Laser welding method

Abstract

The laser welding method of the present invention welds a first coil to a second coil by irradiating the coil with a laser while the coils (components) are butted against each other. This method includes a first step of irradiating the first coil with laser light to form a molten pool, and a second step of continuing irradiating the first coil with laser light until the molten pool grows and adheres to the second coil, forming a bridge between the first and second coils with a width greater than the width of the laser light.

Description

Technical Field

[0001] The invention relates to a laser welding method. Background Art

[0002] Laser welding is a known method for welding stator coils. When laser welding is used, the size of the welded portion can be made more compact compared to conventional TIG welding, thereby miniaturizing the overall product size.

[0003] As a related technology, Japanese Patent Application Laid-Open No. 2019-140839 discloses a method for manufacturing a rotating electrical machine that can prevent or suppress damage to the insulation coating when welding the coil wire and neutral wire of the rotating electrical machine. The manufacturing method disclosed in Japanese Patent Application Laid-Open No. 2019-140839 includes a placement step and a welding step. In the placement step, a connection point set at the coating stripping portion at the end of the insulation-coated coil wire is brought into contact with a connection point set at the neutral wire. In the welding step, laser welding is performed on the contact portion, starting from the side closest to the insulation coating and ending at the side further away from the insulation coating. The starting point of the laser welding is the end of the contact portion closest to the insulation coating, and the end point of the laser welding is the end of the contact portion further away from the insulation coating. The heat input due to welding can be relatively reduced on the side closest to the insulation coating compared to the side further away from the insulation coating. Summary of the Invention

[0004] use Figure 9A 、 Figure 9B 、 Figure 9C , explaining the subject of the present invention. Figure 9A 1 is a diagram showing a schematic structure of a stator 101 according to another related art. The stator 101 includes a stator core 102 and a plurality of coils 110. The stator core 102 is an annular electromagnetic steel sheet arranged in the axial direction of the stator 101 ( Figure 9A The plurality of coils 110 are mounted in slots provided on the inner circumference of the stator core 102 , and the ends (coil ends) of the coils 110 protrude from the upper end surface of the stator core 102 .

[0005] Figure 9B It is along Figure 9A An enlarged view of the axial section A10 of the coil 110 near the end thereof. Figure 9B As shown, a plurality of coils 110 are arranged in a radial direction ( Figure 9B The coils 110 are paired with each other in the x-axis direction (in the x-axis direction). The ends of the paired coils 110 are butted against each other and irradiated with laser light from above, thereby joining the coils 110 to each other.

[0006] Figure 9C Is to further amplify Figure 9BFigure 2 shows a partial area A20 in the image. Figure 9C In the embodiment, the coils 110a and 110b are arranged in radial direction ( Figure 9C The coils 110a and 110b are adjacent in the x-axis direction. When the ends of the coils 110a and 110b are butted against each other, the coils 110a and 110b can be joined by irradiating the coils 110a and 110b with laser light L from above.

[0007] Here, if Figure 9C As shown in the example, other components including coils 110c and 110d are sometimes arranged below coils 110a and 110b. Here, coils 110a and 110b are the objects to be welded, but coils 110c and 110d arranged below them are not the objects to be welded. The metal materials of the coils 110a and 110b to be welded are exposed at their ends for welding. On the other hand, Figure 9C As shown, the coils 110c and 110d that are not to be welded are each covered with an insulating film.

[0008] For example, a single-mode laser with a spot diameter of 0.1 mm is used as laser L. Single-mode lasers have a high energy density and can weld coils together while forming deep keyholes. Therefore, they are good at efficiently melting copper, which is difficult to melt, with a small amount of heat. However, if there is a gap of more than 0.05 mm on the joint surface between coils 110a and 110b, there is a possibility that laser L will penetrate the joint surface and burn the insulation coating of coils 110c and 110d on the lower side. Such burning of the insulation coating may cause a serious quality defect directly related to poor insulation.

[0009] To address this issue, a clamp that precisely clamps the coils to prevent gaps greater than 0.05 mm from forming on the welded joint surface has been considered. However, installing such a clamp hinders product productivity due to limited space and increases manufacturing costs.

