Busbars and Battery Modules

Abstract

This busbar (10) comprises a joining surface (38) having a voltage detection line joined thereto and a position-restricting section (44) provided to at least part of the perimeter of the joining surface (38) and serving to restrict the expansion of a corrosion inhibitor with which the joining surface (38) is coated.

Description

[Technical field]

[0001] The present invention relates to a bus bar and a battery module. [Background technology]

[0002] For example, a battery module in which a plurality of batteries are electrically connected is known as a power source that requires a high output voltage for a vehicle or the like. In the battery module, adjacent batteries are electrically connected via a bus bar. Also, as disclosed in Patent Document 1, for example, a voltage detection line is attached to each bus bar to detect the voltage between each battery. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2017-27831 A Summary of the Invention [Problem to be solved by the invention]

[0004] In order to improve the safety of the battery module, it is necessary to detect the voltage between each battery with high accuracy, and therefore it is desirable to improve the reliability of the connection between the voltage detection line and the bus bar.

[0005] The present invention has been made in consideration of these circumstances, and has an object to provide a technique for improving the connection reliability between a voltage detection line and a bus bar. [Means for solving the problem]

[0006] One aspect of the present invention is a bus bar including a joint surface to which a voltage detection wire is joined, and a position restriction portion provided around at least a portion of the periphery of the joint surface to restrict the spread of a corrosion inhibitor that covers the joint surface.

[0007] Another aspect of the present invention is a battery module including a plurality of batteries, the bus bar of the above aspect that electrically connects the plurality of batteries, and a voltage detection wire that is joined to the bus bar and detects the voltage of the plurality of batteries.

[0008] Any combination of the above components and any conversion of the present invention into a method, device, system, etc. are also valid aspects of the present invention. Effect of the Invention

[0009] According to the present invention, it is possible to improve the reliability of the connection between the voltage detection line and the bus bar. [Brief description of the drawings]

[0010] [Figure 1] FIG. 2 is a plan view of a battery module according to the embodiment. [Diagram 2] FIG. 2 is a perspective view of a portion of a battery stack. [Diagram 3] FIG. 2 is a perspective view of a bus bar according to an embodiment. [Figure 4] Fig. 4(A) is an enlarged perspective view showing a region including a joint surface of the busbar, and Fig. 4(B) is a schematic cross-sectional view of the busbar to which the voltage detection wire is joined. [Diagram 5] Fig. 5(A) is an enlarged perspective view showing a region including a joint surface of a busbar according to Modification 1. Fig. 5(B) is a schematic cross-sectional view of a busbar to which a voltage detection wire is joined. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] The present invention will be described below with reference to the drawings based on preferred embodiments. The embodiments are illustrative and do not limit the invention, and all features and combinations thereof described in the embodiments are not necessarily essential to the invention. The same or equivalent components, members, and processes shown in each drawing are given the same reference numerals, and duplicated descriptions are omitted as appropriate. The scale and shape of each part shown in each drawing are set for convenience to facilitate explanation, and are not to be interpreted as being limiting unless otherwise specified. In addition, when terms such as "first" and "second" are used in this specification or claims, unless otherwise specified, these terms do not represent any order or importance, but are intended to distinguish one configuration from another. In addition, some of the members that are not important in explaining the embodiment in each drawing are omitted.

[0012] Fig. 1 is a plan view of a battery module according to an embodiment. Fig. 2 is a perspective view of a portion of a battery stack. Note that Fig. 1 illustrates only some of the batteries in the battery stack by dashed lines. Figs. 1 and 2 also illustrate the shapes of output terminals and bus bars in schematic form.

