JPH0945458A - Spark plug having resistance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a spark plug having a resistance in which increase of a change rate of an electric resistance value is restricted, and in which generation of current noise is prevented by containing titanium oxide powder coated with an insulating oxide in a composition of the resistance. SOLUTION: A spark plug having a resistance is composed of an insulator 3 held on a main body metal 2, a grouding electrode 4 connected to a tip of the main body metal 2, a center electrode 5 forming a spark discharge gap to a discharge end surface of the grounding electrode 4, a terminal electrode 6 connected to a spark coil, conductive glass seal materials 7, 8 filled in the insulator 3, and a monolithic resistance 9 enclosed between the conductive glass seal materials 7, 8. The resistance 9 has composition comprising glass powder, titanium oxide powder, carbon black, and organic binder. The titanium oxide power is contained by 2-60weight%. The surface of the titanium oxide power is coated with insulating oxide film. The grain size of the titanium oxide powder is desirably about 0.1-2μm.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resistor composition which is attached to an internal combustion engine such as a gasoline engine and which prevents the generation of radio noise by hot pressing together with a terminal electrode in a shaft hole of an insulator. The present invention relates to a resistance plug provided with a heat-sealed resistor.

[0002]

2. Description of the Related Art In recent years, spark discharge energy has increased with the increase in output of internal combustion engines. In conventional resistor compositions, the current energy of the spark discharge flowing through the resistor during use causes The carbon black contained in (1) oxidizes (burns out), and the electrical resistance value increases. Therefore, conventionally, a resistance plug having improved load life characteristics by adding a large amount of titanium oxide as a load life stabilizer to a resistor composition (for example, Japanese Patent Publication No. 4-561 and Japanese Patent Publication No. 5-52641). No. gazette) is proposed.

[0003]

In the conventional resistance plug, however, since titanium oxide is a semiconducting substance, the resistance of the resistor at room temperature during hot pressurization (or high temperature combustion) is high. There is a problem in that the rate of change of the electric resistance value when exposed to gas) is very large and the original radio noise prevention property of the resistor is deteriorated.

An object of the present invention is to provide a resistance plug capable of preventing deterioration of radio noise prevention characteristics by reducing the rate of change of the electric resistance value of the resistor at room temperature and during hot pressing. To provide. Another object of the present invention is to provide a plug with resistance capable of obtaining sufficient load life stability characteristics against the increase in spark discharge energy accompanying the recent increase in output of internal combustion engines.

[0005]

According to the present invention, there is provided an insulator having an axial shaft hole, a center electrode inserted into a shaft hole at a tip side of the insulator, and a rear end side of the insulator. A terminal electrode inserted into the shaft hole, and a resistor sealed in the shaft hole of the insulator by hot pressurizing the resistor composition filled between the center electrode and the terminal electrode. And a resistor composition containing titanium oxide powder in an amount of 2% by weight or more and 60% by weight or less in the resistor composition, and the surface of the titanium oxide powder is insulated. The technical means covered with a porous oxide film was adopted.

As the insulating oxide film, one or more electrically insulating oxides such as aluminum oxide, silicon oxide, zirconium oxide, alkaline earth oxides or rare earth oxides may be used. Further, the film thickness of the insulating oxide film is set to 0.0 of the particle diameter of the titanium oxide powder.
You may make it 1 time or more and 0.2 times or less.

[0007]

According to the present invention, by covering the surface of titanium oxide powder, which is a semiconducting substance, with an insulating oxide film, the electrical resistance value of the resistor at room temperature and during hot pressing is increased. By suppressing the semiconductivity in which the rate of change of the radio wave increases, it is possible to suppress deterioration of the radio noise prevention characteristic. Further, by containing 2 wt% or more and 60 wt% or less of titanium oxide powder in the resistor composition, sufficient load life stability characteristics can be obtained against the increase in spark discharge energy accompanying the recent increase in output of internal combustion engines. Obtainable.

[0008]

【Example】

[Structure of Embodiment] FIG. 1 is a view showing a resistance plug for an internal combustion engine. This resistance plug 1 for internal combustion engine is a spark plug with a resistor that is excellent in preventing radio noise,
It is a spark plug called a resistor plug. A resistance plug 1 for an internal combustion engine includes a tubular metal shell 2, a tubular insulator 3 held by the metal shell 2, a ground electrode 4 joined to a tip surface of the metal shell 2, and a ground electrode 4 of the ground electrode 4. The center electrode 5 forming a spark discharge gap between the discharge end face and
A terminal electrode 6 electrically connected to an ignition coil (not shown) of the ignition device, conductive glass sealing materials 7 and 8 filled in the insulator 3, and between these conductive glass sealing materials 7 and 8. It is composed of a monolithic resistor (hereinafter abbreviated as resistor) 9 and the like, which are sealed to each other.

The metal shell 2 constitutes a housing of the resistance plug 1 for an internal combustion engine, and plays a role of supporting the insulator 3 and mounting it on an internal combustion engine such as a gasoline engine.
A hexagonal portion 11 for applying a tool such as a wrench is formed on the outer periphery on the upper end side of the metal shell 2, and the outer periphery on the lower end side is
A mounting screw portion 12 is formed for screwing into the cylinder head of the internal combustion engine.

The insulator 3 is a ceramic sintered body containing aluminum oxide (alumina) or aluminum nitride as a main component, and the metal shell 2, the center electrode 5 and the terminal electrode 6 are formed.
It is an insulator that electrically insulates from. Inside the insulator 3, an axial shaft hole 13 is formed which is open at the front end surface and the rear end surface. Then, of the insulator 3, the shaft hole 13 of the long leg portion 14 protruding into the combustion chamber of the internal combustion engine
The center electrode 5 is fitted therein. Also, the insulator 3
The terminal electrode 6 is fitted in the shaft hole 13 of the corrugation portion 15 that projects outward from the metal shell 2.

The ground electrode 4 and the center electrode 5 are exposed to high temperature combustion gas during the use of the internal combustion engine, and are therefore made of nickel.
Heat resistant metals such as chrome / iron alloys, nickel / manganese / silicon / chrome alloys are used. Ground electrode 4
Is joined to the tip end surface of the metal shell 2 on the ground side (positive side) by using a joining means such as resistance welding. The center electrode 5 is fitted into the shaft hole 13 in a state of protruding from the shaft hole 13 and is held by the insulator 3.

The terminal electrode 6 is made of, for example, mild steel, and is integrally formed with a terminal portion 16 protruding outward from the shaft hole 13. On the outer circumference of the tip, a male screw portion 17 is formed for increasing the bonding strength with the conductive glass sealing material 8. The terminal electrode 6 and the terminal portion 16 may be formed separately.

The conductive glass sealing materials 7 and 8 are resistors 9
At the same time, it is filled in the shaft hole 13 and heat-sealed in the shaft hole 13 to simultaneously bond the insulator 3 with the center electrode 5 and the terminal electrode 6 and electrically bond the center electrode 5 with the terminal electrode 6. It is something to do. Conductive glass sealing material 7, 8
In the glass seal composition, for example, glass powder such as borosilicate / lithium / barium glass is 50% by weight, metal powder such as copper is 40% to 47% by weight, and P
One type of organic binder such as EG (polyethylene glycol) type, PED (polyethylene oxide) type and dextrin type is used in an amount of 3% by weight to 10% by weight.

The resistor 9 is a conductive glass sealing material 7, 8
At the same time, it is filled in the shaft hole 13 and heat-sealed in the shaft hole 13 to prevent radio noise. This resistor 9
In the resistor composition, for example, glass powder such as borosilicate / lithium / barium glass is added in an amount of 10% to 80% by weight, and titanium oxide (Ti) as a load life stabilizer is used.
2 wt% to 60 wt% of O ₂ ) powder, and 0.1 wt% to 20 wt% of carbon black as the resistor powder,
One type of organic binder such as PEG (polyethylene glycol) type, PED (polyethylene oxide) type and dextrin type is used in an amount of 0.05 to 5% by weight. As the resistor powder, 0.2% by weight of aluminum was added to titanium oxide powder and carbon black, or zirconium oxide (zirconia: Zr).
O ₂ ) may be contained in an amount of 0 to 20% by weight.

The titanium oxide powder has a particle size of 0.1 μm to 2 μm, and its surface is covered with an insulating oxide film. The insulating oxide film may be aluminum oxide (alumina: Al ₂ O ₃ ), silicon oxide (silica: SiO ₂ ), zirconium oxide (zirconia: Zr).
O ₂ ), one kind of an alkaline earth oxide or a rare earth oxide, or two or more kinds of electrically insulating oxides selected from these (for example, SiO ₂ + Al ₂ O ₃ ) is used.
The film thickness of the insulating oxide film is preferably 0.01 to 0.2 times the particle size of the titanium oxide powder, and in this embodiment, it is 1 × 10 ⁻³ μm to 0.4 μm. .

As the alkaline earth oxide (group IIa of the periodic table of elements), magnesium oxide (magnesia: MgO), calcium oxide (CaO), strontium oxide (SrO), barium oxide (BaO), etc. are used. be able to. Further, as the rare earth oxide (group IIIa of the periodic table of elements), yttrium oxide (Y
₂ O ₃ ), lanthanum oxide (La ₂ O ₃ ) and the like can be used.

[Comparative Results of Examples and Comparative Examples] Next, the weight% of the titanium oxide (TiO ₂ ) powder as the load life stabilizer was varied or oxidized in various weight% of the resistor composition components. A plurality of experiments for investigating how load life characteristics, radio noise prevention characteristics, and heating characteristics change by variously changing the insulating oxide film covering the surface of titanium powder will be described.

1) Adjustment of Resistance Material Examples 1 to 5 and Comparative Examples 1 to 1 in Table 1 described later.
The resistor raw material powder of Comparative Example 7 is 10% by weight to 80% by weight.
Borosilicate / lithium / barium glass powder of 1.5
% To 65% by weight of titanium oxide powder and 0.1% to 20% by weight of carbon black are mixed,
An appropriate amount of 05 wt% to 5 wt% dextrin-based organic binder and water were added, and the mixture was granulated and dried to obtain a resistance material (resistor material powder).

2) Method of Forming Insulating Oxide Film The surface of the titanium oxide powder of Examples 1 to 5, Comparative Example 1 and Comparative Example 2 is coated with the insulating oxide film shown in Table 1. did. This insulating oxide film is formed by adding water and a dispersant to a titanium oxide material to form a slurry, and then adding a predetermined amount of an aqueous salt solution of Al, Si, Zr or the like to an alkaline substance or a neutralizing agent. The surface of the titanium oxide particles is coated with a hydrous oxide produced by adding an acidic substance. Finally, the slurry PH is adjusted, filtered, washed with pure water, and then dried with a spray dryer (spray dryer) or the like to form an insulating oxide film on the surface of the titanium oxide particles. The insulating oxide film had a thickness of 0.1 μm because the titanium oxide powder had a particle size of 1 μm.

3) Method for sealing the resistor The center electrode 5 is inserted into the axial long hole 13 side of the alumina insulator 3 on the side of the long leg 14 and 100 mg of the conductive glass sealing material 7 is placed thereon, as described above. 400m of adjusted resistance material
g, 200 mg of the conductive glass sealing material 8 was sequentially filled into the shaft hole 13, and then the terminal electrode 6 was inserted into the shaft hole 13. Next, the entire insulator 3 is heated to a high temperature (for example, 900
(° C) and pressure on the terminal electrode 6 (for example, 40 kgf)
Then, the resistance material and the conductive glass sealing materials 7 and 8 filled in the shaft hole 13 are heat-sealed by hot pressing, and the monolithic resistor 9 is interposed between the conductive glass sealing materials 7 and 8.
I got Then, the ground electrode 4 is formed on the outer periphery of the insulator 3.
The metal shell 2 which is fixed is fixed to 0.5 kΩ to 20 kΩ (desirably 3 kΩ to 20 kΩ) required for suppressing radio noise.
A resistance plug 1 for an internal combustion engine having an electric resistance value within the range of (kΩ) (at room temperature, for example, 20 ° C.) was obtained.

4) Regarding load life characteristics Test device: Automotive transistor ignition device, primary coil side stored energy: 100 mJ, discharge voltage: 30 kV, discharge frequency: 3600 times / min.

Under the above conditions, the rate of change of the electric resistance value of the resistor 9 after 100 hours was measured, and the measurement results are shown in Table 1. In Table 1, the symbol ⊚ indicates that the change rate of the electric resistance value is ±.
20% or less, ◯ indicates a rate of change in electric resistance of ± 21% or more and ± 30% or less, and x indicates a rate of ± 31% or more, which is out of the regulation value.

As can be seen from Table 1, when the content of titanium oxide powder in the composition of the resistor composition (resistive material) is less than 2.0% by weight, the load life characteristics tend to deteriorate rapidly. You can see that Also,
It can be seen that when the content of titanium oxide powder exceeds 60% by weight, the load life characteristics tend to deteriorate rapidly.
Further, it can be seen that 30% by weight tends to be the best in the range of 2.0% by weight to 60% by weight of the titanium oxide powder.

5) Radio noise prevention characteristics Using a 4-cycle 360cc engine, C, I, S,
According to the P, R (International Radio Interference Special Committee) measurement method, 1
The measurement was performed at 20 MHz, and the measurement results are shown in Table 1. In Table 1, ◯ indicates that the radio noise level is within the regulation value of 35 dB or less, and X indicates that the radio noise level is outside the regulation value of 36 dB or more.

As can be seen from Table 1, when the content of titanium oxide powder in the component of the resistor composition (resistive material) is more than 60% by weight, the radio noise prevention property tends to be rapidly deteriorated. I understand.

6) Heating Characteristics Electric resistance value at hot temperature (150 ° C.) after leaving the resistance material in air at 150 ° C. for 2 hours and electric resistance value at room temperature (for example, 20 ° C.) before the test (for example, 5 kΩ) and the rate of change of the electric resistance value were measured, and the measurement results are shown in Table 1. In Table 1, the symbol ⊚ indicates that the change rate of the electric resistance value was −.
25% or less, ∘ indicates a rate of change in electric resistance of −26% or more and −40% or less, and × indicates a rate of −41% or more, which is outside the regulation value.

As can be seen from Table 1, Comparative Example 4 to Comparative Example in which the insulating oxide film was not formed on the surface of the titanium oxide powder and the weight% of the titanium oxide powder was larger than 2% by weight. It can be seen that in No. 7, the heating characteristics tend to deteriorate rapidly. Then, among Examples 1 to 5, it can be seen that Example 2 in which the weight% of the titanium oxide powder is 30% by weight and the insulating oxide film is alumina is the most preferable.

[Table 1]

[Effects of the Embodiment] As described above, the resistance plug 1 for an internal combustion engine has a resistance by forming an insulating oxide film such as alumina on the surface of the titanium oxide powder which is a semiconducting substance. When the body 9 is hot pressed (for example, 850 ° C. to 950 ° C.) with respect to the electric resistance value (for example, 0.5 kΩ to 20 kΩ) at room temperature (for example, 20 ° C.) or exposed to a high-temperature combustion gas (for example, a plug tip). Temperature is 9
It is possible to reduce the rate of change of the electric resistance value at 00 ° C. Therefore, the rate of change of the electric resistance value of the heating characteristic can be reduced, so that the deterioration of the radio noise prevention performance of the resistor 9 can be suppressed.

Further, the resistor 9 contains titanium oxide powder in an amount of 2% by weight or more and 60% by weight or less based on the weight% of the resistor composition, so that the internal combustion engine of recent years can be maintained while maintaining sufficient radio noise prevention performance. It is possible to obtain sufficient load life stability characteristics with respect to the increase in spark discharge energy accompanying the increase in engine output.

[Modification] In this embodiment, borosilicate / lithium / barium glass powder was used as the binder (glass powder) of the resistor 9, but borosilicate glass powder, barium borate-based glass powder, and lead glass were used. You may use powder etc. In particular, barium oxide-containing glass powder has excellent wettability with carbonaceous substances (carbon black). The softening point of the glass powder is preferably higher than about 300 ° C. If the softening point becomes too low, problems such as difficulty in fixing and holding the center electrode 5 and the terminal electrode 6 and fluctuations in the electrical resistance value occur when used in an actual internal combustion engine.

In Examples 1 to 5, the glass powder is set to 10% by weight to 80% by weight in the resistor composition. If the amount of the glass powder is less than 10% by weight, the resistor powder is not firmly adhered to form a porous resistor 9, so that not only the airtightness and the load life characteristics are deteriorated, but also the press-fitting of the terminal electrode 6 is difficult. Therefore, the coupling force between the terminal electrode 6 and the male screw portion 17 is also reduced.

If the glass powder content exceeds 80% by weight, a large amount of glass powder penetrates into the carbon black particles acting as a conductive material, the electrical resistance value of the resistor 9 is greatly increased, and the variation in the electrical resistance value is also increased. In addition, the resistor 9 is not pressed and filled in the direction orthogonal to the longitudinal direction of the terminal electrode 6 during hot pressing of the resistor 9, which makes it difficult to obtain a predetermined electric resistance value. The radio noise prevention performance is also reduced.

In Examples 1 to 5, carbon black was used as the conductive material in the resistance powder, but acetylene black, graphite, pitch powder, or an organic substance that can be carbonized during sintering may be used. Further, a small amount of a semiconductive substance such as zirconium oxide may be mixed in the titanium oxide powder as the load life stabilizing material.

Further, in the present invention, the film thickness of the insulating oxide film is set to 0.01 times or more and 0.2 times or less of the particle diameter of titanium oxide. If the thickness of the insulating oxide film is less than 0.01 times the particle size of titanium oxide,
The performance of suppressing the semiconducting property of titanium oxide, which increases the rate of change in electrical resistance between room temperature and hot pressing, is weak. Also,
If the thickness of the insulating oxide film is thicker than 0.2 times the particle diameter of titanium oxide, the load life stability of titanium oxide will deteriorate.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention.

[Explanation of symbols] 1 Plug with resistance 3 Insulator 5 Center electrode 6 Terminal electrode 7 Conductive glass seal material 8 Conductive glass seal material 9 Monolithic resistor 13 Shaft hole 16 Terminal part 17 Male screw part

Claims (3)

[Claims] 1. An insulator having an axial hole in the axial direction, a center electrode inserted in the shaft hole on the tip side of the insulator, and a terminal inserted in the shaft hole on the rear end side of the insulator. A resistance-filled plug comprising an electrode and a resistor sealed in the axial hole of the insulator by hot pressing a resistor composition filled between the center electrode and the terminal electrode. The resistor composition contains 2% by weight or more and 60% by weight or less of titanium oxide powder in the resistor composition, and the surface of the titanium oxide powder is covered with an insulating oxide film. A plug with resistance that is characterized by that. 2. The resistance-imparted plug according to claim 1, wherein the insulating oxide film has at least one electrical insulating property of aluminum oxide, silicon oxide, zirconium oxide, alkaline earth oxide or rare earth oxide. A plug with resistance, characterized by being made of the oxide of. 3. The resistance-imparted plug according to claim 1, wherein the insulating oxide film has a film thickness of 0.01 times or more and 0.2 times or less of a particle diameter of the titanium oxide powder. A plug with resistance characterized by having.