JPH0222997B2 - - Google Patents

Description

[Detailed description of the invention]

"Industrial Application Field" The present invention relates to a spark plug containing a resistor for preventing noise generation. "Prior Art" An example of a spark plug that has a resistor inside the insulating refractory of the spark plug in order to prevent interference to communication radio waves due to radio frequency emissions from the high voltage ignition circuit of an internal combustion engine is disclosed in Japanese Patent Application Laid-Open No. It is disclosed in 144830-1980, 68131-1982, 105988-1987, etc. JP-A-50-144830 uses an insulating ceramic filler (aggregate) with a relatively large particle size, whereas the other two JP-A-Sho discloses a method using a glassy aggregate. has been done. Tokukai Akira
57-105988 is made by using borosilicate-lithium-calcium glass with a relatively large particle size (all 16 meshes) and mixing it with carbon black, glass powder, and ceramic powder. ``Problems to be Solved by the Invention'' However, conventional glassy coarse aggregates have a specific fire resistance or high softening temperature and have a specific coarse particle size in order to prevent noise. are generally expensive. Further, in these conventional methods, it is still desired to improve the radio wave interference prevention properties. An object of the present invention is to enable the use of common glass having a low softening temperature, and to provide a resistor-containing spark plug that achieves excellent noise prevention effects without using glass of a specific particle size. "Means for solving the problem" (1) Insert an insulator and a center electrode into the lower end of the shaft hole of the insulator, and sandwich the resistor with a terminal electrode on top of the center electrode with a conductive sealing material. In a resistor-containing spark plug comprising a housing that is heat-sealed and has a ground electrode fixed to the outer periphery of the insulator, the resistor has a yield point of 500 to 900°C in terms of weight percent of the resistor; Contains 5 to 90% of glass with a particle size of 150 μm or less and 0 to 85% of insulating ceramic powder with a particle size of 150 μm or less, which are mixed and granulated or calcined before and after granulation to reduce the particle size.
35-90% granulated aggregate with a particle size of 100-800 μm; () 2-55% glass with a yield point of 300-600°C and a particle size of 150 μm or less; 0.1-5% carbon black;
and 10 to 65% of a resistance material containing 5 to 58% of insulating ceramic powder with a particle size of 150 μm or less.
It is a resistor-containing spark plug consisting of. "Function" The resistor-containing spark plug of the present invention has a particle size obtained by mixing glass powder and insulating ceramic powder as coarse aggregate in appropriate proportions as described above, and granulating or additionally calcining the mixture. By using coarse aggregate with a particle diameter of 100 to 800 μm (hereinafter referred to as granulated aggregate), glass powder with a lower softening temperature over a wide range (particle size of 150 μm or less) can be produced without using glass with a specific particle size as it is. can be used to improve the noise prevention effect as shown in Table 1. In addition, even without calcination, the granulated aggregate is subjected to a thermal effect similar to that in the calcination state when sealing the resistor, and at the same time is heated and pressurized to form the aggregate (granules).
The noise prevention effect can be similarly improved even if it is held as "Example" Next, specific examples of the resistor composition of the resistor-containing spark plug of the present invention will be described. The insulating ceramic powder used for the aggregate includes insulating metal oxides such as zirconia, fused silica, and alumina, and refractory ceramic raw materials such as bentonite, frog's eye clay, silica, silica sand, feldspar, mullite, zircon, and β-spodiumene. Mineral or synthetic materials, silicon nitride,
When granulating nitrides such as boron nitride, aluminum nitride, and aggregates before calcination, it is easier to granulate them if they contain caking clay minerals as insulating ceramic powder, and the mixture should be moistened with water or a solvent. You can do it by doing this. As the clay mineral, it is preferable to use bentonite, frog's eye clay, etc., and the blending ratio thereof is 1 to 20% by weight, preferably 3 to 10% by weight, based on the total resistor. Note that granulation is easier when the organic binder is added in an amount of 0.1 to 2.0% by weight, preferably 0.3 to 1.0% by weight. Granulation can also be carried out using other known organic binders for molding aids, and when calcining is performed, the organic binder substantially disappears. An organic binder is used when mixing the granulated aggregate and the resistance material. As this organic binder, an aqueous or solvent solution or emulsion of dextrin, methylcellulose, polyvinyl alcohol, gum arabic, etc. is used. When mixing granulated aggregate and resistance material, it is necessary to mix the organic binder at the same time or
Alternatively, uniform mixing can be facilitated by premixing the aggregate with a separately premixed resistance material. Further, the glass raw materials used in the present invention include those for resistance materials and those for aggregates, but unlike conventional methods, they are not limited to a specific type. However, in view of the sealing properties during sealing, it is desirable to use a relatively low softening temperature glass with a yield point of 300 to 600° C. as the glass for the resistance material. Glass having a relatively high melting point with a yield point of 500 to 900°C is suitable as the glass for aggregate. However, by adjusting the blend with ceramic powder, the apparent softening temperature of the aggregate becomes higher. Typical examples of these glasses include BaO−B ₂ O ₃ series and BaO
−B ₂ O ₃ −SiO ₂ system, BaO−B ₂ O ₃ −SiO ₂ −R ₂ O
(RO) system, PbO−SiO ₂ system, and PbO−B ₂ O ₃ −
Examples include SiO ₂ -Al ₂ O ₃ system. As a high softening temperature glass, SiO ₂ −B ₂ O ₃ −
Al ₂ O ₃ −R ₂ O (RO) system, SiO ₂ −B ₂ O ₅ −Al ₂ O ₃ system,
SiO ₂ −B ₂ O ₃ system, SiO ₂ −B ₂ O ₃ −PbO−R ₂ O (RO)
There are glass types such as SiO ₂ -Al ₂ O ₃ -R ₂ O (RO) series. However, R here represents a metal element in a group of the periodic table, and representative examples of R ₂ O and RO include Na ₂ O,
Examples include K ₂ O, Li ₂ O, MgO, CaO, ZnO, and BaO. The above-mentioned glass is not specific to the present invention, and glasses having various known component ratios can be used. Resistance materials are carbon black 0.1-5% by weight, glass 2-55% by weight based on the entire resistor.
It consists essentially of three components of 5 to 58% by weight of insulating ceramic powder, and the sum of these three components accounts for 10 to 58% of the total resistor.
Make it 65% by weight. Carbon black is a conductive material, and at 0.1 to 5% by weight, a resistance value of 0.5 to 20 KΩ, which is necessary for preventing electrical noise, can be obtained. Carbon black has poor dispersibility, tends to have large variations in resistance value, and also tends to cause fluctuations in resistance value during a load life test. In order to improve this dispersion, 5% or more of ceramic powder is required. If the ceramic powder exceeds 58%, the resistor has poor sinterability and becomes porous, which deteriorates the load life characteristics. Glass is indispensable as a binder during sealing, and if it is less than 2%, the bonding force is weak, and if it exceeds 55%, the dispersibility of carbon deteriorates, resulting in large variations in the R value. Poor sealing deteriorates load life characteristics. The resistance material needs to be uniformly dispersed and sealed in the surrounding space of the granulated aggregate, and the particle size of each component is preferably 150 μm or less, more preferably
100μm or less is preferable. In order to further stabilize the load life characteristics, 5 to 58% of the insulating ceramic powder should contain oxides and carbides of metals and rare earth elements of subgroups a, a, and a of the periodic table, as well as ZnO, _B4C , SiC,
At least one selected from the group consisting of TiB, TiN
It is preferable to substitute at least 30% of species. Note that if it is added in excess of 30%, the load life characteristics will deteriorate. This resistance material and granulated aggregate are mixed to form a resistance element. If the resistance material is less than 10% of the total resistor, the conductive path becomes narrow, current concentration occurs due to the application of high voltage, and the R value increases, and if it exceeds 65%, the effect of adding granulated aggregate does not appear. Noise prevention characteristics deteriorate significantly. Next, aggregate is made by granulating glass powder (5-90%) and insulating ceramic powder (0-85%), but if the yield point of glass is high (600℃ or higher), ceramic powder may not be used. Glass powder alone can also be used as aggregate. In order to sinter the aggregate particles near the sealing temperature, a minimum of 5% aggregate glass is required (therefore a maximum of 85% insulating ceramic powder). Below this range, the aggregate particles exhibit almost no softening properties, poor sealing properties, and unstable load life characteristics. As shown in the examples below, the total amount of aggregate in the resistor is 35 to 90% by weight, preferably 50 to 80% by weight.
Weight%. If the aggregate content is less than 35%, the noise prevention properties will be poor. On the other hand, if it exceeds 90%, the noise prevention properties will not deteriorate, but the amounts of other components will be relatively reduced, resulting in an increase in resistance value and instability in the load life test, resulting in poor practicality. The balance of the aggregate (35-90% by weight) in the total resistor consists essentially of resistive material (65-10% by weight). Granulation of the aggregate is an important aspect of the present invention. Glass powder and ceramic powder (generally 150 μm pass is acceptable) are granulated to a particle size range of 100 to 800 μm. Preferably, this is further calcined and sintered and used as an aggregate, resulting in a resistor structure in which a resistive material phase is continuously formed around it. Furthermore, in the case of the present invention, glass having a low softening temperature can be used particularly as the aggregate glass, so that the sealing density can be easily improved. The apparent softening temperature can be changed quite freely not only by selecting the yield point of the raw material glass but also by changing the mixing ratio of ceramic powder and glass, so you can freely select a composition that is suitable for a predetermined sealing temperature. You can choose. As shown in FIG. 1, the particle size of granulated aggregate in the range of 100 to 800 μm has the best noise prevention properties.
Outside this range, the noise prevention performance deteriorates in both coarse and fine cases. It is desirable that the granules are calcined. Calcination is not necessarily required because granulation can be achieved by including caking clay minerals as ceramic powder aggregate. However, calcining is usually easier to manufacture and results in less variation in the product. Alternatively, granulation can be performed after calcining first. In this case, there is no difference in final performance, so the one that is easier to manufacture should be selected first. Note that it is not preferable to use coarse particles of 150 μm or more from the beginning as a starting material for granulating glass powder or ceramic powder used as granulated aggregate. If the particle size is large, the aggregate granules will be non-uniform, and the softening state of each aggregate granule will be different near the sealing temperature, so the shape of the aggregate will affect the collapse noise prevention properties. The insulating ceramic powder used for the resistance material may be the same as the ceramic powder for the aggregate or different, and is appropriately selected and used. The granulated aggregate is mixed with the resistance material and sintered within the spark plug bore. During this mixing, as mentioned above, it is more suitable to use an organic binder in combination to uniformly disperse and mix the granulated aggregate and the resistance material. "Effects of the present invention" From the above, it can be seen that the grain size in the resistor is 100 to 800μ.
It is possible to manufacture a resistor with excellent noise prevention properties by densely filling aggregate with a relatively large size of m. The present invention, which has fewer restrictions on the type of glass, particle size, etc., can be manufactured more easily than conventional methods. In addition, in terms of cost, it is not necessary to use specific glass grains with a high softening point and a specific coarse particle size as in the conventional method, so the present invention provides a more inexpensive resistor composition. Examples are shown below, but the present invention is not limited thereto. (1) Adjustment of the resistance material The glass powder and ceramic powder shown in Table 1 are all powders that can be passed through a 100 μm sieve.
It was mixed with carbon black at the blending ratio shown in Table 1. (2) Preparation of granulated aggregate Glass powder and ceramic powder shown in Table 2 (through a 100 μm sieve) were mixed, water was added, kneaded, and granulated particles were extruded through a 0.8φ screen using the granulation method. After drying, the particles were sized by sieving to 800 to 100 μm. No. 26 was passed on to the next process as is, while the others were calcined at 900°C in an electric furnace. In addition, as comparative examples, No. 27 using raw material powder of 100 μm or less and No. 28 using raw material powder of 800 μm or more were added to the test. (3) Preparation of resistor base Granulated aggregate and resistance material were mixed as shown in Table 1, an appropriate amount of methylcellulose aqueous solution was added as an organic binder, and the mixture was granulated and dried to obtain a resistor base. (4) Sealing the resistor into the shaft hole of the spark plug insulator Insert the center electrode (ignition electrode) into the lower end of the center shaft hole of the alumina insulator, and place 0.2g of conductive sealing material on top of it. 0.55g of the resistor material adjusted above,
0.2 g of conductive sealing material was sequentially filled, and then a terminal electrode was inserted into the shaft hole. This entire insulator is then heated to 800-950°C and pressure (40
Kg weight) is added and the resistor material is filled into the shaft hole.
The sealing material was sealed by hot pressing. A housing with a grounding electrode fixed to the outer periphery of this insulator is fixed, and the
A spark plug containing a resistor having a resistance value within the range of 20KΩ (preferably 3 to 20KΩ) was obtained. (5) Product performance test The noise electric field strength was measured 5 times at 120MHz for 4 cycles using a 360c.c. engine according to the CISPR standard.
The average value was taken. The results are also shown in Table 1. As a result, carbon black is 0.1 to 5% by weight.
(hereinafter referred to as resistor) almost meets the target resistance value. The amount of glass in the resistance material is 2 to 55% by weight.
The required resistance characteristics and sealing performance are satisfied within the range of . Also, if the total amount of aggregate is 35 to 90% by weight, there will be no problem with resistance value or noise prevention properties, but if it is less than 35% by weight, the noise prevention properties will deteriorate, and if it is more than 90% by weight, current concentration will occur and the resistance value will increase. . A suitable amount of aggregate glass is 5 to 90% by weight. Furthermore, when comparing the same composition with and without calcining (No. 3 and No. 26), it is found that there is no significant difference in properties. On the other hand, the particle size of the aggregate raw material is 100μ
Both those with a thickness of less than 800 μm (No. 27) and those with a diameter of over 800 μm (No. 28) have poor noise prevention properties. (6) Comparative examples No. 8 (with too little aggregate), No. 27 (with aggregate <100 μ
m), No.28 (aggregate>800μm), No.29 (conventional product BaO
−30 parts by weight of B ₂ O ₃ glass, 35 parts by weight of clay,
10 parts by weight of _TiO2 , 1.5 parts by weight of carbon black,
No.30 (Conventional product B ₂ O ₃ −SiO ₂ −ZnO−Na ₂ O glass
50 parts by weight, 50 parts by weight of Si ₃ N ₄ , carbon black
2.3 parts by weight) All raw materials used are 100μm or less.

【table】

[Table] (Note) *marked is outside the scope of the present invention

【table】

Based on [Table].

【table】 [Brief explanation of drawings]

FIG. 1 is a graph showing the relationship between aggregate particle size and noise prevention effect.

Claims (1)

[Scope of Claims] 1. A center electrode is inserted into the lower end of an insulator and a shaft hole of the insulator, and a resistor is sandwiched on top of the center electrode with a conductive sealing material and heat-sealed together with a terminal electrode. In a resistor-containing spark plug consisting of a housing with a grounding electrode fixed to the outer periphery of an insulator, the resistor is made of glass having a yield point of 500 to 900°C and a particle size of 150 μm or less in weight percent of the resistor. 5 to 90% and 0 to 85% of insulating ceramic powder with a particle size of 150 μm or less, mixed together,
Granulation or calcining before and after granulation to achieve particle size of 100~
35-90% of granulated aggregate with a particle diameter of 800 μm; () 2-55% glass with a yield point of 300-600°C and a particle size of 150 μm or less; 0.1-5% carbon black; and insulating ceramic powder with a particle size of 150 μm or less. ~
A spark plug with a resistor consisting of 10 to 65% of a resistor material containing 58%. 2 the insulating ceramic powder 5 of the resistance material;
~58% contains oxides and carbides of metals and rare earth elements of each subgroup of Groups A, A, and A of the Periodic Table, with less than 30% of the components being load life stabilizers.
The spark plug with resistance according to claim 1, characterized in that the spark plug is replaced with at least one selected from ZnO, B ₄ C, SiC, TiB, and TiN.