JP2003068507A - Method for manufacturing thermistor element and apparatus for manufacturing thermistor element material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase the uniformity of a composition of a thermistor material when manufacturing a thermistor element which is mainly made of a metal oxide sintered material. SOLUTION: The method for manufacturing the thermistor element comprises a process of preparing a precursor solution by mixing a precursor of a metal oxide in a liquid phase, a process of obtaining droplets by spraying the precursor liquid, a process of obtaining a thermistor material powder by heat-treating the droplets, and a process of obtaining the metal oxide sintered material by molding and baking the thermistor material powder into a predetermined shape.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a thermistor element mainly composed of a metal oxide sintered body and an apparatus for producing a raw material for such a thermistor element, which is the temperature of automobile exhaust gas. It is suitable for use in a thermistor element used for a sensor or the like and capable of detecting over a high temperature range from room temperature to 1000 ° C.

[0002]

2. Description of the Related Art Conventionally, a thermistor element mainly composed of a metal oxide sintered body of this kind has been known to have an exhaust gas temperature of automobiles, a gas flame temperature of a gas water heater, a heating furnace temperature, etc.
It is used in temperature sensors that measure temperatures in the medium to high temperature range of 1300 ° C.

As the thermistor element of this type, a metal oxide sintered body made of a perovskite-based material or a corundum-based material is mainly used. -20
The one described in Japanese Patent No. 1528 is proposed.

In this device, in order to realize a thermistor element that can be used in a wide temperature range, Y, Sr, Cr, F
A thermistor element is obtained by a so-called solid phase method in which a plurality of oxide raw materials such as e and Ti are mixed at a predetermined composition ratio, and the mixture is pulverized, granulated, and fired.

[0005]

In the above solid-phase method, the thermistor element is prepared by mixing a plurality of oxide raw materials.
The pulverization is performed by, for example, a medium stirring mill or the like. However, mechanical pulverization using a medium agitation mill or the like inherently has a limit in pulverizing ability, and the average particle size of the thermistor element raw material after mixing and pulverizing is limited to 0.3 μm.

That is, when the raw materials are pulverized and mixed at the same time, the particle size of the pulverized raw materials is limited, so that the homogenization of the composition for obtaining a more accurate thermistor element is insufficient. Therefore, the obtained thermistor element has a large resistance variation, which causes deterioration of the temperature accuracy of the temperature sensor using the thermistor element. The temperature accuracy of the conventional temperature sensor using the thermistor element is ± 15 ° C. (room temperature). ~ 8
The limit is about 00 ° C.

In addition, in the mixing and pulverizing operations in the medium agitation mill or the like, components such as zirconia and balls in the pulverizing medium are mixed as impurities into the thermistor raw material, causing resistance variations, and aiming at the thermistor element. There is also a problem that the composition deviates.

Further, in recent years, regarding the temperature sensor of the automobile exhaust gas, a system for detecting the exhaust gas temperature before and after the catalyst for detecting the deterioration of the exhaust gas purifying catalyst of a gasoline vehicle, and the exhaust gas of a diesel vehicle, especially NOx. There is a great need for application to a system that detects the exhaust temperature before and after the catalyst in order to control the temperature of the catalyst that purifies the gas.

However, since the above system cannot be realized with the temperature accuracy of the conventional temperature sensor using the thermistor element, a high-cost thermocouple or platinum resistor is used as the temperature sensor. That is, there has been no temperature sensor using a thermistor element having a temperature accuracy applicable to the system.

The present invention has been made in view of the above problems, and when manufacturing a thermistor element mainly composed of a metal oxide sintered body, variations in the resistance value of the thermistor element are reduced to achieve a better result than the conventional level. It is an object of the present invention to further homogenize the composition of the thermistor raw material in order to obtain temperature accuracy.

[0011]

In order to achieve the above object, the invention according to claim 1 is a method for producing a thermistor element containing a metal oxide sintered body as a main component, which comprises A step of preparing a precursor solution by mixing the precursor in a liquid phase; a step of spraying the precursor solution to obtain droplet particles; a step of heat-treating the droplet particles to obtain a thermistor raw material powder; And a step of molding the raw material powder into a predetermined shape and firing to obtain a metal oxide sintered body.

According to this, the raw materials can be mixed in the state of the precursor solution. In other words, the composition for obtaining the final metal oxide sintered body can be adjusted uniformly in a liquid state in which the particles are finer than in the conventional solid phase method. Can be changed. Further, the grinding medium as in the solid phase method does not mix as impurities.

The metal oxide sintered body, ie, the thermistor element, which is molded and fired using this raw material powder, has less variation in resistance value and can obtain better temperature accuracy than the conventional level.

Here, as in the invention described in claim 2,
As the precursor solution, a solution containing one or more kinds of metal ion complexes can be used.

As a solvent for the precursor solution, water or an organic solvent, or
A mixed liquid of water and an organic solvent can be used.

Further, according to the invention described in claim 4, there is provided a method for producing a thermistor element containing a metal oxide sintered body as a main component, wherein a slurry solution in which particles of metal or metal oxide are dispersed is prepared. A step of spraying a slurry solution to obtain droplet particles, a step of heat-treating the droplet particles to obtain a thermistor raw material powder, and forming the thermistor raw material powder into a predetermined shape and firing the metal oxide firing. And a step of obtaining a united body.

According to this, the raw materials can be mixed in the state of the slurry solution. That is, as in the invention of claim 1, the composition for obtaining the final metal oxide sintered body can be uniformly adjusted in the liquid phase state of finer particles than the conventional solid phase method, and thus the composition is obtained. The composition of the thermistor raw material powder can be further homogenized. Further, similarly, the grinding medium as in the solid phase method is not mixed as an impurity.

The metal oxide sintered body, ie, the thermistor element, which is molded and fired using this raw material powder, has less variation in resistance value and can obtain better temperature accuracy than the conventional level.

Here, as in the invention described in claim 5,
In order to uniformly mix the raw materials, the particles of metal or metal oxide in the slurry solution are preferably 100 nm or less.

Further, as in the sixth aspect of the invention, as the solvent of the slurry solution, water or an organic solvent, or a mixed liquid of water and an organic solvent can be used.

Further, as in the invention described in claim 7 or claim 8, it is preferable to use, as the precursor solution or the slurry solution, one in which a flammable solvent is added and mixed.

According to this, when the sprayed droplet particles are heat-treated, the flammable solvent is mixed and added, whereby the thermal decomposition and combustion of the droplet particles rapidly progress, and a more uniform composition is obtained. A fine thermistor raw material powder is obtained.

Here, as in the invention described in claim 9,
As the flammable solvent, one selected from methanol, ethanol, isopropyl alcohol, ethylene glycol, and acetone can be used.

Further, in the invention described in claim 10, in the step of heat-treating the droplet particles, the heating means (5) which can be controlled so that the temperature is gradually increased from the inlet to the outlet of the droplet particles is used. As a thermistor raw material powder, a powder having a sphericity X defined by the ratio of the maximum particle size Rmax and the minimum particle size Rmin of the powder shown in the following formula 2 is 80% or more is obtained. To do.

[0025]

## EQU00002 ## X = (Rmin / Rmax) .times.100 (%) In the step of heat-treating the droplet particles, a heating means that can be controlled so that the temperature gradually increases from the inlet to the outlet of the droplet particles is used. Thus, the heat treatment temperature of the droplet particles can be gradually increased.

If the heat treatment temperature of the droplet particles is rapidly increased, the droplets are likely to burst, and the resulting thermistor raw material powder is likely to have an indefinite shape. When the amorphous thermistor raw material powder is used for sintering, pores (portions in which air enters the sintered body) are likely to be formed inside the sintered body.

On the other hand, by gradually increasing the heat treatment temperature of the droplet particles, the raw material powder is likely to be spherical, and if the thermistor raw material powder having the sphericity X of 80% or more is used for molding and firing. Since the filling property is improved, the above-mentioned pores do not occur. Therefore, a thermistor element having a high density and uniform sintered particles can be obtained, so that the resistance variation can be further reduced and a high-performance thermistor element can be provided.

According to the invention of claim 11,
The droplet diameter of the droplet particles is preferably 100 μm or less. When the droplet particle diameter is 100 μm or less, more uniform composition can be expected.

In the invention according to claim 12, the metal is
The oxide sintered body is (M1M2) O₃Complex oxide represented by
And a mixed oxide of metal oxide represented by AOx (M1M
2) O ₃・ AOx and complex oxide (M1M2) O₃To
Where M1 is a group other than Group 2A and La of the Periodic Table of the Elements.
At least one element selected from Group 3A elements
And M2 is Group 3B, 4A of the Periodic Table of the Elements.
Group 5, Group 5A, Group 6A, Group 7A and Group 8 elements?
At least one element selected from the group consisting of metal acids
Compound AOx has a melting point of 1400 ° C. or higher, and
-Mistor element shape of AOx alone at 1000 ℃
Characterized by a metal oxide with a resistance value of 1000Ω or more
And

As a temperature sensor used in a wide temperature range, a perovskite structure composite oxide (M1) having a relatively low resistance characteristic in the temperature range of room temperature to 1000.degree.
It is preferable to use a mixed sintered body of M2) O ₃ and a metal oxide AOx having a high resistance value and a high melting point.

If a metal oxide AOx having a melting point of 1400 ° C. or higher and the resistance value of AOx simple substance in the thermistor element shape at 1000 ° C. is 1000Ω or higher, the resistance of the mixed sintered body in the high temperature range is increased. Since the value can be increased and its melting point is high and it has excellent heat resistance,
The high temperature stability of the thermistor element can be enhanced.

