Laser welding method and method for manufacturing rotating electrical machine

Abstract

A laser welding method according to an embodiment of the present invention comprises: a step for alternately irradiating an end of a first linear member and an end of a second linear member adjacent to the first linear member with laser light to form a first weld pool spanning the end of the first linear member and the end of the second linear member; and a step for irradiating the first molten pool with the laser light. In the step of irradiating the first molten pool with the laser light, the center side of the first molten pool is set as the starting point of irradiation of the laser light, and the irradiation position of the laser light gradually moves away from the starting point or staged away from the starting point as the laser light rotates around the starting point.

Description

Technical Field

[0001] The embodiments of the present invention relate to a laser welding method and a method for manufacturing a rotary electric motor. Background Technology

[0002] For example, a proposed technique involves arranging two linear components, irradiating one end of a linear component and the end of an adjacent linear component with a laser, and then welding the ends of the two linear components together. In this case, if there is a gap between the ends of the two linear components, the laser may leak from the gap. If the laser leaks from the gap, it may, for example, incident on a coating disposed on the side of the linear component or on a component disposed near the linear component. If the laser incident on the coating or the component, it may be damaged by the laser.

[0003] Therefore, a technique was proposed to individually irradiate the ends of the two linear components with lasers. This prevents laser light from entering the coating or component through the gap between the ends of the linear components.

[0004] However, it has been found that the laser's trajectory is only moderately effective in suppressing porosity in the weld. Porosity reduces the tensile strength of the weld, thus decreasing the reliability of the joint. Furthermore, since porosity is not intentionally formed, its size, number, and location are random. Therefore, variations in weld quality are more likely to occur.

[0005] Therefore, it is desirable to develop a technology that can suppress the formation of porosity in the welded parts.

[0006] Existing technical documents Patent documents Patent Document 1: Japanese Patent Application Publication No. 2018-20340 Patent Document 2: International Publication No. 2019 / 159737 Summary of the Invention

[0007] The problem that the invention aims to solve The problem to be solved by the present invention is to provide a laser welding method and a method for manufacturing a rotary motor that can suppress the generation of porosity in the welded part.

[0008] Methods for solving problems The laser welding method of this embodiment includes: a step of alternately irradiating a laser onto an end of a first linear member and an end of a second linear member adjacent to the first linear member to form a first molten pool spanning the ends of the first linear member and the second linear member; and a step of irradiating the first molten pool with the laser. In the step of irradiating the first molten pool with the laser, the center side of the first molten pool is designated as the starting point for laser irradiation, and the irradiation position of the laser gradually moves away from the starting point or moves away from the starting point in stages as it rotates around the starting point. Attached Figure Description

[0009] Figure 1 It is a schematic three-dimensional diagram used to illustrate the stator.

[0010] Figure 2 This is a schematic diagram illustrating the section installed before the iron core.

[0011] Figure 3 This is a schematic diagram illustrating a coil mounted on an iron core.

[0012] Figure 4 This is a schematic diagram illustrating the formation of a molten pool.

[0013] Figure 5 This is a schematic diagram illustrating the movement path of the laser irradiation position.

[0014] Figure 6 This is a schematic diagram illustrating the movement path of the laser irradiation position.

[0015] Figure 7 This is a schematic diagram illustrating the movement path of the laser irradiation position in other embodiments.

[0016] Figure 8 This is a schematic diagram illustrating the movement path of the laser irradiation position in other embodiments.

[0017] Figure 9 (a) and (b) are photographs of the cut surfaces of the boundary between the ends of the two conductors and the welded parts.

[0018] Figure 10 It is a photograph of the cut surface of the boundary between the ends of the two conductors and the welded part. Detailed Implementation

[0019] The laser welding method of this embodiment can be used when welding the ends of arranged linear components together. For example, a coil wound around an iron core is provided in a rotating electric machine such as a motor or generator. In recent years, after inserting multiple sections into slots, the ends of the sections and the ends of adjacent sections are irradiated with a laser to weld them together, forming a coil wound around an iron core. Therefore, as an example, a method for manufacturing a stator will be illustrated below, and the laser welding method of this embodiment will be described. That is, the present invention can be applied to the manufacturing method of a rotating electric machine.