[0013] The battery module 1 includes a battery stack 2, a duct plate 4, and a voltage detection wire 6. The battery stack 2 includes a plurality of arranged batteries 8 and a plurality of bus bars 10 that electrically connect the batteries 8. Each battery 8 is a rechargeable secondary battery, such as a lithium ion battery, a nickel-hydrogen battery, or a nickel-cadmium battery. Each battery 8 is a so-called prismatic battery, and includes an outer can 12 that is a flattened rectangular parallelepiped. A substantially rectangular opening (not shown) is provided on one side of the outer can 12, and an electrode body, an electrolyte, and the like are accommodated in the outer can 12 through this opening. A substantially rectangular sealing plate 14 is fitted into the opening of the outer can 12 to cover the opening.

[0014] A pair of output terminals 16 are disposed on the sealing plate 14. Specifically, the positive terminal 16a is disposed near one end in the longitudinal direction, and the negative terminal 16b is disposed near the other end. In the following, when it is not necessary to distinguish the polarities of the pair of output terminals 16, the positive terminal 16a and the negative terminal 16b will be collectively referred to as the output terminals 16.

[0015] The exterior can 12, the sealing plate 14, and the output terminal 16 are conductive and made of a metal such as aluminum, iron, or stainless steel. The exterior can 12 and the sealing plate 14 are joined by, for example, laser welding. Each output terminal 16 is inserted into a through hole formed in the sealing plate 14. An insulating seal member is interposed between each output terminal 16 and each through hole. The exterior can 12 may be covered with an insulating film (not shown) such as a shrink tube. Furthermore, the exterior can 12 and the sealing plate 14 may be made of an insulating resin.

[0016] Each battery 8 has a valve portion 18 on the sealing plate 14. The valve portion 18 is disposed between a pair of output terminals 16 on the sealing plate 14. The valve portion 18 is also called a safety valve, and is configured to open when the internal pressure of the battery 8 rises to a predetermined value or higher, thereby releasing gas inside the battery 8. The valve portion 18 is configured, for example, of a thin-walled portion that is thinner than other portions provided in a part of the sealing plate 14, and a linear groove formed on the surface of the thin-walled portion. In this configuration, when the internal pressure of the battery 8 rises, the thin-walled portion tears starting from the groove, thereby opening the valve portion 18. The valve portion 18 of each battery 8 is connected to a gas duct 20, which will be described later, and gas inside the battery is discharged from the valve portion 18 to the gas duct 20.

[0017] For convenience, in the description of this embodiment, the sealing plate 14 is defined as the upper surface of the battery 8, and the bottom surface of the exterior can 12 facing the sealing plate 14 is defined as the lower surface of the battery 8. The battery 8 also has four side surfaces connecting the upper and lower surfaces. Two of the four side surfaces are a pair of long side surfaces connected to two opposing long sides of the sealing plate 14. Each long side surface is the surface with the largest area among the surfaces of the battery 8, i.e., a main surface. The remaining two side surfaces excluding the two long side surfaces are a pair of short side surfaces connected to the short sides of the sealing plate 14.

[0018] Also, for convenience, the surface on the upper side of the batteries 8 in the battery stack 2 is referred to as the upper surface of the battery stack 2, the surface on the lower side of the batteries 8 is referred to as the lower surface of the battery stack 2, the surface where the short sides of the batteries 8 are gathered together is referred to as the long side of the battery stack 2, and the surface on the long side of the batteries 8 is referred to as the short side of the battery stack 2. These directions and positions are defined for convenience. Therefore, for example, a part defined as the upper surface in this invention does not necessarily mean that it is located above a part defined as the lower surface.

[0019] The multiple batteries 8 are arranged at a predetermined interval so that the main surfaces of adjacent batteries 8 face each other. In this embodiment, the batteries 8 are arranged horizontally. In the following, the direction in which the batteries 8 are arranged is referred to as a first direction X, the horizontal direction intersecting with the first direction X is referred to as a second direction Y, and the vertical direction intersecting with the first direction X and the second direction Y is referred to as a third direction Z. In this embodiment, the first direction X, the second direction Y, and the third direction Z are perpendicular to each other.

