JP2000100604A - Ptc resistor, its manufacture and switch including the ptc resistor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a PTC resistor for stably supplying large rated currents without generating any PTC characteristic manifestation due to its own heating, and a method for manufacturing this PTC resistor, and a switch including this PTC resistor. SOLUTION: This PTC resistor uses vanadium oxide as main components in which the temperature change of a resistance rate in a temperature range from 20 deg.C to 60 deg.C is 60×10-6 Ωcm/ deg.C or less. In a method for manufacturing this PTC resistor, a ceramic powder body using vanadium oxide as main components are molded into a desired shape, and burnt in a reduction atmosphere. In this case, the highest temperature holding time at the time of burning is set 8 hours or more.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a PTC resistor, a method of manufacturing the same, and a switch including the same.

[0002]

_2. Description of the Related Art Vanadium oxide (V ₂ O ₃ ) converts a part of V to C
By substituting with r, it is a material that exhibits PTC characteristics that its temperature rises from room temperature to high temperature and its resistivity increases around 100 times. Since this PTC characteristic occurs at a practical temperature of about 100 ° C., ceramics containing V ₂ O ₃ as a main component have great industrial utility value, and are expected to be put to practical use in PTC resistors and the like. For example, it has been attempted to apply a V ₂ O ₃ ceramic as a current limiting element which is a part of a switch for interrupting a short circuit current.

A conventional PTC resistor mainly composed of V ₂ O ₃ is:
For example, as described in Japanese Patent Application Laid-Open No. 9-162011, the average particle size of V ₂ O ₃ ceramic is limited to 1.0 to 1.5 μm in order to control the PTC transition temperature.

In the conventional method, for example, Japanese Patent Application Laid-Open No. 6-61006
As described in the publication, in order to improve PTC characteristics, a V ₂ O ₃ -based PTC resistor is manufactured by shortening a time for holding a fired body at a maximum temperature in a firing step as much as possible.

[0005]

However, a PTC resistor mainly composed of V ₂ O ₃ manufactured by a conventional method (V ₂ O 3
₃ based PTC resistor), when the rated current for the V ₂ O ₃ based PTC resistor at the room temperature, the resistivity of the PTC resistor is increased by self-heating and a large current value, finally PTC characteristics Was sometimes expressed.

[0006] This problem becomes remarkable when the PTC resistor is used as a current limiting element which is a part of a switch. That is,
When a large rated current is supplied to the switch, the resistivity increases due to self-heating, and the switch cannot be used.
In addition, there is a problem that PTC characteristics are exhibited even if a short circuit accident does not occur. To avoid such a problem, when using V ₂ O ₃ based PTC resistor produced by conventional methods as current limiting element, there is a problem that only a small rated current of several A~10A not be conductive point Was.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a PTC resistor capable of stably supplying a large rated current without inducing PTC characteristics due to self-heating, a method of manufacturing the same, and a switch including the same.

[0008]

Means for Solving the Problems The inventors of the present invention have made intensive studies to solve the above problems and to manufacture a V ₂ O ₃ -based PTC resistor capable of conducting a large rated current. To energize, the PTC resistor V ₂ O ₃
It has been found that the temperature change of the resistivity at room temperature, which is lower than the PTC characteristic manifestation temperature of the base ceramic, needs to be 60 × 10 ⁻⁶ Ωcm / ° C. or lower. Furthermore, they have found that the temperature dependence of the resistivity of a V ₂ O ₃ ceramic at room temperature is closely related to the particle size of the V ₂ O ₃ ceramic. Further, according to the research results of the present inventors, in order to reduce the temperature dependence of the resistivity at room temperature to the above value, it is necessary that the particle size of the V ₂ O ₃ ceramic be 3 μm or more. I understood. In addition, in order to obtain such a particle size, it was found that the time for maintaining the maximum temperature in the firing step had to be 8 hours or more.

According to a first aspect of the present invention, there is provided a PTC resistor using a ceramic containing vanadium oxide as a main component.
P, wherein the temperature change of the resistivity in the temperature range from 60 ° C. to 60 ° C. is 60 × 10 ⁻⁶ Ωcm / ° C. or less.
TC resistor. According to a second aspect of the present invention, there is provided the PTC resistor according to the first aspect, wherein the average particle diameter of the ceramic is 3 μm or more. The invention according to claim 3 is a method for manufacturing a PTC resistor, which comprises a step of molding a ceramic powder containing vanadium oxide as a main component into a desired shape and then firing in a reducing atmosphere. A method for manufacturing a PTC resistor, wherein a holding time is 8 hours or more.

