Laser Welding Method

Abstract

To obtain improved new laser welding method, laser welding device, and electric apparatus each of which enables, for example, further shortening of an exposure section of a core wire of which the coating has been removed for welding.SOLUTION: A laser welding method, for example, performs laser welding of a first end of a core wire exposed from a coating at an end portion in a first direction that is a longitudinal direction of a first conducting wire, and a second end of the core wire exposed from a coating at an end portion in a first direction of a second conducting wire. The method comprises: a step in which the first end and the second end are arranged in such a manner that the first and the second ends extend in the first direction and are adjacent to each other in a second direction crossing the first direction; a step in which at least one of the first end and the second is irradiated with laser beam during a time less than 0.2 [sec] while being swept in a third direction crossing the first direction, thereby forming a molten pool spanned between the first end and the second end; and a step in which the molten pool is solidified.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to a laser welding method. By law Regarding. [Background technology]

[0002] 2. Description of the Related Art There is known a method of laser welding a portion of a conductor such as a rectangular wire, in which a coating is removed to expose the core wire (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2020-142283 A Summary of the Invention [Problem to be solved by the invention]

[0004] In this type of welding, in order to reduce the effect of heat generated during the welding on the coating, a longer portion of the coating may be removed from the welded portion. In this case, the longer the exposed section of the core wire from which the coating has been removed, the more likely it is that a short circuit will occur or that the electrical device including the conductor will be larger in size.

[0005] Therefore, one object of the present invention is to provide an improved and new laser welding method, laser welding apparatus, and electrical device that, for example, makes it possible to shorten the exposed section of the core wire from which the coating has been removed for welding. [Means for solving the problem]

[0006] The laser welding method of the present invention is, for example, a laser welding method for laser welding a first end of a first conductor having a core wire made of a metallic material and a coating surrounding the core wire, the first end of the core wire being exposed from the coating at an end in the first direction, which is the longitudinal direction of the first conductor, and a second end of the core wire being exposed from the coating at an end in the first direction of a second conductor having a core wire made of a metallic material and a coating surrounding the core wire, the method including the steps of: arranging the first end and the second end so that they extend in the first direction and are adjacent to each other in a second direction intersecting the first direction; irradiating at least one of the first end and the second end with a laser beam for a time of less than 0.2 sec while sweeping the laser beam in a third direction intersecting the first direction, thereby forming a molten pool spanning between the first end and the second end; and solidifying the molten pool.

[0007] In the laser welding method, an 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, an exposed length 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 with the second direction.

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

[0012] In the laser welding method, the step of sweeping the laser light multiple times may include a first sweep step of sweeping the laser light, and a second sweep step of sweeping the laser light 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 sweep step.

[0013] In the laser welding method, a sweep speed of the laser light in the second sweeping step may be higher than a sweep speed of the laser light in the first sweeping step.

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

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

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

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

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

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

[0020] In the laser welding method, the multiple beams may be spaced apart in a sweep direction of the laser light.

[0021] In the laser welding method, in the process of forming the molten pool, the laser light may include 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.

[0022] In the laser welding method, in the step of forming the molten pool, the first portion and the second portion may be spaced apart from each other in a sweep direction of the laser light.

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

[0024] In the laser welding method, a ratio of a power of the laser light in the first portion to a power of the laser light in the second portion may be not less than 3 / 7 and not more than 7 / 3.

[0025] In the laser welding method, a sweep speed of the laser light 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 at least another laser beam to the second end portion simultaneously.

[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, the second end, the molten pool, and the coating.

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

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

[0031] The laser welding method of the present invention is a laser welding method for laser welding, for example, a first exposed portion of a core wire of a first conductor having a core wire made of a metallic material and a coating surrounding the core wire, which is exposed from the coating, and a second exposed portion of a core wire of a second conductor having a core wire made of a metallic material and a coating surrounding the core wire, which includes the steps of irradiating at least one of the first exposed portion and the second exposed portion with a laser beam while sweeping the beam for a time of less than 0.2 sec to form a molten pool spanning the first exposed portion and the second exposed portion, and solidifying the molten pool.

