JPS593508Y2 - internal combustion engine spark plug - Google Patents

Description

[Detailed Description of the Invention] This invention relates to an improvement in a spark plug used in a spark-ignition internal combustion engine.

In spark-ignition internal combustion engines, it is necessary to ensure ignition even in lean air-fuel mixture regions where misfires are likely to occur. Various improvements have also been made to plugs.

As an example of these improvements, a spark plug as shown in FIG.
Publication No.).

In this spark plug, a spark gap between a center electrode 1 and a side electrode 2 is surrounded by an electrical insulator 3 such as ceramic to form a discharge space 4 with a small volume, and a spark is generated in this space when a spark is discharged. This plasma-like gas is ejected from the ejection hole 5 into the fuel mixture.

That is, unlike a normal spark plug that directly heats and ignites the air-fuel mixture by spark discharge, this spark plug first generates a spark between the center electrode 1 and the side electrodes 2 to create a high temperature in the discharge space 4. , a high-energy plasma-like gas is generated, and then the plasma-like gas is ejected from the ejection hole 5 into the air-fuel mixture by the pressure increase in the discharge space 4 due to thermal expansion of the plasma-like gas, and this high-temperature, high-energy ejection is performed. The gas flow forms a large number of fire nuclei within the mixture to ensure ignition.

However, in this spark plug, since the inner diameter surface of the threaded portion 6 of the plug body and the electrical insulator 3 surrounding the discharge space 4 are in close contact, the heat value of the plug is "cold type", and the plug is cold. "Plug smoldering" is likely to occur during slow starts or at low speeds and low loads.

For this reason, fuel, carbon deposits, engine oil, etc. adhere to the inner wall of the discharge space 4, causing a short circuit between the electrodes 1 and 2.
A problem has arisen in which spark discharge is no longer performed and misfires occur.

For this reason, the present applicant has developed a spark plug that prevents "plug smoldering" by baking the plug's heat value, but it is impossible to simply prevent smoldering, and once smoldering occurs, it will remain the same as conventional spark plugs. The following phenomenon occurs, and the reality is that the problem has not yet been resolved.

This idea was devised in view of the conventional situation,
By installing the side electrode of the spark plug away from the nozzle hole formed in the discharge space, a discharge occurs in this space and the mixture is ignited, which can also cause misfires if smoldering occurs. It is aimed at providing spark plugs that are never spark plugs.

This invention will be explained below based on the drawings.

FIG. 2 is a diagram showing an embodiment of this invention together with a power supply circuit.

In the figure, 1 is a center electrode, 3 is an electric insulator such as ceramic, 4 is a discharge space, and 5 is an ejection hole provided in this discharge space 4, and these have the same structure as the conventional case.

In this embodiment, the side electrode 2A is connected to the threaded portion 6 of the plug body.
It is set so as to protrude from the tip thereof, and to be separated from the ejection hole 5 by a slight gap l.

In this case, it is preferable that the tip of the side electrode 2A be located on an extension of the circumference of the ejection hole 5.

In addition, in this embodiment, as shown in FIG.
Although two electrodes are provided symmetrically, the number of electrodes may be one or more.

Furthermore, the electrode may be a ring-shaped electrode 2B as shown in FIGS. 3A and 3B.

However, when forming the electrode 2B, consideration must be given so as not to impede the scavenging of burnt gas and to prevent an increase in fire-like cooling.

A power supply circuit 20 is connected to the center electrode 1 .

This power supply circuit 20 is divided into a high voltage power supply circuit 20a and a low voltage power supply circuit 20b.

The high-voltage power supply circuit 20a is similar to a power supply circuit used in a normal spark discharge type ignition plug, and includes a cam 21 that rotates in synchronization with engine rotation, a contact arm 22 and a contact 22a, and an ignition coil 23. , and a power source 24.

