JP2955127B2 - Ceramic heater - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ceramic heater, and more particularly to a ceramic heater which can be used as a heating element mainly used for electric appliances such as a heating element for a rice cooker and a hot plate hot plate.

[0002]

2. Description of the Related Art As shown in FIGS. 14 to 17, a conventional heating heater has a structure in which a sheathed heater 22 and a heating plate 21 are integrated, and heat from the sheathed heater 22 is transferred to the heating plate 21 by heat conduction and radiated. There is known a structure having a structure in which a temperature difference occurs between a portion around the sheathed heater 22 and a portion without the sheathed heater 22 and used for a cooker or the like (for example,
JP-B-54-67070, JP-B-55-43804
Gazette, JP-B-55-48460).

[0003]

Since the above-mentioned hot plate utilizing the conventional sheathed heater is a structure utilizing heat conduction from the sheathed heater, the temperature difference between the portion surrounding the sheathed heater and the portion without the sheathed heater is provided. However, there was a drawback that large occurrences occurred.

The present invention has been made in view of the above circumstances, and has as its main object to provide a heating element (heater) capable of generating heat with almost no temperature difference.

[0005]

Means and operation for solving the Problems] According to the present invention, the conductive ceramic sintered compact ing coupled to the porous silicon nitride silicon carbide particles are formed by nitriding of metal silicon, the conductive A pair of electrode portions attached to the conductive ceramic molded body and the conductor except for the electrode forming portion.
Lithium-based and Koji
Formed by glaze containing at least one of light
A ceramic heater comprising an insulating film is provided.
Further, the conductive ceramics sintered compact has a plate shape.
And a ceramic fiber.
Insulation plate made of the above, said insulation plate and ceramic heater
And a frame that surrounds and bends the periphery of
A panel heater is provided.

The above-mentioned silicon carbide particles are used to form a conductive ceramic sintered compact (or sintered body), and usually have a purity of 99% by weight or more and a content of 1 to 10%.
Those having an average particle size of μm are preferred. Among them, 2
Those having an average particle size of about 7 μm are particularly preferred. If the average particle size is more than 10 μm, abrasion of the molding machine is remarkable and there is a problem in production, and at the same time, abrasion powder is mixed into the raw material, which adversely affects the physical properties and electrical characteristics of the sintered product. On the other hand, if it is less than 1 μm, it is difficult to purify the silicon carbide powder and the formability is deteriorated, and the variation in the electrical characteristics of the sintered body is increased. The silicon carbide particles are obtained by mixing carbon powder and silica stone in an indirect resistance furnace.
It is preferable to use those obtained by heating to 00 to 1900 ° C. and having extremely few impurities such as silicon oxide and iron present on the particle surface as compared with commercially available silicon carbide particles.

The above-mentioned silicon nitride is for binding silicon carbide particles in a porous manner, and has an average particle diameter of 1 to 10 μm.
Can be mixed with silicon carbide particles, and the metal silicon powder can be used by nitriding and binding between the silicon carbide particles. The conductive ceramic sintered compact according to the present invention is used to constitute a heater that generates heat by electric energy, and has a specific resistance of 0.5.
1 to 100 Ω · cm, preferably 0.5 to 50 Ω · cm
Can be used.

Next, a method for producing a conductive ceramic sintered compact according to the present invention will be described.

That is, a molding aid and water are added to a raw material consisting of 60 to 90 parts by weight of silicon carbide powder having an average particle size of 1 to 10 μm and 10 to 40 parts by weight of metal silicon powder having an average particle size of 1 to 10 μm. The mixture is formed into a predetermined shape and then heated and sintered in a nitrogen atmosphere to obtain a conductive ceramic sintered compact.

As a raw material, a raw material comprising 40 to 90 parts by weight of silicon carbide powder having an average particle size of 1 to 10 μm and 10 to 60 parts by weight of metal silicon powder having an average particle size of 1 to 10 μm is used.

