Welded metal structure, battery pack using same, and method for manufacturing battery pack

Abstract

The purpose of the present invention is to enable highly reliable laser welding in the connection of a bus bar and a voltage detection terminal in an in-vehicle battery pack. In order to achieve this, the present invention adopts the following configuration. Namely, this metal welded structure is provided with: a first metal member (16); a second metal member (14) having an overlapping portion that overlaps the first metal member (16); and a welded portion (19) formed on the overlapping portion, the welded portion (19) having a fused portion formed by penetrating the second metal member (14) in the thickness direction and being fused into the first metal member (16), the welded portion having a U-shape as viewed from the overlapping direction, the U-shape having: a first linear portion; and a second linear portion (20) extending from both sides in the longitudinal direction of the first linear portion to each end portion, the width (D1) between two points at the end portion of the welded portion (20) and the weld width (W) of the welded portion (20) being in the relationship D1 / W > = 2.

Description

Technical Field

[0001] The present invention relates to a welding structure of a storage battery, and in particular to a structure of a storage battery having a welding portion of a wiring terminal and a manufacturing method thereof. Background Art

[0002] For example, a battery module for use in a vehicle has a mechanism for detecting voltage information, temperature information, etc. of the mounted battery, and the wiring of this mechanism is often connected through a connection structure of a metal plate (bus bar) connecting the battery body or between batteries and a wiring terminal.

[0003] Here, since the wiring and the terminal are generally connected by mechanical bonding such as riveting, the material of the terminal is mostly a terminal material having relatively high hardness characteristics among copper materials with excellent electrical conductivity, such as phosphor bronze. The terminal composed of this phosphor bronze member is connected to the other side member, and the connection method is various methods such as mechanical bonding such as riveting or pressing, solid phase bonding such as resistance welding or ultrasonic bonding, and welding that locally melts the member such as laser welding, arc welding, or electron beam welding.

[0004] Here, in the final welding method, in the prior art, the mainstream is single spot welding that forms only one point or single weld welding that forms only one simple straight line or curve.

[0005] Patent document 1 describes a molded component having a ridge portion and a reinforcing material installed on the ridge portion by welding to improve impact resistance. Patent document 2 describes a method of laser joining a first metal plate such as a steel plate and an aluminum plate having a lower melting point than the first metal plate. Patent document 3 describes a laser joining method that can improve the peel strength when joining the flange portions of two components having flange portions. Prior art literature Patent Literature

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 2014-87848 Patent Document 2: Japanese Patent 5457605 Patent Document 3: Japanese Patent 6176428 Summary of the invention Problem that the invention aims to solve

[0007] In a vehicle-mounted battery module, the welded portion is required to withstand external environments such as vibration and ensure the strength reliability of power supply. In addition, the shape of the component to be welded is miniaturized according to the trend of miniaturization specifications of products, so there is a tendency to need a welding structure that ensures the bonding area required for the narrow portion of the small terminal. Therefore, a weld shape with a curved portion, or a plurality of straight lines or straight lines, or a circular shape such as an arc or an ellipse, or a weld shape with a plurality of points is formed in the narrow portion, and the distance between the weld directly facing the weld or the adjacent welds or adjacent points has to be small.

[0008] On the other hand, terminal materials with relatively high hardness characteristics, such as phosphor bronze, have high-temperature embrittlement behavior with reduced ductility at high temperatures. The inventors have discovered the following behavior: For a component terminal with such physical property behavior, if welding is performed in a narrow portion such as the above-mentioned weld shape that ensures the welding area, in the welding of the weld of the directly opposite portion or the adjacent portion, due to the heat effect of the welding construction of the rear half weld formed later, the weld metal portion and its surroundings are exposed to high temperature, and the displacement behavior of the material contraction in the cooling process starting from the solidification is fixedly hindered by the weld portion of the first half weld formed previously, and the tensile stress is concentrated in the above-mentioned embrittled high-temperature area, and welding cracks are easily generated in the rear half weld portion.

[0009] Therefore, in order to form a welding structure for a vehicle-mounted battery module with excellent electrical conductivity and strength reliability, it is required to establish a welding shape that can obtain a sufficiently large welding area in a tiny narrow part, and a welding shape that can prevent welding cracks caused by the physical properties of the terminal material with the above-mentioned relatively high hardness characteristics. Technical means of solving problems

[0010] In order to solve the above-mentioned problems of the prior art, the present invention provides a welding method. The present invention is an overlapping structure in which an upper member and a lower member of two members, at least one of which is made of a terminal material having a relatively high hardness characteristic, overlap, and energy is applied from one side to melt and penetrate the upper member and weld it to the lower member. In the shape of the weld seam having a curved portion and a partially facing weld seam portion observed from above, a weld seam shape is formed in which the relationship between the weld seam width W of the facing portion and the distance D between the weld seam center is D / W≥2, thereby avoiding the cause of welding cracks in the phosphor bronze member, that is, the concentration of tensile stress that hinders stress relaxation in the high temperature area during the second half of construction of the adjacent or facing weld seam and causes cracks.

[0011] In addition, the present invention provides a welding method, wherein an upper member and a lower member of two members at least one of which is made of phosphor bronze overlap, energy is applied from one side, the upper member is melted and penetrated, and then welded to the lower member, and in the shape of a weld portion having two or more straight or curved welds as viewed from above, a weld shape is formed in which the distance D between adjacent weld widths W and weld centers is in the relationship of D / W ≥ 2, thereby avoiding the cause of welding cracks in the phosphor bronze member, that is, the concentration of tensile stress that hinders stress relaxation in a high temperature region during the second half of construction of an adjacent or opposite weld and causes cracks.

[0012] In addition, the present invention provides a welding method, which is an overlapping structure in which an upper member and a lower member of two members at least one of which is made of phosphor bronze overlap, and energy is applied from one side to melt and penetrate the upper member and weld it to the lower member. In a shape in which a weld seam viewed from above is an arc or an ellipse, or a contour formed by combining a partial arc and a straight line portion, and has a weld portion that partially faces each other, a weld seam shape is formed in which the distance D between the adjacent weld seam width W and the weld seam center is in the relationship of D / W ≥ 2, thereby avoiding the cause of welding cracks in the phosphor bronze member, that is, the concentration of tensile stress that hinders stress relaxation in a high temperature region during the second half of construction of the adjacent or facing weld seam and causes cracks.

[0013] In addition, the present invention provides a welding method, wherein an upper member and a lower member of two members at least one of which is made of phosphor bronze overlap, energy is applied from one side, the upper member is melted and penetrated, and then welded to the lower member, and an overlapping lap joint structure is formed, and the cause of welding cracks in the phosphor bronze member, that is, the concentration of tensile stress that hinders stress relaxation in the high temperature area of ​​the adjacent or opposite weld during the latter half of the construction and causes cracks, is avoided by forming a welding weld shape in which the welding weld observed from above is a plurality of point shapes, and the width W of the adjacent welding welds and the distance D between the point centers are in the relationship of D / W ≥ 2.

[0014] In addition, the present invention provides a welding method using laser, arc or electron beam as energy for forming the above series of welding seams.

[0015] In addition, the present invention provides a vehicle-mounted battery pack that is compact and highly reliable by having a welded portion formed by the above series of welding methods. Effects of the Invention

[0016] By forming the welding shape of the present invention, in the terminal overlap of the terminal material having a relatively high hardness characteristic, a welding structure having excellent strength reliability and having no welding cracks while ensuring the welding long side can be formed. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1A A schematic diagram showing the shape of the voltage detection terminal and the bus bar in the first embodiment when they are overlapped and welded. Figure 1B This is a cross-sectional view showing laser welding of Example 1. Figure 1C A schematic diagram showing another aspect of Example 1. Figure 1D A schematic diagram showing another embodiment of the first embodiment. Figure 1E A graph showing the relationship between weld shape and weld cracking. Figure 1F A schematic diagram showing another embodiment of the first embodiment. Figure 1G A schematic diagram showing another embodiment of the first embodiment. Figure 1H A schematic diagram showing another embodiment of the first embodiment. Figure 2A A schematic diagram showing the shape of the voltage detection terminal and the bus bar when overlapped and welded in accordance with the second embodiment. Figure 2B This is a cross-sectional view showing laser welding of Example 2. Figure 3A A schematic diagram showing the shape of the overlap welding of the voltage detection terminal and the bus bar according to the third embodiment. Figure 3B A schematic diagram showing the shape of the overlap welding of the voltage detection terminal and the bus bar according to another form of the third embodiment. Figure 3C This is a cross-sectional view showing laser welding of Example 3. Figure 4A A schematic diagram showing the shape of the overlapped welded voltage detection terminal and the bus bar according to the fourth embodiment. Figure 4B A schematic diagram showing the shape of overlapping welding of a voltage detection terminal and a bus bar according to another aspect of the fourth embodiment. Figure 4C This is a cross-sectional view showing laser welding of Example 4. Figure 5A A schematic diagram showing the shape of the overlapped welded voltage detection terminal and the bus bar according to the fifth embodiment. Figure 5B A schematic diagram showing the shape of the overlap welding of the voltage detection terminal and the bus bar according to another aspect of the fifth embodiment. Figure 5C This is a cross-sectional view showing the laser welding of Example 5. Fig. 6A A schematic diagram showing the shape of the voltage detection terminal and the bus bar when overlapped and welded in Example 6. Figure 6B This is a cross-sectional view showing the laser welding of Example 6. Fig. 7A A schematic diagram showing the shape of the overlapped welded voltage detection terminal and the bus bar according to the seventh embodiment. Figure 7B This is a cross-sectional view showing the laser welding of Example 7. Fig. 8A A schematic diagram showing the shape of the overlapped welded voltage detection terminal and the bus bar according to the eighth embodiment. Figure 8B This is a cross-sectional view showing the laser welding of Example 8. Fig.9A A schematic diagram showing the shape of the overlapped welded voltage detection terminal and the bus bar according to the ninth embodiment. Fig. 9B A cross-sectional view showing laser welding of Example 9. Fig. 10A A schematic diagram showing the shape of the overlapped welded voltage detection terminal and the bus bar according to Example 10. Fig. 10B Indicates along Fig. 10A A cross-sectional view of the busbar in the long side direction. Fig. 10C Indicates along Fig. 10A A side view of the short side of the bus bar. Fig. 10D A schematic diagram showing the shape of the overlap welding of the voltage detection terminal and the bus bar according to another aspect of the tenth embodiment. Fig. 10E Indicates along Fig. 10D A side view of the short side of the bus bar. Fig.11A The figure shows a cross-sectional view of a state where a bus bar and a voltage detection terminal are laser-connected in a reversed state and viewed from the short side direction of the bus bar. Fig. 11B The figure shows a cross-sectional view of a state where a bus bar and a voltage detection terminal are laser-connected in a reversed state and viewed from the long side direction of the bus bar. Fig. 11C A schematic diagram showing the shape of the overlapped welded voltage detection terminal and the bus bar according to Example 11. Fig.11D A cross-sectional view showing laser welding of Example 11. Fig.11E A side view showing the relationship between the cell, the bus bar, and the voltage detection terminal in Example 11, as viewed from the longitudinal direction of the cell. Fig. 12A The figure shows a side view of the relationship between the cell, the bus bar, and the voltage detection terminal in Examples 1 to 10 when viewed from the longitudinal direction of the cell. Fig. 12B The figure shows a side view of the relationship between the cell, the bus bar, and the voltage detection terminal in Examples 1 to 10 when viewed from the short side direction of the cell. Fig. 12C A schematic diagram showing the basic structure of the arrangement and welding of the single cells, bus bars, and voltage detection terminals in the vehicle-mounted battery pack of the present invention. Fig.12D The figure shows a side view of the relationship between the cell, the bus bar, and the voltage detection terminal in Examples 1 to 10 when viewed from the short side direction of the cell. Fig.12E The figure shows a side view of the relationship between the cell, the bus bar, and the voltage detection terminal in Examples 1 to 10 when viewed from the longitudinal direction of the cell. Fig.13 A schematic diagram showing a vehicle-mounted battery pack according to the present invention. Fig.14 A plan view showing the relationship between a harness assembly accommodating a voltage detection wire, a voltage detection terminal, and a bus bar in a vehicle-mounted battery pack according to the present invention. DETAILED DESCRIPTION

[0018] Hereinafter, the present invention will be described in detail by way of examples. Example 1

[0019] In the first embodiment, the basic structure of a battery pack including the bus bar for a battery pack and the voltage detection terminal of the present invention is described with reference to the drawings. [Battery pack structure] Fig.13 A battery pack 1 using a terminal welding structure of the present invention is shown. The battery pack 1 has a structure in which a plurality of cells 2 are fixed by a pair of end plates 4 and a pair of side plates 5. The cells 2 are, for example, rectangular secondary cells such as lithium ion secondary cells.

[0020] The square cell 2 has a rectangular parallelepiped shape having an upper surface and a lower surface, a pair of planes with a large area, and a pair of side surfaces with a small area. The cells 2 are arranged in a row with the planes with large areas facing each other, and a bracket 3 is sandwiched between the cells 2, in front of the cell 2 at the head of the row, and behind the cell 2 at the end of the row.

[0021] The single cell 2 has a positive electrode 2a and a negative electrode 2b on the upper side, and all have the same size, shape, and structure. Adjacent single cells 2 are arranged so that the positive electrode 2a and the negative electrode 2b face each other, in other words, the planes of the front and back surfaces are alternately reversed. The positive electrode 2a is formed of, for example, an aluminum-based metal such as aluminum or an aluminum alloy, and the negative electrode 2b is formed of, for example, a copper-based metal such as copper or a copper alloy.

[0022] End plates 4 are arranged in front of the bracket 3 at the beginning of the row and in the rear of the bracket 3 at the end of the row. The pair of end plates 4 are formed of a metal material and have a substantially rectangular shape. Openings 4a for inserting bolts 6 are provided at four corners. A pair of side plates 5 are arranged on the sides of the cells 2 arranged in a row. Each side plate 5 is a rectangular frame having a spanning portion spaced apart from each other and a connecting portion connecting the spanning portions. Openings 5a are formed at each corner of the frame corresponding to the openings 4a of the end plates 4.

[0023] The battery pack 1 is formed by placing the end plate 4 at the head side of the row and the end plate 4 at the rear side of the row inside the front and rear connecting parts of each side plate 5, inserting the bolt 6 through the opening 5a of the side plate 5 and the opening 4a of the end plate 4, and fixing them by fastening. The bolt 6 is screwed into a threaded hole (not shown) formed on the bracket 3, or a nut (not shown) is arranged on the back side of the end plate 4 for fastening. Instead of fastening with the bolt 6, it is also possible to fix it with a rivet.

[0024] An insulating cover 7 is arranged on the upper side of each single cell 2 in a manner that surrounds the positive and negative electrodes 2a, 2b of the single cells 2 arranged in a row. The positive electrodes 2a and negative electrodes 2b of adjacent single cells 2 are connected by a bus bar 10. All single cells 2 are connected in series by the bus bar 10. A bus bar 8 is connected to the positive electrode 2a1 of the single cell 2 at the head of the row and the negative electrode 2b1 of the single cell 2 at the end of the row. The bus bar 10 or the bus bar 8 is welded to the positive and negative electrodes 2a, 2b by laser welding, ultrasonic welding, etc. It is also possible to have a structure that is connected by screw fastening without relying on welding.

[0025] Fig.14 It is a top view of a harness assembly 100 having a voltage detection wiring group 101, a voltage detection terminal 14 connected to the voltage detection wiring group 101, and bus bars 8 and 10 connected to the voltage detection terminal 14. The voltage detection wiring group 101 is connected to the outside through a socket 102. In addition, a voltage measurement wiring is arranged in a branch harness 110 and connected to the voltage detection terminal 14. The bus bar 8 is an end bus bar and is connected only to the outermost single battery. In contrast, the bus bar 10 is connected between the terminals of two single batteries 2. In addition, Fig.14 The bus bars 8 and 10 shown are of the simplest configuration and do not have the size structure shown in the following embodiments. Fig.14 is corresponding to Fig.13 In order not to complicate the diagram, Fig.14 There are no components other than the above components described. The following description uses the voltage detection terminal 14 as an example of the first metal component and the busbars 8, 10 (or their welding construction object parts 16) as an example of the second metal terminal. The first metal component may not be a busbar connecting the battery terminals, but a busbar connecting the battery and the external terminal. It is suitable for places with harsh operating environments such as temperature rise. The second metal component may also be other terminals instead of the voltage detection terminal. As an example, it can also be applied to temperature detection terminals, etc. The "metal welded structure" of the present invention refers to a product having these first metal components and second metal components.

[0026] exist Fig.14 In the embodiment, the welding target portion of the bus bar 10 and the voltage detection terminal 14 overlap, and in this portion, the bus bar 10 and the voltage detection terminal 14 are laser welded. Fig.14 In the embodiment, since each bus bar 10 is directly connected to the positive electrode 2a and the negative electrode 2b of the single cell 2, the terminal voltage of the battery pack 1 is directly transmitted to the voltage detection terminal 14. The weld 19 representing the laser-welded portion is represented by a U-shape. The reliability of the weld in the laser-welded weld 19 is extremely important for the reliability of the entire battery pack. The content of the present invention is described in detail using the following embodiments.

[0027] The welding structure and embodiments of the present invention are shown below. (Basic structure of voltage detection terminal and bus bar) First, the basic structure of the voltage detection terminal and the bus bar in the battery pack to which the present invention is applied will be described with reference to FIG. 12 . Fig. 12A This is a schematic diagram of a battery pack consisting of a single cell 2, a negative side of a busbar 10b, and a voltage detection terminal 14, viewed from the side in the long side direction of the single cell 2. The single cell 2 has a positive electrode 2a and a negative electrode 2b, and a busbar 10 is connected to the upper part of each terminal to conduct electricity between the terminals of the adjacent single cell 2. The voltage detection line 11 is connected to the voltage detection terminal 14, and the voltage detection terminal 14 is arranged on the surface of a welding construction object portion 16 of the terminal that is set in a manner protruding toward the negative side of the busbar 10, and is welded with the structure of the present invention. However, Fig. 12A The direction of the voltage detection line 11 is Fig.13 and Fig.14 Differently, it faces outward relative to the single cell 2. Fig. 12A This is a diagram for explaining the stacking relationship between the bus bar 10 and the voltage detection terminal 14 at the laser-bonded portion, and is not intended to be used as a reference. Fig.13 and Fig.14 The direction shown is the same as the actual product.

[0028] Fig. 12BThis is a schematic diagram of a single cell 2, a bus bar positive side 10a, 10b, and a voltage detection terminal 14, viewed from the side in the short side direction of the adjacent single cell 2 as a battery pack 1. The bus bar positive side 10a and the bus bar negative side 10b are arranged in a manner to connect the negative electrode 2b and the positive electrode 2a of each adjacent single cell 2, and are connected to each terminal. The voltage detection terminal 14 is arranged on the surface of the welding construction object portion 16 of the terminal provided in a protruding manner in the bus bar negative side 10b, and is welded with the structure of the present invention. As an embodiment of the present invention, the upper side of the bus bar negative side 10b when mounted on the battery pack 1 is referred to as the front side, and the lower side is referred to as the back side.

[0029] Next, a basic structure during welding of the voltage detection terminal 14 and the negative-electrode bus bar 10 b to which the present invention is applied will be described. Fig. 12C The figure shows the arrangement of components before welding of the voltage detection terminal 14 and the negative side 10b of the bus bar. The voltage detection terminal 14 is arranged on the upper part of the welding target portion 16 of the voltage detection terminal 14, which is provided so as to protrude from the negative side 10b of the bus bar. Fig.12D and Fig.12E This is a picture of welding construction viewed from the side. Fig.12D This is a diagram viewed from the side of the short side of the busbar. Fig.12E This is a diagram viewed from the side of the long side of the bus bar.

[0030] The surface of the voltage detection terminal 14 arranged as described above is irradiated with laser light, and is welded as an overlap joint with the welding target portion 16 on the negative electrode side 10 b of the bus bar.

[0031] Here, in the present invention, as a method of providing welding energy, not only laser but also arc or electron beam may be used. Hereinafter, a welding method using laser is described in this embodiment. (Material of voltage detection terminal and bus bar) The material of the voltage detection terminal 14 is phosphor bronze. Ni plating or Sn plating is applied to the surface 15 of the corresponding welding construction object part 16 protruding from the busbar 10, or sometimes no plating is applied. On the other hand, in the present embodiment, the material of the welding construction object part 16 of the voltage detection terminal 14 is a pure copper material such as oxygen-free copper, phosphorus deoxidized copper or tough copper or a copper material of phosphor bronze as the material of the busbar 10, and the voltage detection terminal 14 protrudes from the negative side 10b of the busbar connected to the negative electrode 2b or 2b1 of the single cell 2. In addition, the positive side 10a of the busbar connected to the positive electrode 2a or 2a1 of the single cell 2 is an aluminum-based material. The copper material part and the aluminum material part are formed into an electric conduction structure by joining, bonding or fastening. (Example of laser used) The laser light suitable for the implementation of the present invention is blue visible light to near infrared region with a wavelength of 400 to 1100 nm. In addition, the spot diameter of the irradiated laser light is 0.04 to 0.6 mm. (Welded structure) Hereinafter, a characteristic welding structure as an embodiment of the present invention will be described using FIG. 1 . Figure 1A This is a diagram of a welding structure formed according to the present invention, in which the weld bead shape of the surface is U-shaped, viewed from the voltage detection terminal 14 side, that is, the upper side. The negative side 10b of the bus bar is formed with the welding construction object portion 16 of the voltage detection terminal 14 so as to protrude toward the voltage detection line 11 side, and the voltage detection terminal 14 is overlapped and welded on the welding construction object portion 16. In addition, as Figure 1B As shown, in this embodiment, the voltage detection terminal 14 is configured as an upper member, and the welding construction object part 16 of the bus bar is configured as a lower member in a manner that the surface 15 faces upward. It is an overlapping structure as follows: the surface of the voltage detection terminal 14 is irradiated with a continuous beam-shaped laser 17 having the above-mentioned characteristics, the voltage detection terminal 14 is melted and penetrated, and the molten portion 18 reaches a predetermined depth from the surface 15 of the welding construction object part 16 of the bus bar, thereby welding the two members. exist Figure 1A In the embodiment of the present invention, as an example, the example in which the facing portion 20 in the weld bead 19 is used as the second linear portion is described. In addition, the portion between the facing portions 20 on both sides is described as an example of the first linear portion. The weld bead of the facing portion 20 of the weld bead 19 is located on both sides of the long side direction of the weld bead formed with the linear shape.

[0032] like Figure 1A As shown, in the present invention, as the shape of the weld, in the weld 19 having a U-shaped weld with a curved portion and having a weld portion facing, the weld shape of the weld surface is formed such that the weld width W of the facing portion 20 and the distance D1 between the weld center are D1 / W≥2. When there is a deviation in the weld width W of the facing portion 20, an average value may be taken. The same is true in other embodiments. In addition, in this embodiment, the distance between the centers of the welds is used as the width D1 of the two ends of the weld, but it is also possible to use the distance between the two sides of the second linear portion in the long side direction of the first linear portion. When the deviation of the weld width W is small, the measurement becomes easy. In addition, the laser is irradiated in the thickness direction of the member.

[0033] At this time, the welding speed (beam scanning speed) during continuous beam construction is within the range of 50 to 300 mm / s. In addition, during welding, in order to manage the construction atmosphere and ensure the weld shape, it is preferred to spray an inert gas or nitrogen as an auxiliary gas, or air or oxygen as a surface active gas to the construction site, but construction without the above-mentioned gas spraying is also possible.

[0034] Furthermore, in the present invention, under the above-mentioned laser device and welding conditions, in order to obtain sufficient current-carrying area and strength reliability, as Figure 1B As shown, the weld structure has a surface width 21 of the weld bead 19 of 0.4 mm or more, and a weld width 22 of 0.1 mm or more at the interface shown in the figure. When the negative electrode side 10b of the bus bar is made of the copper-based material, the melting depth 23 on the bus bar side is within the range of 0.1 mm or more and 80% or less of the bus bar plate thickness.

[0035] Here, the weld shape of the present embodiment is described as a U-shape, but this shape is not limited to Figure 1A The weld seam 19 shown has a straight bending shape, as Figure 1C The bending shape 24 of the combination of the straight line and the R curve shown, or as Figure 1D The shape 25 of the combination of the curve and the straight line portion shown is also a welded structure having the same meaning.

[0036] Figure 1E The results of experimental verification of the ratio of the weld width W of the opposite part to the distance D1 between the weld center and the probability of cracks in the weld under the above-mentioned welding conditions and weld shape. According to the figure, if the weld is in an adjacent state where the distance is small relative to the width of the weld, the first weld that has been welded when the adjacent second weld is formed during welding may hinder the relaxation of the tensile stress generated during cooling. When the second weld is in a high-temperature brittle state, if the above-mentioned tensile stress is not relaxed but concentratedly applied, cracks are likely to occur. On the other hand, if the weld is a distance that ensures that D1 / W has a relationship of more than 2 times, the tensile stress when the second weld is formed is fully relaxed by the area with a distance from the weld 19, which can avoid stress concentration when in a high-temperature brittle state, and thus prevent cracks.

[0037] By forming such a weld bead shape, the main cause of welding cracks in phosphor bronze components, namely, the concentration of tensile stress that hinders stress relaxation in the high temperature region of the adjacent or opposite weld during the second half of construction and causes cracks, can be avoided, and a welded structure with excellent strength reliability and no cracks can be formed.

[0038] In addition, Figure 1A In the embodiment, the orientation of the welding seam is the shape in which the facing portion 20 faces the direction in which the terminal of the single cell 2 is located. However, in the present invention, the orientation of the welding seam may be different depending on the state of the construction such as the configuration of the fixture or the irradiation direction of the laser 17. Figure 1F As shown, the facing portion 20 is made into a reverse shape, or as Figure 1G , Figure 1H As shown in FIG. 1 , the facing portion 20 is shaped to face the left or right side of the adjacent direction of the single cell 2. Figure 1C , Figure 1D The welds shown have the same shape. Example 2

[0039] As a second embodiment of the present invention, FIG. 2 shows a welding structure in which the shape of the welding seam is two L-shaped shapes arranged in mirror symmetry. Figure 2A As shown, as the shape of the welding seam, the welding seam is arranged in two L-shaped shapes in mirror symmetry. In the shape 25 having the directly opposed weld seam portion, the weld seam shape of the weld portion surface is formed so that the weld seam width W of the directly opposed portion 20 and the distance D2 between the weld seam center are D2 / W≥2. In this embodiment, the welding seam is described as mirror symmetric, but it may not be completely mirror symmetric, but may be roughly mirror symmetric as a whole. For example, it may be considered that the shape of the center of the weld width is composed of two L shapes. In this case, it may be considered that the vertical and horizontal lines of L or the area where the vertical and horizontal lines intersect have curvature.

[0040] like Figure 2B As shown in the figure, the surface width 21 of the weld is 0.4 mm or more, and the weld width 22 at the interface shown in the figure is 0.1 mm or more. The laser specifications, welding conditions, working atmosphere, depth of the weld, and direction of the weld are the same as those described in Example 1.

[0041] In the two L-shaped welds of the present embodiment, the relaxation of tensile stress during welding is more effective, and the main cause of the occurrence of welding cracks in the phosphor bronze member, that is, the concentration of tensile stress that hinders the relaxation of stress in the high temperature area of ​​the adjacent or opposite welds during the second half of the construction and causes cracks can be avoided, thereby forming a welded structure with excellent strength reliability without cracking. Example 3

[0042] As the next embodiment of the present invention, FIG. 3 shows a welding structure when the shape of the welding seam is a straight line or a curve arranged in parallel. Figure 3AAs shown, as the shape of the welding bead, in the shape 26 of the welding bead arranged in parallel in straight lines, the weld bead width W of the facing portion 20 and the distance D3a between the weld bead center are formed to be D3a / W≥2 on the weld surface. In this embodiment, the welding seams are described as being arranged in parallel, but they may also be arranged roughly in parallel with a gap as a whole. For example, it may be considered that the line shape observed from one end to the other end at the center of the weld width is arranged with a gap with other welds. In this case, the gap between one end and the other end is preferably roughly constant. In addition, the line shape may be a straight line or an arc shape.

[0043] Or, if Figure 3B As shown, as the shape of the welding bead, in the shape 27 of the welding bead being arranged in parallel, the weld bead width W of the directly facing portion 20 and the distance D3b between the weld bead center are formed to be D3b / W≥2. Figure 3C As shown, in any of the shapes, the weld structure has a surface width 21 of the weld bead of 0.4 mm or more, and a weld width 22 at the interface shown in the figure of 0.1 mm or more.

[0044] The laser specifications, welding conditions, working atmosphere, depth of the weld, and direction of the weld are the same as those described in Example 1.

[0045] In the parallel-arranged straight or curved welds of the present embodiment, the above-mentioned shape features can relieve the concentration of tensile stress during welding. Therefore, the cause of welding cracks in phosphor bronze components, i.e., the concentration of tensile stress that hinders stress relaxation in the high temperature region during the second half of construction of adjacent or opposite welds and causes cracks, can be avoided, and a welded structure with excellent strength reliability and no cracks can be formed. Example 4

[0046] As the next embodiment of the present invention, FIG. 4 is used to show the welding structure when the shape of the welding seam is circular or elliptical. Figure 4A As shown, in the case of a circular weld bead shape 28, a weld bead shape of the weld portion surface is formed in which the weld bead width W and the diameter D4a of the circle between the weld bead centers satisfy D4a / W≥2.

[0047] Or, if Figure 4B As shown, in the case where the shape of the weld bead is an ellipse 29, the weld bead shape of the weld surface is formed such that the weld bead width W and the weld bead center diameter D4b on the short side of the ellipse are in a relationship of D4b / W≥2. Figure 4CAs shown, in any of the shapes, the weld structure has a surface width 21 of the weld bead of 0.4 mm or more, and a weld width 22 at the interface shown in the figure of 0.1 mm or more.

[0048] The laser specifications, welding conditions, working atmosphere, depth of the weld, and direction of the weld are the same as those described in Example 1.

