JPH0148377B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Technical Field> The present invention relates to an ignition device for an internal combustion engine that supplies fuel into a combustion chamber by a fuel injection valve.

<Prior Art> An example of a conventional compression ignition internal combustion engine equipped with an ignition device is shown in FIG. 1 (see Komatsu Giho Vol. 26, No. 4, 1981).

To explain this, a swirl chamber 4 is formed in the upper part of the main combustion chamber 3 formed between the cylinder head 1 and the piston 2;
The nozzle 6 of the fuel injection valve 5 is facing toward the front.

Further, the ignition plug 7 is placed at or near a normal glow plug position on the side of the vortex chamber 4 so that the tip of the ignition plug 7 is located in the spray flow injected into the vortex chamber 4 from the fuel injection valve 5. is inserted and placed.

During the compression stroke of the engine, the fuel is pushed into the vortex chamber 4 to generate a vortex, and the vortex causes the fuel injected from the fuel injection valve 5 to mix well with high-temperature, high-pressure air and burn it. The discharge by the spark plug 7 is performed at the timing when the fuel spray from the fuel injection valve 5 passes the tip of the spark plug 7, and there is only one discharge point.

However, in such a conventional ignition device for a compression ignition internal combustion engine, the tip of the spark plug 7 is far away from the nozzle 6 of the fuel injection valve 5.
In addition, since there is only one discharge location, the following problems arose.

The first problem is that it is difficult to synchronize the passage of the fuel spray and the discharge timing, and the second problem is that due to deterioration and wear of the fuel injector 5, the direction of the spray, the injection timing, etc. are distorted, and the position of the discharge is changed. The third problem is that a considerable amount of fuel is injected by the time the spray reaches the tip of the spark plug 7, increasing the premix combustion ratio and causing rapid combustion. In the past, there was a problem in that diesel engine was more likely to hit when idling at low engine speeds.

<Purpose of the Invention> In view of these conventional problems, the present invention makes it easy to synchronize the passage of spray and the discharge timing by bringing a plurality of fuel ignition electrodes close to the nozzle of the fuel injection valve, and also to For engines, the ignition system shortens the ignition delay period to cause slow combustion, suppressing the occurrence of diesel knock during idling, and also eliminates discrepancies in the position and timing of discharge due to deterioration and wear of the fuel injector. The purpose is to provide equipment.

<Structure of the Invention> For this reason, the present invention provides a structure in which a fuel injection valve is provided near the nozzle of the fuel injection valve, approximately coaxially with the nozzle, and around the spray flow.
A center electrode to which a high voltage is applied, a ground electrode to be grounded, and an intermediate electrode held in an insulated state between the center electrode and the ground electrode, and By forming a discharge space between the electrode and the ground electrode, the fuel immediately after injection is ignited to achieve the above object.

<Example> An example of the present invention will be explained below with reference to FIGS. 2 to 5.
Go through the diagrams. Incidentally, the same elements as those in the conventional example are given the same reference numerals as in FIG. 1, and the explanation thereof will be omitted.

In FIG. 2, a fuel injection valve 5 facing the swirl chamber 4
A discharge electrode portion 8 is disposed near the nozzle 6 of the fuel cell.

As shown in FIG. 3, the discharge electrode section 8 includes a discharge electrode 12 which is a fuel ignition electrode and is also a center electrode to which a high voltage is applied, a discharge electrode 13 which is a fuel ignition electrode and an intermediate electrode, 14 and a side external electrode 15 which is both a fuel ignition electrode and a ground electrode.
are arranged at equal intervals in the circumferential direction.

Now, returning to FIG. 2, the current inflow electrode 9 as a high voltage application electrode is disposed with its terminal in contact with the outer end of the discharge electrode 12. Further, 10 is a high voltage cord.

In FIGS. 2 to 5, the main body 11 is made of a ring-shaped insulator and has a through hole 11a formed in the center thereof for passage of fuel spray. The through hole 11a is coaxial with the nozzle 6 of the fuel injection valve 5, and
A body 11 is arranged within the cylinder head 1 so as to be located nearby.

Discharge electrodes 12, 13, 14 and side external electrodes 1
5, each of which has its base end buried in the main body 11, and its distal end extends along the inner circumferential surface 11b of the main body 11 to form discharge spaces 16 at equal intervals. A contact surface 11 with a terminal of the current inflow electrode 9 is formed at the outer end of the base end of the discharge electrode 12 . The base end portion of the side external electrode 15 is arranged along the outer periphery of the main body 11 and comes into contact with the cylinder head 1 to be grounded.

With the above configuration, the discharge electrodes 12, 13, 14 and the lateral external electrodes 15 as fuel ignition electrodes are provided near the nozzle 6 of the fuel injection valve 5 and evenly divided into four on the same axis and the same circumference. As a result, a discharge space 16 that is a series gap at equal intervals is formed.

Next, a series of operations of this embodiment will be explained.

The high-voltage current generated in the ignition device is passed from the ignition coil via the high-voltage cord 10 and the current inflow electrode 9 to the discharge electrode 12 . Then, discharge occurs sequentially in the discharge space 16 forming a series gap from the discharge electrode 12 as the + pole side to the lateral external electrode 15 as the negative pole side, generating sparks.

Further, the fuel spray injected from the fuel injection valve 5 sequentially evaporates from droplets and forms a combustible air-fuel mixture on the outer periphery of the spray while mixing with compressed air drawn in from the outer periphery of the spray. A plurality of discharge spaces 16 are formed around this combustible mixture, and since the discharge is performed at the time when the fuel spray approaches the discharge spaces 16, combustion starts from almost the tip of the fuel spray, and the discharge occurs sequentially. Combustion expands.

Therefore, it becomes easier to synchronize the passage of the fuel spray and the discharge timing, so the amount of fuel injected during the ignition delay period is reduced, thereby suppressing the occurrence of diesel knock during idling, low speed, etc.

Furthermore, even if the direction of the spray deviates due to deterioration of the fuel injection valve 5, since a plurality of discharge spaces 16 are formed on the outer periphery of the spray via the discharge electrodes 13 and 14, which are intermediate electrodes, all the discharge spaces At step 16, the spark and the fuel spray always come into contact and the fuel is reliably ignited.

Furthermore, since the fuel is not ignited by the heat of compression of air, low-temperature startability is improved, engine weight is reduced by reducing the compression ratio, fuel efficiency is improved, and fuel with a low cetane number can be used.
In this example, methanol and gasoline could be used as fuel.

Although three discharge spaces 16 are formed in this embodiment, a plurality of discharge spaces 16 may be formed.

The shape of the electrode may not be the shape of this embodiment as long as the discharge electrode 16 is formed on the outer periphery of the spray via the discharge electrode.

<Effects of the Invention> As explained above, in the present invention, a center electrode, an intermediate electrode, and a ground electrode are arranged near the nozzle of the fuel injector, approximately coaxial with the nozzle, and around the spray stream. By providing a plurality of discharge spaces, it is easier to synchronize the passage of fuel spray and the timing of discharge, so the amount of fuel injection during the ignition delay period is reduced, and the generation of combustion noise can be suppressed.

Furthermore, since a plurality of discharge portions are always formed, fuel ignition is reliably performed even if the direction of the spray is shifted due to deterioration of the fuel injector.

Furthermore, because of forced ignition, low-temperature startability is improved, engine weight is reduced by reducing the compression ratio, fuel efficiency is improved, and fuel with a low cetane number can be used.

[Brief explanation of drawings]

Fig. 1 is a vertical cross-sectional view showing a conventional ignition device;
The figure is a longitudinal cross-sectional view showing one embodiment of the present invention, FIG. 3 is a schematic plan view of the same embodiment, and FIG. 4 is a -
The sectional view, FIG. 5, is a - sectional view of FIG. 4. 5...Fuel injection valve, 6...Nozzle port, 8...Discharge electrode part, 9...Current inflow electrode (high voltage application electrode),
12...discharge electrode (fuel ignition electrode), 13,1
4... Discharge electrode (fuel ignition electrode), 15... Side external electrode (fuel ignition electrode).

Claims (1)

[Claims] 1. A center electrode near the nozzle of the fuel injection valve that is approximately coaxial with the nozzle and around the spray flow, to which a high voltage is applied, a grounded electrode that is earthed, and between the center electrode and the grounded electrode. An ignition device for an internal combustion engine, comprising an intermediate electrode held in an insulated state, and a discharge space is formed between the center electrode and the intermediate electrode and between the intermediate electrode and a ground electrode.