JP2017168340A - Welded structure, battery using the same, and method of manufacturing welded structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a stable welded structure having high strength in connection between a bus bar connecting a plurality of battery cells and an electrode terminal member of the cell, and also to provide a battery using the same, and a method of manufacturing the welded structure.SOLUTION: A welded structure includes: a bus bar having a first plate part made of a first metal; a first electrode terminal part made of a second metal; and a first welded part for connecting the first plate part and the first electrode terminal part. The welded structure is used in which a first linear welded part is formed in the longitudinal direction and the right-angle direction of the first plate part. Moreover, the first electrode terminal part and the second electrode terminal part exist in a battery, and the battery having the welded structure is used.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a laser welded part that superimposes and welds a bus bar made of aluminum on an electrode terminal member made of copper, and a joining method thereof. In particular, the present invention relates to a battery system in which a plurality of battery cells are connected in series or in parallel via electrodes called bus bars.

The battery system can increase the output voltage by connecting a plurality of battery cells in series, and can increase the charge / discharge current by connecting them in parallel. For example, a battery system for large current and large output used as a power source for a motor that drives an automobile has a plurality of battery cells connected in series to increase the output voltage.
In the battery system used for this application, a plurality of battery cells are connected by a metal bar. The bus bar is connected to the electrode terminal member of the battery cell constituting the battery system by laser welding. In this connection structure, a notch is provided in the bus bar, the electrode terminal of the battery cell is inserted therein, the laser beam is irradiated to the boundary between the inserted electrode terminal and the bus bar, and both the electrode terminal and the bus bar are bordered. Molten and connected.

      A battery has a positive electrode and a negative electrode. Usually, an aluminum terminal is used on the positive electrode side, and a nickel-plated copper terminal is used on the negative electrode side. The notch portion of the bus bar passes through the electrode terminals of the adjacent battery cells and connects the battery cells in series or in parallel. Therefore, at least two battery cell electrode terminals are connected to one bus bar. When using an aluminum-copper coupling member called a clad material for the bus bar, the aluminum terminal on the positive electrode side should be welded to the aluminum side of the clad material, and the copper terminal on the negative electrode side should be welded to the copper side of the clad material. This is a welding between each other, and the bonding strength per unit area is high, and there are no technical difficulties.

      However, because this clad material is made by stacking aluminum and copper thin plates so that the joints overlap each other and applying pressure while applying heat, the cost of the process is high and the cost of direct materials is also expensive. There is a problem that the cost cannot be reduced.

      Therefore, it is possible to produce an inexpensive and light battery system by using inexpensive aluminum for the bus bar. However, when an aluminum bus bar is used, there is no problem in welding the same kind of material between the aluminum bus bar and the aluminum terminal on the positive electrode side. However, the negative electrode side is welded with dissimilar materials such as an aluminum bus bar and a nickel-plated copper terminal, and it is very difficult to achieve stable and high-quality welding.

      Dissimilar material welding is performed by melting different metal materials together, solidifying them, and then solidifying them. For dissimilar material welding of aluminum and copper, the alloy is sufficiently heated for a certain time above a certain temperature. When melted, an intermetallic compound having a constant ratio of aluminum and copper is formed. This intermetallic compound is a very hard layer with few lattice defects, but it becomes brittle and torn when stress is applied, so simply increasing the melting area does not provide high joint strength, but various gaps in production. It is very difficult to achieve stable and high-quality welding in the presence of variations.

      In the welding of dissimilar materials between aluminum bus bars and copper electrode terminal members in battery systems, the unit of welding is devised in order to maintain sufficient bonding strength in a limited welding space and maintain system functions. There are a method for improving the bonding strength per area and a method for relaxing the stress applied to the weld and maintaining the bonding even at a low bonding strength. Even if these are used alone, the bonding strength can be secured, but by combining both, it is possible to realize a stronger bonding against disturbance.

      About the stress concerning a welding part, it is possible to relieve | moderate by devising a welding pattern (shape), and the invention of the melt mark formed in the curve shape so that a line may not cross is made (patent document 1). reference).

International Publication No. 2012/164839

      However, when the prior art disclosed in Patent Document 1 is applied to welding of an aluminum bus bar and a nickel-plated copper terminal, there are the following problems.

      In the case of Patent Document 1 and normal spot welding, the laser weld is formed in a circular shape. In this case, there is an effect of increasing the bonding strength by applying an isotropic force to the bonding portion from the outside. On the other hand, when stress is applied to the other cell due to movement of one cell due to impact or the like, the bus bar connects the two cells, so stress from the connecting direction of the bus bar is applied to the weld. Become.

      FIG. 13 is a plan view showing a state in which stress is applied to the first welded portion 6a from the connecting direction of the bus bar (upward in the drawing) in the case where the lines in Patent Document 1 are formed so as not to intersect with each other. A terminal (not shown) is arranged on the lower surface of the aluminum bus bar 1 on the welding plate portion 2a of the aluminum bus bar 1, and the first welding portion 6a is formed by irradiating laser light. The stress 7 which tries to peel off the largest welded part concentrates on the upper part of the first welded part 6a closest to the connecting direction. As the distance from this portion increases, the magnitude of the stress 7 decreases.

      FIG. 14 is a plan view showing a state in which stress is similarly applied when a terminal (not shown) is welded to the weld plate portion 2a of the aluminum bus bar 1 when spot welding is performed at one point. As in FIG. 13, the stress 7 that causes the largest first welded portion 6 a to be peeled off concentrates on the upper portion of the first welded portion 6 a that is closest to the connection direction. As the distance from this portion increases, the magnitude of the stress 7 decreases.

      At this time, the stress is concentrated above the first welded portion 6a closest to the next cell as viewed from the connecting direction of the bus bar, that is, the first welded portion 6a in FIGS. Depending on the intermetallic compound and, in some cases, the state of blowhole formation, the welding strength becomes extremely low, and the bonding strength becomes unstable even when manufactured under the same conditions.

      Under such circumstances, stable production of the battery system is difficult, and supply of a low-cost battery system using an aluminum bus bar is difficult.

      Accordingly, an object of the present invention is to manufacture a stable welded structure with high welding strength, a battery using the same, and a welded structure in connection between a bus bar for connecting a plurality of battery cells and an electrode terminal member of the cell. Is to provide a method.

