JP3486108B2 - Power resistor, method of manufacturing the same, and power resistor - Google Patents

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art Generally, power resistor materials are roughly classified into metal-based resistance materials and ceramic-based resistance materials.
Among them, the ceramic-based resistance material has a characteristic that it has a higher voltage-current characteristic and a higher energy withstand capacity for absorbing high electric energy than the metal-based resistance material.

JP-A-58-139401 and JP-A-59-2
Japanese Patent No. 17668 discloses a typical ceramic resistor. Japanese Unexamined Patent Publication (Kokai) No. 58-139401 describes a carbon particle-dispersed ceramic resistor in which electrically conductive carbon powder is dispersed in an insulating aluminum oxide crystal.

In Japanese Patent Laid-Open No. 59-217668, a raw material obtained by adding carbon powder and a binder to an insulating inorganic material powder of aluminum oxide, mullite and calcined clay, mixing, kneading and heat-treating is used as a main raw material. It is described that a carbon-based power resistor is used, in which the carbon powder is a fine powder having a particle size of 0.1 μm or less and a content of 1.5 to 5% by weight.

Further, in Japanese Patent Laid-Open No. 57-52101, aluminum oxide is used as a main raw material, and other clay materials such as silicon oxide and magnesium oxide, and carbon as a conductive material are used in an amount of 3 to 3.
A resistance member containing 10% by weight is described.

By the way, it is generally known that when carbon powder is added to aluminum oxide powder to manufacture a sintered body, the sinterability of aluminum oxide is impaired. Therefore, the carbon particle-dispersed ceramic resistor described above, the aluminum oxide powder is added with carbon powder, and further the sintering of aluminum oxide was added boric purpose clay. However, this clay is simply aluminum oxide particles and aluminum oxide particles in the sintered body,
Only by combining the aluminum oxide particles and the carbon powder, the sinterability is not improved. Therefore, the porosity of the sintered body is as high as 10 to 30% and the compactness is poor. Dense aluminum oxide ceramic has a heat capacity of 3 J / c per unit volume
There is m ³ deg. However, the conventional carbon particle-dispersed ceramic resistor has a low heat capacity per unit volume of 2 J / cm ³ · deg because of its poor denseness. Therefore, the temperature rise of the resistor becomes remarkable as the electric energy is absorbed. In addition, since the carbon powder discharges in the pores when electricity is applied, through discharge occurs.

Further, carbon has a negative resistance value with respect to temperature, and the resistance value decreases as the temperature rises. Therefore, when electric energy is absorbed and the temperature of the resistor rises,
There is a problem that the resistance becomes small and more current flows through the resistor, causing a remarkable temperature rise.

Further, when the power resistor is used in the air, for example, when it is used in the air without being put in a gas filled tank like a vehicle-mounted regenerative current absorbing resistor, the resistor due to energy absorption is used. The increase in temperature causes the carbon particles in the ceramic to be oxidized. As a result, the resistance value becomes high and it cannot be used as a resistor. Conventional carbon particle-dispersed resistors oxidize at about 300 ° C, resulting in insulation. In order to prevent this, it is necessary to equip a cooler such as fins, which causes a problem that the resistor unit becomes large.

By the way, as the composite ceramic of aluminum oxide and a conductive material, another composite is disclosed in addition to the above-mentioned carbon particle dispersion type ceramic. As a typical composite ceramic of aluminum oxide and conductive material,
There is an aluminum oxide-titanium carbide composite ceramic.

Aluminum oxide-titanium carbide composite ceramics are used as cutting tool materials (JP-A-4-367572 and JP-A-4-367572).
4-300241 JP, JP 4-243959 JP, JP 3-2941
No. 01, JP 3-247555 A, JP 2-255561 A, JP 2-116673 A, etc.), magnetic head substrate material
(JP 4-321556 JP, JP 3-119508 JP, JP 2-199808 JP, JP 2-187915 JP, JP 2-15
3860 publication), disc brake rotor disc (
Japanese Patent Application Laid-Open No. 4-224880) and a refractory material (Japanese Patent Application Laid-Open No. 2-229757) are disclosed. Aluminum oxide-
The technology of using the titanium carbide composite ceramic as a power resistor material has not been disclosed yet.

