【発明の詳細な説明】[Detailed description of the invention]
本発明は、電気的特性の優れた電圧非直線抵抗
体の製造方法に関する。
従来の電圧非直線抵抗体の焼結素体はZnO粉未
を主成分とし、副成分としてBi2O3、Sb2O3、
Co2O3、MnOなどの金属酸化物を少量加え、こ
れらを混合、圧縮成形した後、100〜200℃／hrの
速度で昇温し、1200〜1400℃の温度で焼成させた
後放冷もしくは徐冷して得られている。
この様にして得られた電圧非直線抵抗体を電力
用避雷器のごとき大きなサージ耐量を必要とする
ものに利用する場合には、特に非直線抵抗素体に
欠陥のない均一性の良好な、換言すればバリスタ
電圧のバラツキが少く、制限電圧比、耐サージ特
性の優れたものが要求される。すなわちバリスタ
電圧のバラツキが大きいと電圧非直線抵抗体に電
圧を印加した場合、抵抗体内を流れる電流はバリ
スタ電圧の低い部分に集中してジユール熱を発生
しついには抵抗体そのものが熱慕走を起し、所定
の電気的特性が得られなくなるおそれがある。さ
らにサージ電圧に対する安定性や制限電圧比など
の点についても従来のものは不十分であつた。
このため、電気的特性の向上の要求に対して、
種々の改良がなされている。すなわち(1)主成分と
副成分の混合法を改良して素体の欠陥をなくし均
一性をあげる方法、(2)焼結体の比重分布のバラツ
キを小さくするために圧縮成形圧力を減少させる
方法、などの試みが行われているが(1)の方法は主
成分に対して副成分が微量であるため分散が難し
く、不均一な非直線抵抗素体になることが避け難
く、バリスタ電圧のバラツキが大きくなる。(2)の
方法では素体の機械的強度が減少し、成形体の取
扱いに問題が生じ、一方、十分な強度を成形体に
与えると比重分布のバラツキが大きくなりバリス
タ電圧のバラツキが大きくなるなどの欠点があつ
た。
本発明は上記の欠点に鑑みなされたもので、バ
リスタ電圧のバラツキを低減し、制限電圧比、耐
サージ特性の優れた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。
すなわち、本発明の特徴はZnO粉未を主成分と
し副成分としてBi2O3、Sb2O3、CO2O3、MnOな
どの粉未を添加混合し適当な形状に圧縮成形した
後、焼成することによつて非オーム性を有する欠
陥のない均一な電圧非直線抵抗素体を得る電圧非
直線抵抗体の製造方法において、焼成工程の800
〜1200℃の範囲の昇温速度を50℃／hr以下にする
ことにより電圧非直線抵抗体を製造することにあ
る。
以下本発明を一実施例にもとずき説明する。本
発明に係る電圧非直線抵抗素体の組成は主成分と
してZnO99、549〜82.9mol％、副成分として
Bi2O30.1〜3.0mol％、Sb2O30.05〜3.0mol％、
Co2O30.05〜2.0mol％、MnO0.05〜2.0mol％を基
体としてNiO、SiO2、Al2O3、Cr2O3のいずれか
少くとも一種以上をそれぞれ0.05〜2.0mol％、
0.1〜3.0mol％、0.001〜0.1mol％、0.05〜2.0mol
％を含んだ組成のものである。これらの成分に水
を加えポツトミルで混合、圧縮成形した後、電気
炉に入れ第１図中Ａで示すように800℃までを100
℃／hr、800〜1200℃の範囲を25℃／hrの昇温速
度で上昇させ、1200℃で2Hr保持後100℃／hrの
下降速度で冷却した後、素体の研磨を行い45〓×
20tmmの非直線抵抗素体を得る。素体の研磨面を
目視でボイド、ピンホール等を検査後、超音波探
傷機で内部欠陥を調べた。更に素体を洗浄し第２
図に示すように円板状抵抗素体１１の底面に電極
１２を焼付け、上面に放射状に多数の点電極１３
―１，１３―２……を取付けて、バリスタ電圧
（V1nA）のバラツキ、制限電圧比（V10KA／
V1nA）、サージ耐量（電流波形８×20μsec、
10.000Aを10秒間かくで30回印加後のV1nAの変化
率）を測定した。これを従来の方法、すなわち第
１図中Ｂで示す様に、1200℃までの昇温を100
℃／hrで行い降温速度も100℃／hrで行つて得た
焼結素体と比較した。本発明の一実施例と従来例
とのボイド、ピンホール、欠陥等の比較を表(1)
に、各種特性を800〜1200℃の昇温速度を変化さ
せて比較したものを表(2)に示す。
The present invention relates to a method for manufacturing a voltage nonlinear resistor with excellent electrical characteristics. The sintered element body of a conventional voltage nonlinear resistor has ZnO powder as its main component, and its subcomponents include Bi 2 O 3 , Sb 2 O 3 ,
After adding a small amount of metal oxides such as Co 2 O 3 and MnO, mixing and compression molding, the temperature is raised at a rate of 100 to 200℃/hr, fired at a temperature of 1200 to 1400℃, and then left to cool. Or obtained by slow cooling. When using the voltage nonlinear resistor obtained in this way for something that requires a large surge withstand capacity, such as a power surge arrester, it is especially important to use a nonlinear resistor with good uniformity and no defects. Therefore, a varistor with small variations in voltage, excellent limiting voltage ratio, and excellent anti-surge characteristics is required. In other words, when the variation in varistor voltage is large and a voltage is applied to a non-linear resistor, the current flowing inside the resistor concentrates in the part where the varistor voltage is low, generating heat, and eventually the resistor itself becomes hot. There is a possibility that predetermined electrical characteristics may not be obtained. Further, the conventional devices were insufficient in terms of stability against surge voltage and limiting voltage ratio. Therefore, in response to the demand for improved electrical characteristics,
