JPH0448529A - Current limiting fuse - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention is a method for protecting load equipment, electric wires, etc. by cutting off the current and opening the circuit by melting the fusible material.
Regarding flow fuse.

[Conventional technology]

FIG. 3 is a cross-sectional view showing an example of the configuration of a conventional current-limiting fuse. A metal inner cap 3 is attached to cover the inner cap 3, a fusible body 4 whose both ends are conductively connected to each of the inner caps 3 and whose entire length penetrates through the arc extinguishing sand 1 of the fuse tube 2, and each of the inner caps 3. It is comprised of a metal outer cap 5 which is bonded to cover the body from the outside.

Furthermore, FIG. 4 is a view in the direction of arrow P in a state where the outer cap 5 of FIG. It is pulled out from 3A and spot welded to the inner cap 3 at point X.

The fusible body 4 is a thin plate made of copper or silver,
In order to actively determine the starting point of the fuse, a plurality of narrow portions (not shown) with small cross-sectional areas are provided in series in the longitudinal direction (that is, in the axial direction of the fuse tube 2).

When the current is cut off, the narrowed portion first fuses and arcs, and then the arc extends to the non-narrowed portion. Since the arc extinguishing sand 1 with quartz grains is arranged around the fusible body 4, the fusible body 4 is vaporized by the formation of an arc, and an arc tunnel corresponding to the cross-sectional shape of the fusible body 4 is formed in the arc extinguishing sand 1. is formed and the arc is confined inside this arc tunnel.

This arc is subdivided while being cooled by the arc-extinguishing sand 1, increasing the arc voltage and extinguishing while exhibiting a current limiting effect. Since it operates while suppressing the short-circuit current when the current is cut off, a fuse with such a structure is called a current-limiting fuse, and is distinguished from a general fuse that does not have a current-limiting effect.

(Problem to be solved by the invention) However, in the conventional current limiting fuse as described above, if a short circuit current exceeding the rated breaking capacity flows, a hole will open in the outer cap due to arc heat, and in the worst case, the fuse will not be able to interrupt the current. There was a possibility that this could lead to failure of the circuit or an explosion.

In other words, in conventional devices, when the current is cut off, the arc extends to the joint between the fusible material and the inner cap as the arc time elapses, and the arc heat creates a hole in the outer cap, reducing the internal pressure of the fuse cylinder and causing the arc to elapse. This led to 11111 failure to disconnect or an explosion.Normally, when using a fuse, consider the maximum short-circuit current that may flow in the circuit, and select one that has a breaking capacity that can sufficiently withstand this. However, if there is insufficient consideration, failure to shut off the fuse or explosion due to short circuit current may occur.

An object of the present invention is to prevent breakdown failures and explosions by providing a structure in which the influence of arc heat does not extend to damage the outer cap.

[Means to solve the problem]

the above! ! 1! According to this invention, in order to solve H,
An insulating fuse tube filled with arc-extinguishing sand inside, a metal inner cap fixed to both axial ends of the fuse tube from the outside, and a conductive cap at each end of the inner cap. A fusible body that is connected and whose entire length penetrates through the arc-extinguishing sand inside the fuse cylinder, and a metal outer cap that is joined so as to cover each of the inner caps from the outside, wherein the inner cap and A gap is provided in the axial direction between the cap and the outer cap, and this gap is filled with arc-extinguishing sand.

Further, in the above means, instead of filling the axial gap between the inner cap and the outer cap with arc-extinguishing sand, a protective plate having arc resistance is interposed.

[Effect]

According to the first configuration of the present invention, a gap is provided in the axial direction between the inner cap and the outer cap, and the lung is filled with arc-extinguishing sand during this gap, so that the arc-extinguishing sand acts as a buffer against arc heat. As a result, the outer cap is no longer affected by heat that could damage it, eliminating failures and explosions.

Further, according to the second configuration of the present invention, a gap is provided in the axial direction between the inner cap and the outer cap, and a protective plate having heat and arc resistance is interposed in this gap. This protective plate becomes a layer of arc heat and is not affected by the heat that would damage the outer cap, thereby eliminating interruption failure and explosion.

〔Example〕

The present invention will be explained below based on examples.

FIG. 1 is a sectional view showing the configuration of a current limiting fuse according to an embodiment of the present invention, in which a gap is provided in the axial direction between an inner cap 3 and an outer cap 5 on both sides of the fuse tube 2, and this gap is It has a structure in which the arc-extinguishing sand 6 is filled. The rest of the configuration is the same as the conventional device shown in FIG. 3, so the same reference numerals will be used for the same parts and detailed explanation will be omitted.

The arc-extinguishing sand 6 is made of the same material as the arc-extinguishing sand 1 in the fuse tube 2, and is shared through the central hole 3^ of the inner cap 3. Even if the fusible body 4 becomes an arc and the heat reaches the inner cap 3, the arc-extinguishing sand 6 intervenes, so the high heat caused by the arc does not reach the outer cap 5, and damage such as holes in the outer cap 5 is prevented. Does not occur.

FIG. 2 is a sectional view showing the configuration of a current limiting fuse according to a different embodiment of the present invention, in which a gap is provided in the axial direction between the inner cap 3 and the outer cap 5 on both sides of the fuse tube 2, and It has a structure in which a heat-resistant protection plate 7 is interposed in the gap, and in this case as well, the same reference numerals are used for the same parts as in the conventional device, and a detailed explanation will be omitted.

The material of the protective plate 7 is a heat-resistant porcelain plate, an asbestos sheet, a metal plate, etc. Even if the fusible body 4 becomes an arc and the heat reaches the inner cap 3, the protective plate 7 intervenes, so that the outside is not affected. The high heat caused by the arc does not reach the cap 5, and damage such as holes in the outer cap 5 does not occur.Even without the protective plate 7, the outer cap 5 can be easily removed by making the material of the outer cap 5 thick. However, since the outer cap 5 is manufactured from a thin metal plate by pressing, it is not possible to form the outer cap 5 with a material that is too thick, such as the Tsuru order.

The protection plate 7 shown in FIG. 2 is a substitute for the arc-extinguishing sand 6 shown in FIG. It is easy to assemble.

In Fig. 2, there is a partial gap between the protective plate 7 and the inner cap 3, but this is because the thin fusible body 4, which is on the order of 0.1 crane in thickness, has been exaggerated to be thicker in the figure. In reality, there is no such gap.

〔Effect of the invention〕

As described above, this invention is characterized by filling the space between the inner cap and the outer cap with arc-extinguishing sand, or interposing a protective plate instead of the arc-extinguishing sand between the inner cap and the outer cap. Therefore, it is possible to provide a device in which damage to the outer cap due to arc heat is prevented, and failure to shut off or explosion does not occur. moreover,
When a protective plate is interposed instead of filling with arc-extinguishing sand, the gap between the inner cap and the outer cap can be more accurately secured, and there is also the advantage that assembly is easy.

[BRIEF DESCRIPTION OF THE DRAWINGS] FIGS. 1 and 2 are cross-sectional views showing configurations of current-limiting fuses according to mutually different embodiments of the present invention, and FIG. 3 is a cross-sectional view showing an example of the configuration of a conventional current-limiting fuse. , FIG. 4 is a view taken along arrow P in a state where the outer cap of FIG. 3 is removed. 1.6: Arc extinguishing sand, 2: Fuse tube, 3: Inner cap, 3
^: Center hole, 4: Fusible body, 5: Outer cap, 4 stones in one? Figure 1 Figure 2 Figure 1I3 Figure 4

Claims (1)

[Scope of Claims] 1) An insulating fuse tube filled with arc-extinguishing sand, metal inner caps fixed to both axial ends of the fuse tube from the outside, and both ends. The fusible body is conductively connected to each of the inner caps and has its entire length penetrating through the arc-extinguishing sand inside the fuse tube, and a metal outer cap is bonded so as to cover each of the inner caps from the outside. A gap is provided in the axial direction between the inner cap and the outer cap,
A current-limiting fuse characterized by filling this gap with arc-extinguishing sand. 2) An insulating fuse tube filled with arc-extinguishing sand, a metal inner cap fixed to both axial ends of the fuse tube from the outside, and a metal inner cap that covers each end of the fuse tube from the outside. The inner cap is composed of a fusible body that is conductively connected to the fuse cylinder and whose entire length penetrates through the arc-extinguishing sand inside the fuse cylinder, and a metal outer cap that is bonded so as to cover each of the inner caps from the outside. A current-limiting fuse characterized by having an arc-resistant protective plate interposed in the axial gap between the cap and the outer cap.