Busbar manufacturing method

Abstract

To provide a manufacturing method for a busbar further improved and new.SOLUTION: A manufacturing method for a busbar including a plurality of plate-like members and a linear welded part formed by welding two members included in the plurality of members includes, for example, while keeping an end part of one of the two members in a direction intersecting a thickness direction of the one member and the other member of the two members adjacent to each other, emitting laser beams including a plurality of beams, thereby forming a linear welded part between the end part of the one member in the direction intersecting the thickness direction and the other member, and along the end part. In this case, the welded part may be formed while the end part of the one member in the direction intersecting the thickness direction and an end part of the other member in the thickness direction are kept adjacent to each other. The welded part may be formed while the end part of the one member in the direction intersecting the thickness direction and the end part of the other member in a direction intersecting the thickness direction are kept adjacent to each other. In addition, the welded part may be formed while the one member and the other member overlap each other in their thickness directions.SELECTED DRAWING: Figure 2

Description

【Technical Field】 【0001】 The present invention relates to a method for manufacturing a bus bar. 【Background Art】 【0002】 Conventionally, a bus bar has been known which is configured by connecting a plurality of members by spot welding at their contact portions (for example, Patent Document 1). 【Prior Art Document】 【Patent Document】 【0003】 【Patent Document 1】 Japanese Patent Application Laid-Open No. 11-297372 【Summary of the Invention】 【Problems to be Solved by the Invention】 【0004】 However, in spot welding, for example, the joining strength of a plurality of members may be insufficient. 【0005】 Therefore, one of the problems of the present invention is to obtain a novel and improved method for manufacturing a bus bar capable of manufacturing, for example, a bus bar in which a plurality of members are joined by welding with higher joining strength. 【Means for Solving the Problems】 【0006】 In the bus bar of the present invention, for example, a bus bar having a plurality of plate-like members and a linear welding portion that welds two members included in the plurality of members and extends in a first direction, wherein the welding portion is provided across substantially both ends in the first direction of at least one of the two members. 【0007】 In the bus bar, both of the two members may extend in the first direction and also extend in the same direction intersecting the first direction. 【0008】 In the busbar, one of the two members may extend in the first direction and in a second direction intersecting the first direction, and the other of the two members may extend in the first direction and in a third direction intersecting the first and second directions. 【0009】 In the busbar, a plating layer may be provided on the surface of at least one of the two members. 【0010】 In the busbar, at least one of the two members may have an uneven surface. 【0011】 In the busbar, the welded portion comprises a weld metal and a heat-affected zone located around the weld metal, and the weld metal may comprise a first portion and a second portion in which the average value of the cross-sectional area of ​​the crystal grains in the cross section along the depth direction of the weld is larger than that of the first portion. 【0012】 In the busbar, each of the plurality of members may be made of either a copper-based metal material or an aluminum-based metal material. 【0013】 In the busbar, the ratio of the depth of the weld in the thickness direction to the thickness of the thinner of the two members may be 0.8 or more. 【0014】 In the busbar, the thickness of the member may be 0.5 mm or more. 【0015】 The present invention relates to a method for manufacturing a busbar, for example, a busbar having a plurality of plate-shaped members and a linear welded portion extending in a first direction, formed by welding two members included in the plurality of members, wherein the welded portion is formed by irradiation with laser light containing a plurality of beams. 【0016】 In the busbar manufacturing method described above, the plurality of beams may be formed by a beam shaper. 【0017】 In the method for manufacturing the bus bar, the plurality of beams may include a beam formed by first laser light having a wavelength of 800 [nm] or more and 1200 [nm] or less, and a beam formed by second laser light having a wavelength of 550 [nm] or less. 【0018】 In the method for manufacturing the bus bar, the wavelength of the second laser light may be 400 [nm] or more and 500 [nm] or less. 【0019】 In the method for manufacturing the bus bar, the plurality of members may be formed by cutting the plurality of members from a base material by laser cutting. 【0020】 In the method for manufacturing the bus bar, the plurality of members may be formed by cutting an extruded material in a flat plate shape. 【0021】 In the method for manufacturing the bus bar, the welding of the welded portion may be controlled based on a captured image by a camera. 【Advantages of the Invention】 【0022】 According to the present invention, for example, a novel method for manufacturing a bus bar with further improvement can be obtained. 【Brief Description of the Drawings】 【0023】 [Figure 1] FIG. 1 is an exemplary schematic configuration diagram of a laser welding apparatus according to an embodiment. [Figure 2] FIG. 2 is a schematic perspective view of an example of a bus bar as a processing target of the laser welding apparatus according to the embodiment. [Figure 3] FIG. 3 is a schematic perspective view of an example of a bus bar as a processing target of the laser welding apparatus according to the embodiment. [Figure 4] FIG. 4 is a schematic perspective view of an example of a bus bar as a processing target of the laser welding apparatus according to the embodiment. [Figure 5]Figure 5 is a schematic diagram illustrating the laser beam (spot) formed on the surface of a workpiece by the laser welding apparatus of the embodiment. [Figure 6] Figure 6 is a graph showing the light absorption rate of each metal material as a function of the wavelength of the irradiated laser light. [Figure 7] Figure 7 is an explanatory diagram illustrating the concept of the principle of the diffractive optical element included in the laser welding apparatus of the embodiment. [Figure 8] Figure 8 is an exemplary and schematic cross-sectional view of the welded portion of the embodiment. [Figure 9] Figure 9 is an exemplary and schematic cross-sectional view showing a portion of the welded area of ​​the embodiment. [Figure 10] Figure 10 is an exemplary schematic diagram showing the process of cutting out multiple components from a base material by laser cutting in the manufacturing method of the busbar of the embodiment. [Modes for carrying out the invention] 【0024】 Illustrative embodiments of the present invention are disclosed below. The configurations of the embodiments shown below, as well as the actions and results (effects) brought about by such configurations, are examples only. The present invention can also be realized by configurations other than those disclosed in the following embodiments. Furthermore, according to the present invention, it is possible to obtain at least one of the various effects (including derived effects) that can be obtained by the configuration. 