JP7655192B2 - Spark plug for internal combustion engine and internal combustion engine equipped with same - Google Patents

Description

The present invention relates to a spark plug for an internal combustion engine and an internal combustion engine equipped with the same.

For example, as disclosed in Patent Document 1, a spark plug with a secondary combustion chamber at the tip is known. In this spark plug, a cover portion covering the secondary combustion chamber is formed with multiple nozzle holes. This allows a flame to be ejected from the secondary combustion chamber through the nozzle holes into the main combustion chamber, thereby combusting the mixture in the main combustion chamber.

JP 2020-009747 A

However, the spark plug described in Patent Document 1 does not take into consideration the ignition of the mixture in the auxiliary combustion chamber, i.e., the formation of the initial flame itself. In other words, no consideration is given to improving ignition by extending the discharge in the auxiliary combustion chamber.

The present invention was made in consideration of these problems, and aims to provide a spark plug for an internal combustion engine that can improve ignition performance, and an internal combustion engine equipped with the same.

The first aspect of the present invention comprises a cylindrical insulator (3),
a center electrode (4) held on the inner circumferential side of the insulator and having a tip protrusion (41) protruding toward the tip side of the insulator;
a cylindrical housing (2) that holds the insulator on its inner periphery;
a ground electrode (6) forming a discharge gap (G) between itself and the center electrode;
a plug cover (5) provided at a tip end of the housing so as to cover a sub-combustion chamber (50) in which the discharge gap is disposed,
The discharge gap is formed by a front end portion of the center electrode and a base end surface (61) of the ground electrode facing each other in an axial direction (Z),
The plug cover is formed with at least two large nozzle holes (51) and a small nozzle hole (52) having an opening area smaller than that of the large nozzle holes,
The large injection hole and the small injection hole each communicate the auxiliary combustion chamber with the outside,
The large nozzle hole opens at an angle with respect to the plug axial direction so as to extend radially outwardly toward the tip side of the plug,
when the spark plug is divided into a first plug portion (11) and a second plug portion (12) by a predetermined plane (P) including a plug center axis (C), both of the at least two large injection holes are formed in the first plug portion,
The ground electrode protrudes into the auxiliary combustion chamber from a fixed end (62) of the first plug portion that is fixed to the housing or the plug cover,
when viewed from the plug axial direction, in the first plug portion, the fixed end portion is disposed between extension lines (51L) of respective central axes of the at least two large injection holes in the plug circumferential direction,
The large injection hole is formed so that an extension of the central axis of the large injection hole does not pass through the tip projection, and when viewed in the plug axial direction, an intersection (A) of extensions of the central axes of at least two of the large injection holes and the large injection hole are located on opposite sides of the tip projection in the arrangement direction (Y) of the fixed end and the tip projection when viewed in the plug axial direction .
A second aspect of the present invention is a cylindrical insulator (3),
a center electrode (4) held on the inner circumferential side of the insulator and having a tip protrusion (41) protruding toward the tip side of the insulator;
a cylindrical housing (2) that holds the insulator on its inner periphery;
a ground electrode (6) forming a discharge gap (G) between itself and the center electrode;
a plug cover (5) provided at a tip end of the housing so as to cover a sub-combustion chamber (50) in which the discharge gap is disposed,
The discharge gap is formed by a front end portion of the center electrode and a base end surface (61) of the ground electrode facing each other in an axial direction (Z),
The plug cover is formed with at least two large nozzle holes (51) and a small nozzle hole (52) having an opening area smaller than that of the large nozzle holes,
The large injection hole and the small injection hole each communicate the auxiliary combustion chamber with the outside,
The large nozzle hole opens at an angle with respect to the plug axial direction so as to extend radially outwardly toward the tip side of the plug,
when the spark plug is divided into a first plug portion (11) and a second plug portion (12) by a predetermined plane (P) including a plug center axis (C), both of the at least two large injection holes are formed in the first plug portion,
The ground electrode protrudes into the auxiliary combustion chamber from a fixed end (62) of the first plug portion that is fixed to the housing or the plug cover,
when viewed from the plug axial direction, in the first plug portion, the fixed end portion is disposed between extension lines (51L) of respective central axes of the at least two large injection holes in the plug circumferential direction,
At least one of the small injection holes is a projection-side injection hole (521) through which an extension line (6L) of the projection direction of the ground electrode passes when viewed from the plug axial direction,
This spark plug is for an internal combustion engine, and when viewed from the plug axial direction, at least a part of the protruding end portion (63) of the ground electrode is disposed between the tip protruding portion and the protruding side nozzle hole.

