JPH10261504A - Power resistor, method of manufacturing power resistor, power circuit breaker, and neutral ground resistor - Google Patents

Abstract

(57) [Problem] To provide a power resistor having a large heat capacity per unit volume, an appropriate resistance value, and further improved mechanical characteristics. SOLUTION: The sintered body contains aluminum oxide or a composite oxide containing aluminum, 0.3 to 5% by weight of carbon, and 0.1 to 30% by weight of partially stabilized zirconia. (A) a first region containing 0.1 to 30% by weight of the above-mentioned aluminum oxide or aluminum-containing composite oxide and partially stabilized zirconia; and (b) a first region containing the above-mentioned aluminum oxide or aluminum-containing composite oxide, partially stabilized. Zirconia 0.1 to 30% by weight and a second region containing more carbon than the first region: and formed on two opposing surfaces of the sintered body,
A pair of electrodes that are electrically connected to each other by the second region.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a power resistor suitable for absorbing excessive electric energy, for example, a resistor used for a surge absorption resistor of a high-voltage circuit breaker, and a power resistor. , A power circuit breaker and a neutral point grounding resistor.

[0002]

2. Description of the Related Art At present, various power resistors are used for current control of a circuit breaker or the like, various controls for starting and regenerating an electric motor, or grounding when an abnormality occurs in a power transmission system. These resistors are composed of a metal resistor, a ceramic resistor, and a composite thereof.

As a conventional resistor used for a circuit breaker, for example, a carbon particle-dispersed ceramic resistor described in Japanese Patent Application Laid-Open No. 58-139401 is used. This resistor is obtained by mixing carbon powder as a conductive component with aluminum oxide powder as an insulating component and baking it with clay as a binder.
It has a resistivity of 500 Ω · cm.

As a resistor of a neutral point grounding resistor, in addition to a carbon particle dispersed ceramic resistor, for example, zinc oxide as described in Japanese Patent Application Laid-Open No. Hei 7-161505 is used as a main component. A linear resistor having aluminum and magnesium oxide as subcomponents is used.

[0005] Among the resistors, the former carbon particle-dispersed ceramic resistor has an advantage that a resistor having an arbitrary resistivity can be obtained by adjusting the amount of carbon powder added. However, the porosity is 10-30%
And high density, resulting in the following problems.

The first problem is that the heat capacity per volume is 2J.
/ Cm ³ · K. Therefore, the amount of energy that can be absorbed per unit volume becomes small, and the temperature rises significantly when electric energy is absorbed. In order to suppress the temperature rise, many resistors are required.

The second problem is that when a high voltage is applied, a discharge occurs between the carbon powders. When the discharge becomes remarkable, a through discharge occurs.

The third problem is that the mechanical strength is small due to the large porosity (20 MPa in terms of the four-point bending average strength), and thermal shock destruction is caused by the heat generation distribution generated by the resistance distribution inside the resistor. is there.

A fourth problem is that when the temperature becomes 300 ° C. or more in the atmosphere, carbon particles inside the resistor are oxidized through open pores,
It disappears and the resistance value increases, so that the function as a resistor is lost.

[0010] Of the above-mentioned resistors, the latter, which is mainly composed of zinc oxide, has non-linearity in current-voltage characteristics. Power resistors are often used with large currents,
The existence of non-linearity lacks stability of the resistance value and cannot function sufficiently as a resistor. Further, although the mechanical strength is higher than that of the carbon particle-dispersed ceramic resistor, the four-point bending average strength is as small as about 100 MPa, and the thermal shock resistance is poor.

[0011] Under such circumstances, the present inventors have disclosed a new power resistor in Japanese Patent Application Laid-Open No. 8-45702. This is because the use of aluminum oxide powder having a small average particle size of 0.2 μm as the raw material powder has a porosity of 10%.
% Or less. As a result, the heat capacity per unit volume is 1.5 times that of the carbon particle dispersed ceramic resistor described above, and further excellent current-voltage characteristics are exhibited.

[0012]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a power resistor having a large heat capacity per unit volume, an appropriate resistance value, and improved mechanical strength. .

An object of the present invention is to provide a method for manufacturing a power resistor having a large heat capacity per unit volume, an appropriate resistance value, and a stable resistance value.

An object of the present invention is to provide a power circuit breaker having a large breaking capacity, a closing resistance unit having a stable breaking performance, and achieving a small size and high performance.

An object of the present invention is to provide a neutral point grounding resistor having a resistance unit having an appropriate and stable resistance value and capable of effectively suppressing a ground fault current.

[0016]

According to a first aspect of the present invention, there is provided a power resistor comprising aluminum oxide or a composite oxide containing aluminum, and 0.3 to 5% by weight of carbon particles.
And 0.1 to 30% by weight of partially stabilized zirconia, comprising (a) the aluminum oxide or the composite oxide containing aluminum and 0.1 to 30% by weight of partially stabilized zirconia. A first region, and (b) the aluminum oxide or a composite oxide containing aluminum,
Consisting of 0.1-30% by weight of partially stabilized zirconia and a second region containing more carbon particles than said first region: and formed on two opposing surfaces of said sintered body;
A pair of electrodes that are electrically connected to each other by the second region.

According to a second aspect of the present invention, there is provided a method for manufacturing a power resistor, wherein the carbon powder is small or does not contain the carbon powder, and the aluminum oxide powder has an average particle diameter of 1 μm.
m or less of Zr, Y, Mg, Ca, Ti, Si, Hf, B
a, Cr, Mn, Fe, Co, Ni, Cu, Zn, Al
At least one kind of metal powder selected from 0.1
Preparing a first granulated raw material containing 10 to 10% by weight, aluminum oxide powder, carbon powder having an average particle size of 1 μm or less, and Zr, Y, Mg,
Ca, Ti, Si, Hf, Ba, Cr, Mn, Fe, C
o, Ni, Cu, Zn, Al, a second granulated raw material containing at least one or more metal powders selected from the group consisting of 0.1 to 10% by weight and containing more carbon powder than the first granulated raw material. Preparing the first granulated raw material and the second
After mixing the granulated raw material to make the content of the entire carbon powder 0.5 to 3% by weight, forming and sintering to produce a sintered body; Forming a pair of electrodes on the main surface.

A power circuit breaker according to claim 3 of the present invention comprises: main switching means arranged in a current path; connected to the current path so as to be parallel to the main switching means; An auxiliary opening / closing means that is turned on before turning on the power supply; and a plurality of resistors connected in series with the auxiliary opening / closing means and manufactured by the method according to claim 1 or the method according to claim 2. Closing resistance unit;
It is characterized by having.

A neutral point grounding resistor according to claim 4 of the present invention is a grounded container; a lower terminal plate disposed in the container and grounded through a ground wire; and the lower terminal plate mounted on the lower terminal plate. A resistor unit having a structure in which a plurality of resistors according to claim 1 or a plurality of resistors manufactured by the method according to claim 2 are stacked; an upper terminal plate disposed on an uppermost surface of the resistor unit; and an upper surface of the container. A bushing, which is disposed so as to be connected to the upper terminal plate and has an external connection terminal at an upper end.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a power resistor according to the present invention will be described in detail with reference to the drawings.

FIG. 1 is a perspective view showing a power resistor according to the present invention, FIG. 2 is a cross-sectional view of the power resistor of FIG. 1, and FIG. 3 schematically shows a microstructure of the sintered body of FIG. FIG.

The resistor 1 covers a disc-shaped sintered body 2, a pair of electrodes 3 formed on both circular surfaces of the sintered body 2, and an outer peripheral surface including peripheral edges of both sides of the sintered body 2. And the insulating layer 4 formed. As shown in FIG. 3, the sintered body 2 includes a first region 5 having a small amount of carbon or no carbon, and a second region 6 having a larger amount of carbon than the first region 5. The first region 5 substantially exhibits insulation, and the second region 6 exhibits conductivity.
In the sintered body 2, the second regions 6 are connected to each other in a three-dimensional network structure, and are arranged so as to be connected to the pair of electrodes 3. The resistance of the sintered body 2 is controlled by the connection state of the second region 6 and the resistivity of the second region 6 itself.

