Bassba

Abstract

In a structure where aluminum and copper materials are integrated, the structure must be able to accommodate variations in the position of battery cells and their displacement. [Solution] A busbar for electrically connecting multiple battery cells, comprising: a copper plate extending in a first direction; multiple aluminum plates arranged parallel to the copper plate in the first direction; and a copper foil laminate extending in a second direction perpendicular to the first direction and connecting the aluminum plate and the copper plate, wherein the busbar has a first joint where the copper plate and the copper foil laminate are joined by welding, and a second joint where the aluminum plate and the copper foil laminate are joined by welding, the copper foil laminate has a structure in which multiple copper foils are stacked, and the position of the aluminum plate is allowed to be displaced as the copper foil, which is subjected to a load when the aluminum plate is displaced, bends between the first joint and the second joint.

Description

【Technical Field】 【0001】 The present invention relates to a bus bar. 【Background Art】 【0002】 Patent Document 1 discloses that in a power storage module including a bus bar that electrically connects adjacent battery cells and an insulating connection sheet that holds the bus bar, a flexible connection sheet can absorb tolerances by bending. 【Prior Art Documents】 【Patent Documents】 【0003】 【Patent Document 1】 Japanese Unexamined Patent Application Publication No. 2019-176599 【Summary of the Invention】 【Problems to be Solved by the Invention】 【0004】 In the case of a high-output power storage module, since a large current flows through the bus bar, the amount of heat generated in the bus bar increases, and there may be an influence on the battery cells and peripheral machine components due to heat generation during energization. Since the conventional bus bar is made of an aluminum material, if an attempt is made to suppress the heat generation of the bus bar during energization, the cross-sectional area of the aluminum material increases. 【0005】 Therefore, it is conceivable to change the aluminum material to a copper material with low electrical resistance to reduce the size of the bus bar. However, since the terminals of the battery cells are made of an aluminum material, in order to join the bus bar to the terminals by welding, the bus bar at the joint portion also needs to be made of an aluminum material. In the case where the bus bar has a structure in which an aluminum material and a copper material are integrated in order to suppress heat generation during energization, there is room for consideration regarding the variation in the position of the battery cells and the follow-up of the bus bar to the displacement of the battery cells. 【0006】 The present invention has been made in view of the above circumstances, and aims to provide a busbar that can follow variations in the position of battery cells and displacement of battery cells in a structure in which aluminum and copper materials are integrated. [Means for solving the problem] 【0007】 The present invention relates to a busbar for electrically connecting a plurality of battery cells, comprising: a copper plate extending in a first direction; a plurality of aluminum plates arranged parallel to the copper plate in the first direction; and a copper foil laminate extending in a second direction perpendicular to the first direction and connecting the aluminum plate and the copper plate, wherein the busbar has a first joint where the copper plate and the copper foil laminate are joined by welding, and a second joint where the aluminum plate and the copper foil laminate are joined by welding, the copper foil laminate has a structure in which a plurality of copper foils are stacked, and the position of the aluminum plate is permitted to be displaced as the copper foil, subjected to a load when the aluminum plate is displaced, bends between the first joint and the second joint. [Effects of the Invention] 【0008】 In this invention, a structure in which aluminum and copper materials are integrated can accommodate variations in the position of battery cells and displacement of battery cells. [Brief explanation of the drawing] 【0009】 [Figure 1] This is a perspective view showing the busbar in the embodiment. [Figure 2] This diagram shows the busbar as viewed from one side in the Z direction. [Figure 3] This is a diagram illustrating the joint structure of the busbar. [Figure 4] This diagram shows the busbar as viewed from the X direction. [Figure 5] This figure shows a busbar and a stack of multiple battery cells. [Figure 6] This is a diagram illustrating the connection structure between the busbar and the terminal. [Figure 7] This is a diagram illustrating the power supply path of the busbar. [Figure 8] This graph shows the flexibility of a copper foil laminate. [Figure 9] This figure shows a structure in which a copper foil laminate is bonded to a recess in a copper plate. [Figure 10] This figure shows the busbar in the first modified example. [Figure 11] This is a perspective view showing the busbar in the second modified example. [Figure 12] This is a perspective view showing the bus in the third modified example. [Modes for carrying out the invention] 【0010】 The busbar in the embodiments of the present invention will be described in detail below. However, the present invention is not limited to the embodiments described below. 