JPH0286086A - Manufacturing method of exposed heating part ceramic heater - Google Patents

Abstract

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

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for manufacturing a ceramic heater, and in particular to a method for manufacturing a ceramic heater that has excellent rapid heating properties and is suitable for use in glow plugs (preheating plugs), etc. [Prior Art] In a diesel engine, a glow plug is generally provided in a pre-combustion chamber, and at the time of starting, the glow plug is first preheated to around 1000'C to help ignite the fuel. Conventionally, glow plugs in which a metal wire heater is built into a metal outer tube have been used.

[Problem to be solved by the invention]

However, with such glow plugs, it takes a relatively long time for the surface temperature of the metal outer tube to reach around 1000℃ after preheating starts, and especially at low temperatures, the preheating time becomes even longer, and it takes more than 10 seconds to start. The disadvantage is that it requires a long waiting time. This waiting time (preheating time) is a problem in passenger cars, and there is a strong desire to realize rapid starting.

Conventionally, heating elements using ceramics include those in which a metal wire heating resistor made of tungsten, molybdenum, or the like is embedded in a ceramic body of silicon nitride or aluminum oxide. These heating elements combine metals and ceramics, which have different characteristics, so
It is difficult to fire, and even when used as a heat generating element, there are problems with thermal shock due to rapid heating and property changes due to heat cycles due to repeated energization, which limits the temperature at which it can be used.

On the other hand, a U-shaped ceramic heating element has been proposed as an ignition device. (Special Publication No. 57-44892).

However, when such a ceramic heating element is used in a diesel engine glow plug, etc., the U-shaped heating element has an internal space, so its mechanical strength is weak, and engine vibration etc. can cause long-term damage. There were drawbacks that caused problems in use. Furthermore, molding the ceramic heating element into a U-shape has the disadvantage of requiring a lot of manufacturing time.

The purpose of the present invention is to eliminate the above-mentioned drawbacks of the prior art, and to
The heating time to around 000℃ is short.

The present invention provides a method for manufacturing a ceramic heater that is strong, has excellent high-temperature durability, and has a long service life.

[Means to solve the problem]

In order to achieve the above object, 1 the method for manufacturing a ceramic heater according to the present invention is to manufacture a ceramic heater in which a conductive part made of a conductive ceramic sintered body and an insulating part made of an insulating ceramic sintered body are integrally sintered. In the method, the integrally sintered member is cut to form individual heater circuits. Here, the conductive parts are laminated on both sides through the insulating part, and the conductive ceramic sintered body is provided so that the conductive parts on both sides are electrically connected to each other, and cut in the thickness direction to form a U-shape. It is better to form a circuit.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 shows an example of the present invention, in which numeral 1 denotes a heater member having a U-shaped conductive path, and numeral 2 denotes an insulating member that fills the central groove of the U-shaped heater section 1 and is joined together. 3 is a pair of lead terminals joined to the ends of the heater member. Since the heater member 1 made of conductive ceramic is U-shaped, the size of the heater member 1 can be reduced in a limited space such as a glow plug, and the heater member 1 can be made small.
This increases the exposure of fuel and ensures ignition of the fuel.

In addition, the central groove of the U-shaped heater member 1 is not open, but is buried with the insulating member 2, which facilitates mechanical reinforcement, electrical insulation between conductive paths, and airtight structure of the glow plug. Can be done.

The conductive ceramic constituting the heater member 1 includes at least one non-oxide conductive material selected from the group of non-oxide conductive materials such as carbides, borides, or nitrides of elements of group 4a, group 5a, or group 6a of the periodic table, and SiC. and AQ or A, which is a sintering aid for SiC.
Q compound, and the non-oxide conductive material in this sintered body is preferably 20 to 80% by weight.

The reason for choosing the above material for the heater member is as follows.

First, dense Si using AQ or AQ compound as a combustion aid.
The C sintered body has a high heat resistance, high strength, and excellent thermal shock resistance and oxidation resistance, so it is suitable as a matrix material for bonding non-oxide conductive materials. AQ and An20. ,
Addition of AQ compounds such as ARN and Al2Po4 has effects other than those mentioned above.

The resistivity of SiC, which is originally high in resistance, is 0.1 to 10Ωcm.
This has the advantage of making it easier to adjust the resistivity of the heater member in areas where the content of the non-oxide conductive material is small.

The group of non-oxide conductive materials has practically sufficient heat resistance and oxidation resistance within the operating temperature range of glow plugs, and is effective in maintaining stable resistance characteristics even during long-term use. In particular, the non-oxide conductive material has a resistivity as low as that of metal and a positive resistance-temperature characteristic, and as a result, the resistivity of the heater member, which is a composite sintered body with SiC, is 101 to 10-'
It can be freely adjusted within the range of Qcm, and a desired positive temperature coefficient of resistance can be obtained by appropriately selecting the type or combination of non-oxide conductive materials. Providing the heater member with positive resistance-temperature characteristics is an essential characteristic for the heater member because it can prevent thermal damage caused by a sudden increase in current at high temperatures. Furthermore, the content of non-oxide conductive material in the heater member is 20%.
If it is less than 80% by weight, the heater member will have negative resistance-temperature characteristics, and if it is more than 80% by weight, the strength of the heater member will decrease.

