JPS58121588A - Cylindrical ceramic heater - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] Regarding Mick Heater.

Conventional cylindrical ceramic heaters have been used in internal combustion engine glove lugs, soldering irons, etc. because they are thin rod-shaped, compact, and have high heat resistance.

As shown in the cross-sectional view in Figure 1, these structures are made by printing a wiring pattern made of an inorganic conductive material on the main surface of a ceramic cylinder using a thick film method using a silk screen. Ceramic green sheet or paste 3 made separately for the surface of body 1 and wiring pattern 3
As shown in Figure 1, the wiring pattern λ spreads thinly over the surface of the cylindrical body and cannot be sufficiently thick, so it becomes an extremely thin layer especially at the edges of the wiring pattern, reducing the cross-sectional area. It had a relatively large surface area. Furthermore, it is preferable to make the coating layer 3 as thin as possible in order to improve heat transfer, but if it is made too thin, the air will penetrate through its pores and via holes at high temperatures, and oxygen will be delayed in the wiring pattern, causing oxidation and reducing the resistance. When Si3N4 and SiC are used as ceramics for the purpose of improving thermal shock resistance, it is difficult to sinter them densely, and in S L3N4, N2
Since the inorganic conductive material used for the wiring pattern is sintered in a gas, it has a high electrical resistance because it uses nitrides, carbides, and silicides of various metals, and the wiring pattern occupies a large area, so it is difficult to absorb oxygen from the atmosphere. There was a problem in that oxidation occurred and the resistance value increased.

The present invention has been made to improve this problem, and as shown in the cross-sectional view of FIG. 1, the cylindrical body // is the groove /! It consists of an inorganic conductive material /2 filled in the groove, a ceramic layer /3 covering it, and a pair of electrodes (not shown), and the heating pattern is formed in the small groove on the opening surface. Because it is housed, the surface area is small compared to the cross-sectional area, which increases oxidation resistance, reduces electrical resistance, and increases adhesive strength by increasing the bonding area /4' between the cylindrical body // and the coating layer 13. be.

Next, a specific method for manufacturing the ceramic heater of the present invention will be described. It is necessary that the cylindrical body // and the covering layer /3 be substantially insulating materials such as alumina porcelain or 813N4 r SIC. The cylindrical body // is made into a clay by adding an extrusion binder such as oil or fat to these base powders and kneading it, and is a circular base with a convex part /r corresponding to a groove on the inner periphery (third round base). After extruding the paste into the shape shown in Fig. 1 under high pressure using the inorganic conductive material and a well-known organic binder, the paste is extruded into the groove using a nozzle having an outlet smaller than one groove. Fill the body recess Tel / 3. This inorganic conductive material is made of refractory metals such as W and Mo, and
Tj +Zr, filed under No. 3-1141772,
Hf +La, V+Nb +Ta, Cr, Mo
, an inorganic conductive material that is a mixture of nitrides and oxides such as W and is used for forming a Si:+N4 green sheet into a metal frame, and patent application filed under Shota t-'I'l #33, ft Tj,
Zr, f-If +La+V+Nb +Ta +C
An inorganic conductive material used for the SL+N4 green sheet, which is a mixture of nitride such as r + Mo 1w with carbide and a binding material of iron group metal and oxide, may also be used. For SiC cylindrical bodies, a material that forms a metallized surface using a powder of Si with a small amount of Fe + Ni and Co has been applied for in Japanese Patent Application No. 1983-1≠723. is available. The covering layer 13 is preferably dense and thin in order to effectively release heat generated by the wiring pattern in a short period of time. For this purpose, Si3N4 with Mgo or Y2O3 added as a solvent, or SiC
A green sheet made by adding C or B to a powder is made into a slurry by adding an organic binder or solvent, and a green sheet manufactured by the doctor blade method or a green sheet formed by the rolling method is bonded by heat, a solvent, or by pressure. be able to. A slurry prepared by adding a well-known organic binder and a solvent may be directly coated on the powder or powder, and the slurry may be dried. At this time, if the inorganic conductive material does not sufficiently fill the recesses of the cylindrical body, it can be pressurized in a vacuum. It is preferable to compress and remove the gap between the inorganic conductive material/2 coating layer/3. Next, after drying, an inorganic conductive material is applied to the end surface of the cylindrical body where the seven ends of the inorganic conductive material are exposed to form an electrode/B. Further, electrodes /4 and # are provided on the side surface of the other end in the groove in which a groove connecting the opposing end surfaces of the inorganic conductive material is formed.

Next, in a non-oxidizing atmosphere, the temperature of the cylindrical body, the inorganic conductive material, and the coating layer is raised to a sintering temperature to form a ceramic heater in which the entire body is integrated. This front view is shown in Figure A, and the side view is shown in Figure B. An example will be explained below with reference to Examples, but the invention is not limited thereto.

Example/α-8rsN4. with average particle size μ. β-8i: +N</
：Add MgO to the Si3N4 powder contained in ：/, mix it in a ball mill, add oil and knead it to make a clay, and form a concave groove on the inner periphery as shown in the perspective view in Figure 3. A cylindrical body 2/2 with a diameter Im and a length ♂0 is extruded by an extrusion die having a convex portion l etc., as shown in a perspective view in Fig.
to form. Next, a concave ts connecting the concave grooves facing the end face,
A cylindrical body 2/ was created by turning 2 O upside down in a press mold. This side view is shown in Fig. 6, where the concave groove /j is the width/kabura and the depth is O! There are a total of r books in this order. Next is TiN! 0%.

Tic/3%, Hl, 20%, Mo/
0% + Al2O33% was mixed and pulverized with pine oil, ethyl cellulose was added and kneaded, and the paste was extruded through a thin nozzle to create a concave IR groove and a concave groove at one end! B was filled with heat generating wiring pattern. Further, at one end, as shown in Figure B, each was connected with a book wiring pattern to form an electrode/6.

Next, α-8i3N4 j 0%, β-
8i3 N4! Add f%(7)■0 to the powder containing O%, add 3% of isobutyl methacrylate, nitrocellulose/%, and 0.3% of dioctyl phthalate, and further add trichlorenalene and n-butanol as a solvent. Mix in a ball mill to form a fluid slurry.

After defoaming under reduced pressure, this was poured onto a plate to remove heat and evaporate the solvent, thereby forming a green sheet with a thickness of 0.3 rrrs. This was attached to the outer surface and/or end surface of the cylindrical body 2 by heat and pressure bonding. A schematic side view of this is shown in Figure B, and a front view is shown in Figure A. After drying, the board, wiring pattern, and coating layer were sintered together by heating to 1100°C in N2. It was designated as ceramic heater-A. Next, the coating layer/,! α-3iC powder containing B of H and C of O
N? oq1.・, Al2O3io It was molded in the same manner as ceramic heater A except that it was made into a fine powder with a composition of o%, and jO
Ceramic heater B was obtained by heating and sintering at 00° C. in N2 atmosphere at atmospheric pressure. Ceramic heater-AR was manufactured in the same manner as A without providing grooves on the substrate.
A ceramic heater BR was manufactured in the same manner as B, and the changes in resistance before and after heating it in the air at / 000°C for 200 hours are shown in Table 1. As shown, the ceramic heater according to the present invention exhibits a long life with little change in resistance even after use at high temperatures, but this is due to the fact that the surface area of the heating element pattern is small compared to the cross-sectional area. This is because it is difficult to be oxidized by oxygen in the atmosphere. Further, as a result of repeating the heat cycle between iooσ°C and room temperature 500 times, cracks occurred between the substrate and the coating layer in AR and BR, but no abnormality occurred in A and B according to the present invention. This is thought to be because the adhesion area between the substrates and the covering layer in A and B is larger than that in conventional products AR and BR.

In addition, if a tubular body with a through hole in the center is used instead of the cylindrical body 21, and a conductive paste is applied and baked on the inner surface of this tubular body and used as one electrode, the heat capacity of the heater is small and it is resistant to rapid heating and cooling. , it is possible to provide a heater with a fast temperature increase rate.

The shape of the groove may also be changed to a U-shape or a 7-shape.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a conventional ceramic heater, FIG. 1 is a sectional view of a ceramic heater of the present invention, FIG. 3 is an extrusion die used in an embodiment, FIG. Figure B is a side view of the example, Figure J is the extruded product of the example, and Figure 2 is a side view of the extruded product with grooves provided on the end surface.

Claims (1)

[Claims] (1) Consisting of a ceramic cylindrical body with grooves on its surface, a heat-generating wiring pattern made of an inorganic conductive material filled in the grooves, a ceramic coating layer covering this, and/or a pair of electrodes. Cylindrical ceramic heater-0 characterized by
(2) The ceramic heater according to claim 1, wherein the ceramic cylindrical body and/or the coating layer are silicon nitride and/or silicon carbide.