Various improvements have been made. In other words, (1) improving the mixing method of the main component and subcomponents to eliminate defects in the element body and increasing uniformity, and (2) reducing the compression molding pressure to reduce variations in the specific gravity distribution of the sintered body. However, method (1) is difficult to disperse because the subcomponent is small compared to the main component, and it is difficult to avoid creating an uneven nonlinear resistance element. The variation becomes larger. In method (2), the mechanical strength of the element body decreases, causing problems in handling the molded body. On the other hand, if sufficient strength is given to the molded body, the variation in the specific gravity distribution becomes large, which increases the variation in the varistor voltage. There were drawbacks such as: The present invention was made in view of the above-mentioned drawbacks, and an object of the present invention is to provide a method for manufacturing a voltage nonlinear resistor that reduces variations in varistor voltage and has excellent limiting voltage ratio and anti-surge characteristics. That is, the feature of the present invention is that ZnO powder is the main component and powders such as Bi 2 O 3 , Sb 2 O 3 , CO 2 O 3 , MnO are added and mixed as subcomponents, and after compression molding into an appropriate shape, In a method for manufacturing a voltage nonlinear resistor, in which a defect-free, uniform voltage nonlinear resistor element having non-ohmic properties is obtained by firing, 800% of the firing process is performed.
The object of the present invention is to manufacture a voltage nonlinear resistor by controlling the temperature increase rate in the range of ~1200°C to 50°C/hr or less. The present invention will be explained below based on one embodiment. The composition of the voltage nonlinear resistance element according to the present invention is ZnO99 as the main component, 549 to 82.9 mol%, and as a minor component.
Bi2O3 0.1-3.0mol %, Sb2O3 0.05-3.0mol %,
Co 2 O 3 0.05 to 2.0 mol%, MnO 0.05 to 2.0 mol% as a base, at least one or more of NiO, SiO 2 , Al 2 O 3 , Cr 2 O 3 0.05 to 2.0 mol % each,
0.1~3.0mol%, 0.001~0.1mol%, 0.05~2.0mol
%. After adding water to these ingredients, mixing them in a pot mill, and compression molding, they were placed in an electric furnace and heated to 800℃ for 100 minutes as shown by A in Figure 1.
°C/hr, the range of 800 to 1200 °C was raised at a temperature increase rate of 25 °C/hr, held at 1200 °C for 2 hours, and then cooled at a decrease rate of 100 °C/hr, and the element body was polished to 45〓×
Obtain a nonlinear resistive element of 20 t mm. After visually inspecting the polished surface of the element for voids, pinholes, etc., internal defects were examined using an ultrasonic flaw detector. Furthermore, the body is washed and the second
As shown in the figure, an electrode 12 is baked on the bottom surface of the disc-shaped resistive element 11, and a large number of point electrodes 13 are radially arranged on the top surface.
-1, 13-2...... to reduce the variation in varistor voltage (V 1nA ) and limit voltage ratio (V 10KA /
V 1nA ), surge resistance (current waveform 8 x 20μsec,
The rate of change in V 1nA after applying 10.000A for 10 seconds 30 times was measured. This is done using the conventional method, that is, as shown by B in Figure 1, the temperature is raised to 1200°C for 100°C.
It was compared with a sintered body obtained by performing the heating at a temperature of 100°C/hr. Table (1) shows a comparison of voids, pinholes, defects, etc. between an embodiment of the present invention and a conventional example.
Table (2) shows a comparison of various properties by varying the heating rate from 800 to 1200°C.
【表】【table】
【表】
これによると本発明の実施例ではボイド、ピン
ホールもなく超音波探傷による内部欠陥もないの
に対して従来例ではボイド、ピンホールが目視お
よび超音波探傷で多数確認された。特性の面につ
いても本発明の実施例は従来例よりもバリスタ電
圧（V1nA）のバラツキ、制限電圧比（V10KA／
V1nA）及びサージ耐量（△V1nA％）等の特性は
格段に改善されていることが判明した。
本発明においてボイド、ピンホール、内部欠陥
がなくなり電気的特性が大幅に改善された理由と
しては次のようなことが考えられる。
第３図に示すように、ZnO粉未を主成分とし副
成分としてBi2O3、Sb2O3，Co2O3、MnOなどを
添加混合し、圧縮成形された素体は800℃近辺よ
り急峻な収縮を起し1200℃近辺で終了することが
判る。その収縮率は素子径又は厚みに対して約20
％にも及ぶのが普通である。この急峻な収縮過程
中に成分の移動、結晶化反応、生長等がおこりバ
リスタとしての微細構造が形成されることからこ
の間の昇温速度を速くするとスムーズな成分の移
動、結晶化反応、生長が阻害されボイド、ピンホ
ール等の内部欠陥を生じ、微細構造の不均一な焼
結素体になり、結果としてバリスタ電圧のバラツ
キが大きくなり、電気的諸特性も不十分なものと
なつてしまつていたと考えられる。
第４図及び第５図に表(2)の示した各数値をグラ
フ化したものを示す。図より明らかなように800
〜1200℃の昇温速度と各種特性は50℃／hr近傍に
その特性上の分岐点が見られる。即ち、50℃／hr
以下の昇温速度とすることにより、バリスタ電圧
のバラツキの低減、制限電圧比、耐サージ特性の
向上をはかることができることが判明した。
以上、説明した様に、本発明に係るZnO粉未を
主成分とした非直線抵抗素体において、その焼成
工程の800〜1200℃の範囲の昇温速度を50℃／hr
以下とすることにより、前述の急峻な収縮過程中
の成分の移動、結晶化反応、生長がスムーズに行
なわれ、ボイド、ピンホール等の内部欠陥のない
非直線抵抗素体が得られる。そして、これにより
バリスタ電圧のバラツキを低減し、制限電圧比、
耐サージ特性の優れた電圧非直線抵抗体を得るこ
とができる。殊に電力用避雷器の様な大きなサー
ジ耐量を必要とするものについては特にその効果
は大きいものである。[Table] According to this, in the example of the present invention, there were no voids, pinholes, or internal defects by ultrasonic flaw detection, whereas in the conventional example, many voids and pinholes were confirmed by visual inspection and by ultrasonic flaw detection. In terms of characteristics, the embodiment of the present invention has a lower variation in varistor voltage (V 1nA ) and a lower limit voltage ratio (V 10KA /
It was found that characteristics such as V 1nA ) and surge resistance (ΔV 1nA %) were significantly improved. The reason why voids, pinholes, and internal defects are eliminated and the electrical characteristics are significantly improved in the present invention may be as follows. As shown in Figure 3, the compression molded element is made of ZnO powder as the main component and supplementary components such as Bi 2 O 3 , Sb 2 O 3 , Co 2 O 3 , MnO, etc., and the temperature is around 800°C. It can be seen that the contraction occurs more steeply and ends at around 1200℃. Its shrinkage rate is approximately 20% relative to the element diameter or thickness.
It is normal for it to reach up to %. During this steep contraction process, component movement, crystallization reaction, growth, etc. occur, and a fine structure as a varistor is formed. Therefore, if the heating rate during this period is increased, smooth component movement, crystallization reaction, and growth occur. This causes internal defects such as voids and pinholes, resulting in a sintered body with a non-uniform microstructure, resulting in large variations in varistor voltage and poor electrical properties. It is thought that Figures 4 and 5 show graphs of each numerical value shown in Table (2). 800 as shown in the figure
Regarding the temperature increase rate of ~1200℃ and various characteristics, a branching point in the characteristics can be seen around 50℃/hr. That is, 50℃/hr
It has been found that by setting the temperature increase rate as shown below, it is possible to reduce variations in varistor voltage, improve the limiting voltage ratio, and improve anti-surge characteristics. As explained above, in the non-linear resistance element mainly composed of ZnO powder according to the present invention, the temperature increase rate in the range of 800 to 1200 °C in the firing process is 50 °C / hr.
By doing the following, the movement of the components during the steep shrinkage process, crystallization reaction, and growth can be smoothly performed, and a nonlinear resistance element free of internal defects such as voids and pinholes can be obtained. This reduces the variation in varistor voltage and increases the limiting voltage ratio.
A voltage nonlinear resistor with excellent anti-surge characteristics can be obtained. The effect is particularly great for devices that require large surge resistance, such as power surge arresters.
【図面の簡単な説明】[Brief explanation of the drawing]
第１図は従来及び本発明に係る焼成パターンの
比較図、第２図は電圧非直線抵抗体の電気特性試
験を説明する図、第３図は電圧非直線抵抗体の焼
成温度と収縮率の関係図、第４図は800〜1200℃
間の昇温速度の変化に対するバリスタ電圧のバラ
ツキ及びサージ耐量の特性図、第５図は800〜
1200℃間の昇温速度の変化に対する制限電圧比の
特性図である。
Fig. 1 is a comparison diagram of firing patterns according to the conventional method and the present invention, Fig. 2 is a diagram illustrating an electrical characteristic test of a voltage nonlinear resistor, and Fig. 3 is a diagram showing the firing temperature and shrinkage rate of a voltage nonlinear resistor. Relationship diagram, Figure 4 is 800 to 1200℃
Figure 5 is a characteristic diagram of varistor voltage variation and surge withstand capacity with respect to temperature increase rate changes between 800 and 800~
FIG. 3 is a characteristic diagram of the limiting voltage ratio with respect to the temperature increase rate change over 1200°C.