JPH08329819A - High voltage breaking fuse - Google Patents

Abstract

PURPOSE: To provide a high voltage breaking fuse whose reliability is enhance by stopping electric discharge when a circuit concerned is broken. CONSTITUTION: A high voltage breaking fuse concerned is structured so that a tensile spring 6 and heat emitting resistance 4 connected by a solder 5 having a low melting point are installed in an insulative pipe 1 sealed by metal bases 2a, 2b and that the current is shut off with melting of the solder 5 when an abnormal current flows through the resistance 4. An insulative pipe 1 is filled with a certain quantity of insulating oil 7, and a coating is applied to its inner wall.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high voltage cutoff fuse for cutting off a voltage application circuit by detecting an abnormal current of a display device to which a high voltage is applied.

[0002]

2. Description of the Related Art In recent years, there has been known a super-large image display apparatus which is constructed by arranging a large number of arc tubes for applying a high voltage to a device such as a phosphor and exciting light with electrons. In such an ultra-large image display device, for example, when one of the arc tubes malfunctions and an abnormal current flows for some reason, the arc tube is damaged and high voltage leaks to the power supply and its peripheral circuits. May have adverse effects. It is possible to turn off the power when such an abnormality is detected, but this causes the multiple arc tubes to stop emitting light, so a voltage is applied to each arc tube to protect the power supply and its peripheral circuits. A high voltage cutoff fuse is inserted in the circuit.

FIG. 6 is a diagram schematically showing a part of a voltage application circuit in which a high voltage cutoff fuse is inserted. As shown in this figure, the voltage supplied from the power supply HV is supplied to the light emitting tube 13 which is, for example, a high-intensity cathode ray tube through the high voltage cutoff fuse 10. Several other breaking fuses 10 and arc tubes 13 are arranged as described above. The high-voltage cutoff fuse 10 has a configuration in which a heating resistor 11 and a tension spring 13 are connected by a low melting point solder 12, and when an abnormal current flows, the heating resistor 11 detects the abnormal current and 12 is designed to melt. Then, when the solder 12 melts, the connection between the power supply HV and the arc tube 14 is cut off to prevent application of high voltage, and the tension spring 13 contracts to cause the insulation resistance in the air at the heating resistor 11 and the tip of the tension spring 13. It is configured to maintain an insulation distance that does not occur.

[0004]

However, in the conventional high-voltage cutoff fuse 10, when the solder 12 is melted, the melted solder 12 may be scattered in the insulating tube forming the fuse. Further, when the solder 12 is melted, the melted solder 12 is melted while the heating resistor 11 and the tip of the tension spring 13 are separated by an absolute distance that does not cause dielectric breakdown in the air.
And metal scattered by arc discharge adheres to the inner wall of the insulating tube to lower the impedance inside the insulating tube, and even if the terminal of the heating resistor 11 and the tip of the tension spring 13 are separated by an absolute distance, they pass through the inner wall of the insulating tube. There is a problem that the discharge may continue.

[0005]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has a heat generating resistor connected by a low melting point solder in an insulating tube whose both ends are sealed by caps. In a high-voltage cutoff fuse in which a tension spring is disposed and which melts the low-melting point solder to cut off the current when an abnormal current flows in the heating resistor, a high amount of high voltage is obtained by filling the insulating tube with a predetermined amount of insulating oil. Configure a breaking fuse. Further, the insulating oil is filled in an amount that forms a film on the inner wall of the insulating pipe.

[0006]

The high-voltage cutoff fuse of the present invention has a heat generating resistor and a tension spring which are connected to each other by a low melting point solder in an insulating tube such as glass or ceramic, and further has a predetermined amount of insulating oil in the insulating tube. Since it is configured to be enclosed, even if the solder melts due to an abnormal current and arc discharge occurs, the scattered substances such as the melted solder are captured in the insulating oil and attracted toward the base by the electric field at both ends of the base. It is possible to prevent the impedance of the inner wall of the insulating tube from decreasing. Further, since the insulating oil is evaporated by the heat of the arc discharge, the atmospheric pressure in the insulating tube rises and the discharge can be stopped (Paschen's law), and the reliability can be improved.

