JP2021191589A - Welding method, welding device, and battery assembly - Google Patents

Abstract

To provide improved welding method, welding device, and battery assembly which, for example, make it possible to obtain a higher quality weld condition.SOLUTION: A welding method welds, for example, a plurality of metallic members including a metallic member as a battery electrode or a metallic member electrically connected to the electrode, or a metallic member in an electric apparatus by irradiating a surface of at least one metallic member of the plurality of metallic members with laser beam. The laser beam includes a first laser beam having a wavelength of 800 [nm] or more and 1200 [nm] or less, and a second laser beam having a wavelength of 550 [nm] or less. The metallic member may be a battery electrode, the plurality of metallic members may include a plurality of laminated electrode tabs, and the metallic member may be accommodated in a housing of the electric apparatus.SELECTED DRAWING: Figure 1

Description

The present invention relates to welding methods, welding equipment, and battery assemblies.

Conventionally, a power storage device in which a bus bar and a battery electrode are joined by laser welding is known (for example, Patent Document 1). Further, conventionally, an electric device in which a plurality of electric components are integrated, such as a power distribution device mounted on an electric vehicle, is known (for example, Patent Document 2).

Japanese Unexamined Patent Publication No. 2013-145739 Japanese Unexamined Patent Publication No. 2020-78985

In this type of welding, it is important not only to secure the required joint strength but also to prevent welding defects such as spatters and blow holes from occurring in the workpiece.

Therefore, one of the subjects of the present invention is, for example, to obtain an improved new welding method, welding device, and battery assembly that enables a higher quality welded state to be obtained.

In the welding method of the present invention, for example, a plurality of metal members including a metal member as an electrode of a battery, a metal member electrically connected to the electrode, or a metal member in an electric device, the plurality of metals. A welding method in which the surface of at least one metal member of a member is welded by irradiating the surface with a laser beam, wherein the laser beam is a first laser beam having a wavelength of 800 [nm] or more and 1200 [nm] or less. Includes a second laser beam with a wavelength of 550 [nm] or less.

In the welding method, the metal member may be an electrode of the battery.

In the welding method, the plurality of metal members may include a plurality of laminated electrode tabs.

In the welding method, the metal member may be housed in the housing of the electric device.

In the welding method, the wavelength of the second laser beam may be 400 [nm] or more and 500 [nm] or less.

In the welding method, the laser beam is swept on the surface in a sweeping direction, and at least a part of the second spot formed on the surface by the second laser beam on the surface is the first. It may be located in front of the first spot formed on the surface by the laser beam in the sweep direction.

In the welding method, the first spot and the second spot may at least partially overlap on the surface.

In the welding method, on the surface, the second outer edge of the second spot may surround the first outer edge of the first spot.

In the welding method, the thickness of the member irradiated with the laser beam among the plurality of metal members along the irradiation direction of the laser beam is less than 2 [mm], and the surface thereof is subjected to the first laser beam. When is a plane perpendicular to the laser beam, the spot diameter of the first spot formed on the plane is 14 [μm] or more and 150 [μm] or less, and the power of the first laser beam is It is 0.3 [kW] or more and 2.0 [kW] or less, and the spot diameter of the second spot formed on the plane by the second laser beam is 100 [μm] or more and 900 [μm] or less. The power of the second laser beam may be 0.1 [kW] or more and 1 [kW] or less.

In the welding method, the thickness of the member irradiated with the laser beam among the plurality of metal members along the irradiation direction of the laser beam is 2 [mm] or more and 3 [mm] or less, and the said first. When the surface of the surface is a plane perpendicular to the laser beam by one laser beam, the spot diameter of the first spot formed on the plane is 30 [μm] or more and 200 [μm] or less, and the first. The power of the laser beam is 2 [kW] or more and 6 [kW] or less, and the spot diameter of the second spot formed on the plane by the second laser beam is 200 [μm] or more and 1200 [μm]. ] Or less, and the power of the second laser beam may be 0.5 [kW] or more and 2 [kW] or less.

In the welding method, the energy density of the first laser beam per unit volume in the irradiation direction of the laser beam in the welded portion between the metal member and the electrode is 120 [J / mm ³ ] or more, and the welding. The energy density of the second laser beam per unit volume in the irradiation direction of the laser beam in the unit may be 5 [J / mm ³ ] or more and 50 [J / mm ³ ] or less.

In the welding method, the power density of the second laser beam may be 0.15 [MW / cm ² ] or more and 5 [MW / cm ² ] or less on the surface.

In the welding method, the metal member is one of a copper-based metal material, an aluminum-based metal material, a nickel-based metal material, an iron-based metal material, a titanium-based metal material, and a nickel-plated metal material. It may be made of one piece.

The welding apparatus of the present invention includes, for example, a laser oscillator and a metal member as an electrode of a battery, a metal member electrically connected to the electrode, or a metal member in an electric device, for example, a laser oscillator and a laser beam from the laser oscillator. A welding apparatus comprising an optical head that irradiates the surface of at least one of a plurality of metal members with a laser beam to weld the plurality of metal members, wherein the laser beam is 800 [nm]. It includes a first laser beam having a wavelength of 1200 [nm] or less and a second laser beam having a wavelength of 550 [nm] or less.

The welding device may include a beam shaper that divides the laser beam into a plurality of beams.

The welding device may include a galvano scanner that changes the emission direction of the laser beam so as to sweep the laser beam in the sweep direction on the surface.

The welding device may include a spot size variable mechanism capable of changing the size of a spot on the surface of the laser beam.

The battery assembly of the present invention comprises, for example, a metal member as a battery electrode, a plurality of metal members including a metal member electrically connected to the electrode, and a welded portion obtained by welding the plurality of metal members. The welded portion comprises a welded metal extending from at least one surface of the plurality of metal members along a first direction intersecting the surface, and a heat-affected portion located around the welded metal. The weld metal has a first portion and a second portion in which the average value of the cross-sectional area of the crystal grains in the cross section along the first direction is larger than that of the first portion.

In the battery assembly, the average value of the cross-sectional areas of the crystal grains contained in the second portion may be 1.8 times or more the average value of the cross-sectional areas of the crystal grains contained in the first portion.

In the battery assembly, the weld may extend along the surface in a second direction intersecting the first direction.

The battery assembly comprises at least one metal member joined via a weld to the electrodes of the plurality of batteries as the battery and two batteries of the plurality of batteries, respectively, as the metal member. And may be provided.

According to the present invention, it is possible to obtain improved new welding methods, welding devices, and battery assemblies, for example, which make it possible to obtain a higher quality welded state.

FIG. 1 is an exemplary schematic configuration diagram of the laser welding apparatus of the first embodiment. FIG. 2 is an exemplary and schematic cross-sectional view of a connection structure as a processing target by the laser welding apparatus of the first embodiment. FIG. 3 is an exemplary and schematic perspective view of the battery assembly including the connection structure of FIG. FIG. 4 is an exemplary and schematic cross-sectional view of another connection structure as a processing target by the laser welding apparatus of the first embodiment. FIG. 5 is an exemplary and schematic perspective view of the battery assembly including the connection structure of FIG. FIG. 6 is an exemplary and schematic cross-sectional view of yet another connection structure as a processing target by the laser welding apparatus of the first embodiment. FIG. 7 is an exemplary schematic diagram of an electrical device with the connection structure of FIG. FIG. 8 is an exemplary schematic diagram showing a beam (spot) of laser light formed on the surface of the object to be machined by the laser welding apparatus of the first embodiment. FIG. 9 is a graph showing the light absorption rate of each metal material with respect to the wavelength of the irradiated laser light. FIG. 10 is an exemplary and schematic cross-sectional view of the welded portion of the embodiment. FIG. 11 is an exemplary and schematic cross-sectional view showing a portion of the welded portion of the embodiment. FIG. 12 is an exemplary schematic configuration diagram of the laser welding apparatus of the second embodiment. FIG. 13 is an explanatory diagram showing the concept of the principle of the diffractive optical element included in the laser welding apparatus of the second embodiment. FIG. 14 is an exemplary schematic configuration diagram of the laser welding apparatus of the third embodiment. FIG. 15 is an exemplary schematic configuration diagram of the laser welding apparatus of the fourth embodiment. FIG. 16 is an exemplary schematic configuration diagram of the laser welding apparatus of the fifth embodiment. FIG. 17 is a schematic diagram showing an example of a beam (spot) of laser light formed on the surface of a processing target by the laser welding apparatus of the fifth embodiment. FIG. 18 is a schematic diagram showing an example of a beam (spot) of laser light formed on the surface of a processing target by the laser welding apparatus of the fifth embodiment. FIG. 19 is an exemplary schematic configuration diagram of the laser welding apparatus of the sixth embodiment. FIG. 20 is an exemplary and schematic perspective view of the battery assembly of the first modification. FIG. 21 is an exemplary and schematic perspective view of the battery assembly of the second modification. FIG. 22 is an exemplary and schematic perspective view of the battery assembly of the third modification. FIG. 23 is an exemplary and schematic plan view of the connection structure between the metal member and the electrode of the third modification. FIG. 24 is an exemplary and schematic perspective view of the battery assembly of the fourth modification.

