JPS6161495B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a fuse that protects electrical circuits, equipment, etc. by interrupting excessive current such as short-circuit current, and particularly relates to a fuse element thereof.

[Conventional technology]

The structure of a conventional fuse is shown in Figure 4. In the figure, reference numeral 1 denotes a terminal fitting whose both ends of a cylindrical fuse tube 2 are sealed in a cap shape, and numeral 3 denotes a terminal fitting which is housed inside the fuse tube 2 with both ends connected to the terminal fitting 1 and formed into a circular spiral shape. A fuse element 4 is stretched within the fuse tube 2 by its own spring force, and a powder arc extinguishing agent is filled in the fuse tube 2. As for the constituent materials, copper is generally used for the terminal fitting 1, porcelain or resin for the fuse tube 2, a highly conductive metal such as silver or copper for the fuse element 3, and silica sand for the arc extinguisher 4.

Here, the fuse element 3 is formed by being wound around a cylindrical core 5 as shown in FIG.
The winding core 5 is removed and stretched to the length between both terminal fittings 1, and is stretched in the fuse tube 2 with a spring force.

The fuse element 3 of the fuse described above is located in the center of the fuse tube 2 so as not to sag due to its own spring force, but it moves due to vibrations and shocks, and Due to variations in work during assembly, the fuse tube 2 may become eccentric.
It is easy to approach or come into contact with the inner wall of the

When the fuse element 3 approaches or comes into contact with the inner wall of the fuse tube 2, the arc extinguishing agent 4 around the fuse element 3 in the vicinity decreases or disappears, reducing the arc extinguishing performance.
The fuse tube 2 may be destroyed by the thermal stress caused by the arc at .degree.

Figures 6 and 7 show fuse element 3
As can be seen from FIG. 6, in the conventional fuse, the fuse element 3 is formed in a circular spiral shape and is inserted into the cylindrical fuse tube 2. Therefore, in the vicinity of the contact point A between the two, there is no or only a small portion of the arc extinguishing agent 4 between the two over a considerable length, and as can be seen from FIG. Point A occurs for each winding for a certain length in the axial direction, so the arc extinguishing performance deteriorates, and the thermal stress of the arc on the fuse tube 2 is large, causing the fuse tube 2 to be easily destroyed. However, the winding diameter of the fuse element 3 has to be made sufficiently thicker than the winding diameter of the fuse element 3.

In order to improve the above-mentioned drawbacks of conventional fuses, the present inventor has proposed a patent publication published in 1983.
No. 88223 discloses a technique in which a circularly wound fuse element 3 is stretched in a polygonal insulating tube 6 provided inside a fuse tube 2, as shown in FIG. According to this method,
Since the fuse element 3 is completely isolated from the fuse tube 2 and the arc extinguisher 4 is always present between the two, the thermal stress on the fuse tube 2 is more relaxed than in the case shown in FIGS. 6 and 7. Although this is advantageous, it has the disadvantage that the cost is higher due to the polygonal insulating tube 6, and the arc extinguishing performance is also lowered when the fuse element 3 is located at the center of the fuse tube 2, as shown in FIG. Since the distance is lower than that which is ideally placed, there has been a demand for a further improved method.

Furthermore, a fuse using a fuse element formed in a polygonal spiral has also been proposed. As shown in FIG. 9, a fuse element 7 wound in a rectangular spiral shape around a rectangular winding core 8 is extracted from the winding core 8 and stretched in the internal axial direction of the fuse cylinder 2. In such a fuse, as shown in FIG. 10, the fuse element 7 wound in a rectangular spiral is eccentric to the center axis of the fuse tube 2, so that two vertices B for each turn of the rectangle are aligned with the fuse tube 2. Although the worst case is shown in which the apex B is in contact with the inner wall of the fuse cylinder 2, there is of course a case in which one vertex B is in contact with the inner wall of the fuse tube 2 in each turn. In any case, the area where there is no or little arc extinguishing agent 4 near the contact point B is much larger than the conventional fuse in which the fuse element 3 wound in a circular spiral shown in FIG. 6 is eccentric. It becomes less.

[Problem that the invention seeks to solve]

In conventional fuses such as those described above, by using a fuse element formed in a polygonal spiral shape, when the fuse element eccentrically contacts the inner wall of the fuse cylinder, the multiple contact points are relatively close to each other, so the arc is extinguished. There were areas where the agent was absent or decreased, resulting in problems such as a decrease in arc-extinguishing performance and heat stress on the fuse cylinder.