As a result, the resistance value in the temperature range of room temperature to 1000 ° C. is in the range of 100Ω to 100KΩ,
Moreover, it is possible to obtain a thermistor element that has a small change in resistance value due to thermal history and is excellent in stability and can be used in a wide temperature range.

Here, as in the invention described in claim 13, the mixed oxide (M1M2) O ₃ · AOx has a mole fraction of the complex oxide (M1M2) O ₃ of a and a metal oxide A of
When the mole fraction of Ox is b, a and b are 0.0
It is preferable to satisfy the relationship of 5 ≦ a <1.0, 0 <b ≦ 0.95, and a + b = 1.

If the mole fractions a and b are in the above relationship, the effect (resistance value in a predetermined range and resistance stability) of the thermistor element of claim 12 can be achieved more reliably. Further, since the mole fraction can be changed in such a wide range, the resistance value and the temperature coefficient of resistance can be variously controlled in a wide range by appropriately mixing (M1M2) O ₃ and AOx and firing.

The invention as set forth in claim 14 relates to a preferred example of each metal element in the composite oxide (M1M2) O ₃ , wherein M1 is Mg, Ca, Sr, Ba, Y, Ce or P.
r, Nd, Sm, Eu, Gd, Tb, Dy, Ho, E
One or more elements selected from r, Yb and Sc, M2 is Al, Ga, Ti, Zr, Hf, V, N
b, Ta, Cr, Mo, W, Mn, Tc, Re, Fe,
Co, Ni, Ru, Rh, Pd, Os, Ir and Pt
Practically desirable is at least one or more elements selected from the following.

According to the invention described in claim 15,
It is a preferred example of the metal element A in the metal oxide AOx,
As the metal element A, specifically, B, Mg, Al, Si,
Ca, Sc, Ti, Cr, Mn, Fe, Ni, Zn, G
a, Ge, Sr, Y, Zr, Nb, Sn, Ce, Pr,
Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, T
It can be at least one or more elements selected from m, Yb, Lu, Hf and Ta.

According to the invention of claim 16,
The metal oxide AOx is B₂O₃, MgO, Al
₂O₃, SiO₂, Sc₂O₃, TiO₂, Cr₂O₃, Mn
O, Mn₂O₃, Fe₂O₃, Fe₃O_Four, NiO, ZnO,
Ga₂O₃, Y₂O₃, ZrO₂, Nb ₂O_Five, SnO₂, Ce
O₂, Pr₂O₃, Nd₂O₃, Sm₂O₃, Eu₂O, Gd₂
O₃, Tb₂O₃, Dy₂O₃, Ho₂O₃, Er₂O₃, Tm₂
O₃, Yb₂O₃, Lu₂O₃, HfO₂, Ta₂O_Five2Mg
O / SiO₂, MgSiO₃, MgCr₂O_Four, MgAl₂
O_Four, CaSiO₃, YAlO₃, Y₃Al_FiveO₁₂, Y₂Si
O_Five3 Al₂O ・ 2SiO₂At least selected from
It can be one or more metal oxides.

All of these metal oxides have high resistance and high heat resistance, and contribute to the performance improvement of the thermistor element.

According to the invention of claim 17, in the composite oxide (M1M2) O ₃ , M1 is Y and M2 is Cr.
And Mn, and the metal oxide AOx is Y ₂ O ₃ .

At this time, the mixed sintered body is Y (CrMn) O ₃
This is Y ₂ O ₃ , and this mixed sintered body is suitably used for a temperature sensor and can exhibit high performance in a wide temperature range.

According to the eighteenth aspect of the present invention, the mixed sintered body (M1M2) O ₃ .AOx contains C as a sintering aid.
It is characterized by containing at least one of aO, CaCO ₃ , SiO ₂ and CaSiO ₃ . Thereby, a thermistor element having a high sintering density can be obtained.

The invention according to claim 19 is an apparatus for producing a raw material of a thermistor element containing a metal oxide sintered body as a main component, wherein a metal oxide precursor is mixed in a liquid phase. Spraying means (4) for spraying the precursor solution to obtain droplet particles, heating means (5) for heat-treating the droplet particles to obtain thermistor raw material powder, and recovery means for recovering the thermistor raw material powder ( 6) and, including a spraying means, a heating means,
It is characterized in that the collecting means are connected in this order.

The manufacturing apparatus of the present invention has the above-mentioned structure.
The step of spraying the precursor solution by the spraying means to generate droplet particles, heat-treating the droplet particles by the heating means, and collecting the thermistor raw material powder by the collecting means can be continuously performed. Therefore, the production method using the precursor solution according to claim 1 can be suitably realized, and the production time can be continuously obtained by selecting the operating time, the scale of the apparatus, etc. according to the production amount. Can be provided.

The invention as set forth in claim 20 is an apparatus for producing a raw material for a thermistor element containing a metal oxide sintered body as a main component, which comprises a slurry solution in which particles of metal or metal oxide are dispersed. A spraying means (4) for spraying to obtain droplet particles, a heating means (5) for heat-treating the droplet particles to obtain the thermistor raw material powder, and a recovery means (6) for recovering the thermistor raw material powder, Spraying means, heating means,
It is characterized in that the collecting means are connected in this order.

The manufacturing apparatus of the present invention has the above-mentioned structure.
Each step in the manufacturing method using the slurry solution according to claim 4 can be continuously and suitably realized, and the operating time, the scale of the apparatus, etc. can be selected according to the production amount to continuously obtain the raw material powder. A manufacturing apparatus can be provided.

According to the twenty-first aspect of the invention, a droplet diameter detecting means (7) for detecting the diameter of the droplet particles obtained from the spraying means (4) is provided, and the spraying means and the droplet diameter detecting means are provided. The heating means (5) and the recovery means (6) are connected in this order.

By adjusting the spraying means on the basis of the information on the diameter of the droplet particles obtained from the droplet diameter detecting means, the process can be stabilized and, for example, the variation between raw material lots can be reduced, and the product It can contribute to quality control.

Further, in the invention described in claim 22, arithmetic / control means for performing arithmetic / analysis based on the droplet diameter data of the droplet diameter measuring means (7) and controlling the spray state of the spray means (4). (8) is provided. According to this, the automatic control of this device can be performed to a higher degree, the process can be further stabilized, and it can contribute to the quality control of the product.

According to the invention of claim 23,
A two-fluid nozzle, an injection nozzle or an ultrasonic atomizer can be adopted as the spraying means (4) for obtaining the droplet particles.

According to the invention of claim 24,
When the spraying means (4) is a two-fluid nozzle, the carrier gas of the two-fluid nozzle may be selected from air, nitrogen and oxygen.

According to the invention of claim 25,
The spraying means (4) is preferably one which can introduce the flow of droplet particles into the heating means (5) in a swirling flow state. Since the droplet particles move in the heating means while swirling, the distance that the droplet particles pass through the heating means becomes long, which is preferable.

Further, in the twenty-sixth aspect of the present invention, the inside of the tank constituted by the connected means from the spraying means (4) to the collecting means (6) is under negative pressure. . Since a smooth flow of the droplet particles can be generated by setting the negative pressure in the tank, thermistor raw material powder (synthetic raw material) having a more stable and uniform composition can be obtained.

When the inside of the tank is not a negative pressure, the spraying means (4) is provided as in the invention of claim 27.
It is preferable to provide a gas introduction unit for introducing gas into the spray chamber (42) of the spray unit along the flow of the droplet particles generated by.

The flow of the gas introduced from the gas introduction means to the spray chamber can smooth the flow of the sprayed droplet particles, so that a more stable thermistor raw material powder (synthetic raw material) can be obtained. be able to.

Further, in the invention as set forth in claim 28, the heating means (5) has a quartz hollow tube (52) having an inlet for droplet particles and an outlet for discharging the heat-treated thermistor raw material powder.
And an electric furnace (51), and the electric furnace constitutes one or more temperature zones controlled to a constant temperature between the inlet and the outlet of the quartz hollow tube. And

By setting the temperature zone and controlling the temperature of the temperature zone, it is possible to set the temperature according to the thermal behavior of the composition of the starting material, so that the thermistor material powder having a more uniform composition can be synthesized.

Further, as in the invention described in Item 29,
The recovery means (6) may be equipped with a cyclone, a filter or an electric dust collector. These collecting means are suitable means for collecting the thermistor raw material powder, which is a powder raw material.

Further, as in the invention described in Item 30,
As the recovery means (6), a cyclone may be provided on the upstream side and a filter or an electric dust collector may be provided on the downstream side.

A cyclone suitable for recovering a large amount of raw material powder having a relatively large particle size is provided on the upstream side, and a suitable filter or an electrostatic precipitator suitable for recovering a small amount of raw material powder having a relatively small particle size is provided downstream. With the configuration provided on the side, it is possible to provide a means suitable for collecting finer powder raw materials.

Further, as in the invention described in Item 31,
The recovery means (6) is preferably operated by controlling its temperature to 100 ° C. or higher and 200 ° C. or lower.

From the viewpoint of the heat resistance of the material of the filter used in the collecting means, the efficiency of the electrostatic precipitator, etc., the temperature inside the collecting means is set to 200 ° C. or lower, and the steam generated by the heating means is condensed by the collecting means. It is preferable to set the temperature to 100 ° C. or higher from the viewpoint that the thermistor raw material powder thus recovered is not wet.