【0025】 The embodiments shown below have similar configurations. Therefore, the configurations of each embodiment provide similar functions and effects based on those similar configurations. In the following, similar components are given the same reference numerals, and redundant explanations may be omitted. 【0026】 Furthermore, in each figure, the X direction is represented by arrow X, the Y direction by arrow Y, and the Z direction by arrow Z. The X, Y, and Z directions intersect and are orthogonal to each other. Also, for convenience, each figure shows an example where the sweep direction SD on the surface Wa of the laser beam L is aligned with the X direction, but the sweep direction SD only needs to be aligned with the surface Wa and intersect with the Z direction, and does not need to be aligned only with the X direction. 【0027】 Furthermore, in Figures 2-4, the D1, D2, and D3 directions, which indicate the directions of the busbar 10, member 11, and welded joint 14, are represented by arrows D1, D2, and D3, respectively. The D1, D2, and D3 directions intersect and are also perpendicular to each other. 【0028】 Furthermore, in this specification, ordinal numbers are assigned for convenience to distinguish parts, components, sections, laser beams, directions, etc., and do not indicate priority or order. 【0029】 [First Embodiment] Figure 1 is a schematic diagram of the laser processing apparatus 100. As shown in Figure 1, the laser processing apparatus 100 includes a laser device 111, a laser device 112, an optical head 120, an optical fiber 130, and a controller 141. 【0030】 Each laser device 111 and 112 has a laser oscillator and, for example, is configured to output laser light with a power of several kW. Alternatively, each laser device 111 and 112 may have, for example, multiple semiconductor laser elements internally, and be configured to output multimode laser light with a power of several kW as the combined output of these multiple semiconductor laser elements. Furthermore, each laser device 111 and 112 may have various laser light sources such as fiber lasers, YAG lasers, and disk lasers. 【0031】 The laser device 111 outputs a first laser beam with a wavelength of 800 nm or more and 1200 nm or less. The laser device 111 is an example of a first laser device. The laser oscillator in the laser device 111 is an example of a first laser oscillator. 【0032】 On the other hand, the laser device 112 outputs a second laser beam with a wavelength of 550 nm or less. The laser device 112 is an example of a second laser device. The laser device 112 preferably outputs a second laser beam with a wavelength of 400 nm or more and 500 nm or less. The laser oscillator of the laser device 112 is an example of a second laser oscillator. 【0033】 The optical fibers 130 guide the laser light output from the laser devices 111 and 112 to the optical head 120. 【0034】 The optical head 120 is an optical device for irradiating the laser light input from the laser devices 111 and 112 toward the workpiece W. The optical head 120 includes a collimating lens 121, a focusing lens 122, a mirror 123, and a filter 124. The collimating lens 121, focusing lens 122, mirror 123, and filter 124 may also be referred to as optical components. 【0035】 The optical head 120 is configured to change its relative position to the workpiece W in order to sweep the laser beam L while irradiating it onto the surface Wa of the workpiece W. The relative movement between the optical head 120 and the workpiece W can be achieved by moving the optical head 120, moving the workpiece W, or by moving both the optical head 120 and the workpiece W. 【0036】 The optical head 120 may be configured to sweep the laser beam L on the surface Wa by having a galvanometer scanner or the like (not shown). 【0037】 The collimating lenses 121 (121-1, 121-2) each collimate the laser light input via the optical fiber 130. The collimated laser light becomes parallel light. 【0038】 Mirror 123 reflects the first laser beam, which has become parallel light by the collimating lens 121-1. The first laser beam reflected by mirror 123 travels in the opposite direction of the Z-axis and heads towards filter 124. Note that mirror 123 is unnecessary in a configuration where the first laser beam is input to the optical head 120 so that it travels in the opposite direction of the Z-axis. 【0039】 Filter 124 is a high-pass filter that transmits the first laser beam but reflects the second laser beam without transmitting it. The first laser beam passes through filter 124 and travels in the opposite direction in the Z-direction towards the focusing lens 122. On the other hand, filter 124 reflects the second laser beam, which has become parallel light by the collimating lens 121-2. The second laser beam reflected by filter 124 travels in the opposite direction in the Z-direction towards the focusing lens 122. 【0040】 The focusing lens 122 focuses the first laser beam and the second laser beam as parallel light and irradiates the workpiece W with the laser beam L (output light). 【0041】 Furthermore, the laser processing apparatus 100 includes a controller 141 and a drive mechanism 150 whose operation is controlled by the controller 141. 【0042】 The drive mechanism 150 changes the relative position of the optical head 120 with respect to the workpiece W. The drive mechanism 150 includes, for example, a rotation mechanism such as a motor, a reduction mechanism that reduces the rotational output of the rotation mechanism, and a motion conversion mechanism that converts the rotation reduced by the reduction mechanism into linear motion. The controller 141 can control the drive mechanism 150 so that the relative position of the optical head 120 with respect to the workpiece W in the X, Y, and Z directions changes. 【0043】 The controller 141 may, for example, control the switching between operation and deactivation of the laser devices 111 and 112, or the power of the laser light emitted by the laser devices 111 and 112. Furthermore, if the laser processing apparatus 100 is equipped with a gas supply mechanism (not shown) that supplies a gas such as an inert gas to the surface Wa of the workpiece W, the controller 141 may control the gas supply mechanism to switch between supplying and deactivating the gas, or to change the flow rate of the discharged gas. 