JP2007035570A - Spark plug and combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a spark plug hardly generating misfires, capable of obtaining air-fuel mixture of appropriate concentration in the vicinity of ignition part of the spark plug and to provide a combustion engine. <P>SOLUTION: The spark plug 1 has plug body 11, a center electrode 12, and a ground electrode 13, and a dome 24 which forms an ignition chamber 240 where these electrodes 12, 13 are located and has an inlet passage 243 for leading in injection fuel 5 into the ignition chamber 240 and a lead-out passage 244 for leading out ignition flame from the ignition chamber 240. The combustion engine 6, which includes the above spark plug 1 and a fuel injector 2, has a plurality of injection ports 22 from which the fuel injector 2 injects the injection fuel 5, and at least one injection port 22 is oriented toward the inlet passage 243 of the spark plug 1. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an ignition plug and a combustion engine such as a spark ignition engine including the ignition plug.

  An ignition plug ignites an air-fuel mixture in a combustion chamber in an internal combustion engine such as an automobile engine, and has a center electrode that constitutes an ignition part and a ground electrode that faces the center electrode with a gap therebetween for ignition. A spark is generated in the gap to ignite the air-fuel mixture.

  Generally, the center electrode and the ground electrode of the spark plug protrude in the axial direction from one end of the plug body. The spark plug has a plug body attached to the cylinder head, and a center electrode and a ground electrode project into the combustion chamber. A fuel injector attached to the cylinder head along with the spark plug injects fuel into the combustion chamber, and the fuel and air in the combustion chamber mix to generate an air-fuel mixture. The air-fuel mixture is ignited by a spark plug and burned.

  One of the combustion methods performed by the spark plug and the fuel injector is a spray guide combustion method. This spray guide combustion method directly injects fuel in the direction of the spark plug, and ignites with the spark plug before the formed spray hits the wall surface of the piston, cylinder liner, etc. It is a technology that lowers air concentration and improves fuel economy and emissions.

As an ignition plug used in the spray guide combustion method, for example, there is one disclosed in Patent Document 1. This spark plug has a hollow frustoconical ground electrode so as to be opposed to the tip of the center electrode at a distance from the tip of the plug body. The ground electrode is fixed to the plug body by a plurality of pillars having one end fixed to the periphery and the other end fixed to the plug body. Moreover, it has a gas hole in the center of a hollow truncated cone shape.
JP-A-6-208880

  In the spark plug of Patent Document 1 and the combustion engine including the spark plug, a spray guide combustion method is employed. The spark plug of Patent Document 1 has a large gap between adjacent struts, and a gap serving as an ignition part for the center electrode and the ground electrode is open to the outside between the open struts. The fuel spray injected from the fuel injector passes between the struts and directly reaches the ignition part of the plug. The concentration of the air-fuel mixture formed by the sprayed fuel near the spark plug varies greatly between cycles, and there is no combustible air-fuel mixture near the plug when ignited, and the fire type is blown off due to the high spray flow rate. Prone to misfire. That is, misfire occurs with a slight change such that the position of the spark plug is shifted by 1 to several mm, or the ignition possible time is only about several ms, and the operation region is limited.

  Further, there is a problem that plug smoldering is likely to occur due to the sprayed fuel adhering directly to the electrode.

  The present invention further improves the conventional spark plug, and provides an ignition plug in which an air-fuel mixture having an appropriate concentration is obtained in the vicinity of the ignition portion of the spark plug, which prevents misfire and prevents the injected fuel from adhering to the spark plug. With the goal.

  It is another object of the present invention to provide a combustion engine in which an air-fuel mixture having a more appropriate concentration can be obtained near the ignition part of the spark plug.

Means for Solving the Problems and Effects of the Invention

  The spark plug of the present invention includes a plug body, a center electrode that protrudes from the plug body and constitutes an ignition part, and a ground electrode that faces the center electrode through a gap, and is used with a fuel injector. An ignition channel fixed to the plug body, forming an ignition chamber in which the center electrode and the ground electrode are located, and introducing an injection fuel injected from the fuel injector into the ignition chamber, and an ignition flame in the ignition chamber And a dome having a lead-out flow path for leading out.