According to a thirty-second aspect of the present invention, there is provided a temperature sensor including the thermistor element manufactured by the manufacturing method according to any one of the first to eighteenth aspects.

The thermistor element manufactured by the manufacturing method according to any one of claims 1 to 18 has less variation in resistance value and has better temperature accuracy than the conventional level. A temperature sensor using such a thermistor element can detect a temperature over a wide temperature range, has stable resistance value characteristics, and has less resistance variation, so that a high-performance temperature sensor can be realized.

The reference numerals in parentheses of the above means are examples showing the correspondence with the concrete means described in the embodiments described later.

[0065]

BEST MODE FOR CARRYING OUT THE INVENTION The thermistor element of this embodiment is
It is a thermistor element made of a metal oxide sintered body, and its focus is on making the composition uniform by atomizing the thermistor raw material in order to reduce the composition variation of the thermistor raw material.

That is, in the raw material preparation, a precursor solution in which raw material components are uniformly mixed and dispersed in a liquid phase or a slurry solution in which metal or metal oxide particles are dispersed is made into droplet particles by a spraying means, and this liquid is prepared. It is possible to obtain fine thermistor raw material powder (having the same composition as the synthetic raw material and the final metal oxide sintered body) by heat-treating the droplet particles with a heat treatment means. Is.

As a starting material for the thermistor raw material powder, a droplet solution is produced by using a precursor solution prepared by mixing the metal oxide precursor in the final metal oxide sintered body in a liquid phase. This is heat-treated to obtain a thermistor raw material powder having a uniform composition and fine particles. One such precursor solution is
Examples include solutions containing one or more metal ion complexes.

As a starting material for the thermistor raw material powder, a slurry solution in which metal or metal oxide particles are dispersed is used to generate droplet particles, which are heat-treated to obtain a thermistor raw material powder having a uniform composition and fine particles. Obtainable. Here, if the metal or metal oxide particles in the slurry solution have a particle size of 100 nm (nanometer) or less, a more suitable thermistor raw material powder can be obtained.

[Metal Oxide Sintered Body] The metal oxide sintered body constituting the thermistor element of this embodiment is preferably
(M1M2) A mixed sintered body obtained by mixing and firing a composite oxide represented by O ₃ and a metal oxide represented by AOx (M1M2).
2) Consists of O ₃ · AOx.

Here, the complex oxide (M1M2) O ₃ is
M1 is at least one element selected from the elements of Group 2A and Group 3A excluding La of the Periodic Table of Elements, and M2 is Group 3B, Group 4A, and Group 5 of the Periodic Table of Elements.
It is at least one element selected from the group A, the group 6A, the group 7A, and the group 8 elements. Here, La has a high hygroscopic property and has a problem that it reacts with moisture in the atmosphere to form an unstable hydroxide and destroys the thermistor element. Therefore, it is not used as M2.

Concretely, the elements of the 2A group which become M1 are, for example, Mg, Ca, Sr and Ba, and the elements of the 3A group are, for example, Y, Ce, Pr, Nd, Sm and E.
It is selected from u, Gd, Tb, Dy, Ho, Er, Yb and Sc.

The elements of M2 are, for example, Al and Ga as elements of Group 3B, Ti, Zr and Hf as elements of Group 4A, and elements of Group 5A as Group 5A. For example, V, Nb, and Ta are elements of Group 6A, for example, Cr, Mo, and W, elements of Group 7A, such as Mn, Tc, and Re, are elements of Group 8 , For example, Fe, Co, Ni, Ru, Rh, Pd,
One or more elements selected from Os, Ir and Pt are preferably used.

The combination of M1 and M2 can be arbitrarily combined so as to obtain a desired resistance value characteristic, and these M1 and M2 are properly selected (M1M2) O.
₃ is a low resistance value and a low resistance temperature coefficient (for example, 1000
.About.4000 (K)). As such M1 and M2, for example, Y (Cr, Mn) O ₃ is preferably used. In addition, when a plurality of elements are selected as M1 or M2, the molar ratio of each element depends on a desired resistance value characteristic.
It can be set appropriately.

However, when the composite oxide (M1M2) O ₃ is used alone as the thermistor material, the stability of the resistance value is insufficient and the resistance value in the high temperature region tends to be low. Therefore, in the present embodiment, as a material that stabilizes the resistance value of the thermistor element and has a desired range,
The metal oxide AOx is mixed and used.

Therefore, the characteristics required for the metal oxide AOx are that it has a high resistance value in a high temperature range, is excellent in heat resistance and is stable at a high temperature.

Specifically, with respect to the size and shape of an ordinary thermistor element used as a sensor, AOx
Regarding the resistance value of a simple substance (not containing (M1M2) O ₃ ) at 1000 ° C. or more, the melting point is 1400 ° C. or more, which is sufficiently higher than 1000 ° C. which is the maximum normal temperature of the sensor. Should be satisfied.

In order to satisfy the above characteristics, the metal A in the metal oxide AOx is B, Mg or A.
l, Si, Ca, Sc, Ti, Cr, Mn, Fe, N
i, Zn, Ga, Ge, Sr, Y, Zr, Nb, Sn,
Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, H
One or more elements selected from o, Er, Tm, Yb, Lu, Hf and Ta are preferably used.

Specifically, as the metal oxide AOx, B
₂ O ₃ , MgO, Al ₂ O ₃ , SiO ₂ , Sc ₂ O ₃ , Ti
O ₂ , Cr ₂ O ₃ , MnO, Mn ₂ O ₃ , Fe ₂ O ₃ , Fe ₃ O
₄ , NiO, ZnO, Ga ₂ O ₃ , Y ₂ O ₃ , ZrO ₂ , Nb
₂ O ₅ , SnO ₂ , CeO ₂ , Pr ₂ O ₃ , Nd ₂ O ₃ , Sm ₂
O ₃ , Eu ₂ O, Gd ₂ O ₃ , Tb ₂ O ₃ , Dy ₂ O ₃ , Ho _{2
O 3, Er 2 O 3,} Tm 2 O 3, Yb 2 O 3, Lu 2 O 3, Hf
O ₂ , Ta ₂ O ₅ , 2MgO.SiO ₂ , MgSiO ₃ , M
gCr ₂ O ₄ , MgAl ₂ O ₄ , CaSiO ₃ , YAlO ₃ ,
_{Y 3 Al 5 O 12, Y} 2 SiO 5, it is possible to use one or more metal oxides selected from 3Al ₂ O · 2SiO _2.

Preferably, the metal oxide AOx having a high resistance value and excellent heat resistance is, for example, Y ₂ O ₃ . If Y is selected for M1 and Cr and Mn are selected for M2 in the composite oxide (M1M2) O ₃ , a mixed sintered body (M1M2) is obtained.
O ₃ · AOx is represented by Y (CrMn) O ₃ · Y ₂ O ₃ , and the thermistor element composed of this mixed sintered body is suitable for use as a temperature sensor and the like and can exhibit high performance in a wide temperature range. .

Also, a mixed sintered body (M1M2) O ₃ · AO
When the mole fraction of the composite oxide (M1M2) O ₃ in x is a and the mole fraction of the metal oxide AOx is b, a and b are 0.05 ≦ a <1.0, 0 <b ≦ 0.95,
It is preferable to satisfy the relationship of a + b = 1.

By properly selecting the above-mentioned mole fractions a and b within this range, it is possible to realize a desired low resistance value and low temperature coefficient of resistance as a thermistor element. Further, since the mole fractions a and b can be changed in a wide range, these resistance value characteristics can be variously controlled in a wide range.

The mixed sintered body (M1M2) O ₃ ·
AOx is CaO, CaCO ₃ , SiO ₂ as a sintering aid.
It is also possible to contain at least one of CaSiO ₃ and CaSiO ₃ .

These sintering aids are (M1M2) O ₃ and A
It has the effect of forming a liquid phase at the firing temperature of the mixture of Ox and promoting sintering. Thereby, the sintered density of the obtained mixed sintered body is improved, the resistance value of the thermistor element is stabilized, and the dispersion of the resistance value can be reduced with respect to the fluctuation of the sintering temperature. The addition amount of these sintering aids is appropriately adjusted according to the type.

[Thermistor Element Configuration and Temperature Sensor Configuration] Next, an example of the configuration of the thermistor element and the temperature sensor using this thermistor element will be described with reference to the drawings. FIG. 1 shows the mixed sintered body (M1M2) O ₃ · AOx.
It is a block diagram of the thermistor element 1 which consists, and FIG. 2 is a schematic sectional drawing of the temperature sensor S which built in this thermistor element 1. As shown in FIG. In addition, in FIG. 2, (b) is an AA sectional view of (a).

As shown in FIG. 1, the thermistor element 1 is
Each end portion of the two parallel lead wires 11 and 12 is an element portion 13
The element mixture 13 is formed by molding the mixed sintered body into a cylindrical shape having an outer diameter of 1.60 mm, for example.

As shown in FIG. 2, the temperature sensor S has a cylindrical heat-resistant metal case 2, and the thermistor element 1 is arranged in the left half thereof. In the right half of the metal case 2, one end of a metal pipe 3 extending from the outside is located.

As shown in FIG. 2, the metal pipe 3 holds lead wires 31 and 32 inside. These lead wires 31, 32 pass through the inside of the metal pipe 3 and reach the inside of the metal case 2, and the lead wires 11, 12 of the thermistor element 1 are connected.
Respectively connected to.

