JP3849159B2 - Spark plug - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a spark plug for igniting fuel in an engine (internal combustion engine), and more particularly to a spark plug having a branch ground electrode.
[0002]
[Prior art]
The spark plug for engine ignition generates a spark between a center electrode and a ground electrode held by a metal shell attached to the engine, and thereby ignites fuel. In the conventional spark plug, a voltage is applied between a center electrode protruding from an insulator interposed in a metal shell and a strip-shaped ground electrode extending from the metal shell so as to face the center electrode. Sparks are generated and the fuel in the combustion chamber is ignited. However, in such a spark plug, the spark between the center electrode and the ground electrode is considered unstable and does not cause efficient combustion.
[0003]
In order to solve such a point, a spark plug intended to disperse a spark in a wide range by using a ground electrode that branches into two at a portion facing the center electrode as a ground electrode has been proposed (for example, USP No. .4,268,774). This spark plug branches the ground electrode at the portion corresponding to the outer periphery of the center electrode where the ground electrode first encounters, and each branch end extends beyond the portion corresponding to the outer periphery of the center electrode at the other portion. By making it project, the spark first generated at the branch point of the ground electrode sequentially moves to the branch end side and tries to give the spark a spread.
[0004]
However, even in such a spark plug, since a part of the ground electrode covers the center electrode and the branch end protrudes outward beyond a portion corresponding to the outer peripheral portion of the center electrode, the occurrence of the spark is not necessarily performed. It cannot be said that it is stable and the spread of the flame is not sufficient.
[0005]
[Problems to be solved by the invention]
The object of the present invention is to solve the above problems by generating sparks stably at a plurality of points to improve ignition efficiency, and quickly and quickly disperse flames generated near the spark gap in the combustion chamber. It is to provide a plug that can be used for a long period of time by improving combustion efficiency, thereby improving fuel consumption, reducing pollutants in the exhaust gas, and preventing carbon from adhering to the electrode.
[0006]
[Means for Solving the Problems]
The present invention includes a metal shell having a mounting screw portion for an engine,
A central electrode that is held inside the metal shell with an insulator interposed therebetween, and projects in a cylindrical shape from the insulator on the opening end side of the mounting screw portion toward the combustion chamber;
A ground electrode that branches near the tip of the vertical portion that is bent and extends in the vertical direction from the axial portion so as to form a spark gap on the tip side of the center electrode from the metal shell,
The branch end of the ground electrode extends to the position of the diameter of the circular tip of the center electrode in a direction orthogonal to the direction in which the vertical portion extends, and the inner corner of each branch end is the tip of the center electrode. The spark plug is disposed at a position facing an edge of the outer peripheral portion in the diameter direction.
[0007]
The basic structure of the spark plug of the present invention is the same as that of the conventional one, and the center electrode is held inside the metal shell having the mounting screw portion for the engine with an insulator interposed, and the opening of the mounting screw portion is formed. The ground electrode is bent and protrudes from the metal shell so as to form a spark gap between the end insulator and the circular tip of the center electrode protruding in a cylindrical shape toward the combustion chamber of the engine. The opposite side of the center electrode is a terminal, and the ground electrode is grounded through a metal shell.
[0008]
In the present invention, the ground electrode is branched in the vicinity of the tip portion of the vertical portion that is bent and extends in the vertical direction from the axial portion , and each branch end is the tip of the center electrode in the direction orthogonal to the direction in which the vertical portion extends. It extends to the position of the diameter of each part, and is arranged so that the inner corner of each branch end faces the edge of the outer peripheral part in the diametrical direction at the tip of the center electrode to form a spark gap. A notch-shaped opening is formed between the branch portions of the ground electrode, but the tip of the center electrode is exposed to the combustion chamber side through this opening. The center electrode preferably protrudes from the large diameter portion, for example, through a conical cross-sectional area reduction portion, in the vicinity of the tip portion.
[0009]
In the above spark plug, when a voltage is applied between the center electrode and the ground electrode, a spark is generated in the spark gap between the two electrodes, and the mixed gas of fuel and air in the combustion chamber is ignited and burned. At this time, since the corners inside the respective branch ends of the ground electrode are opposed to the edge of the outer peripheral portion of the center electrode, a spark is generated between the corners and the edge.
[0010]
Since the discharge is likely to occur at the pointed portion, the corner plate portion of the ground electrode or the branching point is opposed to the edge portion of the center electrode as in the conventional product, so that the corner is as in the present invention. Sparks are more likely to occur when the part and the edge face each other. For this reason, when a predetermined charge is stored between both electrodes, a spark is generated immediately, and the generation time is stabilized.
[0011]
The above-mentioned sparks are generated almost simultaneously at a plurality of branch end portions, and then spread to the periphery to obtain a stable spark. If a reduced cross section is formed in the vicinity of the tip of the center electrode, the spark spreads in this portion after the first occurrence of spark, so that the spark is stabilized.
[0012]
Here, a flame is generated by the spark, and this flame spreads radially in the combustion chamber through the opening between the branch portions of the ground electrode along with the surface direction of the spark gap between the center electrode and the ground electrode. In the case of a conventional strip-shaped ground electrode, the flame spreads only in the plane direction of the gap, and this plane direction is transverse to the combustion chamber, so it takes time for the flame to reach the entire combustion chamber. However, if a branched ground electrode is used, the flame extends directly in the direction of the combustion chamber through the opening between the branch ends, so the time for the flame to reach the entire combustion chamber is shortened and the combustion efficiency is increased.
[0013]
In the present invention, the opening between the branch portions is large, and the tip of the center electrode is exposed toward the combustion chamber, so that the flame propagates quickly to the entire combustion chamber. Combined with the stability of the spark, the combustion takes place efficiently.
This improves fuel efficiency, reduces the amount of pollutants in the exhaust gas, prevents carbon from adhering to the electrode, and allows the spark plug to be used over a long period of time.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
1 is a front view of a spark plug according to an embodiment, FIG. 2 (a) is a partial side view, (b) is a bottom view, FIG. 3 (a) is a perspective view of a part of FIG. It is a one part enlarged view of FIG.
[0015]
In the figure, reference numeral 1 denotes a spark plug, and a center electrode 4 is held inside a metal shell (housing) 2 having a mounting screw portion 2a for the engine with an insulator 3 made of cylindrical ceramics interposed. The metal shell 2 is formed so that a spark gap 5 is formed between the insulator 3 on the opening end side of the mounting screw portion 2a and the circular tip portion 4a of the center electrode 4 protruding in a cylindrical shape toward the combustion chamber side of the engine. The ground electrode 6 is bent and protrudes from the tip of the mounting screw portion 2a.
[0016]
The center electrode 4 has a small-diameter portion 4d protruding from the large-diameter portion 4b through a conical reduced section 4c in the vicinity of the tip portion 4a, and the tip is the tip portion 4a of the center electrode 4.
The ground electrode 6 has a vertical direction portion 6b that bends in the vertical direction from the axial direction portion 6a, and branch portions 8 and 9 are formed by branching from the branch point 7 in the vicinity of the front end portion of the vertical direction portion 6b.
[0017]
The leading ends of the branch portions 8 and 9 of the ground electrode 6, that is, the branch ends 8a and 9a, extend to the position of the diameter of the tip portion 4a of the center electrode 4 in the direction orthogonal to the direction in which the vertical direction portion 6b extends . The inner corners 8b and 9b of the branch ends 8a and 9a are arranged at positions facing the edge portions 4e and 4f of the outer peripheral portion in the diameter direction of the tip portion 4a of the center electrode 4. A V-shaped opening 10 is formed at the tip of the ground electrode 6 by branching, and the tip 4 a of the center electrode 4 is exposed to the combustion chamber side through the opening 10. The branch point 7 is located outside the outer peripheral portion of the tip portion 4a.
[0018]
The opposite side of the center electrode 4, that is, the outside of the engine is a terminal 4g protruding from the protruding portion 3a of the insulator 3, and can be connected to the ignition circuit. The ground electrode 6 is grounded through the metal shell 2.
[0019]
In the above spark plug 1, when a voltage is applied between the center electrode 4 and the ground electrode 6, a spark is generated in the spark gap 5, and a mixed gas of fuel and air in the combustion chamber is ignited and burned. At this time, the end portions of the branch portions 8 and 9 of the ground electrode 6, that is, the corner portions 8b and 9b inside the branch ends 8a and 9a are opposed to the edge portions 4e and 4f of the outer peripheral portion of the end portion 4a of the center electrode 4. Therefore, a spark occurs between the two first.
[0020]
Since the discharge is likely to occur at the pointed portion, the spark plug 1 of the above-described spark plug 1 is more than the case where the strip-like portion of the ground electrode or the branch point is opposed to the edge portion of the center electrode as in the conventional product. As described above, sparks are more likely to occur when the corner portions 8b and 9b face the edge portions 4e and 4f. For this reason, when a predetermined charge is stored between the electrodes 4 and 6, a spark is generated immediately, and the generation time is stabilized.
In this case, after sparks are generated almost simultaneously on the lines 11a, 12a that connect the corners 8b, 9b and the edge parts 4e, 4f, the spread is spread to the region sandwiched between the lines 11b, 11c and 12b, 12c. A stable spark can be obtained.
[0021]
Here, a flame is generated by the spark. This flame radiates into the combustion chamber through the opening 10 between the branch portions 8 and 9 of the ground electrode 6 as well as the surface direction of the spark gap 5 between the center electrode 4 and the ground electrode 6. spread. In the case of the conventional strip-shaped ground electrode, the flame spreads only in the plane direction of the spark gap, and this plane direction is transverse to the combustion chamber, so that the flame spreads throughout the combustion chamber. Although it took time, when using the branched ground electrode 6 as described above, the flame extends directly in the direction of the combustion chamber through the opening 10 between the branch portions 8 and 9, so the time for the flame to reach the entire combustion chamber is Shorter and higher combustion efficiency.
[0022]
The opening 10 between the branch portions 8 and 9 is larger than the conventional one, and the tip 4a of the center electrode 4 is exposed to the combustion chamber side and is not shielded. Propagation is fast, and this, combined with the accuracy of the timing of the occurrence of the spark and the stability of the spark, results in efficient combustion.
[0023]
In the above embodiment, the opening 10 of the ground electrode 6 is V-shaped, but may be polygonal, arc-shaped, or other shapes. Moreover, the cross-sectional reduction part 4c of the center electrode 4 is good also as a continuous curved surface shape instead of a cone shape.
[0024]
【The invention's effect】
The spark plug of the present invention has a vertical portion in which a central electrode held with an insulator interposed inside a metal shell protrudes in a cylindrical shape toward the combustion chamber and extends by bending vertically from the axial portion of the ground electrode. The branch end that branches near the tip of the electrode extends to the position of the diameter of the circular tip of the center electrode in the direction perpendicular to the direction in which the vertical portion extends, and the inner corner of each branch end of the ground electrode is the center electrode Since the tip of the diametrically opposed edge of the outer peripheral portion in the diametrical direction, the spark is stably generated at a plurality of points to improve the ignition efficiency, and the flame generated in the vicinity of the spark gap can be quickly generated. Widely dispersed in the combustion chamber to increase combustion efficiency, thereby improving fuel efficiency, reducing pollutants in the exhaust gas, and preventing carbon from adhering to the electrode, resulting in a plug that can be used for a long time It is.
[Brief description of the drawings]
FIG. 1 is a front view of a spark plug according to an embodiment.
2A is a side view of a part of FIG. 1, and FIG. 2B is a bottom view.
3A is a perspective view of a part of FIG. 1, and FIG. 3B is an enlarged view of a part thereof.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Spark plug 2 Metal shell 2a Mounting screw part 3 Insulator 4 Center electrode 4a Tip part 4b Large diameter part 4c Small diameter reduced part 4d Small diameter part 4e, 4f Edge part 5 Spark gap 6 Ground electrode 7 Branch point 8, 9 Branch part 8a 9a Branch end 8b, 9b Corner 10 Opening

Claims (2)

A metal shell having a mounting screw to the engine;
A central electrode that is held inside the metal shell with an insulator interposed therebetween, and projects in a cylindrical shape from the insulator on the opening end side of the mounting screw portion toward the combustion chamber;
A ground electrode that branches near the tip of the vertical portion that is bent and extends in the vertical direction from the axial portion so as to form a spark gap on the tip side of the center electrode from the metal shell,
The branch end of the ground electrode extends to the position of the diameter of the circular tip of the center electrode in a direction orthogonal to the direction in which the vertical portion extends, and the inner corner of each branch end is the tip of the center electrode. A spark plug, wherein the spark plug is disposed at a position facing an edge of the outer peripheral portion in the diameter direction.   2. The spark plug according to claim 1, wherein the tip of the center electrode protrudes from the large diameter portion through the cross-sectional area reduction portion in the vicinity of the tip portion.

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