Hereinafter, exemplary embodiments and variations 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.

The embodiments and modifications shown below have similar configurations. Therefore, according to the configurations of the respective embodiments and modifications, the same actions and effects based on the similar configurations can be obtained. Further, in the following, the same reference numerals are given to those similar configurations, and duplicate explanations may be omitted.

Further, in each figure, the direction X is represented by an arrow X, the direction Y is represented by an arrow Y, and the direction Z is represented by an arrow Z. Direction X, direction Y, and direction Z intersect and are orthogonal to each other. Further, in each figure, for convenience, an example in which the sweep direction SD on the surface Wa of the laser beam L is along the X direction is shown, but the sweep direction SD may intersect with the Z direction and is in the X direction. It's not just about.

Further, in the present specification, the ordinal number is given for convenience in order to distinguish parts, members, parts, laser beams, directions, etc., and does not indicate a priority or an order.

[First Embodiment]
FIG. 1 is a schematic configuration diagram of the laser welding apparatus 100 of the first embodiment. As shown in FIG. 1, the laser welding apparatus 100 includes a laser apparatus 111, a laser apparatus 112, an optical head 120, and an optical fiber 130. The laser welding device 100 is an example of a welding device.

Each of the laser devices 111 and 112 has a laser oscillator, and is configured to be capable of outputting, for example, a laser beam having a power of several kW. The laser devices 111 and 112 emit laser light having a wavelength of 380 [nm] or more and 1200 [nm] or less. The laser devices 111 and 112 have a laser light source such as a fiber laser, a semiconductor laser (element), a YAG laser, and a disk laser inside. The laser devices 111 and 112 may be configured to be capable of outputting a multimode laser beam having a power of several kW as the total of the outputs of the plurality of light sources.

The laser apparatus 111 outputs the first laser beam having a wavelength of 800 [nm] or more and 1200 [nm] or less. The laser device 111 is an example of the first laser device. As an example, the laser device 111 has a fiber laser or a semiconductor laser (element) as a laser light source. The laser oscillator included in the laser device 111 is an example of the first laser oscillator.

On the other hand, the laser device 112 outputs a second laser beam having a wavelength of 550 [nm] or less. The laser device 112 is an example of a second laser device. As an example, the laser device 112 has a semiconductor laser (element) as a laser light source. The laser device 112 preferably outputs a second laser beam having a wavelength of 400 [nm] or more and 500 [nm] or less. The laser oscillator included in the laser device 112 is an example of a second laser oscillator.

The optical fiber 130 guides the laser light output from the laser devices 111 and 112 to the optical head 120, respectively.

The optical head 120 is an optical device for irradiating the laser beam input from the laser devices 111 and 112 toward the processing target W. The optical head 120 includes a collimating lens 121, a condenser lens 122, a mirror 123, and a filter 124. The collimating lens 121, the condenser lens 122, the mirror 123, and the filter 124 may also be referred to as optical components.

The optical head 120 is configured so that the relative position with the processing target W can be changed in order to sweep the laser light L while irradiating the surface Wa of the processing target W with the laser light L. The relative movement between the optical head 120 and the processing target W can be realized by the movement of the optical head 120, the movement of the processing target W, or the movement of both the optical head 120 and the processing target W.

The optical head 120 may be configured to be able to sweep the laser beam L on the surface Wa by having a galvano scanner or the like (not shown).

The collimating lenses 121 (121-1, 121-2) collimate the laser beam input via the optical fiber 130, respectively. The collimated laser beam becomes parallel light.

The mirror 123 reflects the first laser beam that has become parallel light by the collimating lens 121-1. The first laser beam reflected by the mirror 123 travels in the opposite direction to the Z direction and heads toward the filter 124. The mirror 123 is not required in the configuration in which the first laser beam is input to the optical head 120 so as to travel in the direction opposite to the Z direction.

The filter 124 is a high-pass filter that transmits the first laser beam and reflects the second laser beam without transmitting it. The first laser beam passes through the filter 124, travels in the opposite direction in the Z direction, and heads toward the condenser lens 122. On the other hand, the filter 124 reflects the second laser beam that has become parallel light by the collimated lens 121-2. The second laser beam reflected by the filter 124 travels in the opposite direction to the Z direction and heads toward the condenser lens 122.

The condenser lens 122 concentrates the first laser beam and the second laser beam as parallel light, and irradiates the processing target W as the laser beam L (output light). The processing target W is a connection structure 10 between the electrode 11 of the battery 21 and the metal member 12. The electrode 11 is an example of a metal member.

FIG. 2 is a cross-sectional view of the connection structure 10. The connection structure 10 has an electrode 11, a metal member 12, and a welded portion 14. The welded portion 14 mechanically and electrically connects the electrode 11 and the metal member 12.

In the present embodiment, the electrode 11 and the metal member 12 are arranged in a direction intersecting the Z direction on the end face 21a in the Z direction of the battery 21. Further, the end surface 11a in the Z direction of the electrode 11 and the end surface 12a in the Z direction of the metal member 12 are arranged in a direction intersecting the Z direction, and are widened in a direction intersecting and orthogonal to the Z direction, respectively. The end face 11a and the end face 12a constitute the surface Wa of the processing target W. In the present embodiment, as an example, the end face 11a and the end face 12a are substantially flush with each other, but the present invention is not limited to this, and a step may be provided between the end face 11a and the end face 12a. In other words, the surface Wa may be a flat surface or a stepped surface. Further, the surface Wa may be a convex curved surface, a concave curved surface, or the like.

The side surface 11b of the electrode 11 and the side surface 12b of the metal member 12 extend in the Z direction and face each other in a direction intersecting the Z direction. The boundary B between the side surface 11b and the side surface 12b extends in the Z direction. At the boundary B, the side surfaces 11b and 12b may be in contact with each other, or a gap may be provided between the side surface 11b and the side surface 12b. The side surfaces 11b and 12b may also be referred to as butt surfaces.

The laser beam L from the optical head 120 is irradiated toward the boundary B in the direction opposite to the Z direction. The surface Wa is an irradiation surface of the laser beam L, and may also be referred to as a facing surface facing the optical head 120. The Z direction is an example of the first direction.

By such irradiation of the laser beam L, the welded portion 14 extends from the surface Wa along the boundary B in the direction opposite to the Z direction. The direction opposite to the Z direction can also be referred to as the depth direction of the welded portion 14. Further, the laser beam L is swept on the surface Wa in the sweep direction SD (X direction in the portion shown in FIG. 2), so that the welded portion 14 has a cross-sectional shape substantially similar to that in FIG. 2 and is swept. It will also extend to the direction SD. The directions orthogonal to the Z direction and the sweep direction SD can also be referred to as the width direction of the welded portion 14.

