JP4628020B2 - Pack battery - Google Patents

Description

  The present invention relates to a battery pack.

  The pack battery is a package of a unit cell, which is a secondary battery, and a control circuit for controlling and protecting the unit cell, and is used for various applications such as a mobile phone and a PDA. Among them, a battery pack in a form in which a resin portion is formed between a part of a unit cell and a circuit board using an insert molding method is excellent from the viewpoint of size and cost and is often used.

  The battery pack is usually provided with a heat sensitive element such as a breaker element in order to control the input / output power according to the temperature of the unit cell. Here, in addition to the breaker element, a PTC (Positive Temperature Coefficient) element, an NTC (Negative Temperature Coefficient) element, and the like are well known as the thermal element. Is difficult to use PTC elements and NTC elements. That is, when the resin material is filled in the portion where the thermal element is formed and insert molding is performed, the initial resistance value of the thermal element does not return after molding.

For such a problem, for example, a method of covering the entire structure including the PTC element or the PTC element with a heat insulating sheet and insert-molding in this state has been proposed (for example, refer to Patent Documents 1 and 2). .
In addition, when the thermal element is covered with a heat insulating sheet or the like as described above, it is considered that the element electrode or the like is corroded, thereby degrading the element performance, but the element electrode of the thermal element is deteriorated. In order to prevent this, a technique of coating the outer surface of the element electrode with an epoxy resin or the like has also been proposed (see, for example, Patent Document 3).
JP 2003-308815 A JP 2003-132860 A JP 09-283263 A

  However, the battery packs disclosed in Patent Documents 1 to 3 are expensive. That is, in the battery pack to which the techniques of Patent Documents 1 and 2 are applied, the heat insulating sheet used for protecting the heat sensitive element causes the high cost of the battery pack. Moreover, in these battery packs, the size of the appearance must be increased by the amount provided with the protective sheet and the protective case.

Furthermore, in the battery packs of Patent Documents 1 and 2, as described above, it is actually necessary to coat with an epoxy resin or the like in order to prevent corrosion of the element electrode of the heat sensitive element, which further increases the cost. It becomes.
The present invention has been made to solve the above-described problems, and includes a thermal element, a structure capable of maintaining the initial resistance characteristics of the thermal element, and capable of reducing the cost. An object of the present invention is to provide a battery pack.

In order to achieve the above object, the battery pack according to the present invention has the following characteristics.
(1) A battery pack according to the present invention includes a unit cell, a thermal element that controls electric power flow between the unit cell and the outside in accordance with self or an ambient temperature, a part of the outer periphery of the unit cell, and a thermal element. Among the constituent elements, the thermosensitive element has an element body made of a polymer material in which metal particles as a conductive material are dispersed. The resin part is formed in a state where the outer surface of the element body part is coated by insert molding .

  (2) The battery pack according to (1), wherein the resin portion is made of a polyamide-based resin.

  As described in (1) above, the battery pack according to the present invention uses a thermal element having an element body portion in which metal particles are dispersed. Since the heat sensitive element used in the present invention has a high resistance value recovery performance, it is possible to maintain the initial resistance characteristics even under the influence of heat during insert molding. For this reason, in the battery pack according to the present invention, it is not necessary to use a heat insulating sheet for protecting the thermal element as in the battery packs of Patent Documents 1 and 2, and this has an advantage in terms of cost.

Further, as described in (1) above, in the battery pack according to the present invention, since the resin part is formed in a state of coating the outer surface of the element body part, the element body part (particularly in the element body part) The dispersed metal particles are not corroded. Thus, in the battery pack according to the present invention, the element main body is suppressed from being corroded, and the entire resistance value of the thermal element is not increased.
The thermosensitive element is composed of an element body part and a pair of element electrodes formed so as to sandwich the element body part. In this case, not only the outer surface of the element body part but also the outside of the element electrode is formed. It is desirable that the surface is also in a coating state at the resin portion. That is, by forming the resin portion in such a state, the battery pack according to the present invention does not have the heat sensitive element electrode coated with the epoxy resin as in Patent Document 3 described above. Corrosion of the device electrode in the device is also suppressed, and this also reduces the cost of the battery pack.

  Therefore, in the battery pack according to the present invention, even when the resin portion is formed by insert molding, it is possible to maintain the initial resistance characteristics of the thermal element and to reduce the cost.

