JPH01283784A - Spur plug with built-in resistance - Google Patents

Abstract

PURPOSE:To enhance the noise preventive effect by forming a resistance element from a film resistance element having a specified thickness and specified effective length on the surface of an insulative columnar base body, and by sealing the surrounding of connections of the film resistance element with a central electrode axis using a conductive sealing material. CONSTITUTION:Seal between a ceramic insulation 1 and a film resistance 4A and a seal 3 at the foremost part of a terminal electrode shaft 6 shall be a plug performed by insulating glass 8. This film resistance 4A shall be a resistance with an effective length over 10mm formed by providing a 1-1000mum thick tin oxide film or carbon film over the surface of an insulative columnar base body. A film resistance 4A in this constitution gives a stable resistance value and can be produced at a low cost. The reason for restricting the film thickness to 1-1000mum is because a greater film thickness lessens the resistance value to cause deterioration of the temp. characteristic of resistance value and reduction of the noise preventive effect, which further results in degradation of durability in spark ignition. This accomplishes good resistance thermo- characteristic and enhanced noise preventing effect.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a spark plug containing a resistor, and particularly to a spark plug that has both a noise prevention effect and spark durability.

(Prior art) The spark discharge of a spark plug has the side effect of generating interference radio waves, which can cause damage to various electronic devices, so in order to prevent this, the spark plug functions as a spark plug and as a preventer. There is also a spark plug with a resistor (hereinafter simply called a plug). Depending on the properties of the resistor, there are two types: monolithic type and cartridge type.

In the former example (for example, Japanese Patent Publication No. 56-19721), a glass resistor composition powder is introduced into the shaft hole of a ceramic insulator in which a center electrode shaft has been installed in advance, and the threaded part of the terminal electrode shaft is heated. It has a structure in which the image electrode shafts are sealed by applying pressure, and is excellent in productivity and durability, but is inferior in noise prevention effect.

As an example of the latter, a wire-wound resistor consisting of a thin resistance wire wound around an insulating core is fixed in a ceramic insulator shaft hole together with a buffer spring between the center electrode shaft and the terminal electrode shaft. The composition is known. As shown in FIG. 2, such a wire-wound resistor-containing plug generates less noise current than the monolithic glass-sealed resistor re-plug, ie, has an excellent noise prevention effect. Additionally, since the wire-wound resistor itself can be produced in a separate process, variations in resistance values can be reduced, but on the other hand, since the resistor is crimped with a spring, contact resistance occurs, making the resistance value unstable. In addition, corona discharge is likely to occur from the electrodes, and rust is likely to occur when outside air enters.
If this progresses, the resistor may burn out, or if it is installed in an engine with severe vibrations, failures such as winding breakage may occur, resulting in poor durability.

On the other hand, a film resistor is used in which a resistance film is formed in a spiral shape on the surface of the insulator, and both ends of the resistor are closely matched to the diameter of the shaft hole, and both ends are connected to the center electrode shaft and the terminal electrode. There is a cartridge-type plug that is directly sealed and held by a conductive glass sealing material that controls the axial hole sealing of the shaft. FIG. 6 is a longitudinal sectional view of this flag containing a cartridge type wire-wound resistor. In the same figure, ceramic insulator 1
The center electrode shaft 2 with a flange 2a made of Ni alloy or the like is inserted into the terminal hole IC, which has the shaft hole 1a divided by the crotch seat 1b.
A first conductive glass powder 3 is filled on the collar 2a of the center electrode shaft 2, a wire-wound resistor 4 is inserted thereon, and a second conductive glass powder 5 is further filled in the ceramic insulator. The body 1 is heated to a predetermined temperature, and the conductive glass powders 3 and 5 are heated.
After softening, the terminal electrode shaft 6 having a threaded portion 6a at the tip is pressed and heat-sealed to incorporate a resistor,
This is the structure fixed to the inner cavity of the metal shell 7.

For wire-wound resistors, for example, spiral grooves are formed on the surface of an insulating material such as ceramic, and a resistance film made of a mixture of iron oxide and carbon is formed on this surface. A wire-wound resistor whose surface is polished to leave a coating only on the spiral grooves (Japanese Unexamined Patent Publication No. 49-116559) or a ceramic sintered rod whose surface is printed with a spiral electric resistor material and then sintered. There are wire-wound resistors (Japanese Unexamined Patent Publication No. 61-135079).

(Problems to be Solved by the Invention) In the wire-wound resistor-containing plug as shown in FIG. Although the conductive glass sealing material is heated and sealed, there is a problem in that the conductive glass sealing material flows onto the resistance film of the wire-wound resistor 4 during heat sealing and covers this, increasing the variation in resistance value. be.

Further, the wire-wound resistor as described above requires many man-hours to process and is expensive.

In recent years, there has been a marked increase in the electronicization of automobile equipment, and there is also a need for cost reductions, so there is a demand for plugs that have even greater noise prevention effects, are durable, and are inexpensive. It became so.

(Means and effects for solving the problem) The present invention has been made in view of the above-mentioned circumstances, and has an excellent noise prevention effect.
Furthermore, the present invention aims to provide a resistor-containing plug that is durable and inexpensive.

Cartridge-type film resistors are manufactured in a separate process from the plug body, so the variation in the resistance value of the resistor itself is small, but as mentioned above, the conductive sealant may leak out and adhere to the resistor film. Therefore, the seal at the tip of the terminal electrode shaft and the seal between the film resistor and the ceramic insulator are made of an insulating glass plug.

Furthermore, a film resistor is coated on the surface of the insulating cylindrical substrate with a thickness of 1 to 110
The resistor is provided with a tin oxide film or a carbon film with a thickness of 0.0j1 and has an effective length of 10n+m or more.

The reason why we chose the above-mentioned film resistor is because conventional wire-wound resistors have a risk of wire breakage and are expensive; ,
This is because we offer plugs that are low priced. The reason why the film thickness is limited to 1 to 1000 mm is that if the film is too thick, the resistance value will become small, the temperature characteristics of the resistance value will deteriorate, the noise prevention effect will be reduced, and the spark ignition durability will decrease. This will worsen the situation, so by limiting it as above,
The resistance temperature characteristics are improved, the noise prevention effect is increased,
This is limited in order to stabilize spark ignition durability.

The reason why the effective length of the film resistor is set to 10 mm or more is that as the effective length becomes longer, the effective dielectric constant between the center electrode axis and the terminal electrode axis becomes smaller, which reduces the capacitive discharge current generated during ignition and causes noise. This is because the prevention effect becomes greater.

(Embodiment) FIG. 1(a) is a longitudinal cross-sectional view of an embodiment of the resistor-containing plug according to the present invention, in which the space between the center electrode shaft 2 and the film resistor 4A is in the shaft hole 1a of the ceramic insulator 10. Frit glass 8□03-5iOz glass and metal starch (Cu
% Fe, Ni, Pea) particle size 100~2
5 On, conductive sealing material 3 with a yield point of 600 to 700° C. is heated and sealed, and the space between the film resistor 4A and the screw portion 6a of the terminal electrode shaft 6 and the inner wall of the shaft hole of the ceramic insulator 1 is B.
Particle size 150 made of a0-B2O2-5iO2 glass
pm, and an insulating sealing material 8 having a yield point of 600 to 700° C. is heated and sealed. The structure other than the above is the same as that of the conventional example shown in FIG. 6, so the same parts are designated by the same reference numerals.

FIG. 1(b) is an external view of the above film resistor 4A,
4a is a resistive film formed on the surface of the cylindrical glass substrate, and 4b is a metal cap attached to both ends. As an example of this film resistor 4A, the composition shown in weight ratio is 98% SiO□, B, 0. is 1.7%, Na,
0 is 0.03%, K2O is 0.01%, Alz (h is 0
60% on the surface of a cylindrical base made of silica glass made of 625%
A tin chloride solution heated to 0 to 800° C. was sprayed to reduce the attached tin chloride and precipitate tin oxide to form a film resistor. In addition, as another example (2), a carbon film was deposited on the surface of a cylindrical silica glass substrate similar to the above by thermally decomposing hydrocarbons such as benzene and methane in a high-temperature vacuum or inert gas at about 1000°C. This made a film resistor. The resistance value of the film resistor 5 having the above configuration was 3 to 10 kΩ. Note that the resistance value can be adjusted by adjusting the temperature, time, degree of vacuum, and further by forming cuts on the surface.

FIG. 2 shows the noise current at each frequency of the embodiment of the resistor-containing plug according to the present invention (Example I and Example ■ are almost the same, so they are shown as ■) and the conventional example. The noise current of this example is much smaller than that of the conventional monolithic glass-sealed resistor-containing plug ■, and the noise prevention effect is as good as or better than that of the cartridge-type wire-wound resistor plug ■. It is shown that.

FIG. 3 shows a comparison of the noise current when the length of the film resistor 4A is changed in the above embodiments I and II, and it can be seen that 10III11 or more is desirable.

Figure 4 shows the noise current versus frequency when the thickness of the film of the film resistor 4A in the film resistor type plug is varied, together with that of the conventional monolithic glass type. It can be seen that (1) and (2) are those using the film resistor according to the present invention, and the noise current is clearly smaller than the others, and the noise effect is excellent.

Figure 5 shows the rate of change in resistance depending on the thickness of the film in a film resistor plug.
is an example according to the present invention, and it can be seen that it is stable with respect to the spark ignition duration.

(Effects of the Invention) In the cartridge-type film resistor type spark plug with a resistor according to the present invention, the surface of the film resistor is sealed with an insulating sealant, so the resistance value when manufactured in a separate process is different after the plug is assembled. The resistance value remains stable, and by using the film resistor of the present invention, the noise prevention effect is equal to or better than that of conventional wire-wound resistor plugs, and in terms of durability, it is superior to monolithic glass-sealed plugs. This is equivalent to a resistor-containing plug, and since the film resistor can be manufactured at low cost, it is possible to provide an inexpensive resistor-containing plug that has the desired high noise prevention effect and high durability.

[Brief explanation of the drawing]

FIG. 1(a) is a longitudinal cross-sectional view of an embodiment of the resistor-containing spark plug according to the present invention, FIG. 1(b) is an external view of the film resistor, and FIG.
The figure is a graph showing a comparison of noise current between this embodiment and conventional glass-sealed and wire-wound resistor-containing spark plugs.
Figure 3 shows Example I and Example II of the present invention as film resistors.
Figure 4 is a graph showing the noise current when the length of the resistor is varied. A graph showing the noise current when the film thickness of the film resistor in this example is varied, and FIG. 5 shows the resistance change rate when the film thickness of the film resistor in this example is varied. The graph and FIG. 6 are longitudinal cross-sectional views of a conventional cartridge-type wire-wound resistor-containing spark plug. 1: Ceramic insulator, 2: Center electrode shaft, 3: Conductive sealant, 4A: Film resistor, 6: Terminal electrode shaft, 8: Insulating sealant.

Claims (1)

[Scope of Claims] 1. A spark plug with a resistor in which a resistor element is sealed and fixed between a center electrode shaft and a terminal electrode shaft facing each other in a shaft hole of a ceramic insulator, wherein the resistor element is insulated. A film resistor element having a thickness of 1 to 1000 μm and an effective length of 10 mm or more is formed on the surface of a cylindrical base, and the area around the connection between the film resistor element and the center electrode shaft is sealed and fixed with a conductive sealing material. A spark plug with a special resistance. 2. In a spark plug with a resistor in which a resistor element is sealed and fixed between a center electrode shaft and a terminal electrode shaft that face each other in a shaft hole of a ceramic insulator, the resistor element is attached to the surface of an insulating cylindrical base. Consisting of a film resistor element with a thickness of 1 to 1000 μm and an effective length of 10 mm or more, the surface of the film resistor element is sealed with an insulating sealant, and the area around the connection point between the film resistor element and the center electrode shaft is sealed. A spark plug with a resistor, which is sealed and fixed with a conductive sealant. 3. The spark plug with a resistor according to claim 1 or 2, wherein the resistance film of the film resistance element is a tin oxide film or a carbon film.