[0032] The laser welding apparatus of the present invention is, for example, a laser welding apparatus that laser welds a first exposed portion of a core wire of a first conductor having a core wire made of a metallic material and a coating surrounding the core wire, and a second exposed portion of a core wire of a second conductor having a core wire made of a metallic material and a coating surrounding the core wire, the laser welding apparatus comprising a light source that outputs laser light and an optical head that outputs the laser light from the light source, and the optical head irradiates at least one of the first exposed portion and the second exposed portion with the laser light for a time of less than 0.2 [sec] while sweeping the laser light, thereby forming a molten pool spanning the first exposed portion and the second exposed portion.

[0033] The electrical device of the present invention comprises, for example, a first conductor having a core wire made of a metallic material and a coating surrounding the core wire, a second conductor having a core wire made of a metallic material and a coating surrounding the core wire, and a welded 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, wherein the exposed length between the welded portion and the coating in at least one of the first exposed portion and the second exposed portion is 10 mm or less. Effect of the Invention

[0034] According to the present invention, it is possible to provide an improved and novel laser welding method, laser welding apparatus, and electrical device that, for example, reduces the thermal effect on the coating and enables the exposed section of the core wire from which the coating has been removed to be shorter. [Brief description of the drawings]

[0035] [Figure 1] FIG. 1 is an exemplary schematic configuration diagram of a laser welding device according to a first embodiment. [Diagram 2] FIG. 2 is an exemplary schematic side view of an object before welding in the laser welding method according to the embodiment. [Diagram 3] FIG. 3 is an exemplary schematic side view of an object after welding according to the laser welding method of the embodiment. [Figure 4] FIG. 4 is an exemplary schematic perspective view of a rectangular wire including a member as an object of the laser welding method according to the embodiment. [Diagram 5] FIG. 5 is a flowchart showing an example of a procedure of the laser welding method according to the embodiment. [Figure 6] FIG. 6 is a schematic plan view showing an example of a beam pattern of laser light in the laser welding device of the first embodiment. [Figure 7] FIG. 7 is a schematic plan view showing an example of a sweep path of a laser beam in the laser welding method according to the embodiment. [Figure 8]FIG. 8 is a graph showing an example of a state of a coating depending on a laser light irradiation time and an exposed length of a core wire in the laser welding method of the embodiment. [Figure 9] FIG. 9 is an X-ray transmission image, viewed from the side, of a sample of an object on which a welded portion in a good condition was obtained by the laser welding method of the embodiment. [Figure 10] FIG. 10 is a schematic plan view showing another example of the beam pattern of the laser light in the laser welding apparatus of the embodiment. [Figure 11] FIG. 11 is a schematic plan view showing another example of a sweep path of the laser beam in the laser welding method according to the embodiment. [Figure 12] FIG. 12 is an exemplary schematic configuration diagram of the laser welding device according to the second embodiment. [Figure 13] FIG. 13 is a schematic plan view showing an example of a beam pattern of a laser beam in the laser welding device of the second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

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

[0037] The following embodiments and modifications have similar components, and in the following description, the same reference numerals will be used to denote the similar components, and duplicated descriptions may be omitted.

[0038] In each figure, the X direction is represented by an arrow X, the Y direction is represented by an arrow Y, and the Z direction is represented by an arrow Z. The X direction, the Y direction, and the Z direction intersect with each other and are perpendicular to each other. The Z direction is the direction in which multiple members that are the target object W extend. Note that the Z direction is approximately vertically upward, but may be inclined relative to the vertically upward direction.

[0039] In this specification, ordinal numbers are given for the sake of convenience to distinguish directions, processes, members, parts, physical quantities, etc., and do not indicate priority or order.

[0040] [First embodiment] [Laser welding equipment and laser welding overview] 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 driving mechanism 140, a sensor 150, and a control device 200.

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

[0042] Each of the multiple members that constitute the target object W can be made of, for example, a copper-based metal material such as copper or a copper alloy, or an aluminum-based metal material such as aluminum or an aluminum alloy. The multiple members may be made of the same metal material, or may be made of different metal materials. The multiple members that constitute the target object W are conductors.

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

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

[0045] Furthermore, 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 output of laser light, and change 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 a single mode laser light, the optical fiber 130 is configured to propagate the single mode laser light. In this case, the M of the single mode laser light 2 The beam quality is set to 1.3 or less. 2 The 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 target object W. The optical head 120 has a collimator lens 121, a condenser lens 122, a mirror 124, a DOE 125, and a galvanometer scanner 126. The collimator lens 121, the condenser lens 122, the mirror 124, the DOE 125, and the galvanometer scanner 126 may also be 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 been collimated by the collimator lens 121 , and directs it toward the galvano scanner 126 .

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

[0052] The condenser lens 122 condenses the laser light coming from the galvano scanner 126 as parallel light, and irradiates the target object W with the laser light L (output light).

[0053] Further, the DOE 125 (DOE: diffractive optical element) shapes the laser light beam that has been collimated by the collimator lens 121. The DOE 125 is an example of a beam shaper.

[0054] The driving mechanism 140 changes the relative position of the optical head 120 with respect to the object W. The driving mechanism 140 has, for example, a rotating mechanism such as a motor, a speed reducing mechanism for reducing the rotation output of the rotating mechanism, and a motion conversion mechanism for converting the rotation reduced by the speed reducing mechanism into a linear motion. The control device 200 can control the driving mechanism 140 so that the relative position of the optical head 120 with respect to the object W in the X direction, Y direction, and Z direction changes. The driving 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). The driving mechanism 140 can also change the irradiation position of the laser light L on the object W. The driving mechanism 140 can also be used to change the irradiation point along with changing the irradiation direction of the laser light L on the object W. Furthermore, the driving mechanism 140 can change the irradiation position in a state in which the laser light L is irradiated on the surface of the object W. That is, the driving mechanism 140 can sweep the laser light L over the surface of the object W.

[0055] Fig. 2 is a side view showing a state before welding of the object W. 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 Z-direction end portions 20a (21a, 22a). The end portions 20a extend across the Z direction. That is, the end portions 20a extend in the X direction and the Y direction. The Z direction is an example of a first direction. The end portions 21a are an example of a first end portion, and the end portions 22a are an example of a second end portion.

[0057] The two members 20 are disposed adjacent to each other in the X direction intersecting the Z direction and aligned 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 the second direction.

[0058] The ends 21a and 22a may be arranged so as to be slightly inclined with respect to the Z direction, and the gap g may become smaller toward the Z direction. That is, the two members 20 may be at least partially in contact with each other. That is, the size of the gap g is equal to or greater than 0. In addition, in the example of FIG. 2, the ends 21a and 22a are aligned in the X direction and are at the same position in the Z direction, but this is not limiting, and the ends 21a and 22a may be shifted in the Z direction.

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

[0060] Moreover, the laser light L may be irradiated to both the end portion 21a and the end portion 22a, or may be irradiated to 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 on the object W. By irradiating one of the two end portions 20a with the laser light L, as shown in FIG. 3, the member 20 melts at each of the end portions 20a, and the welded portion 23 is formed in a state in which it is bridged over the two end portions 20a. The welded portion 23 is formed by cooling and solidifying the molten pool formed in a state in which it is bridged between the two end portions 20a. The molten pool, which is a fluid metal material, has a shape that bulges in the Z direction due to surface tension. Accordingly, the welded portion 23, which is the solidified molten pool, also has a shape that bulges in the Z direction. The welded portion 23 mechanically connects the two members 21 and 22. In addition, since the two members 21 and 22 are made of conductive metal, 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 captures an image of a molten pool formed on the target object W. In this case, the sensor 150 is an example of a motion sensor. The control device 200 can obtain the motion (change over time) of the surface of the molten pool from the image obtained by the sensor 150.

[0063] 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 obtain the temperature of the molten pool from the temperature image obtained by the sensor 150.

[0064] Fig. 4 is a perspective view of the conductor 10 including a member 20. As an example, the member 20 is a core wire (internal conductor) of the conductor 10 as shown in Fig. 4. The conductor 10 has the member 20 and a coating 30 of the member 20. In this embodiment, as an example, the conductor 10 is a rectangular wire.

[0065] The member 20 is made of a conductive metal material and has a substantially rectangular cross section perpendicular to the extension direction of the member 20.

[0066] The coating 30 surrounds the member 20. The coating 30 has insulating properties and is made of, for example, enamel or a synthetic resin material. The coating 30 may have only an enamel layer made of polyimide or polyamideimide, or may have an enamel layer and an extruded resin layer surrounding the enamel layer. An example of the synthetic resin material is polyetheretherketone, but is not limited to this.