The lead wires 11 and 12 have a wire diameter of 0.3, for example.
mm, length 5.0 mm, and the material is Pt100 (pure platinum). As shown in FIG. 2B, magnesia powder 33 is filled inside the metal pipe 3 to ensure insulation of the lead wires 31 and 32 in the metal pipe 3.

Next, a method for manufacturing the thermistor element will be described. These manufacturing methods show various forms of starting materials and various methods for preparing thermistor raw materials, but in any manufacturing method, the starting materials are produced as droplet particles, and the thermistor raw material powder is subjected to heat treatment and recovery means. There is a step of obtaining and molding and firing this.

[First Manufacturing Method] In the first manufacturing method, a precursor of a metal oxide constituting a metal oxide sintered body of a thermistor element is mixed in a liquid phase to prepare a precursor solution. A step of spraying this precursor solution to obtain droplet particles, a step of heat-treating the droplet particles to obtain a thermistor raw material powder, and forming the thermistor raw material powder into a predetermined shape and firing the metal oxide. And a step of obtaining a sintered body.

The precursor of the metal oxide is specifically the metal M1, M2, A alone or salts in the above-described mixed sintered body (M1M2) O ₃ .AOx, and such a precursor. (Starting material) is dissolved in an organic or inorganic solvent (water, an organic solvent, a mixed solution of water and an organic solvent, etc.), for example,
The precursor solution is a complex of these metal ions. In this precursor solution state, the raw materials are uniformly mixed in a desired ratio so that a desired composition ratio of the mixed sintered body can be obtained.

In the step of spraying the precursor solution to obtain droplet particles, the precursor solution in which the raw materials are mixed in a desired ratio in a liquid phase is sprayed with a two-fluid nozzle, an injection nozzle or an ultrasonic atomizer. Atomization is used to obtain droplet particles. Here, the two-fluid nozzle obtains fine droplets by ejecting gas and liquid at the same time.

The injection nozzle is for mechanically extruding liquid by a piezoelectric type or electromechanical transducer to obtain droplet particles, and the ultrasonic atomizer applies ultrasonic waves to the liquid to vibrate it. , To generate fog (droplets). All of these spraying means are generally known.

The obtained droplet particles are fine particles inheriting the uniform mixed state in the precursor solution, and then the droplet particles are heat-treated (pyrolysis, combustion, etc.) to obtain the thermistor raw material powder. . Here, if the droplet diameter of the droplet particles is 100 μm or less, it is easy to realize a thermistor element having a more uniform composition by atomizing the thermistor raw material powder.

An electric furnace or the like is used for the heat treatment of the droplet particles.
By this heat treatment, the liquid of the droplet particles is removed, and at the same time, the metal component (the above M1, M2, A, etc.) in the droplet particles is oxidized to form a metal oxide, whereby a mixed sintered body (M1M
2) Thermistor raw material powder which is fine particles of O ₃ · AOx is obtained.

The thermistor raw material powder obtained is recovered by a recovery means such as a cyclone, a filter or an electrostatic precipitator suitable for recovering the powder raw material. And further,
This thermistor raw material powder is heat-treated to stabilize crystals and remove residual carbon, and then a binder such as PVA (polyvinyl alcohol) is mixed and pulverized to obtain a granulated slurry obtained by mixing the thermistor raw material powder with a binder. obtain.

Next, this granulated slurry is granulated and dried using a spray dryer or the like, and is molded into a predetermined shape incorporating the lead wires 11 and 12 (see FIG. 1) made of Pt or the like, and then fired. . As a result, the mixed sintered body (M1
M2) A high-performance thermistor element 1 made of O ₃ · AOx can be obtained.

In this molding step, molding may be carried out using a mold into which lead wires have been inserted in advance. After molding, holes for giving lead wires to the molded body may be formed by
A lead wire may be loaded and fired. Alternatively, the lead wire may be joined and formed after firing.

Alternatively, a thermistor raw material powder and a binder,
Appropriate viscosity for extrusion molding by mixing and adding resin materials,
The thermistor element 1 on which the lead wires 11 and 12 are formed can be obtained by extrusion-molding the material whose hardness has been adjusted, and then loading and firing the lead wires.

According to the first manufacturing method of this embodiment, the raw materials can be mixed in the state of the precursor solution. In other words, the composition for obtaining the final metal oxide sintered body can be adjusted uniformly in a liquid state in which the particles are finer than in the conventional solid phase method. Can be changed. Further, unlike the conventional solid-phase method, the grinding medium does not mix as impurities.

The metal oxide sintered body (M1M2) O ₃ .AOx, that is, the thermistor element 1 of this embodiment, which is molded and fired using this raw material powder, has less variation in resistance value than the conventional level. Good temperature accuracy can be obtained.

[Second Manufacturing Method] A second manufacturing method is a step of preparing a slurry solution in which metal or metal oxide particles are dispersed, a step of spraying the slurry solution to obtain droplet particles, and a liquid The method includes a step of heat-treating the droplet particles to obtain a thermistor raw material powder, and a step of forming the thermistor raw material powder into a predetermined shape and firing the resulting the metal oxide sintered body.

That is, the second manufacturing method is different from the first manufacturing method in that the slurry solution is used instead of the precursor solution. The slurry solution is composed of the metals M1, M2 in the mixed sintered body (M1M2) O ₃ · AOx described above,
The particles of the simple substance of A or the oxide (starting material) are dispersed in an organic or inorganic solvent (water, an organic solvent, a mixed liquid of water and an organic solvent, or the like).

In the state of this slurry solution, the starting materials are mixed in a desired ratio so that the intended composition ratio of the mixed sintered body can be obtained. Here, in order to uniformly mix the raw materials, it is preferable that the particles of the metal or the metal oxide dispersed in the slurry solution have an average particle size of 100 nm or less, thereby providing a uniform composition. Therefore, the resistance variation in the thermistor element can be reduced and the performance is improved.

The second manufacturing method is the same as the first manufacturing method except that these slurry solutions are used, and spraying, heat treatment, recovery, molding, firing, etc. are carried out in the same manner as described below. It is possible to obtain a high-performance thermistor element having a uniform composition and less variation in resistance value. That is, the same effect as the first manufacturing method can be obtained.

[Third Manufacturing Method] The third manufacturing method uses the precursor solution or the slurry solution to which a flammable solvent is added and mixed in the first and second manufacturing methods. is there.

When the starting material in the solution is heat-treated as droplet particles, the flammable solvent is mixed and added, so that the thermal decomposition and combustion of the droplet particles proceed rapidly, and a more uniform composition is obtained. A fine thermistor raw material powder is obtained. This makes it possible to reduce resistance variations in the thermistor element with a uniform composition and improve the performance.

Here, as the flammable solvent, one selected from methanol, ethanol, isopropyl alcohol, ethylene glycol and acetone can be used. The third manufacturing method is the same as the first manufacturing method except that these flammable solvents are added, and spraying, heat treatment, recovery, molding, firing and the like may be performed by the same method.

[Thermistor Raw Material Manufacturing Apparatus] FIG. 3 shows a manufacturing apparatus that specifically realizes the first to third manufacturing methods.
Shown in. This manufacturing apparatus includes a spraying means 4 for spraying the precursor solution or the slurry solution to obtain droplet particles, a heating means (heat treatment means) 5 for heat-treating the droplet particles to obtain thermistor raw material powder, and a thermistor raw material. A collecting means 6 for collecting the powder is provided, and the spraying means 4, the heating means 5, and the collecting means 6 are connected in this order.

As the spraying means 4, as described above, a two-fluid nozzle, an injection nozzle, an ultrasonic atomizer or the like can be adopted, but the angle of the nozzle can be directed to the heating means 5 to an arbitrary angle, Further, those capable of spraying an arbitrary amount of droplets are preferable. Further, it is preferable that the flow of droplet particles can be arbitrarily changed such as laminar flow, turbulent flow, and swirling flow.

By changing the nozzle angle and the spray amount, it is possible to send the droplet particles according to the size and shape of the spray tank 42 and the heating means 5. For example, it is possible to prevent the sprayed droplet particles from coming into contact with the spray tank 42 or the inner wall of the heating means 5 to be condensed. Further, by changing the flow of the droplet particles, the residence time in the heating means 5 can be controlled according to the composition of the raw material and the like.

Particularly, it is preferable that the flow of the droplet particles can be introduced into the heating means 5 in the subsequent stage in a swirling flow state. This is because the droplet particles move in the heating means 5 while swirling, so that the distance through which the droplet particles pass through the heating means 5 can be increased.

In view of the above, in the example shown in FIG. 3, the spraying means 4 has a two-fluid nozzle 41 for spraying the above-mentioned droplet particles and a spray for spraying the droplet particles from the two-fluid nozzle 41. And a spray tank 42 as a chamber. The two-fluid nozzle 41 sprays the precursor solution or the slurry solution using a carrier gas selected from air, nitrogen and oxygen.

Further, the spraying means 4, the heating means 5 and the collecting means 6 connected to each other constitute a tank through which the droplet particles or the thermistor raw material powder circulate. The inside of this tank is directly connected to the collecting means 6. The pressure is negative due to a blower motor or the like (not shown). This is because a negative pressure in the tank can generate a smooth flow of droplet particles, and a thermistor raw material powder (synthetic raw material) having a more stable and uniform composition can be obtained.

