JP2000021603A - Power resistor, its manufacture and power resistor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power resistor which has high resistivity and superior uniformity of resistivity, compared with the conventional aluminum oxide- titanium carbide composite, and has antioxidant resistance compared with the conventional carbon particle dispersed resistor. SOLUTION: In a power resistor 1 which is provided with a sintered body 2 containing aluminum oxide, titanium carbide and unavoidable impurities, and a pair of electrodes 3 formed on two facing surfaces of the sintered body 2, it is constituted of a first region in which quantity of titanium carbide is low or titanium carbide is not contained, and a second region in which quantity of titanium carbide is greater than that of the first region and which is arranged, so as to be connected with a pair of the electrodes. Thereby the power resistor 1 is dense, and has proper and stable electric resistance and little change in resistance with respect to the temperature change.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a power resistor, a method of manufacturing the same, and a power resistor.

[0002]

2. Description of the Related Art In general, materials for electric power resistors are roughly classified into metal-based resistance materials and ceramic-based resistance materials.
Among these, ceramic-based resistance materials are characterized by having higher voltage-current characteristics and higher energy resistance to absorb high electric energy than metal-based resistance materials.

JP-A-58-139401 and JP-A-59-2
No. 17668 discloses a typical ceramic resistor. JP-A-58-139401 describes a carbon particle-dispersed ceramic resistor in which conductive carbon powder is dispersed in insulating aluminum oxide crystals.

Japanese Patent Application Laid-Open No. Sho 59-217668 discloses that as a main raw material, a carbon powder and a binder are added to an insulating inorganic material powder of aluminum oxide, mullite, and calcined clay, mixed, kneaded, and heat-treated. It describes a carbon-based power resistor, and describes that the carbon powder at this time is a fine powder of 0.1 μm or less and has a content of 1.5 to 5% by weight.

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

Incidentally, it is generally known that when a carbon powder is added to aluminum oxide powder to produce a sintered body, the sinterability of aluminum oxide is hindered. For this reason, in the above-mentioned carbon particle-dispersed ceramic resistor, carbon powder is added to aluminum oxide powder, and clay is further added for the purpose of supplementing the sinterability of aluminum oxide. However, this clay does not improve the sinterability merely by binding the aluminum oxide particles and the aluminum oxide particles, or the aluminum oxide particles and the carbon powder in the sintered body. Therefore, the porosity of the sintered body is as high as 10 to 30%, and is inferior in denseness. Dense aluminum oxide ceramics have a heat capacity per unit volume
3J / cm ³ · deg. However, the conventional carbon particle-dispersed ceramic resistor has a low heat capacity per unit volume of 2 J / cm ³ · deg due to poor denseness. For this reason, the temperature of the resistor increases significantly with the absorption of electric energy. In addition, a penetrating discharge occurs because the carbon powder causes a discharge in the pores when electricity is supplied.

[0007] Carbon has a negative temperature dependence of resistance, and the resistance decreases as the temperature rises. Therefore, when the temperature of the resistor rises due to the absorption of electric energy,
There is a problem that the resistance value decreases and more current flows through the resistor, causing a significant temperature rise.

Further, when the power resistor is used in the air, for example, when the power resistor is used in the atmosphere without being put in a gas-filled tank as in a vehicle-mounted regenerative current absorbing resistor, the resistance of the resistor due to energy absorption is reduced. Due to the temperature rise, the carbon particles in the ceramic are oxidized. As a result, the resistance value increases, and the resistor cannot be used. A conventional carbon particle-dispersed resistor is oxidized at about 300 ° C., resulting in insulation. In order to prevent this, it is necessary to equip a cooler such as a fin, and there has been a problem that the resistor unit becomes large.

By the way, as a composite ceramic of aluminum oxide and a conductive material, other composites are disclosed in addition to the above-mentioned carbon particle dispersed ceramic. As a composite ceramic of representative aluminum oxide and conductive material,
There is an aluminum oxide-titanium carbide composite ceramic.

