JP2003308769A - Thermal fuse - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thermal fuse of low internal resistance and wide application temperature range. <P>SOLUTION: A lead wire, temperature sensitive metal body melting at a designated temperature, a pressing spring, a movable piece, a release spring and ceramic insulating and retaining another lead wire are enclosed in a bottomed metal case in order, and a tip of another lead wire is gotten into contact with the movable piece with repulsing against both springs. The temperature sensitive metal body is plated with nickel to prevent temperature sensitive metal body from scattering in melting. Spring pressures of both springs can be higher as compared to a conventional compressive pellet type to reduce contact resistance and maintain sure break. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an irreversible thermal fuse used in electronic equipment and electronic appliances.

[0002]

2. Description of the Related Art Conventional irreversible thermal fuses are classified into alloy type and pellet type. In the alloy type, an alloy wire that melts at a specific temperature is welded to a lead wire and put in a ceramic pipe. During use, the current always flows through the alloy wire,
There is a limit to the current value. About 2 amps is mainly used. On the other hand, the pellet type is a scientifically pure drug (powder) that melts at a specific temperature and is pressed into pellets. Since the current flows through the lead wire-movable section-metal case-lead wire,
10 amps or more is possible. Further, the movable section employs a highly elastic body obtained by adding a small amount of impurities to pure silver in order to reduce the contact resistance.

[0003]

However, the conventional alloy wire type and pellet type have a limited temperature range, which is not possible at 260 ° C. or higher. With the alloy linear type, current is always flowing, and it is impossible to exceed 10 amperes. Since the pellet has compressibility, the spring pressure of the opening spring 4 cannot be increased so much. This is because the movable piece 3 separates from the lead wire 9 during the encapsulation. Therefore, the movable piece 3 is made of soft pure silver. The present invention provides a metal pipe type inexpensive thermal fuse capable of withstanding a large current, capable of withstanding use even at 260 ° C. or higher, and having a lead wire of about 0.5 mm.

[0004]

[MEANS FOR SOLVING THE PROBLEMS] At the bottom of a bottomed metal case, a lead wire, a temperature-sensitive metal body that melts at a predetermined temperature, a pressing spring, a movable section, an opening spring, and a ceramic that insulates and holds the other lead wire. Sequentially arranged and sealed, the tip of the other lead wire is brought into contact with the movable section against both springs. A pressing spring may be arranged between the temperature-sensitive metal body and the lead wire.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The surface of a rod-shaped or pipe-shaped temperature-sensitive metal body 1 made of 100% tin is nickel-plated. The melting temperature is 220 degrees. The temperature sensitive metal body 1 having a melting temperature of 50 to 350 ° C. can be obtained by blending additives and employing another alloy.
Instead of nickel, chrome, iron, cobalt, gold, platinum, titanium, etc. may be plated or vapor-deposited on the surface of the temperature-sensitive metal body 1. The bottomed metal case 7 is formed mainly of copper with a slight addition of zinc, and the surface is silver-plated. At the bottom of the bottomed metal case 7, a lead wire 8, a rod-shaped temperature-sensitive metal body 1 that melts at a predetermined temperature, a pressing spring 2, a movable section 3, an opening spring 4, and the other lead wire 9 are held in an insulating manner. The ceramic 10 is sequentially arranged and sealed, and the lead wire 9
The tip of the is contacted with the movable piece 3 against both springs. Metal washers 6, 6 are arranged on both sides of the temperature-sensitive metal body 1, and a high melting point copper piece 5 is arranged between the pressing spring 2 and the movable piece 3. The temperature-sensitive metal body 1 is incompressible as compared with the conventional compressible temperature-sensitive pellet, and the pressure spring 2
Is sufficiently compressed and all the compression force is transmitted to the movable segment 3. Therefore, in the present invention, it is possible to increase the spring pressure (compressive force) of the opening spring 4 as compared with the temperature-sensitive pellet type, and it is possible to employ the inexpensive movable piece 3 of silver-plated copper. The movable piece 3 having a bent piece on the outer peripheral edge compresses the open spring 4 and abuts on the tip of the lead wire 9, and at the same time, due to its high elasticity, the bent piece is strong against the inner wall surface of the metal case. Abut (thus lower contact resistance). Ceramic 1
The opening of the metal case 7 is bent along 0 and sealed with the epoxy resin 11.

Next, the operation will be described. When the temperature reaches a predetermined temperature, the temperature-sensitive metal body 1 melts, both springs release the accumulated elastic energy, and the release spring 4 with high spring pressure moves the movable piece 3, the copper piece 5, etc. as shown in FIG. Let The movable piece 3 is separated from the lead wire 9 and the circuit is cut off. The pressure spring 2 bites into the temperature-sensitive metal body 1 having increased fluidity, and further facilitates the movement of the movable segment 3. The flow of the temperature-sensitive metal body 1 in which the highly heat-resistant copper piece 5 is melted is prevented. Since the surface of the temperature-sensitive metal body 1 is nickel-plated, there is no risk of reacting with flux or the like during melting and scattering.

The pressing spring 2 may be arranged between the temperature-sensitive metal body 1 and the lead wire 8. In this case, only one metal washer 6 is required. The rod diameter of the temperature-sensitive metal body 1 is smaller than the inner diameter of the metal case 7. A pipe shape may be used instead of the rod.

[0008]

In summary, according to the present invention, at the bottom of the bottomed metal case 7, the lead wire 8, the incompressible temperature-sensitive metal body 1 that melts at a predetermined temperature, the pressing spring 2, the movable piece 3, and the opening spring 4 are provided. , The ceramic 10 for insulating and holding the other lead wire 9 is sequentially arranged and sealed, and the tip of the lead wire 9 is brought into contact with the movable segment 3 against both springs, so that the electrical resistance is extremely small and the manufacturing is easy A small-diameter thermal fuse has become possible. Absorbency and sublimability like the pellet type and the problems of processing and molding were solved at once. An inexpensive thermal fuse with a wide range of applicable temperatures can be provided.

[Brief description of drawings]

FIG. 1 is a sectional view.

FIG. 2 is a cross-sectional view when a temperature-sensitive metal body is melted.

[Explanation of symbols]

1 temperature-sensitive metal body 2 Pressing spring 3 movable sections 4 Opening spring 5 Copper pieces 6 metal washers 7 metal case 8 lead wires 9 lead wire 10 Ceramic

Claims (8)

[Claims] 1. A lead wire 8, a temperature-sensitive metal body 1 that melts at a predetermined temperature, a pressing spring 2, a movable section 3, an opening spring 4, and the other lead wire 9 are insulated and held on the bottom of a bottomed metal case 7. A thermal fuse in which ceramics 10 are sequentially arranged and sealed, and the tip of the lead wire 9 is brought into contact with the movable section 3 against both springs. 2. Nickel, chrome, iron, cobalt,
The thermal fuse according to claim 1, wherein the surface of the temperature-sensitive metal body 1 is plated or vapor-deposited with gold, platinum, titanium, or the like. 3. The thermal fuse according to claim 1, wherein the movable piece 4 is formed by plating pure copper with silver. 4. The thermal fuse according to claim 1, wherein a copper piece 8 is interposed between the movable piece 4 and the pressing spring 2. 5. The thermal fuse according to claim 4, wherein metal washers 6 are arranged at both ends of the temperature-sensitive metal body 1. 6. A lead wire 8, a pressing spring 2, a temperature-sensitive metal body 1 that melts at a predetermined temperature, a copper piece 5, a movable piece 3, an opening spring 4, and a lead wire 9 are insulated from the bottom of a bottomed metal case 7. The ceramics 10 to be held are sequentially arranged,
Thermal fuse. 7. Nickel, chrome, iron, cobalt,
7. The thermal fuse according to claim 6, wherein the surface of the temperature-sensitive metal body 1 is plated or vapor-deposited with gold, platinum, titanium, or the like. 8. The thermal fuse according to claim 1, wherein the metal case 7 containing copper as a main component is plated with silver.