JP2001284030A - Pipe heater and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pipe heater and its manufacturing method having a glass insulating layer of a high heat-resistant and insulation-proof property. SOLUTION: A base material pipe 3 of the pipe heater 1 is made of ferrous alloy containing chromium 10 to 30 wt.%, and aluminum 0.05 to 7 wt.% or silicon 0.05 to 5 wt.%, and on the surface of base material pipe 3, a coating 15 that does not substantially contain iron oxide is formed. An adhesive property between the surface of base material pipe 3 and the glass insulating layer 5 becomes higher by forming the coating 15. In addition, this prevents iron component from dispersing from the base material pipe 3 into the glass insulating layer 5, and prevents a reduction of insulation properties of the glass insulating layer 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pipe heater for heating a liquid passing therethrough and a method for manufacturing the same.

[0002]

2. Description of the Related Art The present inventors have disclosed in Japanese Patent Application No. 11-22121.
No. 5 proposes the following pipe heater manufacturing method. First, an insulating glass (Microcircuit Ma, manufactured by DUPONT Co., Ltd.) having a thermal expansion coefficient similar to that of stainless steel is placed on a base pipe made of stainless steel (SUS430 or the like).
A glass insulating layer composed of GLAZE3500N (terial) is formed by screen printing or the like. further,
On the glass insulating layer, a heating resistor such as silver palladium is formed by screen printing or the like. An insulating protective layer made of insulating glass is formed on the surface of the heating resistor by screen printing or the like. Both ends of the heating resistor are located outside the insulating protective layer, and serve as electrodes made of silver or the like to form terminals. When a voltage is applied between these terminals, the heating resistor generates heat and acts as a heater.

[0003]

In the above method, the glass insulating layer is formed on the entire surface of the base pipe by screen printing. This glass insulating layer generally needs to have a thickness of about 100 μm from the viewpoint of ensuring the withstand voltage. In order to form a glass insulating layer of this thickness on a substrate pipe by screen printing, the number of times of printing and baking is 3 to 5
Times, which reduces productivity. Further, when screen printing is performed, the film thickness varies between a printing start portion and a printing end portion.

[0004] When screen printing is performed, a paste resin is mixed with a binder resin such as acryl for improving the adhesion to the substrate pipe. In this case, if degreasing is performed at a high temperature, the compactness after sintering is poor,
The insulating property of the glass insulating layer decreases.

[0005] The present invention has been made in view of the above problems, and has as its object to provide a pipe heater which has high heat generation efficiency and is easy to manufacture, and a method of manufacturing the same. In particular, it is an object of the present invention to provide a pipe heater having a glass insulating layer having high heat resistance and high insulation resistance, and a method for manufacturing the same.

[0006]

Means for Solving the Problems To solve the above problems, a pipe heater according to the present invention comprises: a pipe-shaped base material; a glass insulating layer formed on the surface of the base material; A thin-film heating resistor selectively formed so as to draw a pattern; a protection layer formed on the heating resistor and the insulating layer; and a plurality of electrodes connected to ends of the heating resistor. A plurality of terminals connected to the electrodes, wherein a voltage is applied between the terminals, and the pipe heater heats a liquid passing through the inside of the base material; 30% by weight, and 0.05 to 7% by weight of aluminum or 0.05 to 5% by weight of silicon;
And a film substantially free of iron oxide is formed on the surface of the base material.

[0007] By forming a film made of aluminum oxide or an oxide having a low degree of dissociation of oxygen partial pressure and not containing an iron oxide film on the surface of a metal substrate, the adhesion between the substrate surface and the glass insulating layer is improved. Will be higher. In addition, it is possible to prevent iron from diffusing from the base material into the glass insulating layer, and to prevent a decrease in insulating properties of the glass insulating layer. The adhesion between this film and the glass insulation layer is
The adhesion is higher than the adhesion between the base material and the glass insulating layer, and the adhesion can be improved by repeating heating at a high temperature.

[0008] A method for manufacturing a pipe heater according to an embodiment of the present invention includes:
A pipe-shaped substrate, a glass insulating layer formed on the surface of the substrate, a thin-film heating resistor selectively formed so as to draw a pattern on the insulating layer, A protection layer formed on the insulating layer; a plurality of electrodes connected to ends of the heating resistor; and a plurality of terminals connected to the electrodes, wherein a voltage is applied between the terminals. A method of manufacturing a pipe heater for heating a liquid passing through the inside of the base material; using a stainless steel material for the base material, and forming the insulating layer on the surface of the base material by an electrophoretic electrodeposition method. It is characterized by the following.

According to another aspect of the present invention, there is provided a method of manufacturing a pipe heater, comprising: a pipe-shaped substrate; a glass insulating layer formed on a surface of the substrate; and selectively drawing a pattern on the insulating layer. A thin-film heating resistor formed; a protection layer formed on the heating resistor and the insulating layer; a plurality of electrodes connected to ends of the heating resistor; and a plurality of electrodes connected to the electrodes. And a plurality of terminals, wherein a voltage is applied between the terminals, and a method for manufacturing a pipe heater for heating a liquid passing through the inside of the base material; , Aluminum 0.05 ~
An iron-based alloy containing 7% by weight or 0.05 to 5% by weight of silicon is used, a film substantially free of iron oxide is formed on the surface of the base material, and the insulating layer is formed by electrophoretic deposition. It is characterized by being formed on the surface of the substrate by a method.

[0010] Since the glass insulating layer is formed by the electrophoretic electrodeposition method, a uniform and sufficient thickness can be easily formed. Therefore, the heating resistor can be uniformly arranged on the surface of the glass insulating layer, and the liquid passing through the inside of the base pipe can be uniformly heated. Further, the size of the base pipe can be reduced. Furthermore, since it is not necessary to mix a binder resin when forming the glass insulating layer, a dense insulating layer is formed, and the insulating property of the glass insulating layer is improved.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a side sectional view showing a structure of a pipe heater according to an embodiment of the present invention. The pipe heater 1 includes a base pipe 3, a glass insulating layer 5 formed on the surface of the base pipe 3, a strip-shaped heating resistor 7 arranged in a pattern on the glass insulating layer 5, An insulating protective layer 9 covering the insulating layer 5 and the heating resistor 7; conductor films 11 (electrodes) connected to both ends of the heating resistor 7;
Is connected to the terminal 13. A coating 15 is formed on the surface of the base pipe 3.

A method for manufacturing the pipe heater 1 will be described below. An alloy consisting of 10 to 30% by weight of chromium, the balance of iron and unavoidable impurities, and 0.05 to 7% by weight of aluminum or 0.05 to 5% by weight of silicon is used.
A 6 mm base pipe 3 was produced. This substrate pipe 3
Was subjected to a heat treatment in a reducing atmosphere containing hydrogen to form a film 15 on the surface of the substrate pipe 3. This film 15 has a thickness of 1
It has a dense amorphous structure mainly containing aluminum oxide without containing iron and iron oxide at a temperature of 00 to 200 °, and exhibits semiconductor-like electric conductivity.

As a material for the base pipe 3, stainless steel such as SUS444, which has a low coefficient of thermal expansion and excellent corrosion resistance, is preferable because it allows a liquid to pass therethrough while being heated at a high temperature. In addition, SU which has excellent workability and corrosion resistance
S304 is also preferable.

The glass insulating layer 5 is made of a glass material having the same thermal expansion coefficient as that of the base pipe 3. This insulating glass was stirred with an alcohol in a ball mill for 20 hours or more and pulverized, and slurried to an average particle size of 1 to 5 μm to prepare a glass suspension.

While circulating the glass suspension in the electrolytic cell, a counter electrode was arranged on the outer periphery of the electrolytic cell,
The substrate pipe 3 on which 5 was formed was immersed in the glass suspension. At this time, the distance between the base material pipe 3 and each electrode is 15 to 2
0 mm. Then, the substrate pipe 3 was set to a negative voltage, the counter electrode was set to a positive voltage, and a voltage of 300 V DC was applied for 6 seconds.
Thus, crystallized glass particles were precipitated on the surface of the base pipe 3. Since the crystallized glass has a heat resistance temperature of 900 ° C. or higher, a heating resistor such as silver or a silver-palladium alloy which is sintered at 800 ° C. or higher can be formed on the glass insulating layer 5. Next, after drying the substrate pipe 3, 850
Air sintering was performed at 10 ° C. for 10 minutes to form a glass insulating layer 5 on the film 15. The thickness of the glass insulating layer 5 is 120 μm.
m. In addition, when the insulating glass layer is formed on the inner surface of the base pipe 3 when the base pipe 3 is immersed in the glass suspension, the heat transfer coefficient is reduced, and cracks are formed due to thermal shock and may be separated. There is. Therefore, it is preferable to close both ends of the base pipe 3 so that the glass material does not enter the base of the base pipe 3.

On the glass insulating layer 5, a belt-shaped heating resistor 7 having a predetermined pattern was formed by transfer printing or screen printing and sintered. The heating resistor 7 is made of silver or a silver-palladium alloy, and has a sheet resistance of 20 to 50.
0 mΩ / □. The thickness of the heating resistor 7 is 10 μm.
It is. In order to connect to both ends of this heating resistor 7,
The conductor film 11 was formed by screen printing or transfer printing and sintering. The conductor film 11 is formed by mixing glass with silver or a silver-palladium alloy to form a paste, and has a sheet resistance of 10 mΩ / □. The thickness of the conductor film 11 is 10 μm.
m. A power supply terminal 13 is connected to the other end of each conductive film 11.
Was formed.

An insulating protection layer 9 was formed on the heating resistor 7 and the glass insulating layer 5 by transfer printing or screen printing. The insulating protective layer 9 is made of the same glass material as the glass insulating layer 5 or an amorphous glass material. When an amorphous glass material is used, insulation can be ensured even when the film thickness is reduced.

[0018]

As apparent from the above description, according to the present invention, the surface of the metal base pipe is made of aluminum oxide or an oxide having a low degree of dissociation of oxygen partial pressure, and does not include an iron oxide film. By forming the film, the denseness between the surface of the base material and the glass insulating layer is increased, and the insulating property of the glass insulating layer is prevented from lowering. Further, since the glass insulating layer is formed by the electrophoretic electrodeposition method, a uniform and sufficient thickness can be easily formed, and the size of the base pipe can be reduced. Further, since the glass insulating layer is formed of crystallized glass, the heat resistance is high, and the thermal cycle resistance is also improved.

[Brief description of the drawings]

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

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Pipe heater 3 Base pipe 5 Glass insulating layer 7 Heating resistor 9 Insulating protective layer 11 Conductive film 13 Terminal 15 Film

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Takahiro Ohashi 2-1-1 Nakajima, Kokurakita-ku, Kitakyushu-shi, Fukuoka Prefecture (72) Inventor Makoto Hatakeyama 2-1-1 Nakajima, Kokurakita-ku, Kitakyushu-shi, Fukuoka ( 72) Inventor Koji Mine 2-1-1 Nakajima, Kokurakita-ku, Kitakyushu-shi, Fukuoka Prefecture (72) Inventor Yasuo Hamada 2-1-1 Nakajima, Kokurakita-ku, Kitakyushu-shi, Fukuoka F-term (reference) 3K092 PP11 QA02 QB02 QB31 QB74 QB76 QC25 QC38 QC42 QC43 RA03 RD03 RD16 RD26 RD27 TT37 VV06 VV35

Claims (3)

[Claims] 1. A pipe-shaped base material, a glass insulating layer formed on a surface of the base material, a thin-film heating resistor selectively formed so as to draw a pattern on the insulating layer, A protection layer formed on the heating resistor and the insulating layer; a plurality of electrodes connected to ends of the heating resistor; and a plurality of terminals connected to the electrodes. A pipe heater for heating a liquid passing through the inside of the base material by applying a voltage to the base material;
A pipe heater comprising an iron-based alloy containing 7% by weight or 0.05 to 5% by weight of silicon, wherein a film substantially containing no iron oxide is formed on the surface of the base material. 2. A pipe-shaped base material, a glass insulating layer formed on a surface of the base material, a thin-film heating resistor selectively formed on the insulating layer so as to draw a pattern, A protection layer formed on the heating resistor and the insulating layer; a plurality of electrodes connected to ends of the heating resistor; and a plurality of terminals connected to the electrodes. A pipe heater for heating a liquid passing through the inside of the base material by applying a voltage to the base material; using a stainless steel material for the base material, and forming the insulating layer on the base material by electrophoretic electrodeposition. A method for manufacturing a pipe heater, comprising: forming a pipe heater on a surface of a pipe heater; 3. A pipe-shaped substrate, a glass insulating layer formed on the surface of the substrate, a thin-film heating resistor selectively formed on the insulating layer so as to draw a pattern, A protection layer formed on the heating resistor and the insulating layer; a plurality of electrodes connected to ends of the heating resistor; and a plurality of terminals connected to the electrodes. A method for producing a pipe heater for heating a liquid passing through the inside of the base material by applying a voltage to the base material; 10-30% by weight of chromium and 0.05-7% by weight of aluminum or silicon as the base material An iron-based alloy containing 0.05 to 5% by weight is used, a film substantially free of iron oxide is formed on the surface of the substrate, and the insulating layer is formed on the substrate by electrophoretic electrodeposition. A method for manufacturing a pipe heater, comprising: forming a pipe heater on a surface of a pipe heater;