Method for manufacturing stator for rotating electrical machine and apparatus for manufacturing stator for rotating electrical machine

Abstract

Disclosed is a method for manufacturing a stator for a rotating electrical machine, which comprises: a step for bringing the tip of one coil piece and the tip of the other coil piece, which form a stator coil for the rotating electrical machine, into contact with each other; and an irradiation step for irradiating a laser beam having a wavelength of 0.6 [mu] m or less toward one side of the exposed side of the contact surfaces of the tip sections, the irradiation step including annularly scanning while moving the laser beam in a traveling direction including a direction component in which the one side extends. The amount of movement in the direction of travel of each circular scan is equal to or less than the beam diameter of the laser beam.

Description

Technical Field

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

[0002] There is known a technique in which, while the tip portions of one coil piece and another coil piece are in contact with each other, a laser beam is moved in a traveling direction including a direction component parallel to the contact surface of the tip portions and the laser beam is scanned in a ring shape, thereby achieving welding between the coil pieces.

[0003] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2021-44883

[0004] However, in the conventional technique as described above, due to differences in the relationship between the beam diameter of the laser beam and the amount of movement in the traveling direction in each circular scan (hereinafter, also simply referred to as "ring pitch"), it is difficult to efficiently achieve high-quality welding. For example, if the ring pitch is made too large with respect to the beam diameter of the laser beam, there is a concern that the molten pool cannot be properly maintained, resulting in a decrease in welding quality. In addition, if the ring pitch is made too small with respect to the beam diameter of the laser beam, there is a concern that the welding time per unit length and the heat input amount of the welding target portion become too large. Summary of the Invention

[0005] Therefore, in one aspect, an object of the present disclosure is to efficiently achieve high-quality welding between coil pieces of a stator for a rotating electrical machine.

[0006] In one aspect, there is provided a method for manufacturing a stator for a rotating electrical machine,

[0007] The method for manufacturing a stator for a rotating electrical machine includes:

[0008] a step of bringing the end of one coil piece for forming a stator coil of a rotating electrical machine into contact with the tip portion of another coil piece; and

[0009] an irradiation step of irradiating a laser beam having a wavelength of 0.6 μm or less toward one edge on the exposed side of the contact surface of the tip portions,

[0010] The irradiation step includes scanning the laser beam in a ring shape while moving the laser beam in a traveling direction including a direction component in which the one edge extends,

[0011] The amount of movement in the traveling direction in each circular scan is equal to or less than the beam diameter of the laser beam.

[0012] According to the present disclosure, high-quality welding between coil pieces of a stator for a rotating electrical machine can be efficiently achieved. Brief Description of the Drawings

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

[0014] Figure 2 is a top view of a single state of the stator core.

[0015] Figure 3 is a view schematically showing a pair of coil pieces assembled to the stator core.

[0016] Figure 4 is a simplified front view of a coil piece.

[0017] Figure 5 is a view showing the top end portions where the coil pieces are joined together and the vicinity thereof.

[0018] Figure 6 is a view schematically showing the welding target portion as observed from the irradiation side.

[0019] Figure 7 is a cross-sectional view taken along line A-A of the welding target portion Figure 5 thereof.

[0020] Figure 8 is a graph showing the relationship between the laser wavelength and the laser absorption rate for various materials.

[0021] Figure 9 is an explanatory diagram of the change pattern of the absorption rate during welding.

[0022] Figure 10A is a schematic diagram of a keyhole and the like in the case of using green laser.

[0023] Figure 10B is a schematic diagram of a keyhole and the like in the case of using infrared laser.

[0024] Figure 11 is an explanatory diagram of the irradiation mode of the green laser in the manufacturing method of this embodiment.

[0025] Figure 11A is an explanatory diagram of the scanning of the laser beam and an explanatory diagram of the emission center of the laser beam.

[0026] Figure 11B is an explanatory diagram of the scanning of the laser beam and an explanatory diagram of the movement mode of the laser beam.

[0027] Figure 12 is an explanatory diagram of the irradiation mode in the case of the infrared laser of the comparative example.

[0028] Figure 13It is a cross-sectional view along the welding direction on the abutting surface of the present embodiment.

[0029] Figure 14 It is a cross-sectional view along the welding direction on the abutting surface of the comparative example.

[0030] Figure 15 It is an image of the lower end portion of the joint surface of the present embodiment.

[0031] Figure 16 It is an image of the lower end portion of the joint surface of the comparative example.

[0032] Figure 17 It is an explanatory diagram of the robustness with respect to the misalignment of the irradiation position in the radial direction.

[0033] Figure 18 It is a table diagram showing a plurality of conditions (conditions 1 to 3) of the implemented test.

[0034] Figure 19 It is a graph showing the relationship between the swing diameter and the sputtering number according to the conditions.

[0035] Figure 20 It is a graph showing the relationship between the swing diameter and the joint area and the welding depth.

[0036] Figure 21 It is a graph with the horizontal axis being the Y-direction position along the Y direction and the vertical axis being the welding speed, showing the preferred welding speed (the change profile of the welding speed corresponding to the Y-direction position) at each Y-direction position.

[0037] Figure 22 It is an explanatory diagram of the swing pitch in the section from the Y-direction position P1 to the Y-direction position P2.

[0038] Figure 23 It is an explanatory diagram of the swing pitch in the section from the Y-direction position P3 to the Y-direction position P5.

[0039] Figure 24A It is an explanatory diagram of the first comparative example.

[0040] Figure 24B It is an explanatory diagram of the problem points of the first comparative example.

[0041] Figure 25A It is an explanatory diagram of the second comparative example.

[0042] Figure 25B It is an explanatory diagram of the problem points of the second comparative example.

[0043] Figure 26 It is a flowchart schematically showing the process of the manufacturing method of the stator of the motor.

[0044] Figure 27 This is a system structure diagram of a manufacturing device. Detailed implementation manners

[0045] Hereinafter, with reference to the attached drawings, each embodiment will be described in detail. In addition, the dimensional ratios of the drawings are only an example and are not limited thereto. Also, for ease of explanation, there are cases where the shapes in the drawings are partially exaggerated.

[0046] Figure 1 This is a cross-sectional view schematically showing the cross-sectional structure of a motor 1 (an example of a rotating electric machine) of one embodiment.

