JPS5935514B2 - Spark plug for radio noise suppression - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a spark plug, and more particularly, to a spark plug that widens the discharge gap area of the center electrode to increase the capacitance between the center electrode and the ground electrode, thereby preventing interference with external radio reception. The present invention relates to a spark plug for suppressing radio wave noise in an internal combustion engine that does not cause noise.

In an internal combustion engine, radio reception is interfered with by spark plugs, power distributors, charging generators, starting devices, etc., but spark discharge from spark plugs has the greatest influence.

Such interference waves are generated from the surface of the high-voltage cord connected to the spark plug, the contacts of the interrupter, or the gap between the rotor of the power distributor.

In general, as measures to prevent radio noise caused by spark discharge from a spark plug, there are two methods: shielding the spark plug and adding a damping resistor to reduce the current distribution.

The former method of shielding is effective only for radio waves with relatively long wavelengths, and the latter method of inserting a resistor into the high-voltage cord or spark plug does not have a sufficient effect of suppressing radio noise, especially when Almost no deterrent effect can be expected in the high frequency range of 100,100O.

Also, if you put in too much resistance, there is a risk that the spark force will be reduced.

In any case, there are certain limits to its scope of application.

In addition, the cost is high and the reliability is low for mass-produced vehicles.

SUMMARY OF THE INVENTION An object of the present invention is to provide a radio noise suppressing spark plug capable of eliminating the above-mentioned conventional drawbacks and reducing radio noise caused by spark discharge of the spark plug.

By increasing the capacitance between the center electrode and the ground electrode, there is less resistance to high frequency currents, so the high frequency currents do not flow towards the high voltage cord of the spark plug, but instead connect to the ground electrode of the spark plug. flows from the shell to the cylinder block.

In order to increase this capacitance, it is sufficient to increase the opposing area between the center electrode and the ground electrode, but normally the ground electrode is sufficiently wide, and even if the area of the ground electrode is increased further, it will not work. It does not contribute much to increasing capacitance.

In view of this, in the present invention, the tip of the center electrode extends in a direction perpendicular to the axis of the spark plug to form a bent extension, and the tip of the center electrode and the bent extension with respect to the axial direction of the spark plug. A discharge gap is provided between the tip of the shell and the tip of the shell opposite to the tip of the shell.

As a result, the area of the center electrode can be increased, and the tip of the center electrode can be brought sufficiently close to the ground electrode, increasing the capacitance of the discharge gap.

Further, in the present invention, the center electrode is connected to a terminal via a resistor.

In this way, while the discharge current flowing to the ground electrode increases due to the increase in capacitance and the presence of the resistor, the discharge current flowing to the terminal and therefore the high voltage cord is suppressed, and radio noise is effectively suppressed.

Note that if the discharge gap is formed in the radial direction of the spark plug, the area of the portion of the center electrode facing the ground electrode cannot be made sufficiently large, which is extremely disadvantageous in terms of increasing capacitance.

Hereinafter, the present invention will be explained according to the drawings.

FIG. 1 shows a conventional resistor-containing spark plug, in which a resistor 2 of about 3 to 10 Ω is inserted near the center axis of a center electrode 1.

The axial head of the center electrode is connected to a terminal 3 for conducting high voltage.

A shell 5 is arranged around the outer periphery of the center electrode 1 with an insulator 4 in between, and a ground electrode 7 that faces the center electrode and forms a discharge gap 6 extends from the shell.

FIGS. 2 and 3 are partially cutaway side views of a radio noise suppression spark plug showing an embodiment of the present invention.

First, referring to FIG. 2, the end of the ground electrode 7 is connected to the first
As shown in the figure, it is not bent in the radial direction, but extends parallel to the axis of the spark plug.

The center electrode 1 is bent in an L-shape near its tip to form a bent extension 8 .

A discharge gap 6 in the axial direction of the spark plug is formed between the tip of this bent extension 8 and the tip of the shell 5 opposite to the tip of the bent extension 8 in the axial direction of the spark plug.

Furthermore, a resistor 2 similar to that shown in FIG. 1 is sandwiched in the central axis portion of the center electrode 1.

The material of the center electrode 1 is nickel, and the material of the ground electrode 7 is soft iron.

In the embodiment shown in FIG. 3, nickel 9 is embedded in the end of the ground electrode.

Although the ground electrode wears out due to discharge, the durability of the ground electrode is improved in the embodiment of FIG.

Others are the same as shown in FIG.

In such a configuration, the discharge current generated in the spark discharge gap of the ignition plug flows through the center electrode 1, the resistor 2, and the terminal 3.
The electromagnetic wave propagates through the terminal 3 to a high voltage cord (not shown) connected to the terminal 3, and emits electromagnetic waves.

Also, a part of the current flows through the shell to the engine block (not shown) due to the capacitance formed between the shell 5 and the center electrode 1.

Therefore, by widening the center electrode as in the present invention, the capacitance between the center electrode and the shell increases, and due to this increase in capacitance and the presence of the resistor, the distance from the center electrode to the terminal increases. As a result, the high frequency current that would conventionally flow to the high voltage cord due to spark discharge flows through the shell 5 to the engine block, effectively suppressing radio noise. obtain.

FIG. 4 is a graph showing the effects of the spark plug of the present invention in comparison with a conventional spark plug.

In the figure, the vertical axis represents the relative value I of the current flowing into the high voltage cord, and the horizontal axis represents the frequency F.

The white circle A represents the relationship in the conventional spark plug, and the black circle B represents the relationship in the spark plug of the present invention.

As is clear from this figure, the higher the frequency of the spark plug of the present invention, the greater the radio noise suppression effect.

Therefore, the present invention exhibits particularly excellent effects in the high frequency range where conventional resistor-containing spark plugs have poor suppression effects.

[Brief explanation of the drawing]

Figure 1 is a partially cutaway side view of a conventional spark plug with resistor.
2 and 3 are partially cutaway side views of a radio noise suppressing spark plug showing an embodiment of the present invention, and FIG. 4 is a graph showing the effect of the spark plug of the present invention. 1... Center electrode, 2... Resistor, 3... Terminal, 5
... shell, 6 ... discharge gap, 7 ... ground electrode,
8...Bending extension.

Claims (1)

[Claims] 1 The tip of the center electrode connected to the terminal via the resistor extends perpendicularly to the axis of the spark plug to form a bent extension, and the tip of the bent extension and the axis of the spark plug A spark plug for suppressing radio noise, characterized in that a discharge gap is provided between the tip of the bent extension and the tip of the shell facing the tip in the direction.