The weld 14 includes a weld metal 14a. The weld metal 14a extends from the surface Wa toward the inside of the electrode 11 and the metal member 12 in the direction opposite to the Z direction. The weld metal 14a has a first portion 14a1 and a second portion 14a2. The first site 14a1 is formed mainly by irradiation with the first laser beam, and the second site 14a2 is formed mainly by irradiation with the second laser beam. In the example of FIG. 2, the second portion 14a2 extends from the surface Wa in the opposite direction in the Z direction. The second site 14a2 is adjacent to the first site 14a1 in the Z direction. That is, the first portion 14a1 is adjacent to the second portion 14a2 in the direction opposite to the Z direction. Further, the weld metal 14a does not penetrate the connection structure 10 along the Z direction as a whole. The shape of the weld metal 14a is not limited to such a shape. The structure of the weld metal 14a including the first portion 14a1 and the second portion 14a2 will be described in detail later.

FIG. 3 is a perspective view of the battery assembly 20. The battery assembly 20 includes a plurality of batteries 21 and a plurality of metal members 12. In the battery assembly 20, a plurality of batteries 21 are connected in parallel by a metal member 12. The number of batteries 21 included in the battery assembly 20 may be two or four or more. Further, the number of the metal members 12 included in the battery assembly 20 may be one or three or more.

The battery 21 each includes two electrodes 11. In each battery 21, one of the two electrodes 11 is a positive electrode 11 and the other is a negative electrode 11. The electrode 11 may also be referred to as an electrode terminal. The metal member 12 is, for example, a bus bar. The metal member 12 may also be referred to as a conductive member.

The battery 21 is, for example, a square (box-shaped) lithium-ion battery. A storage chamber (not shown) is provided inside the battery 21. A plurality of positive electrode materials, negative electrode materials, and separators (all not shown) are housed in the accommodation chamber. The positive electrode material and the negative electrode material are alternately laminated with a separator interposed therebetween. A plurality of conductors extending from each of the plurality of positive electrode materials are electrically connected to one of the two electrodes 11, and a plurality of conductors extending from each of the plurality of positive electrode materials are electrically connected to the other of the two electrodes 11 from each of the plurality of negative electrode materials. A plurality of extended conductors are electrically connected. The battery 21 is not limited to the lithium ion battery.

The electrode 11 has a columnar shape, and the side surface 11b of the electrode 11 has a cylindrical surface shape (cylindrical outer surface shape). Further, the metal member 12 has a plate-like shape. The metal member 12 is provided with a cylindrical through hole extending in the thickness direction, and the side surface 12b of the through hole has a cylindrical surface shape (cylindrical inner surface shape). By inserting the electrode 11 into the through hole provided in the metal member 12, the boundary B is formed between the side surface 11b and the side surface 12b. The boundary B may also be referred to as an annular gap. In such a state, the welded portion 14 is formed in an annular shape by being swept along the boundary B. That is, the welded portion 14 can also be referred to as an all-around welded portion.

FIG. 4 is a cross-sectional view of the laminated body 10B (10). The laminate 10B has a metal member 11B, a plurality of electrode tabs 12B, and a welded portion 14B (14). The welded portion 14B mechanically and electrically connects the metal member 11B and the plurality of electrode tabs 12B.

As an example, the metal member 11B has a plate-like shape that intersects the Z direction and spreads out. However, the metal member 11B is not limited to the plate-shaped member. The plurality of electrode tabs 12B are laminated in the Z direction on the end face 11Ba in the Z direction of the metal member 11B. The number of electrode tabs 12B included in the laminated body 10B, in other words, the number of electrode tabs 12B stacked on the metal member 11B may be one. The electrode tab 12B is an example of a metal member.

When the laminated body 10B is welded by the laser welding device 100, it is temporarily fixed integrally in the above-mentioned laminated state by a fixture (not shown). For example, the normal direction of the surface Wa of the electrode tab 12B is abbreviated as the Z direction. It is set in a parallel posture. The surface Wa is the end surface of the laminated body 10B in the Z direction, and is the surface of the electrode tab 12B farthest from the metal member 11B among the plurality of electrode tabs 12B, opposite to the metal member 11B. The laser beam L is emitted from the optical head 120 in the direction opposite to the surface Wa in the Z direction, in other words, from the side opposite to the metal member 11B to the surface Wa along the Z direction. The surface of the metal member 11B opposite to the end surface 11Ba is the back surface Wb of the laminated body 10B. The surface Wa is an irradiation surface of the laser beam L, and may also be referred to as a facing surface facing the optical head 120. The Z direction is an example of the first direction. The end surface 11Ba is an example of the first surface, and the surface Wa is an example of the second surface.

By such irradiation of the laser beam L, the welded portion 14B extends from the surface Wa in the direction opposite to the Z direction. The direction opposite to the Z direction can also be referred to as the depth direction of the welded portion 14B. Further, when the laser beam L is swept on the surface Wa in the X direction (sweep direction SD), the welded portion 14B has a cross-sectional shape substantially similar to that in FIG. 4 and extends in the X direction as well. The X direction is an example of the second direction. It may also be referred to as a longitudinal direction or an extension direction of the welded portion 14B. Further, the Y direction can also be referred to as the width direction of the welded portion 14B.

The weld 14B contains a weld metal 14a. The weld metal 14a extends from the surface Wa toward the metal member 11B in the direction opposite to the Z direction. The weld metal 14a has a first portion 14a1 and a second portion 14a2. The first site 14a1 is formed mainly by irradiation with the first laser beam, and the second site 14a2 is formed mainly by irradiation with the second laser beam. In the example of FIG. 4, the second portion 14a2 extends from the surface Wa in the opposite direction in the Z direction. The second site 14a2 is adjacent to the first site 14a1 in the Z direction. That is, the first portion 14a1 is adjacent to the second portion 14a2 in the direction opposite to the Z direction. The second portion 14a2 is formed in at least one electrode tab 12B. The first portion 14a1 extends over the plurality of electrode tabs 12B and the metal member 11B. Further, the weld metal 14a does not penetrate the laminated body 10B along the Z direction as a whole. The shape of the weld metal 14a is not limited to such a shape. The structure of the weld metal 14a including the first portion 14a1 and the second portion 14a2 will be described in detail later.

FIG. 5 is a side view (partial sectional view) of the battery assembly 2B. The battery assembly 2B includes a plurality of batteries 1B and a plurality of metal members 11B. The number of batteries 1B included in the battery assembly 2B may be one, and the number of metal members 11B included in the battery assembly 2B may be one.

The battery 1B each includes two electrode tabs 12B. One of the two electrode tabs 12B is the positive electrode tab 12B, and the other is the negative electrode tab 12B. The electrode tab 12B is an example of a metal member and may also be referred to as an electrode terminal. The metal member 11B is, for example, a bus bar. The metal member 11B and the electrode tab 12B may also be referred to as a conductive member.

The battery 1 shown in FIG. 5 is, for example, a flat laminated lithium-ion battery cell. The battery 1 is provided with a storage chamber (not shown) inside the battery 1. A plurality of positive electrode materials, negative electrode materials, and separators (all not shown) are housed in the accommodation chamber. The positive electrode material and the negative electrode material are alternately laminated with a separator interposed therebetween. A plurality of conductors extending from each of the plurality of positive electrode materials are electrically connected to one of the two electrode tabs 12B, and a plurality of negative electrode materials are connected to the other of the two electrode tabs 12B. A plurality of conductors extending from each are electrically connected. A part of the electrode tab 12B is exposed to the outside of the battery 1. The battery 1 is not limited to the lithium ion battery cell.

FIG. 6 is a cross-sectional view of the connection structure 10C (10). The connection structure 10C has two metal members 11C and 12C and a welded portion 14C (14). The welded portion 14C mechanically and electrically connects the two metal members 11C and 12C.

In the present embodiment, the two metal members 11C and 12C are arranged in the Z direction, in other words, they overlap in the Z direction. The metal member 12C is adjacent to the metal member 11C in the Z direction and faces the optical head 120. The laser beam L emitted from the optical head 120 irradiates the surface Wa, which is the end face in the Z direction of the metal member 12C. The laser beam L travels in the direction opposite to the Z direction, and the surface Wa intersects the Z direction and spreads. In the present embodiment, as an example, the surface Wa is a flat surface, but it may be a stepped surface. Further, the surface Wa may be a convex curved surface, a concave curved surface, or the like.

By such irradiation of the laser beam L, the welded portion 14C extends from the surface Wa in the direction opposite to the Z direction. The welded portion 14C penetrates the metal member 12C and reaches the metal member 11C. The direction opposite to the Z direction can also be referred to as the depth direction of the welded portion 14C. Further, the laser beam L is swept on the surface Wa in the sweep direction SD (X direction in the portion shown in FIG. 6), so that the welded portion 14C has a cross-sectional shape substantially similar to that in FIG. It will also extend to the direction SD. The directions orthogonal to the Z direction and the sweep direction SD can also be referred to as the width direction of the welded portion 14C.

The weld 14C contains a weld metal 14a. The weld metal 14a extends from the surface Wa toward the metal member 12C in the direction opposite to the Z direction. The weld metal 14a has a first portion 14a1 and a second portion 14a2. The first site 14a1 is formed mainly by irradiation with the first laser beam, and the second site 14a2 is formed mainly by irradiation with the second laser beam. In the example of FIG. 6, the second portion 14a2 extends from the surface Wa in the opposite direction in the Z direction. The second site 14a2 is adjacent to the first site 14a1 in the Z direction. That is, the first portion 14a1 is adjacent to the second portion 14a2 in the direction opposite to the Z direction. Further, the weld metal 14a does not penetrate the connection structure 10C along the Z direction as a whole. The shape of the weld metal 14a is not limited to such a shape. The structure of the weld metal 14a including the first portion 14a1 and the second portion 14a2 will be described in detail later.

FIG. 7 is a schematic diagram showing a schematic configuration of a power distribution device 21C as an electric device provided with a connection structure 10C and electrical components around the power distribution device 21C.

The power distribution device 21C is an example of an electric device mounted on an electric vehicle, and can be electrically connected to an external power source 22C, and also includes an inverter 23C, a high pressure battery 24C, and a low pressure battery 25C mounted on the electric vehicle. It is electrically connected.

The power distribution device 21C has a junction box 21Ca, a charger 21Cb, and a DC / DC converter 21Cc as a plurality of electric components housed in the housing 21Ce. The housing 21Ce is also referred to as a case and includes, for example, a body, a base, a cover, a lid, a bracket and the like.

Within the power distribution device 21C, each electrical component is electrically connected via a conductive path 21Cd. The conductive path 21Cd partially includes a connection structure 10C.

The metal members 11C and 12C constituting the connection structure 10C are, for example, a bus bar, a terminal provided in an electric component, a terminal provided in the housing 21Ce, a terminal electrically connected to a conductor of a harness, and the like.

Welding by the laser welding device 100 is a state in which the metal members 11C and 12C are arranged at predetermined positions in the subassembly of the power distribution device 21C, for example, the subassembly in which a part of the housing 21Ce is removed and the inside is exposed. It is done in. Further, the welding is performed in a state where at least one of the metal members 11C and 12C is fixed or temporarily fixed to the subassembly.

That is, when the metal members 11C and 12C are welded, other parts included in the power distribution device 21C are present around the metal members 11C and 12C (connection structure 10C). For this reason, it is not preferable that welding by the laser welding apparatus 100 causes spatter to fly to the periphery of the connection structure 10C or cause a thermal effect on the periphery. In this respect, the laser welding apparatus 100 can perform higher quality welding with less influence on the surroundings by irradiating the laser beam L including the first laser beam and the second laser beam. Suitable for welding in. High-quality welding by the laser welding apparatus 100 will be described later.

FIG. 8 is a schematic diagram showing a beam (spot) of the laser beam L irradiated on the surface Wa. Each of the beam B1 and the beam B2 has, for example, a Gaussian-shaped power distribution in the radial direction of the cross section orthogonal to the optical axis direction of the beam. However, the power distribution of the beam B1 and the beam B2 is not limited to the Gaussian shape. Further, in each figure in which each beam B1 and B2 is represented by a circle as shown in FIG. 8, the diameter of the circle representing the beams B1 and B2 is the beam diameter of each beam B1 and B2. Beam diameter of each beam B1, B2 includes a peak of the beam is defined as the diameter of the region of 1 / e ² or more of the intensity of the peak intensity. Although not shown, in the case of a non-circular beam, ^{the length of a region having an intensity of 1 / e 2} or more of the peak intensity in the direction perpendicular to the sweep direction SD can be defined as the beam diameter. Further, the beam diameter on the surface Wa is referred to as a spot diameter.

As shown in FIG. 8, in the present embodiment, as an example, in the beam of the laser beam L, the beam B1 of the first laser beam and the beam B2 of the second laser beam overlap on the surface Wa, and the beam B2 is formed. It is larger (wider) than the beam B1 and is formed so that the outer edge B2a of the beam B2 surrounds the outer edge B1a of the beam B1. In this case, the spot diameter D2 of the beam B2 is larger than the spot diameter D1 of the beam B1. On the surface Wa, the beam B1 is an example of the first spot, and the beam B2 is an example of the second spot.

Further, in the present embodiment, as shown in FIG. 8, since the beam (spot) of the laser beam L has a point-symmetrical shape with respect to the center point C on the surface Wa, the SD in an arbitrary sweep direction is used. , The shape of the spot will be the same. Therefore, when a moving mechanism for relatively moving the optical head 120 and the processing target W for sweeping the surface Wa of the laser beam L is provided, the moving mechanism should have at least a relatively translatable mechanism. However, the relatively rotatable mechanism may be omitted.

The electrode 11 and the metal member 12 as the processing target W can each be made of a conductive metal material. The metal material is, for example, a copper-based metal material, an aluminum-based metal material, a nickel-based metal material, an iron-based metal material, a titanium-based metal material, a nickel-plated metal material, or the like, and specifically, copper. , Copper alloys, aluminum, aluminum alloys, tin, nickel, nickel alloys, iron, stainless steel, titanium, titanium alloys, nickel-plated copper, nickel-plated copper alloys, nickel-plated aluminum , Nickel-plated aluminum alloy, etc. The electrode 11 and the metal member 12 may be made of the same material or may be made of different materials.

[Wavelength and light absorption rate]
Here, the light absorption rate of the metal material will be described. FIG. 9 is a graph showing the light absorption rate of each metal material with respect to the wavelength of the laser beam L to be irradiated. The horizontal axis of the graph of FIG. 9 is the wavelength, and the vertical axis is the absorption rate. FIG. 9 shows the relationship between wavelength and absorption for aluminum (Al), copper (Cu), gold (Au), nickel (Ni), silver (Ag), tantalum (Ta), and titanium (Ti). It is shown.

Although the characteristics differ depending on the material, for each metal shown in FIG. 9, a blue or green laser beam (second laser) is used rather than using a general infrared (IR) laser beam (first laser beam). It can be understood that the energy absorption rate is higher when light) is used. This feature is remarkable in copper (Cu), gold (Au), and the like.

When the laser beam is applied to the processing target W having a relatively low absorption rate with respect to the wavelength used, most of the light energy is reflected and does not affect the processing target W as heat. Therefore, it is necessary to apply a relatively high power in order to obtain a melting region having a sufficient depth. In that case, energy is suddenly applied to the central part of the beam, so that sublimation occurs and a keyhole is formed.

On the other hand, when the laser beam is applied to the processing target W having a relatively high absorption rate with respect to the wavelength used, most of the input energy is absorbed by the processing target W and converted into thermal energy. That is, since it is not necessary to apply excessive power, heat conduction type melting is performed without forming keyholes.

In the present embodiment, the wavelength of the first laser beam, the wavelength of the second laser beam, and the wavelength of the processing target W are such that the absorption rate of the processing target W with respect to the second laser light is higher than the absorption rate with respect to the first laser light. The material is selected. In this case, when the sweep direction is the sweep direction SD shown in FIG. 9, the portion to be welded (hereinafter referred to as the welded portion) of the work target W due to the sweep of the spot of the laser beam L is first, first. The second laser beam is irradiated by the region B2f of the beam B2 of the second laser beam located in front of the SD in FIG. After that, the welded portion is irradiated with the beam B1 of the first laser beam, and then the second laser beam is irradiated again by the region B2b of the beam B2 of the second laser beam located behind the sweep direction SD. To.

Therefore, in the welded portion, a heat conduction type melting region is first generated by irradiation with a second laser beam having a high absorption rate in the region B2f. After that, a deeper keyhole-type melting region is generated in the welded portion by irradiation with the first laser beam. In this case, since the heat conduction type melting region is formed in advance in the welded portion, the required depth is obtained by the first laser beam having a lower power than in the case where the heat conduction type melting region is not formed. A molten region can be formed. After that, the welded portion is changed in a molten state by irradiation with a second laser beam having a high absorption rate in the region B2b. From such a viewpoint, the wavelength of the second laser beam is preferably 550 [nm] or less, and more preferably 500 [nm] or less.

Further, experimental studies by the inventors have confirmed that welding defects such as spatters and blow holes can be reduced in welding by irradiation with a laser beam L as shown in FIG. This is because the work target W is preheated by the region B2f of the beam B2 before the beam B1 arrives, so that the molten pool of the work target W formed by the beam B2 and the beam B1 becomes more stable. It can be estimated that there is.

[Welding method]
In welding using the laser welding device 100, first, the connection structure 10 in which the electrode 11 and the metal member 12 are integrally temporarily fixed is set so that the laser beam L is irradiated on the surface Wa. .. Then, in a state where the surface Wa is irradiated with the laser beam L including the beam B1 and the beam B2, the laser beam L and the connection structure 10 are relatively moved. As a result, the laser beam L moves (sweeps) in the sweep direction SD on the surface Wa while being irradiated on the surface Wa. The portion irradiated with the laser beam L melts, and then solidifies as the temperature decreases, so that the electrode 11 and the metal member 12 are welded together, and the connection structure 10 is integrated.

[Cross section of weld]
FIG. 10 is a cross-sectional view of a welded portion 14 formed on the processing target W. FIG. 10 is a cross-sectional view perpendicular to the sweep direction SD (X direction in FIG. 10) and along the thickness direction (Z direction). The welded portion 14 extends in the sweep direction SD, that is, in the direction perpendicular to the paper surface of FIG. Note that FIG. 10 shows a cross section of a welded portion 14 formed on a processing target W, which is a single copper plate having a thickness of 2 [mm]. The form of the welded portion 14 formed in the connection structure 10 between the electrode 11 and the metal member 12 is substantially the same as the form of the welded portion 14 formed in the processing target W which is one metal material shown in FIG. It can be estimated that there is.

As shown in FIG. 10, the welded portion 14 has a welded metal 14a extending in the opposite direction in the Z direction from the surface Wa, and a heat-affected zone 14b located around the welded metal 14a. .. The weld metal 14a is a portion that is melted by irradiation with the laser beam L and then solidified. The weld metal 14a may also be referred to as a melt-solidified portion. Further, the heat-affected zone 14b is a portion where the base material of the processing target W is thermally affected and is not melted.

The width of the weld metal 14a along the Y direction becomes narrower as the distance from the surface Wa increases. That is, the cross section of the weld metal 14a has a tapered shape that narrows in the direction opposite to the Z direction.

Further, according to a detailed analysis of the cross section by the inventors, the weld metal 14a includes a first portion 14a1 away from the surface Wa and a second portion 14a2 between the first portion 14a1 and the surface Wa. There was found.

The first portion 14a1 is a region obtained by keyhole-type melting by irradiation with the first laser beam, and the second portion 14a2 is a region located behind the sweep direction SD in the beam B2 of the second laser beam. It is a part obtained by melting by irradiation of B2b. According to the analysis by the EBSD method (electron back scattered diffraction pattern), the size of the crystal grains is different between the first site 14a1 and the second site 14a2, and specifically, the X direction (sweep direction). It was found that the average cross-sectional area of the crystal grains at the second site 14a2 was larger than the average cross-sectional area of the crystal grains at the first site 14a1 in the cross section orthogonal to SD).

The inventors have found that when the processing target W is irradiated with only the beam B1 of the first laser beam, that is, when the region B2b located behind the sweep direction SD in the beam B2 is not irradiated, the second It was confirmed that the site 14a2 was not formed and the first site 14a1 extended deeply from the surface Wa in the opposite direction to the Z direction. That is, in the present embodiment, the second portion 14a2 is formed near the surface Wa by the irradiation of the region B2b located behind the sweep direction SD in the beam B2, so that the first portion 14a1 is the said. It can be presumed that the second portion 14a2 is formed on the opposite side of the surface Wa, in other words, at a position separated from the surface Wa in the opposite direction in the Z direction.

FIG. 11 is a cross-sectional view showing a part of the welded portion 14. FIG. 11 shows the boundaries of the crystal grains obtained by the EBSD method. Further, in FIG. 11, as an example, the crystal grain A having a crystal grain size of 13 [μm] or less is painted black. Note that 13 [μm] is not a threshold value of physical characteristics, but a threshold value set for analysis of the experimental results. Further, from FIG. 11, it is clear that the crystal grains A are relatively abundant in the first site 14a1 and relatively few in the second site 14a2. That is, the average value of the cross-sectional areas of the crystal grains in the second site 14a2 is larger than the average value of the cross-sectional areas of the crystal grains in the first site 14a1. According to an experimental analysis, the inventors have found that the average cross-sectional area of the crystal grains in the second site 14a2 is 1.8 times or more the average cross-sectional area of the crystal grains in the first site 14a1. It was confirmed.

As shown in the region I in FIG. 11, such relatively small crystal grains A are densely packed in a position separated from the surface Wa in the Z direction and elongated in the Z direction. There is. Further, from the analysis at a plurality of locations where the positions in the X direction (sweep direction SD) are different, it is confirmed that the region where the crystal grains A are densely extends extends to the sweep direction SD. Since the welding is performed while sweeping, it can be presumed that crystals are formed in the same shape in the sweep direction SD.

When it is difficult to distinguish between the first portion 14a1 and the second portion 14a2 from the appearance or hardness distribution in the cross section, geometry is performed from the position and width wb of the weld metal 14a on the surface Wa as shown in FIGS. The geographically determined first region Z1 and second region Z2 may be designated as the first region 14a1 and the second region 14a2, respectively. As an example, the first region Z1 and the second region Z2 are rectangular regions extending in the Z direction with a width wm (equal width in the Y direction) in a cross section orthogonal to the sweep direction SD, and the second region Z2. Is a region from the surface Wa to the depth d in the Z direction, and the first region Z1 is a region deeper than the depth d, in other words, a region opposite to the surface Wa with respect to the position of the depth d. can do. The width wm is, for example, 1/3 of the width wb (average value of the bead width) on the surface Wa of the weld metal 14a, and the depth d (height, thickness) of the second region Z2 is, for example, the width wb. Can be 1/2 of. Further, the depth of the first region Z1 can be, for example, three times the depth d of the second region Z2. The inventors have conducted experimental analysis on a plurality of samples, and in such a setting of the first region Z1 and the second region Z2, the average value of the cross-sectional areas of the crystal grains in the second region Z2 is in the first region Z1. It was confirmed that it was larger than the average value of the cross-sectional area of the crystal grains and was 1.8 times or more. Such discrimination can also be evidence that the first portion 14a1 and the second portion 14a2 are formed in the weld metal 14a by welding.

[Experimental result]
The inventors actually welded a plurality of samples and found suitable conditions. Tables 1 to 3 are examples of experimental results when the plurality of metal members to be processed are all copper-based materials. Table 1 shows the experimental results when the thickness of the metal member irradiated with the laser beam L in the Z direction is 0.5 [mm], and Table 2 shows the Z direction of the metal member irradiated with the laser beam L. The experimental results are obtained when the thickness of the metal member is 1.5 [mm], and Table 3 shows the experimental results when the thickness of the metal member irradiated with the laser beam L in the Z direction is 2.5 [mm]. be. In each table, the unit of output is [W], the unit of spot diameter is [μm], the unit of power density is [MW / cm ² ], the unit of energy density is [J / mm ³ ] (described later), and the sweep speed. The unit of is [mm / s]. Further, the penetration depth of the welded portion 14 and the welding quality (the number of spatters and blow holes per unit length of the welded portion 14) are evaluated, and the judgment E is that the penetration depth is insufficient and the welding quality is poor. A defective state, judgment D is a state in which the penetration depth is sufficient, welding defects such as spatter and blow holes during welding are suppressed, and welding quality is improved compared to judgment E, and judgment C is a state in which penetration is improved. Judgment B is a state in which the depth is sufficient and the welding quality is improved from the judgment D, judgment B is a state in which the penetration depth is sufficient and the welding quality is improved from the judgment C, and judgment A is the penetration depth. Is sufficient and the welding quality is in the best condition. The inventors have confirmed that the experimental results were equivalent in the connection structures shown in FIGS. 2, 4, and 6.

From the above experiment, other experiments, simulations, etc., when the thickness of the metal member irradiated with the laser beam L is less than 2 [mm] among the plurality of metal members,
[Condition 1-1]
When the surface of the surface of the first laser beam is a plane perpendicular to the laser beam, the spot diameter of the first spot formed on the plane is 14 [μm] or more and 150 [μm] or less, and the first laser beam. The power of the second spot is 0.3 [kW] or more and 2.0 [kW] or less, and the spot diameter of the second spot formed on the plane by the second laser beam is 100 [μm] or more and 900 [μm]. ] Or less, and when the power of the second laser beam satisfies 0.1 [kW] or more and 1 [kW] or less, the determination is A, B, or C, and a suitable welding state is obtained. It has been found.

Further, when the thickness of the metal member irradiated with the laser beam L is 2 [mm] or more and 3 [mm] or less among the plurality of metal members,
[Condition 1-2]
When the surface of the surface of the first laser beam is a plane perpendicular to the laser beam, the spot diameter of the first spot formed on the plane is 30 [μm] or more and 200 [μm] or less, and the first laser beam. The power of the second spot is 2 [kW] or more and 6 [kW] or less, and the spot diameter of the second spot formed on the plane by the second laser beam is 200 [μm] or more and 1200 [μm] or less. When the power of the second laser beam satisfies 0.5 [kW] or more and 2 [kW] or less, the judgment is A, B, or C, and it is found that a suitable welding state can be obtained. ..

[Energy density]
Further, in the above experimental analysis, the inventors introduced a new index of the energy density of laser light irradiation per unit volume of the connection structure 10, and the conditions under which a suitable welded state can be obtained for the energy density. I found it. The energy density can be expressed by the following equation (1).
_{E n = P n / (V} × D n × Ta) ··· (1)
Here, _{E n} is the energy density ^{[J /} mm 3], the _{P n,} the power of the laser beam by the laser device [W], V is the sweep rate [mm / s], _{D n} is the spot on the surface Wa The diameter [mm] and Ta are the thickness [mm] of the thin member. Here, each parameter is distinguished by the subscript n, where n = 1 indicates the parameter of the first laser beam and n = 2 indicates the parameter of the second laser beam.

Then, in addition to the above [Condition 1-1] or the above [Condition 1-2],
[Condition 2]
_{The energy density E 1} of the first laser beam is 120 [J / mm ³ ] or more, and the energy density E ₂ of the second laser beam is 5 [J / mm ³ ] or more and 50 [J / mm ^3]. ] When the following conditions are satisfied, the judgment is A or B, and it is found that a more suitable welding state can be obtained.

In addition to the above [Condition 1-1] or the above [Condition 1-2],
[Condition 3]
Even when the power density of the second laser beam ^{satisfies 0.15 [MW / cm 2} ] or more and 5 [MW / cm ² ] or less, the judgment is A or B, and a more suitable welding state can be obtained. found.

Further, when all of the above [Condition 1-1] or the above [Condition 1-2], [Condition 2], and [Condition 3] are satisfied, the determination is A, and the most suitable welding state can be obtained. found.

As described above, in the welding method of the present embodiment, for example, the electrode 11 and the metal member 12 are welded via the welded portion 14 by irradiating the surface Wa with the laser beam L. 10 is obtained. Further, the laser beam L includes a beam B1 having a wavelength of 800 [nm] or more and 1200 [nm] or less and a beam B2 having a wavelength of 550 [nm] or less.

Further, in the present embodiment, for example, the wavelength of the second laser beam is 400 [nm] or more and 500 [nm] or less.

With such configurations and methods, higher quality welds with fewer weld defects, such as spatters and blowholes, can be performed.

Further, in the present embodiment, for example, on the surface Wa, at least a part of the beam B2 (second spot) of the second laser beam has a sweep direction SD more than the beam B1 (first spot) of the first laser beam. It is located in front.

Further, in the present embodiment, for example, the beam B1 and the beam B2 partially overlap each other on the surface Wa.

Further, in the present embodiment, for example, on the surface Wa, the beam B2 is wider than the beam B1.

Further, in the present embodiment, for example, on the surface Wa, the outer edge B2a (second outer edge) of the beam B2 surrounds the outer edge B1a (first outer edge) of the beam B1.

As described above, the inventors have confirmed that welding defects can be further reduced in welding by irradiation with a beam of laser light L forming such beams B1 and B2 on the surface Wa. This is because, as described above, the processing target W is preheated by the region B2f of the beam B2 before the beam B1 arrives, so that the molten pool of the processing target W formed by the beam B2 and the beam B1 is further formed. It can be presumed that this is for stabilization. Therefore, according to the laser beam L having such beams B1 and B2, for example, welding with less welding defects and higher welding quality can be performed. Further, according to such settings of the beams B1 and B2, there is an advantage that, for example, the power of the first laser beam can be further lowered. Further, when the beam B1 and the beam B2 are irradiated coaxially, there is an advantage that the relative rotation between the optical head 120 and the processing target W becomes unnecessary.

Further, in the present embodiment, for example, each of the metal member 12 and the electrode 11 is subjected to copper-based metal material, aluminum-based metal material, nickel-based metal material, iron-based metal material, titanium-based metal material, and nickel plating. It is made of any one of the metal materials.

The effect of the welding method of the present embodiment is obtained when each of the metal member 12 and the electrode 11 is made of any of the above materials.

[Second Embodiment]
FIG. 12 is a schematic configuration diagram of the laser welding apparatus 100A of the second embodiment. In this embodiment, the optical head 120 has a DOE 125 between the collimating lens 121-1 and the mirror 123. Except for this point, the laser welding apparatus 100A has the same configuration as the laser welding apparatus 100 of the first embodiment.

The DOE125 forms the shape of the beam B1 of the first laser beam (hereinafter referred to as the beam shape). As conceptually illustrated in FIG. 13, the DOE 125 has, for example, a configuration in which a plurality of diffraction gratings 125a having different periods are superposed. The DOE 125 can form a beam shape by bending or superimposing parallel light in a direction affected by each diffraction grating 125a. DOE125 may also be referred to as a beam shaper.

The optical head 120 has a beam shaper provided after the collimating lens 121-2 to adjust the beam shape of the second laser beam, and a beam shaper provided after the filter 124 to adjust the beam shapes of the first laser beam and the second laser beam. It may have a beam shaper or the like to be adjusted. By appropriately adjusting the beam shape of the laser beam L by the beam shaper, it is possible to further suppress the occurrence of welding defects in welding.