[0067] The laser welding device 100 is applied to laser welding of the ends 20a exposed from the coating 30 of the member 20 serving as the core of such a conductor 10. In this case, prior to welding, the coating 30 is removed near the ends of the two conductors 10 in the extension direction. 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 a first exposed portion, and the exposed section 20b provided at the end 22a is an example of a second exposed portion. The two conductors 10 are an example of a first conductor and a second conductor.

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

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

[0070] Moreover, the conductor wire 10 is not limited to a rectangular wire, but may be another type of conductor wire, such as a round wire.

[0071] In addition, in this embodiment, during welding, gas G is supplied from the gas nozzle 127 toward at least one of the end 20a (21a, 22a), the molten pool, and the coating 30. The gas G is an inert gas, which may also be called an assist gas. Here, the inert gas refers to a gas that is chemically stable and does not easily react, and includes, for example, nitrogen, argon, carbon dioxide, or a mixture of these gases. 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 heat generated during welding can be suppressed.

[0072] Fig. 5 is a flow chart 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 sections 20b of the member 20 (S1).

[0073] Next, the target object W is set (S2). In S2, as shown in Fig. 2, the ends 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, a molten pool is formed by irradiating at least one of the two ends 20a (21a, 22a) with a laser beam L (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, and a weld 23 is formed between the two ends 20a, i.e., between the two conductors 10, as shown in Fig. 3 (S4). In S4, the molten pool may be cooled naturally or forcibly.

[0076] [Laser beam pattern] Fig. 6 is a plan view showing an example of a beam pattern of the laser light L outputted from the optical head 120 of this embodiment. In Fig. 6, the beam B1 is indicated by a solid line, and the beam B2 is indicated by a dashed line.

[0077] 6, the laser light L includes a plurality of beams B1 and B2, including 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 positioned by the DOE 125. Note that by replacing the DOE 125, the shape, position, power density, etc. of the beams B1 and B2 can be changed.

[0078] Each of the beams B1 and B2 has, for example, a Gaussian power distribution in the radial direction of a cross section perpendicular to the optical axis direction of the beam. However, the power distribution of the beams B1 and B2 is not limited to a 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 1 / e of the peak intensity. 2 In the case of a non-circular beam (not shown), the diameter of the region with an intensity of 1 / e of the peak intensity in the direction perpendicular to the sweep direction SD in a plan view is defined as the diameter of the region with an intensity of 1 / e 2 The length of the region where the intensity is equal to or greater than this can be defined as the beam diameter.

[0079] In the laser light L, a portion including the beam B1 is an example of a first portion, and a portion including the beam B2 is an example of a second portion. In the example of Fig. 6, the laser light L includes one beam B1 constituting the first portion and multiple beams B2 constituting the second portion.

[0080] The second portion having the beam B2 is formed in a circumferential shape and is disposed so as to surround the first portion having the beam B1, and the first portion and the second portion are spaced apart in the sweep direction SD.

[0081] In the example of FIG. 6, the width D1 of the first portion in the sweep direction SD is the diameter of the circular beam B1, and is 1 / e 2 The width D2 of the second portion in the sweep direction SD is defined as the distance between the centers of the two beams B2 that are most distant from each other in a direction perpendicular to the sweep direction SD in a plan view.

[0082] [Sweep Path] 7 is an explanatory diagram (plan view) showing an example of the sweep path R1 of the laser light L at the end portions 21a and 22a. In this embodiment, the laser light L is linearly swept in a direction intersecting the Z direction in the order of the sweep paths R11, R12, R13, and R14. The sweep paths R11 and R12 are paths along which the laser light L is swept over the end portion 21a, and the sweep paths R13 and R14 are paths along which the laser light L is swept over the end portion 22a. In this way, the step (S3) of irradiating the end portions 21a and 22a with the laser light L to form a molten pool on the end portions 21a and 22a includes the step of sweeping the laser light L multiple times.

[0083] As shown in Fig. 7, the end 21a and the end 22a are both rectangular in shape in plan view, and in this embodiment, as an example, they have a rectangular shape with sides extending in the X direction and sides extending in the Y direction, and are 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 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 are not limited to this.

[0084] 7, the laser light L is swept in, for example, an area A1 closer to the end 22a than the center C1 of the end 21a in the X direction, and an area A2 closer to the end 21a than the center C2 of the end 22a in the X direction. However, the swept position, i.e., the irradiation area, is not limited to the areas A1 and A2.