[0011]

The use of aluminum oxide-titanium carbide composite ceramics as a power resistor material has the following problems. First, titanium carbide powder is less significant than carbon powder, but interferes with the sinterability of aluminum oxide. Therefore, conventionally, when the aluminum oxide-titanium carbide composite ceramic is used for a cutting tool that requires high density, JP-A-3-247555, JP-A-3-228870, JP-A-3-28159, and JP-A-3-28159. -
As disclosed in JP-A-28158, JP-A-2-2555561, etc., a sintering aid such as magnesium oxide, silicon oxide or the like is added, followed by hot firing or pressure firing such as HIP firing, or Alternatively, as disclosed in Japanese Patent Application Laid-Open No. 2-229757, aluminum oxide powder and titanium carbide powder are finely pulverized to improve sinterability and enable firing under atmospheric pressure. Pressure firing can be performed only in a batch type furnace, and it is possible for a small tool such as a cutting tool, but it is costly as a method for firing a relatively large sintered body such as a power resistor. High and unrealistic. Titanium carbide powder has a high hardness (Vickers hardness: 3
Since it is 200 kg / cm ² ), it takes a long time to pulverize, and it is easy to introduce impurities from the balls used in the pulverizing process, so it is possible to pulverize titanium carbide powder into fine powder.
After all it is not appropriate.

Further, the room temperature resistivity of the aluminum oxide-titanium carbide composite ceramic material disclosed so far is about 10 ^-4 to 10 ^-2 Ωcm. There is no disclosure of a higher resistance aluminum oxide-titanium carbide composite ceramic material. Resistivity of 10 ^-2 Ωcm or less, as disclosed in JP-A-2-271965, JP-A-2-289464, in the advantage that it is easy to process a complicated shape by electrical discharge machining is there. However, as a power resistor,
Generally, a resistivity of at least 10 ^-2 Ωcm or higher is required,
The aluminum oxide-titanium carbide composite ceramic material disclosed so far has a problem that it cannot be used as a power resistor because of its low resistivity.

[0013]

According to a first aspect of the present invention, a sintered body containing aluminum oxide, a compound containing titanium and carbon, and an unavoidable impurity, and two surfaces facing each other of the sintered body are formed. A power resistor comprising a pair of electrodes, wherein the sintered body has a first region containing little compound containing titanium and carbon or containing no compound containing titanium and carbon; A power resistor comprising a large amount of a compound containing titanium and carbon, and a second region arranged so as to be connected to the pair of electrodes.

With such a structure, the controllability of the resistivity is enhanced and a resistor having high sinterability can be obtained. In addition, since a compound containing titanium and carbon, such as titanium carbide, has a thermal expansion coefficient similar to that of aluminum oxide, it is possible to reduce the occurrence of cracks due to the difference in thermal expansion.

In a second aspect of the present invention, the compound containing titanium and carbon is titanium carbide.
The power resistor according to the invention. In the third invention of the present application, the average particle diameter of the compound containing carbon and titanium in the second region is 20 μm or less.
The power resistor according to the invention.

In the first aspect of the present invention, by setting the particle size within the above range, it becomes possible to improve the sinterability of the resistor. The fourth invention of the present application satisfies R _Al / R _TiC ≧ 0.1, where R _Al is the average particle diameter of the aluminum oxide particles in the second region and RT iC is the average particle diameter of the compound containing carbon and titanium. The power resistor according to the first invention is characterized in that.

With such a particle size, a particularly dense sintered body can be obtained. The fifth invention of the present application is
A step of adjusting a first granulation raw material to form a first region containing an aluminum oxide powder containing a small amount of titanium carbide powder or containing no titanium carbide powder; and including the titanium carbide powder and the aluminum oxide powder, the first region A step of adjusting a second granulation raw material forming a second region having a larger amount of titanium carbide powder, and after mixing the first granulation raw material and the second granulation raw material, by molding and sintering A method for producing a power resistor, comprising: a step of forming a sintered body; and a step of forming a pair of electrodes on the main surfaces of the sintered body that face each other.

The sixth invention of the present application comprises a sintered body containing aluminum oxide, titanium carbide and unavoidable impurities, and a pair of electrodes formed on two opposing surfaces of the sintered body. Is a resistor comprising a first region containing less titanium carbide or containing no titanium carbide, and a second region containing a larger amount of titanium carbide than the first region and arranged so as to be connected to the pair of electrodes. A power resistor comprising: a laminated resistor in which a plurality of the resistors are laminated, and a conductive cooling medium interposed between the laminated resistors.

