JPH0817558A - Heater - Google Patents

Abstract

PURPOSE:To form a ceramic layer with low heat capacity, quickly transmit calorie of a heating resistor, and provide accurate temperature control of liquid by covering the heating resistor with a thin ceramic layer. CONSTITUTION:A pair of electrodes 2 separate a heating resistor 3 from a ceramic supporting body 1 and support the heating resistor 3, and supplies electric power to the heating resistor 3 from an outside power source. The heating resistor 3 is made of metal such as platinum and wolfram, and is a filament with remarkably smaller diameter than that of the electrode 2, and generates Joule heat by electric power supplied from the outside electric source to functions as a heater. Since the heating resistor 3 is separated from the ceramic supporting member 1 by the electrode 2, even if the heating resistor 3 is connected to the outside power source and Joule heat is generated, heat is radiated to the outside without being absorbed in the ceramic supporting member 1.

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 used by being 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 for heating a liquid which is soaked in a liquid having a strong corrosive property such as acid or alkali.

In this ceramic heater, a heating resistor made of a refractory metal such as tungsten is embedded inside an insulating substrate made of ceramics having excellent corrosion resistance such as alumina ceramics, and the heating resistor is supplied from an external power source. It functions as a ceramic heater by applying electric power to cause Joule heat generation of the heat generating resistor and discharging the heat to the outside through the insulating base.

Further, this ceramic heater is usually used together with a temperature sensor for measuring the temperature of a liquid, and the heating resistor and an external power source are electrically connected or disconnected based on the temperature data of the liquid measured by the temperature sensor. The temperature of the liquid is maintained within a predetermined range by, for example, when the temperature sensor detects that the temperature of the liquid has reached the upper limit of the predetermined temperature range by heating the ceramic heater, Based on the above, the electrical connection between the heating resistor and the external power supply is cut off, 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 of the temperature has been reached, the heating resistor is electrically connected to the external power source based on this, and the ceramic heater is connected. 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.

In the ceramic heater, when the insulating substrate is made of alumina ceramics, for example, alumina powder, silica powder, calcia powder, magnesia powder and the like are mixed with an appropriate organic binder and solvent to form a sludge-like powder. 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 to be a heating resistor is printed and applied in a predetermined pattern on the upper surface of the ceramic green sheet, A ceramic green sheet, which is substantially the same as the ceramic green sheet, is laminated on the ceramic green sheet on which the metal paste is printed and applied, or the ceramic green sheet is formed on the upper surface of the ceramic green sheet on which the metal paste is printed and applied. Substantially the same 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 green ceramic body serving as the ceramic heater is 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 to be the resistor after printing, the ceramic green sheet is easily deformed, and cracks or peeling are generated in the pattern of the metal paste to be the heating resistor printed and applied on the ceramic green sheet. It is generated, and as a result, the heating resistor of the ceramic heater obtained by firing the green ceramic body is broken. Therefore, the ceramic green sheet forming the green ceramic body serving as the ceramic heater has a thickness of about 250 μm or more. As a result, the ceramic heater obtained by firing the green ceramic body is an insulating substrate in 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 because the thickness of the insulating base is as thick as about 250 μm or more. Therefore, the heating resistor embedded in the insulating base having a large heat capacity is used as an external power source. Even if connected to the Joule to generate Joule heat, a part of the heat is absorbed and stored in the insulating substrate having a large heat capacity, so it takes time to generate heat to a predetermined temperature as a ceramic heater. Even if the Joule heat generation of the heat generating resistor is stopped by disconnecting the connection, the heat absorbed and stored in the insulating substrate having a large heat capacity is released to the outside.

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

[0009]

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

[0010]

The present invention is directed to a ceramic support member, a pair of electrode bodies supported by the ceramic support member so that both ends thereof project, and both electrode bodies at one end side of the pair of electrode bodies. It is characterized by comprising a heating resistor electrically connected and a ceramic coating layer covering one end side of the heating resistor and a pair of electrode bodies to which the heating resistor is connected.

[0011]

In the heater of the present invention, the heating resistor is connected to one end of the pair of electrode bodies protruding from the ceramic support member, and the heating resistor is covered with the thin ceramic coating layer. When the heat capacity of the ceramic coating layer that covers the heating resistor can be small, and as a result, when the heating resistor and an external power source are electrically connected to cause Joule heating in the heating resistor, The heat generated by the heating resistor is quickly absorbed and stored in the ceramic coating layer having a small heat capacity, and is quickly released to the outside. At the same time, the electrical connection between the heating resistor and the external power supply is cut off to prevent Joule heat generation of the heating resistor. Even after the heating 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 quickly stopped.

[0012]

The present invention will now be described in detail with reference to the accompanying drawings.

FIG. 1 is a sectional view showing an embodiment of a heater of the present invention, 1 is a ceramic support member, 2 is an electrode body,
Reference numeral 3 is 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, silicon carbide ceramics, and two through holes 1a penetrating from the upper surface to the lower surface. Is provided, and a pair of electrode bodies 2 are inserted and brazed into the through hole 1a.

The ceramic supporting member 1 serves to electrically insulate and support the electrode body 2 from each other. For example, when it is made of alumina ceramics, alumina, silica,
A raw material powder prepared by adding and mixing an appropriate binder and a solvent to raw material powder such as calcia and magnesia is filled in a mold having a shape corresponding to the shape of the ceramic support member 1 and pressed with a constant pressure. After molding and then
It is manufactured by firing the compact at a temperature of about 1600 ° C.

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

The metallized metal layer 4 is made of molybdenum,
A metal paste made of a refractory metal material such as manganese and mixed with a refractory metal powder such as molybdenum or manganese and a suitable binder and a solvent is printed in the through hole 1a of the ceramic support member 1 and is printed. About 150
The ceramic support member 1 is deposited in the through holes 1a by firing at a temperature of 0 ° C.

The pair of electrode bodies 2 brazed to the metallized metal layer 4 are, for example, cylindrical rod-shaped bodies made of a metal such as platinum, tungsten, molybdenum, and the both ends of which are located above and below the ceramic support member 1. It is supported so as to project, and the heating resistor 3 is electrically connected to one end side of the projection, and the external power supply is connected to the other end side as a lead portion 2a.

The pair of electrode bodies 2 support the heating resistor 3 so as to be separated from the ceramic support 1 and supply electric power from an external power source to the heating resistor 3, and the conventionally known metal working method. It is produced by.

The electrode body 2 is attached to the ceramic support 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 the brazing material R such as nickel or gold is plated on the surface of the metallized metal layer 4. 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 braze is interposed between the metallized metal layer 4 and the electrode body 2 and the brazing material R 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 filament 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. By being electrically connected to an external power source through the electrode body 2, Joule heat is generated and heat is generated as a heater.

Since the heating resistor 3 is held apart from the ceramic support 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 support member. No heat is absorbed and stored in 1 and is released to the outside. The heating resistor 3 is
The ingot of platinum or the like is formed into a predetermined filament by applying a conventionally known metal working method, and the electrode body 2 is welded.
Connected to.

Further, the heating resistor 3 and the heating resistor 3
One end side of the electrode body 2 to which is connected is covered with 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 is a heating resistor 3
And a function of electrically insulating one end side of the electrode body 2 to which the heating resistor 3 is connected from the outside, for example, a thin film forming method such as a conventionally known CVD method, reactive ion plating method, sputtering method, or the like. By the heating resistor 3 and the heating resistor 3
Is attached to the one end side of the electrode body 2 connected to each other in a thickness of 10 to 100 μm.

Since the ceramic coating layer 5 is deposited by the thin film forming method, the thickness thereof can be made extremely thin, and as a result, the heat capacity thereof can be made extremely small. Therefore, when an external power source is electrically connected to the heating resistor 3 to cause Joule heating in the heating resistor 3, the heat is hardly absorbed and stored in the ceramic coating layer 5 having an extremely small heat capacity. When the Joule heat generation of the heating resistor 3 is stopped by promptly releasing it to the outside and disconnecting the electrical connection between the heating resistor 3 and the external power source, the ceramic coating layer 5 having an extremely small heat capacity.
Since the amount of heat absorbed and stored in is extremely small, the heat generation as a heater is quickly stopped.

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 3 of the heater is electrically connected to an external power source based on the measurement data of the temperature sensor. When maintaining the temperature of the liquid within the specified temperature range by refusing, the temperature sensor senses that the temperature of the liquid has reached the upper limit of the specified temperature range due to the heating of the heater, and based on this, the heating resistor Three
When the Joule heat generation of the heating resistor 3 is stopped by disconnecting the electrical connection between the heating power source 3 and the external power source, the slight heat absorbed and stored in the ceramic coating layer 5 is promptly released into the liquid, and heating as a heater is immediately performed. The temperature of the liquid does not exceed the upper limit because it stops, and the temperature sensor detects that the temperature of the liquid has reached the lower limit of the predetermined temperature range by natural cooling,
Based on this, when the heating resistor 3 and the external power source are electrically connected to cause Joule heating in the heating resistor 3, the heat is almost absorbed by the ceramic coating layer 5 and is not stored in the liquid. The temperature of the liquid does not fall below the lower limit because it is released and quickly generates heat to a predetermined temperature as a heater, and the temperature of the liquid can be maintained extremely accurately within a 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 pinholes, and when the heating resistor 3 and the external power source are electrically connected, Leakage into the liquid is caused through the pinhole, and when the thickness exceeds 100 μm, the heat capacity of the ceramic coating layer 5 becomes large,
A large amount of heat is absorbed and stored in the ceramic coating layer 5, and when the heating resistor 3 and an external power source are electrically connected to generate Joule heat, the heating resistor 3 is heated to a predetermined temperature as a heater. It takes a long time to do so, and when the Joule heat generation of the heating resistor 3 is stopped by disconnecting the electrical connection between the heating resistor 3 and the external power source, 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, in the heater of the present invention, the lead portions 2a exposed to the outside of the pair of electrode bodies 2 are connected to an external power source and electric power is applied to the heating resistor 3 so that the heating resistor 3 generates Joule heat and serves as a heater. Will generate heat 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 electrode bodies protruding from the ceramic support member, and the heating resistor is covered with a thin ceramic coating layer. Therefore, the heat capacity of the ceramic coating layer that covers the heating resistor can be made small, and as a result, when the heating resistor and an external power source are electrically connected, the heating temperature can be quickly increased to a predetermined temperature as a heater. When the electric resistance between the heating resistor and the external power supply is cut off, the heat generation as a heater is immediately stopped. 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 an external power source are electrically connected or disconnected based on the measurement data of the temperature sensor. When the temperature of the liquid is maintained within a predetermined temperature range, heating of the liquid by the heater can be quickly performed or stopped based on the measurement data of the temperature sensor. It can be maintained very accurately in the temperature range.

[Brief description of drawings]

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

[Explanation of symbols]

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

Claims (2)

[Claims] 1. A ceramic support member, a pair of electrode bodies supported by the ceramic support member so that both ends thereof project, and heat generation electrically connected to both electrode bodies at one end side of the pair of electrode bodies. A heater comprising a resistor and a ceramic coating layer covering one end side of a pair of electrode bodies to which the heating resistor and the heating resistor are connected. 2. The thickness of the ceramic coating layer is 10 to 1
The heater according to claim 1, wherein the heater has a thickness of 00 μm.