JPH10247581A - Ceramic heater - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve mechanical strength, and prevent reduction in durability at high temperature current-carrying time by arranging a ceramic base body whose mechanical strength is enhanced by enhancing ceramic purity and a covering layer which contains a proper quantity of glass component on its base body and prevents the transformation of a heating part into a porous condition by causing a migration into the heating part. SOLUTION: A pattern of a heating resistor 1 is formed on a covering layer S1 of a ceramic raw sheet using powder such as alumina and beryllia excellent in electric insulating performance and heat conductivity even at high temperature time as a raw material, and an obtained ceramic body is integrally sintered after it is sandwiched by and laminated on a base body S2 together with a pattern of a temperature sensing resistor 3 used as a temperature sensor. When ceramic purity of the ceramic base body 52 is enhanced by a ceramic material to constitute the covering layer 51 having a heating part such as the heating resistor 1 and is preferably set not less than 96%, mechanical strength and high temperature durability of the base body compensate for lack of mechanical strength and lack of high temperature durability of the covering layer, and a ceramic heater having the long service life can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ceramic heater having a heating portion such as a heating resistor pattern.

[0002]

2. Description of the Related Art Conventionally, alumina ceramics has been mainly used as a material of a ceramic heater.
The alumina purity is about 88 to 94% by weight, and the same composition (the same alumina purity) is used for the substrate and the coating layer burying the heat generating portion.

However, since such alumina ceramics have a low alumina purity, they have low mechanical strength and may be broken during ASSY.
In addition, high-temperature durability was not always satisfactory due to migration of various ions.

Therefore, an attempt was made to increase the alumina purity of the above-mentioned alumina ceramics to increase the mechanical strength and the high-temperature durability. However, the higher the purity, the higher the mechanical strength, but the higher the high-temperature durability of the heat generating portion. A situation occurred. That is, it is considered that the diffusion of various ions, particularly the glass component, in the alumina ceramics into the heat-generating portion was reduced and a large number of pores were generated in the heat-generating portion, so that the durability of the heater was rather deteriorated.

For this reason, a glass component was added to the heat generating portion, but no effect was obtained because the glass component was absorbed by the surrounding alumina ceramics from the heat generating portion.

[0006]

SUMMARY OF THE INVENTION The present invention has been developed in view of the above-mentioned circumstances, and has a heating resistor formed on a ceramic substrate having a desired shape such as a plate-like or columnar shape and a ceramic material similar to the ceramic substrate. In addition to providing a coating layer having a heat generating portion such as a body pattern and the like, the ceramic purity of the ceramic substrate is made higher than that of the ceramic material constituting the coating layer, while the mechanical strength of the substrate is improved, so that a machine as a heater is provided. On the other hand, an appropriate amount of glass component is contained in the coating layer to cause migration into the heat-generating part, thereby preventing the heat-generating part from being porous. This aims to provide a ceramic heater having high mechanical strength and excellent high-temperature durability.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a partially developed view showing a state before firing a cylindrical ceramic heater H, and FIG. FIG. 2 is a cutaway view of a main part of the ceramic heater of FIG. 1, including a band-shaped heating portion as a heater and a heating resistor 1 in a cylindrical body made of ceramic, and terminals provided at both ends of the heating resistor 1, A heat is generated by energization, but a heat generating portion for use as a temperature sensor together with the heat generating resistor 1 and a temperature sensitive resistor 3 are formed in a heat generating area where the heat generating resistor 1 is densely formed. It is formed in a structure provided side by side over the entire area of K. By the way, in the manufacturing process of such a cylindrical ceramic heater H, as shown in FIG. 3, coating of a ceramic raw sheet made of a powder of alumina, beryllia or the like having excellent electrical insulation and thermal conductivity even at high temperatures. In order to form the resistor pattern R1 serving as the heating resistor 1 on the layer S1, the resistor pattern R1 may be formed in any shape such as a comb-like shape or a spiral shape in which a resistance value having a required heating value can be set.
Tungsten and molybdenum with specified width, thickness and length
The heating resistor pattern R is formed by using a paste such as manganese by a thick film technique such as screen printing.
After forming the resistor patterns R1 and R2 for use as a temperature sensor at the same time as the formation of the layer 1, the resistor patterns R1 and R2 are sandwiched and laminated on a columnar substrate S2 made of a material similar to that of the coating layer S1 and having a lower ceramic purity than the coating layer S1. The obtained cylindrical raw ceramic body may be sintered and integrated in a firing atmosphere.

The above-mentioned material of the same type refers to a material made of the same type of ceramic material even if the ceramic purity is different, such as alumina for alumina and zirconia for zirconia.

In the step of forming the resistor patterns R1 and R2, terminals U and R are connected to the ends of the resistor patterns R1 and R2.
U ', V, V' are formed in advance. These terminals U,
U ', V, and V' form through holes in the corresponding portions of the coating layer S1 of the raw sheet before printing the resistor patterns R1 and R2, and a conductive material such as tungsten or molybdenum-manganese is formed in the through holes. After filling, the resistor patterns R1 and R2 are printed. After sintering the columnar green ceramic body, the terminal portions U, U ', V, V' are plated with nickel or the like, so that the terminals 2, 2 shown in FIG.
2 'and a lead wire (not shown) is connected by silver brazing. In the case of such a columnar shape, the one in which the resistor patterns R1 and R2 are printed on the coating layer S1 of the ceramic raw sheet is rounded and overlapped on the cylindrical substrate S2. For example, as shown in FIG. 4 and FIG.
It is also possible to obtain a desired shape by processing before firing. Further, the ceramic heater is not limited to the manufacturing method as described above.
A resistor pattern can be printed on a ceramic body pre-fired in a flat plate or a columnar shape, and an insulator can be deposited on the ceramic body and then fired. It can also be manufactured by bonding and printing a resistor pattern, followed by firing and integration.

