Laser welding method and laser welding device

Abstract

To provide a new improved laser welding method and laser welding device that can shorten an exposure section of a core wire from which coating is removed for welding.SOLUTION: A laser welding method for welding a first end of a core wire of a first lead wire and a second end of a core wire of a second lead wire by a laser beam includes the steps of: irradiating at least one of the first end and the second end with a laser beam while sweeping it in a third direction crossing a first direction, and thereby forming a molten pool bridged between the first end and the second end; and solidifying the molten pool. The step of forming the molten pool includes a step of sweeping the laser beam a plurality of times, and the step of sweeping the laser beam the plurality of times includes a first sweeping step of sweeping the laser beam, and a second sweeping step of sweeping the laser beam in a state in which power density per unit area of a virtual plane crossing the first direction is lower than that of the first sweeping step.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to a laser welding method and a laser welding apparatus.

Background Art

[0002] A method of laser welding a portion where the coating of a conductive wire such as a flat wire is removed and the core wire is exposed is known (for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In this type of welding, in order to reduce the influence of the heat generated in the welding on the coating, the coating may be removed longer at the welding location. In this case, the longer the exposed section of the core wire from which the coating has been removed, the more likely a short circuit will occur, or the electrical device having the conductive wire is more likely to be enlarged.

[0005] Therefore, one of the problems of the present invention is to obtain an improved novel laser welding method, a laser welding apparatus, and an electrical device that can make the exposed section of the core wire from which the coating has been removed for welding shorter, for example.

Means for Solving the Problems

[0006] The laser welding method of the present invention is, for example, at the end of the first direction which is the longitudinal direction of the first conductor having a core wire made of a metal material and a coating surrounding the core wire, the first end of the core wire exposed from the coating, and the second end of the core wire exposed from the coating at the end of the first direction of the second conductor having a core wire made of a metal material and a coating surrounding the core wire. A laser welding method for laser welding, comprising the steps of arranging the first end portion and the second end portion so as to extend in the first direction and be adjacent to each other in a second direction intersecting the first direction; irradiating at least one of the first end portion and the second end portion with a laser beam while sweeping in a third direction intersecting the first direction for a time of less than 0.2 [sec] to form a molten pool spanned between the first end portion and the second end portion; and solidifying the molten pool.

[0007] In the laser welding method, the exposed length in the first direction of at least one of the first end portion and the second end portion may be 10 [mm] or less.

[0008] In the laser welding method, the exposed lengths in the first direction of both the first end portion and the second end portion may be 10 [mm] or less.

[0009] In the laser welding method, in the step of forming the molten pool, the laser beam may be swept linearly.

[0010] In the laser welding method, the third direction may intersect the second direction.

[0011] In the laser welding method, the step of forming the molten pool may include a step of sweeping the laser beam a plurality of times.

[0012] In the laser welding method, the step of scanning the laser beam multiple times may include a first scanning step of scanning the laser beam and a second scanning step of scanning the laser beam in a state where the power density per unit area of a virtual plane intersecting the first direction is lower than that in the first scanning step.

[0013] In the laser welding method, the scanning speed of the laser beam in the second scanning step may be higher than the scanning speed of the laser beam in the first scanning step.

[0014] In the laser welding method, the power of the laser beam in the second scanning step may be lower than the power of the laser beam in the first scanning step.

[0015] In the laser welding method, the step of scanning the laser beam multiple times may include a third scanning step of scanning the laser beam at a predetermined intensity and a predetermined scanning speed, and a fourth scanning step of performing at least one of scanning the laser beam at an intensity lower than the predetermined intensity, scanning the laser beam at a scanning speed higher than the predetermined scanning speed, and scanning the laser beam at an intensity lower than the predetermined intensity and at a scanning speed higher than the predetermined scanning speed after the third scanning step.

[0016] In the laser welding method, the step of forming the molten pool may include a step of scanning the laser beam along the third direction and a step of scanning the laser beam along a fourth direction opposite to the third direction.

[0017] In the laser welding method, the step of forming the molten pool may include a step of scanning the laser beam on the first end portion and a step of scanning the laser beam on the second end portion.

[0018] In the laser welding method, in the step of forming the molten pool, the laser beam may include a plurality of beams.

[0019] In the laser welding method, in the step of forming the molten pool, the laser beam may include a plurality of beams having different wavelengths from each other.

[0020] In the laser welding method, the plurality of beams may be spaced apart in the scanning direction of the laser beam.

[0021] In the laser welding method, in the step of forming the molten pool, the laser beam may include a first part including at least one beam having a first power density and a second part including at least one beam having a second power density different from the first power density.

[0022] In the laser welding method, in the step of forming the molten pool, the first part and the second part may be spaced apart from each other in the scanning direction of the laser beam.

[0023] In the laser welding method, the second part may surround the periphery of the first part.

[0024] In the laser welding method, the ratio of the power of the laser beam of the first part to the power of the laser beam of the second part may be 3 / 7 or more and 7 / 3 or less.

[0025] In the laser welding method, the scanning speed of the laser beam may be 150 [mm / sec] or more.

[0026] In the laser welding method, in the step of forming the molten pool, a plurality of laser beams may be irradiated in parallel.

[0027] In the laser welding method, the step of forming the molten pool may include a step of irradiating at least one laser beam to the first end portion and simultaneously irradiating at least one other laser beam to the second end portion.

[0028] In the laser welding method, in the step of forming the molten pool, an inert gas may be supplied toward at least one of the first end portion, the second end portion, the molten pool, and the coating.

