JPS5935517B2 - spark plug - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ignition plug that allows unburned carbon attached to the surface of an insulator leg to be easily removed.

Once a new gasoline-powered vehicle is completed at a car factory, the gasoline engine is activated before the vehicle is delivered to the customer in order to be placed in a motor pool or loaded onto a transport truck or export cargo ship. They are forced to move.

Although the driving for this movement is not uniform, the speed of the vehicle is approximately 30 to 40 -1 per hour, and the driving distance is about 500 m for each drive, and the driving conditions are low speed and short distance.

However, under such low-speed, short-distance driving conditions, the ignition plug installed in the car engine tends to smolder, and this smoldering reduces the insulation resistance of the ignition plug, causing it to thicken. Mobile driving may become unstable.

This smoldering phenomenon is especially common when the outside air gets cold, such as in winter.

Moreover, such smoldering may occur not only in the case of a new car as described above, but also in the case of a car that has already been used, such as during the winter season.

This smoldering phenomenon occurs when the spark plug 1
This is caused by unburned carbon such as soot generated by combustion of gasoline in the engine adhering to the surface of the leg portion 610 of the insulator 6 which is exposed to combustion gas.

In addition, in the drawing, 2 is a housing, 3 is a ground electrode,
4 is a washer, and 5 is a center electrode.

In order to solve the above-mentioned problems, attempts have been made in the past to create a spark plug in which a coating layer of alumina particles (a portion indicated by reference numeral 7 in the figure) is formed on the surface of the insulator leg portion 610.

However, when using a product coated with alumina particles, the alumina particles may fall off during use, causing abnormal wear within the engine.

Furthermore, the leg portions 6 cause a temperature rise during engine operation, which may induce pre-ignition at high speed and high load.

The present invention aims to eliminate the drawbacks of the prior art and provide a spark plug that is designed to facilitate removal of unburned carbon adhering to the surface of the insulator leg 61 and has excellent self-cleaning properties. be.

That is, the present invention provides a spark plug for an internal combustion engine comprising an insulator holding a center electrode and a nozzle disposed around the outer periphery of the insulator and having a ground electrode. The ignition plug is characterized in that a coating layer of a self-cleaning substance made of one or more of rubidium hydroxide, rubidium carbonate, and cesium carbonate is formed on the surface of the leg exposed to the combustion gas.

Therefore, according to the present invention, it is possible to provide a spark plug with excellent self-cleaning properties.

Further, even if the coating layer 7 is gradually removed from the surface of the leg after long-term use of the spark plug, it is easily released to the outside together with the exhaust gas from the engine. There is no risk of engine damage.

Furthermore, the spark plug according to the present invention is free from the risk of pre-ignition as described above.

Furthermore, as will be described later, the coating layer 7 can be simply formed by applying it in the form of an aqueous solution and baking it.

Note that the above-mentioned self-cleaning property means that even if unburned carbon adheres to the surface of the leg portion 610 due to low-temperature, short-distance operation of the engine, the ignition plug temperature will rise due to the temperature rise in the engine room during the next operation. This means that the ignition plug itself will self-clean.

Therefore, this self-cleaning is required to be carried out at as low a temperature as possible, preferably 300° C. or lower.

The best spark plug according to the present invention has a temperature of about 270° C. when rubidium hydroxide is used.

In the present invention, the self-cleaning substances forming the coating layer 7 include rubidium hydroxide (RbOH'), rubidium carbonate (Rb2C03), and cesium carbonate (Cs2CO3).
It is.

These substances can thus be used alone or in mixtures.

The coating layer is formed by applying an aqueous solution of the self-cleaning substance to the surface of the legs 610 of the insulator 6, and after drying, for example,
This is done by heating and baking at 00 to 200°C for about 0.5 to 2 hours.

The above application is performed by dipping the leg portion 61 in a solution;
Alternatively, this can be done by brushing or spraying this area.

In addition, the concentration of the above aqueous solution is 1 to 20% (weight ratio,
The same applies hereinafter) are used, and among these, 5 to 10 are more preferable from the viewpoint of the amount of coating layer deposited and the adhesion force.

The reason why the spark plug according to the present invention exhibits the above-mentioned excellent self-cleaning properties is presumed to be due to the following reasons.

That is, the deposits on the surface of the leg portions 61 are unburned gasoline mainly composed of carbon.

