JP2002373708A - Battery pack - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable a battery pack to be cooled at all times whether it is being charged, discharged or in a standby condition, while enhancing its dustproof property and miniaturizing it. SOLUTION: The heat receiving part of a flat heat pipe 4 is brought into contact with the surface of cell body 3 and is thermally coupled to a heat radiating fin 5 mounted on the outside of a battery case 2b.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a battery pack capable of cooling a unit cell.

[0002]

2. Description of the Related Art Conventionally, a battery pack using a nickel cadmium battery or a nickel hydride battery has been used as a power source for portable electric equipment such as a cordless power tool. These battery packs consist of a plurality of unit cells connected in series and a battery case that stores them inside. However, due to advances in battery technology, the electric capacity per unit cell volume has increased. The charging current increased due to the demand for quick charging. The use of large current discharges has increased. The demand for higher voltage has increased the number of cells connected in series. Due to the demand for miniaturization, the gap between the unit cells in the battery pack has become smaller. Due to such circumstances, the heat generated by charging and discharging is large, and the cooling of the unit cell is not enough with the heat radiated from the battery pack surface. In addition, failures such as internal short-circuits and reduced capacity are likely to occur.

In order to prevent this failure, Japanese Patent Laid-Open No. 11-2
In 19733, cooling air is blown into the battery case by a cooling fan provided in the battery charger with a hole formed in the battery case.
In addition, in Japanese Utility Model Application Laid-Open No. 61-114767, a heat pipe is inserted into a gap between unit cells, a potting material is filled between the heat pipe and the unit cell, and a heat radiating portion of the heat pipe is connected to a cooling fin provided outside a battery case. Connected.

[0004]

However, in the former conventional example, since the unit cells are densely built and the air path resistance is large, not only a strong cooling fan is required, but also the metal powder is removed from the hole of the battery case. There is a risk that dust, rainwater, and the like may enter and cause smoke, burning, corrosion, etc. of the unit cell, and in addition, there is a drawback that the unit is not cooled during standby or discharge. Further, in the latter conventional example, there is a drawback that the work of filling the potting material by avoiding the explosion-proof valve of the unit cell is difficult and cannot be used practically.

An object of the present invention is to eliminate the above-mentioned disadvantages of the prior art and to obtain a small dust-proof battery pack having a cooling function that can be constantly cooled during charging, discharging and standby.

[0006]

SUMMARY OF THE INVENTION The object of the present invention is to provide a flat heat pipe in contact with the surface of a unit cell and to attach a heat radiating fin to the outside of the battery case. This is achieved by combining them together.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the battery pack of the present invention will be described with reference to FIGS.

In the figure, a battery pack 1 includes battery cases 2a and 2b, a plurality of unit cells 3, a flat heat pipe 4,
It is composed of a radiation fin 5.

FIGS. 1 and 2 show the arrangement of the unit cells 3 and the state of attachment of the flat heat pipe 4. The flat heat pipe 4 is, for example, disclosed in JP-A-4-260791, JP-A-4-251189,
It is composed of a meandering thin tube heat pipe made of a metal material having good thermal conductivity disclosed in JP-A-4-190090, JP-A-7-63487 and the like, and the structure is shown in FIGS. 6 and 7. The flat heat pipe 4 includes a thin plate 4a and a thin tube 4b formed therein, and an appropriate amount of hydraulic fluid is sealed in the thin tube 4b. The thin tube 4b is formed so that a large number of flow paths turned back at both ends approach and are parallel to each other, and form a series of meandering flow paths. In this type of heat pipe 4, heat transfer is performed by vibration of the working fluid in the direction of the thin tube 4b, and the movement of the working fluid is not an essential requirement, so that the thin tube 4b can be reduced in diameter and is not affected by gravity. .

Therefore, by adopting this type of flat heat pipe 4, the thickness of the flat heat pipe 4 can be made extremely thin, and a change in thermal conductivity due to the direction of gravity can be eliminated. 3, the battery pack 1 can be downsized by high-density mounting, and fluctuations in the cooling performance of the battery pack 1 depending on the direction to the ground can be eliminated.

In FIG. 1 and FIG.
Are sandwiched in a corrugated shape between three groups of unit cells 3 stacked in a bale and attached so as to come into contact with the surface of each unit cell 3, and this portion serves as a heat receiving portion of the flat heat pipe 4. Both ends of the flat heat pipe 4 are heat radiating parts, and the battery case 2
b is thermally coupled to cooling fins 5 mounted on the outer surface.

FIG. 3 shows a thermal / electrical connection relationship between the plurality of unit cells 3 and the flat heat pipe 4. The unit cells 3 are connected in series by a connection plate 6, and the outer periphery of the unit cells 3 An insulating paper 7 is wound to prevent short circuit between adjacent unit cells 3, and the flat heat pipe 4 is sandwiched by the insulating paper 7.