【0044】 Furthermore, the laser processing apparatus 100 includes a camera 170 and a filter 127 and a mirror 128 as optical components that guide light to the camera 170. The filter 127 is provided between the mirror 123 and the filter 124. The filter 127 transmits the first laser beam from the mirror 123 toward the filter 124 and reflects the light from the surface Wa (e.g., visible light) toward the mirror 128. The light reflected by the mirror 128 is input to the camera 170. With this configuration, the camera 170 can capture an image of the surface Wa. The image captured by the camera 170 may include, for example, an image of the surface Wa and an image of the beam (spot) of the laser beam L. Therefore, the image captured by the camera 170 can be said to be the result of detecting the displacement of the spot formed on the surface Wa from a predetermined position, and the camera 170 can be said to be an example of a sensor that detects such displacement. Furthermore, if the position of the spot within the field of view of the captured image is fixed, the captured image only needs to include the target of the laser beam L, and does not need to include an image of the spot itself. 【0045】 Furthermore, the controller 141 can detect a deviation of the spot from a predetermined position from the image captured by the camera 170 and control the drive mechanism 150 to correct the deviation. The controller 141 may also perform feedback control to ensure that the deviation is within a predetermined threshold. In this case, the controller 141 and the drive mechanism 150 are examples of correction mechanisms. With such a configuration, the accuracy of the laser beam irradiation position can be improved. 【0046】 As shown in Figure 1, the laser processing apparatus 100 irradiates the contact area of ​​two members 11 with laser light L and welds the two members 11 together. Figure 1 shows only one location where two members 11 of the multiple members 11 constituting the busbar 10 are welded together by a welding joint 14. All of the multiple members 11 included in the busbar 10 are made of conductive metallic material. The members 11 may also be called metallic members or conductors. Each welding joint 14 mechanically and electrically connects two members 11. The busbar 10 is formed by the connection of multiple members 11 by each welding joint 14. 【0047】 In the example shown in Figure 1, two members 11 are aligned in the Y direction. The Z-direction end faces of the two members 11 are flush in the Y direction, forming the surface Wa of the workpiece W. Surface Wa extends intersecting the Z direction and faces the optical head 120. The laser beam L emitted from the optical head 120 travels in the opposite direction to the Z direction and irradiates surface Wa. The welded portion 14 extends from surface Wa in the opposite direction to the Z direction. In this example, the depth direction of the welded portion 14 is in the opposite direction to the Z direction. Note that in Figure 1, surface Wa is shown as a plane, but surface Wa may be a stepped surface. Also, surface Wa may be a convex curved surface, a concave curved surface, etc. 【0048】 Furthermore, as the laser beam L is swept across the surface Wa in the sweeping direction SD (the X direction in the area shown in Figure 1), the welded portion 14 extends in the sweeping direction SD with a cross-sectional shape substantially similar to that shown in Figure 1. The sweeping direction SD is also referred to as the elongation direction or longitudinal direction of the welded portion 14, and is an example of the first direction. The Z direction and the direction perpendicular to the sweeping direction SD (the Y direction in the area shown in Figure 1) can also be referred to as the width direction of the welded portion 14. 【0049】 The laser processing apparatus 100 of this embodiment can irradiate the workpiece W with laser light L including a first laser beam and a second laser beam, or it can irradiate with laser light L including only the first laser beam, or it can irradiate with laser light L including only the second laser beam. When only the first laser beam is irradiated, the laser device 112 does not operate, and when only the second laser beam is irradiated, the laser device 111 does not operate. Furthermore, the laser processing apparatus 100 may be a device capable of irradiating only the first laser beam without having the laser device 112, collimating lens 121-2, filter 124, etc., or it may be a device capable of irradiating only the second laser beam without having the laser device 111, collimating lens 121-1, mirror 123, etc. 【0050】 Figures 2-4 are perspective views of the busbar 10 created by the laser processing apparatus 100. In the example shown in Figures 2-4, the multiple members 11 constituting the busbar 10 all have a rectangular and flat shape. This makes it easier to obtain the multiple members 11. However, the multiple members 11 are not limited to such shapes. 【0051】 The busbar 10 illustrated in Figure 2 has four plate-shaped members 11 welded together at welds 14 (14-1, 14-2, 14-3). Each weld 14 welds two members 11 together. 【0052】 The welded joint 14-1 welds two members 11-1 and 11-2. Member 11-1 extends in the D1 and D2 directions, and member 11-2 extends in the D1 and D3 directions. Members 11-1 and 11-2 intersect and are perpendicular to each other. The welded joint 14-1 extends linearly in the D1 direction at two corners that extend in the D1 direction, formed by the butt joint of members 11-1 and 11-2. In the welded joint 14-1, the D1 direction is the width direction of members 11-1 and 11-2. When welding the welded joint 14-1, the laser beam L is irradiated toward the corner and swept in the D1 direction. The welded joint 14-1 is provided between approximately both ends of members 11-1 and 11-2 in the D1 direction, that is, between approximately one end 11a and the other end 11a. Although the welded joints 14-1 are provided on both sides in the thickness direction of member 11-1, this is not limited to this arrangement, and only one of the two welded joints 14-1 may be provided. When welded joints 14-1 are provided on both sides in the thickness direction, the joint strength is higher and the electrical resistance can be reduced compared to when they are provided on only one side in the thickness direction. Also, the two welded joints 14-1 may overlap each other. In the welded joint 14-1, the D1 direction is an example of a first direction, the D2 direction is an example of a second direction, and the D3 direction is an example of a third direction. 【0053】 The weld 14-2 welds two members 11-2 and 11-3. Member 11-2 extends in the D1 and D3 directions, while member 11-3 extends in the D1 and D2 directions. Members 11-2 and 11-3 intersect and are perpendicular to each other. The weld 14-2 extends linearly in the D1 direction at each of the corners and boundaries that extend in the D1 direction, formed by the butt joint of members 11-2 and 11-3. In the weld 14-2, the D1 direction is the width direction of members 11-2 and 11-3. During welding of the weld 14-2, the laser beam L is irradiated toward the corners and boundaries, respectively, and swept in the D1 direction. The weld 14-2 is provided between approximately both ends of members 11-2 and 11-3 in the D1 direction, that is, between approximately one end 11a and the other end 11a. Although the welded joints 14-2 are provided on both sides of the thickness direction of the member 11-3, this is not limited to this arrangement, and only one of the two welded joints 14-2 may be provided. When the welded joints 14-2 are provided on both sides of the thickness direction, the joint strength is higher and the electrical resistance can be reduced compared to when they are provided on only one side of the thickness direction. Also, the two welded joints 14-2 may overlap each other. In the welded joint 14-2, the D1 direction is an example of a first direction, the D3 direction is an example of a second direction, and the D2 direction is an example of a third direction. 