The present invention has been made to solve these problems, and aims to provide a fuse that can minimize deterioration in arc extinguishing performance due to eccentricity of the fuse element and minimize thermal stress on the fuse cylinder.

[Means for solving problems]

In the fuse according to the present invention, the polygons formed by each winding of the polygonal spiral fuse element are sequentially shifted in the circumferential direction in the longitudinal direction of the fuse element.

[Effect]

In this invention, even if the fuse element is eccentric, the polygon formed by one turn has two vertices.
There is no contact with the inner wall of the fuse cylinder at a point or more.

〔Example〕

1 and 2 show a state in which the fuse element of one embodiment of the present invention is eccentric, and the polygon formed by one turn of the fuse element 9 is sequentially shifted in the circumferential direction in the longitudinal direction of the fuse. ing. That is, after the fuse element 7, which is wound so that each side is parallel to each other in FIG. Each side of each adjacent volume of 9 is disposed in such a way that the parallel state is broken.

With the above configuration, even if the fuse element 9 is eccentric, the vertices of the polygon formed by one turn will not come into contact with the inner wall of the fuse tube 2 at two points, as shown in FIG. Therefore, not only the thermal stress applied to the fuse tube 2 is reduced, but also the deterioration of the arc extinguishing performance can be minimized.

FIG. 3 shows another embodiment, in which a polygonal insulating tube 6 is provided inside the fuse tube 2, and the insulating tube 6 shown in FIG.
A fuse element 9 shown in FIG. 2 is provided.

In this case as well, there is no arc extinguishing agent 4 near the contact point between the fuse element 9 and the insulating cylinder 6, or there is only a small amount of arc extinguishing agent 4, so that the deterioration in arc extinguishing performance is small.
Also, the insulating cylinder 6 at the top of the fuse element 9
There is an advantage that not only the contact between the fuse tube 2 and the fuse element 9 is reduced, but also that the thermal stress on the fuse tube 2 is alleviated because the fuse tube 2 and the fuse element 9 do not come into direct contact with each other.

In each of the above embodiments, the polygon is a square, but it goes without saying that other polygons may be used. However, as the number of angles increases, it becomes closer to a circle, so there is a limit.

〔Effect of the invention〕

As described above, according to the present invention, the fuse element is wound in a polygonal spiral shape, and the polygon formed by each winding rotates and shifts little by little in the longitudinal direction of the fuse, and is inserted into the inside of the fuse cylinder. Because the structure is stretched, even if the fuse element is eccentric from the center line of the fuse cylinder and comes into contact with the inner wall of the fuse cylinder, the deterioration in arc extinguishing performance is minimized and the fuse cylinder is prevented from being destroyed due to thermal stress. There is.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of one embodiment of the present invention, and FIG.
The figure is a sectional view taken along the line - in FIG. 1, and FIG. 3 is a cross-sectional view of another embodiment. 4 to 10 show conventional fuses, FIG. 4 is a longitudinal sectional view, FIG. 5 is a perspective view for explaining the manufacture of the fuse element, and FIG. 6 is a cross-sectional view showing the eccentric state of the fuse element. Top view, Figure 7 is - of Figure 6.
8 is a cross-sectional view of another fuse, FIG. 9 is a perspective view for explaining the manufacture of a fuse element of another fuse, and FIG. 10 is a cross-sectional view of another fuse element. FIG. 3 is a cross-sectional view showing an eccentric state. 1... Terminal fitting, 2... Fuse tube, 4... Arc extinguisher, 6... Insulating tube, 9... Fuse element. In each figure, the same reference numerals indicate the same or equivalent parts.

Claims (1)

[Scope of Claims] 1. A fuse tube made of a cylindrical insulator whose both ends are sealed by terminal fittings, and a polygon formed in a polygonal spiral shape, with a polygon formed by each winding extending along the length of the fuse tube. A fuse comprising: a fuse element stretched between the terminal fittings so as to be sequentially shifted in the circumferential direction; and an arc extinguishing agent filled in the fuse cylinder. 2. The fuse according to claim 1, wherein the fuse element is disposed within a polygonal insulating cylinder provided inside the fuse cylinder.