  The same air as that in the combustion chamber exists in the ignition chamber of the dome of the spark plug according to the present invention. The injected fuel injected from the fuel injector is guided to the introduction flow path and flows into the ignition chamber, and an air-fuel mixture is generated in the ignition chamber. Since the injected fuel that reaches the ignition chamber can be controlled by the introduction flow path, an air-fuel mixture having an appropriate concentration suitable for ignition can be easily obtained in the ignition portion of the ignition chamber formed inside the dome. A spark is generated in the gap between the center electrode and the ground electrode to ignite the air-fuel mixture, the flame spreads throughout the ignition chamber, and the ignition chamber is filled with a high-pressure flame. This flame is guided to the lead-out flow path, ejected in a target direction in the combustion chamber, and explosively burns the injected fuel in the combustion chamber.

  According to the ignition plug of the present invention, even if the flow rate of the injected fuel from the fuel injector is high, the dome blocks the injected fuel other than the injected fuel introduced from the introduction flow path, so that the ignition flame is not blown out. The center electrode and the ground electrode that form the ignition part of the spark plug are covered with a dome, and are not directly exposed to the injected fuel injected from the fuel injector, so that the injected fuel does not adhere to the ignition part. Is less likely to occur.

  The introduction channel formed in the dome is a parallel channel with a constant channel cross-section, a reduced channel with a large channel cross-section on the introduction side and a small channel cross-section on the lead-out side, or a small channel cross-section on the introduction side. An enlarged channel having a large channel cross section on the side can be obtained. The introduction flow path first introduces the injected fuel into the other region of the ignition chamber except the ignition unit, and the injected fuel introduced into the other region is then guided to the ignition unit by the dome. Preferably. The injected fuel introduced with the ignition part removed is guided or reflected by the inner surface of the dome and mixed with the air in the ignition chamber to reach the ignition part. For this reason, more reliable ignition becomes possible.

  More specifically, the introduction flow path preferably guides the injected fuel along the inner peripheral surface of the dome and forms a swirling flow in the dome.

  It is preferable that the lead-out flow path leads the ignition flame in a direction different from the fuel ejection direction of the fuel injector. As a result, backfire of the fuel injector toward the injection valve can be suppressed, and the deformation due to incomplete fuel combustion near the injection valve can be suppressed.

  The outlet channel can also be a parallel channel, a reduced channel, or an enlarged channel, like the introduction channel. Since the flame speed can be increased in the reduced flow path, the flame can be ejected long in the ejection axis direction, and the ignition range can be expanded. Since the flame can be ejected at a wide angle in the enlarged flow path, the ignition range can be expanded. These can be properly used depending on the application.

  The dome has a peripheral wall portion protruding from the plug body and a top wall portion that covers the tip of the peripheral wall portion, an introduction flow path is formed in the peripheral wall portion, and a discharge flow path is formed in the top wall portion Is preferable. By adopting this configuration, the injected fuel can be easily introduced into a predetermined position of the ignition chamber of the dome, and the flame in the ignition chamber can be easily ejected to the predetermined position of the combustion chamber.

  Further, it is preferable that the peripheral wall portion has an eccentric cylindrical shape having a wall thickness side and a wall thin side whose inner peripheral surface is eccentric with respect to the outer peripheral surface, and the introduction flow path is provided on the wall thickness side. Accordingly, it is easy to lengthen the introduction flow path, and the introduction direction of the sprayed fuel through the introduction flow path can be controlled more reliably.

