JP7474619B2 - Battery pack - Google Patents

Description

The present invention relates to a battery pack.

Conventionally, in order to increase the output of secondary batteries, battery packs in which multiple batteries are connected in parallel or series have been used. Patent Document 1 discloses the configuration of bus bars that connect multiple batteries in parallel in such battery packs.

JP 2019-114540 A

Generally, busbars generate heat when electricity is passed through them due to their own electrical resistance, causing the temperature to rise. Busbars through which large currents flow, such as battery packs used as power sources for electric vehicles, generate a particularly large amount of heat, raising concerns about excessive temperature rise in the busbar. Therefore, the technology of Patent Document 1 may not only deteriorate the busbar itself, but also deteriorate the connected battery, and may even cause accidents such as battery fire. For this reason, technology capable of suppressing temperature rise in the busbar has been desired.

This disclosure can be realized in the following forms:

(1) According to one embodiment of the present disclosure, a battery pack is provided. The battery pack includes a plurality of rectangular batteries in which positive and negative terminals are arranged in a second direction on the same plane, and a bus bar connecting the positive terminals of the plurality of batteries to each other, the plurality of batteries are arranged in a first direction perpendicular to the second direction, and the positive and negative terminals are arranged in a staggered manner, the bus bar includes a plurality of terminal connection parts connected to the plurality of positive terminals, a pair of main body parts extending in the first direction and formed parallel to each other, each of which is connected to the plurality of terminal connection parts arranged in the first direction, and a conductive part that conducts the pair of main body parts to each other, the plurality of terminal connection parts are each formed to protrude from one of the main body parts of the pair of main body parts in a direction away from the other main body part of the pair of main body parts, and the dimension along the first direction of the downstream terminal connection part located most downstream in the current path of the bus bar among the plurality of terminal connection parts is larger than the dimension along the second direction of the main body part. According to this type of battery pack, the downstream terminal connection part located furthest downstream in the current path of the busbar among the multiple terminal connection parts of the busbar that connect the positive terminals of the multiple batteries to each other has a dimension along the first direction that is greater than the dimension along the second direction of the main body part, so that the heat capacity of the downstream terminal connection part, which is most likely to increase in temperature in the busbar that connects the positive terminals to each other, can be increased, and the current density of the downstream terminal connection part can be reduced. Therefore, the temperature of the busbar can be prevented from increasing excessively due to electrical resistance during current flow.

(2) In the battery pack of the above embodiment, the downstream terminal connection portion and the conductive portion may overlap each other at least in part in the first direction. In this embodiment, the downstream terminal connection portion and the conductive portion overlap each other at least in part in the first direction. This shortens the distance from the downstream terminal connection portion to the branch point between the main body portion and the conductive portion, thereby shortening the distance through which a relatively large current flows within the busbar. This further suppresses the temperature rise of the busbar when current is applied.

(3) According to another aspect of the present disclosure, a battery pack is provided. The battery pack includes a plurality of rectangular batteries in which positive and negative terminals are arranged in a second direction on the same plane, and a bus bar connecting the negative terminals of the plurality of batteries to each other, the plurality of batteries are arranged in a first direction perpendicular to the second direction, and the positive and negative terminals are arranged in a staggered manner, the bus bar includes a plurality of terminal connection parts connected to the plurality of negative terminals, a pair of main body parts extending in the first direction and formed parallel to each other, each of which is connected to the plurality of terminal connection parts arranged in the first direction, and a conductive part that conducts the pair of main body parts to each other, the plurality of terminal connection parts are each formed to protrude from one of the main body parts of the pair of main body parts in a direction away from the other main body part of the pair of main body parts, and the dimension along the first direction of an upstream terminal connection part located most upstream in the current path of the bus bar among the plurality of terminal connection parts is larger than the dimension along the second direction of the main body part. According to this type of battery pack, among the multiple terminal connections of the busbar that connect the negative terminals of the multiple batteries, the upstream terminal connection that is located most upstream in the current path of the busbar has a dimension along the first direction that is larger than the dimension along the second direction of the main body, so that the heat capacity of the upstream terminal connection that is most likely to increase in temperature in the busbar that connects the negative terminals to each other can be increased, and the current density in the upstream terminal connection can be reduced. Therefore, the temperature of the busbar can be prevented from increasing excessively due to electrical resistance during current flow.

(4) In the battery pack of the above embodiment, the upstream terminal connection portion and the conductive portion may overlap each other at least in part in the first direction. In this embodiment, the upstream terminal connection portion and the conductive portion overlap each other at least in part in the first direction. This shortens the distance from the upstream terminal connection portion to the branch point between the main body portion and the conductive portion, thereby shortening the distance through which a relatively large current flows within the busbar. This further suppresses the temperature rise of the busbar when current is applied.

This disclosure can be realized in various forms, such as a secondary battery device equipped with a battery pack, a method for manufacturing a battery pack, etc.