[0019]

DETAILED DESCRIPTION OF THE INVENTION A power resistor according to the present invention will be described in detail with reference to FIGS. 1 is a schematic view showing a power resistor according to the present invention, FIG. 2 is a cross-sectional view showing a power resistor according to the present invention, and FIG. 3 is a schematic diagram showing a microstructure of the sintered body of FIG. FIG. The resistor 1 is composed of a pair of electrodes 3 formed on both circular surfaces of a disc-shaped sintered body 2. As shown in FIG. 3, the sintered body 2 has a structure containing aluminum oxide particles 4a and 4b, titanium carbide particles 5, and unavoidable impurities. Also, the sintered body 2
As shown in FIG. 3, the first region 6 has a small amount of titanium carbide or does not contain titanium carbide, and the second region 7 has a larger amount of titanium carbide than the first region 6. Indicates a substantially insulating property, and the second region 7 indicates a substantially conductive property. In the sintered body 2, the titanium carbide particles 5 in the second region 7 are connected to each other by a three-dimensional network structure. The second regions 7 are connected to each other by a three-dimensional network structure and are arranged so as to be connected to the pair of electrodes 3.

The microstructure of a conventional aluminum oxide-titanium carbide composite ceramic is shown in FIG. Thus, it has a structure containing the aluminum oxide particles 8 and the titanium carbide particles 9. FIG. 5 shows the relationship between the titanium carbide composition and the resistivity of the ceramic having such a structure.

Aluminum oxide, as shown in FIG.
The resistivity of the titanium carbide composite ceramic material can be adjusted by changing the amount of titanium carbide 9 which is a conductive substance. As can be seen from FIG. 5, when the titanium carbide content is 20% by volume or less, the resistivity is 10 ⁻² Ωcm or less, and the change in the resistivity due to the change in the composition is small. It is theoretically not impossible to obtain a sintered body having a resistivity of 10 ^-2 to 10 ¹⁴ Ωcm. However, as can be seen from FIG. 5, the change in resistivity with respect to the change in composition becomes large. For example, resistivity 10 ^-2 to 10 ^-1 Ωcm
Although the compositional difference at 5.2% by volume, the resistivity is 10 ^-1 to 10
⁰ composition difference at Ωcm 1.6 vol%, the composition difference between the resistivity of 10 ⁰ ～10Omucm stood 0.5% by volume, effect, control of the resistivity becomes very difficult. As a result, when multiple resistors are manufactured, the difference in individual resistance values becomes significantly large,
In addition, the resistance value inside one resistor becomes remarkably non-uniform, and it becomes very difficult to manufacture a resistor having a stable resistance value.

In FIG. 3, the first region 6 containing a small amount of titanium carbide or containing no titanium carbide is an insulating material phase,
The second region 7 having a larger amount of titanium carbide than the first region 6
Becomes the conductive material phase. In order to control the adjustment of the resistivity of the conductive material phase with titanium carbide, the relationship between the volume fraction of the second region 7 in the sintered body and the resistivity of the sintered body is as shown in FIG.
In the range of 10 ^-2 to 10 ² Ωcm, it became possible to obtain a sintered body with excellent controllability of resistivity.

Further, as shown in FIG. 3, the first region 6 containing a small amount of titanium carbide or containing no titanium carbide.
And the second region 7 having a larger amount of titanium carbide than the first region 6.
Even if there is titanium carbide that inhibits sinterability, the structure consisting of and improves the overall sinterability because the first region 6 having a small amount of titanium carbide or no titanium carbide is densified. It also has advantages.

The average particle diameter (R _TiC ) of the titanium carbide particles 5 in the second region 7 is preferably 20 μm or less. If the average grain size of the crystal grains is larger than this, the sinterability may be hindered and the sintered body may not be densified. That is, increasing the particle size of titanium carbide particles requires a higher concentration of titanium carbide in order to obtain the same resistivity. for that reason,
This is not preferable because it causes a decrease in the density of the sintered body. In order to obtain a dense sintered body having a relative density of 85% or more, the titanium carbide content in the second region is preferably 70% by volume or less.

