JPH01231283A - Manufacture of ceramic heater - Google Patents

Abstract

PURPOSE:To enable arrangement of a heat emitting body in a ceramic heater with a simple work by applying the surface of a Si3N4 compact with a Si and Nb paste, or by printing the same thereon so as to form the heat emitting body. CONSTITUTION:A heat emitting body forming layer 8 structured by holding Nb paste by means of Si paste is applied on the surface of a Si3N4 compact 3. Next, a Si3N4 compact 4 individually made is overlapped on the surface of the body 3 so as to cover the layer 8. Then, a combined ceramic compact 9 is heated under vacuum, and Si and Nb in the layer 8 are reacted to form NbSi2. Further, the compact 9 is sintered to form a ceramic heater 1 where a heating body 2 made of NbSi2 is buried. It is thus possible to facilitate arrangement of the body 2.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for manufacturing a ceramic heater, and is particularly suitable for manufacturing a ceramic heater that forms an intake heater, a glow plug, or a heat-generating vortex chamber for an automobile engine. It concerns a method.

(Prior Art and its Problems) In recent years, tungsten coils embedded as heating elements in ceramics such as Si3N4 have been used as intake heaters and glow plugs for automobile engines. Such a sintered body is generally called a ceramic heater or a ceramic glow plug.

The above heating elements include tungsten, molybdenum, N
Various materials such as bSi□ are known. A heating element made of these materials is embedded in a ceramic molded body in the following manner. That is, a tungsten wire or a molybdenum wire is prepared in advance, or a molded body of a certain shape made of Nb5iz is formed, and the ceramic powder is sintered while this is embedded in the ceramic powder.
This provides a heating element embedded within the ceramic molded body. Such a method is described, for example, in
It is disclosed in the No. 034 publication.

However, conventional methods involve embedding a heating element of a predetermined shape within ceramic powder. Therefore, there is a problem that the position of the heating element changes during the formation of the ceramic molded body.

Furthermore, with the method described in the above-mentioned publication, in which ceramic powder in which a heating element such as a tungsten wire is embedded is molded by hot pressing, it is difficult to manufacture a ceramic heater with a shape where ffl>lu. However, there is a problem in that it is not suitable for manufacturing parts with relatively large dimensions.

SUMMARY OF THE INVENTION An object of the present invention is to propose a method that can simplify the arrangement of heating elements and easily manufacture ceramic heaters with complicated shapes or relatively large dimensions.

(Means for Solving the Problems) In order to achieve the above object, in the method of the present invention, a ceramic heater is manufactured through the steps shown in FIG. First, a heating element forming layer having a layered structure in which Nb paste is sandwiched between 81 paste is applied or printed on the surface of a Si, N4 molded body. Next, the above-mentioned Si3N on which this heating element forming layer was applied, etc., and the separately produced Si3N on the surface of the molded body.
The N4 molded bodies are overlapped to cover the heating element forming layer. Thereafter, the stacked ceramic molded bodies are heated in a vacuum to cause Si and Nb in the heating element forming layer to react to form Nb5lz. Following this, the stacked Si3N4 compacts are sintered in N2 gas. In this way, a ceramic heater in which a heating element made of Nb5lz is embedded is manufactured.

The above-mentioned Si, N4 compact can be manufactured by sintering SI3N4 powder mixed with a sintering aid into a predetermined shape using a mold press.

Examples of sintering aids include ^1201 and Y2O3.

The heating element forming layer described above is made of S on the surface of the Si3N4 molded body.
Apply i paste to form a layer of Si paste, and apply sb paste on top of this 31 paste layer to form Nl)
This can be easily obtained by forming a layer of paste and then applying Si paste again on this layer of Nb paste to form a layer of Si paste.

The preferred conditions for forming NbSi2 are to place the stacked Si3N4 molded bodies in vacuum (approximately 10-' Torr).
r), the temperature is raised to 1800°C at a rate of about 600°C/hour, and the state of about 1800°C is maintained for about 2 hours.

After reacting and forming NI]S12 under these conditions, the Si3N4 compact can be sintered under the following conditions. That is, the vacuum atmosphere described above is gradually changed to N2 gas, and in this N2 gas, the same < 18
Maintain the temperature at 00°C for about 2 hours. After this, it is cooled to room temperature in N2 gas.

(Effects of the Invention) In the method of the present invention, the heating element in the ceramic heater is made of SI3N4 paste made of Si and Nb.
It can be formed by coating or printing on the surface of the body. Therefore, the heating element can be arranged with a simple operation. Furthermore, it is possible to manufacture ceramic heaters that are more complex and larger in size than if the hot pressing method were used.

(Example) Next, the present invention will be described in detail with reference to the drawings.

FIG. 2 shows the method according to the invention! ! This figure shows the constructed ceramic heater. This ceramic heater 1 has an annular shape with a thickness of 3 mm, and a heat generating layer 2 is embedded in the circumferential direction in the center of the cross section. Both ends 2a and 2b of this heating element 2 are curved toward the outer peripheral surface of the heater main body. The ceramic heater 1 having this configuration was manufactured as follows.

First, sintering aids Al2O3 and Y2O are added to sl3N4.
3 to prepare a mixed powder containing about 9'5% by weight of Si3N4, which was molded with a mold press,
As shown in FIG. 3, a ring-shaped Si3N4 molded body 3 was produced. Similarly, S of the same size as shown in FIG.
i3N4 molded body 4 was manufactured. This molded body 4 was provided with an annular groove 42 on one surface 41 thereof for embedding a heating element.

After this, on one surface of the 5L3N4 molded body 3, at a position corresponding to the groove 42 formed in the other molded body,
SI paste, Nb paste, and Si paste were applied in this order to a thickness of 40 μm. In this way, a heating element forming layer 8 having a layered structure in which the Nll paste layer 5 was sandwiched between 81 paste layers 6 and 7 as shown in FIG. 5 was formed.

Thereafter, as shown in FIG. 6, the Si3N molded body 3 and the other Si3N4 molded body 4 were superimposed so that the heating element forming layer 8 was just placed within the groove 42.

Such a laminate 9 was processed under the conditions shown in FIG. First, in a vacuum atmosphere of approximately 10-'Torr, the laminate 8 is
The temperature was increased to 1800°C at a rate of approximately 600°C/hour.

Furthermore, this temperature state was maintained for 2 hours. After this, while keeping the temperature the same, the vacuum cloud surroundings were gradually changed to N.
The sample was placed in a N2 gas atmosphere for 2 hours, and then slowly cooled to room temperature. In this way, an annular ceramic heater I shown in FIG. 2 was manufactured.

The heating element forming layer of this heater has a thickness of approximately 100 μm.
A heat generating layer 2 consisting of a Nb5lz layer was formed.

The outer peripheral surface of the manufactured ceramic heater was cut out to expose both ends of the heat generating layer 20, and it was determined whether the heat generating layer 2 was suitable as a heat generating element. First, we measured the resistance value of this layer 2 at room temperature and calculated the specific resistance value.
It was about 30 μΩ·cffl. Next, a 12V battery was connected to the formed heat generating layer 2, and the temperature increase characteristics of the ceramic heater 1 were investigated. The measurement point was a surface position A of the heater (see FIG. 1) corresponding to the circumferential center of the heat generating layer. The results are shown in FIG. As can be seen from the results, a maximum temperature increase of about 1000° C. was measured, and it can be seen that this is an excellent ceramic heater.

Next, FIGS. 9 to 11 show a ceramic heater for forming the lower chamber of a heat generating swirl chamber of an engine, manufactured by the method of the present invention.

As shown in FIGS. 9 and 10, two heating layers 12 and 13 are buried in the ceramic heater 11, upper and lower, and a recess 15 for the lower chamber of the swirl chamber 14 is provided at the upper end. It is formed. Ceramic heater 11 of this shape
is formed by sintering an annular ceramic molded body divided into a large number of upper and lower parts. As shown in FIG. 11, this ceramic heater 11 is connected to an upper chamber portion 17 by a shrink fit, a KIJ song 6, thereby forming a heat generating swirl chamber 18.

[Brief explanation of the drawing]

Fig. 1 is a process diagram showing an example of the method of the present invention, Fig. 2 is a perspective view showing an example of a ceramic heater manufactured by the method of the present invention, and Fig. 3 is a diagram showing a ceramic heater used in manufacturing the ceramic heater of Fig. 1. A perspective view showing the NbSi2 molded body, FIG. 4 is a perspective view showing the NbSi2 molded body, and FIG.
FIG. 5 is a cross-sectional view showing a heating element forming layer formed on the surface of the Nb5lz molded product shown in FIG. 3, and FIG. 6 is a stacked NbSi2 molded product shown in FIGS. 3 and 4. Figure 7 is a graph showing the sintering conditions.
FIG. 8 is a graph showing the temperature rise characteristics of the ceramic heater of FIG. 2, FIG. 9 is a plan view showing another example of the ceramic heater according to the present invention, and FIG. 10 is a cross-sectional view of the ceramic heater of FIG. 9. FIG. 11 is a sectional view showing the heat generating swirl chamber equipped with the ceramic heater of FIG. 9. ■ Ceramic heater 2 Heat generating layer 3.4 - NbSi2 molded body 42 groove 5 Nb paste layer 6.731 paste layer 8 Heating element forming layer Fig. 2 Δ Original Fig. 3 Fig. 4

Claims (1)

[Claims] A ceramic molded body containing Si_3N_4 as a main component is produced, and a heating element forming layer having a layered structure in which a layer of paste containing Nb as a main component is sandwiched between layers of paste containing Si as a main component is applied to the surface of the ceramic molded body. The surface of the ceramic molded body on which the heating element forming layer is formed is covered with a ceramic molded body mainly composed of Si_3N_4, which is formed on a portion and produced separately, and the laminated body thus stacked is heated in a vacuum. Si and Nb in the heating element forming layer are heated in an atmosphere.
A method for manufacturing a ceramic heater comprising the steps of reacting with NbSi_2 to produce NbSi_2, and then sintering the stacked ceramic molded bodies in an N_2 gas atmosphere.