【0054】 The weld 14-3 welds two members 11-3 and 11-4. Both members 11-3 and 11-4 extend in the D1 and D2 directions. Members 11-3 and 11-4 are aligned and butted together in the D1 direction. The weld 14-3 extends linearly in the D2 direction at the boundary extending in the D2 direction formed by the butt joint of members 11-3 and 11-4. During welding of the weld 14-3, the laser beam L is irradiated toward the boundary and swept in the D2 direction. The weld 14-3 is provided between approximately both ends of member 11-4 in the D2 direction, that is, between approximately one end 11a and the other end 11a. The weld 14-3 may also be provided on both sides of member 11-3 and member 11-4 in the thickness direction. In welded joint 14-3, the D2 direction is an example of the first direction, and the D1 direction is an example of the same direction intersecting the first direction. 【0055】 With this configuration, the welded portion 14 extends linearly in the first direction and also extends between approximately both ends in the first direction of at least one of the two members 11 that the welded portion 14 is welding. Therefore, the joint strength at the welded portion 14 tends to be higher compared to spot welding. 【0056】 The busbar 10 illustrated in Figure 3 has two plate-shaped members 11 welded together by a weld 14 (14-4). However, the two members 11 are butted together at an oblique angle rather than perpendicularly. In this case as well, the weld 14-4 extends linearly in the D1 direction between approximately both ends of the two members 11 in the D1 direction. Even with this configuration, the same effect as in the example in Figure 2 can be obtained by joining the two members 11 with a weld 14 similar to that in the example in Figure 2. Note that the weld 14-4 is provided on both sides in the thickness direction of the member 11, but is not limited to this, and only one of the two welds 14-4 may be provided. When the weld 14-4 is provided on both sides in the thickness direction, the joint strength is higher than when it is provided on only one side in the thickness direction. 【0057】 The busbar 10 illustrated in Figure 4 has two plate-shaped members 11 welded together at two welds 14 (14-5, 14-6). However, both members 11 extend in the D1 and D2 directions, and their ends overlap in the D3 direction. In this case as well, the welds 14-5 and 14-6 extend linearly in the D1 direction between approximately the two ends of the two members 11 in the D1 direction. Even with this configuration, the same effect as in the example in Figure 2 can be obtained by joining the two members 11 with the same welds 14 as in the example in Figure 2. 【0058】 Furthermore, in the examples shown in Figures 2-4, member 11 may be an extruded material obtained by extrusion molding. An extruded material is a member having a substantially constant cross-sectional shape, such as a wire, a rectangular wire, or a strip-shaped or flat plate-shaped member. Each member 11 can be obtained by cutting the base material 20 at a cross-section intersecting the extrusion direction (longitudinal direction). Such a manufacturing method can, for example, further reduce manufacturing effort and cost. 【0059】 Figure 5 is a schematic diagram showing the beam (spot) of laser light L irradiated onto a planar surface Wa. Each of beams B1 and B2 has a power distribution in the radial direction of the cross-section perpendicular to the optical axis of the beam, for example, a Gaussian shape. However, the power distribution of beams B1 and B2 is not limited to a Gaussian shape. Also, in each diagram where each beam B1 and B2 is represented by a circle as in Figure 5, the diameter of the circle representing the beam B1 and B2 is the beam diameter of each beam B1 and B2. The beam diameter of each beam B1 and B2 includes the peak of the beam and is 1 / e of the peak intensity. 2 This is defined as the diameter of the region with the above intensity. Note that, although not shown in the illustration, for non-circular beams, it is defined as 1 / e of the peak intensity in the direction perpendicular to the sweep direction SD. 2 The length of the region where the intensity is as described above can be defined as the beam diameter. Furthermore, the beam diameter at surface Wa is referred to as the spot diameter. 【0060】 As shown in Figure 5, in this embodiment, as an example, the laser beam L is formed such that the first laser beam B1 and the second laser beam B2 overlap on the surface Wa, with beam B2 being larger (wider) than beam B1, and the outer edge B2a of beam B2 surrounding the outer edge B1a of beam B1. In this case, the spot diameter d2 of beam B2 is larger than the spot diameter d1 of beam B1. On the surface Wa, beam B1 is an example of the first spot, and beam B2 is an example of the second spot. 【0061】 Furthermore, in this embodiment, as shown in Figure 5, the laser beam (spot) on the surface Wa has a point-symmetric shape with respect to the center point C, so the shape of the spot is the same for any sweep direction SD. Therefore, if a moving mechanism is provided to move the optical head 120 and the workpiece W relative to each other for sweeping the laser beam L on the surface Wa, the moving mechanism only needs to have a mechanism that can translate relatively, and a mechanism that can rotate relatively may be omitted. Note that both beams B1 and B2 may be the first laser beam, or both may be the second laser beam. Also, the beam may be just one beam, either the first laser beam or the second laser beam. 【0062】 The two components 11, which are the workpiece W, can each be made of a conductive metallic material. Examples of metallic materials include copper-based materials and aluminum-based materials, specifically copper, copper alloys, aluminum, aluminum alloys, tin-plated copper, tin-plated copper alloys, tin-plated aluminum, and tin-plated aluminum alloys. The two components 11 may be made of the same material or different materials. Furthermore, the plating layer is not limited to tin plating; other platings, such as nickel plating, may also be used. 【0063】 [Wavelength and light absorption rate] Here, we will explain the light absorption rate of metallic materials. Figure 6 is a graph showing the light absorption rate of each metallic material as a function of the wavelength of the irradiated laser light L. In the graph in Figure 6, the horizontal axis is wavelength and the vertical axis is absorption rate. Figure 6 shows the relationship between wavelength and absorption rate for aluminum (Al), copper (Cu), gold (Au), nickel (Ni), silver (Ag), tantalum (Ta), and titanium (Ti). 【0064】 Although the properties differ depending on the material, it can be seen that for each metal shown in Figure 6, the energy absorption rate is higher when using blue or green laser light (second laser light) than when using general infrared (IR) laser light (first laser light). This characteristic is particularly pronounced for copper (Cu) and gold (Au), among others. 