[0029] In the laser welding method, the core wire may be a copper-based metal or an aluminum-based metal.

[0030] In the laser welding method, the coating may contain polyether ether ketone.

[0031] The laser welding method of the present invention is, for example, a laser welding method for laser-welding a first exposed portion exposed from a coating in a core wire of a first conductor having a core wire made of a metal material and a coating surrounding the core wire, and a second exposed portion exposed from the coating in a core wire of a second conductor having a core wire made of a metal material and a coating surrounding the core wire, the method including: a step of forming a molten pool extending between the first exposed portion and the second exposed portion by irradiating at least one of the first exposed portion and the second exposed portion with laser light while scanning the laser light for a time less than 0.2 [sec]; and a step of solidifying the molten pool.

[0032] The laser welding apparatus of the present invention is, for example, a laser welding apparatus for laser-welding a first exposed portion exposed from a coating in a core wire of a first conductor having a core wire made of a metal material and a coating surrounding the core wire, and a second exposed portion exposed from the coating in a core wire of a second conductor having a core wire made of a metal material and a coating surrounding the core wire, the apparatus including: a light source that outputs laser light; and an optical head that outputs the laser light from the light source, wherein the optical head forms a molten pool extending between the first exposed portion and the second exposed portion by irradiating at least one of the first exposed portion and the second exposed portion with laser light while scanning the laser light for a time less than 0.2 [sec].

[0033] The electrical device of the present invention includes, for example, a first conductor having a core wire made of a metal material and a coating surrounding the core wire, a second conductor having a core wire made of a metal material and a coating surrounding the core wire, and a welding portion extending between a first exposed portion exposed from the coating of the first conductor and a second exposed portion exposed from the coating of the second conductor. In at least one of the first exposed portion and the second exposed portion, the exposed length between the welding portion and the coating is 10 [mm] or less.

Effect of the Invention

[0034] According to the present invention, for example, it is possible to obtain an improved and novel laser welding method, a laser welding apparatus, and an electrical device that can reduce the thermal influence on the coating and make the exposed section of the core wire from which the coating has been removed shorter.

Brief Description of the Drawings

[0035]

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DETAILED DESCRIPTION OF THE INVENTION

[0036] Hereinafter, exemplary embodiments and modifications of the present invention will be disclosed. The configurations of the embodiments and modifications shown below, as well as the actions and results (effects) brought about by the configurations, are examples. The present invention can also be realized by configurations other than those disclosed in the following embodiments and modifications. Further, according to the present invention, it is possible to obtain at least one of various effects (including derivative effects) obtained by the configuration.

[0037] The following embodiments and modifications have the same components. Hereinafter, for those same components, common reference numerals may be given and overlapping explanations may be omitted.

[0038] In each figure, the X direction is represented by arrow X, the Y direction is represented by arrow Y, and the Z direction is represented by arrow Z. The X direction, Y direction, and Z direction intersect and are orthogonal to each other. The Z direction is the direction in which a plurality of members serving as the object W extend. Note that the Z direction is substantially vertically upward, but may be inclined with respect to the vertically upward direction.

[0039] Also, in this specification, ordinal numbers are given for convenience in distinguishing directions, processes, members, parts, physical quantities, etc., and do not indicate priority or order.

[0040] [First Embodiment] [Overview of Laser Welding Apparatus and Laser Welding] FIG. 1 is a diagram showing a schematic configuration of a laser welding apparatus 100 according to the first embodiment. As shown in FIG. 1, the laser welding apparatus 100 includes a laser device 110, an optical head 120, an optical fiber 130, a drive mechanism 140, a sensor 150, and a control device 200.

[0041] The laser welding apparatus 100 irradiates the surface of an object W to be laser welded with a laser beam L. By the energy of the laser beam L, the object W is partially melted and cooled and solidified, whereby the object W is welded. The object W has a plurality of members, and a molten pool is formed across the plurality of members by laser welding, and the plurality of members are joined by solidifying the molten pool.

[0042] The plurality of members serving as the object W can be made of, for example, a copper-based metal material such as copper or a copper alloy, an aluminum-based metal material such as aluminum or an aluminum alloy, etc. The plurality of members may be made of the same metal material or may be made of different metal materials from each other. Note that the plurality of members serving as the object W are conductors.

[0043] The laser device 110 is equipped with a laser oscillator and is configured to output single-mode laser light with a power of several kW as an example. Note that the laser device 110 may be configured to include a plurality of semiconductor laser elements inside, for example, and output multi-mode laser light with a power of several kW as the total output of the plurality of semiconductor laser elements. Further, the laser device 110 may be equipped with various laser light sources such as a fiber laser, a YAG laser, and a disk laser. Also, the laser device 110 outputs laser light with a wavelength of 400 [nm] or more and 1200 [nm] or less, for example.

[0044] The laser device 110 outputs laser light with a wavelength of 800 [nm] or more and 1200 [nm] or less, for example. The laser oscillator included in the laser device 110 is an example of a light source.

[0045] Also, the laser device 110 may output a continuous wave of laser light or may output a pulse of laser light.

[0046] The control device 200 can control the operation of the laser device 110. For example, the control device 200 can control the laser device 110 to output laser light, stop the output of laser light, or change the output intensity.

[0047] The optical fiber 130 optically connects the laser device 110 and the optical head 120. In other words, the optical fiber 130 guides the laser light output from the laser device 110 to the optical head 120. When the laser device 110 outputs single-mode laser light, the optical fiber 130 is configured to propagate the single-mode laser light. In this case, the M 2 beam quality of the single-mode laser light is set to 1.3 or less. The M 2 beam quality may also be referred to as the M2 factor.