A third aspect of the present invention is an internal combustion engine (10) including the spark plug for an internal combustion engine according to the first or second aspect ,
A main combustion chamber (101);
an intake valve (72) and an exhaust valve (73) provided in the main combustion chamber;
The spark plug is disposed so that an outer surface (53) of the plug cover faces the main combustion chamber,
The spark plug is disposed in an internal combustion engine such that an outer opening (511) of at least one of the large nozzle holes faces the intake valve side when viewed in the plug axial direction.

A fourth aspect of the present invention is a cylindrical insulator (3),
a center electrode (4) held on the inner circumferential side of the insulator and having a tip protrusion (41) protruding toward the tip side of the insulator;
a cylindrical housing (2) that holds the insulator on its inner periphery;
a ground electrode (6) forming a discharge gap (G) between itself and the center electrode;
a plug cover (5) provided at a tip end of the housing so as to cover a sub-combustion chamber (50) in which the discharge gap is disposed,
The discharge gap is formed by a front end portion of the center electrode and a base end surface (61) of the ground electrode facing each other in an axial direction (Z),
The plug cover is formed with a plurality of nozzle holes (57) that communicate the auxiliary combustion chamber with the outside,
The ground electrode protrudes into the auxiliary combustion chamber from a fixed end (62) fixed to the housing or the plug cover,
when the spark plug is divided into two parts, a first plug part (13) including the fixed end part and a second plug part (14) by a plane (P2) which includes a plug center axis (C) and is perpendicular to a protruding direction of the ground electrode as viewed in the plug axial direction, the injection hole is formed in both the plug cover of the first plug part and the plug cover of the second plug part,
When the nozzle holes formed in the first plug portion are referred to as first nozzle holes (571) and the nozzle holes formed in the second plug portion are referred to as second nozzle holes (572), the number of the first nozzle holes is greater than the number of the second nozzle holes,
the first injection hole opens at an incline with respect to the plug axial direction so as to extend outward in the plug radial direction toward the tip side,
when viewed from the plug axial direction, in the first plug portion, the fixed end portion is disposed between extension lines (571L) of respective central axes of the at least two first injection holes in the plug circumferential direction,
The first injection hole is formed such that an extension line of a central axis of the first injection hole does not pass through the tip projection, and when viewed from the plug axial direction, an intersection (A2) of extension lines of central axes of at least two of the first injection holes and the first injection hole are located on opposite sides of the tip projection in an arrangement direction (Y) of the fixed end and the tip projection when viewed from the plug axial direction .
A fifth aspect of the present invention is a cylindrical insulator (3),
a center electrode (4) held on the inner circumferential side of the insulator and having a tip protrusion (41) protruding toward the tip side of the insulator;
a cylindrical housing (2) that holds the insulator on its inner periphery;
a ground electrode (6) forming a discharge gap (G) between itself and the center electrode;
a plug cover (5) provided at a tip end of the housing so as to cover a sub-combustion chamber (50) in which the discharge gap is disposed,
The discharge gap is formed by a front end portion of the center electrode and a base end surface (61) of the ground electrode facing each other in an axial direction (Z),
The plug cover is formed with a plurality of nozzle holes (57) that communicate the auxiliary combustion chamber with the outside,
The ground electrode protrudes into the auxiliary combustion chamber from a fixed end (62) fixed to the housing or the plug cover,
when the spark plug is divided into two parts, a first plug part (13) including the fixed end part and a second plug part (14) by a plane (P2) which includes a plug center axis (C) and is perpendicular to a protruding direction of the ground electrode as viewed in the plug axial direction, the injection hole is formed in both the plug cover of the first plug part and the plug cover of the second plug part,
When the nozzle holes formed in the first plug portion are referred to as first nozzle holes (571) and the nozzle holes formed in the second plug portion are referred to as second nozzle holes (572), the number of the first nozzle holes is greater than the number of the second nozzle holes,
the first injection hole opens at an incline with respect to the plug axial direction so as to extend outward in the plug radial direction toward the tip side,
when viewed from the plug axial direction, in the first plug portion, the fixed end portion is disposed between extension lines (571L) of respective central axes of the at least two first injection holes in the plug circumferential direction,
At least one of the second nozzle holes is a projection-side nozzle hole (573) through which an extension line (6L) of the projection direction of the ground electrode passes when viewed from the plug axial direction,
This spark plug is for an internal combustion engine, and when viewed from the plug axial direction, at least a part of the protruding end portion (63) of the ground electrode is disposed between the tip protruding portion and the protruding side nozzle hole.

