JPH0878142A - Ceramic heater - Google Patents

Abstract

PURPOSE: To provide a ceramic heater which can be uniformly heated over a long term without thermal deformation by providing a zigzag or spiral ring body consisting of a ceramic having a specified volume natural resistance value, and forming both the ends into electrode taking parts. CONSTITUTION: A heater 1 has electrode parts 5 on both ends of a zigzag or spiral ring body 1 consisting of conductive ceramic. The ring body 2 is cylindrical as the whole, and has a slit 3 in the axial direction and grooves 4 alternately extended from both the end surfaces. When a voltage is applied between both the electrode parts 5, a current is carried to the conductive ceramic ring body 2 itself to heat it. As the conductive ceramic forming the ring body 2, a one having a volume natural resistance value of 10<-4> -10cm is used in order to efficiently heat it. When glass 23 is sealed by use of this heater 1, the deformation by heat cycle is eliminated because the ring body 2 is formed of ceramics, and the resistance value of the heater 1 can be regulated by changing the number of grooves 4 or the width of the heating part.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cylindrical ceramic heater mainly used for vacuum sealing devices for glass tubes.

[0002]

2. Description of the Related Art Conventionally, heaters have been used in various fields such as general industrial fields and semiconductor fields, and plate-shaped or cylindrical heaters have been used depending on the application.

As an example thereof, there is a heater used in a vacuum sealing device for glass tubes. Hereinafter, the vacuum sealing method of the glass tube will be described as an example.

Vacuum sealing of glass tubes is commonly used in the manufacture of lamps and vacuum tubes. As shown in FIG. 5, in the vacuum tube, the electrode 22 is inserted into the glass container 21 sealed on one side, and the glass tube 23 is heated and melted by the heater while degassing from the unsealed side with the vacuum pump. Made by vacuum sealing.

A heater 24 shown in FIG. 6 is used for the above vacuum sealing, and a nichrome wire 25 is used as a heat source in the heater 24. Nichrome wire 25
Has a very small volume resistivity, so in order to obtain the melting temperature of the glass, a thin nichrome wire having a wire diameter of about 0.2 mm is finely wound in a spiral shape of about 2 mm, and this is wound by a cylindrical insulating jig 26. It was loaded in the inner groove. Further, the heater 24 is provided with a certain clearance between the heater 24 and the groove so that the spiral nichrome wire 25 does not collapse and uneven heat is generated even when thermal expansion occurs due to heat generation. It was set in 26.

[0006]

However, since the glass tube 23 is vacuum-sealed by using the heater 24, the axes of the glass tube 23 and the heater 24 are aligned with each other, and a certain clearance is provided on the outer periphery of the glass tube 23. When the heater 24 is arranged and heated in a state of being kept, the upper nichrome wire 25 in the heater 24 gradually hangs down by its own weight, and the glass tube 2
There was a problem that it could not maintain a certain clearance of 3.

As a result, a part of the surface of the glass tube 23 is melted before the others, and the inside of the glass tube 23 cannot be completely vacuum-sealed. In addition, the hanging nichrome wire 2 is used.
When 5 contacts the glass tube 23 and glass adheres to the nichrome wire 25, the load capacity at that portion rapidly increases, the thinness of the wire diameter also helps, and there is a problem such as disconnection.

Since the heater 24 has a small volume specific resistance value of the nichrome wire 25, it is wound in a spiral shape to obtain a desired resistance value. However, in such a complicated structure, unnecessary heat is generated. Many, power consumption was large. Further, since the nichrome wire 25 itself is easily oxidized, the characteristics are deteriorated, and it is difficult to obtain a stable calorific value for a long period of time.

Further, in the heater 24, the electrodes and the power supply line are fixed by using various heat-resistant metals. The fixed portion is subjected to a heat cycle every time the heater 24 is used, and the nichrome wire and the heat-resistant portion of the fixed portion are subjected to the heat cycle. Since the metal repeatedly repeats thermal expansion, strain is gradually generated and the fixing portion is loosened, which causes a problem that the contact portion between the heater electrode and the power supply line is short-circuited and is easily broken.

[0010]

In view of the above, the present invention provides:
A ceramic heater having a volume specific resistance value of 10 ⁻⁴ to 10 Ω · cm is formed into a meandering or spiral ring body, and electrode lead-out portions are formed at both ends thereof.

Further, according to the present invention, the annular body has a slit in the axial direction and is provided with a plurality of grooves alternately from both ends to form a meandering shape, and the electrode lead-out portions at both ends are provided on the same side in the axial direction. It is characterized by

Further, the present invention is characterized in that the electrode lead-out portion is formed by punching both ends of the above-mentioned ring body, inserting the feeder wire into the holes, and caulking and fixing the metal sleeve.

[0013]

According to the present invention, since the heater is made of conductive ceramics, uniform heating can be performed for a long period without causing thermal deformation. Further, since it is a meandering or spiral ring body, the total length and width can be easily adjusted, and it is easy to adjust to a predetermined resistance value.

Further, since the electrode lead-out portion of the heater is not easily affected by the thermal expansion of the heater and the power feed line due to the heat generation, it is possible to avoid the strain occurring in the electrode lead-out portion, and the poor contact between the heater and the power feed line. Etc. can be prevented.

[0015]

EXAMPLES Examples of the present invention will be described below.

The heater 1 shown in FIG. 1 has electrode portions 5 at both ends of a meandering ring body 2 made of conductive ceramics. This annular body 2 has a cylindrical shape as a whole, but has one slit 3 in the axial direction and is provided with grooves 4 alternately extending from both end surfaces to make a meandering shape, and both ends thereof are formed into an electrode portion 5 There is.

When a voltage is applied between both electrode parts 5 and 5, the ring body 2 itself made of a conductive ceramic is energized to generate heat. When the heater 1 is used to seal the gaps between the glasses 23 as shown in FIG. 5, since the ring body 2 is made of ceramics, it is not deformed by a heat cycle and is uniformly heated for a long period of time. You can

In the heater 1 of the present invention, the length of the heat generating portion can be freely changed by adjusting the cut length of the groove 4, and the number of the grooves 4 and the width of the heat generating portion can be changed. The resistance value of the heater 1 can be freely adjusted.

However, it is preferable to form three or more grooves 4 in total. This is because when the number of grooves 4 is less than 3,
This is because it becomes difficult to uniformly heat with the heater 1.

Further, in the heater 1 of the present invention, the electrode parts 5 at both ends are provided on the same side in the axial direction, so that the electrode lead-out structure can be simplified. Moreover, since the heater 1 is made of high-rigidity ceramics, it can be held only by the electrode portion 5, and the fixing structure can be simplified.

The conductive ceramics forming the ring 2 has a volume resistivity value of 10 in order to generate heat efficiently.
^{-4 to} 10 Ω · cm is used. Specifically, lanthanum chromite ceramics, AlTiC, cermet,
Conductive zirconia or other conductive ceramics is used.

The above-mentioned lanthanum chromite ceramics means that, in the composition formula of LaCrO ₃ , a part of La is Ca,
Substituting one or more elements of Group 2a of the periodic table such as Sr and Ba, and replacing a part of Cr with Mn, Co, Fe, Ni, Ce and Zr.
And the like, and elements of Group 3a and Group 4a of the periodic table replaced with one or more. This ceramic has a volume resistivity of 10 ⁻¹ to 10 Ω · cm, and its crystal structure is a perovskite type, so that it has excellent heat resistance and little deterioration in characteristics even at high temperatures.

For example, La _0.8 Ca _0.2 Cr _0.8 Mn _0.2
The heater 1 as shown in FIG. 1 can be obtained by molding, raw-processing, firing, and post-processing this raw material using a material represented by the chemical formula of O ₃ . The coefficient of thermal expansion of ceramics represented by the above chemical formula is 1 × 10 ^-7 / ° C.
The heat capacity of the heater can be suppressed to be small because the heat generation unevenness due to the deformation is small because it is relatively small and the specific heat is small at 0.2 cal / ° C. or less.

Altic means 20 to 80% by weight.
Al ₂ O ₃ and 80 to 20% by weight of TiC as main components, and has a high hardness and a volume resistivity of 10 ^-2 to 10 ^-1 Ω · cm.

Further, the cermet is a composite sintered body composed of a ceramic component forming a hard phase and a metal component forming a binder phase, particularly 10 to 90% by weight of TiC and 5 to 9%.
The main component is 0% by weight of TiN, and 5% as an additive.
A material containing a carbide of a group a metal and an iron group metal as a binder phase is used. This cermet is 10 ^-4 to 10 ^-1 Ω · c
It has a volume resistivity of m.

The conductive zirconia means 70 to 30% by weight.
30 to 70% by weight of NiO is added to and mixed with ZrO ₂ of
It has been subjected to reduction treatment and has a volume resistivity of 10 ^{−4 to} 10 Ω · cm.

In addition, for ceramics having a high resistance value such as alumina, silicon carbide and silicon nitride, TiO ₂ and T
By adding a conductivity-imparting agent such as iN, it is possible to use a conductive ceramic having a volume resistivity within the above range.

Although the meandering ring member 2 is shown in the above embodiment, a spiral ring member 2 such as a coil may be used instead. Also in this case, the resistance value can be freely adjusted by changing the width and pitch of the spiral as in the above case.

Further, in order to manufacture the meandering or spiral ring body 2 in the present invention, the slits 3 and the grooves are formed by cutting or grinding the ceramic raw material in advance into a cylindrical shape, and then, before or after firing. 4 may be formed.
Alternatively, if a meandering or spiral groove is formed on the side surface of a columnar body made of resin or the like, and a ceramic raw material is filled in this groove, and then fired in this state, the columnar body made of resin or the like will be burned off, It is also possible to obtain a meandering or spiral ceramic ring body by sintering the ceramic raw material with which the grooves are filled. The ring body 2 can also be formed by an injection molding method or another method. Further, as another manufacturing method, it is also possible to form a ceramic raw material into a sheet shape, punch this sheet into a meandering shape or a spiral shape, and then wind the sheet around the side surface of a columnar body to form a ring body and fire it. .

Next, the electrode lead-out structure of the heater 1 of the present invention will be described.

As shown in FIG. 2A, a hole 5a having a diameter of about 0.5 mm is formed in the electrode portion 5 of the meandering ring body 2, and a metal such as platinum is applied to the electrode portion 5. Baking,
The metal layer 6 is formed. On the other hand, the electrode part 5 is sandwiched between the metal plates 7 and 7 made of platinum in which a hole 7a having the same diameter as the hole 5a is previously formed, and a platinum feed line 8 is passed through these holes 5a and 7a. After crushing the tip 8a of 8 to prevent it from coming off, while pulling the power supply line 8, the platinum sleeve 9 inserted into the power supply line 8 from the other end side is caulked,
It is fixed as shown in FIG.

With such an electrode lead-out structure, distortion due to the difference in thermal expansion between the electrode portion 5 of the heater 1 and the power supply line 8 is eliminated, and the fixing portion is not loosened due to the heat cycle.
Can be used stably for a long period of time.

The material used for the metal plate 7, the power supply line 8 and the sleeve 9 is platinum-rhodium, in addition to platinum.
Heat resistant alloys such as silver, silver-palladium, nickel and alloys are suitable.

Next, another embodiment of the present invention will be described. FIG.
As shown in, the heater 1 can be incorporated in the cylindrical insulating jig 10. In this case, as shown in the electrode lead-out structure in FIG. 4, the feeding wire 8 is inserted so as to penetrate the electrode portion 5, the metal plates 7, 7 and the insulating jig 10, and the insulating jig 1
The sleeve 9 is caulked and fixed from the outside of 0. By doing so, since the heater 1 is made of high-rigidity ceramics, only the electrode portion 5 needs to be fixed to the insulating jig 10, and the fixing structure can be simplified.

Further, although the cylindrical heater 1 is shown in the above embodiments, it may be a rectangular tube or other tube depending on the application.

Further, the heater 1 of the present invention can be suitably used for sealing a glass tube such as a vacuum tube or heating a fluid in the pipe.

Experimental Example Here, the heater 1 shown in FIGS. La _0.8 C
a _0.2 Cr _0.8 Mn _0.2 O ₃ ceramics is made into a cylindrical body with an outer diameter of 14 mm, an inner diameter of 12 mm, and a wall thickness of 1 mm, and a total of seven grooves 4 are cut from both end faces, and the width of the heating portion is a meandering shape of 3 mm. In such a manner, the center was separated by the slit 3 and the electrode parts 5 and 5 were installed on the same side in the axial direction with a length of about 4 mm. In addition, the number of the grooves 4 was also set to 3 or 2.

Assembling this heater 1 into the insulating jig 10,
The fixing structure of the electrode portion 5 is as shown in FIG. 4, the diameter of the hole 5a is 0.5 mm, and the diameter of the power supply line 8 is 0.3 mm.
The material of the metal plate 7, the metal wire 8 and the sleeve 9 was platinum.

The heater 1 of the present invention thus produced
Then, as a comparative example, a durability test was performed using the conventional heater 24 shown in FIG.

In the experiment, a voltage of about 100 V was applied to each heater, the temperature was raised to 900 ° C. in 30 seconds, the temperature was held for 60 seconds, and the heat cycle was cooled to 50 ° C. or less in 90 seconds, 10,000 times. The heat generation state, durability, and magnitude of strain were measured. The results are shown in Table 1.

[0041]

[Table 1]

As can be seen from Table 1, the heater using the nichrome wire as a comparative example is short-circuited due to the loosening of the electrode extraction portion after 2000 cycles due to the effect of thermal expansion, resulting in a contact failure, and then the wire is broken. It was Further, when the positional accuracy of the nichrome wire after disconnection with respect to the insulating jig groove was measured as a strain, a misalignment of 1-2 mm or a protruding portion was observed from the insulating jig groove.

On the other hand, the heater of the present invention is 1
Withstands a heat cycle test of 0000 times, no looseness of the electrode extraction part is seen, and the distortion of the heater shape is 0.1 mm.
There was only below. Therefore, the heater of the present invention can sufficiently prevent loosening of the electrode fixing portion and change of the heater shape due to the influence of thermal expansion.

However, it was found that the heater of the present invention, which had two grooves, could not be uniformly heated, and therefore the number of grooves was three or more.

[0045]

As described above, according to the present invention, a ceramic having a volume resistivity of 10 ⁻⁴ to 10 Ω · cm is formed into a meandering or spiral ring body, and electrode lead-out portions are formed at both ends thereof. Since the ceramic heater does not cause thermal deformation, uniform heating can be performed for a long period of time, and the resistance value can be freely adjusted by changing the size of the groove or the like.

Further, by punching both ends of the ring body and caulking and fixing the metal sleeve through the power supply line through the holes, the electrode lead-out portion is not affected by thermal expansion and has high durability. A ceramic heater can be obtained.

[Brief description of drawings]

FIG. 1 is a perspective view showing a ceramic heater of the present invention.

2 (a) and 2 (b) are side views showing an electrode lead-out portion of the ceramic heater of the present invention.

FIG. 3 is a partially cutaway side view showing another embodiment of the present invention.

FIG. 4 is a partial cross-sectional view showing an electrode lead-out portion in another embodiment of the present invention.

FIG. 5 is a perspective view of a vacuum tube for explaining a glass tube sealing method.

FIG. 6 is a perspective view showing a conventional heater.

[Explanation of symbols]

 1: Heater 2: Annular body 3: Slit 4: Groove 5: Electrode part 6: Metal layer 7: Metal plate 8: Power supply line 9: Sleeve 10: Insulation jig

Claims (2)

[Claims] 1. A ceramic heater characterized in that a ceramic having a volume resistivity value of 10 ⁻⁴ to 10 Ω · cm is formed into a meandering or spiral ring body, and both ends thereof are electrode take-out portions. 2. The annular body has a slit in the axial direction, and has a meandering shape having a plurality of grooves alternately from both ends, and has an electrode lead-out portion on the same side in the axial direction. The ceramic heater according to claim 1.