[Third Embodiment]
FIG. 14 is a schematic configuration diagram of the laser welding apparatus 100B of the third embodiment. In this embodiment, the optical head 120 has a galvano scanner 126 between the filter 124 and the condenser lens 122. Except for this point, the laser welding apparatus 100B has the same configuration as the laser welding apparatus 100 of the first embodiment.

The galvano scanner 126 has two mirrors 126a and 126b, and by controlling the angles of the two mirrors 126a and 126b, the irradiation position of the laser beam L can be set without moving the optical head 120. It is a device that can be moved to sweep the laser beam L. The angles of the mirrors 126a and 126b are changed by, for example, a motor (not shown). With such a configuration, a mechanism for relatively moving the optical head 120 and the processing target W becomes unnecessary, and for example, there is an advantage that the device configuration can be miniaturized.

[Fourth Embodiment]
FIG. 15 is a schematic configuration diagram of the laser welding apparatus 100C of the fourth embodiment. In this embodiment, the optical head 120 has a DOE125 (beam shaper) between the collimating lens 121-2 and the filter 124. Except for this point, the laser welding apparatus 100C has the same configuration as the laser welding apparatus 100B of the third embodiment. According to such a configuration, the same effect as the third embodiment by having the galvano scanner 126 and the same effect as the second embodiment by having the DOE125 (beam shaper) can be obtained.

Also in this embodiment, the optical head 120 is provided after the collimating lens 121-1 and is provided after the beam shaper for adjusting the beam shape of the first laser beam, and is provided after the filter 124 and is provided with the first laser beam and the second laser beam. It may have a beam shaper or the like that adjusts the beam shape of the laser beam.

[Fifth Embodiment]
FIG. 16 is a schematic configuration diagram of the laser welding apparatus 100D of the fifth embodiment. In the present embodiment, the optical head 120 has a first portion 120-1 for irradiating the first laser beam L1 and a second portion 120 for irradiating the second laser beam L2, which are configured by different bodies (housings). -2 and are provided. Even with such a configuration, the same operations and effects as those of the above embodiment can be obtained.

FIGS. 17 and 18 show examples of laser beam beams B1 and B2 formed on the surface Wa by the laser welding apparatus 100D. As shown in FIGS. 17 and 18, according to the laser welding apparatus 100D, the relative positions of the beams B1 and B2 are set by setting the relative positions and postures of the first portion 120-1 and the second portion 120-2. It can be set arbitrarily. According to the research by the inventors, at least a part of the beam B2 (second spot) is located in front of the beam B1 (first spot) in the sweep direction SD on the surface Wa as shown in FIGS. It has been found that the same effect as in the first embodiment due to the preheating effect of the beam B2 can be obtained when the beam B1 and the beam B2 are in contact with each other or at least partially overlap each other. It has also been found that when at least a part of the beam B2 is located in front of the beam B1 in the sweep direction SD, the beam B1 and the beam B2 may be separated by a minute distance. .. It should be noted that FIGS. 17 and 18 are merely examples, and the arrangement of the beams B1 and B2 obtained by the laser welding apparatus 100D and the sizes of the beams B1 and B2 are not limited to the examples of FIGS. 17 and 18.

[Sixth Embodiment]
FIG. 19 is a schematic configuration diagram of the laser welding apparatus 100E of the sixth embodiment. The laser welding apparatus 100E is modified based on the laser welding apparatus 100B of the third embodiment. As shown in FIG. 19, the laser welding apparatus 100B has a position adjusting mechanism 140 that variably sets the position of the collimating lens 121 in the optical axis direction. The position adjusting mechanism 140 can appropriately change the sizes (spot diameters D1 and D2) of the beams B1 and B2 on the surface Wa of the processing target W. That is, the position adjusting mechanism 140 may also be referred to as a spot size variable mechanism. The same position adjusting mechanism 140 may be applied to the condenser lens 122, may be applied to both the collimating lens 121 and the condenser lens 122, and the laser welding apparatus of another embodiment may be applied. It is also applicable to the collimating lens 121 and the condenser lens 122 of 100, 100A, 100C and 100D.

[First modification]
FIG. 20 is a perspective view of the battery assembly 20F of the first modification of the first embodiment. As shown in FIG. 20, in this modification, a plurality of batteries 21 are connected in series via a metal member 12. Even in such a configuration, the same effect as that of the first embodiment can be obtained.

[Second modification]
FIG. 21 is a perspective view of the battery assembly 20G of the second modification of the first embodiment. As shown in FIG. 21, in this modification, the electrode 11 of the battery 21 penetrates the through hole provided in the metal member 12 and protrudes in the Z direction from the end face 12a. The laser beam L is emitted toward the boundary between the side surface 11b of the electrode 11 and the end surface 12a of the metal member 12 in the direction opposite to the Z direction and in the radial direction of the electrode 11. To. As a result, the welded portion 14 extends from the boundary between the side surface 11b and the end surface 12a in the direction opposite to the Z direction and inward in the radial direction of the electrode 11. Further, also in this modification, the welded portion 14 is formed in an annular shape, whereby a form of full-circle welding can be obtained. Also in this modification, the electrode 11 and the metal member 12 are arranged in a direction intersecting the irradiation direction of the laser beam L. Even in such a configuration, the same effect as that of the first embodiment can be obtained.

[Third modification example]
FIG. 22 is a perspective view of the battery assembly 20H of the third modification of the first embodiment, and FIG. 23 is a plan view of the electrode 11 and the metal member 12 of the present modification when viewed in the opposite directions in the Z direction. Is. As shown in FIGS. 22 and 20, in this modification, the electrode 11 and the metal member 12 are arranged in the Z direction. In other words, the electrode 11 and the metal member 12 overlap each other in the Z direction. The metal member 12 is adjacent to the electrode 11 in the Z direction. The laser beam L is emitted from the opposite side of the electrode 11 toward the end surface 12a as the surface Wa of the metal member 12 in the opposite direction in the Z direction. As a result, the welded portion 14 penetrates the metal member 12 from the end face 12a and enters the inside of the electrode 11. In this case, as shown in FIG. 23, the welded portion 14 is formed so as to fit in the electrode 11 and not protrude from the electrode 11 when viewed in the direction opposite to the Z direction. In this modification, two line segment-shaped welded portions 14 are provided along the Y direction and separated in the X direction, but the welded portions 14 are formed in the electrode 11 and the metal member 12. The specifications such as the shape and the number of welded portions 14 are not limited to this. For example, the welded portion 14 may be formed so as to draw a circle in a plan view.

[Fourth variant]
FIG. 24 is a perspective view of the battery assembly 20I of the fourth modification of the first embodiment. In this modification, the electrode 11 and the metal member 12 are arranged in the X direction. In other words, the electrode 11 and the metal member 12 overlap each other in the X direction. The metal member 12 is adjacent to the electrode 11 in the X direction or in the direction opposite to the X direction. The laser beam L is emitted from the opposite side of the electrode 11 toward the end surface 12a as the surface Wa of the metal member 12 in the X direction or the opposite direction in the X direction. As a result, the welded portion 14 penetrates the metal member 12 from the end face 12a and enters the inside of the electrode 11. In this case as well, as in the case of the third modification, the welded portion 14 is formed so as to fit inside the electrode 11 and not protrude from the electrode 11 when viewed in the X direction. In this modification, two line segment-shaped welded portions 14 are provided along the Y direction and separated in the Z direction. However, the welded portions 14 are formed in the electrode 11 and the metal member 12. The specifications such as the shape and the number of welded portions 14 are not limited to this.

Although the embodiments and modifications of the present invention have been exemplified above, the above-described embodiments and modifications are merely examples, and the scope of the invention is not intended to be limited. The above embodiments and modifications can be implemented in various other embodiments, and various omissions, replacements, combinations, and modifications can be made without departing from the gist of the invention. In addition, specifications such as each configuration and shape (structure, type, direction, model, size, length, width, thickness, height, number, arrangement, position, material, etc.) are changed as appropriate. Can be carried out.

Further, when the laser beam is swept to the object to be processed, the surface area of the molten pool may be adjusted by sweeping by known wobbling, weaving, output modulation or the like.

1B ... Battery 2B ... Battery assembly 10 ... Connection structure 10B ... Laminated body 10C ... Connection structure 11 ... Electrode (metal member)
11B ... Metal member 11C ... Metal member 11a ... End face 11b ... Side surface 11Ba ... End face 12 ... Metal member 12B ... Electrode tab (metal member)
12C ... Metal member 12a ... End face 12b ... Side surface 14 ... Welded part 14B ... Welded part 14C ... Welded part 14a ... Welded metal 14a1 ... First part 14a2 ... Second part 14b ... Heat affected part 20, 20F to 20I ... Battery assembly 21 ... Battery 21a ... End face 21C ... Power distribution device 21Ca ... Junction box 21Cb ... Charger 21Cc ... DC / DC converter 21Cd ... Conductive path 21C ... Housing 22C ... External power supply 23C ... Inverter 24C ... High pressure battery 25C ... Low pressure battery 100, 100A ~ 100E ... Laser welding equipment (welding equipment)
111 ... Laser device (first laser oscillator)
112 ... Laser device (second laser oscillator)
120 ... Optical head 120-1 ... First part 120-2 ... Second part 121, 121-1, 121-2 ... Collimating lens 122 ... Condensing lens 123 ... Mirror 124 ... Filter 125 ... DOE (diffractive optical element)
125a ... Diffraction grating 126 ... Galvano scanner 126a, 126b ... Mirror 130 ... Optical fiber 140 ... Position adjustment mechanism (spot size variable mechanism)
A ... Crystal grain B ... Boundary B1 ... Beam (first spot)
B1a ... Outer edge B2 ... Beam (second spot)
B2a ... Outer edge B2b ... Region B2f ... Region C ... Center point D1 ... Spot diameter (outer diameter)
D2 ... Spot diameter (outer diameter)
D _n ... Spot diameter d ... Depth E _n , E ₁ , E ₂ ... Energy density I ... Region L ... Laser light L1 ... First laser light L2 ... Second laser light Pd1 ... Power density Pd2 ... Power density P _n ... Power SD ... Sweeping direction Ta ... Thickness V ... Sweeping speed W ... Machining target Wa ... Front surface Wb ... Back surface wb ... Width wm (on the surface of the weld metal) ... Width X ... Direction (in the first region and the second region) (Second direction)
Y ... direction Z ... direction (first direction)
Z1 ... First area (first part)
Z2 ... Second area (second part)

Claims (21)

A metal member as an electrode of a battery, a metal member electrically connected to the electrode, or a plurality of metal members including a metal member in an electric device are laser-applied to the surface of at least one of the plurality of metal members. It is a welding method that welds by irradiating light.
The welding method, wherein the laser beam includes a first laser beam having a wavelength of 800 [nm] or more and 1200 [nm] or less, and a second laser beam having a wavelength of 550 [nm] or less. The welding method according to claim 1, wherein the metal member is an electrode of the battery. The welding method according to claim 1 or 2, wherein the plurality of metal members include a plurality of laminated electrode tabs. The welding method according to claim 1, wherein the metal member is housed in a housing of the electric device. The welding method according to claim 1, wherein the wavelength of the second laser beam is 400 [nm] or more and 500 [nm] or less. The laser beam is swept in the sweep direction on the surface.
On the surface, at least a part of the second spot formed on the surface by the second laser beam is in front of the first spot formed on the surface by the first laser beam in the sweep direction. The welding method according to any one of claims 1 to 5, which is located in. The welding method according to claim 6, wherein the first spot and the second spot overlap at least partially on the surface. The welding method according to claim 6, wherein on the surface, the second outer edge of the second spot surrounds the first outer edge of the first spot. Among the plurality of metal members, the thickness of the member irradiated with the laser beam along the irradiation direction of the laser beam is less than 2 [mm].
When the surface of the surface is a plane perpendicular to the laser beam due to the first laser beam, the spot diameter of the first spot formed on the plane is 14 [μm] or more and 150 [μm] or less.
The power of the first laser beam is 0.3 [kW] or more and 2.0 [kW] or less.
The spot diameter of the second spot formed on the plane by the second laser beam is 100 [μm] or more and 900 [μm] or less.
The welding method according to any one of claims 1 to 8, wherein the power of the second laser beam is 0.1 [kW] or more and 1 [kW] or less. Among the plurality of metal members, the thickness of the member irradiated with the laser beam along the irradiation direction of the laser beam is 2 [mm] or more and 3 [mm] or less.
When the surface of the surface is a plane perpendicular to the laser beam due to the first laser beam, the spot diameter of the first spot formed on the plane is 30 [μm] or more and 200 [μm] or less.
The power of the first laser beam is 2 [kW] or more and 6 [kW] or less.
The spot diameter of the second spot formed on the plane by the second laser beam is 200 [μm] or more and 1200 [μm] or less.
The welding method according to any one of claims 1 to 8, wherein the power of the second laser beam is 0.5 [kW] or more and 2 [kW] or less. The energy density of the first laser beam per unit volume in the irradiation direction of the laser beam in the welded portion between the metal member and the electrode is 120 [J / mm ³ ] or more.
Claim 1 that the energy density of the second laser beam per unit volume in the irradiation direction of the laser beam in the welded portion is 5 [J / mm ³ ] or more and 50 [J / mm ³ ] or less. The welding method according to any one of 10. The invention according to any one of claims 1 to 11, wherein the power density of the second laser beam is 0.15 [MW / cm ² ] or more and 5 [MW / cm ^{2] or less on the surface.} Welding method. The metal member is made of any one of a copper-based metal material, an aluminum-based metal material, a nickel-based metal material, an iron-based metal material, a titanium-based metal material, and a nickel-plated metal material. The welding method according to any one of claims 1 to 12. Laser oscillator and
The surface of at least one of a plurality of metal members including a metal member as an electrode of a battery, a metal member electrically connected to the electrode, or a metal member in an electric device, to receive laser light from the laser oscillator. With an optical head that irradiates a laser beam
A welding device that welds the plurality of metal members.
The laser beam is a welding apparatus including a first laser beam having a wavelength of 800 [nm] or more and 1200 [nm] or less, and a second laser beam having a wavelength of 550 [nm] or less. The welding apparatus according to claim 14, further comprising a beam shaper that divides the laser beam into a plurality of beams. The welding apparatus according to claim 14 or 15, further comprising a galvano scanner that changes the emission direction of the laser beam so as to sweep the laser beam in the sweep direction on the surface. The welding apparatus according to any one of claims 14 to 16, further comprising a spot size variable mechanism capable of changing the size of a spot on the surface of the laser beam. A plurality of metal members including a metal member as an electrode of a battery and a metal member electrically connected to the electrode,
Welded parts where multiple metal members are welded, and
Equipped with
The weld is a weld metal extending from at least one surface of the plurality of metal members along a first direction intersecting the surface.
The heat-affected zone located around the weld metal and
Have,
The weld metal is a battery assembly having a first portion and a second portion in which the average cross-sectional area of crystal grains in a cross section along the first direction is larger than that of the first portion. The battery assembly according to claim 18, wherein the average value of the cross-sectional areas of the crystal grains contained in the second portion is 1.8 times or more the average value of the cross-sectional areas of the crystal grains contained in the first portion. The battery assembly according to claim 18 or 19, wherein the weld extends along the surface in a second direction intersecting the first direction. A plurality of batteries as the batteries and
As the metal member, the electrode of each of the two batteries of the plurality of batteries and at least one metal member joined via the welded portion.
The battery assembly according to any one of claims 18 to 20, wherein the battery assembly comprises the above.

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