A sixth aspect of the present invention is an internal combustion engine (10) including the spark plug for an internal combustion engine according to the fourth or fifth aspect ,
A main combustion chamber (101);
an intake valve (72) and an exhaust valve (73) provided in the main combustion chamber;
The spark plug is disposed so that an outer surface (53) of the plug cover faces the main combustion chamber,
The spark plug is disposed in an internal combustion engine such that an outer opening (575) of at least one of the first nozzle holes faces the intake valve side when viewed in the plug axial direction.

In the spark plug for an internal combustion engine according to the first aspect, when viewed from the plug axial direction, the fixed end of the ground electrode in the first plug portion is disposed between the extensions of the central axes of at least two large injection holes in the plug circumferential direction. This makes it easier for the airflow formed in the auxiliary combustion chamber to flow toward the discharge gap by being guided by the base end surface of the ground electrode. This makes it easier for the discharge formed in the discharge gap to extend. As a result, ignition performance can be improved.

The internal combustion engine according to the second aspect has the spark plug according to the first aspect. The spark plug is arranged so that the outer opening of at least one large nozzle hole faces the intake valve side when viewed from the plug axial direction. This allows a large flame to be ejected from the auxiliary combustion chamber to the intake valve side of the main combustion chamber through the large nozzle hole when viewed from the plug axial direction. This makes it possible to improve the ignition of the mixture on the intake valve side of the main combustion chamber when viewed from the plug axial direction. This makes it possible to burn the mixture in the entire main combustion chamber in a balanced manner. As a result, it is possible to suppress combustion abnormalities that cause knocking, etc.

In the spark plug for an internal combustion engine according to the third aspect, when viewed from the plug axial direction, in the first plug portion, the fixed end of the ground electrode is disposed between the extensions of the central axes of at least two first nozzle holes in the plug circumferential direction. Also, the number of first nozzle holes is greater than the number of second nozzle holes. As a result, the airflow formed in the auxiliary combustion chamber is guided to the base end surface of the ground electrode and tends to flow toward the discharge gap. Therefore, the discharge formed in the discharge gap tends to extend. As a result, ignition performance can be improved.

The internal combustion engine according to the fourth aspect has the spark plug according to the third aspect. The spark plug is arranged such that, when viewed from the plug axial direction, the outer opening of at least one first nozzle hole faces the intake valve side. Therefore, the outer opening of the first nozzle hole tends to face the upstream side of the airflow formed in the main combustion chamber. This makes it easier for the airflow to be introduced from the main combustion chamber to the auxiliary combustion chamber via the first nozzle hole. Therefore, the discharge generated in the discharge gap is easily extended by the airflow introduced into the auxiliary combustion chamber via the first nozzle hole. As a result, ignition performance can be reliably improved.

As described above, according to the above aspect, it is possible to provide a spark plug for an internal combustion engine capable of improving ignition performance, and an internal combustion engine including the spark plug.
In addition, the symbols in parentheses described in the claims and the means for solving the problems indicate a correspondence with the specific means described in the embodiments described below, and do not limit the technical scope of the present invention.

