JPH04561B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a resistor composition for a spark plug, and particularly to a resistor composition useful for small spark plugs. [Conventional technology] In recent years, as internal combustion engines have become higher output and more fuel efficient, the shape of the combustion chamber has become more complex, and the installation space for the ignition plug has become increasingly restricted, creating a demand for the development of compact ignition plugs with a small diameter ignition plug installation screw. and the mounting screw diameter is 10mm (C-
E type), 8mm has become necessary.
In addition, the power supply capacity is also increasing to improve ignitability. Resistor compositions for resistor-containing spark plugs generally mainly include glass powder, inorganic powder (alumina, zircon, mullite, silica, clay, silicon nitride, boron nitride, aluminum nitride, or mixtures thereof), and carbonaceous materials (carbon black). , graphite, other organic substances that can be carbonized by sealing and heating such as glycerin, methyl cellulose, and polyvinyl alcohol), and resistance value load life characteristic stabilizers such as TiO ₂ . As a resistive load life characteristic stabilizer
For example, the use of TiO ₂ is disclosed in Japanese Patent Application No. 58-40023, 58.
-64599, 58-7854, 59-215399, etc., but conventionally, in order to prevent an increase in radio noise (electronic noise), the amount added must be less than 30 wt% in the resistor composition. It had been. [Problems to be solved by the invention] However, in the small ignition plug as mentioned above, the diameter of the resistor must be 3.5 mm or less in terms of resistor strength and withstand voltage, and the conventionally known method When a resistor with a different composition is used, the density of the current passing through it increases, and the carbon in the resistor component burns out, resulting in an increase in resistance and a problem in that a stable load life cannot be obtained. Therefore, an object of the present invention is to provide a resistor composition for a small ignition plug that has a stable load life and good electrical characteristics. [Means and effects for solving the problems] The above-mentioned problem of the present invention is to solve the above problems by using a spark plug with a resistor diameter of 3.5 mm or less,
~39.9%, titanium oxide 30~67.9%, ceramic powder other than titanium oxide 0~37.9%, carbon black as a resistance value control material, one or more organic carbonaceous substances 0.1~20%, Al, Mg, Zn, Sn, Ti, Zr, Fe,
Ag, Ga metal or one or more of these alloys 0~
10% and ceramic aggregate with particle size 100-800μm30
This problem can be solved by a resistor composition for a spark plug consisting of ~67.9%. In the resistor composition for small spark plugs of the present invention, the amount of TiO ₂ added is 30 to 30% of the total resistor composition.
The range is 67.9wt%. As mentioned above, in conventional resistor compositions, the amount of TiO ₂ added was less than 30 wt%. It is true that the electrical noise characteristics worsen as the amount of TiO ₂ added increases, but in small spark plugs with a resistor diameter of 3.5 mm or less, the thinner resistor diameter reduces the capacitance and allows high-frequency noise current to pass through. It was found that it is sufficiently durable for practical use because it becomes difficult to use. Also,
In order to prevent the deterioration of electrical characteristics due to the addition of TiO ₂ , more than 30 wt% of ceramic coarse powder (hereinafter referred to as ceramic aggregate) with a particle size of 100 to 800 μm was used, and a zigzag pattern was used to lengthen the current path of the resistor. It is necessary to have a block structure, so TiO ₂
Cannot add more than 67.9wt%. The particle size of TiO ₂ is generally 5 μm or less, preferably 3 μm or less. Since TiO ₂ becomes a semiconductor reduced during the heat sealing process, there is little variation in resistance even when a high-energy current is passed through the resistor. Furthermore, since TiO ₂ improves the dispersibility of carbon black and other carbonaceous substances, a more stable resistor can be obtained. In addition to TiO ₂ , zirconia, zircon, alumina, silicon carbide, aluminum nitride, silicon carbide, mullite, silica, etc. can be used as materials for improving the dispersibility of carbon black and other carbonaceous substances. As glass powder, B ₂ O ₃ −SiO ₂ system, BaO−
B ₂ O ₃ system, SiO ₂ −B ₂ O ₃ −CaO−BaO system, SiO ₂ −
General glass such as ZnO-B ₂ O ₃ type glass having a softening temperature of 300° C. to 600° C. can be used, and the particle size is preferably 100 μm throughout. The amount of glass powder added is 2wt%
If it is less than that, the sinterability will be poor and the load life will not be stable.
If it exceeds 39.9wt%, the amount of aggregate will decrease and the electrical interference prevention performance will deteriorate. Ceramic aggregates include refractory raw materials such as frog's eye clay, silica, feldspar, high melting point glass, silicon nitride, alumina, fused silica, zirconia, zircon, bentonite, and mullite with a particle size of 100 to 800 μm, and glass and ceramic powder. A mixture or a fired product can be used. As mentioned above, the ceramic aggregate is 30wt to prevent the deterioration of electrical properties due to the addition of TiO ₂ .
It is necessary to use more than 67.9wt%, but if it exceeds 67.9wt%, the conductive path will become narrower and the load life will be shortened. As the resistance value control material, carbon black, graphite, or various organic carbonaceous materials that are carbonized by heat sealing can be used. If this amount (carbon equivalent) is less than 0.1 wt%, the resistance value will be excessive, and if it exceeds 20 wt%, the resistance value will be too small to be suitable for use. In addition, in order to improve the dispersion of the resistance value control material, ceramic powders such as quartz glass, zircon, zirconia, alumina, etc. (passed through a 100 μm sieve) should be added at 37.9wt% or less (the effective amount is 0.1wt).
% or more, preferably 10 to 20 wt%). The material of the ceramic powder may be the same as that of the ceramic aggregate. Al, Mg,
Addition of metal powders such as Zn, Sn, Ti, Zr, Fe, Ag, Ga (or alloys thereof) of 10 wt% or less (effective amount is 0.1 wt% or more) is effective. however,
If it exceeds 10wt%, electrical noise characteristics will deteriorate. Examples are shown below. (Example) The raw materials shown in Tables 1 and 2 were wet mixed and then dried to obtain a resistor composition powder. Then, insert the center electrode 3 into the lower end of the inner hole 1a (inner diameter 3 mm) of the alumina porcelain insulator 1 shown in FIG.
A mixture of copper powder and glass powder (50:50) on top of it
0.05 g, 0.20 g of the above resistor powder, and 0.05 g of a mixture of copper powder and glass powder (50:50) were poured in this order, and then the terminal nut 2 was inserted into the inner hole 1a. Next, the entire insulator 1 was heated to 800 to 950 DEG C., and pressure was applied to the terminal nut 2 to adhere and compress the above-mentioned powder filled in the inner hole 1a of the insulator 1. Through this operation, the mixture of copper powder and glass powder on both ends of the resistor powder becomes the conductive glass layers 4 and 6, and the resistor powder becomes the resistor 5. A housing 7 to which a grounding electrode 8 is fixed is fixed around the outer periphery of this insulator 1, and
Resistor-filled spark plugs having resistance values in the range of Ω were obtained (Examples Nos. 1 to 13 and Comparative Examples Nos. 1 to 6). or,
Spark plugs were obtained in the same manner (Examples Nos. 7 to 9) using insulators 1 with an inner diameter of more than 3 mm, and thus with a resistor diameter of more than 3 mm. Using the spark plugs thus obtained, load life and electrical characteristics were tested in the following manner, and the results shown in Table 2 were obtained. Load life test Test equipment: Automotive transistor ignition device Primary coil side storage energy: 100 millijoules Discharge voltage: 30 kV Number of discharges: 3,600 times/min The rate of change in resistance value was measured after 100 hours under the above conditions. Electrical noise characteristics: 120MHz according to CISPR (International Special Committee on Radio Interference) measurement method using 4-cycle 360c.c. engine
Those below the regulation value (35dB) were considered good, and those exceeding the regulation value were considered defective. Measurements were taken at an initial point in time.

【table】

【table】

【table】

[Table] *2. Upper row: carbon black; lower row: dextrin (effects of the invention) Even if a conventional resistor composition is used in a small spark plug with a resistor diameter of 3.5 mm or less, load life characteristics and electrical noise prevention characteristics can be maintained. Although it has been difficult to satisfy both requirements, the resistor composition of the present invention has made this possible.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a resistor-containing spark plug used in an embodiment of the present invention.

Claims (1)

[Claims] 1. Used in a spark plug with a resistor diameter of 3.5 mm or less,
Glass powder 2-39.9% by weight, titanium oxide
30-67.9%, ceramic powder other than titanium oxide
37.9% or less, carbon black as a resistance value control material, 0.1 to 20% of one or more organic carbonaceous substances, Al,
Mg, Zn, Sn, Ti, Zr, Fe, Ag, Ga metals or their alloys at least 10%, and particle size 100
A resistor composition for spark plugs consisting of 30 to 67.9% of ~800 μm ceramic aggregate. 2 Used in spark plugs with a resistor diameter of 3.5 mm or less,
Glass powder 2-39.9% by weight, titanium oxide
30 to 67.9%, carbon black as a resistance control material, 0.1 to 20% of one or more organic carbonaceous substances, Al,
Mg, Zn, Sn, Ti, Zr, Fe, Ag, Ga metals or their alloys at least 10%, and particle size 100
A resistor composition for spark plugs consisting of 30 to 67.9% of ~800 μm ceramic aggregate. 3 Used in spark plugs with a resistor diameter of 3.5 mm or less,
Glass powder 2-39.9% by weight, titanium oxide
30-67.9%, ceramic powder other than titanium oxide
37.9% or less, carbon black as a resistance value control material, 0.1 to 20% of one or more organic carbonaceous substances, and 30 to 67.9% of ceramic aggregate with a particle size of 100 to 800 μm. 4 Used in spark plugs with a resistor diameter of 3.5 mm or less,
Glass powder 2-39.9% by weight, titanium oxide
30 to 67.9%, carbon black as a resistance value control material, 0.1 to 20% of one or more organic carbonaceous substances, and 30 to 67.9% of ceramic aggregate having a particle size of 100 to 800 μm.