten pool of a desired size has been formed by determining whether or not the laser irradiation time has reached the set time.

[0043] FIG. 16 is a schematic diagram showing the shape change of the tip of the flat straight line 52 from the start of welding until a molten pool 56 of a desired size is formed and welding is completed. FIG. 16(a) shows the shape change when there is no step in the pair of flat straight lines 52, and FIG. 16(b) shows the shape change when there is a step in the pair of flat straight lines 52. In both cases, the first molten part 52a and the second molten part 52b formed on each flat straight line 52 are joined to form one molten pool straddling the two flat straight lines 52. In the case of having a step, it is possible to realize the same melting height as in the case of having no step by irradiating the laser slightly longer until the step is absorbed compared to the case of having no step. <Effects of the Embodiment>

[0044] The laser device 1 can suppress the generation of sputtering by irradiating a laser at a predetermined position near the butting surface with respect to the flat straight line 52 having a tapered tip, and can realize high-quality laser welding. As a result, it becomes possible to omit the "trimming process" that has been conventionally performed. In addition, the time until the molten pools formed on each flat straight line 52 are joined can be shortened, and the tact time related to the manufacture of the entire starter is shortened. Further, the laser device 1 forms a molten pool on the workpiece W by rapidly scanning and irradiating a first laser beam L1 having a wavelength of 300 nm to 600 nm and a high light absorption rate for copper. Then, by irradiating a second laser beam L2 having a small condensing diameter and a high energy density inside the formed molten pool, a locally deep penetration depth is realized inside the molten pool, and the formation of the molten pool is promoted.

[0045] Further, compared with conventional welding devices, the laser device 1 can effectively heat and melt the workpiece W by using the first laser beam L1 having a large condensing diameter for welding. Further, the laser device 1 generates a flow in the molten pool by scanning and irradiating the first laser beam L1 and the second laser beam L2 at high speed instead of point irradiation. This discharges the bubbles generated from the molten pool that has reached a high temperature to the outside. Thereby, porosity can be suppressed. Furthermore, it is possible to prevent local heat concentration in the molten pool, stabilize the molten pool, and reduce spatter. Since porosity and spatter are factors causing welding defects such as poor joint, according to the laser device 1 and the welding method using these devices, it is possible to suppress the occurrence of welding defects. Further, since the laser device 1 stops the laser output between the irradiation of the first step and the irradiation of the second step, it is possible to suppress laser leakage from the gap generated when butting the flat angle line 52, and suppress carbonization and insulation failure of the coating portion associated with the laser leakage.

[0046] <Other Modification Examples> As described above, as one embodiment of the present invention, the laser device 1 has been described. However, the present invention is of course not limited to the laser device 1 and the welding method using the laser device 1 described above, and the above embodiment can also be modified as follows. Here, modification examples of the above embodiment will be described. The above embodiment and the modification examples described below can be combined in any way. (1) In the above embodiment, a specific example of the shape of the flat angle line 52 was described with reference to FIG. 11. However, this is just an example, and the flat angle line 52 to be welded by the laser device 1 is not limited to the shape of FIG. 11. In FIG. 11(a), the angles of the inclined surfaces 52a and 52b are symmetrical left and right, but the angles of the inclined surfaces may be asymmetrical. Also, the form of the neck is not limited to the form of the neck 52e in FIG. 11(b), and may be, for example, the form of the neck 52f shown in FIG. 17(a) or the form of the neck 52g shown in FIG. 17(b). As long as at least the tip side of the flat angle line 52 is convex and can suppress snagging during slot insertion, any shape is acceptable.