[0085] In addition, in the sweep paths R11 and R13, the laser light L is swept in the Y direction, and in the sweep paths R12 and R14, the laser light L is swept in the opposite direction to the Y direction. The Y direction and the opposite direction to the Y direction are an example of a third direction. In addition, the Y direction is an example of a fourth direction.

[0086] [Experimental Results] The inventors conducted an experiment in which the ends 21a, 22a were welded by irradiating and sweeping a laser beam L having a beam shape shown in FIG. 6 along a path shown in FIG. 7. In the experiment, the inventors found conditions for the irradiation time of the laser beam L and the length E (exposed length, see FIG. 4) of the exposed section 20b that can reduce the influence of heat generated during welding on the coating 30. Furthermore, the inventors found conditions for the output ratio between the first and second parts of the laser beam L, the width D2 of the second part, and the sweep speed that can perform good welding. In these experiments, the coating 30 was made of polyetheretherketone, and the ends 21a, 22a of the member 20 made of a copper-based metal with a length of about 1.5 [mm] in the X direction and a length of about 3.1 [mm] in the Y direction were irradiated with a laser beam L having a wavelength of 1070 [nm], and the diameter of the spot of the beam B1 at the ends 21a, 22a in a state in which a molten pool was not formed was set to about 200 [μm]. In this experiment, the irradiation time of the laser light L is set to 0.06 [sec] or more, and the ratio (output ratio) of the output of the laser light L at the first portion to the output of the second portion is set to 5 / 5. The output of the laser device is adjusted in the range of 3 [kW] to 6 [kW] so that the welding of the ends 21a and 22a is completed by the irradiation of the laser light L at each irradiation time.

[0087] The inventors investigated the state of the coating 30 according to the irradiation time of the laser light 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 peeled length of the coating, and the horizontal axis representing the laser irradiation time [sec]. In Fig. 8, the state of the coating 30 is indicated as ⊚ for the best state where almost no degradation due to heat is observed, as ◯ for an excellent state where slight degradation due to heat is observed but the required performance such as insulation is obtained, and as × for a poor state where degradation due to heat occurs and the required performance such as insulation is not obtained.

[0088] 8, it was found that by setting the irradiation time of the laser light L to less than 0.2 [sec], more preferably less than 0.1 [sec], the condition of the coating 30 can be maintained in the best or excellent condition even when the length E of the exposed section 20b is shortened to 6 [mm] or more and 10 [mm] or less, or even 6 [mm] or more and 8 [mm] or less. In this way, even when either or both of the lengths E of the exposed sections 20b of the members 21 and 22 are set to 6 [mm] or more and 10 [mm] or less, or even 6 [mm] or more and 8 [mm] or less, welding can be performed while reducing the effects of thermal deterioration of the coating 30.

[0089] The inventors also conducted experiments using the ratio of the output of the first portion to the output of the second portion of the laser light L (output ratio) and the width D2 of the second portion (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 condition in which the number of spatters generated during welding (steps S3 and S4) is 25 or less is indicated by ◎, and an excellent condition in which the number of spatters generated during welding (steps S3 and S4) is more than 25 and 60 or less is indicated by ○. [Table 1] As shown in Table 1, it was found that the width D2 of the second portion is preferably 5 times or less than the width D1 of the first portion, more preferably more than 2 times and 4 times or less, and even more preferably 3.6 times or less. It was also found that the output ratio is preferably 3 / 7 or more, more preferably 7 / 3 or less, and even more preferably 4 / 6 or more and 6 / 4 or less.

[0090] Furthermore, the inventors conducted an experiment using the output ratio and the sweep speed of the laser light 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 condition in which the number of spatters generated during welding was 25 or less was indicated by ◎, while the excellent condition in which the number of spatters generated during welding was more than 25 and less than 60 was indicated by ○, and the good condition in which the number of spatters generated during welding was more than 50 was indicated by △. [Table 2] As shown in Table 2, it was found that the sweep speed is preferably 150 [mm / sec] or more, and more preferably 200 [mm / sec] or more, from the viewpoint of suppressing excessive heat input during welding and reducing the occurrence of spatters. It was also found that the output ratio is preferably more than 3 / 7, more preferably 7 / 3 or less, and even more preferably 4 / 6 or more and 6 / 4 or less.