The ratio (R _Al / R _TiC ) of the average particle size (R _Al ) of the aluminum oxide particles 4b to the average particle size (R _TiC ) of the titanium carbide particles 5 in the second region 7 is: The particle size ratio is preferably 0.1 or more.

The average particle size R _Al of the aluminum oxide particles 4b and the average particle size R of the titanium carbide particles 5 in the second region 7
_If the ratio R _Al / R _TiC to _TiC is less than 0.1, the ratio of titanium carbide particles in the second region 7 remarkably increases because the second region 7 has conductivity. As a result, the sintered body may not be densified.

The individual sizes of the first region containing a small amount of titanium carbide or containing no titanium carbide and the second region 7 containing a larger amount of titanium carbide than the first region 6 are not particularly limited. Not something. However, it is preferable that the second area 7 is within 10 times the size of the first area 6. Above this, a larger amount of second region composition is required to obtain the same resistivity. Therefore, by increasing the concentration of titanium carbide in the sintered body,
This is not preferable because it causes a decrease in the density of the sintered body.

The conductive material contained in the sintered body is not limited to stoichiometrically stoichiometric titanium carbide. Titanium carbide TiC _X , which is a non-scientifically stoichiometric composition, may be used as long as it has a substantially conductive composition. Also,
Titanium carbonitride is also acceptable as long as it has a composition that is substantially conductive.

As described above, the power resistor according to the present invention has a precise, appropriate and stable electric resistance, has a small change in resistance value with respect to temperature changes, and has excellent oxidation resistance at high temperatures. Very good.

In the sintered body 2, if the amount of impurities such as aluminum oxynitride, aluminum oxycarbide, etc. is not large enough to affect the heat capacity, a content of at least about 20% by weight is acceptable. The pair of electrodes 3 formed on both circular surfaces of the sintered body 2 are made of a metal such as aluminum, iron or brass, or a material having good conductivity such as a carbide or nitride of Hf, Nb, Ta or Ti. It is preferably formed.

When the power resistor 1 is used under a high voltage, aluminum oxide is formed on the outer peripheral surface of the sintered body 2 in order to prevent discharge on the surface of the sintered body 2.
Ceramics such as silicon oxide and borosilicate glass. Alternatively, the insulating layer is preferably formed of an insulating heat resistant resin such as polyimide.

The power resistor according to the present invention is not limited to the disk-shaped structure as described above. For example, as shown in FIG. 7, a ring-shaped sintered body 10 and the sintered body 10 are provided.
The power resistor 12 may be composed of the electrodes 11 formed on both of the opposed annular surfaces. Further, as shown in FIG. 8, a rod-shaped sintered body 13 and a pair of electrodes 14 formed on both ends of the sintered body 13
Alternatively, the power resistor 15 may be configured.

Next, a method of manufacturing the power resistor according to the present invention will be described in detail. First, an aluminum oxide powder having an average particle size of 1 μm or less, preferably 0.5 μm or less, which has good sinterability, and titanium carbide having an average particle size of 5 μm or less, preferably 2 μm or less, which does not impair sinterability. The powder is mixed in a ball mill in the presence of water or an organic solvent. In this step, a first mixed powder containing a small amount of titanium carbide powder or containing no titanium carbide powder and a second mixed powder containing more titanium carbide powder than the first powder are prepared.

Next, if necessary, a molding binder such as paraffin or polyvinyl alcohol is added to each of the first and second mixed powders, and the mixture is passed through a sieve having a predetermined opening to obtain first and second powders. Make a granulation raw material. first,
In addition to such a method, the second granulation raw material is prepared by mixing the first and second mixed powders with an organic solvent and a molding binder to prepare a slurry, and spraying the slurry with a spray dryer or the like. It can also be adjusted by removing the solvent with.

Next, the first and second granulation raw materials are dry-mixed in a predetermined ratio by, for example, a V-type mixer, and then molded to obtain a molded body. As the molding means, for example, a die pressing method, an extrusion method, an injection molding method or the like can be adopted. When molding by a die pressing method, the molding pressure is preferably at least 20 MPa or more in order to increase the relative density of the sintered body. If it is less than this, the filling rate of the molded body is small, and there is a possibility that it will not be sufficiently sintered. In order to obtain a molded product having a more uniform filling rate, it is desirable that the inner surface of the mold is sufficiently smooth, and if possible, mirror finished. Applying hydrostatic pressure is effective in making the filling rate of the molded body uniform.