FIG. 3 is a cross-sectional view of the spark plug in the axial direction of the plug near the tip end of the spark plug according to the first embodiment, which is equivalent to a cross-sectional view taken along line II in FIG. 2 . FIG. 2 is a cross-sectional view taken along line II-II of FIG. 3 is a cross-sectional view illustrating the relationship between an extension line of the central axis of the large injection hole and the inner wall surface of the auxiliary combustion chamber in the first embodiment, and corresponds to a cross-sectional view taken along line III-III in FIG. 2 . FIG. FIG. 4 is a cross-sectional view illustrating the position where a large nozzle hole is formed in the first embodiment. FIG. 7 is a cross-sectional view of the internal combustion engine according to the first embodiment, taken along line V-V in FIG. 6. FIG. 6 is a cross-sectional view taken along line VI-VI in FIG. 5 . FIG. 4 is a cross-sectional view of the vicinity of the tip of the spark plug in the first embodiment during the compression stroke and before the discharge extends. 4 is a cross-sectional view of the vicinity of the tip portion of the spark plug when the discharge is extended during the compression stroke in the first embodiment. FIG. 11 is a cross-sectional view of a tip portion of a spark plug according to a second embodiment, taken perpendicular to the plug axial direction. 13 is a cross-sectional view of the tip portion of a spark plug according to a third embodiment, taken perpendicular to the plug axial direction, and corresponds to a cross-sectional view taken along line XX in FIG. 12. FIG. 11 is an explanatory cross-sectional view showing the shortest distance from the protruding end of the ground electrode to the protruding-side nozzle hole when viewed in the plug axial direction in a third embodiment. FIG. 12 is a cross-sectional view taken along line XII-XII in FIG. FIG. 11 is a cross-sectional view illustrating the position of a protruding end portion of a ground electrode in the third embodiment. FIG. 11 is a cross-sectional view of the vicinity of the tip of a spark plug in a third embodiment during an expansion stroke and before a discharge is extended. FIG. 13 is a cross-sectional view of the vicinity of the tip of a spark plug according to a third embodiment when the discharge is extended during the expansion stroke. FIG. 11 is a cross-sectional view taken along the axial direction of a spark plug in a vicinity of a tip portion of a spark plug according to a fourth embodiment. FIG. 13 is a cross-sectional view taken along the axial direction of a spark plug in a vicinity of a tip portion of the spark plug according to a fifth embodiment. FIG. 13 is a cross-sectional view taken along the axial direction of a spark plug in a vicinity of a tip portion of a spark plug according to a sixth embodiment. FIG. 13 is a plan view of the ground electrode according to the seventh embodiment, as viewed from the protruding direction of the ground electrode. FIG. 13 is a cross-sectional view of a tip portion of a spark plug according to an eighth embodiment, taken perpendicular to the plug axial direction. FIG. 13 is a cross-sectional view of a tip portion of a spark plug according to a ninth embodiment, taken perpendicular to the plug axial direction. FIG. 23 is a cross-sectional view of a tip portion of a spark plug according to a tenth embodiment, taken perpendicular to the plug axial direction. FIG. 23 is a cross-sectional view of the tip portion of the spark plug according to the eleventh embodiment, taken perpendicular to the plug axial direction, and corresponds to a cross-sectional view taken along line XXIII-XXIII in FIG. 25. FIG. 24 is a cross-sectional view taken along line XXIV-XXIV in FIG. 23. A cross-sectional view taken along line XXV-XXV in Figure 23. FIG. 23 is a cross-sectional view showing an angle α3 in the eleventh embodiment. FIG. 23 is a diagram showing an internal combustion engine according to an eleventh embodiment, as viewed from the front end side. FIG. 23 is a cross-sectional view of a tip portion of a spark plug according to a twelfth embodiment, taken perpendicular to the plug axial direction. FIG. 23 is a cross-sectional view of a tip portion of a spark plug according to a thirteenth embodiment, taken perpendicular to the plug axial direction. FIG. 32 is a cross-sectional view of the tip portion of a spark plug according to a fourteenth embodiment, taken perpendicular to the plug axial direction, and corresponds to a cross-sectional view taken along line XXX-XXX in FIG. A cross-sectional view taken along line XXXI-XXXI in Figure 30. FIG. 23 is a cross-sectional view taken along the axial direction of a spark plug in the vicinity of a tip portion of the spark plug according to a fifteenth embodiment.

(Embodiment 1)
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a spark plug for an internal combustion engine and an internal combustion engine equipped with the same will be described with reference to FIGS.
1 and 2, a spark plug 1 for an internal combustion engine according to this embodiment has a cylindrical insulator 3, a center electrode 4, a cylindrical housing 2, a ground electrode 6, and a plug cover 5. The center electrode 4 is held on the inner periphery of the insulator 3 and has a tip projection 41 projecting from the tip side of the insulator 3. The housing 2 holds the insulator 3 on its inner periphery. The ground electrode 6 forms a discharge gap G between itself and the center electrode 4. The plug cover 5 is provided at the tip of the housing 2 so as to cover the auxiliary combustion chamber 50 in which the discharge gap G is located.

The discharge gap G is formed by the tip of the center electrode 4 and the base end surface 61 of the ground electrode 6 facing each other in the plug axial direction Z. At least two large injection holes 51 and a small injection hole 52 with an opening area smaller than that of the large injection holes 51 are formed in the plug cover 5. The large injection holes 51 and the small injection holes 52 each communicate with the auxiliary combustion chamber 50 and the outside. As shown in FIG. 3, the large injection hole 51 opens at an angle with respect to the plug axial direction Z so that it moves outward in the plug radial direction as it approaches the tip side.

