JP7340424B2 - spark plug - Google Patents

Description

The present invention relates to a spark plug.

Conventionally, a spark plug is equipped with a sub-chamber having a nozzle hole that communicates with the main combustion chamber, and the air-fuel mixture flows into the sub-chamber through the nozzle hole, and the flame generated in the sub-chamber is sent from the nozzle hole into the main combustion chamber. There is something that makes me gush. For example, Patent Document 1 discloses that by providing the sub-chamber with a protrusion that protrudes inward from the outer surface, the flame kernel in the sub-chamber is separated from the inner peripheral surface of the sub-chamber, thereby promoting flame jetting from the nozzle hole. The configuration is disclosed.

Patent No. 6015678

However, in the configuration disclosed in Patent Document 1, if the length of the flame ejected from the nozzle hole, that is, the penetration is large, the ejected flame collides with the inner wall of the main combustion chamber formed by the cylinder head, causing heat generation. This resulted in increased loss and decreased ignitability. On the other hand, if the penetration is made smaller, the contact area between the flame ejected from the nozzle hole and the air-fuel mixture decreases, which may lead to a decrease in ignitability.

The present invention has been made in view of such problems, and it is an object of the present invention to provide a spark plug with improved ignitability.

One aspect of the present invention includes a sub-chamber (2) located at the tip in the axial direction of the plug, a sub-chamber forming portion (30) forming the sub-chamber (2), and a tip portion (11) located within the sub-chamber. a center electrode (10),
The sub-chamber forming portion has a concave portion whose outer surface is concave toward the proximal end in the axial direction of the plug,
A recess nozzle hole is formed through the recess to communicate the subchamber with the main combustion chamber (3),
The recessed nozzle holes include a first recessed nozzle hole (351) and a second recessed nozzle hole (352),
The first recessed nozzle hole is arranged such that the centerline (L1) of the first recessed nozzle hole is aligned with the first recessed nozzle hole in a first cross section that passes through the main combustion chamber side opening of the first recessed nozzle hole and includes the plug central axis. A first virtual projection line (L1v) projected onto the cross section and the plug center axis are configured to intersect within the main combustion chamber,
The second recessed nozzle hole is arranged such that the centerline (L2) of the second recessed nozzle hole is located at the second The spark plug is configured such that a second virtual projection line (L2v) projected onto the cross section and the plug center axis intersect within the main combustion chamber.
Further, another aspect of the present invention provides a sub-chamber (2) located at the tip in the axial direction of the plug, a sub-chamber forming part (30) forming the sub-chamber (2), and a tip part (11) in the sub-chamber. ) on which the center electrode (10) is located;
The sub-chamber forming portion has a concave portion whose outer surface is concave toward the proximal end in the axial direction of the plug,
A recess nozzle hole is formed through the recess to communicate the subchamber with the main combustion chamber (3),
The auxiliary chamber forming portion is provided with an outer nozzle hole (36) on the outside in the plug radial direction of the recessed portion for communicating the auxiliary chamber with the main combustion chamber,
The opening diameter of the outer nozzle hole is larger than the opening diameter of the recessed nozzle hole in the spark plug.
Still another aspect of the present invention is a sub-chamber (2) located at the tip in the axial direction of the plug, a sub-chamber forming portion (30) forming the sub-chamber (2), and a tip portion ( a center electrode (10) on which a central electrode (11) is located;
The sub-chamber forming portion has a concave portion whose outer surface is concave toward the proximal end in the axial direction of the plug,
A recess nozzle hole is formed through the recess to communicate the subchamber with the main combustion chamber (3),
The auxiliary chamber forming portion is provided with an outer nozzle hole (36) on the outside in the plug radial direction of the recessed portion for communicating the auxiliary chamber with the main combustion chamber,
A plurality of the recessed nozzle holes and the outer nozzle holes are provided,
A first imaginary line (L1a to L4a) extending from the main combustion chamber side opening of the recessed nozzle hole to the main combustion chamber side along each center line, and a first imaginary line (L1a to L4a) extending from the main combustion chamber side opening of the outer nozzle hole, respectively. A spark plug, in which second imaginary lines (M1a to M4a) extending toward the main combustion chamber along the center line of It is in.

In the above-mentioned spark plug, the recessed nozzle hole is formed in the recessed portion provided on the axially leading end side of the plug in the sub-chamber forming portion. As a result, the recessed nozzle hole is located on the axially proximal side of the plug on the axially distal end side of the plug in the auxiliary chamber, increasing the penetration of the flame ejected from the recessed nozzle hole and directing the flame to the main combustion chamber. It can be made difficult to contact the inner wall of the Thereby, it is possible to secure a wide contact area between the flame and the air-fuel mixture, while suppressing cooling loss due to contact of the flame with the inner wall of the main combustion chamber, thereby improving ignitability in the main combustion chamber.

As described above, according to the present invention, it is possible to provide a spark plug with improved ignitability.

Note that the numerals in parentheses described in the claims and means for solving the problem indicate correspondence with specific means described in the embodiments described later, and do not limit the technical scope of the present invention. It's not a thing.

1 is a side view of a spark plug in Embodiment 1. FIG. A partially enlarged cross-sectional view taken along line II-II in FIG. 1. FIG. 3 is a bottom view of the spark plug in Embodiment 1. (a) A conceptual diagram showing how a spark plug is used in Embodiment 1, and (b) a conceptual diagram showing how a spark plug is used in a comparative embodiment. FIG. 3 is a side view of a spark plug in Embodiment 2. A partially enlarged cross-sectional view taken along line IV-IV in FIG. 5. FIG. 3 is a conceptual diagram showing how a spark plug is used in Embodiment 2. FIG. 2 is a partially enlarged cross-sectional view of a position corresponding to line II-II in FIG. 1 in Embodiment 3. FIG. FIG. 7 is a conceptual diagram showing how a spark plug is used in Embodiment 3. FIG. 7 is a conceptual diagram showing how a spark plug is used in Embodiment 4. FIG. 2 is a partially enlarged cross-sectional view of a position corresponding to line II-II in FIG. 1 in Embodiment 5. FIG. 2 is a partially enlarged cross-sectional view of a position corresponding to line II-II in FIG. 1 in Embodiment 6. FIG. 2 is a partially enlarged cross-sectional view of a position corresponding to line II-II in FIG. 1 in Embodiment 7. FIG.

(Embodiment 1)
Embodiments of the spark plug will be described using FIGS. 1 to 4.
As shown in FIG. 1, the spark plug 1 of this embodiment has a subchamber 2 on the tip end side Y1 in the plug axial direction.
As shown in FIG. 2, the spark plug 1 includes a sub-chamber forming portion 30 forming a sub-chamber 2, and a center electrode 10 having a tip portion 11 located within the sub-chamber 2.
The sub-chamber forming portion 30 has a recess 31 in which the outer surface 30a is recessed toward the base end side Y2 in the plug axial direction.
A recess nozzle hole 35 is formed through the recess 31 to communicate the auxiliary chamber 2 with the main combustion chamber 3 .

Hereinafter, the spark plug 1 of this embodiment will be explained in detail.
As shown in FIG. 1, the spark plug 1 of this embodiment is attached to a cylinder head 101 of an internal combustion engine so that its tip is exposed to the main combustion chamber 3 of the internal combustion engine. As shown in FIG. 2, the spark plug 1 has a cylindrical housing 40 whose longitudinal direction is in the plug axial direction Y. A cylindrical insulator 50 is disposed within the housing 40 coaxially with the housing 40 . A sub-chamber forming portion 30 that forms the sub-chamber 2 is provided on the plug axial direction front end side Y1 of the housing 40 . In this embodiment, the housing 40 and the auxiliary chamber forming part 30 are integrated, but instead, they may be formed separately and welded together. Further, the sub-chamber forming portion 30 may be formed integrally with the cylinder head 101.

As shown in FIG. 2, the center electrode 10 is disposed inside the insulator 50 coaxially with the insulator 50. As shown in FIG. The tip portion 11 of the center electrode 10 on the tip end side Y1 in the plug axial direction is exposed in the subchamber 2 . A ground electrode 15 extending from the housing 40 is provided in the subchamber 2 . The tip 16 of the ground electrode 15 faces the tip 11 of the center electrode 10 at a predetermined distance, and a discharge gap G is formed between the two.

As shown in FIG. 2, a recess 31 is formed in the subchamber forming portion 30. As shown in FIG. The recessed portion 31 is recessed from the distal end side Y1 in the plug axial direction of the auxiliary chamber forming portion 30 toward the proximal end side Y2 in the plug axial direction. In this embodiment, the recess 31 has a conical shape with the plug central axis 10a as the axis. Therefore, the outer surface 31a of the recess 31, that is, the surface of the portion of the auxiliary chamber forming part 30 where the recess 31 is formed facing the main combustion chamber 3 is inclined with respect to the plug central axis 10a. On the outer surface 31a, the most proximal position 31b located closest to the proximal end side Y2 in the plug axial direction is located on the plug central axis 10a.

As shown in FIG. 2, a recess nozzle hole 35 is formed on the outer surface 31a of the recess 31. As shown in FIG. As shown in FIG. 3, in this embodiment, the recess nozzle holes 35 include a first recess nozzle hole 351, a second recess nozzle hole 352, a third recess nozzle hole 353, and a fourth recess nozzle hole 354. The recessed injection holes 351 to 354 are evenly arranged in the circumferential direction on a virtual circle C1 centered on the plug central axis 10a.

As shown in FIG. 2, the first recess nozzle hole 351 is located at the center of the first recess nozzle hole 351 in a first cross section that passes through the main combustion chamber side opening of the first recess nozzle hole 351 and includes the plug central axis 10a. A first virtual projection line L1v, which is a projection of the line L1 onto the first cross section, is configured to intersect within the main combustion chamber 3 with the plug center axis 10a. Note that the space within the recess 31 constitutes a part of the main combustion chamber 3. Here, the center line L1 of the first recessed nozzle hole 351 is an imaginary line passing through the center of the opening of the first recessed nozzle hole 351 on the sub-chamber 2 side and the center of the opening on the main combustion chamber side. The center lines L2 to L4 of the other nozzle holes 352 to 354 are similarly defined.

Further, as shown in FIG. 2, the second recessed nozzle hole 352 is located at a second cross section that passes through the main combustion chamber side opening of the second recessed nozzle hole 352 and includes the plug central axis 10a. The plug center axis 10a is configured such that a second virtual projection line L2v, which is obtained by projecting the centerline L2 of the engine onto the second cross section, intersects with the plug center axis 10a within the main combustion chamber 3. Note that the first cross section and the second cross section may be the same cross section, or may be different cross sections.

As shown in FIGS. 2 and 3, the third recess nozzle hole 353 and the fourth recess nozzle hole 354 are configured similarly to the first recess nozzle hole 351 and the second recess nozzle hole 352. In the present embodiment, the center lines L1 to L4 of the recessed nozzle holes 351 to 354 have a twisted positional relationship with each other, and are inclined so as to be closest to each other within the main combustion chamber 3.

The manner of use of the spark plug 1 in this embodiment will be described in detail below.
In the comparative spark plug 9 without the recess 31 shown in FIG. are in contact with each other. On the other hand, in the spark plug 1 according to the present embodiment shown in FIG. is not in contact with

Next, the effects of the spark plug 1 of this embodiment will be described in detail.
In the spark plug 1 of this embodiment, the recessed nozzle hole 35 is formed in the recessed part 31 provided on the front end side Y1 of the sub-chamber forming part 30 in the plug axial direction. As a result, the recess nozzle hole 35 is located at the proximal end side Y2 of the plug axial direction in the plug axial direction front end side Y1 of the subchamber 2, and while increasing the penetration of the flame F1 ejected from the recess nozzle hole 35, It is possible to make it difficult for the flame F1 to come into contact with the main interior wall 3a. As a result, it is possible to secure a wide contact area between the flame F1 and the air-fuel mixture, while suppressing cooling loss due to contact of the flame F1 with the main interior wall 3a, and improving ignitability in the main combustion chamber 3. .

Further, in the present embodiment, in the outer surface 31a of the recess 31, the most proximal position 31b located closest to the proximal end side Y2 in the plug axial direction is located on the plug central axis 10a of the spark plug 1. The recess injection holes 35 are arranged in a well-balanced manner on the outer surface 31a of the recess 31, thereby improving the ignition performance in the main combustion chamber 3.

In this embodiment, the recessed nozzle holes 35 include a first recessed nozzle hole 351 and a second recessed nozzle hole 352. The first recessed nozzle hole 351 is arranged so that the centerline L1 of the first recessed nozzle hole 351 is aligned with the centerline L1 of the first recessed nozzle hole 351 in a first cross section that passes through the main combustion chamber side opening of the first recessed nozzle hole 351 and includes the plug central axis 10a. The first virtual projection line L1v projected onto one cross section and the plug center axis 10a are configured to intersect within the main combustion chamber 3. Furthermore, the second recessed nozzle hole 352 has a center line L2 of the second recessed nozzle hole 352 in a second cross section that passes through the main combustion chamber side opening of the second recessed nozzle hole 352 and includes the plug central axis 10a. The second virtual projection line L2v projected onto the cross section and the plug center axis 10a are configured to intersect within the main combustion chamber 3. As a result, the first recess nozzle hole 351 and the second recess nozzle hole 352 eject the flame F1 toward the main indoor wall 3a that is far from each other, so that the penetration of the flame F1 is maintained for a long time and the air-fuel mixture is The contact area with the main combustion chamber 3 can be increased more reliably, and the ignition performance in the main combustion chamber 3 can be improved.

In this embodiment, the recess nozzle holes 35 are provided with four recess nozzle holes 351 to 354, but the present invention is not limited to this. A recessed nozzle hole 35 may be provided.

Note that the spark plug 1 of this embodiment may include a configuration in which fuel is injected into the subchamber 2. Further, although the spark plug 1 of the present embodiment has a configuration in which an air discharge is generated in the discharge gap G, a configuration in which a creeping discharge is generated in the discharge gap G may be adopted instead. In either case, the same effects as in this embodiment can be achieved.

As described above, according to the present embodiment, it is possible to provide the spark plug 1 with improved ignitability.

(Embodiment 2)
In the spark plug 1 of Embodiment 2, as shown in FIGS. 5 to 7, the sub-chamber forming portion 30 includes an outer injection jet that communicates the sub-chamber 2 with the main combustion chamber 3 on the outside in the plug radial direction of the recess 31. A hole 36 is provided. The opening diameter D2 of the outer nozzle hole 36 is equal to the opening diameter D1 of the recessed nozzle hole 35. Note that the other components are the same as in the first embodiment, and the same reference numerals as in the first embodiment are used in this embodiment, and the explanation thereof will be omitted.

In the second embodiment, as shown in FIG. 7, the outer nozzle holes 36 include a first outer nozzle hole 361, a second outer nozzle hole 362, a third outer nozzle hole 363, and a fourth outer nozzle hole 364. The outer nozzle holes 361 to 364 are evenly arranged in the circumferential direction on a virtual circle C2 centered on the plug central axis 10a.

As shown in FIG. 6, the first outer nozzle hole 361 is formed along the center line M1. As shown in FIG. 7, when viewed from the plug axial direction Y, the center line M1 passes through the center of the main combustion chamber side opening of the first outer nozzle hole 361 and the plug center axis 10a. Similarly, the second outer nozzle holes 362 to the fourth outer nozzle holes 364 are formed along the center lines M2 to M4, respectively, and the center lines M2 to M4 are the second outer nozzle holes 362 to the fourth outer nozzle holes 364, respectively. It passes through the center of each main combustion chamber side opening and the plug central axis 10a.

According to the spark plug 1 of the second embodiment, the same effects as those of the first embodiment are achieved. Furthermore, the flames F1 to F4 are ejected from the first recessed nozzle holes 351 to 354 toward the central area of the main combustion chamber 3, and the flames E1 to E are ejected from the first outer nozzle holes 361 to the fourth outer nozzle hole 364 into the main combustion chamber 3. The fuel can be ejected toward the wall 3a, and the ignitability in the main combustion chamber 3 can be further improved.

(Embodiment 3)
In the second embodiment, as shown in FIG. 7, the opening diameter D2 of the outer nozzle hole 36 was made equal to the opening diameter D1 of the recessed nozzle hole 35, but instead of this, in the third embodiment, FIG. As shown in FIG. 9, the opening diameter D2 of the outer nozzle hole 36 is larger than the opening diameter D1 of the recessed nozzle hole 35. Note that the other components are the same as in the second embodiment, and the same reference numerals as in the second embodiment are used in the third embodiment, and the explanation thereof will be omitted.

According to the spark plug 1 of the third embodiment, the same effects as those of the second embodiment are achieved. Furthermore, since the penetration of the flames E1 to E4 ejected from the first outer nozzle hole 361 to the fourth outer nozzle hole 364 is shorter than that in the second embodiment, the flames E1 to E4 are formed by the cylinder head 101. It becomes difficult to contact the main interior wall 3a, and cooling loss can be suppressed. As a result, the ignitability in the main combustion chamber 3 is improved.

(Embodiment 4)
In the spark plug 1 of Embodiment 4, as shown in FIG. The first imaginary lines L1a to L4a and the second imaginary lines M1a to M4a extending from the main combustion chamber side openings of the outer nozzle holes 361 to 364 toward the main combustion chamber side along their respective center lines are in the plug axial direction Y. When viewed from above, they are alternately located in the circumferential direction around the plug central axis 10a. Note that the other components are the same as in the second embodiment, and the same reference numerals as in the second embodiment are used in the fourth embodiment, and the description thereof will be omitted.

According to the spark plug 1 of the fourth embodiment, the same effects as those of the second embodiment are achieved. Furthermore, since the first imaginary lines L1a to L4a and the second imaginary lines M1a to M4a are alternately located in the circumferential direction around the plug central axis 10a when viewed from the plug axial direction Y, the flames of each other are Since interference between F1 to F4 and E1 to E4 is suppressed and the penetration of each flame F1 to F4 and E1 to E4 is maintained and ejected, ignitability in the main combustion chamber 3 is improved.

(Embodiment 5)
In the spark plug 1 of the fifth embodiment, as shown in FIG. 11, the tip portion 11 of the center electrode 10 extends to the tip side Y1 in the plug axial direction, and is located on the inner surface of the proximalmost position 31b in the recess 31. They are facing each other at a distance. A portion of the sub-chamber forming portion 30 that forms the recess 31 constitutes the ground electrode 15, and a portion of the inner surface of the proximal end position 31b of the sub-chamber forming portion 30 constitutes the tip portion 16 of the ground electrode 15. , a discharge gap G is formed between the tip 16 of the ground electrode 15 and the tip 11 of the center electrode 10. The tip 16 of the ground electrode 15 is formed at an acute angle. The other configurations are the same as in the first embodiment, and the same reference numerals as in the first embodiment are used in the fifth embodiment, and the explanation thereof will be omitted.

The spark plug 1 of the fifth embodiment also has the same effects as the first embodiment. Furthermore, in the fifth embodiment, since it is not necessary to protrude the ground electrode from the housing 40 into the subchamber 2, heat loss can be reduced accordingly. In addition, since the tip 16 of the ground electrode 15 forms an acute angle, electrolytic concentration occurs and the voltage required for discharge can be reduced.

(Embodiment 6)
In the spark plug 1 of the sixth embodiment, as shown in FIG. 12, the curvature of the proximal end position 31b of the recess 31 is small, forming a gentle surface. The other configurations are the same as in the first embodiment, and the same reference numerals as in the first embodiment are used in the sixth embodiment, and the explanation thereof will be omitted.

The sixth embodiment also provides the same effects as the first embodiment. Furthermore, according to the spark plug 1 of the sixth embodiment, since the surface area of the recess 31 inside the subchamber 2 is reduced, cooling loss of the flame within the subchamber 2 is reduced, flame growth is promoted, and ignitability is improved. It is possible to improve the

(Embodiment 7)
In the spark plug 1 of the seventh embodiment, as shown in FIG. 13, the recess 31 includes a protrusion 32 that protrudes toward the tip end side Y1 in the plug axial direction at a position on the plug center axis 10a. A sub-chamber recess 22 is provided inside the sub-chamber 2. The most protruding position 32 a of the protruding portion 32 located closest to the tip end side Y1 in the plug axial direction is located within the recess 31 . The other configurations are the same as in the first embodiment, and the same reference numerals as in the first embodiment are used in the seventh embodiment, and the explanation thereof will be omitted.

The seventh embodiment also provides the same effects as the first embodiment. In the seventh embodiment, one protrusion 32 is provided in the recess 31, but the present invention is not limited to this, and a plurality of protrusions 32 may be provided so that the wall surface of the recess 31 has a plurality of irregularities.

The present invention is not limited to the above-mentioned embodiments, but can be applied to various embodiments without departing from the gist thereof.

DESCRIPTION OF SYMBOLS 1... Spark plug, 2... Subchamber, 3... Main combustion chamber, 3a... Main interior wall, 10... Center electrode, 10a... Plug central axis, 11... Tip part, 30... Subchamber forming part, 31... Recessed part, 31a ...outer surface, 31b...most proximal position, 35, 351-354...concave nozzle hole, 36, 361-364...outer nozzle hole, G...discharge gap

Claims (7)

A sub-chamber (2) located at the tip in the axial direction of the plug, a sub-chamber forming part (30) forming the sub-chamber (2), and a center electrode (10) having a tip (11) located within the sub-chamber. , comprising;
The sub-chamber forming portion has a concave portion whose outer surface is concave toward the proximal end in the axial direction of the plug,
A recess nozzle hole is formed through the recess to communicate the subchamber with the main combustion chamber (3),
The recessed nozzle holes include a first recessed nozzle hole (351) and a second recessed nozzle hole (352),
The first recessed nozzle hole is arranged such that the centerline (L1) of the first recessed nozzle hole is aligned with the first recessed nozzle hole in a first cross section that passes through the main combustion chamber side opening of the first recessed nozzle hole and includes the plug central axis. A first virtual projection line (L1v) projected onto the cross section and the plug center axis are configured to intersect within the main combustion chamber,
The second recessed nozzle hole is arranged such that the centerline (L2) of the second recessed nozzle hole is located at the second An ignition plug configured such that a second virtual projection line (L2v) projected onto the cross section and the plug center axis intersect within the main combustion chamber. The ignition plug according to claim 1 , wherein the auxiliary chamber forming portion is provided with an outer nozzle hole (36) located outside the recess in the plug radial direction to communicate the auxiliary chamber with the main combustion chamber. A sub-chamber (2) located at the tip in the axial direction of the plug, a sub-chamber forming part (30) forming the sub-chamber (2), and a center electrode (10) having a tip (11) located within the sub-chamber. , comprising;
The sub-chamber forming portion has a concave portion whose outer surface is concave toward the proximal end in the axial direction of the plug,
A recess nozzle hole is formed through the recess to communicate the subchamber with the main combustion chamber (3),
The auxiliary chamber forming portion is provided with an outer nozzle hole (36) on the outside in the plug radial direction of the recessed portion for communicating the auxiliary chamber with the main combustion chamber,
The opening diameter of the outer nozzle hole is larger than the opening diameter of the recessed nozzle hole . A plurality of the recessed nozzle holes and the outer nozzle holes are provided,
A first imaginary line (L1a to L4a) extending from the main combustion chamber side opening of the recessed nozzle hole to the main combustion chamber side along each center line, and a first imaginary line (L1a to L4a) extending from the main combustion chamber side opening of the outer nozzle hole, respectively. The second imaginary lines (M1a to M4a) extending toward the main combustion chamber along the center line of the plug are alternately located in the circumferential direction around the plug center axis when viewed from the plug axis direction. The spark plug described in 3 . A sub-chamber (2) located at the tip in the axial direction of the plug, a sub-chamber forming part (30) forming the sub-chamber (2), and a center electrode (10) having a tip (11) located within the sub-chamber. , comprising;
The sub-chamber forming portion has a concave portion whose outer surface is concave toward the proximal end in the axial direction of the plug,
A recess nozzle hole is formed through the recess to communicate the subchamber with the main combustion chamber (3),
The auxiliary chamber forming portion is provided with an outer nozzle hole (36) on the outside in the plug radial direction of the recessed portion for communicating the auxiliary chamber with the main combustion chamber,
A plurality of the recessed nozzle holes and the outer nozzle holes are provided,
A first imaginary line (L1a to L4a) extending from the main combustion chamber side opening of the recessed nozzle hole to the main combustion chamber side along each center line, and a first imaginary line (L1a to L4a) extending from the main combustion chamber side opening of the outer nozzle hole, respectively. A spark plug, in which second imaginary lines (M1a to M4a) extending toward the main combustion chamber along the center line of . The recessed nozzle holes include a first recessed nozzle hole (351) and a second recessed nozzle hole (352),
The first recessed nozzle hole is arranged such that the centerline (L1) of the first recessed nozzle hole is aligned with the first recessed nozzle hole in a first cross section that passes through the main combustion chamber side opening of the first recessed nozzle hole and includes the plug central axis. A first virtual projection line (L1v) projected onto the cross section and the plug center axis are configured to intersect within the main combustion chamber,
The second recessed nozzle hole is arranged such that the centerline (L2) of the second recessed nozzle hole is located at the second The spark plug according to any one of claims 3 to 5 , wherein a second virtual projection line (L2v) projected onto the cross section and the plug center axis intersect within the main combustion chamber. The outer surface (31a) of the recessed portion, the most proximal position (31b) located closest to the proximal end in the axial direction of the plug is located on the plug central axis (10a) of the ignition plug . 6. The spark plug according to any one of Item 6 .

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