JPS63218181A - Two-step discharge type ignition plug - 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 (Industrial Application Field) The present invention relates to an improvement in a two-stage discharge type spark plug, and in particular, to prevent melting damage to the center electrode by forming the intermediate electrode and the outer electrode in a mountain-like or saw-blade shape. This relates to a significantly reduced number of spark plugs.

(Prior art) Spark plugs used in internal combustion engines of automobiles are required to have as low a voltage as possible, to have a fast flame speed, and to have low spark-flying performance due to requirements such as the engine's output function, fuel efficiency, and exhaust gas purification. A good spark plug satisfies these conditions. Under such circumstances, the inventor of the present application has already proposed a two-stage discharge spark plug described in Japanese Patent Application Laid-Open No. 61-32980. The electrodes of the plug include a center electrode, an intermediate annular electrode disposed on an insulating member, and an outer annular electrode grounded to the cylinder, which are coaxially arranged with a predetermined radial gap, and are arranged coaxially with each other with a predetermined radial gap. A plurality of protrusions are provided at equal intervals along the circumferential direction to generate sparks, and slits are bored in the annular electrodes at the middle and outer poles at positions radially opposite to the protrusions. Each of these has a configuration in which a substantially rectangular plate-shaped projection is provided. Then, any single protrusion selected from the middle and outer protrusions is bent and deformed inward to form a discharge gap, and sparks are caused to fly in this gap. When this protrusion wears out, it restores itself and the next protrusion is deformed and used. It is something to do.

(Problems to be Solved by the Invention) In the two-stage discharge type electrode of the plug as described above, the plurality of protrusions for flying sparks provided in the middle and the outside have an annular wall with a slight slit-like gap. The center electrode is surrounded by a double annular wall. On the other hand, normally air-fuel gas flows in a spiral shape inside the cylinder before and after ignition and combustion, but the gas around the center electrode is blocked by the front and rear double annular walls and stays in a cage. In particular, the high-temperature gas after combustion repeatedly heats and damages the small-diameter central electrode, and in particular, the smaller protrusions that protrude from the electrode melt and wear out in an extremely short period of time, causing damage to the middle and outer electrodes. Since the electrode protrusion moves the position where sparks occur, the ignition performance deteriorates and a higher voltage is required, which has the disadvantage that the plug body must be replaced sooner.

(Technical Policy) Therefore, in the present invention, the high temperature gas remaining in the center electrode portion should be moved and dissipated by the fluidity of the swirling gas in the cylinder. Therefore, the distance between the plurality of protrusions provided on the intermediate and outer electrodes is increased to improve gas flow, and the raised edges of the protrusions are deformed to facilitate fluid flow. Furthermore, it is an object of the present invention to keep the position of flying sparks constant at the tip edge of the protrusion.

(Means for Solving the Problems) Structure and Operation This invention has a plurality of protrusions on each of the annular intermediate electrode and the outer electrode, which are formed coaxially with the center electrode with a gap therebetween, and are formed in a sawtooth shape. The valleys between adjacent protrusions are formed to have as wide a space as possible while the protrusions maintain their strength as discharge electrodes. When such a wide space is formed, the combustion gas flowing in a spiral in the cylinder always passes through the center electrode portion in all directions, so that no stagnation occurs. Therefore, the center electrode is less likely to melt and wear.

Usually, a secondary high voltage generated by a coil connected to a battery is applied to the center electrode and discharged between the center electrode and the grounded outer electrode. On the other hand, a selected arbitrary protrusion of each of the intermediate electrode and the outer electrode is slightly bent inward from the standard gap at the time of manufacture to form a discharge gap, and sparks occur in this discharge gap. The space between each electrode acts as a capacitor, and therefore the center electrode forms one pole of the capacitor. The discharge between the center electrode and the intermediate electrode continues until the potential of the intermediate electrode reaches the potential of the center electrode (it is instantaneous in terms of time). Then, when the potential of the intermediate electrode increases, a discharge is started between the intermediate electrode and the outer electrode. That is, a delayed time occurs between the negative discharge and the secondary discharge. This delay time is extremely short and is determined by the electrostatic capacity between the center electrode and the intermediate electrode. Due to this secondary discharge, the mixed gas in the cylinder is ignited and combusted, but the unburned gas remaining during the movement of the piston is completely combusted by the sparks of the secondary discharge that is generated with a delay. This has the advantage of effectively utilizing the fuel consisting of the mixed gas and promoting purification of the exhaust gas.

Furthermore, since the discharge occurs only between the sharp tips of the protrusions of each electrode where sparks occur, the ignition point is always at a constant position.
Since the flame propagation conditions do not change, there is no drawback such as engine vibration. Furthermore, since the protrusions are in the shape of a saw blade, the flow of combustion gas is extremely improved.

(Example) Configuration An example of the present invention will be described below with reference to the accompanying drawings. Reference number lO shown in FIGS. 1 and 2 is a spark plug equipped with an electrode portion 12 according to the present invention.

The spark plug 10 includes a center conductor 1 having a high voltage terminal 13 and a center electrode 14 in a shaft hole of a cylindrical insulator 11 made of ceramic.
6 is fixed through the hole. An annular intermediate electrode 16 is fitted into the annular step at the lower end of the cylindrical insulator 11 . Furthermore, insulator 1
A cylindrical conductive metal case 18 having an ergonomic outer electrode 17 at its tip is fitted and locked to the cylindrical case 1 . The metal case 18 has a thread 1 on which the upper part of the outer electrode is threaded onto the cylinder.
A body portion 20 is provided on the upper side of the thread 19, and a screw-in nut portion 21 is formed on the upper side of the body portion 20.

As shown in FIGS. 2 and 3, six discharge protrusions 14a are provided on the tip surface of the center electrode 14 by drilling three grooves at equal angles in the diametrical direction passing through the center. .

The middle and outer annular electrodes are provided with six protrusions 16a and 17a, respectively, whose tips are disposed downwardly facing each other in the radial direction of the six protrusions 14a. Both protrusions 16a and 17a are curved slightly radially inward, with a standard gap G between the tips of the electrodes.
1. Place it in G2. Among the six protrusions 16a and 17a each having this standard gap, any one selected protrusion 16a+ and 17a+ is further bent radially inward to change the gap between the inner electrode tip and the discharge gap G1m. G! , to form. At that time, any one protrusion 17al of the outer electrode
A discharge gap Gta is formed by opposing the protrusion 16a formed in the standard gap of the intermediate electrode. It is preferable that the secondary discharge GIM and the secondary discharge Gem are located at opposing positions in the diametrical direction of the electrode portion 12, so that the protrusions 16a1 and 17a1 are located at opposing positions in the diametrical direction. and select 17a.

This maximizes the interval between negative and secondary sparks, thereby increasing the combustion efficiency of unburned gas.

Operation When a high voltage is applied to the terminal 14 of the spark plug 10 according to the embodiment of the present invention constructed as described above, the discharge gap G1. A secondary discharge occurs, and the mixed gas in the cylinder ignites and burns, causing the piston to move. While the piston is moving, a secondary discharge occurs in the discharge gap 02m after an instantaneous delay time at a position distant from the ignition position. As a result, the unburned gas that was not completely combusted in the secondary discharge is combusted and completely combusted.

As mentioned above, the secondary discharge and the secondary discharge occur between the tips of the predetermined electrode protrusions, and the positions are constant and the intervals are constant.
Furthermore, since the piston moving within the cylinder explodes at a predetermined position with a certain minute delay time difference, irregular vibrations do not occur when the engine operates at low speed. The unburned gases such as Co2, HC, No, etc. remaining after the -flame combustion are completely combusted by the secondary discharge, and the combustion is used effectively and the unburnt gases are not released outside the vehicle.

The intermediate electrode and the outer electrode are formed by cutting out a tube-shaped or annular member from the distal end thereof to form a plurality of mountain-shaped or saw-blade-shaped protrusions, and the valleys between the mountain-shaped protrusions form wide spaces. Therefore, the mixed gas and combustion gas flowing inside the cylinder freely pass through the center electrode 14 part from the space between the protrusions, and the high temperature combustion gas that tends to stay in this part is moved, thereby reducing the temperature. lowers the raised center electrode to prevent melt damage. In particular, the gas in the cylinder is a vortex,
It is preferable that the protrusion group is formed into a sawtooth shape so that this vortex flow can easily flow into the central electric rod portion from the space between the protrusions.

The edge portion of the electrode with the wide trough is formed into a tapered shape by cutting from the inner circumferential surface of the upper end edge to the outer circumferential surface of the lower portion. By forming this tapered part, the gas that flows is not only the gas that flows inward in the radial direction of the electrode, but also the gas that flows diagonally toward the electrode part from the outside of the proximal end of the plug, and the pressure is increased. This moves the high-temperature gas at the center electrode part as it increases, blowing it away.

As the spark plug of this embodiment is used, the protrusions 16a+ and 17a+ that were first used and the protrusions 16a and 17a that were discharged in opposition to both protrusions gradually wear out as the usage time progresses.
Due to this state of wear, the protrusions 16a+ and 17a+ are
After restoring outward to the gap between G1 and G2, the unused opposing protrusions 16a and 17a are moved to G1. , G2. It deforms into the gap and causes the next discharge.

Although the diameters of the annular intermediate electrode and the outer electrode do not need to be particularly limited, the standard gap between the tips of the protrusions in this example is as follows: G is 0.8 mm, G2 is 1. On+m and None,
Glm is 0.7 mark, G2. By setting the value to 0.8, a durable and suitable discharge was obtained. Further, the gap between adjacent protrusions of the center electrode is set to 1.0 mm.

As shown in FIG. 3, the protrusions of the intermediate electrode and outer electrode according to the present invention have a saw blade shape with the tip side inclined clockwise.
The shape is not limited to this, but may be inclined counterclockwise depending on the direction of the vortex flow within the cylinder, or the protrusions of the intermediate electrode and the outer electrode may be inclined in opposite directions. In short, it is preferable that the tips of the protrusions in the middle and outside of the protrusion of the center electrode are aligned along the radial direction.

(Effects) In the spark plug of the present invention having the above-mentioned action, the middle and outer annular electrodes that double surround the center electrode form mountain-shaped or saw-blade-shaped protrusions through a wide fluid circulation space. Since the fuel-air mixture gas and combustion gas flowing in a spiral form constantly and freely pass through the center electrode, there is no accumulation of high-temperature gas, and the protrusion of the center electrode is prevented from melting. Ta. Therefore, the protrusion of the center electrode will only wear out in the same way as the protrusions of the middle and outer electrodes wear out over time due to discharge, and if the other unused protrusions separated by the middle and outer electrodes are transformed into a discharge gap, Correspondingly, sparks are generated from unused projections of the center electrode, and the spark plug can be used for a long period of time.

Furthermore, the tips of the conventional intermediate and outer electrode protrusions were formed in a long arc shape, and the position where sparks were generated was constantly moving; however, the protrusions of the present invention are mountain-shaped or saw-blade shaped.
Since flying sparks occur only from the sharp tip, the internal combustion engine no longer produces vibrations.

[Brief explanation of the drawing]

Fig. 1 is a partially cutaway overall front view of a two-stage discharge type ignition plug according to the present invention, Fig. 2 is an enlarged end view of the electrical excavation part, Fig. 3 is an enlarged bottom view of the electrode part, and Fig. 4 is the electrode part. FIG. IO...Spark plug, 11...Insulator, 12...
Electrode part, 16...center electrode Annular intermediate electrode, 17...
...Outer electrode, 18...Metal case, 16a, 17a
...Standard gap protrusion, G,, G2...Standard gap, 1
6a+. 17a1...Protrusion having a discharge gap, G la+
Gta...discharge gap

Claims (5)

[Claims] (1) A center electrode connected to a power source, an annular intermediate electrode disposed on an insulator, and a grounded annular outer electrode are arranged coaxially with a standard gap between them, and the center electrode A plurality of spark projections are provided at equal intervals in the circumferential direction from the tip surface, and the intermediate and outer electrodes are provided with a plurality of projections each having a sharp tip and a wide trough, and and the protrusions provided on the outer electrodes are arranged so that at least the tip portion thereof faces each protrusion provided on the center electrode along the radial direction, and any one selected protrusion on the center electrode is deformed inward to form a discharge gap, and a protrusion of the outer electrode that faces an arbitrary protrusion disposed in the standard gap of the intermediate electrode is deformed inward to form a discharge gap. No, the second method is characterized in that the protrusion formed in the discharge gap is restored to the standard gap due to deterioration over time, and other unused intermediate and outer electrode protrusions are sequentially transformed into the discharge gap and used. Staged discharge spark plug. (2) The two-stage discharge type spark plug according to claim (1), wherein the protrusions of the intermediate and outer electrodes are formed in a chevron shape. (3) The two-stage discharge type spark plug according to claim (1), wherein the protrusions of the intermediate and outer electrodes are formed in the shape of a saw blade. (4) The saw blade-shaped protrusions of the intermediate and outer electrodes may be inclined in any direction to the left or right of the annular direction, and the protrusions of the intermediate electrode and the outer electrode may be inclined in opposite directions. A two-stage discharge type ignition plug according to claim (3), characterized in that it has a configuration in which: (5) A patent characterized in that the protrusion formed in the discharge gap of the intermediate electrode and the protrusion formed in the discharge gap of the outer electrode are formed at positions opposite to each other in the diametrical direction with respect to the plug axis. A two-stage discharge type ignition plug according to claim (1).