【0065】 When laser light is shone onto a workpiece W with a relatively low absorption rate relative to the wavelength used, most of the light energy is reflected and does not affect the workpiece W as heat. Therefore, relatively high power is required to obtain a melted region of sufficient depth. In that case, the rapid energy input to the center of the beam causes sublimation and the formation of a keyhole. 【0066】 On the other hand, when laser light is irradiated onto a workpiece W with a relatively high absorption rate relative to the wavelength used, much of the input energy is absorbed by the workpiece W and converted into thermal energy. In other words, since there is no need to apply excessive power, the melting process is thermal conduction type and does not involve the formation of a keyhole. 【0067】 In this embodiment, the wavelength of the first laser beam, the wavelength of the second laser beam, and the material of the workpiece W are selected such that the absorption rate of the workpiece W to the second laser beam is higher than the absorption rate to the first laser beam. In this case, when the sweep direction is the sweep direction SD shown in Figure 6, the welding area of ​​the workpiece W (hereinafter referred to as the workpiece) is first irradiated with the second laser beam by the region B2f of the second laser beam B2 located in front of SD in Figure 5, as the spot of the laser beam L is swept. Subsequently, the workpiece is irradiated with the first laser beam B1, and then the workpiece is irradiated again with the second laser beam B2 by the region B2b of the second laser beam B2 located behind the sweep direction SD. 【0068】 Therefore, first, a heat conduction type melting region is created in the area to be welded by irradiation with a second laser beam that has a high absorption rate in region B2f. Subsequently, a deeper keyhole type melting region is created in the area to be welded by irradiation with a first laser beam. In this case, since a heat conduction type melting region has already been formed in the area to be welded, a melting region of the required depth can be formed with a first laser beam of lower power compared to when such a heat conduction type melting region is not formed. Furthermore, the melting state of the area to be welded changes due to irradiation with a second laser beam that has a high absorption rate in region B2b. From this viewpoint, it is preferable that the wavelength of the second laser beam be 550 [nm] or less, and more preferably 500 [nm] or less. 【0069】 Furthermore, experimental studies by the inventors have confirmed that welding defects such as spatter and blowholes can be reduced in welding using laser beam L as shown in Figure 5. This is presumed to be because preheating the workpiece W by region B2f of beam B2 before the arrival of beam B1 stabilizes the molten pool of the workpiece W formed by beams B2 and B1. 【0070】 [Welding Method] In welding using the laser processing device 100, first, the workpiece W, in which two members 11 are tacked together, is set up so that the laser beam L is irradiated onto its surface Wa. Then, while the laser beam L is irradiating the surface Wa, the laser beam L and the workpiece W are moved relative to each other. As a result, the laser beam L moves (sweeps) across the surface Wa in the sweeping direction SD while being irradiated onto the surface Wa. The part irradiated with the laser beam L melts, and then solidifies as the temperature decreases, thereby welding the two members 11 together. Welding of the two members 11 is performed at one or more locations to form a busbar 10. 【0071】 [DOE] Furthermore, as shown in Figure 1, the optical head 120 has a DOE 125 between the collimating lens 121-1 and the mirror 123. 【0072】 DOE125 shapes the shape of the first laser beam B1 (hereinafter referred to as the beam shape). As conceptually illustrated in Figure 7, DOE125 has a configuration in which multiple diffraction gratings 125a with different periods are superimposed. DOE125 can shape the beam by bending or superimposing parallel light in the direction influenced by each diffraction grating 125a. DOE125 may also be called a beam shaper. 【0073】 The optical head 120 may also include a beam shaper provided downstream of the collimating lens 121-2 to adjust the beam shape of the second laser beam, or a beam shaper provided downstream of the filter 124 to adjust the beam shapes of the first and second laser beams. By appropriately shaping the beam of the laser beam L with the beam shapers, the occurrence of welding defects in welding can be further suppressed. In addition, the DOE 125 can split the beam of the first laser beam into multiple beams. The optical head 120 does not necessarily have to have the DOE 125. 【0074】 [Cross-section of the welded joint] Figure 8 is a cross-sectional view showing an example of a welded joint 14 formed on the workpiece W. Figure 8 is an example of the case where laser light L, which includes beam B1 from the first laser beam and beam B2 from the second laser beam, is irradiated. Note that the cross-sectional shape differs depending on the laser light irradiated. 【0075】 Figure 8 is a cross-sectional view perpendicular to the sweep direction SD (X direction in Figure 8) and along the thickness direction (Z direction, the depth direction of the weld 14). The weld 14 also extends in the sweep direction SD, that is, in the direction perpendicular to the plane of paper in Figure 8. Figure 8 shows a cross-section of a weld 14 formed on a workpiece W, which is a single copper plate with a thickness of 2 mm. It can be estimated that the shape of the weld 14 joining the two members 11 is approximately the same as the shape of the weld 14 formed on the workpiece W, which is a single metal material, as shown in Figure 8. 【0076】 As shown in Figure 8, the weld 14 has a weld metal 14a extending in the opposite direction from the surface Wa in the Z direction, and a heat-affected zone 14b located around the weld metal 14a. The weld metal 14a is the part that melted due to irradiation with laser light L and then solidified. The weld metal 14a may also be called the molten and solidified part. The heat-affected zone 14b is the part of the base material (base material for welding) of the workpiece W that has been affected by heat, but has not melted. 【0077】 The width of the weld metal 14a along the Y direction narrows as it moves away from the surface Wa. In other words, the cross-section of the weld metal 14a has a tapered shape that narrows in the opposite direction to the Z direction. 【0078】 Furthermore, detailed analysis of the cross-section by the inventors revealed that the weld metal 14a includes a first portion 14a1 separated from the surface Wa, and a second portion 14a2 between the first portion 14a1 and the surface Wa. 