JP3199575B2 - 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 heater, and more particularly to a heater immersed in a liquid.

[0002]

2. Description of the Related Art Conventionally, a ceramic heater excellent in corrosion resistance has been used as a heater immersed in a liquid, particularly a highly corrosive liquid such as an acid or an alkali, for heating the liquid.

In this ceramic heater, a heating resistor made of a refractory metal such as tungsten is embedded inside an insulating base made of ceramics having excellent corrosion resistance such as alumina ceramics. By applying power and causing the heating resistor to generate Joule heat, the heat is released to the outside via the insulating base to function as a ceramic heater.

The ceramic heater is usually used together with a temperature sensor for measuring the temperature of a liquid, and electrically connects or disconnects the heating resistor and an external power supply based on temperature data of the liquid measured by the temperature sensor. To maintain the temperature of the liquid within a predetermined range.Specifically, when the temperature sensor senses that the temperature of the liquid has reached the upper limit of the predetermined temperature range due to heating of the ceramic heater, this is The electric connection between the heating resistor and the external power supply is cut off based on the above, the heating by the ceramic heater is stopped, the liquid is cooled naturally, and the temperature of the liquid is lowered. When the temperature sensor detects that the lower limit has been reached, the heating resistor and the external power supply are electrically connected based on this, and the ceramic heater Do to raise the temperature of the liquid by adding heat by, so as to maintain the temperature of the liquid in a predetermined range by repeating these operations at any time.

When the insulating base is made of, for example, alumina ceramics, the ceramic heater is formed into a slurry by adding and mixing an appropriate organic binder and a solvent to a raw material powder of alumina, silica, calcia, magnesia, etc. A ceramic green sheet is obtained by adopting a sheet forming method such as a doctor blade method to obtain a ceramic green sheet, and then a metal paste serving as a heating resistor is printed and applied in a predetermined pattern on the upper surface of the ceramic green sheet. A ceramic green sheet substantially the same as the ceramic green sheet is laminated on the ceramic green sheet on which the metal paste is printed, or the ceramic green sheet is laminated on the upper surface of the ceramic green sheet on which the metal paste is printed. Substantially identical Material powder to obtain a green ceramic body as a ceramic heater by a ceramic paste to the printed coating containing, are fabricated by sintering at a temperature of the last about 1600 ° C. in a reducing atmosphere the raw ceramic body.

When the thickness of the ceramic green sheet constituting the raw ceramic body serving as the ceramic heater is thin, less than about 250 μm, the strength of the ceramic green sheet becomes extremely weak, and the ceramic green sheet generates heat. When an external force is applied to the metal paste after printing the metal paste serving as a resistor, the ceramic green sheet is easily deformed, and cracks and peeling occur in the pattern of the metal paste serving as a heating resistor printed and applied to the ceramic green sheet. As a result, the heating resistor of the ceramic heater obtained by firing the green ceramic body is disconnected. Accordingly, a ceramic green sheet constituting a green ceramic body serving as a ceramic heater has a thickness of about 250 μm or more. As a result, a ceramic heater obtained by firing the green ceramic body is an insulating substrate on which a heating resistor is embedded. Has a thickness of about 250 μm or more.

[0007]

However, this ceramic heater has a large heat capacity since the thickness of the insulating base is as large as about 250 μm or more. Therefore, the heating resistor embedded in the insulating base having a large heat capacity is connected to an external power supply. Even if it is connected to the Joule, Joule heat is generated, and part of the heat is absorbed and stored in the insulating base having a large heat capacity, so it takes time to generate heat at a predetermined temperature as a ceramic heater. Even if the connection is cut off and the Joule heating of the heating resistor is stopped, the heat absorbed and stored in the insulating base having a large heat capacity is released to the outside.

For this reason, the temperature sensor detects that the temperature of the liquid has reached the upper limit of the predetermined temperature range due to the heating of the ceramic heater, and based on this, disconnects the electrical connection between the heating resistor and the external power supply and cuts off the heating resistor. Even if the Joule heating of the body is stopped, the heat absorbed and stored in the insulating base is released, so the heating by the ceramic heater does not stop immediately, the temperature of the liquid exceeds the upper limit, and the liquid is cooled by natural cooling. The temperature sensor senses that the temperature of the heating resistor has reached the lower limit of the predetermined temperature range, and based on this, the heating resistor is electrically connected to an external power supply to generate Joule heat in the heating resistor. It takes time for part of the heat to be absorbed and stored in the insulating base and to generate heat to the predetermined temperature as a ceramic heater, and the temperature of the liquid falls below the lower limit, so that the temperature of the liquid is accurately maintained within the predetermined range. It had the disadvantage that it is difficult to.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned drawbacks, and has as its object to provide a heater capable of accurately maintaining the temperature of a liquid within a predetermined range.

[0010]

SUMMARY OF THE INVENTION The present invention provides a ceramic support member, a pair of electrode members supported at both ends by the ceramic support member, and a pair of electrode members at one end of the pair of electrode members. A heating resistor electrically connected to the heating resistor and a ceramic coating layer formed by a thin film forming method so as to cover one end of a pair of electrodes connected to the heating resistor and the heating resistor; It is characterized by the following.

[0011]

According to the heater of the present invention, a heating resistor is connected to one end of a pair of electrodes protruding from the ceramic supporting member, and the heating resistor is covered with a thin ceramic coating layer. In the case where the heat capacity of the ceramic coating layer covering the heating resistor can be small, as a result, when the heating resistor is electrically connected to an external power supply to cause the heating resistor to generate Joule heat, The heat generated by the heat generating resistor is quickly released to the outside without being absorbed and stored in the ceramic coating layer having a small heat capacity, and at the same time, the electrical connection between the heat generating resistor and the external power supply is cut off to generate Joule heat of the heat generating resistor. Even after the heat is stopped, the heat absorbed and stored in the ceramic coating layer having a small heat capacity is small, so that the heat generation as the heater is immediately stopped.

[0012]

BRIEF DESCRIPTION OF THE DRAWINGS FIG.

FIG. 1 is a sectional view showing an embodiment of a heater according to the present invention, wherein 1 is a ceramic support member, 2 is an electrode body,
Reference numeral 3 denotes a heating resistor.

The ceramic support member 1 is, for example, a rectangular plate made of ceramics having excellent corrosion resistance, such as alumina ceramics, silicon nitride ceramics, and silicon carbide ceramics. Are provided, and a pair of electrode bodies 2 are inserted and brazed in the through hole 1a.

The ceramic supporting member 1 functions to electrically insulate and support the electrode bodies 2 from each other. For example, when the ceramic supporting member 1 is made of alumina ceramics, alumina, silica,
A raw material powder prepared by adding and mixing a suitable binder and a solvent to the raw material powder of calcia, magnesia, etc. is filled into a mold having a shape corresponding to the shape of the ceramic support member 1 and pressed at a constant pressure. After molding,
The compact is manufactured by firing at a temperature of about 1600 ° C.

A metallized metal layer 4 serving as a base metal for brazing the electrode body 2 is adhered to the inner wall of the through hole 1a provided in the ceramic support 1.
A pair of electrode bodies 2 are brazed to the metallized metal layer 4.

The metallized metal layer 4 is made of molybdenum,
A metal paste made of a high melting point metal material such as manganese and obtained by adding and mixing a suitable binder and a solvent to a high melting point metal powder such as molybdenum and manganese is printed in the through hole 1a of the ceramic support member 1 and printed. About 150
By firing at a temperature of 0 ° C., the ceramic support member 1 is attached in the through hole 1 a.

The pair of electrode bodies 2 to be brazed to the metallized metal layer 4 are, for example, cylindrical rods made of a metal such as platinum, tungsten, molybdenum or the like. The heating resistor 3 is electrically connected to one end of the projection, and the other end thereof is connected to an external power supply as a lead 2a.

The pair of electrode bodies 2 support the heating resistor 3 at a distance from the ceramic support 1 and act to supply power from an external power source to the heating resistor 3. Produced by

The electrode body 2 is connected to the ceramic supporting member 1.
In order to braze the metallized metal layer 4 deposited in the through hole 1a, first, a metal film having excellent wettability with a brazing material R such as nickel or gold is plated on the surface of the metallized metal layer 4 by a plating method. And then the ceramic support member 1
The electrode body 2 is inserted into the through hole 1a, and a brazing material R such as silver brazing is interposed between the metallized metal layer 4 and the electrode body 2, and this is heated to a temperature of about 900 ° C. It is brazed by melting.

The heating resistor 3 connected to one end of the electrode body 2 is a linear body made of a metal such as platinum, tungsten or molybdenum and having a diameter significantly smaller than the diameter of the electrode body 2. When electrically connected to an external power supply via the electrode body 2, Joule heat is generated, and an action of generating heat as a heater is performed.

Since the heating resistor 3 is held apart from the ceramic supporting member 1 by the electrode body 2, even if the heating resistor 3 is connected to an external power source to generate Joule heat, the heat is generated by the ceramic supporting member. 1 is not absorbed and stored, but is discharged outside. The heating resistor 3 is
An ingot of platinum or the like is formed into a predetermined line by applying a conventionally known metal working method, and the electrode body 2 is welded.
Connected to.

The heating resistor 3 and the heating resistor 3
Is connected to a ceramic coating layer 5 having excellent corrosion resistance, such as alumina ceramics, silicon nitride ceramics, and silicon carbide ceramics.

The ceramic coating layer 5 includes a heating resistor 3
And one end of the electrode body 2 to which the heating resistor 3 is connected is electrically insulated from the outside. For example, a thin film forming method such as a conventionally known CVD method, a reactive ion plating method, or a sputtering method is used. The heating resistor 3 and the heating resistor 3
Is attached to one end of the connected electrode body 2 to a thickness of 10 to 100 μm.

Since the ceramic coating layer 5 is applied by a thin film forming method, it can be formed to have a very small thickness, and as a result, its heat capacity can be made very small. Therefore, when an external power supply is electrically connected to the heating resistor 3 to cause the heating resistor 3 to generate Joule heat, the heat is hardly absorbed and stored in the ceramic coating layer 5 having a very small heat capacity. When the Joule heating of the heating resistor 3 is stopped by cutting off the electrical connection between the heating resistor 3 and the external power supply, the ceramic coating layer 5 having an extremely small heat capacity is released.
Since the heat absorbed and stored in the heater is extremely small, the heat generation as a heater stops immediately.

For this reason, the heater of the present invention is used together with a temperature sensor for measuring the temperature of the liquid, and the heating resistor 3 of the heater and the external power supply are electrically connected based on the measurement data of the temperature sensor. When the temperature of the liquid is maintained within a predetermined temperature range by turning off, the temperature sensor detects that the temperature of the liquid has reached the upper limit of the predetermined temperature range by heating the heater, and based on this, the heating resistor is used. 3
When the electrical connection between the heating resistor 3 and the external power supply is cut off and the Joule heating of the heating resistor 3 is stopped, the slight heat absorbed and stored in the ceramic coating layer 5 is immediately released into the liquid and the heating as the heater is immediately performed. The temperature of the liquid does not exceed the upper limit because it stops, and the temperature sensor senses that the temperature of the liquid has reached the lower limit of the predetermined temperature range due to natural cooling,
When the heating resistor 3 and the external power supply are electrically connected based on this to cause the heating resistor 3 to generate Joule heat, the heat is hardly absorbed and stored in the ceramic coating layer 5 in the liquid. Since the liquid is discharged and quickly generates heat to a predetermined temperature as a heater, the temperature of the liquid does not fall below the lower limit, and the temperature of the liquid can be maintained extremely accurately in the predetermined temperature range.

If the thickness of the ceramic coating layer 5 is less than 10 μm, the ceramic coating layer 5 tends to have a pinhole, and when the heating resistor 3 is electrically connected to an external power supply, the ceramic coating layer 5 has a pinhole. Leakage into the liquid is caused through the pinhole, and if the thickness exceeds 100 μm, the heat capacity of the ceramic coating layer 5 becomes large,
When a large amount of heat is absorbed and stored in the ceramic coating layer 5 and the heating resistor 3 is electrically connected to an external power supply to cause the heating resistor 3 to generate Joule heat, the heating resistor 3 generates heat to a predetermined temperature as a heater. In addition, it takes a long time, and when the electrical connection between the heating resistor 3 and the external power supply is cut off and the Joule heating of the heating resistor 3 is stopped, the heat absorbed and stored in the ceramic coating layer 5 tends to be released for a long time. It is in. Therefore, the thickness of the ceramic coating layer 5 is preferably in the range of 10 to 100 μm.

Thus, the heater of the present invention connects the lead portions 2a exposed to the outside of the pair of electrode bodies 2 to an external power source and applies electric power to the heating resistor 3, whereby the heating resistor 3 generates Joule heat and serves as a heater. Will be generated at a predetermined temperature.

[0029]

According to the heater of the present invention, a heating resistor is connected to one end of a pair of electrodes protruding from the ceramic support member, and the heating resistor is thinly formed by a thin film forming method. With the structure in which the heating resistor is coated with the ceramic coating layer, the heat capacity of the ceramic coating layer that covers the heating resistor can be reduced. As a result, when the heating resistor is electrically connected to an external power supply, ,
When the heater quickly generates heat to a predetermined temperature and cuts off the electrical connection between the heat generating resistor and the external power supply, the heat generation as the heater stops immediately. Therefore, the heater of the present invention is used together with a temperature sensor for measuring the temperature of a liquid, and the heating resistor of the heater and the external power supply are electrically connected or disconnected based on the measurement data of the temperature sensor. When the temperature of the liquid is maintained within the predetermined temperature range, the heating of the liquid by the heater can be quickly performed or stopped based on the measurement data of the temperature sensor, and as a result, the temperature of the liquid can be maintained at the predetermined temperature. It can be maintained very accurately in the temperature range.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of a heater according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Ceramic support member 2 ... A pair of electrode body 3 ... Heating resistor 5 ... Ceramic coating layer

Claims (2)

(57) [Claims] 1. A ceramic support member, a pair of electrode bodies supported by the ceramic support member so that both ends protrude, and a heating element electrically connected to the two electrode bodies at one end of the pair of electrode bodies. A thin-film resistor is formed so as to cover one end side of the resistor and a pair of electrode bodies to which the heating resistor and the heating resistor are connected.
A heater comprising a ceramic coating layer applied by a synthetic method . 2. The method according to claim 1, wherein said ceramic coating layer has a thickness of 10 to 1.
The heater according to claim 1, wherein the thickness is 00 µm.