[0048] The optical head 120 is an optical device that transmits and outputs the laser light from the laser device 110 and irradiates the object W. The optical head 120 includes a collimating lens 121, a focusing lens 122, a mirror 124, a DOE 125, and a galvanometer scanner 126. The collimating lens 121, the focusing lens 122, the mirror 124, the DOE 125, and the galvanometer scanner 126 can also be collectively referred to as optical components.

[0049] The collimating lens 121 collimates the laser light input via the optical fiber 130. The collimated laser light becomes parallel light.

[0050] The mirror 124 reflects the laser light that has become parallel light by the collimating lens 121 and directs it toward the galvanometer scanner 126.

[0051] The galvanometer scanner 126 has a plurality of mirrors 126a, 126b. By changing the angles of the plurality of mirrors 126a, 126b, the emission direction of the laser light L from the optical head 120 can be switched, and thereby, the irradiation position of the laser light L on the surface of the object W can be changed. The angles of the mirrors 126a, 126b are each changed by a motor (not shown) controlled by, for example, the control device 200. By changing the emission direction of the laser light L while irradiating the laser light L, the laser light L can be scanned on the surface of the object W.

[0052] The focusing lens 122 focuses the laser light as parallel light that has arrived from the galvanometer scanner 126 and irradiates the object W as the laser light L (output light).

[0053] Also, the DOE 125 (DOE: diffractive optical element) shapes the beam of the laser light that has become parallel light by the collimating lens 121. The DOE 125 is an example of a beam shaper.

[0054] The drive mechanism 140 changes the relative position of the optical head 120 with respect to the object W. The drive mechanism 140 includes, for example, a rotation mechanism such as a motor, a speed reduction mechanism that reduces the rotational output of the rotation mechanism, a motion conversion mechanism that converts the rotation reduced by the speed reduction mechanism into linear motion, and the like. The control device 200 can control the drive mechanism 140 so that the relative positions of the optical head 120 with respect to the object W in the X direction, Y direction, and Z direction change. The drive mechanism 140 can change (switch) the object W to be laser welded among a plurality of objects W supported by a support mechanism (not shown). Further, the drive mechanism 140 can change the irradiation position of the laser beam L on the object W. Also, the drive mechanism 140 can be used to change the irradiation point as the irradiation direction of the laser beam L with respect to the object W is changed. Furthermore, the drive mechanism 140 can change the irradiation position while the laser beam L is being irradiated on the surface of the object W. That is, the drive mechanism 140 can scan the laser beam L on the surface of the object W.

[0055] FIG. 2 is a side view showing the state of the object W before welding. As shown in FIG. 2, the object W has two members 20 (21, 22). Both of the two members 20 are made of a metal material.

[0056] Both of the two members 20 extend in the Z direction and have end portions 20a (21a, 22a) in the Z direction. The end portion 20a extends so as to intersect the Z direction. That is, the end portion 20a extends in the X direction and also extends in the Y direction. The Z direction is an example of a first direction. The end portion 21a is an example of a first end portion, and the end portion 22a is an example of a second end portion.

[0057] The two members 20 are arranged adjacent to each other in the X direction intersecting the Z direction and side by side in the X direction. A gap g is formed between the side surfaces 21a1 and 22a1 facing each other in the X direction. The X direction is an example of a second direction.

[0058] Note that the end portions 21a and 22a may each be slightly inclined with respect to the Z direction and arranged such that the gap g becomes smaller as it extends in the Z direction. That is, the two members 20 may be at least partially in contact. In other words, the size of the gap g is 0 or more. Also, in the example of FIG. 2, the end portion 21a and the end portion 22a are arranged side by side in the X direction and have the same position in the Z direction, but this is not limiting, and the end portion 21a and the end portion 22a may be displaced in the Z direction.

[0059] Further, when welding the object W, that is, the two members 20, the optical head 120 irradiates the end portion 20a with the laser beam L. The irradiation direction of the laser beam L is the direction opposite to the Z direction or a direction inclined with respect to the direction opposite to the Z direction.

[0060] Also, the laser beam L may irradiate both the end portion 21a and the end portion 22a, or may irradiate only one of the end portion 21a and the end portion 22a.

[0061] FIG. 3 is a side view showing a state in which a welded portion 23 (molten pool) is formed in the object W. By irradiating the laser beam L to one of the two end portions 20a, as shown in FIG. 3, the members 20 are melted at each of the end portions 20a, and the welded portion 23 is formed in a state of being spanned over the two end portions 20a. The welded portion 23 is formed by cooling and solidifying the molten pool formed in a state of being spanned between the two end portions 20a. The molten pool, which is a metal material having fluidity, has a shape bulged in the Z direction due to surface tension. Accordingly, the welded portion 23 obtained by solidifying the molten pool also has a shape bulged in the Z direction. The welded portion 23 mechanically connects the two members 21 and 22. Also, since the two members 21 and 22 are metals having conductivity, the welded portion 23 electrically connects the two members 21 and 22.

[0062] The sensor 150 (see FIG. 1) is, for example, a camera that photographs the molten pool formed on the object W. In this case, the sensor 150 is an example of a motion sensor. The control device 200 can acquire the movement (change over time) of the surface of the molten pool from the image acquired by the sensor 150.