【0079】 The first region 14a1 was obtained by keyhole-type melting due to irradiation with the first laser beam, and the second region 14a2 was obtained by melting due to irradiation of region B2b located behind the sweep direction SD in the beam B2 of the second laser beam. Analysis using the EBSD method (electron back scattered diffraction pattern) revealed that the crystal grain sizes differ between the first region 14a1 and the second region 14a2. Specifically, in a cross-section perpendicular to the X direction (sweep direction SD), the average cross-sectional area of ​​the crystal grains in the second region 14a2 was found to be larger than the average cross-sectional area of ​​the crystal grains in the first region 14a1. 【0080】 The inventors confirmed that when only the first laser beam B1 is irradiated onto the workpiece W, that is, when the region B2b located behind the sweep direction SD in beam B2 is not irradiated, the second portion 14a2 is not formed, and the first portion 14a1 extends deeply from the surface Wa in the opposite direction to the Z direction. In other words, in this embodiment, since the second portion 14a2 is formed near the surface Wa by the irradiation of the region B2b located behind the sweep direction SD in beam B2, it can be inferred that the first portion 14a1 is formed on the opposite side of the surface Wa from the second portion 14a2, or in other words, at a position away from the surface Wa in the opposite direction to the Z direction. 【0081】 Figure 9 is a cross-sectional view showing an example of a part of the welded joint 14. Figure 9 shows the boundaries of crystal grains obtained by the EBSD method. In Figure 9, as an example, crystal grains A with a grain size of 13 [μm] or less are colored black. Note that 13 [μm] is not a threshold for physical properties, but a threshold set for the analysis of the experimental results. Furthermore, from Figure 9, it is clear that crystal grains A are relatively abundant in the first part 14a1 and relatively few in the second part 14a2. That is, the average value of the cross-sectional area of ​​crystal grains in the second part 14a2 is larger than the average value of the cross-sectional area of ​​crystal grains in the first part 14a1. The inventors confirmed through experimental analysis that the average value of the cross-sectional area of ​​crystal grains in the second part 14a2 is 1.8 times or more than the average value of the cross-sectional area of ​​crystal grains in the first part 14a1. 【0082】 As shown in region I in Figure 9, these relatively small crystal grains A are densely clustered in an elongated shape in the Z direction, at a position away from the surface Wa in the Z direction. Furthermore, analysis at multiple locations with different positions in the X direction (sweep direction SD) has confirmed that the region where crystal grains A are densely clustered also extends in the sweep direction SD. Since welding is performed while sweeping, it can be inferred that crystals form in a similar morphology in the sweep direction SD. 【0083】 In cases where it is difficult to distinguish between the first part 14a1 and the second part 14a2 from the appearance or hardness distribution in the cross-section, the first region Z1 and the second region Z2, which are geometrically defined from the position and width wb on the surface Wa of the weld metal 14a as shown in Figures 8 and 9, may be designated as the first part 14a1 and the second part 14a2, respectively. For example, the first region Z1 and the second region Z2 are rectangular regions with a width wm (equal width in the Y direction) extending in the Z direction in a cross-section perpendicular to the sweep direction SD, the second region Z2 is the region from the surface Wa to a depth d in the Z direction, and the first region Z1 can be a region even deeper than the depth d, in other words, the region on the opposite side of the surface Wa from the position of depth d. The width wm can be, for example, 1 / 3 of the width wb (average bead width) on the surface Wa of the weld metal 14a, and the depth d (height, thickness) of the second region Z2 can be, for example, 1 / 2 of the width wb. Furthermore, the depth of the first region Z1 can be, for example, three times the depth d of the second region Z2. Through experimental analysis of multiple samples, the inventors confirmed that, with such settings for the first region Z1 and the second region Z2, the average value of the cross-sectional area of ​​the crystal grains in the second region Z2 was greater than the average value of the cross-sectional area of ​​the crystal grains in the first region Z1, and was at least 1.8 times greater. Such a distinction can also serve as evidence that the first region 14a1 and the second region 14a2 are formed in the weld metal 14a by welding. 【0084】 Furthermore, research, including experiments conducted by the inventors, has revealed that, in the welded joint 14, the ratio of the depth of the welded joint 14 (the length of the weld metal 14a in the thickness direction) to the thickness of the thinner of the two members 11 welded by the welded joint 14 is preferably 0.8 or more, and more preferably 0.9 or more. By forming such deep penetration, it becomes possible to ensure joint strength and realize a complex busbar structure, while also reducing electrical resistance. Moreover, by performing welding by irradiation with laser light L including a first laser beam and a second laser beam with different wavelengths, it is possible to suppress the occurrence of welding defects such as spatter and blowholes. 【0085】 Furthermore, the thickness of member 11 is preferably 0.5 mm or more, more preferably 1.0 mm or more, and even more preferably 2.0 mm or more. According to the welding method of this embodiment, a deeper penetration can be formed, so even when welding two members 11 of such thickness, a stronger joint state can be obtained and electrical resistance can be reduced. Moreover, by performing welding by irradiation with laser light L including a first laser beam and a second laser beam with different wavelengths, it is possible to suppress the occurrence of welding defects such as spatter and blowholes even when welding two members 11 of such thickness. 【0086】 As described above, in the busbar 10 of this embodiment, the welded portion 14 that welds the two members 11 extends linearly in the first direction and is provided between approximately both ends of at least one of the two members 11 in the first direction. 【0087】 With this configuration, for example, compared to the case where two members 11 are joined by spot welding, advantages can be obtained, such as higher joint strength at the welded joint 14 and lower electrical resistance at the welded joint 14. Furthermore, if the busbar 10 is manufactured by pressing, the cost of the mold for pressing will be high, which tends to increase the manufacturing cost of the busbar 10 and, consequently, the price of the busbar 10. In this respect, according to this embodiment, since the busbar 10 can be configured in any shape by welding multiple members 11, the advantage of being able to manufacture the busbar 10 at a lower cost can also be obtained. 【0088】 Furthermore, in the busbar 10 of this embodiment, for example, the two members 11-3 and 11-4 welded by the weld portion 14-3 extending in the D2 direction (first direction) may both extend in the D2 direction and in the D1 direction (same direction) intersecting the D2 direction. Alternatively, one of the two members 11 welded by the weld portion 14-1, member 11-1, may extend in the D1 direction (first direction) and in the D2 direction (second direction) intersecting the D1 direction, while the other member 11 of the two members 11, member 11-2, may extend in the D1 direction and in the D3 direction (third direction) intersecting the D1 and D2 directions. In this way, the weld portion 14 of this embodiment can be applied to welding two members 11 arranged in various positions, and consequently, a busbar 10 of any shape can be obtained. 【0089】 Furthermore, in the busbar 10 of this embodiment, a plating layer may be provided on the surface of at least one of the two members 11, or minute irregularities (uneven texture) may be provided on the surface of at least one of the two members 11 by surface treatment such as sandblasting, shot peening, laser processing, or chemical etching. The welded joint 14 of this embodiment can be applied to joining such two members 11. With this configuration, for example, it is possible to obtain the effect of preventing damage or corrosion by providing a plating layer on the surface of the member 11, and the effect of improving heat dissipation by providing minute irregularities on the surface of the member 11. It is preferable to apply the surface treatment that forms the plating layer or irregularities to the flat member 11 before welding with the welded joint 14. This makes it easier to apply the surface treatment compared to applying the surface treatment to the assembled busbar 10, or to apply the surface treatment under conditions suitable for obtaining the required characteristics in each location. 【0090】 Furthermore, in the manufacturing method of the busbar 10 of this embodiment, the welded portion 14 may be formed by irradiation with laser light containing multiple beams, for example. With such a manufacturing method, for example, the preheating effect of a sub-beam irradiated before the main beam makes it possible to form a higher quality welded portion 14 in which spatter and blowholes are suppressed. 【0091】 Furthermore, in the busbar manufacturing method of this embodiment, for example, multiple beams may be formed by a DOE125 (beam shaper). With such a manufacturing method, multiple beams can be formed from a single laser beam, which offers advantages such as being able to weld higher quality welds 14 with a simpler laser processing device 100, or reducing the energy consumption of the laser processing device 100 for welding. 【0092】 Furthermore, in the busbar of this embodiment, the welded portion 14 has a weld metal 14a and a heat-affected zone 14b, and the weld metal 14a may have a first portion 14a1 and a second portion 14a2 in which the average value of the cross-sectional area of ​​crystal grains in a cross section along the depth direction of the welded portion 14 is larger than that of the first portion 14a1. 【0093】 Furthermore, in the busbar manufacturing method of this embodiment, the multiple beams B1 and B2 may include a beam B1 from a first laser beam with a wavelength of 800 nm or more and 1200 nm or less, and a beam B2 from a second laser beam with a wavelength of 400 nm or more and 500 nm or less. 【0094】 As described above, the inventors confirmed that in welding by irradiation with a laser beam L that forms such beams B1 and B2 on a surface Wa, welding defects can be further reduced, and that in the welded part 14, a weld metal 14a having a first part 14a1 and a second part 14a2, and a heat-affected zone 14b are formed. This can be presumed to be because, as described above, the workpiece W is preheated by the region B2f of beam B2 from the second laser beam before the arrival of beam B1 from the first laser beam, thereby further stabilizing the molten pool of the workpiece W formed by beams B2 and B1. Therefore, with a laser beam L having such beams B1 and B2, for example, it is possible to perform welding with fewer welding defects and higher welding quality. This effect is more pronounced than when a single laser beam is split by a DOE 125 (beam shaper), and becomes even more pronounced when multiple beams B1 and B2 are further split by a DOE 125. Furthermore, this beam B1 and B2 configuration offers advantages such as the ability to lower the power of the first laser beam. Additionally, when beams B1 and B2 are irradiated coaxially, there is the advantage that relative rotation between the optical head 120 and the workpiece W is unnecessary. 【0095】 Furthermore, in this embodiment, for example, each of the two members 11 is made of either a copper-based metal material or an aluminum-based metal material. If the busbar 10 is used in an environment with high vibration, for example, there is a risk that the connection points between the busbar 10 and other members may be damaged by such vibration. In such cases, by making at least one of the multiple members 11 constituting the busbar 10 from a highly springy material, the flexibility of the busbar 10 can be increased, and consequently, undesirable events caused by vibration can be suppressed in the busbar 10 and other members connected to the busbar 10. In this case, a more suitable busbar 10 can be manufactured by appropriately selecting or combining materials according to the required mechanical properties, electrical properties, etc. Examples of highly springy materials include phosphor bronze, beryllium copper, C7025, C64770, C18142, C18045, etc. 【0096】 Furthermore, in this embodiment, for example, the welding of the welded portion 14 may be controlled based on images captured by the camera 170. With such a manufacturing method, the welded portion 14 can be formed with greater precision. 【0097】 [Second Embodiment] Figure 10 is a perspective view showing a method for manufacturing multiple members 11 according to this embodiment. As shown in Figure 10, the multiple members 11 can be formed by cutting the base material 20 (the base material for cutting) by irradiation with laser light L. If the members 11 were formed by pressing, the cost of the mold for pressing would be high, which would increase the manufacturing cost of the members 11 and the busbar 10, and consequently the price of the busbar 10. In this respect, according to this embodiment, since multiple members 11 can be formed by laser cutting the base material 20, there is also the advantage that the multiple members 11 and consequently the busbar 10 can be manufactured at a lower cost. 【0098】 Furthermore, the laser beam L for laser cutting the base material 20 to obtain multiple components 11 can be irradiated from the optical head 120 of the laser processing device 100. In this case, the settings of each part of the laser processing device 100 are changed depending on whether laser cutting is performed on the base material 20 or laser welding is performed on the two components 11, i.e., to form a welded joint 14. For example, only the first laser beam (beam B1) may be irradiated when laser cutting, while the first laser beam (beam B1) and the second laser beam (beam B2) may be irradiated when laser welding, or the output of the laser devices 111 and 112 may be set lower when laser welding than when laser cutting. In addition, the laser processing device 100 may be equipped with a gas supply mechanism that can blow inert gas from the optical head 120 or from a nozzle other than the optical head 120 toward the workpiece W as needed when laser cutting. Note that the differences in the settings of the laser processing device 100 between laser cutting and laser welding are not limited to these. 【0099】 Although embodiments of the present invention have been illustrated above, these embodiments are merely examples and are not intended to limit the scope of the invention. The above embodiments can be implemented in various other forms, and various omissions, substitutions, combinations, and modifications can be made without departing from the spirit of the invention. Furthermore, each configuration, shape, and other specifications (structure, type, orientation, model, size, length, width, thickness, height, number, arrangement, position, material, etc.) can be modified as appropriate. 【0100】 For example, when sweeping the laser beam over the workpiece, the surface area of ​​the molten pool may be adjusted by sweeping using known methods such as wobbling, weaving, or output modulation. [Explanation of Symbols] 【0101】 10... Bus bar 11, 11-1~11-4… Components 11a...end part 14, 14-1~14-6…Welded section 14a...Weld metal 14a1…first part 14a2…Second part 14b…Heat affected zone 20… (Cutting) base material 100…Laser processing equipment 111…Laser device (first laser oscillator) 112…Laser device (second laser oscillator) 120…Optical head 121, 121-1, 121-2… Collimating lenses 122... Focusing lens 123...Mirror 124... Filter 125...DOE (Diffractive Optical Element) 125a...Diffraction grating 127... Filter 128...Mirror 130… Fiber optic 141... Controller 150…Drive mechanism 170... Camera A...Crystal grain B1... Beam (First Spot) B1a...outer edge B2... Beam (Second Spot) B2a...outer edge B2b…area B2f…area C...center point d1…Spot diameter (outer diameter) d2…Spot diameter (outer diameter) d... depth D1~D3... Direction L... Laser light SD…Sweep direction W...Item to be processed Wa... Surface wb… (width on the surface of the weld metal) wm... (width of the first and second regions) X…direction Y... Direction Z…direction Z1...first area (first part) Z2...Second area (second part)

Claims

[Claim 1] A method for manufacturing a busbar having a plurality of plate-shaped members and a linear welded portion formed by welding two members included in the plurality of members, With the end of one of the two members in a direction intersecting the thickness direction and the other of the two members adjacent to each other, a linear welded portion along the end is formed between the end of the one member in the direction intersecting the thickness direction and the other member by irradiation with laser light containing multiple beams. At the end of the first member in a direction intersecting the thickness direction, the welded portion is formed between each of the ends in the thickness direction and the other member. The aforementioned welded joint is Weld metal and The heat-affected zone located around the weld metal, It has, A method for manufacturing a busbar, wherein the weld metal comprises a first portion and a second portion in which the average value of the cross-sectional area of ​​crystal grains in the cross section along the depth direction of the weld is larger than that of the first portion. [Claim 2] A method for manufacturing a busbar having a plurality of plate-shaped members and a linear welded portion formed by welding two members included in the plurality of members, With the end of one of the two members in a direction intersecting the thickness direction and the other of the two members adjacent to each other, a linear welded portion along the end is formed between the end of the one member in the direction intersecting the thickness direction and the other member by irradiation with laser light containing multiple beams. The aforementioned welded joint is Weld metal and The heat-affected zone located around the weld metal, It has, A method for manufacturing a busbar, wherein the weld metal comprises a first portion and a second portion in which the average value of the cross-sectional area of ​​crystal grains in the cross section along the depth direction of the weld is larger than that of the first portion. [Claim 3] A method for manufacturing a busbar according to claim 1 or 2, wherein the end of the first member in a direction intersecting the thickness direction and the end of the other member in the thickness direction are adjacent to each other, and the welded portion is formed in this manner. [Claim 4] A method for manufacturing a busbar according to claim 1 or 2, wherein the end of one of the members in a direction intersecting the thickness direction and the end of the other member in a direction intersecting the thickness direction are adjacent to each other. [Claim 5] The method for manufacturing a busbar according to claim 4, wherein the end of the first member in a direction intersecting the thickness direction and the end of the other member in a direction intersecting the thickness direction are adjacent, and the thickness direction of the first member and the thickness direction of the other member are parallel, and the welded portion is formed in this manner. [Claim 6] The method for manufacturing a busbar according to claim 4, wherein the end of the first member in a direction intersecting the thickness direction and the end of the other member in a direction intersecting the thickness direction are adjacent, and the welded portion is formed in such a state that the thickness direction of the first member and the thickness direction of the other member are not parallel. [Claim 7] The method for manufacturing a bus bar according to claim 2, wherein the first member and the other member are stacked in the thickness direction of each other to form the welded portion. [Claim 8] A method for manufacturing a bus bar according to claim 2 or 7, wherein the welded portion is formed only between one end in the thickness direction and the other member at the end in a direction intersecting the thickness direction of the first member. [Claim 9] The method for manufacturing a busbar according to any one of claims 1 to 8, wherein the plurality of beams are formed by a beam shaper. [Claim 10] A method for manufacturing a busbar according to any one of claims 1 to 9, wherein the plurality of beams include a beam from a first laser beam with a wavelength of 800 nm or more and 1200 nm or less, and a beam from a second laser beam with a wavelength of 550 nm or less. [Claim 11] The method for manufacturing a busbar according to claim 10, wherein the wavelength of the second laser beam is 400 nm or more and 500 nm or less. [Claim 12] A method for manufacturing a busbar according to any one of claims 1 to 11, wherein the plurality of members are formed by cutting them from a base material by laser cutting. [Claim 13] A method for manufacturing a bus bar according to any one of claims 1 to 11, wherein the plurality of members are formed by cutting a flat extruded material. [Claim 14] A method for manufacturing a busbar according to any one of claims 1 to 13, wherein the welding of the welded portion is controlled based on an image captured by a camera.