As shown in FIG. 3, the first region 5 includes aluminum oxide particles 7 and partially stabilized zirconia particles 8.
And has a substantially insulating property.

As shown in FIG. 3, the second region 6 has a form in which conductive carbon 11 is present at the grain boundaries of the insulating aluminum oxide particles 9 and the partially stabilized zirconia particles 10. The plurality of second regions 6 are electrically connected to each other.

The first region 5 occupies most of the sintered body 2 and the remainder is occupied by the second region 6.
It is preferable to electrically connect the pair of electrodes 3 with the carbon in the region 6. In particular, the first region 5 and the second region 6 in the sintered body 2 are present such that the first region 5 is 60 to 95% by weight and the second region 6 is 5 to 40% by weight. Is preferred.

In the sintered body 2 having such a form of the first region 5 and the second region 6, the amount of carbon in the sintered body 2 is 0.5 to 3% by weight, Preferably, the carbon content of No. 5 is less than 0.2% by weight (including 0% by weight), and the carbon content of the second region 6 is 0.2 to 5% by weight.

The reason for limiting the amount of carbon in the first region 5 and the second region 6 in the sintered body 2 is as follows.

The amount of carbon in the sintered body is 0.5% by weight.
If it is less than, the conductivity of carbon is not exhibited, and as a result, the resistivity of the sintered body becomes 10 ⁵ Ω · cm or more,
The resistivity of the power resistor may be too high. On the other hand, if the amount of carbon in the sintered body exceeds 3% by weight, the electric resistance becomes as low as 10 Ω · cm or less, which is similarly unsuitable as a power resistor. More preferably, the amount of carbon in the sintered body 2 is 0.5 to 2% by weight.

The first region 5 has a carbon content of 0.2
If the content is not less than% by weight, it is difficult to provide the first region 5 with insulating properties.

The resistivity of the second region 6 is controlled by its carbon content. When the carbon content of the second region 6 is less than 0.2% by weight, the resistivity is 10 ⁵ Ω ·
cm or more, and the resistivity of the power resistor may be too high. On the other hand, when the carbon content of the second region 6 exceeds 5% by weight, it is difficult to obtain the effect of the present invention in which the first region and the second region constitute a sintered body. More preferably, the carbon content of the second region 6 is 0.5
３3% by weight.

When the carbon in the first region 5 is relatively large in the above range (less than 0.2% by weight), the electrical conduction between the pair of electrodes 3 is in the second region 6. Not only carbon but also carbon in the first region 5 is allowed.

The average particle diameter of the aluminum oxide particles in the second region 6 is preferably smaller than that of the aluminum oxide particles in the first region 5. Specifically, the average particle diameter of the aluminum oxide particles in the second region 6 is 0.2 to 0.1.
The size of the aluminum oxide particles in the first region 5 may be 2 to 8 times, more preferably 3 to 6 times the size of the aluminum oxide particles in the second region. As described above, the power resistor including the sintered body 2 including the first region 5 and the second region 6 having the aluminum oxide particles having different particle diameters has good switching surge absorption.

In the sintered body 2, the partially stabilized zirconia particles contain 0.1 to 30% by weight of aluminum oxide.
Be blended. As the partially stabilized zirconia, for example, calcium oxide-added partially stabilized zirconia, cerium oxide-added cubic partially stabilized zirconia, or yttrium oxide-added tetragonal partially stabilized zirconia is used. In particular, yttrium oxide-added tetragonal partially stabilized zirconia is preferable.

[0034] The partially stabilized zirconia is 0.2 to
It preferably has an average particle size of 4.0 μm.

The reason why the mixing range of the partially stabilized zirconia is specified is as follows.

If the proportion of the partially stabilized zirconia is less than 0.1% by weight, the effect of addition is poor, and it is difficult to sufficiently improve the mechanical properties of the resistor (particularly, the sintered body). On the other hand, if the proportion of the partially stabilized zirconia exceeds 30% by weight, the following problem occurs.
(1) The density of the partially stabilized zirconia is about 1.5 times (5.9 g / c) of aluminum oxide (4.0 g / cm ³ ).
m ³ ), the resistor becomes heavy when the amount of the partially stabilized zirconia is increased. When such a heavy resistor is applied to, for example, a resistance unit in a power device, it is necessary to increase the strength of a member holding the unit, and as a result, the cost of the power device increases. (2) Partially stabilized zirconia has a heat capacity of aluminum oxide (3.0 J /
(cm ³ · K) 10% smaller (2.7 J / cm ³ ·
K). For this reason, when the amount of the partially stabilized zirconia is increased, the heat capacity of the sintered body is reduced, the amount of electric energy that can be absorbed is reduced, and in the case of the same amount of energy, the temperature rise becomes remarkable. (3) The energy withstand value of the resistor decreases. It is considered that partially stabilized zirconia and aluminum oxide have a difference in coefficient of thermal expansion. When the amount of partially stabilized zirconia increases, cracks are generated inside and the mechanical strength is reduced. A more preferable mixing ratio of the partially stabilized zirconia is 1 to 20% by weight.

In the sintered body 2, a composite oxide in which at least one oxide selected from magnesium oxide, silicon oxide and calcium oxide is mixed with aluminum oxide, for example, may be used instead of aluminum oxide.

The sintered body 2 is allowed to contain impurities such as aluminum oxynitride and aluminum oxycarbide in an amount that does not affect the heat capacity.

The electrode 3 is preferably made of a metal such as aluminum or nickel, or a carbide of Hf, Nb, Ta, Ti or TiN.

The insulating layer 4 is formed on the sintered body 2 to prevent creeping discharge on the side surface of the sintered body 2.
The insulating layer 4 is made of, for example, aluminum oxide, silicon oxide,
It is preferably formed from a ceramic such as borosilicate glass or an insulating heat-resistant resin such as polyimide.

The power resistor according to the present invention described above comprises aluminum oxide or a composite oxide containing aluminum, 0.3 to 5% by weight of carbon particles, and 0.1 to 30% by weight of partially stabilized zirconia. Comprising a sintered body containing
The sintered body includes: (a) a first region containing 0.1 to 30% by weight of the composite oxide containing aluminum oxide or aluminum and partially stabilized zirconia; and (b) a composite oxide containing aluminum oxide or aluminum. 0.1-30% by weight of partially stabilized zirconia and the first
And a second region containing more carbon particles than the region.
Since such a sintered body is improved in denseness and uniformity, a power resistor including the sintered body has a large heat capacity per unit volume, has an appropriate and stable electric resistance value, and has a surge resistance. It has the characteristic that the change in resistance value with time due to absorption is small. Further, the resistor provided with the sintered body has excellent mechanical strength.

That is, the purity of 99.sup.
Aluminum oxide having a relative density of 5% or more and a relative density of 99% or more has a bending strength of 400 MPa or more and a fracture toughness value of 3 to 4 MPa · m.
^Shows about ^1/2 mechanical properties. However, the sintered body used for the power resistor described in JP-A-8-45702 described above contains 0.3 to 5% by weight of carbon. Carbon severely inhibits sintering of aluminum oxide. For this reason, the resistor does not include the first carbon-free resistor.
The region serves as a main component, and the relative density of the sintered body is improved by densifying the first region. However, since the second region contains carbon, densification hardly proceeds as compared with the first region. Further, carbon weakens the bonding force between the aluminum oxide particles. Therefore, when a stress is applied from inside or outside of the sintered body, the sintered body may be broken starting from the second region containing carbon.

For the above-mentioned reason, Japanese Patent Application Laid-Open No. H8-4570
The sintered body used for the power resistor described in Japanese Patent Publication No. 2 may have a lower mechanical strength than a commercially available aluminum oxide sintered body having a purity of 99.5% or more.
The bending strength of the sintered body is 350 MPa, which is a decrease of about 10%, but the fracture toughness value may be reduced to 2-3 MPa · m ^1/2 .