      In order to achieve the above object, a bus bar made of a first metal and having a first plate portion, a first electrode terminal portion made of a second metal, and the first plate portion and the first electrode terminal portion are connected. And a welded structure in which the linear first welded portion is formed in a direction perpendicular to the longitudinal direction of the first plate portion.

      Moreover, the said 1st electrode terminal part and the said 2nd electrode terminal part exist in a battery, and the battery which has the said welded structure is used.

      Further, the plate portion of the bus bar made of the first metal is superposed on the electrode terminal member made of the second metal, and the surface of the plate portion is irradiated with the first laser beam in the first trajectory to thereby form the plate portion and the electrode. The first laser step of forming a third welded portion on the terminal member, and the laser beam having a lower output than the first laser beam in a second orbit parallel to the first track and the surface of the plate portion. A second laser step of scanning to form a fourth welded portion, wherein the direction of the first track and the second track is a longitudinal direction of the plate portion and a direction perpendicular to the plate portion, respectively. Is used.

      Further, the plate portion made of the first metal is superposed on the electrode terminal member made of the second metal, and the surface of the plate portion is irradiated with the first laser beam in the first orbit to thereby form the plate portion and the electrode terminal member. And scanning the surface of the plate portion with a laser beam having a scanning speed higher than that of the first laser beam in a first laser step for forming a third welded portion and a second orbit parallel to the first track. And a second laser process for forming a fourth welded portion, wherein the direction of the first track and the second track is a longitudinal direction of the plate portion and a direction perpendicular to the plate portion, respectively. Use.

  The welded structure and the welding method of the present invention are a stable welded structure and welding method with high welding strength in connection with a bus bar connecting a plurality of battery cells and an electrode terminal member of the cell.

(A) The perspective view which showed the state which connected the electrode terminal of embodiment with the aluminum bus bar, (b) The detailed figure when stress is applied to a welding part, (c) The stress is further applied to a welding part Detailed view when (A) The perspective view which showed the state which connected the conventional electrode terminal with the aluminum bus bar, (b) The detailed figure when the stress is applied to the conventional welding part (A) The perspective view which showed the state which connected the conventional electrode terminal with the aluminum bus bar, (b) The detailed figure when the stress is applied to the conventional welding part (A) The perspective view which showed the state which connected the conventional electrode terminal with the aluminum bus bar, (b) The detailed figure when the stress is applied to the conventional welding part (A) The top view which expanded the 1st welding part 6a at the time of carrying out laser oscillation continuously, (b) The top view which expanded the 1st welding part 6a at the time of carrying out pulse oscillation of a laser The perspective view which showed the state which has connected the electrode terminal of embodiment with the aluminum bus bar The perspective view which showed the state which has connected the electrode terminal of embodiment with the aluminum bus bar (A) The perspective view which showed the state which connected the electrode terminal of embodiment with the aluminum bus bar, (b) The perspective view which showed the state which connected the electrode terminal of embodiment with the aluminum bus bar, (c) ) Perspective view showing a state in which the electrode terminals of the embodiment are connected by an aluminum bus bar (A) The top view which looked at the welding part vicinity of the welding plate part from the upper part, (b) The top view which looked at the welding part vicinity of the welding plate part from the upper part (A) The top view which looked at the welding part vicinity of the welding plate part from the upper part, (b) The top view which looked at the welding part vicinity of the welding plate part from the upper part (A) The top view which looked at the welding part vicinity of the welding plate part from the upper part, (b) The top view which looked at the welding part vicinity of the welding plate part from the upper part (A) The top view which looked at the welding part vicinity of the welding plate part from the upper part, (b) The top view which looked at the welding part vicinity of the welding plate part from the top, (c) The welding part vicinity of the welding plate part of embodiment The top view which looked at from the upper part, (d) The top view which looked at the welding part vicinity of the welding plate part of embodiment from upper direction Plan view of welded portion in Patent Document 1 Plan view of welded part when spot welding is performed at one point in the prior art

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. For simplification of description, components having substantially the same function are denoted by the same reference numerals.

(First embodiment)
FIG. 1A is a perspective view showing a state in which a negative electrode terminal of a battery cell and a positive electrode terminal of an adjacent cell are connected by an aluminum bus bar in the first embodiment of the present invention. .

      The weld plate portions 2a and 2b of the aluminum bus bar 1 are superposed on the negative electrode terminal 3 made of Ni-plated copper of the cell and the positive electrode terminal 4 made of aluminum of the adjacent cell. The weld plate portions 2a and 2b are connected by a connecting portion 8.

      When the convex portions are formed on the upper surfaces of the electrode terminals 3 and 4, the notched portions 5 for guiding the convex portions to the inside may be provided in the weld plate portions 2 a and 2 b of the aluminum bus bar 1. The notch 5 may be a through hole or a part of the plate.

      The welding plate portion 2 a overlapping the electrode terminal 3 is irradiated with a laser beam and welded through to form a first welded portion 6 a. Similarly, the welding plate portion 2 b overlapping the electrode terminal 4 is irradiated with laser light to form a second welding portion 6 b by penetration welding, and the electrode terminal 3 and the electrode terminal 4 are connected via the aluminum bus bar 1. Are electrically connected.

Thus, the electrode terminals 3 and 4 of each cell are sequentially connected by the aluminum bus bar 1. At this time,
When vibration or impact is applied to the electrode terminal 4, the displacement of the electrode terminal 4 is transmitted to the first welded part 6 a through the aluminum bus bar 1, and a stress 7 that tries to peel off the first welded part 6 a is generated.

      In the present embodiment, in order to relieve the stress 7, the direction perpendicular to the direction in which the stress 7 is applied to the first weld 6a, that is, the direction perpendicular to the connection direction of the aluminum bus bar 1 (upper right direction in the figure) (in the figure, The first welded portion 6a is formed in a straight line from the lower right to the upper left. Moreover, the said direction is a orthogonal direction with the longitudinal direction of the welding plate part 2a which is a rectangular parallelepiped shape. The following directions are the same in the other embodiments.

