JPH09266060A - Ceramic heater and ceramic heater unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ceramic heater which can surely prevent leakage and a ceramic heater unit. SOLUTION: In a ceramic heater 10 in which heater wiring 20 is placed between ceramic layers 12, 14, crack-detecting wiring 22 and a ceramic layer 16 are placed on the upper surface of the ceramic layer 14. If the ceramic layer 16 is cracked and the heater wiring 20 is exposed, the crack detecting wiring 22 is disconnected. A detecting circuit 82 detects the disconnection of the crack detecting wiring 22, stopping the supply of power to the heater wiring 20.

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 for heating water such as a ceramic heater for a bath that keeps the hot water at a temperature that allows constant bathing or a ceramic heater for an electric water heater, and a ceramic heater. It is about units.

[0002]

2. Description of the Related Art Instead of a sheathed heater in which a nichrome wire is arranged in a glass tube, a ceramic heater having a metallized heater wiring built in between ceramic layers is used for heating a liquid. Ceramic heaters are characterized by their smaller size and longer life than sheathed heaters, but they are vulnerable to thermal shock and, for example, when air bubbles or foreign matter in the liquid adheres to the surface, only the temperature of that part However, there is a problem that the ceramic layer is likely to be cracked due to the increase of the temperature. In particular, when the ceramic heater is used in a highly conductive liquid, the heater wiring may be exposed at the cracked portion, which may cause electric leakage.

[0003]

Conventionally, when a ceramic heater is used for heating water, an earth line is provided in parallel with the heater wiring of the ceramic heater, and when a large current flows through the heater wiring due to an electric leakage or the like. In general, a safety device has been widely used in which a current is mainly supplied to the earth line side and a large current is not supplied to the heater wiring side. However, in household electric appliances, the earth line is not always properly grounded. Here, if the earth line is not properly connected to the earth side, the safety device described above cannot operate properly, and even if the ceramic heater is cracked and the heater wiring is exposed in water, there is a leakage current. There was a case where it could not be prevented sufficiently. Also,
Since the safety device instantaneously stops the supply of the current when a large current flows and a large current flows, it is impossible to prevent the occurrence of the leakage.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a ceramic heater and a ceramic unit capable of surely preventing electric leakage.

[0005]

In order to achieve the above-mentioned object, the ceramic heater according to claim 1 is a ceramic heater comprising a ceramic layer containing a heater wiring, and the crack detection is provided in the ceramic layer. Wiring for
The technical feature is to have.

A ceramic heater according to a second aspect is characterized in that, in the first aspect, the crack detection wiring and the heater wiring are arranged between the same ceramic layers.

A ceramic heater according to a third aspect of the present invention is characterized in that, in the first aspect, the crack detection wiring is arranged on an upper surface of a ceramic layer containing the heater wiring.

A ceramic heater according to a fourth aspect of the present invention is characterized in that, in the third aspect, the crack detection wiring is arranged on the pattern of the heater wiring.

In order to achieve the above object, in the ceramic heater unit according to a fifth aspect of the present invention, there is provided a ceramic heater comprising a ceramic layer containing a heater wire, the crack detecting wire being provided in the ceramic layer, A technical feature is that a crack detecting means for detecting a crack in the ceramic layer due to a break in the crack detecting wiring is provided.

A ceramic heater unit according to a sixth aspect of the present invention is characterized in that, in the fifth aspect, the crack detection wiring and the heater wiring are arranged between the same ceramic layers.

According to a seventh aspect of the present invention, there is provided the ceramic heater unit according to the fifth aspect, wherein the crack detecting wiring is arranged on the upper surface of the ceramic layer containing the heater wiring.

A ceramic heater unit according to a fourth aspect of the present invention is characterized in that, in the seventh aspect, the crack detection wiring is arranged on the pattern of the heater wiring.

[0013]

According to the first aspect of the present invention, when the ceramic layer is cracked and the heater wiring is exposed, the crack detection wiring is broken due to the cracking of the ceramic layer, and an external wire is recognized as an electrical break. Can be made.

