JPH07109745B2 - How to reset the alloy type thermal fuse - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Field of Industrial Application> The present invention relates to a method for restoring an alloy type thermal fuse.

<Prior Art> In an alloy type thermal fuse, a low melting point fusible alloy having a specific melting point corresponding to an allowable temperature of an electric device to be protected is used for a fuse element, and a portion of the electric device to be protected that easily generates heat. Attach it to and use it. Then, when an overcurrent flows through the electric device and the electric device heats up and reaches the allowable temperature, the fuse element of the temperature fuse is melted, the electric power to the electric device is cut off, and the electric device is thermally damaged and extended. Can prevent a fire from occurring.

<Problems to be Solved> By the way, in the conventional alloy type thermal fuse, it is practically impossible to return to the original state once the fuse element is melted, and it is originally intended for such purpose. Absent. As for the electric device, the part that causes heat generation is repaired and reused, but the thermal fuse is replaced with a new one.

The ideal local conditions for attaching a thermal fuse to electrical equipment are the locations where heat is most prominent when the equipment is abnormal, or the locations where heat is the weakest, but these locations are often insulators. Is covered, or
It is often practically impossible to replace the thermal fuse, for example, in a deep part of the equipment. For this reason, conventionally, the thermal fuse is attached to a location where replacement of the thermal fuse is easy and the above-mentioned positional conditions can be satisfied as much as possible.

In addition, due to the recent diversification of equipment, the allowable temperature of equipment has been varied. Therefore, the operating temperature of the alloy type thermal fuse is determined by the melting point of the low melting point fusible metal, and the melting point is regulated by the metal added to Pb and Sn. Therefore, depending on the allowable temperature of a specific device, it may be necessary to use an expensive alloy containing a noble metal, and it is uneconomical to dispose of such an expensive thermal fuse.

As described above, in the conventional alloy type thermal fuse, since it is assumed to be used for replacement or disposable, there is an irrational point such as a restriction on the mounting place or uneconomical. However, if the fuse element can be returned to the original connection state after the alloy type thermal fuse is actuated, that is, after the fuse element is blown, such irrationalities can be eliminated.

It is an object of the present invention to provide a method that can easily restore an alloy type thermal fuse.

<Means for Solving the Problems> A method for recovering an alloy type thermal fuse according to the present invention is such that a fuse element of an alloy type thermal fuse is formed of a low melting point fusible metal containing magnetic powder, and after the fuse element is cut off. The method is characterized in that the fusing fuse element is made deformable by heating from the outside, and the separating fuse element is coupled by magnetic force by causing magnetic force lines to act under such a condition.

<Description of Embodiments> Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows an alloy type thermal fuse used in the present invention.

In FIG. 1, 1.1 is a pair of lead conductors. Two
Is a low melting point fusible metal piece containing magnetic powder as a fuse element that can be bridged between lead conductors. It is possible to use Sn-Pb type alloy with magnetic powder such as iron type, cobalt type or nickel type added. . Reference numeral 3 is a flux coated on the fuse element. Reference numeral 4 is a heat-resistant insulating cylinder inserted on the fuse element, and 5 and 5 are heat-resistant adhesives for sealing between each end of the insulating cylinder and each lead conductor. Reference numeral 6 is a heater wound around an insulating cylinder, and an induction heating coil or an electric heating wire can be used.

In FIGS. 2A to 2D, A indicates the above-mentioned alloy type thermal fuse, which is attached to a predetermined position of the electric device to be protected.

FIG. 2A shows the normal state, the fuse element 2 is in the conductive state, and the induction heating coil 6 is cut off from the heating power source.

When the electrical equipment to be protected generates heat due to overcurrent and reaches the melting point of the low melting point soluble metal piece, the low melting point soluble metal piece melts as shown in FIG. 2B, and due to the surface tension of the molten metal. Spheroidize and divide (shown as 20 in FIG. 2). Due to this division, the electric power to the electric device is cut off, the electric device returns to normal temperature, and the separated soluble metal is fixed.

After inspecting the cause of heat generation in the electrical equipment and repairing the equipment, as shown in FIG. 2C, the induction heating coil 6 is energized to cut and fuse the fuse element piece 20.
2 to induce a deformable state by induction heating, and after that, the induction heating is stopped, and while the fuse element is still soft, a magnetic force line J in a direction substantially parallel to the lead conductor is made to act on the lead conductor.
Connect the fuse element pieces as shown in FIG.

The magnetic lines of force may be applied by using a magnet from outside the thermal fuse. Alternatively, the coil 6 may be ignited with a DC or AC voltage. In this case, as shown in FIG. 3, if the center of the end portion of the lead conductor is made of metal 10 having a high magnetic permeability, a high-density magnetic force line (magnetic flux) can be applied along the center of the lead conductor.

Although the induction heating coil is used as the heater in the above-described embodiment, a film resistor may be formed on the outer surface or the inner surface of the insulating cylinder so that the resistance is energized to generate heat, and a thermal fuse is incorporated. The equipment or components themselves may be heated.

The alloy type thermal fuse is not limited to a linear type, and various types can be used. For example, as shown in FIG. 4, electrodes are formed on the inner surfaces of heat-resistant insulating substrates 71 and 72 facing each other.
81.82 are provided, the lead conductor 1.1 is connected to each electrode 81.82, the low melting point soluble metal body 2 containing magnetic powder is bridged between both electrodes, and the flux is surrounded by the soluble metal body. A layer 3 may be provided, the periphery of which is molded with the heat-resistant resin 9, and the heater 6 is embedded in the molded body. In order to manufacture the thermal fuse shown in FIG. 4, a blacks material (for example, rosin) is melted, a low melting point soluble metal material (solder) and magnetic powder are mixed, and a block is formed from this mixture. Frame-molded, sandwich this block between insulating substrates with electrodes, wrap them around with a heat-resistant insulator (eg epoxy resin) with a melting point higher than that of the low melting point fusible metal, and then insulate The whole body is heated at a temperature slightly lower than the melting point of the body to melt the block, and under this melting, a magnetic flux of a method of attracting the magnetic powder between the electrodes is applied, and the magnetic powder and the molten state are melted together. A method of concentrating the melting point metal between the electrodes, wetting the electrode with the concentrated molten metal to electrically conduct the two, and then cooling the whole while stopping heating and applying the above magnetic flux. Can be used.

<Effects of the Invention> As described above, in the method for restoring the alloy-type thermal fuse according to the present invention, the fuse element is heated by the heater after the thermal fuse is actuated, that is, after the fuse element is blown, and then the magnetic field lines are applied. Is a method of reconnecting the divided fuse elements by means of a magnet, and as long as the lines of magnetic force can be exerted by the magnet, they are not restricted by the mounting position of the thermal fuse. Therefore, the thermal fuse can be mounted at a desired position. Further, even if an expensive metal having a low melting point is used, it can be reused upon restoration, which is economically advantageous.

[Brief description of drawings]

FIG. 1 is an explanatory view showing an alloy type thermal fuse used in the present invention, FIG. 2A, FIG. 2B, FIG. 2C and FIG.
FIG. D is an explanatory view of the fuse element of the present invention before and after fusing, and at the time of heating at the time of returning and after returning, and FIGS. 3 and 4 respectively show another example of the alloy type thermal fuse used in the present invention. FIG. 2 ... Low melting point metal piece containing magnetic powder, 6 ... Heater, J ... Magnetic field lines.

Claims (1)

[Claims] 1. A fuse element of an alloy type thermal fuse is formed of a low melting point fusible metal containing magnetic powder, and after the fuse element is cut off, the blown fuse element is made deformable by external heating. A method for recovering an alloy type thermal fuse, characterized in that magnetic field lines act in such a state to connect the separate fuse elements by magnetic force.