JPS6129975Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention relates to an internal combustion engine ignition system using a spark plug, and more specifically, the present invention relates to an internal combustion engine ignition system using a spark plug, and more specifically, a spark is applied to the spark plug multiple times at different positions during one ignition timing. The present invention relates to an ignition device for an internal combustion engine that generates electric discharge and improves ignitability.

[Conventional technology]

In recent years, the ignition system of automobile engines has been required to recirculate a large amount of exhaust gas for exhaust purification, or to reliably ignite a thin air-fuel mixture.In particular, in automobile engines equipped with a catalytic converter, when a misfire occurs, a large amount of gas is generated. There is a risk that the unburned gas will react in the catalytic converter and burn out the catalyst.
Improving ignitability is important.

[Problem that the invention attempts to solve]

Conventionally, from this point of view, attempts have been made to increase the gap between the electrodes of the spark plug and improve ignition performance through the flame-extinguishing action of the electrodes, but this has the disadvantage of increasing costs as it requires combination with a reinforced power source, and also increases the ignition performance. Attempts have been made to improve ignitability by applying high voltage to the plug multiple times, but the discharge interval is as long as 1000 μs (microseconds, the same applies hereinafter), so the number of spark discharges that occur during one ignition timing is small. ,
Further, since no consideration was given to widely distributing the locations of flying sparks, the effect of producing spark discharge, which can improve the ignitability of the engine, was low except during startup and in extremely low rotational speed ranges.

The purpose of the present invention is to provide an ignition device that can reliably generate spark discharge in the discharge gap between all the outer electrodes and the middle electrode of a multi-gap spark plug during a single ignition timing, and can significantly improve ignition performance. Furthermore, the durability of such an ignition device can be improved.

[Means for solving problems]

The ignition system for an internal combustion engine of the present invention has an ignition timing of 50
It is equipped with a circuit device that applies multiple pulsed high voltages to the spark plug at intervals of ~500 microseconds, and a multi-gap spark plug that has two or more outer electrodes with a tip area of 1 mm ² or less, and has a single ignition timing. The main idea is to cause spark discharges to occur multiple times at different discharge gaps.

[Effect]

The present invention will be explained in detail below with reference to the drawings.

In spark plugs, a single spark is normally generated between the electrodes for each spark plug, and it was thought to be difficult to simultaneously generate multiple spark discharges at different positions between the same electrodes.

Through experiments, the inventors of this invention discovered that when a pulsed high voltage is applied multiple times at a certain interval (100 μs intervals were adopted in this example) between the spark plug electrodes, the next pulsed high voltage is generated at the point where the discharge occurred earlier. It was discovered that spark discharge does not occur when the voltage is applied, but spark discharge occurs at other positions.

In this phenomenon, as shown in FIG. 7, spark discharge first occurs in the space A between the spark plug electrodes where the ion density is highest. In the discharge space A, a plasma state in which positive and negative ions are mixed suddenly occurs, and after the spark discharge ends, the plasma density in the discharge space A rapidly decreases due to consumption, and as shown in the graph of FIG. The density also decreases more rapidly than in spaces B and C where there is no spark discharge. 500 without applying high voltage
After ~1000 μs, the ion density in all spaces A, B, and C decreases to the same level as before the spark discharge. However, when a pulsed high voltage (with an interval of 100 μs) is again applied between the spark plug electrodes when this ion density remains to some extent, spaces B and C with a large amount of remaining ions change to space A with a small amount of remaining ions. State with higher ion density {B, C>
A (in this case, B>C)}. Therefore, the electric field strength in space B becomes stronger than in other spaces C and A, and spark discharge inevitably occurs in space B.

Furthermore, after the spark discharge in space B ends, the plasma density in discharge space B rapidly decreases due to consumption, and as shown in the graph of Figure 9, the ion density also decreases rapidly compared to spaces A and C where there is no spark discharge. do. Eventually, the ion density in all spaces A, B, and C decreases to the same level as before the spark discharge. When a pulsed high voltage (at intervals of 100 μs) is again applied between the spark plug electrodes when this ion density remains to some extent, the space C with a large amount of ions remaining becomes the space A with a small amount of ions remaining and the space A with a small amount of ions remaining. The state becomes a state where the ion density is higher than that of B {C>A>B}. The electric field strength in space C is stronger than in spaces A and B, and spark discharge inevitably occurs in space C. Continuing this experiment,
When a pulsed high voltage was applied multiple times at intervals of 100 μs between the spark plug electrodes, it was confirmed that a large number of spark discharges occurred at various positions as shown in FIG.

The multi-gap spark plug may be either the air gap type shown in Figure 3 or the semi-creeping gap type shown in Figure 4, but the area of the tip of the outer electrode protruding from the metal shell must be 1 mm ² or less,
The following experimental example supports this.

Example As shown in Fig. 3, an air gap type multi-gap spark plug has three outer electrodes, a central electrode diameter of 1.6φ, unipolarity, and a discharge gap of 1.5 mm.
The graph in FIG. 5 shows the ratio of spark discharge to all three outer electrodes when the pulsed high voltage (pulse interval 100 μs) shown in FIG. 2 is applied while changing the outer electrode tip area. From this graph, it can be confirmed that when the outer electrode tip area is 1.0 mm ² or less, spark discharge occurs almost 100% evenly on the entire outer electrode, but when it exceeds 1.0 mm ² , this probability decreases rapidly. .

〔Example〕

Next, one embodiment will be described with reference to the drawings.

A is an internal combustion engine ignition device according to the present invention, 1
2 is a battery, 2 is a DC-DC converter, 3 is a pulsed high voltage generating circuit, 4 is a metal shell, and 5 is a multi-gap spark plug in which an outer electrode 51 protruding from the tip has a tip area of 1 mm ² or less. The multi-gap spark plug 4 may be either an air gap type shown in FIG. 3 or a semi-creeping gap type shown in FIG. 4.

In the above configuration, the output of battery 1 is DC-DC
The converter 2 boosts the voltage to several hundred volts, and the output of the converter 2 is converted to a second voltage by the pulsed high voltage generating circuit 3.
As shown in the figure, a high voltage pulse wave with an interval of 50 to 500 μs is applied to the multi-gap spark plug 4.

In order to improve the ignitability of the spark plug 4, it is desirable to generate as many spark discharges in a wide range of positions as possible, but it is desirable that the pulsed high voltage generation interval of the pulsed high voltage generation circuit 3 is limited to approximately 50 to 500 μs. is 70 to 400 μs. Many spark discharges are difficult to occur at 50 μs or less, and at 500 μs
In this case, the number of spark discharges that occur at one ignition timing decreases, and the rate of contribution to improving ignition performance is low.

Furthermore, experiments have shown that when the center electrode is made unipolar, a large number of spark discharges are generated at different positions in the discharge gap even if pulsed high voltage is applied at shorter intervals than when the center electrode is made polarized. did.

Furthermore, in the ignition device according to the present invention, several times more spark discharge occurs in the spark plug discharge gap than in the conventional ignition device, and the outer electrode tip area is narrow, so the outer electrode tip is easily worn out. As shown in FIG. 2, durability can be improved by fixing a chip electrode 53 made of a noble metal such as platinum, which has excellent heat resistance and is a good electrical conductor, to the tip of the outer electrode by welding or the like.

[Effect of idea]

The present invention has the above configuration, and the ignition timing
It has a circuit device that applies a plurality of pulsed high voltages to the spark plug at intervals of 500 μs, and a multi-gap spark plug that has two or more outer electrodes with a tip area of 1 mm ² or less, so that no spark occurs during a single ignition timing. Discharge can be reliably generated in the discharge gaps between all the outer electrodes and the center electrode of the multi-gap spark plug, the ignition performance can be significantly improved, and the durability can be improved by attaching the tip electrode.

[Brief explanation of the drawing]

Figure 1 is a configuration diagram of the ignition device according to the present invention, Figure 2
The figure is a time chart of the voltage applied to the spark plug, Figures 3 and 4 are front views of the multi-gap spark plug, Figure 5 is a graph showing the area of the outer electrode tip and the proportion of sparks spreading evenly to all the outer electrodes, and Figure 6 The figure is a front view of the tip of a multi-gap spark plug according to another embodiment, FIG. 7 is a side view showing the state of spark discharge of the multi-gap spark plug by the ignition system for an internal combustion engine according to the present invention, and FIG. 8 is a front view of the tip of a multi-gap spark plug according to the present invention. FIG. 9 is a side view showing a spark discharge state of a multi-gap spark plug by an ignition system of an internal combustion engine, and is a time chart of ion density in spaces A, B, and C, which are discharge gaps. In the figure, 1...Battery, 2...DC-DC converter, 3...Pulse high voltage generation circuit, 4...Multi-gap spark plug, 51...Outer electrode, 5
2... Outer electrode tip surface, 53... Chip electrode.

Claims (1)

[Claims for Utility Model Registration] 1. A circuit device that applies a plurality of pulsed high voltages to a spark plug at intervals of 50 to 500 microseconds during ignition timing, and two or more outer electrodes with a tip area of 1 mm ² or less. 1. An ignition device for an internal combustion engine, characterized in that the ignition device is equipped with a multi-gap spark plug, and is configured to cause spark discharge at different discharge gaps multiple times during a single ignition timing. 2. The ignition system for an internal combustion engine according to claim 1, wherein the multi-gap spark plug has a structure in which a tip electrode made of a noble metal alloy is attached to the tip of the outer electrode.