In the second aspect of the invention, since the crack detection wiring and the heater wiring are arranged between the same ceramic layers, it is not necessary to provide a ceramic layer for burying the crack detection wiring. Therefore, the ceramic heater can be constructed at low cost.

According to the third aspect of the present invention, the crack detection wiring is arranged between the ceramic layer different from the heater wiring, so that the crack detection wiring can be freely arranged.

In the structure of claim 4, since the crack detection wiring is arranged on the pattern of the heater wiring, the crack detection wiring is always broken when the ceramic layer is broken and the heater wiring is exposed. Therefore, it is possible to reliably detect the exposure of the heater wiring.

In the structure of claim 5, when the ceramic layer is cracked to expose the heater wiring, the crack detection wiring is disconnected due to the cracking of the ceramic layer. The break detecting means detects the disconnection of the break detecting wire.

In the structure of claim 6, since the crack detection wiring and the heater wiring are arranged between the same ceramic layers, it is not necessary to provide a ceramic layer for burying the crack detection wiring. Therefore, the ceramic heater can be constructed at low cost.

In the structure of claim 7, since the crack detecting wiring is arranged between the ceramic layer different from the heater wiring, the crack detecting wiring can be freely arranged.

In the structure of claim 8, since the crack detection wiring is arranged on the heater wiring pattern, when the ceramic layer is cracked and the heater wiring is exposed, the crack detection wiring is always broken. Therefore, it is possible to reliably detect the exposure of the heater wiring.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments embodying the present invention will be described below with reference to the drawings. FIG. 1 shows a ceramic heater according to a first embodiment of the present invention with a part cut away. The ceramic heater 10 is formed by arranging three layers of ceramic layers 12, 14, 16 on the outer circumference of a hollow ceramic porcelain tube 30. The heater wiring 20 is arranged between the first ceramic layer 12 and the second ceramic layer 14. In addition, the crack detection wiring 22 is provided between the second ceramic layer 14 and the third ceramic layer 16.
Are arranged. On the outer periphery of the ceramic heater 10,
A flange 32 is attached. Above the flange 32, terminals 20a, 20 for connection to the heater wiring 20 are provided.
b is attached, and terminals 22a and 22b for connecting to the crack detection wiring 22 are provided on the back surface in the figure.

The ceramic heater of the first embodiment is used for keeping the hot water of the bath at a temperature at which it can be bathed at all times, and is arranged in a purification tank (not shown) for pumping the hot water of the bath and purifying it with ozone. . This ceramic heater 1
0 is immersed in the hot water of the purification tank by inserting the lower portion from the flange 32 through the through hole formed in the upper surface of the purification tank, and the current flowing in the heater wiring 20 causes the current to flow. It is configured to heat hot water.

Next, a method of manufacturing the ceramic heater of the first embodiment will be described with reference to FIGS. First, a method of manufacturing the first, second and third ceramic layers 12, 14 and 16 will be described. 2% MgO in alumina powder
(Weight ratio, same below), CaO ₂ % and SiO ₂ 4% are mixed, wet pulverized in a ball mill for 50 to 80 hours, and then dehydrated and dried. To this powder, isobutyl methacrylate 3%, butyl ester 3%, nitrocellulose 1
%, Dioctyl phthalate 0.5%, trichlorethylene and n-butanol as solvents, and mixed in a ball mill to form a fluid slurry. This is degassed under reduced pressure, then poured out in a plate shape and gradually cooled to diffuse the solvent, and the first and second ceramic layers 12 and 14 having a thickness of 0.5 mm are formed as shown in FIG. 3 (A). Then, the second alumina green sheets 12γ, 14γ and the third alumina green sheet 16γ having a thickness of 0.05 mm to be the third ceramic layer 16 are formed.

Then, in order to form the crack detection wiring 22, tungsten powder is slurried to form a metallized ink. This tungsten metallized ink is screen-printed on the second alumina green sheet 14γ to form a metal paste layer 22γ. FIG. 2 (A)
The second alumina green sheet 14 shown in FIG.
The top view which looked at (gamma) along the C arrow is shown. here,
FIG. 3A corresponds to the EE cross section of FIG.

