JP2011165723A - Thermistor element and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thermistor element that can enhance the resistance furthermore and can carry out broader resistance control, and to provide a method of manufacturing the same. <P>SOLUTION: The thermistor element includes a metal oxide sintered compact 2 for thermistor in which at least a pair of insertion holes 2a are formed, and at least a pair of lead wires 3 inserted into the insertion holes 2a and bonded to the metal oxide sintered compact 2 for thermistor, wherein a hollow hole 2b is formed in the metal oxide sintered compact 2 for thermistor. Especially, the hollow hole 2b is formed between a pair of insertion holes 2a. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a thermistor element used for temperature measurement such as in automobiles and a method for manufacturing the thermistor element.

  Generally, a thermistor temperature sensor is employed as a temperature sensor for measuring the catalyst temperature around the automobile engine, the exhaust system temperature, and the like. The thermistor element used in this thermistor temperature sensor is, for example, used as a temperature sensor for the above-mentioned automobile-related technology, information equipment, communication equipment, medical equipment, housing equipment, etc., and is an oxide semiconductor having a large negative temperature coefficient. A sintered element is used.

  In recent years, there is an increasing demand for thermistor elements that can be measured with a single element from room temperature to high temperature. In particular, in order to measure the catalyst temperature and the like around an automobile engine, a thermistor element capable of measuring up to a high temperature around 1000 ° C. is required. As a characteristic required for such an application, the B constant is required to be as small as about 3000K or less. However, since the resistance value tends to decrease as the B constant decreases, in general, when used as a small sensor, the resistance value is low and difficult to use as it is.

  Therefore, conventionally, a method of adding an insulator to the thermistor material to obtain a mixed sintered body in order to increase the resistance value is generally used (see, for example, Patent Document 1 and Non-Patent Document 1). In this method, the resistance value can be increased to about 100 times.

Japanese Patent No. 3362651

Kurano, “Development of catalyst temperature sensor for NOx catalyst control”, Denso Technical Review, Vol. 5, no. 2, 2000

The following problems remain in the conventional technology.
That is, in the method using the mixed sintered body to which the insulator is added, as the size is reduced, it is necessary to add a considerable amount of the insulator in order to obtain desired characteristics. However, if an insulator is further added to significantly increase the resistance value exceeding 100 times, the resistance changes greatly due to a slight difference in the composition of the insulator, so that there is a disadvantage that the composition control is difficult and the characteristics vary. . Also, as a method of increasing the resistance value of the thermistor element in terms of shape, methods such as thinning the element or increasing the interval between lead wires can be considered structurally, but if the element body is made too thin, the element body However, there is a problem in that it is easy to break, and there is a size limit to widen the space between lead wires.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a thermistor element capable of further increasing resistance and capable of performing a wider resistance value control and a method for manufacturing the thermistor element.

  The present invention employs the following configuration in order to solve the above problems. That is, the thermistor element of the present invention includes a thermistor metal oxide sintered body having at least a pair of insertion holes, and at least a pair of thermistor metal oxide sintered bodies inserted into the insertion holes and joined to the thermistor metal oxide sintered body. A hollow hole is formed in the metal oxide sintered body for the thermistor.

  In this thermistor element, since the hollow hole portion is formed in the metal oxide sintered body for the thermistor, the metal oxide sintered body for the thermistor has a hollow structure by the hollow hole portion, so that the metal oxide for the thermistor is formed. It is possible to maintain the required strength by suppressing the strength reduction compared with the case where the entire sintered body is made thin, and the conductive path in the metal oxide sintered body for the thermistor is restricted by the hollow hole so that it has high resistance. Can be achieved.

In the thermistor element of the present invention, the hollow hole is formed between the pair of insertion holes.
That is, in this thermistor element, since the hollow hole portion is formed between the pair of insertion holes, the hollow hole portion is arranged between the lead wires inserted into the insertion hole, and the electrical characteristics are improved. In particular, the conductive path between the contributing lead wires is detoured by the hollow hole and becomes long and narrow, so that the resistance can be further increased.