[0063] Alternatively, the sensor 150 may be a thermal camera capable of detecting the temperature of the molten pool. In this case, the sensor 150 is an example of a temperature sensor. The control device 200 can acquire the temperature of the molten pool from the temperature image acquired by the sensor 150.

[0064] FIG. 4 is a perspective view of the wire 10 including the member 20. The member 20 is, as an example, the core wire (inner conductor) of the wire 10 as shown in FIG. 4. The wire 10 has the member 20 and the coating 30 of the member 20. In the present embodiment, as an example, the wire 10 is a flat wire.

[0065] The member 20 is made of a metallic material having conductivity. The shape of the cross section of the member 20 orthogonal to the extending direction is substantially rectangular.

[0066] Further, the coating 30 surrounds the member 20. The coating 30 has insulating properties and is made of, for example, enamel, a synthetic resin material, or the like. The coating 30 may have only an enamel layer composed of polyimide or polyamideimide, or may have an enamel layer and an extrusion resin layer surrounding the enamel layer. Further, the synthetic resin material is, as an example, polyetheretherketone, but is not limited thereto.

[0067] The laser welding apparatus 100 is applied to the laser welding of the exposed ends 20a of the members 20 serving as the core wires of the such conducting wires 10 to each other. In this case, prior to welding, the coating 30 is removed in the vicinity of the ends in the extending direction of the two conducting wires 10. The length E of the exposed section 20b of the member 20 is the length in the longitudinal direction (Z direction) from the end 20a of the member 20 to the end 30a of the coating 30, and is an example of the exposed length. The exposed section 20b provided at the end 21a is an example of the first exposed part, and the exposed section 20b provided at the end 22a is an example of the second exposed part. Also, the two conducting wires 10 are examples of the first conducting wire and the second conducting wire.

[0068] As shown in FIG. 2, the exposed sections 20b including the ends 20a of the two members 20 arranged adjacent to each other in a posture facing the same direction (extending direction) are welded by the laser welding apparatus 100.

[0069] The conducting wire 10 may constitute a segment coil (winding) provided in a rotating electric machine as an electric device. The laser welding method by the laser welding apparatus 100 of the present embodiment can be applied to the welding of the ends of the segment coils adjacent to each other set on the stator core. That is, the object W shown in FIG. 3 may be a part of an electric device.

[0070] Also, the conducting wire 10 is not limited to a flat wire, and may be, for example, another conducting wire such as a round wire.

[0071] Also, at the time of welding, in the present embodiment, the gas G is supplied from the gas nozzle 127 toward at least any one of the end 20a (21a, 22a), the molten pool, and the coating 30. The gas G is an inert gas and may also be referred to as an assist gas. The inert gas here refers to a gas that is chemically stable and hardly reacts, and includes, for example, nitrogen, argon, carbon dioxide, or a mixed gas thereof. By supplying the gas G, oxidation of the end 20a and the molten pool can be suppressed, and the end 20a, the molten pool, the coating 30, etc. can be appropriately cooled, and deterioration of the coating 30 due to the heat generated in welding can be suppressed.

[0072] FIG. 5 is a flowchart showing the procedure of the laser welding method. As shown in FIG. 5, first, the coatings 30 of the two conductive wires 10 as the object W are partially removed to form the exposed section 20b of the member 20 (S1).

[0073] Next, the object W is set (S2). In S2, as shown in FIG. 2, the end portions 20a (21a, 22a) are arranged so as to extend in the Z direction and be adjacent to each other in the X direction.

[0074] Next, at least one of the two end portions 20a (21a, 22a) is irradiated with the laser beam L to form a molten pool (S3). In S3, the laser beam L is irradiated while being swept in a direction intersecting the Z direction.

[0075] Next, the molten pool is cooled and solidified to form a welded portion 23 extending between the two end portions 20a, that is, between the two conductive wires 10, as shown in FIG. 3 (S4). In S4, the molten pool may be cooled naturally or forcedly.

[0076] [Beam pattern of laser beam] FIG. 6 is a plan view showing an example of the beam pattern of the laser beam L output from the optical head 120 of the present embodiment. In FIG. 6, the beam B1 is shown by a solid line and the beam B2 is shown by a broken line.

[0077] As shown in FIG. 6, the laser beam L includes a plurality of beams B1 and B2, and includes at least one beam B1 and at least one beam B2. The power densities of the beams B1 and B2 may be different from each other. Such beams B1 and B2 can be formed and arranged by the DOE 125. Note that by replacing the DOE 125, the shape, arrangement, power density, etc. of the beams B1 and B2 can be changed.

[0078] Each of the beam B1 and the beam B2 has a power distribution, for example, in a Gaussian shape, in the radial direction of a cross-section orthogonal to the optical axis direction of the beam. However, the power distributions of the beam B1 and the beam B2 are not limited to the Gaussian shape. In FIG. 6, the diameter of the circle representing the beams B1 and B2 is the beam diameter of each of the beams B1 and B2. The beam diameter of each of the beams B1 and B2 includes the peak of the beam and is defined as the diameter of the region with a peak intensity of 1 / e 2 or more. Also, although not shown, in the case of a non-circular beam, the length of the region with a peak intensity of 1 / e 2 or more in the direction perpendicular to the sweeping direction SD in a plan view can be defined as the beam diameter.

[0079] Among the laser light L, the part including the beam B1 is an example of the first part, and the part including the beam B2 is an example of the second part. In the example of FIG. 6, the laser light L includes one beam B1 constituting the first part and a plurality of beams B2 constituting the second part.

