JPH01197984A - Auxiliary gap member for spark plug for internal combustion engine - Google Patents

Abstract

PURPOSE:To stabilize spark voltage by disposing conductive matter electrically insulated from an anode and surrounding this anode. CONSTITUTION:Because the degree of expansion of corona at electrode edge part 4a(5a) is controlled by action of conductive matter 6 electrically insulated from an anode 4(5) and disposed in an enclosing tube 1 surrounding this anode 4(5), fluctuation in spark voltage at a spark gap becomes small. By setting the conductive matter 6 to have an equal potential to a cathode 5(4), potential inclination at the electrode edge part 4a(5a) becomes sharp further, and fluctuation in spark voltage becomes small further. Spark voltage can thus be stabilized.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an auxiliary gap body that improves the fouling resistance of a spark plug for an internal combustion engine.

[Conventional technology]

In internal combustion engines such as automobiles, depending on the operating conditions of the engine, carbon, etc. generated due to unburned combustion may adhere to the surface of the insulator that electrically insulates the spark plug electrodes, reducing the electrical insulation resistance of the spark plug. Therefore, the voltage necessary for ignition is no longer applied to the electrode gap of the spark plug, and the spark plug may misfire.

In order to prevent this problem, it is conventionally known to provide an auxiliary gap body in the secondary circuit of the ignition circuit in series with the electrode gap of the spark plug.

Regarding the action of this auxiliary gap body, the voltage applied to the auxiliary gap body is kept sufficiently high before spark discharge occurs, and this high voltage is almost instantaneously applied to the electrode gap of the spark plug, so the spark plug Even if the insulator is contaminated with carbon, etc., the electrical leakage at the contaminated part is extremely small, so the high voltage necessary for ignition is applied to the electrode gap of the spark plug, and as a result,
This will cause ignition.

By the way, as a conventionally well-known auxiliary gap body, as disclosed in Japanese Patent Publication No. 51-32180, a spark gap is arranged in a sealed glass tube and a discharge gas such as N2 is filled. There are pipe types. In order to maintain the spark voltage in the spark gap within the tube at a predetermined value, the discharge tube type described above has a structure that is not easily affected by disturbances such as temperature and humidity that cause fluctuations in the spark voltage.

(Problem to be solved by the invention) However, even in a discharge in a sealed chamber filled with gas such as N2, the spark voltage is unstable, and the higher the spark voltage is set, the greater the fluctuation in the spark voltage becomes. I have a problem with becoming.

Second, during the discharge in the spark gap formed by the two electrodes, the area near the electrodes is partially ionized due to the generation of corona due to the increase in the applied voltage between the gaps, and as the applied voltage increases, the corona increases. This is because the corona expands and eventually electrical breakdown occurs between the gaps, leading to spark discharge, but the voltage during this spark discharge, that is, the spark voltage, depends on the degree of expansion of the corona.

Incidentally, the corona generally expands more easily than the edge portion of the electrode, and therefore, the electrode edge portion has a sudden potential frequency, which makes it easier to ionize the gas in the spark gap space, thereby making it easier for sparks to fly between the spark gaps.

Therefore, in order to stabilize the spark voltage, it is necessary to control the degree of expansion of the corona.In a series of experiments regarding the stabilization of the spark voltage, the inventor found that By applying a conductive material around the enclosing tube in the gap body, the degree of corona expansion is controlled,
It was discovered that the spark voltage was stabilized.

The present invention aims to stabilize the spark voltage by controlling the extent of corona expansion as described above.

[Means to solve the problem]

In order to achieve the second object, the auxiliary gap body of the spark plug for an internal combustion engine of the present invention has the following features: In the auxiliary gap body of a spark plug for an internal combustion engine, in which an anode and a cathode electrode are enclosed and a spark gap is formed by the electrodes, the anode is electrically insulated from the anode, and at least the anode is surrounded and conductive. It is for arranging things.

(b) Note that the location where the conductive material is disposed is preferably the enclosed tube of the auxiliary gap body.

(c) It is also effective to make the conductive material have the same potential as the cathode.

[Function] When a conductive material is provided to surround the electrode and to be electrically insulated from the anode of the counter electrode that forms the spark gap, the potential gradient at the edge of the electrode becomes steeper, promoting the expansion of the corona.
Moreover, there is a tendency to converge.

The present invention utilizes this phenomenon.

