WO2024080097A1 - Rotating electric machine stator manufacturing method and rotating electric machine stator manufacturing device - Google Patents

Abstract

Disclosed is a rotating electric machine stator manufacturing method including: a step for bringing the leading end portions of one coil piece and another coil piece for forming a stator coil of a rotating electric machine into contact with each other; and an irradiation step for irradiating a laser beam having a wavelength of 0.6 μm or less toward one side on the exposed side of the contact surface of the leading end portions. The irradiation step involves scanning the laser beam in a loop shape while moving the laser beam in the travel direction, which includes a directional component along which the one side extends. The amount of movement in the travel direction per scanning loop is less than or equal to the diameter of the laser beam.

Description

Manufacturing method and device for manufacturing a stator for a rotating electric machine

This disclosure relates to a method and an apparatus for manufacturing a stator for a rotating electric machine.

A technology is known that achieves welding between coil pieces by bringing the tips of one coil piece and another coil piece into contact with each other and scanning a laser beam in a loop while moving it in a direction that includes a directional component parallel to the contact surface of the tips.

JP 2021-44883 A

However, in the conventional techniques described above, depending on the relationship between the beam diameter of the laser beam and the amount of movement in the forward direction per one loop-shaped scan (hereinafter also referred to simply as the "loop pitch"), it is difficult to efficiently achieve high-quality welding. For example, if the loop pitch is too large compared to the beam diameter of the laser beam, the molten pool cannot be properly maintained, and there is a risk of reduced welding quality. Also, if the loop pitch is too small compared to the beam diameter of the laser beam, there is a risk of excessive welding time and heat input per unit length of the area to be welded.

In one aspect, the present disclosure aims to efficiently achieve high-quality welding between coil pieces of a stator for a rotating electric machine.

According to one aspect, a step of bringing a tip end portion of one coil piece and a tip end portion of another coil piece into contact with each other to form a stator coil of a rotating electric machine;
and an irradiation step of irradiating a laser beam having a wavelength of 0.6 μm or less toward one side of an exposed side of the contact surface between the tip portions,
the irradiation step includes scanning the laser beam in a loop while moving the laser beam in a traveling direction including a directional component in which the one side extends,
The method for manufacturing a stator for a rotating electric machine is provided, wherein the amount of movement in the traveling direction per one loop-shaped scan is equal to or smaller than the beam diameter of the laser beam.

In one aspect, the present disclosure makes it possible to efficiently achieve high-quality welding between coil pieces of a stator for a rotating electric machine.

1 is a cross-sectional view showing a schematic cross-sectional structure of a motor according to an embodiment; FIG. 2 is a plan view of the stator core in a single component state. 3A and 3B are diagrams illustrating a pair of coil pieces to be assembled to a stator core. FIG. 2 is a schematic front view of one coil piece. 1 is a diagram showing the tip portions of the coil pieces joined together and their vicinity; FIG. FIG. 2 is a diagram illustrating a schematic view of a welding target portion as viewed from the irradiation side. 6 is a cross-sectional view taken along line AA in FIG. 5 through the area to be welded. FIG. 1 is a diagram showing the relationship between the laser wavelength and the laser absorptance of various solid materials. FIG. 4 is an explanatory diagram of a change in absorption rate during welding. FIG. 13 is an image diagram of a keyhole etc. when a green laser is used. FIG. 13 is an image diagram of a keyhole etc. when an infrared laser is used. 4A to 4C are explanatory diagrams of the irradiation mode of a green laser according to the manufacturing method of this embodiment. FIG. 2 is an explanatory diagram relating to scanning of a laser beam, and is an explanatory diagram of an emission center of a laser beam. FIG. 2 is an explanatory diagram relating to laser beam scanning, and is an explanatory diagram of a movement mode of the laser beam. FIG. 13 is an explanatory diagram of an irradiation mode in the case of an infrared laser according to a comparative example. FIG. 4 is a cross-sectional view taken along the welding direction on the contact surface according to the present embodiment. FIG. 11 is a cross-sectional view taken along the welding direction on the contact surface according to the comparative example. 13 is an image of the bottom edge of the bonded surface according to the present embodiment. 13 is an image of the lower end of the joint surface according to the comparative example. FIG. 13 is an explanatory diagram of robustness against deviation of the irradiation position in the radial direction. FIG. 1 is a table showing multiple conditions (conditions 1 to 3) of the tests carried out. FIG. 11 is a graph showing the relationship between the wobbling diameter and the number of sputters under different conditions. FIG. 11 is a graph showing the relationship between the wobbling diameter and the bonding area and welding depth. 1 is a diagram showing a preferred welding speed for each Y direction position (a change profile of the welding speed according to the Y direction position) with the horizontal axis representing the Y direction position along the Y direction and the vertical axis representing the welding speed. 11 is an explanatory diagram of the wobbling pitch in the section from Y-direction position P1 to Y-direction position P2. FIG. 13 is an explanatory diagram of the wobbling pitch in the section from Y direction position P3 to Y direction position P5. FIG. FIG. 11 is an explanatory diagram of a first comparative example. FIG. 11 is an explanatory diagram of a problem in the first comparative example. FIG. 11 is an explanatory diagram of a second comparative example. FIG. 13 is an explanatory diagram of a problem in the second comparative example. 4 is a flowchart illustrating a manufacturing method of a motor stator. FIG. 2 is a system configuration diagram of the manufacturing apparatus.

Each embodiment will be described in detail below with reference to the attached drawings. Note that the dimensional ratios in the drawings are merely examples and are not limiting. Also, shapes in the drawings may be partially exaggerated for the sake of explanation.

FIG. 1 is a cross-sectional view that shows a schematic cross-sectional structure of a motor 1 (an example of a rotating electric machine) according to one embodiment.

In Figure 1, the rotating shaft 12 of the motor 1 is shown. In the following description, the axial direction refers to the direction in which the rotating shaft (center of rotation) 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. Additionally, the circumferential direction corresponds to the direction of rotation around the rotating shaft 12.

Motor 1 may be a motor for driving a vehicle, such as that used in a hybrid vehicle or an electric vehicle. However, motor 1 may also be used for any other purpose.

The motor 1 is an inner rotor type, with the stator 21 surrounding the radial outside of the rotor 30. The radial outside of the stator 21 is fixed to the motor housing 10.

The rotor 30 is disposed radially inside the stator 21. The rotor 30 includes a rotor core 32 and a rotor shaft 34. The rotor core 32 is fixed to the radial outside of the rotor shaft 34 and rotates integrally with the rotor shaft 34. The rotor shaft 34 is rotatably supported in the motor housing 10 via bearings 14a and 14b. The rotor shaft 34 defines the rotating shaft 12 of the motor 1.

The rotor core 32 is formed, for example, from laminated steel plates of a circular magnetic material. Permanent magnets 321 are inserted into the magnet holes 320 of the rotor core 32. The number and arrangement of the permanent magnets 321 are optional. In a modified example, the rotor core 32 may be formed from a green compact in which magnetic powder is compressed and solidified.

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

As shown in FIG. 1, 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 may function as an oil passage. For example, as shown by arrow R1 in FIG. 1, oil is supplied to the hollow portion 34A from one axial end, and the oil flows along the radially inner surface of the rotor shaft 34, thereby cooling the rotor core 32 from the radially inner side. In addition, the oil flowing along the radially inner surface of the rotor shaft 34 may be ejected radially outward through oil holes 341, 342 formed at both ends of the rotor shaft 34 (arrows R5, R6), and may be used to cool the coil ends 220A, 220B.

Note that while FIG. 1 shows a motor 1 with a specific structure, the structure of the motor 1 is arbitrary as long as it has a stator coil 24 (described below) joined by welding. Thus, for example, the rotor shaft 34 may not have a hollow portion 34A, or may have a hollow portion with an inner diameter significantly smaller than that of the hollow portion 34A. Also, while FIG. 1 shows a specific cooling method, the cooling method of the motor 1 is arbitrary. Thus, for example, an oil introduction pipe inserted into the hollow portion 34A may be provided, or oil may be dripped from an oil passage in the motor housing 10 from the radial outside toward the coil ends 220A, 220B.

In addition, while FIG. 1 shows an inner rotor type motor 1 in which the rotor 30 is disposed inside the stator 21, the present invention may be applied to other types of motors. For example, the present invention may be applied to an outer rotor type motor in which the rotor 30 is disposed concentrically outside the stator 21, or a dual rotor type motor in which the rotor 30 is disposed both outside and inside the stator 21.

Next, the configuration of the stator 21 will be explained in detail with reference to Figure 2 onwards.

Figure 2 is a plan view of the stator core 22 in a standalone state. Figure 3 is a schematic diagram of a pair of coil pieces 52 assembled to the stator core 22. Figure 3 shows the relationship between the pair of coil pieces 52 and the slots 220 with the radially inner side of the stator core 22 unfolded. Also, in Figure 3, the stator core 22 is shown by a dotted line, and some of the slots 220 are not shown.

The stator 21 includes a stator core 22 and a stator coil 24 (see Figure 1).

The stator core 22 is made of, for example, a circular ring-shaped laminated steel plate of a magnetic material, but in a modified example, the stator core 22 may be formed of a green compact in which magnetic powder is compressed and solidified. The stator core 22 may be formed of a split core that is split in the circumferential direction, or may not be split in the circumferential direction. A plurality of slots 220 around which the stator coil 24 is wound are formed on the radially inner side of the stator core 22. Specifically, as shown in FIG. 2, the stator core 22 includes a circular back yoke 22A and a plurality of teeth 22B that extend radially inward from the back yoke 22A, and the slots 220 are formed between the plurality of teeth 22B in the circumferential direction. The number of slots 220 is arbitrary, but in this embodiment, as an example, there are 48 slots 220.

The stator coil 24 includes a U-phase coil, a V-phase coil, and a W-phase coil (hereinafter, when U, V, and W are not distinguished, they will be referred to as "phase coils"). The base end of each phase coil is connected to an input terminal (not shown), and the end of each phase coil is connected to the end of the other phase coil to form the neutral point of the motor 1. In other words, the stator coil 24 is star-connected. However, the connection mode of the stator coil 24 may be changed as appropriate depending on the required motor characteristics, etc. For example, the stator coil 24 may be delta-connected instead of star-connected.

Each phase coil is formed by joining multiple coil pieces 52. FIG. 4 is a schematic front view of one coil piece 52. The coil pieces 52 are in the form of segment coils in which the phase coil is divided into units that are easy to assemble (for example, units that can be inserted into two slots 220). The coil pieces 52 are formed by coating a linear conductor (rectangular wire) 60 with a rectangular cross section with an insulating coating 62. In this embodiment, the linear conductor 60 is formed from copper, as an example. However, in a modified example, the linear conductor 60 may be formed from another conductive material such as iron.

Before being assembled to the stator core 22, the coil pieces 52 may be formed into a generally U-shape having a pair of straight portions 50 and a connecting portion 54 connecting the pair of straight portions 50. When assembling the coil pieces 52 to the stator core 22, the pair of straight portions 50 are each inserted into a slot 220 (see FIG. 3). As a result, the connecting portion 54 extends circumferentially so as to straddle a plurality of teeth 22B (and therefore a plurality of slots 220) at the other axial end side of the stator core 22, as shown in FIG. 3. The number of slots 220 that the connecting portion 54 straddles is arbitrary, but is three in FIG. 3. After being inserted into the slot 220, the straight portions 50 are bent circumferentially midway, as shown by the two-dot chain line in FIG. 4. As a result, the straight portion 50 becomes a leg portion 56 that extends axially within the slot 220, and a bridge portion 58 that extends circumferentially at one axial end of the stator core 22.