The obtained molded product is debindered at a temperature suitable for the binder used. For example, when paraffin is used as the binder, the temperature is preferably 500 to 600 ° C. When the firing step is performed in a furnace different from the binder removal step, it is preferable to perform the firing step as soon as possible after the binder removal step. Further, the firing is preferably performed in the range of 1300 to 1800 ° C. At 1300 ° C or lower, sintering does not proceed and the compactness of the sintered body is poor. As a result, the heat capacity per unit volume becomes small. On the other hand, if the temperature is 1800 ° C. or higher, the reaction between titanium carbide and aluminum oxide in the sintered body becomes remarkable, and the conductivity of the titanium carbide particles is lost, which is not preferable. The rate of temperature increase up to the holding temperature is preferably 500 ° C./hour or less. If the temperature is raised faster than this, the molded body may be broken due to uneven shrinkage of the molded body. The holding time is preferably 1 hour or more. If it is shorter than this, sintering will not proceed and the compactness of the sintered body will be poor.

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

Both main surfaces of the obtained sintered body are polished, and a metal such as aluminum or nickel or Hf, Nb, Ta or
An electrode 3 made of Ti carbide or TiN is formed.

When a high voltage is applied to the resistor, an insulating layer is formed on the outer peripheral surface of the sintered body, if necessary. As a material for the insulating layer, there are an organic material and an inorganic material, but the inorganic material is preferable from the viewpoint of heat resistance. Further, it is preferable that the coefficient of thermal expansion is similar to that of the sintered body 2. If there is a large difference between the two, a crack occurs at the contact interface between the insulating layer and the sintered body, and the insulating layer peels off. Further, in order to obtain a sufficient shielding effect, it is necessary to form a dense layer having a porosity of 10% or less. Due to the above restrictions, the insulating layer is formed of a glass material such as borosilicate glass or lead glass, aluminum oxide, and / or an inorganic coating material containing silicon oxide as a main component, for example, a coating containing aluminum oxide and aluminum phosphate as a main component. The material is optimal.

The above material is applied with a brush to form a film by a method such as spray coating or dip coating, and then heat treated at a temperature suitable for the material to form an insulating layer. The thickness of the insulating layer depends on the shape of the resistor and the current and voltage used, but it is desirable that the thickness be 100 μm or more when used as a power resistor.

As described above, the method of manufacturing a power resistor according to the present invention has a precise, appropriate and stable electric resistance, has a small change in resistance value with respect to a temperature change, and has an acid resistance at a high temperature. It is possible to provide a power resistor having extremely excellent conversion characteristics.

Next, the power resistor according to the present invention is shown in FIG.
Will be described with reference to. The power resistor 16 is an insulating indicator rod.
17 and a pair of insulating support plates 18a and 18b, a plurality of hollow cylindrical resistors 19, cooling fins 22, and an elastic body 20.

The pair of insulating support plates 18a and 18b are fitted in the indicator rod 17 as described above. The plurality of hollow cylindrical resistors 19 have a plurality of cooling fins 25 made of, for example, stainless steel or aluminum interposed therebetween, and are fitted into the indicator rod 17 portion located between the support plates 18a and 18b. There is. The elastic body 20 is arranged between one support plate, for example, the support plate 18a and the plurality of resistors 19 in which the cooling fins 22 are interposed, and is fitted into the support rod 17. The elastic body 20, the plurality of resistors 19 and
It is used to apply an elastic force to a plurality of cooling fins 22 interposed therebetween and to stack them on the support rod 17.
The nuts 21a and 21b are screwed onto both ends of the support rod 17. The nuts 21a and 21b are used to press the elastic body 20 arranged between the support plates 18a and 18b.

The resistor (power resistor) 19 incorporated in the closing resistor unit is formed on the annular sintered body 10 and on both of the opposing annular surfaces of the sintered body 10 as shown in FIG. The electrode 11 constitutes a power resistor 12. The sintered body has a first region containing less titanium carbide or containing no titanium carbide, and a larger amount of titanium carbide than the first region,
And a second region arranged so as to be connected to the pair of electrodes.

As described above, according to the present invention, a plurality of dense, appropriate and stable electric resistances, having a small change in resistance value with respect to temperature changes, and having extremely excellent oxidation resistance at high temperatures are provided. By disposing the cooling fin adjacent to the power resistor, the temperature rise due to absorption of electric energy can be dissipated by the cooling fin, and the temperature rise of the resistor can be suppressed below the oxidation temperature of the resistor. . Since such a power resistor including a plurality of resistors can be used stably at high temperatures, the power resistor can be made smaller and have higher performance.

[0046]

The preferred embodiments of the present invention will be described in detail below. Examples 1 to 22 First, a solution prepared by adding 5% by weight of paraffin emulsion to water was mixed with aluminum oxide powder having an average particle size of 0.2 μm or less, and the mixture was slurried, and then the average particle size was 100 μm using a spray dryer. Then, the first granulated powder was obtained. Next, aluminum oxide powder having an average particle diameter of 0.2 μm or less and titanium carbide powder having an average particle diameter of 0.5 μm were weighed and mixed in a ball mill in the presence of an ethanol solvent. After drying this, a solution of paraffin emulsion added to water in an amount of 5% by weight was added to this dry mixed powder to form a slurry, which was then granulated to an average particle size of 100 μm using a spray drier, and a second granulated powder was obtained. Obtained. The first granulated powder and the second granulated powder were mixed at a ratio shown in Table 1 using a V-type mixer to obtain a mixed granulated powder.

Using a steel mold, these mixed granulated powders were molded at a molding pressure of 500 kg / cm ² into a disk shape having a diameter of 12.5 cm and a thickness of 3.1 cm to obtain a molded body. After chamfering the boundary between the upper and lower circular surfaces and the outer peripheral surface of this molded body by 1 mm, by holding in nitrogen gas at 600 ° C. for 4 hours,
The binder was removed. Next, this degreased body is heated at a temperature of 200 ° C./hour in an argon gas atmosphere, and then heated at 1500 ° C. for 1 hour.
By holding for a time, a sintered body having a diameter of 10 cm and a thickness of 2.5 cm was obtained.

The upper and lower end surfaces of this sintered body were ground with a No. 400 grindstone, and aluminum electrodes were formed on this surface by a thermal spraying method.
A power resistor was obtained. Regarding the obtained power resistor,
First region in the sintered body, titanium carbide content in the second region,
The resistivity of the center of the sintered body, the resistance ratio in the sintered body, the resistance temperature characteristic, and the oxidation resistance in air were investigated. The results are shown in Table 1. The method of each survey is as follows.

(1) Content of Titanium Carbide The first granulation raw material and the second granulation raw material were individually molded using a die press without mixing. After removing the binder, 15000 in an argon atmosphere
It hot-pressed at 50 degreeC and 50 degreeC for 1 hour. This sinter was pulverized with a silicon carbide pestle and a mortar and pulverized, and then the carbon composition was quantitatively analyzed by a high frequency heating infrared absorption method, and titanium was quantitatively analyzed by an ICP absorption spectroscopy method to obtain a titanium carbide composition. For convenience, the amount of titanium carbide in each region is used. The true density of titanium carbide is calculated to be 4.9 g / cm ³ from the weight composition to the volume composition.
Went as.

(2) Particle size of aluminum oxide particles and titanium carbide particles in the sintered body After cutting the sintered body with a diamond cutter, the cut surface was mirror-polished. This surface was chemically etched to visualize the grain boundaries, and the average grain size of each grain was measured.

(3) Resistivity of the center of the sintered body From the center of the sintered body, using a diamond cutter,
A 2 × 2 × 30 mm test piece was cut out. An electrode was formed by the sputtering method, and the resistivity was measured by the 4-terminal method.

(4) Resistance One electrode of the resistivity body in the sintered body was ground and removed, and 185 electrodes having a diameter of 4 mm were formed on the exposed surface of the sintered body at equal intervals. The resistance value between the point electrode and the facing electrode was measured, and the ratio of the minimum value and the maximum value of this value was defined as the resistance ratio in the sintered body. In practice, the resistance ratio is preferably 10 or less.

(5) Resistance-temperature characteristics, oxidation resistance in air The resistance value was measured by placing the resistance element in a thermostat or electric furnace whose temperature can be controlled. As for the oxidation resistance, the resistance value was calculated by placing the resistor in an electric furnace at an arbitrary temperature for a certain period of time and before putting it in an electric furnace. The temperature at which the ratio of the resistance values exceeded 2 was defined as the oxidation temperature.

