JPH11329801A - Electric resistor element and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric resistor element, which can be manufactured by a simple method, stands the use under a rapid temperature rise and a high temperature and has excellent oxidation resistance. SOLUTION: This is an electric resistance element which is constituted of an insulating base material and whose main body is silicon nitride, a laminated sintered body with the inner conductor of tungsten-carbon composite system, the terminal electrode which is formed by simultaneous burning at the exposed part of the above described inner conductor, and the lead wire connected to the electrode. Here, the insulating base material, whose main body is silicon nitride and the inner conductor of the tungsten-carbon composite system are laminated and sintered. The plate-shaped or linear electrode comprising high melting point, low resistance metal, which is connected to the lead wire, is directly burned and attached to the exposed part of the above described inner conductor and manufactured.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an electric resistance element suitable as a heating element for igniting gaseous and liquid fuels such as gas and petroleum, and more specifically, without using a control device such as a computer. The temperature rises rapidly to 1100 ° C or higher in a short time, and it can ignite fuels such as natural gas, propane gas, and kerosene. The present invention relates to an electric resistance element suitable as a heating element and a method for manufacturing the same.

[0002]

2. Description of the Related Art A heating element for igniting a gas or liquid fuel such as gas or petroleum requires 100 to 100 seconds within a short time of 2 to 3 seconds.
Since the temperature must be raised rapidly to a temperature of 0 ° C. or higher and withstand this high temperature, excellent thermal shock resistance and oxidation resistance are required.

[0003] In order to meet such a demand, a heating portion mainly composed of titanium nitride has been provided in or on a silicon nitride sintered body, and a conductive material mainly composed of tungsten carbide has been applied to both ends thereof. A ceramic heater (JP-A-63-136485) serving as an electrode extraction lead portion, a heater having a heating resistor embedded in a ceramic body is provided at a front end portion, and a holding mechanism of the heater is energized at a rear end portion. In a ceramic heating element having a mechanism, a ceramic material forming a heater and a metal body forming a holding mechanism are hermetically sealed with a brazing material (Japanese Patent Application Laid-Open No.
JP-A-30076), a ceramic heater in which a heating element is embedded inside a base made of dense ceramics, wherein both ends of the heating element have an average particle size of 0.1 to 100.
One having a metal terminal obtained by sintering metal particles of μm (Japanese Patent Application Laid-Open No. 9-306664), a ceramic base, a ceramic heating element embedded therein, and an electrode part having one end embedded in the ceramic heating element. An interference portion for preventing or suppressing relative movement of the embedded portion with respect to the ceramic heating element and / or rotation about its own axis is formed in the embedded portion of the electrode heating portion where the ceramic heating element is embedded (Japanese Patent Application Laid-Open No. Hei 9 (1998) -107). 184621) have been proposed, but these have a complicated structure, prevent miniaturization, and inevitably increase the cost. Therefore, many problems remain in practical use. .

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an electric resistance element which can be manufactured by a simple method and has good oxidation resistance which can withstand rapid temperature rise and use under high temperature. It is a thing.

[0005]

The inventor of the present invention has conducted intensive studies on a heating element having an oxidation-resistant terminal electrode with a lead wire. A metal mainly composed of nickel is adhered to the exposed silicon nitride of the inner conductor, so that the inner conductor does not come into direct contact with air, and a terminal electrode with excellent oxidation resistance can be formed, and the lead wire can be formed. Conventionally, two steps, electrode formation and lead wire connection, were required by using an integrated electrode with a mark, but the manufacturing process can be shortened to one step, and furthermore, since an integrated metal is used, The present inventors have found that a structure having a simple structure and excellent in structural strength can be provided with high work efficiency and low cost, and the present invention has been made based on this finding.

That is, the present invention provides a laminated sintered body of an insulating base material mainly composed of silicon nitride, a tungsten-carbon composite internal conductor, and a terminal formed by simultaneous baking on an exposed portion of the internal conductor. An electrical resistance element comprising an electrode and a lead wire connected thereto; an insulating base mainly composed of silicon nitride;
A carbon composite internal conductor is laminated and sintered, and a plate or linear terminal electrode made of a high melting point low resistance metal connected to a lead wire is directly baked on an exposed portion of the internal conductor with an active metal. And a method for manufacturing an electric resistance element. The active metal used here is preferably one containing titanium, for example, a Ti-Ag-Cu-based alloy, a Ti-Ag-based alloy, or a Ti-Ag-Cu-Ni-based alloy, but particularly Ti-Ag- Cu-based alloys are preferred.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in more detail with reference to the accompanying drawings. FIG. 1 shows one of the electric resistance elements of the present invention.
FIG. 3 is a perspective view showing an example, in which a tungsten-carbon composite inner conductor 2 is sandwiched between insulating substrates 1 and 1 mainly composed of silicon nitride, and an end of the conductor 2 has an exposed region 3. These are integrated by sintering. Area 3
The active metal 5 is applied to the exposed portion of the conductor, and the terminal electrode 4
And integrated with this terminal electrode by baking. In FIG. 1, only one of the terminal electrodes 4 provided on both sides is shown.

The insulative bases 1 and 1 constituting the electric resistance element of the present invention are mainly composed of silicon nitride,
It is made of a material containing aluminum oxide or the like.
The silicon nitride content of this material is in the range of 50-95% by weight. However, it can also be used satisfactorily in a system in which rare earth oxide-alumina or rare earth oxide-silica is added to commonly used silicon nitride.

Further, a tungsten-carbon composite material is used as the inner conductor 2 of the electric resistance element of the present invention, and the composition is such that the atomic ratio of tungsten to carbon is 1: 0.25 to 1: 1. .1, preferably 1:
It is selected in the range of 0.4 to 1: 0.98. Such a composition usually has a melting point of 2000 ° C. or higher, a coefficient of thermal expansion of 6.0 × 10 ⁻⁶ / ° C. or lower, and an electric resistance of 10 ⁻⁵ Ω · cm.
It is as follows.

[0010] When a material containing sialon as a main component is used as the insulating base material, a part of the tungsten of the conductor is silicified at the time of sintering or at the time of heat generation, and the silicide of the tungsten has a thermal expansion coefficient. It is known that the strength is large and the strength becomes weak. For this reason, a characteristic test such as an increase in the resistance value is likely to occur in a cycle test in which energization is repeatedly turned on and off.

Also, tungsten carbide having a tungsten to carbon atomic ratio of 1: 1 is usually used as a super hard material. It is known to cause a decrease. In fact, if you add too much carbon,
In the cycle test, the resistance value increases rapidly after about 40,000 times. If the atomic ratio of tungsten to carbon is within the above range, the characteristics of the above cycle test are not significantly affected by the ratio of tungsten to carbon.

Usually, since the conductor 2 is provided by printing a paste-like material, a part of the organic binder used for making the paste remains as carbon during firing.
The carbon content increases by this amount. For example, in hot press firing, usually about 1 atomic% of carbon remains. Therefore, when selecting the composition of the tungsten-carbon composite internal conductor, it is necessary to determine in consideration of this point.

Next, as the terminal electrode 4 of the electric resistance element of the present invention, one made of a metal having a high melting point and a low resistance is used, and nickel or an alloy mainly containing nickel, for example, nickel-tungsten is preferable.

The electric resistance element according to the present invention has an insulating substrate in which a tungsten-carbon composite inner conductor is printed on one of the insulating substrates 1 and 1 mainly made of, for example, silicon nitride, and the rest is not printed thereon. After stacking and sintering conductive base materials,
It is manufactured by cutting into a required shape, bonding the terminal electrode 4 to the exposed inner conductor 3 formed at that time with a paste made of an active metal such as silver, copper and titanium, and baking.

In the electric resistance element of the present invention thus obtained, the oxidation-resistant terminal electrode, the lead wire or the plate is integrally attached, and the internal conductor which is easily oxidized is completely shielded from the air. Oxidation resistance of the entire device is improved, high reliability can be ensured, and it can be manufactured with fewer steps than before, and the structure is simple. The troubles in use, such as the defective resistance value, disconnection due to insufficient strength, and oxidation at the connection part, are eliminated, and low cost and high reliability can be secured.

[0016]

Next, the present invention will be described in more detail by way of examples.

EXAMPLE An insulating composition comprising 92% by weight of silicon nitride, 3.5% by weight of silicon oxide and 4.5% by weight of aluminum oxide was formed into a sheet, and one surface thereof was provided with an atomic ratio of tungsten to carbon of 1: 0. .5 by pattern printing the conductive composition comprising
An inner conductor was formed. After unprinted sheets were overlaid on the printing surface, they were fired at 1700 ° C. to obtain a sintered body. Next, this sintered body was cut into strips, and the length was 4 cm.
A plate-like ceramic having a width of 4 mm and a thickness of 1 mm was produced.
An exposed portion of the internal conductor was observed only at the end of the cut surface. Next, a Ti-A
g-Cu based active metal [manufactured by Tokyo Blaze Co., Ltd., "Active Alloy Blazing (Active Alloy)
Brazing)]], and a U-shaped part of a 200 μm-thick and 1 mm-wide nickel plate processed into a U-shape is fitted and baked at 930 ° C. in an argon atmosphere. Thus, an electric resistance element was manufactured.

COMPARATIVE EXAMPLE A 1: 1 weight ratio of nickel and tungsten was applied to the exposed portion of the internal conductor of the plate-shaped ceramic produced in the same manner as in the example.
Paste prepared from the powder mixture of
After baking at 300 ° C., nickel plating was applied, and a phosphor bronze lead wire having a thickness of 200 μm, a width of 1 mm, and a length of 25 mm was connected by silver brazing to manufacture an electric resistance element.

Reference Example 10 minutes from the junction of the electric resistance elements obtained in Examples and Comparative Examples.
The upper ceramic part was heated by the combustion flame of propane gas. This combustion flame was adjusted to the intensity of the sparks used in homes. As a result of the heating in this manner, the part hit by the combustion flame glowed dark red. Thus, 20
Table 1 shows the rate of change of the resistance value after the 00-hour flame resistance test, and the results of a tensile test performed by applying a load of 1 kg to the lead wire.
Shown in

[0020]

[Table 1]

[0021]

The present invention provides an electric resistance element which is suitable as a heating element for igniting a gaseous fuel or a liquid fuel and has excellent resistance to oxidization at a high temperature by rapidly raising and lowering the temperature in a short period of time and oxidizing at a high temperature. .

[Brief description of the drawings]

FIG. 1 is a perspective view showing an example of the structure of an electric resistance element of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Insulating base material 2 Internal conductor 3 Conductor exposed area 4 Terminal electrode 5 Active metal

Claims (3)

[Claims] 1. An insulating substrate mainly composed of silicon nitride,
A laminated sintered body with a tungsten-carbon composite inner conductor,
An electric resistance element comprising: a terminal electrode formed by simultaneous baking on an exposed portion of the internal conductor; and a lead wire connected to the terminal electrode. 2. An insulating substrate mainly composed of silicon nitride,
Laminating and sintering a tungsten-carbon composite-based internal conductor, and directly baking a plate-shaped or linear terminal electrode made of a high-melting-point low-resistance metal connected to a lead wire on an exposed portion of the internal conductor with an active metal A method for manufacturing an electric resistance element, comprising: 3. The method according to claim 2, wherein the terminal electrode is an alloy mainly composed of nickel.