From the above, according to the present invention, by blending partially stabilized zirconia particles in a sintered body containing aluminum oxide and carbon, excellent bending strength (1000 MPa or more) of the partially stabilized zirconia particles is obtained.
The mechanical strength of the sintered body can be improved by mechanical properties such as a fracture toughness value. As a result, the resistor provided with the sintered body has more excellent mechanical properties than the power resistor described in JP-A-8-45702. In particular, yttrium oxide-added tetragonal partially stabilized zirconia undergoes a phase transition accompanied by a volume change from tetragonal to monoclinic due to stress-induced, and the sintered body containing this partially stabilized zirconia has a stress relaxation effect. High and have excellent mechanical properties.

The carbon content of the first region is 1% by weight.
And the carbon content of the second region is 1 to 1
When the content is in the range of 0% by weight, in addition to the above-described excellent characteristics, it is possible to further secure a resistivity suitable for a power resistor and a sufficient density.

The average particle size of the aluminum oxide particles in the second region is in the range of 0.2 to 0.5 μm, and the aluminum oxide particles in the first region are 2 to 8 times the aluminum oxide particles in the second region. By setting the size, it is possible to secure more excellent sinterability in addition to the above-mentioned excellent characteristics.

The amount of the first region in the sintered body is set to 60 to 95% by weight, and the amount of the second region in the sintered body is set to 60 to 95% by weight.
By setting the amount of the region to 5 to 40% by weight, in addition to the above-described excellent characteristics, electrical connection between the second regions can be easily performed, and the electrical resistivity of the sintered body can be easily increased. Can be controlled. In particular, since the second regions can be connected to each other in a three-dimensional network structure, the second regions can be arranged so as to be connected to the pair of electrodes, and include a sintered body having an appropriate and stable electric resistivity. A resistor can be realized.

Next, a preferred method for manufacturing the above-described power resistor will be described.

(First Step) First, the average particle diameter is 1 μm or less,
Preferably, aluminum oxide powder having a good sinterability of 0.5 μm or less, carbon powder having an average particle diameter of 0.1 μm or less, and partially stabilized zirconia powder having an average particle diameter of 0.5 μm or less are mixed with water or an organic solvent. Mix in a ball mill below. In this step, a first mixed powder having a small amount of carbon powder or containing no carbon powder and a second mixed powder having more carbon powder than the first mixed powder are prepared.

The first mixed powder forming the first region is:
It is preferable to determine the content of the carbon powder so that the first region has a higher resistivity than the second region, from the viewpoint of substantially exhibiting insulating properties. For example, if the amount of carbon powder is 1
Desirably, it is less than 0.2% by weight, more preferably less than 0.2% by weight (including zero).

The second mixed powder forming the second region preferably has a carbon content of 1.0 to 10% by weight. If the carbon content is less than 1.0% by weight, the electrical resistivity may exceed 10 ⁵ Ω · cm, which may result in an undesired resistivity as a power resistor. On the other hand, if the carbon content exceeds 10% by weight, the compactness of the sintered body may be reduced.

The partially stabilized zirconia powder contained in the first and second mixed powders is blended in an amount of 0.1 to 30% by weight based on the aluminum oxide powder. The amount of the partially stabilized zirconia powder is specified for the same reason as described above.

It should be noted that a composite oxide powder containing aluminum oxide may be used instead of the aluminum hydroxide powder.

(Second Step) An organic solvent and a molding binder are added to the first and second mixed powders, respectively, and mixed to prepare slurries. By removing, a first granulated raw material and a second granulated raw material are respectively prepared. Here, the first granulated raw material forms a first region after forming and firing described later, and the second granulated raw material forms a second region after forming and firing described later. As the molding binder, it is preferable to select a material having a small amount of carbon remaining after degreasing in a non-oxidizing atmosphere described later.
As such a molding binder, for example, paraffin is preferable.

The second granulated raw material has an average particle diameter of the first granulated material.
It is preferably smaller than that of the granulated raw material.

(Third Step) The first and second granulated raw materials are mixed at a predetermined ratio and then molded to produce a molded body.
Subsequently, the molded body is degreased and then sintered to produce a sintered body.

In the mixing of the first and second granulated raw materials, the total amount of carbon powder is preferably in the range of 0.5 to 3% by weight.

The mixing ratio of the first granulated raw material forming the first region and the second granulated raw material forming the second region is 60-95% by weight of the first granulated raw material, Of the granulated raw material is preferably 5 to 40% by weight. If the mixing ratio of the second granulated powder is less than 5% by weight, electrical connection between the second regions becomes difficult, and it becomes difficult to control the resistivity of the sintered body. The mixing ratio of the second granulated powder is 40% by weight.
When the value exceeds, the resistivity of the sintered body becomes substantially close to the resistivity of the second region, and it becomes difficult to obtain the effect of the present invention.

For mixing the first and second granulated raw materials, it is preferable to use, for example, a V-type mixer having a structure shown in FIGS. 4A and 4B. That is, the V-shaped mixer is provided with two shafts 10a and 102b extending horizontally.
A V-shaped mixer body 101 rotatably arranged by 3a and 103b is provided. The shafts 103a, 103b
Is rotated by a drive mechanism (not shown). The mixer main body 101 is provided at one end side with a charging section 104 for two mixed substances.
a, 104b, and a discharge section 105 for discharging the mixture after mixing at the other end. Openable and closable lid 106a, 1
Reference numeral 06b is attached to the input sections 104a and 104b. The opening / closing member 107 is attached to the discharge unit 105.

In the V-shaped mixer having such a configuration, for example, the lid 106a is opened and the first
After the granulation raw material 108 composed of the second granulation raw material is charged into the mixer main body 101 and the lid 106a is closed,
When the shafts 104a and 104b are rotated by a drive mechanism (not shown), the mixer main body 101 is turned into the FIG. 6A,
FIG. Rotate like 6B. Mixer body 101
Is rotated, the granulated raw material 108 therein is mixed with the mixer body 101 as shown in FIG. It is gathered when it becomes 6A posture,
When the mixer main body 101 is a FIG. The operation of being dispersed into the forked portion when the posture of 6B is reached is repeated and mixed. Thus, in the V-type mixer, the granulated raw material 10
No. 8 is simply mixed and does not receive a breaking force like a screw mixer. Therefore, the first and second granulated raw materials of the granulated raw material 108 are not uniformly mixed with each other, but are uniformly mixed with each other while maintaining the mass of the granulated raw materials. .

Accordingly, a mixed granulated raw material obtained by mixing the two granulated raw materials using a V-type mixer is formed and fired to form a first region composed of the first granulated raw material and the second granulated raw material. And a sintered body in which these regions are separated from each other can be obtained. Also, for example, the first granulated raw material does not contain carbon,
Even if the composition contains carbon only in the granulation raw material and they are mixed with each other before firing, the first and second granulation raw materials are uniformly mixed with each other in a lump as described above. The weights of the first and second granulation raw materials are the first and second, respectively.
Area.

As the molding means, for example, a die pressing method, an extrusion method, an injection molding method and the like can be adopted. When the die molding method is adopted, it is preferable to perform the molding at a pressure of 200 kg / cm ² or more in order to increase the relative density of the sintered body. If the molding pressure is less than 200 kg / cm ² , the relative density of the sintered body decreases, and the heat capacity per unit volume may decrease.

In the case where paraffin is used as a binder, the degreasing treatment of the molded body is preferably performed at 500 to 600 ° C.

The holding time during the sintering may be adjusted according to the size of the compact and the filling amount in the furnace. For example, if the diameter is 100 mm and the thickness is about 20 mm, at least 4 hours are required. If the furnace is capable of performing the sintering step following degreasing, degreasing and sintering may be performed continuously. When sintering is performed in another furnace, cooling is preferably performed at 500 ° C./hour or less after the temperature is maintained in the degreasing step. If the cooling rate is further increased, cracks and the like may occur in the obtained sintered body, and this is particularly remarkable in the case of a large-sized sintered body.