FIG. 2 is a perspective view showing a schematic configuration of a battery pack. FIG. 2 is a top view showing a schematic configuration of a battery pack. FIG. 1 is a perspective view showing a schematic configuration of a battery. FIG. 4 is a perspective view showing a detailed configuration of a bus bar. FIG. 4 is a top view showing a detailed configuration of the bus bar. FIG. 6 is a view taken along the arrow A in FIG. 5 . FIG. 11 is a perspective view showing a detailed configuration of a bus bar included in a battery pack according to a second embodiment. FIG. 11 is a top view showing a detailed configuration of a bus bar included in a battery pack according to a second embodiment. FIG. 4 is a perspective view showing a detailed configuration of a bus bar included in a battery pack of a comparative example. FIG. 13 is an explanatory diagram showing a simulation of the maximum temperature. FIG. 13 is an explanatory diagram showing a simulation of the temperature distribution of sample A. FIG. 13 is an explanatory diagram showing a simulation of the temperature distribution of sample B. FIG. 13 is an explanatory diagram showing a simulation of a current density distribution.

A. First embodiment:
FIG. 1 is a perspective view showing a schematic configuration of a battery pack 100 according to an embodiment of the present disclosure. FIG. 2 is a top view showing a schematic configuration of the battery pack 100. A plurality of battery packs 100 are arranged side by side to be modularized as described later, and constitute a part of a secondary battery device (not shown). In this embodiment, the secondary battery device is mounted on an electric vehicle (not shown), but may be mounted on any moving body or stationary power source that uses electricity as a power source, not limited to electric vehicles. The battery pack 100 includes a plurality of rectangular batteries 10 and two bus bars 20. In addition, in FIG. 1 and FIG. 2, two conductive members 90 (described later) are illustrated together with the battery pack 100.

Figure 3 is a perspective view showing the schematic configuration of battery 10. Battery 10 in this embodiment is configured to include a lithium ion battery, but is not limited to lithium ion batteries and may be configured to include any type of secondary battery, such as a nickel-metal hydride battery. Battery 10 has a battery body 12, two negative electrode terminals 14, and two positive electrode terminals 16. That is, battery 10 in this embodiment is formed by connecting two unit batteries, each having one negative electrode terminal 14 and one positive electrode terminal 16.

The battery body 12 has a flat, approximately rectangular parallelepiped external shape. The negative terminal 14 and the positive terminal 16 are formed on the upper surface 13 of the battery body 12, protruding upward. That is, the negative terminal 14 and the positive terminal 16 are arranged on the same plane. The negative terminal 14 and the positive terminal 16 are each formed with a female screw (not shown). In the following description, in a plane parallel to the upper surface 13 of the battery body 12, the short side direction of the battery 10 is also referred to as the first direction D1, and the long side direction of the battery 10, i.e., the direction perpendicular to the first direction D1, is also referred to as the second direction D2. The two unit batteries constituting the battery 10 are connected by swapping the arrangement of the negative terminal 14 and the positive terminal 16 in the second direction D2. Thus, in the battery 10, the negative terminal 14 and the positive terminal 16 are formed side by side along the second direction D2, and the negative terminal 14 and the positive terminal 16 are formed side by side along the first direction D1. Further, on the upper surface 13 of the battery body 12, measuring terminals 18 are formed between the negative electrode terminal 14 and the positive electrode terminal 16 that are formed side by side along the second direction D2. Each measuring terminal 18 is used when measuring the intermediate potential.

1 and 2, in the battery pack 100 of this embodiment, three batteries 10 are arranged along the first direction D1, and the negative terminals 14 and the positive terminals 16 are arranged in a staggered manner. Therefore, in the battery pack 100, the negative terminals 14 and the positive terminals 16 are arranged alternately along the first direction D1. To explain the staggered arrangement in detail, at one end side (lower side in FIG. 2) of the second direction D2, the positive terminal 16 is arranged at the most end side (left side in FIG. 2) of the first direction D1, and the positive terminals 16 and the negative terminals 14 are arranged alternately toward the other end side (right side in FIG. 2) of the first direction D1. On the other hand, at the other end side (upper side in FIG. 2) of the second direction D2, the negative terminal 14 is arranged at the most end side (left side in FIG. 2) of the first direction D1, and the positive terminals 16 and the negative terminals 14 are arranged alternately toward the other end side (right side in FIG. 2) of the first direction D1. The number of batteries 10 in the battery pack 100 is not limited to three, and may be any number, such as two or four. The battery pack 100 is modularized by arranging multiple batteries 100 along the first direction D1. For convenience of illustration, only one battery pack 100 is shown in Figs. 1 and 2.

The conductive member 90 has a generally rectangular plate-like appearance in plan view with the first direction D1 as its longitudinal direction, and electrically connects adjacent battery packs 100 in series in the first direction D1. More specifically, the conductive member 90 connects the negative terminal 14 of a certain battery pack 100 to the positive terminal 16 of the battery pack 100 adjacent to the battery pack 100. The conductive member 90 has two through holes 92 formed side by side along the first direction D1, each penetrating the plate thickness direction. Each through hole 92 is used to connect the conductive member 90 to the negative terminal 14 and the positive terminal 16, as described below.