[0049] In the circular or elliptical weld of the present embodiment, the above-mentioned shape features can relieve the concentration of tensile stress during welding. Therefore, the main cause of the occurrence of welding cracks in phosphor bronze components, that is, the concentration of tensile stress that hinders the stress relaxation in the high temperature area of ​​the adjacent or opposite weld during the second half of the construction and causes cracks, can be avoided, and a welded structure with excellent strength reliability without cracks can be formed. Example 5

[0050] As the next embodiment of the present invention, FIG. 5 is used to show the welding structure when the shape of the welding seam is a rectangle. Figure 5A As shown in the figure, in the shape 30 of the weld bead being a rectangle, the weld bead shape of the weld portion surface is formed such that the weld bead width W of the directly opposed portion and the distance D5a between the weld bead center are D5a / W≥2. Alternatively, the weld bead shape is formed such that the weld region having the distance D5a shown in the figure is not a straight line but a curved line.

[0051] Or, if Figure 5B As shown, in the trapezoidal rectangular shape 31 where the opposing portions are not parallel, a weld shape of the weld surface is formed in which the weld width W of the opposing portions and the distance D5b between the weld centers are in the relationship of D5b / W≥2.

[0052] like Figure 5C As shown in the figure, in any shape, the surface width 21 of the weld is 0.4 mm or more, and the weld width 22 at the interface shown in the figure is 0.1 mm or more. The laser specifications, welding conditions, working atmosphere, depth of the weld, and direction of the weld are the same as those described in Example 1.

[0053] In the rectangular weld of the present embodiment, the above-mentioned shape feature can relieve the concentration of tensile stress during welding. Therefore, the main cause of the occurrence of welding cracks in phosphor bronze components, that is, the concentration of tensile stress that hinders the stress relaxation in the high temperature area of ​​the adjacent or opposite weld during the second half of the construction and causes cracks, can be avoided, and a welded structure with excellent strength reliability without cracks can be formed. Example 6

[0054] As a next embodiment of the present invention, FIG. 6 shows a welding structure in which the shape of the welding seam is not continuous but is in the shape of a point. Fig. 6A This is a diagram of a weld 32 formed of two spot shapes according to the present invention as viewed from the upper side as the voltage detection line side. As shown in this figure, the weld shape is formed such that the distance D6 between the center of the adjacent weld beads 32 and W is D6 / W ≥ 2. The number of spot welds is not limited to 2, and may be more as long as the above relationship is satisfied. In this embodiment, the point shape is recorded as the welding point as the welding seam method, and the width D6 of the two point centers of the weld portion uses the distance between the above-mentioned point centers in this embodiment, but it is also possible to use the distance between the one side ends in the direction between the connection points. When the deviation in the size of the welding point is small, the measurement becomes easy.

[0055] At this time, the laser irradiation can be in the form of either a pulsed laser or a continuous beam, and the spot diameter of the laser is 0.04 to 0.6 mm. In addition, in the case of a continuous beam, a point-shaped welding beam shape can be formed by scanning a small beam accompanied by the swing of the beam. In addition, the construction atmosphere of the auxiliary gas, etc. is the same as that of Example 1.

[0056] In addition, if Figure 6B As shown, in order to obtain a sufficient current-carrying area and strength reliability, the weld structure has a surface width 21 of the welded portion of 0.4 mm or more, and a weld width 22 at the interface shown in the figure of 0.1 mm or more.

[0057] By adopting the welding bead shape having the above relationship of the present invention, even in the case of a spot-welded structure, it is possible to avoid the concentration of tensile stress which is the main cause of welding cracks in phosphor bronze components, that is, the stress relaxation in the high temperature region adjacent to or directly opposite to the weld during the second half of construction and causes cracks, thereby forming a welded structure with excellent strength reliability without causing cracks. Example 7

[0058] As a next embodiment of the present invention, FIG. 7 shows a welding structure in which the welding target portion on the negative electrode side of the bus bar is not made of the copper material shown in Embodiment 1 but is made of the same aluminum material as the positive electrode side of the bus bar. Fig. 7A This is a view showing a weld seam formed according to the present invention of a welding construction target portion 34 which is made of an aluminum material and is provided in a form protruding from a bus bar 33, as viewed from the upper side as a voltage detection line side. Figure 7B When the material of the welded portion 34 to be welded to the voltage detection terminal 14 is aluminum, the welded portion has increased crack sensitivity due to embrittlement of the copper-aluminum compound in addition to crack sensitivity due to high-temperature embrittlement of the phosphor bronze member.

[0059] At this time, if Fig. 7A As shown, similarly to Example 1, as the shape of the welding weld, in the welding weld 35 in which the welding weld is a U-shape with a curved portion and has a shape of a directly opposed weld portion, the weld shape of the weld surface is formed in such a way that the weld width W of the directly opposed portion 20 and the distance D7 between the weld center are D7 / W≥2.

[0060] Here, as the shape of the welding bead, not only the shape of the welding bead 35 but also the shapes described in Examples 1 to 6 are also applicable. Figure 7B As shown, in any of the weld bead shapes, the weld structure has a surface width 21 of the weld bead of 0.4 mm or more, and a weld width 22 at the interface shown in the figure of 0.1 mm or more.

[0061] The specifications of the laser and the specifications related to the welding conditions are also the same as those of Examples 1 to 6. In addition, as shown in the figure, by controlling the melting depth 36 on the bus bar side of the welding construction object portion 34 composed of aluminum material to be 0.1 mm or more and the upper limit being 1.5 times or less of the plate thickness T of the voltage detection terminal 14 regardless of the bus bar plate thickness, the promotion of cracks caused by brittle compounds can be reduced.

[0062] By controlling the shape and penetration of the welding bead, a welded structure having excellent strength and reliability can be formed, which can prevent welding cracks caused by the phosphor bronze material and reduce crack promotion caused by the compound with the aluminum bus bar. Example 8

[0063] As a next embodiment of the present invention, an example of a change in the position of the welding portion relative to the bus bar is shown with reference to FIG. 8 . Fig. 8A The welding construction object part 37 of the voltage detection terminal of the bus bar is arranged as a flat part at the outer end of the single battery cell adjacent to the negative side 10b of the bus bar, and the voltage detection terminal 38 with a shape consistent with the shape of the flat part is overlapped and arranged as the shape of the welding weld. In the shape 39 of the welding weld which is a U-shape with a curved portion and has a directly opposite weld portion, the weld shape of the welding portion surface is formed in which the weld width W of the directly opposite portion 20 and the distance D8 between the weld center are D8 / W≥2.

[0064] Here, as the welding bead shape, not only shape 39 but also the shapes of the various materials described in Examples 1 to 7 are also applicable. Figure 8B As shown, in any of the shapes, the weld structure has a surface width 21 of the weld bead of 0.4 mm or more, and a weld width 22 at the interface shown in the figure of 0.1 mm or more.

[0065] The laser specifications, welding conditions, working atmosphere, depth of the weld, direction of the weld or point shape are the same as those described in the previous embodiments 1 to 7. With this welding structure, a margin is generated in the area of ​​the bus bar of the battery pack and the end of the harness of the voltage detection line, and a more compact or high-density battery pack mounting structure can be formed. Example 9

[0066] As a next embodiment of the present invention, another variation of the position of the welding portion relative to the negative electrode side 10b of the bus bar is shown with reference to Fig. 9. This embodiment discloses a second configuration showing a variation of the position of the joint portion. Fig.9A No protruding flat portion is provided on the negative side 10b of the bus bar, but a voltage detection terminal 40 of a specified shape is overlapped and arranged near the outer diameter end of the construction portion connected to the terminal of the single battery 2 on the negative side 10b of the bus bar. In the shape of the welding weld of the present invention, that is, the welding weld is a U-shape with a curved portion and has a shape 41 of a directly opposed weld portion, the weld shape of the weld surface is formed in a relationship where the weld width W of the directly opposed portion 20 and the distance D9 between the weld center are D9 / W≥2.

[0067] like Fig. 9B As shown, it is a weld structure having a surface width 21 of a weld seam of 0.4 mm or more, and a weld width 22 at the interface shown in the figure of 0.1 mm or more. Here, as the weld seam shape, not only the shape 41 but also the shapes of the various materials described in Examples 1 to 7 are also applicable.

[0068] The laser specifications, welding conditions, working atmosphere, depth of the weld, direction of the weld or point shape are the same as those described in the previous embodiments 1 to 7. With this welding structure, a margin is generated in the area of ​​the wiring harness end of the bus bars 8 and 10 of the battery pack 1 and the voltage detection line 11, and at the same time, the bus bar 10 can be made smaller, and a smaller or higher-density battery pack 1 mounting structure can be formed. Example 10

[0069] As a next embodiment of the present invention, still another variation of the shape of the welded portion with respect to the bus bar is shown with reference to FIG. 10 . Fig. 10A This is a diagram of the following configuration viewed from above: the welding construction object portion 42 of the voltage detection terminal of the bus bar is bent upward while protruding toward the outer diameter end of the adjacent unit side, and on the other hand, the voltage detection terminal 43 is bent into a U-shape or a square shape, and the voltage detection terminal 43 is the outer side and the two are temporarily fixed by fitting or insertion. In addition, Fig. 10B It is a cross-sectional view of a fitting portion between a welding target portion 42 of a bus bar and a voltage detection terminal 43 .

[0070] The right side surface 44 of the fitting portion in the figure is irradiated with laser 17 from obliquely above, and the welding is overlapped in the lateral direction. Fig. 10C This is a diagram of the fitting portion of the welding construction object portion 42 and the voltage detection terminal 43 and the weld surface observed from the side of the short side near the center of the negative side 10b of the bus bar. In the shape of the welding bead of the present invention, that is, the welding bead 45 is a U-shaped welding bead with a curved portion and has a directly opposed weld bead portion, the weld bead width W of the directly opposed portion and the distance D10a between the weld center are formed to be D10a / W≥2.

[0071] In addition, if Fig. 10D As shown, it is a welding structure having a surface width 21 of the welding bead 45 of 0.4 mm or more, and a welding width 22 at the interface shown in the figure of 0.1 mm or more. Here, as the welding bead shape, not only the welding bead 45 but also the shapes of the various materials described in Examples 1 to 7 are also applicable.

[0072] The laser specifications, welding conditions, working atmosphere, depth of the welded portion, direction of the weld and spot shape are the same as those described in Examples 1 to 7 above.

[0073] Furthermore, in this shape, since the strength effect of the interlocking fixation can also be obtained, Fig. 10E As shown, even if the weld bead shape does not have a curved facing portion, the strength reliability is excellent. Even if the weld bead shape of the present invention is formed, that is, the distance D10b between the weld centers is the weld length, and the weld width W and the weld length D10b are in the relationship of D10b / W≥2, the weld bead 46 on the weld surface can obtain excellent strength, so that the construction object part can be smaller and the strength reliability is excellent. The weld bead 46 is not limited to being formed on Fig. 10E The side surfaces of the bent portions shown can also be formed on the mating upper surfaces. Embodiment 11

[0074] As a next embodiment of the present invention, FIG11 is used to show a variation of the upper and lower positional relationship between the negative electrode side 10b of the bus bar and the voltage detection terminal 14. FIG11 is a diagram showing the following construction: the upper and lower sides of the bus bar when mounted on the battery pack 1 are the front and back sides, the bus bar 10 is arranged in such a way that the back side surface 47 defined above is the upper side during welding construction, the voltage detection terminal 14 is arranged on the upper part, and the surface of the voltage detection terminal is irradiated with laser 17 for welding. Fig.11A This is a diagram viewed from the side of the short side of the busbar. Fig. 11B This is a diagram viewed from the side of the long side of the bus bar.

[0075] Fig. 11CThis is a diagram viewed from above the side irradiated by the laser. As shown in this figure, as the shape of the weld, in the shape of the weld of the present invention, that is, the weld is a U-shaped weld with a curved portion and has a weld portion facing each other, the weld width W of the facing portion 20 and the distance D11 between the weld center are formed to be D11 / W≥2. In addition, as Fig.11D As shown in FIG. 1 , the weld structure has a surface width 21 of the weld bead of 0.4 mm or more, and a weld width 22 of 0.1 mm or more at the interface shown in the figure.

[0076] Here, as the structure of the welded joint or the shape of the weld bead, not only the shape 48 but also the joint structures or welding shapes of the various materials described in Examples 1 to 10 are applicable. The laser specifications, welding conditions, working atmosphere, depth of the welded portion, direction of the weld and spot shape are the same as those described in Examples 1 to 7 above. Fig.11E The structure in which the bus bar negative electrode side 10b and the voltage detection terminal 14 welded in the above manner are mounted as the battery pack 1 is shown. The voltage detection terminal 14 is welded to the lower side of the bus bar negative electrode side 10b and 16 when mounted as the battery pack 1. Fig.11E In the figure, the welding construction object portion 16 of the negative electrode side 10b of the bus bar protrudes to the outside of the single cell 2, but this is a figure for explaining the embodiment 11. In the actual product, the welding construction object portion 16 and the voltage detection terminal 14 are as shown in FIG. Fig.13 and Fig.14 As shown, it is toward the inner side of the single cell 2 .

[0077] By forming the welding structure shown in this embodiment, when the surface of the back side of the busbar 10 is highly flat, a welding structure with excellent adhesion to the voltage detection terminal and excellent welding quality can be obtained. Furthermore, as the assembly state of the components in actual machine construction, not only is the construction method in which the busbar 10 is welded to the voltage detection terminal in a separate configuration, but also the following construction method can be adopted: even when the busbar is assembled to the resin busbar housing of the wiring harness and busbar mounted on the upper part of the battery pack, the height of the resin part on the back side of the housing does not interfere with the clamp, and the effect of reducing the thermal influence on the resin part during laser welding can be obtained. Explanation of symbols

[0078] 1…battery pack, 2…cell, 2a…positive electrode, 2b…negative electrode, 3…bracket, 4…end plate, 4a…opening, 5…side plate, 5b…opening, 6…bolt, 7…insulating cover, 8…end bus bar, 10…bus bar, 11…voltage detection line, 14…voltage detection terminal, 15…bus bar surface, 16…welding work target portion, 17…laser, 19, 20…welding seam, 21…surface width of welding seam, 22…width of welding seam on bus bar side, 23…melting depth, 25-32, 33…bus bar, 34 …welding construction object part, 35…welding weld, 36…melting depth, 37…welding construction object part, 38…voltage detection terminal, 39…welding weld, 40…voltage detection terminal, 41…welding weld, 42…welding construction object part, 43…U-shaped voltage detection terminal, 44…surface of U-shaped voltage detection terminal, 45…welding weld, 46…welding weld, 47…back side surface of bus bar, 48…welding weld, 49…U-shaped welding weld, 100…wiring harness assembly, 101…wiring group, 102…socket, 110…branch harness.

Claims

1. A metal welded structure, comprising: a first metal component; a second metal member having an overlapping portion overlapping the first metal member; and a welding portion formed at the overlapping portion, The metal welded structure is characterized in that: The weld portion has a molten portion formed by penetrating the second metal member in the thickness direction and melting into the first metal member. The welded portion viewed from the overlapping direction has a U-shape, and the U-shape has a first linear portion and a second linear portion extending from both sides of the first linear portion in the longitudinal direction to each end. The relationship between the width D1 between two points at the end of the weld portion and the weld width W of the weld portion is D1 / W≥2.

2. A metal welded structure, comprising: a first metal component; a second metal member having an overlapping portion overlapping the first metal member; and a welding portion formed at the overlapping portion, The metal welded structure is characterized in that: The weld portion has a molten portion formed by penetrating the second metal member in the thickness direction and melting into the first metal member. The welded portion viewed from the overlapping direction has two L-shaped portions arranged in substantially mirror symmetry. The width D2 between two points at the farthest end of the weld portion and the weld width W of the weld portion are in a relationship of D2 / W≥2.

3. A metal welded structure, comprising: a first metal component; a second metal member having an overlapping portion overlapping the first metal member; and a welding portion formed at the overlapping portion, The metal welded structure is characterized in that: The weld portion has a molten portion formed by penetrating the second metal member in the thickness direction and melting into the first metal member. The welded portion viewed from the overlapping direction has a plurality of straight line shapes or arc shapes arranged substantially in parallel, The relationship between the width D3 between the two closest lines of the welded portion and the weld width W of the welded portion is D3 / W≥2.

4. A metal welded structure, comprising: a first metal component; a second metal member having an overlapping portion overlapping the first metal member; and a welding portion formed at the overlapping portion, The metal welded structure is characterized in that: The weld portion has a molten portion formed by penetrating the second metal member in the thickness direction and melting into the first metal member. The welded portion viewed from the overlapping direction is circular or elliptical, The shortest diameter D4 of the weld portion and the weld width W of the weld portion are in a relationship of D4 / W≥2.

5. A metal welded structure, comprising: a first metal component; a second metal member having an overlapping portion overlapping the first metal member; as well as a welding portion formed at the overlapping portion, The metal welded structure is characterized in that: The weld portion has a molten portion formed by penetrating the second metal member in the thickness direction and melting into the first metal member. The welded portion has a rectangular shape when viewed from the overlapping direction, The width D5 of the short side of the weld portion and the weld width W of the weld portion are in a relationship of D5 / W≥2.

6. A metal welded structure, comprising: a first metal component; a second metal member having an overlapping portion overlapping the first metal member; and a welding portion formed at the overlapping portion, The metal welded structure is characterized in that: The weld portion has a molten portion formed by penetrating the second metal member in the thickness direction and melting into the first metal member. The welded portion viewed from the overlapping direction has two or more point shapes, The width D6 between the centers of the two points of the weld portion and the weld width W of the weld portion are in a relationship of D6 / W≥2.

7. The metal welded structure according to any one of claims 1 to 6, characterized in that: The welded portion is welded by any one of laser, arc and electron beam.

8. The metal welded structure according to any one of claims 1 to 7, characterized in that: The molten metal is phosphor bronze or bronze.

9. A battery pack, wherein a first single cell having a first terminal and a second single cell having a second terminal are arranged in a first direction, the battery pack comprising: a bus bar connecting the first terminal and the second terminal in the first direction; and a voltage detection terminal for measuring a voltage on the bus bar, The battery pack is characterized in that When the bus bar is formed as a first metal member and the voltage detection terminal is formed as a second metal member, the first metal member and the second metal member form the metal welded structure according to claims 1 to 8 .

10. A method for manufacturing a battery pack, wherein a first single cell having a first terminal and a second single cell having a second terminal are arranged in a first direction, the battery pack comprising: a bus bar connecting the first terminal and the second terminal in the first direction; and A voltage detection terminal, which is used to measure the voltage of the bus bar, The manufacturing method of the battery pack is characterized in that: When the bus bar is formed as a first metal member and the voltage detection terminal is formed as a second metal member, the first metal member and the second metal member are welded so as to form the metal welded structure according to claims 1 to 8 .

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