[0010] Aluminum oxide-titanium carbide composite ceramics are used as cutting tool materials (Japanese Patent Application Laid-Open Nos.
JP-A-4-300241, JP-A-4-43959, JP-A-3-2941
No. 01 gazette, JP-A-3-247555, JP-A-2-255561, JP-A-2-16673, etc.), substrate material for magnetic head
(JP-A-4-321556, JP-A-3-119508, JP-A-2-199808, JP-A-2-87915, JP-A-2-15
No. 3860), disc brake rotor disc (
Application to a refractory material (Japanese Unexamined Patent Publication No. 2-229757) is disclosed. Aluminum oxide
The technique of using the titanium carbide composite ceramic for the power resistor material has not yet been disclosed.

[0011]

The use of aluminum oxide-titanium carbide composite ceramic as a power resistor material has the following problems. First, titanium carbide powder is not as significant as carbon powder, but impairs the sinterability of aluminum oxide. Therefore, conventionally, when using an aluminum oxide-titanium carbide composite ceramic for a cutting tool requiring denseness, Japanese Unexamined Patent Application Publication Nos. 3-247555, 3-228870, 3-28159, 3-28159, and 3 -
No. 28158, as disclosed in JP-A-2-255561, etc., after adding a sintering aid such as magnesium oxide, silicon oxide, etc., hot pressing or pressure firing such as HIP firing, Alternatively, as disclosed in Japanese Patent Application Laid-Open No. 2-229757, sinterability is improved by finely pulverizing an aluminum oxide powder and a titanium carbide powder to enable firing at atmospheric pressure. Pressure sintering can be performed only in a batch type furnace, and it is possible to use a small one such as a cutting tool. However, as a method for sintering a relatively large sintered body such as a power resistor, the cost is high. Higher, not realistic. Titanium carbide powder has high hardness (Vickers hardness; 3
200 kg / cm ² ), it takes a long time to grind, and it is easy to introduce impurities from the balls used in the grinding process.
Again not appropriate.

Further, the resistivity at room temperature 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 an aluminum oxide-titanium carbide composite ceramic material having a higher resistance. That the resistivity is 10 ^-2 Ωcm or less, as disclosed in JP-A-2-271965 and JP-A-2-289864, the advantage that machining of a complicated shape by electric discharge machining becomes easy. is there. However, as a power resistor,
Generally, a resistivity of at least 10 ^-2 Ωcm or more 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 opposing surfaces of the sintered body are formed. A power resistor including a pair of electrodes, wherein the sintered body is a first region containing a small amount of a compound containing titanium and carbon or containing no compound containing titanium and carbon, A power resistor characterized by comprising a second region having a large amount of a compound containing titanium and carbon and being arranged so as to be connected to the pair of electrodes.

With such a structure, the controllability of the resistivity is improved and a resistor having a high sinterability can be obtained. Further, a compound containing titanium and carbon, such as titanium carbide, has a thermal expansion coefficient similar to that of aluminum oxide, so that cracks due to a difference in thermal expansion can be reduced.

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

In the first aspect of the invention, by setting the particle diameter in the above range, it is possible to particularly improve the sinterability of the resistor. The fourth invention of the present application satisfies R _Al / R _TiC ≧ 0.1 when the average particle diameter of the aluminum oxide particles in the second region is RAl, and the average particle diameter of the compound containing carbon and titanium is RTiC. A power resistor according to the first aspect of the invention.

With such a particle size, a particularly dense sintered body can be obtained. The fifth invention of the present application is directed to a step of adjusting a first granulated powder forming a first region containing a small amount of titanium carbide powder or containing aluminum oxide powder not containing titanium carbide powder; And a step of adjusting a second region in which the amount of titanium carbide powder is larger than that of the first region, and after mixing the first granulated raw material and the second granulated raw material, molding and sintering A method for manufacturing a power resistor, comprising: a step of forming a body; and a step of forming a pair of electrodes on opposing main surfaces of the sintered body.