Furthermore, the thermistor element of the present invention is characterized in that the hollow hole portion is formed in a long hole shape having a long cross-sectional shape in a direction intersecting with a direction connecting the paired insertion holes. To do.
That is, in this thermistor element, the hollow hole portion is formed in the shape of a long hole having a long cross-sectional shape in a direction intersecting the direction connecting the pair of insertion holes, and thus inserted into the insertion hole. By arranging the long hole-like hollow hole so as to block the conductive path between the lead wires, the conductive path is large and the hollow hole is bypassed, so that the resistance can be further increased.

The thermistor element manufacturing method of the present invention is the above-described thermistor element manufacturing method of the present invention, wherein a thermistor raw material powder made of a metal oxide, an organic binder powder and a solvent are mixed and kneaded to form a clay. A step of forming a rod-shaped green molded body having a plurality of through holes that serve as the insertion hole and the hollow hole portion by extruding the clay with a mold for a molded body, and the rod-shaped green A step of drying the molded body to obtain a rod-shaped dry molded body, a step of cutting the rod-shaped dry molded body to a predetermined length to obtain a cut molded body having the insertion hole and the hollow hole portion, Inserting the lead wire into the insertion hole of the cut molded body and firing in this state, thereby making the cut molded body the metal oxide sintered body for the thermistor. Features.
That is, in this method of manufacturing the thermistor element, a clay-like mold is extruded to form a rod-shaped green molded body having a plurality of through-holes that serve as insertion holes and hollow hole portions. Since the dried rod-shaped dry molded body is cut into a predetermined length to obtain a cut molded body having an insertion hole and a hollow hole portion, the insertion hole and the hollow hole portion can be simultaneously formed by extrusion molding, and are different. By changing to a mold for a molded body having a through hole shape, hollow hole portions having various hole shapes can be easily formed.

The present invention has the following effects.
That is, according to the thermistor element according to the present invention, since the hollow hole portion is formed in the metal oxide sintered body for the thermistor, the required strength can be maintained and the resistance can be increased. . Moreover, according to the manufacturing method of the thermistor element which concerns on this invention, the hollow hole part of various hole shape can be easily formed by extrusion molding, and it can respond easily to various types of manufacture.
Therefore, the thermistor element of the present invention can maintain a sufficient strength for practical use and can realize a higher resistance, and is particularly suitable as a high-temperature measurement sensor for detecting a catalyst temperature and an exhaust system temperature around an automobile engine.

It is the bottom view and AA arrow sectional drawing which show 1st Embodiment of the thermistor element which concerns on this invention. In 1st Embodiment, it is sectional drawing which shows a thermistor temperature sensor. In 1st Embodiment, it is simple sectional drawing which shows the extrusion molding machine using the metal mold | die for molded objects. In 1st Embodiment, it is the side view and front view which show a rod-shaped green molded object. In 1st Embodiment, it is the side view and front view which show the cutting molded object which inserted the lead wire. It is a bottom view which shows 2nd Embodiment of the thermistor element which concerns on this invention. It is a bottom view which shows 3rd Embodiment of the thermistor element which concerns on this invention.

  Hereinafter, a first embodiment of a thermistor element according to the present invention will be described with reference to FIGS. In each drawing used for the following description, the scale is appropriately changed in order to make each member recognizable or easily recognizable.

As shown in FIGS. 1 and 2, the thermistor element 1 of the present embodiment includes a thermistor metal oxide sintered body 2 having a pair of insertion holes 2a and a metal oxide for thermistor inserted into the insertion hole 2a. A pair of lead wires 3 joined to the sintered product 2.
The metal oxide sintered body 2 for the thermistor is formed in, for example, a cylindrical shape, and a pair of insertion holes 2a which are through holes along the axis is formed.
Further, the metal oxide sintered body 2 for the thermistor has a hollow hole 2b that is a through hole having a circular cross section in the center. That is, the hollow hole portion 2b is formed between the paired insertion holes 2a.

