JPH05114454A - Spark plug for internal combustion engine - Google Patents

Abstract

PURPOSE:To improve sparking property by thinning a center electrode to correspond to the tip part of a ground electrode and at the same time installing a plate- or rod-like igniting electrode made of a noble metal or a noble metal alloy in the surroundings of the thin part. CONSTITUTION:Corresponding to the flat tip part 13 of one or a plurality of ground electrodes 10 to be joined with the tip of a screw 9 of a main metal fitting, the tip part of a center electrode 4 to be held by an insulator 2 is thinned. In the surroundings of the thin part 16 of the center electrode 4, a circular or square plate-or columnar or prismatic rod-like igniting electrode 15 made of a noble metal or a noble metal alloy is installed. Consequently, even if the igniting electrode 15 is consumed, the effective surface area of the igniting electrode 15 is its cross section surface area and always constant, so that sparking property is effectively improved even for the thinned center electrode 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a spark plug mounted on an internal combustion engine, and more particularly to a structure of a center electrode held at the tip of a shaft hole of an insulator.

[0002]

2. Description of the Related Art In recent years, as the performance of an internal combustion engine has improved, a spark plug mounted on the internal combustion engine is sucked into the combustion chamber of the internal combustion engine so that inspection and maintenance are not required for a long period of time. There is a demand for a center electrode with excellent wear resistance when igniting a mixed gas as described above. Therefore, the diameter of the center electrode held by the insulator is reduced, or a noble metal tip is bonded to the tip of the center electrode. The structure and the like are adopted.

[0003]

However, in the above-mentioned conventional one, in the case of using the center electrode which is made of a noble metal and has a reduced diameter in order to improve the wear resistance at the time of igniting the air-fuel mixture, the main electrode is mainly used. In the case of a single-pole plug with a single ground electrode joined to the screw part at the end of the metal fitting,
Since spark discharge for igniting the air-fuel mixture in the combustion chamber is performed between the tip surface of the center electrode and the ground electrode arranged at a position facing the tip portion of the center electrode, long-term use Therefore, even if the tip surface of the center electrode is worn, the effective area for spark discharge of the center electrode having a constant diameter is always the cross-sectional area of the center electrode and is constant, so that the ignitability is not significantly deteriorated. On the other hand, in a multi-pole plug having a plurality of ground electrodes corresponding to the side circumference of the center electrode held by the insulator, ignition of the air-fuel mixture does not occur even if the diameter of the center electrode is reduced. This is done at the tip of multiple ground electrodes, and the effective area for spark discharge is large compared to the cross-sectional area of the center electrode in a single-pole plug, and there is little improvement in ignitability by reducing the diameter of the center electrode. There is a drawback.

Therefore, the present invention aims to improve the drawbacks of the above-mentioned conventional ones, and to improve the ignitability of the air-fuel mixture in the combustion chamber in the center electrode having a reduced diameter.

[0005]

To this end, the tip of the center electrode held by the insulator is thinned corresponding to the tip of one or a plurality of ground electrodes joined to the tip of the threaded portion of the metal shell. At the same time, a plate-shaped or rod-shaped ignition electrode made of a single or a plurality of noble metals or noble metal alloys is arranged on the side peripheral portion of the thin portion.

[0006]

With the above construction, even if the ignition electrode for igniting the air-fuel mixture in the combustion chamber of the internal combustion engine is worn out by using it while being mounted on the internal combustion engine for a long period of time, The spark discharge that ignites the air is generated between the ground electrode that is joined to the threaded portion at the tip of the metal shell and the ignition electrode that is arranged on the side periphery of the center electrode so as to correspond to the tip of this ground electrode. Since the effective area of the ignition electrode that performs spark discharge even if the ignition electrode is consumed is always constant with the cross-sectional area of the ignition electrode,
The ignitability can be effectively improved even in a center electrode having a reduced diameter.

Further, the structure in which the center electrode is made thin and the ignition electrode is provided on the side peripheral portion of the thin portion reduces the extinguishing effect of the center electrode, so that the ignitability can be further improved.

In the ignition electrode disposed on the side peripheral portion of the center electrode, since a noble metal is used, it has excellent wear resistance, so that the spark plug can be used even for a long period of time. The durability of itself can be improved.

[0009]

The present invention will be further described with reference to the embodiments shown in the drawings. (1) is a spark plug for an internal combustion engine which is an embodiment of the present invention. The spark plug (1) for an internal combustion engine holds a center electrode (4) at the tip of a shaft hole (3), At the rear end of (3), an insulator (2) containing and holding a conductive glass seal (6) and a resistor (7) together with the terminal electrode (5), and this insulator (2). ) Is fixed to the pedestal (11) through the packing (12), and
The metal shell (8) is formed by disposing a ground electrode (10) at a position facing the tip of the center electrode (4) held by the insulator (2) at the tip of the screw part (9).

The insulator (2) is attached to the flat tip (13) of the ground electrode (10) or the plurality of ground electrodes (10) joined to the tip of the screw (9) of the metal shell (8). The center electrode (4) to be held has a thinned tip, and a circular or rectangular shape made of a noble metal or a noble metal alloy or a plurality of noble metals or a noble metal alloy on the side peripheral portion (17) of the thin part (16) of the center electrode (4). The ignition electrode (15) having a plate shape (18) or a rod shape (19) such as a cylinder or a prism is disposed (FIG. 3).

Since the present invention has the above-mentioned structure, by using the spark plug (1) for an internal combustion engine mounted on the internal combustion engine for a long period of time, it is possible to obtain a mixture in the combustion chamber of the internal combustion engine. Even if the ignition electrode (15) for igniting is consumed, the spark discharge for igniting the air-fuel mixture includes the ground electrode (10) joined to the screw portion (9) at the tip of the metallic shell (8) and the plurality of electrodes. The tip of the center electrode (4) held by the insulator (2) is thinned so as to correspond to the tip of the firing electrode (10), and the side of the thin part (16) of the center electrode (4) This is performed by disposing the plate-shaped (18) or rod-shaped (19) firing electrode (15) made of one or more precious metals or precious metal alloys in the peripheral portion (17). Even if the battery is exhausted, Effective area of the electrode (15), since it is constant always cross-sectional area of the ignition electrodes (15), can also effectively improves the ignitability in diameter reduction has been the center electrode (4).

Further, the cooling of the center electrode (4) is small due to the formation of the side peripheral portion (17) by thinning the center electrode (4), and the growth of the flame kernel is promoted, so that the ignitability is further improved. You can

Further, since the noble metal is used in the ignition electrode (15) arranged on the side peripheral portion (14) of the center electrode (4), it has excellent wear resistance, so that it can be used for a long period of time. The durability of the spark plug (1) itself can be increased even when it is used over a long period of time.

Even in the spark plug (1) having a single ground electrode (10), a spark discharge is generated between the thinned side peripheral portion (17) of the center electrode (4) and the ground electrode (10). It works effectively in things that do.

[0015]

As described above, the center electrode is thinned so as to correspond to the tip of the ground electrode or the plurality of ground electrodes joined to the threaded portion of the tip of the metallic shell, and the side wall of the thin portion is By arranging a plate-shaped or rod-shaped ignition electrode made of a noble metal or a noble metal alloy, the effective area for spark discharge in the ignition electrode can be kept constant even if the ignition electrode is consumed by the spark discharge. It is possible to improve the ignitability of the spark plug itself, and by reducing the thickness of the center electrode, the extinguishing effect is reduced and the ignitability can be further improved, and the spark durability of the spark plug itself is improved by using the ignition electrode made of a noble metal. It has an excellent effect that can achieve.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional view of a spark plug for an internal combustion engine that is an embodiment of the present invention.

FIG. 2 is an enlarged side view and an enlarged front view of a main part of a center electrode of the spark plug.

FIG. 3 is an enlarged perspective view of a main part of the center electrode in the example.

[Explanation of symbols]

 1 Spark Plug 2 Insulator 3 Shaft Hole 4 Center Electrode 5 Terminal Electrode 6 Conductive Glass Seal 7 Resistor 8 Metal Fitting 9 Screw Part 10 Grounding Electrode 11 Step Seat 12 Packing 13 Tip of Grounding Electrode 14 Center Circumference of Central Electrode 15 Ignition electrode 16 Thin part of center electrode 17 Side part of thin part 18 Plate-shaped ignition electrode 19 Rod-shaped ignition electrode

Claims (1)

[Claims] 1. The center electrode tip held by an insulator is thinned corresponding to the tip of one or a plurality of ground electrodes joined to the tip of the threaded portion of the metal shell, and the side of this thin portion is formed. A spark plug for an internal combustion engine, comprising a plurality of plate-shaped or rod-shaped ignition electrodes made of a single or a plurality of noble metals or noble metal alloys, provided around the periphery thereof.