  The combustion engine of the present invention includes an engine body having a combustion chamber, a fuel injector held by the engine body and having a tip portion protruding into the combustion chamber, and an ignition plug held by the engine body and having a tip portion protruding into the combustion chamber. The spark plug includes a plug body, a center electrode protruding from the plug body, a ground electrode facing the center electrode through a gap serving as an ignition portion, and being fixed to the plug body. A dome that forms an ignition chamber in which the center electrode and the ground electrode are located, and that has an introduction channel for introducing the injected fuel injected from the fuel injector into the ignition chamber and a lead-out channel for deriving the ignition flame in the ignition chamber The fuel injector has a plurality of jets for injecting the injected fuel, and at least one of the jets is directed to the introduction flow path of the spark plug. The features.

  In the combustion engine of the present invention, since the fuel injector has a jet port directed to the introduction flow path of the ignition plug, a part of the injected fuel is reliably injected into the introduction flow path of the dome of the ignition plug. As a result, the injected fuel is introduced into the ignition chamber of the dome, and an air-fuel mixture having an appropriate concentration is reliably generated. As a result, ignition in the ignition chamber becomes more reliable, and the ignition flame can be ejected in a predetermined direction in the combustion chamber by the outlet flow path, and combustion in the combustion chamber can be made more reliable.

  The lead-out flow path formed in the dome of the spark plug constituting the combustion engine ejects and detonates the flame in the ignition chamber of the dome toward the injected fuel injected by the fuel injector. In addition, the injected fuel injected from the fuel injector outlet toward the introduction flow path is introduced from the direction intersecting the introduction direction of the introduction flow path so that the flame ejected from the introduction flow path does not go in the direction of the fuel injector. It is preferable to enter the flow path.

[Embodiment]
Examples of the ignition plug of the present invention and a combustion engine including the ignition plug will be described below to describe the present invention more specifically.

Example 1
FIG. 1 shows a spark plug having a cross section of a part of the embodiment. The spark plug 1 includes a plug body 11, a center electrode 12, a ground electrode 13 and a dome 14. The plug body 11 includes a nipple portion 111 that constitutes the other end portion of the center electrode 12 and serves as an external terminal, a metal outer cylinder portion 112 that is electrically coupled to the ground electrode 12, and the nipple portion 111 and the outer portion. It consists of a ceramic insulating part 113 interposed between the cylinder part 112.

  The center electrode 12 protrudes in the axial direction from the central portion on one end side of the plug body 11 and has a large-diameter base 121 and a small-diameter shaft 122 that is integrally formed with the base 121 and protrudes further coaxially. Consists of. The ground electrode 13 protrudes from the side of one end side of the plug body 11, and has a J-shaped bent tip so that the tip is close to the tip of the shaft portion 122 of the center electrode 12.

  The dome 14 is made of heat-resistant ceramics, and an eccentric cylindrical peripheral wall portion 141 in which the axial center of the outer peripheral surface and the axial center of the inner peripheral surface are parallel to each other, and a top wall that is integrally formed with the peripheral wall portion 141 and closes the distal end side. Part 142. The other end of the peripheral wall 141 is integrally fixed to the plug body 11. An ignition chamber 140 is defined by one end face of the plug body 11, the inner peripheral surface of the peripheral wall portion 141, and one surface of the top wall portion 142. The ignition chamber 140 has a cylindrical shape whose axis is eccentric with respect to the plug body 11. Since the ignition chamber 140 is eccentric and biased to one side, one wall of the peripheral wall portion 141 is a thin wall portion with a thin wall, and the opposite side is a thick wall portion with a thick wall.

  An introduction flow path 143 formed of a rectangular through hole having a lateral width equal to the diameter of the ignition chamber 140 and a vertical width smaller than the lateral width is formed at a distal end portion of the thick wall portion on the top wall portion 142 side of the peripheral wall portion 141. FIG. 2 shows a spark plug with the introduction channel as the front. A lead-out flow path 144 that is coaxial with the eccentric shaft of the top wall portion 142 and is formed of a thin through hole is formed in the axial center of the ignition chamber.