When the inside of the tank does not have a negative pressure, a hole (gas introducing means, not shown) for introducing gas from the outside to the inside of the spray tank (spray chamber) 42 of the spray means 4 is provided. From this hole, air may be introduced along the flow of the droplet particles generated by the two-fluid nozzle 41. The flow of the gas introduced from the gas introduction means into the spray tank 42 can smooth the flow of the sprayed droplet particles.

In the example of FIG. 3, the heating means 5 has a quartz hollow tube 52, one end of which is connected to the spray tank 42 and the other end of which is connected to the recovery means 6, and a quartz hollow tube 52 having an outer circumference. And an electric furnace 51 arranged. In the hollow tube 52, the end on the spray tank 42 side is an inlet for the droplet particles, and the end on the recovery means side is an outlet for the heat-treated thermistor raw material powder.

The electric furnace 51 forms one or more temperature zones controlled at a constant temperature between the inlet and the outlet of the quartz hollow tube 52. In this example, four zones 51a, 5
1b, 51c, 51d are configured so that the temperature can be controlled to increase sequentially from the inlet (upstream) of the droplet particles toward the outlet (downstream).

By adjusting the constitution of such temperature zones 51a to 51d and the temperature control mode, it is possible to set the temperature according to the thermal behavior of the composition of the starting material, so that the thermistor material powder having a more uniform composition can be obtained. Can be synthesized.

As described above, the recovery means 6 may be provided with a cyclone, a filter or an electrostatic precipitator suitable for recovering the thermistor raw material powder which is the powder raw material. In the example shown in FIG. 3, a cyclone 61 is provided on the upstream side and a filter (bag filter) 63 is provided on the downstream side.
The downstream side may be an electric dust collector instead of the filter 63.

The collecting means 6 of this example is suitable for collecting a small amount of a relatively small particle size raw material powder on the upstream side of a cyclone 61 suitable for collecting a large amount of a relatively large particle size raw material powder. By providing the filter 63 or the electrostatic precipitator on the downstream side, it is possible to provide a suitable means for recovering finer powder raw materials.

Here, in this example, two cyclones 61 are connected in series, and a recovery jar 62 made of stainless steel is attached to the bottom of each cyclone 61 and flows from the hollow pipe 52. Coming thermistor raw material powder (synthetic raw material)
Are stored in each collection jar 62. The filter 63 following the cyclone 61 collects ultrafine powder that cannot be removed by the cyclone 61.

The recovery means 6 has a temperature of 100.degree.
It is preferable to control the temperature above 200 ° C. and operate.
For example, the temperature of the collecting means 6 can be adjusted by providing a hole (secondary air introducing hole) for introducing air from the outside of the collecting means 6 into the inside and adjusting the amount of introduced air.

Considering the heat resistance of the material of the filter 63 used in the recovery means 6 and the efficiency of the electrostatic precipitator, the temperature inside the recovery means 6 is preferably 200 ° C. or lower, and the temperature generated in the heating means 5 is generated. 100 to prevent the thermistor raw material powder collected by the water vapor and the like that is condensed by the collecting means 6 from collecting.
This is because it is preferable to set the temperature to not less than ° C.

With this configuration, this manufacturing apparatus sprays the precursor solution or the slurry solution by the spraying means 4 to generate droplet particles, and heat-treats the droplet particles by the heating means 5 to obtain the thermistor raw material powder, which is then recovered. The step of collecting the thermistor raw material powder by means 6 can be continuously performed.

Therefore, the first to third aspects of the present embodiment described above.
It is possible to suitably realize the third manufacturing method and to provide a manufacturing apparatus that continuously obtains the thermistor raw material powder by selecting the operating time, the scale of the apparatus, etc. according to the production amount.

Further, in the manufacturing apparatus shown in FIG. 3, the heating means 5 can be controlled so that the temperature of the droplet particles gradually increases from the inlet to the outlet. Therefore, in the step of heat treating the droplet particles, there is an advantage that the heat treatment temperature of the droplet particles can be gradually increased.

If the heat treatment temperature of the droplet particles is rapidly increased, the droplets are likely to rupture and the resulting thermistor raw material powder is likely to have an indefinite shape. When the amorphous thermistor raw material powder is used for sintering, pores (portions containing air) are likely to be formed inside the sintered body.

In this respect, by gradually increasing the heat treatment temperature of the droplet particles, the raw material powder is likely to be spherical, and if the spherical thermistor raw material powder is used for molding and firing, the filling property is improved. Therefore, the above-mentioned pores do not occur.
Therefore, a thermistor element having a high density and uniform sintered particles can be obtained, so that the resistance variation can be further reduced and a high-performance thermistor element can be provided.

Specifically, the thermistor raw material powder coming out of the heating means 5 has a maximum particle diameter Rm of the powder represented by the following mathematical formula 3.
The sphericity X defined by the ratio of ax and the minimum particle size Rmin is 80.
If it is made of powder having a content of at least%, the above-mentioned pores can be preferably prevented.

[0130]

## EQU3 ## X = (Rmin / Rmax) × 100 (%) The sphericity X can be measured by, for example, sampling the thermistor raw material powder from the outlet of the heating means 5 and observing with a microscope such as TEM.

Next, another device for manufacturing the thermistor raw material according to this embodiment is shown in FIG. The manufacturing apparatus shown in FIG. 4 is different from that shown in FIG. 3 in that a droplet diameter detecting means 7 for detecting the diameter of the droplet particles obtained from the spraying means 4 is provided. The detection means 7, the heating means 5, and the recovery means 6 are connected in this order, and the spraying state of the spraying means 4 is controlled by calculation and analysis based on the droplet diameter data of the droplet diameter measuring means 7. It is characterized in that it comprises a calculation / control means 8 for

As the droplet diameter detecting means 7, a laser diffraction type particle size distribution measuring device integrated in an evaluation cell can be used. One end of the evaluation cell is connected to the spray tank 42 and the other end is a hollow tube. It is connected to 52. By adjusting the spraying means 4 based on the information on the diameter of the droplet particles obtained from the droplet diameter detecting means 7, the process can be stabilized and, for example, the variation between raw material lots can be reduced, and the quality of the product can be reduced. Can contribute to management.

Here, adjustment of the spraying means 4 and the like may be performed manually, but in the example shown in FIG. 4, it is automatically performed by the calculation / control means 8. Specifically, the calculation / control means 8
Uses a personal computer, and controls the operation of the spraying means 4 based on the data of the droplet particle diameter from the droplet diameter detecting means 7.

The spraying means 4 includes a raw material tank 43 for storing the precursor solution and the slurry solution, a liquid amount adjusting valve 44 for adjusting the amount of the solution supplied from the raw material tank 43 to the two-fluid nozzle 41, and a two-fluid nozzle 41. An air flow rate / pressure adjusting valve 45 for adjusting the flow rate and pressure of air as a carrier gas to be supplied is provided. The tank 43 and the valves 44 and 45 are also provided in the device shown in FIG.

In the apparatus of FIG. 4, these valves 44 and 45 are
Is operated and controlled by the calculation / control means 8. The calculation / control means 8 can calculate and control the temperature / viscosity / concentration of the solution to be sprayed, the spray pressure, the spray flow rate, etc. while taking in the diameter data of the droplet particles.

Therefore, by adjusting the flow rate of the raw material to the two-fluid nozzle 41, the flow rate of air, the pressure, etc. by the calculation / control means 8 based on the diameter data of the droplet particles,
The diameter of the sprayed droplets can be kept constant.

Further, the calculation / control means 8 can input and calculate the set temperature and the actual temperature of each temperature zone 51a to 51d of the electric furnace 51 which is the heating means 5, and can execute the control output of the electric furnace 51. ing. Therefore, by controlling the set temperature of each temperature zone, it is possible to perform the optimum heat treatment according to the diameter of the droplet particles, which is suitable for improving the sphericity X and homogenizing the composition of the resulting raw material powder, for example. is there.

As described above, according to the manufacturing apparatus shown in FIG.
By providing the droplet diameter detection means 7 and the calculation / control means 8, it becomes possible to control the present apparatus to a higher degree, and the spraying means 4
It is possible to perform feedback control on the calculation / control means 8 with respect to fluctuations in the power source, fluctuations in nozzle pressure, etc. in the heating means 5.

Therefore, the process is further stabilized,
It can contribute to product quality control. As a result, it is possible to obtain a high-performance thermistor element with stable quality by eliminating variations between raw material lots. Further, the calculation / control means 8 enables the unmanned continuous automatic operation of the manufacturing apparatus, and the same effects of the unmanned cost reduction and the stable quality of the thermistor raw material can be obtained.

[Fourth Manufacturing Method] The manufacturing method using the manufacturing apparatus shown in FIG. 4 is described in the description of the manufacturing apparatus of FIG. 4, but here, the fourth manufacturing method of the present embodiment. I will summarize it as a method.

The fourth manufacturing method is a step of preparing the precursor solution or the slurry solution used in the first to third manufacturing methods, a step of spraying these solutions to obtain droplet particles, and a droplet A step of heat-treating the particles to obtain the thermistor raw material powder, a step of detecting the diameter of the droplet particles and controlling the spraying state and the heat treatment condition based on the data of the detected diameter, and the thermistor raw material powder having a predetermined shape. Molding and firing to obtain a metal oxide sintered body.

[Characteristics of Thermistor Element] The thermistor element 1 of this embodiment obtained by the above-mentioned manufacturing method is
A mixed sintered body (M1M2) O ₃ .AOx in which (M1M2) O ₃ and AOx are uniformly mixed through grain boundaries is formed.
This thermistor element 1 has a temperature from room temperature (eg, 27 ° C.) to 1
In the high temperature range of about 000 ° C., a low resistance value of 100 Ω to 100 KΩ required for the temperature sensor S is exhibited, and the temperature coefficient of resistance β can be adjusted in the range of 2000 to 4000 (K).

Temperature accuracy was evaluated using 100 temperature sensors S incorporating the thermistor element 1 of this embodiment. In addition, the evaluation method of the temperature accuracy is to calculate the standard deviation σ (sigma) of the resistance value at 800 ° C. from the resistance value temperature data of 100 temperature sensors, and calculate the standard deviation σ of 6 times the variation width of the resistance value (both sides). ) And the value A obtained by halving the value obtained by converting the resistance value variation width into temperature was expressed as temperature accuracy ± A ° C and evaluated.

As a result, the temperature accuracy was ± 5 ° C. or less in all cases. It should be noted that this temperature accuracy is a level of high accuracy applicable to the system for detecting the exhaust gas temperature before and after the automobile exhaust gas catalyst described above.

As described above, according to this embodiment, when the thermistor element mainly composed of a metal oxide is manufactured, the composition of the thermistor raw material can be further homogenized, so that the resistance value of the thermistor element varies. It is possible to provide a temperature sensor in which the temperature is reduced and which has better temperature accuracy than the conventional level.

Next, the present embodiment will be described more specifically by the following Examples 1 to 4, but the present embodiment is not limited to these Examples.

[0147]

EXAMPLES Example 1 In this example, the mixed sintered body (M1
M2) in O ₃ · AOx (M1M2) to O ₃ Y (Cr
_0.5 Mn _0.5 ) O ₃ and Y ₂ O ₃ for AOx were mixed sintered bodies 38Y (Cr _0.5 Mn _0.5 ) O ₃ .62Y ₂ O ₃ by the first manufacturing method using the above precursor solution. It is manufactured. The manufacturing process of the thermistor element of the first embodiment is shown in FIG.

First, Y (Cr _0.5 Mn _0.5 ) O ₃ and Y ₂ O
The precursor solution of ₃ was prepared as a starting material, and after being sprayed, heat-treated, and collected by the manufacturing apparatus shown in FIG. 3, 38Y (Cr _0.5 Mn _0.5 ) O as thermistor material powder (synthetic material) was obtained.
Get a ₃ · 62Y ₂ O _3.

First, in the blending process, any purity was 9
9.9% or more of inorganic metal compounds and nitrates,
_{Y (NO 3) 3 · 6H} 2 O and _{Mn (NO 3) 2 · 6H} 2 O and C
r the _{(NO 3) 3 · 9H 2} O is prepared as a starting material.

Finally, the composition of the thermistor element is 38Y.
The starting materials Y (NO ₃ ) ₃ 6H ₂ O and Mn (NO ₃ ) ₂ 6 are adjusted so that (Cr _0.5 Mn _0.5 ) O ₃ .62Y ₂ O ₃ is obtained.
Was weighed of H ₂ O and _{Cr (NO 3) 3 · 9H} 2 O.

Further, as a raw material of Ca as a sintering additive, Ca (NO
_{3) 3} · 4H ₂ O and _{38Y (Cr 0.5 Mn 0.5) O} 3 · 62Y
_It was weighed so as to be 4.5 wt% with respect to ₂ O ₃ .

Next, assuming that the number of moles of citric acid is a and the value obtained by converting the total amount of each element of the composition Y, Cr, and Mn of the thermistor element by the number of moles is b, the citric acid concentration is b / a = 4 times. An equal amount of citric acid was dissolved in pure water to obtain a citric acid solution.

Subsequently, the weighed starting material and Ca
The _{(NO 3) 3 · 4H 2} O was added to the citric acid solution, each element ions (Y, Cr, Mn, Ca ) is reacted with citric acid, and these metal ions are dissolved becomes complex A precursor solution was obtained. This 38Y (Cr _0.5 Mn _0.5 ) O
Using the precursor solution of ₃ · 62Y ₂ O _3, the thermistor raw material powder is obtained by the manufacturing apparatus shown in FIG.

In this example, the two-fluid nozzle 41 of the spraying means 4 is used.
As an example, an air atomizing nozzle manufactured by Spraying Systems was used to obtain droplet particles having an average particle diameter of 5 to 10 μm. Air was used as the carrier gas of the two-fluid nozzle 41, and the pressure of the air was about 4 kg / cm ² . Spray tank 4
2 is 50 by a blower motor directly connected to the collecting means 6.
Maintained with a negative pressure of ˜70 mmaq.

The precursor solution of this example was sprayed from the nozzle 41 to the spray tank 42, and the droplet particles were introduced into the quartz hollow tube 52 as the heating means 5. Here, the droplet particles in the electric furnace 51 were heat-treated at a flow rate of 0.5 m / sec. Electric furnace 51
Are controlled in four temperature zones (see FIG. 3). From the upstream side, the first zone 51a is 200 ° C., the second zone 51b is 400 ° C., the third zone 51c is 600 ° C., and the fourth zone 5 is
Id was controlled at 900 ° C.

Droplet particles thermally reacted and decomposed in the electric furnace 51
The particle composition of the particles is 38Y (Cr_{0. Five}Mn_0.5) O₃・ 6
2Y₂O₃Thermistor raw material as a synthetic raw material which is the same as
It becomes powder. This raw material powder was recovered by the recovery means 6.

In the recovery means 6, the thermistor raw material powder was stored in the recovery jars 62 of the two cyclones 61, and the ultrafine powder that could not be removed by the cyclone 61 was recovered by the filter 63. The filter 63 is made of heat resistant aramid fiber and Teflon (registered trademark) film,
A cartridge-type filter (VC-20R manufactured by Nippon Vilene) having heat resistance at ° C was used.

Most of the raw material powder (synthetic raw material) can be collected by the cyclone 61, and about 0.3% of the total synthetic raw material is collected by the filter 63. By using this filter 63 as well, 99.999% of the synthesized raw material powder could be recovered. Further, the filter 63 can prevent the thermistor raw material powder from diffusing into the atmosphere.

Next, the obtained thermistor raw material powder (synthetic raw material) was put into a 99.7% alumina crucible to stabilize the crystal and remove a slight amount of residual carbon.
Heat treatment was performed at 200 ° C.

Next, the thermistor raw material powder was pulverized using a medium stirring mill in order to make the raw material particle size uniform. Pearl mill device (RV1V manufactured by Ashizawa Co., Ltd. as a medium stirring mill,
Effective volume: 1.0 liter, actual volume: 0.5 liter)
Was used. This pearl mill device uses zirconia balls having a diameter of 0.5 mm as a grinding medium, and fills 82% of the volume of the stirring tank with the zirconia balls. The operating conditions are a peripheral speed of 12 m / sec and a rotation speed of 4000 rpm.

A dispersant was added to the raw material powder in order to suppress aggregation of the raw material particles, and the raw material powder was pulverized for 2 hours. Further, in the above pulverization, a binder, a release agent, etc. were added and pulverized at the same time. The thermistor raw material slurry (granulation slurry) obtained after pulverization had an average particle size of 0.2 μm.

Next, this thermistor raw material slurry was dried with a spray dryer and granulated to obtain 38Y (Cr _0.5 M).
A granulated powder of n _0.5 ) O ₃ · 62Y ₂ O ₃ was obtained. Then, using this granulated powder, a thermistor element 1 having the same shape as that shown in FIG. 1 was manufactured.

Molding is carried out by a mold molding method, and the lead wires 11,
12 is pure platinum (Pt) with an outer diameter of 0.3 mm and a length of 5 mm.
100), and the outer diameter φ
Using a 1.89 mm mold, pressure of about 1000 kgf / c
By molding at m ² , a molded body of the thermistor element having an outer diameter of φ1.9 mm in which the lead wires 11 and 12 were embedded was obtained.

The molded body of this thermistor element is made of Al ₂ O ₃
Arranged in a wave-making type setter, baked in air at 1550 ° C. for 4 hours, and mixed sintered body 38Y (Cr _0.5 Mn _0.5 ) O ₃ .62Y ₂
A thermistor element 1 made of O ₃ and having an outer diameter of 1.6 mm was obtained. This thermistor element 1 was incorporated into a temperature sensor assembly as shown in FIG.

As a result of evaluating the temperature accuracy of the 100 temperature sensors of the first embodiment, the above-mentioned temperature accuracy of ± A ° C.
A temperature accuracy of ± 5 ° C was obtained. As described above, in this example, the thermistor element can synthesize the thermistor raw material powder as droplet particles with a uniform composition, so that it is possible to provide a highly accurate temperature sensor with a small resistance variation.

(Example 2) In this example, the mixed sintered body 38 is used.
Y (Cr _0.5 Mn _0.5 ) O ₃ .62Y ₂ O ₃ is manufactured by the second manufacturing method using the slurry solution. FIG. 6 shows the manufacturing process of the thermistor element of the second embodiment.

First, Y ₂ O ₃ particles, Cr ₂ O ₃ particles and MnC
A slurry solution in which O ₃ particles and CaCO ₃ particles are dispersed in water is prepared as a starting material, and sprayed, heat-treated, and recovered by the manufacturing apparatus shown in FIG. 3, and 38Y (Cr _{0.5 Mn 0.5) O 3 · 62Y 2} O
_{Get three} .