Then, in order to form the heater wiring 20,
A high resistance metallized ink is formed by mixing a large amount of impurities such as alumina into tungsten powder to form a slurry. This tungsten metallized ink is screen-printed on the first alumina green sheet 12γ to form a metal paste layer 20γ. In FIG. 2 (B), FIG.
The top view which looked at the 1st alumina green sheet 12g shown to (A) along the D arrow is shown. 2A and FIG.
As can be seen from (B), in the first embodiment, the wiring pattern of the metal paste layer 22γ forming the crack detection wiring 22 is located immediately above the wiring pattern of the metal paste layer 20γ forming the heater wiring 20. Has been adjusted to.

Then, the first, second and third green sheets 12γ, 14γ and 16γ are thermocompression bonded as shown in FIG. 3 (B). Then, through holes 40a, 40b for forming terminals 20a, 20b for connection from the heater wiring are bored at one end of the thermocompression bonded alumina green sheets 12γ, 14γ, 16γ, and crack detection is performed. Through holes 42a and 42b for forming the terminals 22a and 22b of the wiring 22 are bored and the through holes 40a, 40b, 42a and 42b are filled with metallized ink for terminals. The alumina green sheets 12γ, 14γ, 16γ thus laminated are wound around the ceramic porcelain tube 30 shown in FIG.
Simultaneous firing is performed in a non-oxygen atmosphere at 600 ° C. A glass-made flange 32 shown in FIG. 1 is attached to the ceramic heater formed by firing, and the terminals 20a, 2
After nickel plating is applied to 0b, 22a, and 22b, a lead wire is soldered to the terminal to complete the ceramic heater.

Subsequently, the ceramic unit 11 having the crack detection circuit for the ceramic heater according to the present embodiment.
0 will be described with reference to FIG. The detection circuit 82, which is one of the crack detection means, includes a gate A1, a resistor R1 and a transistor TR1. The output of TR1 turns on the power supply of AC100V to the power supply circuit 80.
It is configured to control the relay RE1 that turns off. The power supply circuit 80 is connected to the AC100 via the relay RE1.
When commercial power of V is supplied, it is stepped down to 24V and then applied to the heater wiring 20 of the ceramic heater 10,
The bath water described above is heated.

On the other hand, DC5V is supplied to one input terminal A1a of the gate A1 of the detection circuit 82, and this potential is also supplied to the terminal 22a side of the crack detection wiring 22. On the other hand, the potential lowered by the crack detection wiring 22 is applied to the other input terminal A1b of the gate A1 connected to the terminal 22b.

Here, the ceramic heater unit 110
Is operating normally, that is, when the ceramic layer 16 shown in FIG. 1 is not cracked and the crack detection wiring 22 is not broken, the input terminal A1b of the gate A1 is compared with the input terminal A1a. Then, a low potential is input, and the gate A1 outputs a high level. As a result, the transistor TR1 is energized, the relay RE1 is turned on, and power of AC 100 V is supplied to the power supply circuit 80.

On the other hand, when bubbles in the water or foreign matter in the hot water adhere to the surface of the third ceramic layer 16 and only the temperature of that portion rises and the third ceramic layer 16 is cracked, that is, when heat is generated. When the third ceramic layer 16 is cracked by the impact, the heater wiring 20 may come into contact with the hot water and continue to leak if the operation is continued. Third ceramic layer 16
When cracks occur in the cracks, the crack detection wiring 22 is broken. Due to the disconnection of the crack detection wiring 22, the gate A
The same potential as that of the input terminal A1a is applied to the first input terminal A1b. As a result, the output of the gate A1 becomes low level, the conduction of the transistor TR1 is stopped, and the relay R1
E1 is turned off, and the power supply to the power supply circuit 80 is interrupted.

In the first embodiment, when the surface of the ceramic heater is cracked due to thermal shock or the like, the crack detection wiring 2 is always used.
Since No. 2 is cut off, the supply of electric power to the heater wiring 20 side can be instantaneously stopped to prevent electric leakage. Here, when water reaches the heater wiring 20 earlier than when the crack detection wiring 22 is cut, it may theoretically be considered that electric leakage occurs instantaneously, but cracks due to thermal shock are usually small. Yes, the first ceramic layer 16 disposed on the surface, and
Since it takes time for the water to reach the heater wiring 20 through the second ceramic layer 14, no electric leakage occurs instantly.

Further, in this first embodiment, FIG.
As described above with reference to FIGS. 2A and 2B, since the crack detection wiring 22 is arranged immediately above the pattern of the heater wiring 20, the crack detection wiring 22 is positioned below the crack detection wiring 22 and Second ceramic layer 14 carrying wiring 20
Is cracked and the heater wiring 20 is exposed,
The crack detection wiring 22 is always disconnected. Therefore, before the heater wiring 20 is exposed in water, it is possible to reliably detect the crack and stop the power supply to the heater wiring 20.

Next, a modified example of the first embodiment will be described with reference to FIGS. In the configuration example described above with reference to FIG. 1, the crack detection wiring 22 and the heater wiring 20.
, And were arranged between ceramic layers different from each other, but in this modified example, as shown in FIG.
2 and the heater wiring 20 are arranged between the second ceramic layer 14 and the first ceramic layer 12.

FIG. 6A shows green sheets 14γ and 12γ forming the ceramic heater according to the modified example. Further, FIG. 6 (B) shows a state of the green sheet 12γ shown in FIG. 6 (A) viewed from the F side. This ceramic heater is a ceramic insulator tube 30 shown in FIG.
A green sheet 14γ that constitutes the second ceramic layer 14 and a green sheet 12γ that constitutes the first ceramic layer 12 are wound around the outer periphery of and are fired. In this modification, the metal paste layer 20γ forming the heater wiring 20 is arranged on the green sheet 12γ forming the first ceramic layer 12, and the crack detection wiring 22 is formed so as to surround the metal paste layer 20γ. Metal paste layer 22
γ is arranged.

Here, the ceramic heater 10 shown in FIG.
The second ceramic layer 14 disposed on the surface
When a crack is generated in the crack, the crack reaches the peripheral portion. In other words, if a crack occurs in the central portion of the second ceramic layer 14, this crack will almost certainly extend to the peripheral portion. Here, when the crack extends to the peripheral portion, the crack detection wiring 22 is broken. The detection circuit 82 detects the disconnection of the crack detection wiring 22 as described above, and the power supply to the heater wiring 20 is stopped. The modified example shown in FIG. 5 is characterized in that the manufacturing cost is low and the thermal conductivity is high because the third ceramic layer is omitted.

Next, a second embodiment of the present invention will be described with reference to FIGS. 7 and 8. In the above-described embodiment, the example in which the present invention is applied to the cylindrical ceramic heater is given, but in the second embodiment, the present invention is applied to the plate-shaped ceramic heater. As shown in FIG. 7, the ceramic heater 110 according to the second embodiment has first, second, and third surfaces on the front surface (the front surface in the drawing) and the back surface (the back surface in the drawing) of the ceramic plate 130. Third three-layer ceramic layer 1
2, 14, 16 are arranged. First ceramic layer 12
The heater wiring 20 is disposed between the second ceramic layer 14 and the second ceramic layer 14, and the crack detection wiring 22 is disposed between the second ceramic layer 14 and the third ceramic layer 16. . Also in this second embodiment, FIG.
Similar to the first embodiment described above with reference to FIG. (B), the crack detection wiring 22 is arranged immediately above the pattern of the heater wiring 20.

Also in this second embodiment, when bubbles in water or foreign matter in hot water adhere to the surface of the third ceramic layer 16 and only the temperature of the portion increases, the third ceramic layer 16 is cracked. Disconnection occurs in the crack detection wiring 22. When the detection circuit 82 described above with reference to FIG. 4 detects the disconnection of the crack detection wiring 22, the power supply circuit 8
The power supply to 0 is interrupted.

FIG. 8 shows the ceramic heater 11 shown in FIG.
0 shows a modified example. In the configuration example described above with reference to FIG. 7, the crack detection wiring 22 and the heater wiring 20 are arranged between different ceramic layers, but in this modified example, as shown in FIG. The heater wiring 20 and the heater wiring 20 are disposed between the first ceramic layer 12 and the second ceramic layer 14. Also in this modified example, when a crack is formed in the second ceramic layer 14 disposed on the surface, the crack reaches the peripheral portion and causes a break in the crack detection wiring 22. The detection circuit 82 detects the disconnection of the crack detection wiring 22 and stops the power supply to the heater wiring 20.

In the above-described embodiment, a ceramic material containing alumina as a main component is used as the ceramic constituting the ceramic layer, but various ceramic materials such as AlN, glass ceramic, SiC, mullite, glass ceramic are used. Can be adopted. Further, the material of the metal paste layer forming the heater wiring and the crack detection wiring may be appropriately selected according to the ceramic material.
Tungsten, molybdenum, copper, silver or the like can be used. Further, in the above-described embodiment, the ceramic heater used to heat the hot water in the bath is described as an example, but the present invention can be suitably applied to the ceramic heater that heats various liquids having conductivity. Although the detection circuit is composed of a discrete circuit in this embodiment, it is possible to detect the breakage of the crack detection wiring by various devices such as an IC.

[0040]

As described above, according to the ceramic heater and the ceramic unit of the present invention, the power supply to the heater wiring is stopped when the ceramic layer is cracked, so that it is possible to prevent the electric leakage. . Also, crack detection can be realized with a simple and inexpensive structure.

[Brief description of drawings]

FIG. 1 is a perspective view showing a ceramic heater according to a first embodiment of the present invention.

2 is a plan view of a green sheet constituting the ceramic heater shown in FIG. 1, FIG. 2 (A) is a C arrow view of the second green sheet shown in FIG. 3 (A), and FIG. FIG. 4 is a view on arrow D of the first green sheet shown in FIG.

3A and 3B are vertical cross-sectional views of a green sheet constituting the ceramic heater shown in FIG. 1, FIG. 3A showing a state before lamination, and FIG. 3B showing a state in which they are laminated.

FIG. 4 is a circuit diagram of a power supply circuit and a detection circuit of the ceramic heater unit according to the first embodiment.

FIG. 5 is a perspective view showing a ceramic heater according to a modification of the first embodiment of the present invention.

FIG. 6 shows a green sheet that constitutes the ceramic heater shown in FIG. 5, FIG. 6 (A) is a vertical cross-sectional view of the green sheet, and FIG. 6 (B) is a view on arrow F of FIG. 6 (A). is there.

FIG. 7 is a perspective view of a ceramic heater according to a second embodiment of the present invention.

FIG. 8 is a perspective view of a ceramic heater according to a modified example of the second embodiment of the present invention.

[Explanation of symbols]

 10 Ceramic Heater 12 First Ceramic Layer 14 Second Ceramic Layer 16 Third Ceramic Layer 20 Heater Wiring 22 Crack Detection Wiring 80 Power Circuit 82 Detection Circuit (Crack Detection Means) 110 Ceramic Unit

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[Procedure amendment]

[Submission date] May 28, 1996

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] Name of invention

[Correction method] Change

[Correction contents]

Title: Ceramic heater and ceramic heater unit

Claims (8)

[Claims] 1. A ceramic heater comprising a ceramic layer containing a heater wiring, comprising: a crack detection wiring disposed in the ceramic layer. 2. The ceramic heater according to claim 1, wherein the crack detection wire and the heater wire are arranged between the same ceramic layers. 3. The ceramic heater according to claim 1, wherein the crack detection wiring is arranged on an upper surface of a ceramic layer containing the heater wiring. 4. The crack detection wiring is arranged on the heater wiring pattern.
Ceramic heater. 5. A ceramic heater comprising a ceramic layer containing a heater wiring, the crack detecting wiring being disposed in the ceramic layer, and a crack for detecting a crack in the ceramic layer by disconnection of the crack detecting wiring. A ceramic heater unit comprising a detecting means. 6. The ceramic heater unit according to claim 5, wherein the crack detection wiring and the heater wiring are arranged between the same ceramic layers. 7. The ceramic heater unit according to claim 5, wherein the crack detection wiring is arranged on an upper surface of a ceramic layer containing the heater wiring. 8. The crack detection wiring is arranged on a pattern of the heater wiring.
Ceramic heater unit.