[0080] The second part having the beam B2 is formed in a circumferential shape and is arranged so as to surround the first part having the beam B1. Also, the first part and the second part are separated in the sweeping direction SD.

[0081] In the example of FIG. 6, the width D1 in the sweeping direction SD of the first part is the diameter of the circular beam B1 and is defined as the diameter of the region with a peak intensity of 1 / e 2 or more. Also, the width D2 in the sweeping direction SD of the second part is defined as the distance between the centers of the two beams B2 that are most separated from each other in the direction perpendicular to the sweeping direction SD in a plan view.

[0082] [Scanning path] FIG. 7 is an explanatory diagram (plan view) showing an example of the scanning path R1 of the laser beam L at the ends 21a and 22a. In the present embodiment, the laser beam L is linearly scanned in a direction intersecting the Z direction in the order of the scanning paths R11, R12, R13, and R14. The scanning paths R11 and R12 are the paths along which the laser beam L is scanned on the end 21a, and the scanning paths R13 and R14 are the paths along which the laser beam L is scanned on the end 22a. Thus, the step (S3) of irradiating the ends 21a and 22a with the laser beam L to form a molten pool on the ends 21a and 22a includes the step of scanning the laser beam L a plurality of times.

[0083] As shown in FIG. 7, both the end 21a and the end 22a have a rectangular shape in plan view. In the present embodiment, as an example, they have a side extending in the X direction and a side extending in the Y direction, and have a rectangular shape that is relatively short in the X direction and relatively long in the Y direction. In this case, the Y direction can be referred to as the width direction or the longitudinal direction of the cross section, and the X direction can be referred to as the thickness direction or the short side direction of the cross section. In the example of FIG. 7, as an example, the end 21a and the end 22a have the same shape, but it is not limited thereto.

[0084] In the example of FIG. 7, the laser beam L is scanned, for example, in a region A1 closer to the end 22a than the center C1 in the X direction of the end 21a and in a region A2 closer to the end 21a than the center C2 in the X direction of the end 22a. However, the position to be scanned, that is, the irradiation region, is not limited within the regions A1 and A2.

[0085] Also, in the scanning paths R11 and R13, the laser beam L is scanned in the Y direction, and in the scanning paths R12 and R14, the laser beam L is scanned in the direction opposite to the Y direction. The Y direction and the direction opposite to the Y direction are an example of the third direction. Also, the Y direction is an example of the fourth direction.

[0086] [Experimental Results] The inventors conducted an experiment to weld the ends 21a and 22a by scanning while irradiating the laser beam L with the beam shape shown in FIG. 6 along the path shown in FIG. 7. In this experiment, regarding the irradiation time of the laser beam L and the length E of the exposed section 20b (exposed length, see FIG. 4), conditions were found under which it is possible to reduce the influence on the coating 30 due to the heat generated during welding. Furthermore, the inventors found conditions under which good welding can be performed regarding the output ratio between the first part and the second part of the laser beam L, the width D2 of the second part, and the scanning speed. In these experiments, the coating 30 was made of polyetheretherketone, and the ends 21a and 22a of the member 20 made of a copper-based metal with a length in the X direction of about 1.5 [mm] and a length in the Y direction of about 3.1 [mm] were irradiated with the laser beam L having a wavelength of 1070 [nm], and the diameter of the spot of the beam B1 at the ends 21a and 22a in a state where no molten pool was formed was set to about 200 [μm]. In this experiment, the irradiation time of the laser beam L was set to 0.06 [sec] or more, and the ratio of the output of the first part to the output of the second part of the laser beam L (output ratio) was set to 5 / 5. Also, the output of the laser device was adjusted in the range of 3 [kW] to 6 [kW] so that the welding of the ends 21a and 22a was completed by the irradiation of the laser beam L at each irradiation time.

[0087] The inventors examined the state of the coating 30 according to the irradiation time of the laser beam L and the length E of the exposed section 20b of the member 20 as the core wire at the end 20a. FIG. 8 is a graph showing an example of the experimental results, with the vertical axis representing the exposed length [mm] corresponding to the peeling length of the coating and the horizontal axis representing the irradiation time [sec] of the laser. In FIG. 8, regarding the state of the coating 30, the best state in which almost no deterioration due to heat is observed is marked as ◎, the excellent state in which slight deterioration due to heat is observed but the required performance such as insulation is obtained is marked as ○, and the poor state in which deterioration due to heat occurs and the required performance such as insulation cannot be obtained is marked as ×.

[0088] As shown in FIG. 8, by setting the irradiation time of the laser beam L to less than 0.2 [sec], more preferably less than 0.1 [sec], even when the length E of the exposure section 20b is shortened to 6 [mm] or more and 10 [mm] or less, further 6 [mm] or more and 8 [mm] or less, it has been found that the state of the coating 30 can be maintained in the best state or excellent state. In this way, even if either one or both of the lengths E of the exposure sections 20b of the members 21 and 22 are 6 [mm] or more and 10 [mm] or less, further 6 [mm] or more and 8 [mm] or less, welding can be performed while reducing the influence of deterioration of the coating 30 due to heat.

[0089] In addition, the inventors conducted experiments using the ratio of the output of the first part to the output of the second part (output ratio) of the laser beam L and the width D2 of the second part (see FIG. 6) as parameters, and found conditions under which good welding can be performed. Table 1 shows an example of the experimental results. In Table 1, the best state where the number of spatters generated during welding (steps S3, S4) is 25 or less is marked as ◎, and the excellent state ○ where it exceeds 25 and is 60 or less.