First, in the blending process, any purity was 9
Y ₂ O ₃ particles, Cr ₂ O ₃ particles, MnCO ₃ particles, and C, which are sol particles having an average particle size of 9.9% or more and about 100 nm or less.
Prepare aCO ₃ particles as a starting material.

Finally, the composition of the thermistor element is 38Y.
The starting raw material Y ₂ O ₃ particles, Cr ₂ O ₃ particles and MnCO ₃ particles were weighed so that (Cr _0.5 Mn _0.5 ) O ₃ · 62Y ₂ O ₃ was obtained. Further, as a raw material for Ca, which is a sintering aid component, CaCO ₃ particles were added to 38Y (Cr _0.5 M
n _0.5 ) O ₃ · 62Y ₂ O ₃ was weighed so as to be 4.5 wt%.

Next, the weighed Y ₂ O ₃ particles and Cr ₂
O ₃ particles, MnCO ₃ particles and CaCO ₃ particles were dispersed in pure water to obtain a slurry solution. Thereafter, in the same manner as in Example 1, the particles were sprayed, heat-treated and recovered, and the composition of particles was 38Y (Cr
A thermistor raw material powder as a synthetic raw material which is the same as _0.5 Mn _0.5 ) O ₃ .62Y ₂ O ₃ was obtained. The resulting thermistor raw material powder (synthetic raw material) was heat-treated using an alumina crucible as in Example 1.

Then, in the same manner as in Example 1, a dispersant, a binder, and a release agent were added, and the mixture was pulverized by a medium stirring mill, and similarly to Example 1, a thermistor raw material slurry having an average particle size of 0.2 μm ( Granulation slurry) was prepared. Next, in the same manner as in Example 1, the thermistor element 1 of Example 2 was obtained through drying, granulation, molding and firing.

A temperature sensor S incorporating the thermistor element 1 was manufactured and the temperature accuracy was measured in the same manner as in Example 1. As a result, the temperature sensor S according to the second embodiment obtained a temperature accuracy of ± 5 ° C.

As described above, in this example, since the thermistor element can synthesize the thermistor raw material powder as droplet particles with a uniform composition, it is possible to provide a highly accurate temperature sensor with a small resistance variation.

Example 3 In this example, the mixed sintered body 38 is used.
Y (Cr _0.5 Mn _0.5 ) O ₃ .62Y ₂ O ₃ is manufactured by the third manufacturing method using the precursor solution to which the flammable solvent is added. FIG. 7 shows the manufacturing process of the thermistor element of the third embodiment.

First, as in the first embodiment, 38Y (C
A precursor solution of r _0.5 Mn _0.5 ) O ₃ .62Y ₂ O ₃ was prepared, and 1 part of an ethylene glycol solution (Wako Pure Chemical Industries, purity 99.9%) as a flammable solvent was prepared with respect to the precursor solution.
0% was added.

This ethylene glycol-added precursor solution was used as the precursor solution of this example, and sprayed, heat-treated, and recovered by the manufacturing apparatus shown in FIG. 38Y as raw material)
Was obtained _{(Cr 0.5 Mn 0.5) O 3} · 62Y 2 O 3.

The thermistor raw material powder (synthetic raw material) was subjected to heat treatment, pulverization, drying / granulation, molding and firing in the same manner as in Example 1 to obtain a thermistor element 1. A temperature sensor S incorporating this thermistor element 1 was manufactured, and Example 1
Similarly, the temperature accuracy was measured.

As a result, the temperature sensor according to the third embodiment has a temperature accuracy of ± 4.5 ° C., which is slightly higher than those of the first and second embodiments. It is considered that this is because the addition of the flammable solvent increased the thermal reaction / decomposition rate during the thermal decomposition, thereby improving the homogenization of the composition.

Therefore, according to the third embodiment as well, the thermistor element can synthesize the thermistor raw material as droplet particles with a uniform composition, so that it is possible to provide a highly accurate temperature sensor with a small resistance variation.

Example 4 In this example, the mixed sintered body 38 is used.
Y (Cr _0.5 Mn _0.5 ) O ₃ .62Y ₂ O ₃ is produced using the same precursor solution as in Example 1 above.
In this example, the droplet detecting means 7 and the calculation
It is manufactured by the fourth manufacturing method using the manufacturing apparatus having the control means 8.

First, in this example, the same preparation process as in Example 1 was performed to make 38Y (Cr _0.5 Mn _0.5 ) O ₃ .62Y ₂ O ₃
A precursor solution of is obtained. Using this precursor solution, the thermistor raw material powder is obtained by the manufacturing apparatus shown in FIG.

In FIG. 4, in the spraying means 4, the above precursor solution is supplied from the raw material tank 43 at 3 liters / hr, air as a carrier gas is 40 liters / minute, and the air pressure is about 4 kg / cm ² with two fluids. It was supplied to the nozzle 41, and droplet particles were generated in the spray tank 42. The spray tank 42 has a blower motor 50 to 7 connected directly to the collecting means 6 in the subsequent stage.
It was maintained at a negative pressure of 0 mmaq.

The droplet particles passed through the evaluation cell as the droplet diameter detecting means 7 and were introduced into the electric furnace 51 as the heating means 5.
The droplet diameter detecting means 7 is a laser diffraction type particle size distribution measuring device (made by Malvern, Mastersizer 20) integrated with the evaluation cell.
00) was used to measure the droplet particle size. The average particle size of the droplets in this example is 8 μ at a constant value during continuous operation.
It was m.

At this time, the calculation / control means 8 controls the flow rate of the raw material, the flow rate of the air, the pressure, and the electric furnace 5 as the heat treatment means.
By controlling the set temperature of each of the temperature zones 51a to 51d of No. 1, the droplet particle diameter can be made a constant value.

Next, the droplet particles introduced into the electric furnace 51.
Is an electric furnace 51 (hollow tube 5 at a flow rate of 0.5 m / sec).
2) was passed to perform heat treatment. Hereafter, the same as in Example 1
Then, spray, heat treat, collect, and collect thermistor raw material powder
38Y (Cr) as (synthetic raw material) _0.5Mn_0.5) O₃・
62Y₂O₃Got

The thermistor raw material powder (synthetic raw material) was subjected to heat treatment, pulverization, drying / granulation, molding and firing in the same manner as in Example 1 to obtain a thermistor element 1. A temperature sensor S incorporating this thermistor element 1 was manufactured, and Example 1
The temperature accuracy was measured in the same manner as in.

As a result, in the temperature sensor according to the fourth embodiment, the temperature accuracy of ± 3.5 ° C. was obtained, and the accuracy was improved as compared with the first to third embodiments. This is because the diameter of the resulting raw material powder can be made constant by controlling the droplet particle size to a constant value.
It is considered that since the pores and the like during sintering can be reduced, a thermistor element having a more uniform composition can be obtained.

Therefore, according to Example 4 as well, the thermistor element can synthesize the thermistor raw material as droplet particles with a uniform composition, so that it is possible to provide a highly accurate temperature sensor with a small resistance variation.

As described above, the present invention focuses on making the composition uniform by atomizing the thermistor raw material in order to reduce the compositional variation of the thermistor raw material.
In the raw material preparation, a precursor solution in which raw material components are uniformly mixed and dispersed in a liquid phase, or a slurry solution in which metal or metal oxide particles are dispersed is formed into droplet particles by a spraying means,
By heat-treating the droplet particles with a heating means (heat treatment means), it is possible to obtain a synthetic raw material which is fine and has a uniform composition.

Therefore, by using the above-mentioned synthetic raw material, a thermistor element having a more uniform composition and less variation in resistance value than the conventional one can be obtained, so that a temperature sensor having highly accurate characteristics can be provided.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a thermistor element according to an embodiment of the present invention.

FIG. 2 is a schematic sectional view of a temperature sensor incorporating the thermistor element shown in FIG.

FIG. 3 is a diagram schematically showing a configuration of a thermistor raw material manufacturing apparatus according to the embodiment.

FIG. 4 is a diagram schematically showing the configuration of another thermistor raw material manufacturing apparatus according to the embodiment.

FIG. 5 is a diagram showing a manufacturing process of the thermistor element of Example 1.

FIG. 6 is a diagram showing a manufacturing process of the thermistor element of Example 2;

FIG. 7 is a diagram showing a manufacturing process of the thermistor element of Example 3;

[Explanation of symbols]

4 ... Spraying means, 5 ... Heating means, 6 ... Collecting means, 7 ... Droplet diameter detecting means, 8 ... Calculation / control means, 42 ... Spraying tank.

Continued front page    (72) Inventor Daisuke Makino             14 Iwatani Shimohakaku-cho, Nishio-shi, Aichi Stock Association             Company Japan Auto Parts Research Institute (72) Inventor Kaoru Kuzuoka             1-1, Showa-cho, Kariya city, Aichi stock market             Inside the company DENSO F term (reference) 4G030 AA08 AA12 AA22 AA25 AA37                       BA05 GA04 GA05 GA08 GA14                       GA16 GA22                 5E034 BB01 DA02 GA01

Claims (32)

[Claims] 1. A method of manufacturing a thermistor element containing a metal oxide sintered body as a main component, comprising: mixing a precursor of the metal oxide in a liquid phase to prepare a precursor solution; Spraying the precursor solution to obtain droplet particles; heat treating the droplet particles to obtain thermistor raw material powder; molding the thermistor raw material powder into a predetermined shape and firing the metal oxide; A method of manufacturing a thermistor element, comprising the step of obtaining a sintered body. 2. The method of manufacturing a thermistor element according to claim 1, wherein the precursor solution is a solution containing one or more metal ion complexes. 3. The method for producing a thermistor element according to claim 1, wherein the solvent of the precursor solution is water and / or an organic solvent. 4. A method of manufacturing a thermistor element containing a metal oxide sintered body as a main component, comprising the steps of preparing a slurry solution in which particles of metal or metal oxide are dispersed, and spraying the slurry solution. A step of obtaining droplet particles by heat treatment, a step of heat-treating the droplet particles to obtain a thermistor raw material powder, and a step of forming the thermistor raw material powder into a predetermined shape and firing it to obtain the metal oxide sintered body. A method of manufacturing a thermistor element, comprising: 5. The method of manufacturing a thermistor element according to claim 4, wherein the metal or metal oxide particles in the slurry solution have a particle size of 100 nm or less. 6. The solvent according to claim 4, wherein the solvent of the slurry solution is water and / or an organic solvent.
A method for manufacturing the thermistor element according to 1. 7. The method of manufacturing a thermistor element according to claim 1, wherein a flammable solvent is added and mixed as the precursor solution. 8. A method in which a flammable solvent is added and mixed as the slurry solution is used.
7. A method for manufacturing a thermistor element according to any one of items 1 to 6. 9. The method of manufacturing a thermistor element according to claim 7, wherein a solvent selected from methanol, ethanol, isopropyl alcohol, ethylene glycol, and acetone is used as the flammable solvent. 10. In the step of heat-treating the droplet particles, a heating means (5) that can be controlled so that the temperature of the droplet particles gradually increases from the inlet to the outlet is used, and as the thermistor raw material powder, The sphericity X defined by the ratio of the maximum particle size Rmax and the minimum particle size Rmin of the powder shown in the following mathematical formula 1 is as follows: X = (Rmin / Rmax) × 100 (%) 80% or more 10. The method for manufacturing a thermistor element according to claim 1, wherein the thermistor element is made of powder. 11. The method of manufacturing a thermistor element according to claim 1, wherein the droplet diameter of the droplet particles is 100 μm or less. 12. The metal oxide sintered body is (M1M
2) A mixed sintered body (M1M2) O ₃ .AOx of a complex oxide represented by O ₃ and a metal oxide represented by AOx, wherein M 1 is the periodic table of elements in the complex oxide (M 1 M 2) O ₃ . At least one element selected from the elements of Group 3A excluding 2A and La, and M
2 is the Periodic Table 3B, 4A, 5A, 6
At least one element selected from Group A, Group 7A, and Group 8 elements, wherein the metal oxide AOx has a melting point of 1400 ° C. or higher, and is a single element of AOx in the thermistor element shape. 1
The method for producing a thermistor element according to claim 1, wherein the thermistor element is a metal oxide having a resistance value at 1000 ° C. of 1000Ω or more. 13. The mixed sintered body (M1M2) O ₃ .A
When a mole fraction of the composite oxide (M1M2) O ₃ in Ox is a and a mole fraction of the metal oxide AOx is b, a and b are 0.05 ≦ a <1.0, 0 < b ≦
13. The method of manufacturing a thermistor element according to claim 12, wherein the relation of 0.95 and a + b = 1 is satisfied. 14. M1 in the composite oxide (M1M2) O ₃ is Mg, Ca, Sr, Ba, Y, Ce, P.
r, Nd, Sm, Eu, Gd, Tb, Dy, Ho, E
One or more elements selected from r, Yb and Sc, wherein M2 is Al, Ga, Ti, Zr, Hf, V, N
b, Ta, Cr, Mo, W, Mn, Tc, Re, Fe,
Co, Ni, Ru, Rh, Pd, Os, Ir and Pt
14. The method of manufacturing a thermistor element according to claim 12, wherein the thermistor element is one or more elements selected from the group consisting of: 15. The metal A in the metal oxide AOx
, B, Mg, Al, Si, Ca, Sc, Ti, Cr,
Mn, Fe, Ni, Zn, Ga, Ge, Sr, Y, Z
r, Nb, Sn, Ce, Pr, Nd, Sm, Eu, G
d, Tb, Dy, Ho, Er, Tm, Yb, Lu, Hf
15. The method of manufacturing a thermistor element according to claim 12, wherein the thermistor element is one or more elements selected from Ta and Ta. 16. The metal oxide AOx is B ₂ O ₃ or M.
gO, Al ₂ O ₃ , SiO ₂ , Sc ₂ O ₃ , TiO ₂ , Cr ₂
O ₃ , MnO, Mn ₂ O ₃ , Fe ₂ O ₃ , Fe ₃ O ₄ , Ni
O, ZnO, Ga ₂ O ₃ , Y ₂ O ₃ , ZrO ₂ , Nb ₂ O ₅ ,
_{SnO 2, CeO 2, Pr 2} O 3, Nd 2 O 3, Sm 2 O 3, E
u ₂ O, Gd ₂ O ₃ , Tb ₂ O ₃ , Dy ₂ O ₃ , Ho ₂ O ₃ , E
r ₂ O ₃ , Tm ₂ O ₃ , Yb ₂ O ₃ , Lu ₂ O ₃ , HfO ₂ , T
a ₂ O ₅ , 2MgO.SiO ₂ , MgSiO ₃ , MgCr ₂
O ₄ , MgAl ₂ O ₄ , CaSiO ₃ , YAlO ₃ , Y ₃ Al
_{5 O 12, Y 2 SiO 5} , 3Al 2 method for producing a thermistor element according to claims 12 to 14, characterized in that the O · 2SiO ₂ is one or more metal oxides selected. 17. The M1 is Y, and the M2 is Cr and Mn.
The method of manufacturing a thermistor according to claim 12 or 13, wherein the metal oxide AOx is Y ₂ O ₃ . 18. The mixed sintered body (M1M2) O ₃ .A
18. The thermistor element according to claim 12, wherein Ox contains at least one of CaO, CaCO ₃ , SiO ₂ and CaSiO ₃ as a sintering aid. Production method. 19. An apparatus for producing a raw material for a thermistor element containing a metal oxide sintered body as a main component, wherein a precursor solution prepared by mixing the metal oxide precursor in a liquid phase is sprayed. Spraying means (4) for obtaining droplet particles by heating, heating means (5) for obtaining thermistor raw material powder by heat-treating the droplet particles, and collecting means (6) for collecting the thermistor raw material powder, An apparatus for producing a thermistor element material, characterized in that the spraying means, the heating means, and the collecting means are connected in this order. 20. An apparatus for producing a raw material for a thermistor element containing a metal oxide sintered body as a main component, wherein a slurry solution in which metal or metal oxide particles are dispersed is sprayed to obtain droplet particles. Means (4), heating means (5) for obtaining thermistor raw material powder by heat-treating the droplet particles, and recovery means (6) for recovering the thermistor raw material powder, the spraying means, the heating means An apparatus for producing a thermistor element raw material, characterized in that the recovery means is connected in this order. 21. A droplet diameter detecting means (7) for detecting the diameter of droplet particles obtained from said spraying means (4) is provided, said spraying means, said droplet diameter detecting means, and said heating means (5). ) And the recovery means (6) are connected in this order, and the thermistor element raw material manufacturing apparatus according to claim 19 or 20. 22. An arithmetic / control means (8) for calculating / analyzing based on the droplet diameter data of the droplet diameter measuring means (7) and controlling the spray state of the spray means (4). 22. The thermistor element raw material manufacturing apparatus according to claim 21. 23. The thermistor element raw material according to claim 19, wherein the spraying means (4) is a two-fluid nozzle, an injection nozzle or an ultrasonic atomizer. apparatus. 24. The spraying means (4) is the two-fluid nozzle, and one selected from air, nitrogen and oxygen is used as a carrier gas of the two-fluid nozzle. Equipment for manufacturing thermistor element materials. 25. The spraying means (4) is capable of introducing the flow of the droplet particles into the heating means (5) in a swirling flow state. The production device for the thermistor element raw material described in 1. 26. The inside of a tank constituted by each means from the spraying means (4) to the collecting means (6) connected to each other is negative pressure. An apparatus for manufacturing a thermistor element raw material according to any one of the above. 27. A gas introduction means for introducing a gas into a spray chamber (42) of the spray means along a flow of droplet particles generated by the spray means (4). 25. The thermistor element raw material manufacturing apparatus according to any one of 25. 28. The heating means (5) comprises a quartz hollow tube (52) having an inlet for the droplet particles and an outlet for the heat-treated thermistor raw material powder, and an electric furnace (51). The electric furnace is configured between an inlet and an outlet of the quartz hollow tube,
The thermistor element raw material manufacturing apparatus according to any one of claims 19 to 27, which constitutes one or more temperature zones controlled to a constant temperature. 29. The collecting means (6) is a cyclone,
29. The thermistor element raw material manufacturing apparatus according to claim 19, further comprising a filter or an electrostatic precipitator. 30. The recovery means (6) comprises a cyclone on the upstream side and a filter or an electrostatic precipitator on the downstream side, according to any one of claims 19 to 28. Equipment for manufacturing thermistor element materials. 31. The recovery means (6) adjusts its temperature to 1
29. The device for producing a thermistor element raw material according to claim 19, which is controlled to operate at a temperature of 00 ° C. or higher and 200 ° C. or lower. 32. A temperature sensor comprising a thermistor element manufactured by the manufacturing method according to claim 1.