[0010] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a laser welding method that can reduce the possibility of laser light penetrating between components to be welded.

[0011] The laser welding method according to the present invention welds the first and second components by irradiating the components with laser light while the components are butted against each other. The laser welding method comprises:

[0012] a first step of irradiating the first member with the laser to form a molten pool; and

[0013] The second step is to continue irradiating the first member with the laser until the width of a bridge formed between the first and second members by the molten pool growing and adhering to the second member becomes wider than a width of the laser.

[0014] According to the present invention, there is provided a laser welding method capable of reducing the possibility of laser light penetrating between components to be welded. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Hereinafter, features, advantages, and technical and industrial significance of exemplary embodiments of the present invention will be described with reference to the accompanying drawings, in which like numerals represent like elements.

[0016] Figure 1 It is a perspective view showing the schematic structure of a stator.

[0017] Figure 2 This is a diagram schematically showing the end portion of a coil.

[0018] Figure 3 It is a side view showing a joining portion in the laser welding method according to the embodiment.

[0019] Figure 4 It is a side view showing a joining portion in the laser welding method according to the embodiment.

[0020] Figure 5 It is a side view showing a joining portion in the laser welding method according to the embodiment.

[0021] Figure 6 It is a side view showing a joining portion in the laser welding method according to the embodiment.

[0022] Figure 7 It is a plan view showing a joining portion in the laser welding method according to the embodiment.

[0023] Figure 8 These are photographs showing the appearance of a joined portion in the laser welding method according to the embodiment.

[0024] Figure 9A It is an explanatory diagram showing a laser welding method according to the related art.

[0025] Figure 9B It is an explanatory diagram showing a laser welding method according to the related art.

[0026] Figure 9C It is an explanatory diagram showing a laser welding method according to the related art. DETAILED DESCRIPTION

[0027] Hereinafter, specific embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the present invention is not limited to the following embodiments. In addition, the following description and drawings are appropriately simplified for the purpose of clarity.

[0028] First, use Figure 1 The structure of the stator 100 including the coils 10 welded using the laser welding method according to this embodiment will be described. Figure 1 1 is a perspective view showing the schematic structure of the stator 100. Figure 1 As shown, a stator 100 serving as a stator of a motor includes a stator core 15 and a plurality of coils 10 .

[0029] The stator core 15 is formed by annular electromagnetic steel sheets arranged in the axial direction of the stator 100 ( Figure 1 The stator core 15 is stacked (in the z-axis direction) and has a generally cylindrical shape as a whole. The inner circumference of the stator core 15 is provided with teeth 13 that protrude inward and extend in the axial direction of the stator 100, as well as slots 14 that form grooves between adjacent teeth 13. A coil 10 is mounted in each slot 14. Each coil 10 is formed into a generally U-shape, with the ends of the coils 10 protruding from the upper end surface of the stator core 15.

[0030] The coil 10 can be, for example, a rectangular wire, i.e., a flat wire. The coil 10 is typically made of pure copper, but is not limited thereto. The coil 10 can also be made of a highly conductive metal material such as aluminum, copper, or an aluminum-based alloy.

[0031] Figure 1 The right-handed xyz coordinate system shown is a coordinate used to facilitate the description of the positional relationship of the components. Generally, the positive direction of the z-axis is vertically upward, and the xy plane is a horizontal plane, which is consistent between the drawings. The x-axis represents the radial direction of the stator 100. Here, the direction from the center of the stator 100 toward the outside is set as the positive direction of the x-axis. In addition, the y-axis represents the circumferential direction of the stator 100. Figure 1 In the cross section A1 along the axial direction of the coil 10, the direction from the front to the back of the paper is defined as the positive y-axis direction. Then, the z-axis represents the axial direction of the stator 100. The vertical direction from bottom to top in the stator 100 is defined as the positive z-axis direction.

[0032] In this embodiment, the ends of the coils 10 adjacent in the radial direction (x-axis direction) are welded to each other by laser L, forming a joint 20 described later. Adjacent coils 10 form a joint 20 in pairs, and multiple joints 20 are formed on the entire stator 100. The multiple joints 20 can also be arranged in a circular shape in the circumferential direction of the stator core 15. In addition, the joints 20 arranged in a circular shape can also be arranged in multiple rows along the radial direction.

