JPS6282684A - Ignition plug for internal combustion engine - 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 (Field of Industrial Application) The present invention relates to a spark plug for an internal combustion engine, and more particularly to a spark plug with improved fouling resistance.

(Prior Art) As is generally known, spark plugs for internal combustion engines are
The device includes a housing having a center electrode, an insulator, and a ground electrode arranged concentrically, and a spark discharge is generated between the center electrode and the ground electrode to ignite the air-fuel mixture in the combustion chamber of an internal combustion engine. In this spark plug, a gap is provided between the insulator and the housing surrounding it in order to ensure insulation, but air-fuel mixture or combustion gas flows into this space during engine operation. However, carbon and water produced by the combustion adhere to the insulator, staining its surface.

The above-mentioned fouling of the insulator becomes more noticeable under operating conditions where the spark plug receives less heat and therefore has a lower temperature, such as when the internal combustion engine continues to operate at low speed. This operating condition is
Taking the example of an automobile internal combustion engine, extremely low-speed operation due to traffic congestion or the like corresponds to operation immediately after starting in a cold region. Under such operating conditions, the air-fuel mixture is not completely combusted, and carbon and water produced by combustion gradually accumulate on the surface of the insulator. Carbon and water are conductive substances, so if the surface of the insulator is covered with carbon and water and its insulation resistance drops to about 1MΩ or less, it will no longer be possible to discharge at the spark gap, and as a result, the internal combustion engine will not function normally. Driving becomes difficult.

As a countermeasure for this phenomenon, conventionally,
As shown in the above publication, a structure of a spark plug has been proposed in which the surface of an insulator is provided with irregularities to suppress the inflow of air-fuel mixture or combustion gas. Furthermore, as seen in Japanese Patent Laid-Open No. 57-25685, a method is known in which a liquid mixture containing silicone is applied to the surface of an insulator to form an insulating film to prevent the insulation from deteriorating. There is.

(Problem to be Solved by the Invention) However, in the former method of improving the stain resistance of spark plugs, it is necessary to manufacture the insulator by forming irregularities on the surface, which increases the manufacturing cost of the spark plug. This is a contributing factor to the increase in Furthermore, once carbon is deposited in the recesses on the surface of the insulator, maintenance problems arise in that it takes time and effort to remove it. On the other hand, the latter method described above has the disadvantage that the coating layer is exposed to high-temperature combustion gas and the coating material deteriorates over time, so that the effect of improving stain resistance does not last for a long period of time.

Therefore, in view of the above-mentioned problems of the prior art, the present invention provides a spark plug for an internal combustion engine that is excellent in improving fouling resistance and its durability without significantly changing the basic structure of the conventional spark plug. The purpose is to

(Means for Solving the Problems and Their Effects) For the above purpose, the present invention provides a spark plug for an internal combustion engine, which includes a center electrode having a tip portion exposed into the combustion chamber of the internal combustion engine; It has an insulator that holds the center electrode, a ground electrode that is attached opposite to the tip of the center electrode to form a spark gap, a cylindrical housing that surrounds the insulator, and a ground electrode that is concentric with the tip of the housing. A ignition plug for an internal combustion engine is provided, which includes a cylindrical member provided in the cylindrical member and protruding into the combustion chamber. The inner diameter of the cylindrical member is D≧7.5
It is a gate and the protrusion length L into the combustion chamber is 8/2.
It is formed so that D2#≧shi≧/2D−2mm.

In this configuration, a spark discharge occurs in the spark gap formed between the center electrode and the ground electrode, as in the case of a conventional spark plug, and the air-fuel mixture in the combustion chamber is ignited to operate the internal combustion engine. On the other hand, during engine operation, a cylindrical member surrounding the insulator and protruding into the combustion chamber shields the insulator from unburned air-fuel mixture and combustion gases flowing through the combustion chamber, and these mixtures enter the air gap around the insulator. suppresses the inflow of air and combustion gases. This cylindrical member is formed so that its dimensions are within the above range, thereby providing an effective air-fuel mixture and combustion gas shielding function, as well as the required thermal properties.
(hereinafter referred to as heat value) can be satisfied.

(Examples) Hereinafter, the present invention will be described in detail based on examples shown in the accompanying drawings.

Here, a case where the present invention is applied to a spark plug for an internal combustion engine of an automobile will be explained. FIG. 1 shows the overall structure of a spark plug according to an embodiment of the present invention, and the spark plug in the figure is designated by reference numeral 1 as a whole. The spark plug 1 includes an elongated cylindrical center electrode 11, an insulator 12 that holds the center electrode 11, and a cylindrical housing 13. They are arranged concentrically with tHf111 at the center. As in the case of conventional spark plugs, the center electrode 11 is made of nickel alloys such as rIi7B and 0.
(It is made of an alloy that is resistant to corrosion.The insulator 12 is made of an insulating material such as high alumina ceramic, and
It is generally cylindrical in shape with a longitudinal hole for 411.

The center electrode 11 has its tip exposed 7 and is attached to a vertical hole in the insulator 12. - On the other hand, the housing 13 is made of general steel material and is fixed to the outer periphery of the insulator 12 by caulking or the like. The space between the center electrode 11, the insulator 12, and the housing 13 is maintained airtight by filling with a sealing material and caulking.

Further, the housing 13 is provided with a mounting screw portion 13a provided with a thread on the outer periphery at the lower portion. The spark plug 1 is configured such that the tip of the center electrode 11 protrudes into the combustion chamber by screwing the mounting screw portion 13a into a screw hole drilled in the wall portion 15 of the internal combustion engine forming the combustion chamber 16. It is attached to the engine body. In the spark plug according to the present invention, a concentric cylindrical member protruding into the combustion chamber is provided at the tip of the housing. 13b. The cylindrical portion 13b is formed so that its inner diameter and the length of its protrusion into the combustion chamber are within the ranges described in detail below.

Further, this cylindrical portion 13b has an elongated ground electrode 14.
are provided integrally, and the ground electrode 14 is bent so that its front end side faces the end surface of the center electrode 11, and forms a spark gap in the combustion chamber together with the center electrode.

In this large-wheeled example, the length of the center electrode 11 and the insulator 12 that protrude into the combustion chamber 16 is also extended in accordance with the length of the protrusion of the cylindrical portion 13b, and the tip of the insulator 12 extends beyond the cylindrical portion 1.
3b, but the present invention is not limited thereto. For example, the insulator may have a length such that its tip is hidden inside the cylindrical portion.

The structure of the spark plug according to the present invention may be the same as that of a conventional spark plug except for the part protruding into the combustion chamber. Therefore, for the sake of brevity, the structure of this embodiment will not be described in more detail here. No explanation provided.

FIG. 2 shows the spark plug of the above embodiment installed in the engine body, and FIG. 3 is an enlarged view of the same state. Further, for comparison with this embodiment, an example of mounting a conventional spark plug is shown in FIG. The relationship between the spark plug and the flow of the mixture or combustion gas will be explained with reference to these drawings. First, in the case of the conventional example shown in FIG.
6, a part of the mixture 28 is introduced into the wall portion 25 of the combustion chamber.
flows along. The flow along this wall portion 25 passes through the end face of the mounting screw portion 23a of the housing and reaches the tip of the insulator 22, where a portion of the flow is removed.
and the insulator 22. The air-fuel mixture, especially when the ambient temperature is low, contains many liquid particles of the fuel that has not completely vaporized, and these liquid particles are mixed into the insulator 2.
It adheres to the surface of the insulator and becomes carbon without being completely burnt out during combustion and is deposited on the surface of the insulator.

On the other hand, after the air-fuel mixture is combusted, a portion of the combustion gas (not shown) also flows into the space between the mounting screw portion 23a of the spark plug and the insulator 22, as in the case of the air-fuel mixture. In this case, carbon contained in the combustion gas adheres to the surface of the glass 22 and directly stains the surface.

In the embodiment of the invention shown in FIG. 3, as in the conventional example shown in FIG. 4, the mixture 18 and part of the combustion gas flow along the wall portion 15 of the combustion chamber; 16
The inwardly projecting cylindrical portion 13b of the housing acts as an xi plate to divert this flow towards the center of the combustion chamber 16 and around the cylindrical portion 13b. As a result, the amount of air-fuel mixture 18 and combustion gas flowing into the space around insulator 12 is reduced, and the stain resistance of spark plug 1 is improved.

