【発明の詳細な説明】[Detailed description of the invention]
本発明は酸化亜鉛（ZnO）を主成分とする電圧
非直線抵抗体の製造方法、特にその側面絶縁方法
に関するものである。
従来、ZnOを主成分とする電圧非直線抵抗体
（以下抵抗体と略する。）の側面絶縁においては、
焼成後抵抗体側面にエポキシ系有機物を塗布して
絶縁するか、あるいは抵抗体の焼成前に種々の無
機化合物を抵抗体側面に塗布後焼成し、ガラス質
又は結晶質の絶縁被膜を形成させて絶縁してい
た。
しかし、前者の方法においては、塗布するエポ
キシ系有機物と抵抗体との密着性が悪いため抵抗
体に水分が吸着され、特性劣化が大きく短波尾耐
量も弱くなる欠点がある。又、抵抗体とエポキシ
系有機物との間に熱膨張の差があるため熱衝撃で
エポキシ系有機物にクラツクが入り劣化の原因と
なる欠点がある。又、後者の方法においては、焼
成時に抵抗体と無機化合物との収縮率を一致させ
る必要があり、このため１次焼成してある程度抵
抗体を収縮させた後に無機化合物を塗布して本焼
成し、側面絶縁被膜を形成させている。従つてこ
の場合には、焼成を２回に分けて行なうこととな
り、燃料（電力を含む）費が上昇するとともに焼
成装置を２回使用するので製造コストが上昇する
欠点がある。又、両者の方法とも側面絶縁被膜を
必要厚に均一にするためには相当の技術と装置を
要する欠点がある。
本発明は上記の欠点を除去して、電圧非直線抵
抗体の側面絶縁被膜を密着性良く形成することが
できるとともに高抵抗な側面絶縁被膜を製作容易
で安価に形成することができる電圧非直線抵抗体
の製造方法を提供することを目的とする。
以下本発明の一実施例を図面とともに説明す
る。まず、焼成装置の構成を第１図によつて説明
すると、１はアルミナ質の鞘（焼成用容器）、２
は鞘１の内底部に載置された耐熱性セラミツク材
から成る台座で、台座２の材質はアルミナ質又は
酸化亜鉛系焼結板等が良く、特に酸化亜鉛系焼結
板は抵抗体の主成分と同質であるので抵抗体の特
性を損ねる恐れがない。３は圧縮成形されたZnO
を主成分とする電圧非直線抵抗体で、抵抗体３は
敷粉４を介して台座２の上面に載置される。敷粉
４は台座２と抵抗体３との溶着を防ぐためのもの
で、抵抗体３の成分に類似又は同質のものが要求
され、アルミナ質や抵抗体３の造粉末又は抵抗体
３を仮焼して砕いた粉等が用いられる。台座２を
抵抗体３と同質系とした場合には敷粉４はなくて
も良い。５は鞘１の内側面に塗布された抵抗体３
に側面絶縁被膜を形成するためのＳbからなるス
ラリー状の塗布剤、６は鞘１の上部をほぼ密閉状
におおう蓋で、蓋６は鞘１と同質性の部材により
形成する。前記塗布剤５は鞘１の内面の一部又は
全部あるいは蓋６の内面に塗布しても良く、要は
焼成用の容器内に設けられていれば良い。尚、実
際には抵抗体３の上面には絶縁被膜が形成される
のを防ぐためのしやへい部材が設けられる。
次に上記の焼成装置を用いた製造方法について
述べると、まず抵抗体３はZnO（91mol％）に
Sb2O3，Bi2O3，CO2O3，MnO2，Cr2O3，SiO2な
どを合計9mol％加え、充分混合した後に適当な
形状に圧縮成形する。例えば直径40mmφ、厚さ30
mmの円柱形の成形体とする。又、塗布剤５は水を
加えて充分に混合して得られたスラリーを鞘１の
内壁に塗布して乾燥させる。
そして、鞘１内に第１図のように抵抗体３を配
置し、蓋６で鞘１をほぼ密閉する。この状態で
1000℃〜1400℃（1100℃〜1300℃が好ましい。）
の温度範囲で焼成すると、塗布剤５中のＳbが蒸
発し、鞘１内はＳbの蒸気で満たされ、抵抗体３
内のZnO，Bi2O3等と気―固相反応し、抵抗体３
の表面に高抵抗の絶縁被膜が形成される。この絶
縁被膜はＸ線回折により調べると第２図に示すよ
うになり、スピネル（Zn2.33 Sb0.67 O4）が主成分
で形成されていることが判明した。このことはＸ
線マイクロアナライザーにより調べても同様であ
つた。
上述した鞘１内での抵抗体３とＳbの蒸気との
気―固相反応は次の様な反応形態となる。すなわ
ち、鞘１内に収容されたＳbは空気中或いは酸素
中で融点（630.5℃）以上で燃焼してSb2O3とな
る。このSb2O3は更に高温で蒸発し始め、1000℃
以上では非常に活発となる。また、焼成を不活性
ガス雰囲気（Ar2N2等）で行なう場合、Ｓbは次
に示すよう蒸気圧が高いため、Ｓb蒸気が発生す
る。
Ｓbの蒸気圧（mmHg）は焼成温度と対応すると
次表のようになる。
The present invention relates to a method for manufacturing a voltage nonlinear resistor whose main component is zinc oxide (ZnO), and particularly to a method for insulating its side surfaces. Conventionally, in the side insulation of voltage nonlinear resistors (hereinafter abbreviated as resistors) whose main component is ZnO,
After firing, an epoxy-based organic substance is applied to the side surface of the resistor for insulation, or before the resistor is fired, various inorganic compounds are applied to the side surface of the resistor and then fired to form a glassy or crystalline insulating film. It was insulated. However, the former method has the disadvantage that moisture is adsorbed to the resistor due to poor adhesion between the applied epoxy-based organic substance and the resistor, resulting in significant deterioration of characteristics and weakening of short-wave tail resistance. Furthermore, since there is a difference in thermal expansion between the resistor and the epoxy organic material, there is a drawback that the epoxy organic material cracks due to thermal shock, causing deterioration. In addition, in the latter method, it is necessary to match the shrinkage rates of the resistor and the inorganic compound during firing, so after the resistor is first fired to shrink to some extent, the inorganic compound is applied and the main firing is performed. , a side insulation coating is formed. Therefore, in this case, firing is performed twice, which increases fuel (including electricity) costs, and the firing apparatus is used twice, which increases manufacturing costs. Furthermore, both methods have the disadvantage that considerable skill and equipment are required to make the side insulating coating uniform to the required thickness. The present invention eliminates the above-mentioned drawbacks, makes it possible to form a side insulating coating of a voltage nonlinear resistor with good adhesion, and makes it possible to form a high resistance side insulating coating easily and inexpensively. An object of the present invention is to provide a method for manufacturing a resistor. An embodiment of the present invention will be described below with reference to the drawings. First, the configuration of the firing device will be explained with reference to Fig. 1. 1 is an alumina sheath (firing container);
is a pedestal made of heat-resistant ceramic material placed on the inner bottom of the sheath 1. The material of the pedestal 2 is preferably alumina or zinc oxide sintered plate, and in particular, zinc oxide sintered plate is used as the main material of the resistor. Since it is of the same quality as the components, there is no risk of impairing the characteristics of the resistor. 3 is compression molded ZnO
The resistor 3 is placed on the upper surface of the pedestal 2 with a pad 4 interposed therebetween. The bedding powder 4 is used to prevent welding between the pedestal 2 and the resistor 3, and is required to be similar or of the same composition as the resistor 3, and may be made of alumina, a powder for the resistor 3, or a temporary powder for the resistor 3. Roasted and crushed powder is used. If the pedestal 2 is made of the same material as the resistor 3, the bedding powder 4 may be omitted. 5 is a resistor 3 applied to the inner surface of the sheath 1
A slurry-like coating agent made of S b is used to form an insulating coating on the side surface of the sheath 1. Reference numeral 6 is a lid that covers the upper part of the sheath 1 in a nearly hermetically sealed manner, and the lid 6 is formed of a material that is the same as that of the sheath 1. The coating agent 5 may be applied to a part or all of the inner surface of the sheath 1 or the inner surface of the lid 6, and it is sufficient if it is provided inside the firing container. In fact, a shielding member is provided on the upper surface of the resistor 3 to prevent the formation of an insulating film. Next, we will discuss the manufacturing method using the above firing equipment. First, resistor 3 is made of ZnO (91 mol%).
A total of 9 mol % of Sb 2 O 3 , Bi 2 O 3 , CO 2 O 3 , MnO 2 , Cr 2 O 3 , SiO 2 and the like are added, thoroughly mixed, and compression molded into a suitable shape. For example, diameter 40mmφ, thickness 30
A cylindrical molded body with a diameter of mm. Further, the coating agent 5 is obtained by adding water and thoroughly mixing the resulting slurry, which is coated on the inner wall of the sheath 1 and dried. Then, the resistor 3 is placed inside the sheath 1 as shown in FIG. 1, and the sheath 1 is substantially sealed with a lid 6. in this state
1000℃~1400℃ (1100℃~1300℃ is preferable.)
