JPS62140386A - 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 [Field of Industrial Application] The present invention relates to a ceramic heater, and particularly to a ceramic heater suitable for use in a glow plug for preheating the inside of a diesel engine cylinder.

[Prior Art] Generally, diesel engines are equipped with a glow plug in the preheating combustion chamber, and when started, the engine first glows.

Preheat the plug to around 1000℃ to help ignite the fuel.

This method is generally used. Conventionally, in a heat-resistant metal sheath used as a glow plug, 1VHI02i: Which heat-resistant insulating powder was filled in the heating coil and its surroundings? In addition, so-called sheath heaters are used. However, with such a sheath heater, it takes about 50 minutes from the start of preheating to the time when the sheath surface temperature reaches the humidity level at which it can be started.
It takes more than a second and lacks rapid heating properties.

Let's go. However, if you increase the current by 1° to increase the heating speed, the heating coil will melt or become overheated.

As a result, the sheath is more likely to be damaged, and its durability is significantly reduced. Therefore, there is a strong desire for a glow plug heater that has quick startability and excellent high-temperature durability.

Also, traditionally, ceramics are used! [As a heating element, there is one in which a metal wire heating resistor made of tungsten, molybdenum, etc. is embedded in a ceramic body of silicon nitride or aluminum oxide.

These heating elements are a combination of metals and ceramics, which have different characteristics, so they are hard to fire and
The structure is complicated, and when used as a heating element,
Thermal shock caused by rapid heating and changes in properties due to thermal cycles caused by repeated energization become a problem, and the disadvantage is that the temperature at which it can be used is limited by this problem.

[Problem to be solved by the invention] The present invention is directed to a conventional sheath heater or cella.

Solved the problems with the heating characteristics and high temperature durability of heaters using mixes, and has excellent rapid heating performance and high temperature durability.
Moreover, the structure is simpler than conventional heaters.

Direct heating type ceramic that can also be made smaller and lighter.

It provides a heater.

[Means for solving problems] 2. To achieve rapid heating, which is the main objective of the present invention. .

In order to achieve this, it is sufficient to reduce the resistance value of the heater and instantaneously apply a large current, and in order to obtain high-temperature durability, the composition of the heater material must have a high FAl! It is sufficient to use a material that has excellent oxidation resistance. ;1) The heater material prevents fusing due to runaway current that occurs in (Heater heat generation) □゛, and uses its temperature resistance coefficient to heat the heater.

It is desirable to have a positive temperature coefficient of resistance because it is easier to control the current to keep the material constant. As a result of a thorough inspection of heater materials with these characteristics, the inventors found that
TiN powder, which improves conductivity, is dispersed in a sintered iron sintered body containing a sintering aid.

Specifically, composite sintering from (Sialon-TiN).

The electrical resistivity of the body at room temperature is 1Ω・cm or less, which is positive.

and glow plug heaters with a temperature coefficient of resistance of .

We found that it has temperature durability in the operating humidity range of 1.

That is, in the present invention, 5 to 10 wt% of Si3N4
Y20a, 2-12 wt% AlN polytype.

Adding 1-5 wt% of A120a, these Si3N4.
Y20a, ΔIN polytype, Al2O3,! By adding more than 30vo 1% and less than 70vo 1% of TiN to the mixture of 0 and 3-, mixing, molding, and pressureless sintering, a ceramic made of a composite sintered body of SiAlON and TiN is produced. The goal is to obtain heater material.

Here, the reason for adding 5 to 10 wt% of Y2O3 is to enable pressureless sintering, and Y20a is 5°w.
If it is less than t%, the sintered body will not be densified and Y20a.

If it exceeds iowt%, the high-temperature strength decreases significantly. The reason for limiting the amount of A1゜N polytype to 2 to 12 wt% is that if it is less than 2゜wt%, the high-temperature strength will decrease significantly, and 121
If it exceeds 0wt%, the sintered body will deteriorate and its strength will decrease.
This is because that. The reason why the amount of Al2O3 is limited to 1 to Swt% is that if it is less than 1wt%, the sintered body will deteriorate and it will be difficult to increase the density, and if it exceeds 5wt%, the high temperature and strength will be significantly lowered. 1゜Here,
The reason for using TiN as a conductive material is to add carbides, nitrides, etc. of the IVa group.

This is because TiN exhibits the best strength characteristics and oxidation resistance, although it is possible to obtain conductivity.

This TiN addition amount exceeds 30vo 1% and 70vo 1
Less than %, τ4- means 30vo 1% or less, the electrical resistivity is 1
It is not less than Ω・cm and the conductivity is insufficient, 70vo
This is because if it exceeds 1%, the high-temperature strength decreases significantly and the reliability at high temperatures deteriorates. 'As described above, the composite sintered body of Sialon and TiN obtained according to the present invention has an electrical resistivity of 1Ω·Cm.

Below, the resistance shows a positive humidity coefficient, and at high temperatures.

Indicates durability.

[Examples] The present invention will be further explained by examples. IO Example 1 S+3N4 powder (particle size o, zμm, a conversion rate 93%)
・87wt%, Y2O3 powder (particle g 1μm)
5wt%.

AlN polytype powder (crystal type 21R1 particle size 2μm)
.

3wt%, Al2O3 powder (particle size 0.511m)
TiN powder (particle size.

2 μm) was added at 40 vol% (1), then 2 μm with an organic solvent.
Day.

After mixing the above, drying, 1.5t by cold isostatic press.
Mold under a pressure of 7 cm2. Thereafter, the compact was sintered at 1800° C. for 3 hours in a nitrogen gas atmosphere of 1 atm. The composite sintered body of (Sialon-TiN) thus obtained had a relative density of 99% and was heated at room temperature and 1000°C.
Bending strength: approx. 70 kg/mm2 (JIS 3-point bending) Coefficient of thermal expansion: 5. I X 1o->C, resistance at room temperature.

rate 0.7x10-'Ω-am, temperature coefficient of resistance (room temperature ~ 1
000''°C) (-0.3%/°C).

　　　　.

Example 2 Sialon obtained by the same method as in Example 1.

-TiN) A glow plug heater having the shape shown in FIG. 1 was manufactured using a composite sintered body. At both ends 1.2 shown in Fig. 1 1.), (Sialon-TiN) - Thermal expansion coefficient α'-, 5, IX of the composite sintered body Fe - exhibiting a thermal expansion coefficient similar to 10y°C High-rise N+-〇〇 alloy
For joining by wave pressure welding and connecting lead wires.

Electrodes 3.4 were provided. 1゜Figure 2 shows this heater connected to a DC power supply circuit.

This figure shows the result of applying 11V to the battery. .

The horizontal axis is the current application time, and the vertical axis is the surface temperature of the tip portion 5 shown in FIG. The ceramic heater according to the present invention can rapidly heat up to 900° C. in about 2 seconds, and has much better rapid heating performance than conventional sheath heaters (5 to 10 seconds up to 900° C.). In addition, the heater temperature is saturated at 1000°C, and this month has a positive temperature coefficient of resistance.
Good as a glow plug heater.

It shows desirable characteristics.

Example 3 It is not shown in FIG. 1 by a move v1 that is exactly the same as in Example 2.

A glow plug heater was created. FIG. 3 shows the results of continuous energization of this heater during popular use. The temperature did not change at all even after 1000 hours of current application (11) from the initial temperature of 1000°C; even after 2000 hours of current application, the temperature decreased by about 50°C, indicating sufficient high-temperature durability.

(Sialon-TiN) composite sintering according to the present invention.

Due to its low resistivity, the body has excellent rapid heating properties, and has 1. .

Since the resistance temperature coefficient is positive, there will be no melting due to current runaway.

Since it has characteristics such as a high melting point and oxidation resistance, it is suitable for direct heating type plug heaters that require rapid temperature heating speed and high temperature durability. Roughly speaking, since the heater material according to the present invention has the following characteristics: 1, τ7- high density and high strength, the shape of the heater is not limited to the above-mentioned U-shape, but can also be a rod-like, plate-like structure, or the like.

Furthermore, since the heater according to the present invention is a direct heating type, it has a simpler structure and can be made smaller and lighter than conventional metal sheath heaters or heaters in which metal resistance wires are embedded in ceramic.

Note that the present invention is applicable to glow plug heaters.

The invention is not limited to this, and can be applied to various heating elements, ignition devices for various fuels, and the like. IO

[Brief explanation of drawings]

FIG. 1 is a diagram showing an example of a heater for a glow plug using the heater material of the present invention, and FIG. Temperature increase of a glow plug heater according to an embodiment of the present invention. A diagram showing the characteristics, FIG. 3, is an example of the present invention. FIG. 5 is a diagram showing the high temperature durability of the No. 5 glow plug heater in a continuous energization test. , τ8-th/Seki 2nd figure

Claims (3)

[Claims] (1) Y_2O_35-10 wt%, AlN polytype sialon 2-12 wt%, Al_2O_31-5 wt%
%, and 30 vol for the total of the remaining Si_3N_4
A ceramic heater comprising a composite sintered body of Sialon and TiN containing more than 70% by volume of TiN. (2) In what is stated in claim (1),
A ceramic heater characterized in that the grain boundary layer is an amorphous phase containing Y, Si, O, N, and Al. (3) The ceramic according to claim (1) or (2), which has an electrical resistivity of Ω·cm or less at room temperature and a positive temperature coefficient of resistance. heater.