Table 1

[0090] Furthermore, the inventors conducted experiments using the output ratio and the scanning speed of the laser beam L as parameters, and found conditions under which good welding can be performed. Table 2 shows an example of the experimental results. In Table 2, the best state where the number of spatters generated during welding is 25 or less is marked as ◎, the excellent state ○ where it exceeds 25 and is 60 or less, and the good state △ where it exceeds 50.

Table 2

[0091] Also, from the inventors' experimental research, in the step (S3) of forming the molten pool, when performing multiple scans, by making the power density per unit area of a virtual plane (for example, a virtual plane substantially overlapping the end face of the end portion 20a) that intersects the irradiation direction of the laser beam L in the subsequent scanning step lower than the power density per unit area of the virtual plane in the previous scanning step, it has been found that a better welding state with fewer welding defects such as spatter and blowholes can be obtained. The previous scanning step is an example of the first scanning step, and the subsequent scanning step is an example of the second scanning step.

[0092] FIG. 9 is an X-ray transmission image when viewing a sample of the object W in which a welded portion 23 in a good welding state is obtained from the side. The materials of the members 21, 22 (20) constituting the object W are oxygen-free copper. In the welding of the object W, the irradiation time of the laser beam L is 0.064 [sec], the output is 6 [kW], the output ratio is 5 / 5 (= 1), and the scanning speed is 200 [mm / sec]. As is clear from FIG. 9, in this sample, the number of blowholes was extremely small.

[0093] The power density per unit area of the virtual plane decreases as the scanning speed increases and also decreases as the power of the laser beam L decreases. Therefore, in a subsequent scanning process, by increasing the scanning speed higher than that in the previous scanning process, or decreasing the power of the laser beam L lower than that in the previous scanning process, or increasing the scanning speed higher than that in the previous scanning process and at the same time decreasing the power of the laser beam L lower than that in the previous process, it is possible to make the power density per unit area of the virtual plane lower than that in the previous scanning process in the subsequent scanning process, and thus obtain a better welding state. More specifically, for example, when performing scanning a predetermined number of times (e.g., 3 times or more) in the step (S3) of forming the molten pool, a scan that increases the scanning speed faster than during scanning before the predetermined number of times, a scan that reduces the power of the laser beam L lower than during scanning before the predetermined number of times, and a scan that increases the scanning speed faster than during scanning before the predetermined number of times and at the same time reduces the power of the laser beam L lower than during scanning before the predetermined number of times, by performing at least one of these scans, a better welding state can be obtained.

[0094] As described above, according to the laser welding method and the laser welding apparatus 100 of the present embodiment, in the step (S3) of forming the molten pool, the laser beam L is irradiated in less than 0.2 [sec] while scanning in the Y direction or the opposite direction (third direction) of the Y direction that intersects the Z direction (first direction) on at least one of the end portion 21a (first end portion) and the end portion 22a (second end portion), thereby forming a molten pool spanned between the end portion 21a and the end portion 22a.

[0095] By such irradiation of the laser beam L, deterioration of the coating 30 due to heat generated during welding can be suppressed. Also, in the wire 10, the length E of the exposed section 20b for welding can be made relatively short, for example, 10 [mm] or less. Therefore, for example, it becomes less likely for a short circuit to occur through the exposed section 20b, and an effect such as suppressing the enlargement of the electrical device including the wire 10 having the member 20 and the coating 30 can be obtained.

[0096] Also, in the present embodiment, the coating 30 of the conductor 10 with a relatively short length E of the exposed section 20b as described above can be made of a material containing polyetheretherketone as a synthetic resin material. That is, according to the present embodiment, as the coating 30 of the conductor 10 of the electrical device, a coating 30 containing polyetheretherketone with higher insulation, that is, higher breakdown voltage than polyimide or the like can be adopted. Therefore, for example, an electrical device with higher breakdown voltage, less likely to cause a short circuit, and easier to configure in a more compact manner can be formed.

[0097] Also, in the present embodiment, a first part including the beam B1 of the laser beam L and a second part including the beam B2 are at least separated from each other in the scanning direction SD. According to the present embodiment, for example, before a molten pool in a keyhole state is formed by the first part of the laser beam L including the beam B1, the end portions 21a and 22a can be preliminarily heated by the second part of the laser beam L including the beam B2, thereby suppressing a rapid temperature rise of the end portions 21a and 22a. As a result, the molten pool can be made more stable, and thus, the occurrence of welding defects such as sputtering and blowholes can be suppressed.

[0098] [Another example of beam shape (modification example)] FIG. 10 is a plan view showing another example of the beam pattern of the laser beam L. In the example of FIG. 10, the second part including the beam B2 does not have an annular (circular) shape. However, also in this example, the second part including the beam B2 is arranged spaced apart from the first part of the laser beam L including the beam B1 in the scanning direction SD and the direction opposite to the scanning direction SD. Also with a beam pattern like that of FIG. 10, the object W can be preliminarily heated by the second part of the laser beam L before the first part of the laser beam L is irradiated, so the same effects as in the above-described embodiment can be obtained. Further, according to the example of FIG. 10, even when the laser beam L is scanned in a direction opposite to the scanning direction SD of FIG. 10 without rotating the optical head 120 around the Z axis, the effect of suppressing welding defects by preheating can be obtained. Also, as in the example of FIG. 6, when the second part has an annular shape, when scanning in an arbitrary direction intersecting the Z direction without rotating the optical head 120 around the Z axis, the effect of suppressing welding defects by preheating can be obtained. That is, if at least a part of the second part including the beam B2 exists in front of the first part including the beam B1 in the scanning direction, the effect of suppressing welding defects by preheating can be obtained.