[0047] (2) In the above embodiment, two laser beams with different wavelengths (the first laser beam L1 and the second laser beam L2) are superimposed to perform welding on the flat angle line 52. However, this is just an example, and welding of the flat angle line 52 may be performed with a single laser beam by using a high-power blue laser or green laser. The device configuration at this time is shown in FIG. 18. What is different between the laser device 1a in FIG. 18 and the laser device 1 in FIG. 4 is that there is no oscillator 3 for the IR laser, and a normal galvanometer scanner 10a is used instead of the hybrid galvanometer scanner 10. The galvanometer scanner 10a describes, as an example, a 3D galvanometer scanner having a focus shifter function in the z direction. However, the configuration is not limited to this, and a configuration combining a 2D galvanometer scanner that does not have a focus shifter function and only performs scanning in the xy direction and an fθ lens may also be used. (3) In the above embodiment, it was described that the irradiation trajectories l1 and l2 each perform 1.5 reciprocations of linear reciprocating irradiation, but it is of course not limited to 1.5 reciprocations, and 2 reciprocations or 2.5 reciprocations may also be used. It is preferable to determine an appropriate irradiation time in consideration of the balance between the melting amount of the flat angle line 52 and the time loss due to the jump step.

[0048] In addition, the trajectories of the laser irradiation in the first step and the second step are not limited to linear reciprocating irradiation. In the first step and the second step, circular swirling irradiation may be performed on the inclined surface 52b of each flat angle line 52, or elliptical swirling irradiation may be performed as shown by the irradiation trajectories l3 and l4 in FIG. 19. It is preferable to use machining pattern data suitable for the size and shape of the flat angle line 52. Note that swirling irradiation across the two flat angle lines 52 is not suitable for the welding process of this embodiment. Since there is a gap between the two flat angle lines 52, it is necessary to stop the laser output while crossing the gap. As a result, the on / off control of the laser output will occur frequently, and this on / off control will have an adverse effect on the tact time.

[0049] (4) In the above embodiment, the height of each pin is measured by the image processing unit 9 and the midpoint thereof is set as the focus position, but this is not an essential configuration. The image processing unit 9 may not measure the height of each pin and may use a predetermined reference position as the focus position. Predict the approximate height variation and set the position that can absorb this variation as the reference position. By setting the same reference position as the focus position for all pairs of welding processes, it is not necessary to perform control to change the focus position for each pair. In this way, if the same reference position is set as the focus position for all pairs of welding processes, the function of height measurement by image processing can be omitted, and the cost related to the image processing system can be reduced. In addition, the number of management parameters for processing conditions in motor production can be reduced. (5) Also, when the image processing unit 9 measures the height of each pin as in the above embodiment, it is preferable to increase the total irradiation time for the higher flat angle line compared to the lower flat angle line to melt the higher flat angle line more. Thereby, a beautiful molten pool with uniform left and right can be formed in a short time.

[0050] (6) When the temperature of the workpiece W rises rapidly during welding, spatter may occur. Therefore, instead of irradiating the first laser beam L1 and the second laser beam L2 simultaneously, only the first laser beam L1 with a high absorption rate for the workpiece W may be irradiated first, and after a predetermined time has elapsed, the second laser beam L2 may be additionally irradiated. Thereby, a rapid temperature rise of the welding surface can be suppressed, and the generation of spatter can be suppressed. Further, since the absorption rate of the wavelength of the second laser beam L2 increases for the welding surface whose temperature has been increased by the first laser beam L1, the energy of the second laser beam L2 can be efficiently absorbed by the workpiece W, leading to a reduction in the processing time. In this case, it is desirable that the second laser beam L2 be irradiated with a delay of 1 msec or more after the irradiation of the first laser beam L1.

[0051] (7) The condensing diameter of the first laser beam L1 is not limited to 1050 μm. The condensing diameter of the first laser beam L1 can be appropriately selected according to the cross-sectional area of the flat angle line 52. For example, the condensing diameter of the first laser beam L1 can be 1 percent to 30 percent of the cross-sectional area. Also, the condensing diameter of the second laser beam L2 is not limited to 40 μm. The condensing diameter of the second laser beam L2 can be about 10 to 100 μm, and it is preferably 1 / 10 or less of the condensing diameter of the first laser beam L1. The condensing 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 condensing lens, and can be calculated by condensing diameter = core diameter of the transmission fiber × (focal length of the condensing lens / focal length of the collimating lens). Therefore, by adjusting these optical systems, it is possible to change the condensing diameter of each laser beam.

[0052] (8) In the above embodiment, the scanning speeds of the first laser beam L1 and the second laser beam L2 were described as 500 mm / s, but the scanning speeds of the first laser beam L1 and the second laser beam L2 are not limited thereto, and may be in the range of 100 to 1000 mm / s. (9) In the above-described embodiment, the irradiation in the first step and the irradiation in the second step are repeated until a molten ball of a desired size is formed. However, this is just an example. When it is not particularly necessary to form a molten ball, the irradiation in the first step and the irradiation in the second step may be repeated until a part of the molten portion formed on one flat straight line 52 and a part of the molten portion formed on the other flat straight line 52 enter the gap. Also, the irradiation in the first step and the irradiation in the second step may be repeated until the first molten portion and the second molten portion are joined.

[0053] (10) In the above-described embodiment, it was explained that the first laser beam L1 is multimode and the second laser beam L2 is single mode, but this is just an example, and the beam mode of each laser beam is not limited. (8) In the above-described embodiment, side nozzle type shield gas nozzles 19a and 19b were used to avoid interference with the operations of the image processing unit 9 and the hybrid galvanoscanner 10 and to supply nitrogen effectively. However, the shield gas nozzle is of course not limited to the side nozzle type. The shield gas nozzle may be any nozzle that can blow nitrogen at an inclination angle of 0 to 90° with respect to the welding surface and perform welding in a nitrogen atmosphere. (11) In the above-described embodiment, 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 to this. For example, an elliptical beam or a rectangular beam may be used. In this case, it is preferable that the longitudinal direction is the major axis in the rectangular flat cross section.

[0054] (12) In the above-described embodiment, the speed at which the laser irradiation position is moved in step S110 and step S113 may be higher than the laser irradiation speeds in the first step and the second step. For example, it may be 1000 mm / s, which is twice the laser irradiation speeds in the first step and the second step. This makes it possible to shorten the tact time. (13) In the above laser device 1, information such as the condensing diameter, output power of each of the first laser L1 and the second laser L2, and the irradiation trajectories (processing graphic data) of the first step and the second step, irradiation time, irradiation speed, irradiation frequency, etc. may be input in advance via the input unit 203 of the control PC12 with appropriate values corresponding to the size of the flat angle line. Further, when the work size, the finished shape of the molten ball, etc. are input, the control unit 201 may be configured to determine the condensing diameter, output power, irradiation trajectory, irradiation time, irradiation speed, irradiation frequency, etc. of the laser according to a predetermined algorithm.

Explanation of Signs

[0055] 1 Laser device 2 First oscillator (blue semiconductor laser) 3 Second oscillator (IR fiber laser) 9 Image processing unit 10 Hybrid galvano scanner 11 Workset stage 12 Control PC (galvano PC) 13 PLC 14 Laser controller 19a, 19b Shield gas nozzle 50 Stator 52 Flat angle line (first member, second member) 100 Control panel 101 Lighting device 102 Imaging device 103 Controller 201 Control unit 211 CPU 212 RAM 202 Storage unit 203 Input unit 204 Communication unit 205 Display unit

Claims

1. A welding method in which a first member and a second member with convex-shaped tip ends are abutted against each other, and the tips are opposed to a laser device and welded with laser light, including a first step of irradiating the laser light at a position near the butting surface of the tip end of the first member to form a first molten portion, and a second step of irradiating the laser light at a position near the butting surface of the tip end of the second member to form a second molten portion. A welding method characterized by the above.

2. The first member and the second member are flat wires constituting a stator coil, wherein the convex shape on the tip end side is a gable roof shape having a first inclined surface formed at the tip end of the flat wire and a second inclined surface formed non-parallel to the first inclined surface, and in the first step and the second step, the laser light is irradiated onto one of the inclined surfaces located closer to the butting surface among the first inclined surface and the second inclined surface. The welding method according to claim 1, characterized by the above.

3. In the first step, the first molten portion is formed by reciprocally irradiating the inclined surface located near the butting surface in the first member in a substantially straight line, and in the second step, the second molten portion is formed by reciprocally irradiating the inclined surface located near the butting surface in the second member in a substantially straight line. The welding method according to claim 2, characterized by the above.

4. In the welding method, the laser irradiation in the first step and the laser irradiation in the second step are alternately and repeatedly performed. The welding method according to claim 3, characterized by the above.

5. In the welding method, the laser irradiation in the first step and the laser irradiation in the second step are alternately and repeatedly performed until the first molten portion and the second molten portion are joined. The welding method according to claim 4, characterized by the above.

6. In the welding method, the laser irradiation in the first step and the laser irradiation in the second step are alternately and repeatedly performed until the first molten portion and the second molten portion are joined and a molten ball of a predetermined size is formed. The welding method according to claim 4, characterized by the above.

7. There is a gap between the first member and the second member, and in the welding method, the laser irradiation in the first step and the laser irradiation in the second step are alternately and repeatedly performed until the first molten portion and the second molten portion enter the gap. The welding method according to claim 4, characterized by the above.

8. The welding method further includes, While alternately repeating the laser irradiation in the first step and the laser irradiation in the second step, after performing the laser irradiation on one of the flat angle lines, a jump step of moving the laser irradiation position to the other flat angle line with the laser irradiation stopped is included. The welding method according to any one of claims 4 to 7, characterized by the above.

9. In the first step, the laser beam is irradiated on the inclined surface of the first member in a substantially straight line reciprocating 1.5 times. In the second step, the laser beam is irradiated on the inclined surface of the second member in a substantially straight line reciprocating 1.5 times. The welding method according to claim 8, characterized by the above.

10. The welding method includes: an imaging step of imaging the first member and the second member to be welded; a control step of analyzing the image captured in the imaging step to obtain the position information of the first member and the second member, and determining the irradiation position of the laser beam based on the obtained position information. The welding method according to claim 1, characterized by including the above.

11. The welding method includes: an imaging step of imaging the first member and the second member to be welded; a control step of analyzing the image captured in the imaging step to obtain the height information of the first member and the second member, and determining the midpoint of the heights of the first member and the second member as the focus position based on the obtained height information. The welding method according to claim 1, characterized by including the above.

12. The laser beam is composed of a first laser beam and a second laser beam having different wavelengths from each other. The welding method according to claim 1, characterized by the above.

13. The wavelength of the first laser beam is 300 to 600 nm. The welding method according to claim 12, characterized by the above.

14. The wavelength of the second laser beam is 780 nm to 1100 nm. The welding method according to claim 12, characterized by the above.

15. The output powers of the first laser beam and the second laser beam are 500 W to 3 kW. The welding method according to claim 12, characterized by the above.

16. The condensing diameter of the second laser beam is smaller than the condensing diameter of the first laser beam. The welding method according to claim 12, characterized by the above.

17. The condensing diameter of the second laser beam is 1 / 10 or less of the condensing diameter of the first laser beam. The welding method according to claim 16, characterized by the above.

18. The condensing diameter of the second laser beam is 10 μm to 100 μm. The welding method according to claim 16, characterized in that...

19. Nitrogen is blown against the tip portion at a flow rate of 5 L / min to 100 L / min and an inclination angle with respect to the tip portion of 0 to 90° simultaneously with or before the irradiation of the laser beam, until or beyond the end of the irradiation. The welding method according to claim 1, characterized in that...

20. A laser device for butting a first member and a second member having a convex shape on the tip side and welding the tips, comprising: An oscillator that oscillates a laser beam; A galvanoscanner unit that displaces and irradiates the laser beam in an arbitrary direction; A control unit that controls the oscillator and the galvanoscanner unit, wherein the control unit controls the oscillator and the galvanoscanner unit so as to irradiate the laser beam at a position near the butting surface of the tip of the first member to form a first molten portion, and irradiate the laser beam at a position near the butting surface of the tip of the second member to form a second molten portion. The laser device, characterized in that...

21. The laser device further comprises: An image processing unit that images the first member and the second member and detects position information; The control unit determines the irradiation position of the laser beam using the position information detected by the image processing unit. The laser device according to claim 20, characterized in that...

Images