Each of the two bus bars 20 has a substantially plate-like external shape and electrically connects the three batteries 10 in parallel to each other in the assembled battery 100. One of the two bus bars 20 connects the negative terminals 14 of the batteries 10 to each other, and the other of the two bus bars 20 connects the positive terminals 16 of the batteries 10 to each other. That is, each bus bar 20 connects the terminals of the same polarity of the batteries 10 to each other. As described below, each bus bar 20 is assembled on the negative terminals 14 or positive terminals 16 of the batteries 10. The bus bar 20 (hereinafter also referred to as the negative bus bar 24) that connects the negative terminals 14 of the batteries 10 to each other and the bus bar 20 (hereinafter also referred to as the positive bus bar 26) that connects the positive terminals 16 of the batteries 10 to each other have the same configuration and are assembled opposite each other in a state of being inverted in the plate thickness direction. In the following description, the case where the bus bar 20 is the positive bus bar 26 will be described as a representative example.

Figure 4 is a perspective view showing the detailed configuration of the busbar 20. Figure 5 is a top view showing the detailed configuration of the busbar 20. Figure 6 is a view taken along the arrow A in Figure 5. The busbar 20 has multiple terminal connection portions 40, a pair of main body portions 50, and two conductive portions 60.

The multiple terminal connections 40 are each connected to the positive terminals 16 of the batteries 10. As described above, the battery pack 100 of this embodiment includes three batteries 10, and each battery 10 has two positive terminals 16, so the bus bar 20 of this embodiment has six terminal connections 40. In other words, the bus bar 20 of this embodiment has three terminal connections 40 arranged along the first direction D1, and the bus bar 20 connects three batteries 10. Each terminal connection 40 is formed along a plane along the first direction D1 and the second direction D2, that is, along a plane parallel to the top surface 13 of the battery 10.

The pair of body parts 50 are formed parallel to each other, extending in the first direction D1. In the following description, one of the pair of body parts 50 is also referred to as the first body part 51, and the other of the pair of body parts 50 is also referred to as the second body part 52. That is, the first body part 51 and the second body part 52 are each connected to three terminal connection parts 40 arranged along the first direction D1. In other words, the first body part 51 and the second body part 52 are each formed in a straight line connecting the farthest terminal connection parts 40 among the three terminal connection parts 40 arranged along the first direction D1. In this embodiment, the dimensions of the first body part 51 and the second body part 52 along the first direction D1 are equal to each other.

The terminal connection parts 40 are formed so as to protrude from one of the pair of body parts 50 in a direction away from the other of the pair of body parts 50 along the second direction D2. More specifically, the three terminal connection parts 40 connected to the first body part 51 are formed so as to protrude from the second body part 52 in the second direction D2, and the three terminal connection parts 40 connected to the second body part 52 are formed so as to protrude from the first body part 51 in the second direction D2. Each terminal connection part 40 has a through hole 42 formed therethrough in the plate thickness direction. Each through hole 42 is used to connect the bus bar 20 and the positive terminal 16, as described later.

In the following description, among the multiple terminal connection parts 40 that the busbar 20 has, the terminal connection part 40 that is located most downstream in the current path of the busbar 20 as the positive electrode busbar 26 is also referred to as the downstream terminal connection part 44.

In the negative busbar 24, the direction of current flow is reversed. Therefore, in the negative busbar 24, the terminal connection 40 that functions as the downstream terminal connection 44 in the positive busbar 26 functions as the upstream terminal connection 45 located most upstream in the current path of the busbar 20. The downstream terminal connection 44 of the positive busbar 26 and the upstream terminal connection 45 of the negative busbar 24 are connected to each other by the conductive member 90, so that adjacent battery packs 100 in the first direction D1 are electrically connected in series.

In the following description, among the multiple terminal connection parts 40 of the busbar 20, the terminal connection part 40 located in a position that is point-symmetrical with respect to the downstream terminal connection part 44 is also referred to as a symmetric terminal connection part 48. In this embodiment, the "point-symmetrical position" means a point-symmetrical position with the center of gravity of the busbar 20 as the center point on a plane along the first direction D1 and the second direction D2. The symmetric terminal connection part 48 corresponds to the terminal connection part 40 that is formed in a position farthest from the downstream terminal connection part 44 among the multiple terminal connection parts 40.

In this embodiment, the dimensions of the downstream terminal connection portion 44 and the symmetric terminal connection portion 48 along the first direction D1 are both larger than the dimensions of the other terminal connection portions 40, excluding the downstream terminal connection portion 44 and the symmetric terminal connection portion 48, along the first direction D1. In addition, the dimensions of the downstream terminal connection portion 44 and the symmetric terminal connection portion 48 along the first direction D1 are both larger than the dimensions of the main body portion 50 along the second direction D2. In this embodiment, the downstream terminal connection portion 44 and the symmetric terminal connection portion 48 are both formed by extending toward the side approaching the terminal connection portion 40 adjacent to the first direction D1, so that the dimensions along the first direction D1 are both large.