According to a sixth aspect of the present invention, there is provided 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. A resistor comprising a first region having a small amount of titanium carbide or not containing titanium carbide and a second region having a larger amount of titanium carbide than the first region and connected to the pair of electrodes. A power resistor comprising: a multilayer resistor in which a plurality of the resistors are stacked; and a conductive cooling medium interposed between the multilayer resistors.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A power resistor according to the present invention will be described in detail with reference to FIGS. FIG. 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 sides of a disk-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. 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 in a three-dimensional network structure. The second regions 7 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.

FIG. 4 shows the microstructure of a conventional aluminum oxide-titanium carbide composite ceramic. Thus, it has a structure including aluminum oxide particles 8 and 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 the titanium carbide 9 as the conductive substance. As can be seen from FIG. 5, when titanium carbide is 20% by volume or less, the resistivity is 10 ⁻² Ωcm or less, and the change in resistivity with respect to the change in composition is small. It is not theoretically 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 the resistivity with respect to the change in the composition is large. For example, resistivity 10 ^-2 to 10 ^-1 Ωcm
Is 5.2% by volume, whereas 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 a plurality of resistors are manufactured, the difference between the individual resistance values becomes extremely large,
In addition, the resistance value inside one resistor becomes extremely non-uniform, and it becomes very difficult to produce a resistor having a stable resistance value.

In FIG. 3, the first region 6 having a small amount of titanium carbide or containing no titanium carbide has an insulating material phase,
The second region 7 having a larger amount of titanium carbide than the first region 6
Becomes a conductive substance phase. In order to control the adjustment of the resistivity of the conductive substance 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.
It has become possible to obtain a sintered body having good controllability of resistivity in the range of 10 ^-2 to 10 ² Ωcm.

Further, as shown in FIG. 3, the first region 6 containing a small amount of titanium carbide or containing no titanium carbide is used.
And a second region 7 having a larger amount of titanium carbide than the first region 6.
By the structure comprising, even if titanium carbide that inhibits sinterability is present, the amount of titanium carbide is small or the first region 6 containing no titanium carbide is densified, so that the overall sinterability is improved. It also has advantages.

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

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

The average particle size R _Al of the aluminum oxide particles 4b in the second region 7 and the average particle size R of the titanium carbide particles 5
_When the ratio R _Al / R _TiC to _TiC is less than 0.1, the ratio of titanium carbide particles in the second region 7 is significantly increased in order for the second region 7 to have conductivity. Accordingly, the sintered body may not be densified.

The respective sizes of the first region having 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 are particularly limited. Not something. However, the size of the second region 7 is preferably within 10 times the size of the first region 6. If it is larger than this, a larger amount of the second region composition is required to obtain the same resistivity. Therefore, by increasing the concentration of titanium carbide in the sintered body,
It is not preferable because the density of the sintered body is reduced.

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

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

The sintered body 2 is allowed to have at least about 20% by weight of impurities, such as aluminum oxynitride and aluminum oxycarbide, in such an amount that does not affect the heat capacity. The pair of electrodes 3 formed on both circular surfaces of the sintered body 2 are made of a metal having good conductivity, such as a metal such as aluminum, iron, or brass, or a carbide or nitride of Hf, Nb, Ta, or Ti. Preferably, it is formed.

When the power resistor 1 is used under a high voltage, aluminum oxide, aluminum oxide, or the like is applied to 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 using an insulating heat-resistant resin such as polyimide.

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

Next, a method of manufacturing a 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, and preferably having an average particle size of 2 μm or less which does not hinder 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 thereby form the first and second mixed powders. Make granulated raw materials. first,
In addition to the above method, the second granulated raw material is mixed with the first and second mixed powders, respectively, with an organic solvent and a molding binder to prepare slurries. It can also be adjusted by removing the solvent using

Next, the first and second granulated raw materials are dry-mixed at a predetermined ratio using, for example, a V-type mixer, and then molded to obtain a molded body. As the molding means, for example, a mold 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. Below this, there is a possibility that the filling rate of the compact is small and the compact is not 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 be sufficiently smooth, and if possible, be mirror-finished. Applying hydrostatic pressure is effective in making the filling rate of the molded body uniform.