      In this case, since the welding plate portions 2a and 2b are rectangular, the direction of the first welding portion 6a is the direction of the vertical side of the rectangle.

      As an example, the width L of the weld plate portion 2a is 10 mm. The weld width of the first weld 6a is 1 mm. If the weld length is 1 mm (10% or more), the strength that satisfies the specifications will be obtained (30 N or more). The range that can be actually used is preferably 4 mm or more (40% or more, 80 N or more) in consideration of variations such as gaps.

The actual pattern is 6 mm closest to the connecting portion 8 and becomes slightly longer for each number of strips. The point is to satisfy the weld strength required for the stack rather than the ratio to the width, and the absolute length is important. (The size and width of the bus bar varies depending on the model depending on the design.)
FIGS. 1B and 1C are detailed views of the vicinity of the first welded portion 6a when the stress 7 is applied to the first welded portion 6a. Stress 7 is applied from the flat state of the aluminum bus bar 1 in FIG. 1A, and the aluminum bus bar 1 bends upward from the upper right end of the first welded portion 6a as shown in FIG. 1B. . If the bonding strength of the first weld 6a is low, after the aluminum bus bar 1 in FIG. 1 (a) is in a flat state or the aluminum bus bar 1 as shown in FIG. 1 (b) is slightly bent, The first weld 6a is broken. In the case of a non-defective product having a sufficiently high joint strength of the first welded portion 6a, the first welded portion 6a does not break even when the aluminum bus bar 1 is bent at a right angle as shown in FIG. The reason is that, as shown in FIGS. 1B and 1C, the first welded portion 6a is perpendicular to the direction in which the stress 7 is applied (in the direction perpendicular to the longitudinal direction of the rectangular parallelepiped weld plate portion 2a). This is because the stress 7 can be evenly distributed by the length of the end of the first welded portion 6a and the stress concentration can be prevented from being concentrated at a location where the joint strength is low.

<Example 1>
A specific example will be described in the first embodiment.

    In FIG. 1A, an aluminum bus bar 1 having a thickness of 1 mm is placed on a copper electrode terminal 3 having a thickness of 2 mm and plated with a nickel plating having a thickness of 6 μm, and the aluminum bus bar 1 (not shown) is pushed downward from above. The jig was placed so that the gap was not opened as much as possible. A laser beam with an output of 1500 W continuously oscillated from a fiber laser from the surface of the aluminum bus bar 1 is focused to a spot diameter of about 50 μm at a processing point at a speed of 500 mm / s and connected on the aluminum bus bar 1 as shown in the figure. The aluminum bus bar 1 was penetrated and welded to the aluminum bus bar 1 and welded to the negative electrode terminal 3 by scanning 10 mm in a direction perpendicular to the upper right direction (the upper right direction in the figure).

      When the tensile strength (peel strength) upward in FIG. 1 (c) at this time was measured, it was 103N, 109N, and 116N for three samples produced in the same manner, and all showed high tensile strength exceeding 100N. It was.

      In this way, the first weld 6a is formed in a direction perpendicular to the direction in which the stress 7 is applied to the first weld 6a. Accordingly, even when an intermetallic compound such as welding of aluminum and copper is generated and the bonding strength is reduced, a high bonding strength can be realized in welding with a limited area.

      In this embodiment, examples of the plating thickness, the thickness of the electrode terminals 3 and 4, and the thickness of the aluminum bus bar 1 are shown, but the present invention is not limited to this value. In addition, conditions such as laser output, welding speed, spot diameter, welding length, etc. are not limited to the above because they depend on the total heat capacity including the material and surface state of the metal member to be welded, the plate thickness, and the jig. .

<Comparative Example 1>
Welding was performed in the same manner as in Example 1 except that the welding direction was the same on the aluminum bus bar 1 in the connecting direction (upper right direction in the figure, the longitudinal direction of the weld plate portion 2a).

      As shown to Fig.2 (a), the welding plate part 2a which has overlapped with the electrode terminal 3 was irradiated with a laser beam, and the penetration welding was carried out, and the 1st welding part 6a was formed. At this time, the area of the 1st welding part 6a of Fig.1 (a) and Fig.2 (a) was made the same. Similarly, when the tensile strength when welding was measured, the tensile strength was lower than that of Example 1, which was 76N, 50N, and 97N, and the variation was large.

      This is because the first weld 6a is formed in the same direction as the direction in which the stress 7 is applied to the first weld 6a, as shown in FIG. Disperse the stress with a short part). For this reason, the stress per unit length becomes very large compared with Example 1. FIG. As a result, the first welded portion 6a breaks with a relatively low stress. In addition, if there is a weak portion on the short side, stress concentrates on the short portion and fracture starts, resulting in a large variation in bonding strength.

      Thus, when the 1st welding part 6a is formed in the same direction as the direction where the stress 7 is applied to the 1st welding part 6a, since tensile strength is low and its dispersion | variation is large, stable production cannot be performed.

<Comparative example 2>
Welding was performed in the same manner as in Example 1 except that the welding direction was circumferential.

      As shown in FIG. 3A, a circumferential first weld 6 a was formed around the notch 5. Similarly, when the tensile strength when welding was measured, the tensile strength was lower than that of Example 1, 89N, 104N, and 98N.

      This is because, by forming the first welded portion 6a in a circumferential shape, stress concentrates on one arc-shaped point of the first welded portion 6a as shown in FIG. 3 (b).

      Compared to FIG. 2A of Comparative Example 1, the outer diameter of the first welded portion 6a is large and relatively close to a straight line. For this reason, some stress is dispersed around the periphery. For this reason, although tensile strength falls from Example 1, higher strength than Comparative Example 1 can be maintained.

      However, if the first welded portion 6a is formed in a circumferential shape, it is difficult to perform stable production because the tensile strength is low.

<Comparative Example 3>
Welding was performed in the same manner as in Example 1 except that a pulsed YAG laser was used.