When the battery pack 1 is charged or discharged, each unit cell 3 generates heat due to chemical reaction and resistance loss.
The generated heat is transmitted to the radiation fins 5 by the action of the flat heat pipe 4 and is radiated to the atmosphere. Since no external driving force is used for heat dissipation, the heat dissipation to the atmosphere is continued even when the battery pack 1 is in a standby state, and cooling proceeds effectively.

Further, since the heat conductivity of the flat heat pipe 4 is much higher than that of a single metal, the temperature of the central portion of the battery pack 1 where the heat is easily stored is substantially the same as the temperature of the radiation fins 5 outside the battery case 2b. .

Accordingly, not only the temperature of each unit cell 3 is lowered but also the unit cells 3 can be kept at a uniform temperature, so that the heat deterioration of the unit cells 3 can be prevented.

The flat heat pipe 4 may be a flat heat pipe having a heat radiating portion and a heat receiving portion. The material of the flat heat pipe 4 is made of a synthetic resin having good heat conductivity in addition to metal. The electrical insulation between them can be improved. Furthermore, by forming the flat heat pipe 4 with a synthetic resin having flexibility, the thermal coupling between the flat heat pipe 4 and the unit cells 3 can be improved.

Next, a second embodiment of the present invention will be described with reference to FIGS.

FIGS. 8 and 9 show a configuration in which a sheet 8 is interposed between the flat heat pipe 4 and the insulating paper 7. FIG.
By using an electrical insulator having flexibility and heat conductivity such as a silicon rubber sheet as the sheet 8, thermal coupling between the flat heat pipe 4 and the unit cell 3 due to variation in dimensional accuracy of members. It is possible to prevent a decrease in the electrical properties and to improve the electrical insulation between the flat heat pipe 4 and the unit cells 3.

Next, a third embodiment of the present invention will be described with reference to FIG.
Explanation will be made using 0.

FIG. 10 shows a configuration in which grease or adhesive 9 is interposed between the flat heat pipe 4 and the insulating paper 7. By using, for example, silicon grease or a thermally conductive adhesive as the grease or the adhesive 9,
It is possible to prevent a decrease in the thermal connectivity between the flat heat pipe 4 and the unit cell 3 due to a variation in the dimensional accuracy of the members, and to prevent the parts from falling off during the assembly process.

[0021]

According to the present invention, it is possible to eliminate the air holes in the battery case and to mount a plurality of unit cells at a high density, thereby obtaining a small-sized battery pack having good dustproofness and capable of being constantly cooled. I can do it.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a first embodiment of a battery pack of the present invention.

FIG. 2 is a longitudinal sectional view of the battery pack of FIG.

FIG. 3 is a partial longitudinal sectional view showing a relationship between a unit cell and a heat pipe in the battery pack of FIG. 1;

FIG. 4 is a top view showing the battery pack of FIG. 1;

FIG. 5 is an external side view showing the battery pack of FIG. 1;

FIG. 6 is a perspective plan view showing an example of a flat heat pipe constituting the present invention.

FIG. 7 is a sectional view taken along the line AA of FIG. 6;

FIG. 8 is a cross-sectional view showing a second embodiment of the battery pack of the present invention.

FIG. 9 is a longitudinal sectional view showing a relationship between a unit cell and a heat pipe in the battery pack of FIG. 8;

FIG. 10 shows a third embodiment of the battery pack of the present invention,
FIG. 3 is a longitudinal sectional view showing a relationship between a unit cell and a heat pipe.

[Explanation of symbols]

2a and 2b are battery cases, 3 is a unit cell, 4 is a flat heat pipe, 5 is a radiation fin, 6 is a connection plate, and 7 is insulating paper.

Claims (8)

[Claims] 1. A battery pack comprising a plurality of unit cells connected in series and a battery case accommodating them therein, wherein a flat heat pipe is brought into contact with a surface of at least one of the unit cells to be attached thereto. And a heat radiation fin is attached to the outside of the battery case, and the heat radiation fin is thermally coupled to a heat radiation part of the flat heat pipe. 2. The battery pack according to claim 1, wherein the plurality of unit cells are cylindrical. 3. A flat heat pipe is deformed into a corrugated plate shape through the flat heat pipe while a plurality of cylindrical cells are stacked in a bale, and the flat heat pipe is brought into contact with the cells so as to be sandwiched by the cells. The battery pack according to claim 2, wherein the battery pack is attached. 4. A meandering thin-tube heat pipe in which at least one continuous thin tube formed in such a manner that the flat heat pipe is folded at both ends in the longitudinal direction so as to be close to and parallel to each other is provided in a flat plate. The battery pack according to any one of claims 1 to 3, wherein 5. The battery pack according to claim 1, wherein the flat heat pipe is formed of a synthetic resin having good heat conductivity. 6. The battery pack according to claim 1, wherein the flat heat pipe is formed of a synthetic resin having flexibility. 7. The battery pack according to claim 1, wherein an electric insulator having flexibility and heat conductivity is interposed between the flat heat pipe and the unit cell. 8. The battery pack according to claim 1, wherein a grease or an adhesive having thermal conductivity is interposed between the flat heat pipe and the unit cell.