JP2003142049A - Battery pack - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a compact and lightweight battery pack of high energy density. SOLUTION: In this battery pack wherein a battery and a wiring material are accommodated in a case formed by fitting a first case 2 and a second case 3, a fitting part of at least one of the first case and the second case is transparent, and the fitting parts are joined by an ultraviolet ray curable resin 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a battery pack containing a battery and the like in a housing.

2. Description of the Related Art With the recent trend toward smaller and lighter electronic devices and portable devices, the demand for battery packs as power sources is increasing rapidly. As batteries used in battery packs, generally chargeable and dischargeable lead-acid batteries, nickel-cadmium batteries, nickel-hydrogen batteries, etc. are widely used, and recently, non-aqueous batteries such as lithium ion batteries having high energy density. The ratio of is increasing. Under such circumstances, a smaller and lighter battery pack and a method for manufacturing the battery pack at low cost are required. For example, a battery pack using a non-aqueous secondary battery has a core pack housed in a resin casing. Here, the “core pack” means a unit cell, an electric circuit called a protection circuit, terminals, and the like joined by metal leads.

A housing is generally called a case and is made up of two resin molded products that are fitted together. Conventionally, the fitting portion of these two resin molded products is made of a resin which is a case material. Bonding was done using a solvent that dissolves. A problem with this method is that the bonding force of the housing is exhibited when the solvent dries, so it was necessary to dimensionally fix the battery pack until the solvent dries. In general,
This required about 10 minutes and was a production method with low efficiency. This is called a solvent bonding method.

It has been attempted to shorten the time by dissolving a resin useful for adhesion such as ABS resin in a solvent in advance, but this also requires 5 minutes or more.

In response to such a problem in the solvent method, recently, a method of joining two cases using ultrasonic waves is widely used. This is called an ultrasonic bonding method. In the ultrasonic bonding method, a wedge-shaped protrusion called a welding rib is provided on one case, and ultrasonic vibration is concentrated on this welding rib to generate heat at this portion, thereby thermally welding the two cases. is there. In the case of this method, there is no need for a long standing period, which is required in the solvent bonding method, and there is an advantage that the joining operation of the two cases can be efficiently advanced.

On the other hand, however, new problems have arisen in the recent miniaturization of battery packs. This means that it is necessary to further reduce the thickness of the casing as the battery pack becomes smaller. For example, in the region where the thickness of the casing is less than 0.7 mm, the ultrasonic energy is higher than that of the welding ribs. It becomes easier to disperse in the core pack,
The damage may occur in these parts.

[0006] Usually, in order to prevent such a problem, a design gap is provided between the case on the horn side for generating ultrasonic waves and the core pack so that the ultrasonic waves are not directly transmitted. However, since the strength of the case becomes weaker as the thickness of the case becomes thinner, it is necessary to make the gap larger by design. As a result, a space volume that is originally unnecessary for the battery pack is generated, and there is a problem that the energy density per volume is reduced.

Another problem in the production by the ultrasonic method is that the use of the thin case causes a great loss of time due to the adjustment of the ultrasonic welding conditions. This occurs due to dimensional variations and deformation of the resin molded product that is the case. Since the resin molded product is thin, it is affected by the fluidity of the resin pellets as the raw material, and the dimensions and warpage vary.

Also, a slight dimensional difference of the molded product occurs for each mold. Due to these factors, the size of the battery pack, which is a finished product, varies, so it is necessary to adjust the ultrasonic welding conditions each time the state of the resin molded product changes. Although such adjustment is appropriately performed in the production line, a loss time of usually about 1 hour per day, and in a significant case, several hours per day may occur.

Recently, as a solution to the problem in the ultrasonic method, as described in Japanese Patent Laid-Open No. 2000-315483, a polyamide resin or a polyurethane resin that melts at a low temperature is used to form a core pack. A method of directly forming a housing on the outside has been proposed.
This is called a low temperature resin molding method.

In this method, after the core pack is placed in a molding die, a polyamide or polyurethane resin that melts at a relatively low temperature is filled in the die to coat the surface of the core pack with the resin. To do. With this method,
Since there is no gap between the housing and the core pack, which is necessary for ultrasonic welding, the problem of lowering the energy density per volume does not occur.

