JPH019315Y2 - - Google Patents

Description

[Detailed explanation of the idea] Industrial applications This invention relates to electric wire fuses.

Conventional technology Conventionally, electric wire fuses have lead wire connection terminals fitted to both ends of an insulating cylinder, and a large current interrupting part and a small current interrupting part made of a low-alloy metal are connected in series between the two connecting terminals. When a low magnification current (hereinafter referred to as a small current) that exceeds the current flows, the low alloy alloy is designed to melt.

However, since no biasing force is applied to the low-alloy metal to open the gap between the poles, it is difficult to melt when the low-alloy metal is melted, and there is also the problem that the low-alloy metal may deform and sag, contacting the insulating cylinder, and causing burnout.

In order to solve this problem, it has been proposed that a tension spring is provided in the small current interrupting section to open the small current interrupting section when a small current passes through the small current interrupting section.

However, not only is the tension of the tension spring concentrated at the joint between the small current interrupting section and the large current interrupting section, but also the temperature rises due to heat generation in the vicinity of the joint due to the allowable current. There is a problem that a creep phenomenon occurs in low-alloy metals, resulting in deterioration.

Purpose of the invention The purpose of this invention is to eliminate the above-mentioned drawbacks, prevent creep from occurring at the joint between the large current interrupting part and the small current interrupting part, and to prevent creep during long-term use. An object of the present invention is to provide an electric wire fuse that can secure a sufficient insulation distance at times.

Structure of the invention In the electric wire fuse of this invention, a shape memory alloy is provided in the large current interrupting part to separate the small current interrupting part and the large current interrupting part when a small current flows.

Embodiment An embodiment embodying this invention will be described below with reference to FIGS. 1 and 2. 1 is an insulating cylinder made of heat-resistant transparent synthetic resin such as polycarbonate; A locking step portion 2 is formed around the periphery. Reference numerals 3 and 4 designate support cylinders made of synthetic resin that are fitted and bonded to the inner periphery of both ends of the insulating cylinder 1.

Reference numerals 5 and 6 denote lead wire connection terminals whose base ends are inserted and fixed into both support tubes 3 and 4 of the insulating tube 1, respectively, and connections for connecting lead wires are provided on the outer end surface protruding from the insulating tube 1. Holes 5a and 6a are recessed. A pair of protective covers 7 are fitted and bonded to the outer periphery of both ends of the insulating cylinder 1 and a part of the outer periphery of each of the connecting terminals 5 and 6, respectively, and seal the insulating cylinder 1.

Reference numeral 8 denotes a synthetic resin terminal cover formed in a substantially cylindrical shape, and is attached by engaging its base end engaging portion 8a with an engaging groove provided on the outer periphery of the distal end of each protective cover 7. This protects the outer periphery of the connection terminals 5 and 6.

Reference numeral 9 denotes a packing made of asbestos or the like that is inserted into one of the connecting terminals 5 and placed inside the insulating cylinder 1 so as to come into contact with the inner end of the support cylinder 3. 10 is the insulating cylinder 1
It is an inner cylinder made of heat-resistant transparent glass that is internally arranged so that a slight gap is formed between the
One end is brought into contact with the locking stepped portion 2 and the other end is brought into contact with the gasket 9.

Reference numerals 11 and 12 denote a pair of silver wire elements constituting a large current interrupting section 13 connected to the inner ends of both lead wire connection terminals 5 and 6, respectively, and conductive connecting tubes 14 and 15 are connected to the inner ends of the silver wire elements 11 and 12, respectively. It is worn tightly. Between the two connecting pipes 14 and 15 is a conductive tubular heat storage body 17 whose both ends are fixed by a low-alloy metal as a small current interrupting part 16 on its outer peripheral surface.
is connected. The low alloy alloy has a predetermined fusing characteristic of fusing when a small current passes through it. and,
One end of the heat storage body 17 has the lead wire connection terminal 6
is caulked to the end of the silver wire element 11,
A shape memory alloy 18 constituting a large current interrupting section is caulked together with 12, and the whole is arranged in a winding manner around the outer periphery of the silver wire element 12. The shape memory alloy 18 is made of an alloy such as nickel or titanium, has a transformation temperature slightly lower than the melting point of the low alloy alloy of the small current interrupting part 16, and is formed into a tightly wound spring shape for 30 minutes at 400 to 500°C This shape is memorized by heat treatment. And this shape memory alloy 1
8 is deformed beyond its elastic limit and above its yield point, as shown in FIG.