[0091] Furthermore, the inventors' experimental research has revealed that when multiple sweeps are performed in the step (S3) of forming a molten pool, a better welding condition with fewer welding defects such as spatters and blowholes can be obtained by making the power density per unit area of ​​a virtual plane intersecting the irradiation direction of the laser light L in the later sweep step (for example, a virtual plane that roughly overlaps with the end face of the end portion 20a) lower than the power density per unit area of ​​the virtual plane in the earlier sweep step. The earlier sweep step is an example of a first sweep step, and the later sweep step is an example of a second sweep step.

[0092] Fig. 9 is an X-ray transmission image of a sample of the object W in which a welded portion 23 in a good welded state was obtained, viewed from the side. The material of the members 21, 22 (20) constituting the object W is oxygen-free copper, and in welding the object W, the irradiation time of the laser light L was 0.064 [sec], the output was 6 [kW], the output ratio was 5 / 5 (=1), and the sweep speed was 200 [mm / sec]. As is clear from Fig. 9, the sample had very few blowholes.

[0093] The power density per unit area of ​​the virtual plane is lower as the sweep speed is higher and is lower as the power of the laser light L is lower. Therefore, in the subsequent sweep step, the sweep speed is higher than in the previous sweep step, the power of the laser light L is lower than in the previous sweep step, or the sweep speed is higher than in the previous sweep step and the power of the laser light L is lower than in the previous step, so that the power density per unit area of ​​the virtual plane in the subsequent sweep step is lower than in the previous sweep step, and thus a better welding state can be obtained. More specifically, for example, in the step (S3) of forming a molten pool, when sweeping is performed a predetermined number of times (for example, three times) or more, a better welding state can be obtained by performing at least one of a sweeping with a faster sweep speed than in the previous sweep, a sweeping with a lower power of the laser light L than in the previous sweep, and a sweeping with a faster sweep speed than in the previous sweep and a lower power of the laser light L than in the previous sweep.

[0094] As described above, according to the laser welding method and laser welding apparatus 100 of this embodiment, in the step (S3) of forming a molten pool, by irradiating laser light L to at least one of end 21a (first end) and end 22a (second end) for a time of less than 0.2 sec while sweeping in the Y direction intersecting the Z direction (first direction) or the opposite direction to the Y direction (third direction), it is possible to form a molten pool spanning between end 21a and end 22a.

[0095] Such irradiation with laser light L can suppress deterioration of coating 30 due to heat generated during welding. Furthermore, in conductor 10, length E of exposed section 20b for welding can be made relatively short, for example, to 10 mm or less, which has the effect of making it more unlikely for a short circuit to occur via exposed section 20b and suppressing an increase in size of an electrical device including conductor 10 having member 20 and coating 30.

[0096] In addition, in this embodiment, the coating 30 of the conductor 10, whose exposed section 20b has a relatively short length E, can be made of a material containing polyetheretherketone as a synthetic resin material, as described above. That is, according to this embodiment, the coating 30 of the conductor 10 of an electric device can be made of a coating 30 containing polyetheretherketone, which has higher insulation properties than polyimide or the like, i.e., higher voltage resistance, and therefore it is easier to configure an electric device that has a higher voltage resistance, is less likely to cause a short circuit, and is more compact.

[0097] In this embodiment, the first portion including the beam B1 of the laser light L and the second portion including the beam B2 are spaced apart from each other at least in the sweep direction SD. According to this embodiment, for example, before a molten pool in a keyhole state is formed by the first portion of the laser light L including the beam B1, the end portions 21a, 22a can be preliminarily heated by the second portion of the laser light L including the beam B2, which can suppress a rapid increase in temperature of the end portions 21a, 22a, thereby making the molten pool more stable and thus suppressing the occurrence of welding defects such as spatters and blowholes.

[0098] [Another example of beam shape (variation)] FIG. 10 is a plan view showing another example of the beam pattern of the laser light L. In the example of FIG. 10, the second portion including the beam B2 does not have a circumferential (annular) shape. However, even in this example, the second portion including the beam B2 is disposed apart from the first portion of the laser light L including the beam B1 in the sweep direction SD and in the opposite direction to the sweep direction SD. Even with the beam pattern as shown in FIG. 10, the target W can be preliminarily heated by the second portion of the laser light L before the first portion of the laser light L is irradiated, so that the same effect as the above embodiment can be obtained. Also, according to the example of FIG. 10, even when the laser light L is swept in the opposite direction to the sweep direction SD of FIG. 10 without rotating the optical head 120 around the Z axis, the effect of suppressing welding defects by preliminary heating can be obtained. Also, as in the example of FIG. 6, when the second portion has an annular shape, the effect of suppressing welding defects by preliminary heating can be obtained when the optical head 120 is swept in any direction intersecting the Z direction without rotating the optical head 120 around the Z axis. That is, if at least a part of the second portion including the beam B2 is present in front of the first portion including the beam B1 in the sweep direction, the effect of suppressing welding defects by preliminary heating can be obtained.

[0099] [Another example of sweep path (variation)] 11 is an explanatory diagram (plan view) showing an example of the sweep paths R1 and R2 of the laser light L at the end portions 21a and 22a different from that shown in FIG. 7. In this example, the laser light L is irradiated simultaneously and in parallel to a plurality of locations (for example, two locations) on the end portion 20a to form a molten pool. Specifically, the laser light L is swept along a sweep path R21 (R2) on the end portion 22a in parallel with the laser light L being swept along a sweep path R11 (R1) on the end portion 21a, and then the laser light L is swept along a sweep path R22 (R2) on the end portion 22a in parallel with the laser light L being swept along a sweep path R12 (R1) on the end portion 21a.

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

[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 similar to the first embodiment and outputs a first laser light having a wavelength of, for example, 800 [nm] or more and 1200 [nm] or less. The laser device 111 may also be called a first laser device. The laser oscillator of the laser device 111 is a light source and may also be called a first laser oscillator.

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

[0104] For copper-based materials and aluminum-based materials, the second laser light has a higher absorptance and a lower reflectance than the first laser light.

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

[0106] The filter 123 is a high-pass filter that transmits the first laser light and reflects but does not transmit the second laser light. The first laser light from the mirror 124 transmits through the filter 123 and travels toward the galvano scanner 126. On the other hand, the second laser light from the collimator lens 121 is reflected by the filter 123 and travels toward the galvano scanner 126. The filter 123 may also be referred to as an optical component.

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

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

[0109] The pattern of the beams B1 and B2 having different wavelengths is not limited to the example in Fig. 13, and may be configured such that, when the laser light L is swept in the sweep direction SD, the second portion by the beam B2 reaches each position of the ends 21a and 22a before the first portion by the beam B1 reaches the respective positions. In other words, if at least a part of the second portion including the beam B2 is present ahead of the first portion including the beam B1 in the sweep direction, the effect of suppressing welding defects by preliminary heating can be obtained.

[0110] Although the embodiment and the modified examples of the present invention have been illustrated above, the above-mentioned embodiment and the modified examples are merely examples and are not intended to limit the scope of the invention. The above-mentioned embodiment and the modified examples can be implemented in various other forms, and various omissions, substitutions, combinations, and modifications can be made without departing from the gist of the invention. In addition, the specifications of each configuration, shape, and the like (structure, type, direction, model, 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 components. Furthermore, the multiple components included in the object do not have to be the same components. Furthermore, the object is not limited to multiple components arranged side by side or butted together, but may be multiple components that are overlapped.

[0112] Furthermore, the exposed section of at least one of the plurality of conductors may be provided at a midpoint in the longitudinal direction of the conductor.

[0113] Furthermore, 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 symbols]

[0114] 10...Conductor (first conductor, second conductor) 20…Material 20a...End 20b...Exposed section (first exposed part, second exposed part) 21...Component (core wire) 21a...End (first end) 21a1…side 22...Component (core wire) 22a...End (second end) 22a1…side 23...Welded part (molten pool) 30…Covering 30a...end 100,100A...Laser welding equipment 110, 111, 112...Laser device (light source) 120, 120A...Optical head 121...Collimating lens 122...Condenser lens 123…Filter 124…Mirror 125…DOE 126...Galvanometer scanner 126a, 126b…Mirror 127…Gas nozzle 130...Optical fiber 140...Drive mechanism 150…Sensor 200...Control device A1,A2…area B1…Beam (first part) B2…Beam (second part) C1,C2…center D1…width D2…width E…Length (exposed length) g…Gap G…Gas L: Laser light R1, R11, R12, R13, R14, R2, R21, R22...Sweep path SD…Sweep 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 conductor having a core wire made of a metallic material and a coating surrounding the core wire, the first end of the core wire being exposed from the coating at an end in a first direction, which is a longitudinal direction of the first conductor, and a second end of the core wire being exposed from the coating at an end in the first direction of a second conductor having a core wire made of a metallic material and a coating surrounding the core wire, the method comprising the steps of: Arranging the first end portion and the second end portion so as to be adjacent to each other in a second direction intersecting the first direction; irradiating at least one of the first end and the second end with a laser beam for a time period of less than 0.2 [sec] while sweeping the laser beam in a third direction intersecting the first direction, thereby forming a molten pool spanning between the first end and the second end; solidifying the molten pool; A laser welding method comprising:

2. 2. The laser welding method according to claim 1, wherein an 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.

3. 2. The laser welding method according to claim 1, wherein an exposed length in the first direction of both the first end portion and the second end portion is 10 mm or less.

4. 4. The laser welding method according to claim 1, wherein in the step of forming the molten pool, the laser beam is swept linearly.

5. The laser welding method according to any one of claims 1 to 4, wherein the third direction intersects with the second direction.

6. 6. The laser welding method according to claim 1, wherein the step of forming the molten pool includes the step of sweeping the laser beam a plurality of times.

7. 7. The laser welding method according to claim 6, wherein the step of sweeping the laser light a plurality of times includes a first sweeping step of sweeping the laser light, and a second sweeping step of sweeping the laser light in a state in which a power density per unit area of ​​a virtual plane intersecting the first direction is lower than that in the first sweeping step.

8. The laser welding method according to claim 7 , wherein a sweep speed of the laser beam in the second sweeping step is higher than a sweep speed of the laser beam in the first sweeping step.

9. 9. The laser welding method according to claim 7, wherein a power of the laser beam in the second sweeping step is lower than a power of the laser beam in the first sweeping step.

10. 7. The laser welding method according to claim 6, wherein the step of sweeping the laser beam a plurality of times includes: a third sweep step of sweeping the laser beam at a predetermined intensity and a predetermined sweep speed; and a fourth sweep step of performing, after the third sweep step, at least one of sweeping of the laser beam at an intensity lower than the predetermined intensity, sweeping of the laser beam at a sweep speed faster than the predetermined sweep speed, and sweeping of the laser beam at an intensity lower than the predetermined intensity and at a sweep speed faster than the predetermined sweep speed.

11. 7. The laser welding method according to claim 1, wherein the step of forming the molten pool includes the steps of sweeping the laser beam along the third direction and sweeping the laser beam along a fourth direction that is opposite to the third direction.

12. 12. The laser welding method according to claim 1, wherein the step of forming the molten pool includes the steps of sweeping the laser beam over the first end and sweeping the laser beam over the second end.

13. 13. The laser welding method according to claim 1, wherein in the step of forming the molten pool, the laser light includes a plurality of beams.

14. The laser welding method according to claim 13 , wherein in the step of forming the molten pool, the laser light includes a plurality of beams having mutually different wavelengths.

15. 15. The laser welding method according to claim 13 or 14, wherein the plurality of beams are spaced apart in a sweep direction of the laser light.

16. 16. The laser welding method according to claim 13, wherein in the step of forming the molten pool, the laser light 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.

17. The laser welding method according to claim 16 , wherein in the step of forming the molten pool, the first portion and the second portion are spaced apart from each other in a sweep direction of the laser light.

18. The laser welding method of claim 16 , wherein the second portion circumscribes the first portion.

19. 19. The laser welding method according to claim 18, wherein a ratio of a power of the laser light in the first portion to a power of the laser light in the second portion is equal to or greater than 3 / 7 and equal to or less than 7 / 3.

20. 20. The laser welding method according to claim 1, wherein a sweep speed of the laser light is 150 mm / sec or more.

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

22. 22. The laser welding method of claim 21, wherein forming the molten pool includes irradiating the first end with at least one laser beam and simultaneously irradiating the second end with at least one other laser beam.

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

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

25. The laser welding method of any one of claims 1 to 23, wherein the coating comprises polyetheretherketone.

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