Note that the presence of the cylindrical portion 13b deflects the flow of the air-fuel mixture to the spark l#ii gap between the center and the ground electrode, which has the advantage of improving the ignitability of the air-fuel mixture.

Next, appropriate dimensions of the cylindrical member or cylindrical portion provided at the tip of the housing will be explained.

In order to determine the size range of the cylindrical portion, the inventor conducted evaluation tests on spark plugs with various combinations of dimensions regarding the inner diameter of the cylindrical portion and the length of the protrusion into the combustion chamber, and examined and analyzed the results. I did it.

In the evaluation test, water-cooled 41 Noikle total exhaust FF11800
A CC automobile engine was used as the test internal combustion engine, and the basic shape of the test spark plug was Wl 6EX-IJ (manufactured by Denso Co., Ltd., model name), which is the most applicable engine for automobiles. The spark plug fouling test was carried out at an outside temperature of -10°C and both oil and water temperatures at -10°C.
The operation of the test internal combustion engine to obtain the evaluation data of 'Ir5 loss life was carried out under the test conditions of
Racing - A pattern driving was performed in which light loads (equivalent to a maximum vehicle speed of 201/h) were repeated. Additionally, at the same time as the spark plug fouling test through pattern driving, we also evaluated the heat value of the spark plug under high load.

The heat value was evaluated using the ignition timing (crank angle) of the engine.

As an example of the above evaluation test results, the inner diameter of the cylindrical part of the spark plug is 8.0 m, and the protruding length of the cylindrical part is 0.1.2.
FIG. 5 shows the results of staining tests and heat value evaluations conducted by changing to 3.4 and 5#l111. In the figure, the contamination life point of the spark plug is indicated by the repeated cycle of pattern operation when the insulation resistance of the insulator has decreased to a predetermined value, and the heat value is indicated by the repeated cycle of pattern operation when the temperature of the sparking part of the spark plug has increased. The upper limit of ignition timing that can be operated continuously without premature ignition is indicated by the engine crank angle. As is clear from the figure, for a spark plug with a cylindrical part inner diameter D = 8.0 mm, the life point becomes longer when the cylindrical part protrudes well ≧2.0,
On the other hand, the heat value tends to decrease at 24.0 m. Therefore, in this spark plug, the protrusion length of the circular tube portion is 2InIn≦L≦
It can be seen that it should be set within the range of 4 mm. In addition, the fifth
The J3 shown in the diagram is a basic shape spark plug (W16EX-U)
is shown separately from the test spark plug with a cylindrical part,
This is a basic shape spark plug with an internal diameter of 8.6 screws.
This is due to the fact that it is M.

Similarly, an evaluation test was conducted by changing the inner diameter of the cylindrical portion of the spark plug, and the overall results are shown in FIG.

In the figure, there is a dimensional range of the cylindrical portion that extends the contamination life point of the spark plug and does not reduce the heat value, in the area indicated by diagonal lines. This diagonal I! i! When the area is limited by a formula using the inner diameter of the cylindrical portion and the protrusion length L as factors, the following formula (1) is obtained.
It can be expressed as

Therefore, the dimensions of the cylindrical portion provided at the tip of the housing of the spark plug must be set so that its inner diameter and protrusion length satisfy the above formula (1).

Another embodiment of the present invention is shown in FIGS. 7a to 7c. In the embodiment shown in FIG. 7a, the ground electrode 34 is disposed with its tip surface facing the side of the center electrode 31. In the embodiment shown in FIG. The embodiment shown in FIG. 7b is a modification of the embodiment shown in FIG. 7a, and in this modification, a pair of contact types 1i44a are arranged to sandwich the center electrode 41.

44b is provided. In the embodiment shown in FIG. 7C, the ground electrode 54 is disposed with its side surface facing the edge of the center electrode 51 so as to form a spark gap therebetween. The configurations of these three embodiments other than those described above are the same as those of the embodiment shown in FIG. 1, and the effect of improving stain resistance can be obtained in the same manner as in the embodiment of FIG.

Although the present invention has been described above based on specific embodiments shown in the accompanying drawings, the present invention is not limited to these embodiments. For example, in the above explanation, the cylindrical part was formed by extending the tip of the spark plug mounting screw part, but if the fixation can be maintained even under high temperature conditions, a cylindrical member can be manufactured separately and the cylindrical part can be formed as appropriate. It is also possible to fix it to the tip of the mounting screw part of the housing by any suitable means. As described above, it will be understood that the present invention can be modified in various ways within the scope of the claims.

(Effects of the Invention) As is clear from the above description, the present invention provides a cylindrical member of a predetermined size that protrudes into the combustion chamber of an internal combustion engine at the tip of the housing of the ignition plug, thereby making the ignition plug for internal combustion reformation resistant to fouling. It is something that causes inclination. Therefore, the contamination life of the spark plug is extended, its reliability is improved, and maintenance time and costs are reduced. Furthermore, this improvement in fouling resistance can be achieved with only a slight increase in manufacturing costs, without making any major changes to the structure of conventional spark plugs. Furthermore, by using the spark plug according to the present invention,
Even in an internal combustion engine operated under adverse conditions, normal operation can be maintained for a relatively long period of time, and the degree of freedom in operating the internal combustion engine is increased.

[Brief explanation of drawings]

FIG. 1 is a partially sectional side view showing the overall structure of a spark plug according to an embodiment of the present invention, FIG. 2 is a sectional view showing the embodiment of FIG. 1 installed in an internal combustion engine, and FIG. The figure is an enlarged view of the main part of Fig. 2, Fig. 4 is a view similar to Fig. 3, showing the installed state of a conventional spark plug, and Fig. 5 is a spark plug evaluation test conducted to achieve the present invention. Diagram showing example results, No. 6
The figure is a pictorial diagram showing the size range of a cylindrical member provided at the tip of a spark plug in the present invention, and Figures 7a, 7b, and 7c are sectional views of main parts showing other embodiments of the present invention. In the figure, 1... Spark plug, 11, 31.41° 51... Center electrode, 12... Insulator, 13... Housing, 13b... ...Cylindrical part, 14.34°44a, 44b, 54...
Ground electrode, 15...Wall part of internal combustion engine, 16.
... Combustion chamber.

Claims (8)

[Claims] (1) A center electrode that is used as a spark plug for an internal combustion engine and has a tip portion that is exposed into the combustion chamber of the internal combustion engine;
a cylindrical housing surrounding the insulator; an insulator for holding the center electrode; a grounding electrode mounted opposite to the tip of the center electrode to form a spark gap; and a cylindrical housing surrounding the insulator; and a cylindrical member that is provided concentrically and projects into the combustion chamber, the cylindrical member has an inner diameter D of D≧7.5 mm, and a protrusion length L into the combustion chamber of 8-1/2 D mm. A spark plug for an internal combustion engine, characterized in that it is formed so that ≧L≧1/2D-2 mm. (2) The ignition plug for an internal combustion engine according to claim 1, wherein the cylindrical member is formed integrally with the housing as an extension of the housing. (3) According to claim 1 or 2, the lengths of the center electrode and the insulator are extended in accordance with the length of the cylindrical member protruding into the combustion chamber. Spark plugs for internal combustion engines. (4) The internal combustion engine according to claim 1 or 2, wherein the lengths of the center electrode and the insulator are maintained at standard lengths in the case where the cylindrical member is not provided. spark plug. (5) Any one of claims 1 to 4, wherein the ground electrode is formed in an elongated shape, and its side portion is arranged to face the end surface of the tip of the center electrode. The spark plug for an internal combustion engine according to item (1). (6) Any one of claims 1 to 4, wherein the ground electrode is formed in an elongated shape, and its tip surface is arranged opposite to the side surface of the center electrode tip part. The spark plug for an internal combustion engine according to item (1). (7) The spark plug for an internal combustion engine according to claim 6, wherein a plurality of the ground electrodes are provided around the center electrode. (8) The ground electrode is formed into an elongated shape and is disposed opposite to the edge of the tip of the center electrode so as to form a discharge gap between the side thereof and the edge of the tip of the center electrode. A spark plug for an internal combustion engine according to any one of claims 1 to 4.