WO2013021637A1

WO2013021637A1 - Fusible link

Info

Publication number: WO2013021637A1
Application number: PCT/JP2012/005042
Authority: WO
Inventors: Asako Takahashi
Original assignee: Yazaki Corporation
Priority date: 2011-08-09
Filing date: 2012-08-08
Publication date: 2013-02-14
Also published as: CN103608888A; JP2013037929A; BR112013033305A2; KR101534277B1; KR20140036004A; CN103608888B; JP6023410B2

Abstract

A fusible link (1) includes: an elongated conducting body (10) having wire parts (15) provided at both end portions in a longitudinal direction of the conducting body (1), and a fusion-cutting part (11) provided at an intermediate portion of the conducting body (1) in the longitudinal direction, the fusion-cutting part (11) being formed by a rolling process so as to have a cross section smaller than each of cross sections of the wire parts (15) and being fusible by flow of current having a predetermined value; a low-fusing-point metal body (13) welded to the fusion-cutting part (11) and having a lower fusing point than the conducting body (10); and a fire-proof insulating body (12) configured to cover at least the fusion-cutting part (11) and the low-fusing-point metal body (13).

Description

FUSIBLE LINK

The present invention relates to a fusible link having a fusion-cutting part fusion-cut when current of a predetermined value or higher flows therein.

A fusible link is used for, e.g., distributing and feeding current of an automobile battery to a load connected to the battery. Fig. 1 illustrates a fusible link 101 disclosed in Patent Literature 1. The fusible link 101 has a conducting body 102 having a thin strip-plate shape. A first terminal part 103 to be connected to a battery terminal of a battery is provided at one end in a longitudinal direction of the thin plate conducting body 102, and a second terminal part 104 to be connected to a connecting wire from a load in an automobile body is provided at the other end in the longitudinal direction thereof. A fusion-cutting part 105 is formed at an intermediate portion of the thin plate conducting body 102 in the longitudinal direction thereof. The conducting body 102 having such a configuration is covered in its entirety by an insulating coating.

The fusion-cutting part 105 is formed into a thin strip shape. That is, the fusion-cutting part 105 is formed thinner than other portions of the conducting body 102 and has a smaller cross section area than other portions of the conducting body 102. Accordingly, the fusion-cutting part 105 has a higher electric resistance than other portions of the conducting body 102. In such a fusible link 101, when current having a value equal to or higher than a predetermined value (i.e., overcurrent) flows in the conducting body 102, the fusion-cutting part 105 generates more heat than other portions of the conducting body 102, and the fusion-cutting part 105 is fusion-cut by the generated heat. This can prevent overcurrent from flowing in the connecting wire from the load to thereby prevent the load from being adversely affected due to the overcurrent, which in turn prevent the load from being damaged.

DE 19512113 A1

However, in the fusible link 101 of the related art, the fusion-cutting part 105 is merely formed thinner than other portions of the conducting body 102, but a fusion-cutting temperature of the fusion-cutting part 105 is equal to the fusion-cutting temperature of other portions of the conducting body 102. Thus, a time required for fusion-cutting the fusion-cutting part 105 becomes longer in an interlayer short-circuit area to make it difficult to achieve fast and reliable fusion-cutting, which may result in deterioration of safety. Further, flowing of low current may cause the insulating coating to burn.

An object of the present invention is to provide a fusible link capable of reliably fusion-cutting the fusion-cutting part at short times and lowering the risk that the insulating coating may burn.

An aspect of the present invention is a fusible link including: an elongated conducting body having wire parts provided at both end portions in a longitudinal direction of the conducting body, and a fusion-cutting part provided at an intermediate portion of the conducting body in the longitudinal direction, the fusion-cutting part being formed by a rolling process so as to have a cross section smaller than each of cross sections of the wire parts and being fusible by flow of current having a predetermined value; a low-fusing-point metal body welded to the fusion-cutting part and having a lower fusing point than the conducting body; and a fire-proof insulating body configured to cover at least the fusion-cutting part and the low-fusing-point metal body.

According to the aspect, the fusion-cutting part has a smaller cross-section than the wire part of the conducting body to make an electric resistance of the fusion-cutting part higher than that of the wire part, with the result that efficient temperature rise of the fusion-cutting part can be achieved by current flowing therein. That is, the fusion-cutting part exhibits a significant temperature rise. Further, the low-fusing-point metal body is welded to the fusion-cutting part to cause allowing and diffusion of the low-fusing-point metal body with/to the fusion-cutting part, making the fusing point of the fusion-cutting part lower than that of the wire part of the conducting body. This makes the fusion-cutting temperature of the fusion-cutting part lower than that of the wire part of the conducting body, allowing the fusion-cutting part to be fusion-cut at a temperature lower than a temperature at which the wire part is fusion-cut. Further, the fire-proof insulating body covers the fusion-cutting part and the low-fusing-point metal body, which prevents the heat generated in the fusion-cutting part from escaping outside to allow the temperature of the fusion-cutting part to rise efficiently. Thus, when current having a value equal to or higher than a predetermined value flows in the fusible link, the fusion-cutting part is fusion-cut reliably at short times, so that the connecting wire on the load side can be protected either in an inter-layer short-circuit area or a dead short-circuit area. Further, the insulating coating can be prevented from burning.

The fire-proof insulating body may include: an insulating cylinder body made of ceramics configured to cover the fusion-cutting part and the low-fusing-point metal body; and a fire-proof insulating tape configured to cover the insulating cylinder body and the wire parts of the conducting body.

According to the above configuration, the fire-proof insulating body is constituted by the insulating cylinder body made of ceramics which covers the fusion-cutting part and the low-fusing-point metal body and the fire-proof insulating tape which covers the insulating cylinder body and the wire parts of the conducting body, thereby allowing the ceramic insulating cylinder body to be fixed by the fire-proof insulating tape so as to reliably cover the fusion-cutting part. The ceramic insulating cylindrical body fixed so as to cover the fusion-cutting part prevents heat generated from the fusion-cutting part from escaping outside to allow the fusion-cutting part to be fusion-cut reliably at short times, whereby a connecting wire on the load side can be protected.

The insulating cylinder body may have a higher fusing point than at least the conducting body.

According to the above configuration, the insulating cylinder body has a higher fusing point than the conducting body, which prevents the insulating cylinder body from being fused by the heat of the fusion-cutting part, thereby allowing a state where the insulating cylinder body covers the fusion-cutting part to be maintained. This reliably can prevent the heat of the fusion-cutting part from escaping outside.

The insulating cylinder body may be fixed to outer peripheral surfaces of the wire parts on both sides of the fusion-cutting part in such a manner as not to contact the fusion-cutting part having the low-fusing-point metal body welded thereon.

According to the above configuration, the insulating cylinder body is fixed to the outer peripheral surfaces of the wire parts on the both sides of the fusion-cutting part in such a manner as not to contact the fusion-cutting part. Thus, the insulating cylinder body covering the fusion-cutting part can trap the heat of the fusion-cutting part thereinside. In addition, the heat of the fusion-cutting part is not transferred to the insulating cylinder body since the fusion-cutting part and insulating cylinder body do not contact each other. Thus, the temperature of the fusion-cutting part rises efficiently, allowing the fusion-cutting part to be fusion-cut at short times.

Fig. 1 is a perspective view illustrating a fusible link according to a related art. Figs. 2(a) to 2(d) are perspective views illustrating a fusible link according to an embodiment of the present invention along a production process thereof. Figs. 3(a) and 3(b) are a plan view and a side view, respectively, illustrating the fusible link according to the embodiment of the invention. Fig. 4 is a graph representing fusion-cutting characteristics.

Hereinafter, an embodiment of the present invention will be described concretely with reference to the drawings.

Figs. 2(a) to 2(d) illustrate a production process of a fusible link 1 according to the embodiment of the invention, and Figs. 3(a) and 3(b) illustrates a shape of the produced fusible link 1.

The fusible link 1 has an elongated conducting body 10 (Fig. 2(a)), a fusion-cutting part 11 (Fig. 2(b)) provided at an intermediate portion of the conducting body 10, a low-fusing-point metal body 13 (Fig. 2(c)) welded to the fusion-cutting part 11, and a fire-proof insulating body 12 (Figs. 2(c), 2(d) and Fig. 3) covering the fusion-cutting part 11. The fire-proof insulating body 12 is constituted by an insulating cylinder body 17 and a fire-proof insulating tape 18 (Figs. 3(a) and 3(b)).

The conducting body 10 is formed into an elongated rod-like shape using a thin twisted wire made of a conductive metal. Alternatively, the conducting body 10 may be formed into an elongated shape using a conductive metal strip. Examples of the conductive metal include copper, silver, aluminum, and an alloy thereof.

The fusion-cutting part 11 is provided at an intermediate portion of the conducting body 10 in a longitudinal direction thereof. The fusion-cutting part 11 is obtained by rolling the intermediate portion of the conducting body 10 and, thus, the fusion-cutting part 11 has a smaller cross section area than other portions of the conducting body 10. That is, the fusion-cutting part 11 is formed so as to have a smaller cross section than a wire part 15 of the conducting body 10 denoted by a symbol D of Fig. 2(b). The smaller cross section area of the fusion-cutting part 11 results in a smaller heat capacity thereof than the wire part 15. Further, an electric resistance of the fusion-cutting part 11 becomes higher than that of the wire part 15. It follows that the fusion-cutting part 11 generates more heat than the wire part 15 and exhibits a more significant temperature rise than the wire part 15.

The low-fusing-point metal body 13 is welded to the fusion-cutting part 11. The low-fusing-point metal body 13 is made of a metal having a lower fusing point than the conducting body 10. Examples of this metal include tin, cadmium, lead, bismuth, indium, and an alloy thereof. The welding of the low-fusing-point metal body 13 to the fusion-cutting part 11 causes alloying of the low-fusing-point metal body 13 with the fusion-cutting part 11 and diffusion of the low-fusing-point metal body 13 to the fusion-cutting part 11. The alloying and diffusion of the low-fusing-point metal body 13 makes a meting point of the fusion-cutting part 11 lower than that of the wire part 15, which in turn makes a fusion-cutting temperature of the fusion-cutting part 11 lower than that of the wire part 15.

The fire-proof insulating body 12 covers the fusion-cutting part 11 and the low-fusing-point metal body 13 and prevents heat generated in the fusion-cutting part 11 from escaping outside. This achieves efficient temperature rise of the fusion-cutting part 11.

The fire-proof insulating body 12 is constituted by the insulating cylinder body 17 made of ceramics (Fig. 2(c)) and fire-proof insulating tape 18 (Figs. 3(a) and 3(b)) for fixing the insulating cylinder body 17 to the wire part 15 of the conducting body 10.

The insulating cylinder body 17 has a cylinder body having a length longer than that of the fusion-cutting part 11. An inner diameter of the insulating cylinder body 17 is equal to or slightly larger than an outer diameter of the conducting body 10 so as to allow the conducting body 10 to be inserted through the insulating cylinder body 17. The insulating cylinder body 17 is inserted through the conducting body 10 and disposed so as to cover the fusion-cutting part 11 to which the low-fusing-point metal body 13 has been welded and traps heat generated from the fusion-cutting part 11 thereinside to prevent the heat from escaping outside.

When the insulating cylinder body 17 is to be provided so as to cover the fusion-cutting part 11, both end portions of the insulating cylinder body 17 are fixed to outer peripheral surfaces of the wire parts 15 on both ends of the fusion-cutting part 11. This fixation is made by looping the fire-proof insulating tape 18 around the insulating cylinder body 17 and wire part 15. Since the fusion-cutting part 11 is smaller in cross section area than the wire part 15 of the conducting body 10, the insulating cylinder body 17 that has been fixed to the outer peripheral surfaces of the wire parts 15 does not contact the fusion-cutting part 11. The non-contact state between the insulating cylinder body 17 and fusion-cutting part 11 prevents heat generated in the fusion-cutting part 11 from being transferred to the insulating cylinder body 17. This can achieve efficient temperature rise of the fusion-cutting part 11.

The insulating cylinder body 17 is made of ceramics having a higher fusing point than the conducting body 10, which prevents the insulating cylinder body 17 from being fused by the heat of the fusion-cutting part 11 earlier than the conducting body 10. This allows a state where the insulating cylinder body 17 covers the fusion-cutting part 11 to be maintained reliably.

As the fire-proof insulating tape 18, a fire-proof mica tape having insulation properties, etc., is used. The fire-proof insulating tape 18 is looped around an outer peripheral surface of the insulating cylinder body 17 and an outer peripheral surface of the wire part 15. As a result, the insulating cylinder body 17 is fixed to the wire part 15 of the conducting body 10 so as to cover the fusion-cutting part 11. The fire-proof insulating tape 18 functions as an insulating coating covering the fusible link 1.

The following describes a production procedure of the fusible link 1 according to the embodiment. A rolling process is applied to the longitudinal direction intermediate portion of the conducting body 10 in a state of Fig. 2(a) to form the fusion-cutting part 11 having a smaller cross section than the wire part 15 (Fig. 2(b)). The low-fusing-point metal body 13 is then welded to the formed fusion-cutting part 11 (Fig .2(c)). Subsequently, the conducting body 10 is inserted through the insulating cylinder body 17 until the insulating cylinder body 17 is located at a position covering the fusion-cutting part 11 (Fig. 2(d)). In this case, the insulating cylinder body 17 may be temporarily fixed by a not illustrated clip or the like to the conducting body 10, whereby the insulating cylinder body 17 can temporarily be fixed to the conducting body 10 so as to cover the fusion-cutting part 11.

In addition, terminal metal members 20 are fitted to both end portions of the conducting body 10. Each of the terminal metal members 20 has a caulking part 21 and a terminal part 22, and the caulking part 21 is caulked onto the conducting body 10 to thereby fit the terminal metal member 20 to the conducting body 10. The terminal parts 22 on both ends of the conducting body 10 are connected to connecting wires from a battery terminal and a load, respectively.

Thereafter, as illustrated in Figs. 3(a) and 3(b), the fire-proof insulating tape 18 is looped around the outer peripheral surfaces of the insulating cylinder body 17 and wire part 15, whereby the insulating cylinder body 17 is fixed to the position covering the fusion-cutting part 11.

Fig. 4 represents fusion-cutting characteristics. A solid-line curve represents a conducting body of a comparative example having the fusion-cutting part 11 and low-fusing-point metal body 13 which are not welded to each other, and a broken-line curve represents the fusible link 1 according to the present embodiment having the fusion-cutting part 11 and low-fusing-point metal body 13 which are welded to each other. In the present embodiment, the conducting body 10 has the fusion-cutting part 11 having a smaller cross section area than the wire part 15, so that the temperature of the fusion-cutting part 11 rises efficiently. The insulating cylinder body 17 covers the fusion-cutting part 11 in a non-contact manner, which prevents heat of the fusion-cutting part 11 from being transferred to the insulating cylinder body 17 and further prevents the heat from escaping outside the insulating cylinder body 17. As a result, the fusion-cutting characteristics change from a of Fig. 4 to b as denoted by an arrow. Further, the low-fusing-point metal body 13 is welded to the fusion-cutting part 11 to cause allowing and diffusion of the low-fusing-point metal body 13 with/to the fusion-cutting part 11, making the fusing point of the fusion-cutting part 11 lower than that of the wire part 15. As a result, the fusion-cutting characteristics change from c of Fig. 4 to d as denoted by an arrow.

According to the embodiment described above, the fusion-cutting part 11 is formed so as to have a smaller cross section than the wire part 15 of the conducting body 10 to make the electric resistance of the fusion-cutting part 11 higher than that of the wire part 15, thereby achieving efficient temperature rise of the fusion-cutting part 11. Further, the low-fusing-point metal body 13 is welded to the fusion-cutting part 11 to cause allowing and diffusion of the low-fusing-point metal body 13 with/to the fusion-cutting part 11, making the fusing point of the fusion-cutting part 11 lower than that of the wire part 15 of the conducting body 10, which in turn makes the fusion-cutting temperature of the fusion-cutting part 11 lower than that of the wire part 15 of the conducting body 10. Further, the fire-proof insulating body 12 covers the fusion-cutting part 11 and the low-fusing-point metal body 13, which prevents the heat from escaping outside to allow the temperature of the fusion-cutting part 11 to rise efficiently. Thus, when current having a value equal to or higher than a predetermined value flows in the fusible link 1, the fusion-cutting part 11 is fusion-cut reliably at short times, the connecting wire on the load side can be protected either in an inter-layer short-circuit area or a dead short-circuit area. Further, the fire-proof insulating tape 18 can be prevented from burning.

In the fire-proof insulating body 12, the insulating cylinder body 17 made of ceramics is fixed by the fire-proof insulating tape 18 so as to reliably cover the fusion-cutting part 11. This can prevent heat generated from the fusion-cutting part 11 from escaping outside to allow the fusion-cutting part 11 to be fusion-cut reliably at short times, whereby the connecting wire on the load side can be protected.

The insulating cylinder body 17 has a higher fusing point than the conducting body 10, which prevents the insulating cylinder body 17 from being fused by the heat of the fusion-cutting part 11, thereby allowing a state where the insulating cylinder body 17 covers the fusion-cutting part 11 to be maintained. This reliably can prevent the heat of the fusion-cutting part 11 from escaping outside.

The cylinder body 17 covers the fusion-cutting part 11 in a non-contact manner, allowing the heat of the fusion-cutting part 11 to be trapped inside the insulating cylinder body 17 and preventing the heat of the fusion-cutting part 11 from being transferred to the insulating cylinder body 17. Thus, the temperature of the fusion-cutting part 11 rises efficiently, allowing the fusion-cutting part to be fusion-cut at short times.

Although the present invention has been described above by reference to the embodiments, the present invention is not limited to those and the configuration of parts can be replaced with any configuration having a similar function.

The entire content of Japanese Patent Application No. 2011-173716, filed on August 9, 2011, is herein incorporated by reference.

Claims

A fusible link comprising:
an elongated conducting body having wire parts provided at both end portions in a longitudinal direction of the conducting body, and a fusion-cutting part provided at an intermediate portion of the conducting body in the longitudinal direction, the fusion-cutting part being formed by a rolling process so as to have a cross section smaller than each of cross sections of the wire parts and being fusible by flow of current having a predetermined value;
a low-fusing-point metal body welded to the fusion-cutting part and having a lower fusing point than the conducting body; and
a fire-proof insulating body configured to cover at least the fusion-cutting part and the low-fusing-point metal body.
The fusible link according to claim 1, wherein the fire-proof insulating body comprises:
an insulating cylinder body made of ceramics configured to cover the fusion-cutting part and the low-fusing-point metal body; and
a fire-proof insulating tape configured to cover the insulating cylinder body and the wire parts of the conducting body.
The fusible link according to claim 2, wherein the insulating cylinder body has a higher fusing point than at least the conducting body.
The fusible link according to any one of claims 2 and 3, wherein the insulating cylinder body is fixed to outer peripheral surfaces of the wire parts on both sides of the fusion-cutting part in such a manner as not to contact the fusion-cutting part having the low-fusing-point metal body welded thereon.