In FIG. 4, the pair of straight portions 50 are bent in a direction away from each other, but this is not limited thereto. For example, the pair of straight portions 50 may be bent in a direction toward each other. The stator coil 24 may also have a neutral point coil piece for connecting the ends of the three phase coils to form a neutral point.

In one slot 220, multiple legs 56 of the coil piece 52 shown in FIG. 4 are inserted side by side in the radial direction. Therefore, multiple circumferentially extending bridge portions 58 are lined up in the radial direction at one axial end of the stator core 22. As shown in FIG. 3, the bridge portion 58 of one coil piece 52 protruding from one slot 220 and extending to a first circumferential side (e.g., clockwise) is joined to the bridge portion 58 of another coil piece 52 protruding from another slot 220 and extending to a second circumferential side (e.g., counterclockwise).

In this embodiment, as an example, six coil pieces 52 are assembled in one slot 220. Hereinafter, they are also referred to as the first turn, second turn, and third turn, starting from the radially outermost coil piece 52. In this case, the first turn coil piece 52 and the second turn coil piece 52 have their tip portions 40 joined together by a joining process described below, the third turn coil piece 52 and the fourth turn coil piece 52 have their tip portions 40 joined together by a joining process described below, and the fifth turn coil piece 52 and the sixth turn coil piece 52 have their tip portions 40 joined together by a joining process described below.

As described above, the coil pieces 52 are covered with an insulating coating 62, but the insulating coating 62 is removed only from the tip portion 40. This is to ensure electrical connection with the other coil pieces 52 at the tip portion 40.

FIG. 5 is a diagram showing the tip 40 of the coil pieces 52 joined together and its vicinity. FIG. 5 also shows a schematic representation of the circumferential range D1 of the area 90 to be welded. FIG. 6 is a schematic representation of the area 90 to be welded as viewed from the irradiation side. FIG. 7 is a cross-sectional view taken along line A-A in FIG. 5, which passes through the area 90 to be welded. FIG. 7 also shows a schematic representation of the range of the molten pool formed during welding, as indicated by the hatched area 1102. FIG. 8 is a diagram showing the relationship between the laser wavelength and the laser absorptance of various individual materials.

In Figure 5, the Z direction along the axial direction is defined. In the following explanation, for the sake of explanation, the Z1 side in the Z direction (i.e. the side irradiated with the laser beam) is referred to as the "upper side" and the Z2 side in the Z direction is referred to as the "lower side". Also, in Figure 6, the X direction along the radial direction and the X1 side and X2 side along the X direction are defined.

When joining the tip portions 40 of the coil pieces 52, one coil piece 52 and another coil piece 52 are abutted in the radial direction while their respective tip portions 40 overlap in the view (diametrically viewed) shown in FIG. 5. In the following description, for the sake of distinction, the structure relating to one coil piece 52 may be designated by adding the letter "A" after the reference numeral, such as tip portion 40A, and the structure relating to the other coil piece 52 may be designated by adding the letter "B" after the reference numeral, such as tip portion 40B. In other embodiments, the tip portions 40 may cross each other in an X-shape. In this case, each tip portion 40 may be cut so that no protruding portion is formed on the upper side of the X-shape.

In this case, the area to be welded 90 extends linearly along the abutment surface 401, as shown by range D1 in Fig. 6. That is, the area to be welded 90 extends linearly over range D1 in the Y direction with a width of range D2 in the X direction as shown in Fig. 7, as viewed from the side irradiated with the laser beam (see arrow W in Fig. 5). Note that in this embodiment, the abutment surface 401 has a rectangular shape surrounded by axial outer end faces 42A, 42B and extension direction end faces 44A, 44B when viewed in the radial direction, but may have other shapes.

In this embodiment, the welding target area 90 is set along the upper side (the exposed upper side of the four sides of the rectangle) formed by the axially outer end faces 42A, 42B of both tip portions 40 in the view (viewed radially) shown in FIG. 5. Note that in this embodiment, the welding target area 90 extends horizontally, but in the view (viewed radially) shown in FIG. 5, it may extend in an upwardly convex C-shape or in other shapes depending on other shapes that the tip portion 40 can take. Also, in the examples shown in FIGS. 5 and 6, the axially outer end faces 42A, 42B extend in the XY plane, but may be inclined relative to the XY plane.

In this embodiment, welding is used as a joining method when joining the tip portions 40 of the coil pieces 52. In this embodiment, the welding method is not arc welding, such as TIG welding, but laser welding using a laser beam source as a heat source. By using laser welding instead of TIG welding, the axial length of the coil ends 220A, 220B can be reduced. That is, in the case of TIG welding, it is necessary to bend the tips of the coil pieces to be abutted axially outward and extend them in the axial direction, whereas in the case of laser welding, such bending is not necessary, and as shown in FIG. 5, welding can be achieved in a state in which the tip portions 40 of the coil pieces 52 to be abutted extend in the circumferential direction. This allows the axial length of the coil ends 220A, 220B to be reduced compared to when the tip portions 40 of the coil pieces 52 to be abutted are bent axially outward and extend in the axial direction.

In laser welding, as shown in FIG. 5, a welding laser beam is applied to the welding target area 90 of the two abutted tip portions 40. The irradiation direction (propagation direction) of the laser beam is approximately parallel to the axial direction, and is directed from the axial outside toward the axially outer end faces 42 (including the exposed sides of the abutment faces 401) of the two abutted tip portions 40. Laser welding allows localized heating, so that only the tip portions 40 and their vicinity can be heated, effectively reducing damage (carbonization) of the insulating coating 62. As a result, multiple coil pieces 52 can be electrically connected while maintaining appropriate insulation performance.

Figure 8 is a diagram showing the relationship between the laser wavelength and the laser absorptance (hereinafter simply referred to as "absorption rate") for individual materials. In Figure 8, the horizontal axis represents the wavelength λ and the vertical axis represents the absorptance, and the characteristics of individual materials, copper (Cu), aluminum (Al), silver (Ag), nickel (Ni), and iron (Fe), are shown.

Incidentally, the infrared laser (with a wavelength of 1064 nm) commonly used in laser welding has a low absorption rate of about 10% for copper, the material of the linear conductor 60 of the coil pieces 52, as shown by the black circle at the intersection with the dotted line of λ2 = 1.06 μm in Figure 8. In other words, in the case of an infrared laser, most of the laser beam is reflected by the coil pieces 52 and not absorbed. For this reason, a relatively large amount of heat input is required to obtain the required joint area between the coil pieces 52 to be joined, which can cause significant thermal effects and unstable welding.

In consideration of this, in this embodiment, a green laser is used instead of an infrared laser. Note that the concept of a green laser includes not only a laser with a wavelength of 532 nm, i.e., an SHG (Second Harmonic Generation) laser, but also lasers with wavelengths close to 532 nm. Note that in a modified example, a laser with a wavelength of 0.6 μm or less that does not belong to the category of green lasers may be used. The wavelength of a green laser can be obtained by converting the fundamental wavelength generated by, for example, a YAG laser or YVO4 laser through an oxide single crystal (for example, LBO: lithium triborate).

In the case of a green laser, as shown by the black circle at the intersection with the dotted line of λ1 = 0.532 μm in Figure 8, the absorption rate is high at about 50% for copper, which is the material of the linear conductor 60 of the coil piece 52. Therefore, according to this embodiment, it is possible to ensure the necessary joint area between the coil pieces 52 with a smaller amount of heat input compared to when an infrared laser is used.

The characteristic that the absorption rate is higher with a green laser than with an infrared laser is particularly evident in the case of copper, as shown in FIG. 8, but this can also be seen in many other metal materials, not just copper. Therefore, welding with a green laser can be achieved even if the material of the linear conductor 60 of the coil piece 52 is something other than copper.

Figure 9 is an explanatory diagram of how the absorption rate changes during welding. In Figure 9, the horizontal axis represents the laser power density and the vertical axis represents the laser absorption rate of copper, and the characteristics 100G for a green laser and 100R for an infrared laser are shown.

Figure 9 shows points P100 and P200 at which copper starts to melt for the green laser and the infrared laser, as well as point P300 at which a keyhole is formed. As shown by points P100 and P200 in Figure 9, it can be seen that the green laser can start melting copper at a lower laser power density than the infrared laser. Also, due to the difference in absorptivity described above, it can be seen that the difference between the absorptivity at point P300 at which a keyhole is formed and the absorptivity at the start of irradiation (i.e., the absorptivity when the laser power density is 0) is smaller for the green laser than for the infrared laser. Specifically, in the case of the infrared laser, the change in absorptivity during welding is about 80%, while in the case of the green laser, the change in absorptivity during welding is about 40%, which is about half.

As such, with infrared lasers, the change (drop) in absorption rate during welding is relatively large at approximately 80%, making the keyhole unstable and prone to variations in weld depth and width, and disturbance of the molten pool (e.g., spatter, etc.). In contrast, with green lasers, the change (drop) in absorption rate during welding is relatively small at approximately 40%, making the keyhole less likely to become unstable, and also less likely to cause variations in weld depth and width, and disturbance of the molten pool (e.g., spatter, etc.). Spatter refers to metal particles that fly off when a laser or other device is irradiated.

In the case of infrared lasers, since the absorption rate is low as described above, it is common to make the beam diameter relatively small (for example, φ0.075 mm) to compensate for the low absorption rate. This also causes the keyhole to become unstable. Note that FIG. 10B is an image diagram of a keyhole when an infrared laser is used, where 1100 indicates a weld bead, 1102 indicates a molten pool, and 1104 indicates a keyhole. The arrow R1116 also shows a typical state of gas escape. The arrow R110 also shows a typical state in which the irradiation position of the infrared laser is moved due to the small beam diameter. In this way, in the case of infrared lasers, since the absorption rate is low as described above and it is difficult to make the beam diameter relatively large, a relatively long movement trajectory of the irradiation position including meandering (continuous irradiation time) tends to be required to obtain the required fusion width.

On the other hand, in the case of a green laser, since the absorption rate is relatively high as described above, it is possible to make the beam diameter relatively large (for example, φ0.15 mm or more), and the keyhole can be made large and stabilized. This improves gas escape and effectively reduces the occurrence of spatters, etc. FIG. 10A is an image of a keyhole when a green laser is used, and the meaning of the symbols is as described above with reference to FIG. 10B. In the case of a green laser, it is easy to understand from FIG. 10A how the keyhole is stabilized and gas escape is improved due to the expansion of the beam diameter. In addition, in the case of a green laser, in contrast to the case of an infrared laser, since the absorption rate is relatively high as described above and the beam diameter can be made relatively large, the movement trajectory (irradiation time) of the irradiation position required to obtain the required fusion width (see the radial range D2 of the welding target part 90 shown in FIG. 7) can be made relatively short (shortened) (described later).

Below, we will disclose a manufacturing method that uses such a green laser to efficiently achieve high-quality welding.

