JPH0684446A - Arc-free fuse - Google Patents

Abstract

PURPOSE:To prevent a melted conductive substance of low melting point from being splashed and attaching to the inner surface of the case of a fuse which interrupts current as the conductive substance of low melting point is melted by heating due to abnormal current and to maintain the electrical distance between electrodes so as to enhance the interrupting performance by forming a heat-resisting, electrically insulative curing film over the surface of the conductive substance of low melting point. CONSTITUTION:A resistor 2 which is heated by overcurrent is mounted on a case 1 and a spring 4 is joined to one end of the resistor 2 using a conductive substance 5 of low melting point, which is coated with a film 6 of cured resin. The spring 4 has the other end secured to the case 1 while being warped.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuse for cutting off a high voltage circuit by fusing a low melting point conductor due to heat generated by the abnormal current when an abnormal current flows through the high voltage electric circuit.

[0002]

2. Description of the Related Art In a high-voltage fuse, it is important to complete the breaking without generating an arc in a high-voltage circuit, since the arc is likely to continue during the breaking and may not be broken. It is also a feature that both the rated current and the abnormal current are relatively small currents. In this regard, various techniques have been conventionally disclosed. Basically, these have a resistor inside the fuse and generate heat by an abnormal current to open the contact by the heat, but each has its own characteristics regarding the contact mechanism.
There is one such as 7605 in which a conductive wire having a spring property is joined by a low melting point conductor and the joint portion is melted by heat generation at the time of abnormality to operate the spring to open the contact. Alternatively, as disclosed in Japanese Patent Application Laid-Open No. 2-273434, a contact is formed of a shape memory alloy, and the shape memory alloy is activated by the heat generated in an abnormal state to open the contact.

[0003]

Since the present invention solves only the former problem, that is, the problem in the case of using a low melting point conductor, the former is abbreviated as prior art in the following description. In the prior art, when the low-melting conductor is melted by heat, the conductive wire having a spring property, which was urged when the low-melting conductor is semi-molten, is vigorously pulled away from the resistor, so that the low-melting conductor is scattered. Since the scraps adhere to the inner wall of the fuse case, there is a problem in that a sufficient high-voltage cutoff distance cannot be obtained after the cutoff and arc discharge continues, making it difficult to maintain the high voltage. The present invention was devised to solve this problem, and an object of the present invention is to provide a high-voltage fuse that functions accurately when shutting down against overcurrent and has a sufficient withstand voltage even after shutting off.

[0004]

In order to achieve the above object, a high voltage fuse of the present invention has a resistor connected to one terminal of a case to generate heat due to overcurrent, and the other end of the resistor is a spring. In a high voltage fuse in which one end is connected with a low melting point conductor and the spring is held at the other end terminal of the case in a biased state, a hardened resin that is heat resistant and electrically insulating on the surface of the low melting point conductor in a high voltage fuse It is characterized by forming a film.

[0005]

Embodiments of the present invention will be described with reference to the drawings. First
The figure shows a cross-sectional view of a fuse according to the invention. The terminal 3-a of the resistor 2 that generates heat due to overcurrent is attached to the case 1, and the spring 4 is joined to the terminal 3-b of the resistor 2 by the low-melting conductor 5. Wrapped in film 6. The spring 4 is attached to the case 1 in a bent state. Further, these are housed in the case 7. FIG. 2 shows details of the low melting point conductor 5 and the film 6. In the case of the embodiment, the resin film 6 has a viscosity of 30 to 90C. P. (25
C.) about one drop (about 20 to 50 mg) of a one-part curable silicone coating liquid was applied to the surface of the low-melting conductor 5 with a pipette and cured in the air for 72 hours while volatilizing the solvent (xylene). . As a result, a film having a thickness of 10 to 100 μm was obtained on the surface of the low melting point conductor 5. In this embodiment, in order to prevent the film from connecting between the resistor and the low-melting conductor 5, in order to prevent the film from being hardened, the low-melting conductor 5 and the base of the resistor lead are cut off with a sharp blade after the film is cured. The film was separated. A state in which this is incorporated into a fuse and operated is shown in a sectional view (FIG. 3) after the operation of the embodiment. Table 1 shows the results of concrete interruption of the examples and the conventional examples regarding the scattering state of the low-melting-point conductor, and the effect of the present invention is confirmed.

[0006]

[Table 1] Next, a conventional example of a high voltage fuse used for comparison is shown in FIG. A resistor 2 that generates heat due to overcurrent is attached to the case 1, and a spring 4 is joined to the other end of the resistor 2 by a low melting point conductor 5. The spring 4 is attached to the case 1 in a bent state. Compared to the example, the conventional example has a film 6
The difference is that it is not attached. Therefore, in the conventional example, when the low-melting conductor 5 is half melted due to heat generation of the resistor 2 due to overcurrent, the joint is separated by the returning force of the spring 4 and the low-melting conductor 5 collapses and scatters as shown in FIG. As a result, a large number of scraps are scattered inside the case and the electrical distance between both terminals is shortened, which causes continuous arc discharge.

[0007]

As is apparent from the above description, according to the high voltage fuse of the present invention, when the low melting point conductor is half melted by the heat generation of the resistor due to the overcurrent, the joint is separated by the spring. By wrapping the low melting point conductor in a cured resin adhesion film having electrical insulation and heat resistance, collapse and scattering are suppressed and scattering of this waste into the fuse case is prevented. As a result, the retention of high voltage inside the case is improved, and it becomes possible to terminate the arc generation due to interruption in an extremely short time.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention.

FIG. 2 is a partially enlarged view of the embodiment of the present invention.

FIG. 3 is a cross-sectional view showing a state after the operation of the embodiment.

FIG. 4 is a cross-sectional view of a conventional example.

FIG. 5 is a cross-sectional view showing a state after the operation of the conventional example.

[Explanation of symbols]

 The same reference numerals are used in FIGS. 1 case 2 resistor 3-a terminal 3-b terminal 4 spring 5 low melting point conductor 6 resin film 7 case

Claims (1)

[Claims] A resistor that generates heat due to overcurrent is connected to one of the electrically insulating cases, and a spring is urged to the other end of the resistor by melting and adhering a spring with a low melting point conductor that melts due to the heat generation. In the fuse held in the other side of the case, the low melting point conductive material has heat resistance and electrical insulation obtained by applying a gaseous or liquid resin material to the surface of the low melting point conductor and then curing it. A fuse that does not generate an arc when it is blown by forming a film that adheres to the surface of the body.