According to the above-described method, a ceramic heater was obtained in which the ceramic purity of the ceramic base S2 was higher than that of the ceramic material constituting the coating layer S1 having the heat generating portion such as the thermal resistor 1.

In the ceramic heater of the present invention thus configured, the ceramic purity of the coating layer provided with the heat generating portion is kept low as before, and the glass component contains an appropriate amount of glass component, and the glass component diffuses into the heat generating portion. Since the heat-generating portion becomes denser by going, the high-temperature durability of the heat-generating portion does not deteriorate. In contrast, the ceramic purity of the substrate is high,
The mechanical strength and high-temperature durability of the base make up for the lack of mechanical strength and high-temperature durability of the coating layer. Therefore, this ceramic heater is a long-life heater having high mechanical strength and high-temperature durability.

The ceramic purity of the ceramic constituting the coating layer S1 is preferably in the range of 80 to 96%. If the purity is less than 80%, the vitreous quality of the heat generating portion such as the heat generating resistor is excessive. The durability may be insufficient, while if it exceeds 96%, the amount of the glass component diffused into the heat generating portion may be insufficient, and the heat generating portion may not be sufficiently densified during firing.

The ceramic constituting the substrate preferably has a ceramic purity of 96% or more. If the purity is less than 96%, the mechanical strength may be insufficient.

The ceramic purity is measured by the heater H
Can be carried out by quantitatively analyzing the end face of the sample with an EMPA (wavelength dispersive X-ray microanalyzer). More specifically, quantitative analysis of 50 μm ² was repeated at the center of the substrate S2 and at the outer periphery of the coating layer S1, and the average value was obtained.

(Experimental Example 1) Strength Test The alumina purity of the coating layer S1 was 92% and the alumina purity of the substrate S2 was 99% (the remainder contains oxides such as MgO, CaO, SiO ₂ , ZrO ₂ ). The cylindrical ceramic heater H of the above embodiment was manufactured. Dimensions are φ4.15 × L6
0 (the thickness of the coating layer S1 = 0.95).

According to the heater H of the present invention, the span 3
When a three-point bending test was performed at 0 mm, the strength was 23.6.
It was 8 kg.

As a comparative example, a cylindrical ceramic heater H was prepared in which both the alumina purity of the coating layer S1 and the alumina purity of the substrate S2 were 92%, and a three-point bending test was performed in the same manner. As a result of the test, the strength of the comparative example product was 15.29 kg.
Met.

As described above, the strength of the product of the present invention was about 1.5 times that of the product of the comparative example.

[0019] was prepared (Example 2) Similar ceramic heater H in Experimental Example 1 was use indicating the alumina purity alumina purity and substrate temperature durability experimental coating layers S1 in Tables 1.

[0020]

[Table 1]

The following experiments were conducted to confirm the high-temperature durability of the heater H and the comparative example of the experimental example 1.

The maximum temperature portion of the heater H was adjusted to 1200 ° C., and a continuous energization durability test was performed. still,
The resistance value was adjusted so as to have the same resistance at the time of fabrication, so that it could be evaluated under the same applied voltage. this is,
This is to cancel the influence of the applied voltage on the durability.
For the evaluation, the disconnection or the resistance value was 2 times the initial resistance.
The point in time when the number was doubled was determined to be the life.

As a result, as is clear from Table 1, all of the samples 1 to 4 had a longer life than the comparative example of the above-mentioned Example 1. In particular, the samples except for the sample and the sample had an extremely long life of 1.5 to 2 times that of the comparative example.

A three-point bending test was performed in the same manner as in Experimental Example 1. As a result, the product of Comparative Example in Experimental Example 1 was 15.2.
As apparent from Table 1, the weight of the sample was 9 to 1.5 times that of the comparative example, while the weight was 9 kg.

From the above results, it was confirmed that the ceramic purity of the coating layer S1 is preferably 80% to 96%, and the ceramic purity of the substrate S2 is preferably 96% or more.

[0026]

As described above, according to the present invention, the ceramic purity of the ceramic substrate is made higher than that of the ceramic material constituting the coating layer having the heat generating portion such as a thermal resistor. Purification can significantly improve the mechanical strength of the ceramic heater, and the glass component migrates to the heat-generating part in the coating layer and densifies the heat-generating part. And is extremely reliable.

As described above, according to the present invention, an industrially versatile heater can be provided.

[Brief description of the drawings]

FIG. 1 is a partial development view showing a state before firing of a ceramic heater according to an embodiment of the present invention.

FIG. 2 is a fragmentary cutaway view of the ceramic heater before firing in FIG. 1;

FIG. 3 is a development view of a raw sheet constituting the ceramic heater before firing in FIG. 1;

FIG. 4 is a partial development view showing a state before firing of a ceramic heater according to another embodiment of the present invention.

FIG. 5 is a cutaway view of a main part of the ceramic heater before firing in FIG. 4;

[Explanation of symbols]

 H Ceramic heater 1 Heating resistor 2, 2 'terminal 3 Temperature sensitive resistor S1 Coating layer R1, R2 Resistor pattern U, U', V, V 'terminal portion S2 Base K Heating region L Temperature sensitive region

Claims (2)

[Claims] 1. A ceramic substrate having a desired shape such as a plate or a column is provided with a coating layer provided with a heating portion such as a heating resistor pattern on a ceramic material similar to the ceramic substrate. A ceramic heater having a ceramic purity higher than that of the ceramic material constituting the coating layer. 2. The ceramic substrate according to claim 1, wherein said ceramic substrate has a ceramic purity of 9%.
The ceramic heater according to claim 1, wherein the ceramic purity of the coating layer is 80% to 96%.