JPH10302939A - Ceramic heater - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ceramic heater capable of reducing temperature rise time, uniformly heating over a period of time without causing thermal deformation or the like, and free from function degrading even by shock due to drop or the like. SOLUTION: A heating element constituting this ceramic heater comprises a cylindrical ceramic body 10 having its conductivity. A thick stage top part is formed continuously at a flange 18. In addition, a metal layer is formed partly on an end face of the flange 18, a power supply plate 32 is bonded with this metal layer, further, an insulation spacer 39 having its substantially same thickness as the power supply plate 32 is bonded with a remaining dividing flange 18 (holding part 15), and by means by a press plate (insulation plate 36), both of the power supply plate 32 and the ceramic space 39 are engagingly locked with an above casing 35 simultaneously.

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 used particularly for vacuum sealing a glass tube.

[0002]

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

As one application, there is a heater used for vacuum sealing a glass tube. Hereinafter, the prior art will be described using a vacuum sealing method of a glass tube as an example.

Generally, vacuum sealing of a glass tube is performed by using a lamp,
Used in the manufacture of vacuum tubes or cathode ray tubes. The vacuum tube is made by inserting an electrode into a glass container sealed on one side, heating and fusing the glass tube with a heater, and vacuum-sealing the inside while degassing with a vacuum pump from the unsealed side.

A jig 51 as shown in FIG. 4 is used for the above-mentioned vacuum sealing. The jig 51 has a built-in cylindrical heater 53 inside a heat insulating material 52. The glass tube of the vacuum tube is inserted inside the heater 53 to heat and blow.

As shown in FIG. 5, the structure of the heater 53 is such that a heater wire 57 spirally provided on the front and back of a cylindrical insulating spacer 56 is provided inside a case 55 made of a heat-resistant metal. A lead wire 54 leading to 57 is led out. As the heater wire 57, a metal heater such as a nichrome wire is used. However, since the volume resistivity is very small, the width 2 is required to obtain a temperature at which the glass tube is blown.
mm and a thickness of about 0.5 mm, and as shown in FIG.

[0007]

However, the above jig 5
When the glass tube is vacuum-sealed by using the glass tube 1 and the jig 51, the outer periphery of the glass tube is
If the jig 51 is arranged and the heating is repeated while maintaining a certain clearance between the three, the metal heater 53 is deformed due to the influence of thermal expansion, and there is a problem that a certain clearance from the glass tube cannot be maintained. Was.

As a result, a part of the glass tube is melted before the others, so that not only the inside of the glass tube cannot be completely vacuum-sealed, but also the deformed heater wire 57 comes into contact with the glass tube, and When glass adheres to the wire, there is an inconvenience that the portion changes in resistance, causing rapid heating and disconnection.

Further, since the heater 53 has a small volume resistivity value of the heater wire 57, a desired resistance value is obtained by spirally winding the belt-like heater wire 57 through an insulating spacer 56. In such a complicated structure, not only is it difficult to generate heat evenly, but also much heat is wasted, and power consumption is large. Further, since the heater wire 57 itself is easily oxidized, the characteristics are deteriorated, and there is also a problem that it is difficult to obtain a stable calorific value for a long period of time.

In the jig 51, the heater wire 57
The power supply unit and the lead wire 54 for supplying power are fixed using various heat-resistant metals, but the fixed part is subjected to a heat cycle during use, and the heater wire 57 and the heat-resistant metal repeat thermal expansion. Since the strain is gradually generated and loosens, the power supply portion of the heater wire 57 and the lead wire 5
There was also a problem that the contact portion of No. 4 was short-circuited and the wire was easily broken.

Further, when an impact or vibration due to a drop is applied to the jig 51, not only does the heater 53 deviate from the fixed position of the jig 51, but also the problem that the glass tube is not sealed well occurs. There is also a problem that the lead wire 54 is twisted and disconnected.