The obtained molded body 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 removing step, it is preferable to perform the firing step as quickly as possible after the binder removing step. Further, it is preferable that the firing is performed in the range of 1300 to 1800 ° C. At a temperature of 1300 ° C. or lower, sintering does not proceed and the sintered body is inferior in density. As a result, the heat capacity per unit volume decreases. On the other hand, when the temperature is 1800 ° C. or more, the reaction between titanium carbide and aluminum oxide in the sintered body becomes remarkable, and the conductivity of the titanium carbide particles is lost. 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 body may be broken due to uneven shrinkage of the molded body. The holding time is preferably one hour or more. If it is shorter than this, sintering will not proceed and the sintered body will be inferior in density.

In order to obtain a uniform temperature, the molded body is preferably placed in a box made of carbon or aluminum oxide and fired. 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 a metal such as 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 as necessary. As a material of the insulating layer, there are an organic material and an inorganic material, and from the viewpoint of heat resistance, an inorganic material is preferable. Further, the coefficient of thermal expansion is preferably the same as that of the sintered body 2. If there is a large difference between the two, a crack will be generated at the contact interface between the insulating layer and the sintered body, and the insulating layer will peel off. 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 made of a glass material such as borosilicate glass and lead glass, aluminum oxide, and / or an inorganic coating material mainly containing silicon oxide, for example, a coating mainly containing aluminum oxide and aluminum phosphate. The material is optimal.

The above material is coated with a brush, formed into 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 to be used. However, when used as a power resistor, the thickness is preferably 100 μm or more.

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

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

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

As shown in FIG. 7, the resistor (power resistor) 19 incorporated in the closing resistor unit is formed on the annular sintered body 10 and on both opposed annular faces of the sintered body 10. An electrode 11 constitutes a power resistor 12. The sintered body has a low titanium carbide or a first region containing no titanium carbide, and a large amount of titanium carbide than the first region,
And a second region arranged to be connected to the pair of electrodes.

As described above, according to the present invention, there are provided a plurality of fine and excellent electric resistances having a small resistance change with respect to temperature change, and having excellent resistance to oxidation at high temperature. By arranging the cooling fins adjacent to the power resistor, the temperature rise caused by the absorption of electric energy can be dissipated by the cooling fins, and the temperature rise of the resistor can be suppressed below the oxidation temperature of the resistor. . Such a power resistor provided with a plurality of resistors can be used stably at a high temperature, so that the power resistor can be reduced in size and improved in performance.

[0046]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail. Examples 1 to 22 First, a solution obtained by adding 5% by weight of a paraffin emulsion to water was added to aluminum oxide powder having an average particle diameter of 0.2 μm or less, and the mixture was slurried. To obtain a first granulated powder. Next, an aluminum oxide powder having an average particle size of 0.2 μm or less and a titanium carbide powder having an average particle size of 0.5 μm were weighed and mixed in a ball mill in the presence of an ethanol solvent. After drying, a solution obtained by adding 5% by weight of a paraffin emulsion to water is added to the dried mixed powder to form a slurry, and the slurry is granulated to have an average particle diameter of 100 μm using a spray drier. Obtained. The first granulated powder and the second granulated powder were mixed at a ratio as shown in Table 1 using a V-type mixer to obtain a mixed granulated powder.

Using a steel mold, the mixed granulated powder was molded into a disk having a diameter of 12.5 cm and a thickness of 3.1 cm at a molding pressure of 500 kg / cm ² to obtain a molded body. 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 held at 600 ° C. for 4 hours in a nitrogen gas.
The binder was removed. Next, the degreased body was heated at a rate of 200 ° C./hour in an argon gas atmosphere.
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 are ground with a No. 400 grindstone, and aluminum electrodes are formed on this surface by thermal spraying.
A power resistor was obtained. About 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. Table 1 shows the results. The method of each survey is as follows.