Examples 23 to 45 Aluminum oxide powder used as a raw material had an average particle size of 0.9.
except using powders μm creates a power resistor in the same manner as in Example 1-22 method was evaluated in the same manner as in Example 1-2 2 method. The results are shown in Table 2.

Examples 46 to 66 A power resistor was prepared in the same manner as in Examples 1 to 22 except that the titanium carbide powder used as a raw material was a powder having an average particle size of 1.4 μm. It was evaluated in to 2 2 the same way. The results are shown in Table 3.

[0056]

[Table 1]

[0057]

[Table 2]

[0058]

[Table 3]

Example 47 Using the same raw materials as in Examples 1 to 22, in the same manner as in Examples 1 to 22 , an annular power having an outer diameter of 125 mm, an inner diameter of 25 mm, and a thickness of 25 mm as shown in FIG. I made a resistor.
The resistance value of this resistor was 0.03Ω. As shown in FIG. 9, a predetermined number of these resistors are stacked through aluminum cooling fins having an outer diameter of 200 mm, an inner diameter of 25 mm, and a thickness of 2 mm, and insulation made of aluminum oxide penetrating the center of each resistor and cooling fin. A resistor was constructed by being supported by a sex indicator rod and an elastic body. The resistance value of this resistor is 1Ω
Met. 6k at 100V voltage to this resistor in the air
The electric energy of W was kept flowing. As a result, after 2 hours, the resistance value of the resistor was 1.3Ω and the temperature became constant at 480 ° C. It was confirmed that the resistance value did not change even if the current was continued as it was.

Comparative Examples 1-3 Examples 1-22 using only the second granulated powder of Examples 1-22
Create a molded body similar to, in the same manner as in Examples 1 to 22,
A power resistor was created and evaluated.

Comparative Examples 4 to 6 Examples 1 to 22 using only the second granulated powder of Examples 1 to 22
A molded body similar to that was prepared.

Comparative Examples 7 to 9 Only the second granulated powder of Examples 23 to 45 was used in Examples 23 to.
A molded body similar to 45 was prepared.

Comparative Examples 10 to 12 Only the second granulated powder of Examples 46 to 66 was used in Examples 46 to 66.
A molded body similar to 66 was prepared.

After removing the binder, the above molded body was hot pressed at 1500 ° C. and 50 MPa for 1 hour in an argon atmosphere. After that, a power resistor was prepared and evaluated in the same manner as in Examples 1 to 66. The results of the comparative example are shown in Table 4 above.

[0065]

[Table 4]

Comparative Example 13 The same raw material as in Comparative Example 4 was used and the same method was used to produce an annular power resistor having an outer diameter of 125 mm, an inner diameter of 25 mm and a thickness of 25 mm as shown in FIG. The resistance value of this resistor is 0.
It was 03Ω. As shown in FIG. 9, a predetermined number of these resistors are stacked through aluminum cooling fins having an outer diameter of 200 mm, an inner diameter of 25 mm, and a thickness of 2 mm, and insulation made of aluminum oxide penetrating the center of each resistor and cooling fin. A resistor was constructed by being supported by a sex indicator rod and an elastic body. The resistance value of this resistor was 1 Ω. In the air, 6 kW of electrical energy was continuously applied to this resistor at a voltage of 100V. As a result, after one hour, due to a partial abnormal heat generation inside the resistor, cracks occurred in a plurality of the resistors,
The resistor was destroyed.

[0067] above, wherein the As is clear from Table 1-4, the first region where the titanium carbide contains no less to or titanium carbide, many titanium carbide content than the first region,
Further, in the power resistor including the second region arranged so as to be connected to the pair of electrodes, the resistivity is higher and the resistance ratio in the resistor is 10 as compared with the conventional aluminum oxide-titanium carbide composite. It can be seen that a resistor having excellent uniformity can be manufactured as follows. Further, it can be seen that a resistor having an oxidation resistance as high as about 300 ° C. can be manufactured as compared with the conventional carbon particle-dispersed resistor. On the other hand, among the resistors of Comparative Example in which titanium carbide particles are uniformly dispersed,
Those calcinated under atmospheric pressure do not become densified. On the other hand, when pressure firing is performed, the density is increased to almost the true density, but the resistance ratio in the resistor becomes 10 or more, and it is understood that the uniformity is poor.

