JP2750891B2 - Alloy type thermal fuse - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an improvement in an alloy type thermal fuse.

<Prior Art> As shown in FIG. 2, a low melting point fusible metal 2 '(usually solder) is welded between lead conductors 1', 1 'coated with an insulating layer 11', as shown in FIG. The low melting point soluble metal 2 'is coated with a flux 3', and both lead conductors 1 '
Insert the insulating cylinder 4 'over the end of the insulating layer 1',
It is known that the space between each end of the insulating cylinder and each lead conductor insulating layer is sealed with a sealing material 5 'such as an epoxy resin.

As is well known, the thermal fuse is used by being attached to a portion of the electrical equipment to be protected where heat is easily detected.
Thus, when the electrical equipment to be protected generates heat due to an overcurrent, the temperature fuse is heated by the generated heat to melt the low melting point fusible alloy, the molten alloy is cut off, and the power supply to the electrical equipment is cut off. In addition, abnormal heating of the equipment is prevented.

In the above-described mechanism for dividing the molten alloy, the molten alloy tends to be spherical due to its surface tension, and the molten alloy is divided along with the spheroidization. In this case, if an oxide film is present on the surface of the low-melting-point fusible alloy before the melting, the oxide film becomes an insoluble hard outer skin, so that spheroidization is difficult even when the outer skin is in a molten state. . Thus, a flux is applied to the surface of the low melting point fusible alloy piece in order to prevent the formation of such an oxide film. In such a flux, it is necessary to impart an activity of rapidly reacting with an oxide to solubilize the oxide at a high temperature at which the low melting point fusible alloy is melted. Is used.

<Problem to be Solved> By the way, in the current interrupting operation of the alloy type thermal fuse, at the moment when the molten alloy is cut by the progress of spheroidization, the cutting distance is still short, so that it is in a state of conduction by an arc. When the arcing progresses and the division distance increases, and the arc discharge cannot be maintained, the interruption is completely performed. Thus, a part of the flux is carbonized by the arc at the instant of the division, and the carbonized flux loses its activity and slows the spheroidization of the molten alloy. Usually, the amount of flux in solder is smaller than the amount of solder,
In the case of a thermal fuse, as described above, a part of the flux is carbonized during the cutting of the molten metal and substantially disappears.
%), It is necessary to use a larger amount of flux. In the thermal fuse shown in FIG. 2, the low melting point alloy 2 'welded between the lead conductors 1' and 1 'is used.
Flux 3 'is applied on top, then low melting point alloy 2'
When inserting the insulating cylinder 4 'while guiding it on the outer surface of the insulating layer, the applied flux is wiped at the tip of the insulating cylinder 4', and the amount of the flux to be wiped off is large. In this case, the amount of flux becomes smaller than the amount of low-melting metal, which is disadvantageous for the above-mentioned division, which is a problem in the operation of the thermal fuse.

In view of the fact that the amount of the flux wiped off by the insulating cylinder is influenced by the outer diameter of the insulating coating layer of the lead wire, an object of the present invention is to provide a ratio of the outer diameter of the low melting point metal to the outer diameter of the coating layer. The purpose of the present invention is to provide an alloy type thermal fuse excellent in operability by ensuring a sufficient amount of flux with respect to the amount of low melting point metal.

<Means for Solving the Problems> An alloy-type thermal fuse according to the present invention is characterized in that a low-melting-point fusible metal is joined between insulating-coated lead conductors, and the low-melting-point fusible metal is coated with a flux. The insulating cylinder is inserted over the end of the insulating coating layer of the conductor, and the gap between each end of the insulating cylinder and the insulating coating layer of each insulating coating lead conductor is sealed with a sealing material. The low melting point of the outer diameter of the soluble metal This is a configuration characterized by the following.

<Description of Example> Hereinafter, an example of the present invention will be described with reference to the drawings.

In FIG. 1, reference numeral 1.1 denotes a lead conductor, which is an insulating layer.
11 (vinyl chloride, nylon, polyethylene, etc.). Reference numeral 2 denotes a low-melting-point fusible metal body welded between lead conductors, and solder can be used. The outer diameter of the low melting point fusible metal body is usually 0.8 to 1.3 times the lead conductor diameter. Reference numeral 3 denotes a flux coated on the low-melting-point fusible alloy body 2, and a flux obtained by adding an activator to rosin as necessary can be used. Reference numeral 4 denotes an insulating cylinder that extends over both ends of the insulating layer and is inserted on the low-melting-point fusible alloy 2, and a ceramic tube can be used. Reference numeral 5 denotes a sealing material, which can use an epoxy resin.

In the above, the outer diameter R of the insulating layer 11 is equal to the outer diameter r of the low melting point fusible metal body 2. There is.

In the manufacture of the thermal fuse, the flux is applied slightly thicker than the outer diameter R of the insulating layer, and then the insulating tube 4 is inserted. In this case, the insulating cylinder moves while being guided by the outer surface of the insulating layer, and the outer peripheral portion of the thick coating flux is wiped on the front end surface of the insulating cylinder. Thus, the ratio between the low melting point metal amount v and the flux amount V is And Because Therefore, the amount of flux can always be made larger than the amount of low melting point metal.

In general, the amount of flux with respect to solder is at most 30 to 40%. However, in the alloy-type thermal fuse according to the present invention, the amount of flux can be increased with respect to the amount of solder. Even when the flux is carbonized and loses the flux action at the instant of fusing, since a sufficient amount of the flux is still retained, the subsequent spheroidization and division of the molten metal can be smoothly promoted. In the above description, the reason why the outer diameter R of the insulating layer is set to 2.4 or less of the outer diameter of the low-melting soluble metal body is that above this, the amount of flux becomes more than necessary, and the gap between the insulating cylinder and the insulating layer becomes too small. This is because it becomes difficult to inject the sealing material into the gap.

<Effect of the Invention> As described above, in the alloy type thermal fuse according to the present invention, the spheroidization of the molten metal during the operation of the thermal fuse can be promoted well despite the carbonization of the flux by the arc, and the operation speed is improved. Can be improved.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory view showing an embodiment of the present invention, and FIG. 2 is an explanatory view showing a conventional example. 1 ... lead conductor, 11 ... insulating layer, 3 ... flux,
4 ... insulating cylinder, 5 ... sealing material.

Claims (1)

(57) [Claims] 1. A low-melting-point fusible metal is joined between insulating-coated lead conductors, the low-melting-point fusible metal is coated with a flux, and an insulating cylinder is laid over the ends of the insulating coating layers of the two insulating-coated lead conductors. Insert, seal between each end of the insulating cylinder and the insulating coating layer of each insulating coated lead conductor with a sealing material, and change the outer diameter of the insulating coating layer to the outer diameter of the low melting point fusible metal. An alloy-type thermal fuse characterized by the following.