【0011】 Figure 1 is a perspective view showing a busbar in an embodiment. The busbar 1 electrically connects multiple battery cells. The busbar 1 has a joint structure in which aluminum material and copper material are joined by welding. The busbar 1 comprises an aluminum plate 2, a copper plate 3, and a copper foil laminate 4. 【0012】 Busbar 1 is composed of three types of parts, including an aluminum plate 2, a copper plate 3, and a copper foil laminate 4, and has a structure in which these three types of parts are integrated. The aluminum plate 2 is a part for joining to the terminals of the battery cell by welding. The copper plate 3 is a part for reducing the size while suppressing heat generation when current is applied. The copper foil laminate 4 is a part for accommodating variations in the battery cells during assembly and displacement of the battery cells during use. 【0013】 The aluminum plate 2 is a base bus bar that joins to the terminals of the battery cells. As shown in FIGS. 2 and 3, the aluminum plate 2 is formed in a rectangular shape with the X direction as the longitudinal direction and the Y direction as the short side direction. The aluminum plate 2 has a first flat plate portion 21, a second flat plate portion 22, and an inclined portion 23. The first flat plate portion 21 is the portion that joins to the terminals of the battery cells. The second flat plate portion 22 is the portion that joins to the copper foil laminate 4. The inclined portion 23 is provided between the first flat plate portion 21 and the second flat plate portion 22 in the X direction, and is inclined such that the height in the Z direction changes as it extends in the X direction. In the Z direction, the first flat plate portion 21 is formed at a lower position than the second flat plate portion 22. The aluminum plate 2 includes one first flat plate portion 21, two second flat plate portions 22, and two inclined portions 23. When viewing the aluminum plate 2 from the Z direction, the first flat plate portion 21 is formed in a rectangular shape. The second flat plate portions 22 are formed at both ends in the X direction of the first flat plate portion 21 via the inclined portions 23. The aluminum plate 2 is connected to the copper plate 3 via the copper foil laminate 4. 【0014】 The copper plate 3 is a bus bar connected to a plurality of aluminum plates 2. The copper plate 3 is formed in a flat plate shape and extends along the X direction. The copper plate 3 is formed in a rectangular shape with the X direction as the longitudinal direction and the Y direction as the short side direction. The bus bar 1 has a pair of copper plates 3 arranged in parallel. The pair of copper plates 3 are formed in the same shape and are arranged so as to sandwich the aluminum plate 2 from both sides in the Y direction. The bus bar 1 has a structure in which four aluminum plates 2 are arranged side by side in the X direction parallel to the copper plates 3. 【0015】 The copper foil laminate 4 is a laminated bus bar in which a plurality of copper foils are laminated. The copper foil laminate 4 connects the aluminum plate 2 and the copper plate 3. The copper foil laminate 4 is formed in a strip shape with the Y direction as the longitudinal direction and the X direction as the short side direction. The copper foil laminate 4 extends in the Y direction between the pair of copper plates 3 and connects the pair of copper plates 3 to each other. 【0016】 The copper foil laminate 4 is joined to the aluminum plate 2 and the copper plate 3 by welding. In the copper foil laminate 4, the central portion in the Y direction is joined to the aluminum plate 2, and the portions on both ends in the Y direction are joined to the copper plate 3. 【0017】 As shown in FIGS. 3 and 4, the bus bar 1 has a first joint portion 11 which is a joint portion between the aluminum plate 2 and the copper foil laminate 4, and a second joint portion 12 which is a joint portion between the copper plate 3 and the copper foil laminate 4. Both the first joint portion 11 and the second joint portion 12 are formed by welding. 