The pair of main body portions 50 are formed along a plane parallel to the formation surface of the terminal connection portion 40. The pair of main body portions 50 and each terminal connection portion 40 are connected via a bent portion 46. The bent portion 46 is formed along a direction approximately perpendicular to the first direction D1 and the second direction D2. In this embodiment, the dimension of the bent portion 46 along the first direction D1 is approximately equal to the dimension of the terminal connection portion 40 along the first direction D1.

The two conductive parts 60 each electrically connect the pair of main body parts 50 to each other. The two conductive parts 60 are each formed along the second direction D2 on the same plane as the pair of main body parts 50. Therefore, the two conductive parts 60 are formed in parallel to each other. In this embodiment, one of the two conductive parts 60 is provided in the first direction D1 between the terminal connection parts 40 adjacent to each other along the first direction D1.

The busbar 20 and conductive member 90 of this embodiment are made of copper plate and formed by punching and bending. In this embodiment, the dimension of each conductive portion 60 in the first direction D1 is approximately the same as the dimension of the main body portion 50 in the second direction D2. In addition, the busbar 20 of this embodiment is formed to have a substantially constant thickness.

The negative busbar 24 and the positive busbar 26 shown in Figs. 1 and 2 have the same configuration as described above, and are assembled facing each other with the plates inverted in the plate thickness direction. The terminal connection portion 40 of the negative busbar 24 and the terminal connection portion 40 of the positive busbar 26 are assembled on the same plane. Therefore, the main body portion 50 of the negative busbar 24 is located below the terminal connection portion 40, and the main body portion 50 of the positive busbar 26 is located above the terminal connection portion 40. With this configuration, the negative busbar 24 and the positive busbar 26 are insulated from each other without contacting each other. In addition, when viewed from above, at least a portion of each main body portion 50 overlaps.

When assembling the battery pack 100, the negative busbar 24 is placed on the negative terminal 14 of the three batteries 10, and the positive busbar 26 is placed on the positive terminal 16. Then, the conductive member 90 is placed across the downstream terminal connection portion 44 located at the most downstream side in the current path of the positive busbar 26 and the upstream terminal connection portion 45 located at the most upstream side in the current path of the negative busbar 24. At this time, each busbar 20 and the conductive member 90 are placed in a position where the through hole 42 formed in each busbar 20 and the through hole 92 formed in the conductive member 90 correspond to the female threads formed in the negative terminal 14 and the positive terminal 16, respectively. Then, a bolt (not shown) is inserted into the through hole 42, 92, and the male thread of the bolt and the female thread of each terminal 14, 16 are screwed together and fastened, so that each busbar 20 and the conductive member 90 are fixed to each terminal 14, 16 and electrically connected. In addition, each bus bar 20 and conductive member 90 may be electrically connected to each terminal 14, 16 by any method, such as welding, not limited to fastening with bolts.

In this embodiment, the conductive portion 60 of the negative busbar 24 and the conductive portion 60 of the positive busbar 26 are assembled by overlapping each other when viewed from the top-bottom direction. Each conductive portion 60 is located in the first direction D1 between the negative terminal 14 and the positive terminal 16 that are adjacent to each other along the first direction D1. Note that each conductive portion 60 does not have to be located in the first direction D1 between the negative terminal 14 and the positive terminal 16 that are adjacent to each other along the first direction D1. Also, each main body portion 50 is located in the second direction D2 between the terminals 14, 16 formed on each battery 10 and the measurement terminal 18.

When energized, the current that flows through the busbar 20 flows from each terminal connection portion 40 through a pair of body portions 50 and conductive portions 60 to the downstream terminal connection portion 44. For this reason, the temperature of the busbar 20 tends to increase toward the downstream side when energized, and the temperature tends to increase most easily at the downstream terminal connection portion 44. However, in the busbar 20 of this embodiment, the downstream terminal connection portion 44 is formed with a large dimension along the first direction D1, so that the current density at the downstream terminal connection portion 44 can be reduced.

According to the battery pack 100 of the first embodiment described above, the dimension along the first direction D1 of the downstream terminal connection portion 44 located at the most downstream side in the current path of the busbar 20 among the terminal connection portions 40 provided in the busbar 20 is larger than the dimension along the second direction D2 of the main body portion 50. Therefore, the dimension along the first direction D1 of the downstream terminal connection portion 44, which is most likely to increase in temperature in the busbar 20, is formed large. Therefore, the heat capacity of the downstream terminal connection portion 44 can be increased. In addition, the surface area of the downstream terminal connection portion 44 is increased, so that the heat dissipation property can be improved. Furthermore, the increase in the current density of the downstream terminal connection portion 44 can be suppressed. Therefore, the amount of heat generated by the downstream terminal connection portion 44 can be suppressed. Therefore, the temperature of the busbar 20 can be suppressed from excessively increasing due to electrical resistance during current flow.

