JPS5893184A - Ignition plug - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a modified spark plug for an internal combustion engine to improve its anti-fouling properties.

- Kouki 1 spark plug has a porcelain insulator ignition leg tip OII
*When the temperature is about 100℃ or less, carbon, moisture (steam), which is a product of unburnt carbon, moisture (steam), and IJ:0 conductive substances adhere to the legs of the skeleton, and the insulation resistance between the electrodes decreases to /MΩ or less. If this happens, the sparks will fly out and cause a national disaster, making it impossible to obtain a normal spark discharge.

In particular, the ζO1K phenomenon is relatively common in the automobile manufacturing industry IK, from the installation of a large point plug at Ichinoseki until the vehicle is delivered to Aeser, or when the vehicle is in a state where the mileage is too short since it was new. Due to repeated short operations such as this, a malfunction occurs in which conductive material adheres to the surface of the ignition leg of the ignition bladder porcelain insulator, causing misfires.

Therefore, in order to prevent smoldering contamination (bridging contamination), the present inventors applied silicone-based oil or fluorine-based oil to the ignition leg of the porcelain insulator or the scissor ignition leg and the inner surface of the metal shell. A patent application has already been filed for the formation of a coating layer containing paraffin to prevent smoldering and fouling.
-iooi da 3. It was proposed in a patent application of $11-/At/JJ.

Furthermore, as a result of various investigations, the present inventors have found that among the unburned carbon of the conductive substance and water vapor, the influence of water vapor is particularly large, and that water plays a large role in connecting carbon particles, causing a decrease in insulation resistance. It turns out. Therefore, this invention focuses on moisture resistance and water resistance, and is based on the result that oil-based resins also have excellent heat resistance and are effective in preventing smoldering and staining by coating them with an organic resin.

An object of the present invention is to provide a spark plug that exhibits excellent smoldering and fouling effects over a long period of time by forming a coating layer mainly composed of an organic resin with excellent water-repellent properties.

The present invention will be explained in detail below.

FIG. 7 is an enlarged sectional view of main parts of a spark plug showing an embodiment of the present invention), l is a main metal fitting equipped with an engine mounting screw, C is a center electrode, J is a porcelain made of high aluminum, etc. Hold the central electric &co in the shaft hole with an insulator. This porcelain insulator J is housed in the crotch seat lb of the inner crosspiece of the metal shell / through a packing T, and is sealed and fixed by a known method, and the ignition leg is exposed on the inner surface / & of the combustion chamber side of the metal shell I. 117a. The coating layer of the present invention is formed on the inner surface Jb of the firing leg Ja. Reference numeral j denotes a spark plug having a ground electrode connected to the lower end surface of the metal shell l to form a spark gap with the center electrode.

Incidentally, the coating layer is applied to the igniting leg '1.' of the porcelain insulator J. - The reason for restricting the memory to the central surface Jb of J is that if it is formed at the tip of the firing leg J, it will not be purified unless the temperature is high enough for self-cleaning. The coating layer of the present invention may be formed on the deep side of both the firing leg Ja of the porcelain insulator J and the inner surface /a of the metal shell l, respectively. As mentioned above, the central surface Jb of the firing leg 11sja of the porcelain insulator J
Although it is recognized that the effect of improving the stain resistance is sufficient by itself, by forming it on the inner surface / & side of the metal shell 1, combined with the effect of preventing short circuit of the current to the main metal 1, the stain resistance is improved. This can be further improved.

The coating layer of the present invention may be made of organic resins with excellent water resistance, silicone, resins containing elemental fluorine, or resins containing both, polyethylene, polystyrene,
/filt of polyvinylidene chloride and vinyl chloride resin
Or two or more types can be used. Among these, synthetic resins containing fluorine are particularly useful due to their high heat resistance. Examples of such resins include polytetrafluoroethylene (Teflon: a trade name of DuPont), polychlorotrifluoroethylene,
Vinyl fluoride, ethylene trifluoride, vinylidene fluoride,
Polymers or copolymers such as hexafluoropylene are preferred.