Metal oxide sintered body 2 for the thermistor, for example, the general _{formula: 1-w (La 1-} z Y z) 1-y A y (Cr 1-x Mn x) O 3 + wY 2 O 3 ( where A = Ca, Sr 0.0 ≦ x ≦ 1.0, 0.0 ≦ y ≦ 1.0, 0.0 ≦ z ≦ 1.0, 0 ≦ w ≦ 0.9) It is preferable that the sintered body is included.

Note that the B constant, which is a parameter indicating the electrical characteristics of the thermistor element 1, changes the x, y, z amount of (Y _1−z La _z ) _1−y A _y (Cr _1−x Mn _x ) O _3. Adjust by. However, for example, as the B constant decreases, the resistance value also decreases. Therefore, if the resistance cannot be adjusted by changing the shape, it is necessary to mix and sinter the insulator material to increase the resistance value. In this embodiment, the insulator material is Y ₂ O ₃ , but this may be changed to another insulator material, for example, ZrO ₂ , MgO, Al ₂ O ₃ , or CeO ₂ .

  The lead wire 3 inserted through the insertion hole 2a is an electrode wire, preferably a metal wire having a high melting point of 1400 ° C. or higher, a Pt wire or a wire containing Rh in Pt, and containing Ir in Pt The line etc. currently used are employ | adopted.

  Next, a method for manufacturing the thermistor element 1 of the present embodiment will be described with reference to FIGS.

  The thermistor element 1 is manufactured by mixing a thermistor powder made of metal oxide, an organic binder powder and a solvent and kneading them into a clay, as shown in FIGS. A step of forming a rod-shaped green molded body 15 having a plurality of through-holes 14 to be the insertion holes 2a and the hollow-shaped hole portions 2b by extruding the clay with the metal mold 13; The step of drying to form a rod-shaped dry molded body, and as shown in FIG. 5, the rod-shaped dry molded body is cut into a predetermined length to obtain a cut molded body 16 having an insertion hole 2a and a hollow hole 2b. And a step of inserting the lead wire 3 into the insertion hole 2a of the cut molded body 16 and performing firing in this state to make the cut molded body 16 a metal oxide sintered body 2 for the thermistor. ing.

More specifically, for example, La ₂ O ₃ , Ca, Cr ₂ O ₃ , and MnO ₂ powders, which are thermistor raw material powders, are weighed and placed in a ball mill, and then mixed with Zr balls and pure water for about 24 hours. Do. Next, these powders are taken out and dried, and then calcined at 1100 ° C. for 5 hours to obtain a calcined powder of (La _0.8 Ca _0.2 ) (Cr _0.5 Mn _0.5 ) O ₃ . Thereafter, the calcined powder is pulverized using Zr balls and pure water and then dried.

Further, Cr ₂ O ₃ , MnO ₂ , Y ₂ O ₃ is added to the calcined powder and mixed in the same manner by a ball mill, and calcined at 1400 ° C. (La, Ca, Y) (Cr _0.5 Mn _{0 .5} ) Obtain O ₃ calcined powder. Next, Y ₂ O ₃ powder is added to this mixed calcined powder, and further mixed by a ball mill and sufficiently dried. Then, mix with a binder and water in a mixer and mix well to make a wet powder.

Furthermore, after passing through a screw-type kneader several times, it is made into clay. Thereafter, a molding die 13 is attached to the tip of the extrusion molding machine 12.
The extrusion molding machine 12 has a structure in which what is kneaded while being evacuated can be extruded as it is. The molding die 13 is a three-hole molding die, and has a plurality of extrusion holes 13b for extruding clay into a cylindrical hollow mold 13a and three through holes 14. For this purpose, three round rod portions 13c for pig nose extending along the axis are provided in the mold 13a.