However, a problem with this method is that the resin flows into all the gaps existing between the core pack and the housing, which increases the mass. That is, there is a problem that the energy density per mass is reduced. In addition, the unit cells are not a little affected by heat and change in volume due to gasification of the electrolytic solution and the like, which causes a problem that dimensional accuracy is reduced.

[0012]

Among the conventional battery pack manufacturing methods, the solvent bonding method requires a certain drying time, is a low-efficiency manufacturing method, and does not require the ultrasonic bonding method. Since the space volume is required, the energy density per volume of the battery pack is lowered, and the loss time of the production line is large. Further, the low-temperature resin molding method has a problem that there is a large amount of unnecessary resin and the energy density per mass of the battery pack is reduced.

The present invention has been made in order to solve these problems in the prior art, and an object of the present invention is to provide a small-sized, lightweight battery pack having a large energy density.

[0014]

The invention according to claim 1 is the first
A battery pack in which a battery and a wiring material are housed in a case in which the case and the second case are fitted, wherein at least one fitting portion of the first case and the second case is transparent, It is characterized in that the fitting portion is joined with an ultraviolet curable resin.

According to the invention of claim 1, since the fitting portion of at least one of the first case and the second case is transparent, ultraviolet rays can reach the ultraviolet curable resin through the case. The fitting parts of the two cases can be reliably joined together. Further, since there is almost no heat generation during the curing of the ultraviolet curable resin, the thermal influence on the battery is at a level that can be ignored.

According to a second aspect of the present invention, there is provided a battery pack in which a battery and a wiring member are housed in a case in which the first case and the second case are fitted together. The fitting portion is provided with a gap of 0.05 mm or more continuous with the outside of the case, and the fitting portions of the first case and the second case are joined with an ultraviolet curable resin.

According to the second aspect of the present invention, the fitting portion of the first case and the second case is connected to the outside of the case by 0.0.
By providing a gap of 5 mm or more, ultraviolet rays are irradiated to the ultraviolet curable resin through this gap, and the fitting portions of the two cases can be reliably joined together.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, the ultraviolet curable resin is generally used in many applications such as paints for surface treatment.
In the initial state, a resin that is fluid but has the property of solidifying is used. That is, generally, a so-called prepolymer, which is obtained by polymerizing some monomers, has fluidity in the preceding stage of the polymer,
Polymerization to the polymer is started by irradiating with ultraviolet rays,
Finally, it becomes a polymer and solidifies.

Therefore, an embodiment of claim 1 of the present invention will be described with reference to FIG. FIG. 1 shows a cross-sectional structure of an example of the battery pack according to claim 1. In FIG. 1, 1 is an ultraviolet curable resin, 2 is a first case, 3 is a second case, 4 is a core pack, 5 is a cell, 6 is an electrical wiring member (lead), and 7 is a cell. A minus terminal, 8 is an insulating material, and 9 is an ultraviolet ray irradiation direction. Further, FIG. 2 is an enlarged view of a joint portion between the first case 2 and the second case 3 in FIG. 1, and shows the same symbols 1, 2, and 3 in FIG. 2, 9a and 9b. Indicates the irradiation direction of ultraviolet rays.

The battery pack shown in FIG. 1 has a first case 2 as an upper case and a second case 3 as a lower case.
The core pack 4 is housed in a housing made of, and the first case 2 is fitted after the UV curable resin 1 is applied to the fitting portion of the second case 3, and then the second case 3 is irradiated with ultraviolet rays. Are joined together. The gap between the first case (upper case) 2 and the unit cell 5 is zero.

FIG. 2 is an enlarged view of the joint portion. In FIG. 2, the portions of the first case 2 and the second case 3 indicated by fine hatching are transparent, and ultraviolet rays 9a
Alternatively, when the light is irradiated from the direction 9b, the ultraviolet rays reach the ultraviolet curable resin through the first case 2 and the second case 3.

In the present invention, as shown in FIG. 2, both the fitting portion of the first case and the fitting portion of the second case may be transparent. Only one of the fitting part of the second case and the fitting part of the second case may be transparent. Furthermore, it is not necessary that only the fitting portion of the first case or the fitting portion of the second case be transparent.
At least one of the case and the second case may be entirely transparent.

Next, a second embodiment of the present invention will be described with reference to FIGS. 3, 4 and 5. FIG. 3 shows a sectional structure of an example of the battery pack according to claim 2. 4 and 5 are enlarged views of the joint portion between the first case and the second case in FIG. The symbols 1 to 9 in FIGS. 3, 4 and 5 are the same as those in FIG. Note that, also in FIG. 3, as in FIG. 1, the gap between the first case (upper case) 2 and the unit cell 5 is zero.

In the battery pack shown in FIG. 3, the first
A colored resin containing a pigment is used for the case 2 and the second case 3. Then, as shown in enlarged views in FIGS. 4 and 5, the fitting portion of the first case 2 and the second case 3 is provided with a gap of 0.05 mm or more continuous with the outside of the case, When the ultraviolet curable resin is poured into the fitting portion between the case 2 and the second case 3 and the ultraviolet ray is irradiated from the direction 9, the ultraviolet ray is directly irradiated to the ultraviolet ray curable resin, and the first case 2 And the second case 3 are joined.

The gap formed between the first case 2 and the second case 3 and continuous with the outside of the case must be 0.05 mm or more. If this gap is smaller than 0.05 mm, the bonding strength becomes weak. Further, even if this gap becomes too large, the bonding strength becomes weak, so the gap is preferably 0.5 mm or less.

In the battery pack of the present invention, the material used for the first case and the second case is not limited, but considering the thinning of the casing resin, use of polycarbonate / ABS polymer alloy or the like. Is desirable.

As the type of battery used in the battery pack, various batteries such as a lead storage battery, a nickel-cadmium battery, a nickel-hydrogen battery, a non-aqueous secondary battery such as a lithium ion battery or a polymer electrolyte battery are used. can do.

[0028]

EXAMPLES Next, the present invention will be explained in detail based on examples, but the present invention is not limited to the following examples, and may be appropriately modified and carried out within a range not changing the gist thereof. It is possible.

[Embodiment 1] The sectional structure of the battery pack according to Embodiment 1 of the present invention is the same as that shown in FIG.
A core pack 4 is housed in a first case (upper case) 2 and a second case (lower case) 3 which are casings,
After the ultraviolet curable resin 1 is applied to the fitting portion of the second case 3 with the first case 2, the first case 2 is fitted and then irradiated with ultraviolet rays to be joined.

In this battery pack, a pigmented polycarbonate resin is used for the second case 3,
The thickness of the side part is 0.7 mm, the thickness of the bottom part is 0.3 mm
Is. A transparent polycarbonate resin is used for the first case 2 and has a thickness of 0.3 mm. By using a transparent resin for the first case, ultraviolet rays can reach the ultraviolet curable resin through the first case.

The gap between the first case 2 and the unit cell 5 is zero. This was designated as battery pack A. This battery pack had external dimensions of 6.2 × 32 × 52.5 mm, a mass of 19 g, a capacity of 740 mAh, and a voltage of 3.6 V.

[Embodiment 2] The cross-sectional structure of the battery pack according to Embodiment 2 of the present invention is similar to that shown in FIG.
A core pack 4 is housed in a second case (lower case) 3 and a first case (upper case) 2 which are casings,
After the ultraviolet curable resin 1 is applied to the fitting portion of the second case 3, the first case 2 is fitted, and then the second case 3 is irradiated with ultraviolet rays to be joined.

In this battery pack, a pigmented polycarbonate resin is used as the first case 2 and the second case 3, and since the ultraviolet curable resin is directly irradiated with ultraviolet rays, the first case 2 is used. A gap of 0.1 mm is provided in the fitting portion between the second case 3 and the case.

As in the first embodiment, the first case 2
The gap between the cell and the unit cell 5 is zero. This is battery pack B
And Further, the battery pack B has the same outer dimensions of 6.2 × 32 × 52.5 mm as the battery pack A of the first embodiment.
The mass was 19 g, the capacity was 740 mAh, and the voltage was 3.6 V.

[Comparative Example 1] FIG. 6 shows a cross-sectional structure of a conventional battery pack of Comparative Example 1 using the ultrasonic welding method. 6, symbols 2 to 8 are the same as those in FIG. 1, 10 is an ultrasonic welding rib, and 11 is a direction of ultrasonic vibration.

In this battery pack, a core pack 4 is housed in a second case (lower case) 3 and a first case (upper case) 2 which are casings. After the core pack 4 is housed in the case 3, the first case 2 is fitted, and then the fitting portion is joined by applying ultrasonic vibration from the first case 2.

In this battery pack, a pigmented polycarbonate resin is used as the first case 2 and the second case 3, and the gap between the first case 2 and the unit cell 5 is 0.1 mm. This was designated as Battery Pack C. The external dimensions of the battery pack C are 6.3 × 32 × 52.
5 mm, the mass was 19 g, the capacity was 740 mAh, and the voltage was 3.6 V.

[Comparative Example 2] FIG. 7 shows a sectional structure of a battery pack of Comparative Example 2 according to a conventional low temperature resin molding method. In FIG. 7, symbols 4 to 8 are the same as those in FIG. 1, 12 is a low temperature resin molding die, 13 is a low temperature resin injection port, and 14 is a housing made of low temperature resin. Here, a polyamide resin was used as the low temperature resin.

In this battery pack, the core pack 4 is housed in a housing 14 made of low-temperature resin. After the core pack 4 is housed in a mold 12 for molding low-temperature resin, a low-temperature resin injection port 13 is provided. It is manufactured by filling a case with a polyamide resin.

This was designated as battery pack D. Battery pack D
Has an external size of 6.2 × 32 × 52.5 mm and a mass of 1
The voltage was 9.2 g, the capacity was 740 mAh, and the voltage was 3.6 V.

Next, the charge / discharge characteristics of the four types of battery packs manufactured by the above method were measured. Charge / discharge cycle test conditions were constant current-constant voltage charging at 740 mA-4.2 V for 3 hours and discharging to 2.7 V at 740 mA constant current. Then, the energy density per volume and per mass was obtained from the discharge characteristics at the 10th cycle. Table 1 shows the content and energy density of each battery pack. In addition,
The energy density in Table 1 is an average value of 10 battery packs each.

[0042]

[Table 1]

From Table 1, the battery pack A of the embodiment of the present invention is shown.
It was found that and B have higher energy density per volume as compared to the ultrasonic welding type battery pack C, while they are superior to the low temperature resin molding type in terms of energy density per mass. . That is, according to the present invention, it is possible to obtain a small-sized and lightweight battery pack having a high energy density.

Further, since the ultraviolet curable resin is instantly solidified by irradiating it with ultraviolet rays, there is no reduction in the productivity which was the conventional solvent bonding method. The strength of the joint between the battery packs A and B of the present invention is sufficiently high, and the height is 1.
Even in the drop test from 5 m, the strength of the joint was not insufficient.

[0045]

As described above, according to the present invention, it is possible to obtain a small-sized and lightweight battery pack having a high energy density.

In Example 1 of the present invention, a transparent resin case was used as a member of the first case (upper case) for transmitting ultraviolet rays, but when it is necessary to use a colored product, The first case and the second case colored with a dye are used, and the fitting portion of the first case and the second case is provided with a gap of 0.05 mm or more continuous with the outside of the case. be able to.

[Brief description of drawings]

FIG. 1 is a diagram showing a cross-sectional structure of an example of a battery pack according to claim 1.

FIG. 2 is a first case 2 and a second case 3 in FIG.
FIG.

FIG. 3 is a diagram showing a cross-sectional structure of an example of the battery pack according to claim 2;

FIG. 4 is an enlarged view of a joint portion between the first case and the second case in FIG.

FIG. 5 is an enlarged view of a joint portion between the first case and the second case in FIG.

FIG. 6 is a view showing a cross-sectional structure of a conventional battery pack using an ultrasonic welding method.

FIG. 7 is a view showing a cross-sectional structure of a conventional battery pack manufactured by a low temperature resin molding method.

[Explanation of symbols]

1 UV curable resin 2 First case 3 second case 4 core pack 5 cells 6 electrical wiring materials 9,9a, 9b UV irradiation

Claims (2)

[Claims] 1. A battery pack in which a battery and a wiring member are housed in a case in which a first case and a second case are fitted, and at least one of the first case and the second case is fitted. A battery pack, wherein the portion is transparent, and the fitting portion is joined with an ultraviolet curable resin. 2. A battery pack in which a battery and a wiring member are housed in a case in which a first case and a second case are fitted together, wherein a fitting portion between the first case and the second case comprises: A battery pack, wherein a gap of 0.05 mm or more continuous with the outside of the case is provided, and a fitting portion of the first case and the second case is joined with an ultraviolet curable resin.