On the other hand, the low voltage power supply circuit 20b includes a resistor 25 and a coil 2.
6 and capacitor 27 are connected in series, and resistor 2
8 and a power supply 29 is connected to the capacitor 2.
7 in parallel.

Both power supply circuits 20a and 20b are connected to the center electrode 1 via respective diodes 30 and 31.

Next, the action will be explained.

Now, when the contact arm 22 is driven by the cam 21 rotating in synchronization with the engine rotation and the contact point 22a opens, the primary current flowing through the primary coil 23a of the ignition coil 23 is cut off, and the primary current flowing through the secondary coil 23b is cut off. Since a high voltage is generated, spark discharge occurs in the discharge path between the center electrode 1 and the side electrodes 2A.

This spark discharge breaks down the insulation of the discharge path, making spark discharge possible even at a relatively low voltage, and spark discharge continues in the discharge space 4 due to the direct current supplied from the low voltage power supply circuit 20b. It is done.

When the discharge continues, the gas in the discharge space 4 turns into a high-temperature plasma gas, which is ejected from the jet hole 5 into the air-fuel mixture due to thermal expansion, and the air-fuel mixture is ignited.

At this time, spark discharge also occurs in the gap l between the ejection hole 5 and the side electrode 2A, but the ignition of the air-fuel mixture is mainly performed by plasma gas.

Next, when the air-fuel mixture in the combustion chamber is incompletely combusted and carbon etc. adhere to the discharge space 4 due to so-called "plug smoldering", the insulation resistance between the center electrode 1 and the nozzle hole 5 decreases, and the discharge Spark discharge no longer occurs within the space 4.

Therefore, no high-temperature plasma-like gas is generated within the discharge space, and therefore no plasma-like gas is ejected from the ejection holes.

However, in the gap l between the nozzle hole and the side electrode, spark discharge occurs even when the above-mentioned smoldering occurs, and the ignition of the mixture is performed by the spark generated between this gap, and combustion continues and carbon You will perform self-purification by burning such tectonic bodies.

This self-purification burns the deposits in the discharge space and improves the insulation in the discharge space, and then plasma-like gas is generated again in the discharge space, and the plasma-like gas is ejected from the ejection hole and ignited.

This allows the plasma ignition plug to fully demonstrate its original function.

Examples of various fields of this invention are shown in FIGS. 4A, B to 8A, B.

In the embodiments shown in FIGS. 4A and 4B, the side electrode 2C is formed of an annular member, and this is attached to the electrical insulator 3 in a state of adhesion, while the inner diameter end thereof is larger than the diameter of the jet hole 5. The jet hole 5 and the side electrode 2C are spaced apart from each other.

In this embodiment, when the plug smolders and deposits etc. adhere to the inner surface of the discharge space, plasma gas is not ejected as in the previous embodiment, but the center electrode The creeping discharge between the side electrode and the side electrode makes it possible to ignite the air-fuel mixture, and the effect is similar to that of the previous embodiment.

In addition to the embodiment shown in FIG. 4, the embodiment shown in FIGS. 5A and 5B further includes CrO2, 203. Nb2O3
A sintered coating 7 of a conductive material such as the like is formed.

That is, in the embodiment shown in FIG. 4, the creeping discharge path is extremely curved at the nozzle hole, so the voltage for discharge (required voltage) becomes high, and the fluctuations in the required voltage also become large.
In this embodiment, the required voltage can be lowered and fluctuations in the required voltage can be reduced by sintering the electrically conductive material over the severely curved ejection hole.

Incidentally, instead of sintering and covering the conductive material, a metal ring formed of the conductive material may be fitted.

In the embodiments shown in FIGS. 6A and 6B, the body 3a of the insulator 3 is formed into a conical shape so as to be thinner than the inner diameter of the threaded portion 6 of the spark plug body, thereby increasing the heat value of the spark plug and improving self-cleaning properties. It is a further improvement.

The side electrodes 20 are placed apart from the surface of the insulator 3 with a predetermined gap in the same way as in the embodiment shown in FIG. 2, and their function is similar to that in the embodiment shown in FIG.

