JPH0795418B2 - Flat thermal fuse - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The present invention relates to an alloy type flat type thermal fuse used for protecting the above-mentioned equipment from abnormal temperature rise.

<Prior Art> In an alloy type flat type thermal fuse that uses a low melting point fusible metal piece for a fuse element, when an electric current to be protected occurs in an electric device, the generated heat melts the fuse element to blow it to the device. Turn off the power. Among such alloy type thermal fuses, a flat type body is advantageous in that it is thin and compact and the arrangement is stable. Conventionally, those shown in FIGS. 5 and 6 are known. There is.

In the flat type thermal fuse shown in FIG. 5, a pair of film electrodes 13 ', 13' are arranged in parallel on one surface of an insulating substrate 2 ', and a tip portion 12' of a lead conductor 1 ', 1'is flattened. The flat part
Weld 12 'and 12' to electrodes 13 'and 13', connect low melting point metal pieces 3'between the electrodes, provide a flux layer 4'on the metal pieces, and form an insulating layer on one surface of the insulating substrate. 5'is coated.

On the other hand, in the flat type thermal fuse shown in FIG. 6, a pair of lead conductors 1 ′ and 1 ′ having flattened tip portions 12 ′ are arranged in parallel, and a low melting point fusible metal is provided between the flat portions of these lead conductors. Connect pieces 3 ', apply flux 4'to the metal piece,
These are surrounded by an insulator 5 '(sheet-like insulator).

<Problems to be Solved> However, in the structure shown in FIG. 5, it is necessary to form the film electrode on the insulating substrate, which is disadvantageous in that the number of manufacturing steps is large. On the other hand, the one shown in FIG. 6 does not have such a disadvantage. However, in any of the thermal fuses shown in FIGS. 5 and 6, the pair of lead conductors 1 ′ and 1 ′ are close to each other, and insulation between the lead conductors is caused during voltage application after the fuse element is blown. A creeping discharge is likely to occur along the body surface.
In order to prevent this creeping discharge, it is effective to widen the distance between the lead wires 1'and 1 ', but this causes the width of the thermal fuse main body to be wide, which is disadvantageous in making the thermal fuse compact.

However, the above-mentioned creeping discharge or increase in size can be eliminated by making the thermal fuse an axial type, but if the thermal fuse shown in FIG. 5 or FIG. 6 is simply made an axial type, it becomes a lead conductor. When tensile force or torsion moment acts, it is difficult to avoid mechanical damage.

An object of the present invention is to provide an axial type flat type thermal fuse capable of imparting sufficient strength to tensile force and torsion moment.

<Means for Solving Problems> In a flat-type thermal fuse according to the present invention, a tip portion of a round wire conductor is flattened, and a pair of lead conductors provided with protrusions on both sides of the tip portion of the flat portion are aligned. The flat parts of each lead conductor are abutted on one side of the insulating substrate, and the protrusions on both sides of the tip of each flat part are embedded in the above-mentioned one side of the insulating substrate. A low melting point metal piece is connected to, and the insulating substrate is covered with an insulating layer so as to cover the one surface.

<Description of Embodiments> Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a partially cutaway top view showing an embodiment of the present invention, FIGS. 2 and 3 are II-II sectional views and III in FIG.
-III is a sectional view.

In FIGS. 1 to 3, reference numeral 1.1 denotes a pair of lead conductors, which are arranged so as to face each other in a straight line. As shown in FIG. 4, a round wire conductor (for example, a copper wire) 11 is flattened by crushing the leading end of the lead wire, as shown in FIG.
It uses the one formed by bending both sides of the tip of the to form a protrusion 13/13. Reference numeral 2 denotes an insulating substrate. The flat portions 12, 12 of the lead conductors 1, 1 are provided on one side of the insulating substrate, and the protrusions 13, 13 at both ends of the flat portion are embedded in the insulating substrate. I'm wearing it. For this embedding, when the insulating substrate is plastic, a method of forming the tip of the protrusion into a blade shape and press-fitting it into the substrate surface, a method of heating the protrusion and pressing and welding it onto the substrate, and the like can be used. When the insulating substrate is an inorganic plate such as a ceramic plate or a glass plate, it is possible to use a method of providing a protrusion embedding groove in the insulating plate and inserting the protrusion into the groove. 3 is both lead conductors 1
It is a low melting point fusible metal piece that can be connected between the flat parts 12 and 12 of 1 and can be used in both round and flat cross sections, and each flat part is welded between the low melting point fusible metal piece. . The composition of the low-melting point soluble metal piece is selected according to the operating temperature of the thermal fuse, and for example, one having Sn-Pb as a base and having an appropriate melting point to which Bi, Cd or the like is added can be used. No. 4 is a flux applied on the low melting point soluble metal piece, and includes rosin (natural rosin, purified rosin, polymerized rosin, modified rosin,
Hydrogenated rosin, disproportionated rosin) as a main component, and if necessary, an activator (diethylamine hydrochloride, hydrobromide) may be used. Reference numeral 5 is an insulating layer which covers the insulating substrate so as to cover one side thereof, and an epoxy resin layer can be used, for example.

In the above, when a tensile force F or a torsion moment M acts on the lead conductor, a tensile reaction force or a moment reaction force acts on the contact surface between each flat portion of the lead conductor and the insulating substrate and the contact surface between the flat portion and the insulating layer. To do. If the reaction force per unit length of flat portion is α or β and the distance to the front of the tip of the flat portion is L, the tensile force f and torsion moment m acting on the tip are And f and m are large because α and β are relatively small. However, since both sides of the tip portion are embedded in the insulating substrate by the protrusions, the tensile strength and torsion moment strength of the tip portion can be increased, and the tip portion can be stably fixed to the above f and m. . Therefore, the low melting point fusible metal piece (low strength) can be well protected from the tensile force and the torsion moment.

In the above, when the protrusion of the flat portion of the lead conductor is provided on the insulating side of the insulating substrate, L = 0 and f = F and m = M in the formulas and formulas, and the protrusion forming part is located ahead of The contact interface between the flat portion of the lead conductor and the insulating substrate or the insulating layer cannot contribute to the tensile force load or the torsion moment load at all, and the entire load is applied to the protrusion.
It is mechanically disadvantageous. However, in the present invention, as is apparent from the above equations and equations, the tensile force or the torsion moment is also applied to the portion other than the protrusion, and there is no such disadvantage.

<Effects of the Invention> As described above, the flat-type thermal fuse according to the present invention is an axial type having sufficient strength against a tensile or torsion moment, and both lead conductors when a low melting point fusible metal piece melts down. Since the creeping insulation distance between them is a long distance over half the circumference of the insulating substrate, the same as above can sufficiently secure the insulating strength at the time of fusing, and even if the insulating substrate width is made small, this insulating strength can be well retained. It is possible to reduce the size of the mold temperature fuse body.

[Brief description of drawings]

1 is a partially cutaway top view showing an embodiment of the present invention, FIG.
2 and 3 are sectional views taken along line II-II and III-III in FIG. 1, respectively. FIG. 4 is a perspective view showing a lead conductor used in the present invention, and FIGS. 5 and 6 are conventional examples. FIG. 1 ... Lead conductor, 12 ... Flat part 13 ... Projector, 2 ... Insulating substrate 3 ... Low melting point fusible metal piece, 5 ... Insulating layer

Claims (1)

[Claims] 1. A flattened end portion of a round wire conductor, and a pair of lead conductors provided with protrusions on both sides of the end portion of the flattened portion are arranged to face each other, and the flattened portion of each lead conductor is made of an insulating substrate. Abut on one side, embed the protrusions on both sides of the tip of each flat part on the one side of the insulating substrate, connect the low melting point metal piece between both flat parts, and cover the one side on the insulating substrate. A flat type thermal fuse characterized by being covered with an insulating layer.