11 is an explanatory diagram of the irradiation mode of the green laser according to the manufacturing method of this embodiment. FIG. 11A is an explanatory diagram of the scanning of the laser beam, and is an explanatory diagram of the emission center Ct0 of the laser beam. FIG. 11B is an explanatory diagram of the scanning of the laser beam, and is an explanatory diagram of the movement mode of the laser beam. FIG. 12 is an explanatory diagram of the irradiation mode in the case of an infrared laser according to a comparative example. FIGS. 11 and 12 are schematic diagrams viewed in the laser irradiation direction, and the laser irradiation area (or the area to be irradiated) at the welding target part 90 at a certain point during welding is shown as a hatched area. In FIGS. 11 and 12, the circles 110 and 110' of the laser beam indicate the irradiation range at a certain point during welding, and the beam diameters φA and φA' are also shown. In addition, in FIGS. 11 and 12, the line Lref represents the abutment surface 401 (the upper side of the abutment surface 401).

As shown diagrammatically in FIG. 11, the manufacturing method of this embodiment involves scanning the laser beam in a loop (see arrow R112) while moving it in the welding direction (travel direction). Note that the travel direction is along the upper edge of the contact surface 401 described above (i.e., a direction parallel to the upper edge), but may be slightly inclined relative to that edge due to errors, etc. Note that, hereinafter, "on the contact surface 401" refers to the portion that forms the upper edge of the contact surface 401 (see line Lref).

The term "loop-shaped" is a concept including any shape that can form a loop, such as a circle, an ellipse, and does not need to be completely closed, and may be a spirally continuous shape. In this embodiment, as an example, the loop shape is a shape in which circles are spirally continuous. Such a loop shape can be realized, for example, by using a laser beam emitted (scanned) from the emission part in a manner that draws a circular trajectory a certain number of times per unit time. In FIG. 11A, the circular trajectory (scanning) of the laser beam when the laser beam (emission part) is not moved is shown in the hatched region R11. When the laser beam is not moved, the circle 110 rotates around the emission center Ct0 (= center of the circular trajectory), and the circle 110 draws a circular orbit around the emission center Ct0 (= center of the circular trajectory). In this case, the loop-shaped trajectory of the circle 110 can be realized by moving the emission center Ct0 (= center of the circular trajectory) in a straight line. At this time, the emission center Ct0 of the laser beam is aligned with the abutment surface 401, thereby realizing a traveling direction along the upper side of the abutment surface 401. Note that in Figures 11 and 11B, the dashed dotted line TRct represents the trajectory (arrow indicates the traveling direction) of the center Ct1 of the laser beam when such a movement of the laser beam (linear movement along the upper side of the abutment surface 401) is performed.

The diameter of the circle associated with the loop (hereinafter also referred to as the "wobbling diameter φB") is arbitrary, but a preferred range will be described later. For example, the wobbling diameter φB may be larger than the beam diameter φA of the laser beam.

In this embodiment, the amount of movement in the direction of travel per one loop scan (hereinafter also referred to as "wobbling pitch pt") is equal to or less than the beam diameter φA of the laser beam. Note that "per one loop scan" refers to one revolution from one phase of the circle to the same phase. This allows the irradiation range for one loop and the irradiation range for the next loop to be set continuously along the welding direction on the contact surface 401, as shown in FIG. 11. For example, if the wobbling pitch pt is 1/2 the beam diameter φA of the laser beam, the irradiation range for one loop and the irradiation range for the next loop will overlap by 1/2 the beam diameter φA on the contact surface 401.

In this case, the molten pool formed in the area to be welded 90 can be moved in the welding direction on the contact surface 401 while maintaining the molten pool. In other words, according to this embodiment, the molten pool can be moved in the welding direction on the contact surface 401 by the wobbling pitch pt for each loop while maintaining the molten pool.

The wobbling pitch pt is constant for one welding target portion 90, but may be variable. The size of the beam diameter φA may be the size at the emission end. In this case, the beam diameter φA represents a Gaussian beam diameter (1/e ² ), but in the case of an elliptical beam, the length of the major axis or minor axis of the elliptical spot may be substituted.

In this embodiment, the beam diameter φA is preferably φ0.1 mm or more, and more preferably φ0.15 mm or more. Here, by increasing the beam diameter φA, the wobbling pitch pt can also be increased under the condition that the laser beam has a beam diameter φA or less. As a result, as described above with reference to FIG. 10A and explained below in comparison with the comparative example, the movement trajectory (irradiation time) required to obtain the required fusion width can be made relatively short, and efficient welding can be achieved.

In this embodiment, the laser beam is continuously irradiated with a laser output of 3.0 kW or more for multiple loop scans. For example, the laser beam may be continuously irradiated to the entire area 90 to be welded. This makes it easier to maintain the molten pool and shortens the welding time, although the output may be lower than with irradiation using pulsed oscillation.

In the comparative example shown in FIG. 12, the beam diameter φA' is relatively small, for example φ0.08 mm, due to the use of an infrared laser as described above. Also, the wobbling pitch pt' is 0.1 mm. In this case, as shown in FIG. 12, the irradiation range for each loop is discontinuous along the welding direction on the contact surface 401.

13 is a cross-sectional view taken along line B-B in FIG. 11 for this embodiment (cross-sectional view taken along the welding direction on the abutment surface 401), and FIG. 14 is a cross-sectional view taken along line C-C in FIG. 12 for the comparative example. A schematic diagram showing the state of the joint surface when cut at the abutment surface 401. In FIG. 13 and FIG. 14, the joint surface is shown as a schematic diagram by hatched areas SC13 and SC14. The joint surface refers to the surface of the abutment surface 401 that is joined due to welding. Also, FIG. 15 and FIG. 16 show images of a part of the joint surface (the lower end of the joint surface) when cut at the abutment surface 401, FIG. 15 shows an image according to this embodiment, and FIG. 16 shows an image according to the comparative example. The conditions of this embodiment according to FIG. 15 were, for example, beam diameter φA = 0.27 mm, wobbling diameter φB = 0.6 mm, and wobbling pitch pt = 0.2 mm. In addition, the conditions for the comparative example shown in FIG. 14 were beam diameter φA' = 0.08 mm, wobbling diameter φB' = 0.7 mm, and wobbling pitch pt' = 0.1 mm.

In the comparative example, as described above, the irradiation ranges for each loop are discontinuous along the welding direction on the abutting surface 401, so the height H1' of the lower end of the joint surface (welding depth H1') varies greatly along the welding direction, as shown in Figures 14 and 16. That is, between the irradiation ranges for each loop, there are areas where the height H1' suddenly becomes small (the welding depth suddenly becomes shallow). As a result, there is an inconvenience that the joint area (the area of the joint surface) tends to become insufficient. To address this, it is possible to further reduce the wobbling pitch pt' so that the irradiation ranges for each loop overlap, but such a measure is likely to cause other inconveniences, such as excessive welding time or excessive heat input.

In contrast, according to this embodiment, as described above, the irradiation ranges of each loop are continuous along the welding direction on the contact surface 401. This reduces or prevents the inconveniences that occur in the comparative example described above. That is, the height H1 of the lower end of the joint surface (welding depth H1) is approximately constant without fluctuating significantly along the welding direction, as shown in Figures 13 and 15. In addition, since the beam diameter φA is relatively large, even if the wobbling pitch pt is increased, the irradiation ranges of each loop can be continuous, and the welding time and heat input can be reduced (efficient). In this regard, in this embodiment, the wobbling pitch pt may be 1/4 or more of the beam diameter φA of the laser beam under conditions of the beam diameter φA or less, more preferably 1/3 or more of the beam diameter φA, and most preferably 1/2 or more.

FIG. 17 is an explanatory diagram of robustness against deviations in the radial irradiation position. In FIG. 17, the horizontal axis represents the laser radial deviation amount, and the vertical axis represents the bonding area, and characteristic curves 1701, 1702, and 1703 for three different methods are shown. The laser radial deviation amount represents the radial position of the center of the irradiation area when the abutment surface 401 is set to "0", and negative values represent the radial inward position.

Characteristic curve 1701 shows the case of this embodiment, characteristic curve 1702 shows the case of the first comparative example, and characteristic curve 1703 shows the case of the second comparative example. The first comparative example corresponds to the comparative example described with reference to FIG. 12 etc., and had a beam diameter φA' = 0.08 mm and a wobbling diameter φB' = 0.7 mm. The second comparative example uses a green laser, but the scanning method is linear scanning, unlike this embodiment. That is, in the second comparative example, the green laser scans linearly along the welding direction on the abutment surface 401. The condition of the second comparative example was a beam diameter = 0.293 mm. The condition of this embodiment was a beam diameter φA = 0.27 mm and a wobbling diameter φB = 0.6 mm.

As shown in Fig. 17, the second comparative example has the lowest robustness against deviation of the irradiation position in the radial direction, and for example, when the irradiation position is shifted 0.2 mm inward in the radial direction, the bonding area falls to ³ mm2 or less. Note that when the deviation amount = 0, the bonding area is significantly larger than 4 ^mm2 . In contrast, the present embodiment and the first comparative example have relatively high robustness against deviation of the irradiation position in the radial direction, and even if the irradiation position is shifted 0.2 mm inward or outward in the radial direction, the bonding area does not fall to ^{3 mm2} or less. In the case of the present embodiment, it can be seen that in the region where the irradiation position is shifted 0.4 mm or more inward or outward in the radial direction, the robustness is higher than that of the first comparative example.

Next, with reference to Figures 18 to 20, the preferred range of the wobbling diameter φB in this embodiment will be explained based on test results.

FIG. 18 is a table showing the multiple conditions (conditions 1 to 3) under which the test was conducted. FIG. 19 is a graph showing the relationship between the wobbling diameter φB and the number of spatters for each condition, and FIG. 20 is a graph showing the relationship between the wobbling diameter φB and the joint area and the weld depth. In FIG. 20, graph 201 relates to the weld area, and graph 202 relates to the weld depth. In FIGS. 19 and 20, plot p1 relates to condition 1, plot p2 relates to condition 2, and plot p3 relates to condition 3.

As shown in FIG. 18, the laser scanning speed is adjusted so that the heat input is the same under conditions 1 to 3. In FIG. 18, the laser scanning speed corresponds to the length of the laser beam irradiation path per unit time (the length along the loop-shaped path). The welding speed is the movement distance of the laser beam irradiation position per unit time, and is a value obtained by, for example, dividing the movement distance of the laser beam irradiation position over a certain time period (the movement distance along the welding direction on the contact surface 401) by the same time period. The conditions common to each condition (fixed conditions) are that a green laser is used, that the beam diameter φA is 0.273 mm, and that the output distribution density is a Gaussian distribution.

As shown in Figure 19, the larger the wobbling diameter φB, the more stable the molten pool becomes and the less spatter there is. Note that, similar to the principle described above with reference to Figures 10A and 10B, if the wobbling diameter φB is relatively small, the keyhole becomes unstable and disturbances in the molten pool (e.g., spatters) are likely to occur.

As shown in Figure 20, when the heat input is the same, the smaller the wobbling diameter φB, the greater the weld depth (penetration depth). Similarly, when the heat input is the same, the smaller the wobbling diameter φB, the greater the joint area.

Thus, a larger wobbling diameter φB is advantageous from the viewpoint of reducing the number of spatters, but a smaller wobbling diameter φB is advantageous from the viewpoint of increasing the welding depth and the joining area. Therefore, taking these trade-offs into consideration, a preferred range of the wobbling diameter φB may be adapted. For example, when the wobbling diameter φB is less than φ0.4, the number of spatters may increase sharply as the wobbling diameter φB decreases, so the wobbling diameter φB may preferably be φ0.4 mm or more. Furthermore, when the wobbling diameter φB exceeds φ0.75 mm, the joining area becomes relatively small, so the wobbling diameter φB may preferably be φ0.75 mm or less. In this case, the wobbling diameter φB is between 1.46 and 2.74 times the beam diameter φA of the laser beam. Therefore, the wobbling diameter φB may be adapted to be between 1.4 and 2.8 times the beam diameter φA of the laser beam.