In other words, the degree of corona expansion at the electrode edge is controlled by the action of a conductive material that is electrically insulated from the anode and placed in the encapsulating tube surrounding the electrode. Fluctuations in the spark voltage become smaller and stabilized. In addition,
By setting the conductive material at the same potential as the cathode, the potential gradient at the electrode edge becomes even more similar, and the fluctuation in the spark voltage becomes even smaller.

Further, even when the auxiliary gap member is required to have a high spark voltage in practical use, the same effect as described above is obtained.

[Example] An auxiliary gap body for a spark plug for an internal combustion engine according to the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment of the auxiliary gap body of the present invention, in which electrodes 4 and 5 made of tungsten or the like form a spark gap 3 in an enclosed tube 1 such as a glass tube.
Leads 7 made of iron, nickel, etc. are bonded to and 5, respectively.
and 8 are placed opposite each other, and inside the enclosure tube 1 is Nz.

Gas such as He or Ar is sealed. Reference numeral 6 denotes a conductive material t4 made of PT, Aig, etc., which is applied in paste form to the outer periphery of the enclosure tube l so as to cover the electrodes 4 and 5, and is then dried and adhered. A gap body 10 is configured.

Note that 4a indicates an edge portion of the electrode 4, and 5a indicates an edge portion of the electrode 5.

Next, a plug camp for electrically connecting and fixing the above-mentioned auxiliary gap body 10 between a spark plug and a high voltage cord will be described.

FIG. 2 shows an embodiment of the plug cap of the present invention incorporating an auxiliary gap body, in which the auxiliary gap body 10 is housed in a cylindrical body 16 made of epoxy resin or the like. One side of the lead of the gap body IO is joined to a contact metal 14 made of brass or the like that houses a contact spring 15 made of spring steel or the like, and the other side of the lead of the auxiliary gap body IO is connected to a contact metal 14 made of brass or the like. 17, and the contact metal 17 is electrically connected to a high voltage cord 18.

Reference numeral 13 denotes a seal rubber 13 made of silicone rubber or the like that maintains airtightness between the body 16 and the spark plug 30 and fits into the insulator portion of the spark plug 30; 19 denotes a seal rubber between the body 16 and the high voltage cord 18; A seal rubber 19 made of silicone rubber or the like keeps the gap airtight, and the plug cap 20 is configured as described above.

By pushing the terminal of the spark plug 30 into the contact spring 15 of the plug cap 20, the auxiliary gap body 10 is electrically connected and fixed between the spark plug 30 and the high voltage coil F'18. .

Next, regarding the auxiliary gap body of the present invention shown in FIG.
FIGS. 3 and 4 show the fluctuation values of the spark voltage when Ag is used as the conductive material and the position and length of the conductive material on the outer periphery of the sealed tube are changed. The experiment was conducted using a car (
This was done using a negative voltage ignition coil for four-wheel vehicles.

In Figure 3, a glass tube with an outer diameter of 8 m+n and a thickness of 1 mm is used as the encapsulating tube, and two tungsten electrodes with an outer diameter of 3 mm are placed facing each other in the encapsulating tube so that the spark gap is 6 mm. Then, 3 times N2 gas with a purity of 99.9% or more was introduced into the sealed tube.
This is the result of an experiment conducted with a sample sealed under atmospheric pressure. As can be seen from Figure 3, the fluctuation of the spark voltage can be reduced by disposing a conductive material surrounding the anode and cathode that form the spark gap, and by electrically connecting this conductive material to the cathode to maintain the same potential. However, it is necessary to surround the electrode portion with a conductive material for at least the anode. Figure 4 shows the spark gap changed from 6 nun to 2 under the experimental conditions of Figure 3.
Although the experimental results were conducted by shortening the length to mm, the fluctuation of the spark voltage showed almost the same tendency as in the case of FIG. 3.

In addition, Fig. 5 shows the experimental level (A in Fig. 3) that was most effective in the experiment shown in Fig. 3, with a glass tube having an outer diameter of 7 mm and a thickness of 1 mm, and a glass tube with an outer diameter of 6 mm. Peng, thickness 1ff
Make lfl+ and set the distance between the conductor and the electrode to 2.5
A similar experiment was conducted by shortening the length from 2mm to 2+++++++ to 1.5mm, but the distance between the conductive material and the electrode was narrower (I see, the fluctuation in the spark voltage was becoming smaller).

Also, Fig. 6 shows the same results as in the experiment shown in Fig. 3, with the spark gap reduced by 1 mm from 611111 for the most effective experimental level (A in Fig. 3), as in the experiment shown in Fig. 5. However, when the spark gap becomes 4 mm or less, the fluctuation of the spark voltage becomes somewhat large.

Next, in this embodiment, the conductive material is disposed on the outer circumference of the electrically insulating encapsulated tube, but it may also be disposed on the inner periphery of the encapsulated tube as shown in FIG. As shown in the figure, it may be arranged in the inner core of the sealed tube.

Note that the conductive material may be electrically connected to the cathode to have the same potential, and the conductive material may be placed on the outer periphery of the sealed tube as shown in FIG. 9(a), or as shown in FIG. 9(b). Alternatively, as shown in FIG. 9(C), it may be arranged at the inner core of the enclosure tube.

Furthermore, the same effect can be obtained by disposing the conductive material in the electrically insulating body of the plug cap containing the auxiliary gap body instead of disposing the conductive material in the sealed tube.

That is, at the position of the body of the plug cap that covers the electrode part of the auxiliary gap body, the conductive material may be arranged on the outer periphery of the body as shown in FIG. 10(a), or as shown in FIG. 10(b). It may be arranged on the inner periphery of the body as shown in FIG.
It may be arranged in the inner tube core of the body as shown in Figure (C).

In addition, assuming that the conductive material has the same potential as the cathode of the auxiliary gap body,
The conductive material may be arranged on the outer periphery of the body as shown in FIG. 11(a), or may be arranged on the inner periphery of the body as shown in FIG. 11(b). As shown in (C), it may be arranged in the inner tube core of the body.

In this example, a method of applying a paste-like conductive material was used, but a powder-like conductive material may also be glued or baked.
Alternatively, a plate-shaped conductive material may be bonded or fitted, or the conductive material itself may be embedded.

〔Effect of the invention〕

Since the present invention is configured as described above, it produces the effects described below.

(a) By disposing a conductive material that is electrically insulated from the anode and surrounding the anode, the extent of corona expansion at the electrode edge is controlled, so fluctuations in spark voltage are reduced. It becomes a highly reliable auxiliary gap body.

(b) By disposing the conductive material in the sealed tube, the auxiliary gap body becomes highly reliable and easy to manufacture.

(c) By setting the conductive material to the same potential as the cathode,
Fluctuations in spark voltage become even smaller.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view showing an embodiment of the auxiliary gap body of the present invention, FIG. 2 is a longitudinal sectional view showing an embodiment of a plug cap incorporating the auxiliary gap body of the present invention, FIG. Figure 4 shows the relationship between the placement position of the conductive material in the auxiliary gap body and the spark voltage fluctuation, and Figure 5 shows the relationship between the spark voltage fluctuation and the distance between the conductive material and the electrode in the auxiliary gap body. Figure 6 is a diagram showing the relationship between the gap size in the auxiliary gap body and the spark voltage fluctuation, Figures 7, 8, and 9 (a), (b), and (C) are the main A vertical sectional view showing another embodiment of the auxiliary gap body of the invention, FIG. 10(a)
. (b), (C) and Figure 11 (a), (b), (
C) is a longitudinal sectional view showing another embodiment of the plug cap of the present invention incorporating an auxiliary gear 71 body. 1... Enclosed tube, 2... Enclosed gas, 3... Spark gap. 4.5... Electrode, 6... Conductor, 10... Auxiliary gap body, 20... Plug cap, 30... Spark plug. Representative Patent Attorney Takashi Okabe Fig. 1 (Length flower cap 6mm) K7 Fig. 3 (゛Spark Ki゛shi, 2)゛2mm) VI AE3 Figure 7 Figure 8 (C) Figure 9

Claims (3)

[Claims] (1) Auxiliary gap of a spark plug for an internal combustion engine, in which opposing anode and cathode electrodes are enclosed in a sealed tube filled with inert gas or stable gas, and a spark gap is formed by the electrodes. An auxiliary gap body for a spark plug for an internal combustion engine, the body being electrically insulated from the anode and having a conductive material surrounding at least the anode. (2) The auxiliary gap body for a spark plug for an internal combustion engine according to claim 1, wherein the conductive material is disposed in the sealed tube. (3) The auxiliary gap body for a spark plug for an internal combustion engine according to claim 1 or 2, wherein the conductive material has the same potential as the cathode.