When the amount of the silicon carbide powder is less than 40 parts by weight, the specific resistance of the obtained conductive ceramic sintered compact is undesirably large, and when it is more than 90 parts by weight, the toughness is undesirably reduced. Among them, especially 50 to 8
0 parts by weight is preferred.

If the amount of the metallic silicon powder is less than 10 parts by weight, the toughness of the obtained conductive ceramic sintered compact is unfavorably reduced, and if it is more than 60 parts by weight, the specific resistance is undesirably increased. Among them, especially 20 to 5
0 parts by weight is preferred.

A molding aid and water are added to the above raw materials and mixed. Examples of the molding aid include an organic resin binder, a surfactant, and the like. Usually, a total amount of silicon carbide powder and metal silicon powder is 1
5 to 20 parts by weight can be used for 00 parts by weight. Water can be used usually in an amount of 15 to 30 parts by weight.

When the organic resin binder is heated to 1000 ° C. in a nitrogen gas atmosphere, 80 to 98% is vaporized by thermal decomposition, and 2 to 20% remains as a carbon-based organic resin binder (for example, polymer cellulose). It is preferable to use a resin such as a resin.
In addition, it is possible to prevent the metal silicon from being oxidized. That is, when heated to 1000 ° C. in a nitrogen atmosphere, a small amount of oxygen and carbon contained in the nitrogen gas atmosphere react preferentially during firing because an organic resin-based binder remaining as 2 to 20% carbon is used. At high temperatures, it also reacts with metallic silicon to produce part of silicon carbide.
As a result, silicon carbide and metal silicon in the raw material are prevented from being oxidized, and the specific resistance of the fired product is reduced and the variation in specific resistance is reduced. If the residual amount of the organic resin binder is 2% or less, the antioxidant effect is poor, and if it is 20% or more, the sinterability is adversely affected and the strength is reduced. As the surfactant, for example, a nonionic surfactant such as fatty acid sorbitan ester polyethylene glycol is preferable. It is preferable that the mixing is usually performed by mixing with a mixer and kneading with a kneader.

In the present invention, this mixture is formed into a predetermined shape, dried, and then heated and sintered in a nitrogen gas atmosphere to form a porous silicon carbide particle of 0.1 to 100 Ω · cm. To form a conductive ceramic sintered compact having the specific resistance described above. This molding can be performed using, for example, an extrusion molding machine, a casting molding machine, or the like into a shape such as a plate shape, a honeycomb shape, a dish shape, or a container shape.

In the heat sintering, the dried mixture is heated in a nitrogen gas atmosphere, for example, at 400 to 600 ° C. for 2 to 6 hours to remove gas-generating substances such as molding aids, and then re-heated in a nitrogen gas atmosphere. And then raise the temperature to 1300-1450 ° C
Reaction sintering can be performed for 24 hours.

The obtained conductive ceramic sintered compact is appropriately processed into a predetermined size, and an electrode is formed thereon to form a heater such as a heater or a cooker.

[0018] Silicon oxide and iron present on the surface of the silicon carbide particles are dissolved and removed to purify the silicon carbide particles, and the highly purified silicon carbide forms a conductive ceramic sintered compact to lower the specific resistance. . In addition, in sintering by silicon nitride performed by heating metal silicon together with silicon carbide particles in a nitrogen gas atmosphere, the silicon carbide particles are not oxidized, and nitrogen atoms are partially dissolved in the silicon carbide particles. A porous, lightweight and tough conductive ceramic sintered compact having a specific resistance is formed.

In the present invention, a pair of electrodes is formed on the sintered conductive ceramics compact. This electrode portion is preferably formed by first forming a conductive layer on the surface of the molded body, and bonding an electrode plate to the conductive layer. The conductive layer is formed by, for example, spraying aluminum onto the surface of the molded body.

