JP4685608B2 - Plasma jet ignition plug - Google Patents

Description

  The present invention relates to a plasma jet ignition plug for an internal combustion engine that forms plasma and ignites an air-fuel mixture.

  Conventionally, spark plugs for igniting an air-fuel mixture by spark discharge are used for ignition plugs of internal combustion engines such as automobile engines. In recent years, there has been a demand for higher engine output and lower fuel consumption, and the ignition plug has high ignitability that allows rapid ignition of combustion, and can reliably ignite a lean air / fuel ratio (A / F). As such, a plasma jet ignition plug is known.

  Such a plasma jet ignition plug has a structure in which a spark discharge gap between a center electrode and a ground electrode is surrounded by an insulating material such as ceramics to form a small volume discharge space called a cavity. Yes. Then, a high voltage is applied between the center electrode and the ground electrode to cause a spark discharge, and the current can flow at a relatively low voltage due to the dielectric breakdown that occurs at this time. In this way, the discharge state is changed, and thereby plasma formed in the cavity is ejected from the opening (ejection hole) to ignite the air-fuel mixture (see, for example, Patent Document 1).

For example, as one of the geometric shapes of plasma, there is a form that blows out in the form of a fire column from an opening (hereinafter, such a form of plasma is referred to as “frame shape”). Since this flame-shaped plasma extends in the ejection direction, it has a feature that the contact area with the air-fuel mixture is large and the ignitability is high. In order to further improve the ignitability of the plasma jet ignition plug that forms such a frame-shaped plasma, it is preferable to increase the amount of energy supplied to the spark discharge gap to form a larger frame-shaped plasma. This makes it possible to ignite at a position farther away from the wall in the combustion chamber where the flame extinguishing action is exerted, so that the spread of combustion is accelerated and the ignitability is improved.
Japanese Patent Laid-Open No. 57-15377

  However, if the amount of energy supplied to the spark discharge gap is increased, the energy consumption of the battery that is the energy source will be accelerated, and more energy will be required to charge the battery. There was a risk that the efficiency would rather decrease. In addition, the higher the plasma energy, the higher the temperature in the cavity, and the center electrode and the ground electrode may be consumed more quickly and the durability may be reduced.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a plasma jet ignition plug that can improve ignitability while suppressing energy consumption.

In order to achieve the above object, a plasma jet ignition plug according to a first aspect of the present invention has a center electrode and an axial hole extending in the axial direction, and the central electrode is accommodated in the axial hole and the central electrode. An insulator for holding the insulator, a metal shell that surrounds and holds the periphery of the insulator in the radial direction, a ground electrode that is electrically connected to the metal shell and forms a spark discharge gap with the center electrode, At the tip of the insulator, a spark discharge path in the spark discharge gap passes through the first opening, and a recess is formed by the first opening, and plasma formed inside the spark discharge is generated inside the insulator. A spark discharge path in the spark discharge gap passes through a second opening different from the first opening at the first cavity ejected in a frame shape extending in the axial direction and the tip of the insulator. , A recess formed by the second opening, spark formed in the interior during the fire flower discharge and a second cavity to be ejected.

  In addition to the configuration of the invention according to claim 1, the plasma jet ignition plug of the invention according to claim 2 has an ejection direction of a fire type formed in the second cavity and ejected from the second opening, It has directivity with respect to the ejection direction of the plasma ejected in a frame shape from the first opening of the first cavity.

  According to a third aspect of the present invention, there is provided the plasma jet ignition plug according to the first or second aspect, wherein the first opening of the first cavity is formed on the tip surface of the insulator. An opening formed by a hole, wherein the first cavity has a concave shape having an inner peripheral surface of the shaft hole continuous from the first opening and a tip surface of the center electrode as its boundary. The second opening of the second cavity is formed as an opening of the second cavity formed around the radial direction of the first cavity.

  According to a fourth aspect of the present invention, in addition to the configuration of the third aspect of the invention, the second cavity is formed as an annular recess surrounding the first cavity. Features.

  According to a fifth aspect of the present invention, in addition to the configuration of the fourth aspect of the invention, the plasma jet ignition plug has a through hole formed in the center and covers and protects the ground electrode from the front end side of the metal shell. An insulating protective member is provided, and the inner diameter of the through hole of the protective member is larger than the inner diameter of the first opening.

  In the plasma jet ignition plug according to the first aspect of the present invention, since the plasma ejected from the first cavity is in a frame shape, the contact area with the air-fuel mixture can be increased, and the ignitability can be improved. In addition to this, it is possible to increase the chances of ignition of the air-fuel mixture by ejecting fire species from the second cavity, so that the ignition can be done without increasing the energy supplied to the plasma and forming a larger frame-shaped plasma than before. The property can be further improved.

  In the plasma jet ignition plug of the invention according to claim 2, since the fire type ejected from the second cavity has directivity to the plasma ejected in a frame shape from the first cavity, the fire type of the second cavity Can collide with the plasma in the first cavity. Then, the combustion gas composed of the plasma in the first cavity and the mixture ignited by the plasma is pushed out in the direction of jetting the fire type, and reaches a position farther away from the wall surface of the combustion chamber and the plasma jet ignition plug body that exerts the flame extinguishing action. be able to. Thereby, the air-fuel mixture that spreads is difficult to extinguish, and the ignitability can be improved. In addition, ignition can be performed at a position closer to the center of the combustion chamber, and when the ignited air-fuel mixture burns and spreads, there is no obstacle or flame extinguishing action in the surroundings, so combustion is not hindered, and the air-fuel mixture Increases the speed at which it spreads throughout the combustion chamber, and higher ignitability can be obtained. Furthermore, since the plasma ejected from the first cavity has a frame shape, the contact area with the air-fuel mixture is large, and the ignition limit can be increased.

  In the plasma jet ignition plug according to the third aspect of the present invention, the first cavity is formed using the shaft hole of the insulator, so that the structure of the insulator and the discharge path in the spark discharge gap are simplified. be able to. In addition, as a fire type ejected from the second cavity, combustion gas whose pressure has been increased by expansion in the second cavity may be ejected, or plasma generated by high energy may be ejected. Or both may be ejected. By ejecting this fire type from the second opening, it becomes possible for the fire type to ignite the air-fuel mixture at a position away from the wall surface of the combustion chamber and the plasma jet ignition plug that exert a flame extinguishing action. If such a fire type is ejected in combination with the flame-shaped plasma from the first cavity, the ignition limit can be increased by the flame-shaped plasma having a large contact area with the air-fuel mixture, and the plasma or plasma The ignited combustion gas can be pushed toward a position closer to the center of the combustion chamber. When the air-fuel mixture ignited at a position closer to the center of the combustion chamber burns and spreads, there is no obstacle or extinguishing action around it, so combustion is not hindered, and the speed at which the air-fuel mixture burns and spreads throughout the combustion chamber Can be accelerated and higher ignitability can be obtained.

  In the plasma jet ignition plug of the invention according to claim 4, by forming the second cavity as an annular recess surrounding the first cavity, the configuration of the second cavity can be simplified, and the plasma jet ignition It is possible to reduce the trouble in the manufacturing process of the plug. Moreover, even if the insulator formed in the cylindrical body centering on the axis has such a structure of the first cavity and the second cavity, it can be easily manufactured.

  In the plasma jet ignition plug of the invention according to claim 5, by reducing the exposure of the ground electrode by the protective member, the chance that the combustion gas or the air-fuel mixture directly contacts the ground electrode in the combustion chamber can be reduced. Thereby, the influence of the thermal cycle can be reduced, and the ground electrode can be protected from wear. Moreover, adjustment of the injection direction of the fire type injected from a 2nd cavity can be performed by adjusting the magnitude | size of the through-hole of a protection member. In other words, the fire type ejected from the second cavity has directivity toward the plasma ejected from the first cavity, and the configuration for extruding the plasma from the first cavity and the combustion gas ignited by the plasma is easily achieved. Obtainable.

  If the first opening is arranged in front of the second opening in the direction of the axis O, the first cavity is ejected from the second cavity with a passage between the peripheral wall of the first opening and the through hole of the protective member. If the fire type to be guided is guided, directivity can be given to the fire type ejection direction with a simple configuration.

  Hereinafter, an embodiment of a plasma jet ignition plug embodying the present invention will be described with reference to the drawings. First, the structure of a plasma jet ignition plug 100 will be described as an example of the plasma jet ignition plug according to the present invention with reference to FIGS. FIG. 1 is a partial cross-sectional view of a plasma jet ignition plug 100. FIG. 2 is an enlarged cross-sectional view of the tip portion of the plasma jet ignition plug 100. In FIG. 1, the axis O direction of the plasma jet ignition plug 100 is defined as the vertical direction in the drawing, and the lower side is described as the front end side or front side of the plasma jet ignition plug 100, and the upper side is described as the rear end side or rear side.

  As shown in FIG. 1, the plasma jet ignition plug 100 generally includes an insulator 10, a metal shell 50 that holds the insulator 10, a center electrode 20 that is held in the insulator 10 in the direction of the axis O, A ground electrode 30 provided at the front end portion 59 of the metal shell 50, a protection member 35 provided on the front end side of the ground electrode 30, and a terminal metal fixture 40 provided at the rear end portion of the insulator 10. Has been.

  The insulator 10 is a cylindrical insulating member that is formed by firing alumina or the like and has an axial hole 90 in the direction of the axis O as is well known. A flange portion 19 having the largest outer diameter is formed substantially at the center in the direction of the axis O, and a rear end side body portion 18 is formed on the rear end side. Further, a front end side body portion 17 having an outer diameter smaller than that of the rear end side body portion 18 on the front end side from the flange portion 19, and a further outer diameter than the front end side body portion 17 on the front end side of the front end side body portion 17. A small leg length 13 is formed. Between the leg long part 13 and the front end side body part 17, it is formed in a step shape.

  As shown in FIG. 2, the distal end portion 11 of the insulator 10 is formed with a distal end central portion 12 and a distal end peripheral portion 15 at the distal end so as to form a double ring centering on the axis O. The inner circumference of the long leg portion 13 is continuous with the shaft hole 90 and is formed as an electrode housing hole 91 having a smaller diameter than the shaft hole 90. Furthermore, the inner periphery of the tip center portion 12 is formed as a tip small-diameter hole 93 having a smaller diameter than the electrode housing hole 91. And the center electrode 20 is hold | maintained in the electrode accommodation hole 91, and the front end surface 26 of the front-end | tip part 21 (It mentions later, More specifically, the front end surface 26 of the electrode tip 25 integrated with the center electrode 20). Are in contact with the stepped portion 92 between the electrode housing hole 91 and the tip small-diameter hole 93 having different diameters. As a result, a bottomed cylindrical cavity 60 is formed in the distal end central portion 12 by the distal end surface 26 of the center electrode 20 and the distal end small diameter hole 93. The cavity 60 is a small space for forming plasma to be ejected from its own opening 61, and the opening 61 is in a position protruding forward in the direction of the axis O from the tip peripheral edge 15. The cavity 60 is configured such that the depth (the length in the direction of the axis O) is longer than the inner diameter thereof.

  Further, an annular cavity 70 centering on the axis O is formed in a groove shape at the distal end portion 11 of the insulator 10 between the distal end central portion 12 and the distal end peripheral portion 15. Further, an annular ground electrode 30 to be described later is in contact with the distal end surface 16 of the distal end peripheral portion 15 so as to cover a part of the cavity 70.

  Next, the center electrode 20 is a cylindrical electrode rod formed of Ni-based alloy such as Inconel (trade name) 600 or 601 and has a metal core 23 made of copper or the like having excellent thermal conductivity. ing. For example, a noble metal such as Pt, Ir, Rh, or an alloy thereof, W, or the like, and a disk-like electrode tip 25 having excellent spark wear resistance are welded to the tip portion 21 so as to be integrated with the center electrode 20. Yes. As described above, the center electrode 20 is formed in the electrode receiving hole 91 in a state where the outer peripheral edge of the tip end surface 26 of the electrode tip 25 is brought into contact with the stepped portion 92 of the shaft hole 90 and a part thereof is exposed in the cavity 60. Is held in. The rear end side of the center electrode 20 is enlarged in a bowl shape, and this bowl-shaped portion is positioned in contact with the stepped portion that is the starting point of the electrode housing hole 91 in the shaft hole 90.

  Further, as shown in FIG. 1, the center electrode 20 is electrically connected to the terminal fitting 40 on the rear end side via the conductive seal body 4 made of a mixture of metal and glass provided in the shaft hole 90. It is connected to the. With this seal body 4, the center electrode 20 and the terminal fitting 40 are fixed and conducted in the shaft hole 90. A high voltage cable (not shown) is connected to the terminal fitting 40 via a plug cap (not shown) so that a high voltage is applied from an ignition device not shown.

  Next, the ground electrode 30 shown in FIG. 2 is composed of a chip made of a ring metal, a noble metal, or an alloy thereof having high spark resistance, and W, Pt, Ir, Rh, etc. are used as an example. The ground electrode 30 is formed in a circular plate shape having an outer diameter substantially the same as the inner diameter of the metal shell 50, and has a through-hole having an inner diameter larger than the outer diameter of the front end central portion 12 of the insulator 10 at the center. 31 is provided with a hole. The ground electrode 30 is positioned in the through hole 31 so that the center 12 of the tip is positioned in the cylindrical hole 58 of the metal shell 50 with the thickness direction being the direction of the axis O and in contact with the tip surface 16 of the insulator 10. It is arranged. Further, the outer peripheral surface of the ground electrode 30 is engaged in close contact with the inner peripheral surface of the cylindrical hole 58 of the metal shell 50, and the metal shell 50 and the ground electrode 30 are electrically connected.

  Further, a protective member 35 having a circular plate shape with a through-hole 36 provided in the center is provided at the front end side in the axis O direction from the ground electrode 30 in the same manner as the ground electrode 30. The through hole 36 of the protection member 35 has an inner diameter b larger than the inner diameter a of the opening 61 of the cavity 60. Further, the through hole 36 has a diameter enlarged on the ground electrode 30 side and is continuous with the through hole 31 of the ground electrode 30. The protective member 35 covers and protects the front surface of the ground electrode 30 in the direction of the axis O.

  The protection member 35 covers the open portion of the cavity 70 toward the front side in the direction of the axis O, and the inside of the cavity 70 is formed by the outer periphery of the tip center portion 12 of the insulator 10 and the through hole 36 of the protection member 35. An opening 71 having a narrow gap is formed that leads to the outside of the plasma jet ignition plug 100.

  The cavity 70 of the insulator 10 is communicated to the outside through the opening 71, the through hole 31 and the through hole 36, and the cavity 60 is communicated to the outside through the opening 61, the through hole 31 and the through hole 36. At this time, the opening position of the opening 71 formed by the inner peripheral surface of the through hole 31 of the ground electrode 30 and the outer surface of the front end central portion 12 of the insulator 10 with reference to the substantially central position in the cavity 70. Is at a position closer to the inner circumference on the tip side in the direction of the axis O. Further, the through hole 36 of the protection member 35 is formed with a smaller diameter than the through hole 31 of the ground electrode 30. For this reason, a direction R (indicated by an arrow in FIG. 2) from the substantially central position in the cavity 70 to the outside of the plasma jet ignition plug 100 through the opening 71 and through the through hole 36 of the protection member 35. , Having directivity that approaches the axis O toward the front in the direction of the axis O.

  More specifically, the term “having directivity” refers to the flame-shaped plasma ejected from the cavity 60 such that the ejection direction of the fire species ejected from the cavity 70 in the cross section of the plasma jet ignition plug 100 including the axis O is the same. It means having a directional component approaching and a directional component directed in the direction of the plasma ejection. That is, the fire type ejected from the cavity 70 has a direction to collide with the plasma while proceeding in the ejection direction of the frame-shaped plasma ejected from the cavity 60. For this reason, the case where the ejection direction of the fire type ejected from the cavity 70 is only parallel to the axis O direction or only the direction orthogonal to the axis O direction is not included.

  Next, a metal shell 50 shown in FIG. 1 is a cylindrical metal fitting for fixing the plasma jet ignition plug 100 to an engine head of an internal combustion engine (not shown). The metal shell 50 surrounds the insulator 10 in the cylinder hole 58. Hold on. The metal shell 50 is formed of an iron-based material, and a tool engaging portion 51 to which a plasma jet ignition plug wrench (not shown) is fitted, and a screw portion 52 to be screwed to an engine head provided on the upper portion of the internal combustion engine (not shown). And.

  As shown in FIG. 2, the distal end portion 59 on the distal end side with respect to the screw portion 52 is configured as a locking portion 49, with the inner peripheral side of the distal end surface 57 projecting inward toward the inside. The protective member 35 inserted into the cylindrical hole 58 from the rear end side of the metal shell 50 is locked to the locking portion 49 in a state where the thickness direction is aligned with the axis O direction. The ground electrode 30 is disposed so as to be linked to the layer 35. When the insulator 10 is inserted into the cylindrical hole 58 from the rear end side of the metal shell 50 in this state, the tip center portion 12 is accommodated in the through hole 31 and the tip surface 16 contacts the ground electrode 30. Is done.

  In addition, annular ring members 6 and 7 are interposed between the metal shell 50 from the tool engaging portion 51 to the caulking portion 53 and the rear end side body portion 18 of the insulator 10. Talc (talc) 9 powder is filled between the ring members 6 and 7. A caulking portion 53 is provided on the rear end side of the tool engaging portion 51. By caulking the caulking portion 53, the insulator 10 is connected to the metal shell 50 via the ring members 6, 7 and the talc 9. It is pressed toward the tip side. As a result, the stepped portion between the long leg portion 13 and the front end side body portion 17 is supported via the annular packing 80 on the locking portion 56 protruding from the inner peripheral surface of the metal shell 50, The metal shell 50 and the insulator 10 are integrated. Furthermore, the airtightness between the metal shell 50 and the insulator 10 is maintained by the packing 80, and the outflow of combustion gas is prevented. Further, a flange 54 is formed between the tool engaging portion 51 and the screw portion 52, and the gasket 5 is inserted into the vicinity of the rear end side of the screw portion 52, that is, the seat surface 55 of the flange 54. ing.

  By the way, in the plasma jet ignition plug 100 of the present embodiment, the spark discharge gap formed between the ground electrode 30 and the center electrode 20 has an inner peripheral surface of the through hole 31 of the ground electrode 30 and the insulator 10. An air discharge gap in which a discharge occurs due to dielectric breakdown in the air layer at the opening 71, and an origin of the air discharge gap on the side of the insulator 10; That is, along the surface of the insulator 10 in the part from the position where the spark discharge is performed between the outer surface of the tip center portion 12 and the ground electrode 30 to the center electrode 20 through the opening 61. And a creeping discharge gap where discharge is performed.

  Further, as described above, the plasma jet ignition plug 100 according to the present embodiment has the two types of cavities 60 and 70, and the form of the sparks ejected from the cavity 70 in association with the spark discharge in the spark discharge gap is as follows. The shape of the plasma formed and ejected in the cavity 60 is different. As shown in FIG. 2, the cavity 60 is configured such that its depth (length in the direction of the axis O) is longer than its inner diameter. The plasma generated in the bottomed cylindrical cavity 60 is induced in the shape of the cavity 60 while expanding in the cavity 60, and becomes a fire column shape (frame shape) extending in the axis O direction from the opening 61. Erupted. On the other hand, the cavity 70 has a large internal space and a small opening 71 in the cross section of the plasma jet ignition plug 100 including the axis O. In the cavity 70 having such a shape, since the opening 71 is small, the ignited air-fuel mixture is increased in internal pressure due to expansion in the cavity 70 and is ejected vigorously from the opening 71 as a fire type. In some cases, transition to a plasma state may occur depending on the energy of the fire type.

  Next, with reference to FIG. 3, the operation when the air-fuel mixture is ignited by the plasma jet ignition plug 100 will be described. FIG. 3 is a cross-sectional view schematically showing an ignition process in the plasma jet ignition plug 100.

  When the air-fuel mixture is ignited by the plasma jet ignition plug 100 of the present embodiment as the internal combustion engine is operated, a spark is generated by an ignition device (not shown) based on ignition timing information received from an ECU (not shown). A high voltage is applied to the discharge gap, and spark discharge occurs due to dielectric breakdown. Further, high energy such as electrostatic energy stored in a capacitor in advance is supplied to the spark discharge gap in a state where the insulation resistance is reduced due to dielectric breakdown.

  Then, plasma is formed in the cavity 60, and as shown in the first process of FIG. 3, the internal pressure reaches a critical point before the cavity 70 because the volume is small and the opening 61 is large. As described above, it is shaped like a frame and is ejected toward the front end side in the direction of the axis O (the form of the ejected plasma is schematically shown as plasma S in the figure). Then, the air-fuel mixture around the plasma is ignited (a state in which the air-fuel mixture is ignited is schematically shown as a combustion gas T in the figure).

  On the other hand, since the cavity 70 has a larger volume than the cavity 60 and the opening 71 is small, the internal pressure reaches a critical level at a slightly delayed timing, and a fire type is ejected from the opening 71. At this time, as described above, since there is a directivity that approaches the axis O in the direction from the substantially central position in the cavity 70 to the outside, the fire type ejected from the cavity 70 is the first in FIG. As shown in the second process, the laser beam travels from the periphery of the axis O toward the axis O (indicated by an arrow P in the figure).

  Then, the plasma ejected from the cavity 60 collides with the fire type ejected from the cavity 70. At this time, the plasma (plasma S) from the cavity 60 and a part of the combustion gas (combustion gas T) ignited by the plasma are pushed out in the direction in which the fire type is ejected from the cavity 70 (of the pushed combustion gas). The portion is schematically shown as a bulging portion U in the drawing).

  Further, as shown in the third process of FIG. 3, when the portion of the extruded combustion gas (the bulging portion U) grows, a position closer to the center in the combustion chamber due to the extrusion effect by the fire type from the cavity 70. Move to. For this reason, the air-fuel mixture burns and spreads at a position further away from the wall surface of the combustion chamber and the plasma jet spark plug 100 main body that exert a flame extinguishing action. In addition, because it is pushed out into a space free of obstacles, when the ignited air-fuel mixture burns and spreads, there is no obstacle or flame extinguishing action in the surroundings, so combustion is not hindered and the speed of burning spread ( (Burning rate) is improved. On the other hand, since the plasma ejected from the cavity 60 has a frame shape, the contact area with the air-fuel mixture is wide, and the fire type is not easily extinguished at the early stage of ignition. In addition, like the plasma V schematically shown in the third process, a plasma spreading on the surface of the protective member 35 may be formed by the energy of the fire type ejected from the cavity 70, and the surrounding air-fuel mixture may be formed. Also ignite. As described above, since the ignition to the air-fuel mixture by the high energy of plasma and the extinguishing action due to the extrusion of the ignited combustion gas and plasma are performed, the plasma jet ignition plug 100 of the present embodiment has the ignition limit. As a result, the air-fuel ratio can be further increased, and higher ignitability can be obtained.

