Method for manufacturing stator for rotating electrical machine

Abstract

Disclosed is a method for manufacturing a stator for a rotating electric machine, comprising: a step of bringing a coil sheet (52) and a front end portion (40) of another coil sheet (52) used to form a stator coil (24) of a rotating electric machine (1) into contact with each other; and a welding step of irradiating a laser beam (110) having a wavelength of less than 0.6 μm to a welding target portion of the abutting front end portion, wherein the laser beam is generated in each pulse oscillation of a laser oscillator in a manner having a laser output of more than 3.0 kW, and during at least a portion of one pulse oscillation, the laser beam moves in a manner such that the irradiation position changes linearly parallel to the abutting surface (401) of the front end portion.

Description

Technical Field

[0001] The present disclosure relates to a method for manufacturing a stator for a rotating electrical machine. Background Art

[0002] A method for manufacturing a stator is known, in which the front ends of a coil sheet and another coil sheet forming a stator coil of a rotating motor are brought into contact with each other, and a laser beam is irradiated toward the welding target portion of the abutting front ends in a manner that moves the irradiation position in a circular manner (for example, see Patent Document 1).

[0003] Patent Document 1: Japanese Patent Application Laid-Open No. 2018-20340

[0004] Patent Document 2: Japanese Patent Application Laid-Open No. 2007-229725

[0005] However, the conventional technology described in Patent Document 1 utilizes infrared laser (fiber laser), and therefore requires a relatively large heat input to obtain the required joining area between coil pieces. This has a significant thermal impact and may cause unstable welding. Summary of the Invention

[0006] Therefore, the purpose is to ensure the required joining area between coil pieces with a relatively small amount of heat input.

[0007] In one aspect, a method for manufacturing a stator for a rotating electrical machine is provided, comprising:

[0008] a step of bringing front end portions of one coil piece and another coil piece, which form a stator coil of a rotating electrical machine, into contact with each other; and

[0009] The welding process includes irradiating a laser beam having a wavelength of 0.6 μm or less to the welding target portion of the abutting front end portion.

[0010] In the welding process, the laser beam is generated in a laser oscillator in a manner having a laser output of 3.0 kW or more for each pulse oscillation.

[0011] During at least a portion of one pulse oscillation, the laser beam moves so that the irradiation position changes linearly parallel to the abutting surface of the front end portion.

[0012] According to the present disclosure, it is possible to ensure a required joining area between coil pieces with a relatively small amount of heat input. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 This is a cross-sectional view schematically showing the cross-sectional structure of a motor according to an embodiment.

[0014] Figure 2 This is a top view of the stator core alone.

[0015] Figure 3 This is a diagram schematically showing a pair of coil pieces assembled into a stator core.

[0016] Figure 4 This is a three-dimensional diagram of the area around the coil end of the stator.

[0017] Figure 5 This is a perspective view showing a portion of the coil piece of the same phase extracted.

[0018] Figure 6 This is a simplified front view of a coil sheet.

[0019] Figure 7 This is a diagram showing the front end portions of the coil pieces joined to each other and their vicinities.

[0020] Figure 8 Is along the welding object part Figure 7 Cross-sectional view along line AA.

[0021] Figure 9 This is a graph showing the relationship between laser wavelength and laser absorptivity for various materials.

[0022] Figure 10 This is a diagram explaining how the absorptivity changes during welding.

[0023] Figure 11A This is an image of a keyhole, etc., when a green laser is used.

[0024] Figure 11B This is an image of a keyhole, etc., when an infrared laser is used.

[0025] Figure 12A This is a graph showing the relationship between laser output and welding depth in the case of green laser.

[0026] Figure 12B This is a graph showing the relationship between laser output and welding depth in the case of green laser.

[0027] Figure 13 This is an explanatory diagram of the green laser welding method of this embodiment.

[0028] Figure 14 This is an explanatory diagram schematically showing the changing characteristics of the laser output and the welding heat input according to the irradiation position (irradiation method without a downward slope).

[0029] Figure 15 This is an explanatory diagram showing how the irradiation position changes in each process.

[0030] Figure 16This is an explanatory diagram schematically showing the changing characteristics of the laser output and the welding heat input according to the irradiation position (irradiation mode with a downward slope).

[0031] Figure 17 This is an explanatory diagram of the case where welding is achieved by two processes in the same welding direction.

[0032] Figure 18 This is an explanatory diagram of the case where welding is achieved through two processes with different welding directions.

[0033] Figure 19 This is an explanatory diagram of protrusions and the like caused by volume expansion.

[0034] Figure 20 This diagram illustrates a welding method that can reduce protrusions and pores.

[0035] Figure 21 Yes means through Figure 20 The diagram shows a cross section of a welded portion in which welding is achieved by two processes.

[0036] Figure 22 This diagram illustrates another welding method that can reduce protrusions and porosity.

[0037] Figure 23 This diagram illustrates another welding method that can reduce protrusions and porosity.

[0038] Figure 24A It is an explanatory diagram of a welding method using green laser light as a comparative example.

[0039] Figure 24B This is a diagram showing a cross section of a welded portion when welding is performed in a comparative example.

[0040] Figure 25 This is a flowchart schematically showing the manufacturing process of the stator.

[0041] Figure 26 This is a diagram showing the measurement results of the temperature history during welding using a green laser.

[0042] Figure 27 This diagram illustrates a test for verifying foreign matter resistance. DETAILED DESCRIPTION

[0043] Hereinafter, each embodiment will be described in detail with reference to the accompanying drawings. In addition, in this specification, "prescribe" is used to mean "predetermine in advance".

[0044] Figure 1 It is a cross-sectional view schematically showing a cross-sectional structure of a motor 1 (an example of a rotating electrical machine) according to an embodiment.

[0045] Figure 1 , the figure shows the rotating shaft 12 of the motor 1. In the following description, the axial direction refers to the direction in which the rotating shaft (rotation center) 12 of the motor 1 extends, and the radial direction refers to the radial direction centered on the rotating shaft 12. Therefore, the radially outer side refers to the side away from the rotating shaft 12, and the radially inner side refers to the side toward the rotating shaft 12. In addition, the circumferential direction corresponds to the direction of rotation around the rotating shaft 12.

[0046] The motor 1 may be a vehicle driving motor used in, for example, a hybrid vehicle or an electric vehicle, but the motor 1 may also be used for any other purpose.

[0047] The motor 1 is an inner rotor type, and the stator 21 is provided so as to surround the radially outer side of the rotor 30. The radially outer side of the stator 21 is fixed to the motor housing 10.

[0048] The rotor 30 is arranged radially inward of the stator 21. The rotor 30 includes a rotor core 32 and a rotor shaft 34. The rotor core 32 is fixed radially outward of the rotor shaft 34 and rotates integrally with the rotor shaft 34. The rotor shaft 34 is rotatably supported by the motor housing 10 via bearings 14a and 14b. The rotor shaft 34 also defines the rotating axis 12 of the motor 1.

[0049] The rotor core 32 is formed, for example, from an annular, magnetic, laminated steel plate. Permanent magnets 321 are inserted into the rotor core 32. The number and arrangement of the permanent magnets 321 are arbitrary. In a modified embodiment, the rotor core 32 can also be formed from a compacted powder body formed by compressing and compacting magnetic powder.

[0050] End plates 35A and 35B are attached to both axial sides of the rotor core 32. In addition to supporting the rotor core 32, the end plates 35A and 35B may also have a function of adjusting the imbalance of the rotor 30 (a function of eliminating the imbalance by cutting, etc.).

[0051] like Figure 1 As shown, the rotor shaft 34 has a hollow portion 34A. The hollow portion 34A extends over the entire axial length of the rotor shaft 34. The hollow portion 34A can also function as an oil passage. For example, in the hollow portion 34A, Figure 1 As shown by arrow R1, oil is supplied from one axial end side and flows along the radially inner surface of rotor shaft 34, thereby cooling rotor core 32 from the radially inner side. Furthermore, the oil along the radially inner surface of rotor shaft 34 can be ejected radially outward (arrows R5 and R6) through oil holes 341 and 342 formed at both ends of rotor shaft 34, thereby cooling coil tail ends 220A and 220B.

[0052] In addition, Figure 1, a motor 1 of a specific structure is shown, but the structure of the motor 1 is arbitrary as long as it has a stator coil 24 (described later) joined by welding. Therefore, for example, the rotor shaft 34 may not have the hollow portion 34A, or may have a hollow portion with an inner diameter significantly smaller than the hollow portion 34A. In addition, Figure 1 , a specific cooling method is disclosed, but the cooling method of the motor 1 is arbitrary. Therefore, for example, an oil introduction pipe inserted into the hollow portion 34A may be provided, or oil may be dripped from the oil passage in the motor housing 10 from the radially outer side toward the coil tail ends 220A, 220B.

[0053] In addition, Figure 1 In the embodiment, the present invention shows an inner rotor type motor 1 in which the rotor 30 is arranged inside the stator 21. However, the present invention is also applicable to other types of motors. For example, the present invention is also applicable to an outer rotor type motor in which the rotor 30 is arranged concentrically outside the stator 21, or a dual rotor type motor in which the rotor 30 is arranged both outside and inside the stator 21.

[0054] Next, refer to Figure 2 The structure related to the stator 21 will be described in detail in the following figures.

[0055] Figure 2 It is a plan view of the stator core 22 alone. Figure 3 Schematically shows a pair of coil pieces 52 assembled to the stator core 22. Figure 3 , the relationship between a pair of coil pieces 52 and the slots 220 is shown in a state where the radial inner side of the stator core 22 is unfolded. Figure 3 In FIG. 1 , the stator core 22 is indicated by a dotted line, and a portion of the slots 220 is omitted from the illustration. Figure 4 It is a perspective view of the periphery of the coil tail end 220A of the stator 21 . Figure 5 This is a perspective view showing a portion of the coil piece of the same phase extracted.

[0056] The stator 21 includes a stator core 22 and a stator coil 24 .

[0057] The stator core 22 is composed of, for example, annular magnetic laminated steel plates. However, in a modified embodiment, the stator core 22 may be formed of a powder compacted by compressing magnetic powder. In addition, the stator core 22 may be formed of a split core that is divided in the circumferential direction, or may be in a form that is not divided in the circumferential direction. A plurality of slots 220 for winding the stator coil 24 are formed on the radial inner side of the stator core 22. Specifically, as Figure 2As shown, the stator core 22 includes an annular back yoke 22A and a plurality of teeth 22B extending radially inward from the back yoke 22A. Slots 220 are formed circumferentially between the teeth 22B. The number of slots 220 is arbitrary, but in this embodiment, 48 are used as an example.

[0058] The stator coil 24 includes a U-phase coil, a V-phase coil, and a W-phase coil (hereinafter referred to as a "phase coil" when not distinguishing between U, V, and W). The base end of each phase coil is connected to an input terminal (not shown), and the terminal end of each phase coil is connected to the terminal end of the other phase coils to form the neutral point of the motor 1. In other words, the stator coil 24 is connected in a star configuration. However, the connection method of the stator coil 24 can be appropriately modified according to the desired motor characteristics, etc. For example, the stator coil 24 can be connected in a delta configuration instead of a star configuration.

[0059] Each phase coil is formed by joining a plurality of coil pieces 52 together. Figure 6 This is a schematic front view of a coil sheet 52. The coil sheet 52 is a segmented coil formed by dividing the phase coil into easily assembled units (e.g., units inserted into two slots 220). The coil sheet 52 is formed by covering a linear conductor (flat wire) 60 having a roughly rectangular cross-section with an insulating film 62. In this embodiment, the linear conductor 60 is formed of copper as an example. However, in a modified embodiment, the linear conductor 60 may also be formed of another conductive material such as iron.

[0060] The coil piece 52 may be formed into a substantially U-shape having a pair of straight portions 50 and a connecting portion 54 connecting the pair of straight portions 50 before being assembled to the stator core 22. When the coil piece 52 is assembled to the stator core 22, the pair of straight portions 50 are respectively inserted into the slots 220 (see FIG. Figure 3 ). Therefore, if Figure 3 As shown, the connecting portion 54 extends circumferentially on the other axial end side of the stator core 22 so as to span a plurality of teeth 22B (and a plurality of slots 220 associated with the plurality of teeth 22B). The number of slots 220 spanned by the connecting portion 54 is arbitrary, but Figure 3 In addition, after the straight portion 50 is inserted into the groove 220, as shown in Figure 6 As shown by the two-dot chain line in FIG, the straight portion 50 is bent in the circumferential direction.

[0061] In addition, Figure 6In the embodiment, the pair of straight portions 50 bends in a direction away from each other, but this is not limiting. For example, the pair of straight portions 50 may be bent in a direction toward each other. Furthermore, the stator coil 24 may also include a neutral point coil piece, etc., for connecting the ends of the three-phase coils to form a neutral point.

[0062] Multiple Figure 6 The legs 56 of the coil pieces 52 shown are arranged in the radial direction and inserted into one slot 220. Therefore, a plurality of lap portions 58 extending in the circumferential direction are arranged in the radial direction on one axial end side of the stator core 22. Figure 3 and Figure 5 As shown, the overlapping portion 58 of a coil sheet 52 extending from one slot 220 and extending to the first circumferential side (e.g., clockwise) is joined to the overlapping portion 58 of another coil sheet 52 extending from another slot 220 and extending to the second circumferential side (e.g., counterclockwise).

[0063] In this embodiment, as an example, six coil pieces 52 are assembled into one slot 220. Hereinafter, the coil pieces 52 from the radially outermost sides are referred to as the first turn, the second turn, and the third turn. In this case, the coil pieces 52 of the first turn and the coil pieces 52 of the second turn are joined to each other at the front end portion 40 through a joining process described later, the coil pieces 52 of the third turn and the coil pieces 52 of the fourth turn are joined to each other at the front end portion 40 through a joining process described later, and the coil pieces 52 of the fifth turn and the coil pieces 52 of the sixth turn are joined to each other at the front end portion 40 through a joining process described later.

[0064] Here, the coil piece 52 is covered with the insulating film 62 as described above, but the insulating film 62 is removed only from the front end portion 40. This is to ensure electrical connection with other coil pieces 52 through the front end portion 40. Figure 5 and Figure 6 As shown, the final axially outer end surface 42 of the front end portion 40 of the coil piece 52, that is, one end surface in the width direction of the coil piece 52, is formed as an arcuate surface protruding axially outward.

[0065] Figure 7 4 is a diagram showing the front end portion 40 and its vicinity of the mutually joined coil pieces 52. Figure 7 Schematically shows a range D1 of the welding target portion 90 in the circumferential direction. Figure 8 The welding object is 90 degrees along the Figure 7 Cross-sectional view along line AA.

[0066] When the front end portions 40 of the coil pieces 52 are joined, one coil piece 52 and the other coil piece 52 are joined with their respective front end portions 40 at Figure 7The view shown (viewed from a direction perpendicular to the abutting surface 401) forms a C-shaped docking. At this time, when the front end portions 40 of the coil sheets 52 are joined, the two front end portions 40 joined together can be joined by overlapping in the thickness direction in a manner such that the central axes of the respective arc surfaces (axially outer end surfaces 42) are aligned. By overlapping by aligning the central axes in this way, even when the flexion angle α is relatively large or relatively small, the axially outer lines of the two front end portions 40 joined together can be aligned and appropriately overlapped.

[0067] Here, in this embodiment, welding is used as a joining method when joining the front end portion 40 of the coil piece 52. Also, in this embodiment, as a welding method, arc welding represented by TIG welding is not used, but laser welding using a laser beam source as a heat source is used. By using laser welding instead of TIG welding, the axial length of the coil tail ends 220A and 220B can be reduced. That is, in the case of TIG welding, the front end portions of the abutting coil pieces need to be bent axially outward and extended axially, whereas in the case of laser welding, this bending is not required, as shown in FIG. Figure 7 As shown, welding can be achieved while the front end portions 40 of the abutting coil pieces 52 are extended circumferentially. Thus, compared with the case where the front end portions 40 of the abutting coil pieces 52 are bent axially outward and extended axially, the axial length of the coil tail ends 220A, 220B can be reduced.

[0068] In laser welding, Figure 5 As shown schematically, a welding laser beam 110 is irradiated toward the welding target portion 90 of the two abutting front end portions 40. Furthermore, the irradiation direction (propagation direction) of the laser beam 110 is substantially parallel to the axial direction, and is directed from the axially outer side toward the axially outer end surfaces 42 of the two abutting front end portions 40. Laser welding allows for localized heating, thus only heating the front end portions 40 and their vicinity, effectively reducing damage (carbonization) to the insulating coating 62. As a result, multiple coil pieces 52 can be electrically connected while maintaining appropriate insulation performance.

[0069] like Figure 7 As shown, the circumferential range D1 of the welding target portion 90 is the portion of the entire circumferential range D0 of the axial outer end surface 42 in the contact portion between the front end portions 40 of the two coil sheets 52, excluding the two ends. Due to the protruding arc surface of the axial outer end surface 42 at the two ends, it is difficult to ensure a sufficient welding depth (see Figure 7 The circumferential range D1 of the welding target portion 90 can be adapted to ensure a required joint area between the coil sheets 52, a required welding strength, and the like.

[0070] like Figure 8As shown, the radial range D2 of the welding target portion 90 is centered on the abutment surface 401 of the front end portions 40 of the two coil pieces 52. The radial range D2 of the welding target portion 90 can correspond to the diameter (beam diameter) of the laser beam 110. In other words, the laser beam 110 is irradiated in a manner such that the irradiation position does not actually change in the radial direction but changes linearly along the circumferential direction. In other words, the laser beam 110 moves so that the irradiation position changes linearly parallel to the abutment surface 401.

[0071] Figure 9 This is a graph showing the relationship between the laser wavelength and the laser absorptivity (hereinafter simply referred to as "absorptivity") of each material. Figure 9 , the horizontal axis represents wavelength λ and the vertical axis represents absorptivity, showing individual characteristics of each material: copper (Cu), aluminum (Al), silver (Ag), nickel (Ni), and iron (Fe).

[0072] However, infrared lasers (lasers with a wavelength of 1064 nm) are commonly used in laser welding. Figure 9 As shown by the black circle at the intersection with the dashed line of λ2 = 1.06μm, the absorption rate of copper, the material of the linear conductor 60 of the coil piece 52, is as low as approximately 10%. In other words, in the case of infrared lasers, most of the laser beam 110 is reflected by the coil piece 52 and not absorbed. Therefore, a relatively large amount of heat input is required to achieve the required bonding area between the coil pieces 52 to be bonded, resulting in significant thermal effects and the possibility of unstable welding.

[0073] In view of this, in this embodiment, a green laser is used instead of an infrared laser. Furthermore, the term "green laser" encompasses not only lasers with a wavelength of 532 nm, i.e., SHG (Second Harmonic Generation) lasers, but also lasers with wavelengths close to 532 nm. Furthermore, in a modified embodiment, lasers with wavelengths of 0.6 μm or less, which do not fall within the scope of green lasers, may also be used. The wavelength of a green laser is obtained by, for example, converting the fundamental wavelength generated by a YAG laser or a YVO4 laser through an oxide single crystal (e.g., LBO: lithium triborate).

[0074] In the case of green laser, Figure 9 As shown by the black circle at the intersection with the dotted line of λ1 = 0.532 μm, the absorption rate is as high as approximately 50% for copper, which is the material of the linear conductor 60 of the coil piece 52. Therefore, according to this embodiment, the required bonding area between the coil pieces 52 can be ensured with less heat input than when using infrared lasers.

[0075] In addition, if Figure 9As shown, the higher absorption rate of green laser light compared to infrared laser light is particularly noticeable in copper, but this property can also be observed in many other metal materials, not just copper. Therefore, welding using green laser light is possible even when the material of the linear conductor 60 of the coil piece 52 is other than copper.

[0076] Figure 10 This is a diagram explaining how the absorption rate changes during welding. Figure 10 In the figure, the horizontal axis uses laser power density (labeled as "Laser Power Density") and the vertical axis uses the laser absorption rate of copper (labeled as "Laser Absorption Rate"), showing characteristics 100G in the case of green laser and characteristics 100R in the case of infrared laser.

[0077] exist Figure 10 In FIG. 1 , points P1 and P2 where copper starts to melt in the case of green laser and infrared laser are shown, and point P3 where a keyhole is formed is shown. Figure 10 As shown by points P1 and P2 in the figure, it can be seen that the green laser can initiate copper melting at a lower laser power density than the infrared laser. Furthermore, due to the aforementioned difference in absorptivity, the difference between the absorptivity at point P3, where the keyhole is formed, and the absorptivity at the start of irradiation (i.e., the absorptivity at zero laser power density) is smaller for the green laser than for the infrared laser. Specifically, the absorptivity changes during welding by approximately 80% for the infrared laser, while the absorptivity changes during welding by approximately 40% for the green laser, which is about half the change.

[0078] As such, with infrared lasers, the variation (fluctuation) in absorptivity during welding is relatively large, at approximately 80%. This can lead to keyhole instability, and can easily cause variations in weld depth and weld width, as well as fusion zone disturbances (e.g., spattering). In contrast, with green lasers, the variation (fluctuation) in absorptivity during welding is relatively small, at approximately 40%. This reduces the likelihood of keyhole instability, weld depth and weld width variations, and fusion zone disturbances (e.g., spattering). Spattering refers to metal particles scattered by laser irradiation, etc.

[0079] In addition, in the case of infrared laser, as mentioned above, the absorption rate is low, so the beam diameter is usually set to be relatively small (for example, φ0.075mm), thereby compensating for the low absorption rate. This aspect also becomes the main factor that makes the keyhole unstable. In addition, Figure 11BThis is an image of a keyhole, etc., using an infrared laser. 1100 represents the weld bead, 1102 represents the molten pool, and 1104 represents the keyhole. Arrow R1116 schematically illustrates the degassing pattern. Arrow R110 also schematically illustrates the movement of the infrared laser irradiation position due to a small beam diameter. As mentioned above, with infrared lasers, due to the low absorptivity, it is difficult to achieve a relatively large beam diameter. Therefore, achieving the desired melt width tends to require a relatively long irradiation position movement trajectory (continuous irradiation time) that includes snaking.

[0080] On the other hand, in the case of green laser, the absorption rate is relatively high as mentioned above, so the beam diameter can be made relatively large (for example, φ0.1mm or more), and the keyhole can be enlarged and stabilized. As a result, degassing becomes good and the generation of sputtering can be effectively reduced. In addition, Figure 11A This is an image diagram showing a keyhole or the like when a green laser is used. The meanings of the reference numerals refer to Figure 11B As mentioned above, in the case of green laser, according to Figure 11A As an image, it is easy to understand that the keyhole is stabilized and degassing is improved due to the expansion of the beam diameter. In addition, in the case of green laser, compared with the case of infrared laser, the absorption rate is relatively high as mentioned above, and the beam diameter can be relatively large, so it is possible to obtain the desired melting width (see Figure 8 The radial range D2 of the welding target portion 90 shown in FIG. 1 is small, and the required movement trajectory of the irradiation position (irradiation time) is relatively short.

[0081] Figure 12A and Figure 12B This is a graph showing the relationship between laser output and welding depth in the case of green laser. Figure 12A In the figure, the horizontal axis uses the welding speed (marked as "Welding Speed") and the vertical axis uses the welding depth (marked as "Welding Depth", the same below), showing the various characteristics under various laser outputs (here 1.0kW, 2.5kW, 3.0kW, 3.5kW). Figure 12B In the graph, the horizontal axis represents welding heat input (labeled as "Welding Heat Input", the same below), and the vertical axis represents welding depth, showing various characteristics under various laser outputs (here, 1.0 kW, 2.5 kW, 3.0 kW, and 3.5 kW).

[0082] according to Figure 12A and Figure 12BIt can be seen that the laser output has a greater impact on the welding depth (penetration depth). On the other hand, if the welding speed is reduced, the welding heat input increases, but the impact on the welding depth (penetration depth) is relatively small. For example, Figure 12A and Figure 12B As shown, while the weld heat input at curve point PL1, when the laser output is 3.0 kW and the welding speed is approximately 35 mm / s, is relatively high at approximately 90 J / mm, the weld depth is approximately the same as that at curve point PL2, when the laser output is 3.5 kW and the welding speed is approximately 150 mm / s (see arrow Q1). This demonstrates that higher laser output leads to more efficient welding with higher heat input efficiency.

[0083] Figure 13 This is an explanatory diagram showing the green laser welding method of this embodiment. Figure 13 In the figure, the horizontal axis uses time (labeled as "Time", the same below), and the vertical axis uses laser output (labeled as "Output", the same below), schematically showing the timing waveform of the laser output during welding.

[0084] In this embodiment, if Figure 13 As shown in the figure, welding is achieved by pulse irradiation of green laser with a laser output of 3.8kW. Figure 13 In the process, the laser oscillator is pulsed with a laser output of 3.8kW for only 10msec, and after an interval of 100msec, the laser oscillator is pulsed with a laser output of 3.8kW for only 10msec again. Hereinafter, the amount of pulse irradiation (10msec pulse irradiation) that can be performed by such a single pulse oscillation is also referred to as "one process". In addition, in Figure 13 In the embodiment, the pulse waveform 130G represents the irradiation of the first process (N=1) to the third process (N=3), and N represents the Nth process (hereinafter, Figure 17 The same is true for ). In addition, Figure 13 , for comparison, a pulse waveform 130R of pulse irradiation in the case of infrared laser light is also shown.

[0085] In the case of green lasers, the output of the laser oscillator is relatively low (e.g., a maximum of 400W during continuous irradiation), making it difficult to achieve the high output required to ensure deep penetration (e.g., a high laser output of 3.0kW or higher). Specifically, since green laser light is generated by passing through a wavelength conversion crystal such as an oxide single crystal, as described above, its output decreases when passing through the wavelength conversion crystal. Therefore, continuous irradiation with a green laser beam cannot achieve the high output required to ensure deep penetration.

[0086] In this regard, as described above, in this embodiment, pulsed green laser irradiation ensures the high output required to ensure deep weld penetration (e.g., a high laser output of 3.0 kW or more). This is because even with continuous irradiation, which can only achieve a maximum output of 400 W, pulsed irradiation can achieve a high output of 3.0 kW or more. Pulsed irradiation is achieved by accumulating continuous energy to increase peak power and then performing pulse oscillation. Furthermore, in this embodiment, a single weld target area is irradiated with a green laser beam generated through multiple pulse oscillations. In other words, in this embodiment, two or more irradiation processes using relatively high laser output (e.g., a laser output of 3.0 kW or more) are performed on a single weld target area. Consequently, even when the circumferential range D1 of the weld target area 90 is relatively wide, deep weld penetration can be easily achieved throughout the entire weld target area 90, enabling high-quality welding.

[0087] In addition, Figure 13 In the example, the interval is a specific value of 100msec, but the interval can be arbitrary and can be minimized within the range of ensuring the required high output. Figure 13 In the embodiment, the laser output is a specific value of 3.8 kW. However, the laser output can be appropriately changed within a range that ensures a desired welding depth as long as it is 3.0 kW or more.

[0088] exist Figure 13 In the figure, a pulse waveform 130R is also shown when the infrared laser is continuously irradiated for a relatively long time of 130 msec with a laser output of 2.3 kW. Unlike the green laser, the infrared laser can be continuously irradiated with a relatively high laser output (2.3 kW). However, as mentioned above, in order to obtain the desired melting width, a relatively long irradiation position movement trajectory (continuous irradiation time) including a serpentine is required in the case of the infrared laser. In this case, the heat input is about 312 J, which is relatively large compared to the green laser. Figure 13 The heat input in the case of the green laser shown is approximately 80 J (in the case of two processes), which is significantly larger.

[0089] Thus, according to this embodiment, by using green laser, it is possible to weld the material (copper in this example) of the linear conductor 60 of the coil piece 52 using a laser beam having a higher absorptivity than when using infrared laser. Figure 8The radial range (D2) of the weld target portion 90 shown in FIG. The required irradiation position movement trajectory (time) is relatively short. Specifically, due to the increased keyhole size per pulse oscillation based on the relatively large beam diameter, the number of pulse oscillations required to achieve the desired melt width can be reduced. As a result, the required bonding area between the coil pieces 52 can be ensured with relatively low heat input.

[0090] In addition, according to this embodiment, by performing two or more processes of green laser irradiation on one welding target part, even when the circumferential range D1 of the welding target part 90 is relatively wide, it is easy to ensure deep penetration throughout the entire welding target part 90, thereby achieving high-quality welding.

[0091] Next, refer to Figures 14 to 23 , a preferred example of laser irradiation based on green laser is described.

[0092] Figure 14 It indicates the laser output and welding line energy of a process according to the irradiation position (in Figure 14 The figure schematically shows a variation characteristic 150P of the laser output according to the irradiation position and a variation characteristic 150L of the welding energy input according to the irradiation position. Figure 15 The way the irradiation position changes for each process (in Figure 15 The moving distance as the amount of change in the irradiation position is marked as "Distance"), and it is an explanatory diagram of how the irradiation position changes with respect to time.

[0093] In this embodiment, as an example, in one process, the speed of change of the irradiation position, that is, the welding speed is as follows: Figure 15 The figure shows a constant value. The change in irradiation position (the distance traveled by laser beam 110) over a period of approximately 10 msec is preferably within a range of 1 mm to 2 mm. In this embodiment, it is approximately 1.45 mm, as an example. Furthermore, in this embodiment, as an example, the length of range D1 in the circumferential direction of weld target portion 90 is approximately 2.9 mm. Furthermore, the maximum irradiation time per pulse (approximately 10 msec in this embodiment) is actually determined by the irradiation energy of the green laser beam per pulse. Therefore, under the same welding speed, increasing the irradiation energy per pulse increases the distance traveled by laser beam 110 per pulse.

[0094] Specifically, if Figure 14As shown, one process starts from position P10. That is, one pulse oscillation starts from position P10. In this case, at position P10, the laser output rises to a specified value (in this example, 3.8 kW as an example) (see arrow R140). And, the irradiation position changes linearly at a constant speed from position P10 to position P12. During this period, the laser output is maintained at a specified value (in this example, 3.8 kW as an example) (see arrow R141). If the irradiation position reaches position P12, the laser output drops from the specified value (in this example, 3.8 kW as an example) to 0 (see arrow R142). That is, one pulse oscillation ends. In addition, even if the irradiation position reaches position P12, the irradiation position may change until it moves to a further separation distance Δ1 (for example, see arrow R142). Figure 15 During this period, a small amount of welding line energy is generated due to the residual laser output (refer to Figure 14 In addition, in a modified example, when the irradiation position reaches position P12 or a position immediately before it (not shown), the change of the irradiation position (change at a constant speed) may be ended.

[0095] According to this irradiation method, at position P10, the laser output rises to the specified value (in this example, 3.8kW), but the welding heat input does not increase to the maximum value immediately until the actual laser output reaches the specified value. Figure 14 As shown by variation characteristic 150L, ​​the weld energy gradually increases from position P10 to position P11. Furthermore, at position P12, the laser output momentarily drops to zero, but the weld energy is maintained at its maximum value until immediately before that point. Hereinafter, to distinguish it from other irradiation methods described below, this irradiation method in which the laser output momentarily drops to zero is also referred to as a "non-decline irradiation method."

[0096] Therefore, in the irradiation method without a downslope, the welding heat input at the start position of one process tends to be significantly smaller than the welding heat input at the end position of the one process.

[0097] Figure 16 This is an illustration of another irradiation method (hereinafter, for the sake of distinction, also referred to as "irradiation method with downhill slope"), which is different from Figure 14 Similarly, this is a diagram showing how the laser output and weld line energy of one process change depending on the irradiation position. Figure 14 Likewise, in Figure 16 , a variation characteristic 150P of the laser output according to the irradiation position and a variation characteristic 150L of the welding energy input according to the irradiation position are schematically shown.

[0098] In addition, regarding the irradiation method with a downhill slope, the same as the irradiation method without a downhill slope, the change speed of the irradiation position, that is, the welding speed, is the same as the irradiation method without a downhill slope. Figure 15 Shown as constant.

[0099] Specifically, if Figure 16 As shown, one process starts at position P10. That is, one pulse oscillation begins at position P10. In this case, at position P10, the laser output rises to a specified value (in this example, 3.8 kW) (see arrow R140). Furthermore, the irradiation position changes linearly at a constant speed from position P10 to position P12. Between position P10 and position P14, the laser output is maintained at a specified value (in this example, 3.8 kW) (see arrow R141). When the irradiation position reaches position P14, the laser output decreases in stages from the specified value (in this example, 3.8 kW) to 0 (see arrow R143). Specifically, when the irradiation position reaches position P14, the laser output decreases by one level. When the irradiation position reaches position P12, the laser output decreases by another level. When the irradiation position reaches position P15, the laser output decreases to 0. Furthermore, even when the irradiation position reaches position P15, the irradiation position changes until it moves to position P16, which is further separated by a distance Δ1. During this period, a small amount of welding line energy is generated due to the residual laser output (refer to Figure 16 The distance Δ1 may be the same as that in the above-described irradiation method without a downhill slope, or may be shorter than that in the above-described irradiation method without a downhill slope. Furthermore, in a modified example, the change in irradiation position (change at a constant speed) may be terminated when the irradiation position reaches position P16.

[0100] According to this irradiation method (irradiation method with a downhill slope), the laser output rises to the specified value (in this example, 3.8kW) at position P10, but the welding heat input does not increase to the maximum value immediately until the actual laser output reaches the specified value. Figure 16 As shown, the weld energy gradually increases from position P10 to position P11. The characteristics up to this point are the same as those in the irradiation method without a downhill slope described above. Furthermore, while the laser output decreases at position P14, the weld energy is maintained at its maximum value until immediately before that point. After passing position P14, the laser output gradually decreases to reach zero at position P15, resulting in a more gradual decrease in weld energy compared to the irradiation method without a downhill slope described above.