Further, a power resistor comprising a laminated resistor in which a plurality of the resistors are laminated and a conductive cooling fin interposed between the laminated resistors is a stable resistor even when continuously used. Can be used as

[0069]

As described above, according to the present invention,
A power resistor that has a precise, appropriate, and stable electrical resistance, has little change in resistance value with temperature changes, and has excellent oxidation resistance at high temperatures, and a power resistor in which a plurality of these resistors are stacked. Can provide a resistor for use.

[Brief description of drawings]

FIG. 1 is a conceptual diagram showing a power resistor of the present invention.

FIG. 2 is a cross-sectional view showing a power resistor of the present invention.

FIG. 3 is a diagram schematically showing a microstructure of a sintered body in the resistor of FIG.

FIG. 4 is a view schematically showing a microstructure of a conventional aluminum oxide-titanium carbide composite sintered body.

FIG. 5 is a graph showing the relationship between the titanium carbide composition and the resistivity of a conventional aluminum oxide-titanium carbide composite ceramic material.

FIG. 6 is a graph showing the relationship between the composition of the second region and the resistivity of the aluminum oxide-titanium carbide composite ceramic material of the present invention.

FIG. 7 is a diagram showing another form of the power resistor of the present invention.

FIG. 8 is a diagram showing another embodiment of the power resistor of the present invention.

FIG. 9 is a diagram showing a power resistor of the present invention.

[Explanation of symbols]

1, 12, 15 ... Power resistors 2, 10, 13 ... Sintered body 3, 11, 14 ... Electrodes 4a, 4b, 8 ... Aluminum oxide particles 5, 9 ... Titanium carbide particles 6 ... First area 7 ... Second area

   ─────────────────────────────────────────────────── ─── Continued front page       (56) References JP-A-8-45702 (JP, A)                 Japanese Patent Laid-Open No. 10-106802 (JP, A)                 JP-A-61-104581 (JP, A)                 JP 58-135183 (JP, A)                 JP-A-7-147204 (JP, A)                 JP 61-230281 (JP, A)                 JP-A-5-114506 (JP, A)

Claims (6)

(57) [Claims] 1. A power resistor comprising a sintered body containing aluminum oxide, a compound containing titanium and carbon, and an unavoidable impurity, and a pair of electrodes formed on two opposing surfaces of the sintered body. The sintered body is a first region containing less compound containing titanium and carbon or containing no compound containing titanium and carbon, and having a larger amount of compound containing titanium and carbon than the first region, and A power resistor comprising a second region arranged so as to be connected to the pair of electrodes. 2. The power resistor according to claim 1, wherein the compound containing titanium and carbon is titanium carbide. 3. The power resistor according to claim 1, wherein an average particle diameter of the compound containing carbon and titanium in the second region is 20 μm or less. 4. When the average particle size of the aluminum oxide particles in the second region is R _Al and the average particle size of the compound containing carbon and titanium is R _TiC , R _Al / R _TiC ≧ 0.1 is satisfied. The power resistor according to claim 1, characterized in that 5. A step of adjusting a first granulation raw material for forming a first region containing an aluminum oxide powder which is low in titanium carbide powder or does not contain titanium carbide powder, comprising titanium carbide powder and aluminum oxide powder Forming a second region having a larger amount of titanium carbide powder than the first region
A step of preparing a second granulation raw material , a step of mixing the first granulation raw material and the second granulation raw material, and then forming and sintering the mixture to form a sintered body, the sintered body And a step of forming a pair of electrodes on the main surfaces facing each other, the method for manufacturing a power resistor. 6. A sintered body containing aluminum oxide, titanium carbide and unavoidable impurities, and a pair of electrodes formed on two opposing surfaces of the sintered body, wherein the sintered body contains titanium carbide. A first region containing less or no titanium carbide, and having a larger amount of titanium carbide than this first region,
And a resistor comprising a second region arranged so as to be connected to the pair of electrodes, a laminated resistor in which a plurality of the resistors are laminated, and a conductive cooling medium interposed between the laminated resistors. A resistor for electric power, comprising: