JPH09162011A - PTC resistor and method of manufacturing the same - Google Patents

Abstract

(57) 【Abstract】 PROBLEM TO BE SOLVED: To provide a PTC resistor (V _1-X Cr _X ) as a current limiting element.
The resistance of ₂ O ₃ (however 0.0025 ≦ X ≦ 0.005) controls the rising temperature that starts to increase rapidly. SOLUTION: A material corresponding to the composition is subjected to primary wet mixing and pulverization and calcination, and then placed in a ball mill, subjected to secondary wet mixing and pulverization, molded, and finally fired. During the secondary wet mixing and crushing, the wet mixing and crushing time was adjusted to 10 to 35 hours, and the average particle size was 1.0.
˜1.5 μm.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a PTC resistor having a large PTC (positive temperature coefficient) characteristic used as a current limiting element for suppressing overcurrent and a method for manufacturing the same.

[0002]

2. Description of the Related Art As a current limiting device for suppressing overcurrent
And ceramics with large PTC characteristics,_TwoO_Three
Obtained by adding Cr (chromium) to (vanadium trioxide)
(V _1-XCr_X)_TwoO_ThreeIt has been known. 〔example
Ba, Iida et al., Institute of Electrical Engineers switchgear protection device study material, SPD
-87-40] In addition, this current limiting element is used for a kind of overcurrent protection device.
In case of
It was found necessary to control at 0 ° C.

[0003]

[Problems to be Solved by the Invention] (V _1-X Cr _X ) ₂ O
PTC characteristics of _3, metal - is based on insulator transition, to control a conventional _{(V 1-X Cr X)} 2 temperature of the resistivity rise of the O ₃ is changing the content of Cr, Alternatively, the amount of additives such as Fe has been changed. For example,
The higher the content ratio of Cr, the lower the rising temperature of the specific resistance. To control the rising temperature to 110 to 150 ° C., the Cr content ratio is 0.0025 to 0.005.
Is appropriate.

In that case, however, the rising temperature is determined at the time when the composition of the material is determined, and when this resistor is incorporated in equipment, the ambient temperature is high or low.
The timing of the PTC characteristic may be shifted, and the secondary device may be damaged. Further, the deviation of the composition of the material directly affects the rising temperature. Therefore,
As a main factor that determines the rising temperature, even if it depends on the material composition, it is desirable to have a method that can control the rising temperature by the composition of the material.

In view of the above problems, it is an object of the present invention to provide a PTC resistor whose rising temperature can be easily controlled and a method for manufacturing the PTC resistor.

[0006]

In order to solve the above problems, the PTC resistor of the present invention comprises (V _1-X Cr _X ) ₂ O ₃ (where 0.0025 ≦ X ≦ 0.005) as a main component. Let P
It is a TC resistor having an average particle size of 1.0 to 1.5 μm. As a method of manufacturing such a PTC resistor, the pulverization and mixing time after calcination is changed, and the pulverization and mixing time after calcination is set to 10 to 35 hours.

By doing so, the rising temperature of the PTC resistor can be adjusted, and can be controlled to 110 to 150 ° C., which is suitable for use in an overcurrent prevention device. In addition, in the range other than the above, the rising temperature deviates from the optimum temperature.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION

Example 1 As described above, the PTC resistor (V _1-X
The cr _{X) 2} rising temperature of the specific resistance of the O ₃ one hundred ten to one
Cr content ratio X as a main factor for controlling at 50 ° C
Is preferably 0.0025 ≦ X ≦ 0.005. In this embodiment, X = 0.0035.

Flow of manufacturing process of PTC resistor of the present invention
The chart is shown in FIG. The manufacturing method is explained based on this figure.
I will tell. First, as a starting material, V_TwoO_FiveAnd Cr_TwoO_Three
And, (V_0.9965Cr_0.0035) _TwoO_ThreeTo get
Weigh and add 5% by weight of Fe as a sintering aid. this
Put in a ball mill, add pure water for 48 hours, primary wet
Mixed and pulverized. The powder obtained by drying this, water
Calcination at 1100 ° C for 2 hours in a reducing atmosphere
went.

The calcinated mass was placed in a ball mill, pure water was added, and secondary wet mixing and pulverization was performed. At this time, the secondary wet mixing and pulverizing time was 5, 24 and 48 hours under three conditions.
These three types of samples were dried and pressure-molded at a pressure of 1.5 ton / cm ² to prepare a molded body. The temperature rising / falling rate was 800 ° C./h, firing was performed at 1600 ° C. in an air stream having a C0 ₂ / H ₂ ratio of 0.01, and PTC resistor samples 1 to
3 were obtained and their specific resistance-temperature characteristics were compared.

The PTC characteristics of these samples are shown in FIG. The longer the secondary wet mixing and crushing time, the lower the rising temperature. Table 1 shows a summary of rising temperatures.

[0012]

[Table 1] Since the cause of the difference in PTC characteristics of these samples is due to the secondary wet mixing and pulverizing time, it is considered to be due to the particle size distribution of the powder after the secondary wet mixing and pulverizing, and the average particle size was measured by the specific surface area method. did. The results are also shown in Table 1. It can be seen that the average particle size decreases as the secondary wet mixing and pulverization time increases.

FIG. 1 shows the relationship between the rising temperature of the specific resistance and the average particle size. From this figure, it can be seen that the average particle diameter can be controlled to 1.0 to 1.5 μm in order to make the rising temperature of the specific resistance 110 ° C. to 150 ° C.
FIG. 2 shows the relationship between the rising temperature and the secondary wet mixing and pulverizing time. From this figure, the rising temperature of the resistivity is 110
It can be seen that the secondary wet mixing and pulverizing time may be 10 to 35 hours in order to adjust the temperature to 150 to 150 ° C.

As described above, according to the present invention, it was confirmed that a PTC resistor whose rise temperature can be easily controlled even after mixing materials having a certain composition was obtained and was reproducible.

[0015]

According to the present invention, (V _1-X Cr _X ) ₂ O
_In a PTC resistor whose main component is ₃ (however, 0.0025 ≦ X ≦ 0.005), the average particle diameter is changed by changing the mixing and pulverizing time after calcination, for example, to increase the specific resistance. The temperature can be controlled to an appropriate temperature, and a PTC resistance element with improved reliability can be obtained.

[Brief description of the drawings]

FIG. 1 is a diagram showing a relationship between a rising temperature and a particle size.

FIG. 2 is a diagram showing a relationship between a rising temperature and a secondary mixing and pulverizing time.

FIG. 3 is a flow chart of a manufacturing process of a PTC resistor.

FIG. 4 is a graph showing the dependency of PTC characteristics on mixing and grinding time.

Claims (3)

[Claims] (1) (V _1-X Cr _X ) ₂ O ₃ (however, 0.00
25 ≦ X ≦ 0.005) as a main component, wherein the PTC resistor has an average particle size in the range of 1.0 to 1.5 μm. 2. (V _1-X Cr _X ) ₂ O ₃ (provided that 0.00
25 ≦ X ≦ 0.005) as a main component, wherein the resistance rising temperature is controlled by changing the grinding and mixing time after calcination. . 3. The method for producing a PTC resistor according to claim 2, wherein the crushing and mixing time after calcination is 10 to 35 hours.