[0020] In addition, a linear member with a quadrilateral cross-sectional shape was used as an example to illustrate the method of manufacturing the stator, but the present invention can also be applied to linear members with a polygonal cross-sectional shape, etc.

[0021] Furthermore, in this specification, the movement path of the laser irradiation position refers to the movement path of the center of the laser spot when the laser is irradiated, and the movement path of the center of the laser spot when the laser irradiation has stopped, assuming that a laser spot has been formed. For example, the movement path of the laser irradiation position can be predetermined. The data of the predetermined movement path is stored, for example, in the controller of the laser welding apparatus, and is used when performing the laser welding method described later. The movement path of the laser irradiation position will be described later.

[0022] Hereinafter, embodiments will be illustrated with reference to the accompanying drawings. Furthermore, in each drawing, the same reference numerals are used to label the same constituent elements, and detailed descriptions are omitted where appropriate.

[0023] First, let's take stator 1 as an example.

[0024] Figure 1 This is a schematic three-dimensional diagram used to illustrate stator 1.

[0025] like Figure 1 As shown, the stator 1 is provided with an iron core 2 and a coil 3.

[0026] The core 2 is, for example, a ring-shaped magnetic component along the axial direction of the stator 1. Figure 1 Multiple teeth 2 are stacked together in the Z direction (of the stator). The magnetic components are formed, for example, from electromagnetic steel sheets (silicon steel sheets). The core 2 has a yoke 21 and multiple teeth 22. The yoke 21 is cylindrical and located on the outer periphery of the core 2. Multiple teeth 22 are equally spaced on the inner periphery of the yoke 21. Each tooth 22 has a shape that protrudes from the inner periphery of the yoke 21 toward the center of the core 2 and extends along the axial direction of the stator 1. In addition, the slots provided between the teeth 22 are called slots 23. Furthermore, the shape, number, and size of the teeth 22 are not limited to the illustrated case and can be appropriately changed according to the purpose, size, and specifications of the rotary motor on which the stator 1 is provided.

[0027] Coil 3 includes multiple sections 31.

[0028] Figure 2 This is a schematic diagram illustrating the section 31 installed before the iron core 2.

[0029] like Figure 2 As shown, section 31 has a conductor portion 31a (corresponding to an example of the first and second linear members) and an insulating film 31b. The conductor portion 31a, installed before the iron core 2, can be approximately U-shaped. The conductor portion 31a is formed of a material with high conductivity. For example, the conductor portion 31a is formed of so-called pure copper or a material with copper as the main component. In addition, the conductor portion 31a can be formed of a flat wire. A flat wire is a linear member with a quadrilateral cross-section. The cross-sectional size of the flat wire can be, for example, about 1 mm to 4 mm.

[0030] An insulating film 31b covers the outer surface of the conductor portion 31a. However, the insulating film 31b is not provided near the ends on both sides of the conductor portion 31a, leaving the conductor portion 31a exposed. The insulating film 31b may contain, for example, enamel.

[0031] Figure 3 This is a schematic diagram illustrating the coil 3 mounted on the iron core 2.

[0032] like Figure 3 As shown, segment 31 is disposed inside slot 23. Both ends of segment 31 protrude from one end of iron core 2. The portion of segment 31 protruding from one end of iron core 2 extends in a direction approaching adjacent segment 31.

[0033] Furthermore, the area near the portion of conductor 31a exposed from insulating film 31b along the axial direction of core 2 ( Figure 3 Extending in the Z direction. In the circumferential direction (around the central axis of the core 2), the portion of the conductor portion 31a exposed from the insulating film 31b overlaps with the portion of the adjacent conductor portion 31a exposed from the insulating film 31b.

[0034] The ends of adjacent conductor sections 31a are laser-welded to each other. Multiple sections 31 are connected via welding sections 31c, thereby forming a coil 3.

[0035] In this case, multiple coils 3 can be arranged radially along the core 2 (in a direction passing through the central axis of the core 2 and orthogonal to the Z direction). For example, three coils 3, namely the U-phase, V-phase, and W-phase, can be provided. Furthermore, the appearance, shape, number, and size of the coils 3 and the sections 31 are not limited to the illustrated case and can be appropriately changed according to the purpose, size, and specifications of the rotating electric machine on which the stator 1 is provided. For example, four coils 3 can also be arranged radially along the core 2.

[0036] Next, the manufacturing method of stator 1 will be illustrated.

[0037] First, the iron core 2 is formed. For example, multiple plate-shaped magnetic components are formed, each having a yoke 21 and portions forming multiple teeth 22. For example, the magnetic components are formed by punching an electromagnetic steel sheet with a thickness of approximately 0.05 mm to 1.0 mm. Then, the multiple magnetic components are stacked, for example, by welding or riveting the multiple magnetic components to form the iron core 2. Alternatively, the iron core 2 can also be formed by pressing magnetic material powder and resin binder together.

[0038] Next, multiple segments 31 are formed that become constituent elements of coil 3.

[0039] First, an insulating film 31b is formed by coating the outer surface of the flat wire with a coating containing enamel or the like. Alternatively, flat wires that have undergone enamel coating or the like can also be purchased.

[0040] Next, the insulating film 31b located near the ends on both sides of the conductor portion 31a is peeled off to expose the conductor portion 31a. Then, the exposed portion of the conductor portion 31a is cut to a predetermined length. Alternatively, the insulating film 31b can be peeled off near the ends on both sides of the cut portion after the conductor portion 31a with the insulating film 31b formed thereon has been cut to a predetermined length. Alternatively, the peeling of the insulating film 31b and the cutting of the conductor portion 31a can be performed simultaneously.

[0041] Next, as Figure 2 As shown, the conductor portion 31a is formed by bending the conductor portion 31a exposed from the insulating film 31b near the ends on both sides into a roughly U-shape.

[0042] As described above, multiple segments 31 can be formed.

[0043] Next, as Figure 3 As shown, multiple segments 31 are respectively installed in designated slots 23 of the iron core 2. For example, multiple segments 31 are respectively installed from the axial direction of the iron core 2 ( Figure 1 The coil 31 is inserted into the designated slot 23 in the Z direction. At this time, one segment 31 is inserted across multiple slots 23. The coil 3 in this embodiment can be a so-called distributed winding coil. Alternatively, the coil 3 in this embodiment can also be a so-called wave-wound coil.

[0044] Next, as Figure 3 As shown, the portion of section 31 protruding from the iron core 2 is bent toward the adjacent section 31. Then, the portion of conductor 31a exposed from the insulating film 31b is bent along the axial direction of the iron core 2. Figure 3(Z-direction) bending. In the circumferential direction of the core 2, the portion of the conductor 31a exposed from the insulating film 31b overlaps with the portion of the adjacent conductor 31a exposed from the insulating film 31b.

[0045] Then, by repeatedly performing the above steps, multiple sets of multiple sections 31 arranged in the circumferential direction of the iron core 2 will be set in the radial direction of the iron core 2.

[0046] Furthermore, an example is shown where bending is performed after multiple segments 31 are installed in the slots 23, but this is not a limitation. For example, multiple segments 31 may be bent, and the bent segments 31 may be installed in designated slots 23 respectively. In this case, the bent segments 31 can be installed from the inside to the outside of the core 2.

[0047] Alternatively, a cylindrical insulating cover can be installed inside the iron core 2, which has multiple sections 31, to block the opening of the slot 23.

[0048] Next, the ends of adjacent sections 31 (conductor sections 31a) are welded together to form a plurality of coils 3 installed in slot 23.

[0049] During welding, a clamp can be used to bring the ends of adjacent conductor portions 31a closer together. For example, a clamp can be used that has annular members disposed on the inner sides of multiple segments 31 arranged circumferentially along the core 2 and annular members disposed on the outer sides of the multiple segments 31. When the annular members disposed on the inner sides of the multiple segments 31 are installed, one end of each of the multiple conductor portions 31a is pressed towards the outer side of the core 2. When the annular members disposed on the outer sides of the multiple segments 31 are installed, the other end of each of the multiple conductor portions 31a is pressed towards the inner side of the core 2. Therefore, the clamp moves the ends of adjacent conductor portions 31a toward each other. Furthermore, the clamp holds the multiple conductor portions 31a in place.

[0050] Furthermore, the structure of the fixture is not limited to the illustrated case. The fixture only needs to be able to bring the ends of adjacent conductor portions 31a close to each other. Alternatively, welding can be performed without a fixture. However, using a fixture can improve the quality of the welded portion 31c or improve the workability of the welding operation.

[0051] The ends of adjacent conductor portions 31a can be welded together by irradiating the ends of the conductor portions 31a with a laser. That is, the ends of adjacent conductor portions 31a can be laser welded together.

[0052] Laser welding can use infrared lasers or shorter wavelengths of blue to green lasers. If a laser with an infrared wavelength is used, it is easier to irradiate with a relatively high output. For example, the laser output can be set to around 4kW.

[0053] The laser welding apparatus used for welding the end of the conductor portion 31a can be, for example, a fiber laser welding apparatus or a disk laser welding apparatus. Preferably, the laser welding apparatus is a CW (continuous wave laser) welding apparatus capable of continuously emitting laser light. Furthermore, the laser irradiation position of the laser welding apparatus can be moved. For example, the laser welding apparatus can be equipped with a current mirror, etc.

[0054] By welding the ends of adjacent conductor portions 31a together, a structure is formed. Figure 1 and Figure 3 The illustrated welding section 31c. Furthermore, multiple sections 31 (conductor sections 31a) are connected in series to form a coil 3. Additionally, multiple coils 3 are formed arranged radially along the iron core 2. For example, three coils 3, representing the U phase, V phase, and W phase, can be formed.

[0055] Next, resin or the like is applied to the exposed portion of the conductor portion 31a of the coil 3 for insulation.

[0056] Next, multiple coils 3 are fixed to the iron core 2. For example, varnish is dripped into the gap between the slot 23 and the coil 3, and the varnish is allowed to cure, thereby fixing the coil 3 to the iron core 2.

[0057] As described above, stator 1 can be manufactured.

[0058] Here, if there is a gap between the ends of adjacent conductor portions 31a, the laser may enter the insulating film 31b of section 31 and the component disposed near section 31 through the gap. If the laser enters the insulating film 31b and the component, the insulating film 31b and the component may be damaged by the laser.

[0059] In this case, if the aforementioned clamp is used, the gap between the ends of adjacent conductor portions 31a can be reduced. However, there are dimensional deviations, shape deviations, deformations, etc., at the ends of conductor portions 31a. Therefore, even if a clamp is used, it is difficult to eliminate the gap between the ends of adjacent conductor portions 31a.

[0060] Furthermore, if the two ends of the adjacent conductor portion 31a are individually irradiated with laser, it is possible to suppress the laser from entering the insulating film 31b and the component through the gap. However, this makes it easier for pores to form in the weld portion 31c, and the welding time also increases.

[0061] Therefore, in the laser welding method of this embodiment, the ends of adjacent conductor portions 31a are welded to each other as follows.

[0062] First, laser light is alternately irradiated onto the end of conductor 31a and the end of conductor 31a adjacent to it to form a molten pool 101 (an example of a first molten pool) spanning the end of one conductor 31a and the end of another conductor 31a.

[0063] Figure 4 This is a schematic diagram illustrating the formation of the molten pool 101.

