JP2010282811A - Pack battery - Google Patents

Abstract

An object of the present invention is to provide a battery pack capable of exhibiting excellent battery performance and safety by electrically connecting a unit cell and a lead member.
[Solution]
A plurality of cylindrical unit cells 2 are arranged side by side in the axial direction, and are housed in a pair of battery holders 3A and 3B from both ends. Lead groups 4A and 4B composed of a plurality of lead plates 40A to 42A and 40B to 42B are fitted on the outer surfaces of the plate portions 30A and 30B of the battery holders 3A and 3B. And the edge part and lead plate of each unit cell 2 are bonded with the wire 5 which consists of aluminum or an aluminum material through each opening part provided in plate part 30A, 30B and a lead board.
[Selection] Figure 1

Description

  The present invention relates to a battery pack, and more particularly to a technique for satisfactorily electrically connecting a unit cell and a lead plate.

In recent years, applications of secondary batteries have rapidly expanded and are widely used as power sources for personal computers, mobile phones, electric tools, electric vehicles, hybrid vehicles, electric assist bicycles, and the like. Typical secondary batteries include nickel cadmium secondary batteries, nickel metal hydride secondary batteries, lithium ion secondary batteries (polymer batteries), and the like.
Secondary batteries may be used as single cells, but in applications that require relatively high output and large current, such as electric vehicles, hybrid vehicles, electric bicycles, electric tools, etc., there are multiple secondary cells. A connected battery pack (assembled battery) is used.

  In a general battery pack, a plurality of unit cells are electrically connected to each other by resistance welding via a coupling (lead or tab) member. Or after connecting a some unit cell via a lead member and comprising a battery module, the terminal part of a some battery module is connected and comprised by lead members, such as a bus bar. The lead member is fixed to the battery module by a method such as screwing.

JP 2008-91233 A JP 2008-66000 A JP 2008-66001 A

However, the conventional battery pack has several problems regarding the connection between the unit cell and the lead member.
The battery pack is required to exhibit its output well and to efficiently dissipate the unit cell whose temperature rises during use. From this viewpoint, it is preferable to use a lead member having a sufficient thickness to sufficiently reduce the internal resistance and increase the heat capacity. However, in practice, when the thickness of the lead member is increased, it becomes difficult to electrically connect the lead member and the unit cell by resistance welding.

Further, as the material of the lead member, copper (Cu) or iron (Fe) is preferable from the viewpoint of conductivity and production cost. However, when these materials are used for the lead member, resistance welding cannot be performed well, which may affect the yield when manufacturing the battery pack.
On the other hand, when the lead member is fixed with screws as described above, such a problem of resistance welding can be avoided. However, since there is a movable element in the electrical connection part, vibration and impact are applied to the battery pack when it is used, so that the screw loosens, the conductivity becomes unstable, and the current may be cut off by dropping the screw. . For this reason, it can be said that the problem which should further improve reliability remains.

Furthermore, there are points to consider in terms of safety in the battery pack. When any of the plurality of unit cells causes an internal short circuit during use, current flows from the other unit cells into the unit cell in which an abnormality has occurred. For this reason, the unit cell in which an abnormality has occurred becomes overheated, and the battery pack may burst or the power supply target device may be damaged.
As described above, the battery pack still has room to be solved.

  The present invention has been made in view of the above problems, and provides a battery pack capable of exhibiting excellent battery performance and safety by electrically connecting a unit cell and a lead member. For the purpose.

In order to solve the above problems, the present invention provides a plurality of unit cells accommodated in an outer case so that the electrode terminals are exposed to the outside, and a lead member is disposed in the outer case, and the electrode terminals of the unit cells and the The lead member is configured to be electrically connected by wire bonding.
Specifically, the unit cell is cylindrical, the outer case is configured by a pair of battery holders, and each unit cell is sandwiched between the pair of battery holders at both ends in the longitudinal direction. An opening is formed on the outer surface of each of the battery holders for exposing the electrode end of each of the stored unit cells to the outside, and each of the openings is further formed on the outer surface. A plurality of lead members each having an opening corresponding to the above are disposed, and the electrode terminal of each unit cell is wire-bonded to the lead member via each opening of the battery holder and the lead member. it can.

In the exterior case, a region where the lead member is disposed is formed in a concave shape,
The bonded wire may be arranged so as to be accommodated in the concave region.
The lead member can be composed of a member containing any of Cu, Fe, and Ni.
Moreover, the said wire can also set a diameter to 100 micrometers or more and 500 micrometers or less.

The wire can also be composed of aluminum or an aluminum alloy.
As said unit cell, a lithium ion secondary battery is suitable.

  In the battery pack of the present invention having the above configuration, since the unit cell is electrically connected to the lead member by wire bonding, it is not necessary to connect using resistance welding as in the conventional case. Since wire bonding is not subject to restrictions on the thickness of the lead member and its material like resistance welding, even if the lead member thickness is considerably increased or the material is changed to some extent, the lead member and the unit cell Can be electrically connected with good stability. Therefore, in the present invention, a lead member having a large thickness, which is difficult to use in conventional resistance welding, is used to reduce the internal resistance of the lead member, to improve the heat dissipation characteristics by increasing the heat capacity, or to have other excellent conductivity. A lead member can be comprised with a material.

  Further, in the present invention, since the unit cell and the lead member are connected by wire bonding, there is no movable element in the connection portion unlike the fixing method of the lead member by screwing. Therefore, even when the battery pack of the present invention is used as a power source for an electric vehicle, a power assisted bicycle, etc., it is possible to fundamentally avoid the problem of loosening screws due to vibration and impact and impairing connection reliability, and excellent battery performance over a long period of time. Can be maintained.

  Moreover, when performing wire bonding, a wire shape can be determined comparatively flexibly. For this reason, the unit cell and the lead member can be securely fixed, and the vibration resistance of the battery pack can be further improved. Therefore, it can be said that the present invention is particularly suitable for applications such as electric vehicles, electric assist bicycles, electric tools, and the like in which vibration and impact are easily applied to the battery pack during use.

  Furthermore, in the present invention, when a specific unit cell is used, an internal short circuit occurs when a wire bonding is used, and when a large current flows into the wire, the wire connected to the unit cell is quickly heated by Joule heat. Blown out. For this reason, the distribution of abnormal current can be immediately interrupted, and high safety can be exhibited. In addition, by wire bonding each unit cell and the lead member, energization of only the unit cell that generates abnormal Joule heat can be cut off, and energization of other unit cells can be stably maintained. For this reason, it is possible to take detailed safety measures such that the output of the entire battery pack can be maintained to some extent even after the abnormality of the unit cell occurs, and problems due to the output stop of the entire battery pack can be prevented. Note that the setting of the fusing of the wire can be performed by adjusting the diameter of the wire and the number of bondings per unit cell, for example, so that the practicality is high.

Aluminum or aluminum alloy material is suitable for the wire in terms of performance and cost.
Such a present invention can be realized by wire bonding a unit cell and a lead member in a battery pack having a conventional configuration. For this reason, it can be constructed at a relatively low cost and has high feasibility.

1 is a set diagram illustrating a configuration of a battery pack according to Embodiment 1. FIG. It is the front view and side view which show the structure of a battery pack. It is sectional drawing which shows the internal structure of a battery pack. It is an expanded sectional view which shows the internal structure of a battery pack. It is an enlarged view of a battery pack. It is a figure which shows the mode of the manufacturing process of a battery pack. It is a figure which shows the mode of the manufacturing process of a battery pack.

Embodiments of the present invention will be described below, but the present invention is naturally not limited to these configurations. That is, the present invention can be implemented with appropriate modifications without departing from the technical scope of the present invention.
<Embodiment>
FIG. 1 is an assembled view showing the configuration of the battery pack 1 of the first embodiment. 2A, 2B, and 2C are a side view, a top view, and a front view of the battery pack 1, respectively.

  As shown in FIG. 1, the battery pack 1 is a long rectangular parallelepiped having the Y direction as a long direction and the X direction as a short (width) direction. A plurality of cylindrical unit cells 2 as power generation elements are juxtaposed with the Z direction as an axial direction, and are housed between a pair of battery holders (end plates) 3A and 3B. Lead groups 4A and 4B are disposed on the outer surfaces of the battery holders 3A and 3B, and the lead groups 4A and 4B and the unit cells 2 are bonded using wires 5 made of aluminum or the like.