[0020] The batteries 8 are arranged so that the output terminals 16 face the same direction. In this embodiment, the batteries 8 are arranged so that the output terminals 16 face vertically upward. When adjacent batteries 8 are connected in series, the batteries 8 are arranged so that the positive terminal 16a of one battery 8 and the negative terminal 16b of the other battery 8 are adjacent to each other. When adjacent batteries 8 are connected in parallel, the batteries 8 are arranged so that the positive terminal 16a of one battery 8 and the positive terminal 16a of the other battery 8 are adjacent to each other.

[0021] A separator (not shown) is disposed between two adjacent batteries 8. This provides electrical insulation between the two batteries 8. The separator is also called an insulating spacer, and is made of, for example, an insulating resin sheet. Examples of resins that make up the separator include polypropylene (PP), polybutylene terephthalate (PBT), polycarbonate (PC), and Noryl (registered trademark) resin (modified PPE).

[0022] The multiple batteries 8 are sandwiched in the first direction X by a pair of end plates (not shown). The pair of end plates are adjacent to the batteries 8 located at both ends in the first direction X, with separators interposed between them. Each end plate is a metal plate made of a metal such as iron, stainless steel, or aluminum.

[0023] The multiple batteries 8 are restrained in the first direction X by a pair of restraining members (not shown). The pair of restraining members, also called bind bars, are elongated members that are long in the first direction X. The pair of restraining members are arranged, for example, in the second direction Y. Each restraining member is made of a metal such as iron or stainless steel.

[0024] The batteries 8 are sandwiched between a pair of end plates in a first direction X in a state where they are alternately arranged with the separators. The pair of restraining members are arranged to sandwich the batteries 8, the separators, and the pair of end plates in the second direction Y, and both ends of each restraining member are fixed to the pair of end plates. For example, the restraining member has bent portions at both ends in the first direction X that overlap with the main surfaces of the end plates, and these bent portions are fixed to the end plates by screws or the like. The batteries 8 are restrained in the first direction X by the pair of restraining members, and positioned in the first direction X. The separators, end plates, and restraining members have known structures, so illustrations and detailed descriptions are omitted.

[0025] The output terminals 16 of adjacent batteries 8 are electrically connected to each other by a bus bar 10. The bus bar 10 is a metal member having an approximately strip shape. The bus bar 10 in this embodiment is made of aluminum. One end of the bus bar 10 is connected to the positive electrode terminal 16a of one of two adjacent batteries 8, and the other end is connected to the negative electrode terminal 16b of the other battery 8. The bus bar 10 may connect the output terminals 16 of the same polarity of adjacent batteries 8 in parallel to form a battery block, and further connect the battery blocks in series. An external connection terminal 22 is attached to the output terminal 16 of the outermost battery 8 in the first direction X. The external connection terminal 22 is connected to an external load (not shown).

[0026] A duct plate 4 is placed on the top surface of the battery stack 2. The duct plate 4 is a plate-shaped member that covers the top surface of the battery stack 2, i.e., the surface on which the valve portions 18 of each battery 8 are located. The duct plate 4 has a base plate 24, multiple openings 26, and a gas duct 20. The base plate 24 extends along the top surface of the battery stack 2. The multiple openings 26 and the gas duct 20 are provided in the base plate 24.

[0027] The multiple openings 26 are provided at positions overlapping with the output terminals 16 of each battery 8 in the third direction Z, and expose the output terminals 16. A bus bar 10 is placed in each opening 26. The multiple bus bars 10 are supported by the duct plate 4. Therefore, the duct plate 4 also functions as a so-called bus bar plate.

[0028] The gas duct 20 is a flow path into which gas ejected from each battery 8 flows. The base plate 24 has a plurality of openings (not shown) at positions corresponding to the valve portions 18 of each battery 8, through which the valve portions 18 are exposed. The gas duct 20 extends in the first direction X and overlaps with each valve portion 18 in the third direction Z. Each valve portion 18 is in communication with the gas duct 20 via an opening provided in the base plate 24.