The operation of the electric wire fuse configured as above will be explained.

Now, when a small current exceeding the rated current flows between the connecting terminals 5 and 6 due to overload etc. for a predetermined period of time, heat is generated in the shape memory alloy 18 as the large current interrupting part, the silver wire elements 11 and 12, and the connecting tubes 14 and 15. happens. That heat is stored in the heat storage body 17, so when the shape memory alloy 18 reaches its transformation temperature due to that heat, it tries to return to its original tight spring-wound shape due to its characteristics, but at this point the small current interrupting part 16 is fused. The state shown in Fig. 1 is maintained because it has not been updated. When the melting point of the low-alloy metal in the small current interrupting part 16 is reached, the low-alloy metal is fused and the heat storage body 17 is pulled toward the connection terminal 6 by the return action of returning to the shape memory alloy 18. Both connecting pipes 1 as shown in the figure
4 and 15 are separated. After disconnection, both connecting pipes 14,
There is a predetermined insulation distance between the shape memory alloys 15 and 15, and the shape memory alloy 18 has a tightly wound spring shape.

This fused state can be easily confirmed through the transparent insulating cylinder 1 and inner cylinder 10.

Further, when a large current flows between the lead wire connection terminals 5 and 6 due to a short circuit or the like, the shape memory alloy 18 and the silver wire elements 11 and 12 are fused and gas is generated. Since the metal vapor in the gas adheres to the inner circumferential surface of the inner cylinder 10, the cut-off state of the large current interrupting section can be easily confirmed through the insulating cylinder 1 and the inner cylinder 10.

In this way, in the rated current range used below the transformation temperature of the shape memory alloy 18 constituting the large current interrupting section, there is no tensile load on the low alloy alloy of the small current interrupting section 16, and therefore, there is no tensile load on the low alloy alloy of the small current interrupting section 16. Current interrupter 1
A creep phenomenon due to tension does not occur in the joint portion of No. 3, and the blocking performance can be reliably maintained.

Effects of the invention As detailed above, in this invention, a pair of lead wire connection terminals at both ends are inserted and fixed in the insulating cylinder, and a large current interrupting part and a small current interrupting part are connected in series between the two connecting terminals. In electric wire fuses where both ends of the tube are closed by protective covers, a shape memory alloy is provided in the large current interrupting section to separate the small current interrupting section and the large current interrupting section when the small current is interrupted. Even when used over a long period of time, it prevents creep from occurring at the joint between the large current interrupting part and the small current interrupting part, and also has the excellent effect of ensuring a sufficient insulation distance when interrupting, making it an excellent product for industrial use. It is an idea.

[Brief explanation of drawings]

FIG. 1 is a longitudinal cross-sectional view of an electric wire fuse according to an embodiment of this invention, and FIG. 2 is a longitudinal cross-sectional view of the electric wire fuse when a small current is passed through. 1... Insulating tube, 3... Support tube, 4... Support tube,
5... Lead wire connection terminal, 6... Lead wire connection terminal, 7... Protective cover, 10... Inner cylinder, 11...
Silver wire element, 12...Silver wire element, 13
...large current interrupting section, 14... connecting pipe, 15... connecting pipe, 16... small current interrupting section, 17... heat storage body,
18...Shape memory alloy.

Claims (1)

[Scope of Claim for Utility Model Registration] 1. A pair of lead wire connection terminals are inserted and fixed at both ends of the insulating cylinder, and a large current interrupting part and a small current interrupting part are connected in series between the two connecting terminals. An electric wire fuse in which the electric wire fuse is closed by a protective cover, and the electric wire fuse is characterized in that a shape memory alloy is provided in the large current interrupting part to separate the small current interrupting part and the large current interrupting part from each other when the small current interrupting part is interrupted. 2. The large current interrupting part consists of a pair of silver wire elements, one end of which is connected to the inner ends of both lead wire connection terminals, one end of which is connected to the inner end of one of the connection terminals, and the other end of which is connected to a conductive heat storage element. A utility model in which the small current interrupting part is a low alloy metal which is a means for fixing both ends of the heat storage body to the connecting tubes which are caulked to the opposite ends of both silver wire elements. An electric wire fuse according to registered claim 1.