When the busbar 20 is a negative busbar 24, the direction of the current flowing through the busbar 20b is reversed, and the downstream terminal connection portion 44 functions as the upstream terminal connection portion 45. Even in this case, the amount of heat generated by the upstream terminal connection portion 45 can be suppressed for the same reason. Therefore, it is possible to suppress an excessive rise in the temperature of the busbar 20 due to electrical resistance when electricity is applied.

In addition to the downstream terminal connection portion 44, the busbar 20 also has a large dimension along the first direction D1 for the symmetrical terminal connection portion 48 located at a point symmetrical position with respect to the downstream terminal connection portion 44. Here, the negative busbar 24 and the positive busbar 26 are used by being inverted in the plate thickness direction. Therefore, the busbar 20 can be made into the negative busbar 24 simply by inverting the front and back directions. Therefore, while the negative busbar 24 and the positive busbar 26 have the same configuration, the dimension along the first direction D1 of the upstream terminal connection portion 45 located at the most upstream side in the current path of the busbar 20 can be made large in the negative busbar 24, and the dimension along the first direction D1 of the downstream terminal connection portion 44 located at the most downstream side in the current path of the busbar 20 can be made large in the positive busbar 26. In other words, a busbar 20 in which the downstream terminal connection portion 44 located at the most downstream side in the current path of the busbar 20 serving as the positive electrode busbar 26 has a large dimension along the first direction D1 can be used as both the negative electrode busbar 24 and the positive electrode busbar 26.

In addition, since the busbar 20 has two conductive parts 60 that mutually connect the pair of main body parts 50, the current path of the busbar 20 can be dispersed compared to a busbar with one conductive part. This makes it possible to suppress an increase in current density in the busbar 20 when electricity is passed through it, and therefore to suppress heat generation. This further suppresses the temperature rise of the busbar 20 due to electrical resistance when electricity is passed through it.

In addition, the two conductive parts 60 are formed in parallel with each other and each connects a pair of main body parts 50 to each other, which increases the mechanical strength of the busbar 20 and improves vibration resistance.

In addition, between the terminal connection parts 40 adjacent to each other along the first direction D1, one of the two conductive parts 60 is provided in the first direction D1. This makes it possible to effectively disperse the current flowing through the terminal connection part 40 into the main body part 50 or the current flowing through the main body part 50 into the downstream terminal connection part 44. This further suppresses the increase in current density in the busbar 20, thereby further suppressing the rise in temperature of the busbar 20.

The pair of main body portions 50 and each terminal connection portion 40 are connected via a bent portion 46 formed along a direction approximately perpendicular to the first direction D1 and the second direction D2, respectively. Therefore, when the negative electrode bus bar 24 and the positive electrode bus bar 26 are inverted in the plate thickness direction and assembled to the battery 10, the negative electrode bus bar 24 and the positive electrode bus bar 26 do not come into contact with each other, thereby suppressing the occurrence of a short circuit.

In addition, the pair of main body parts 50 are each connected to three terminal connection parts 40. That is, the bus bar 20 has three terminal connection parts 40 arranged along the first direction D1, and the bus bar 20 connects three batteries 10 in parallel. Therefore, the bus bar 20 of this embodiment tends to have a large current flow and a high temperature rise compared to a bus bar that connects two batteries 10 in parallel, that is, a configuration in which a pair of main body parts 50 are each connected to two terminal connection parts 40. However, according to the bus bar 20 of this embodiment, the downstream terminal connection part 44, which is most likely to increase in temperature in the bus bar 20, is formed with a large dimension along the first direction D1, so that the temperature rise of the bus bar 20 can be effectively suppressed. Even if the bus bar 20 is a negative electrode bus bar 24, the upstream terminal connection part 45, which is most likely to increase in temperature, is formed with a large dimension along the first direction D1, so that the temperature rise of the bus bar 20 can be effectively suppressed.

B. Second embodiment:
FIG. 7 is a perspective view showing a detailed configuration of the busbar 20b included in the battery pack 100 of the second embodiment. FIG. 8 is a top view showing a detailed configuration of the busbar 20b included in the battery pack 100 of the second embodiment. The busbar 20b of the second embodiment is different from the busbar 20 of the first embodiment in that it has a pair of main body parts 50b instead of the pair of main body parts 50, and further has two second conductive parts 60b in addition to the two conductive parts 60. Since the other configurations are the same as those of the busbar 20 of the first embodiment, the same reference numerals are given to the same configurations, and detailed descriptions thereof are omitted. In the following description, the conductive part 60 included in the busbar 20 of the first embodiment is also referred to as the first conductive part 60. In addition, a case where the busbar 20b is a positive electrode busbar 26 will be described as a representative example.

Compared to the pair of body parts 50 of the first embodiment, the pair of body parts 50b are formed by extending in the first direction D1, so that the positions of both ends in the first direction D1 of the first body part 51 and the second body part 52 are the same.