[0029] The duct plate 4 of this embodiment is made of resin such as polypropylene (PP), polybutylene terephthalate (PBT), polycarbonate (PC), Noryl (registered trademark) resin (modified PPE), etc., except for the top surface facing each valve portion 18 of the gas duct 20. The top surface of the gas duct 20 is made of a metal plate such as iron or aluminum.

[0030] A voltage detection wire 6 is placed on the duct plate 4. Therefore, the duct plate 4 also functions as a support plate that supports the voltage detection wire 6. The voltage detection wire 6 is a member for detecting the voltage of multiple batteries 8. The voltage detection wire 6 has a structure in which multiple conductors 28 are assembled. The conductors 28 in this embodiment are made of copper.

[0031] One end of each conductor 28 is connected to the connector 30, and the other end is joined to the corresponding bus bar 10. This electrically connects each bus bar 10 to the connector 30. Some of the conductors 28 electrically connect the external connection terminals 22 to the connector 30. The connector 30 is connected to an external battery ECU or the like. The battery ECU detects the voltage, etc. of each battery 8 and controls the charging and discharging of each battery 8, etc.

[0032] Fig. 3 is a perspective view of a busbar 10 according to an embodiment. Fig. 4(A) is an enlarged perspective view of a region including a joint surface of the busbar 10. Fig. 4(B) is a schematic cross-sectional view of the busbar 10 to which a voltage detection wire 6 is joined. The busbar 10 includes a first connection portion 32, a second connection portion 34, a linking portion 36, a joint surface 38, a support portion 40, a clip portion 42, and a position restriction portion 44.

[0033] The first connection portion 32 is located at one end of the band-shaped bus bar 10, and is electrically connected to the output terminal 16 of one of two adjacent batteries 8. The second connection portion 34 is located at the other end of the bus bar 10, and is electrically connected to the output terminal 16 of the other battery 8. The first connection portion 32 and the second connection portion 34 are joined to the output terminal 16 by, for example, laser welding or ultrasonic bonding.

[0034] The connecting portion 36 connects the first connection portion 32 and the second connection portion 34. The connecting portion 36 in this embodiment has a curved shape that protrudes in the third direction Z. Therefore, the connecting portion 36 has a substantially U-shape when viewed from the second direction Y. The connecting portion 36 elastically deforms in response to the relative displacement between the battery 8 to which the first connection portion 32 is connected and the battery 8 to which the second connection portion 34 is connected. This makes it possible to absorb the relative displacement between the two batteries 8.

[0035] The bonding surface 38 is a surface to which the conductor 28 of the voltage detection line 6 is bonded. In this embodiment, the bonding surface 38 is provided at a position adjacent to the first connection portion 32, as an example. The bonding surface 38 is a flat surface facing away from the battery stack 2. With the tip of the conductor 28 placed on the bonding surface 38, a process such as ultrasonic bonding is performed, whereby the conductor 28 is bonded to the bonding surface 38.

[0036] The support portion 40 supports a neck portion adjacent to the tip portion of the conductor 28. The support portion 40 has a mounting surface 46 that continues from the joint surface 38. The mounting surface 46 is provided flush with the joint surface 38. This makes it possible to create a state in which at least the tip portion and the neck portion of the conductor 28 extend in a straight line.

[0037] The clip portion 42 is an arch-shaped member, and is disposed so as to cover the mounting surface 46. One end of the clip portion 42 is connected to the support portion 40. The clip portion 42 can rotate about the one end as a fulcrum to move toward or away from the mounting surface 46. The other end of the clip portion 42 fits into the support portion 40 when the clip portion 42 is close to the mounting surface 46. This restricts the rotation of the clip portion 42. When the other end of the clip portion 42 is fitted into the support portion 40, the neck of the conductor 28 is clamped between the mounting surface 46 and the inner surface of the clip portion 42. This fixes the conductor 28.

[0038] The joint surface 38 to which the tip of the conductor 28 is joined is covered with a corrosion inhibitor 48. Examples of the corrosion inhibitor 48 include liquid corrosion inhibitors in which a resin such as silicon resin, epoxy resin, or urethane resin is dispersed in a solvent. The corrosion inhibitor 48 is subjected to a predetermined hardening treatment to become a corrosion prevention layer.

[0039] In this embodiment, the busbar 10 is made of aluminum, and the conductor 28 is made of copper. Therefore, the joint between the joint surface 38 and the conductor 28 is a dissimilar metal joint. In this case, if water adheres to the joint, dissimilar metal corrosion (galvanic corrosion) may occur, increasing the resistance between the busbar 10 and the conductor 28, or the conductor 28 may become detached from the busbar 10. In particular, when a vehicle equipped with the battery module 1 runs along a coastal area, seawater may adhere to the joint, making it more likely that galvanic corrosion will occur. In response to this, the corrosion inhibitor 48 is applied (potted) to the joint surface 38 to cover the joint, thereby making it possible to suppress the occurrence of galvanic corrosion at the joint between the joint surface 38 and the conductor 28.

[0040] The position restricting portion 44 is provided at least in a part of the periphery of the joint surface 38 to restrict the spread of the corrosion inhibitor 48 covering the joint surface 38. The position restricting portion 44 in this embodiment is configured as a recess recessed from the joint surface 38 in the thickness direction of the busbar 10 (the third direction Z in this embodiment). If the position restricting portion 44 is not provided around the joint surface 38, when the corrosion inhibitor 48 is applied to the joint surface 38, the corrosion inhibitor 48 may spread excessively, and a sufficient coating thickness may not be obtained, or the coating thickness may become uneven. In this case, the strength of the corrosion prevention layer formed by the corrosion inhibitor 48 may become insufficient at least in a part, and the corrosion prevention layer may crack due to vibration or the like during use of the battery module 1, or the corrosion prevention layer may detach from the joint surface 38. Furthermore, if the coating thickness of the corrosion inhibitor 48 is insufficient, a part of the conductor 28 may be exposed, and the anticorrosive function of the corrosion prevention layer may be impaired.

[0041] In response to this, by providing a recess as a position restriction portion 44 around the periphery of the joint surface 38, it is possible to restrict the corrosion inhibitor 48 applied to the joint surface 38 from spreading outward beyond the recess. As a result, it is possible to cover the joint between the joint surface 38 and the conductor 28 with a sufficient amount of corrosion inhibitor 48.

[0042] The busbar 10 of the present embodiment has a non-forming region 50 of the position restriction portion 44 between the joint surface 38 and the mounting surface 46. Providing the non-forming region 50 makes it possible to obtain a uniform surface from the mounting surface 46 to the joint surface 38. By placing the conductor wire 28 on this surface, the conductor wire 28 can be kept straight from its neck to its tip, thereby improving the connection reliability between the conductor wire 28 and the joint surface 38.

[0043] As described above, the busbar 10 according to this embodiment includes the joint surface 38 to which the voltage detection wire 6 is joined, and the position restricting portion 44 that is provided on at least a portion of the periphery of the joint surface 38 and restricts the spread of the corrosion inhibitor 48 that covers the joint surface 38. By surrounding the periphery of the joint surface 38 with the position restricting portion 44, the joint portion between the joint surface 38 and the voltage detection wire 6 can be more stably protected by the corrosion inhibitor 48. This can improve the reliability of the connection between the voltage detection wire 6 and the busbar 10.

[0044] Moreover, the battery module 1 according to this embodiment includes a plurality of batteries 8, a bus bar 10 that electrically connects the plurality of batteries 8, and a voltage detection wire 6 that is joined to the bus bar 10 and detects the voltage of the plurality of batteries 8. This can improve the safety of the battery module 1.

[0045] Moreover, the position restricting portion 44 of this embodiment is configured as a recess that is recessed further than the joint surface 38 in the thickness direction of the busbar 10. By configuring the position restricting portion 44 as a recess, the position restricting portion 44 can be easily formed by pressing a metal plate or the like.

[0046] Moreover, the voltage detection wire 6 of the present embodiment has a copper conductor 28 joined to the joint surface 38, and the bus bar 10 is made of aluminum. Therefore, the joint between the conductor 28 and the joint surface 38 is a dissimilar metal joint, which is prone to corrosion due to electrolytic corrosion. In response to this, the joint surface 38 is covered with a corrosion inhibitor 48 to protect the joint, thereby making it possible to further improve the reliability of the connection between the voltage detection wire 6 and the bus bar 10. Furthermore, by making the bus bar 10 out of aluminum, it is possible to reduce the weight and cost of the bus bar 10 and, in turn, the battery module 1.

[0047] The above describes the embodiments of the present invention in detail. The above-mentioned embodiments merely show specific examples of implementing the present invention. The contents of the embodiments do not limit the technical scope of the present invention, and many design changes such as changes, additions, and deletions of components are possible within the scope of the invention as defined in the claims. A new embodiment with design changes has the effects of the combined embodiments and modifications. In the above-mentioned embodiments, the contents for which such design changes are possible are emphasized by adding notations such as "in this embodiment" and "in this embodiment", but design changes are permitted even in contents without such notations. Any combination of components included in the embodiments is also valid as an aspect of the present invention.

[0048] (Variation 1) Fig. 5(A) is an enlarged perspective view of a region including joint surface 38 of busbar 10 according to Modification 1. Fig. 5(B) is a schematic cross-sectional view of busbar 10 to which voltage detection wire 6 is joined. While position restriction portion 44 in the embodiment is configured as a recess, position restriction portion 44 in this modification is configured as a protrusion that protrudes beyond joint surface 38 in the thickness direction of busbar 10.

[0049] By providing a convex portion as the position restricting portion 44 around the joint surface 38, it is possible to restrict the corrosion inhibitor 48 applied to the joint surface 38 from spreading outward beyond the convex portion. Furthermore, by forming the position restricting portion 44 as a convex portion, it is possible to increase the coating thickness of the corrosion inhibitor 48. Thus, it is possible to protect the joint surface 38 and the conductor 28 with a thicker corrosion protection layer, and it is possible to further improve the connection reliability between the voltage detection wire 6 and the bus bar 10. Alternatively, it is possible to improve the connection reliability between the voltage detection wire 6 and the bus bar 10 while reducing the amount of corrosion inhibitor 48 applied.

[0050] (Other variations) There is no particular limit to the number of batteries 8 included in the battery module 1. There is no particular limit to the structure of each part of the battery stack 2, including the structure for restraining the multiple batteries 8. The batteries 8 may be cylindrical, for example. [Explanation of symbols]

[0051] 1 battery module, 6 voltage detection wire, 8 battery, 10 bus bar, 28 conductor, 38 joint surface, 44 position control portion, 48 corrosion inhibitor.

Claims

1. a joining surface to which a tip end of a conductor of the voltage detection line is joined; a position restriction portion provided on at least a portion of the periphery of the joint surface and restricting the spread of the corrosion inhibitor covering the joint surface; a support portion having a mounting surface continuous with the joint surface and configured to support a neck portion of the conductor adjacent to the tip portion on the mounting surface; a non-forming region of the position restriction portion provided between the joint surface and the placement surface; A bus bar comprising:

2. The bus bar according to claim 1 , wherein the position restriction portion is formed as a recess that is recessed below the joining surface.

3. The bus bar according to claim 1 , wherein the position restriction portion is formed of a protrusion protruding from the joining surface.

4. the conducting wire is made of copper; The busbar according to claim 1 , wherein the busbar is made of aluminum.

5. A number of batteries; The bus bar according to claim 1 , which electrically connects the plurality of batteries; a voltage detection line connected to the bus bar for detecting a voltage of the plurality of batteries; A battery module comprising:

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