JPH07167435A - Ceramic heat-generating member - Google Patents

Abstract

PURPOSE:To provide a ceramic heat-generating member in which a close fitness of a metalized metallic layer, an air-tightness and anti-oxidization characteristics are superior, an electrode terminal is not peeled off, a heat generating member within silicon nitride sintered member is not oxidized, no variation in resistance may occur, a continuous operation can be carried out at a high temperature for a long period of time and it has a superior durability. CONSTITUTION:Metalized metallic layers 6 and 7 which is comprized of 95wt.% of at least one of gold, nickel, and paradium, or at least one of copper, cobalt, silicon, and a balance of at least one of banadium and molybdenum, or at least one of group 4a elements and manganese are coated on at least electrode taking-out parts 4, 5 of the heat generating resistor 3 comprised of non-organic conductive material buried in the silicon nitride sintered body 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high temperature ceramic heating element used for heating heaters for various heating devices and measuring devices, ignition plugs for various combustion devices and glow plugs for starting assistance of diesel engines. .

[0002]

2. Description of the Related Art Conventionally, as a glow plug used for accelerating the starting of a diesel engine including heaters for heating and igniting various measuring instruments, etc., a sheath made of refractory metal and a refractory metal wire together with refractory insulating powder are used. A sheathed heater having a heating resistor embedded therein was used.

However, since the sheathed heater transfers the heat of the heat-generating resistor through the heat-resistant insulating powder filled in the sheath made of heat-resistant metal, it is difficult to rapidly raise the temperature in a short time and, in addition, it has abrasion resistance. There was a problem of poor durability.

Therefore, as a highly reliable heating element which is capable of rapid temperature rise in a short time and which is excellent in wear resistance and durability, a heating resistor made of an inorganic conductive material is used as a ceramic sintered body, especially in heat resistance. Ceramic heating elements embedded in an excellent silicon nitride sintered body have come to be widely used for glow plugs and the like of internal combustion engines, including the above-mentioned heaters for heating.

The ceramic heating element based on the above-mentioned silicon nitride sintered body is connected to the electrode terminals by using a conventionally known refractory metal such as molybdenum (Mo) or tungsten (W) and alumina ( Al ₂ O ₃ ), silica (Si
O ₂ ), magnesia (MgO), etc. were added to one or more paste-like powder mixture to cover the connection portion and fired to form a metallized metal layer, which was then joined with silver solder or the like.

However, although the metallized metal layer has sufficient adhesion when an oxide ceramics such as alumina (Al ₂ O ₃ ) is baked with a glass component having a low melting point and metal powder, it is mainly composed of silicon nitride. For adhesion with the non-oxide ceramic sintered body as a component or the electrode terminal, etc.,
Since the reactivity between the metallized metal layer and the silicon nitride sintered body is low, the electrode terminals are peeled off when the temperature of the electrode portion rises, or the adhesiveness is insufficient. At the electrode extraction portion exposed on the side surface of the bonded body, the heating resistor oxidizes at a high temperature, and as a result, the heating resistor may change in resistance, resulting in poor durability.

Therefore, a method of depositing a metallized metal layer having a high strength of adhesion on a ceramic containing silicon nitride as a main component by using a mixture containing molybdenum and lithium aluminosilicate is disclosed in Japanese Patent Publication No. 5-131.
It is proposed in Japanese Patent No. 15, etc.

[0008]

However, in the method for depositing the metallized metal layer, the maximum heat generation portion is 1000.
Although it is considered that it can be used without problems when the electrode extraction portion is kept at a relatively low temperature under a temperature condition of less than 0 ° C., a ceramic heating element based on a silicon nitride sintered body has been used in recent years. When used for high temperatures of 1000 ° C or higher required for various heating and ignition heaters and glow plugs, generally the maximum heat generation part is 30% above the set temperature when energized.
The temperature rises by about 0 ° C., and some of them are exposed to the high temperature of the surroundings and become higher than the set temperature above 350 ° C., and the temperature rise of the electrode extraction part due to heat conduction cannot be avoided.
Due to insufficient adhesion of the metallized metal layer, the electrode terminals may peel off and the heating resistor may oxidize, causing a resistance change in the ceramic heating element itself, resulting in poor durability.

[0009]

SUMMARY OF THE INVENTION The present invention has been developed in view of the above-mentioned problems, and an object thereof is to adhere the metallized metal layer, that is, the airtightness and the oxidation resistance even when the ceramic heating element is heated to a high temperature of 1000 ° C. or higher. The electrode terminals are not peeled off, and the heating resistor embedded in the silicon nitride sintered body does not oxidize to cause resistance change without damaging It is to provide a ceramic heating element.

[0010]

The ceramic heating element of the present invention comprises at least one of gold (Au) and nickel (Ni) or palladium (Pd), or copper (Cu), cobalt (Co), silicon ( The total amount with any one of Si) is 95% by weight or more, the balance is any one or more of vanadium (V) or molybdenum (Mo), or any one of the Group 4a elements of the periodic table and manganese (Mn). The metallized metal layer made of is formed on at least the electrode extraction portion of the ceramic heating element in which a heating resistor made of an inorganic conductive material is embedded in a silicon nitride sintered body.

In the ceramic heating element of the present invention, the composition of the metallized metal layer includes gold (Au) and nickel (N).
i) or one or more of palladium (Pd), or copper (Cu), cobalt (Co), silicon (S)
The total amount with any one of i) is less than 95% by weight, and the balance is one or more of vanadium (V) or molybdenum (Mo), or any one of the Group 4a elements of the periodic table and manganese (Mn). When it is composed of one kind, the ratio of refractory metal such as vanadium (V), molybdenum (Mo), Group 4a element of the periodic table or manganese (Mn) increases, and as a result, the temperature at which the metallized metal layer is deposited is formed. 130
The temperature becomes 0 ° C. or higher, and at that temperature, decomposition and sublimation of the silicon nitride sintered body itself of the base material will start, and the metallized metal layer cannot be deposited.
% Or more, particularly preferably 97% or more.

The total amount of gold (Au) is 95%.
As a result, vanadium (V), molybdenum (M
o), when neither group 4a element of the periodic table nor manganese (Mn) is contained, the reducing power is weak and the reactivity with the silicon nitride sintered body is low, so that the metallized film has sufficient adhesive strength. Since the metal layer cannot be formed by deposition, the balance is one or more of vanadium (V) and molybdenum (Mo), or the periodic table 4a.
Specified as one of the group elements and manganese (Mn),
Particularly, one or more of vanadium (V) and molybdenum (Mo) is preferable.

[0013]

According to the ceramic heating element of the present invention, the metallized metal layer is formed of at least one of gold (Au) and nickel (Ni) or palladium (Pd), or copper (C).
u), cobalt (Co), and silicon (Si) in a total amount of 95% by weight, and the balance is one or more of vanadium (V) or molybdenum (Mo),
Alternatively, since it is formed of any one of elements of Group 4a of the periodic table and manganese (Mn), it promotes the reaction with the silicon nitride based sintered body forming the base body and improves the wettability to the surface of the sintered body. However, peeling of the electrode terminals and deterioration of the oxidation resistance of the metallized metal layer due to insufficient adhesion of the metallized metal layer can be prevented.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the ceramic heating element of the present invention will be described below with reference to the drawings. 1 is a perspective view showing an embodiment of a ceramic heating element of the present invention, and FIG. 2 is an enlarged sectional view showing a main part of FIG.

In FIGS. 1 and 2, reference numeral 1 is a ceramic heating element in which a heating resistor 3 made of an inorganic conductive material is embedded in a silicon nitride sintered body 2.
Part of the lead wires 10 and 11 connected to the heating resistor 3 are exposed to form the electrode lead-out portions 4 and 5, respectively, and the metallized metal layers 6 and 7 are formed so as to cover at least the exposed portions of the electrode lead-out portions 4 and 5, respectively. After being respectively formed by adhesion, the electrode terminals 13 and 14 and the fittings 15 and 16 are connected through a brazing filler metal 12 having a high melting point such as silver brazing and led out as positive and negative electrode terminals.

The metallized metal layers 6 and 7 are made of gold (A
u) and one or more of nickel (Ni) and palladium (Pd), or copper (Cu), cobalt (C)
o) and the total amount of silicon (Si) are 9
5% by weight or more, and the balance consisting of one or more of vanadium (V) or molybdenum (Mo), or one of Group 4a elements of the periodic table and manganese (Mn). The layers 6 and 7 are one or more of gold (Au) and nickel (Ni) or palladium (Pd) from the silicon nitride sintered body 2 side, or copper (Cu), cobalt (Co), silicon (Si). 1 or more of any one of vanadium (V) and molybdenum (Mo), or any one of the Group 4a elements of the periodic table and manganese (Mn) as a main component consisting of any one of
It is formed of the first layer 8 containing a relatively large amount in the range of up to 5% by weight and the second layer 9 containing them in an amount of less than 1% by weight.

The composition of the metallized metal layer is most preferably such that the total amount of gold (Au) and nickel (Ni) is 97% by weight or more, and the balance is vanadium (V) and molybdenum (Mo).

The heating resistor made of an inorganic conductive material which constitutes the heating resistor 2 may be a wire material of a refractory metal such as tungsten (W), molybdenum (Mo), rhenium (Re) or an alloy thereof, for example, Tungsten Carbide (W
C), titanium nitride (TiN) and zirconium boride (Zr
It is also preferable to use a carbide or nitride of Group 4a, Group 5a, Group 6a such as B ₂ ) formed in a linear or layered form by means of printing or the like.

In evaluating the ceramic heating element of the present invention, first, a silicon nitride (Si ₃ N ₄ ) powder having a purity of 99% is oxidized with a Group 3a element such as ytterbia (Yb ₂ O ₃ ) as a sintering aid. The raw material powder obtained by adding and mixing
The mixture was wet-mixed in a ball mill for an hour, and the slurry of the mixture was spray-dried and granulated, and a rod-shaped silicon nitride molded body was produced by a press molding method.

Next, a heating resistance wire made of a tungsten wire wound in a substantially U-shaped coil shape on the plane of the molded body, and a tungsten wire forming a lead wire portion connected to the heating resistance wire. The heating resistor made of was placed, and another silicon nitride molded body of the same shape was stacked so as to sandwich the heating resistor, and pressure-fired.

The side faces of the thus obtained sintered body 2 are polished to expose a part of the lead wires 10 and 11, and at least the exposed portions, that is, the electrode lead-out portions 4 and 5 are shown in Tables 1 and 2. A metallized metal layer was added so as to have a composition so as to form a sample for evaluation of adhesion and oxidation resistance of the metallized metal layer.

The composition of the metallized metal layer baked on the silicon nitride sintered material is confirmed by measuring the respective components of the first layer and the second layer by a fluorescent X-ray method after firing, and confirming from the total amount. did.

[0023]

[Table 1]

[0024]

[Table 2]

The metallized metal layer adhesion was evaluated by immersing the sample for evaluation in a fluorescent penetrant flaw detection solution for 1 hour and 30 minutes, and then cutting the sample in a direction perpendicular to the embedded lead wire portion to form a tungsten lead wire. It was confirmed whether or not the fluorescent penetrant flaw detection liquid had entered the boundary with the silicon nitride sintered body.

Next, as a method of evaluating the oxidation resistance, the resistance change rate was calculated from the resistance value of the ceramic heating element before and after holding at each temperature for 200 hours, and the resistance change rate was 2%.
● 2% to less than 5% ○ ○ 5%
The above was evaluated as x.

The evaluation sample on which the metallized metal layer was deposited was made of nickel (Ni) and had a diameter of 0.6.
mm electrode terminals are joined using silver solder equivalent to BAg-8 standard, and the total load when the electrode terminals are peeled off in the direction perpendicular to the joining surface is 12 Kgf or more is best, 10 Kgf or more 1
The adhesive strength of the metallized metal layer was evaluated by setting less than 2 Kgf as good and less than 10 Kgf as poor. The above results are shown in Tables 3 and 4.

[0028]

[Table 3]

[0029]

[Table 4]

The ceramic heat generating element of the present invention is used as a glow plug for starting assistance of a diesel engine, and 1400
After rapidly raising the temperature to ℃, after stopping the energization and blowing compressed air for 1 minute to forcibly cool the cycle, the high temperature high load endurance test, which was one cycle, was continued until the wire was broken and no heat was generated. It was confirmed that the glow plug had about 25,000 cycles, whereas the ceramic heating element of the present invention had no abnormality up to 40,000 cycles.

[0031]

As described above, the ceramic heating element of the present invention is one or more of gold (Au) and nickel (Ni) or palladium (Pd), or copper (Cu), cobalt (Co), silicon. 95% by weight or more of the total amount of (Si) and any one or more of vanadium (V) or molybdenum (Mo), or any one of manganese (Mn) of Group 4a of the periodic table. A metallized metal layer of one kind is formed on at least the electrode extraction portion of a ceramic heating element in which a heating resistor made of an inorganic conductive material is embedded in a silicon nitride sintered body, so that a metallized metal layer and a substrate are formed. The reaction with the silicon nitride-based sintered body is promoted, the adhesion of the metallized metal layer, that is, the airtightness and the oxidation resistance are improved, and the heating resistor does not oxidize and cause a resistance change. Possible prolonged continuous operation of, it is possible to obtain a ceramic heating element having excellent durability.

[Brief description of drawings]

FIG. 1 is a perspective view showing an embodiment of a ceramic heating element of the present invention.

FIG. 2 is an enlarged cross-sectional view of an essential part for explaining a metallized metal layer of the ceramic heating element of FIG.

[Explanation of symbols]

 1 Ceramic Heating Element 2 Silicon Nitride Sintered Body 3 Heating Resistor 4, 5 Electrode Extraction Section 6, 7 Metallized Metal Layer

Claims (1)

[Claims] 1. In a ceramic heating element in which a heating resistor made of an inorganic conductive material is embedded in a silicon nitride sintered body, the metallized metal layer deposited and formed on at least the electrode extraction portion of the ceramic heating element is gold ( Au) and nickel (N
i) or one or more of palladium (Pd), or copper (Cu), cobalt (Co), silicon (S)
The total amount with any one of i) is 95% by weight or more, the balance is any one or more of vanadium (V) or molybdenum (Mo), or any one of the Group 4a elements of the periodic table and manganese (Mn). A ceramic heating element comprising: