JP2000123705A - Thin current fuse - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thin current fuse which can shut off current safely, without melting the resin base film when overcurrent doesn't exceeds two times the rated current. SOLUTION: In this current fuse where a pair of electrodes 21, 21 are mounted on a resin base film 11. A current fuse element 3 is connected between the electrodes 21, 21. The resin base film is sealed by a case-like resin cover film, gap is arranged between the current fuse element 3 and the resin base film 11. Accordingly, even overcurrent not exceeding two times the rated current can be shut off in its flow safely certainly, and the thin current fuse can be mounted to a lithium ion secondary battery to thereby prevent an accident caused by the overcurrent due to internal short-circuiting.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin current fuse, and is useful for maintenance of a small device such as a lithium ion secondary battery.

[0002]

2. Description of the Related Art Recently, rechargeable and rechargeable secondary batteries have been used as power sources for portable telephones, PHSs, video cameras, portable personal computers, and the like. Are widely used because of their high life, long life cycle, and high operating voltage. In this lithium ion secondary battery, if an internal short circuit occurs, its high energy is released at once, and the battery is exposed to a dangerous state. Therefore, it is safe to incorporate a current fuse into the battery pack. The current fuse is required to be as thin as possible in order to guarantee the miniaturization of the battery pack. As this thin current fuse, a pair of strip-shaped leads are formed on a resin base film. There has been proposed a configuration in which the tip of a conductor is fixed, a current fuse element is connected between the tip of the conductor, and the temperature fuse element is sealed with a resin cover film.

[0003]

In the case of a current fuse, if the overcurrent is about twice the rated current, it takes several seconds to several tens of seconds to blow the fuse element. The fuse element is exposed to a temperature which is below the melting point of the fuse element, but considerably higher. However, in the conventional thin current fuse described above, when the fuse element is exposed to a high temperature for several tens of seconds, the resin base film remains in a state where the fuse element is not melted. It is melted and its insulating property is greatly reduced by heat melting, and it is difficult to operate the current fuse satisfactorily due to a short ground.

[0004] It is an object of the present invention to provide a thin current fuse that can safely prevent current from being melted and break down of a resin-based film even when the overcurrent is about twice the rated current. .

[0005]

A thin current fuse according to the present invention comprises a resin base film having a pair of electrodes, a current fuse element connected between the electrodes, and a resin base film. In which a gap is provided between the current fuse element and the resin base film, wherein the current fuse is sealed with a container-like resin cover film. It is preferable that the center of the resin base film is depressed.

[0006]

Embodiments of the present invention will be described below with reference to the drawings. 1A is a drawing showing a thin current fuse according to the present invention, and FIG.
FIG. In FIG.
Reference numeral 11 denotes a resin base film. Reference numerals 2 and 2 denote a pair of strip-shaped lead conductors. The leading ends of the respective lead conductors are fixed to the back surface of the resin base film 11 and a part thereof is exposed on the front side to form a pair of electrodes 21 and 21. Is provided. The fixation of the interface between the tip of each strip-shaped lead conductor 2 and the resin base film 11 can be performed by an adhesive or heat fusion. Reference numeral 3 denotes an arc-shaped current fuse element connected between the electrodes 21 and 21 by welding or the like, and a gap g is provided between the electrode fuse 21 and the resin base film 11. Numeral 12 denotes a container-shaped resin cover film, which has a hollow central portion, and the current fuse element 3 is sealed by bonding or fusing to the peripheral portion of the resin base film 11. “a” indicates a central depression.

[0007] The resin base film 11 and the current hue
The maximum gap between the elements 3 is 0.05 mm to 1.0 m
m, which corresponds to 0.5 to 10 times, preferably 3 to 7 times, the thickness of the strip-shaped lead conductor 2 or 0.25 to 20 times, preferably 1 to 15 times, the outer diameter of the current fuse element.

In the above description, the resin base film 11 and the resin cover film 12 have a thickness of 0.1 to 0.25 mm.
Thermoplastic resin film, preferably, an engineering plastic film such as polyamide, polyimide, polyethylene terephthalate, polybutylene terephthalate, or polysulfone. Is usually (3.0-
7.0) mm × (6.0 to 15.0) mm.

As the strip-shaped lead conductor 2, a thin plate of, for example, iron-nickel alloy, copper, copper-nickel alloy, nickel, copper-plated nickel or the like can be used, and its size is usually a thickness (70 to 120) μm × The width (3.0 to 5.0) mm.

[0010] The adhesive includes a polyamide-based, rubber-based,
Acrylic, epoxy, polyester, phenol, vinyl acetate, etc. hot melt, adhesive or thermosetting adhesives can be used.

The current fuse element 3 includes a metal having a solidus temperature of 600 ° C. or higher, for example, a silver-copper alloy, copper,
Copper-nickel alloy, nichrome or the like can be used, and the wire diameter is usually on the order of several hundreds to several tens of μm.

In contrast to the above embodiment, as shown in FIG. 2, the entire leading end of the strip-shaped lead conductor 2 is fixed to the surface side of the resin base film 11 by heat sealing or an adhesive or the like. 21 and 21 can also be provided.

In order to manufacture a thin current fuse according to the present invention, electrodes 21 and 21 are provided by fixing the respective tips of a pair of lead conductors 2 to a resin base film 11, and these electrodes are provided. A fuse body E having a current fuse element 3 connected between them is manufactured. In FIG. 3, first, a resin base film 11 of the fuse body E is set on a base 4.
On the resin base film 11, a fuse body E
In the direction orthogonal to the longitudinal direction of the conductor 2, a long groove-shaped molded resin cover film 120 (elongated resin cover film 1) is formed.
20 and the resin base film 11 are extended (equal width) and placed (spaced in FIG. 3 for convenience of illustration) and lengthened by an alignment jig (not shown). The length of the resin cover film 120 is aligned, and a concave c having an outer shell smaller than the outer shell of the resin base film 11 is formed.
(The bottom surface of the concave portion is raised to depress the central portion of the resin cover film.) The heating mold 5 having the lower portion is lowered to heat the long resin base film 120 to the resin base film 11. At the same time as fusing, resin cover film 12
Depress the center of 0.

In the heating mold 5, a resin base film 1
A Thomson blade is provided so as to cut the resin cover film 120 at both end edges of a width of 1 and the resin cover film 120 is cut at the same time as the above-mentioned heat fusion, or a heat mold 5 is provided separately. The resin cover film 120 is cut by the cutter after the above-mentioned heat fusion, thereby completing the production of the thin current fuse according to the present invention. Instead of the heating mold 5, ultrasonic welding can be performed using an ultrasonic welding tool horn having a concave portion.

In the above manufacturing method, if a fuse body (FIG. 1) having a lead wire tip fixed to the back side of the resin base film and partly exposed to the front side is used, The resin base film and the resin cover film can be directly fused without sandwiching the lead conductor, which is advantageous in sealing work.

In the above, the long resin cover film 1
20 is extended into the space above the resin base film 11, and both ends thereof are supported by a clamp or the like with a constant low gripping force, so that the heating mold resists the low gripping force of the long resin cover film. Thus, the lowering may be performed under a low tension (a low tension that does not substantially cause elongation of the long resin cover film). In the above, a plurality of fuse bodies are arranged in parallel,
It is also possible to arrange a long groove-shaped molded resin cover film on these, and to use this long resin cover film to seal all the fuse bodies arranged in parallel at once.

In the thin current fuse according to the present invention,
When an overcurrent of about twice the rated current flows, the current fuse element 3 is heated by the Joule generated heat to a temperature which is lower than the melting point of the current fuse element 3 but is considerably high for several seconds to several tens of seconds. You. However, since the central portion of the resin cover film is depressed, as soon as the air in contact with the current fuse element is heated by the heat generated by the joule and rises, the heat flow dissipates to both sides of the inner space of the cover. As a result, the temperature rise in the cover is reduced, and since a gap is provided between the current fuse element and the resin base film, the heating of the resin base film is reduced. The current fuse element can be heated to the melting temperature (solidus temperature) and melted without melting the base film. Therefore, even if an overcurrent of about twice the rated current flows, a ground fault due to thermal destruction of the resin base film at the stage where the current fuse element is not blown can be eliminated, and the current fuse can be prevented. The element can be safely melted.

[0018]

In the thin current fuse according to the present invention, energization can be safely and reliably interrupted even with an overcurrent of about twice the rated current, and since it is thin, it can be mounted on a lithium ion secondary battery. An accident caused by an overcurrent due to an internal short circuit or the like can be prevented.

[Brief description of the drawings]

FIG. 1 is a view showing an embodiment of a thin current fuse according to the present invention.

FIG. 2 is a view showing another embodiment of the thin current fuse according to the present invention.

FIG. 3 is a view illustrating a method of manufacturing a thin current fuse according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Resin base film 12 Resin cover film 2 Strip lead conductor 21 Electrode 3 Current fuse element a Depression of resin cover film g Gap

Claims (2)

[Claims] A pair of electrodes provided on a resin base film;
A current fuse element is connected between the electrodes, and a resin base is connected.
A current fuse formed by sealing a base film with a container-shaped resin cover film, wherein a gap is provided between the current fuse element and the resin base film. Z. 2. The thin current fuse according to claim 1, wherein a central portion of the container-shaped resin base film is depressed.