      As shown in FIG. 4A, the direction perpendicular to the direction in which the stress 7 is applied to the first welded portion 6a, that is, the direction perpendicular to the connecting direction of the aluminum bus bar 1 (upper right direction in the figure) (from lower right to upper left in the figure). The first weld 6a was formed in the direction). Laser beam with an average output of 600 W pulsed from the YAG laser from the surface of the aluminum bus bar 1 is focused to a spot diameter of about 300 μm at the processing point and connected on the aluminum bus bar 1 as shown in the figure at a speed of 20 mm / s. The aluminum bus bar 1 and the electrode terminal 3 were welded by scanning 10 mm in a direction perpendicular to the direction (upper right direction in the drawing) (in the drawing, lower right to upper left direction), through the aluminum bus bar 1. When the tensile strength (peel strength) in the upper direction of FIG. 1C was measured at this time, it was 107N, 101N, and 100N for three samples produced in the same manner, and all showed high tensile strength exceeding 100N. However, compared with Example 1, all were low intensity | strength.

      This is because the stress is concentrated on a part of the arc-shaped circle of each pulse as shown in FIG.

      Fig.5 (a) is the top view to which the 1st welding part 6a at the time of carrying out the continuous oscillation of the laser shown in FIG.1 (c) was expanded. In this case, since the end of the first weld 6a is linear, the stress is dispersed over the entire surface, and the stress at each location is reduced.

      FIG. 5B is an enlarged plan view of the first weld 6a when the pulse laser oscillation shown in FIG. In this case, circles are formed by the number of pulses, and the stress is concentrated on each circle, so that the strength decreases. However, since the number of pulses is large and the number of circles is large, the stress is dispersed, so that the tensile strength tends to be higher than those of Comparative Examples 1 and 2.

      Thus, when the 1st welding part 6a is formed with a pulsed laser, since tensile strength is low, it is difficult to perform stable production.

      From the above, in the welding of Example 1, stable welding with high tensile strength is possible even when an intermetallic compound is generated, and welding with high yield and low cost can be realized.

(Second Embodiment)
FIG. 6 is a perspective view showing a state in which the negative electrode terminal 3 of the cell and the positive electrode terminal 4 of the adjacent cell are connected by the aluminum bus bar 1 in the second embodiment of the present invention. Items not described are the same as those in the first embodiment.

      The aluminum bus bar 1 has a pair of welding plate portions 2a and 2b formed by welding to a negative electrode terminal 3 and an adjacent positive electrode terminal 4. Moreover, the aluminum bus bar 1 has a connecting portion 8 formed by connecting the weld plate portions 2a and 2b. The connecting portion 8 has a U-curved portion 9 that is U-curved. The direction of the U-curve may be either upward or downward.

      The aluminum bus bar 1 has a U-curved portion 9 in the middle of the connecting portion 8. As a result, even if the electrode terminal 4 of the positive electrode of the adjacent cell is vibrated or shocked in the X direction (in FIG. 6, diagonally from the upper left to the lower right), it occurs at the U-curved portion 9 of the connecting portion 8 of the aluminum bus bar 1. The displacement in the X direction is absorbed.

      As a result, the weld plate portion 2a of the aluminum bus bar 1 welded to the negative electrode terminal 3 is not greatly displaced in the X direction. Further, since the stress 7 applied to the first welded portion 6a is reduced, the weld strength of the first welded portion 6a can be kept high with respect to the threshold value.

      Similarly, even if the electrode terminal 4 of the positive electrode of the adjacent cell is vibrated or shocked in the Y direction (in FIG. 6, diagonally from the upper right to the lower left), the welding plate portions 2a and 2b and the U-curved portion 9 of the aluminum bus bar 1 are applied. The connecting portion 8 that is in contact is bent at a right angle from the X direction to the Y direction. For this reason, the displacement in the Y direction is absorbed in this portion. As a result, the weld plate portion 2a of the aluminum bus bar 1 welded to the negative electrode terminal 3 is not significantly displaced in the Y direction. Further, since the stress 7 applied to the first welded portion 6a is reduced, the weld strength of the first welded portion 6a can be kept high with respect to the threshold value.

      From the above, the difference between the required strength required for the first welded portion 6a and the actual fracture strength can be increased, and the stability of the process is improved and the battery system can be manufactured at a low cost. It becomes.

<Example 2>
A specific example will be described in the second embodiment.

    In FIG. 6, when the tensile strength of what was welded similarly to Example 1 except having the U curved part 9 in the connection part 8 of the aluminum bus bar 1, it was 116N, 105N, and 111N. Also showed high tensile strength exceeding 100N.

      Thus, even in welding using the aluminum bus bar 1 having the U-curved portion 9 in the connecting portion 8, the first welded portion 6 a is formed in a direction perpendicular to the direction in which the stress 7 is applied to the first welded portion 6 a, thereby forming aluminum. Even when an intermetallic compound such as welding of copper and copper is generated and the bonding strength is lowered, high bonding strength can be realized in welding of a limited area.

      In this example, conditions such as laser output, welding speed, spot diameter, welding length, etc. depend on the total heat capacity including the material and surface state of the metal member to be welded, the plate thickness, and the jig. It is not limited content.

(Third embodiment)
FIG. 7 is a perspective view showing a state in which the negative electrode terminal 3 of the cell and the positive electrode terminal 4 of the adjacent cell are connected by the aluminum bus bar in the third embodiment of the present invention. Items not described are the same as those in the first embodiment.

      In FIG. 7, there are a first connecting portion 10a and a second connecting portion 10b provided with welding plate portions 2a and 2b. There are a first rising portion 11a and a second rising portion 11b that are connected to the first connecting portion 10a and the second connecting portion 10b via a bent portion. Furthermore, it has the intermediate | middle connection part 12 which connects both ends to the 1st rising part 11a and the 2nd rising part 11b via the bending part, and the U-curved part 9 is provided in the intermediate | middle connection part 12. .

      Even if the positive electrode terminal 4 of the adjacent cell is vibrated or shocked in the Z direction (vertical direction in FIG. 7), the displacement in the Z direction generated at the bent portion of the aluminum bus bar 1 with the rising portion 11a or 11b is not. Absorbed.

      As a result, the weld plate portion 2a of the aluminum bus bar 1 welded to the electrode terminal 3 is not greatly displaced in the Z direction, and the stress 7 applied to the first weld portion 6a is reduced, so that the first weld portion 6a is joined. The intensity can be kept high relative to the threshold.