In order to impart heat resistance to the organic resin, the coating layer l of the present invention is made of non-conductive materials such as titanium oxide, aluminum oxide, zinc oxide, vanadium 9 oxide, niobium oxide, silica, mullite, mica, etc. Mixing the inorganic fine powder into the above-mentioned organic resin slows down the process. The amount added is preferably 10% by weight or less of the organic resin, and the particle size of the powder is preferably ioμ or less.

Furthermore, paraffin (a paraffin hydrocarbon substance) can be melted or mixed into the coating layer of the present invention in order to improve the hydrophobicity of the organic resin. The preferred amount of addition is 1% of the above organic resin or the mixture with the above inorganic fine powder.
0 weight or less, these coating layers are applied to the central surface of the firing leg J of the porcelain insulator and the inner surface 11 of the metal shell by known coating means using an appropriate solvent for the resin. 4 can be formed by baking.

Example 1 Now, a coating layer was formed using each of the resins listed in Table I or a material in which these resins were mixed with inorganic fine powder and/or paraffin. The real part surface Jl) and the inner surface laVcm of the main metal fitting l, and i
A fouling test was conducted using spark plugs prepared by drying them at zo° C. for 1 hour. Representative sample si at that time.

Ko, 3. Da, 7, 1. ri, 10, //, /J
The test results for , /1 are shown in Figure 1. The engine used in this experiment was a two-cycle single-cylinder engine, and the test conditions were a rich mixture with a closed cylinder at idle (07 o rpm). The car was driven for 30 seconds, followed by racing 5 times with the throttle fully open, and the cycle of stopping the car for a few minutes was repeated.

As a result, compared to the conventional uncoated spark plug 17 (which does not form a single layer), it contains less resins such as silicone resin, fluororesin, polyethylene, polyvinylidene chloride, and vinyl heptafluoride, inorganic fine powder, and paraffin. In all of the spark plugs of the present invention, the number of cycles increases and the fouling resistance is significantly improved. 1 In addition to the resin alone, inorganic fine powders such as zinc oxide, alumina, and titanium oxide, as well as vanadium oxide, niobium oxide, silica, mullite,
It has been confirmed that when a bulk substance is mixed, the stain resistance hardly changes and the heat resistance increases, making the coating layer stable for a long time against temperature. Furthermore, the one containing pufffin and having nine coating layers is most effective in improving stain resistance.

/ 7/''/' , 77'5・''/' , 7.1 /' Table l As described above, the spark plug of the present invention has at least the surface of the ignition leg of the porcelain insulator that has a highly resistant to water generation. By forming a coating layer mainly composed of organic resin, conductive substances such as carbon and moisture are difficult to adhere to the surface and maintain high insulation resistance even after repeated low-speed and low-load operation. This makes it possible to effectively prevent smoldering and fouling of spark plugs, especially in new cars. Further, by mixing non-conductive inorganic fine powder into the organic resin, heat resistance is increased, and the stain-resistant effect can be maintained for a long time even when the vehicle is repeatedly driven at relatively high temperatures. Furthermore, by incorporating paraffins into the mixture of the organic resin or inorganic fine powder, it has an excellent effect of further improving the stain resistance effect. .

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a main part of a spark plug showing an example of the present invention, and FIG. 2 is a graph showing typical results of a comparison experiment on stain resistance. L... Metal shell, /,... Inner surface, C... Center electrode, J... Porcelain insulator, 3a... Firing leg, Jb...
・Real part surface, reference... coating layer Figure 1

Claims (2)

[Claims] (1) In a spark plug consisting of a porcelain insulator that holds a center electrode contained in a metal shell, the metal shell is
A coating layer mainly composed of an organic resin with excellent water-drying properties is formed on at least the inner surface of the opening leg of the surrounding porcelain insulator on the combustion chamber side. Ignition bladder. (2) The organic resin is an organic resin containing silicone and/or silicone, polyethylene, polyethylene,
A spark plug according to claim 8, comprising polyvinylidene chloride and a vinyl chloride resin. a) In order to impart heat resistance to the organic resin, a non-conductive mold powder such as titanium oxide, alonium oxide, zinc oxide, vanadium oxide, niobium oxide, silica, mullite, or the like may be mixed into the organic resin. Therefore, the scope of the patent claim is a spark plug according to Clause 2. C) The dot-sized plug according to claim 1 or 3, wherein paratwins are mixed in the organic resin in the form of powder before melting in order to improve water agitation properties.