The best mode for carrying out the present invention will be described below with reference to the drawings.
1. Configuration of Pack Battery 1 The configuration of the pack battery 1 according to the present embodiment will be described with reference to FIGS.
As shown in FIG. 1, a battery pack 1 is formed at one end portion of a lithium ion secondary battery (hereinafter simply referred to as “secondary battery”) as a substantially thin rectangular battery cell. And a resin mold portion 20. Among these, three input / output terminals 31 provided on the protection circuit board 30 are exposed from a part of the resin mold portion 20. Further, on the same outer peripheral surface of the resin mold portion 20, there is a submerged seal 40 affixed on a test terminal 32 described later.

  As shown in FIG. 2, the secondary battery 10 has a protection circuit board 30 attached to the side where the negative electrode terminal 13 is provided. Further, between the secondary battery 10 and the protection circuit board 30, a PTC element 50, leads 61 and 62, an insulating plate 70, and the like are interposed. The PTC element 50 includes an element main body 51 and a pair of element electrodes 52 and 53 so as to sandwich the element main body 51, and the element electrode 52 is connected to the negative electrode terminal 13 of the secondary battery 10. Yes. The other element electrode 53 in the PTC element 50 is connected to the lead 34 on the negative electrode side of the protection circuit board 30 with the lead 62 interposed therebetween.

  A clad plate 14 is connected to a part of the battery lid 12 in the secondary battery 10, and leads 61 are connected to the clad plate 14. The lead 61 is connected to the lead 33 on the positive electrode side of the protection circuit board 30. Here, the clad plate 14 is made of, for example, Al—Ni, etc., in order to achieve good bonding between the battery lid 12 of the secondary battery 10 made of an Al alloy and the lead 61 made of Ni. Is provided.

  An insulating plate 70 between the PTC element 50 and the battery cover 12 of the secondary battery 10 is inserted in order to insulate between the element electrodes 52 and 53 and the battery cover 12 of the secondary battery 10. . Further, the battery lid 12 of the secondary battery 10 is provided with a safety valve 15, but the insulating plate 70 also serves to prevent the resin forming the resin mold portion 20 from flowing into the safety valve 15.

  The input / output terminal 31 and the test terminal 32 are provided on the main surface of the protection circuit board 30 opposite to the side facing the secondary battery 10. Although not shown, the other main surface of the protection circuit board 30 is controlled between the leads 33 and 34 to control the power flow between the secondary battery 10 and the external device. A protection circuit for protecting the secondary battery 10 is formed. Since this is a well-known thing, description here is abbreviate | omitted.

The secondary battery 10 is formed by sealing with a battery lid 12 after an electrode body (not shown) is inserted into the internal space of an outer can 11 made of an Al alloy and filled with an electrolyte (not shown). ing.
The resin mold part 20 shown in FIG. 1 is formed so as to cover the battery lid 12 and the protection circuit board 30 of the secondary battery 10. The resin mold part 20 includes an acrylonitrile butadiene styrene (ABS) resin, a polyvinyl chloride (PVC) resin, a polycarbonate (PC) resin, a polypropylene (PP) resin, a polyethylene (PE) resin, a polyamide (PA) resin, and a urethane resin. However, in this embodiment, PA resin is used as an example.

2. Next, the configuration of the PTC element 50 and the resin mold part 20 are the most characteristic part of the battery pack 1 according to the present embodiment. The relationship will be described with reference to FIG. FIG. 3 is a cross-sectional view showing the inside of the resin mold portion 20.
As shown in FIG. 3, the PTC element 50, the leads 33, 34, 62, 63, the insulating plate 70, and the like are accommodated in the portion where the resin mold portion 20 is formed. The protective circuit board 30 is also housed in the resin mold portion 20 except for the input / output terminals 31 and the test terminals 32. The test terminal 32 is not exposed to the outside from the surface of the resin mold portion 20 by applying a submerged seal 40.

  As shown in the enlarged portion of FIG. 3, the PTC element 50 inside the resin molding portion 20 is in a state where the entire outer surface of the device main body portion 51 and the device electrodes 52 and 53 are coated with the resin mold portion 20. ing. That is, in the battery pack 1 according to the present embodiment, it is possible to prevent the element main body 51 of the PTC element 50 from being corroded by coating with the resin mold part 20.

  The PTC element 50 provided in the battery pack 1 according to the present embodiment has a structure in which the element main body 51 has a structure in which metal particles are dispersed as conductive particles in a polymer material. Carbon black used in general PTC elements is replaced with metal particles. The PTC element 50 having the element body 51 in which metal particles are dispersed has a higher resistance recovery performance than the conventional PTC element having the element body having a structure in which carbon black is dispersed. The initial resistance characteristics of the PTC element 50 can be maintained even if the insert molding is performed without using the heat insulating sheet as in Patent Documents 1 and 2.

Specifically, when insert molding is performed using PA resin, the PTC element 50 is exposed to heat of about 200 to 250 (° C.) and trips, but the PTC element 50 in the present embodiment. Has the ability to return close to the initial resistance value.
As described above, in the battery pack 1 according to the present embodiment, the PTC element 50 having the element main body 51 in which the metal particles are dispersed is used. Therefore, a heat insulating sheet or the like is not disposed around the PTC element 50. Even when insert molding is performed, the initial resistance characteristics of the PTC element 50 can be maintained. Therefore, the battery pack 1 is advantageous in terms of cost because it is not necessary to use a heat insulating sheet or the like.

Further, in the battery pack 1 according to the present embodiment, the element main body 51 of the PTC element 50 and the outer surfaces of the element electrodes 52 and 52 are coated with the resin mold part 20. In spite of the metal particles dispersed therein, there is no problem that the resistance value of the PTC element 50 increases due to oxidation or the like.
Furthermore, since the resin mold part 20 exists in a state where the outer surfaces of the element electrodes 52 and 53 of the PTC element 50 are also coated, the outer surface of the element electrode is previously coated with an epoxy resin or the like as in Patent Document 3 above. From this point of view, the battery pack 1 according to the present embodiment can keep the cost low.

Therefore, in the battery pack 1 according to the present embodiment, the initial resistance characteristic of the PTC element 50 can be maintained while the resin mold portion 20 formed by insert molding is provided, and the cost can be reduced. It is also possible.
In addition, although the resin mold part 20 can also use a urethane-type resin, in that case, the molding temperature at the time of insert molding is about 120 (degreeC), and it is from a viewpoint of maintaining the initial stage resistance characteristic of the PTC element 50. It is more dominant.

3. Other Matters In the above embodiment, the battery pack is provided with the lithium ion secondary battery 10 as a unit cell, but the present invention is not limited thereto. For example, a nickel hydride secondary battery or a nickel cadmium secondary battery may be provided as a unit cell, and the number of unit cells is not necessarily one, and may be two or more.

Moreover, in the said embodiment, although PA resin was used as a forming material of the resin mold part 20, as mentioned above, other resin materials, for example, ABS resin, PVC resin, PC resin, PP resin, PE Resins, urethane resins and the like can also be used.
Furthermore, as a heat sensitive element, besides a PTC element. An element provided with a thermal resistor can be used. For example, an NTC element or the like can be employed.

  The present invention can be applied to a battery pack used as a power source for a mobile phone or a PDA.

1 is an external perspective view of a battery pack 1 according to an embodiment of the present invention. 2 is a developed perspective view of the battery pack 1. FIG. 2 is a partial cross-sectional view of the battery pack 1. FIG.

Explanation of symbols

1. Pack battery 10. Lithium ion secondary battery 11. Exterior can 12. Battery cover 13. Negative terminal 14. Clad plate 15. Safety valve 20. Resin part 30. Protection circuit board 31. Input / output terminal 32. Test terminals 33, 34, 61, 62. Lead 40. Submerged seal 50. PTC element 51. Element body 52, 53. Element electrode 70. Insulation plate

Claims (2)

A unit for packaging a unit cell, a thermal element that controls power flow between the unit cell and the outside in accordance with self or the temperature of the atmosphere, and a part of the outer periphery of the unit cell and the thermal unit. A battery pack comprising:
The thermal element is made of a polymer material in which metal particles as a conductive material are dispersed.
That device has a body portion,
The resin portion, the battery pack, characterized in that the insert molding and is formed in a state of coating the outer surface of the device body unit. The battery pack according to claim 1, wherein the resin portion is made of a polyamide-based resin.

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