JP4845348B2 - Pack battery - Google Patents

Description

  The present invention relates to a battery pack including a unit cell and a circuit board incorporating a current control circuit.

The battery pack is an indispensable driving power source for portable electronic devices such as mobile phones and PDAs, and it is required to make the portable electronic devices smaller, thinner and lighter while keeping the same size and thickness as the portable electronic devices. ing.
In order to meet this requirement, in the battery pack, the outer can of the unit cell is made of a light metal such as aluminum (Al) or Al alloy, and the outer dimensions of the outer can are reduced. Is arranged on a sealing plate that seals the opening of the outer can (for example, Patent Document 1) to take a shape that prevents the outer can from becoming thicker.

On the other hand, since it is necessary to describe necessary items such as battery specifications and ratings on the outer surface of the battery pack, an insulating tape on which necessary items are printed is attached to the outer peripheral surface of the outer can. If the bottom surface of the outer can is included in the coverage area of the tape, the tape may bend and the appearance quality of the battery pack may be deteriorated. Therefore, as shown in FIG. 5, as the tape is attached only to the outer peripheral surface of the outer can, the thin resin plate 400 is attached to the outer can 2 on the outer surface of the outer can where the tape is not attached. Therefore, it is common to prevent contact with the outside air and prevent the outer can 2 from corroding.
JP2003-282036

  However, the resin plate provided on the bottom of the outer can has a considerable thickness no matter how the formation method is devised, and this has pushed the limit of downsizing of the battery pack, further downsizing the battery pack It is a bottleneck to plan. Further, as shown in FIG. 5, when the resin plate is composed of the engagement portion 400b of the outer can 2 and the portion 400a that covers the bottom surface of the outer can, the thickness H1 of each of the engagement portions 400c and 400d can be part of the battery pack. A thick part will be formed. If the resin plate is not mounted in order to solve this problem, the metal surface of the outer can is exposed, and the problem of corrosion becomes unavoidable. Furthermore, if the color difference from the tape attached to the outer peripheral surface of the outer can is conspicuous, there is also a problem that the design of the battery pack is impaired.

 The present invention has been made in view of the above problems, and provides a highly practical battery pack capable of preventing corrosion without having a thickness like a resin plate and also eliminating the problem of a difference in color with a tape. For the purpose.

Therefore, the present invention adopts the following configuration in order to solve the above problems.
A battery pack provided with a unit cell in which an outer can made of a material containing aluminum is sealed with a sealing plate, and a portion of the outer surface of the outer can excluding its bottom is covered with a covering material In addition, the outer surface of the bottom surface is subjected to alumite treatment in a state where there is a portion on the outer periphery of the outer can that is not subjected to alumite treatment .
In the case where the balance between the covering material and the color of the portion of the battery pack subjected to the anodized treatment is balanced, a film is formed on the outer surface of the outer can where the anodized treatment is performed. It is desirable to be in a state.

Further, the following configuration is preferable. In addition to the bottom surface, the alumite treatment is also applied to a region from the side of the bottom surface side to the height of a certain distance on the side surface of the outer can. And the outer can is a thin square shape, the fixed distance is 60 % or more of the height from the bottom side edge to the sealing plate mounting position on the side surface of the outer can, and Up to the vicinity of the mounting position.

  In the present invention, of the outer surface of the outer can, the portion other than the bottom surface is covered with a coating material, and the outer surface of the outer surface of the outer can is subjected to alumite treatment, thereby preventing corrosion over the entire outer can. In addition, insulation is ensured. Further, since it is not necessary to attach a resin plate to the bottom surface, the thickness due to the resin plate and the thickness due to the engaging portion of the resin plate can be omitted, leading to the downsizing and thinning of the battery pack. Further, since the cost required for the resin plate is reduced, it is useful for reducing the manufacturing cost of the battery pack.

  If the color difference from the coating material is conspicuous in the portion subjected to the alumite treatment, it is easy to color by film formation, so that it can be colored to match the color of the coating material. The occurrence of bending which is a concern when covering the bottom part with the covering material is also eliminated in the configuration of the present invention. For these reasons, the configuration of the present invention also has an effect of preventing deterioration of the appearance quality of the battery pack.

  Furthermore, if the alumite treatment is applied not only to the bottom surface but also from the bottom surface to at least the central part of the outer can main surface, this alumite treatment improves the strength against deformation of the outer can. Even when the stored unit cell expands and, as a result, the expansion of the battery pack is predicted, the effect of preventing the expansion of the battery pack is also obtained.