Next, the preferred welding speed change profile of this embodiment will be described with reference to Figures 21 to 25.

21 is a diagram showing a preferred welding speed for each Y-direction position (a profile of changes in the welding speed according to the Y-direction position), with the horizontal axis representing the Y-direction position along the Y-direction and the vertical axis representing the welding speed. The positive side of the horizontal axis corresponds to the Y2 side described above, and in this example, the Y1 side of the welding target portion 90 (see FIG. 6) is set as the welding start position, and the laser beam emission center Ct0 (see FIG. 11A) is moved from the Y1 side to the Y2 side during welding. In addition to the profile of changes in the welding speed, FIG. 21 also shows a preferred laser output for each Y-direction position (a profile of changes in the laser output according to the Y-direction position) in the form of a waveform R21. In FIG. 21, the Y-direction position P1 indicates the irradiation start position, and the Y-direction position P5 indicates the irradiation end position. The section from the Y-direction position P1 to the Y-direction position P5 corresponds to the range D1 described above with reference to FIG. 5 and FIG. 6.

In this embodiment, the welding speed is lowest at the start of irradiation and is increased thereafter. In the example shown in FIG. 21, the welding speed = V1 in the section from Y-direction position P1 to Y-direction position P2, the welding speed = V2 in the section from Y-direction position P2 to Y-direction position P3, and the welding speed = V3 in the section from Y-direction position P3 to Y-direction position P5. And, V1 < V2 < V3.

Welding speed V1 is preferably significantly smaller than 80 mm/s, for example in the range of 5-35 mm/s, and may be approximately 20 mm/s. Welding speed V3 is preferably 80 mm/s or greater, for example approximately 100 mm/s. In this case, welding speed V2 may be the intermediate value between welding speed V1 and welding speed V3 (= (V1 + V3) / 2).

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

The section from Y-direction position P1 to Y-direction position P2 is preferably less than 20% of range D1, and preferably 10% or less. The section from Y-direction position P2 to Y-direction position P3 may be shorter than the section from Y-direction position P1 to Y-direction position P2.

The laser output is preferably highest in the section from Y-direction position P3 to Y-direction position P4. For example, as shown in FIG. 21, the laser output may gradually increase from Y-direction position P1 and be maintained at a constant value in the section from Y-direction position P3 to Y-direction position P4. The laser output may then be reduced toward 0 (output off) using the section from Y-direction position P4 to Y-direction position P5. In this case, the laser output is maximized in the section from Y-direction position P3 to Y-direction position P4 within the section of welding speed V3, and the main portion of the welding target area 90 can be welded with high quality in a short time.

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

22 and 23 each show two circles 110 (see FIG. 11) related to the laser beam on the line Lref (contact surface 401) shown in FIG. 11. The distance in the Y direction between these two circles 110 corresponds to the wobbling pitch pt. Here, it is assumed that the laser scanning speed is constant over the entire section from the Y direction position P1 to the Y direction position P5. As can be seen by comparing FIG. 22 and FIG. 23, when the welding speed increases, the wobbling pitch pt increases accordingly. On the other hand, when the welding speed increases, the lap ratio (area of overlapping part/area of circle x 100) of the two circles 110 decreases accordingly. The welding speed V3 may be set so that the lap ratio (area of overlapping part/area of circle x 100) of the two circles 110 is preferably 15% or more and 20% or less.

Here, we will explain the effect of the welding speed change profile of this embodiment described above with reference to Figures 21 etc., while also referring to Figures 24A to 25B.

24A and 24B are explanatory diagrams of the first comparative example, and 24B is an explanatory diagram of the problem associated with the first comparative example. 25A and 25B are explanatory diagrams of the second comparative example, and 25B is an explanatory diagram of the problem associated with the second comparative example. Both Figs. 24A and 25A are diagrams showing preferred welding speeds for each Y direction position (profile of changes in welding speed according to Y direction position) with the horizontal axis representing Y direction position along the Y direction and the vertical axis representing welding speed, similar to Fig. 21 described above for this embodiment. Both Figs. 24B and 25B are diagrams showing schematic views of the welding target location 90' or 90" as viewed from the irradiation side, similar to Fig. 6 described above for this embodiment.

In the first comparative example, as shown in FIG. 24A, the welding speed is constant at a relatively high speed (= welding speed V3) throughout the entire section from Y-direction position P1 to Y-direction position P5.

In this case, the laser beam moves in the Y direction at a relatively high speed before the molten pool becomes large enough at the welding start position (Y direction position P1), making it easier for the laser beam to irradiate the outside of the molten pool. For example, when the laser beam moves from the Y1 side to the Y2 side, the laser beam is easier to irradiate the outside of the molten pool on the Y2 side. In this case, as shown diagrammatically in FIG. 24B, defects are more 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 (solid) of the irradiated area at the tip 40 of the coil piece 52 is blown away, making it easier for a cavity (represented by the unhatched area in FIG. 24B) to occur.

In contrast, according to this embodiment, as described above, a relatively small welding speed V1 is used in the section from Y-direction position P1 to Y-direction position P2. This makes it difficult for the laser beam to be irradiated to the outside of the molten pool before the molten pool becomes sufficiently large. As a result, the inconveniences that occur in the first comparative example can be reduced.

In this embodiment, the length of the section from Y-direction position P1 to Y-direction position P2 is preferably set so that in this section, the circle 110 is formed two or more times at the corresponding wobbling pitch pt (see FIG. 23), and more preferably, is set so that in this section, the circle 110 is formed 7 to 13 times at the corresponding wobbling pitch pt. This allows the molten pool to be properly formed before moving to the section after Y-direction position P2 (for example, the section related to welding speed V3).

In the second comparative example, as shown in FIG. 25A, the welding speed is constant at a relatively low speed (= welding speed V1) over the entire section from Y-direction position P1 to Y-direction position P5. In this case, as shown in FIG. 24B, the fusion width w2 (see the radial range D2 of the welding target portion 90 shown in FIG. 7) is likely to be larger than the desired value, as shown in FIG. 25B. For example, when the laser beam is moved from the Y1 side to the Y2 side, the fusion width w2 becomes larger as it moves toward the Y2 side (the same applies to the welding depth H1 shown in FIG. 13). As a result, not only the welding quality is deteriorated, but also inconveniences (such as damage to the jig for positioning the tip portion 40 of the coil piece 52, etc.) may occur due to the excessive fusion width w2 and welding depth H1. In addition, there is also the inconvenience that the welding time (time required for welding) per welding target portion 90 becomes relatively long.

In contrast, according to this embodiment, as described above, a relatively slow welding speed V1 is used in the section from Y-direction position P1 to Y-direction position P2, but a higher welding speed (particularly welding speed V3) is used in the subsequent section. This makes it possible to make the fusion width w2 and the welding depth H1 approximately constant throughout the entire welding area 90 (i.e., throughout the entire section from Y-direction position P1 to Y-direction position P5). In addition, the welding time (time required for welding) per welding area 90 can be made relatively short. In other words, the inconveniences that arise in the second comparative example can be reduced.

In the welding speed change profile of this embodiment described above with reference to FIG. 21 etc., three types of welding speeds V1, V2, and V3 are used, but welding speed V1 or welding speed V3 may be used instead of welding speed V2. Alternatively, four or more types of welding speeds may be used.

Next, referring to FIG. 26, the manufacturing method of this embodiment and the manufacturing apparatus 300 will be outlined.

FIG. 26 is a flow chart showing the outline of the manufacturing method for the stator 21 of the motor 1. FIG. 27 is a system configuration diagram of the manufacturing device 300.

First, this manufacturing method includes an assembly process (step S150) in which the coil pieces 52 are attached to the stator core 22. In addition, after the assembly process, this manufacturing method includes a joining process (step S152) in which the tip ends 40 of the coil pieces 52 are joined together by laser welding. The method of joining the tip ends 40 of the coil pieces 52 together by laser welding is as described above.

In this case, the joining process includes a setting process (step S1521) in which the tip portions 40 of each pair of coil pieces 52 are set so as to abut against each other in the radial direction, as described above. In the setting process, the state in which the tip portions 40 of each pair of coil pieces 52 are abutted against each other in the radial direction may be maintained using a jig 302.

The joining process includes an irradiation process (step S1522) in which, after the setting process, a laser beam is irradiated from the irradiation device 304 to the welding target points 90 as described above. The manner of irradiation of the laser beam from the irradiation device 304 is as described above, and may be controlled by the control device 301. The setting process and the irradiation process may be performed as a set for one or more predetermined number of welding target points 90, or may be performed collectively for all welding target points 90 related to one stator 21. The present manufacturing method may end by completing the stator 21 by appropriately performing various necessary processes after the joining process.

Although each embodiment has been described in detail above, it is not limited to a specific embodiment, and various modifications and changes are possible within the scope of the claims. It is also possible to combine all or some of the components of the above-mentioned embodiments.

1: motor (rotating electric machine), 24: stator coil, 52: coil piece, 40: tip, 401: contact surface, 110: circle related to laser beam, 300: manufacturing device, 302: jig, 304: irradiation device

Claims (8)

1. a step of bringing a tip end portion of one coil piece and a tip end portion of another coil piece into contact with each other to form a stator coil for a rotating electric machine;
   and an irradiation step of irradiating a laser beam having a wavelength of 0.6 μm or less toward one side of an exposed side of the contact surface between the tip portions,
   the irradiation step includes scanning the laser beam in a loop while moving the laser beam in a traveling direction including a directional component in which the one side extends,
   a movement amount in the advance direction per one loop-shaped scan is equal to or less than a beam diameter of the laser beam.
2. The method for manufacturing a stator for a rotating electric machine according to claim 1, wherein in the irradiation process, the laser beam is continuously irradiated with a laser output of 3.0 kW or more for multiple revolutions of the loop-shaped scan.
3. The method for manufacturing a stator for a rotating electric machine according to claim 1, wherein the diameter or length in the major axis direction of the loop is between 1.4 and 2.8 times the beam diameter of the laser beam.
4. The method for manufacturing a stator for a rotating electric 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 electric machine according to any one of claims 1 to 4, wherein the irradiation process includes setting the amount of movement in the direction of travel per one revolution of the loop-shaped scan to a first amount of movement at the start of irradiation, and then changing it to a second amount of movement that is greater than the first amount of movement.
6. The method for manufacturing a stator for a rotating electric machine according to claim 5, wherein the irradiation step includes increasing the laser output of the laser beam in the second movement range compared to the first movement range.
7. The method for manufacturing a stator for a rotating electric machine according to claim 6, wherein the irradiation step includes drawing at least two circles in the first movement distance section using the laser beam emitted in a manner that draws a circle a fixed number of times per unit time.
8. a jig for bringing tip portions of one coil piece and another coil piece into contact with each other to form a stator coil for a rotating electric machine;
   an irradiation device that irradiates a laser beam having a wavelength of 0.6 μm or less toward one side of an exposed side of the contact surface between the tip portions,
   the irradiation device scans the laser beam in a loop while moving the laser beam in a traveling direction including a directional component in which the one side extends,
   a movement amount in the advancement direction per one loop-shaped scan is equal to or less than a beam diameter of the laser beam.