[0012]

According to the present invention, as a means adopted to solve such a problem, a heating element constituting a heater is firstly constituted by a cylindrical ceramic body having conductivity. Further, a thick step upper part and a flange continuous with the thick step upper part are formed on one end side of the cylindrical ceramic body,
By engaging and fixing this flange to the casing,
The ceramic body was mounted in a casing. In addition to these means, in the present invention, a power supply plate is joined to a metal layer formed on a part of the end face of the flange,
An insulating spacer having substantially the same thickness as the power supply plate is joined to the end face of the remaining flange, and both the power supply plate and the insulating spacer are simultaneously pressed and fixed to a predetermined portion of the casing by a pressing plate, whereby the ceramic body is formed. Is provided in a casing.

Thus, in order to solve the above-mentioned problems, the present invention energizes a tubular conductive ceramic body having a thick stepped upper portion on one end side and a continuous flange formed on the thick stepped upper portion to generate heat. The power supply plate is joined to a metal layer formed on a part of the end face of the flange,
An insulating spacer having substantially the same thickness as the power supply plate is joined to the end face of the remaining flange, and both the power supply plate and the insulating spacer are simultaneously pressed and fixed to a predetermined portion of the casing by a pressing plate, whereby the ceramic body is formed. Is provided in a casing.

[0014]

According to the present invention, the heating element constituting the heater is constituted by a cylindrical ceramic body having conductivity.
The heating time can be shortened, and uniform heating can be performed for a long time without causing thermal deformation or the like.

Further, by forming a flange at one end of the cylindrical ceramic body and engaging and fixing the flange to the casing, it is possible to improve the assembly accuracy with the casing and increase the joining strength. In addition, since the thick step portion is formed continuously with the flange, the breaking stress at the root of the flange can be absorbed and reduced, and the heater can be prevented from being damaged.

A metal layer is formed on part or all of the end face of the flange, a power supply plate is joined to the metal layer, and both the power supply plate and the insulating spacer are simultaneously held at predetermined positions in the casing by a holding plate. Even if a thermal expansion difference occurs between the power supply portion of the ceramic body and the metal power supply plate and the insulating spacer because of the pressure fixing structure, the thermal expansion difference can be absorbed by the displacement of the press contact surfaces in the radial direction,
Distortion and loosening can be avoided, and due to the adhesion, the fracture stress at the base of the flange can be absorbed and alleviated, and breakage of the heater can be prevented.

[0017]

Embodiments of the present invention will be described below. FIG. 1 shows only the ceramic body 10 constituting the ceramic heater of the present invention.

The ceramic body 10 has a meandering cylindrical body made of conductive ceramics at both ends as power supply portions 12. That is, the ceramic body 10 has a cylindrical shape as a whole, but has one slit 14 in the axial direction, and has grooves 13 extending alternately from both end faces to form the meandering heating portion 11, and On one end side, a thick step upper part 16 and a split flange 18 continuous with the thick step upper part 16
The split flanges 18 located on both sides of the slit 14 and forming both ends of the meandering cylindrical body are formed by the feeder 1.
2. The other split flanges 18 are holding parts.

When a voltage is applied between the power supply units 12, the meandering cylindrical ceramic body 10 made of conductive ceramics is energized to generate heat.
The metal layers 31 are formed on the rear end surfaces of the two power supply portions 12 of the ceramic body 10 by applying and baking a metal paste such as platinum.

Next, the structure of the ceramic heater having the ceramic body 10 will be described. FIG. 2 is a sectional view of the ceramic heater. As shown in FIG. 2, a casing 35 made of an insulating material such as ceramic is a cylindrical body, and one end face is provided with two counterbores 35a and 35b and
Then, the ceramic body 10 is fitted by matching the holding portions 15.

Further, as shown in FIG.
An insulating plate 36 as a pressing plate made of ceramics or the like is fitted into the outer counterbore 35b, and the metal plate 37 is further covered from above, and the metal plate 37 is screwed and fixed to the casing 35 with screws 40. The ceramic body 1
A concave portion 17 is formed in the power feeding portion 12 and the holding portion 15 of the
Protrusions 36b corresponding to the insulating plate 36 are formed to enable positioning and prevent misalignment.

In order to explain this structure in detail, as shown in FIG.
a in this state.
Each of the power supply plates 32 is brought into contact with the metal layer 31 provided in the second power supply 2, and the remaining divided flanges 18 where the metal layer 31 is not provided have substantially the same thickness as the power supply plate and have the same thickness as the power supply plate. A ceramic spacer 39 as an insulating spacer having a thermal expansion coefficient is joined, and the power supply plate 32
A screw 38 is passed between the
Screwed in. When screwing the power supply plate 32 to the two power supply portions 12, the power supply line 33 is wound around the screw 38 and fixed with the nut 39, and the other end of the power supply line 33 passes through the through hole 35 e of the casing 35. It is derived outside. Therefore, when a voltage is applied between the power supply lines 33, the ceramic body 10 can be energized to generate heat. The power supply plate 32 is provided with a claw 32a (see FIG. 2). The claw 32a is aligned with the side surface of the power supply section 12 and the groove 35d (see FIG. 3) of the casing 5 so that the power supply plate 32 rotates in the rotational direction of the ceramic body 10. Positioning is performed.

FIG. 3 is a rear view of the ceramic heater in this state, and thereafter, as shown in FIG.
And the metal plate 37 is overlaid to complete the assembly.

In the ceramic heater configured as described above, the casing 35 and the insulating plate 36 act as a pressing plate.
The power supply plate 32 can be pressed against the metal layer 31 and firmly fixed. Moreover, at this time, the holding portion 15 provided on the ceramic body 10 is also fixed by being sandwiched between the casing 35 and the insulating plate 36. Therefore, the end face of the ceramic body 10 can be fixed around the entire circumference, and the ceramic body 10 can be mounted firmly and with high assembling accuracy.

Further, by forming a step 36a corresponding to the power supply plate 32 on the insulating plate 36 and supporting it at the same time as the holding portion 15, breakage due to impact inertia can be prevented.

Further, even when a large shock or vibration is applied to the casing 35, as shown in FIG. 1, the thick step portion 16 is provided continuously to the power supply portion 12 and the holding portion 15 of the ceramic body 10. The breakage of the boundary 13a between the power supply unit 12 and the holding unit 15 and the heat generating unit 11 where the breaking stress is concentrated can be prevented.

Further, at room temperature, the volume resistivity is 0.3 to 0.4 Ω · cm, but the melting point of glass is 90 °.
At 0 to 1000 ° C., the temperature is as low as 3 × 10 ⁻⁴ Ω · cm, and the TCR has a negative characteristic.

In the above embodiment, the ceramic body 1
In the case of manufacturing the ceramic material 0, the length of the heat generating portion 11 can be freely changed by adjusting the cut length of the groove 13 after the ceramic raw material is formed into a cylindrical shape. By changing the width of 11, the resistance value of the ceramic body 10 can be freely adjusted. However,
Preferably, a total of three or more grooves 13 are formed. This is because if the number of the grooves 13 is less than three, it is difficult to uniformly heat. Furthermore, the power supply structure can be simplified by forming the power supply portions 12 at both ends on the same side in the axial direction.

Further, the ceramic body 10 can be formed in a spiral shape. In the above example, the ceramic body 10 has a substantially cylindrical shape. However, the ceramic body 10 may have a rectangular tube shape or another shape.

The conductive ceramic constituting the ceramic body 10 has a volume specific resistance of 10 ⁻⁴ to 10 Ω · cm and a temperature coefficient of resistance (TC) in order to generate heat efficiently.
R) indicates a negative value. Here, that the TCR is negative means that the resistance value decreases as the temperature increases, and there is an effect that the rate of temperature rise from room temperature to a high temperature can be extremely increased.

Specifically, a lanthanum chromite ceramic is used as the conductive ceramic satisfying the above characteristics. Lanthanum chromite ceramic is LaC
With respect to the composition of rO ₃ , part of La is replaced by one or more elements of Group 2a of the periodic table such as Ca, Sr, and Ba, and part of Cr is replaced by Mn, Co, Fe, Ni, Ce, Zr, etc. It is substituted by one or more of the elements, elements of the 3a group and 4a group of the periodic table. This ceramic has a volume specific resistance of 10 ⁻⁴ to 10 Ω · cm, and has a perovskite crystal structure, so that it has excellent heat resistance and has little characteristic deterioration even at high temperatures.

Further, lanthanum chromite ceramics have a characteristic that their TCR shows a negative value, and thus can be said to be a material suitable for a case where a rapid temperature rise to a high temperature is required.

For example, using a material represented by the chemical formula La _0.8 Ca _0.22 CrO ₃ , this raw material is molded, raw-processed,
By firing and post-processing, a ceramic body 10 as shown in FIG. 1 can be obtained. The thermal expansion coefficient of ceramics represented by the above chemical formula is relatively small, 1 × 10 ⁻⁷ / ° C., so that the heat capacity of the heater can be suppressed to a small value.

Further, as the material of the ceramic spacer 39, a material having the same thermal expansion coefficient as the material of the power supply plate 32 is used. For example, platinum (thermal expansion coefficient = 8.9 × 10 ⁻⁾ is used for the power supply plate 32. ⁶ / ° C.), alumina (thermal expansion coefficient = 8 ×
10 ⁻⁶ / ° C.). In the present embodiment, the insulating spacer is made of the spacer 39 made of ceramic. However, an insulating material other than ceramic that can absorb thermal expansion, such as mica, may be used.

Further, in the above example, a heater for sealing glass of a vacuum tube has been described. However, the ceramic heater of the present invention can be suitably used for heating a fluid in a pipe and other various uses.

The casing 35 and the insulating plate 36 are preferably made of a material having excellent insulation and heat resistance and made of a ceramic such as cordierite.

As the metal forming the metal layer 31, the power supply plate 32, and the power supply line 33, a heat-resistant metal or alloy such as platinum-rhodium, silver, silver-palladium or nickel is used in addition to platinum.

Example 1 Two types of ceramic bodies 10 and 20 shown in FIGS. 1 and 6 were experimentally manufactured. The difference between these ceramic bodies 10 lies in the presence or absence of the thick stepped portion 16. La _0.8 Ca _0.22 CrO ₃
A ceramic having a composition of 12 mm in outer diameter and 10 mm in inner diameter
mm, a total of 12 grooves 13 are cut from both end faces so that the groove width becomes 0.5 mm, and a slit 1 is formed at the center.
4, the feeding part 12 is made 1 mm thicker than the heat generating part 11 to 2 mm, and the holding part 15 having the same thickness as the feeding part 12 is formed.
Was formed.

With respect to the ceramic body 10 shown in FIG.
A thick stepped upper part 16 of 0.5 mm, 1.5 mm, and 1.5 mm was formed in the radial direction.

The ceramic body 10 was mounted on a ceramic casing 35 with the structure shown in FIGS. The power supply plate 32 is made of platinum and has a thickness of 0.4 mm. The casing 35 and the insulating plate 36 are made of cordierite ceramics.
The ceramic spacer 39 was formed of alumina ceramics.

As a mounting structure of the ceramic bodies 10 and 20, a configuration in which the ceramic spacer 39 in which the insulating plate 36 is joined to the holding portion 15 and the feeding plate 32 in contact with the feeding portion 12 are simultaneously pressed, and only the holding portion 15 is pressed. Two types of ceramic heaters were prepared, and the above-mentioned two types of ceramic bodies 10 and 20 were mounted on each of them to prepare a total of four types of ceramic heaters.

The ceramic heaters were dropped naturally from a height of 35 cm, and then a sealing test of the glass tube was performed to confirm the shape of the melting part. Table 2 shows the results.

[0043]

[Table 1]

As can be seen from Table 1, each of the ceramic heaters mounted with the ceramic body 20 having no thick stepped portion was broken. Further, even when the ceramic body 10 provided with the thick step upper part is mounted, the thickness of the thick step upper part in the shaft and radial direction is 0.5 mm, and the holding plate is the holding part 15.
In the case where only the pressure was applied, breakage occurred at the tip groove. This phenomenon occurs because the power supply unit 12 is supported by the power supply plate 32,
On the other hand, since the holding portion 15 is supported by the insulating plate 36, it is considered that the influence due to the difference in the inertial force at the time of impact has appeared on the tip side.

In addition to the above, the holding plate is not
As a result of the sealing test, there was a defective type in which only the pressure contact was performed. This is considered to be due to the occurrence of a positional shift due to the impact due to the drop.

On the other hand, the length in the axial and radial directions is 0.5
mm thick section upper part is provided, and the holding plate is
In the case of pressing only 5, there was no breakage due to dropping, and the sealing test result was also good.

Example 2 A ceramic body 10 shown in FIG. 1 was experimentally manufactured. La _0.8 Ca
A ceramic having a composition of _0.22 CrO ₃ was prepared with an outer diameter of 12 m.
m, a cylindrical body having an inner diameter of 10 mm, a total of 12 grooves 13 are cut from both end faces so that the groove width becomes 0.5 mm, and the center is cut off by a slit 14.
The holding portion 15 was formed to be 1 mm thicker to 2 mm and the same thickness as the power feeding portion 12.

A thick stepped upper portion 16 of 2 mm in the axial direction and 2 mm in the radial direction was formed with respect to the power supply portion 12 and the holding portion 15.

The ceramic body 10 was attached to a ceramic casing 35 with the structure shown in FIGS. The power supply plate 32 was made of platinum and had a thickness of 0.4 mm, and the casing 35 and the insulating plate 36 were formed of cordierite ceramics. In addition, a ceramic spacer 39 made of cordierite ceramics (thermal expansion coefficient = 8.9 × 10 ⁻⁶ / ° C.), an alumina ceramic spacer, and a ceramic spacer without the ceramic spacer 39 were prepared.

These ceramic heaters were rapidly heated (1
000 ° C.), and it was confirmed whether or not cracks occurred in the ceramic body 10. Table 2 shows the results.

[0051]

[Table 2]

As is clear from Table 2, only the ceramic spacer using alumina was able to withstand the rapid temperature rise test.

[0053]

As described above, according to the present invention, since the heating element constituting the heater is formed of a cylindrical ceramic body having conductivity, the time required for temperature rise can be shortened, and thermal deformation and the like can be reduced. It is possible to perform uniform heating for a long period of time without occurrence, and furthermore, a flange is formed on one end side of the cylindrical ceramic body, and this flange is fixed to a predetermined position of the casing by press-fitting. And the joining strength can be increased, and since the thick step is formed continuously with the flange, the fracture stress at the root of the flange can be absorbed and reduced.
This has an excellent effect that the heater can be prevented from being damaged.

A power supply plate is joined to a metal layer formed on a part of the end face of the flange, an insulating spacer having substantially the same thickness as the power supply plate is joined to the end face of the remaining flange, and the power supply plate is pressed by a holding plate. According to the structure in which both the plate and the insulating spacer are simultaneously pressed and fixed to a predetermined portion of the casing, even if a difference in thermal expansion occurs between the power supply portion of the ceramic body and the metal power supply plate and the insulating spacer, the pressure contact between the two is performed. When the surface is displaced in the radial direction, the difference in thermal expansion can be absorbed, distortion and loosening can be avoided, and the breakage stress at the root of the flange can be absorbed and alleviated due to the adhesion, so that heater breakage can be prevented.

[Brief description of the drawings]

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

FIG. 2 is a partially exploded sectional view of the ceramic heater of the present invention.

FIG. 3 is a rear view of the ceramic heater, showing a state where a metal plate and an insulating plate are removed.

FIG. 4 is a perspective view of a conventional heater.

FIG. 5 is a perspective view of a heat generating part constituting the heater of FIG. 5;

FIG. 6 is a perspective view of a ceramic body used in a comparative example.

[Explanation of symbols]

Reference Signs List 10, 20 ceramic body 11 heat generating portion 12 power supply portion 13 groove 14 slit 15 holding portion 16 thick step upper portion 17 boundary portion 18 divided flange 31 metal layer 32 power supply plate 33 power supply line 35 casing 36 insulating plate 37 metal plate 38 screw 39 ceramic Spacer (insulating spacer)

Claims (1)

[Claims] 1. A heater configured to generate heat by energizing a cylindrical conductive ceramic body having a thick stepped upper part on one end side and a flange continuous with the thick stepped upper part,
A power supply plate is joined to a metal layer formed on a part of an end face of the flange, an insulating spacer having substantially the same thickness as the power supply plate is joined to an end face of the remaining flange, and a plate for holding the power supply plate and the insulating spacer is provided. A ceramic heater in which the above-mentioned ceramic body is mounted in a casing by pressing and fixing to a predetermined portion of the casing.