[0101] In addition, Figure 16In the example shown, the laser output decreases from a specified value to 0 via two intermediate values, but the number of intermediate values ​​may be one or more than three. In addition, the value of each intermediate value itself is also arbitrary, and each intermediate value may be set so that the laser output decreases in stages from the specified value at a constant decrease rate, or may be set so that the laser output decreases in stages from the specified value at a variable decrease rate. In addition, the positions P14 and P12 where the laser output decreases in stages, and the position P15 where the laser output is 0 are arbitrary and can be adapted to obtain the desired characteristics (the variation characteristics 150L of the welding line energy corresponding to the irradiation position). For example, if possible, Figure 16 The position P14 shown (the position where the downslope starts) may also coincide with a position 1.45 mm from the position P10 (a position corresponding to the position P12 in the figure).

[0102] As described above, in this embodiment, two or more green laser irradiation processes are performed on a single weld target area. In this case, laser irradiation can be performed using the aforementioned non-decline irradiation method for all processes on a single weld target area, or using the aforementioned irradiation method with a decline for all processes. Alternatively, the aforementioned non-decline irradiation method and the aforementioned irradiation method with a decline can be combined, with the irradiation method varying for each process on a single weld target area.

[0103] Furthermore, the welding direction (the direction of change of the irradiation position) of each of the two or more processes for one welding target portion may be the same, or the welding direction may be different from that of some other processes.

[0104] Below, refer to Figure 17 and Figure 18 Regarding the case where two processes of laser irradiation are performed on one welding target portion, an example of a combination of the two process irradiation methods will be described.

[0105] Figure 17 This is an explanatory diagram of the case where welding is achieved by two processes with the same welding direction (direction of change of irradiation position). The upper side schematically shows the change characteristics of laser output according to the irradiation position, and the lower side schematically shows the change characteristics of welding line energy according to the irradiation position. The change characteristics of welding line energy according to the irradiation position are shown separately for each process. Figure 14 and Figure 16 The area W1 is related to the heat input of the first process, and the area W2 is related to the heat input of the second process. Figure 17In FIG. 1 , arrows R171 and R172 are used to represent the welding direction, corresponding to the change characteristics of the welding line energy corresponding to the irradiation position. Arrow R171 is the welding direction of the first process, and arrow R172 is the welding direction of the second process. The meanings of arrows R140, R141, and R142 are as follows: Figure 14 As described in . Figure 17 In the description, the X direction, and the X1 side (an example of the first side) and the X2 side (an example of the second side) along the X direction (an example of the first direction) are defined.

[0106] exist Figure 17 In the example shown, both the first and second steps utilize the aforementioned non-downhill irradiation method. Furthermore, as indicated by arrows R171 and R172, the welding direction (the direction in which the irradiation position changes) is the same for both steps, with the irradiation position changing from the X1 side to the X2 side along the X direction.

[0107] exist Figure 17 In the example shown, the first process is achieved by irradiating a first area D11 with a single pulse of laser beam 110, and the second process is achieved by irradiating a second area D12 with the next pulse of laser beam 110. The first and second process welds cooperate to cover the entire circumferential area D1 of the weld target portion 90.

[0108] In addition, if Figure 17 As shown, the first range D11 and the second range D12 include different parts. Specifically, the first range D11 and the second range D12 are set in a continuous manner without overlapping in the X direction. That is, the position where the second process starts (corresponding to Figure 14 The position P10) is different from the position where the first process actually ends (corresponding to Figure 14 The position of P12 is consistent.

[0109] However, in a modified example, the first range D11 and the second range D12 may also include overlapping portions. For example, the position where the second process is started (corresponding to Figure 14 The position P10) can also be relative to the position where the first process actually ends (corresponding to Figure 14The position P12 is offset to the X1 side. In this case, although the end of the downstream side (X2 side) of the first range D11 in the welding direction overlaps with the end of the upstream side (X1 side) of the welding direction within the second range D12, the other part does not overlap with the second range D12. In addition, although the end of the upstream side (X1 side) of the welding direction of the second range D12 overlaps with the end of the downstream side (X2 side) of the welding direction within the first range D11, the other part does not overlap with the first range D11. In this case, the position where the second process starts (corresponding to Figure 14 The position P10 is preferably set so that the laser output in the second process is maintained within the range of the prescribed value (corresponding to Figure 14 The range from position P11 to position P12) is maintained at a predetermined value relative to the laser output in the first process (corresponding to the range from position P11 to position P12). Figure 14 There is no significant overlap in the X direction between the positions P11 and P12. This effectively increases the range D1 of the circumferential direction of the welding target portion 90 that can be covered by the two processes (i.e., the range obtained by combining the first and second ranges).

[0110] Alternatively, the position at which the second process starts can be slightly offset toward the X2 side relative to the position at which the first process actually ends. In this case, the range of the circumferential range D1 of the weld target portion 90 that can be covered by the two processes (i.e., the range obtained by combining the first and second ranges) can be maximized. However, in this case, the position at which the second process starts is set so that the welded portion achieved by the first process and the welded portion achieved by the second process are not separated in the X direction (i.e., so that the seam is properly welded).

[0111] In addition, Figure 17 In the example shown, both the first process and the second process are the above-mentioned irradiation method without a downhill slope, but either or both of them may be the above-mentioned irradiation method with a downhill slope.

[0112] Figure 18 This is an explanatory diagram of welding achieved through two processes with different welding directions (directions of change in irradiation position). The upper side schematically shows the variation characteristics of laser output according to the irradiation position, and the lower side schematically shows the variation characteristics of welding line energy according to the irradiation position. The variation characteristics of welding line energy according to the irradiation position are shown separately for each process, and Figure 14 and Figure 16 The area W1 is related to the heat input of the first process, and the area W2 is related to the heat input of the second process. Figure 17 In addition, the meanings of arrows R140, R141 and R142 are as follows: Figure 14 As explained in .

[0113] exist Figure 18 In the example shown, Figure 17 Similarly, in the example shown, the first process is achieved by irradiating a first range D11 with a single pulse of laser beam 110, and the second process is achieved by irradiating a second range D12 with the next pulse of laser beam 110. The welding process based on the first process and the welding process based on the second process cooperate to cover the entire circumferential range D1 of the welding target portion 90.

[0114] In addition, Figure 18 In the example shown, Figure 17 In the example shown, both the first process and the second process are the above-mentioned irradiation method without downslope.

[0115] However, in Figure 18 In the example shown, relative to Figure 17 In the example shown, the welding direction (the direction of change in irradiation position) differs between the first and second steps. Specifically, in the first step, the irradiation position of laser beam 110 within first range D11 changes linearly along the X-direction from the X1 side to the X2 side, while in the second step, the irradiation position of laser beam 110 within second range D12 changes linearly along the X-direction from the X2 side to the X1 side. In other words, in both the first and second steps, irradiation begins from the outside, toward the center of range D1 in the circumferential direction of the weld target part 90.

[0116] In addition, Figure 18 In the example shown, Figure 17 The example shown is similar, as Figure 18 As shown, the first range D11 and the second range D12 include different parts. Specifically, the first range D11 and the second range D12 are set in a continuous manner without overlapping in the X direction. That is, the position where the second process actually ends (corresponding to Figure 14 The position P12) is different from the position where the first process actually ends (corresponding to Figure 14 The position of P12 is consistent.

[0117] However, in a modified example, the first range D11 and the second range D12 may also include overlapping portions. That is, the position where the second process actually ends (corresponding to Figure 14 The position P12) can also be relative to the position where the first process actually ends (corresponding to Figure 14 The position P12 is slightly offset to the X1 side, and can also be slightly offset to the X2 side.

[0118] Here, in Figure 18In the example shown, at both ends (ends on the X1 side and the X2 side) within the circumferential range D1 of the welding target portion 90, the actual laser output is smaller than the specified value. Figure 17 In the example shown, in contrast, the actual laser output is smaller than the specified value only at the end portion on the X1 side within the circumferential range D1 of the welding target portion 90. More specifically, Figure 18 In the example shown, the weld heat input gradually increases as it approaches the X2 side at the X1-side end within the circumferential range D1 of the weld target portion 90, and the weld heat input gradually increases as it approaches the X1 side at the X2-side end. This characteristic is suitable for a structure where the weld depth dimension of the weld target (individual) decreases at both ends of the weld target portion 90 in the X direction. This is because if the weld heat input is relatively high at a portion of the weld target (individual) where the weld depth dimension is insufficient, the weld quality may be degraded due to keyhole penetration, for example.

[0119] In this regard, in this embodiment, Figure 7 As shown, the two tip ends 40 forming the weld target portion 90 have a tapered shape (with the axially outer end surfaces 42 curved). Therefore, with respect to the weld depth dimension of the overlapping range of the abutting tip ends 40 (i.e., the dimension along the irradiation direction of the laser beam 110 within the overlapping range when viewed radially), the dimension L1 at both ends of the weld target portion 90 in the X direction is significantly smaller than the dimension L0 at the center of the weld target portion 90 in the X direction. Consequently, the dimension of the overlapping range of the abutting tip ends 40, as measured in the irradiation direction of the laser beam 110, is smaller on the X1 side within the first range D11 than on the X2 side within the first range D11, and smaller on the X2 side within the second range D12 than on the X1 side within the second range D12.

[0120] Therefore, according to Figure 18 In the example shown, a high-quality weld can be formed on the welding object part 90 in the front end portion 40 having a curved axial outer end face 42 by two processes in which the welding direction (the direction of change of the irradiation position) is different and the irradiation is started from the outside toward the center of the circumferential range D1 of the welding object part 90.

[0121] In addition, Figure 18 In the example shown, both the first process and the second process are the above-mentioned irradiation method without a downhill slope, but either or both of them may be the above-mentioned irradiation method with a downhill slope as described later.

[0122] In addition, Figure 18 The example shown (about Figure 17In the example shown in FIG. 1 , the entire circumferential range D1 of the welding target portion 90 is covered by two processes, but it may be covered by three or more processes.

[0123] However, welding is usually performed in an environment where a shielding gas (such as nitrogen) is not used or in an environment where a shielding gas is used. In an environment where a shielding gas is not used, the solidified portion of the portion of the front end portion 40 that is melted by the laser beam 110 combines with the air component and produces volume expansion. That is, oxygen in the atmosphere dissolves in the molten pool, and volume expansion occurs due to oxides and the like during solidification. If such volume expansion occurs, the size of the motor 1 tends to increase accordingly (when performing resin molding described later, the thickness of the resin portion tends to increase and the size of the motor 1 tends to increase). In addition, such volume expansion has the tendency to be easily located at the position where the irradiation actually ends during the process of utilizing the above-mentioned no-downslope irradiation method (compared to the position where the irradiation actually ends). Figure 14 This is considered to be because the laser output drops steeply at the position where the irradiation actually ends, and the coagulation rate becomes faster (thus making it easier to trap oxygen).

[0124] Figure 19 This is an illustration of the protrusions caused by volume expansion. Figure 18 The diagram shows a cross section of a welded portion in which welding is achieved by two processes. Figure 19 In the figure, one of the two abutting front end portions 40 is shown, and the area 1900 surrounded by the dotted line is the welding portion (indicating the welding depth). Figure 19 , the first range D11 of the first process and the second range D12 of the second process are shown together.

[0125] according to Figure 19 It is known that through Figure 18 When welding is achieved through the two steps shown, unevenness is generated in the weld target portion 90 on the axially outer end surface 42. In particular, relatively large protrusions 1902 (protrusions protruding axially outward) are generated at the location where irradiation in the second step, using the aforementioned no-dip irradiation method, effectively ends. Furthermore, pores 1904 are generated at the boundary (joint) between the first and second steps.

[0126] Therefore, in this embodiment, it is preferred to use the above-mentioned downhill irradiation method to reduce the protrusions and pores. Figures 20 to 23 Provide explanation.

[0127] Figure 20 This is an explanatory diagram of a welding method capable of reducing protrusions and pores, schematically showing the changing characteristics of laser output according to the irradiation position for each of the two processes. Figure 20The view (described later) Figure 22 and Figure 23 Same as above Figure 17 Same. Figure 20 In the figure, arrows R140, R141 and R143 mean as follows: Figure 16 In addition, the arrow R143 is labeled (1) for the first process and (2) for the second process.

[0128] exist Figure 20 In the example shown, Figure 18 Similarly, in the example shown, the first process is achieved by irradiating first range D11 with one pulse of laser beam 110 (an example of the first pulse), and the second process is achieved by irradiating second range D12 with the next pulse of laser beam 110 (an example of the second pulse). Welding based on the first process and welding based on the second process cooperate to cover the entire circumferential range D1 of the welding target portion 90.

[0129] In addition, Figure 20 In the example shown, Figure 18 In the example shown, the welding direction (direction of change of irradiation position) is different between the first and second steps. That is, irradiation is started from the outside toward the center of the circumferential range D1 of the welding target part 90 in both the first and second steps.

[0130] However, in Figure 20 In the example shown, Figure 18 Unlike the examples shown, the first process and the second process are both the above-mentioned irradiation methods with a downhill slope.

[0131] Specifically, in the first process, at position P20, which is the end point on the X1 side of the first range D11, the laser output rises to a predetermined value (in this example, 3.8 kW as an example) (see arrow R140), and maintains the predetermined value (in this example, 3.8 kW as an example) (see arrow R141) until position P21, which is located on the X2 side at a predetermined distance d1 (not shown) relative to position P20. Furthermore, at position P21, the laser output drops to a first intermediate value (in this example, 2.0 kW as an example), and then drops to 0 at position P22, which is located on the X2 side at a predetermined distance d2 (not shown) relative to position P21 (see arrow R143 (1)).

[0132] In the second process, the laser output rises to a predetermined value (in this example, 3.8 kW as an example) at position P30, which is the end point on the X2 side of the second range D12 (see arrow R140), and maintains the predetermined value (in this example, 3.8 kW as an example) until it reaches position P31, which is located at a predetermined distance d3 (not shown) on the X1 side relative to position P30 (see arrow R141). Furthermore, at position P31, the laser output drops to a first intermediate value (in this example, 2.0 kW as an example), then drops to a second intermediate value (in this example, 1.0 kW as an example) at position P32, which is located at a predetermined distance d4 (not shown) on the X1 side relative to position P31, and then drops to 0 at position P33, which is located at a predetermined distance d5 (not shown) on the X1 side relative to position P32 (see arrow R143 (2)).

[0133] In addition, Figure 20 In the example shown, the position P21 at which the laser output of the first process begins to decrease in stages coincides with the position P31 at which the laser output of the second process begins to decrease in stages, but they may be separated in the X direction. For example, the position P31 may be offset toward the X1 side relative to the position P21, or toward the X2 side relative to the position P21.

[0134] As Figure 19 The contrast, Figure 21 Yes means through Figure 20 The diagram shows a cross section of a welded portion where welding is achieved by the two processes shown. Figure 21 In the figure, one of the two abutting front end portions 40 is shown, and the area 2000 surrounded by the dotted line is the welding portion. Figure 21 , the first range D11 of the first process and the second range D12 of the second process are shown together.

[0135] according to Figure 21 It is known that through Figure 20 When the welding is completed by the two processes shown, a relatively smooth curved surface is also maintained in the welding target portion 90 in the axial outer end surface 42. Figure 20 The two processes shown achieve a reduction in welding Figure 19 The unevenness shown in FIG. 1 is not particularly large, and no protrusion 1902 is generated (see FIG. Figure 19 This is considered to be because the irradiation from the vicinity of position P31 to position P33 in the second process will reduce the protrusions ( Figure 191902 shown in FIG. This is because the second process of irradiation from near position P31 to position P33 remelts the protrusion that solidified in the first process, thereby flattening the protrusion. Furthermore, in this embodiment, since green laser light is used as described above, the absorption rate is high, and even with relatively low laser outputs, such as the first intermediate value, the protrusion can be melted. This is in contrast to infrared laser light, which is likely unable to melt the protrusion even with such relatively low laser outputs.

[0136] In addition, according to Figure 21 It is known that through Figure 20 The two processes shown achieve welding without producing Figure 19 The pores 1904 are shown. This is considered to be because the end region on the X2 side of the first region D11 (the region near the end position of the first region) is melted again by irradiation from the vicinity of position P31 to position P33 in the second process.

[0137] Thus, according to Figure 20 In the example shown, by including the second range D12 of the second process near the end position of irradiation in the first range D11 of the first process, the protrusion caused by the solidified portion that tends to form near the end position of irradiation in the first range D11 of the first process can be melted, resulting in a reduction in the height of the protrusion. This reduces the axial size of the motor 1.

[0138] In addition, according to Figure 20 In the example shown, the laser output is gradually reduced in the portion of the second range D12 of the second process that overlaps with the end position of the irradiation in the first range D11 of the first process (the portion of the second process from near position P31 to position P33). This allows the aforementioned protrusions to be melted in a manner that is less likely to cause bubbles, etc., using an intermediate value (such as the first intermediate value) lower than the specified value (in this example, 3.8 kW). This reduces the occurrence of protrusions caused by the second process itself, even in an environment without the use of a shielding gas, and can smoothly smooth these protrusions.

[0139] In addition, Figure 20 In the example shown, the first process is the aforementioned irradiation method with a downslope, but the aforementioned irradiation method without a downslope can also be used. In addition, the first process is an irradiation method with a downslope using one intermediate value, but the irradiation method with a downslope using two or more intermediate values ​​can also be used.

[0140] In addition, Figure 20In the example shown, the second process is an irradiation method with a downhill slope using two intermediate values, but it may also be an irradiation method with a downhill slope using one or more than three intermediate values.

[0141] In addition, Figure 20 In the example shown, the second process is the above-mentioned irradiation method with a downhill slope, but it can also be the above-mentioned irradiation method without a downhill slope. In this case, Figure 22 As shown, Figure 17 Similarly to the example shown, the welding directions of the first and second processes (see arrows R171 and R172) can be made the same, and the position where the second process starts (corresponding to Figure 14 The position P10) is relative to the position where the first process actually ends (corresponding to Figure 14 The position P12 of the second process is offset to the X1 side. In this case, the portion of the second range D12 of the second process that overlaps with the end position of the irradiation in the first range D11 of the first process is the stage before the actual laser output reaches the specified value (in this case, 3.8kW as an example). Thus, the laser output before reaching the specified value (in this case, 3.8kW as an example) can melt the above-mentioned protrusion in a manner that is less likely to generate bubbles. Thus, Figure 20 In the example shown, the above-mentioned protrusions can also be smoothly leveled.

[0142] In addition, Figure 22 In the illustrated modification, the first and second steps are irradiation methods without a downslope, but at least one of the first and second steps may be an irradiation method with a downslope.

[0143] In addition, Figure 20 In the example shown, the entire circumferential range D1 of the welding target portion 90 is covered by two processes, but it is also possible to cover the entire circumferential range D1 of the welding target portion 90 by two processes as described below. Figure 23 As in the example shown, coverage is performed through three or more processes.

[0144] Figure 23 This is an explanatory diagram of another welding method that can reduce protrusions and pores. It schematically shows the changing characteristics of laser output corresponding to the irradiation position for each of the three processes. Furthermore, area W3 is related to the heat input in the third process. Arrow R143 is labeled (1) for the first process, (2) for the second process, and (3) for the third process. Arrow R172 indicates the welding direction for the third process.

[0145] exist Figure 23In the example shown, the welding direction (the direction of change in the irradiation position) is the same in the first and second steps, running from the X1 side toward the X2 side. On the other hand, the welding direction (the direction of change in the irradiation position) is different in the second and third steps. Specifically, the direction in the third step is from the X2 side toward the X1 side.

[0146] exist Figure 23 In the example shown, the first to third processes are all the above-mentioned irradiation methods with a downhill slope. Figure 22 The relationship between the first process and the second process shown is actually the same except that both the first process and the second process are irradiated in a downhill manner. Figure 20 The relationship between the first and second processes shown is practically the same.

[0147] Specifically, in the first process, Figure 23 As shown by the solid line characteristic, at position P40, which is the end point on the X1 side of the first range D11, the laser output rises to a predetermined value (in this example, 3.8 kW as an example) (see arrow R140), and maintains the predetermined value (in this example, 3.8 kW as an example) until position P41 on the X2 side relative to position P40 (see arrow R141). Furthermore, at position P41, the laser output drops to a first intermediate value (in this example, 2.0 kW as an example), and then drops to 0 at position P42 on the X2 side relative to position P41 (see arrow R143 (1)).

[0148] In addition, in the second process, as Figure 23 As shown by the dotted line characteristic, at the end point on the X1 side of the second range D12, that is, position P50, which is closer to the X1 side than position P41, the laser output rises to a predetermined value (in this example, 3.8 kW as an example) (see arrow R140), and maintains the predetermined value (in this example, 3.8 kW as an example) until position P51 on the X2 side relative to position P50 (see arrow R141). Furthermore, at position P51, the laser output drops to a first intermediate value (in this example, 2.0 kW as an example), and then drops to 0 at position P52 on the X2 side relative to position P51 (see arrow R143 (2)).

[0149] In addition, in the third process, if Figure 23As shown by the dot-dash line characteristic, at position P60, which is the end point on the X2 side of the third range D13, the laser output rises to a specified value (in this example, 3.8 kW as an example) (see arrow R140), and maintains the specified value (in this example, 3.8 kW as an example) until position P61 on the X1 side relative to position P60 (see arrow R141). Furthermore, at position P61, the laser output drops to a first intermediate value (in this example, 2.0 kW as an example), then drops to a second intermediate value (in this example, 1.0 kW as an example) at position P62 on the X1 side relative to position P61, and then drops to 0 at position P63 on the X1 side relative to position P62 (see arrow R143 (3)).

[0150] according to Figure 23 The example shown can also be Figure 22 The same principle as in the example shown above is used to melt the protrusions caused by the solidified portion that is likely to be generated near the end position of the irradiation in the first range D11 of the first process through the second process, and Figure 20 Using the same principle as in the example shown, the protrusions caused by the solidified portion that is likely to form near the end position of irradiation within the second range D12 of the second process are melted in the third process. This can reduce the protrusions that may form in the welded portion and reduce the axial size of the motor 1.

[0151] In addition, according to Figure 23 The example shown is similar to the above Figure 18 Similarly, in the example shown, the actual laser output is less than the specified value at both ends (the X1 and X2 ends) within the circumferential range D1 of the weld target portion 90. This characteristic is suitable for a structure in which the weld depth dimension of the weld target (individual) decreases at both ends of the weld target portion 90 in the X direction.

[0152] In this regard, in this embodiment, Figure 7 As shown, the two front end portions 40 forming the welding target portion 90 are in a tapered shape (a shape in which the axially outer end surface 42 is curved). Therefore, the size of the range in which the front end portions 40 abutting against each other overlap and the size in the irradiation direction of the laser beam 110 are smaller on the X1 side within the first range D11 than on the X2 side within the first range D11, and smaller on the X2 side within the third range D13 than on the X1 side within the third range D13. Therefore, according to Figure 23 The example shown is similar to the above Figure 18Similarly to the example shown, by welding in two processes (the first process and the third process) in which the irradiation is performed from the outside toward the center of the circumferential range D1 of the welding object part 90 in two processes with different welding directions (the direction of change of the irradiation position), a high-quality weld can be formed in the welding object part 90 in the front end portion 40 that is curved relative to the axial outer end face 42.

[0153] In addition, Figure 23 In the example shown, position P51, where the laser output of the second process begins to decrease in stages, coincides with position P61, where the laser output of the third process begins to decrease in stages. However, these positions may be separated in the X direction. For example, position P61 may be offset toward X1 relative to position P51, or toward X2 relative to position P51.

[0154] Next, refer to Figure 24A and Figure 24B , further effects of this embodiment are explained by comparison with the comparative example.

[0155] Figure 24A This is an explanatory diagram of a green laser welding method based on a comparative example. Figure 24A In FIG, the horizontal axis represents time and the vertical axis represents laser output, schematically showing a timing waveform of laser output during welding.

[0156] In the comparative example, Figure 24A As shown in the figure, welding is achieved by pulse irradiation of green laser with a laser output of 3.8kW. Figure 24A In the process, the laser oscillator is pulsed oscillated by maintaining the laser output at 3.8 kW for only 2 msec, and after an interval of 38 msec, the laser oscillator is pulsed oscillated again by maintaining the laser output at 3.8 kW for 2 msec.

[0157] In addition, in contrast to this, in this embodiment, as shown in FIG. Figure 13 As described above, the laser oscillator is pulsed at a laser output of 3.8 kW for 10 msec, and after a 100 msec interval, the laser oscillator is pulsed again at a laser output of 3.8 kW for 10 msec.

[0158] Furthermore, in the comparative example, unlike the present embodiment, the irradiation position of the laser beam is fixed for each process. Specifically, in the present embodiment, as described above, the irradiation position of the laser beam 110 changes (moves) linearly at a constant speed during each pulse oscillation, whereas in the comparative example, the irradiation position of the laser beam does not move during each pulse oscillation.

[0159] Figure 24B: is a diagram showing a cross section of a welded portion when welding is achieved by a comparative example. Figure 24B In FIG, one of the two abutting tip portions 40 is shown, and a region 2400 surrounded by a dotted line is a weld portion (indicating weld depth). In the comparative example, 11 irradiation processes are performed on one weld target portion 90.

[0160] according to Figure 24B It can be seen that when welding is performed in 11 steps according to the comparative example, unevenness is generated in the welding target portion 90 in the axially outer end surface 42. Figure 24B It can be seen that when welding was performed in 11 steps in the comparative example, sharp irregularities were generated in the weld bottom 2401. Such irregularities in the weld bottom 2401 are prone to stress concentration caused by the force applied from the jig during welding, resulting in problems such as reduced fatigue strength.

[0161] In this regard, according to this embodiment, as described above Figure 19 As shown, the weld bottom is smooth, which can reduce the disadvantages (such as reduced fatigue strength) that occur in the comparative example. Thus, according to this embodiment, while ensuring the laser output to obtain the required penetration depth relative to the welding target part 90, the irradiation position of the laser beam 110 can be moved linearly at an appropriate movement speed (welding speed). This can achieve high-quality welding while ensuring the weld cross-sectional area required for product function.

[0162] In addition, according to this embodiment, compared with the comparative example, the number of pulse oscillations per welding target portion 90 is reduced, and the overlap range of each process is reduced, which can effectively ensure the welding cross-sectional area required for product function. In other words, the welding time required to ensure the welding cross-sectional area required for product function can be shortened. For example, in the comparative example, Figure 24B As shown, the welding time is about 440msec by 11 pulse oscillations, and in this embodiment, as described above Figure 13 As shown, for example, in the case of using two pulse oscillations, a welding time of approximately 220 msec (time until immediately before the third process) is sufficient.

[0163] Next, refer to Figure 25 The manufacturing process of the stator 21 is summarized. Figure 25 1 is a flowchart schematically showing a manufacturing process of the stator 21 .

[0164] The method for manufacturing the stator 21 includes the steps of first preparing the stator core 22 and preparing the straight coil pieces 52 (the coil pieces 52 before forming) for forming the stator coils 24 ( S12 ).

[0165] Next, the manufacturing method of the stator 21 includes a step (S14) of removing the insulating film 62 from the front end portion 40 (starting and ending ends) of the coil piece 52. The method for removing the insulating film 62 is arbitrary, and for example, the insulating film 62 can be removed mechanically using a cutter, or chemically by etching, etc. Alternatively, the insulating film 62 can be removed thermally using a laser.

[0166] In order to join the coil pieces 52 to each other, it is sufficient to remove at least the insulating film 62 on the surface of the front end portion 40 that is actually joined, and the insulating film 62 on other surfaces (the back surface or the other surface of the front surface, and the side surfaces) may be left.

[0167] Next, the manufacturing method of the stator 21 includes a forming step (S16) of bending and forming the straight coil piece 52 using a mold or the like after the removal step. For example, the coil piece 52 is formed into Figure 6 As shown, the substantially U-shaped structure includes a pair of straight portions 50 and a connecting portion 54 connecting the pair of straight portions 50. In addition, the order of step S16 and step S14 may be reversed.

[0168] Next, the method for manufacturing the stator 21 includes, after the forming step, an installation step (S18) of inserting the coil pieces 52 into the slots 220 of the stator core 22. The insertion step is completed when all the coil pieces 52 have been inserted.

[0169] Next, the manufacturing method of the stator 21 includes a deformation step (S20) in which, after the insertion step, a dedicated jig is used to circumferentially bend the portion of the linear portion 50 that protrudes from each slot 220. This deforms the linear portion 50 into a leg portion 56 extending axially within the slot 220 and a lap portion 58 extending circumferentially at one axial end.

[0170] Next, the manufacturing method of the stator 21 includes a step (S22) of bringing the front end portion 40 of the overlap portion 58 of one coil piece 52 extending toward the first circumferential side (e.g., clockwise) into contact with the front end portion 40 of the overlap portion 58 of another coil piece 52 extending toward the second circumferential side (e.g., counterclockwise) after the deformation step. In this case, for example, a jig (not shown) is used to maintain the plurality of sets of front end portions 40 in contact with each other.

[0171] Next, a joining step (S24) is included in which the multiple groups of tip ends 40 are joined together by sequentially irradiating the multiple welding target locations with the laser beam 110 while the multiple groups of tip ends 40 are in contact with each other. In this embodiment, as described above, each pair of tip ends 40 is joined by welding. The details of the joining step (laser welding) are described above. Welding is performed for each pair of tip ends 40, and the joining step is completed when all the groups of tip ends 40 are welded.

[0172] Next, the manufacturing method of stator 21 includes a finishing step (S26) of performing finishing after the joining step. The finishing step may include, for example, a step of insulating the coil tail ends 220A and 220B formed by assembling coil sheets 52 as described above. The insulation treatment may include molding with resin to seal the entire coil tail ends 220A and 220B, or applying varnish or the like.

[0173] Next, refer to Figure 26 The influence of welding heat by green laser is described.

[0174] Figure 26 This is a graph showing the measurement results of the temperature history when welding using a green laser. Figure 26 In the figure, the horizontal axis is time and the vertical axis is temperature (in Figure 26 ), marked as "Temperature", shows the temperature history when welding using a green laser. Figure 26 The temperature history shown is based on the results of measuring the temperature near the welding target portion 90 of the axially outer end surface 42 using a thermocouple. Figure 26 In FIG, time t1 indicates the irradiation start time.

[0175] However, since welding generally generates heat, the insulating coating 62 of the coil piece 52 may be damaged (carbonized) by the heat generated by welding. Since it is difficult to apply an insulating material (e.g., resin, varnish, etc.) to the damaged (carbonized) insulating coating 62, the insulation performance of the stator coil 24 after welding may be degraded.

[0176] In this regard, according to this embodiment, Figure 26 As shown in FIG. 1 , the maximum temperature during welding remains at approximately 99°C. This is because the heat input is significantly reduced as described above by using a green laser. In addition, approximately 99°C is significantly lower than 180°C, which is the temperature at which enamel is carbonized. Thus, according to this embodiment, by using a green laser, it is possible to prevent the insulating film 62 of the coil sheet 52 from being damaged. Therefore, according to this embodiment, in the step (S14) of removing the insulating film 62 (see FIG. Figure 25), it is possible to remove only the insulating film 62 on the surface to be joined in the front end portion 40, while leaving the insulating film 62 on the other surfaces.

[0177] Next, refer to Figure 27 , explaining the foreign matter resistance of green laser welding.

[0178] Figure 27 This is an illustration of a test for verifying foreign matter resistance. Figure 27 As shown, the overlapping area of ​​the abutting tip portions 40 was divided into six sections. In any of the six sections, A1 to A6, a small piece of the enamel film forming the insulating film 62 was sandwiched (radially sandwiched between the tip portions 40) and green laser welding was performed. Furthermore, the sandwiching area and size of the small piece were varied, and green laser welding was performed to evaluate foreign matter resistance. For example, in areas A1 and A3, even when a small piece measuring 0.7 mm x 0.7 mm was sandwiched, no defects such as holes were generated on the weld bead surface. Similarly, in area A2, even when a small piece measuring 1.0 mm x 1.0 mm was sandwiched, no defects such as holes were generated on the weld bead surface. The same was true for the other sections. In contrast, when infrared laser welding was performed, holes were generated on the weld bead surface when a small piece measuring 0.2 mm x 0.2 mm was sandwiched, confirming the high foreign matter resistance of green laser welding.

[0179] Although the embodiments have been described in detail above, the present invention is not limited to the specific embodiments and various modifications and changes can be made within the scope of the claims. In addition, all or multiple components of the above-described embodiments can be combined.

[0180] For example, in the above embodiment, the stator coil 24 is formed of a plurality of segment coil pieces 52, but the present invention is not limited thereto. For example, the stator coil 24 may be a concentrated winding coil wound (formed) multiple times around the teeth 22B.

[0181] Description of Reference Numerals

[0182] 1 ...motor (rotating electric machine), 24 ...stator coil, 52 ...coil piece, 40 ...front end portion, 401 ...contact surface, 110 ...laser beam, 90 ...welding target portion.

Claims

1. A method for manufacturing a stator for a rotating electrical machine, characterized in that: include: a step of bringing front end portions of one coil piece and another coil piece, which form a stator coil of a rotating electrical machine, into contact with each other; and The welding process includes irradiating a laser beam having a wavelength of 0.6 μm or less to the welding target portion of the abutting front end portion. In the welding process, the laser beam is generated in a manner having a laser output of 3.0 kW or more in each pulse oscillation of the laser oscillator, and the pulse oscillation is performed in a manner of accumulating continuous energy for pulse oscillation. During at least a portion of one pulse oscillation, the laser beam moves so that the irradiation position changes linearly parallel to the abutting surface of the distal end portion.

2. The method for manufacturing a stator for a rotating electrical machine according to claim 1, wherein: In the welding process, the laser beam is irradiated to one of the welding target parts by two or more pulse oscillations. The one pulse oscillation constitutes the two or more pulse oscillations.

3. The method for manufacturing a stator for a rotating electrical machine according to claim 1 or 2, wherein: The pulse oscillation is performed so that energy accumulated in a period preceding the oscillation period is concentrated in the oscillation period.

4. The method for manufacturing a stator for a rotating electrical machine according to claim 2, wherein: The two or more pulse oscillations include: a first pulse oscillation for irradiating a first range of the welding target portion with the laser beam; and a second pulse oscillation for irradiating the second range of the welding target portion with the laser beam; The first range partially overlaps with the second range, A moving direction of the irradiation position of the laser beam in the first pulse oscillation and a moving direction of the irradiation position of the laser beam in the second pulse oscillation are opposite to each other.

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