On the other hand, the insulating ceramic that fills the central groove of the U-shaped heater member should be selected to have high strength, heat resistance, oxidation resistance, and electrical insulation properties at high temperatures, and to have a sintering temperature that is approximately the same as that of the heater member. is desirable. Considering these points, insulating ceramic 7') is SiC, Si
, N, , AflN or A1120° as the main component.

Furthermore, the conductive ceramic contains SiC as a component,
If the insulating ceramic has SiC as its main component, the bonding properties between the two will be good and the difference in coefficient of thermal expansion between the two can be reduced. Also, the coefficient of thermal expansion is approximately 4 x 1
0-'/'C SiC and thermal expansion coefficient of 7~8X10''''
T x + Z r t that is 6/°C or higher
In the case of conductive ceramics made by combining carbides such as Nb, nitrides, borides, etc., the coefficient of thermal expansion is 6.
The AQ of insulation can be approximately X10-'/''C.
The coefficient of thermal expansion can be made approximately equal to that of N.

A manufacturing example of the ceramic heater of the present invention will be explained based on the drawings. First, a heater member composition and an insulating material composition are each temporarily formed into a flat plate shape, cut into a molded body of a predetermined shape, and then laminated as shown in FIG. In the figure, 11, 12,
13 and 14 are heater member composition molded bodies, and 15 are insulating member composition molded bodies. This laminate is subjected to main molding at a predetermined pressure to produce a molded body of a ceramic heater, and then hot press sintered to obtain a heater material. This heater material is cut into a predetermined shape as shown in Fig. 3 (A in the figure).

B indicates the cutting direction), and then a lead terminal is joined to the end of the heater part. In this way, the desired ceramic heater can be mass-produced.

In the present invention, a thin portion may also be formed at the tip of the heater. By forming the thin part, the tip of the heater becomes red hot locally, so that the fuel can be ignited more reliably. Furthermore, by adjusting the inner thickness of the thin portion, it is also possible to adjust the electrical resistance of the tip. Further, an insulating layer can be provided on the side surface of the heater member to ensure insulation between the heater member and the plug body, and a thin insulating layer can also be provided over the entire surface of the heater member to protect the heater member. As such an absolute AI layer.

A ceramic heater having the same composition as the insulating ceramic buried in the central groove of the heater member, a ceramic heater formed by heating the obtained ceramic heater in advance at 1200 to 1500°C in the atmosphere,
It can be formed using a heat-resistant inorganic adhesive containing AQ203 as a main component.

Please pay ¥ before use! By providing the edge layer, improvement in corrosion resistance and environmental resistance can be expected without reducing the heat resistance of the heater member.

FIG. 4 shows an example in which a thin portion is formed at the tip of the heater. An insulating member 23 is buried in the central groove of a U-shaped heater member 22, and a material with an insulating layer 21 provided on the side surface of the heater member 22 is cut as shown in FIG. 3, and then the tip of the heater is cut. A thin portion 25 is formed by this. Next, a lead terminal 24 is connected to the end of the heater member 22.

Still another example of the heater in which a thin wall portion is formed at the tip of the heater in FIG.
Before cutting in direction B), both ends of the heater material are cut to form thin walled portions 41, and then the cutting process shown in FIG. 3 is performed. Also in this embodiment, there is no need to perform cutting for each heater material after cutting, so mass productivity is improved.

Example 1 Black SiC powder 49% by weight, An20. A molded binder (5%
% PVA solution) was added, mixed for 30 minutes using a Raikai machine, and then passed through a 16-mesh sieve to form the heater part composition! I! I have adjusted it.

On the other hand, 20 parts by weight of a molding binder (5% PVA solution) was added to the AQN powder, mixed, and then sized using a 16-mesh sieve to prepare an insulation composition.

Next, the heater part composition and the insulating part composition were temporarily molded into a flat plate shape, and a molded body of a predetermined shape was cut out from the plate as shown in FIG. 2, and then laminated. This vLfFj body was subjected to final molding at a predetermined pressure to produce a ceramic heater molded body.

Subsequently, the above molded body was heated using a vacuum hot press device at a pressure of 300 kg/a1 and a temperature of 1950'C1 for a holding time of 1.
A heater material was obtained by hot press sintering under the conditions of h.

After cutting this heater material into a predetermined shape as shown in FIG. 3, Ni lead terminals were bonded to the ends of the heater portion by high-temperature metallization to create a ceramic heater similar to that shown in FIG. 1.

The obtained ceramic heater has a resistance value of about 0.0 at room temperature.
1Ω (resistivity is approximately 1.5 x 10″4ΩC+a),
The resistance value when the tip portion is heated to 1000° C. is approximately 0.3Ω, and has a resistance temperature characteristic suitable for a heater for a glow plug. In addition, the AQN sintered body that is the insulating member of the heater is dense with a relative density of 98.5%, and has a relative density of 1011% at room temperature.
It has a resistivity of Ωam or more.

Even when the tip of the heater was heated to about 1200° C., the insulation properties were not lost.

Regarding the ceramic heater of this example, the temperature increase performance and the results of a temperature increase repetition test are shown in FIGS. 6 and 7. As for the temperature increase performance, as shown by curve A in FIG. 6, it takes about 0.9 seconds for the tip red-hot portion to reach 1000° C. when 12V is applied, and extremely rapid heating is possible. In addition, as shown in Figure 7, the resistance value fluctuation after 100,000 cycles was approximately 3% in the repeated heating test at room temperature and 1100°C.
It is small and has excellent durability when carrying electricity. Further, the temperature of the tip of the ceramic heater of this example was controlled at 1000±100° C., and the resistance value fluctuation after being continuously energized for 1000 hours was about 3%, and it also has excellent high-temperature durability.

Furthermore, a glow plug as shown in Fig. 8 was made using the ceramic heater of this example, and an ignition test was conducted by installing it in a 6-cylinder diesel engine. As a result, ignition started in all cylinders within about 1 second. However, it was possible to start as quickly as a gasoline engine without preheating. This startup test was repeated approximately 10,000 times, but no problems such as heater damage occurred.

Further, the variation in heater resistance value was within 3%.

Example 2 49% by weight of black SiC powder, 1% by weight of AQN powder as a sintering aid, and 50% by weight of TiC powder as a conductive material were mixed,
A heater part composition was prepared in the same manner as in Example 1.

On the other hand, an insulation composition consisting of 99% by weight of edge-colored SiC powder and 11% by weight of Be was prepared in the same manner as in Example 1.

A heater molded body was prepared from both of the above acid groups by the same method as in Example 1, and then hot press sintered using a vacuum hot press machine at a pressure of 300 kg/cJ and a temperature of 2000°C for 1 hour. The heater material was obtained. A heater element similar to that shown in FIG. 3 was cut out from this heater material, and Ni leads were joined to obtain a ceramic heater having the same structure as shown in FIG. 1.

The obtained ceramic heater has a resistance value of 0.1 at room temperature.
Ω, and the resistance value when the tip of the heater was heated to 1000° C. was approximately 0.28 Ω. Further, the SiC insulating part is dense with a relative density of 98.5%, has a resistivity of 1014 ΩcI11 or more at room temperature, and does not lose its insulating properties even when the tip is heated to 1200°C.

Furthermore, the glow plug made using the ceramic heater of this example was also subjected to heating performance, repeated heating tests, and ignitability tests using an actual engine in the same manner as in Example 1, but none of the characteristics were as described above. The results were similar to those in Example 1.

In the above embodiments, glow plug heaters were explained as an example, but the present invention can also be applied to various heaters for home appliances and industrial equipment, as well as gas and liquid fuel ignition devices for gas ranges, heating appliances, boilers, etc. You can also do it.

〔Effect of the invention〕

According to the present invention, since the heater part is a U-shaped exposed direct heating type, the temperature rise rate up to around 1000°C is very fast.
Since the U-shaped central groove is integrally joined and reinforced with an insulating member, it can be made mechanically strong.

Further, since the heater member and the insulating member can have high heat resistance d, a ceramic heater with excellent high temperature stability and current durability can be obtained.

[Brief explanation of drawings]

FIG. 1(A) is a plan view showing an example of the configuration of a ceramic heater according to the present invention, FIG. 1(B) is a side view of FIG. 1(A), and FIGS. FIG. 4A is an explanatory diagram showing the manufacturing process of the ceramic heater according to the present invention, and FIG.
Figure (B) is a side view of Figure 4 (A), Figure 5 is a side view showing still another example of the configuration of the ceramic heater according to the present invention,
FIG. 6 is a characteristic diagram showing the temperature increase performance of the ceramic heater according to the present invention, FIG. 7 is a diagram showing the change in resistance value over time in repeated heating tests of the ceramic heater according to the present invention, and FIG. FIG. 1 is a partially cutaway view showing a glow plug using the ceramic heater of the present invention. 1.22.31...Heater member, 2,23.32...
Insulating member, 3.24...Lead terminal.

Claims (1)

[Scope of Claims] 1. A method for manufacturing a ceramic heater in which a conductive part made of a conductive ceramic sintered body and an insulating part made of an insulating ceramic sintered body are integrally sintered, wherein the integrally sintered member A method for manufacturing a ceramic heater, characterized in that the ceramic heater is cut to form individual heater circuits. 2. The conductive parts are laminated on both sides through the insulating part, and the conductive ceramic sintered body is provided so that the conductive parts on both sides are electrically connected to each other, and cut in the thickness direction to form a U-shaped circuit. A method of manufacturing a ceramic heater according to claim 1, which comprises forming a ceramic heater.