  Needless to say, the present invention can be modified in various ways. For example, in the present embodiment, the cavity 70 is formed as an annular and groove-shaped recess surrounding the periphery of the opening 61 of the cavity 60 with the axis O as the center. It may be an assembly of recesses or a single recess. In such a case, if a pair of cavities are formed at positions symmetrical with respect to the axis O, and the plasma from the cavity 60 and the ignited combustion gas are pushed forward in the direction of the axis O, the cavity can be efficiently moved away from the wall of the combustion chamber Extrude is preferred. However, it may be configured such that the jetted plasma and the ignited combustion gas are pushed out in an arbitrary direction, for example, blown out from the cavity 70 so as to be pushed out toward the fuel jetted from the injector in the combustion chamber. You may adjust the ejection direction of the fire type. As long as it has directivity as described above, the fire type ejected from the cavity 70 may also be flame-shaped plasma. Moreover, although the ground electrode 30 has a circular plate shape and has a through hole 31 in the center in the present embodiment, it may have a rod shape. Further, the ignition method for the plasma jet ignition plug 100 may be arbitrary.

1 is a partial cross-sectional view of a plasma jet ignition plug 100. FIG. 2 is an enlarged cross-sectional view of a tip portion of a plasma jet ignition plug 100. FIG. 3 is a cross-sectional view schematically showing an ignition process in the plasma jet ignition plug 100. FIG.

DESCRIPTION OF SYMBOLS 10 Insulator 12 Tip center part 20 Center electrode 30 Ground electrode 35 Protection member 36 Through-hole 50 Metal shell 60,70 Cavity 61,71 Opening 90 Shaft hole 100 Plasma jet ignition plug

Claims (5)

A center electrode;
An insulator having an axial hole extending in the axial direction, containing the central electrode in the axial hole and holding the central electrode;
A metal shell that surrounds and holds the periphery of the insulator in the radial direction;
A ground electrode electrically connected to the metal shell and forming a spark discharge gap with the center electrode;
At the tip of the insulator, a spark discharge path in the spark discharge gap passes through the first opening, and a recess is formed by the first opening, and plasma formed inside the spark discharge is generated inside the insulator. A first cavity ejected in a frame shape extending in the axial direction;
Wherein at the distal end portion of the insulator, the passes through the second opening which is different from the path of spark discharge in the spark discharge gap of the first opening, a recess formed by the second opening, the fire flower discharge A plasma jet ignition plug comprising: a second cavity through which a fire species formed therein is ejected.   The direction in which the fire is ejected from the second opening formed in the second cavity has directivity with respect to the direction in which the plasma is ejected in a frame shape from the first opening in the first cavity. The plasma jet ignition plug according to claim 1, wherein the plasma jet ignition plug is provided. The first opening of the first cavity is an opening formed in the tip surface of the insulator by the shaft hole, and the first cavity is an opening of the shaft hole continuous from the first opening. It is formed in a concave shape having an inner peripheral surface and the tip surface of the center electrode as its boundary,
3. The plasma according to claim 1, wherein the second opening of the second cavity is configured as an opening of the second cavity formed around the radial direction of the first cavity. 4. Jet spark plug.   The plasma jet ignition plug according to claim 3, wherein the second cavity is formed as an annular recess surrounding the first cavity. A through hole is formed in the center, and includes an insulating protective member that covers and protects the ground electrode from the front end side of the metal shell,
The plasma jet ignition plug according to claim 4, wherein an inner diameter of the through hole of the protection member is larger than an inner diameter of the first opening.

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