JPH0648791Y2 - Surge absorber - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a surge absorber in which a fuse for discharging an overcurrent is connected in series to a discharge type surge absorbing element, and in particular, the arrangement of the fuse is carefully devised. The present invention relates to a surge absorber that improves the safety by increasing the fusing speed of a fuse in the event of a failure.

[Prior Art] A discharge surge absorber 2 of that type, which has been widely known as a gas arrester, has lead wires 8 and 8 connected to a pair of discharge electrodes 7 and 7, as shown in FIG. And a discharge gap 9 is formed between the discharge electrodes 7 and 7 and sealed together with a discharge gas in an airtight container 6 made of glass, and the lead wires 8 and 8 are placed outside the airtight container 6. It has the structure derived to. The discharge type surge absorbing element is used by being connected to a telephone line or the like, and when a surge such as dielectric lightning is applied to this, arc discharge is generated in the discharge gap, and a large current of this arc discharge is generated. The surge is absorbed through the device to prevent the surge from entering the telephone and the like.

By the way, telephones have been subjected to overvoltage tests in accordance with safety standards such as CSA and UL. The overvoltage test is based on the assumption that the power line comes into contact with the telephone line.
Rated voltage of discharge type surge absorber (DC discharge start voltage)
An AC voltage higher than is applied. Therefore, when the above-described overvoltage test is performed, the applied AC voltage causes the arc discharge between the discharge electrodes to continue, and the heat of the discharge melts the discharge electrodes to cause a short circuit. Furthermore, this short circuit increases the amount of current and generates a large amount of heat,
The airtight container is also melted and entangled with the discharge electrode, and eventually the circuit board on which the discharge type surge absorbing element is mounted burns out. Of course, the test fails. Further, if the above-mentioned phenomenon occurs during use, a fire may occur.

As a countermeasure against this, it is conceivable that a fuse is connected in series to the discharge type surge absorbing element to form a surge absorber in an open failure mode, and the fuse is blown out when an overcurrent continuously flows.

[Problems to be solved by the invention] However, in the above surge absorber, if the allowable current value of the fuse is set to be small in order to speed up the response speed against overcurrent, the surge current flowing by normal surge application causes the fuse to flow. Will melt and the surge absorption function will be lost. On the other hand, if a fuse with a large allowable current value is used in order to avoid this, there is a risk that the discharge electrode may melt and short-circuit before the fuse is blown by a continuous overcurrent.

The present invention has been devised in view of the above-mentioned point, and when a normal surge is applied, the fuse does not blow, and the arc discharge becomes a continuous state due to an overvoltage test or a line failure according to safety standards. If the fuse blows,
The purpose of the present invention is to realize a highly safe discharge type surge absorbing element that prevents burning accidents by blocking arc discharge before the discharge electrode melts and short-circuits and that conforms to safety standards.

[Means for Solving the Problems] In order to achieve the above-mentioned object, the surge absorber of the present invention comprises:
In a surge absorber formed by sealing discharge electrodes opposite to each other across a discharge gap together with a discharge gas in an airtight container to form a discharge type surge absorbing element, and connecting a fuse thereto in series. Is formed using glass,
A substantially ring-shaped metallic member is fitted in the vicinity of the tip of the discharge electrode on the outer peripheral surface of the hermetic container, and the fuse is pressed by the metallic member to be placed in contact with the surface of the hermetic container.

[Operation] According to the present invention, which has the above-described configuration, the airtight container is formed of glass, and a substantially ring-shaped metal member is fitted around the outer periphery of the airtight container, and the fuse is made of the metal member. Since it is pressed and placed in contact with the surface of the airtight container, when the arc discharge is sustained by the continuous application of overvoltage, a large amount of heat released from this arc discharge causes the above fuse to flow through the airtight container. When heated, the fuse fuses immediately with the heat generated by the electric current, causing the fuse to blow out immediately. Therefore, the power supply to the discharge type surge absorbing element is stopped and the arc discharge in the discharge gap is interrupted. In this case, since the influence of the heat due to the continuous arc discharge is great, it is possible to use a fuse having a large allowable current value to the extent that it is not blown by a short-time energization due to normal surge absorption.

Further, even if the fusing of the fuse is delayed a little due to the relationship between the value of the current flowing through the fuse by the arc discharge and the allowable current value of the fuse, the relationship with the heat radiation amount of the arc discharge, etc., the airtight container is made of glass, and its Since a substantially ring-shaped metal member is fitted around the outer periphery, when arc discharge continues and a large amount of heat is released, the specific heat of the airtight container and the metal member are different, so A temperature difference occurs in the airtight container, a thermal strain occurs in a portion of the airtight container that is in contact with the metal member, and the thermal strain causes a crack in the airtight container,
Air is mixed in the discharge gas to stop the arc discharge.