[0047] In Figure 1 the rotational axis 12 of the motor 1 is illustrated. In the following description, the axial direction refers to the direction in which the rotational axis (rotation center) 12 of the motor 1 extends, and the radial direction refers to the radial direction centered on the rotational axis 12. Therefore, the radially outer side refers to the side away from the rotational axis 12, and the radially inner side refers to the side toward the rotational axis 12. In addition, the circumferential direction corresponds to the rotational direction around the rotational axis 12.

[0048] The motor 1 can be, for example, a motor for vehicle drive used in a hybrid vehicle or an electric vehicle. However, the motor 1 can also be used for any other purpose.

[0049] The motor 1 is an inner rotor type, and the stator 21 is disposed around the radially outer side of the rotor 30. The radially outer side of the stator 21 is fixed to the motor housing 10.

[0050] The rotor 30 is disposed on the radially inner side of the stator 21. The rotor 30 includes a rotor core 32 and a rotor shaft 34. The rotor core 32 is fixed to the radially outer side of the rotor shaft 34 and rotates integrally with the rotor shaft 34. The rotor shaft 34 is supported by the motor housing 10 via bearings 14a and 14b so as to be rotatable. In addition, the rotor shaft 34 defines the rotational axis 12 of the motor 1.

[0051] The rotor core 32 is formed, for example, by laminated steel sheets of an annular magnetic material. Permanent magnets 321 are inserted into the magnet holes 320 of the rotor core 32. The number, arrangement manner, etc. of the permanent magnets 321 are arbitrary. In a modified example, the rotor core 32 can also be formed by a compacted powder body obtained by compressing magnetic powder and solidifying it.

[0052] End plates 35A and 35B are mounted on both axial sides of the rotor core 32. In addition to the supporting function of supporting the rotor core 32, the end plates 35A and 35B can also have an unbalance adjustment function of the rotor 30 (a function of eliminating unbalance by means such as cutting).

[0053] As Figure 1As shown, the rotor shaft 34 has a hollow portion 34A. The hollow portion 34A extends throughout 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, as shown by the arrow R1 in Figure 1 , oil is supplied from one axial end side, and the oil flows along the inner surface of the rotor shaft 34 in the radial direction, whereby the rotor core 32 can be cooled from the inner side in the radial direction. Alternatively, the oil flowing along the inner surface of the rotor shaft 34 in the radial direction may pass through the oil holes 341 and 342 formed at both ends of the rotor shaft 34 and be ejected outward in the radial direction (arrows R5 and R6) to provide cooling to the coil ends 220A and 220B.

[0054] In addition, in Figure 1 , the motor 1 with 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 that of the hollow portion 34A. Also, in 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 toward the coil ends 220A and 220B from the outer side in the radial direction.

[0055] In addition, although in Figure 1 , the motor 1 is an inner rotor type in which the rotor 30 is disposed inside the stator 21, this application can also be applied to other types of motors. For example, this application can also be applied to an outer rotor type motor in which the rotor 30 is concentrically disposed outside the stator 21, a double rotor type motor in which the rotor 30 is disposed on both the outer side and the inner side of the stator 21, and the like.

[0056] Next, with reference to Figure 2 and the subsequent drawings, the structure related to the stator 21 will be described in detail.

[0057] Figure 2 is a top view of the stator core 22 in a single state. Figure 3 is a diagram schematically showing a pair of coil pieces 52 assembled to the stator core 22. In Figure 3 , the relationship between the pair of coil pieces 52 and the slots 220 is shown in a state where the inner side in the radial direction of the stator core 22 is unfolded. Also, in Figure 3 , the stator core 22 is shown by a dashed line, and part of the slots 220 is omitted from the illustration.

[0058] The stator 21 includes a stator core 22 and a stator coil 24 (refer to Figure 1 ).

[0059] The stator core 22 is formed of, for example, laminated steel sheets of a ring-shaped magnetic material. However, in a modified example, the stator core 22 may also be formed of a compacted body obtained by compressing magnetic powder and solidifying it. In addition, the stator core 22 may be formed of segmented cores divided in the circumferential direction, or may be in a form not divided in the circumferential direction. A plurality of slots 220 for winding the stator coil 24 are formed on the radially inner side of the stator core 22. Specifically, as Figure 2 shown, the stator core 22 includes a ring-shaped back yoke 22A and a plurality of teeth 22B extending radially inward from the back yoke 22A, and slots 220 are formed between the plurality of teeth 22B in the circumferential direction. Although the number of slots 220 is arbitrary, in this embodiment, as an example, the number of slots 220 is 48.

[0060] The stator coil 24 includes a U-phase coil, a V-phase coil, and a W-phase coil (hereinafter, referred to as "phase coils" without distinguishing U, V, and W). The base ends of the respective phase coils are connected to input terminals (not shown), and the ends of the respective phase coils are connected to the ends of other phase coils to form the neutral point of the motor 1. That is, the stator coil 24 is star-connected. However, the wiring method of the stator coil 24 may be appropriately changed according to required motor characteristics and the like. For example, the stator coil 24 may be delta-connected instead of star-connected.

[0061] Each phase coil is constituted by joining a plurality of coil pieces 52. Figure 4 is a simplified front view of one coil piece 52. The coil piece 52 is in the form of a segmented coil divided in units (for example, units inserted into two slots 220) that are easy to assemble the phase coils. The coil piece 52 is formed by covering a linear conductor (flat wire) 60 having a rectangular cross section with an insulating film 62. In this embodiment, as an example, the linear conductor 60 is formed of copper. However, in a modified example, the linear conductor 60 may also be formed of other conductor materials such as iron.

[0062] Before being assembled to the stator core 22, the coil piece 52 can 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. 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 Figure 3 ). Thus, as Figure 3 shown, the connecting portion 54 extends in the circumferential direction on the other axial end side of the stator core 22 so as to straddle a plurality of teeth 22B (and a plurality of slots 220 accompanying the plurality of teeth 22B). The number of slots 220 straddled by the connecting portion 54 is arbitrary, but in Figure 3 it is three. In addition, after the straight portion 50 is inserted into the slot 220, as Figure 4As shown by the double-dot dash line, it buckles circumferentially midway. Thus, the straight portion 50 becomes a leg portion 56 extending axially within the slot 220 and a lapping portion 58 extending circumferentially on the axial one end side of the stator core 22.

[0063] In addition, in Figure 4 the pair of straight portions 50 buckle in directions separating from each other, but it is not limited to this. For example, the pair of straight portions 50 may also buckle in directions approaching each other. Additionally, the stator coil 24 sometimes further has a neutral point coil piece or the like for connecting the ends of the phase coils of the three phases to form a neutral point.

[0064] Figure 4 As shown, a plurality of leg portions 56 of the coil piece 52 are arranged radially and inserted into one slot 220. Therefore, a plurality of lapping portions 58 extending circumferentially are arranged radially on the axial one end side of the stator core 22. As Figure 3 shown, the lapping portion 58 of one coil piece 52 extending from one slot 220 and extending in the first circumferential side (e.g., clockwise direction) is joined to the lapping portion 58 of another coil piece 52 extending from another slot 220 and extending in the second circumferential side (e.g., counterclockwise direction).

[0065] In the present embodiment, as an example, six coil pieces 52 are assembled in one slot 220. Hereinafter, starting from the outermost coil piece 52 in the radial direction, they are sequentially also referred to as the first turn, the second turn, and the third turn. In this case, the top end portions 40 of the first turn coil piece 52 and the second turn coil piece 52 are joined to each other through a joining process described later, the top end portions 40 of the third turn coil piece 52 and the fourth turn coil piece 52 are joined to each other through a joining process described later, and the top end portions 40 of the fifth turn coil piece 52 and the sixth turn coil piece 52 are joined to each other through a joining process described later.

[0066] Here, the coil piece 52 is coated with the insulating film 62 as described above, but only the top end portion 40 is removed from the insulating film 62. This is to ensure the electrical connection between this coil piece 52 and other coil pieces 52 through the top end portion 40.

[0067] Figure 5 is a view showing the top end portions 40 where the coil pieces 52 are joined to each other and the vicinity thereof. In addition, in Figure 5 the circumferential range D1 of the welding target portion 90 is schematically shown. Figure 6 is a view schematically showing the welding target portion 90 as observed from the irradiation side. Figure 7 is a cross-sectional view along line A - A passing through the welding target portion 90. In Figure 5 the range of the molten pool formed during welding is schematically shown by the shaded area 1102. Figure 7 Figure 8 ​It is a graph showing the relationship between the laser wavelength and the laser absorption rate for individuals of various materials.

[0068] In Figure 5 , the Z - direction along the axis is defined. Hereinafter, in the description, the Z1 side (i.e., the laser beam irradiation side) in the Z - direction is set as the "upper side", and the Z2 side in the Z - direction is set as the "lower side". Additionally, in Figure 6 , the X - direction along the radial direction and the X1 side and X2 side along the X - direction are defined.

[0069] When joining the tip portions 40 of the coil pieces 52, one coil piece 52 and the other coil piece 52, in the view shown in Figure 5 (when observed in the radial direction), overlap their respective tip portions 40 and make their respective tip portions 40 abut in the radial direction. Hereinafter, in the description, there are cases where, when making a distinction, for the structure of one coil piece 52, such as in the case of the tip portion 40A, a symbol "A" is appended after the reference numeral, and for the structure of the other coil piece 52, such as in the case of the tip portion 40B, a symbol "B" is appended after the reference numeral. In addition, in other embodiments, the tip portions 40 may also cross in an X - shape. In this case, each tip portion 40 may also be cut so as not to produce the protruding portion on the upper side in the X - shape.

[0070] In this case, the welding target portion 90 extends linearly along the abutment surface 401 as shown in the range D1 in Figure 6 . That is, for the welding target portion 90, when observed from the laser beam irradiation side (refer to the arrow W in Figure 5 ), with the width of the range D2 in the X - direction shown in Figure 7 , the welding target portion 90 extends linearly over the range D1 in the Y - direction. Additionally, in the present embodiment, when observed in the radial direction, the abutment surface 401 is in the form of a rectangle surrounded by the axially outer end faces 42A, 42B and the extending - direction end faces 44A, 44B, but it may also be in other forms.

[0071] In the present embodiment, in the view shown in Figure 5 (when observed in the radial direction), the welding target portion 90 is set along the upper - side edge (the exposed upper - side edge among the four edges of the rectangle) formed by the axially outer end faces 42A, 42B of the tip portions 40 on both sides. Additionally, in the present embodiment, the welding target portion 90 extends in the horizontal direction, but in the view shown in Figure 5 (when observed in the radial direction), depending on other adoptable shapes of the tip portion 40, it may extend in a C - shape protruding upward, or may be in other forms. Additionally, in Figure 5 and Figure 6In the example shown, the axially outer end faces 42A and 42B extend in the XY plane. However, the axially outer end faces 42A and 42B may also be inclined with respect to the XY plane.

[0072] In the present embodiment, welding is used as the joining method when joining the tip portions 40 of the coil pieces 52. Further, in the present embodiment, as the welding method, laser welding using a laser beam source as a heat source is employed instead of arc welding typified by TIG welding. By using laser welding instead of TIG welding, the axial length of the coil tails 220A and 220B can be reduced. That is, in the case of TIG welding, it is necessary to bend the tip portions of the coil pieces that are formed to abut against each other outward in the axial direction and extend in the axial direction. In the case of laser welding, such bending is not required. As Figure 5 shown, welding can be achieved in a state where the tip portions 40 of the coil pieces 52 that are formed to abut against each other extend in the circumferential direction. Thereby, the axial length of the coil tails 220A and 220B can be reduced compared to the case where the tip portions 40 of the coil pieces 52 that are formed to abut against each other are bent outward in the axial direction and extend in the axial direction.

[0073] In laser welding, as Figure 5 schematically shown, a laser beam for welding is irradiated onto the welding target portion 90 at the two abutting tip portions 40. Further, the irradiation direction (propagation direction) of the laser beam is substantially parallel to the axial direction and is in the direction from the axially outer side toward the axially outer end faces 42 (including the exposed side edge of the abutting surface 401) of the two abutting tip portions 40. In the case of laser welding, local heating is possible, so that only the tip portions 40 and their vicinity can be heated, and damage (carbonization) of the insulating film 62 can be effectively reduced. As a result, a plurality of coil pieces 52 can be electrically connected while maintaining appropriate insulation performance.