  Thereafter, extrusion molding is performed while performing vacuum degassing to produce a rod-shaped green molded body 15 which is a cylindrical extruded molded body. The rod-shaped green molded body 15 has three through-holes 14 formed therein. For example, the diameter is about 2 mm, and a hole of about 0.8 mm serving as a hollow hole 2b is opened at the center. A hole of about 0.3 mm serving as an insertion hole 2a for inserting the lead wire 3 is opened on both sides of the central hole.

Thereafter, the extruded molded body is sufficiently dried to obtain a rod-shaped dry molded body, and then cut into 1 mm in the length direction to form a cut molded body 16 as shown in FIG. Thereafter, the lead wire 3 is inserted into the insertion hole 2a, debinding, fired at about 1600 ° C., and the ceramic portion is sintered to obtain the metal oxide sintered body 2 for the thermistor. The contact with the metal oxide sintered body 2 is secured and bonded and fixed to each other. At this time, a Y ₂ O ₃ layer, which is an insulating film, is deposited on the surface of the metal oxide sintered body 2 for the thermistor during firing. In this way, the thermistor element 1 is manufactured.

  In order to use the thermistor element 1 as the thermistor temperature sensor 10, as shown in FIG. 2, first, an insulating ceramic tube 7 is fitted so as to wrap around the thermistor metal oxide sintered body 2. Further, the two lead wires 3 are inserted into the respective holes 8a of the two-hole insulating tube 8 made of alumina, and the lead wires 3 are protected to the root by the two-hole insulating tube 8. Then, the thermistor temperature sensor 10 is obtained by putting the thermistor element 1 in this state into a cylindrical stainless steel case 9 whose tip is closed to ensure hermeticity.

  Thus, in the thermistor element 1 of this embodiment, since the hollow hole 2b is formed in the thermistor metal oxide sintered body 2, the thermistor metal oxide sintered body 2 is formed by the hollow hole 2b. By having a hollow structure, the metal oxide sintered body 2 for the thermistor 2 can be maintained at the required strength by suppressing the strength reduction as compared with the case where the entire thermistor metal oxide sintered body 2 is thinned. The conductive path is limited by the hollow hole 2b, and the resistance can be increased.

  Further, since the hollow hole 2b is formed between the pair of insertion holes 2a, the hollow hole 2b is arranged between the lead wires 3 inserted into the insertion hole 2a, and the electrical characteristics are improved. In particular, the conductive path between the contributing lead wires 3 is detoured by the hollow hole 2b and becomes long and narrow, so that the resistance can be further increased.

  Further, in the method for manufacturing the thermistor element 1, a rod-shaped green molded body 15 having a plurality of through holes 14 formed by extruding the kneaded material with a molded body mold 12 to form an insertion hole 2a and a hollow hole 2b. The rod-shaped dry molded body that has been dried is cut into a predetermined length to obtain a cut molded body 16 having the insertion hole 2a and the hollow hole 2b. Therefore, the insertion hole 2a and the hollow shape are formed by extrusion molding. The hole 2b can be formed at the same time, and the hollow hole 2b having various hole shapes can be easily formed by changing to the molding die 12 having a different through hole shape.

  Next, second and third embodiments of the thermistor element according to the present invention will be described below with reference to FIGS. In the following description of each embodiment, the same constituent elements described in the above embodiment are denoted by the same reference numerals, and the description thereof is omitted.

The difference between the second embodiment and the first embodiment is that, in the first embodiment, the hollow hole 2b is formed in a circular cross section, whereas the thermistor element 21 of the second embodiment is hollow. The point is that the hole 22b is formed in an elliptical cross section.
That is, in the second embodiment, the hollow hole portion 22b is formed in a long hole shape having an elliptical cross section having a long cross sectional shape in a direction intersecting the direction connecting the paired insertion holes 2a.