When the sintering step is performed in a furnace different from the degreasing step, it is preferable to perform the sintering step as soon as possible after the degreasing step. This sintering is preferably performed in the range of 1300 to 1800 ° C. If the temperature is lower than 1300 ° C., sintering does not proceed, and the denseness of the sintered body may be reduced. As a result,
The obtained resistor has a small heat capacity per unit volume and a small energy resistance. On the other hand, when the temperature exceeds 1800 ° C., carbon in the sintered body is diffused, resulting in a high resistance, which makes it difficult to use as a resistor. The rate of temperature rise up to the holding temperature is preferably 500 ° C./hour or less. If the temperature is raised earlier than this, the molded article may be broken due to uneven shrinkage of the molded article. The holding time is preferably about 1 to 10 hours. If it is shorter than this, sintering does not proceed. On the other hand, if the length is too long, the disappearance of carbon and the growth of aluminum oxide particles in the sintered body will occur, cutting the conductive path and increasing the resistance of the resistor.

In the sintering step, it is preferable that the compact is placed in a box made of carbon or aluminum oxide in order to obtain a uniform temperature. The atmosphere is preferably in a non-oxidizing atmosphere such as nitrogen or argon gas.

(Fourth Step) Both main surfaces of the obtained sintered body are polished, and a metal such as aluminum or nickel, or a metal such as Hf,
An electrode made of Nb, Ta, Ti carbide or TiN is formed. Thereafter, an insulating layer is formed on the outer peripheral surface of the sintered body as necessary by baking a ceramic such as aluminum oxide, silicon oxide, borosilicate glass, or an insulating heat-resistant resin such as polyimide, coating, and drying. Then, a resistor is manufactured.

According to the method described above, FIG.
Has a characteristic that the heat capacity per unit volume is large, the electric resistance value is appropriate and stable, and the change with time of the resistance value due to surge absorption is small. Thus, a power resistor having more excellent mechanical strength can be obtained.

Next, another method of manufacturing a power resistor according to the present invention will be described.

(First Step) First, the average particle size is 1 μm or less,
Preferably, aluminum oxide powder having a good sinterability of 0.5 μm or less, carbon powder having an average particle diameter of 0.1 μm or less, and Zr, Y, Mg, Ca, T having an average particle diameter of 1 μm or less.
i, Si, Hf, Ba, Cr, Mn, Fe, Co, N
0.1 to 10% by weight of at least one metal powder selected from i, Cu, Zn and Al is mixed in a ball mill in the presence of water or an organic solvent. In this step, a first mixed powder having a small amount of carbon powder or containing no carbon powder and a second mixed powder having more carbon powder than the first mixed powder are prepared.

The first mixed powder forming the first region is:
It is preferable to determine the content of the carbon powder so that the first region has a higher resistivity than the second region, from the viewpoint of substantially exhibiting insulating properties. For example, if the amount of carbon powder is 1
Desirably, it is less than 0.2% by weight, more preferably less than 0.2% by weight (including zero).

The second mixed powder forming the second region is:
When the carbon content is 1.0 for the same reason as described above.
It is preferable to set it to 10 to 10% by weight.

The metal powder is formed by forming a granulated raw material and sintering, as will be described later, to remove the surface adsorbed oxygen and residual moisture preferentially by an oxidation reaction of the metal powder. It is added to suppress or prevent oxidation and disappearance of the carbon powder due to moisture.
The oxidation reaction of carbon generally starts at 400 ° C. or higher.
Therefore, the oxidation temperature of the metal powder to be added needs to be lower than that of carbon. Further, the boiling point or the sublimation temperature of the metal oxide formed after the oxidation reaction is lower than the firing temperature of the sintered body, and even if it disappears, there is no problem because the characteristics of the obtained resistor are not affected. However, lead, which is harmful to the human body,
It is naturally undesirable to add cadmium or the like. Thus, the metal species is Zr, Y, Mg, Ca, T
i, Si, Hf, Ba, Cr, Mn, Fe, Co, N
It is necessary to be selected from i, Cu, Zn, and Al.
In particular, considering the problem of contamination in the furnace, and furthermore, environmental pollution caused by exhausting the inside of the furnace, regardless of the form of the metal or its oxide, the metal species that disappears during the firing step, for example, Mo,
It is not preferable to use W, In, and Sb.

The reason for defining the mixing ratio of the metal powder is as follows.
This is for the following reasons. If the mixing ratio of the metal powder is less than 0.1% by weight, the adsorbed oxygen and residual moisture cannot be sufficiently removed in the degreasing step, and it becomes difficult to obtain a resistor having a stable resistance value. On the other hand, if the compounding ratio of the metal powder exceeds 10% by weight, the unoxidized metal powder may remain in the sintered body to form a conductive path and lower the resistivity of the resistor. A more preferable mixing ratio of the metal powder is 0.5 to 7% by weight.

The metal powder has an average particle size of 1 μm or less. When the average particle size of the metal powder exceeds 1 μm,
Not only does the specific surface area become so small that a sufficient effect of addition cannot be exhibited, but sinterability in the sintering step described later may be hindered.

A composite oxide powder containing aluminum oxide may be used instead of the aluminum hydroxide powder.

(Second Step) Water or an organic solvent and a molding binder are added to the first and second mixed powders, respectively, and mixed to prepare slurries, and the slurries are respectively sprayed using a spray dryer or the like. The first granulated raw material and the second granulated raw material are prepared by removing the solvent. Here, the first granulated raw material forms a first region after forming and firing described later, and the second granulated raw material forms a second region after forming and firing described later.

As a solvent for preparing the granulated raw material, it is preferable to use water which is easy to handle.

For the molding binder, it is preferable to select a material having a small amount of carbon remaining after degreasing in a non-oxidizing atmosphere described later. As such a molding binder, for example, paraffin is preferable.

The first and second granulated raw materials are 0.01 to
It preferably has an average particle size of 1 mm.

(Third Step) The first and second granulated raw materials are mixed at a predetermined ratio, and the total amount of carbon powder is reduced to 0.5 to
After adjusting to 3% by weight, it is molded to form a molded body. Then,
After degreasing the molded body, the molded body is sintered to produce a sintered body.

When the proportion of carbon powder in the mixed granulated raw material is less than 0.5% by weight, the obtained sintered body is not provided with conductivity by carbon, and as a result, the resistivity of the sintered body is 10 ⁵ Ω · cm or more, and the resistivity of the power resistor may be too high. On the other hand, if the compounding ratio of the carbon powder exceeds 3% by weight, the electric resistance of the obtained sintered body becomes as low as 10 Ω · cm or less, and is similarly unsuitable as a power resistor. A more preferable mixing ratio of the carbon powder is 0.5 to 2% by weight.

The mixing ratio of the first granulated raw material forming the first region and the second granulated raw material forming the second region is 60 to 95% by weight of the first granulated raw material, Of the granulated raw material is preferably 5 to 40% by weight. If the mixing ratio of the second granulated powder is less than 5% by weight, electrical connection between the second regions becomes difficult, and it becomes difficult to control the resistivity of the sintered body. The mixing ratio of the second granulated powder is 40% by weight.
When the value exceeds, the resistivity of the sintered body becomes substantially close to the resistivity of the second region, and it becomes difficult to obtain the effect of the present invention.

For mixing the first and second granulated raw materials, it is preferable to use the V-type mixer having the structure shown in FIGS. 4A and 4B. By using such a V-shaped mixer, the first and second granulated raw materials are mutually uniformly mixed while maintaining the mass of the granulated raw materials without the respective components being uniformly mixed. Mixed. Accordingly, a mixed granulated raw material obtained by mixing the two granulated raw materials using a V-shaped mixer is formed and fired to form a first region composed of the first granulated raw material and a second region composed of the second granulated raw material. It is possible to obtain a sintered body having two regions and these regions are separated from each other. Further, for example, even if the first granulated raw material does not contain carbon and the second granulated raw material contains carbon, and these are mixed with each other before firing, as described above, the first and second granules are mixed. Since the granulated raw materials are uniformly mixed with each other in a lump, the weights of the first and second granulated raw materials correspond to the first and second regions, respectively.

As the molding means, for example, a die pressing method, an extrusion method, an injection molding method and the like can be adopted. When the die molding method is adopted, it is preferable to perform the molding at a pressure of 200 kg / cm ² or more in order to increase the relative density of the sintered body. If the molding pressure is less than 200 kg / cm ² , the relative density of the sintered body decreases, and the heat capacity per unit volume may decrease.

The degreasing treatment of the molded body is preferably performed at 500 to 600 ° C. when paraffin is used as a binder.

The holding time during the sintering may be adjusted according to the size of the compact and the filling amount in the furnace. For example, if the diameter is 100 mm and the thickness is about 20 mm, at least 4 hours are required. If the furnace is capable of performing the sintering step following degreasing, degreasing and sintering may be performed continuously. When sintering is performed in another furnace, cooling is preferably performed at 500 ° C./hour or less after the temperature is maintained in the degreasing step. If the cooling is performed earlier than this, the molded body may be broken. In particular, it is remarkable in a large molded product. When the sintering step is performed in a furnace different from the degreasing step, the sintering step is preferably performed as soon as possible after the degreasing step. This sintering is preferably performed in the range of 1300 to 1800 ° C. If the temperature is lower than 1300 ° C., sintering does not proceed, and the denseness of the sintered body may be reduced. As a result, the obtained resistor has a small heat capacity per unit volume and a small energy withstand. On the other hand, when the temperature exceeds 1800 ° C., carbon in the sintered body is diffused, resulting in a high resistance, which makes it difficult to use as a resistor. The rate of temperature rise up to the holding temperature is preferably 500 ° C./hour or less. If the temperature is raised earlier than this, the molded article may be broken due to uneven shrinkage of the molded article. The holding time is preferably about 1 to 10 hours. If it is shorter than this, sintering does not proceed. On the other hand, if the length is too long, the disappearance of carbon and the growth of aluminum oxide particles in the sintered body will occur, cutting the conductive path and increasing the resistance of the resistor.

In the sintering step, it is preferable that the compact is placed in a box made of carbon or aluminum oxide in order to obtain a uniform temperature. The atmosphere is preferably in a non-oxidizing atmosphere such as nitrogen or argon gas.

(Fourth Step) Both main surfaces of the obtained sintered body are polished, and a metal such as aluminum or nickel, or a metal such as Hf,
An electrode made of Nb, Ta, Ti carbide or TiN is formed. Thereafter, an insulating layer is formed on the outer peripheral surface of the sintered body as necessary by baking a ceramic such as aluminum oxide, silicon oxide, borosilicate glass, or an insulating heat-resistant resin such as polyimide, coating, and drying. Then, a resistor is manufactured.

According to the method according to the present invention described above, the addition of, for example, during sintering due to the surface adsorbed oxygen and residual moisture contained in the granulated powder obtained by granulating the mixed powder. By suppressing or preventing oxidation and disappearance of the carbon powder, a power resistor including a sintered body having an appropriate and stable resistance value can be manufactured.

That is, in a resistor provided with an aluminum oxide-based sintered body containing carbon as a conductive material, conduction is established by connection of carbon existing at the grain boundaries of aluminum oxide particles in the sintered body. Therefore, the resistance value of the resistor greatly depends on the amount of carbon in the sintered body.

The present inventors have studied in detail resistors having different resistance values among resistors manufactured under the same conditions. As a result, they found that although the amount of carbon powder added at the raw material stage (granulated raw material) was the same, the amount of carbon in the sintered body was different. As a result of further study on the cause, it was found that the cause was caused by surface adsorbed oxygen and residual moisture contained in the granulated powder obtained by granulating the raw material powder.

As described above, the sintered body used for the resistor of the present invention is formed by mixing an aluminum oxide powder and a carbon powder and using an appropriate molding binder to improve the molding density during molding. . Various methods have been proposed so far for granulation, and in any method, the aluminum oxide powder and the carbon powder are added to a solution obtained by dissolving a molding binder in water or a non-aqueous organic solvent, and the resulting mixture is dried. A granulated raw material having a size of about 0.01 to 1 mm is used. As described above, a non-aqueous organic solvent may be used as the solvent, but it is more convenient to use water for handling. The granulated raw material is molded using a mold or the like, degreased, and sintered to produce a sintered body. In the degreasing step, although it depends on the binder used, in a non-oxidizing atmosphere, approximately 400 to 7
At a temperature of 00 ° C. and in a non-oxidizing atmosphere at 1300 ° C.
１1800 ° C., the surface adsorbed oxygen described above,
If there is residual moisture, carbon added as a conductive material is oxidized and disappears.

As one of the methods for solving such a problem, it is conceivable to dry the granulated material sufficiently, and immediately carry out molding and sintering. However, industrially, it is difficult to take a sufficient time for drying, or conversely, the steps after molding may be performed several days after granulation. In the latter case, even if it is sufficiently dried after granulation, it absorbs moisture in the air after several days, and the drying step has to be performed again, which is troublesome. Some types of molding binders have a relatively low melting point. For example, the melting point of paraffin is 60-100 ° C. Therefore, drying must be performed at a temperature lower than this, and sufficient drying may not always be performed.

Resistors (especially sintered bodies) manufactured under the same conditions
However, the reason why the resistance values are not exactly the same occurs during the period from the granulation step to the molding step, as described above. It is considered that the difference in the amount of water in the granulated raw material is particularly large.

Thus, the present invention provides a method of adding a metal powder, such as Zr, which reacts with oxygen, moisture, and the like at a lower temperature than carbon, to the aluminum oxide powder and the carbon powder, thereby producing the powder. When the granular raw material is formed and sintered, the surface adsorbed oxygen and residual moisture are preferentially removed by the oxidation reaction of the metal powder, thereby suppressing the oxidation and disappearance of the carbon powder caused by the surface adsorbed oxygen and residual moisture. Or can be prevented. Therefore, a power resistor provided with a sintered body having an appropriate and stable resistance value can be manufactured.

The power resistor manufactured by the method of the present invention is formed, for example, on the disc-shaped sintered body 2 shown in FIGS. And a pair of electrodes 3 and an insulating layer 4 covering the outer peripheral surfaces including the peripheral edges of both surfaces of the sintered body 2. The sintered body 2
As shown in FIG. 5, which schematically shows the microstructure, the first region 5 has a small amount of carbon or does not contain carbon, and the second region 6 has a large amount of carbon than the first region 5. The first region 5 is substantially insulative, and the second region 5
Region 6 shows conductivity. The first region 5 has a form in which a metal oxide 12 such as Zr is present at the grain boundaries of the aluminum oxide particles 7. The second region 6 contains more carbon than the first region 5, and has a form in which a metal oxide 12 such as Zr and conductive carbon 11 are present at the grain boundaries of the aluminum oxide particles 9, for example. The plurality of second regions 6 are electrically connected to each other by the carbon 11. However, when a sublimable material such as Mo or W is used as the metal powder, the aluminum oxide particles 7 and 9 in the first and second regions 5 and 6 are used.
No or little oxide is present at the grain boundaries. The aluminum oxide particles 7 in the first region 5 are present in a state where the particle size is larger than the particle size of the aluminum oxide particles 9 in the second region 6. In the sintered body 2, the second regions 6 are connected to each other in a three-dimensional network structure, and are arranged so as to be connected to the pair of electrodes 3. The sintered body 2 is determined by the connection state of the second region 6 and the resistivity of the second region 6 itself.
Is controlled.

The power resistor provided with the sintered body 2 having the microstructure shown in FIG. 5 has a large heat capacity per unit volume, has an appropriate and stable electric resistance value, and has a resistance value due to surge absorption. Has a characteristic that changes with time are small, and a power resistor having more excellent mechanical strength can be obtained.

The power resistor according to the present invention is not limited to the above-described disk-shaped structure. For example, as shown in FIGS. 6 and 7, an annular sintered body 21, electrodes 22 formed on both opposed annular surfaces of the sintered body 21,
The power resistor 25 may be composed of the insulating layers 23 and 24 coated on the outer peripheral surface and the inner peripheral surface of the sintered body 21.