By setting the maximum temperature holding time to 8 hours or more in the firing step of the V ₂ O ₃ ceramic as a PTC resistor, the grain growth of the V ₂ O ₃ ceramic proceeds, and a grain size of 3 μm or more is obtained. Can be When the particle diameter of the V ₂ O ₃ ceramic is 3 μm or more, the temperature dependence of the resistivity at room temperature is 60%.
× 10 ⁻⁶ Ωcm / ° C. or less. Furthermore, this allows the switch including the vanadium oxide-based PTC resistor to stably supply a large rated current.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 V ₂ O ₃ 20.0 g and Cr ₂ O
_{3 and} 0.102 g were weighed and mixed. This is calcined and then reground,
It was molded into a shape of 12.0 mm x 6.5 mm x 20.0 mm. This is H ₂ 3
% While maintaining the maximum temperature at 1500 ° C
By firing for 0 hour, a PTC resistor according to one embodiment of the present invention was produced. The temperature change of the resistivity of the manufactured PTC resistor was measured, and the temperature change of the resistivity from 20 ° C. to 60 ° C. was determined by the least square method. As a result, it was 26 × 10 ⁻⁶ Ωcm / ° C. The temperature change of the PTC resistor when an AC current of 200V-15A-50Hz was applied at an ambient temperature of 40 ° C. was measured. As shown in FIG. It became constant in minutes. The average particle size of the PTC resistor after the energization test was 5 μm as measured by a metallurgical microscope.

Embodiment 2 FIG. V ₂ O ₃ 20.0 g and Cr ₂ O ₃ 0.102 g
And 1.01 g of metal Ni powder were weighed and mixed. This was calcined and then pulverized again to form a shape of 12.0 mm × 6.5 mm × 20.0 mm.
This was calcined in an Ar gas stream containing 3% of H ₂ for 80 hours while maintaining a maximum temperature of 1750 ° C.
A C resistor was manufactured. The temperature change of the resistivity of the manufactured PTC resistor was measured, and the temperature change of the resistivity from 20 ° C. to 60 ° C. was determined by the least square method. As a result, 18 × 10 ⁻⁶ Ωcm /
° C. The temperature change of the PTC resistor when an AC current of 200V-15A-50Hz was applied at an ambient temperature of 40 ° C. was measured. As shown in FIG. It became constant in minutes. When the particle size of the PTC resistor after the current test was measured with a metallurgical microscope, the average particle size was 2
It was 0 μm.

Embodiment 3 V ₂ O ₃ 20.0 g and Cr ₂ O ₃ 0.102 g
And were weighed and mixed. This is calcined and then re-crushed to 12.0mm ×
It was molded into a shape of 6.5 mm x 20.0 mm. Ar this containing H ₂ 3%
In a gas stream, firing was performed for 40 hours while maintaining the maximum temperature of 1480 ° C., to produce a PTC resistor according to one embodiment of the present invention. The temperature change of the resistivity of the manufactured PTC resistor was measured, and the temperature change of the resistivity from 20 ° C. to 60 ° C. was determined by the least square method. As a result, it was 32 × 10 ⁻⁶ Ωcm / ° C. Book
The PTC resistor was built in the no-fuse circuit breaker as shown in Fig. 2, and the temperature change of this PTC resistor when an AC current of 200V-15A-50Hz was applied at an ambient temperature of 40 ° C was measured. As shown in FIG. 1, the temperature of the PTC resistor became constant 40 minutes after the start of energization. 2, 1 is a current limiting unit housing, 2 is a power supply side terminal, 3 is an inside of the current limiting unit,
4 is a PTC low antibody, 5 is a fixed contact, 6 is a movable contact, 7
Is a grid, 8 is a handle, 9 is an opening / closing mechanism, 10 is a circuit breaker housing, 11 is an inside of the circuit breaker, and 12 is a load terminal. The average particle size of the PTC resistor after the energization test was measured by a metallographic microscope, and the average particle size was 8 μm.