[0064] In addition, Figure 4 In the example shown, a gap 31a1 is formed between the ends of the conductor portion 31a, but the same applies if the ends of the conductor portion 31a are in contact with each other (without gap 31a1) by using the aforementioned clamp.

[0065] like Figure 4 As shown, a laser is alternately irradiated at one end of a conductor portion 31a and the end of another conductor portion 31a adjacent to it. Through alternating laser irradiation, the ends of the two conductor portions 31a melt separately, forming two molten pools 101a and 101b (an example of a second and third molten pool). As the melting of the ends of the two conductor portions 31a progresses, the molten pools 101a and 101b gradually increase in size. If the molten pools 101a and 101b increase in size, they merge to form a molten pool 101 spanning the two ends. At this time, the opening of the gap 31a1 is covered by the molten pool 101.

[0066] In this case, laser irradiation can be performed, for example, by following these steps.

[0067] First, such as Figure 4 As shown, at the end of a conductor portion 31a, a laser is irradiated along a moving path 100 of the irradiation position of the laser in a ring shape.

[0068] Next, the laser irradiation is stopped, and the laser irradiation position is moved along the linear laser irradiation position movement path 100b from one end of the conductor 31a to the other end of the conductor 31a.

[0069] Next, at the end of another conductor section 31a, laser irradiation begins again, and the laser is irradiated along the moving path 100 of the circular laser irradiation position.

[0070] Next, the laser irradiation is stopped, and the laser irradiation position is moved from the end of another conductor 31a to the end of a conductor 31a along a straight laser irradiation position movement path 100b.

[0071] The position of the laser irradiation can be moved, for example, by using a current mirror or similar device installed in the laser welding apparatus.

[0072] As explained above, in the process of forming the molten pool 101 spanning the two ends, the laser irradiation is stopped when the laser irradiation position is moved from one end to the other. Therefore, even if a gap 31a1 is formed between the ends, it is possible to suppress the laser from entering the insulating film 31b and the component through the gap 31a1.

[0073] Furthermore, by repeatedly performing the aforementioned steps, molten pools 101a and 101b are formed at the two ends respectively. As melting progresses at the two ends, molten pools 101a and 101b gradually increase in size, thus molten pools 101a and 101b merge to form molten pool 101 spanning the two ends. At this time, the opening of gap 31a1 is covered by molten pool 101.

[0074] In this case, the moving path 100 of the annular irradiation position can be the same in shape and size, or at least one of the shapes and sizes can be different.

[0075] For example, if adjacent linear members (conductor portion 31a) have the same cross-sectional shape and size, the shape and size of the movement path 100 can be made the same. For example, if at least one of the cross-sectional shape and cross-sectional size of adjacent linear members is different, at least one of the shape and size of the movement path 100 can be made different.

[0076] Furthermore, the shape of the movement path 100 is not particularly limited. The shape of the movement path 100 can be set to a shape composed of curves such as circles and ellipses, etc. Figure 4 The illustrated shape is composed of curves and straight lines, as well as shapes composed of straight lines such as quadrilaterals and polygons. However, if the shape of the moving path 100 has corners, sputtering is likely to occur when the laser is irradiated at the corners of the moving path 100. Therefore, the shape of the moving path 100 is preferably composed of curves, or a shape composed of curves and straight lines.

[0077] Furthermore, the size of the moving path 100 of the annular irradiation position is not particularly limited. However, as... Figure 4 As illustrated, preferably, at the end of one conductor portion 31a, the shortest distance L between the outer edge of the laser spot 100a and the outer edge of the end of one conductor portion 31a is constant. Furthermore, preferably, at the end of the other conductor portion 31a, the shortest distance L between the outer edge of the laser spot 100a and the outer edge of the end of the other conductor portion 31a is constant.

