JP3441130B2 - Ceramic heater - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ceramic heater which can be uniformly heated and has excellent heat resistance. 2. Description of the Related Art Conventionally, heaters have been used in various fields such as the general industrial field, the semiconductor field, and the optical communication field, and heaters having a plate shape or a cylindrical shape are used depending on the purpose of use. Was used. As one example, there is a process for manufacturing a picture tube, and a heater is used for sealing the picture tube. Hereinafter, a description will be given of an example of a picture tube manufacturing process. In general, as shown in FIG. 6, an electron gun 13 is disposed in a cylindrical portion 11b which forms the rear end of a glass container 11 having a funnel shape.
The panel 12 provided with the anode 14 and the phosphor 15 was covered in the opening 11a on the tip side. To vacuum seal the inside of the picture tube 10, a pump (not shown) is connected to a glass cylinder tube 16 formed integrally with the rear end face of the cylindrical portion 11b, and the picture tube 1
After evacuation of the inside of the tube 10 to 10 ^-7 torr, the cylindrical tube 16 is heated and melted by the heater 20 to vacuum seal the inside of the picture tube 10. As shown in FIG. 5, a nichrome wire 21 is used as a heat source for the heater 20 for heating and fusing the glass cylindrical tube 16, and the nichrome wire 21 has a volume specific resistance value. Since it is very small at about 10 ^-4 Ωcm, a wire diameter of 0.2 m
The nichrome wire 21 having a small diameter of m was tightly wound into a spiral having a diameter of about 2 mm, and the nichrome wire 21 was inserted into a groove 22a formed on the inner wall of an insulating jig 22 having a cylindrical shape. The heater 20 is inserted in a state where a certain clearance is provided between the heater 20 and the groove 22a so that the ring size of the nichrome wire 21 is not collapsed due to thermal expansion at the time of heat generation and uneven heat generation occurs. It had been. However, in order to vacuum seal the inside of the picture tube 10 using the heater 20, the axis of the cylindrical tube 16 made of glass and the axis of the heater 20 are aligned. When the heater 20 is arranged in a state of maintaining a certain clearance on the outer periphery of the cylindrical tube 16 to generate heat, the upper nichrome wire 21 gradually drops down by its own weight,
There has been a problem that a certain clearance from the cylindrical tube 16 cannot be maintained. As a result, the portion located at the upper part of the cylindrical tube 16 is melted first, so that the inside of the picture tube 10 cannot be completely vacuum-sealed.
If it is sucked into the inside, the anode 14 and the electron gun 13 may be damaged. Furthermore, when the hanging nichrome wire 21 comes into contact with the cylindrical tube 16 and glass adheres to the nichrome wire 21, the wire is too thin to withstand a sudden increase in load capacity and is cut off. . Since the heater 20 has a small volume resistivity of the nichrome wire 21 and is wound in a spiral to obtain a desired resistance, the heater 20 has such a complicated structure. Therefore, there is a problem that it is difficult to reduce power consumption because much heat is wasted, and that the nichrome wire 21 itself is easily oxidized, which causes characteristic deterioration, and makes it difficult to obtain a stable calorific value for a long period of time. Therefore, it has been proposed to use a ceramic heater capable of uniformly generating heat instead of the heater 20 using the nichrome wire 21 as a heat source. However, a ceramic heater in which a heating resistor such as tungsten is buried in an alumina ceramic body is difficult to form in a thin cylindrical shape, so that it is not practically used, and the ceramic itself is used as a heating element. The silicon carbide ceramic heater that can be manufactured has a small volume resistivity value of about 10 ⁻³ Ωcm, not only does not provide a predetermined calorific value, but also oxidizes violently when exposed to high temperatures in the air, causing early deterioration of characteristics. There has been a problem of inviting such a heater, and at present, a practical picture tube manufacturing heater has not yet been manufactured. [0015] Means for Solving the Problems] Therefore, a heater heat-generating portion is made of ceramics in the present invention, the ceramic has its chemical _{formula, (La 1-X A X} ) (Cr 1-Y B Y A) O ₃ 0.1 ≦ X ≦ 0.5, 0 ≦ Y ≦ 0.5 A: At least one element from Group 2a of the periodic table such as Ca, Sr, Ba, etc. B: Mn, Co, Fe, Ni , Ce, Zr, and the like, and at least one element of Group 3a and Group 4a of the Periodic Table, wherein a part of La is replaced by an A element, and a part of Cr is B
It is replaced with an element, and its volume resistivity value is 0.1.
It is formed of ceramics having a porosity of 1 to 10 Ωcm and a porosity of 5 to 20%. According to the present invention, since the heat generating portion is made of conductive ceramics, heat can be uniformly generated. In addition, the above ceramics are represented by the chemical formula A
If B and B are substituted in a predetermined range, the volume resistivity can be set in the range of 0.1 to 10 Ωcm, and a desired heat generation can be obtained. The above ceramics are composed of a high melting point oxide and have a perovskite crystal structure, so that they have excellent heat resistance and little deterioration in characteristics even at high temperatures. Therefore, for example, when the ceramic heater of the present invention is used in the step of sealing the picture tube, the picture tube can be completely sealed. Embodiments of the present invention will be described below. FIG. 1 is a perspective view of a ceramic heater 1 according to an embodiment of the present invention, which is made of conductive ceramic and has an outer diameter of 14 mm, an inner diameter of 12 mm, and a width of 5 mm.
An electrode 3 is formed by baking platinum on both ends of the outer periphery of the cylindrical body 2 to form an electrode 3 and a power supply member 4 is attached to the electrode 3. When a voltage is applied to the ceramic heater 1 via the power supply member 4, the cylindrical portion 2 is made of conductive ceramics, so that the heat generating portion can uniformly generate heat. The shape of the ceramic heater 1 can be appropriately designed according to the purpose of use. For example, FIG.
As shown in FIG. 2B, the heater 1 is composed of a substantially cylindrical body 2a in which a heat generating portion is formed in a split sleeve shape, electrodes 3 are attached to both ends thereof, and a power supply member 4 is attached to the electrodes 3.
The coil 2b has a heat generating portion spirally wound as shown in FIG. 1 and electrodes 3 are attached to both ends of the coil 2b.
A heater 1 having a power supply member 4 attached thereto, or a heating unit as shown in FIG. 3 formed of a plate-like body 2c, electrodes 3 attached to both end surfaces thereof, and a heater 1 having a power supply member 4 attached to this electrode 3 The heater 1 as shown in FIG. 4 may be a heater 1 having a rod-shaped body 2d, electrodes 3 attached to both end surfaces thereof, and a power supply member 4 attached to the electrodes 3. As a material of the electrode 3 for applying a voltage to the heating portion, a heat-resistant alloy such as platinum-rhodium, silver, palladium, silver-palladium, nickel, and alloy can be used in addition to platinum. Alternatively, the power supply member 4 may be attached to the electrodes 3 by laser brazing or caulking. Incidentally, the conductive ceramics constituting the heat generating portion of the ceramic heater 1 according to the embodiment of the present invention are formed of ceramics represented by the following chemical formula. (La _1−X A _X ) (Cr _1−Y B _Y ) O ₃ 0.1 ≦ X ≦ 0.5 0 ≦ Y ≦ 0.5 where A: period of Ca, Sr, Ba, etc. At least one element of group 2a of the periodic table; B: at least one element of elements of group 3a, 4, and a of the periodic table; L: elements such as Mn, Co, Fe, Ni, Ce, and Zr;
Part of a is replaced with element A, and part of Cr is replaced with element B. This is because a lattice defect is formed inside the ceramic, hopping conduction is contributed to La or Cr, and the conductivity is increased. And
As shown in Table 1, the ceramics obtained by substituting the elements A and B at the above-mentioned substitution ratios X and Y can have a volume resistivity of 0.1 to 10 Ωcm. [Table 1] That is, the amount of heat generated by the heater 1 is determined by the shape of the heat generating portion and the volume specific resistance value of the material. The shape of the heat generating portion is set to an optimum shape according to the purpose of use. Therefore, if the volume resistivity value of the ceramics is set in the range of 0.1 to 10 Ωcm, it is possible to generate heat to the extent that it can be practically used, and to obtain a desired calorific value. However, if the volume specific resistance is less than 0.1 Ωcm, wasteful heat generation becomes too large and power consumption increases. Conversely, if the volume specific resistance is larger than 10 Ωcm. This is because it is difficult to obtain a desired calorific value. On the other hand, the reason why the substitution ratio X of La is set to 0.1 ≦ X ≦ 0.5 in the above chemical formula is that if the substitution ratio X is smaller than 0.1, the heat resistance is inferior, and the heater 1 itself is damaged. When the substitution ratio X exceeds 0.5, the volume specific resistance value exceeds 10 Ωcm, so that a desired heating value cannot be obtained unless a higher voltage is applied, thereby increasing power consumption. This is because it will occur. The reason why the substitution ratio Y of Cr is 0 ≦ Y ≦ 0.5 is that when the substitution ratio Y exceeds 0.5, the substitution ratio X of La is 0.1 ≦ X ≦ 0.5. This is because the volume specific resistance value cannot be set in a predetermined range even if it is set in the range. Further, La constituting the above ceramics
The oxides of Cr and Cr are high melting point oxides, and the crystal structure of the ceramic is a perovskite type, so that it has excellent heat resistance and has little characteristic deterioration even at high temperatures. In addition, since the specific heat is as low as 0.2 cal / ° C. or less, the heat capacity of the heater 1 can be suppressed small, so that the power consumption can be reduced. The ceramic has a thermal expansion coefficient of 1 ×.
