JP2007092591A - Ignition device for engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ignition device of a simple structure and excellent mountability, including a plurality of outer electrodes enabling selection of the outer electrode lifting flame. <P>SOLUTION: The ignition device 10 provided with facing a combustion chamber, is provided with a center electrode 11 generating electrical spark, a plurality of outer electrodes 12a, 12b arranged around the center electrode 11, and a grounding change over means 14a, 14b changing over whether the outer electrodes 12a, 12b are grounded or not. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an engine ignition device.

  In an engine spark plug, the electrode is consumed due to spark energy, oxidation, etc. each time it is burned. In view of this, a multipolar electrode type spark plug having excellent durability by providing a plurality of outer electrodes (ground electrodes) has been proposed.

  However, conventional multi-electrode electrode type spark plugs cannot select a specific outer electrode and cause a spark. Therefore, the conventional multipolar electrode type ignition plug cannot designate the ignition position according to the operating condition of the engine.

Therefore, a multipolar electrode that has the same number of center electrodes corresponding to a plurality of outer electrodes, and can control the ignition position according to the operating state of the engine by selecting a specific center electrode and causing a spark discharge. A spark plug has been proposed (see Patent Document 1).
JP 2000-161193 A

  However, the above-described conventional multipolar electrode type spark plug requires an ignition coil and a distributor for each center electrode. Therefore, the structure of this multipolar electrode type spark plug becomes complicated, and there is a problem in mounting property and cost in actually mounting it on the engine.

  The present invention has been made paying attention to such conventional problems, and it is possible to select a sparking outer electrode for a multipolar electrode type spark plug having a plurality of outer electrodes, while having a structure. However, the present invention aims to provide a low-cost ignition device that is simple and excellent in mountability.

  The present invention solves the above problems by the following means. In addition, in order to make an understanding easy, although the code | symbol corresponding to embodiment of this invention is attached | subjected, it is not limited to this.

  The present invention is an ignition device (10) provided facing a combustion chamber, and includes a center electrode (11) for generating an electric spark, and a plurality of outer electrodes (around the center electrode (11)). 12a, 12b) and ground switching means (14a, 14b) for switching whether or not the outer electrodes (12a, 12b) are grounded.

  According to the present invention, it is possible to select the outer electrode where the electric spark generated from the center electrode jumps by grounding only the specific outer electrode, and to select the ignition position of the flame. Therefore, for example, the occurrence of knocking can be suppressed by igniting at a position close to a region where unburned gas tends to accumulate. Furthermore, since the outer electrode that sparks can be dispersed, the durability of the outer electrode can be improved.

  Hereinafter, embodiments of the present invention will be described in more detail with reference to the drawings.

  FIG. 1 is a view showing a state in which a spark plug 10 according to the present invention is mounted on an engine. FIG. 1 (A) is a sectional view, and FIG. 1 (B) is a view of FIG. It is a figure.

  The spark plug 10 is provided in the cylinder head 1 of the engine. The spark plug 10 includes a center electrode 11 and outer electrodes 12a and 12b. In the present embodiment, as shown in FIG. 1 (B), a multi-electrode electrode type spark plug having two outer electrodes 12a and 12b around a center electrode 11 is used.

  A high voltage current is applied to the center electrode 11 from an ignition coil (not shown), and an electric spark is generated from its tip. The center electrode 11 is required to have a low spark discharge voltage, durability that does not increase the discharge voltage even when used for a long time, and thermal conductivity that allows a high temperature during an explosion to escape quickly. Platinum, iridium, or the like is used for the center electrode 11.

The center electrode 11 is insulated by an insulator 16 so that a high-voltage current does not flow to other than the center electrode. The insulator 16 needs to have an insulating property that can withstand a high voltage, and a thermal shock resistance that can withstand an explosion in a combustion chamber and a thermal cycle. The insulator 16 is formed of a ceramic sintered body mainly composed of high-purity alumina (Al ₂ O ₃ ).

  The outer electrodes 12a and 12b are attached to the cylinder head 1 via insulating portions 13a and 13b described later so as to surround the center electrode. The outer electrodes 12 a and 12 b are installed perpendicular to the cylinder head 1. The outer electrodes 12 a and 12 b are formed in a substantially L shape with their tip portions directed toward the center electrode 11. There is a gap between the outer electrodes 12 a and 12 b and the center electrode 11. This gap is the spark discharge gap 20.

  When a high voltage is applied to the center electrode 11, the insulation of the spark discharge gap 20 is broken and a discharge phenomenon occurs, generating an electric spark. This electric spark ignites the compressed mixture and causes an ignition explosion. This occurs when the fuel particles present in the spark discharge gap 20 are activated by the spark discharge. When activated, the fuel particles cause an oxidation reaction and generate heat of reaction to generate flame nuclei. When this flame kernel is generated, the surrounding air-fuel mixture is activated and the combustion spreads.

  However, if the extinguishing action of the electrode is greater than the exothermic action of the flame kernel, the flame kernel disappears and misfires. The electrode extinguishing action is an action in which the electrode absorbs heat and extinguishes the flame. In addition, when the distance between the center electrode 11 and the outer electrodes 12a and 12b is wide, that is, when the spark discharge gap 20 is large, the flame kernel can be increased and the extinguishing action can be reduced. However, if the spark discharge gap 20 is excessively widened, a larger discharge voltage is required. Therefore, if the limit of the ignition coil performance is exceeded, ignition cannot be performed.

  In a general spark plug, all outer electrodes are directly grounded. Therefore, the electric spark generated by the center electrode is usually directed toward the outer electrode that is likely to ignite depending on the degree of consumption of the electrode.

  On the other hand, in this embodiment, the outer electrodes 12a and 12b are provided with insulating portions 13a and 13b between the cylinder head 1 and the outer electrodes 12a and 12b. Therefore, if the outer electrode is insulated as in the present embodiment, it will not be possible to ignite any outer electrode.

  Therefore, in this embodiment, as shown in FIG. 1A, the outer electrodes 12a and 12b are connected to the collector terminals of the transistors 14a and 14b. The emitter terminals of the transistors 14a and 14b are grounded. Furthermore, an electronic control unit (hereinafter referred to as “ECU”) 30 (not shown) is connected to the base terminals of the transistors 14a and 14b. By sending a signal to the base terminals of the transistors 14a and 14b, the ECU 30 can energize the emitter and the collector and ground the outer electrodes 12a and 12b. In this way, the ECU 30 can perform control so that any outer electrode 12a, 12b jumps.

  FIG. 2 is a view showing the arrangement of the spark plug 10. The upper side of the figure is the intake side, and the lower side is the exhaust side. The cylinder head 1 includes two intake ports 2a and 2b and two exhaust ports 3a and 3b. A spark plug 10 is disposed between the intake ports 2a and 2b and the exhaust ports 3a and 3b.

  As described above, the ECU 30 can select which one of the outer electrodes 12a and 12b is ignited by switching the energization of the transistors 14a and 14b. Thus, in the present embodiment, the air-fuel mixture can be ignited by selecting the intake side or the exhaust side according to the operating state of the engine or the like.

  The propagation speed of the flame is slow in the low temperature region. In such a region, before the flame arrives, the unburned air-fuel mixture is compressed in front of the flame, so that self-ignition is likely to occur, and knocking is likely to occur. Since the region close to the intake port 21 has a low temperature and a distance from the spark plug, the unburned mixture tends to stay, and knocking is likely to occur.

  Accordingly, by causing the outer electrode 12a on the intake side to ignite and ignite the air-fuel mixture, it is possible to quickly propagate the flame toward the low temperature region and prevent the occurrence of knocking.

  FIG. 3 is a graph showing the outer electrode of the spark plug 10 that ignites according to the operating state of the engine according to the present invention, where the vertical axis indicates the engine torque and the horizontal axis indicates the engine speed.

  In the state of the region R1, which is a high rotation / high load region, only the transistor 14a is energized. By doing so, the outer terminal 12b on the exhaust side remains insulated, and an electric spark can be caused to fly only to the outer terminal 12a on the intake side. Therefore, the remaining unburned gas can be preferentially burned from the intake side, and the occurrence of knocking can be suppressed.

  On the other hand, in a case other than the state of the region R1 (region R2), both transistors 14a and 14b are energized. In this way, it is not possible to select which outer electrode is ignited as in the case of the conventional spark plug, but it is possible to obtain the effect of extending the life of the plug by dispersing the ignited outer electrode.

  Therefore, it can be realized by a simple control in which both the transistors 14a and 14b are energized during normal operation, and the energization of the transistor 14b is cut off when the engine is operating at a high speed and high load. Alternatively, the outer electrode 12a may be always grounded without going through a transistor, and the energization of the transistor 14b may be switched only for the other outer electrode 12b.

  The effect of this embodiment will be described.

  According to the present embodiment, the outer electrodes can be insulated and disposed, and each electrode can be connected to the transistor, whereby any outer electrode can be ignited. Thus, the air-fuel mixture can be ignited by selecting the intake direction and the exhaust direction according to the operating state of the engine. Therefore, it is possible to promote the growth of the flame in the region where knocking is likely to occur by selecting the outer electrode to be ignited, so that the occurrence of knocking can be effectively prevented.

  In addition, according to the present embodiment, in a state where it is not necessary to ignite a specific outer electrode, the transistors 14a and 14b are energized alternately or both, so that only the specific outer electrode is ignited to cause a biased electrode. Can be prevented from being consumed.

  Furthermore, according to the present embodiment, since the above-described effect can be obtained only by providing a transistor for each electrode, an increase in cost can be suppressed to a minimum.

  The present invention is not limited to the embodiment described above, and various modifications and changes can be made within the scope of the technical idea, and it is obvious that these are equivalent to the present invention.

  For example, the number of outer electrodes need not be limited to two, and the same effect can be obtained even if the number is three or four or more. By increasing the number of outer electrodes, the durability of the spark plug can be further improved. Furthermore, since the number of options for the flame growth direction can be increased, more detailed control can be performed according to the operating state of the engine.

  Further, when stratified combustion is performed by adopting the present invention in a direct injection type internal combustion engine, ignition can be performed at a position close to a region where the concentration of the air-fuel mixture is high.

  The shapes of the firing portions of the center electrode and the outer electrode are not limited to the shapes shown in the present embodiment. For example, by making the shape of the ignition part into a creeping shape, it can be made strong against smoldering contamination and the self-cleaning function can be further strengthened.

  When a multi-point ignition system with a plurality of ignition plugs in the combustion chamber is adopted, an outer electrode is selected and ignited for each ignition plug so that the combustion flame grows in an area where unburned mixture tends to remain. be able to. By doing so, the occurrence of knocking can be suppressed more effectively.

It is a figure which shows the ignition device of the internal combustion engine by this invention. It is a figure which shows the position which provides the ignition device of the internal combustion engine by this invention. 4 is a graph showing a region for selecting an outer electrode to be ignited according to an operating state by an ignition device for an internal combustion engine according to the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Cylinder head 11 Center electrode 12a, 12b Outer electrode 13a, 13b Insulation part (grounding switching means)
14a, 14b Transistor (ground switching means)
16 Isogo 20 Spark discharge gap

Claims (5)

An ignition device provided facing the combustion chamber,
A central electrode that generates electrical sparks;
A plurality of outer electrodes disposed around the central electrode;
A ground switching means for switching whether to ground the outer electrode;
An engine ignition device comprising: The ground switching means connects the outer electrode and the transistor, and switches the grounding of the outer electrode by switching energization of the transistor.
The engine ignition device according to claim 1. The ground switching means is provided in all outer electrodes,
The engine ignition device according to claim 1 or 2, wherein the engine ignition device according to claim 1 or 2 is provided. The ground switching means selects and switches the ground of the outer electrode so as to evenly ignite each outer electrode,
The engine ignition device according to claim 3. The ground switching means switches so that the outer electrode arranged on the intake side is grounded when the engine is operating at a high rotation and high load.
The engine ignition device according to any one of claims 1 to 4, wherein the engine ignition device is provided.

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