[0033] Figure 2It will Figure 1 FIG. 1 is a diagram showing an enlarged view of the section A1 of the coil 10 and schematically illustrating the end of the coil 10. The plurality of coils 10 are paired with the other coils 10 adjacent in the radial direction. For example, Figure 2 , a group of four coils 10 is shown. By butting the ends of adjacent coils 10 together and irradiating the butted portions with laser light L, a joint 20 is formed between the coils 10. This allows the adjacent coils 10 to be welded together.

[0034] Here, in Figure 2 The following describes an example in which the coils 10a (first member) and the coil 10b (second member) are welded together by irradiating the coils 10a and 10b with laser light L from above while the coils 10a and 10b are butted against each other.

[0035] As shown in the figure, coils 10a and 10b are covered with insulating films 12a and 12b, respectively. Insulating films 12a and 12b can be formed, for example, by baking enamel or coating with a vinyl chloride resin. Furthermore, at the ends 11a and 11b of coils 10a and 10b, insulating films 12a and 12b are peeled off, exposing the metal material (e.g., copper). Laser light L is irradiated at these ends 11a and 11b to form a joint 20, thereby welding coils 10a and 10b.

[0036] A plurality of joints 20 are formed by welding the ends of radially adjacent coils 10 to each other, and are arranged in an annular shape in the circumferential direction of the stator core 15. The annular joints 20 are arranged in a plurality of radial rows.

[0037] Coils 10a and 10b are positioned so that, when laser light L penetrates coils 10a and 10b, laser light L can irradiate components other than coils 10a and 10b. Here, multiple other coils 10 not intended for welding are positioned below coils 10a and 10b (in the negative z-axis direction). These multiple coils 10 not intended for welding are entirely covered, including their ends, with an insulating coating 12. Therefore, if laser light L is irradiated onto coils 10a and 10b positioned above, there is a risk that the laser light L could penetrate the gap between coils 10a and 10b, potentially burning the multiple coils 10 not intended for welding.

[0038] Next, refer to Figures 3 to 6 , describing the laser welding method involved in this embodiment. Figures 3 to 6 This is a side view of the vicinity of the joint 20 of the coils 10a and 10b. For example, a laser light source having a coarse diameter of approximately 1.0 mm can be selected as the laser light L. For example, the laser light L may be a ring mode laser.

[0039] Figure 31 is a diagram illustrating a first step. As shown in the diagram, first, the end portion 11a of the coil 10a is irradiated with laser light L to form a molten pool 30 at the end portion 11a (first step).

[0040] Figure 4 This diagram illustrates the second step. Laser light L is continuously irradiated at a fixed point on end 11a, causing a molten pool 30 to grow. The growth and vibration of molten pool 30 cause it to adhere to end 11b. This forms a bridge (film) of molten pool 30 between ends 11a and 11b. After the bridge is formed, irradiation of end 11a with laser light L is continued until the width of the bridge formed between ends 11a and 11b becomes wider than the width W (not shown) of laser light L (second step).

[0041] Here, the width W of laser light L represents the spot diameter of laser light L irradiated onto ends 11a and 11b. For example, if the shape of laser light L is circular, the width W of laser light L can be the diameter of laser light L at the irradiation position on ends 11a and 11b. Furthermore, if the shape of laser light L is elliptical, the width W of laser light L can be the major or minor diameter of laser light L at that irradiation position. To prevent laser light L from penetrating the gap between ends 11a and 11b, laser light L is continuously irradiated onto end 11a, forming a bridge, taking into account the width W of laser light L and the shape of laser light L. This forms a bridge of molten pool 30 between ends 11a and 11b, with a width wider than the width W of laser light L.

[0042] Furthermore, in the second step, the duration of laser light L irradiation of the end portion 11a can be preset. For example, by using a high-speed camera to record the welding process and observing the weld depth in a cross-sectional view of the joint 20 during or after welding, an appropriate irradiation time can be set in advance. Presetting the irradiation time allows for efficient welding and prevents defects.

[0043] Then, if Figure 5 As shown, laser light L is moved from end 11a to end 11b so as to pass through the bridge. Since the bridge is formed wider than the width W of laser light L, laser light L can be moved without passing between ends 11a and 11b.

[0044] Then, if Figure 6 As shown, irradiation of end 11b with laser light L continues until the coil is sufficiently melted into end 11b. This forms a joint 20 formed by a molten pool 30 between end 11a and 11b. The irradiation time of laser light L on end 11b can be pre-set using a high-speed camera, etc., similar to the irradiation time on end 11a.

[0045] By repeating the above-mentioned process according to the length (y-axis direction) of the gap to be filled between the end portions 11 a and 11 b , the welding of the coils 10 a and 10 b can be completed.

[0046] Next, use Figure 7 and Figure 8 , describing the above-mentioned process viewed from different directions. Furthermore, the description herein uses the case where the above-mentioned process is repeated. In the above-mentioned example, the molten pool 30 and the bridge are formed from end 11a toward end 11b in the first and second steps. However, here, the same process is also performed from end 11b toward end 11a. Therefore, the following description also includes the third and fourth steps corresponding to the first and second steps.

[0047] Figure 7 FIG. 2 is a top view showing a joint portion 20 in the laser welding method according to the present embodiment. Figure 7 The coils 10a and 10b are welded by irradiating the laser beam L in the order of irradiation positions (1) to (8). Figure 8 is with Figure 7 The photographs of the appearance of the bonding portion 20 corresponding to the irradiation positions (1) to (8) of the laser light L are shown.

[0048] use Figure 7 The irradiation path of the laser light L will be described. First, at the irradiation position (1), the end portion 11a of the coil 10a is irradiated with the laser light L, and a molten pool 30 is formed at the end portion 11a (first step).

[0049] Next, molten pool 30 grows at a fixed point on end 11a by continuing irradiation with laser light L. As molten pool 30 grows and vibrates, it adheres to end 11b. This forms a bridge made of molten pool 30 between ends 11a and 11b. After the bridge is formed, irradiation of end 11a with laser light L continues until the width of the bridge formed between ends 11a and 11b becomes wider than the width W of laser light L (second step).

[0050] Thus, a larger width W than the laser light L is formed between the ends 11a and 11b (see Figure 8 (1)) A bridge of a wide molten pool 30. The duration of irradiation of the end portion 11a with the laser light L can be set in advance using a high-speed camera or the like.

[0051] After the above second step, Figure 7 As shown in the irradiation position (2), the laser light L is moved to the end portion 11b. By moving the laser light L on the bridge formed in the first step and the second step, the laser light L can be moved from the end portion 11a to the end portion 11b without penetrating between the end portions 11a and 11b.

[0052] After moving toward end 11b, laser light L is continuously irradiated onto end 11b until the coil is sufficiently melted into end 11b. In this way, joint 20 is formed between ends 11a and 11b. The irradiation time of laser light L onto end 11b can be pre-set using a high-speed camera, etc., similar to the irradiation time onto end 11a.

[0053] Next, as shown in irradiation position (3), laser light L is moved toward the insulating coating 12b side (y-axis negative direction). At irradiation position (4), laser light L is continuously irradiated to the end portion 11b to form a molten pool 30 (third step).

[0054] Next, at irradiation position (4), irradiation with laser light L is continued, causing the molten pool 30 to grow. As the molten pool 30 grows and vibrates, it adheres to the end portion 11a. Thus, a second bridge formed by the molten pool 30 is formed between the ends 11a and 11b. After the second bridge is formed, irradiation of the end portion 11b with laser light L is continued until the width of the bridge formed between the ends 11a and 11b becomes wider than the width W of the laser light L (fourth step).

[0055] As a result, a second bridge of a molten pool 30 having a width wider than the width W of the laser light L is formed between the ends 11a and 11b. The duration of the irradiation of the end 11b with the laser light L can be set in advance using a high-speed camera or the like. Furthermore, since the end 11b has already been heated by the laser light L, a shorter irradiation time can be set than the irradiation time for the end 11a during the formation of the first bridge.

[0056] After the fourth step, the laser light L is moved to the end 11a as shown in the irradiation position (5). By moving the laser light L on the second bridge formed by the third and fourth steps, the laser light L can move from the end 11b to 11a without penetrating between the ends 11a and 11b.

[0057] After moving toward end 11a, laser L continues irradiating end 11a until the coil is sufficiently melted into end 11a. In this way, a second joint 20 is formed between ends 11a and 11b. The irradiation time of laser L on end 11a can be pre-set using a high-speed camera, for example, in the same manner as the irradiation time on end 11b. Furthermore, since end 11a has already been heated by laser L, a shorter irradiation time can be set than the irradiation time for end 11b when forming first joint 20.

[0058] Next, as shown at irradiation position (6), laser light L is moved toward insulating coating 12a (in the positive y-axis direction). Then, as shown at irradiation positions (7) and (8), laser light L is moved in the positive x-axis direction and the negative y-axis direction to fill the gap between ends 11a and 11b. In this way, joint 20 between ends 11a and 11b is integrated, and the welding of coils 10a and 10b is completed.

[0059] In addition, Figure 7 In the figure, the arrows at the irradiation positions (1) to (8) are shown as non-overlapping, but the present invention is not limited thereto. For example, the end point of the arrow at the irradiation position (6) may overlap with the irradiation position (1). In addition, for example, the end point of the arrow at the irradiation position (8) may be located on the line of the arrow at the irradiation position (5). In addition, when the bridge is formed by not penetrating the ends 11a and 11b with the laser L, as shown in FIG. Figure 7 As shown, the irradiation positions may be set so that the arrows do not overlap.

[0060] In addition, the irradiation position of the laser L is not limited to Figure 7 For example, the laser light L may be irradiated in a zigzag pattern along the y-axis direction.

[0061] As described above, according to the laser welding method of this embodiment, a bridge formed by the molten pool 30 can be formed so as to cover the gap between the ends 11a and 11b. Furthermore, since the irradiation of the laser light L to the end 11a or 11b is continued until the width of the bridge is wider than the width W of the laser light L, the laser light L can be prevented from penetrating the gap between the ends 11a and 11b.

[0062] Therefore, even when a gap exists between ends 11a and 11b, laser light L is prevented from irradiating other components located below. Consequently, even when other coils 10 or components not intended for welding are positioned below the coils 10a and 10b being welded, the possibility of burning these components is reduced, while enabling proper welding. Furthermore, this simplifies the clamping jig and reduces its cost.

[0063] Furthermore, according to the laser welding method of this embodiment, the laser light L forms a plurality of bridges between the ends 11a and 11b, and the laser light L can be continuously irradiated back and forth between the ends 11a and 11b. Therefore, the plurality of coils 10 can be welded efficiently.

[0064] In addition, the present invention is not limited to the above-mentioned embodiment, and can be modified appropriately within the scope of the main purpose. For example, in the above description, one laser beam L is used, but it is not limited thereto, and multiple laser beams L can also be used. For example, in the case of using two laser beams L, Figure 7The irradiation positions (1) and (4) shown are used as the irradiation start positions of the respective laser beams L, and irradiation is started simultaneously.

Claims

1. A laser welding method, wherein a first component and a second component are welded by irradiating the first component with a laser while the first component and the second component are butted against each other, the laser welding method comprising: A first step includes irradiating the first component with the laser to form a molten pool; a second step of continuing irradiating the first member with the laser until a width of a bridge formed between the first and second members by causing the molten pool to grow and adhere to the second member becomes wider than a width of the laser; A third step, after the second step, moving the laser to the second member and continuously irradiating the second member with the laser to form a molten pool; and The fourth step is to continue irradiating the second member with the laser until the molten pool formed on the second member grows and adheres to the first member, thereby causing the width of a bridge formed between the first and second members to become wider than the width of the laser.

2. The laser welding method according to claim 1, characterized in that: The first member and the second member are coils provided with an insulating coating.

3. The laser welding method according to claim 1 or 2, characterized in that: The first member and the second member are arranged at positions such that, when the laser light passes through between the first member and the second member, the laser light can irradiate members other than the first member and the second member.

4. The laser welding method according to claim 1 or 2, characterized in that: The time for which the irradiation of the first member with the laser beam is continued in the second step is set in advance.

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