【0018】 The first joint portion 11 is a portion where the central portion on the Y-direction side of the copper foil laminate 4 and the second flat portion 22 of the aluminum plate 2 are joined by welding. The second joint portion 12 is a portion where the portions on both end sides in the Y direction of the copper foil laminate 4 are joined to the copper plate 3 by welding. The copper foil laminate 4 is configured to allow the position of the aluminum plate 2 to be displaced by the copper foil receiving the load when displacement of the aluminum plate 2 occurs to bend between the first joint portion 11 and the second joint portion 12. The first joint portion 11 and the second joint portion 12 are provided at different positions in the Z direction. 【0019】 The copper foil laminate 4 has a first flat portion 41 joined to the aluminum plate 2, a second flat portion 42 joined to the copper plate 3, and an inclined portion 43 inclined between the first flat portion 41 and the second flat portion 42. Both the first flat portion 41 and the second flat portion 42 are flat portions extending in the Y direction, and a plurality of copper foils are laminated in the Z direction. 【0020】 The first flat portion 41 includes the central portion on the Y-direction side of the copper foil laminate 4. The first flat portion 41 is joined to the second flat portion 22 by the first joint portion 11. The first joint portion 11 is formed on the first flat portion 41 in the copper foil laminate 4 and on the second flat portion 22 in the aluminum plate 2. The second flat portion 22 is joined to the copper foil laminate 4 by the first joint portion 11. Four first joint portions 11 are formed on the aluminum plate 2. Two first joint portions 11 are formed side by side in the Y direction on the first flat portion 41. 【0021】 The first flat portion 41 includes a first joint surface 44 which is a joint surface with the aluminum plate 2. The first joint surface 44 is an aluminum joint surface. The first joint surface 44 is a part of the lower surface of the first flat portion 41 and faces the upper surface of the aluminum plate 2. 【0022】 The second flat portion 42 includes the portions of the copper foil laminate 4 at both ends in the Y direction. The second flat portion 42 is formed on both sides of the first flat portion 41 in the Y direction. The second flat portion 42 is joined to the copper plate 3 by the second joint portion 12. The second joint portion 12 is formed in the second flat portion 42. The first flat portion 41 and the second flat portion 42 are offset in the Z direction. In the Z direction, the first flat portion 41 is formed at a higher position than the second flat portion 42. 【0023】 The second flat portion 42 includes a second joining surface 45, which is the joining surface with the copper plate 3. The second joining surface 45 is the copper plate joining surface. The second joining surface 45 is part of the upper surface of the second flat portion 42 and faces the lower surface of the copper plate 3. The first joining surface 44 and the second joining surface 45 are offset in the Z direction. In the Z direction, the first joining surface 44 is formed at a higher position than the second joining surface 45. 【0024】 The inclined portion 43 is the part that connects the first flat portion 41 and the second flat portion 42. The inclined portion 43 is inclined with respect to the Y direction. In the inclined portion 43, multiple copper foils are stacked in a direction inclined with respect to the Z direction. The inclined portion 43 is formed on both ends of the first flat portion 41 in the Y direction. 【0025】 In the copper foil laminate 4, the flexibility direction of the copper foil is adjusted by offsetting the first bonding surface 44 and the second bonding surface 45 in the Z direction, thereby improving the busbar 1's ability to follow the displacement of the battery cell. The copper foil laminate 4 has flexibility in the Z direction because multiple copper foils are laminated in the Z direction in the first flat section 41 and the second flat section 42. Furthermore, the copper foil laminate 4 is given flexibility in the Y direction by giving the copper foil an inclination angle in the inclined section 43. As a result, the copper foil of the copper foil laminate 4 flexes and follows the vertical variations and displacements of the battery cell. The greater the distance between the first bonding section 11 and the second bonding section 12 in the Y direction, the greater the flexibility of the copper foil laminate 4. 【0026】 As shown in Figure 5, when a busbar 1 is attached to a battery cell 50, the energy storage module 60 is provided with multiple busbars 1. The energy storage module 60 has a cell stack in which multiple battery cells 50 are stacked. The busbar 1 electrically connects four battery cells 50. The terminals 51 of the battery cells 50 are made of aluminum. The aluminum plate 2 is welded to the terminals 51 of the battery cells 50. For the sake of explanation, Figure 5 shows a portion where no busbars 1 are provided. 【0027】 As shown in Figure 6, the aluminum plate 2 and the terminal 51 are joined by a third joint 13. The third joint 13 is a joint formed by welding aluminum materials together, specifically the joint between the aluminum plate 2 and the terminal 51. The first flat plate portion 21 is joined to the terminal 51 by the third joint 13. In the Z direction, the first joint 11 is located at a higher position than the third joint 13. 【0028】 As shown in Figure 5, each aluminum plate 2 is joined to only one terminal 51. In one busbar 1, four aluminum plates 2 are joined to four terminals 51. In the entire energy storage module 60, the number of aluminum plates 2 is equal to the number of terminals 51. The aluminum plates 2 are positioned above the terminals 51. The copper plates 3 are arranged in pairs adjacent to the aluminum plates 2 in the width direction of the battery cells 50, and extend from each other in the stacking direction of the battery cells 50. The copper foil laminate 4 extends between the pair of copper plates 3 in the width direction of the battery cells 50. The busbars 1 provided in the energy storage module 60 are capable of following the displacement of each battery cell 50. 【0029】 As shown in Figure 7, in busbar 1, current flows from two aluminum plates 2 connected to the two positive terminals to two aluminum plates 2 connected to the two negative terminals. One busbar 1 connects two parallel-connected battery cells 50 in series with two other parallel-connected battery cells 50. The first aluminum plate 2A is joined to the positive terminal of the first battery cell. The second aluminum plate 2B is joined to the positive terminal of the second battery cell. The third aluminum plate 2C is joined to the negative terminal of the third battery cell. The fourth aluminum plate 2D is joined to the negative terminal of the fourth battery cell. In the stacking direction of the battery cells 50, the first to fourth battery cells are arranged in that order, and the first to fourth aluminum plates 2A to 2D are arranged in that order. 【0030】 In busbar 1, the cross-sectional area of ​​the copper foil laminate 4 is smaller than the cross-sectional area of ​​the copper plate 3. The copper foil laminate 4, with its smaller cross-sectional area, generates more heat when energized. In busbar 1, the amount of heat generated tends to be large relative to the energized current because the cross-sectional area of ​​the copper foil laminate 4 is small. Therefore, the thickness of the copper plate 3 is set to have a thermal mass that takes into account the heat generated by the copper foil laminate 4. 【0031】 In busbar 1, the first bonding surface 44 and the second bonding surface 45 are located at different positions in the height direction of the battery cell 50, thereby adjusting the direction in which the copper foil flexes and improving its ability to follow the displacement of the battery cell 50. In busbar 1, the inclined portion 43 gives the copper foil an inclination angle, thereby providing flexibility in the width direction of the battery cell 50 to the copper foil laminate 4. When the copper foil laminate 4 receives a load that causes the terminal 51 to flex in the width direction of the battery cell 50, the copper foil laminate 4 deforms to allow the terminal 51 to flex in the width direction of the battery cell 50. When the copper foil laminate 4 receives a load that causes the terminal 51 to flex in the height direction of the battery cell 50, the copper foil laminate 4 deforms to allow the terminal 51 to flex in the height direction of the battery cell 50. The aluminum plate 2 is displaceable in the width and height directions of the battery cell 50 due to the flexing of the copper foil of the copper foil laminate 4. 【0032】 In busbar 1, the copper foil of the copper foil laminate 4 can flex to accommodate vertical variations in the battery cells 50 during assembly and displacement of the battery cells 50 during use. The longer the distance between the first joint 11 and the second joint 12, the more flexible the copper foil laminate 4 becomes. 【0033】 As shown in Figure 8, the load required to displace the battery cell 50 is reduced, and the flexibility of the copper foil laminate 4 is improved. As a comparative example, a structure was formed in which multiple aluminum plates 2 were joined to a single copper foil laminate 4 without using copper plates 3. In the comparative example, the load required for the copper foil laminate 4 to displace 1.0 mm was 40 N. In the busbar 1, the load required for the copper foil laminate 4 to displace 1.0 mm was approximately 13 N. The busbar 1 can reduce the load required for displacement by approximately 70% compared to the comparative example. 【0034】 As described above, according to the embodiment, the busbar 1 can follow variations in the assembly of the battery cell 50 and displacement during use. This allows the busbar 1 to absorb vertical variations and displacements of the battery cell 50. 【0035】 In addition, in busbar 1, a joint with the copper foil laminate 4 may be formed by placing a copper plate 3. As shown in Figure 9, the copper plate 3 has a recess 31 that is recessed upward in the height direction of the battery cell 50 to the same depth as the thickness of the copper foil laminate 4. The recess 31 is formed to match the shape of the copper foil laminate 4. The copper foil laminate 4 is joined to the recess 31. The second joining surface 45 is in contact with the bottom surface of the recess 31. The second joining portion 12 is a joint where the copper foil laminate 4 and the recess 31 are joined by welding. 【0036】 Furthermore, the copper foil laminate 4 may have a structure that does not include the inclined portion 43. As shown in Figure 10, the copper foil laminate 4 may be composed entirely of flat portions. 【0037】 Alternatively, a cooling structure may be provided in which the copper plate 3 is made thinner and the cooler is in contact with the copper plate 3. By making surface contact between the cooler and the upper surface of the copper plate 3, the busbar 1 can be used as a heat conductor, and the terminal 51 can be cooled by the cooler. 【0038】 Furthermore, the number of aluminum plates 2, copper plates 3, and copper foil laminates 4 only needs to correspond to the number of battery cells 50, and can be set according to conditions such as installation space. A modified example of this is shown in Figures 11 and 12. For example, the number of aluminum plates 2 in one busbar 1 is not limited to four; it can be an even number such as two or four. However, if the number is reduced, the conductive surface area decreases and the amount of heat generated increases, so measures such as increasing the thickness of the copper plates 3 to increase the heat mass are necessary. 【0039】 As shown in Figure 11, in the second modified busbar 1, the copper plate 3 is made up of only one component. In the second modified busbar 1, four aluminum plates 2, one copper plate 3, and eight copper foil laminates 4 are integrated into one unit. 【0040】 As shown in Figure 12, the busbar 1 of the third modified example has a structure in which an aluminum plate 2 is connected to a copper plate 3 by a single copper foil laminate 4. In the busbar 1 of the third modified example, four aluminum plates 2, one copper plate 3, and four copper foil laminates 4 are integrated into one unit. [Explanation of symbols] 【0041】 1 Busba 2 aluminum plate 3 copper plate 4 Copper foil laminate 11 1st joint 12 Second joint 31 Recess 44 1st joint surface 45 Second joint surface 50 battery cells 51 terminals

Claims

[Claim 1] A busbar that electrically connects multiple battery cells, A copper plate extending in the first direction, A plurality of aluminum plates arranged in the first direction parallel to the copper plate, A copper foil laminate extending in a second direction perpendicular to the first direction, connecting the aluminum plate and the copper plate, Equipped with, A first joint formed by welding the copper plate and the copper foil laminate, It has a second joint where the aluminum plate and the copper foil laminate are joined by welding, The copper foil laminate has a structure in which multiple copper foils are stacked, and when the load is applied when the aluminum plate is displaced, the copper foils bend between the first joint and the second joint, thereby allowing the aluminum plate to be displaced. A bass guitar characterized by its features. [Claim 2] The cross-sectional area of ​​the copper foil laminate is smaller than the cross-sectional area of ​​the copper plate. The bus bar according to feature 1. [Claim 3] The first joint and the second joint are provided at different positions in the height direction of the battery cell. The aluminum plate is joined to the terminals of the battery cell by welding, and is displaceable in the second direction and in the height direction of the battery cell due to the bending of the copper foil. The bass bar according to feature 2. [Claim 4] The copper plate is formed in a shape that matches the shape of the copper foil laminate, and has a recess that is recessed upward in the height direction of the battery cell to the same depth as the thickness of the copper foil laminate. The first joint is a joint formed by welding the copper foil laminate, which is fitted into the recess, to the recess. The bus bar according to feature 3. [Claim 5] The copper plates are arranged so as to sandwich the plurality of aluminum plates from both sides in the second direction, and include a pair of copper plates arranged parallel to each other in the first direction. The copper foil laminate extends in the second direction between the pair of copper plates, connecting the pair of copper plates. The aluminum plate is integrated with the pair of copper plates via the copper foil laminate. A bus bar according to any one of claims 1 to 4.

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