Moreover, since the metal member is fitted on the outer peripheral surface of the airtight container corresponding to the vicinity of the tip of the discharge electrode where the amount of heat emitted from the arc discharge is maximum, the fuse is blown by the continuous arc discharge. Or the time to crack the airtight container is shortened.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a perspective view of a surge absorber according to an embodiment of the present invention. In the figure, a surge absorber 1 has a discharge type surge absorbing element 2 and a fuse 3 mounted on a substrate 4 and connected in series. Further, the discharge type surge absorbing element 2 has a structure in which a substantially ring-shaped metal member 10 is fitted around the airtight container 6 and the fuse 3 is pressed by this to contact the surface of the airtight container 6. .

The discharge type surge absorbing element 2 has a pair of rod-shaped discharge electrodes 7 and 7 formed by covering the surface of a metal such as nickel having a good discharge characteristic with an emitter material such as BaO or BaO.Al ₂ O ₃ . At the base end, a lead wire made of dumet wire 8,8
The discharge electrodes 7,7
A discharge gap 9 is formed between them, and this is also hermetically sealed by forming both ends of a glass tube with a discharge gas mainly composed of a rare gas such as Ne, Ar or He or an inert gas such as nitrogen gas. Container 6
Then, the lead wires 8 are led out of the airtight container 6.

As shown in FIG. 2, the metal member 10 is formed by cutting a wire material made of phosphor bronze or the like having a spring property into a predetermined length, bending the wire material into a round shape, and folding back both cut ends thereof. The engaging portions 10a, 10a for engaging with No. 4 are formed, and the shape thereof is a substantially ring shape. The discharge type surge absorber 2 can be fixed to the substrate 4 by hooking the engaging portions 10a, 10a in the holes of the substrate 4.

When an arc discharge is generated in the discharge gap 9 between the discharge electrodes 7, 7 of the discharge type surge absorbing element 2, the amount of heat released from this arc discharge is maximum near the tips of the discharge electrodes 7, 7. Become. Therefore, if the fitting position of the substantially ring-shaped metal member 10 to the airtight container 6 is set to the position corresponding to the tip of the discharge electrodes 7, 7, the time until the fuse 3 is blown by the continuous arc discharge, or The time taken for the airtight container 6 to crack is further shortened.

[Effects of the Invention] As described in detail above, in the surge absorber of the present invention, the airtight container is formed of glass, and a substantially ring-shaped metal member is fitted around the outer periphery of the airtight container to secure the fuse. Since it is pressed by a metal member and placed in contact with the surface of the airtight container,
When the arc discharge is sustained due to overvoltage, the fuse heats up due to the heat generated by this discharge, and the fuse itself heats up due to the current, which immediately melts the fuse and interrupts the power supply before the discharge electrode melts and shorts. can do. Also, even if the fuse is slightly blown, thermal strain occurs in the portion of the airtight container that is in contact with the metal member,
Due to this thermal strain, the airtight container can be cracked and the discharge can be stopped. Moreover, since the metal member is fitted on the outer peripheral surface of the airtight container corresponding to the vicinity of the tip of the discharge electrode where the amount of heat emitted from the arc discharge is maximum, the fuse is blown by the continuous arc discharge. Or the time to crack the airtight container is shortened. Therefore, it is possible to prevent a burnout accident in a test based on a safety standard or in a normal use state, and obtain high safety.

[Brief description of drawings]

FIG. 1 is a perspective view showing an embodiment of the present invention, and FIG.
FIG. 3 is a front view of a metal member, and FIG. 3 is a schematic cross-sectional view of a discharge type surge absorbing element used in a conventional example. 1 ... Surge absorber, 2 ... Discharge type surge absorber, 3
...... Fuse, 6 ... Airtight container, 7 ... Discharge electrode, 9 ...
… Discharge gap, 10 …… Metal member.

Claims (1)

[Scope of utility model registration request] 1. A surge absorber formed by sealing discharge electrodes opposite to each other across a discharge gap together with a discharge gas in an airtight container to form a discharge type surge absorbing element, and a fuse connected in series thereto. The airtight container is formed of glass, and a substantially ring-shaped metal member is fitted near the tip of the discharge electrode on the outer peripheral surface of the airtight container, and the fuse is pressed by the metal member. A surge absorber characterized by being placed in contact with the surface of an airtight container.