(1) Titanium Carbide Content The first granulated raw material or the second granulated raw material was molded independently using a mold press without mixing. After removing the binder, 15000 in an argon atmosphere
It hot-pressed at 50 degreeC and 50 degreeC for 1 hour. After pulverizing this sintered body with a silicon carbide pestle and a mortar and pulverizing it, the carbon composition is quantitatively analyzed by high frequency heating infrared absorption method, and the titanium is quantitatively analyzed by ICP absorption spectrometry to obtain the titanium carbide composition. For convenience, the amount of titanium carbide in each region was used. The conversion from the weight composition to the volume composition is obtained by calculating the true density of titanium carbide to 4.9 g / cm ^3.
Went as.

(2) Particle Size of Aluminum Oxide Particles and Particle Size of Titanium Carbide Particles in 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 at the center of the sintered body From the center of the sintered body, using a diamond cutter,
A test piece of 2 × 2 × 30 mm was cut out. Electrodes were formed by a sputtering method, and the resistivity was measured by a four-terminal method.

(4) Resistance Ratio in the Sintered Body One electrode of the resistor was removed by grinding, and 185 electrodes having a diameter of 4 mm were formed at equal intervals on the exposed surface of the sintered body. The resistance value between the point electrode and the facing electrode was measured, and the ratio of the minimum value to the maximum 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 resistors were placed in a constant temperature bath or an electric furnace whose temperature could be controlled, and the resistance value was measured. The oxidation resistance was determined by placing a resistor in an electric furnace at an arbitrary temperature for a certain period of time, and calculating a ratio of resistance values before and after the resistor was placed. The temperature at which the ratio of the resistance values exceeds 2 was defined as the oxidation temperature.

Examples 23 to 45 The aluminum oxide powder used as a raw material had an average particle size of 0.9.
Power resistors were prepared in the same manner as in Examples 1 to 22, except that a powder of μm was used, and evaluated in the same manner as in Examples 1 to 24. Table 2 shows the results.

Examples 46 to 66 A power resistor was prepared in the same manner as in Examples 1 to 22 except that a powder having an average particle size of 1.4 μm was used as the titanium carbide powder used as a raw material. 2424 were evaluated in the same manner. Table 3 shows the results.

[0056]

[Table 1]

[0057]

[Table 2]

[0058]

[Table 3]

Example 47 An outer diameter of 125 mm and an inner diameter of 25 mm as shown in FIG.
An annular power resistor having a thickness of 25 mm and a thickness of 25 mm was prepared. The resistance value of this resistor was 0.03Ω. As shown in FIG. 9, this resistor has an outer diameter of 200 mm, an inner diameter of 25 mm, and a thickness of 2 mm.
A predetermined number of the resistors were stacked via the aluminum cooling fins, and an insulating indicator rod made of aluminum oxide penetrating through each resistor and the center of the cooling fins, and supported by an elastic body to constitute a resistor. The resistance value of this resistor was 1Ω. 6kW at 100V voltage in air
Continued to flow electrical energy. As a result, two hours later,
The resistance value of the resistor became constant at 1.3Ω and the temperature was 480 ° C. It was confirmed that the resistance value did not change even if the energization was continued as it was.

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

Comparative Examples 7 to 9 Examples 23 to 45 were obtained using only the second granulated powder of Examples 23 to 45.
A molded product similar to that of No. 45 was produced.

Comparative Examples 10 to 12 Only the second granulated powders of Examples 46 to 66 were used.
A molded product similar to that of No. 66 was produced.