      Similarly, even if the positive electrode terminal 4 of the adjacent cell is vibrated or shocked in the X direction (in the diagonally upper left to the lower right direction in FIG. 7), it is generated at the U-curved portion 9 of the intermediate connecting portion 12 of the aluminum bus bar 1. The displacement in the X direction is absorbed.

      As a result, the welding plate portion 2a of the aluminum bus bar 1 welded to the electrode terminal 3 is not greatly displaced in the X direction, and the stress 7 applied to the first welding portion 6a is reduced, so that the welding of the first welding portion 6a is performed. The intensity can be kept high with respect to the threshold.

      Furthermore, even if the electrode terminal 4 is vibrated or shocked in the Y direction (in FIG. 7, diagonally from the upper right to the lower left), the bent portion of the aluminum bus bar 1 is in contact with the rising portion 11a or 11b and the U bent portion 9. Since the connecting portion 12 is bent at right angles from the X direction to the Y direction, the displacement in the Y direction is absorbed in this portion, and the weld plate portion 2a of the aluminum bus bar 1 welded to the negative electrode terminal 3 is in the Y direction. There is no significant displacement. As a result, since the stress 7 applied to the first welded part 6a is reduced, the weld strength of the first welded part 6a can be kept high with respect to the threshold value.

      From the above, the difference between the required strength required for the first welded portion 6a and the actual fracture strength can be increased, and the stability of the process is improved and the battery system can be manufactured at a low cost. It becomes.

<Example 3>
In the third embodiment, specific examples will be described.

    In FIG. 7, the connection part 8 of the aluminum bus bar 1 has the first connection part 10a and the second connection part 10b provided at the both ends of the aluminum bus bar 1 and provided with welding plate parts 2a and 2b, A first rising portion 11a and a second rising portion 11b which are connected to the connecting portion 10a and the second connecting portion 10b via a bent portion; a first rising portion 11a and a second rising portion 11b; The intermediate connecting part 12 is formed by connecting both ends via a bent part. The tensile strength of the welded material was measured in the same manner as in Example 1 except that the U-curved portion 9 was provided in the intermediate connecting portion 12. As a result, the tensile strength was 112N, 110N, and 106N, and all showed high tensile strength exceeding 100N.

      In this way, the U-curved portion 9 is provided in the rising portions 11a and 11b and the intermediate connecting portion 12, and the first welded portion 6a is formed in a direction perpendicular to the direction in which the stress 7 is applied, thereby welding aluminum and copper. Even when such an intermetallic compound is produced and the joint strength is lowered, a high joint strength can be realized in welding of a limited area.

      In this example, conditions such as laser output, welding speed, spot diameter, welding length, etc. depend on the total heat capacity including the material and surface state of the metal member to be welded, the plate thickness, and the jig. It is not limited content.

(Fourth embodiment)
FIG. 8A is a perspective view showing a state in which the negative electrode terminal of the cell and the positive electrode terminal of the adjacent cell are connected by the aluminum bus bar in the fourth embodiment of the present invention. Items not described are the same as those in the first embodiment.

      The welded plate portions 2a and 2b of the aluminum bus bar 1 are superposed on the negative electrode terminal 3 made of Ni-plated copper of the cell and the positive electrode terminal 4 made of aluminum of the adjacent cell. In the case where a convex portion is formed on the upper surface of the electrode terminal, a cutout portion 5 for guiding the protruding portion of the electrode terminal to the inside may be provided on the welding plate portion 2a or 2b on the upper surface of the electrode terminal of the aluminum bus bar 1. .

      The welding plate portion 2a where the negative electrode terminal 3 and the aluminum bus bar 1 overlap is irradiated with laser light to form the first first welding portion 6a and the first welding portion 13a by through welding. The first first welded part 6a and the first welded part 13a are opposed to each other with the notch part 5 interposed therebetween.

      Similarly, a laser beam is applied to the weld plate portion 2b where the positive electrode terminal 4 and the aluminum bus bar 1 are overlapped to form the first second weld portion 6b and the second weld portion 13b by through welding. . Thus, the negative electrode terminal 3 and the positive electrode terminal 4 are electrically connected via the aluminum bus bar 1.

      When the negative electrode terminal 3 and the first first welded portion 6a and the first welded portion 13a of the aluminum bus bar 1 are used as a reference, when the electrode terminal 4 of the adjacent cell moves due to vibration or impact, The displacement is transmitted to the first first welded portion 6a and the first welded portion 13a through the aluminum bus bar 1, and becomes the stresses 7 and 14 for peeling the first first welded portion 6a and the first welded portion 13a. . At this time, since the first welds 6a and 13a are formed in a direction perpendicular to the direction in which the stresses 7 and 14 are applied to the welds, the first welds 6a and 13a are subjected to the stresses 7 and 14 in the first weld. The lengths of the ends of the portions 6a and 13a can be evenly distributed.

      Compared with the first embodiment, in this embodiment, in addition to the large welding area, the first first welded portion 6a is broken by the stress 7 applied to the first first welded portion 6a. After that, the first welded portion 13a maintains the joining, and the fracture does not occur until a larger stress 14 is applied. Therefore, a higher and more stable joining strength between the welded plate portion 2a and the negative electrode terminal 3 can be obtained. .

<Example 4>
A specific example will be described in the fourth embodiment.

    In FIG. 8 (a), the welded portions in the welded plate portions 2a and 2b of the aluminum bus bar 1 are implemented except that the first welded portions 6a and 6b and the first welded portions 13a and 13b are included. Similar to Example 1. When the tensile strength was measured, they were 127N, 135N, and 123N, and all showed high tensile strength exceeding 100N.

      In this way, by having two welds formed in a direction perpendicular to the direction in which the stress is applied to the welds, the stress is distributed to each of the two welds. Even when such an intermetallic compound is generated and the bonding strength is lowered, a high bonding strength can be realized in welding of a limited area.

      In the present embodiment, conditions such as laser output, welding speed, spot diameter, welding length, and distance between welding locations are the total heat capacity including the material and surface state of the metal member to be welded, the plate thickness, and the jig. This is not limited to the above.

