JPH0722033B2 - Arrester - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an arrester which is a surge absorbing element that utilizes the discharge phenomenon of a discharge gap enclosed in an airtight container, and more particularly to a discharge for forming a discharge gap. The present invention relates to an arrester in which an electrode is formed by coating the surface of an electrode substrate with an emitter layer.

[Prior Art] Conventionally, in order to protect an electronic circuit element from a transient abnormal voltage applied to an electronic device or a surge such as an induced lightning, discharge of a discharge gap enclosed in a varistor composed of a voltage non-linear resistor or an airtight container. Various surge absorbing elements such as a surge absorbing element such as an arrester utilizing a phenomenon or a surge absorbing element having a parallel connection structure of a voltage non-linear resistor and a discharge gap are used.

Of the surge absorbing elements, the arrester utilizing the discharge phenomenon forms a discharge gap 3 by facing electrodes 2 made of nickel, aluminum, etc., as shown in FIG. Are connected to each other and sealed in the airtight container 5 together with the discharge gas.

[Problems to be Solved by the Invention] In this type of arrester, since a surge is absorbed by the arc discharge between the electrodes, a large surge is repeatedly applied (for example, a current waveform of 8/20 μsec,
Current value 1000A, application frequency 500 times or more, application interval 10
sec), the ions accelerated by the strong electric field due to the surge collide with the electrode and the constituent material of the electrode sputters, which may deteriorate the discharge characteristics and the life.
Further, although nickel and aluminum, which are the above-mentioned electrode materials, are easy to obtain and process, they have a high work function. Therefore, the discharge start voltage of the arrester using this is 140 to 150.
It becomes about V, and it becomes impossible to absorb the surge of voltage lower than this.

The present invention has been devised in view of the above points, and provides an arrester that is excellent in current withstand capability and life characteristics and that can absorb a low voltage surge by imparting sputtering resistance to the electrode. With the goal.

[Means for Solving the Problem] In order to achieve the above object, the arrester according to the present invention has a plurality of discharge electrodes formed by coating the surface of an electrode substrate with an emitter layer having conductivity to a predetermined discharge gap. In an arrester in which they are opposed to each other with a discharge gas and sealed in an airtight container together with a discharge gas, the emitter layer is formed of a substance consisting of molybdenum, tungsten, or a substance of aluminum alone or a mixture having a thin layer of alumina formed on the surface thereof, and a rare earth element. Element tetraboride, rare earth element oxide, complex compound of alkaline earth metal element oxide and molybdate of the element, complex of alkaline earth metal element oxide and tungstate of the element A compound, a mixture of at least one substance selected from the group consisting of a complex compound of an oxide of an alkaline earth metal element and an aluminate of the element. It is characterized by being formed more.

[Operation] The above-mentioned molybdenum, tungsten, and aluminum having a thin layer of alumina formed on the surface thereof are electrically conductive materials that are less worn by ion collision, and their work functions are relatively large. On the other hand, the tetraboride of the rare earth element, the oxide of the rare earth element, the composite compound of the oxide of the alkaline earth metal element and the molybdate of the element, the oxide of the alkaline earth metal element and the tungstic acid of the element The complex compound with a salt and the complex compound of an oxide of an alkaline earth metal element and an aluminate of the element each have a work function smaller than that of molybdenum and the like, and wear due to ion collision is small.

Therefore, the emitter layer formed of the mixture of the two is less worn by ion collision and can exhibit excellent sputter resistance. Further, the work function of the emitter layer can be adjusted by appropriately adjusting the mixing ratio of the two, and as a result, the discharge start voltage of the arrester can be set to an arbitrary value. Of course, the work function of the emitter layer can be easily reduced by increasing the mixing ratio of the latter (a substance having a relatively small work function such as tetraboride of rare earth element).

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

FIG. 1 is a sectional view showing an arrester 1 according to an embodiment of the present invention. In the figure, an arrester 1 includes a pair of discharge electrodes 2, 2 formed in a rod shape or a plate shape, which are arranged in parallel and face each other to form a discharge gap 3 between the discharge electrodes 2, 2. External terminals 4, 4 made of Dumet wire or 42-6 alloy wire are connected to one end of 2. Further, this is sealed in a hermetic container 5 formed of a glass tube together with a discharge gas mainly containing an inert gas such as rare gas (He, Ne, Ar, etc.) or nitrogen gas, and the external terminals 4, 4 are the same. It is led out from the airtight container 5 in the same direction.

The discharge electrodes 2,2 are such that the surface of the electrode substrate 2a, 2a made of nickel, aluminum or the like is coated with an emitter layer 6,6 made of a conductive material having a relatively small work function and less wear due to ion collision. Formed by.

The emitter layers 6 and 6 are made of a mixture of a substance having a small wear due to ion collision and a relatively large work function, and a substance having a small wear due to ion collision and a relatively small work function.

The substance having a relatively large work function specifically corresponds to molybdenum (Mo), tungsten (W), or a single substance or a mixture of aluminum (Al) having a thin layer of alumina formed on the surface.

Further, the substance having a relatively small work function is specifically a tetraboride of a rare earth element (YB ₄ , GdB _4, etc.) or an oxide of a rare earth element (Y ₂ O ₃ , La ₂ O ₃ , CeO ₂ , Gd ₂ O ₃ etc.), a complex compound of an oxide of an alkaline earth metal element (MgO, SrO etc.) and a molybdate of said element, an oxide of an alkaline earth metal element and a tungstate of said element complex compounds, there is an oxide and complex compounds aluminate of said element _{(aMgO · bAl 2 O 3,} aBaO · bSrO · cAl 2 O 3 , etc.) or the like of an alkaline earth metal element.

A composite compound of the oxide of the alkaline earth metal element and molybdate of the element, a composite compound of the oxide of the alkaline earth metal element and tungstate of the element, and the oxidation of the alkaline earth metal element A complex compound of a compound with an aluminate of the element is obtained by thermally decomposing an alkaline earth metal element molybdate, an alkaline earth metal tungstate and an alkaline earth metal aluminate, respectively. It is what is done.

Among the above substances, molybdenum, tungsten or aluminum on which a thin layer of alumina is formed, tetraboride of rare earth element has conductivity, oxide of rare earth element,
A composite compound containing an oxide of an alkaline earth metal element is insulating. Then, in order to secure the conductivity of the emitter layer, it is necessary to mix a conductive material in a capacity ratio of 60% or more.

Needless to say, when a substance with a small work function is mixed with a substance with a large work function, the discharge start voltage becomes lower as the amount of the substance having a smaller work function increases, but the mixing ratio is appropriately adjusted according to the voltage value of the surge to be dealt with. By doing so, an arbitrary discharge starting voltage can be realized.

The method for forming the emitter layers 6 and 6 can be easily performed by using a usual deposition technique such as coating, plating, vapor deposition, plasma spraying, or coating film thermal decomposition method.

In addition, in the above-mentioned embodiment, the case where the discharge electrode is a pair is shown, but as shown in FIG. 2, it may be three discharge electrodes 2,2,2 and the external terminals 4,4. The direction of derivation is not limited to the same direction, but may be the direction deduced in the opposite direction as shown in FIG.

[Effects of the Invention] As described in detail above, in the arrester of the present invention, a substance having a large work function and less wear due to ion collision and a substance having a small work function and less wear due to ion collision are provided on the surface of the electrode substrate. Since it has a discharge electrode coated with a conductive emitter layer made of a mixture of the above, the discharge electrode hardly sputters even if a discharge due to surge absorption occurs, so the discharge characteristic, that is, the surge absorption characteristic, is stable for a long period of time. However, the current withstanding capability and life characteristics are improved. Moreover, by adjusting the mixing ratio of the substances forming the emitter layer, an arbitrary discharge starting voltage can be realized. Therefore, the discharge starting voltage can be easily lowered depending on the mixing ratio, and it becomes possible to cope with a low voltage surge of, for example, about 80V.

[Brief description of drawings]

FIG. 1 is a sectional view of an embodiment of the present invention, FIGS. 2 and 3 are sectional views showing examples of shapes of other embodiments, and FIG. 4 is a sectional view of a conventional example. 1 ... Arrestor, 2 ... Discharge electrode, 2a ... Electrode substrate, 3 ... Discharge gap, 5 ... Airtight container, 6 ... Emitter layer.

Claims (1)

[Claims] 1. An arrester in which a plurality of discharge electrodes each having a conductive emitter layer coated on the surface of an electrode substrate are opposed to each other with a predetermined discharge gap therebetween and are enclosed together with a discharge gas in an airtight container. In the above, the emitter layer is formed of a substance consisting of molybdenum, tungsten or a simple substance of aluminum having a thin layer of alumina formed on the surface thereof or a mixture thereof, a tetraboride of a rare earth element, an oxide of a rare earth element, and an alkaline earth metal element A complex compound of an oxide and a molybdate of the element, a complex compound of an oxide of an alkaline earth metal element and a tungstate of the element, an oxide of an alkaline earth metal element and an aluminate of the element. An arrester formed by mixing with at least one substance selected from the group consisting of complex compounds of.