The power resistor according to the present invention includes a fixed resistor, a variable resistor, and a resistor used for a closing resistor, a high-voltage device, and a large-capacity capacitor charging / discharging device of a power circuit breaker described later. Can be applied to arrays.

Next, a power circuit breaker according to the present invention is shown in FIG.
This will be described with reference to FIG.

FIG. 8 is a block diagram of a circuit breaker according to the present invention.
FIG. 9 is a perspective view showing a closing resistor. The circuit breaker 31
Main contact 3 arranged in arc-extinguishing chamber 32 and connected to current path
3 is provided. The auxiliary contact 34 is connected to the main path 33 in parallel with the current path. The closing resistance unit 35 is connected to the auxiliary contact 34 in series. The insulating rod 36 that moves up and down is the switch 3 that tilts.
7. In the power circuit breaker having such a configuration, when the insulating rod 36 is driven upward, the switch 37 is tilted and the auxiliary contact 34 is turned on before the main contact 33 is turned on. At this time, since the closing resistance unit 35 is connected in series to the auxiliary contact 34, the voltage of the current flowing through the current path in which the auxiliary contact 34 is interposed can be reduced to the closing resistance unit 35. As a result, it is possible to prevent an arc from being generated when the auxiliary contact 34 is turned on. Immediately before the main contact 33 is turned on, the current flows through the current path in which the closing resistance unit 35 and the auxiliary contact 34 are interposed, and the current flows in the current path in which the main contact 33 is interposed. Therefore, when the main contact 33 is turned ON, no high voltage is applied to the contact. As a result, it is possible to prevent an arc from being generated when the main contact 33 is turned on.

The closing resistance unit 35 is, for example, as shown in FIG.
, A pair of insulating support plates 39a and 39b, and a plurality of hollow cylindrical resistors 40 as shown in FIG.
And an elastic body 41. The pair of insulating support plates 39a and 39b are fitted into the support rod 38. A plurality of hollow cylindrical resistors 40 are fitted into the support bar 38 located between the support plates 39a and 39b. The elastic body 41 is disposed between the one (right end) support plate 39 a and the plurality of resistors 40, and is fitted into the support rod 38. The elastic body 4
1 is used to apply elastic force to the plurality of resistors 40 and stack them on the support rod 38. The nuts 42a and 42b are screwed to both ends of the support rod 38. The nuts 42a and 42b are connected to the support plate 39.
a, 39b is used to press the elastic body 41 disposed between them. The insulating support rod 38 is made of an organic material for reasons such as high strength, light weight, and easy workability. Generally, the temperature of the closing resistor increases when the switching surge is absorbed. For this reason, it is difficult to maintain the strength of the support bar made of the organic material having poor heat resistance. However, since the input resistor having a composition described later has a large heat capacity, it is possible to suppress a temperature rise during absorption of the switching surge to a certain temperature or less. As a result, it becomes possible to use a support rod made of the organic material. In addition, it becomes possible to make the volume smaller as the input resistor has a larger heat capacity.

The resistor (power resistor) 40 incorporated in the closing resistor unit 35 includes an annular sintered body 21 as shown in FIGS. A pair of electrodes 22 formed on the sintered body 2
Insulating layers 23 and 24 coated on the outer peripheral surface and inner peripheral surface
It is composed of

The sintered body 21 has a composition containing aluminum oxide or a composite oxide containing aluminum, carbon, and 0.1 to 30% by weight of partially stabilized zirconia. The sintered body 21 has a first region composed of, for example, aluminum oxide particles or composite oxide particles containing aluminum and 0.1 to 30% by weight of partially stabilized zirconia particles; aluminum oxide particles and partially stabilized zirconia particles 0; .1 to 30% by weight, which are present at the grain boundaries of the aluminum oxide particles and the partially stabilized zirconia particles, respectively, contain more carbon than the first region, and are arranged so as to be connected to the pair of electrodes 22. A second area; Particularly, in the sintered body 21, the second regions are connected to each other in a three-dimensional network structure, and are arranged so as to be connected to the pair of electrodes 22. The resistance value of the sintered body is controlled by the connection state of the second region and the resistivity of the second region itself.

Further, another form of the sintered body 21 is the first region 5 containing a small amount of carbon or containing no carbon as shown in FIG. 5 manufactured from the method load of the present invention.
And a second region 6 having a larger amount of carbon than the first region 5. The first region 5 substantially exhibits insulation, and the second region 6 exhibits conductivity. The first region 5 has a form in which a metal oxide 12 such as Zr is present at the grain boundaries of the aluminum oxide particles 7. The second area 6
Has a form in which an oxide 12 of a metal such as Zr and a conductive carbon 11 are present at the grain boundaries of the aluminum oxide particles 9, respectively. Plural second regions 6
Are electrically connected to each other. Further, the first region 5
The inner aluminum oxide particles 7 exist in a state where the particle diameter is larger than the diameter of the aluminum oxide particles 9 in the second region 6. In the sintered body 2, the second regions 6 are connected to each other in a three-dimensional network structure, and are arranged so as to be connected to the pair of electrodes 3. The resistance of the sintered body 2 is controlled by the connection state of the second region 6 and the resistivity of the second region 6 itself.

The power circuit breaker according to the present invention described above includes a closing resistor unit including a sintered body having the above-described structure, having a large heat capacity per unit volume, and incorporating a resistor having an appropriate resistance value. Have. Such a closing resistor unit has a large breaking capacity, can have a smaller volume than a closing resistor unit in which a conventional carbon dispersed ceramic resistor is incorporated, and has more stable breaking performance. Therefore, the power circuit breaker provided with the closing resistance unit can be reduced in size and performance.

Next, the neutral point grounding resistor according to the present invention will be described with reference to FIG.

In the grounding container 51, a lower terminal plate 53 grounded through a ground wire 52 and an upper terminal plate 54 located at a desired distance from the terminal plate 53 are arranged. The plurality of resistance units 55 are connected to the lower terminal plate 5.
3 and the upper terminal plate 54.
These resistance units 55 are stacked vertically with an insulating support bar 56 erected on the lower terminal plate 53 and fitted on the support bar 56 via an elastic piece (not shown). And a plurality of hollow cylindrical resistors 58 pressed and fixed by a coil spring 57 disposed on the side. Bushing 60 having terminal 59 for external connection
Are arranged on the upper surface of the container 51 so as to be connected to the upper terminal plate 54.

As shown in FIGS. 6 and 7, the resistor (power resistor) 57 incorporated in the resistor unit 55 is formed on the annular sintered body 21 and on both sides of the annular body of the sintered body 21. It comprises a pair of electrodes 22 formed and insulating layers 23 and 24 covering the outer and inner peripheral surfaces of the sintered body 21.

The sintered body 21 has a composition containing aluminum oxide or a composite oxide containing aluminum, carbon, and 0.1 to 30% by weight of partially stabilized zirconia. The sintered body 21 has a first region composed of, for example, aluminum oxide particles or composite oxide particles containing aluminum and 0.1 to 30% by weight of partially stabilized zirconia particles; aluminum oxide particles and partially stabilized zirconia particles 0; .1 to 30% by weight, which are present at the grain boundaries of the aluminum oxide particles and the partially stabilized zirconia particles, respectively, contain more carbon than the first region, and are arranged so as to be connected to the pair of electrodes 22. A second area; Particularly, in the sintered body 21, the second regions are connected to each other in a three-dimensional network structure, and are arranged so as to be connected to the pair of electrodes 22. The resistance value of the sintered body is controlled by the connection state of the second region and the resistivity of the second region itself.

Further, another form of the sintered body 21 is the first region 5 having a small amount of carbon or containing no carbon as shown in FIG. 5 manufactured from the method load of the present invention.
And a second region 6 having a larger amount of carbon than the first region 5. The first region 5 substantially exhibits insulation, and the second region 6 exhibits conductivity. The first region 5 has a form in which a metal oxide 12 such as Zr is present at the grain boundaries of the aluminum oxide particles 7. The second area 6
Has a form in which an oxide 12 of a metal such as Zr and a conductive carbon 11 are present at the grain boundaries of the aluminum oxide particles 9, respectively. Plural second regions 6
Are electrically connected to each other. Further, the first region 5
The inner aluminum oxide particles 7 exist in a state where the particle diameter is larger than the diameter of the aluminum oxide particles 9 in the second region 6. In the sintered body 2, the second regions 6 are connected to each other in a three-dimensional network structure, and are arranged so as to be connected to the pair of electrodes 3. The resistance of the sintered body 2 is controlled by the connection state of the second region 6 and the resistivity of the second region 6 itself.