As shown in FIG. 2, when the spark plug 1 is divided into a first plug portion 11 and a second plug portion 12 by a predetermined plane P including the plug center axis C, both of the at least two large injection holes 51 are formed in the first plug portion 11. The ground electrode 6 protrudes into the auxiliary combustion chamber 50 from a fixed end portion 62 of the first plug portion 11 that is fixed to the housing 2 or the plug cover 5. As shown in FIG. 2, when viewed from the plug axial direction Z, in the first plug portion 11, the fixed end portion 62 is disposed between the extension lines 51L of the central axes of the at least two large injection holes 51 in the plug circumferential direction.

The spark plug 1 of this embodiment can be used as an ignition means in an internal combustion engine of an automobile, cogeneration, etc. As shown in FIG. 5, the mounting screw portion 21 formed on the outer peripheral surface of the housing 2 is screwed into the female screw portion of the plug hole 761 of the cylinder head 76, and the spark plug 1 is attached to the internal combustion engine 10. One end of the axial direction Z of the spark plug 1 is placed in the main combustion chamber 101 of the internal combustion engine 10. In the axial direction Z of the spark plug 1, the side exposed to the main combustion chamber 101 is called the tip side, and the opposite side is called the base side. The axial direction Z of the spark plug 1 is also referred to as the plug axial direction Z or simply the Z direction as appropriate. As shown in FIG. 2, the arrangement direction Y of the fixed end portion 62 and the tip protrusion portion 41 when viewed from the Z direction is also referred to as the Y direction as appropriate. The plug radial direction means the radial direction of a circle centered on the central axis C of the spark plug 1 on a plane perpendicular to the central axis C of the spark plug 1. In addition, the plug circumferential direction refers to the circumferential direction centered on the central axis C of the spark plug 1 on a plane perpendicular to the central axis C. In addition, the plug central axis C refers to the central axis C of the spark plug 1.

As shown in FIG. 1, the plug cover 5 is joined to the tip of the housing 2 by welding or the like. When the spark plug 1 is attached to the internal combustion engine, the plug cover 5 separates the auxiliary combustion chamber 50 from the main combustion chamber.

The auxiliary combustion chamber 50 includes the space on the inner periphery of the tip of the housing 2 around the tip protrusion 41 of the center electrode 4. The auxiliary combustion chamber 50 also includes a pocket portion 501, which will be described later. Therefore, the inner wall surface 502 of the auxiliary combustion chamber 50 includes the inner surface of the plug cover 5 as well as the inner surface of the tip of the housing 2.

As shown in FIG. 1, the insulator 3 has a tapered tip 31 that narrows toward the tip. A portion of the outer circumferential surface of the insulator 3 is engaged with a portion of the inner circumferential surface of the housing 2. The portion of the insulator 3 on the tip side of this engagement portion forms the tapered tip 31. An annular pocket 501 is formed between the outer surface of the tapered tip 31 and the inner surface of the housing 2. In other words, the pocket 501 is an annular space formed between the tapered tip 31 and the housing 2 in the plug radial direction.

The plug cover 5 also has a peripheral wall portion 54 that covers part of the outer periphery of the auxiliary combustion chamber 50, a bottom wall portion 55 that covers the tip side of the auxiliary combustion chamber 50, and a corner portion 56 that connects the peripheral wall portion 54 and the bottom wall portion 55. The large injection hole 51 and the small injection hole 52 are each formed in the corner portion 56.

In this embodiment, as shown in FIG. 2, the plug cover 5 is formed with two large injection holes 51 and three small injection holes 52. Each injection hole 51, 52 is formed in a substantially cylindrical shape. The inner diameter of the large injection hole 51 can be, for example, 1.2 to 1.4 times the inner diameter of the small injection hole 52. The opening area of the large injection hole 51 can be, for example, 1.4 to 2.0 times the opening area of the small injection hole 52. In this embodiment, the opening areas of the multiple large injection holes 51 are equal to each other.

As shown in Figures 1 and 3, each of the nozzle holes 51 and 52 opens at an angle to the Z direction so that it moves outward in the plug radial direction as it approaches the tip side. As shown in Figures 1 to 3, the nozzle holes 51 and 52 open radially.