In the embodiment shown in FIG. 7, the body 3a of the insulator 3 is made thin as in the previous example, and the side electrodes 2E are provided so as to be in contact with the side edges of this body 3a. 2E is the creeping discharge path.

Needless to say, it is sufficient that the number of side electrodes 2E is one or more.

Further, the side electrodes may be provided on the surface of the insulator at a position away from the nozzle and at a position where creeping discharge is possible.

Furthermore, as shown in FIG. 5, a sintered coating of a conductive material may be formed on the opening edge of the ejection hole 5, or a member made of the same material may be fitted.

According to this embodiment, in addition to the effects of the embodiments shown in FIGS. 4 and 5, it is also possible to improve the self-cleaning performance due to the increased heat value of the spark plug.

8A and 8B are examples in which the center electrode has been slightly modified, and the side electrodes 2F are brought into contact with the surface of the insulator 3 and have an inner diameter larger than the diameter of the nozzle hole 5, so that the creepage While adopting a configuration that utilizes discharge, when the inner diameter of the discharge space 4 is larger than the diameter of the center electrode 1A, the tip portion 1a of the center electrode 1A is formed to have a large diameter so as to be approximately equal to the diameter of the discharge space. There is.

In this way, by making the diameter of the tip 1a of the center electrode 1A large, it is possible to ensure creeping discharge even when the diameter of the discharge space is large, making it even more reliable to ensure ignition during smoldering. It can be made into something.

Incidentally, in order to further increase the volume of the discharge space 4, the tip portion 1b of the center electrode IA may be formed into a cylindrical shape, as shown in FIG.

Also in this case, since the outer diameter of the tip portion 1b is equal to the inner diameter of the discharge space, a good creeping discharge effect can be obtained.

As described above, according to this invention, since the side electrodes are installed apart from the ejection hole of the discharge space formed of an insulator,
Even if smoldering occurs in the discharge space, sparks are generated in the separated parts and the mixture can be ignited, so the ignition performance of the mixture does not deteriorate, and the self-purifying action ensures ignition by plasma gas. This has great practical effects, such as reducing harmful exhaust components such as unburned hydrocarbons and not causing deterioration of drivability.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of a conventional plasma ignition plug, Fig. 2 is a diagram showing the ignition plug of this invention together with a power supply circuit, A is a sectional view, B is an end view, and Fig. 3 is a modified example A. B is a partial sectional view, B is an end view, FIGS. 4 to 8 each show different embodiments, each figure A is a partial sectional view, B is an end view, FIG.
This figure is a sectional view showing a modification of FIG. 8. 1.1A...center electrode, la, lb...
・Tip part, 2, 2A to 2F...Side electrode, 3・
...Electric insulator, 4...Discharge space, 5.
...Blowout hole, 6...Threaded part, 7...
...Conductive substance, 20...Power circuit, l...
···gap.

Claims (5)

[Scope of utility model registration request] (1) Most of the periphery of the spark gap between the center electrode and the side electrodes is surrounded by an electrical insulator to form a discharge space with a small volume, and plasma-like gas is generated in this discharge space during spark discharge. In the spark plug for an internal combustion engine, the spark plug for an internal combustion engine is configured to eject fuel into a fuel mixture from a nozzle opening in the discharge space, wherein the side electrode is installed apart from the nozzle. spark plug. (2) A spark plug for an internal combustion engine according to claim 1, wherein the side electrode is provided apart from the electrical insulator. (3) A spark plug for an internal combustion engine according to claim 1, wherein the side electrode is provided in contact with an electrical insulator. (4) The spark plug for an internal combustion engine as set forth in claim 3, wherein a conductive material is disposed in the opening line of the nozzle hole. (5) The spark plug for an internal combustion engine according to any one of claims 1 to 4, wherein the body of the electrical insulator is formed to have a smaller diameter than the inner diameter of the threaded part.