      In the present embodiment, the welding example of the U-curved aluminum bus bar 1 as shown in FIG. 1A is shown, but an aluminum bus bar having a U-curved portion 9 in the connecting portion 8 shown in FIG. The same effect can be obtained by using an aluminum bus bar such as an aluminum bus bar provided with the first rising portion 11a and the second rising portion 11b shown in FIG.

      In this embodiment, an example having two welds in a straight line is described, but a quadrangle as shown in FIGS. 8B and 8C or a welded part shape with rounded corners. The same effect can be obtained.

(Fifth embodiment)
9 (a) and 9 (b) show the first welded portion 6a of the welded plate portion 2a when the aluminum bus bar 1 is arranged on the upper surfaces of the electrode terminals 3 and 4 in FIG. 1 (a) in the first embodiment. It is the top view which looked at the vicinity from the upper part. Items not described are the same as those in the first embodiment.

      First, FIG. 9A will be described. In order to form the first welded portion 6a in a direction perpendicular to the direction of stress applied to the first welded portion 6a, the melted portion 16 is formed by scanning in the above direction while irradiating a laser beam. Next, the position of the laser beam is moved in the Y direction (vertical direction in the figure) and scanned in the same manner. This is repeated to form the first welded portion 6a in which the melting portion 16 is continuous in the Y direction.

      When stress is applied to the first welded portion 6a, stress is first applied to the end of the first welded portion 6a on the stressed side (the upper end of the first welded portion 6a in FIG. 9A). At this time, since the stress dispersed by the weld length is applied uniformly to each location, the stress per unit length is reduced. As a result, since stress concentration can be avoided, the first welded portion 6a does not break even when a considerably high stress is applied as a whole. When a higher stress is applied, the melted portion 16 is broken when only one melted portion 16 is formed.

      As shown in FIG. 9 (a), when the plurality of melted portions 16 are formed and the area of the first welded portion 6a is large in the direction in which stress is applied, the first fracture occurs compared to the case where one melted portion 16 is formed. Even if this occurs, since the force for holding the joint is large, it will not break unless a higher stress is applied, and the joint strength will be improved.

      Next, FIG. 9B will be described. At first, as in FIG. 9A, in order to form the first welded portion 6a in a direction perpendicular to the direction of stress applied to the first welded portion 6a, the melted portion is scanned in the above direction while irradiating a laser beam. 16 is formed. Next, the position of the laser beam is moved in the Y direction (vertical direction in the figure), and the laser beam is scanned at a lower output than the laser beam irradiated first, thereby forming the melted portion 17. Similarly, the melted portions 16 and 17 are alternately formed, and this is repeated to form the first welded portion 6a in which the melted portions 16 and 17 are continuous in the Y direction.

      By alternately scanning a high-power laser beam and a low-power laser beam, deep melting depth and shallow melting depth are alternately formed, so that a wider bonding area can be secured, as in the anchor effect. In addition, since the deeply melted portion 16 enters the electrode terminal like a wedge, the first welded portion 6a having higher bonding strength can be obtained.

<Example 5>
A specific example will be described in the fifth embodiment.

      In FIG. 9A, the laser beam having an output of 1500 W continuously oscillated from a fiber laser is focused to a spot diameter of about 50 μm at the melting point 16 of the first weld 6a in the weld plate 2a of the aluminum bus bar 1. Then, at a speed of 500 mm / s, as shown in the figure, the aluminum bus bar 1 was formed by scanning 10 mm in a direction perpendicular to the connection direction (upper right direction in the figure) (lower right to upper left direction in the figure). Next, the scanning position was moved by 100 μm with respect to the connection direction, and similarly, scanning with 7 mm at a speed of 500 mm / s with an output of 1500 W was performed to form the second melt portion 16. By repeating this, a total of 8 melted portions 16 were generated and designated as the first welded portion 6a.

      When the tensile strength of the first welded portion 6a at this time was measured, it was 138N, 137N, and 132N, and the weld strength was increased, so that the joint strength was high and stable.

      Next, as shown in FIG. 9B, the first line scans the laser with an output of 1500 W as in FIG. 9A, moves the scanning position by 100 μm with respect to the connection direction, and outputs 1200 W. Scanning was performed 10 mm at a speed of 500 mm / s to form a second melt portion 17. The melted portions 16 and 17 were repeated to generate a total of 8 melted portions 16 as the first welded portion 6a.

      When the tensile strength of the first weld 6a at this time was measured, it was 143N, 144N, and 147N, and the joint strength was further high and stable.

      Thus, a high and stable joint strength can be obtained by forming the welded portion by scanning with a plurality of laser beams and increasing the weld area. In particular, by alternately scanning a high output and a low output, a higher and more stable bonding strength can be obtained.

      In the present embodiment, conditions such as laser output, welding speed, spot diameter, welding length, and distance between welding locations are the total heat capacity including the material and surface state of the metal member to be welded, the plate thickness, and the jig. This is not limited to the above.

      In the present embodiment, the welding example of the U-curved aluminum bus bar 1 as shown in FIG. 1A is shown, but an aluminum bus bar having a U-curved portion 9 in the connecting portion 8 shown in FIG. The same effect can be obtained by using an aluminum bus bar such as an aluminum bus bar provided with the first rising portion 11a and the second rising portion 11b shown in FIG.

<Example 6>
10 (a) and 10 (b) show that when the aluminum bus bar 1 shown in FIG. 7 is arranged on the upper surface of the electrode terminal, the first welded portion 6a of the weld plate portion 2a is a square type shown in FIG. 8 (c). It is the top view which looked at the 1st welding part 6a vicinity from the upper direction when it is a welding part shape where the angle | corner became round.

      FIG. 10A will be described. First, the molten portion 16 of the first welded portion 6a in the weld plate portion 2a of the aluminum bus bar 1 is focused on a laser beam having an output of 1500 W continuously oscillated from a fiber laser to a spot diameter of about 50 μm at a processing point of 500 mm / s. As shown in the figure, the periphery of the notch 5 that guides the protruding portion of the electrode terminal inward is scanned in a shape with rounded square corners. Next, the scanning position is moved inward by 100 μm from the fusion part 16, and scanning is performed in the same manner with a slightly smaller orbit. This was repeated to generate a total of five circumferentially-shaped melted portions 16 as first welded portions 6a.