The two second conductive portions 60b are formed on both ends of the busbar 20b in the first direction D1. Both of the two second conductive portions 60b are formed parallel to the first conductive portion 60 along the second direction D2. Therefore, both of the two second conductive portions 60b are formed in parallel with the first conductive portion 60. In this embodiment, the pair of main body portions 50b and each of the second conductive portions 60b are connected to each other via an R-shape.

In this embodiment, the downstream terminal connection portion 44, which is located most downstream in the current path of the busbar 20b, and the second conductive portion 60b overlap each other in the first direction D1. That is, the downstream terminal connection portion 44 and the second conductive portion 60b are formed on the same straight line along the second direction D2. In other words, the downstream terminal connection portion 44 and the second conductive portion 60b overlap each other when viewed from the second direction D2.

In this embodiment, the total number of first conductive portions 60 and second conductive portions 60b is four, and the number of terminal connection portions 40 aligned along the first direction D1 is three. Therefore, the total number of first conductive portions 60 and second conductive portions 60b is greater than the number of terminal connection portions 40 aligned along the first direction D1. Also, in this embodiment, the dimension of the main body portion 50b along the second direction D2 and the dimensions of the first conductive portions 60 and second conductive portions 60b along the first direction D1 are both approximately the same.

Instead of the conductive member 90 for electrically connecting the battery pack 100 in series, a conductive member 90b that covers the entire downstream terminal connection portion 44 in the first direction D1 may be connected to the battery pack 100 including the bus bar 20b of this embodiment, as shown by the dashed line in FIG. 8. The conductive member 90b has a larger dimension along the first direction D1 than the conductive member 90 connected to the battery pack 100 of the first embodiment. By connecting the conductive member 90b that covers the entire downstream terminal connection portion 44 in the first direction D1, the contact area between the downstream terminal connection portion 44 and the conductive member 90b can be further increased. Therefore, the current density of the bus bar 20b can be further dispersed, and the temperature rise of the bus bar 20b can be further suppressed.

In this embodiment, the second conductive portion 60b corresponds to the conductive portion in this disclosure.

The battery pack 100 including the busbar 20b of the second embodiment described above provides the same effects as the first embodiment. In addition, since the busbar 20b further has two second conductive portions 60b, the current paths of the busbar 20b can be further dispersed, and as a result, the temperature rise of the busbar 20b during current flow can be further suppressed.

The downstream terminal connection portion 44 and the second conductive portion 60b are formed to overlap each other in the first direction D1. This shortens the distance from the downstream terminal connection portion 44 to the branch point between the main body portion 50b and the second conductive portion 60b, thereby shortening the distance through which a relatively large current flows within the busbar 20b. This further suppresses the temperature rise of the busbar 20b when current is applied.

When the busbar 20b is the negative busbar 24, the direction of the current flowing through the busbar 20b is reversed, and the downstream terminal connection portion 44 functions as the upstream terminal connection portion 45. Even in this case, the distance from the upstream terminal connection portion 45 to the branch point between the main body portion 50b and the second conductive portion 60b can be shortened, so the distance through which a relatively large current flows within the busbar 20b can be shortened. This further suppresses the temperature rise of the busbar 20b when current is applied.

In addition, since the total number of the first conductive portions 60 and the second conductive portions 60b is greater than the number of the terminal connection portions 40 arranged along the first direction D1, the current flowing through the terminal connection portions 40 to the main body portion 50b or the current flowing through the main body portion 50b to the downstream terminal connection portion 44 can be more effectively dispersed. Therefore, the temperature rise of the busbar 20b during current flow can be further suppressed.

In addition, according to the embodiment in which the conductive member 90b is connected to cover the entire downstream terminal connection portion 44 in the first direction D1, the current density of the busbar 20b can be further dispersed, so that the temperature rise of the busbar 20b can be further suppressed.

C. Comparative Example:
9 is a perspective view showing a detailed configuration of a bus bar 120 included in a battery pack (not shown) of a comparative example. In the bus bar 120 of the comparative example, the dimensions of the six terminal connection portions 140 along the first direction D1 are as follows: Therefore, the dimension in the first direction D1 of the downstream terminal connection portion 144 located at the most downstream side in the current path of the bus bar 120 of the comparative example and the symmetric terminal connection portion 148 is is formed to have the same dimension along the first direction D1 as the other terminal connection portions 140 except for the downstream terminal connection portion 144 and the symmetric terminal connection portion 148. The dimension of the portion 148 in the first direction D1 is formed to be substantially the same as the dimension of the main body portion 150 in the second direction D2.

In the battery pack equipped with the comparative busbar 120, the dimension of the downstream terminal connection portion 144 in the first direction D1 is formed to be substantially the same as the dimension of the main body portion 150 in the second direction D2, so that the current density at the downstream terminal connection portion 144 increases. Therefore, the temperature of the busbar 120 is likely to increase due to electrical resistance when electricity is applied.

