JPS588124B2 - Antimony-containing voltage nonlinear resistance material and noise prevention device using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention consists of a sintered body of titanium oxide, antimony oxide, and bismuth oxide, whose resistance value is highly dependent on voltage, and whose characteristics are voltage nonlinear due to the sintered body itself. The present invention relates to a static resistance material and a noise prevention element using the same.

In recent years, with the rapid progress and spread of audio equipment, control equipment, and small power equipment, prevention of noise caused by small electric motors, protection from overvoltage, protection of relay contacts, etc. have become important issues.

However, since these devices are generally becoming cheaper, it is necessary to take this point into consideration when solving the above-mentioned problems.

Hitherto, known voltage nonlinear resistance materials include silicon carbide sintered varistors, selenium and cuprous oxide varistors, and zinc oxide sintered varistors.

By the way, the voltage-current characteristics of a varistor are generally expressed by the formula I=(V/C)α It is expressed as

Here, V is the voltage applied to the varistor, I is the current flowing through the varistor, and C is a constant corresponding to the voltage when a predetermined current flows.

Further, the index α is a nonlinear coefficient, and can be obtained by the following equation.

Here, V1 and V2 are given currents I1 and I2, respectively.
is the voltage at .

A resistor with α=1 is a normal resistor that follows Ohm's law, and it can be said that the larger α is, the better the voltage nonlinearity is. It can be used as a guideline.

Further, a desirable value for C varies depending on the use of the varistor, but in a varistor for low voltage use, it is preferable that the C value is low and that a value suitable for the use can be easily achieved.

Among the known varistors that have been used so far, silicon carbide varistors are manufactured by baking silicon carbide particles with a particle size of around 100μ in clay, and their voltage nonlinearity depends on the voltage dependence of the resistance between particles. Due to C
The value of can be adjusted by changing the thickness of the varistor, that is, the number of grain boundaries in the direction of current flow.

However, in the case of low voltage applications, since the C value per grain boundary is high, the number of grain boundaries must be reduced, and reducing the number of grain boundaries causes a problem in that the withstand voltage property decreases.

In addition, this material has a relatively small non-linearity index α of 3 to 7, and since the silicon carbide is hard, the mold used for molding suffers from severe wear and is difficult to form into a precise shape.

On the other hand, selenium and cuprous oxide based varistors have a nonlinear index α
is as small as 2 to 3, and has the disadvantage that the limiting voltage cannot be increased, so it cannot be said to be a satisfactory material.

Furthermore, zinc oxide-based varistors generally have a large nonlinearity index α of 10 to 50, and the particle system can be made as small as about 10 μ, so the voltage range can be changed from 10 to 1000 V, which is the main advantage. Since zinc oxide, which is a component, is chemically unstable, nonlinearity deteriorates over time, and furthermore, manufacturing is labor-intensive and expensive.

In order to improve these drawbacks of conventional varistors,
A material made by adding antimony oxide and bismuth oxide as additives to titanium oxide and sintering it was proposed.

This has the advantage that the nonlinearity index α is higher than that of silicon carbide-based varistors, selenium, or cuprous oxide-based varistors, and that a desired C value can be achieved without changing the α value.

However, this method has the disadvantage that it is difficult to uniformly disperse the additive components antimony oxide and bismuth oxide into the sintered body, resulting in variations in quality.

The inventors of the present invention have conducted extensive research to overcome these drawbacks and develop antimony-containing titanium oxide-based voltage nonlinear resistance materials with stable quality. By adding antimony oxide to a powder mixture of raw materials and sintering it, they succeeded in obtaining a product with stable quality while using a smaller amount of antimony oxide than known products.

That is, the present invention provides antimony oxide 0.002 to 0.09 mol% (Sb2O3
(converted), bismuth oxide 0.05-10 mol% (Bi2
The present invention provides a voltage nonlinear resistance material having a composition of a titanium oxide (O3 equivalent) and a titanium oxide residue.

The antimony oxide raw material used in the present invention includes antimony compounds that can be converted into antimony oxide by calcination.
Any material may be used as long as it becomes a solution when dissolved in water or other volatile solvent.

Examples of such antimony compounds include antimony chloride, antimony sulfate, and antimony hydroxide.

This antimony compound is added to other raw material mixtures as a solution with a concentration of about 0.001 to 2%.

In addition, titanium oxide raw materials and bismuth oxide raw materials include:
Usually powdered titanium oxide and bismuth oxide are used, but
In addition, it is also possible to use a substance that can form titanium oxide or bismuth oxide upon firing.

These are used as powders with an average particle size of about 5 to 300 μm.

To manufacture the voltage nonlinear resistance material of the present invention, for example, a solution containing a predetermined amount of antimony oxide raw material is added into a powder mixture in which titanium oxide raw material powder and bismuth oxide raw material powder are mixed at a predetermined ratio. Add and mix thoroughly using a wet ball mill or the like.

Next, after drying this mixture, it is calcined at a temperature of 800 to 1000°C, and this calcined body is pulverized.

A suitable binder such as polyvinyl alcohol, CMC, etc. is added to this pulverized material, formed into granules, further press-molded into an appropriate shape, and heated in air or an inert atmosphere for 11 hours.
Sinter at a temperature of 00-1400°C.

At this time, the temporary firing step can be omitted if it is not particularly necessary.

The material of the present invention has an antimony oxide content of 0.002 to 0.09 mol% when converted to Sb2O3, and a bismuth oxide content of 0.05 to 10 mol% when converted to Bi2O3.
and titanium oxide (TiO2).

If the antimony oxide content is less than 0.002 mol%, good nonlinearity cannot be obtained.

Moreover, when this exceeds 0.09 mol %, no improvement in nonlinearity is particularly observed, and in addition, nonlinearity in a high current region decreases.

On the other hand, if the bismuth oxide content is less than 0.05 mol% or more than 10 mol%, good nonlinearity cannot be obtained.

Since the voltage nonlinearity of the voltage nonlinear resistance material of the present invention depends on the sintered body itself, the desired C can be achieved by changing the thickness in the direction of current flow without changing the α value.
It has the characteristic of easily realizing value.

In addition, the C value per unit thickness is low, making it easy to create low-voltage devices, and since it can be made homogeneous, it has high reliability in terms of voltage resistance, and the α value is significantly higher than that of silicon carbide varistors. It can be made large, so it can be used for a wide range of purposes.
It has the advantage of being cheaper because it requires fewer types of raw materials.

Next, the voltage nonlinear resistance material of the present invention has a voltage of 3 to 12.3
Since the nonlinear index α can be increased at a low voltage of V, it is suitable as a noise prevention element for a micromotor.

The noise in this micromotor is caused by the spark phenomenon that occurs between the commutator and the brushes.

More specifically, in motors that generally use a commutator, the commutator is usually formed into a cylindrical shape with several commutator pieces attached at predetermined intervals, and there is always an insulating layer between each commutator piece. A gap occurs.

Therefore, when the commutator is rotating, the brush jumps across the gap between the commutator pieces and moves on to the next commutator piece. Due to the presence of large self-inductance of the rotor, spike-like voltage sparks occur.

These sparks cause electrical noise and tend to wear out the commutator and brushes, shortening the life of the motor.

By the way, this spike-shaped spark is a bipolar oscillating voltage, its peak value is 20 to 50 times the motor power supply voltage, the connection time is approximately 100 μs, and it has a high frequency component of 2 to 5 MHz, so these should be eliminated. As mentioned above, a varistor is used that has a nonlinearity index as large as possible at a low voltage of 3 to 12.3 V, and also has characteristics that allow it to absorb high frequency components and eliminate these noises to near the operating voltage of the motor. element is required.

The voltage nonlinear resistance material of the present invention has all of these characteristics, and an element formed by providing electrodes thereon can be said to be very suitable for noise prevention in a micromotor. .

In this case, the electrode may be non-ohmic or ohmic, as long as it does not impair the characteristics of the specified material, and any method such as baking, plating, vapor deposition, sputtering, thermal spraying, etc. may be used for attachment. be able to.

Next, the present invention will be explained in more detail with reference to Examples.

Example 1 A 0.1 molar aqueous solution of antimony chloride was added to a mixture of titanium oxide powder (average particle size 10 μm or less) and bismuth oxide powder (average particle size 10 μm or less) in the proportions shown in the following table. Thoroughly mixed using a wet ball mill.

Next, after drying this mixture, it was charged into an electric furnace for about 10 minutes.
Temporary firing was performed at 00°C for 30 minutes.

After pulverizing this calcined material to a size that passes through 48 mesh,
2 polyvinyl alcohol per total weight as a binder
%, and once it is made into granules, it is made into 16m in diameter.
It was press-molded into a disk shape with a thickness of 1.2 mm and a thickness of 1.2 mm.

Next, this molded body was fired at about 1300° C. for 1 hour to obtain a desired voltage nonlinear resistance material.

Silver-baked electrodes were provided on both sides of the various materials thus obtained, and voltage-current characteristics were measured.

The results are shown in the table below.

In the table, the C value is the voltage (V/mm) when a current of 10 mA/cm2 is applied.

As can be seen from this table, α exceeds 5 when antimony and bismuth oxides are in the range of 0.002 to 0.09 mol% and 0.05 to 10 mol%, respectively, in the form of Sb2O3 and Bi2O3. The α value is as high as 10, which is sufficiently high compared to silicon carbide varistors.

Furthermore, the C value per unit thickness shows a wide range of values, making it suitable as a varistor for low voltage.

Example 2 The element obtained in Example 1 was attached between the coils of a micromotor at each working voltage (approximately 80% of the applied voltage), and the noise cut voltage was measured using an oscilloscope.

The results are shown in the table below. Example 3 Voltage nonlinear resistance material A, Fe2O3-based material BSnO2-based material C, ZnO-based material D having a composition of 0.05 mol% antimony oxide, 0.5 mol% bismuth oxide, and 99.45 mol% titanium oxide. A noise cut test was conducted in the same manner as in Example 2 on a micromotor for use at a working voltage of 5 V.

The noise cut state for each sample is shown in the attached drawing.

As is clear from this figure, the material of the present invention exhibits superior properties compared to materials used for conventional noise cutting.

[Brief explanation of drawings]

The drawing is an oscillograph diagram showing the noise cutting state when the material of the present invention and the known material are used as a noise prevention element of a micromotor.

Claims (1)

[Claims] 1. Antimony oxide 0.0, which is formed by adding a solution of an antimony oxide raw material to a powder mixture of other raw materials and sintering the solution.
A voltage nonlinear resistance material having a composition of 02 to 0.09 mol 5 (in terms of Sb2O3), 0.05 to 10 mol % of bismuth oxide (in terms of Bi2O3), and the remainder of titanium oxide. 2 Antimony oxide 0.00, formed by adding a solution of antimony oxide raw material to a powder mixture of other raw materials and sintering.
A noise prevention device for a micromotor comprising electrodes provided on a voltage nonlinear resistance element having a composition of 2 to 0.09 mol% (in terms of Sb2O3), 0.05 to 10 mol% of bismuth oxide (in terms of Bi2O3), and the remainder of titanium oxide. element.