The neutral point grounding resistor according to the present invention described above includes a sintered body having the above-described structure, has a large heat capacity per unit volume, and incorporates a resistor having an appropriate resistance value. Therefore, it is possible to effectively suppress the ground fault current when the circuit breaker connected to the external connection terminal operates.

[0114]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail.

Example 1 First, 3 mol% of yttrium oxide was added to aluminum oxide powder having an average particle size of 0.2 μm.
0.1% by weight of zirconium oxide powder having an average particle size of 0.2 μm dissolved in solid was added, and ethanol was used as a solvent.
Mixing using an alumina pot and alumina balls,
Pulverization was performed and this was dried. Subsequently, the dry mixed powder was added to a solution obtained by adding and mixing 5% by weight of a paraffin emulsion in water, and the mixture was slurried, and then granulated to an average particle diameter of 100 μm using a spray drier. A granular raw material was prepared.

Further, starting from the same aluminum oxide powder as the first granulated raw material, 3 wt% of carbon powder having an average particle size of 50 nm was added, and 3 mol% of yttrium oxide was dissolved in an average particle size of 0.2 μm. Was added and further mixed and pulverized using ethanol as a solvent by using an alumina pot and alumina balls, and dried. Subsequently, the dry mixed powder was added to a solution obtained by adding and mixing 5% by weight of a paraffin emulsion in water, and the mixture was slurried, and then granulated to an average particle diameter of 100 μm using a spray drier. A granular raw material was prepared.

Next, 75% by weight of the first granulated raw material and 25% by weight of the second granulated raw material were used as shown in FIG.
A mixed granulated raw material was prepared by mixing using a V-type mixer shown in (b). As described above, in the mixing by the V-type mixer, the first and second granulated raw materials are mixed with each other while maintaining the mass of the granulated raw materials, without their respective components being uniformly mixed. .

Next, the mixed granulated powder was molded using a steel mold at a molding pressure of 500 kg / cm ² to obtain a disk-shaped compact having a diameter of 12.5 cm and a thickness of 3.1 cm. Subsequently, the boundary between the upper and lower circular surfaces and the outer peripheral surface of the molded body was chamfered by 1 mm, and then subjected to a degreasing treatment at 600 ° C. for 4 hours in a nitrogen gas atmosphere. Subsequently, the degreased molded body was placed in an argon gas atmosphere for 2 hours.
The temperature was raised at a rate of 00 ° C./hour, and the temperature was maintained at 1500 ° C. for 1 hour to produce a sintered body having a diameter of 10 cm and a thickness of 2.5 cm.

Next, the upper and lower end faces of the sintered body were
An electrode was formed by grinding with a # 2 grindstone and spraying aluminum on this surface. Continue. A water-soluble paste composed of aluminum phosphate, alumina fine powder and silica fine powder is applied to the outer peripheral surface of the sintered body, and dried at 150 ° C. for 1 hour to form an insulating layer on the outer surface except for the electrode end, thereby providing power. A resistor was manufactured.

(Examples 2 to 8 and Comparative Examples 1 to 5) Amounts of yttrium oxide-stabilized zirconia powder blended in the first and second granulated raw materials and carbon powder blended in the second granulated raw material A power resistor was manufactured in the same manner as in Example 1 except that the power resistance was changed.

The obtained Examples 1 to 8 and Comparative Examples 1 to 5
For the power resistor, the proportion of the second region in the sintered body, the carbon content of the first region and the second region of the sintered body,
The carbon content of the entire sintered body, the partially stabilized zirconia of the entire sintered body, and the average particle size of the aluminum oxide particles in the first and second regions were measured. The results are shown in Table 1 below.
Further, the resistance value, the average four-point bending strength average fracture toughness value (measured by an indentation fracture method), and the energy resistance of the power resistors of Examples 1 to 8 and Comparative Examples 1 to 5 were measured. The results are shown in Table 2 below.

[0122]

[Table 1]

[0123]

[Table 2]

As is clear from Tables 1 and 2, Example 1 provided with a sintered body containing 0.1 to 30% by weight of partially stabilized zirconia and 0.3 to 5% by weight of carbon.
It can be seen that the power resistors of Nos. To 8 have an appropriate resistance value and mechanical strength, and have a higher energy resistance.
On the other hand, the power resistor of Comparative Example 5 including the sintered body in which the amount of the partially stabilized zirconia exceeds 30% by weight has a low energy resistance and is not suitable. Therefore, when the resistors of Examples 1 to 8 have the same volume as the resistor of Comparative Example 5, it is possible to absorb 20% more energy, and the volume of the resistor unit is reduced, and the power equipment is reduced. Has become possible.

Example 9 0.1% by weight of zirconium powder having an average particle size of 0.2 μm was added to aluminum oxide powder having an average particle size of 0.2 μm, and ethanol was used as a solvent.
Mixing using an alumina pot and alumina balls,
Pulverization was performed and this was dried. The dry mixed powder was added to a solution in which 5% by weight of paraffin emulsion was added to water and mixed, and the mixture was slurried, and then granulated to an average particle diameter of 100 μm using a spray drier to prepare a first granulated raw material.

Further, starting from the same aluminum oxide powder as the first granulated raw material, 3 wt% of carbon powder having an average particle diameter of 50 nm was added, and 1 wt% of zirconium powder having an average particle diameter of 0.2 μm was added. Further, mixing and pulverization were carried out using an alumina pot and alumina balls using ethanol as a solvent, and the mixture was dried. A second granulated raw material was prepared by adding the dry mixed powder to a solution in which 5% by weight of a paraffin emulsion was added to water, forming a slurry, and granulating to an average particle diameter of 100 μm using a spray dryer.

Next, 75% by weight of the first granulated raw material and 25% by weight of the second granulated raw material were used as shown in FIG.
A mixed granulated raw material was prepared by mixing using a V-type mixer shown in (b). As described above, in the mixing by the V-type mixer, the first and second granulated raw materials are mixed with each other while maintaining the mass of the granulated raw materials, without their respective components being uniformly mixed. .

Next, the mixed granulated powder was molded using a steel mold at a molding pressure of 500 kg / cm ² to obtain a disk-shaped compact having a diameter of 12.5 cm and a thickness of 3.1 cm. Subsequently, after demarcation of the boundary line between the upper and lower circular surfaces and the outer peripheral surface of the molded body by 1 mm, the molded body was kept in a nitrogen gas atmosphere at 400 ° C. for 4 hours and subsequently at 600 ° C. for 4 hours to perform a degreasing treatment. went. Subsequently, the degreased molded body was heated at a rate of 200 ° C./hour in an argon gas atmosphere and kept at 1500 ° C. for 1 hour to produce a sintered body having a diameter of 10 cm and a thickness of 2.5 cm.

Then, the upper and lower end faces of the sintered body were
An electrode was formed by grinding with a # 2 grindstone and spraying aluminum on this surface. Continue. A water-soluble paste composed of aluminum phosphate, alumina fine powder and silica fine powder is applied to the outer peripheral surface of the sintered body, and dried at 150 ° C. for 1 hour to form an insulating layer on the outer surface except for the electrode end, thereby providing power. A resistor was manufactured.

The obtained resistor of Example 9 had a resistance value of 64.
Ω.

Again, nine power resistors were manufactured in exactly the same manner, and a total of ten resistors were manufactured. The average resistance (ρ _AV ) of the ten resistors is 64Ω, the maximum resistance (ρ _MAX ) is 66Ω, the minimum resistance (ρ _MIN ) is 62Ω,
The difference (ρ _δ ) was about 4Ω (about 6% of the average resistance value).