In contrast, in the battery pack 100 including the busbars 20, 20b of the first and second embodiments, the positive busbar 26 has a large dimension along the first direction D1 of the downstream terminal connection 44, which is the busbar 20, 20b most likely to have a high temperature, and therefore the temperature of the busbars 20, 20b can be effectively prevented from rising. Similarly, in the negative busbar 24, the upstream terminal connection 45, which is the busbar 20, 20b most likely to have a high temperature, has a large dimension along the first direction D1, and therefore the temperature of the busbars 20, 20b can be effectively prevented from rising.

D. Experiments:
D-1. Experiment 1
A simulation experiment of maximum temperature and temperature distribution was performed for the busbar 20b included in the battery pack 100 of the second embodiment and the busbar 120 included in the battery pack of the comparative example. The simulation was performed for the battery pack 100 equipped with the busbar 20b of the second embodiment and the battery pack equipped with the busbar 120 of the comparative example under boundary conditions in which the total current output from each battery 10 was 200 [A] in a windless atmospheric environment at 20°C. Note that the maximum temperature means the maximum value of the temperature change in each of the busbars 20b and 120 based on a state in which no current flows. In addition, the busbars 20b and 120 used in the simulation are both positive electrode busbars 26.

<Sample>
Sample A: Comparative example bus bar 120
Samples B and C: Busbar 20b of the second embodiment

Sample C is a sample in which conductive member 90b is assembled instead of conductive member 90. Note that samples A and B both have the same conductive member 90 assembled as in the first embodiment.

<Maximum temperature simulation results>
Fig. 10 is an explanatory diagram showing a simulation of the maximum temperature, in which the vertical axis indicates the temperature change (ΔT (°C)) with respect to a state in which no current is flowing.

From the results shown in FIG. 10, it can be seen that the maximum temperature of both samples B and C is lower than that of sample A, and that the temperature rise is suppressed. The reason for this is that the dimension of the downstream terminal connection part 44 of samples B and C along the first direction D1 is larger than the dimension of the downstream terminal connection part 144 of sample A of the comparative example along the first direction D1. In samples B and C, the downstream terminal connection part 44, which is most likely to rise in temperature when current is applied, has an increased heat capacity, a large surface area, improved heat dissipation, and a reduced current density. These factors suppress heat generation. Also, a comparison between samples B and C shows that the temperature rise is further suppressed by increasing the contact area between the downstream terminal connection part 44 and the conductive member 90b.

<Temperature distribution simulation results>
11 and 12 are explanatory diagrams showing simulations of temperature distributions in samples A and B, respectively. In Fig. 11 and 12, the difference in temperature is indicated by hatching. From the results shown in Fig. 11 and 12, it can be seen that in both samples A and B, the temperature tends to increase toward the downstream side of the current path.

D-2. Experiment 2
A simulation experiment of current density distribution was performed for the same samples A to C as in Experiment 1. The simulation was performed for the battery pack 100 equipped with the bus bar 20b of the second embodiment and the battery pack equipped with the bus bar 120 of the comparative example, in a windless atmospheric environment at 20° C., under boundary conditions where the total current output from each battery 10 was 200 [A].

<Simulation results of current density distribution>
Fig. 13 is an explanatory diagram showing a simulation of current density distribution. In Fig. 13, differences in current density are indicated by hatching. Fig. 13 shows an enlarged view of the periphery of downstream terminal connection portions 44, 144 from two directions, the front and back, in the simulation for samples A to C. In Fig. 13, the busbar seen from the front side refers to the busbar seen from above the battery pack 100 shown in Fig. 1, and the busbar seen from the back side refers to the busbar seen from the battery 10 side of the battery pack 100 shown in Fig. 1.

From the results shown in FIG. 13, it can be seen that in all of samples A to C, the current density tends to increase especially around the bent portions 46, 146 connecting the main body portion 50b, 150 and the downstream terminal connection portion 44, 144. In samples B and C, the dimension of the downstream terminal connection portion 44 along the first direction D1 is larger than that of sample A. Therefore, in samples B and C, the current flowing through the main body portion 50b to the downstream terminal connection portion 44 and the current flowing through the second conductive portion 60b to the downstream terminal connection portion 44 are suppressed from being added together. In addition, in samples B and C, even when the currents are added together, the distance over which the current flows is short, so the current density is reduced. In addition, in sample C, the current density of the downstream terminal connection portion 44 is reduced compared to sample B. The reason for this is that the contact area between the downstream terminal connection portion 44 and the conductive member 90b is larger, so the current in the busbar 20b can be more dispersed.

E. Other embodiments:
E-1. Other embodiment 1:
In the above embodiment, the conductive members 90, 90b and the bus bars 20, 20b are made of copper, but they may be made of any conductive material such as aluminum, silver, etc. With such a configuration, the same effects as those of the above embodiments can be achieved.