Comparative Example 1 20.0 g of V ₂ O ₃ and 0.102 g of Cr ₂ O ₃ were weighed and mixed. This is calcined and re-crushed, 12.0mm x 6.5m
It was molded into a shape of m × 20.0 mm. This was baked for 6 hours in an Ar gas stream containing 3% of H ₂ at a maximum temperature of 1520 ° C. while maintaining the temperature to produce a PTC resistor. The temperature change of the resistivity of the manufactured PTC resistor was measured, and the temperature change of the resistivity from 20 ° C. to 60 ° C. was determined by the least square method.
^-6 Ωcm / ° C. 200V-15A at ambient temperature 40 ℃
When the temperature change of the present PTC resistor when an AC current of -50 Hz was applied was measured, the temperature of the PTC resistor increased as shown in FIG. The measurement was stopped. When the particle size of the present PTC resistor after the power-on test was measured with a metallurgical microscope, the average particle size was 2 μm.

The results of the temperature change of the resistivity from 20 ° C. to 60 ° C. obtained by the above-described embodiment and comparative example obtained by the least square method are shown in Table 1 below.

[0016]

[Table 1]

Embodiment 1 ~ 3. And Comparative Example 1 above. Comparative As is apparent from the, V ₂ O is a PTC resistor
_By increasing the maximum temperature holding time in the firing process for ₃ series ceramics to 8 hours or more, the conventional V ₂ O ₃ series
The thermal stability at the time of the rated current supply that was not obtained with the PTC resistor was obtained. This is because the V ₂ O ₃ ceramics grows to have a particle size of 3 μm or more by increasing the maximum temperature holding time in the firing step, whereby the temperature dependency of the room temperature resistivity is 60 × 10 3. ^-6 Ωcm / ° C or lower. In particular, Embodiment 1. ~ 3. It can be seen that 15 A can be supplied more stably when the current is 40 × 10 ⁻⁶ Ωcm / ° C. or less as shown in FIG.

In the above embodiment, the rated current is 15 A
Was turned on, but as described in the embodiment, the PT
This is a value that allows stable conduction when the shape of the C resistor is 12.0 mm x 6.5 mm x 20.0 mm. Depending on the ratio between the cross-sectional area and the length of the PTC resistor, it is possible to stably supply a larger rated current. In the embodiment, the above-described shape is adopted in order to further increase the maximum resistance value obtained when the PTC characteristic is exhibited.

For example, in Embodiment 2. In manner, V by adding metal powder such as ₂ O ₃ based ceramic the Ni, the particle size of the V ₂ O ₃ based ceramic the maximum resistance value obtained at PTC characteristic expression compared with the case of no addition of metal powder Tend to increase.

The temperature dependence of the room temperature resistivity of the V ₂ O ₃ -based PTC resistor is reduced to 60 × 10 ⁻⁶ Ωcm / ° C. or less by setting the particle size of the V ₂ O ₃ -based ceramic to 3 μm or more. Was obtained as an experimental result of the present inventors. If the particle size of the V ₂ O ₃ ceramic is 3 μm or more, why the temperature dependency of the room temperature resistivity of the V ₂ O ₃ PTC resistor becomes 60 × 10 ⁻⁶ Ωcm / ° C. or less, at this stage Unknown.

Further, the present inventors have studied and found that the maximum temperature in the firing step is desirably 1400 ° C. or more in order to obtain an average particle diameter of the V ₂ O ₃ ceramic of 3 μm or more. Although the maximum temperature in the present embodiment was 1750 ° C. in terms of the performance of the equipment used for manufacturing, it goes without saying that the same effect can be obtained even at a higher temperature if there is room in the capacity of the manufacturing equipment.

In the above embodiment, the maximum value of the time for maintaining the maximum temperature is set to 80 hours. This is because the effect of lowering the temperature dependency of the normal temperature resistivity by increasing the maximum temperature holding time is as follows. Approaching the asymptote from around 60 hours 8
This is because it becomes constant in 0 to 100 hours. Therefore, even if the maximum temperature holding time is made longer, the same effect as in the present embodiment can be obtained, but the cost is increased due to an increase in energy consumption in the manufacturing process, and therefore, there is little industrial merit.

In consideration of the advantage obtained by extending the maximum temperature holding time and the energy consumption therefor, it is desirable that the maximum temperature be 1500 ° C. to 1700 ° C. and the maximum temperature holding time be 10 hours to 80 hours. .
Naturally, these numerical values depend on the composition of the material, the presence or absence and type of the added metal, the characteristics of the manufacturing equipment, and the like, and thus may be appropriately determined.

Embodiment 3 above. As shown in the above, by incorporating the PTC resistor according to the present invention in the no-fuse circuit breaker which is a switch, the no-fuse circuit breaker
It is possible to stably supply the rated current of Thereby, the reliability of the switch using the PTC resistor of the present invention as a current limiting element can be improved. This can also be expected to reduce switch costs.

[0025]

According to the first aspect of the present invention, there is provided a PTC resistor using a ceramic containing vanadium oxide as a main component.
The PTC resistor is characterized in that the temperature change of the resistivity in the temperature range from 0 ° C. to 60 ° C. is 60 × 10 ⁻⁶ Ωcm / ° C. or less.
There is an effect that a large rated current can be stably supplied without inducing PTC characteristics.

According to a second aspect of the present invention, there is provided the PTC according to the first aspect, wherein the average particle diameter of the ceramic is 3 μm or more.
Since the PTC resistor is a resistor, there is an effect that a large rated current can be stably supplied to the PTC resistor without inducing PTC characteristics due to self-heating.

A third aspect of the present invention provides a method for manufacturing a PTC resistor, comprising the steps of: forming a ceramic powder containing vanadium oxide as a main component into a desired shape; and firing in a reducing atmosphere. since the maximum temperature holding time is in the manufacturing method of the PTC resistor, characterized in that at least 8 hours, can be an average particle size of V ₂ O ₃ based ceramic than 3 [mu] m, also by this, V ₂ The temperature change of the resistivity of the O ₃ -based PTC resistor in the temperature range from 20 ° C. to 60 ° C. can be reduced to 60 × 10 ⁻⁶ Ωcm / ° C. or less,
There is an effect that a PTC resistor that can stably supply a large rated current can be obtained without causing PTC characteristics to be exhibited by self-heating.

According to a fourth aspect of the present invention, there is provided a switch including the PTC resistor according to the first or second aspect, so that the reliability is improved and the manufacturing is possible at low cost. Play.

[Brief description of the drawings]

FIG. 1 is a characteristic diagram showing a temperature change of a PTC resistor during energization.

FIG. 2 is a diagram for explaining a switch including a PTC resistor.

[Explanation of symbols]

1 Current limiting unit housing, 2 Power supply terminal, 3 Inside of current limiting unit, 4 PTC low antibody, 5 Fixed contact, 6 Movable contact, 7 Grid, 8 Handle, 9 Opening / closing mechanism, 1
0 Circuit breaker housing, 11 Inside the circuit breaker, 12 Load side terminal.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Susumu Kawamata 2-3-2 Marunouchi, Chiyoda-ku, Tokyo Mitsui Electric Co., Ltd. (72) Inventor Hiroshi Chujo 2-3-2 Marunouchi, Chiyoda-ku, Tokyo Rishi Electric Co., Ltd. (72) Inventor Tatsuya Hayashi 2-3-2 Marunouchi, Chiyoda-ku, Tokyo Mitsui Electric Co., Ltd. (72) Inventor Sadajiro Mori 2-3-2 Marunouchi, Chiyoda-ku, Tokyo Mitsui Electric F term in the company (reference) 4G030 AA19 AA22 BA05 CA04 GA08 GA26 GA27 5E034 AA10 AB01 AC01 AC18 DA02 DE07 5G013 AA01 AA02 BA01 CA02

Claims (4)

[Claims] 1. A PTC resistor with a ceramic mainly composed of vanadium oxide, the temperature change in resistivity in the temperature range from 20 ° C. to 60 ° C. is 60 × 10 ^- 6
A PTC resistor characterized by being Ωcm / ° C or less. 2. The PTC resistor according to claim 1, wherein the ceramic has an average particle size of 3 μm or more. 3. A method for manufacturing a PTC resistor, comprising a step of molding a ceramic powder containing vanadium oxide as a main component into a desired shape, followed by firing in a reducing atmosphere. Is 8 hours or more. 4. A switch comprising the PTC resistor according to claim 1 or 2.