[0099] [Another example (modification) of the scanning path] FIG. 11 is an explanatory view (plan view) showing an example different from FIG. 7 of the scanning paths R1 and R2 of the laser beam L at the ends 21a and 22a. In this example, a molten pool is formed by irradiating the laser beam L simultaneously and in parallel at a plurality of locations (for example, two locations) on the end 20a. Specifically, in parallel with scanning the laser beam L on the end 21a along the scanning path R11 (R1), the laser beam L is scanned on the end 22a along the scanning path R21 (R2), and then, in parallel with scanning the laser beam L on the end 21a along the scanning path R12 (R1), the laser beam L is scanned on the end 22a along the scanning path R22 (R2).

[0100] According to such a method, the process of forming the molten pool can be completed in a shorter time, so that the deterioration of the coating 30 due to the heat generated during welding can be further suppressed. Note that the irradiation of the laser beam L to such a plurality of locations may be performed by a plurality of optical heads 120, or a plurality of laser beams L may be branched from one optical head 120 for irradiation.

[0101] [Second Embodiment] FIG. 12 is a diagram showing a schematic configuration of a laser welding apparatus 100A according to the second embodiment. As shown in FIG. 12, the laser welding apparatus 100A has a plurality of laser devices 111, 112 (110).

[0102] The laser device 111 is the same as that in the first embodiment, and outputs, for example, a first laser beam having a wavelength of 800 [nm] or more and 1200 [nm] or less. The laser device 111 may also be referred to as a first laser device. The laser oscillator included in the laser device 111 is a light source and may also be referred to as a first laser oscillator.

[0103] On the other hand, the laser device 112 outputs, for example, a second laser beam having a wavelength of 300 [nm] or more and 600 [nm] or less. The laser device 112 may also be referred to as a second laser device. The laser oscillator included in the laser device 112 is a light source and may also be referred to as a second laser oscillator.

[0104] Regarding copper-based materials and aluminum-based materials, the second laser beam has a higher absorption rate and a lower reflectance than the first laser beam.

[0105] Also, the laser devices 111 and 112 may each output a continuous wave of the laser beam or may output a pulse of the laser beam.

[0106] Filter 123 is a high-pass filter that transmits the first laser light and reflects it without transmitting the second laser light. The first laser light from mirror 124 passes through filter 123 and heads towards galvanometer scanner 126. On the other hand, the second laser light from collimating lens 121 is reflected by filter 123 and heads towards galvanometer scanner 126. Filter 123 may also be referred to as an optical component.

[0107] Although not shown in the figure, optical head 120A may appropriately have DOE 125 that shapes the beam of the first laser light or the second laser light.

[0108] FIG. 13 is a plan view showing an example of the beam pattern of laser light L output from optical head 120A of the present embodiment. As shown in FIG. 6, laser light L includes a plurality of beams B1 and B2. Beam B1 is a beam by the first laser light and constitutes the first part of laser light L. Further, beam B2 is a beam by the second laser light and constitutes the second part of laser light L. Beam B2 has a high absorption rate by object W and forms a heat conduction type molten pool. According to the present embodiment, by scanning in the scanning direction SD, a more gentle heat conduction type molten pool is formed before the keyhole type molten pool is formed by beam B1, so that a rapid temperature rise at ends 21a and 22a is suppressed, and as a result, welding defects such as spatter and blowholes can be suppressed.

[0109] The patterns of beams B1 and B2 having different wavelengths are not limited to the example of FIG. 13, and when laser light L is scanned in the scanning direction SD, at each position of ends 21a and 22a, the second part by beam B2 may reach before the first part by beam B1 reaches. That is, if at least a part of the second part including beam B2 exists in front of the first part including beam B1 in the scanning direction, the effect of suppressing welding defects by preliminary heating can be obtained.

[0110] The above-described embodiments and modified examples of the present invention have been illustrated. However, the above embodiments and modified examples are merely examples and are not intended to limit the scope of the invention. The above embodiments and modified examples can be implemented in various other forms, and various omissions, replacements, combinations, and changes can be made without departing from the gist of the invention. Also, each configuration, shape, etc. of the specifications (structure, type, direction, type, size, length, width, thickness, height, number, arrangement, position, material, etc.) can be appropriately changed and implemented.

[0111] For example, the object may include three or more members. Also, the plurality of members included in the object do not have to be the same member. Further, the object is not limited to a plurality of members arranged or butted against each other, and may be a plurality of members superimposed on each other.

[0112] Also, the exposed section of at least one of the plurality of conductive wires may be provided at an intermediate position in the longitudinal direction of the conductive wire.

[0113] Also, when irradiating the laser beam, known wobbling, weaving, output modulation, etc. may be performed to adjust the surface area of the molten pool.