Comparative Example 6 First, aluminum oxide powder having an average particle size of 0.2 μm was pulverized with ethanol as a solvent using an alumina pot and alumina balls, and dried. 5% by weight of paraffin emulsion
Was added to water, and the dry powder was added to a mixed solution to form a slurry.
The first granulated raw material was prepared by granulating to 00 μm.

Also, using aluminum oxide powder similar to the first granulated raw material as a starting material, 3% by weight of carbon powder having an average particle size of 50 nm was added, and using ethanol as a solvent, an alumina pot and alumina balls were used. The mixture was mixed and pulverized, and dried. The dry mixed powder was added to a solution in which 5% by weight of paraffin emulsion was added to water, and the mixture was slurried, and then granulated to an average particle diameter of 100 μm using a spray drier to prepare a second granulated raw material.

Next, 75% by weight of the first granulated raw material and 25% by weight of the second granulated raw material were used as shown in FIG.
A mixed granulated raw material was prepared by mixing using a V-type mixer shown in (b). Thereafter, a molded body is prepared in the same manner as in Example 9, and then subjected to a degreasing and sintering process to obtain a 10c diameter.
A sintered body having a thickness of 2.5 cm and a thickness of 2.5 cm was prepared, and an electrode and an insulating layer were formed in the same manner as in Example 9 to manufacture a power resistor.

The obtained resistor of Comparative Example 6 had a resistance value of 7
At 8Ω, the resistance was increased by 22% compared to the resistor of Example 9.

Again, nine power resistors were manufactured in exactly the same manner, and a total of ten power resistors were manufactured. As a result, ρ _AV = 310Ω, ρ _MAX = 355Ω, ρ _MIN = 25
9Ω, ρ _δ = 96Ω (about 31% of the average resistance value),
The variation of the resistance value was larger than that of the power resistor of Example 9.

(Examples 10 to 29 and Comparative Examples 7 and 8)
Except that the type and amount of the metal powder blended in the first and second granulation raw materials and the amount of carbon powder blended in the second granulation raw material were changed as shown in Tables 3 and 5, below, In the same manner as in Example 9, ten power resistors were manufactured.

With respect to the obtained power resistors of Examples 10 to 29 and Comparative Examples 7 and 8, the second
The ratio of the regions, the carbon content of the first region and the second region of the sintered body, the amount of carbon in the entire sintered body, and the amount of metal oxide in the entire sintered body were measured. The results are shown in Tables 3 and 5 below. Further, with respect to the power resistors of Examples 10 to 29 and Comparative Examples 7 and 8, the average particle diameter, the average resistance, the maximum resistance, and the minimum resistance of the aluminum oxide particles in the first and second regions of the sintered body. The difference between the values was examined. The results are shown in Tables 4 and 6 below. Tables 3 to 6 show that the second occupancy in the sintered body in the power resistors of Example 9 and Comparative Example 6 described above.
Ratio of regions, carbon content of first and second regions of sintered body, carbon amount of entire sintered body, metal oxide amount of entire sintered body, oxidation in first and second regions of sintered body The average particle size of the aluminum particles and the difference between the maximum resistance value and the minimum resistance value are also described.

[0139]

[Table 3]

[0140]

[Table 4]

[0141]

[Table 5]

[0142]

[Table 6]

As is clear from Tables 3 to 6, the power resistors of Examples 10 to 29 manufactured using the first and second granulated raw materials containing the metal species containing zirconium are as follows.
It turns out that it has a stable resistance value. In addition, it can be seen that the power resistors of Comparative Examples 9 and 10 each having a sintered body having a carbon amount in the range of 0.5 to 3% by weight have a variation in resistance value.

[0144]

As described above, according to the present invention, it is possible to obtain a resistor having a large mechanical property, particularly a high fracture toughness value. As a result, a larger amount of energy can be absorbed by a resistor having the same volume, which is very effective in reducing the size of a resistance unit used in a power device such as a circuit breaker or a neutral grounding resistor.

Further, according to the present invention, the disappearance of carbon is prevented by blending a metal powder which reacts with oxygen, moisture, etc. into the raw material (granulated raw material) at a temperature lower than that of carbon to prevent the disappearance of carbon. A power resistor having the specified resistance value can be manufactured. As a result, the reliability and durability of power devices such as a circuit breaker and a neutral grounding resistor have been improved.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a power resistor according to the present invention.

FIG. 2 is a sectional view of the resistor shown in FIG. 1;

FIG. 3 is a view schematically showing a microstructure of a sintered body in the resistor shown in FIG. 1;

FIG. 4 is a schematic diagram showing a V-type mixer used for manufacturing a power resistor according to the present invention.

FIG. 5 is a view schematically showing a microstructure of a sintered body in a power resistor according to the present invention.

FIG. 6 is a perspective view showing another embodiment of the power resistor according to the present invention.

FIG. 7 is a sectional view of the resistor shown in FIG. 6;

FIG. 8 is a configuration diagram showing a power circuit breaker according to the present invention.

FIG. 9 is a configuration diagram showing a closing resistance unit which is a component of the power circuit breaker of FIG. 8;

FIG. 10 is a schematic cross-sectional view showing a neutral point grounding resistor according to the present invention.

[Explanation of symbols]

 1, 25, 40, 58: power resistor, 2, 21: sintered body, 3, 22: electrode, 5: first region, 6: second region, 7, 9: aluminum oxide particles, 10: part Stabilized zirconia, 11: carbon, 12: metal oxide particles, 10 arc-extinguishing chamber 31: circuit breaker, 35: closing resistance unit, 51: ground container, 55: resistance unit, 60: bushing.

Claims (4)

[Claims] 1. A sintered body containing aluminum oxide or a composite oxide containing aluminum, 0.5 to 3% by weight of carbon, and 0.1 to 30% by weight of partially stabilized zirconia, wherein (a) A first region containing 0.1 to 30% by weight of the aluminum oxide or aluminum-containing composite oxide and partially stabilized zirconia; and (b) a composite oxide containing the aluminum oxide or aluminum and partially stabilized zirconia 0.1. ~ 30% by weight
And a second region containing more carbon than the first region: and a pair of electrodes formed on two opposing surfaces of the sintered body and electrically connected to each other by the second region. A power resistor characterized in that: 2. An aluminum oxide powder having an average particle size of 1 or less containing little or no carbon powder.
μm or less of Zr, Y, Mg, Ca, Ti, Si, Hf,
Ba, Cr, Mn, Fe, Co, Ni, Cu, Zn, A
at least one metal powder selected from the group consisting of
Preparing a first granulated raw material containing 1 to 10% by weight, aluminum oxide powder, carbon powder having an average particle diameter of 1 μm or less, and Zr, Y, Mg, C having an average particle diameter of 1 μm or less.
a, Ti, Si, Hf, Ba, Cr, Mn, Fe, C
o, Ni, Cu, Zn, Al, a second granulated raw material containing at least one or more metal powders selected from the group consisting of 0.1 to 10% by weight and containing more carbon powder than the first granulated raw material. And mixing the first granulated raw material and the second granulated raw material to make the total carbon powder content 0.5 to 3% by weight, and then molding and sintering. A method for producing a power resistor, comprising: a step of producing a sintered body; and a step of forming a pair of electrodes on opposing main surfaces of the sintered body. 3. main switching means arranged in a current path; auxiliary switching means connected to the current path in parallel with the main switching means and turned on before turning on the main switching means; And a closing resistor unit connected in series with the auxiliary switching means and incorporating a plurality of resistors according to claim 1 or a plurality of resistors manufactured by the method according to claim 2. Circuit breaker. 4. A grounded container; a lower terminal plate disposed in the container and grounded through a ground wire; a resistor according to claim 1 or a method mounted on the lower terminal plate. A resistance unit having a structure in which a plurality of manufactured resistors are laminated; an upper terminal plate disposed on the uppermost surface of the resistance unit; and an upper terminal plate disposed on the upper surface of the container so as to be connected to the upper terminal plate, and having an external terminal at an upper end. A neutral point grounding resistor, comprising: a bushing having a connection terminal.