The battery pack 1 is further housed in an exterior case (not shown) when used.
Here, a lithium ion secondary battery in which a spiral electrode body is housed in a cylindrical outer can and sealed inside with a sealing plate is used as the unit cell 2. Both ends in the longitudinal direction of the unit cell 2 are a positive electrode terminal or a negative electrode terminal. In the battery pack 1, a total of 40 unit cells 2 are arranged in a predetermined arrangement (in the case of FIG. 1, two unit cells 2 adjacent in the Y direction are set as one set, four sets are connected in parallel, and 5 series × 8 arranged in parallel). With this configuration, the battery pack 1 can obtain a predetermined output.
The arrangement and the number of the unit cells 2 are based on the assumption that the battery pack 1 is used for an electric assist bicycle. Therefore, the arrangement and the number of the unit cells 2 in the battery pack 1 can be arbitrarily set according to the request on the power supply target device side.

The unit cell 2 is not limited to a lithium ion secondary battery, and other secondary batteries such as a nickel hydrogen secondary battery, a nickel cadmium secondary battery, and a lithium ion polymer secondary battery can be used. Further, the battery exterior shape is not limited to the cylindrical shape, and may be other shapes such as a square shape.
When a lithium ion secondary battery is used as the unit cell 2, a control board (not shown) is accommodated in the battery holders 3A and 3B. The control board controls the output of the unit cell 2, and is mounted with a thermistor element for temperature management of the unit cell 2, a microcomputer having a function such as calculating a remaining capacity and detecting an abnormality.

  Each of the pair of battery holders 3A and 3B is provided with a plurality of cylindrical storage portions 31A and 31B for standing and storing the unit cell 2 on one main surface of the plate-shaped plate portions 30A and 30B. Each of them is manufactured by injection molding an engineering plastic material (ABS in this case) that is excellent in mechanical strength and insulation. The plate portions 30A and 30B are provided with openings 300A and 300B in accordance with the positions where the storage portions 31A and 31B are formed, and each end of the unit cell 2 stored in the storage portions 31A and 31B is the opening portion. It is exposed to the outside through 300A and 300B. The inner diameters of the storage portions 31A and 31B are set slightly tighter than the outer diameter of the unit cell 2, and when the unit cell 2 is stored, it comes into close contact with the cylindrical side surface of the unit cell 2 and can be fixed by friction. ing. In addition, this invention is not limited to friction fixation, You may use well-known fixing means, such as screwing.

  3A is a cross-sectional view of the battery pack (a cross-sectional view taken along the line AA in FIG. 2A), and FIG. 3B is an enlarged cross-sectional view of the Z portion in FIG. 3A. is there. In the battery pack 1, the storage portions 31 </ b> A and 31 </ b> B have a form in which the peripheral edges of the openings are abutted, and the unit cell 2 is sandwiched from both ends in the longitudinal direction (FIGS. 2A, 2 </ b> C, and 3 </ b> B). a), (b)). At this time, the electrode terminals of the unit cells 2 are accommodated in the battery holders 3A and 3B so as to be exposed to the outside.

  Each of the lead groups 4A and 4B includes a plurality of long lead plates 40A to 42A and 40B to 42B each having a plurality of openings 400A to 420A and 400B to 420B. The material is preferably copper phosphate or nickel-plated steel plate having excellent conductivity, but is not limited thereto. The lead plates 40A to 42A and 40B to 42B are respectively provided at predetermined positions (recessed regions 32A, 33A, and 34A extended in the Y direction in FIG. 1) provided on the outer surfaces of the plate portions 30A and 30B of the battery holders 3A and 3B. , 32B, 33B, 34B). At this time, the positions of the openings 400A to 420A and 400B to 420B of the lead plates 40A to 42A and 40B to 42B are the positions of the openings 300A and 300B on the side of the plate parts 30A and 30B, as shown in FIG. It is set to suit. In the battery pack 1, the lead plates 40 </ b> A to 42 </ b> A and 40 </ b> B to 42 </ b> B connect the unit cells 2 provided along the Y direction in parallel and are connected in series with the unit cells 2 provided adjacent in the X direction. It is used as a lead member connected to One end in the longitudinal direction of each of the lead plates 40A to 42A and 40B to 42B (in FIG. 1, the left rear side in the drawing) is projected so as to be used as an output terminal or an intermediate electrode.

  The wire 5 is a thin wire (as an example, a diameter of 100 μm or more and 500 μm or less) made of aluminum or an aluminum alloy, and is a bonding material for electrically connecting the lead plates 40 </ b> A to 42 </ b> A and 40 </ b> B to 42 </ b> B to the unit cell 2. As shown in FIGS. 3A and 3B, the wire 5 is connected to the end portion of the unit cell 2 and each of the lead plates 40A to 42A and 40B to 42B in a crank shape, and is bonded with good adhesion strength. ing. The connection strength is sufficiently secured so that the battery pack 1 will not drop out even if some vibration is applied to the battery pack 1.

FIG. 4 is an enlarged cross-sectional perspective view around the wire of the battery pack. Further, FIG. 5 is an enlarged perspective view specifically showing a state of bonding by the wire 5. In the battery pack 1, bonding is performed using three wires per terminal of the unit cell 2, but the number of wires 5 is not limited to this number.
In the battery pack 1 having the above configuration, in the electrical connection between the unit cell 2 and the lead members (respective lead plates 40A to 42A, 40B to 42B), connection means such as resistance welding or screwing is not used as in the conventional case. It is assumed that they are connected by wire bonding. Connection by wire bonding is not greatly restricted by selection of the shape (including thickness) and material of the lead member. Therefore, even if the member thicknesses of the lead plates 40A to 42A and 40B to 42B are considerably increased in the battery pack 1, the lead plates 40A to 42A, 40B to 42B and the unit cell 2 can be electrically connected satisfactorily. it can. Thereby, in the battery pack 1, it is possible to use lead plates 40A to 42A and 40B to 42B having large thicknesses (that is, having a large cross-sectional area) that have been difficult to use in conventional resistance welding.

  Also, Fe, Cu, etc., which are difficult to weld well by conventional resistance welding, can be used relatively easily as the materials of the lead plates 40A to 42A and 40B to 42B. By using such a material, the internal resistance of the lead plates 40 </ b> A to 42 </ b> A and 40 </ b> B to 42 </ b> B can be reduced, the heat capacity can be increased, and the heat dissipation characteristics of the battery pack 1 can be effectively improved. As a result, power loss can be suppressed as much as possible, and excellent battery performance can be expected by radiating heat generated during use.

Furthermore, in the battery pack 1, by adopting wire bonding, it is not necessary to fix the lead member to the unit cell side by screwing as in the conventional case. Therefore, it is possible to fundamentally avoid the problem of lowering the reliability of the electrical connection due to the screws loosening or falling off.
In the battery pack 1, each end of the unit cell 2 is bonded to each lead plate 40 </ b> A to 42 </ b> A, 40 </ b> B to 42 </ b> B with a plurality of (three in this example) wires 5. Even if 5 falls off, the unit cell 2 and the lead plates 40A to 42A and 40B to 42B are maintained connected by the remaining two wires 5. Therefore, the output of the battery pack 1 can be stably obtained as long as all of the three wires 5 at each end of the unit cell 2 are not cut.

  Furthermore, in the wire bonding in the battery pack 1, as shown in FIG. 5, the wire shape can be determined flexibly according to the level difference between the surface of the terminal of the unit cell 2 and the surfaces of the lead plates 40A to 42A and 40B to 42B. it can. For this reason, an excessive stress (stress) is not applied to the wire 5 at the time of electrical connection, and the unit cell 2 and the lead plates 40A to 42A and 40B to 42B can be reliably fixed. Thus, the vibration resistance can be further improved as compared with the prior art because the electrical connection can be made without applying an excessive stress (stress).

Such various effects are particularly effective when the battery pack 1 is used as a power source for an electric vehicle, a power-assisted bicycle, a power tool, a portable electronic device, or the like, which is easily exposed to vibration or impact.
Furthermore, in the battery pack 1, when a specific unit cell 2 is short-circuited during use and abnormally heated, a large current flows from the surrounding unit cell 2 into the unit cell 2, and thus the unit cell 2 The connected wire 5 is melted by Joule heat. For this reason, the distribution of a large current can be cut immediately, and safety measures can be taken to suppress the runaway of the unit cell 2 in which an abnormality has occurred. Moreover, since this current cut is performed by fusing the wire 5 through which a large current flows, an abnormality is detected among the plurality of unit cells 2 electrically connected in common to any of the lead plates 40A to 42A and 40B to 42B. Fusing can be performed by concentrating the generated unit cell 2, and normal energization of other unit cells 2 can be maintained. For this reason, since the output of the battery pack 1 can be maintained to a certain extent even after the occurrence of an abnormality, for example, when the battery pack 1 is used in a computer, a user who knows the abnormality of the battery pack 1 backs up the data. If a certain amount of time is not secured, detailed safety measures will be realized.

  In order to obtain this effect satisfactorily, the diameter of the wire 5 and the number of bondings per unit cell are appropriately adjusted. As a material that easily obtains such performance, aluminum or an aluminum alloy material is suitable for the wire 5 from the balance of performance and cost. As described above, the present invention is characterized by extremely high practicality because it can set the fusing of the wire by a relatively simple method.

The present invention can be realized by wire bonding the unit cell 2 and the lead plate with a predetermined material while sharing many of the configurations of the conventional battery packs. For this reason, it can be configured at a relatively low cost and has high feasibility.
<Method of manufacturing a battery pack>
Here, a method for manufacturing a battery pack is illustrated with reference to FIGS.

First, the plate portion 30B is leveled such that the battery holder 3B is disposed on the upper surface of the storage portion 31B. In this state, the unit cells 2 are put in the respective storage portions 31B and are erected in the Z direction (FIG. 6A). The unit cell 2 is set by being erected so that the upper and lower ends are alternated along the X direction.
Next, the battery holder 3 </ b> A is disposed from above the standing unit cell 2. At this time, the battery holder 3A faces the storage portion 31A downward, and pushes down the plate portion 30A so as to store the unit cell 2 therein. At this time, the unit cell 2 is fitted and fixed to the battery holders 3A and 3B by friction (FIG. 6B).

  Subsequently, lead plates 40A to 42A and 40B to 42B are fitted and set on the outer surfaces of the battery holders 3A and 3B (FIG. 7A). In this state, each lead plate and the end of each unit cell 2 exposed to the outside from the opening are wire-bonded (FIG. 7B). The bonded wire 5 is formed so as to fit in the concave regions 32A, 33A, 34A, 32B, 33B, 34B of the battery holders 3A, 3B. Therefore, even if each surface of the battery holders 3A and 3B after the wire bonding process is placed on the surface of the work table, the wire 5 is not deformed or damaged by contacting the surface of the work table. Thereby, the wire 5 can be favorably bonded.

  The battery pack 1 is manufactured through the above steps.

  The battery pack of the present invention can be widely used as a power source for, for example, a power-assisted bicycle or a power tool. In particular, it is considered effective when a relatively large battery pack is used stably.

1 pack battery 2 unit cell 3A, 3B battery holder 4A, 4B lead group 5 bonding wire 30A, 30B main surface part 31A, 31B storage part 40A, 41A, 42A, 40B, 41B, 42B lead plate 300A, 300B opening part 400A, 410A 420A, 400B, 410B, 420B Lead opening

Claims (7)

A plurality of unit cells are housed in the outer case so that the electrode terminals are exposed to the outside, and lead members are disposed on the outer surface of the outer case,
A battery pack, wherein the electrode terminal of the unit cell and the lead member are electrically connected by wire bonding. The unit cell is cylindrical, and the outer case is composed of a pair of battery holders,
Each unit cell is stored so that the periphery of both ends in the longitudinal direction is sandwiched between the pair of battery holders,
An opening is formed on the outer surface of each battery holder to expose the electrode end of each stored unit cell to the outside, and a plurality of lead members having openings are formed on the outer surface. Arranged so that the position of the opening of the lead member is aligned with the position of the opening of
The battery pack according to claim 1, wherein the electrode terminal of each unit cell is wire-bonded to the lead member via each opening of the battery holder and the lead member. In the exterior case, a region where the lead member is disposed is formed in a concave shape,
The battery pack according to claim 1, wherein the bonded wires are arranged so as to be accommodated in the concave region. The battery pack according to any one of claims 1 to 3, wherein the lead member is made of a material containing any one of copper, iron, and nickel. 5. The battery pack according to claim 1, wherein the wire has a diameter of 100 μm or more and 500 μm or less. The said battery consists of aluminum or aluminum alloy. The battery pack of any one of Claims 1-5 characterized by the above-mentioned. The battery pack according to claim 1, wherein the unit cell is a lithium ion secondary battery.

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