[0007]

Embodiments of the high voltage breaking fuse of the present invention will be described below. FIG. 1A is a diagram showing a configuration of a high-voltage interrupting fuse of this embodiment, and FIG. 1B is a diagram showing cross-sections of caps formed at both ends of the high-voltage interrupting fuse. . The insulating tube 1 is made of, for example, glass, ceramics, or the like in a tubular shape, and forms the body of a high-voltage breaking fuse. The bases 2a and 2b are attached to the ends of the insulating tube 1, respectively, and serve as contacts with a circuit in which a high-voltage cutoff fuse is arranged and also seal the insulating tube 1. The adhesives 3a and 3b are applied to the entire circumference of the fitting portion of the insulating pipe 1 and the bases 2a and 2b, and the insulating pipe 1 and the base 2a,
2b is completely sealed.

Inside the insulating tube 1, a heating resistor 4 and a tension spring 6 are connected by a low melting point solder 5 which melts at a predetermined temperature. As shown in FIG. 2, for example, the connecting portion of the tension spring 6, that is, the tip 6a is formed straight and is configured to be shorter than the conventional one by, for example, about 1.5 mm to insulate when the solder 5 is melted. The scattering of the inner wall of the pipe 1 is reduced.

The heating resistor 4 is a resistor for detecting an abnormal current of a device to which a high voltage is applied (for example, a fluorescent substance of an arc tube) like the above-mentioned conventional high-voltage cutoff fuse. When is detected, the solder 5 arranged at the tip portion is melted and the bases 2a and 2b are cut off. At this time. For example, as shown in FIG. 3, the tension spring 6 is contracted so that the insulation distance is maintained so that the heat generating resistor 4 and the tip of the tension spring 6 do not cause dielectric breakdown in the air. For example, when this high voltage cutoff fuse is used at a high voltage of 9 Kv, the absolute distance R is set to about 9 mm.

A predetermined amount of insulating oil 7 is filled in the insulating tube 1, and when the solder 5 melts and an arc discharge occurs, the solder 5
And capture metal spatter. The filling amount of the insulating oil 7 may be such that the insulating oil 7 is attached between the inner wall of the insulating pipe 1 and the tension spring 6 by tension. For example, NEOIL-S is used as the insulating oil 7.
Mineral oils such as S and NEOIL-SSC, synthetic oils such as fombri oil and the like are used. In particular, NEOIL-SS has a certain degree of viscosity, and even if the solder 5 melts and the tension spring 6 contracts, the tension causes it to adhere between the insulating tube 1 and the tension spring 6, so that it is easy to handle. With that, high reliability can be obtained.

Next, the filling amount of the insulating oil 7 will be described in detail with reference to FIGS. 4 and 5. The amount of insulating oil 7 and the discharge state described below are determined by partially applying the adhesive 3a.
It is measured with a slightly lower degree of sealing than the high voltage breaking fuse shown in. FIG. 4 is a graph showing the relationship between the time until the solder 5 is melted and the filling amount of the insulating oil 7 when a voltage of 11 Kv or 12 Kv is applied to the high-voltage cutoff fuse of this embodiment. The melting time of 11 Kv in the figure is ■
The mark, 11 Kv arc discharge duration is ◆ mark, 12 Kv
The melting time is indicated by □, the duration of 12 Kv arc discharge is indicated by ◇, and the filling amount of insulating oil 7 is 0 to 60 mg.
It is shown in the range of. As shown in FIG. 4, when the filling amount of the insulating oil 7 is increased, the insulating oil 7 adheres to the heating resistor 4 to increase the heat capacity, and the time until the solder 5 is melted becomes longer, but the arc discharge Little difference in duration can be seen.