[0078] Furthermore, when moving along the movement path 100 from the annular irradiation position at one end of a conductor portion 31a to the annular irradiation position at the other end of a conductor portion 31a, for example, as... Figure 4 As shown, in the direction in which the ends of adjacent conductor portions 31a are arranged, a pair of straight irradiation position movement paths 100b can be provided, connecting the annular irradiation position movement path 100 of one conductor portion 31a end to the annular irradiation position movement path 100 of the other conductor portion 31a end. The movement path 100b can be a straight line tangent to the two annular movement paths 100 (sharing a common external tangent). In the irradiation position movement path 100b, laser irradiation is stopped.

[0079] Furthermore, heating of the ends of conductor portions 31a occurs within the movement path 100. Therefore, even if laser irradiation is stopped and restarted at a position far from the outer edge of the ends of conductor portions 31a in the direction in which the ends of adjacent conductor portions 31a are arranged, heating of the ends of conductor portions 31a will not be suppressed. For example, in the direction in which the ends of adjacent conductor portions 31a are arranged, the position where laser irradiation is stopped can be set approximately at the center of the end of one conductor portion 31a, and the position where laser irradiation is restarted can be set approximately at the center of the end of another conductor portion 31a. Therefore, even if there are dimensional deviations, shape deviations, deformations, etc., at the ends of conductor portions 31a, or if there are dimensional deviations in the gap 31a1, laser irradiation into the gap 31a1 can be effectively suppressed.

[0080] In addition, such as Figure 4 As shown, if the shortest distance L between the outer edge of the laser spot 100a and the outer edge of the end of the conductor portion 31a is kept constant, it is possible to more effectively suppress the irradiation of laser into the gap 31a1.

[0081] Furthermore, if the movement paths 100 of the annular irradiation positions are of the same shape and size at each end of adjacent conductor portions 31a, the control procedures related to laser irradiation can be simplified.

[0082] Furthermore, if the movement path 100b of the irradiation position is a straight line tangent to the movement paths 100 of the two annular irradiation positions (sharing a common external tangent), then a straight-line movement from one irradiation position movement path 100 to another irradiation position movement path 100 is possible. Therefore, the movement time from one irradiation position movement path 100 to another irradiation position movement path 100 can be shortened, thereby shortening the production cycle time.

[0083] Here, when two molten pools 101a and 101b are formed by laser irradiation, gas (e.g., air) located near the end of the conductor portion 31a is drawn into the interior of the molten pools 101a and 101b. In this case, even if the molten pools 101a and 101b merge to form a molten pool 101 spanning both ends, the drawn-in gas will remain inside the molten pool 101. If gas is present inside the molten pool 101, pores will be generated inside the weld portion 31c when the molten pool 101 cools to form the weld portion 31c. If pores are generated, the tensile strength of the weld portion 31c decreases, thus reducing the reliability of the joint. Furthermore, since the pores are not intentionally formed, their size, number, and location are random. Therefore, the quality deviation of the weld portion 31c is prone to increase.

[0084] Therefore, next, a laser is irradiated onto the molten pool 101, causing the gas contained inside the molten pool 101 to be discharged to the outside of the molten pool 101.

[0085] Figure 5 and Figure 6 This is a schematic diagram illustrating the movement path of the laser irradiation position.

[0086] First, such as Figure 5 and Figure 6 As shown, the center side of the molten pool 101 is designated as the starting point 31d for laser irradiation. The starting point 31d for laser irradiation can be located between the ends of one conductor portion 31a and the ends of another conductor portion 31a (for example, the center of the gap 31a1). As described above, the opening of the gap 31a1 is covered by the molten pool 101. Therefore, when the laser irradiates the molten pool 101, even if the starting point 31d is located above the gap 31a1, it is possible to suppress the laser from irradiating the insulating film 31b, etc., through the gap 31a1.

[0087] Furthermore, the endpoint of the laser irradiation can be set at the end of one conductor portion 31a or the end of another conductor portion 31a.

[0088] Next, the laser irradiation position is moved. In this case, such as Figure 5 As shown, the laser irradiation position can gradually move away from the starting point 31d as it rotates around the starting point 31d. In this case, the shape of the laser irradiation position movement path 102 can be set to a shape formed by a curve that gradually moves away from the starting point 31d as it rotates around the starting point 31d. For example, as... Figure 5 As shown, the shape of the moving path 102 of the laser irradiation position can be made into a vortex shape.

[0089] In addition, such as Figure 6As shown, the shape of the movement path 102a of the laser irradiation position can be set to a shape consisting of a straight line that gradually moves away from the starting point 31d as it rotates around the starting point 31d. For example, as... Figure 6 As shown, the shape of the moving path 102a of the laser irradiation position can be a square vortex.

[0090] In addition, the shape of the movement path of the laser irradiation position can also be set to a shape composed of curves and straight lines that gradually move away from the starting point 31d as the laser rotates around the starting point 31d.

[0091] That is, the laser irradiation position only needs to gradually move away from the starting point 31d as it rotates around the starting point 31d.

[0092] However, as mentioned above, if the shape of the moving path has corners, sputtering is likely to occur when the laser is irradiated at the corners of the moving path. Therefore, the shape of the moving path is preferably a shape composed of curves, or a shape composed of curves and straight lines.

[0093] Furthermore, there are no specific restrictions on the direction of rotation within the movement path. The direction of rotation can be, for example, clockwise or counterclockwise.

[0094] If the shape of the moving path of the laser irradiation position is such that it gradually moves away from the starting point 31d as it rotates around the starting point 31d, a flow from the center to the periphery can be formed inside the molten pool 101. Therefore, the gas contained inside the molten pool 101 can be discharged to the outside of the molten pool 101.

[0095] Furthermore, the molten pool 101 can be expanded outward by the flow inside the molten pool 101 (flow from the center to the periphery) and the impact when the laser is incident. Therefore, the molten pool 101 can be provided in almost the entire area at the ends of the two conductor portions 31a, and thus the weld portion 31c can be provided.

[0096] Figure 7 and Figure 8 This is a schematic diagram illustrating the movement path of the laser irradiation position in other embodiments.

[0097] like Figure 7 As shown, the shape of the moving path 102b for the laser irradiation position can be set as multiple circles whose size gradually increases. For example, the shape of the moving path 102b can be set as concentric circles centered on the starting point 31d. In this case, the irradiation position is moved sequentially from the moving path 102b closest to the starting point 31d to the moving path 102b adjacent to the outside of the moving path 102b.

[0098] like Figure 8As shown, the shape of the moving path 102c of the laser irradiation position can be set as multiple polygons whose size increases in stages. For example, the shape of the moving path 102b can be set as a concentric polygon centered on the starting point 31d. Figure 8 The illustrated moving path 102c has a concentric quadrilateral shape centered on the starting point 31d. In this case, the irradiation position is moved sequentially from the moving path 102c closest to the starting point 31d to the moving path 102c adjacent to the outside of the moving path 102c.

[0099] Furthermore, examples of movement paths being multiple circles or multiple polygons have been shown, but the shape of the movement path can be any shape composed of curves, straight lines, or a combination of curves and straight lines. However, as mentioned above, to suppress sputtering, it is preferable that the movement path has no corners. Additionally, the direction of rotation in the movement path is not particularly limited. The direction of rotation can be, for example, clockwise or counterclockwise.

[0100] As explained above, the laser irradiation position can also move away from the starting point 31d in stages as it rotates around the starting point 31d.

[0101] In this way, the same effect as described above can be achieved. That is, a flow from the center to the periphery can be formed inside the molten pool 101, thus allowing the gas contained inside the molten pool 101 to be discharged to the outside of the molten pool 101. In addition, since the molten pool 101 can be pushed outward, the molten pool 101 can be provided over almost the entire area at the ends of the two conductor portions 31a, thereby providing the welding portion 31c.

[0102] Figure 9 (a) and (b) are photographs of the cut surfaces of the boundary between the ends of the two conductor portions 31a and the weld portion 31c. Figure 9 (a) and (b) are cases where, after the molten pool 101 is formed, the process of discharging the gas contained inside the molten pool 101 to the outside of the molten pool 101 is not carried out.