A portion of the volatile matter in this deposit evaporates at a relatively low temperature (approximately 150° C. or lower) when the engine is started.

The deposits become residual volatile matter and a large amount of carbon black.

Next, when the temperature of the leg portion 61 reaches 300 to 400° C., the substance of the coating layer 7 on the leg portion 61 enters into the pores of the carbon black, and the pores of the carbon black are expanded, and finally leads to rapid collapse.

The ultra-fine pieces of collapsed carbon black are agitated by the airflow in the engine compartment and are scattered and removed from the surfaces of the legs 61 and the coating layer 70.

Some of the removed fine particles are burned, and some are emitted outside the engine compartment by exhaust gas.

Therefore, even if unburned carbon adheres to the leg portion 61 again due to engine operation, the deposit will be removed due to the presence of the coating layer 7 in the same manner as described above during the next engine operation.

EXAMPLE Three commercially available spark plugs on which the coating layer 7 is not formed are prepared, and an aqueous solution of the self-cleaning substance according to the present invention is applied to the surface of the legs 610 of the insulator 6 for each spark plug. Apply the cleaning substance at the ratio of one type, and after drying, heat it in an electric furnace for 10 minutes.
Baking was carried out at 0° C. for 1 hour to produce three types of spark plugs in which the coating layer according to the present invention was formed on the surface of the leg portion 610 (Boxes 1 to 3 in FIG. 2).

The amount of the above aqueous solution was 5 times, and the application was carried out by dipping the leg portion 61 once in the aqueous solution.

Further, the coating was performed up to 10 mm above the tip of the leg portion 61.

For comparison, 12 types of comparative spark plugs were manufactured in the same manner as above using other self-cleaning substances as shown in FIG. 2 (&, C1 to Cl2 in FIG. 2).

Next, the above-mentioned spark plug is attached to the automobile engine by a conventional method, and the engine is operated while the engine wall is cooled with cooling water so that the temperature of the leg portion 610 of the insulator 6 of the spark plug is 150° C. or less. A large amount of carbon was attached to the surface of the leg portion 610.

Next, the spark plug was removed from the engine, placed in an electric furnace, and the temperature at which deposits were removed was measured.

The engine was operated at an air-fuel ratio of 5 to 6, a rotational speed of 1000 rpm, and an operating time of 8 minutes.

The results are shown in FIG. 2 for each coating material.

In the figure, the shaded area is the removable temperature.

Since the superior officer's illumination was carried out while increasing the temperature inside the electric door, the lowest temperature indicated by diagonal lines (for example, 270°C in A1) is the lowest temperature at which deposits can be removed. be.

The figure also shows similar measurement results for a spark plug (AC13) that does not have the coating layer according to the present invention, that is, a commercially available spark plug.

As can be seen from FIG. 2, the spark plug (A
1 to 3) are commercially available spark plugs (with no coating layer formed).
It can be seen that deposits can be removed at temperatures 180 to 250°C lower than AC13).

Furthermore, the spark plug according to the present invention is a comparative spark plug (Haruka C1
It can be seen that deposits can be removed at a lower temperature compared to ~Cl2).

Among these, it can be seen that when RbOH is used, it can be removed at a low temperature of about 270° C., demonstrating excellent performance.

It can be seen that all coating layers have the ability to remove deposits at temperatures below 300°C.

Furthermore, it can be seen that the three types of self-cleaning substances of the present invention exhibit particularly excellent effects when compared with the case where substances similar to the self-cleaning substance of the present invention, such as RbNO3 and CsOH, are used.

However, apart from the above-mentioned examples, when the spark plug according to the present invention was installed in an engine and operated at low speed and over a short distance in the same manner as in the actual case, the spark plug with any coating layer did not smolder. It has been shown that it is an excellent spark plug.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a main part of a spark plug, and FIG. 2 is a diagram showing measurement results in an example. 1... Spark plug, 2... Housing, 6
...Insulator, 61...Legs, 7...
...Coating layer according to the present invention.

Claims (1)

[Claims] 1. In a spark plug for an internal combustion engine comprising an insulator holding a center electrode and a housing disposed around the outer periphery of the insulator and having a ground electrode, the insulator is exposed to the combustion gas of the internal combustion engine. A spark plug characterized in that a coating layer of a self-cleaning substance made of one or more of rubidium hydroxide, rubidium carbonate, and cesium carbonate is formed on the surface of the leg.