In the present invention, an insulating film is formed on the surface of the conductive ceramic sintered compact except for the above-mentioned electrode portion forming portion. This insulating film is coated with, for example, a lithia-based and cordierite-based glaze with a thickness of about 100 μm,
It is formed by firing in a nitrogen gas atmosphere.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail based on an embodiment shown in the drawings. Note that the present invention is not limited to this.

First, in FIG. 1, a ceramic heater (4) has a width of 12 mm by spraying a plate-shaped ceramic sintered compact (flat heater element) (4a) and an aluminum material along two opposing sides on the back surface of the compact. , Thickness 100μ
m), and an electrode layer (2) (2) formed of
The insulating portion (film) (1) formed on the surface and the back surface other than the electrode layer (2) (2) forming portion, and the aluminum portion formed by ultrasonic welding on the surface of the electrode portion (2) (2) It comprises electrode plates (3) and (3). The electrode portions are composed of the electrode layers (3) and (3) and the electrode layers (2) and (2).

The formation of the ceramic sintered compact (4a) will be described later in detail, but the insulating part (1) molded on the surface of the ceramic sintered compact (4a) is made of a lithia cordierite or porcelain glaze with a thickness of 100 μm. It is applied and fired in a nitrogen gas atmosphere.

Preparation of Silicon Carbide Powder By passing a linear current through a mixture of carbonized powder (coke) and silica stone, a mass of silicon carbide generated by igniting at 1800 to 1900 ° C. is crushed, pulverized, and washed with water to obtain a particle size. In addition, the silicon carbide powder is further treated with an aqueous acid solution to remove impurities such as iron generated and attached to the surface of the silicon carbide powder during the manufacturing process (during the synthesis or pulverization of silicon carbide). A high-purity silicon carbide powder having a thickness of 5.5 μm and a purity of 99% or more is produced. The aqueous acid solution is hydrochloric acid, sulfuric acid, nitric acid, hydrofluoric acid, or a mixed acid aqueous solution thereof.
The average particle size and purity of the obtained silicon carbide powder and the commercially available silicon carbide powder for comparison are as shown in Table 1.

[0025]

[Table 1]

Production of conductive ceramic sintered compact Silicon carbide powder (purity 98% or more, average particle size 5.5 μm)
70 parts by weight, metal silicon powder (average grain: 5.9 μm) 3
0 parts by weight, a total of 12 parts by weight of a methylcellulose-based organic resin binder and a fatty acid sorbitan ester polyethylene glycol (nonionic surfactant) as a molding aid,
Then, 21 parts by weight of water is added and mixed for about 5 minutes with a mixer.
After sufficiently kneading the mixture with a continuous kneader, a sheet having a thickness of 1 mm and a width of 70 mm is extruded with a high-pressure vacuum extruder at a molding pressure of 30 kg / cm ² to obtain a plate-shaped test piece. These dried greens were debindered at 500 ° C. for 3 hours in a nitrogen gas atmosphere, and then reacted and sintered at 1400 ° C. for 6 hours in a nitrogen gas atmosphere to form a plate-shaped ceramic sintered compact.

Physical Properties and Electrical Properties of Sintered Conductive Ceramics Compact The physical properties and resistivity of the plate-shaped conductive ceramics sintered compact obtained as described above are as shown in Table 2.

[0028]

[Table 2]

After cutting the plate-shaped ceramic sintered compact to a diameter of 20 mm to form an electrode, the specific resistance to temperature was measured. As a result, it was confirmed that the obtained conductive ceramic sintered compact had lower specific resistance than the comparative example described later, and the variation thereof was remarkably improved.

Comparative Example 1 In Example 1, instead of using the silicon carbide powder prepared as described above, a commercially available silicon carbide powder A shown in Table 1 was used. The specific resistance of the ceramic sintered compact is 1940Ω · c at room temperature.
m, which was remarkably high.

The conductive ceramic sintered compact produced in this way uses inexpensive SiC and metallic silicon and can be mass-produced in a relatively simple manufacturing process. A low heat expansion heater having a low coefficient of thermal expansion and good durability can be obtained.

Example 2 In Example 1, instead of setting the mixing ratio of silicon carbide powder and metal silicon powder to 70/30, 80/20, 7
5/25, 70/30 and 65/35 were used, and the others were the same as in the actual example to prepare a conductive ceramic sintered body. The physical property values and specific resistance values of the obtained plate-shaped ceramic sintered compact are as shown in Table 3.

[0033]

[Table 3]

As described above, by changing the mixing ratio of silicon carbide and metal silicon, it is possible to produce sintered bodies having different specific resistances as needed. If the compounding ratio of silicon carbide is 90% or more, the strength is remarkably reduced, so that the material is not suitable as a heater material. If the compounding ratio is 40% or less, the specific resistance is remarkably increased and the material is not suitable as a heater material.

Example 3 A sheet having a thickness of 2.5 mm and a thickness of 280 mm was extruded at a molding pressure of 35 kg / cm ² using a large-sized extruder with the same raw materials as in Example 1. After drying, these molded products are cut into appropriate dimensions and fired under the same conditions as in Example 1.

Next, when two ceramic heaters (4) are used in the explanatory view prepared as described above, a wall-mounted panel heater (11) as shown in FIG. 2 is obtained. That is, the wall-mounted panel heater (11) includes two ceramic heaters (4), (4), a heat insulating plate (5) made of ceramic fibers overlapped with these ceramic panel heaters, and a heat insulating plate and a ceramic heater. (4)
(4) and a frame (6) that surrounds the peripheral edges thereof and holds them in an overlapped state.

Two ceramic heaters (4) (4)
Are the electrode portions (2) in the same plane as shown in FIG.
(2) are arranged in contact with each other so as to be in contact with each other, and the electrode portions (2) and (2) are bridged by the electrode plate (3), and both heaters (4) and (4) are connected in series.

The heat insulating plate (5) has a concave step (7) into which the ceramic heaters (4) and (4) are fitted as shown in FIG.
And a through hole (8) for allowing the electrode plate (3) to penetrate to the opposite side to prevent contact with the electrode plate (3). The outer dimensions of the heat insulating plate (5) are 595 × 295 × 20
mm.

The frame (6) has a substantially U-shaped channel in cross section in FIG. 4, and is obtained by extruding aluminum or heat-resistant synthetic resin into four parts (or two parts).
It is composed. In FIG. 4B, a = 25 mm,
b = 15 mm and c = 2 mm.

Production Example 1 The ceramic panel heater (1
1) is adhered to the concave step portion (7) of the heat insulating plate (5) with an appropriate inorganic adhesive layer (about 2 mm), and the frame (6) is fitted into the outer peripheral portion to be integrated and completed. .

When a voltage is applied to the ceramic panel heater (11), the adhesive layer is dried and integrated.

Production Example 2 As another production example, as shown in FIG. 5, a ceramic panel heater (11) was placed in a mold having good releasability, and a semi-kneaded inorganic adhesive layer (10) of about 2 mm was further provided. After a semi-kneaded ceramic fiber and a heat insulating material (5) are filled in the upper part, they are fitted so that the electrode plate (3) passes through the through hole (8). When electricity is supplied to the electrode plates (3) and (3), the adhesive layer (10) is dried and the entire structure is integrated and completed. The obtained wall-mounted panel heater (11) had a surface temperature of 80 ° C and a surface temperature via the heat insulating plate (5) of 50 ° C or less (rated voltage 100V, output 250W). The state of use is shown in FIG.
Shown in Art design of wall-mounted panel heater (1) Coloring by applying silicon heat-resistant paint.

(2) Designing by painting for pottery.

(3) Silk screen using heat-resistant pigment,
Designing by transcription.

An art design such as the above can be applied.

As shown in FIG. 6, a large number of wall-mounted panel heaters (11) can be combined into a large panel heater in the same plane. FIG. 6A shows an outer dimension 600.
× 283 mm, and FIG. 6B shows the external dimensions of 300 × 283.
mm and a large unit with a long side dimension of 1800 m and a short side dimension of 849 m so that these panel heaters can be combined under a standard window to provide the heating function, heat insulation function, and soundproofing function of the panel heater. It was embedded under the window of the room as an interior building material. Thus the rated voltage 1
A large panel heater having a power of 00 V and an output of 1200 W was obtained. The front surface temperature was 60 ° C., and the back surface temperature via the heat insulating material was 30 ° C. This panel heater acts as a warm air curtain due to its draft effect, so that it can prevent cold air entering from the upper window, and has an effective heating effect. An example of use is shown in FIG.

By using the unit as an interior building material for the ceiling as shown in FIG.
It is also possible to obtain a pleasant heating effect that. Further, as shown in FIG. 7D, the unit can be used as a floor material to perform floor heating. The output of the panel in the above embodiment can be arbitrarily selected by changing the resistance value.

As is clear from the above description, the panel heater has a heating function, a heat insulating function, and a soundproofing function embedded in a panel heater installed under a desk, a wall-mounted panel heater, a wall surface, a ceiling, a floor surface, and the like. It can be used as an economical interior building material with combined dimensions, and can be freely dimensioned and heated according to each location. By applying various art designs, it is possible to provide products rich in art sense.

Unlike the above embodiment, the conductive ceramic sintered compact is not formed in a plate shape having a uniform thickness, but in FIG.
As shown in Fig. 9, it is formed in a disk shape whose thickness decreases in the radial direction,
The metal spray electrode (2) is placed in the opposite direction of the compact (23).
4a) While forming (24b), the molded article (23)
An insulating film (26) may be formed on the entire surface except for the electrodes (24a) and (24b) on the surface. The molded body (23) was formed by a casting method (another molding method, for example, a plastic molding method can be employed).

Thus, by applying an AC voltage (25) of 100 V to the electrodes (24a) and (24b) of the molded body (23), the entire molded body (23) generates heat uniformly and the output is 500W. That is, since the thickness is largely adjusted (maximum 21.5 to minimum 3 mm) in order to make the current density of the molded body (23) above the electrode (24b) uniform, the surface of the flat part above the molded body (23) 300 ° C with almost uniform temperature
And the temperature difference of the flat part 175φmm is about 10 ° C
Therefore, a good temperature distribution can be obtained.

As a conventional technique, a heating plate 21 having a thickness of 4 mm and a diameter of 175 mm as shown in FIGS. In this example, the temperature difference between the periphery of the sheath heater 21 and the portion without the sheath heater 21 is about 30 ° C., which is extremely large, because the temperature difference between the periphery of the sheath heater 21 and the portion without the sheath heater 21 is thermally conducted from the sheath heater 22 to the hot plate 21. Further, the molded body 23 has a bulk density of 2.1 g / c.
m ³ , bending strength 10 kg / mm ² is thermal conductivity 0.03 ca
Since it is as high as 1 / cm · sec ° C. and the coefficient of thermal expansion is as low as 4 × 10 ⁶ , it is strong against thermal shock and is excellent as a heating element.

In the above, the molded body 23 is made of Si
Actual measurement results when using C-Si ₃ N ₄ ceramics are shown, but high-purity SiC ceramics and recrystallized SiC
The same effect can be obtained by using ceramics. Furthermore, an insulating film (2) is formed on the entire surface of the three-dimensional structure (container type).
6) shows a structure that can be used as a cooker or the like without danger of electric leakage at all. In other words, the function as a uniform heating type heating element and the function as a container such as a cooking product can be obtained. This is very suitable as a heating element for heating a cooker or a liquid.

As described above, according to the conductive ceramic sintered compact of FIGS. 8 and 9, the current density of the heating element can be made uniform by adjusting the wall thickness, and the structure of the molded article such as cast molding (three-dimensional structure) can be obtained. (Formed body structure), can be used as a heating element suitable for product use, and furthermore, by forming an insulation film on the entire heating element, there is no danger of electric leakage even if you touch your hand during energization. Body can be provided.

In addition, the conductive ceramic sintered compact can be formed into a dish shape as shown in FIGS. 10 to 11 and a container shape as shown in FIGS. 12 and 13, similarly to FIGS. 8 and 9, the thickness is adjusted to make the current density uniform.

[0055]

According to the present invention, almost all of the components are heating elements (heaters), so there is almost no difference in temperature, and the panel is used as an excellent panel heater under a desk, on a wall, on a ceiling, or on a floor. Can be. Except for the electrode formation part
The surface of the conductive ceramic sintered compact
Glaze containing at least one of gillite
By forming a film, conductive ceramic sintering
Since an insulating film is integrally formed on the surface of the
Bending conductive ceramic sintered compact while actually insulating
Strength and thermal shock resistance can be increased.

[Brief description of the drawings]

FIG. 1 is a configuration explanatory view illustrating an embodiment of a ceramic heater according to the present invention, in which (A) shows a front surface, (B) shows a back surface, and (C) shows a CC cross section.

FIGS. 2A and 2B are explanatory diagrams illustrating a configuration of a ceramic panel heater as another embodiment, wherein FIG. 2A is a front view and FIG.

3A and 3B are explanatory views of a structure of the ceramic panel heater shown in FIG. 2, wherein FIG. 3A is a front view of a conductive ceramic sintered compact, FIG. 3B is a front view of a heat insulating plate, and FIG. −
The C section is shown.

4A and 4B are explanatory diagrams of the configuration of the ceramic panel heater similarly shown in FIG. 2, wherein FIG. 4A is a front view of a frame, and FIG.

FIG. 5 is an explanatory view of an apparatus configuration for explaining a method of manufacturing the ceramic panel heater shown in FIG. 2;

FIG. 6 is a front view illustrating a large panel heater as another embodiment.

FIG. 7 is an explanatory diagram showing an example of use of various ceramic panel heaters in a room.

FIG. 8 is a sectional view of a ceramic heater as another embodiment.

FIG. 9 is a bottom view of the ceramic heater of FIG. 8;

FIG. 10 is a diagram corresponding to FIG. 8 of another embodiment.

FIG. 11 is a diagram corresponding to FIG. 9;

FIG. 12 is a view corresponding to FIG. 8 of still another embodiment.

FIG. 13 is a diagram corresponding to FIG. 9;

FIG. 14 is a diagram corresponding to FIG. 8 showing a conventional example.

FIG. 15 is a diagram corresponding to FIG. 9;

FIG. 16 is a diagram corresponding to FIG. 8, showing another conventional example.

FIG. 17 is a diagram corresponding to FIG. 9;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Insulation part (film) 2 Electrode layer 3 Electrode plate 4 Ceramic heater 5 Heat insulation plate 6 Frame

Claims (2)

(57) [Claims] 1. A conductive ceramic sintered compact ing coupled to the porous silicon nitride which carbonization silicon particles are formed by nitriding of metal silicon, the conductive ceramic molding
Removing the electrode portions of the pair which is set with the body, the electrode forming portion
Lithia on the surface of the conductive ceramic sintered compact
With glaze containing at least one of chlorinated and cordierite
A ceramic heater comprising an insulating film to be formed . 2. A ceramic heater of the electrically conductive ceramic sintered compact is 請 Motomeko 1 Ru plate der, a heat insulating plate made of ceramic fibers, and their peripheral overlapping the insulation plate and the ceramic heater囲撓A ceramic panel heater consisting of a frame.