When fired in a temperature range of
A gas-solid phase reaction occurs with ZnO, Bi 2 O 3 , etc. in the resistor 3.
A high-resistance insulating film is formed on the surface of the This insulating film was examined by X-ray diffraction as shown in FIG. 2, and it was found that the main component was spinel (Zn 2 . 33 Sb 0 . 67 O 4 ). This is X
The same result was obtained when examined using a line microanalyzer. The gas-solid phase reaction between the resistor 3 and the S b vapor within the sheath 1 described above takes the following reaction form. That is, the S b housed in the sheath 1 burns in air or oxygen at a temperature higher than its melting point (630.5° C.) and becomes Sb 2 O 3 . This Sb 2 O 3 begins to evaporate at even higher temperatures, reaching 1000℃.
Above that, it becomes very active. Furthermore, when firing is performed in an inert gas atmosphere (such as Ar 2 N 2 ), S b vapor is generated because S b has a high vapor pressure as shown below. The vapor pressure (mmHg) of S b corresponds to the firing temperature as shown in the table below.
【表】
一方、抵抗体３は800℃〜1000℃の温度領域で
体積比で約40％収縮され、ZnOの他、Zn2SiO4、
パイロクロア（Zn2Sb3Bi3O14）、スピネル、
Bi2O314Bi2O3―Cr2O3等の結晶相が形成される。
抵抗体３表面では鞘１内にＳbが燃え、Sb2O3か
ら発生した蒸気（空気中、酸素中）或いはＳb蒸
気（不活性ガス中）と抵抗体３中のZnOが反応し
て、その表面にスピネルが形成される。形成され
たスピネル被膜は抵抗体３とともに焼成されるた
め緻密で均一の結晶粒を有する側面絶縁被膜が形
成される。
以上述べたように、本発明によれば、焼成容器
内にアンチモンを配置し、前記焼成と同時に気―
固相反応により側面絶縁被膜を形成するようにし
たので、抵抗体と絶縁被膜との密着性が極めて良
くなるとともに抵抗体焼成温度領域で高抵抗な側
面絶縁被膜が簡単にしかも安価に得られる。ま
た、従来のように無機側面剤を塗布する方法のよ
うに抵抗体と側面剤との収縮率を考慮する必要が
なく製作が容易となる等の効果がある。[Table] On the other hand, resistor 3 is shrunk by about 40% by volume in the temperature range of 800°C to 1000°C, and in addition to ZnO, Zn 2 SiO 4 ,
Pyrochlore (Zn 2 Sb 3 Bi 3 O 14 ), spinel,
Crystal phases such as Bi 2 O 3 14Bi 2 O 3 -Cr 2 O 3 are formed.
Sb is burned in the sheath 1 on the surface of the resistor 3, and the vapor generated from Sb 2 O 3 (in air, oxygen) or Sb vapor (in inert gas) reacts with ZnO in the resistor 3. , a spinel is formed on its surface. Since the formed spinel coating is fired together with the resistor 3, a side insulating coating having dense and uniform crystal grains is formed. As described above, according to the present invention, antimony is placed in the firing container, and the air is heated at the same time as the firing.
Since the side insulating coating is formed by solid-phase reaction, the adhesion between the resistor and the insulating coating is extremely good, and a side insulating coating having high resistance in the resistor firing temperature range can be easily and inexpensively obtained. In addition, unlike the conventional method of applying an inorganic side surface agent, there is no need to consider the shrinkage rate of the resistor and the side surface agent, and there are advantages such as ease of manufacturing.
【図面の簡単な説明】[Brief explanation of the drawing]
第１図は本発明の一実施例を述べるための焼成
装置の縦断正面図、第２図は本発明に得られた側
面絶縁被膜のＸ線回折図である。
１…鞘（焼成用容器）、３…電圧非直線抵抗
体、５…塗布剤、６…蓋。
FIG. 1 is a longitudinal sectional front view of a firing apparatus for describing an embodiment of the present invention, and FIG. 2 is an X-ray diffraction diagram of a side insulating coating obtained according to the present invention. 1... Sheath (container for firing), 3... Voltage nonlinear resistor, 5... Coating agent, 6... Lid.