[0103] from Figure 9 As shown in (a) and (b), pores are generated inside the welded portion 31c. Therefore, the tensile strength of the welded portion 31c is reduced, thus reducing the reliability of the joint.

[0104] Furthermore, the size, number, and location of the resulting pores are random. Therefore, the quality deviation of weld 31c is prone to increase.

[0105] Figure 10 It is a photograph of the cross-section of the boundary between the ends of the two conductor portions 31a and the weld portion 31c. Figure 10This refers to a process where, after the molten pool 101 is formed, the gas contained inside the molten pool 101 is discharged to the outside of the molten pool 101. From Figure 10 It is understood that by performing a process that discharges the gas contained inside the molten pool 101 to the outside of the molten pool 101, the generation of porosity inside the weld portion 31c can be suppressed. Therefore, the reduction in tensile strength of the weld portion 31c can be suppressed, thereby improving the reliability of the joint. In addition, the quality deviation of the weld portion 31c can be reduced.

[0106] The above embodiments of the present invention have been illustrated, but these embodiments are provided as examples and are not intended to limit the scope of the invention. These new embodiments can be implemented in various other ways, and various omissions, substitutions, modifications, etc., can be made without departing from the spirit of the invention. These embodiments or variations thereof are included within the scope or spirit of the invention, and are included within the scope of the invention as described in the claims and its equivalents. Furthermore, the above-described embodiments can be combined with each other for implementation.

[0107] Explanation of reference numerals in the attached figures 1. Stator; 2. Iron core; 3. Coil; 31. Section; 31a. Conductor section; 31a1, gap; 31b, Insulating film 31c. Welding section; 31d, the starting point of irradiation; 100. Movement path; 100b, Movement Path; 102. Movement path; 102a. Movement path; 102b. Movement path; 102c, Movement path; 101. Molten pool; 101a, Molten Pool; 101b, Molten Pool.

Claims

1. A laser welding method comprising: a step of alternately irradiating a laser to an end portion of a first linear member and an end portion of a second linear member adjacent to the first linear member to form a first molten pool across the end portion of the first linear member and the end portion of the second linear member; and a step of irradiating the laser to the first molten pool, wherein in the step of irradiating the laser to the first molten pool, a center side of the first molten pool is set as a start point of irradiation of the laser, and an irradiation position of the laser gradually moves away from the start point or moves away from the start point in stages as the start point is revolved.

2. The laser welding method according to claim 1, wherein in the step of forming the first molten pool, a second molten pool formed at the end portion of the first linear member and a third molten pool formed at the end portion of the second linear member are combined to form the first molten pool.

3. The laser welding method according to claim 1 or 2, wherein in the step of irradiating the laser to the first molten pool, a shape of a movement path of the irradiation position of the laser is a spiral line shape.

4. The laser welding method according to claim 1 or 2, wherein in the step of irradiating the laser to the first molten pool, a shape of a movement path of the irradiation position of the laser is a plurality of circular shapes that gradually increase in size in stages or a plurality of polygonal shapes that gradually increase in size in stages.

5. The laser welding method according to claim 1 or 2, wherein in the step of irradiating the laser to the first molten pool, the start point of the irradiation of the laser is a position between the end portion of the first linear member and the end portion of the second linear member, and an end point of the irradiation of the laser is a position of the end portion of the first linear member or a position of the end portion of the second linear member.

6. The laser welding method according to claim 1 or 2, wherein in the step of irradiating the laser to the first molten pool, a gas contained in the first molten pool is discharged to an outside of the first molten pool.

7. A manufacturing method of a rotary electric machine comprising a step of arranging a coil in a plurality of slots, the coil including a plurality of segments, wherein in the step of arranging the coil, end portions of conductor portions of the plurality of segments are welded by the laser welding method according to claim 1 or 2. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

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