Explanation of Reference Numerals

[0114] 10... Conductive wire (first conductive wire, second conductive wire) 20... Member 20a... End portion 20b... Exposed section (first exposed portion, second exposed portion) 21... Member (core wire) 21a... End portion (first end portion) 21a1... Side surface 22... Member (core wire) 22a... End portion (second end portion) 22a1... Side surface 23... Weld portion (molten pool) 30... Coating 30a... End portion 100, 100A... Laser welding apparatus 110, 111, 112... Laser device (light source) 120, 120A… Optical head 121… Collimating lens 122… Condensing lens 123… Filter 124… Mirror 125… DOE 126… Galvanometer scanner 126a, 126b… Mirror 127… Gas nozzle 130… Optical fiber 140… Driving mechanism 150… Sensor 200… Control device A1, A2… Regions B1… Beam (first part) B2… Beam (second part) C1, C2… Centers D1… Width D2… Width E… Length (exposure length) g… Gap G… Gas L… Laser light R1, R11, R12, R13, R14, R2, R21, R22… Scanning paths SD… Scanning direction W… Object X… Direction (second direction) Y… Direction (third direction, fourth direction) Z… Direction (first direction)

Claims

1. A laser welding method for laser-welding a first end portion of the core wire exposed from the coating at an end portion in a first direction which is the longitudinal direction of a first conductor having a core wire made of a metal material and a coating surrounding the core wire, and a second end portion of the core wire exposed from the coating at the end portion in the first direction of a second conductor having a core wire made of a metal material and a coating surrounding the core wire, comprising: a step of arranging the first end portion and the second end portion adjacent to each other in a second direction intersecting the first direction; a step of forming a molten pool spanned between the first end portion and the second end portion by irradiating at least one of the first end portion and the second end portion with a laser beam while sweeping in a third direction intersecting the first direction; a step of solidifying the molten pool; and comprising: the step of forming the molten pool includes a step of sweeping the laser beam a plurality of times; the step of sweeping the laser beam a plurality of times includes a first sweeping step of sweeping the laser beam and a second sweeping step of sweeping the laser beam in a state where the power density per unit area of a virtual plane intersecting the first direction is lower than that in the first sweeping step. A laser welding method.

2. The wavelength of the laser beam is 400 [nm] or more and 1200 [nm] or less. The laser welding method according to Claim 1.

3. The exposed length in the first direction of at least one of the first end portion and the second end portion is 10 [mm] or less. The laser welding method according to Claim 1 or 2.

4. The exposed lengths in the first direction of both the first end portion and the second end portion are 10 [mm] or less. The laser welding method according to Claim 1 or 2.

5. In the step of forming the molten pool, the laser beam is swept linearly. The laser welding method according to any one of Claims 1 to 4.

6. The third direction intersects the second direction. The laser welding method according to any one of Claims 1 to 5.

7. The sweeping speed of the laser beam in the second sweeping step is higher than the sweeping speed of the laser beam in the first sweeping step. The laser welding method according to any one of Claims 1 to 6.

8. The power of the laser beam in the second sweeping step is lower than the power of the laser beam in the first sweeping step. The laser welding method according to any one of Claims 1 to 7.

9. The step of scanning the laser beam a plurality of times includes a third scanning step of scanning the laser beam at a predetermined intensity and a predetermined scanning speed, and after the third scanning step, scanning the laser beam at an intensity lower than the predetermined intensity, scanning the laser beam at a scanning speed higher than the predetermined scanning speed, and performing at least one of scanning the laser beam at an intensity lower than the predetermined intensity and at a scanning speed higher than the predetermined scanning speed. The laser welding method according to any one of claims 1 to 8.

10. The step of forming the molten pool includes a step of scanning the laser beam along the third direction and a step of scanning the laser beam along a fourth direction opposite to the third direction. The laser welding method according to any one of claims 1 to 9.

11. The step of forming the molten pool includes a step of scanning the laser beam on the first end portion and a step of scanning the laser beam on the second end portion. The laser welding method according to any one of claims 1 to 10.

12. In the step of forming the molten pool, the laser beam includes a plurality of beams. The laser welding method according to any one of claims 1 to 11.

13. In the step of forming the molten pool, the laser beam includes a plurality of beams having different wavelengths from each other. The laser welding method according to claim 12.

14. The plurality of beams are spaced apart in the scanning direction of the laser beam. The laser welding method according to claim 12 or 13.

15. In the step of forming the molten pool, the laser beam includes a first portion including at least one beam having a first power density and a second portion including at least one beam having a second power density different from the first power density. The laser welding method according to any one of claims 12 to 14.

16. In the step of forming the molten pool, the first portion and the second portion are spaced apart from each other in the scanning direction of the laser beam. The laser welding method according to claim 15.

17. The second portion surrounds the periphery of the first portion. The laser welding method according to claim 15.

18. The ratio of the power of the laser beam of the first portion to the power of the laser beam of the second portion is 3 / 7 or more and 7 / 3 or less. The laser welding method according to claim 17.

19. The laser welding method according to any one of claims 1 to 18, wherein the scanning speed of the laser beam is 150 [mm / sec] or more.

20. The laser welding method according to any one of claims 1 to 19, wherein in the step of forming the molten pool, a plurality of laser beams are irradiated in parallel.

21. The laser welding method according to claim 20, wherein the step of forming the molten pool includes a step of irradiating at least one laser beam to the first end portion and simultaneously irradiating at least one other laser beam to the second end portion.

22. The laser welding method according to any one of claims 1 to 21, wherein in the step of forming the molten pool, an inert gas is supplied toward at least one of the first end portion, the second end portion, the molten pool, and the coating.

23. The laser welding method according to any one of claims 1 to 22, wherein the core wire is a copper-based metal or an aluminum-based metal.

24. The laser welding method according to any one of claims 1 to 22, wherein the coating contains polyether ether ketone.

25. A laser welding apparatus for performing the laser welding method according to any one of claims 1 to 24, a light source that outputs a laser beam, an optical head that outputs the laser beam from the light source, The laser welding apparatus is provided with.

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