Further, the difference between the third embodiment and the first embodiment is that, in the first embodiment, the hollow hole portion 2b is formed in a circular cross section, but in the thermistor element 31 of the third embodiment. The hollow hole 32b is formed in a rectangular cross section.
That is, in 3rd Embodiment, the hollow-shaped hole part 32b is formed in the oblong hole shape of a cross-sectional rectangle which has a long cross-sectional shape in the direction which cross | intersects with respect to the direction which connects the paired insertion holes 2a.

  As described above, in the thermistor elements 21 and 31 of the second and third embodiments, the hollow hole portions 22b and 32b have a long cross-sectional shape in a direction intersecting with the direction connecting the paired insertion holes 2a. Since it is formed in a hole shape, the long and hollow hole portions 22b and 32b are arranged so as to block the conductive path between the lead wires 3 inserted into the insertion hole 2a, so that the conductive path is large and hollow. This will bypass the hole portions 22b and 32b, and can further increase the resistance.

Table 1 shows the results of measuring the resistance value when the temperature was changed for Examples 1 and 2 in which the thermistor element 1 of the first embodiment was actually manufactured by changing the inner diameter of the hollow hole 2b. .
Here, a hollow hole 2b having a diameter of 0.4 mm was taken as Example 1, and a hollow hole 2b having a diameter of 0.8 mm was taken as Example 2. For comparison, Table 1 also shows the result of measuring the resistance value in the same manner as a conventional example without the hollow hole 2b. The measurement temperature was measured at three temperatures of −40 ° C., 25 ° C., and 900 ° C.

  As can be seen from this result, in the conventional example, the resistance value at 900 ° C. is too low as 20Ω, and sufficient sensitivity cannot be obtained, whereas in Examples 1 and 2 of the present invention, the resistance value is 900 ° C. The value is 30Ω or more, and a usable value is obtained. In particular, in Example 2 in which a hollow hole 2b larger than Example 1 was formed, a higher resistance value than Example 1 was obtained. Even in Example 2 in which the hollow hole 2b has a diameter of 0.8 mm, the thermistor element is not damaged during sintering and thermal shock tests, and sufficient strength for practical use is obtained.

The technical scope of the present invention is not limited to the above embodiments and examples, and various changes can be made without departing from the spirit of the present invention.
For example, in each of the above embodiments, one hollow hole is formed, but a plurality of hollow holes may be formed.

  1, 2, 31 ... Thermistor element, 2 ... Metal oxide sintered body for thermistor, 2a ... Insertion hole, 2b, 22b, 32b ... Hollow hole, 3 ... Lead wire, 12 ... Mold for molding, 14 ... through hole, 15 ... rod-shaped green molded body, 16 ... cut molded body

Claims (4)

A thermistor metal oxide sintered body having at least a pair of insertion holes;
And at least a pair of lead wires inserted into the insertion hole and joined to the metal oxide sintered body for the thermistor,
A thermistor element, wherein a hollow hole is formed in the sintered metal oxide for thermistor. The thermistor element according to claim 1,
The thermistor element, wherein the hollow hole portion is formed between the paired insertion holes. The thermistor element according to claim 2,
The thermistor element, wherein the hollow hole portion is formed in a long hole shape having a long cross-sectional shape in a direction intersecting a direction connecting the paired insertion holes. It is a manufacturing method of the thermistor element according to any one of claims 1 to 3,
A thermistor raw material powder made of metal oxide, an organic binder powder and a solvent are mixed and kneaded to form clay,
Forming a rod-shaped green molded body having a plurality of through-holes that serve as the insertion hole and the hollow hole portion by extruding the clay with a mold for a molded body;
Drying the rod-shaped green molded body to form a rod-shaped dry molded body;
Cutting the rod-shaped dry molded body into a predetermined length to form a cut molded body having the insertion hole and the hollow hole portion;
And inserting the lead wire into the insertion hole of the cut molded body and firing in this state, thereby making the cut molded body the metal oxide sintered body for the thermistor. A method for manufacturing a thermistor element.

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