FIG. 5 is a graph showing the discharge state of the high-voltage cutoff fuse. In the figure, the failure rate when a voltage of 11 Kv is applied is indicated by □, and the failure rate when a voltage of 12 Kv is applied. Rates are indicated by ■. In addition, for example, when a voltage of 10 Kv is applied, the defect rate is almost the same as when a voltage of 11 Kv is applied. The defect rate is not always improved as the filling amount of the insulating oil 7 increases, and
It is stable between 10 mg and 20 mg as shown in. In other words, in consideration of the fact that the insulating oil 7 filled at the time of manufacturing the fuse is accumulated on the heating resistor 4 side, the filling amount may be, for example, about 20 mg in order to rotate the fuse to the tension spring 6 side. Therefore, the reliability of the pressure resistance can be improved by filling the insulating oil 7 of about 20 mg, for example. Further, even if the structure is not of a completely hermetic type as shown in FIG. 1, it can be said that a withstand voltage of 12 Kv can be guaranteed by filling about 20 mg of insulating oil 7 as described above.

By filling the insulating tube 1 with the insulating oil 7 as described above, the solder 5 and metal spatters are trapped in the insulating oil 7 and disappear, even when arc discharge occurs.
Since the electric field of the caps 2a and 2b pulls it toward the cap, it is possible to prevent the impedance of the inner wall of the insulating tube 1 from being lowered. Further, the insulating oil 7 is vaporized by the heat of the arc discharge, the atmospheric pressure in the insulating tube 1 is increased, and the direct discharge can be reduced, and the reliability can be improved.

[0014]

As described above, in the high-voltage cutoff fuse of the present invention, even when the solder is melted by an abnormal current and an arc discharge occurs, the melted solder and metal spatter are captured in the insulating oil. Since the electric field at both ends of the base is attracted toward the base, it is possible to prevent the impedance of the inner wall between the insulations from being lowered. Further, since the insulating oil evaporates due to the heat of the arc discharge, the air pressure inside the insulating tube rises and the discharge can be stopped, and the reliability of the fuse can be improved. Therefore, even when it is inserted into a high voltage application circuit of a device such as a fluorescent substance of an arc tube that applies a high voltage, an abnormal current flows through the device and the discharge is surely stopped after the solder is melted, so that the high voltage application circuit is You will be able to shut off.

[Brief description of drawings]

FIG. 1 is a front view showing a high voltage breaking fuse according to an embodiment of the present invention.

FIG. 2 is a diagram showing a joint portion of a tension spring of the high voltage cutoff fuse of the present embodiment.

FIG. 3 is a diagram showing a case where the solder of the high-voltage cutoff fuse of this embodiment is melted.

FIG. 4 is a graph showing the time until the solder of the high-voltage cutoff fuse of this embodiment is melted and the duration of arc discharge.

FIG. 5 is a graph showing a defective rate of insulating oil of the high-voltage cutoff fuse of the present embodiment.

FIG. 6 is a diagram schematically showing an example of a high voltage application circuit in which a high voltage cutoff fuse is inserted.

[Explanation of Codes] 1 Insulation tube 2a, 2b Base 3 Adhesive 4 Heat generating resistance 5 Solder 6 Tension spring 7 Insulating oil

Claims (4)

[Claims] 1. A heat generating resistor and a tension spring connected to each other by low melting point solder are disposed in an insulating tube whose both ends are sealed by a base, and the low melting point solder is provided when an abnormal current flows through the heat generating resistor. A high-voltage cutoff fuse for melting a current to cut off an electric current, wherein a predetermined amount of insulating oil is filled in the insulating tube. 2. The insulating oil forms a film on the inner wall of the insulating pipe.
The high-voltage cutoff fuse described in. 3. The high-voltage cutoff fuse according to claim 1, wherein an adhesive agent is applied to the fitting portion between the insulating tube and the cap all around. 4. The high voltage breaking fuse according to claim 1, wherein the end portion of the tension spring is formed straight.