[0074] Figure 8 is a graph showing the relationship between the laser wavelength and the laser absorption rate (hereinafter, also simply referred to as "absorption rate") for each of various materials. In Figure 8 it, the horizontal axis represents the wavelength λ, and the vertical axis represents the absorption rate, showing the characteristics of each of various materials such as copper (Cu), aluminum (Al), silver (Ag), nickel (Ni), and iron (Fe).

[0075] However, infrared lasers (lasers with a wavelength of 1064 nm) commonly used in laser welding, as Figure 8As indicated by the black dots at the intersections formed by the dashed lines with λ2 = 1.06 μm, for copper, which is the material of the linear conductor 60 of the coil piece 52, the absorption rate is as low as approximately 10%. That is, in the case of infrared laser, most of the laser beam is reflected by the coil piece 52 without being absorbed. Therefore, in order to obtain the required bonding area between the coil pieces 52 to be joined, a relatively large amount of heat input is required, the thermal influence is large, and the welding may become unstable.

[0076] In view of this, in the present embodiment, instead of infrared laser, green laser is used. In addition, green laser is a concept that includes not only laser with a wavelength of 532 nm, that is, SHG (Second Harmonic Generation), but also laser with wavelengths close to 532 nm. In addition, in a modified example, laser with a wavelength of 0.6 μm or less that does not fall within the category of green laser can also be used. The wavelength of green laser is obtained by, for example, passing the fundamental wavelength generated by a YAG laser or a YVO4 laser through an oxide single crystal (for example, LBO: lithium triborate) and forming a conversion.

[0077] In the case of green laser, as Figure 8 indicated by the black dots at the intersections formed by the dashed lines with λ1 = 0.532 μm, for copper, which is the material of the linear conductor 60 of the coil piece 52, the absorption rate is as high as approximately 50%. Therefore, according to the present embodiment, compared with the case of using infrared laser, the required bonding area between the coil pieces 52 can be ensured with a smaller amount of heat input.

[0078] In addition, the characteristic that the absorption rate of green laser is higher than that of infrared laser is as Figure 8 shown, which is significant in the case of copper, but can be confirmed not only when the material is copper, but also when many other metal materials are used. Therefore, even when the material of the linear conductor 60 of the coil piece 52 is other than copper, welding using green laser can be achieved.

[0079] Figure 9 is an explanatory diagram of the change mode of the absorption rate during welding. In Figure 9 it, the horizontal axis represents the laser power density, the vertical axis represents the laser absorption rate of copper, and the characteristics 100G in the case of green laser and the characteristics 100R in the case of infrared laser are shown.

[0080] In Figure 9 it, the points P100 and P200 where the melting of copper starts in the case of green laser and in the case of infrared laser are shown, and the point P300 where a keyhole is formed is also shown. As Figure 9As shown by the midpoints P100 and P200, it can be seen that, compared with infrared lasers, green lasers can initiate melting of copper with a small laser power density. Additionally, it can be seen that due to the above-mentioned difference in absorption rates, the difference between the absorption rate at the point P300 where the keyhole is formed and the absorption rate at the start of irradiation (i.e., the absorption rate when the laser power density is 0) is smaller for green lasers than for infrared lasers. Specifically, in the case of infrared lasers, the change in the absorption rate during welding is approximately 80%, while in the case of green lasers, the change in the absorption rate during welding is approximately 40%, which is about half.

[0081] Thus, in the case of infrared lasers, the change (drop) in the absorption rate during welding is relatively large, at approximately 80%. Therefore, the keyhole becomes unstable, and deviations in welding depth, welding width, and disturbances in the molten pool (e.g., sputtering, etc.) are likely to occur. In contrast, in the case of green lasers, the change (drop) in the absorption rate during welding is relatively small, at approximately 40%. Therefore, the keyhole is less likely to become unstable, and deviations in welding depth, welding width, and disturbances in the molten pool (e.g., sputtering, etc.) are less likely to occur. Additionally, sputtering refers to metal particles, etc., that are scattered due to laser irradiation, etc.

[0082] Furthermore, in the case of infrared lasers, as described above, the absorption rate is low. Therefore, generally, by making the beam diameter relatively small (e.g., ), the low absorption rate is compensated for. This also becomes an important factor for the instability of the keyhole. Additionally, Figure 10B is a schematic diagram of the keyhole, etc., in the case of using an infrared laser. 1100 represents the weld seam, 1102 represents the molten pool, and 1104 represents the keyhole. Additionally, the arrow R1116 schematically represents the way gas escapes. Additionally, the arrow R110 schematically represents the situation where the irradiation position of the infrared laser moves due to the small beam diameter. Thus, in the case of infrared lasers, since it is difficult to make the beam diameter relatively large due to the low absorption rate as described above, there is a tendency to require a relatively long movement trajectory (continuous irradiation time) of the irradiation position that includes meandering in order to obtain the required melting width.

[0083] On the other hand, in the case of green lasers, as described above, the absorption rate is relatively high. Therefore, it is possible to make the beam diameter relatively large (e.g., or more), which can make the keyhole larger and more stable. As a result, gas escape becomes better, and the generation of sputtering, etc., can be effectively reduced. Additionally, Figure 10A is a schematic diagram of the keyhole, etc., in the case of using a green laser. The meanings of the reference numerals are as described in Figure 10B and as described above. In the case of green lasers, according to Figure 10A, it is easy to understand in the form of an image the situation where the keyhole is stabilized due to the expansion of the beam diameter and the gas escape becomes good. In addition, compared with the case of infrared laser, in the case of green laser, as described above, the absorption rate can be relatively high and the beam diameter can be relatively large, so that the movement locus (irradiation time) of the irradiation position required to obtain the required melting width (refer to the radial range D2 of the welding target part 90 shown in Figure 7 ) can be relatively short (small) (described later).

[0084] Hereinafter, a manufacturing method for efficiently achieving high-quality welding using such a green laser will be disclosed.

[0085] Figure 11 is an explanatory diagram of the irradiation mode of the green laser of the manufacturing method of this embodiment. Figure 11A is an explanatory diagram related to the scanning of the laser beam and is an explanatory diagram of the emission center Ct0 of the laser beam. Figure 11B is an explanatory diagram related to the scanning of the laser beam and is an explanatory diagram of the movement mode of the laser beam. Figure 12 is an explanatory diagram of the irradiation mode in the case of the infrared laser of the comparative example. Figure 11 and Figure 12 are schematic diagrams observed in the laser irradiation direction, and the irradiation area (or the predetermined irradiation part) of the laser at the welding target part 90 at a certain moment during welding is schematically shown in the shaded area. In Figure 11 and Figure 12 , the circles 110, 110' related to the laser beam represent the irradiation range at a certain moment during welding, and the beam diameter is shown together In addition, in Figure 11 and Figure 12 , the line Lref represents the abutment surface 401 (the upper side edge of the abutment surface 401).

[0086] As schematically shown in Figure 11 , the manufacturing method of this embodiment includes scanning in a ring shape (refer to arrow R112) while moving the laser beam in the welding direction (travel direction). In addition, the travel direction is along the upper side edge of the above-mentioned abutment surface 401 (that is, the direction parallel to the upper side edge), but due to errors, etc., it may be slightly inclined with respect to this edge. In addition, hereinafter, the upper part of the abutment surface 401 refers to the part forming the upper side edge of the abutment surface 401 (refer to the line Lref).

[0087] "Annular" is a concept that includes not only a circle but also any shape that can form a ring, such as an ellipse. In addition, it does not need to be completely closed and can also be a continuously spiral shape. In this embodiment, as an example, the annular shape is a continuously spiral shape of a circle. Such an annular shape can be realized, for example, by using a laser beam that is emitted (scanned) from the emission part in a way that draws a circular trajectory a predetermined number of times per unit time. In Figure 11A , in the shaded area R11, the circular trajectory (scanning) of the laser beam is schematically shown in the case where the laser beam (emission part) does not move. When the laser beam does not move, the circle 110 rotates around the emission center Ct0 (= the center of the circular trajectory), and the circle 110 draws a circular orbit around the emission center Ct0 (= the center of the circular trajectory). In this case, the annular trajectory of the circle 110 is realized by moving the emission center Ct0 (= the center of the circular trajectory) linearly. At this time, by making the emission center Ct0 of the laser beam along the abutment surface 401, the traveling direction along the upper side edge of the abutment surface 401 is realized. In addition, in Figure 11 and Figure 11B , the dotted line TRct represents the trajectory (the arrow is the forward direction) of the center Ct1 of the laser beam when such a movement of the laser beam (linear movement along the upper side edge of the abutment surface 401) is performed.

[0088] The diameter of the annular circle (hereinafter, also referred to as "swing diameter ") is arbitrary, but the preferred range will be described later. For example, the swing diameter can be larger than the beam diameter of the laser beam

[0089] In this embodiment, the movement amount in the traveling direction for each annular scan (hereinafter, also referred to as "swing pitch pt") is the beam diameter of the laser beam or less. In addition, "for each annular scan" means that one cycle is defined as the rotation from a certain phase of the circle to the same phase. Thus, as Figure 11 shown, it is possible to continuously set an annular irradiation range and the next annular irradiation range along the welding direction on the abutment surface 401. For example, if the swing pitch pt is 1 / 2 of the beam diameter of the laser beam , the irradiation range of one annular shape and the irradiation range of the next annular shape overlap by 1 / 2 of the beam diameter on the abutment surface 401.

[0090] In this case, the molten pool formed in the welding target portion 90 can be moved on the abutment surface 401 in the welding direction while maintaining the molten pool. That is, according to this embodiment, the molten pool can be moved on the abutment surface 401 in the welding direction by the swing pitch pt for each annular cycle while maintaining the molten pool.

[0091] The swing pitch pt is constant relative to a welding target portion 90, but can also be variable. Beam diameter The size of can be the size at the exit end. In this case, the beam diameter represents the Gaussian beam diameter (1 / e 2 ), but in the case of an elliptical beam, the length of the major or minor axis of the elliptical spot can also be used instead.

[0092] In this embodiment, the beam diameter The size is preferably More preferably Here, if the beam diameter is increased The size of the laser beam diameter The swing pitch pt can also be increased under the following conditions. Figure 10A As described above and described below in comparison with the comparative example, the movement trajectory (irradiation time) for obtaining a desired molten width can be made relatively short, and efficient welding can be achieved.

[0093] In this embodiment, the laser beam is continuously irradiated in a manner that the laser output is 3.0 kW or more for several cycles of circular scanning. For example, the laser beam can be continuously irradiated to the entire welding target part 90. Thus, compared with the irradiation of pulse oscillation, the output itself may be lower, but the molten pool can be easily maintained and the welding time can be shortened.

[0094] Here, in Figure 12 In the comparative example shown, as described above, since infrared laser is used, the beam diameter is Smaller, for example In addition, the swing pitch pt' is 0.1 mm. In this case, Figure 12 As shown, the irradiation range involved in each ring is continuous along the welding direction on the abutting surface 401.

[0095] Figure 13 In this embodiment, Figure 11 A cross-sectional view taken along the line BB of (a cross-sectional view along the welding direction on the abutment surface 401), Figure 14 In the case of the comparative example, Figure 12Cross-sectional view taken along line C-C (cross-sectional view along the welding direction on the abutment surface 401). It is a schematic diagram showing the state of the joint surface when cutting is performed at the abutment surface 401. In Figure 13 and Figure 14 the joint surfaces are schematically shown in the shaded regions SC13 and SC14. In addition, the joint surface refers to the surface in the abutment surface 401 that is joined by welding. Additionally, Figure 15 and Figure 16 show an image of a part (lower end portion of the joint surface) of the joint surface when cutting is performed at the abutment surface 401, Figure 15 shows an image of this embodiment, Figure 16 shows an image of a comparative example. As an example, Figure 15 the conditions of this embodiment of swing diameter swing pitch pt = 0.2 mm. Additionally, Figure 14 the conditions of the comparative example of swing diameter swing pitch pt' = 0.1 mm.

[0096] In the comparative example, as described above, the respective annular irradiation ranges become discontinuous along the welding direction on the abutment surface 401. Therefore, as Figure 14 and Figure 16 shown, the height H1' (welding depth H1') of the lower end portion of the joint surface varies greatly along the welding direction. That is, between the respective annular irradiation ranges, there are portions where the height H1' suddenly decreases (the welding depth suddenly becomes shallower). As a result, there is a defect that the joint area (area of the joint surface) is likely to be insufficient. In response to this, a countermeasure of overlapping the respective annular irradiation ranges by further reducing the swing pitch pt' can also be considered, but in this countermeasure, other defects such as an excessive welding time or an excessive heat input amount are likely to occur.

[0097] In contrast, according to this embodiment, as described above, the respective annular irradiation ranges are continuous along the welding direction on the abutment surface 401. Thereby, the inconveniences generated in the above comparative example can be reduced or prevented. That is, as Figure 13 and Figure 15 shown, the height H1 (welding depth H1) of the lower end portion of the joint surface does not vary greatly along the welding direction but is substantially constant. Additionally, since the beam diameter is relatively large, even if the swing pitch pt is increased, the irradiation ranges related to the respective annuli can be made continuous, and a reduction in welding time and heat input amount (efficiency improvement) can be achieved. In this regard, in this embodiment, under the condition that the beam diameter of the laser beam is or less, the swing pitch pt can be the beam diameter of the laser beam more than 1 / 4, more preferably the beam diameter more than 1 / 3, most preferably more than 1 / 2.

[0098] Figure 17 is an explanatory diagram of the robustness with respect to the misalignment of the irradiation position in the radial direction. In Figure 17 , the horizontal axis represents the laser radial misalignment amount, the vertical axis represents the bonding area, and the characteristic curves 1701, 1702, and 1703 related to three methods are shown. The laser radial misalignment amount represents the position in the radial direction of the center of the irradiation area when it is set to "0" on the abutment surface 401, and negative indicates the inner side in the radial direction.

[0099] The characteristic curve 1701 represents the case of this embodiment, the characteristic curve 1702 represents the case of the first comparative example, and the characteristic curve 1703 represents the case of the second comparative example. The first comparative example corresponds to the comparative example described with reference to Figure 12 etc., and the beam diameter oscillation diameter Although the second comparative example uses a green laser, the scanning method is different from that of this embodiment and is a straight-line scan. That is, in the second comparative example, the green laser scans linearly along the welding direction on the abutment surface 401. In addition, the condition of the second comparative example is that the beam diameter = 0.293 mm. The condition of this embodiment is the beam diameter oscillation diameter

[0100] As Figure 17 shown, in the second comparative example, the robustness with respect to the misalignment of the irradiation position in the radial direction is the lowest. For example, if it is misaligned 0.2 mm inward in the radial direction, the bonding area is reduced to 3 mm 2 or less. In addition, the bonding area when the misalignment amount = 0 is significantly larger than 4 mm 2 . In contrast, in this embodiment and the first comparative example, the robustness with respect to the misalignment of the irradiation position in the radial direction is relatively high. Even if it is misaligned 0.2 mm inward or outward in the radial direction, the bonding area will not be reduced to 3 mm 2 or less. In the case of this embodiment, it can be seen that in the region where the misalignment in the radial direction is 0.4 mm or more, the robustness is higher than that of the first comparative example.

[0101] Next, referring to Figures 18 to 20 , based on the test results, the preferred range of the oscillation diameter of this embodiment will be described.

[0102] Figure 18 is a table diagram showing multiple conditions (conditions 1 to 3) of the implemented test. Figure 19 shows the oscillation diameter according to the conditions A graph showing the relationship with the number of sputtering Figure 20 represents the swing diameter A graph showing the relationship with the bonding area and the welding depth. In Figure 20 , the line graph 201 is related to the welding area, and the line graph 202 is related to the welding depth. In Figure 19 and Figure 20 , the curve p1 is related to condition 1, the curve p2 is related to condition 2, and the curve p3 is related to condition 3.

[0103] As Figure 18 shown, in conditions 1 to 3, the laser scanning speed is adjusted so that the heat input is the same. In addition, in Figure 18 , the laser scanning speed corresponds to the length of the irradiation trajectory of the laser beam per unit time (the length along the circular trajectory). In addition, the welding speed refers to the moving distance of the irradiation position of the laser beam per unit time. For example, it is a value obtained by dividing the moving distance of the irradiation position of the laser beam (the moving distance along the welding direction on the abutment surface 401) in a certain period of time by the same time. The common conditions (fixed conditions) in each condition are to use a green laser, the beam diameter and the output distribution density is a Gaussian distribution.

[0104] As Figure 19 shown, the larger the swing diameter, the more stable the molten pool and the fewer the number of sputtering. In addition, referring to Figure 10A , Figure 10B by the same principle as above, when the swing diameter is relatively small, the keyhole becomes unstable and it is easy to generate disorders in the molten pool (such as sputtering, etc.).

[0105] As Figure 20 shown, it can be known that when the heat input is the same, the smaller the swing diameter, the greater the welding depth (penetration depth). Similarly, it can be known that when the heat is the same, the smaller the swing diameter, the larger the bonding area.

[0106] In this way, from the viewpoint of reducing the number of sputtering, the larger the swing diameter, the more advantageous. However, from the viewpoints of increasing the welding depth and the bonding area, the smaller the swing diameter, the more advantageous. Therefore, considering the opposite viewpoints of these viewpoints, an appropriate range of the swing diameter can be suitable. For example, considering that when the swing diameter is insufficient, the number of sputtering will increase sharply with the decrease of the swing diameter, the swing diameter The above. In addition, when the swing diameter exceeds , the joint area is relatively small. Therefore, the swing diameter is preferably or less. In this case, the swing diameter is between 1.46 times and 2.74 times the beam diameter of the laser beam . Therefore, it is appropriate for the swing diameter to be between 1.4 times and 2.8 times the beam diameter of the laser beam .

[0107] Next, with reference to Figures 21 to 2 Fig. 5, the change profile of the preferred welding speed of this embodiment will be described.

[0108] Figure 21 is a graph showing the preferred welding speed (the change profile of the welding speed corresponding to the Y-direction position) at each Y-direction position, with the horizontal axis being the Y-direction position along the Y direction and the vertical axis being the welding speed. In addition, the positive side of the horizontal axis corresponds to the above-mentioned Y2 side. Here, the Y1 side of the welding target portion 90 (refer to Figure 6 ) is the welding start position, and during welding, the emission center Ct0 of the laser beam (refer to Figure 11A ) is moved from the Y1 side toward the Y2 side. In Figure 21 , in addition to the change profile of the welding speed, the preferred laser output (the change profile of the laser output corresponding to the Y-direction position) at each Y-direction position is also shown together as the waveform R21. In Figure 21 , the Y-direction position P1 represents the irradiation start position, and the Y-direction position P5 represents the irradiation end position. The interval from the Y-direction position P1 to the Y-direction position P5 corresponds to the above-mentioned range D1 with reference to Figure 5 and Figure 6 .

[0109] In this embodiment, the welding speed is the lowest at the start of irradiation and then increases. In the example shown in Figure 21 , in the interval from the Y-direction position P1 to the Y-direction position P2, the welding speed = V1, in the interval from the Y-direction position P2 to the Y-direction position P3, the welding speed = V2, and in the interval from the Y-direction position P3 to the Y-direction position P5, the welding speed = V3. Moreover, V1 < V2 < V3.

[0110] The welding speed V1 is preferably significantly less than 80 mm / s, for example, within the range of 5 - 35 mm / s, and can be about 20 mm / s. The welding speed V3 is preferably 80 mm / s or more, for example, can be about 100 mm / s. In this case, the welding speed V2 can also be the intermediate value of the welding speed V1 and the welding speed V3 (= (V1 + V3) / 2).

[0111] The section from the Y-direction position P1 to the Y-direction position P2 is preferably shorter than the section from the Y-direction position P3 to the Y-direction position P5, and more preferably shorter than the section from the Y-direction position P3 to the Y-direction position P4.

[0112] The section from the Y-direction position P1 to the Y-direction position P2 is preferably less than 20% with respect to the range D1, and preferably 10% or less with respect to the range D1. The section from the Y-direction position P2 to the Y-direction position P3 can be shorter than the section from the Y-direction position P1 to the Y-direction position P2.

[0113] Preferably, the laser output is the highest in the section from the Y-direction position P3 to the Y-direction position P4. For example, as Figure 21 shown, the laser output can gradually increase from the Y-direction position P1, and be maintained at a constant value in the section from the Y-direction position P3 to the Y-direction position P4. Moreover, the laser output can be reduced toward 0 (output off) using the section from the Y-direction position P4 to the Y-direction position P5. In this case, in the section from the Y-direction position P3 to the Y-direction position P4 in the range of the welding speed V3, the maximization of the laser output is achieved, and the main part of the welding object part 90 can be welded with high quality in a short time.

[0114] Figure 22 is an explanatory diagram of the swing pitch pt (swing pitch pt at the welding speed V1) in the section from the Y-direction position P1 to the Y-direction position P2 (an example of the "first movement amount"). Figure 23 is an explanatory diagram of the swing pitch pt (swing pitch pt at the welding speed V3) in the section from the Y-direction position P3 to the Y-direction position P5 (an example of the "second movement amount").

[0115] In Figure 22 and Figure 23 are respectively schematically shown two circles 110 related to the laser beam on the line Lref (abutment surface 401) shown in Figure 11 . The distance in the Y-direction between these two circles 110 corresponds to the swing pitch pt. Here, throughout the entire section from the Y-direction position P1 to the Y-direction position P5, the laser scanning speed is constant. Comparing Figure 11 ) Figure 22 and Figure 23It can be seen that, on the one hand, when the welding speed increases, the oscillation pitch pt increases accordingly. On the other hand, when the welding speed increases, the overlapping rate of the two circles 110 (area of the overlapping part / area of the circle × 100) decreases accordingly. The welding speed V3 can be set such that the overlapping rate of the two circles 110 (area of the overlapping part / area of the circle × 100) is preferably 15% or more and 20% or less.

[0116] Here, referring to Figures 24A to 25B and explaining the effects related to the change overview of the welding speed of the above-mentioned present embodiment with reference to Figure 21 and the like.

[0117] Figure 24A and Figure 24B are explanatory diagrams of the first comparative example, Figure 24B is an explanatory diagram of the problem points of the first comparative example. Figure 25A and Figure 25B are explanatory diagrams of the second comparative example, Figure 25B is an explanatory diagram of the problem points of the second comparative example. Figure 24A and Figure 25A are both the same as Figure 21 that appeared earlier in the present embodiment. It is a graph with the horizontal axis being the Y-direction position along the Y direction and the vertical axis being the welding speed, showing the preferred welding speed (change overview of the welding speed corresponding to the Y-direction position) at each Y-direction position. Figure 24B and Figure 25B are both the same as Figure 6 that appeared earlier in the present embodiment. They are diagrams schematically showing the welding object part 90’ or 90” observed from the irradiation side.

[0118] In the first comparative example, as Figure 24A shows, throughout the entire range from the Y-direction position P1 to the Y-direction position P5, the welding speed is constantly a relatively high speed (= welding speed V3).

[0119] In this case, before the molten pool becomes large enough at the welding start position (Y-direction position P1), the laser beam moves in the Y direction at a relatively fast moving speed, and the laser beam is likely to irradiate outside the molten pool. For example, when the laser beam moves from the Y1 side towards the Y2 side, for the molten pool, the laser beam is likely to irradiate outside the Y2 side. In this case, as Figure 24B schematically shows, defects are likely to occur at the welding start position (Y-direction position P1). For example, at the welding start position (Y-direction position P1), the material (individual) of the irradiation part at the tip 40 of the coil piece 52 is blown away, and voids are likely to occur (represented by the non-shaded area in Figure 24B ).

[0120] In contrast, according to the present embodiment, as described above, a relatively small welding speed V1 is used in the section from the Y-direction position P1 to the Y-direction position P2. As a result, before the molten pool becomes large enough, the laser beam is less likely to irradiate the outside of the molten pool. As a result, the defective conditions generated in the first comparative example can be reduced.

[0121] Here, in the present embodiment, the length of the section from the Y-direction position P1 to the Y-direction position P2 is preferably set such that circles 110 are formed more than twice at a corresponding swing pitch pt (refer to Figure 23 ), and more preferably set such that circles 110 are formed within a range of 7 to 13 times at the corresponding swing pitch pt in this section. Thus, after the molten pool is properly formed, it is possible to move to the section after the Y-direction position P2 (for example, the section with the welding speed V3).

[0122] In the second comparative example, as Figure 25A shown, throughout the entire section from the Y-direction position P1 to the Y-direction position P5, the welding speed is constantly a relatively low speed (= welding speed V1). In this case, as Figure 24B schematically shown, in this case, as Figure 25B schematically shown, the melting width w2 (refer to Figure 7 the radial range D2 of the welded object portion 90 shown) is likely to be larger than the desired value. For example, when the laser beam is moved from the Y1 side toward the Y2 side, the melting width w2 increases as it moves toward the Y2 side (the same applies to the welding depth H1 shown in Figure 13 ). As a result, not only does the welding quality decrease, but also defective conditions caused by the excessive melting width w2 and welding depth H1 (such as damage to the fixture for positioning the top portion 40 of the coil piece 52, etc.) occur. In addition, there is also a defective condition that the welding time (the time required for welding) for each welded object portion 90 is relatively long.

[0123] In contrast, according to the present embodiment, as described above, although a relatively small welding speed V1 is used in the section from the Y-direction position P1 to the Y-direction position P2, a relatively large welding speed (especially the welding speed V3) is used in the subsequent section. Thus, it is possible to make the melting width w2 and the welding depth H1 substantially constant throughout the entire welded object portion 90 (that is, throughout the entire section from the Y-direction position P1 to the Y-direction position P5). In addition, the welding time (the time required for welding) for each welded object portion 90 can be made relatively short. That is, the defective conditions generated in the second comparative example can be reduced.

[0124] In addition, when referring to Figure 21In the above-described change overview of the welding speed of the present embodiment, three welding speeds V1, V2, and V3 are used, but a structure in which the welding speed V1 or the welding speed V3 is used instead of the welding speed V2 is also possible. Alternatively, four or more welding speeds can be used.

[0125] Next, with reference to Figure 26 , the process of the manufacturing method of the present embodiment and the manufacturing apparatus 300 will be outlined.

[0126] Figure 26 is a flowchart schematically showing the process of the manufacturing method of the stator 21 of the motor 1. Figure 27 is a system configuration diagram of the manufacturing apparatus 300.

[0127] First, this manufacturing method includes an assembling step (step S150) of assembling the coil pieces 52 to the stator core 22. In addition, this manufacturing method includes a joining step (step S152) of joining the top ends 40 of the coil pieces 52 to each other by laser welding after the assembling step. The method of joining the top ends 40 of the coil pieces 52 to each other by laser welding is as described above.

[0128] In this case, the joining step includes a setting step (step S1521) of arranging the top ends 40 of each pair of coil pieces 52 to abut against each other in the radial direction as described above. In addition, in the setting step, the jig 302 can be used to maintain the state in which the top ends 40 of each pair of coil pieces 52 abut against each other in the radial direction.

[0129] Moreover, the joining step includes an irradiation step (step S1522) of irradiating a laser beam from the irradiation device 304 to the welding target portion 90 as described above after the setting step. The irradiation mode of the laser beam from the irradiation device 304 can be controlled by the control device 301 as described above. In addition, the setting step and the irradiation step can be executed in groups for each of one or more specified amounts of welding target portions 90, or can be executed together for all the welding target portions 90 related to one stator 21. In addition, this manufacturing method can complete the stator 21 and end by appropriately performing various necessary steps after the joining step.

[0130] As described above, each embodiment has been described in detail, but it is not limited to a specific embodiment, and various deformations and changes can be made within the scope described in the claims. In addition, the constituent elements of all or multiple of the above-described embodiments can be combined.

[0131] Description of Reference Numerals

[0132] 1... Motor (rotating electric machine); 24... Stator coil; 52... Coil sheet; 40... Tip portion; 401... Contact surface; 110... Circle of laser beam; 300... Manufacturing apparatus; 302... Fixture; 304... Irradiation device.

Claims

1. A method for manufacturing a stator for a rotating electrical machine, wherein, the method for manufacturing a stator for a rotating electrical machine includes: a step of bringing the top end portion of one coil sheet for forming a stator coil of a rotating electrical machine into contact with the top end portion of another coil sheet; and an irradiation step of irradiating a laser beam having a wavelength of 0.6 μm or less toward one edge on the exposed side of the contact surface between the top end portions, the irradiation step includes performing a circular scan while moving the laser beam in a traveling direction including a direction component in which the one edge extends, and in each circular scan, the amount of movement in the traveling direction is equal to or less than the beam diameter of the laser beam.

2. The method for manufacturing a stator for a rotating electrical machine according to claim 1, wherein, in the irradiation step, the laser beam is continuously irradiated in such a manner that the laser output is 3.0 kW or more for a plurality of circular scans.

3. The method for manufacturing a stator for a rotating electrical machine according to claim 1, wherein, the length of the diameter of the circle or the length in the major axis direction is between 1.4 times and 2.8 times the beam diameter of the laser beam.

4. The method for manufacturing a stator for a rotating electrical machine according to claim 1, wherein, the beam diameter of the laser beam is 0.15 mm or more.

5. The method for manufacturing a stator for a rotating electrical machine according to any one of claims 1 to 4, wherein, the irradiation step includes: for the amount of movement in the traveling direction in each circular scan, setting the first movement amount at the start of irradiation, and thereafter, changing the movement amount to a second movement amount larger than the first movement amount.

6. The method for manufacturing a stator for a rotating electrical machine according to claim 5, wherein, the irradiation step includes: for the laser output of the laser beam, making the laser output in the interval of the second movement amount larger than the laser output in the interval of the first movement amount.

7. The method for manufacturing a stator for a rotating electrical machine according to claim 6, wherein, the irradiation step includes: using the laser beam that emits in a manner of drawing a circle a predetermined number of times per unit time, and drawing at least two circles in the interval of the first movement amount.

8. A manufacturing apparatus for a stator for a rotating electrical machine, wherein, the manufacturing apparatus for a stator for a rotating electrical machine includes: a jig for bringing the top end portion of one coil sheet for forming a stator coil of a rotating electrical machine into contact with the top end portion of another coil sheet; and an irradiation device for irradiating a laser beam having a wavelength of 0.6 μm or less toward one edge on the exposed side of the contact surface between the top end portions, the irradiation device performs a circular scan while moving the laser beam in a traveling direction including a direction component in which the one edge extends, and in each circular scan, the amount of movement in the traveling direction is equal to or less than the beam diameter of the laser beam.

Images