Hereinafter, the best mode for carrying out an alumite treatment in a battery pack according to the present invention will be described with reference to the drawings. The embodiment described below is an example for explaining the characteristics of the configuration and operation of the present invention, and the present invention is not limited to this.
(Pack battery configuration)
A battery pack according to an embodiment of the present invention will be described with reference to FIGS. 1 is a perspective view showing the top of the battery pack 1, and FIG. 2 is a perspective view showing the bottom of the battery pack 1. As shown in FIG.

As shown in FIG. 1, the battery pack 1 has a resin mold 20 formed on a lithium ion battery having an outer can 2 made of an aluminum (Al) alloy, and covers the outer peripheral surface of the outer can 2 5 is arranged. The outer can 2 is alumite-treated on the bottom surface (not shown) and a part of the outer peripheral surface.
The outer can 2 included in the lithium ion battery has an elliptical shape in the YZ section and a thin three-dimensional shape with the X direction as the longitudinal direction.

  As shown in FIG. 1, the resin mold 20 is provided on the end surface on the negative direction side in the X direction of the outer can 2. The YZ cross section is the same size as the outer can 2, but the length in the X direction is smaller than that of the outer can 2. This resin mold 20 is formed by injecting polyamide resin into a gap between a circuit board (not shown) having a control circuit section and the like and an outer can 2 of the lithium ion battery by insert molding. In that case, a circuit board etc. are arrange | positioned so that the flow of the favorable resin material may be ensured using a metal mold | die. Thereby, a circuit board etc. are reliably connected and fixed with the lithium ion battery. However, the resin material is not limited to polyamide resin, and other resin materials can be used as long as they can be insert-molded at a low temperature and have insulating properties.

  External resin input / output terminals 31, 32, and 33 are exposed to the outside from the resin mold 20. Of these, the terminal 31 is a positive terminal, and the terminal 32 is a negative terminal. Via these terminals 31 and 32, the battery pack 1 inputs and outputs power to and from an external circuit. The terminal 33 is called a model discrimination resistor terminal, and is provided for the device side to determine the type of battery when the battery pack 1 is attached to the device. Further, a submerged seal 40 is also provided on the main surface of the resin mold 20, and claw portions 34 are exposed vertically on the upper and lower surfaces of the resin mold 20 (the lower side is not shown).

  As described above, the outer can 2 of the lithium battery 10 is anodized, and as shown in FIG. 2, the anodized part (hereinafter referred to as “alumite treatment unit”). Consists of a bottom 7a of the outer can 2 and a part 7b of the outer peripheral surface. However, a portion 7b of the outer peripheral surface is formed on the negative side in the X direction from the bottom 7a because it is alumite-treated continuously from the bottom 7a. If the depth of this alumite treatment is small, it is difficult to prevent corrosion and ensure insulation. Thus, the depth at which the alumite treatment is performed is not particularly limited, but is preferably 25 to 30 μm, for example, 50 μm at the maximum. For example, as compared with the case where the thickness of the resin plate disposed on the bottom surface of the outer can 2 in the conventional case is at least 100 to 200 μm, the battery pack 1 ensures insulation by the thickness of the resin plate. It is clear that it is miniaturized. Further, as will be described later, by changing the conditions of the alumite treatment, it is easy to color the bottom with various colors, so the appearance quality of the battery pack 1 can be improved in accordance with the color tone of the covering material 5 and the like.

  As shown in FIG. 3, which is an XY plan view of the battery pack 1 in FIG. 2 (however, for convenience, the covering material 5 is omitted), an alumite treatment covering a part of the outer periphery of the lithium ion battery The portion 7b has a length of H1 from the bottom portion 7a (the side opposite to the portion where the resin mold 20 is formed) to the X direction negative direction side. The present inventors have investigated that the lithium ion battery swells by repeatedly using the lithium ion battery repeatedly, particularly in the central part, and the length of the outer can 2 in the X direction is increased. When the ratio of H1 to H is about 60% (H1 / H = 0.6) or more, it leads to improvement of the strength of the outer can 2, and at least the central part of the outer peripheral surface of the outer can 2 is also anodized. Therefore, the outer can 2 has an effect sufficiently useful for preventing the expansion of the outer can 2. In addition, the edge near the top of the outer peripheral surface of the outer can 2 has not been anodized so as not to interfere with the welding of the main body portion and the lid portion of the outer can 2, but after the welding, Anodizing may be performed.

The covering material 5 is thin, has a strip shape with the Y direction as the longitudinal direction, and is made of an insulating resin material. The length of the covering material 5 in the longitudinal direction is at least the outer peripheral length of the outer can 2 and is preferably substantially equal to the outer peripheral length. The length in the short direction has at least the length H in the X direction of the outer can 2 as shown in FIG. 3 and is substantially equal to the length of the H. Is desirable. Then, as shown in FIG. 2, the covering material 5 is positioned so that one side in the X direction overlaps the outer periphery of the bottom of the outer can 2 and is mounted so as to cover the outer peripheral surface of the outer can 2. The
(Anodizing method)
Hereinafter, a method of anodizing will be described with reference to FIG. FIG. 4 is a schematic diagram showing the concept of the alumite treatment method.

  The alumite treatment is an anodic oxidation treatment in which the surface of aluminum is oxidized with an anode in an electrolytic solution to form a strong oxide film on the surface of the Al. As shown in FIG. 4, an outer can 2 made of Al is used as an anode in dilute sulfuric acid 80, which is an electrolytic solution in an electrolytic cell 90, and a direct current is passed through the negative electrode 60 using carbon. As a result, electrolysis proceeds in the electrolytic solution, an aluminum oxide film is formed on the surface of the main body of the outer can 2 that is the anode, and hydrogen is generated from the negative electrode. The material used for the negative electrode is not limited to carbon, and any material that contributes to the formation of an aluminum oxide film on the surface of an outer can made of Al using lead or the like is applicable. Similarly, the current value, immersion time, and dilute sulfuric acid used in the electrolyte solution are not limited to these, and other numerical values and other substances can be applied if the same effect can be obtained. . Furthermore, an alumite film with higher quality performance can be formed by performing a pretreatment such as a pretreatment such as buffing or hairline, or a cleaning step such as degreasing or etching before the above step.

  The color tone can be changed according to the combination of the Al alloy, the type of electrolyte, and the current waveform. Furthermore, by performing an electrolysis process using an aqueous solution of Ni, Sn, Cu, Ag, etc., a film is formed on the above-mentioned alumite-treated film. By forming, further coloring can be easily performed. As a result, the color of the bottom of the battery pack 1 can be changed in accordance with the color tone of the covering material 5 and the resin mold 20 used when forming the battery pack 1, so that the appearance quality of the battery pack 1 is improved. It leads to.

  By the way, the lithium ion battery in the present embodiment is formed by a method in which the outer can 2 is sealed with a sealing plate (a surface on which the resin mold 20 is grounded), and the sealed portion is laser-welded. Therefore, when carrying out the above laser welding, this anodized film prevents the aluminum alloy from being welded, so the edge of the upper end opening of the outer can 2 is masked in advance so as not to be anodized, or laser It is necessary to remove the coating before welding. After the laser welding, the welded portion may be subjected to an oxide film treatment. Further, it is preferable to form an alumite film on the inner surface of the outer can 2 or the lid before sealing, since corrosion of the inner surface can be prevented. Note that the sealing plate may also be anodized. Further, anodizing may be performed after the outer can 2 is sealed with a sealing plate. In this case, since it is after welding, alumite treatment may be performed over the entire outer can.

In particular, a hard anodized film can be formed by anodizing such as increasing the current density by performing anodizing at a temperature lower than the normal temperature. Since the hard anodized film is more durable than a normal anodized film, the hard anodized film is suitable for use.
(Other matters)
The above embodiment is an example of the present invention, and the present invention is not limited to the above embodiment. Although a pack battery including one lithium ion battery is described as an example, other sealed secondary batteries may be used. Further, the shape and number of mounted batteries are not limited to this, and can be applied in other cases. In addition, the material of the outer can is applicable as long as it is made of a material containing Al.

  The present invention is particularly useful for the production of a battery pack that can be reduced in thickness and weight, and can stably distribute power over a long period of time.

It is a perspective view which shows the top part of the battery pack which concerns on embodiment of this invention. It is a perspective view which shows the bottom part of the battery pack which concerns on embodiment of this invention. It is a principal surface top view of a battery pack. It is a schematic diagram of the alumite process which concerns on embodiment of this invention. It is a perspective view of the battery pack concerning the conventional case.

Explanation of symbols

1 pack battery
2 Exterior can
5 Coating material
7 Anodized processing section
20 Resin mold
31, 32, 33 External input / output terminals

Claims (2)

A battery pack provided with a unit cell in which an outer can made of a material containing aluminum is sealed with a sealing plate,
Of the outer surface of the outer can, the portion excluding its bottom is covered with a covering material,
In a state where there is a portion where the alumite treatment is not performed on the outer periphery of the outer can,
The outer surface of the bottom surface is anodized,
In addition to the bottom surface, the alumite treatment is also applied to a region of the side surface of the outer can from the bottom side edge to a height of a certain distance. The outer can is a thin square shape,
2. The battery pack according to claim 1, wherein the certain distance is 60 % or more of a height from an end of the bottom surface side to the sealing plate mounting position on a side surface of the outer can.

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