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

[0065]

[Table 4]

COMPARATIVE EXAMPLE 13 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.
03Ω. As shown in FIG. 9, a predetermined number of such resistors are stacked via aluminum cooling fins having an outer diameter of 200 mm, an inner diameter of 25 mm, and a thickness of 2 mm, and an insulating material made of aluminum oxide penetrating the center of each resistor and the cooling fins. The resistor was supported by the sex indicator rod and an elastic body. The resistance value of this resistor was 1 Ω. In air, the resistor continued to flow 6 kW of electrical energy at 100V voltage. As a result, one hour later, due to partial abnormal heat generation inside the resistor, cracks occur in a plurality of the resistors,
The resistor has been destroyed.

Abnormality, As is apparent from Tables 1 to 4,
In a power resistor comprising a first region in which titanium carbide is small or does not contain titanium carbide, and a second region arranged so as to be connected to the pair of electrodes, the amount of titanium carbide being larger than the first region, and It can be seen that a resistor having high resistivity and a resistance ratio within the resistor of 10 or less and excellent in uniformity can be manufactured as compared with the conventional aluminum oxide-titanium carbide composite. Further, it can be seen that a resistor having oxidation resistance higher by about 300 ° C. can be manufactured as compared with a conventional carbon particle dispersed resistor. On the other hand, among the resistors of the comparative example in which the titanium carbide particles are uniformly dispersed, those which are fired under the atmospheric pressure are not densified. On the other hand, when pressure sintering is performed, although the density is reduced to almost the true density, the resistance ratio in the resistor becomes 10 or more, which indicates that the uniformity is poor.

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

[0069]

As described above, according to the present invention,
A power resistor that has a dense, appropriate and stable electric resistance, has a small change in resistance value with respect to temperature change, and is extremely excellent in oxidation resistance at high temperatures, and a power resistor in which a plurality of such resistors are laminated Resistors can be provided.

[Brief description of the drawings]

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

FIG. 2 is a sectional view showing a power resistor according to the present invention.

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

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

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

FIG. 6 is a view 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 view showing another embodiment 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 according to the present invention.

[Explanation of symbols]

 1, 12, 15 ... Power resistor 2, 10, 13 ... Sintered body 3, 11, 14 ... Electrodes 4a, 4b, 8 ... Aluminum oxide particles 5, 9 ... Titanium carbide particles 6 ... First region 7 ... No. 2 areas

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4G030 AA16 AA36 AA45 AA60 BA02 CA03 CA04 GA05 GA24 GA28 5E032 AB10 BA23 BB01 CA11 CC05 CC06 CC14 5E033 AA43 BA01 BD11

Claims (6)

[Claims] 1. A power resistor comprising: a sintered body containing aluminum oxide, a compound containing titanium and carbon, and unavoidable impurities; and a pair of electrodes formed on two opposing surfaces of the sintered body. In the sintered body, the first region not containing a compound containing titanium and carbon or containing no compound containing titanium and carbon, the amount of the compound containing titanium and carbon is larger than the first region, and A power resistor comprising a second region arranged 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 the compound containing carbon and titanium in the second region has an average particle size of 20 μm or less. 4. When the average particle diameter of the aluminum oxide particles in the second region is R _Al , and the average particle diameter of the compound containing carbon and titanium is R _TiC , R _Al / R _TiC ≧ 0.1 is satisfied. 2. The power resistor according to claim 1, wherein: 5. A step of preparing a first granulated powder for forming a first region containing a small amount of titanium carbide powder or containing aluminum oxide powder containing no titanium carbide powder, and comprising a titanium carbide powder and an aluminum oxide powder. A step of adjusting a second region in which the amount of titanium carbide powder is larger than that of the first region, and mixing the first granulated raw material and the second granulated raw material, followed by molding and sintering to obtain a sintered body. And a step of forming a pair of electrodes on opposing main surfaces of the sintered body. 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. A first region containing less or no titanium carbide and 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 multilayer resistor in which a plurality of the resistors are stacked, and a conductive cooling medium interposed between the multilayer resistors. A power resistor characterized by comprising: