JP2020021628A - Bus bar - Google Patents

Abstract

To provide a bus bar that can be deformed by following a change in a distance between connected terminals.SOLUTION: The bus bar for connecting a plurality of terminals, includes: a plurality of stacked conductive plates 25; and a curved portion 24 curved in the stacking direction and provided between a plurality of connecting portions 23 connected to the plurality of terminals.SELECTED DRAWING: Figure 2

Description

  The present disclosure relates to a bus bar that connects terminals arranged apart from each other.

  The assembled battery is formed by arranging a plurality of unit cells side by side, and the electrode terminals of the unit cells adjacent to each other are connected by a bus bar. When the unit cell expands or contracts due to charging and discharging with a large current, the distance between the electrode terminals varies.

  A bus bar that can be deformed following such a change in the distance between the electrode terminals is disclosed in Japanese Patent Application Laid-Open No. 2018-060740 (Patent Document 1).

  The bus bar disclosed in Patent Literature 1 includes a pair of fixing portions fixed to the electrode terminals, and a connecting portion connecting the pair of fixing portions. By bending at least a part of the connection portion and rotating the connection portion by approximately 90 ° with respect to the pair of fixed portions, one or more displacement absorbing pieces that can follow a change in the distance between the electrode terminals are formed.

JP 2018-060740 A

  In recent years, higher currents have been required. When the thickness of the bus bar is small, it is difficult to flow a large current. In Patent Literature 1, since the bus bar is formed by bending a single conductive plate, it is difficult to bend the connection portion when the thickness is increased. By providing a plurality of slits parallel to the length direction of the bus bar at the connection portion so as to be arranged in the width direction, each of the divided regions of the connection portion divided into a plurality of portions in the width direction is bent, and the width direction of the bus bar is In the case where a plurality of displacement absorbing pieces are formed so as to line up with each other, the processing becomes more difficult. When bending becomes difficult as described above, it becomes difficult for the bus bar to be deformed following the change in the distance between the electrode terminals.

  The present disclosure has been made in view of the above-described problems, and an object of the present disclosure is to provide a bus bar that can be deformed by following a change in a distance between connected terminals.

  A bus bar according to the present disclosure connects a plurality of terminals, a plurality of conductive plates are stacked, and a stacking direction of the conductive plates is between a plurality of connection portions connected to the plurality of terminals. A curved portion is provided.

  With the above configuration, when a plurality of terminals are connected using a bus bar, a curved portion is arranged between a plurality of connection portions connected to the plurality of terminals. Further, the bus bar is formed by stacking a plurality of conductive plates. For this reason, compared with the case where the bus bar is formed of a single conductive plate, the thickness of each conductive plate is reduced, thereby reducing the tensile stress or the compressive stress acting on the surface of each conductive plate. be able to.

  Thereby, even when the distance between the terminals connected by the bus bar fluctuates due to expansion and contraction of the structure provided with the terminals due to heat or the like, the curved portion can be deformed in the elastic region. This makes it possible to deform the bus bar so as to follow a change in the distance between the terminals.

  According to the present disclosure, it is possible to provide a bus bar that can be deformed by following a change in the distance between connected terminals.

FIG. 2 is a plan view showing the battery module according to the embodiment. FIG. 3 is a perspective view showing a bus bar according to the embodiment. FIG. 3 is an enlarged view showing a region surrounded by a line III shown in FIG. 2. It is a figure showing the 1st process in the 1st manufacturing method of manufacturing a bus bar concerning an embodiment. It is a figure showing the 2nd process in the 1st manufacturing method of manufacturing a bus bar concerning an embodiment. It is a figure showing the 3rd process in the 1st manufacturing method of manufacturing a bus bar concerning an embodiment. It is a figure showing the 1st process in the 2nd manufacturing method of manufacturing a bus bar concerning an embodiment. It is a figure showing the 2nd process in the 2nd manufacturing method of manufacturing a bus bar concerning an embodiment. It is a figure showing the 3rd process in the 2nd manufacturing method of manufacturing a bus bar concerning an embodiment. FIG. 9 is a diagram illustrating a bus bar used in a first verification experiment performed to verify the effect of the embodiment. FIG. 9 is a diagram showing the results of a first verification experiment performed to verify the effect of the embodiment. FIG. 9 is a diagram showing the results of a second verification experiment performed to verify the effect of the embodiment.

  Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. Note that, in the embodiments described below, a case where a bus bar connects electrode terminals provided in power storage cells arranged so as to be adjacent to each other will be described as an example. In the following embodiments, the same or common portions are denoted by the same reference numerals in the drawings, and description thereof will not be repeated.

(Assembled battery)
FIG. 1 is a plan view showing the battery pack according to the embodiment. With reference to FIG. 1, an assembled battery 1 according to Embodiment 1 will be described.

  The assembled battery 1 is mounted on a vehicle. The assembled battery 1 can be applied not only to a hybrid vehicle but also to an electric vehicle or a fuel cell vehicle. The battery pack 1 can be applied to any of a series system, a parallel system, and a series-parallel system in a hybrid vehicle. Further, the hybrid vehicle to which the battery pack 1 is applied is not limited to a hybrid vehicle provided with two rotating electric machines, but may be applied to a so-called one-motor hybrid provided with one rotating electric machine.

  As shown in FIG. 1, the battery pack 1 as a power storage module is configured by connecting a plurality of chargeable / dischargeable cells 10 in series. In the assembled battery 1, a plurality of cells 10 having the same shape are connected in series to constitute the assembled battery 1. In addition, the number of the cells 10 constituting the assembled battery 1 is not particularly limited.

  Each of the cells 10 is arranged at a distance from each other. The plurality of unit cells 10 are arranged such that the side surfaces having the largest area of each unit cell 10 face each other. A cooling plate or a buffer plate (not shown) is arranged in a gap between two adjacent unit cells 10.

  The cell 10 has a positive electrode terminal (electrode terminal) 3 and a negative electrode terminal (electrode terminal) 4. The plurality of unit cells 10 are arranged one by one so that the terminals 3 and the terminals 4 are alternately arranged. The plurality of unit cells 10 are arranged so that one terminal 3 of two adjacent unit cells 10 and the other terminal 4 are close to each other.

  The unit cell 10 is, for example, a secondary battery such as a nickel metal hydride battery or a lithium ion battery. The cell has, for example, a square shape. The unit cell is not limited to the square shape, but may be a cylindrical shape. The secondary battery may use a liquid electrolyte or may use a solid electrolyte.

  The assembled battery 1 includes a bus bar 2 that connects adjacent cells 10 to each other. The bus bar 2 connects one terminal 3 of the two adjacent unit cells 10 to the other terminal 4 and electrically connects the one terminal 3 and the other terminal 4. As a result, the plurality of cells 10 are connected in series, and the assembled battery 1 having a desired voltage is constructed.

(Bus bar configuration)
FIG. 2 is a perspective view showing a bus bar according to the embodiment. FIG. 3 is an enlarged view showing a region surrounded by line III shown in FIG. A bus bar 2 according to the embodiment will be described with reference to FIGS.

  As shown in FIGS. 2 and 3, the bus bar 2 has a plurality of conductive plates 25 stacked thereon and includes a curved portion 24 curved in the stacking direction between a plurality of connection portions 23 connected to a plurality of terminals. .

  Specifically, the bus bar 2 includes a stacked body 22 in which a plurality of conductive plates 25 are stacked, and a pair of joints 21. The pair of joining portions 21 are provided on a pair of connecting portions 23 described later. The pair of joining portions 21 extend along the width direction of the bus bar 2 (the direction DR1 in FIG. 2). The pair of joining portions 21 join the plurality of conductive plates 25 at both ends in the length direction of the bus bar 2 (the direction DR2 in FIG. 2). The pair of joints 21 are formed by, for example, laser welding or the like.

  The laminate 22 has a pair of connecting portions 23 and a curved portion 24. The pair of connecting portions 23 are provided at both ends of the stacked body 22 in the length direction. The pair of connecting portions 23 are provided so as to be substantially flat.

  The bending portion 24 is provided between the pair of connection portions 23. The bending portion 24 is provided so as to bridge the pair of connection portions 23. The bending portion 24 bends in the direction in which the plurality of conductive plates 25 are stacked (the direction DR3 in FIG. 2).

  The plate thickness of the laminate 22 is equal to or greater than the minimum thickness necessary for a large current of a desired value to flow when the bus bar is formed of a single conductive plate. The thickness of each of the plurality of conductive plates 25 is substantially the same, and is equal to or less than half the minimum thickness. Each thickness of the plurality of conductive plates 25 can be determined, for example, by the following equation (1).

(Fatigue limit of busbar / maximum stress) × (expansion / shrinkage / precompression) × minimum thickness ≧ the thickness of each conductive plate 25 (Equation 1)
The maximum stress is based on the amount of expansion and contraction (the amount of deformation) of the laminate 22 required in accordance with the expansion and contraction of the unit cell 10 when the bus bar is formed of a single conductive plate having the minimum thickness. This is the maximum stress applied to the single conductive plate. As described above, the expansion and contraction amount is the expansion and contraction amount (deformation amount) of the stacked body 22 that is required according to the expansion and contraction of the unit cell 10. The pre-compression amount is a compression amount to be pre-loaded on the laminate 22 when the bus bar is attached.

  The length along the surface of the multilayer body 22 from one end side to the other end side of the multilayer body 22 is longer than the length obtained by adding the fluctuation amount of the inter-terminal distance during expansion to the normal distance between the terminals. ing. The length along the surface of the curved portion 24 is such that a change in the distance between terminals during expansion or expansion or contraction can be tolerated.

  The conductive plate 25 is made of, for example, a conductive metal plate such as aluminum, and can have a thickness of 0.1 mm. In this case, the number of the plurality of conductive plates 25 can be about 30. In this case, the bulging amount (curving height) at which the curved portion bulges from the pair of connecting portions 23 can be, for example, 2.9 mm, and the length of the bus bar can be 23 mm.

  When attaching the bus bar 2 between the terminals, it is preferable to attach the laminate 22 in a state where the laminate 22 is compressed in the longitudinal direction in advance. For example, by compressing the laminate 22 by 50%, the stress acting on the laminate 22 due to the compression and expansion of the unit cell 10 can be reduced by at most 50%.

  When the plurality of terminals 3 and 4 are connected using the bus bar 2 according to the embodiment configured as described above, the curved portion is provided between the plurality of connection portions 23 connected to the plurality of terminals 3 and 4. 24 will be arranged. Further, the bus bar 2 is configured by stacking a plurality of conductive plates 25. For this reason, compared with the case where the bus bar 2 is formed of a single conductive plate, the thickness of each conductive plate 25 is reduced, so that the tensile stress or the compressive stress acting on each conductive plate surface is reduced. Can be reduced.

  Thereby, even when the distance between the terminals connected by the bus bar 2 fluctuates due to expansion and contraction of the unit cell 10 provided with the terminals due to heat or the like, the bent portion 24 is deformed in the elastic region. It is possible to deform the bus bar 2 so as to follow the variation in the distance between the terminals.

(First manufacturing method)
4 to 6 are diagrams showing first to third steps in a first manufacturing method for manufacturing a bus bar according to the embodiment. A first manufacturing method of the bus bar 2 according to the embodiment will be described with reference to FIGS.

  As shown in FIG. 4, in the first step of the first manufacturing method of the bus bar 2, a plurality of conductive plates 30 are stacked. The conductive plate 30 is made of the same material as the conductive plate. The thickness of the conductive plate 30 is a value determined by the above equation (1).

  Subsequently, as shown in FIG. 5, in a second step, an upper mold 41 and a lower mold 42 are prepared. The upper mold 41 has a mold surface 41a that curves so as to be concave upward. The lower mold 42 has a mold surface 42a that curves so as to protrude upward.

  Next, the plurality of conductive plates 30 (laminated body 35) stacked using the upper die 41 and the lower die 42 are pressed. Specifically, the plurality of conductive plates 30 are sandwiched between the mold surfaces 41a and 42a. Thereby, the curved portion 24 is formed. Both outer sides of the curved portion 24 are flat.

  In the state where the plurality of conductive plates 30 are pressed, the plurality of conductive plates 30 are not joined. Therefore, at the time of pressing, adjacent conductive plates 30 can relatively slide with each other, and the tensile stress and the compressive stress in the in-plane direction can be reduced.

  Subsequently, the plurality of conductive plates 30 are joined. The plurality of conductive plates 30 may be joined while being sandwiched between the upper mold 41 and the lower mold 42. When joining the plurality of conductive plates 30, a laser is applied to the plurality of conductive plates 30 on both outer sides of the curved portion 24 along the width direction of the conductive plates 30. Thereby, a pair of joining parts 21 are formed.

  Next, as shown in FIG. 6, in a third step, the plurality of conductive plates 30 on which the pair of joints 21 are formed are cut. Specifically, the plurality of conductive plates 30 are cut outside the pair of joints 21 along the dividing line SL extending in the width direction. Thereby, the length of the conductive plate 30 is changed to a predetermined length, and the bus bar 2 including the stacked body 22 in which the plurality of conductive plates 25 are stacked is formed. Through the above steps, the bus bar 2 according to the embodiment can be manufactured.

(Second manufacturing method)
7 to 10 are diagrams showing the first to third steps in the second method of manufacturing the bus bar according to the embodiment. With reference to FIGS. 7 to 10, a second method of manufacturing the bus bar 2 according to the embodiment will be described.

  In the second manufacturing method of the bus bar 2, first, as shown in FIG. 7, in a first step, a wound body 36 around which a sheet-shaped conductive plate 30 is wound is formed. Specifically, the sheet-shaped conductive plate 30 is wound around the core 31.

  Next, as shown in FIG. 8, in a second step, the wound conductive plate 30 is joined in the radial direction of the wound body. A plurality of joining portions are formed. A plurality of sets of a pair of joints 21 arranged at a predetermined pitch in the circumferential direction according to the length of the bus bar are formed at predetermined intervals in the circumferential direction. The joint 21 is formed by irradiating a laser or the like. Note that a portion located between the pair of joints 21 has a curved shape curved in the radial direction.

  Subsequently, the wound body on which the plurality of pairs of the joining portions 21 are formed is cut. Specifically, a gap between a pair of joints 21 arranged at a predetermined pitch in accordance with the length of the bus bar and another pair of joints 21 adjacent to the pair of joints 21 is defined as a dividing line SL. Cut along. Thereby, the bus bar 2 including the stacked body 22 in which the plurality of conductive plates 25 are stacked such that the radial direction of the wound body 36 is the stacking direction is formed. The bus bar 2 according to the embodiment may be manufactured through the above steps.

  In the case of using the second manufacturing method, the conductive plate 30 can be wound around the core in the first step as compared with the first manufacturing method. As a result, the manufacturing time can be reduced. In addition, by winding around the core, a curved portion curved in the stacking direction can be formed, so that the manufacturing time can be further reduced.

[Verification experiment]
FIG. 10 is a diagram illustrating a bus bar used in a first verification experiment performed to verify the effect of the embodiment. FIG. 11 is a diagram illustrating the results of a first verification experiment performed to verify the effect of the embodiment. With reference to FIGS. 10 and 11, a first verification experiment performed to verify the effect of the embodiment will be described.

  In the first verification experiment, using the bus bar according to the embodiment, the relationship between the elongation of the bus bar and the stress applied to the bus bar in the elongation direction was evaluated by CAE analysis. The direction in which the bus bar extends is a direction parallel to the direction in which the two terminals are arranged.

  As shown in FIG. 10, the bus bar used was a stack of 30 conductive plates 25 each having a thickness of 0.1 mm. Aluminum (A1050) was used for the conductive plate 25. The bending height at the center of the bending portion 24 was 2.9 mm, and the length of the bus bar was 23 mm.

  When the bus bar is expanded and contracted in the elongation direction, the stress in the elongation direction (σy upper surface, σy center, σy) acting on each of the upper surface, the center, and the lower surface in the plate thickness direction at the center of the curved portion 24 in the length direction. (Lower surface) was subjected to stress analysis.

  As shown in FIG. 11, the stress at the upper surface in the plate thickness direction (σy upper surface), the stress at the center in the plate thickness direction (σy center), and the stress at the lower surface in the plate thickness direction (σy upper surface) all increase in the busbar elongation. Proportional.

  The stress ([sigma] y upper surface) on the upper surface in the thickness direction is approximately 22 MPa when the busbar elongation is -0.10 mm (when the busbar reduction amount is 0.10 mm), and when the busbar elongation is 0.10 mm. , Approximately -22 MPa.

  The stress ([sigma] y lower surface) on the lower surface in the thickness direction is approximately -22 MPa when the busbar elongation is -0.10 mm (when the busbar reduction amount is 0.10 mm), and when the busbar elongation is 0.10 mm. And became approximately 22 MPa.

  The slope of the proportional relationship indicating the relationship between the stress on the upper surface in the thickness direction (σy upper surface) and the elongation of the bus bar, and the slope of the proportional relationship indicating the relationship between the stress on the lower surface in the thickness direction (σy lower surface) and the elongation of the bus bar. The sign was reversed. The stress at the center in the thickness direction (σy center) was approximately 0 MPa.

  From the results of the stress analysis, the fatigue limit at which fatigue failure does not occur even when the bus bar repeatedly expands and contracts during repeated expansion and contraction of the single cell 10 due to rapid charging and the like was set to 35 MPa. With a stress smaller than the fatigue limit, the bending portion 24 can be deformed within the elastic range, and the expansion and contraction amount (permissible deformation amount) of the bus bar becomes less than 0.30 mm. Thereby, it was confirmed that the bus bar can be deformed by following the fluctuation between terminals less than 0.30 mm.

  FIG. 12 is a diagram illustrating the results of a second verification experiment performed to verify the effect of the embodiment. The second verification experiment will be described with reference to FIG.

  In the second verification experiment, the relationship between the thickness of each conductive plate 25 and the amount of expansion and contraction (allowable deformation) of the bus bar was evaluated. Specifically, using a conductive plate 25 having a plate thickness of 0.10 mm and a conductive plate 25 having a plate thickness of 0.03 mm, a bus bar in which the conductive plates 25 are laminated so as to have a thickness of approximately 3 mm is used. Got ready.

  The bus bar was attached between the terminals with the amount of compression applied to the prepared bus bar being 50% in advance, the distance between the terminals was varied, and the elastic range of the bus bar was evaluated.

  As shown in FIG. 12, when the sheet thickness per sheet is set to 0.10 mm, the expansion and contraction amount (permissible deformation amount) of the bus bar becomes less than 0.3 mm, and the sheet thickness per sheet becomes 0.1 mm. When it was set to 03 mm, the expansion and contraction amount (allowable deformation amount) of the bus bar was less than 0.9 mm. Thereby, it was confirmed that the permissible deformation amount of the bus bar can be increased by reducing the thickness per sheet.

  In the above-described embodiment, the case where the power storage module is the assembled battery 1 has been described as an example. However, in addition to the assembled battery, a capacitor module (power storage unit) including a plurality of unit capacitors (unit power storage units) arranged in one direction. Module).

  In the above-described embodiment, the case where the structure provided with the terminal is a unit cell has been described as an example. However, the present invention is not limited to this. The structure can be appropriately selected as long as the distance between the terminals provided on the structures adjacent to each other is changed by expansion and contraction of the structure.

  As described above, the embodiments disclosed this time are illustrative in all aspects and are not restrictive. The scope of the present invention is defined by the appended claims, and includes all modifications within the scope and meaning equivalent to the claims.

  Reference Signs List 1 battery pack, 2 busbars, 3, 4 terminals, 10 cells, 21 joints, 22 laminated bodies, 23 connected parts, 24 curved parts, 25 conductive plates, 30 conductive plates, 35 laminated bodies, 36 wound bodies, 41 Upper mold, 41a, 42a Mold surface, 42 Lower mold.

Claims (1)

A bus bar connecting a plurality of terminals,
A bus bar, comprising: a plurality of conductive plates stacked on each other; and a curved portion curved in a stacking direction of the conductive plates between a plurality of connection portions connected to the plurality of terminals.

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