JPS5832764B2 - Manufacturing method of voltage nonlinear resistor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a voltage nonlinear resistor mainly made of zinc oxide, and its purpose is to eliminate structural defects such as cracks inside a large sintered body. The purpose is to provide a large voltage non-linear resistor that does not require large voltages.

Conventionally, voltage nonlinear resistors made of metal oxide sintered bodies containing zinc oxide as a main component have been developed and put into practical use.

This zinc oxide voltage nonlinear resistor is made by adding a small amount of bismuth oxide, lead oxide, barium oxide, etc. to zinc oxide, mixing it uniformly, molding it, and then placing it in the air at a temperature of 800 to 150.
It was sintered at 0° C., and a pair of electrodes were formed on this sintered body.

This voltage nonlinear resistor has extremely large nonlinearity in voltage-current characteristics, and has been widely used for voltage stabilization, surge absorption, and the like.

Recently, it has come to be used in high-voltage circuits as a characteristic element of lightning arresters.

Generally, the surge current flowing through a lightning arrester is extremely large, and in order for the characteristic elements to absorb the surge without any problem, the volume of the sintered body must necessarily be large.

Normally, a 2500A class lightning arrester has an element diameter of 32 mm and a thickness of 2
A sintered body with an element diameter of 56 m71L and a thickness of 20 to 25 mm is used for a 100OOA class lightning arrester.

However, in conventional manufacturing methods, some sintered bodies have structural defects such as cracks inside them, resulting in unstable performance and problems.

This was due to a problem with the molding method, and conventionally the first
As shown in the figure, a granule 1 made by adding an organic binder to a mixture consisting mainly of zinc oxide and a small amount of metal oxide is placed in iron cylinders 2a and 2b, and an upper iron punch 3 and a lower Compression molding was performed using punch 4.

In this method, especially when the thickness of the molded body exceeds 10 peaks, the pressure is not applied uniformly to the molded body, but is concentrated on the end face and the periphery, and no pressure is applied to the center.

In this way, pressure unevenness occurs inside the molded body, and when the molded body is fired, cracks and the like occur inside the sintered body.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the conventional problems and provide a voltage nonlinear resistor that does not cause internal cracks even in a large sintered body and has stable performance.

In order to achieve this objective, the voltage nonlinear resistor of the present invention uses a method of forming a mixture of raw materials into thin plates, stacking them, and crimping them to eliminate pressure unevenness in the molded body and eliminate internal structural defects. This is an attempt to obtain a sintered body that does not

Hereinafter, the method for manufacturing a voltage nonlinear resistor of the present invention will be described in detail using an embodiment shown in FIG. 2, which is an accompanying drawing.

In FIG. 2, 5 is a thin plate of a mixture of raw materials mainly containing zinc oxide, 6 is an upper punch of the compressor made of iron or the like, and 7 is a lower punch of the compressor.

First, bismuth oxide Bi2O3 is added to zinc oxide ZnO powder.
, cobalt oxide Co01 manganese oxide MnO, antimony oxide 5b203 and silicon oxide SiO2 powders are added in a proportion of 0.01 to 10 mol each, and polyvinyl butyral 3 to 6% is added as an organic binder to this powder raw material.
Weight section, methyl alcohol as organic solvent 25-35
Add 1 to 10 parts by weight of dibutyl phthalate as a plasticizer and mix for 12 to 24 hours to obtain a slurry.

This slurry is sheeted onto a glass plate or polyester film using a blade or the like to a thickness of 0.02-2.

After drawing the sheet, dry at 60-100'C for 2-3 hours.

Thereafter, the sintered body is cut to an appropriate size (in the case of an element diameter of 32 mm, it is cut into a disk shape with a diameter of 40 mm).

Thereafter, the mixture is peeled off from the glass plate or film to obtain a thin plate 5 of the mixture.

Next, an appropriate number of thin plates 5 are stacked, placed on the lower punch 7 of the compressor, and the upper punch 6 is lowered to a pressure of 300~
A molded body was obtained by pressure bonding at 600 kg/cd.

This molded body is placed in air at a temperature of 800°C to 1500°C.
This sintered body was sintered, and At--Cu metallicon was applied to both end faces of this sintered body to form electrodes, thereby obtaining a voltage nonlinear resistor.

Almost no structural defects were observed inside the sintered body thus obtained, and it was found that the thinner the thin plate of the mixture, the better the uniformity inside the sintered body.

The upper limit for the thickness is 2 mm, and anything more than that can cause cracks in the thin plate itself, so it must be avoided.

In addition, when drying after drawing the sheet, if the drying time is too long or the temperature is too high, the thin plate may crack, so it must be avoided.

In addition, in the examples, for zinc oxide ZnO, bismuth oxide B12O3, cobalt oxide Co01 manganese oxide Mn01 antimony oxide 5b203, and silicon oxide Si
Although we used one containing O2, we also added lead oxide PbO1.
Calcium oxide Cab, strontium oxide 5rO1, barium oxide BaO, uranium oxide UO2, etc. may be added, and are effective as long as they form a layer exhibiting voltage nonlinearity at the boundary between particles in the zinc oxide sintered body.

In addition, aluminum oxide At203, nickel oxide N mill, magnesium oxide MgO, chromium oxide Cr203, tin oxide S
No. 2 or titanium oxide (TiO2) may be added, but even in such cases, the effects of the present invention are not impaired in any way.

[Brief explanation of the drawing]

FIG. 1 is a diagram illustrating a conventional method for molding a voltage nonlinear resistor, and FIG. 2 is a diagram illustrating a method for molding a voltage nonlinear resistor according to the present invention.

Claims (1)

[Claims] 1 Bismuth oxide B 120s in zinc oxide ZnO powder
, cobalt oxide Co01 manganese oxide MnO, antimony oxide 5b203, and silicon oxide S t 02 powders each in a proportion of 0.01 to 10 mol each, and an organic binder and a plasticizer were added to form a mixture into a thin plate with a thickness of 0.02 to 2 mw. A method for manufacturing a voltage nonlinear resistor, which comprises stacking and crimping the formed products to form a molded body.