JPH0731970B2 - Thermal fuse - Google Patents

Description

TECHNICAL FIELD The present invention relates to a thermal fuse that instantly opens an open circuit when a set temperature is reached.

[Conventional technology]

A thermal fuse is used to protect the circuit of an electric device from abnormal current and heat generation, and to prevent fire by opening the circuit at a preset ambient temperature or Joule heat in the circuit. In the conventional thermal fuse generally used, a spring plate is bridged between two lead wires facing each other or parallel to each other, and the spring material and each lead wire end are welded with a fusible alloy.

[Problems to be Solved by the Invention] In a conventional thermal fuse, when a temperature preset in the electric circuit itself is reached by ambient temperature of electric equipment or Joule heat, a fusible alloy bridged between lead wires is melted to cause electric circuit. Is released. However, the time required for the fusible alloy to melt after the temperature reaches the set temperature and the electric circuit is opened by the elastic force of the spring material is 20 to 30 seconds, which delays the opening of the electric circuit. Various electric devices in the remarkable era of technological innovation in recent years have been refined, and it is desirable to open the circuit as soon as possible when the set temperature is reached in order to protect the circuit and each component of the device.

In view of this, it is an object of the present invention to provide a thermal fuse that sequentially opens electric circuits at a speed of about 1/10 of the conventional one.

[Means for Solving the Problems]

The thermal fuse of the present invention is made in order to achieve the above-mentioned object, and a coil spring is erected in a state where the end portions are extended between two lead wires facing each other with a predetermined separation distance. One end side of the is welded or caulked, the other end side is brazed with a fusible alloy that melts at a set temperature to be integrated with both lead wires, and the stretched coil spring is filled with a fusible alloy that melts at the set temperature A coil spring is erected in a state in which a solidified operating piece is formed or the two ends of the coil spring are extended between the two lead wires facing each other with a predetermined separation distance, and both ends of the coil spring are welded or An actuating piece that is crimped and integrated with both lead wires, and is filled with a fusible alloy that melts at a set temperature in the stretched coil spring and then solidified, and then the central portion is cut. And brazing in fusible alloy which dissolves the cutting unit at a set temperature and summarized in that was integrally.

[Action]

One end of the coil spring pulled between the opposing lead wires is fixed to one lead wire, and the other end is brazed to the other lead wire with a fusible alloy that is a fuse alloy. Since the operating piece filled with and solidified with the fusible alloy is integrally provided, the temperature of the temperature fuse itself due to the ambient temperature of this temperature fuse or Joule heat reaches a preset temperature, and the fusible alloy is melted. Once started, if the brazing force between the coil spring and the lead wire becomes less than the contracting force of the coil spring even if it is not completely melted, the contracting force of this coil spring separates it from the brazing side lead wire of the coil spring and welds it. Or it is pulled by caulking to the fixed lead wire side, and the lead wire ends have a predetermined spacing, and the electric circuit is opened about 1/10 instantly compared to the conventional product. It

Also, when the coil spring is extended and both ends are fixed to the opposing lead wire, the fusible alloy begins to melt in the thermal fuse in which the fusible alloy is filled and solidified and then cut and brazed again. The cut surface of the coil spring instantly draws it toward both sides of the spring, and the electric circuit is instantly opened from the central portion of the coil spring to both sides with a predetermined separation distance.

This makes it possible to more reliably protect the electric circuit and the electric device.

〔Example〕

 The present invention will be described below based on the illustrated embodiments.

In the figure, 1 and 2 are lead wires which face each other, and which have required conductivity and thickness, and are arranged such that the facing end portions of the lead wires 1 and 2 have a predetermined separation distance. This is determined so that the lead wires 1 and 2 can be reliably separated from each other and the electric path can be opened even after the fusible alloy is melted. Reference numeral 3 denotes a coil spring bridged in a tensioned state between the opposing end portions of the lead wire. In the first embodiment, one end portion of one lead wire 1 is fitted with one end of the coil spring 3.
After welding by welding or by caulking the end of the coil spring to firmly fix it to the lead wire 1, the other end side pulls the coil spring to fit the lead wire 2, and then fits the lead wire 2 and the coil spring. The parts are brazed with a fusible alloy 4 which is a fuse alloy, and thereby the coil spring 3 is fixed in a tensioned state between the opposing lead wires 1 and 2. The ends of the lead wires 1 and 2 are inserted into a cylindrical or flat box-shaped casing 5 made of ceramic or other material, and the casing end faces are sealed and compounded with epoxy resin or the like to be integrated.

In addition, a fuse alloy, which is a fusible alloy, is melted, filled and solidified in the coil spring 3 that is stretched before fitting and fixing the one obtained by bridging the coil spring 3 between the opposing lead wires. Let it be the operating piece 4. The operating piece 4 may be filled in the inside of the coil spring 3, that is, in the hollow portion, but the entire coil spring may be covered with a fusible alloy.

A sectional view of the first embodiment is shown in FIG. 1, and its operating state is shown in FIG. When the temperature reaches the set temperature, the fuse alloy is designed to melt, so when the temperature fuse reaches this set temperature, the fusible alloy begins to melt, and even if it does not completely melt, the lead wire and coil spring are When the adhesion force becomes weak, the contracting force of the coil spring in the tensioned state causes the spring to be forcibly drawn to the fixed side, and the electric circuit is opened as shown in FIG. In this case, the melted fusible alloy is moved together by the contracting force of the coil spring to the fixed side. Therefore, as compared with the conventional product, the time required to open the electric circuit is 1/10 or less as shown in FIG. 3, and the operation is accurate.

FIG. 4 shows a second embodiment in which a coil spring is bridged in a tension state between opposing lead wires 1 and 2, and both ends of the coil spring 3 are connected to the lead wires 1 and 2, respectively.
Fix it to 2 by welding or caulking. Then, after the fusible alloy is melted and filled in the coil spring and solidified to form the operating piece 4, the central portion of the operating piece 4 is cut. By this cutting, the coil spring is restrained in a tension state by the solidified fusible alloy, but it is cut into two. Next, the cut surface is pressed and brazed with the fusible alloy and integrated again to form a thermal fuse.

In this embodiment, when the fusible alloy is melted, the coil spring is attracted from the cutting position in the left and right directions, and the fusible alloy of the operating piece is moved to both the lead wires 1 and 2, and a required separation distance is provided in the central portion. This is what you do.

FIG. 5 shows a third embodiment in which the current capacity is increased and the whole is flattened. Lead wires 11 and 12 are flat lead plates and are provided between the opposing lead wires 11 and 12. Is 2
The coil springs 31 and 32 are bridged in a tension state and filled with a fusible alloy to make the operating piece flat, and the casing 50
Is also flat.

FIG. 6 shows a fourth embodiment, and a casing with one surface opened.
Insert the ends of the two lead wires 1 and 2 into the 51 with different lengths, fix one end of the coil spring 33 to the shorter lead wire by welding or caulking, and bend the coil spring. And the other end side is brought into contact with the side surface of the other lead wire 2, brazed with a fusible alloy, and the inside of the bent coil spring is filled and solidified with the fusible alloy to form an operating piece.
In this case, when the fusible alloy is melted, the coil spring in the bent state is released from the restrained state by the fusible alloy to be in an upright state, and the electric circuit is opened.

〔Test method〕

Raise the container filled with silicone oil at a rate of 1 ° C / min,
Raise each sample to the operating temperature of the thermal fuse and keep it at a constant temperature with a temperature controller, then measure each sample at the time of charging and when melting, calculate the time required for melting and calculate the average value of three times And compared.

This is shown in FIG.

〔The invention's effect〕

In the conventional thermal fuse, when the fusible alloy melts, it separates naturally and slowly in the direction of the two opposing lead wires due to the pine resin type flux action and surface tension, so the response speed of the alloy is slow and the electric circuit is opened. The ambient temperature may rise further and damage the parts of equipment. On the other hand, in the present invention, the response speed at the time of melting of the alloy is fast, the circuit can be opened quickly by the forced operation of the coil spring at the operating point, and the organic substance such as flux is not used unlike the conventional case, so that the current interruption is prevented. It is possible to maintain stable quality for a long period of time without deterioration or aging of functions, and to obtain a product with high accuracy and reliability. Furthermore, since it does not use pine resin type flux, it has the advantage that it can be used as a high temperature temperature fuse that operates at 100 ° C or higher.

[Brief description of drawings]

FIG. 1 is a sectional view of the first embodiment, FIG. 2 is an operation explanatory view, FIG. 3 is a test comparison diagram of the product of the present invention and a conventional product, and FIG.
5 is a sectional view of the third embodiment, and FIG. 6 is a sectional view of the fourth embodiment. 1, 2 are lead wires, 3 are coil springs, 4 are actuating pieces,
5 is a casing

Claims (2)

[Claims] Claim: What is claimed is: 1. A coil spring is erected between two lead wires facing each other with a predetermined separation distance from each other, and one end of the coil spring is welded or caulked, and the other end is set. It is characterized in that a fusible alloy that melts at a temperature is brazed to be integrated with both lead wires, and a working piece is formed by filling and solidifying a fusible alloy that melts at a set temperature in the expanded coil spring. Thermal fuse. 2. A coil spring is installed so as to extend between two lead wires facing each other with a predetermined separation distance from each other, and both ends of the coil spring are welded or caulked to be integrated with both lead wires. And, after the melted alloy that melts at the set temperature is filled and solidified in the expanded coil spring, the cut part of the operating piece whose central part is cut is brazed with the melted alloy that melts at the set temperature. A thermal fuse characterized by being integrated.