JPH0697626B2 - Discharge type surge absorber - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a discharge type surge absorbing element that utilizes a discharge phenomenon in a discharge gap housed in an airtight container, and particularly has excellent responsiveness to surge absorption and a long life. The present invention relates to a discharge type surge absorbing element which is intended to be prolonged.

[Prior Art] Conventionally, as a surge absorbing element for protecting an electronic circuit from a surge such as inductive lightning applied to the electronic circuit, a varistor made of a high resistance element having a voltage non-linear characteristic and a discharge gap are sealed in an airtight container. Stored arresters are widely used.

However, although the varistor is excellent in response to surge absorption, it has a relatively small current withstanding capacity per unit cross-sectional area,
Therefore, it is difficult to efficiently absorb a large surge current. Further, the arrester can increase the current withstanding capacity by generating an arc discharge in its discharge gap, but the time required from the application of a surge to the arc discharge is slower than that of the varistor, and its response Had a sex problem.

To improve the surge absorption response of the arrester, a conductor thin film is applied to the surface of a substantially cylindrical insulator, and a microgap having a width of about 0.1 mm is formed on the conductor thin film. A surge absorbing element has been proposed in which a conductor thin film is divided into a plurality of pieces by forming a book or a plurality of pieces in a circular shape, and discharge electrodes are formed at both ends of the insulator.

When a surge is applied to the surge absorbing element having the microgap, a potential difference is first generated between the conductor thin films via the microgap, whereby electrons are emitted to the microgap and a creeping discharge occurs. Then, a creeping discharge occurs between the discharge electrodes due to the priming effect of electrons generated by this creeping discharge. Then, this creeping discharge is converted into arc discharge due to an increase in surge current, and the surge is absorbed by this arc discharge. In this way, the surge absorbing element having a microgap is
Since it uses creeping discharge, which has a fast response speed, it has substantially the same excellent responsiveness as the above varistor and has a large current withstand capability.

[Problems to be Solved by the Invention] However, in the surge absorbing element having the microgap as described above, the electrical insulation of the microgap is caused by the creeping discharge formed between the conductor thin films during repeated surge absorption. However, there is a drawback that the property deteriorates and eventually the insulation becomes defective and the function as a microgap is not exhibited. There is also a problem that it takes some time to transition from the creeping discharge in the micro gap to the creeping discharge between the discharge electrodes.

Therefore, the present invention solves the above problems and realizes a discharge type surge absorbing element that is excellent in response to surge absorption and that has a long life without deterioration of insulation even if surge absorption is repeated. To aim.

[Means for Solving the Problems] In order to achieve the above-mentioned object, in the discharge type surge absorbing element of the present invention, the discharge electrodes opposed to each other with a discharge gap therebetween are housed in an airtight container filled with a discharge gas. In the discharge type surge absorbing element, a mixture of a powdery and granular conductive material and a powdery and granular insulating material, which is fired with a minute space provided between the powdery and granular conductive materials, is interposed between the discharge electrodes. It is characterized by that.

It is preferable that the conductive material includes a semiconductor, and the insulating material is a porous material.

[Operation] Since the discharge type surge absorbing element of the present invention has the above-mentioned configuration, when a surge is applied to the surge absorbing element,
A potential difference is generated between the powdery and granular conductive materials through the minute space,
When this exceeds a predetermined value, electrons are immediately emitted from the conductive material, and a creeping discharge is generated on the surface of the insulating material between the conductive materials. The creeping discharge generates electrons with the discharge, and the electrons are transferred between the discharge electrodes by the priming effect of the electrons. In this case, the creeping discharge between the discharge electrodes is first formed between the discharge electrode and the conductive material in the vicinity of this electrode, which expands like a stepping stone by using the conductive material in the closer vicinity as a foot, and discharges. A discharge path is formed between the electrodes. This creeping discharge increases the voltage drop between the discharge electrodes with its extension, and finally shifts to a gas phase discharge between the discharge electrodes. For this reason, glow discharge is generated in the discharge gap, and this is transferred to arc discharge due to an increase in surge current, and the surge is absorbed through the large current of arc discharge.

The creeping discharge that occurs between the solid phase and the vapor phase is a discharge phenomenon in which the discharge time delay is very small as compared with the vapor phase discharge, and in the present invention, there are many minute spaces in which the creeping discharge occurs. Moreover, since the creeping discharge extends like stones between the line electrodes, the discharge path between the discharge electrodes is formed in a short time. Therefore, the time from the application of the surge to the formation of the vapor-phase discharge between the discharge electrodes becomes extremely short, and the response characteristic is improved.

Further, the minute spaces (three-dimensionally present rather than two-dimensionally) between the powdery and granular conductive materials correspond to the microgaps in the conventional surge absorbing element, and the number thereof is the same as that of the conventional groove-shaped. It is so huge that it is needless to say compared with the micro gap. As a result, when a surge is applied to the discharge type surge absorbing element, electrons are emitted everywhere in the powdery and granular conductive material, which facilitates the occurrence of creeping discharge in a minute space. Furthermore, when surge absorption is repeatedly performed, even if a conductive material is sputtered by the creeping discharge and deposited on the insulating material, it is not easy to cause insulation deterioration over the entire minute space. Therefore, compared with the conventional surge absorbing element having a planar microgap, it is possible to prevent the shortening of the life caused by insulation deterioration of the microgap and improve the life characteristic of the surge absorbing element. is there.

Further, if the conductive material is composed of a semiconductor, electrons can be easily emitted when a surge is applied, and the creeping discharge in the minute space can be generated more quickly.

Further, by forming the powdery granular insulating material from a porous material, even if the conductive material is sputtered by a creeping discharge, the conductive material can be adhered to all the numerous pores of the powdery granular insulating material. In addition, life deterioration due to insulation deterioration between conductive materials can be prevented, and life characteristics can be further improved. Moreover, an insulating material having a large specific surface area generated from the porous structure can get rid of impure gases having a large polarity and ionicity such as carbon dioxide gas, oxygen, and nitrogen oxides released into the airtight container by discharge ion bombardment by its gettering action. By adsorbing, the discharge starting voltage can be kept constant and the discharge operation of the surge absorbing element can be stabilized.

Embodiments Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic sectional view of a discharge type surge absorber according to an embodiment of the present invention, and FIG. 2 is a structural explanatory view of a mixture used in the present invention. In the figure, a discharge type surge absorbing element 1 comprises a pair of discharge electrodes 3, 3'made of a material having a good discharge characteristic such as nickel, iron or an alloy thereof on both ends of a mixture 2 of a conductive material 2a and an insulating material 2b. To form a discharge gap 4 between the opposing outer edges of the discharge electrodes 3, 3 '.
This is housed in an airtight container 5 formed by sealing sealing caps 5b, 5b 'made of Dumet wire at both ends of an outer casing 5a made of a glass tube, and the discharge electrodes 3, 3'and the sealing caps. Five
It has a structure in which b and 5b 'are respectively connected. Furthermore,
A discharge gas composed of an inert gas mainly containing a rare gas such as neon, argon or xenon is enclosed in the airtight container 5, and external terminals 6 and 6'are provided on the outer surfaces of the sealing caps 5b and 5b ', respectively. Connected.

The mixture 2 is composed of a conductive material 2a made of powdery metal such as nickel, zinc or molybdenum, and a porous material such as activated alumina, zeolite or clay, or a powdery insulating material 2b made of glass. It is mixed in a ratio and baked into a desired shape to form a pellet. The conductive material 2a becomes a good conductor if the mixed material is fired in a deoxygenated atmosphere, and becomes a semiconductor by forming a thin oxide film on the surface of the metal if the mixed material is fired in an oxidizing atmosphere.
In the case of a semiconductor, depending on the material, electrons tend to be easily emitted when a surge is applied. When the conductive substance 2a is composed of a semiconductor, a semiconductor material mainly composed of a metal oxide such as nickel oxide, zinc oxide, molybdenum oxide or a semiconductor material other than a metal oxide such as silicon carbide is used from the beginning. It goes without saying that you can do it.

The fine structure inside the mixture 2 is as shown in FIG. 2, in which the granular insulating material 2b is dispersed substantially uniformly between the granular conductive material 2a to form a minute space 2c between the conductive materials 2a. Is
The conductive materials 2a are prevented from being connected to each other for a long time.

The manufacturing process of the discharge type surge absorber 1 of this embodiment will be described in detail below.

First, the discharge electrodes 3 and 3'are fitted to both ends of the mixture 2 of the conductive material 2a and the insulating material 2b so as to face each other with a discharge gap 4 therebetween. Next, a substantially cylindrical sealing cap 5b made of Dumet wire, to which external terminals 6 made of copper-coated steel are connected by soldering or the like, is fitted into one end of an outer casing 5a made of a glass tube. Then, the mixture 2 to which the electrodes 3 and 3'are connected is inserted from the open end of the outer envelope 5a, and then the sealing cap 5b 'to which the external terminal 6'is connected is fitted into the open end of the outer envelope 5a. . After assembling in this way, the inside of the envelope 5a is evacuated in the tank, and a discharge gas consisting of an inert gas mainly containing a rare gas such as neon, argon, or xenon is introduced into the envelope 5a. Encapsulate. In addition, heat this to the enclosure
The airtight container 5 is formed by sealing the 5a and the sealing caps 5b and 5b '. Due to this heating action, the outer envelope made of glass tube
5a contracts, which causes the discharge electrodes 3, 3'and the sealing cap 5
b and 5b 'are crimped and securely connected.

In addition, in the above-described embodiment, the granular conductive material and the granular insulating material are mixed to form a pellet-like mixture, but the present invention is not limited to this example. For example, a mixture of a powdery and granular conductive material and a powdery and granular insulating material may be applied in layers on the surface of the insulating material as a support.
Further, in the present embodiment, the discharge type surge absorbing element 1 provided with the external terminals 6 and 6'has been described, but of course the chip type discharge type surge absorbing element 1 having no external terminal may be used. It doesn't matter.

[Effects of the Invention] As described in detail above, according to the present invention, a granular space conductive material and a granular insulation material are mixed between the discharge electrodes to form a minute space between the granular conductive materials. By interposing the mixture fired in the state, there is a minute space where a creeping discharge occurs everywhere between the discharge electrodes, and moreover, because the creeping discharge expands like a stepping stone with the conductive substance as a foothold, The time required for transition from creeping discharge to arc discharge is shortened, and in addition to the large current withstand capability originally possessed by the discharge type surge absorbing element, a discharge type surge absorbing element excellent in responsiveness can be realized.

Moreover, since the number of the above-mentioned minute spaces becomes enormous,
Insulation deterioration of all minute spaces cannot easily occur due to the deposition of the sputtered conductive material, and it is possible to make the discharge type surge absorption element have a longer life than the conventional surge absorption element having a micro gap. it can.

Then, by configuring the conductive material with a semiconductor,
Electron discharge in the minute space is facilitated, and the response characteristics are further improved. In addition, since the insulating material is a porous material, the insulating material has an extremely large specific surface area due to many pores, so that the insulation deterioration due to the sputtered conductive material is less likely to occur, and the life characteristics are improved. It will be further improved.

Furthermore, when the insulating substance is a porous substance, the porous substance adsorbs an impure gas generated at the time of surge absorption by its getter action, so that the discharge starting voltage is not increased,
The discharge characteristics of the discharge type surge absorbing element can be stabilized.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of a discharge type surge absorbing element according to an embodiment of the present invention, and FIG. 2 is a structural explanatory view of a mixture used in the discharge type surge absorbing element of the present invention. DESCRIPTION OF SYMBOLS 1 ... Discharge type surge absorber, 2 ... Mixture, 2a ... Conductive material, 2b ... Insulating material, 2c ... Micro space, 3, 3 '... Discharge electrode,
4 ... Discharge gap, 5 ... Airtight container

Claims (3)

[Claims] 1. A discharge type surge absorbing element in which discharge electrodes facing each other across a discharge gap are housed in an airtight container filled with a discharge gas, wherein a powdery conductive material and a powdery insulating material are mixed. A discharge type surge absorbing element, characterized in that a mixture fired in a state where a minute space is provided between the powdery and granular conductive materials is interposed between the discharge electrodes. 2. The discharge type surge absorbing element according to claim 1, wherein the conductive material is a semiconductor. 3. The surge absorbing element according to claim 1, wherein the insulating material is a porous material.