Since it is about 10 ⁻⁷ / ° C., which is smaller than that of alumina or silicon carbide, heat generation unevenness is small. However, the porosity of the ceramic heater 1 is set to 5 to 20% in order to provide a thermal shock resistance which is practically no problem as a rapidly heated heater. This is because if the porosity is less than 5%, the thermal shock resistance is reduced and the material is liable to be damaged during rapid heating. Conversely, if the porosity is more than 20%, the mechanical strength is reduced and the material is easily damaged during handling. It is. Next, a method for manufacturing the ceramic heater 1 according to the present invention will be described. To manufacture the ceramic heater 1 according to the present invention, La ₂ O ₃ and Cr ₂ O ₃ powders are mixed as main raw materials, and CaO, SrO
For example, Mn ₂ O ₃ , Fe ₂ O ₃ , 3a of the periodic table, etc.
A predetermined amount of an oxide of a Group 4a element is added. Further, an organic binder or the like is added and kneaded to form a heat generating portion having a predetermined shape by a forming method such as extrusion forming or mechanical pressing, and the heat generating portion is formed by firing in an oxidizing atmosphere at 1400 to 1600 ° C. A heating resistor is obtained.
Thereafter, a paste-like electrode material is applied to both ends of the outer periphery of the heat-generating portion, baked at about 1200 ° C. to form an electrode, and a power supply member is attached to the electrode to obtain the ceramic heater 1 according to the present invention. . As described above, the ceramic heater 1 according to the present invention is very excellent in that it can uniformly generate heat, maintain its performance for a long period of time, and reduce power consumption. For example, if the ceramic heater 1 of the present invention shown in FIG. 1 is used as a heater for sealing a picture tube, the picture tube can be completely heated and melted to completely seal the picture tube, thereby greatly increasing the yield. Can be improved. Experimental Example 1 Here, the chemical formula is (La ₁ -XA _X ) (Cr _{1 -Y BY} ) O
_The ceramic heaters 1 shown in FIG. 1 were manufactured by replacing a part of La of the ceramics represented by ₃ with Ca and a part of Cr with Mn, and changing the substitution ratios X and Y variously. An experiment was conducted on the durability of each heater 1. In this experiment, each heater 1 was formed on a cylindrical body 2 having an outer diameter of 14 mm, an inner diameter of 12 mm, and a width of 5 mm, and platinum electrodes 3 were formed on both ends of the outer circumference of the cylindrical body 2. A power supply member 4 is attached to the electrode 3. Each of the heaters 1 is provided with a power supply member 4 to 20.
A voltage of about 0 V was applied, the temperature was raised to 950 ° C. in 30 seconds, held for 30 seconds, and a thermal cycle test of cooling to 40 ° C. or less in 60 seconds was performed 10,000 times. The replacement ratios X and Y of each heater 1 and the results are as shown in Table 2. [Table 2] As can be seen from Table 2, the heaters of samples 4 to 6 which are out of the range of the present invention are inferior in heat resistance because the substitution ratio X of La is smaller than 0.1, and are damaged by 50 heat cycles. I have. Further, in the heaters of samples 7 to 9 which are out of the range of the present invention, since the La substitution ratio X is larger than 0.5,
The volume specific resistance exceeded 10 Ωcm, and it was not possible to obtain a calorific value enough to melt the glass. On the other hand, the heaters of Samples 1 to 3 according to the present invention were extremely stable in spite of 10000 thermal cycles, and showed no change in heat generation over time. Experimental Example 2 Next, among the ceramic heaters 1 according to the present invention,
Using the heater 1 of the sample 3 shown in Table 2, a picture tube sealing experiment was performed. As a comparative example, a similar experiment was conducted by experimentally producing a heater 20 shown in FIG. 3 for generating heat from a nichrome wire 21 and an alumina ceramic heater having a heating resistor made of tungsten embedded therein. However, the resistance values of the respective heaters are set to be substantially the same. As shown in FIG. 6, a method of sealing the picture tube is a glass tube 16 having a diameter of about 6 mm which is integrally formed at the end of the picture tube 10 on which the electron gun 13 and the like are already set.
And a vacuum pump (not shown) composed of a rotary pump and a diffusion pump to evacuate the inside of the picture tube 10 to a degree of vacuum of the order of 10 ⁻⁷ torr.
The cylindrical tube 16 is heated and melted by generating heat at a temperature of not less than 00 ° C., and the inside of the picture tube 16 is vacuum-sealed.
Repeated 00 times. As a result, the alumina ceramic heater was
It was found that if heated to 900 ° C. within minutes, it would be damaged and would not be practical. Also, the heater 20 composed of the nichrome wire 21 cannot maintain a constant clearance with the cylindrical tube 16 due to poor accuracy, and often breaks due to the adhesion of the glass. could not. On the other hand, the heater 1 according to the present invention
Even after repeating 0000 times, there is no abnormality and the glass cylindrical tube 16 can be uniformly heated and melted,
The inside of the obtained picture tube 10 was completely sealed in vacuum, and it was found that the picture tube 10 could be used stably. In the embodiment of the present invention, the heater 1 for sealing the picture tube is shown. However, it goes without saying that the heater 1 can be used in various fields such as the general industrial field, the semiconductor field, and the optical communication field. No. [0052] According to the present invention, the heating portion of the ceramic heater, a chemical _{formula, (La 1-X A X} ) (Cr 1-Y B Y) O 3 0.1 ≦ X ≦ 0. 5, 0 ≦ Y ≦ 0.5 A: at least one element from Group 2a of the periodic table such as Ca, Sr, and Ba B: elements such as Mn, Co, Fe, Ni, Ce, and Zr, and the periodic table It is represented by at least one of the elements of Group 3a and Group 4a, in which part of La is replaced by element A and part of Cr is replaced by B
The heat-generating part can be made to generate heat evenly by using ceramics that are replaced with elements, and because of its excellent heat resistance, its performance can be maintained for a long period of time. Can be extended. In addition, since the power consumption can be reduced as compared with the conventional heater, it is very practical. Therefore, for example, when the ceramic heater of the present invention is used as a heater for sealing a picture tube, the glass can be uniformly heated and melted, and the picture tube can be completely vacuum-sealed. , The yield can be greatly improved.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a ceramic heater according to the present invention. FIGS. 2A and 2B are perspective views showing another ceramic heater according to the present invention. FIG. 3 is a perspective view showing another ceramic heater according to the present invention. FIG. 4 is a perspective view showing another ceramic heater according to the present invention. FIG. 5 is a perspective view showing a conventional heater used for vacuum sealing of a picture tube. FIG. 6 is a view showing a process of manufacturing a general picture tube. [Description of Signs] 1 Ceramic heater 2 Cylindrical body 3 Electrode 4 Power supply member

Claims (1)

(57) a heater made of Claims 1. A heating unit is a ceramic, the ceramic has its chemical _{formula, (La 1-X A X} ) (Cr 1-Y B Y) O 3 0.1 ≦ X ≦ 0.5, 0 ≦ Y ≦ 0.5 A: At least one element of Group 2a of the periodic table such as Ca, Sr, Ba, etc. B: Mn, Co, Fe, Ni, Ce, elements such as Zr, group 3a of the periodic table, represented by one or more of the first group 4a elements, a part of La is replaced with the element a, and the Cr one
A ceramic heater in which a part is replaced with a B element, and the ceramic heater has a volume resistivity of 0.1 to 10 Ωcm 2 and a porosity of 5 to 20% .