JP2004257248A - Ignition device for internal-combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the following problem: in a multi-position ignition system constituted by placing a plurality of spark plugs in a mixing chamber, when an in-cylinder injection type injector for conducting a stratified combustion is adopted to enhance fuel-economy, a plurality of spark plugs and one injector become necessary in the head part of a combustion chamber, where a sufficient space is hardly obtained. <P>SOLUTION: An insulation member is formed around a nozzle tip of the injector for in-cylinder direct fuel-injection further protrusively into the combustion chamber than the nozzle tip. The plurality of ignition electrodes are placed arcuately on the surface of the insulation member or protrusively therefrom. Further, the plurality of ignition electrodes are constituted electrically in series with intervals of spark gaps. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a spark igniter in which a plurality of ignition gaps for igniting an air-fuel mixture are formed in a combustion chamber of an internal combustion engine. The present invention relates to an ignition device for an internal combustion engine that increases a propagation speed.
[0002]
[Prior art]
For example, according to Patent Literature 1, in a gasoline engine that mainly performs combustion in a homogeneous air-fuel mixture form, a lean airflow (for example, an air-fuel ratio of about 20) is realized by promoting the mixing of fuel and air by strong airflow. We are trying to improve. In recent years, engines equipped with two spark plugs in one cylinder have been put into practical use, and have overcome the problem of a reduction in flame propagation speed that occurs when burning a lean mixture by two-point ignition. Normally, the multi-point ignition system is configured by arranging a plurality of spark plugs in a mixing chamber.However, when an in-cylinder injection type injector that performs stratified combustion for the purpose of further improving fuel efficiency is employed, a combustion chamber head is provided. It is necessary to arrange a plurality of spark plugs and one injector in the part.
[0003]
For example, Japanese Unexamined Patent Application Publication No. 2002-138933 discloses an example in which one injector and a spark plug are arranged in one cylinder. However, it is difficult to arrange a plurality of spark plugs here in terms of space. Understand.
[0004]
[Patent Document 1]
JP-A-2002-138933
[Problems to be solved by the invention]
However, since the combustion chamber head has only a limited area, there has been a problem that sufficient space cannot be provided for arranging a plurality of valves, a plurality of spark plugs, and an injector.
[0006]
[Means for Solving the Problems]
In order to solve the above problem, the ignition device of the present invention forms an insulating member protruding into the combustion chamber from the nozzle tip around the nozzle tip of the injector that directly injects fuel into the cylinder, and The plurality of ignition electrodes are arranged in an arc shape on a surface or in a shape protruding from the surface, and the plurality of ignition electrodes are formed so as to be electrically in series with an ignition gap therebetween.
[0007]
The insulating member is formed of ceramics or the like having excellent insulating properties and heat resistance, is integrated with a plurality of electrodes having two or more shapes, and is integrally formed with the injector while ensuring sealing without loss of combustion pressure. Installed on the engine.
[0008]
The high voltage for generating sparks at the plurality of electrodes is usually supplied from a separate ignition coil, but can be integrated for further miniaturization.
[0009]
As a fuel injection method in the case of the above-described ignition device, there is a method of performing fuel injection by dividing into the first half of the intake stroke and approximately twice the ignition timing. By doing so, the homogeneous lean mixture formed by the first fuel injection is reliably ignited by a plurality of spark ignitions, and the air generated by the movement of the spray by the second fuel injection injected almost simultaneously with the ignition timing. The turbulence effectively promotes flame propagation.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0011]
FIG. 1 is a configuration diagram of an ignition device according to one embodiment of the present invention.
[0012]
A plurality of electrodes 3a, 3b, 3c are arranged on the nozzle circumference at the nozzle tip 4a of the in-cylinder injector 4, and the insulation distance between the electrodes 3a, 3b, 3c and the injector 4 is reduced. The insulating member 2 covers the electrodes 3a, 3b, 3c so as to keep several millimeters. Further, electrodes 3a, 3b and 3c are arranged at positions slightly protruding from the nozzle tip 4a of the injector 4.
[0013]
Since the insulating member 2 is partially exposed in the combustion chamber reaching several hundred degrees Celsius, it is necessary to have excellent heat resistance. The resin has a heat resistance of 200 to 300 [deg.] C. and thus may be melted. Therefore, ceramics such as alumina having excellent heat resistance (500 ° C. or higher) are suitable for the insulating member 2.
[0014]
In this embodiment, after the insulating member 2 and the electrodes 3a, 3b, 3c are integrally formed, they are also integrated with the injector 4. The spring 16 of the ignition coil 6 for generating a high voltage is joined to the electrode 7 for coil connection, and the vicinity of the electrode connection 8 is also insulated by the insulating member 5 for connection, so that the ignition coil 6 is also integrated into a compact ignition. The device 1 can be used. As a result, the layout design and the mountability on the engine side can be improved.
[0015]
Further, the presence of a plurality of electrodes 3a, 3b, 3c means that a plurality of ignition gaps 13 are provided. If the distance between the ignition gaps 13 is the same, the gap discharge voltage becomes the same for each gap. The voltage V to be obtained is the gap discharge voltage Vg × the number of ignition gaps n. Therefore, ignition energy more than twice as much as usual is required for ignition, so that a high energy type ignition coil 6 is required. In such a case, a plug-top type suitable for miniaturization and high energy consumption is suitable. This type of ignition coil 6 has excellent magnetic efficiency because the magnetic circuit is a closed magnetic circuit, and can achieve high energy while minimizing the size of the coil.
[0016]
As the electrode material, a Ni alloy, a platinum alloy, an iridium alloy, or the like, which is excellent in heat resistance and abrasion resistance as in a normal plug electrode material, is used. The gap position is arranged in the spray direction of the injector. By doing so, it is possible to obtain the flame propagation utilizing the turbulence of the air generated by the movement of the spray by the second fuel injection.
[0017]
In order to assemble the igniter 1 of this embodiment into an engine, an insulating member step 10 for positioning in the height direction at the time of assembling and a pressure seal 9 to prevent the combustion pressure in the combustion chamber from leaking are required. In the height direction, the position with respect to the engine side is fixed by a positioning insulating member stepped portion 10, and pressure leakage in the combustion chamber is prevented by a pressure seal portion 9 having a spring action provided outside the insulating member 2.
[0018]
Next, a second embodiment will be described with reference to FIG.
[0019]
In this embodiment, a plurality of electrodes 3a, 3b, 3c are assembled after the insulating member 2 is formed as a single unit. This method is used when the electrodes 3a, 3b, 3c and the insulating member 2 cannot be integrally formed. .
[0020]
Since the sintering temperature of the ceramic of the insulating member 2 is about 1600 ° C., the metal used as the electrodes 3a, 3b and 3c also needs to have a high melting point. Ceramics shrink more during molding than metals. Therefore, when integrally molding with a metal, it is necessary to pay sufficient attention to the above two points, and it is easier to adopt a separate structure in the process.
[0021]
The insulating member 2 has a shape in which a plurality of electrode holes 17 are opened as shown in FIG. 5 for assembling the electrodes 3a, 3b, 3c in a later step. The electrodes 3a, 3b, 3c are assembled in the electrode holes 17, and the electrodes 3a, 3b, 3c are roughly classified into two types. As shown in FIG. 3, one is an electrode 3a and a GND electrode 3b connected to the high voltage side of the ignition coil 6, that is, the first and last electrodes, so that the electrode length is large. The other is the other intermediate electrode 3c. The intermediate electrode 3c is preferably T-shaped as shown in FIG. 6 in order to fix it to the insulating member 2 and to serve as a negative electrode of the previous ignition gap 13 and a positive electrode of the next ignition gap 13. The other high-voltage electrode 3a and GND electrode 3b are also substantially T-shaped although not shown. The shape of the electrode tip 18 is made thinner than the electrode main body and the edge is made an edge in order to supply a stable discharge voltage and reduce the discharge voltage. When assembling the electrodes 3a, 3b, and 3c into the electrode holes 17 provided separately in the insulating member 2, a glass powder serving as both an electrode fixing and sealing is filled around the electrodes. Then, the glass is melted by sintering again, and the glass seal 11 is obtained.
[0022]
Further, by making the insulating member 2 tapered in the engine mounting direction as in the present embodiment, the area protruding into the combustion chamber is small and interference with the valve is suppressed, so that the layout can be improved.
[0023]
Further, in this embodiment, since the positioning with the injector 4 is required, a step 19 is partially provided for the positioning. A metal or rubber seal packing 9 or the like is provided on this step to ensure the sealing property between the injector 4 and the insulating member 2.
[0024]
When the ignition device of the present invention is used, since the spray of the injector is used for assisting the combustion, it is effective to make the number and the position of the electrodes 3c approximately coincide with the spray number and the direction of the fuel injection.
[0025]
【The invention's effect】
With the above configuration, the ignition device can be compactly mounted on the engine as shown in FIG. Thus, the homogeneous lean mixture formed by the first fuel injection can be reliably ignited by a plurality of spark ignitions, and the turbulence of the air caused by the spray movement of the second fuel injection injected almost simultaneously with the ignition timing causes the flame Propagation is promoted and flammability is improved.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of an ignition device for an internal combustion engine showing one embodiment of the present invention.
FIG. 2 is a configuration diagram of an ignition device for an internal combustion engine showing another embodiment of the present invention.
FIG. 3 is an enlarged view of an electrode portion of the ignition device for an internal combustion engine showing one embodiment of the present invention.
FIG. 4 is a configuration diagram when an embodiment of the present invention is mounted on an engine.
FIG. 5 is a structural diagram of an insulating member according to one embodiment of the present invention.
FIG. 6 is a diagram showing an electrode structure according to an embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Ignition device, 2 ... Insulation member, 3a ... High voltage electrode, 3b ... GND electrode, 3c ... Intermediate electrode, 4 ... Injector, 5 ... Connection insulation member, 6 ... Ignition coil, 7 ... Coil connection electrode, 8 ... Electrode connection part, 9 ... Pressure seal part, 10 ... Insulating member step part,
11: Glass seal, 12: Seal packing, 13: Ignition gap, 14: Valve, 15: Combustion chamber head, 16: Spring, 17: Electrode hole, 18: Electrode tip, 19: Injector positioning step.

Claims (9)

A plurality of ignition electrodes are arranged in an arc shape on the surface of an insulating member formed on a part of the combustion chamber wall surface or in a shape protruding from the surface, and the plurality of ignition electrodes are electrically connected in series with an ignition gap therebetween. An ignition device for an internal combustion engine, wherein a nozzle of an injector for directly injecting fuel into a cylinder is arranged at a center position of the plurality of electrodes. 2. The ignition device for an internal combustion engine according to claim 1, wherein the plurality of ignition electrodes protrude into a combustion chamber from a tip of a nozzle of the in-cylinder injector. The ignition device for an internal combustion engine according to claim 1, wherein the plurality of ignition electrodes have a substantially T shape, and two or more types of electrodes are combined to form a plurality of electrodes. . The in-cylinder injector and a plurality of ignition electrodes are insulated by an insulating member, and the insulating member is formed as a single piece and then assembled with a plurality of electrodes. Ignition device for internal combustion engines. 4. The ignition device for an internal combustion engine according to claim 1, wherein the in-cylinder injector and the plurality of ignition electrodes are insulated by an insulating member, and are integrally formed with the injector. The ignition device for an internal combustion engine according to claim 4, wherein the insulating member has a tapered shape toward a tip end portion of the injector. The ignition device for an internal combustion engine according to claim 4, wherein a step is provided in a part of the insulating member in a direction perpendicular to an axial direction of the injector. 4. The ignition device for an internal combustion engine according to claim 1, wherein a ceramic such as alumina is used as an insulating member between the in-cylinder injector and the plurality of ignition electrodes. 6. The ignition device for an internal combustion engine according to claim 5, wherein a glass powder is used for a seal between the ignition electrodes and the insulating member.

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