  The center electrode 12 located in the ignition chamber 140 is biased to the thick wall portion of the ignition chamber 140, and the ground electrode 13 is biased to the thin wall portion of the ignition chamber 140. The introduction channel 143 has a positional relationship that opens further to the tip side than the tops of the center electrode 12 and the ground electrode 13. In addition, the lead-out flow path 144 is in a relationship of being located on an extension line of an intermediate line between the center electrode 12 and the ground electrode 13 in parallel with the axial direction of the center electrode 12 and the ground electrode 13.

  The spark plug 1 of this embodiment introduces the injected fuel from its introduction flow path 143. The injected fuel injected into the introduction channel 143 is introduced into a portion of the dome 14 near the top wall 142 in the ignition chamber 140. This part is a part further ahead of the tips of the center electrode 12 and the ground electrode 13 constituting the ignition part. For this reason, the injected fuel introduced from the introduction flow path 143 does not directly hit the center electrode 12 and the ground electrode 13. In the ignition chamber 140, the injected fuel contacts the inner wall surface of the dome 14 and mixes with the air in the ignition chamber 140 to reach an ignition part. Here, a high voltage is applied between the center electrode 12 and the ground electrode 13 to generate a spark. The air-fuel mixture is ignited by the spark, and the ignition chamber 140 is explosively burned to generate a high-pressure flame. This flame is ejected to the outside through the outlet channel 144 and the inlet channel 143, and the air-fuel mixture around the spark plug 1 is ignited and burned explosively.

  In the spark plug 1 of the present embodiment, even if the flow rate of the injected fuel from the fuel injector is high, the dome 14 blocks off the injected fuel other than the injected fuel introduced from the introduction flow path 143, so that the ignition flame can be blown out. Absent. The center electrode 12 and the ground electrode 13 forming the ignition part of the spark plug 1 are covered with a dome 14, and are not directly exposed to the injected fuel injected from the fuel injector, so that the injected fuel does not adhere to the ignition part. Therefore, plug smolder is less likely to occur. Further, since the high-pressure flame generated in the ignition chamber 140 is ejected at a higher speed than the outlet channel 144 and the inlet channel 143, the mixture of the injected fuel and air around the spark plug 1 can be quickly and explosively burned. Becomes easy.

  FIGS. 3 and 4 show a cross section of the main part having the domes 24 and 25 in which the shapes of the introduction flow path 143 and the discharge flow path 144 of the dome 14 of the first embodiment are changed.

  The dome 24 shown in FIG. 3 has an introduction channel 243 as a reduced channel and an outlet channel 244 as an enlarged channel. The introduction flow path 243 that is a reduced flow path has a smaller cross section on the inlet side and a larger cross section on the outlet side that opens to the ignition chamber 240. Conversely, the outlet channel 244 that is an enlarged channel has a smaller opening on the inlet side that opens to the ignition chamber 240 and a larger opening on the outlet side.

  The dome 24 shown in FIG. 3 includes an eccentric cylindrical peripheral wall portion 241 and a disc-shaped top wall portion 242 formed integrally therewith like the dome of the first embodiment, and an introduction flow path to the peripheral wall portion 241. The outlet flow path 244 is formed on the top wall portion 242. The introduction flow path 243 is a reduced flow path, and has a large cross section on the inlet side and a small cross section on the outlet side that opens to the ignition chamber 240. Similarly, the outlet channel 244 is a reduced channel, and the opening on the inlet side that opens into the ignition chamber 240 is made larger and the opening on the outlet side is made smaller.

  FIG. 3 shows an injection state of the injected fuel 5. In this example, the injected fuel 5 is injected from the introduction channel 243 from the plug body 11 side, and the injected fuel 5 enters the wide inlet of the introduction channel 243 from an oblique direction while spreading in a narrow fan shape. FIG. 3 illustrates this state. The injected fuel 5 is guided by the reduced diameter flow path of the introduction flow path 243 and concentratedly guided to a portion near the top wall portion 242 of the ignition chamber 240, and is mixed with the air in the ignition chamber 240 to become an air-fuel mixture. Meet. In this state, a high voltage is applied between the center electrode 12 and the ground electrode 13 to generate a spark. The air-fuel mixture is ignited by the spark, and the ignition chamber 140 is explosively burned to generate a high-pressure flame. This flame is throttled by passing through the outlet channel 244, which is a reduced channel, to increase the flow velocity and to be ejected outside. As a result, a distant mixture can be ignited. Further, in the reverse direction, the flame spreads through the introduction flow path 243 serving as an expansion flow path and is ejected to the outside, so that a wide range of air-fuel mixture can be ignited. In this way, the air-fuel mixture around the spark plug is ignited and burns explosively.

  The dome 25 shown in FIG. 4 is a lead-out channel 243 that is a reduced flow channel of the dome 24 of FIG. The flow path 244 is a discharge flow path 254 that is a reverse enlarged flow path.

  In the dome 25 of FIG. 4, since the inlet opening of the introduction flow path 253 is small, it is difficult to receive the atomized fuel 5. However, the atomized fuel 5 entering from the inlet expands in the introduction channel 253, and therefore enters the ignition chamber 250 in a state where the flow rate is reduced and widened. The high-pressure flame that is ignited and generated in the ignition chamber 250 is subjected to the reverse action of FIG. 3, and the air-fuel mixture around the spark plug is ignited and explosively burned.

  Although FIG. 3 and FIG. 4 show the introduction channel and the outlet channel having the enlarged channel and the reduced channel, the inlet channel and the outlet channel have other different cross-sectional shapes and directions depending on the purpose. be able to.

(Example 2)
FIG. 5 shows a cross section of the main part of the internal combustion engine of the present invention.

  The internal combustion engine 6 includes a cylinder 61, a piston 62, a cylinder head 63, a spark plug 1, and a fuel injector 2. A piston 62 is fitted into the cylinder 61 so as to be slidable in the vertical direction. A cylinder head 63 covers one end opening of the cylinder 61 and forms a combustion chamber 64 together with the piston 62. An intake port 65 and an exhaust port (not shown) are formed in the cylinder head 63, and an intake valve 66 and an exhaust valve 67 are provided respectively.

  The fuel injector 2 is installed at the center of the cylinder head 63, the spark plug 1 is adjacent to the fuel injector 2, and the extension line on the tip side of the fuel injector 2 and the extension line on the tip side of the spark plug 1 are in the combustion chamber 64. The cylinder head 63 is installed in an oblique direction so as to cross each other.

  The fuel injector 2 has a fuel injector main body 21 and a plurality of injection ports 22 for injecting fuel. The injected fuel 5 is injected into the combustion chamber 64 from each injection port 22. As will be described later, one jet port 22 is directed to the introduction flow path 243 of the spark plug 1.

  As shown in FIGS. 1 and 3, the spark plug 1 covers and ignites the plug body 11, the center electrode 12, the ground electrode 13 that faces the center electrode 12 through a gap, and the center electrode 12 and the ground electrode 13. And a dome 24 that partitions the chamber 240.

  The dome 24 is shown in FIG. 3 described above, and is made of ceramics and has a peripheral wall portion 241 and a disc-shaped top wall portion 242 shown in FIG. 3 protruding from the plug body 11. The peripheral wall portion 241 is a thin thin wall portion opposite to the thick wall portion of one wall, and the cylindrical ignition chamber 240 defined by the inner peripheral surface of the peripheral wall portion 241 is the central axis of the plug body 11. Is formed at a position biased to one side.

  The introduction channel 243 is formed as a reduced channel in the thick wall portion of the peripheral wall portion 241, and the opening of the introduction channel 243 has a narrow rectangular shape extending in the circumferential direction on the outer peripheral surface of the peripheral wall portion 241. The outlet channel 244 is biased toward the thin wall portion of the peripheral wall portion 241 from the center of the top wall portion 242, penetrates in the axial direction, and is formed as a through hole serving as a reduced channel that connects the ignition chamber 41 and the combustion chamber 14. Has been.

  The center electrode 12 is located at a position that is coaxial with the plug body 11, and the ground electrode 13 is located at a position that is biased toward the thin wall portion of the peripheral wall portion 241. Note that the opening position of the introduction flow path 243 that opens into the ignition chamber 240 is located further forward than the tips of the center electrode 12 and the ground electrode 13.

  The internal combustion engine 6 assembled with the spark plug 1 of this embodiment has the above-described configuration.

  Next, the function of the internal combustion engine 6 will be described. The intake valve 66 is opened and new air enters the combustion chamber 64 from the intake port 65. Next, the intake valve 66 is closed, the piston 62 rises, the air in the combustion chamber 64 is compressed, and the injected fuel 5 is injected from the injection port 22 of the fuel injector 2 immediately before the piston 62 reaches the top dead center. Generate qi. Immediately thereafter, the spark plug 1 ignites the air-fuel mixture, the ignition flame caused by the ignition spreads to the combustion chamber 64, and the piston 62 is pushed down. Thereafter, the exhaust valve 67 is opened and the exhaust is discharged from an exhaust port (not shown). Thus, the internal combustion engine 6 repeats the cycle of intake, compression, explosion, and exhaust.

  In this internal combustion engine, only a part of the injected fuel 5 injected from the fuel injector 2 goes to the dome 24 of the ignition lug 1 and enters the introduction flow path 243 formed in the peripheral wall portion 241 of the dome 24, and enters the dome 24. To the ignition chamber 240. Only part of the injected fuel 5 is directed to the introduction flow path 243, and most of the other injected fuel 5 is divided into a wide range of the combustion chamber 64. Since there is little injected fuel 5 toward the introduction flow path 243, misfire that blows off the ignition flame generated in the ignition chamber 240 of the dome 24 is unlikely to occur.

  Since the inflow channel 243 is formed as a reduced channel, it accepts the injected fuel from a wide opening and is throttled as the channel cross-section is reduced to increase the flow velocity, and further from the tips of the center electrode 12 and the ground electrode 13 of the ignition chamber 240. Guided to the previous part. And it mixes with the air in the ignition chamber 240, and produces | generates air-fuel | gaseous mixture. The injected fuel 5 does not directly adhere to the center electrode 12 and the ground electrode 13, and an air-fuel mixture having an appropriate concentration is generated.

  Further, since the injected fuel 5 is confined in the ignition chamber 240, even if the injected fuel 5 enters the ignition chamber 240 at a high speed, the fuel is quickly decelerated in the narrow ignition chamber 240. As a result, the sparks generated in the gap are difficult to blow out and are difficult to misfire.

  Then, the air-fuel mixture in the ignition chamber 240 is ignited, and the ignition chamber 240 becomes high pressure due to the ignition flame, and is led from the ignition chamber 240 to the lead-out flow path 243. Is squeezed out and jetted into the combustion chamber 64 at high speed. As a result, the air-fuel mixture in the combustion chamber 64 is ignited quickly, and the air-fuel mixture in the combustion chamber 64 burns.

  In this embodiment, the high-pressure ignition flame in the ignition chamber 240 is jetted to the combustion chamber 64 through the introduction flow path 243. The opening of the introduction flow path 243 opens toward the jet port 22 of the fuel injector 2, but when the introduction flow path 243 is viewed from the jetting direction, it becomes an enlarged flow path, and the ignition flame passes through the introduction flow path 243. Then, it is ejected into the combustion chamber 64 while expanding. For this reason, the ignition flame that reaches the jet port 22 of the fuel injector 2 is thin and weak, but there is little possibility that the fuel injector 2 is backfired.

  Furthermore, in this embodiment, a part of the jet ports 22 of the fuel injector 2 can be directed to the opening of the introduction flow path 243 of the dome 24 of the spark plug 1. Therefore, a predetermined amount of the injected fuel 5 can be more reliably introduced into the introduction flow path 243, and the amount of fuel adhering to the outer wall surface of the dome 24 can be reduced. For this reason, the fuel adhering to the plug can be reduced and the plug contamination can be reduced as compared with the open valve spray and the porous hollow cone spray in which the injected fuel spreads in a fan shape.

It is a partial cross section figure of the ignition plug of a present Example. It is the figure which made the introduction flow path of the ignition plug of a present Example the front. FIG. 6 is a cross-sectional view of a main part showing a modification of the dome of the spark plug according to the first embodiment. FIG. 6 is a cross-sectional view of a main part showing another modification of the dome of the ignition plug according to the first embodiment. FIG. 3 is a cross-sectional view of a main part of an internal combustion engine according to a second embodiment.

Explanation of symbols

1: Spark plug 11: Plug body 12: Center electrode 13: Ground electrode 4, 24, 25: Domes 140, 240, 250: Ignition chamber 141, 241, 251: Peripheral wall portions 142, 242, 252: Top wall portion 143 243, 253: Introducing flow paths 144, 244, 254: Deriving flow paths 6: Internal combustion engine 61: Cylinder 62: Piston 63: Cylinder head 64: Combustion chamber 2: Fuel injector 22: Injection outlet 5: Injection fuel

Claims (8)

In a spark plug used with a fuel injector, having a plug body and a center electrode constituting an ignition part protruding from the plug body and a ground electrode facing the center electrode via a gap,
An ignition channel fixed to the plug body, forming an ignition chamber in which the center electrode and the ground electrode are located, and introducing an injection fuel injected from the fuel injector into the ignition chamber, and an ignition flame in the ignition chamber A spark plug characterized by having a dome having a lead-out flow path for leading out.   The introduction channel is a parallel channel having a constant channel cross section, a reduced channel having a large channel section on the introduction side and a small channel section on the derivation side, or a channel on the derivation side having a small channel section on the introduction side. The spark plug according to claim 1, wherein the spark plug is an enlarged flow path having a large cross section.   The introduction flow path first introduces the injected fuel into another region of the ignition chamber except for the ignition unit, and the injected fuel introduced into the other region is then guided to the ignition unit by the dome. The spark plug according to claim 1 or 2.   The spark plug according to any one of claims 1 to 3, wherein the introduction flow path guides the injected fuel along an inner peripheral surface of the dome to form a swirl flow in the dome.   The spark plug according to any one of claims 1 to 4, wherein the lead-out passage leads the ignition flame in a direction different from a fuel ejection direction of the fuel injector.   The dome has a peripheral wall portion protruding from the plug body and a top wall portion covering the tip of the peripheral wall portion, the introduction flow path is formed in the peripheral wall portion, and the outlet flow path is formed in the top wall portion. The spark plug according to claim 1, wherein the spark plug is formed.   The peripheral wall portion is an eccentric cylinder having a wall thickness side and a wall thin side whose inner peripheral surface is eccentric with respect to the outer peripheral surface, and the introduction flow path is provided on the wall thickness side. Spark plug. In a combustion engine having an engine body having a combustion chamber, a fuel injector held by the engine body and having a tip portion protruding into the combustion chamber, and an ignition plug held by the engine body and having a tip portion protruding into the combustion chamber,
The spark plug includes a plug body, a center electrode projecting from the plug body and constituting an ignition part, a ground electrode facing the center electrode through a gap serving as an ignition part, and fixed to the plug body and the center electrode and An ignition chamber in which the ground electrode is located is formed, and a dome having an introduction flow path for introducing the injected fuel injected from the fuel injector into the ignition chamber and a discharge flow path for deriving the ignition flame in the ignition chamber is provided. And
The combustion engine, wherein the fuel injector has a plurality of injection ports for injecting the injected fuel, and at least one of the injection ports is directed to the introduction flow path of the ignition plug.

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