E-2. Other embodiment 2:
In each of the above embodiments, the conductive portion 60 is provided in the first direction between the terminal connection portions 40 adjacent to each other along the first direction D1, but the present disclosure is not limited thereto. For example, between the terminal connection portions 40 adjacent to each other along the first direction D1, there may be a portion where the conductive portion 60 is not provided in the first direction D1. That is, one of the two conductive portions 60 may be omitted. In addition, for example, between the terminal connection portions 40 adjacent to each other along the first direction D1, a plurality of conductive portions 60 may be provided in the first direction D1. According to this aspect, the current flowing into the main body portions 50, 50b through the terminal connection portion 40 or the current flowing into the downstream terminal connection portion 44 through the main body portions 50, 50b can be more effectively dispersed, so that the temperature rise of the busbars 20, 20b can be further suppressed.

E-3. Other embodiment 3:
The configurations of the busbars 20, 20b in the above-described embodiments are merely examples and may be modified in various ways. For example, the dimension of the symmetrical terminal connection portion 48 along the first direction D1 may be the same as the dimension of the other terminal connection portions 40 except for the downstream terminal connection portion 44. For example, in the busbar 20b of the second embodiment, one of the two second conductive portions 60b may be omitted. For example, in the busbar 20b of the second embodiment, the downstream terminal connection portion 44 and the second conductive portion 60b may at least partially overlap each other in the first direction D1. Even with such a configuration, the same effects as those of the above-described embodiments can be achieved.

E-4. Other embodiment 4:
In the battery pack 100 of the first embodiment, the conductive member 90b connected to the battery pack 100 of the second embodiment may be connected in place of the conductive member 90 for connecting the battery packs 100 in series. With this configuration, the current density at the downstream terminal connection portion 44 can be further reduced, and the temperature rise of the bus bar 20 can be further suppressed.

The present disclosure is not limited to the above-described embodiments, and can be realized in various configurations without departing from the spirit of the present disclosure. For example, the technical features in each embodiment corresponding to the technical features in each form described in the Summary of the Invention column can be replaced or combined as appropriate to solve some or all of the above-described problems or to achieve some or all of the above-described effects. Furthermore, if a technical feature is not described in this specification as essential, it can be deleted as appropriate.

10... battery, 12... battery main body, 13... upper surface, 14... negative electrode terminal, 16... positive electrode terminal, 18... measurement terminal, 20, 20b... bus bar, 24... negative electrode bus bar, 26... positive electrode bus bar, 40... terminal connection portion, 42... through hole, 44... downstream terminal connection portion, 45... upstream terminal connection portion, 46... bending portion, 48... symmetrical terminal connection portion, 50, 50b... main body portion, 51... first main body portion, 52... second main body portion, 60... conductive portion (first conductive portion), 60b... second conductive portion, 90, 90b... conductive member, 92... through hole, 100... assembled battery, 120... bus bar, 140... terminal connection portion, 144... downstream terminal connection portion, 148... symmetrical terminal connection portion, 150... main body portion

Claims (4)

a plurality of rectangular batteries, each having a positive electrode terminal and a negative electrode terminal aligned along a second direction on the same plane, and a bus bar connecting the positive electrode terminals of the plurality of batteries to each other, the plurality of batteries being arranged along a first direction perpendicular to the second direction, and the positive electrode terminals and the negative electrode terminals being arranged in a staggered manner,
The bus bar is
A plurality of terminal connection parts respectively connected to the plurality of positive electrode terminals;
a pair of main body portions each connected to a plurality of the terminal connection portions arranged along the first direction and extending in the first direction and parallel to each other;
a conductive portion that electrically connects the pair of main body portions to each other;
Equipped with
each of the plurality of terminal connection portions is formed to protrude from one of the pair of body portions in a direction away from the other of the pair of body portions;
a dimension along the first direction of a downstream terminal connection portion located at the most downstream side in a current path of the bus bar among the plurality of terminal connection portions is larger than a dimension along the second direction of the main body portion,
Battery pack. 2. The battery pack according to claim 1,
The downstream terminal connection portion and the conductive portion at least partially overlap each other in the first direction.
Battery pack. a plurality of rectangular batteries, each having a positive electrode terminal and a negative electrode terminal aligned along a second direction on the same plane, and a bus bar connecting the negative electrode terminals of the plurality of batteries to each other, the plurality of batteries being arranged along a first direction perpendicular to the second direction, and the positive electrode terminals and the negative electrode terminals being arranged in a staggered manner,
The bus bar is
A plurality of terminal connection parts respectively connected to the plurality of negative electrode terminals;
a pair of main body portions each connected to a plurality of the terminal connection portions arranged along the first direction and extending in the first direction and parallel to each other;
a conductive portion that electrically connects the pair of main body portions to each other;
Equipped with
each of the plurality of terminal connection portions is formed to protrude from one of the pair of body portions in a direction away from the other of the pair of body portions;
a dimension along the first direction of an upstream terminal connection portion located most upstream in a current path of the bus bar among the plurality of terminal connection portions is larger than a dimension along the second direction of the main body portion,
Battery pack. The battery pack according to claim 3,
The upstream terminal connection portion and the conductive portion at least partially overlap each other in the first direction.
Battery pack.

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