      When the tensile strength of the 1st welding part 6a at this time was measured, they were 140N, 144N, and 158N, and joining strength became high.

      Next, FIG. 10B will be described. The first line is scanned with the laser in the same manner as in FIG. 10A, the scanning position is moved inward by 100 μm, and the scanning is performed in the same shape at a speed of 500 mm / s at an output of 1200 W. Formed. The melted portions 16 and 17 were repeated to generate a total of 5 melt-like melted portions 16 and 17, which were designated as the first welded portion 6 a.

      When the tensile strength of the first weld 6a at this time was measured, it was 149N, 147N, and 150N, and the joint strength was high and stable.

      In this way, by having two welds formed in a direction perpendicular to the direction in which the stress is applied to the welds, the stress is distributed to each of the two welds. Even when such an intermetallic compound is generated and the bonding strength is lowered, a high bonding strength can be realized in welding of a limited area. In particular, by alternately scanning a high output and a low output, a higher and more stable bonding strength can be obtained.

      In the present embodiment, conditions such as laser output, welding speed, spot diameter, welding length, and distance between welding locations are the total heat capacity including the material and surface state of the metal member to be welded, the plate thickness, and the jig. This is not limited to the above.

      In the present embodiment, the welding example of the U-curved aluminum bus bar 1 as shown in FIG. 1A is shown, but an aluminum bus bar having a U-curved portion 9 in the connecting portion 8 shown in FIG. The same effect can be obtained by using an aluminum bus bar such as an aluminum bus bar provided with the first rising portion 11a and the second rising portion 11b shown in FIG.

(Sixth embodiment)
FIG. 11 is a plan view of the vicinity of the first welded portion 6a of the weld plate portion 2a when the aluminum bus bar 1 is arranged on the electrode terminal plane in FIG. Items not described are the same as those in the first embodiment.

      Since FIG. 11A is the same as FIG. 9A in the fourth embodiment, a description thereof will be omitted.

      Next, FIG. 11B will be described. At first, as in FIG. 11A, in order to form the first welded portion 6a in a direction perpendicular to the direction of stress applied to the first welded portion 6a, the melted portion 16 is scanned in the above direction while irradiating a laser beam. Form. Next, the position of the laser beam is moved in the Y direction (vertical direction in the figure), and the laser beam is scanned at a high scanning speed with the same output as the laser beam irradiated first, thereby forming the melted portion 18. Similarly, the melted portions 16 and 18 are alternately formed, and this is repeated to form the first welded portion 6a in which the melted portions 16 and 18 are continuous in the Y direction.

      By alternately scanning a laser beam with a low scanning speed and a fast scanning, a deep melting depth and a shallow melting depth are alternately formed, so that a wider bonding area can be secured, and a deep melting portion like an anchor effect can be secured. Since 16 enters the electrode terminal like a wedge, it is possible to obtain the first welded portion 6a having higher bonding strength.

<Example 7>
A specific example will be described in the sixth embodiment.

      In FIG. 11 (a), the molten portion 16 of the first welded portion 6a in the weld plate portion 2a of the aluminum bus bar 1 is focused on a laser beam having an output of 1500 W continuously oscillated from a fiber laser so that the spot diameter of the processing point is about 50 μm. Then, at a speed of 500 mm / s, as shown in the figure, the aluminum bus bar 1 was formed by scanning 10 mm in a direction perpendicular to the connection direction (upper right direction in the figure) (lower right to upper left direction in the figure). Next, the scanning position was moved by 100 μm with respect to the connection direction, and similarly, scanning was performed 10 mm at an output of 1500 W at a speed of 500 mm / s to form the second melted portion 16. By repeating this, a total of 8 melted portions 16 were generated and designated as the first welded portion 6a.

      When the tensile strength of the 1st welding part 6a at this time was measured, they were 138N, 137N, and 132N.

      In FIG. 11B, the first line was scanned with the laser in the same manner as in FIG. Next, the scanning position was moved by 100 μm with respect to the connection direction, the speed was increased to 650 mm / s with an output of 1500 W, and scanning was performed for 10 mm to form the second melted portion 18. The melted portions 16 and 18 were repeated to generate a total of 8 melted portions 16 and 18, thereby forming the first welded portion 6 a.

      When the tensile strength of the 1st welding part 6a at this time was measured, it became 155N, 152N, and 155N, and also the joint strength was high and stabilized.

      Thus, a high and stable joint strength can be obtained by forming the welded portion by scanning with a plurality of laser beams and increasing the weld area. In particular, by alternately scanning at a low scanning speed and a high scanning speed, a higher and more stable bonding strength can be obtained.

      In the present embodiment, conditions such as laser output, welding speed, spot diameter, welding length, and distance between welding locations are the total heat capacity including the material and surface state of the metal member to be welded, the plate thickness, and the jig. This is not limited to the above.

      In the present embodiment, the welding example of the U-curved aluminum bus bar 1 as shown in FIG. 1A is shown, but an aluminum bus bar having a U-curved portion 9 in the connecting portion 8 shown in FIG. The same effect can be obtained by using an aluminum bus bar such as an aluminum bus bar provided with the first rising portion 11a and the second rising portion 11b shown in FIG.

<Example 8>
FIG. 12A shows a welding in which the first welded portion 6a of the weld plate portion 2a is rounded at the square corner shown in FIG. 7 when the aluminum bus bar 1 shown in FIG. 7 is arranged on the upper surface of the electrode terminal. It is the top view which looked at the 1st welding part 6a vicinity from the upper direction when it is a part shape.

      FIG. 12A will be described. First, the molten portion 16 of the first welded portion 6a in the weld plate portion 2a of the aluminum bus bar 1 is focused on a laser beam having an output of 1500 W continuously oscillated from a fiber laser to a spot diameter of about 50 μm at a processing point of 500 mm / s. As shown in the figure, the periphery of the notch 5 that guides the protruding portion of the electrode terminal inward is scanned in a shape with rounded square corners.

      Next, the scanning position is moved inward by 100 μm from the fusion part 16, and scanning is performed in the same manner with a slightly smaller orbit. This was repeated to generate a total of five circumferentially-shaped melted portions 16 as first welded portions 6a. When the tensile strength of the 1st welding part 6a at this time was measured, they were 140N, 144N, and 158N.

      Next, FIG. 12B will be described. As in FIG. 12A, the first line scans the laser at a speed of 1500 W and 500 mm / s, moves the scanning position inward by 100 μm, and scans in the same shape at a speed of 650 mm / s with an output of 1500 W. Then, the melted part 18 of the second line was formed. The melted portions 16 and 18 were repeated to generate a total of 5 circular melted portions 16 and 18 as the first welded portion 6a.

      When the tensile strength of the first welded part 6a at this time was measured, it was 152N, 150N, and 153N, and the joint strength was high and stable.

      In this way, by having two welds formed in a direction perpendicular to the direction in which the stress is applied to the welds, the stress is distributed to each of the two welds. Even when such an intermetallic compound is generated and the bonding strength is lowered, a high bonding strength can be realized in welding of a limited area. In particular, by alternately scanning a high output and a low output, a higher and more stable bonding strength can be obtained.

      In the present embodiment, conditions such as laser output, welding speed, spot diameter, welding length, and distance between welding locations are the total heat capacity including the material and surface state of the metal member to be welded, the plate thickness, and the jig. This is not limited to the above.

      In the present embodiment, the welding example of the U-curved aluminum bus bar 1 as shown in FIG. 1A is shown, but an aluminum bus bar having a U-curved portion 9 in the connecting portion 8 shown in FIG. The same effect can be obtained by using an aluminum bus bar such as an aluminum bus bar provided with the first rising portion 11a and the second rising portion 11b shown in FIG.

      In the present embodiment, as shown in FIG. 12 (b), the first welded portion 6a of the welded plate portion 2a has been described with respect to a welded portion shape in which the square corners are rounded, but as shown in FIG. 12 (c). In addition, the essence is the same in a welding pattern that is further irradiated in a straight line, and a welding pattern in which a portion that is irradiated in two straight lines as shown in FIG. can get.

<Overall>
The following can be said throughout.

      In addition, the welding plate parts 2a and 2b, the 1st welding parts 6a and 13a, the connection parts 10a and 10b, and the 2nd welding parts 6b and 13b are not each required, and one side may be sufficient.

      In addition, although the above was welding of aluminum and copper, there exists a possibility of application also in the case of Ti and Al, Ni and Al, Fe and Al, and Mo and Si.

In this embodiment, a fiber laser is used as the laser oscillator. However, the same effect can be obtained by using another laser such as a disk laser, a YAG laser, a CO ₂ laser, or a semiconductor laser capable of obtaining a high output. .

      Although it is assumed that the first electrode terminal portion and the second electrode terminal portion exist in the battery, other structural portions and products can be used similarly. It can be used for connection between metals.

      The above embodiments can be combined with each other.

  The welded structure of the present invention can be used for welding between two metals. Enables welding of dissimilar materials of aluminum and nickel plating copper at high quality and low cost. Therefore, a battery system can be provided at low cost. Furthermore, it can be applied as a vehicle-mounted battery or a stationary power storage system that requires high output.

DESCRIPTION OF SYMBOLS 1 Aluminum bus bar 2a Welding plate part 2b Welding plate part 3 Electrode terminal 4 Electrode terminal 5 Notch part 6a 1st welding part 6b 2nd welding part 7 Stress 8 Connection part 9 U curved part 10a Connection part 10b Connection part 11a Up part 11b Up Part 12 Intermediate connecting part 13a First welded part 13b Second welded part 14 Stress 16 Melting part 17 Melting part 18 Melting part

Claims (13)

A bus bar made of a first metal and having a first plate portion;
A first electrode terminal portion made of a second metal;
A first weld that connects the first plate portion and the first electrode terminal portion;
A welded structure in which the linear first welded portion is formed in a direction perpendicular to the longitudinal direction of the first plate portion. Furthermore, there is a second electrode terminal made of the second metal, a second welded portion, and a second plate portion on the bus bar,
The welded structure according to claim 1, wherein the second weld portion connects the second plate portion and the second electrode terminal.     The welding structure according to claim 1 or 2, wherein the bus bar has a U-shaped portion between the first welded portion and the second welded portion. The bus bar
Having a first rising part between the first weld and the U-shaped part;
4. The welded structure according to claim 2, further comprising a second rising portion between the second welded portion and the U-shaped portion. There are a plurality of the first welds,
The welded structure according to any one of claims 1 to 4, wherein the plurality of first welds are aligned in parallel. The first electrode terminal portion has a protrusion;
The said bus-bar is a welding structure of any one of Claims 1-5 which have a notch part which the said protrusion penetrates.     The welding structure according to claim 6, wherein the first welded portion is disposed around the notch portion. There are a plurality of the first welds,
The welded structure according to claim 5 or 6, wherein the plurality of first welded portions surround the periphery of the cutout portion a plurality of times. There are a plurality of the first welds,
The welded structure according to any one of claims 1 to 8, wherein the plurality of first welds have different shapes.     The welding structure according to claim 1, wherein the first electrode terminal portion is copper, and the bus bar is aluminum.     The battery having the welded structure according to claim 1, wherein the first electrode terminal portion and the second electrode terminal portion are present in the battery. The plate portion of the bus bar made of the first metal is superposed on the electrode terminal member made of the second metal, and the surface of the plate portion is irradiated with the first laser beam in the first trajectory to thereby form the plate portion and the electrode terminal member. A first laser process for forming a third welded portion in
A second laser step of forming a fourth weld by scanning the surface of the plate portion with a laser beam having a lower output than the first laser beam in another second orbit parallel to the first orbit. ,
The method of manufacturing a welded structure, wherein the directions of the first track and the second track are perpendicular to the longitudinal direction of the plate portion. The plate portion made of the first metal is superposed on the electrode terminal member made of the second metal, and the surface of the plate portion is irradiated with the first laser beam in the first orbit to form the plate portion and the electrode terminal member. A first laser process for forming a third weld,
A second laser step of forming a fourth weld by scanning the surface of the plate portion with a laser beam having a scanning speed higher than that of the first laser beam in another second orbit parallel to the first orbit. Including
The method of manufacturing a welded structure, wherein the directions of the first track and the second track are perpendicular to the longitudinal direction of the plate portion.

Images