As shown in FIG. 2, when viewed from the Z direction, the large injection holes 51 are formed such that the extension lines 51L of the central axes of the two large injection holes 51 sandwich the ground electrode 6 in the plug circumferential direction. In this embodiment, each large injection hole 51 is formed such that the extension line 51L of the central axis of the large injection hole 51 substantially passes through the plug central axis C.

As shown in FIG. 2, when the spark plug 1 is divided into two by a predetermined plane P including the plug center axis C, the large injection hole 51 is formed and the side where the fixed end 62 of the ground electrode 6 is located is the first plug portion 11. In other words, when viewed from the Z direction, the multiple large injection holes 51 are formed biased toward the first plug portion 11 side. In other words, all of the multiple large injection holes 51 are formed on one side of the spark plug 1 divided into two by the plane P.

As shown in Figures 2 and 3, an extension line 51L of the central axis of each large injection hole 51 intersects with the inner wall surface 502 of the auxiliary combustion chamber 50 in the second plug portion 12. As shown in Figure 3, in a cross section including both the plug central axis C and the extension line 51L of the central axis of the large injection hole 51, the angle α1 at which the extension line 51L intersects with the inner wall surface 502 of the auxiliary combustion chamber 50 is an obtuse angle on the base end side of the extension line 51L.

As shown in FIG. 4, when viewed from the Z direction, a straight line along the Y direction is defined as a straight line YL. When viewed from the Z direction, the inclination angles α2 of the extension lines 51L of the central axes of the large nozzle holes 51 with respect to the straight line YL are equal to each other. In other words, the inclination angles of the extension lines 51L of the central axes of the large nozzle holes 51 with respect to the protruding direction of the ground electrode 6 when viewed from the Z direction are equal to each other. The angle α2 can be, for example, 15° to 60°. Furthermore, the angle between the extension lines 51L of the central axes of the large nozzle holes 51 when viewed from the Z direction can be, for example, 30° to 120°.

In addition, in this embodiment, three small injection holes 52 are formed in the second plug portion 12. However, the number and arrangement of the small injection holes 52 are not particularly limited. (See embodiments 8 to 10 described below.)

In this embodiment, as shown in FIG. 2, one small injection hole 52 is a protruding side injection hole 521 through which an extension line 6L of the protruding direction of the ground electrode 6 passes when viewed from the plug axial direction Z. When viewed from the Z direction, the fixed end portion 62 of the ground electrode 6 and the protruding side injection hole 521 are arranged on opposite sides of the tip protruding portion 41 of the center electrode 4. In other words, when viewed from the Z direction, the fixed end portion 62 and the protruding side injection hole 521 are arranged on opposite sides of the auxiliary combustion chamber 50.

As shown in FIG. 2, the ground electrode 6 is fixed to the first plug portion 11 so as to extend along the plug radial direction when viewed from the Z direction. In this embodiment, the fixed end portion 62 of the ground electrode 6 is fixed to the housing 2 of the first plug portion 11. After the ground electrode 6 is fixed to the housing 2, the plug cover 5 is fixed to the housing 2, thereby manufacturing the spark plug 1 of this embodiment.

The base end surface 61 of the ground electrode 6 has a flat surface in the longitudinal direction of the ground electrode 6, at least from the portion facing the tip protruding portion 41 in the Z direction to the protruding end portion 63.

In this embodiment, the ground electrode 6 has a generally rectangular prism shape. In other words, the ground electrode 6 has four flat side surfaces, one of which is the base end surface 61. In other words, the entire base end surface 61 is a flat surface. In addition, the base end surface 61 faces the tip surface 411 of the center electrode 4 in the Z direction, as shown in FIG. 1.

The base end surface 61 of the ground electrode 6 also has an inclined surface 611. The inclined surface 611 is inclined with respect to the plug axial direction Z so as to move toward the tip side as it approaches the protruding end portion 63 of the ground electrode 6.

In this embodiment, the entire base end surface 61 is an inclined surface 611. In other words, the tip surface 411 of the center electrode 4 and the inclined surface 611 face each other in the Z direction, forming a discharge gap G. It is also possible to join tips to the tip surface 411 of the center electrode 4 and the base end surface 61 of the ground electrode 6, which face each other in the Z direction (not shown). In other words, a discharge gap G can be formed between the tip joined to the tip surface 411 of the center electrode 4 and the tip joined to the base end surface 61 of the ground electrode 6. The tip can be made of a precious metal such as iridium or platinum, or an alloy mainly composed of these metals.

Next, an internal combustion engine 10 equipped with the above-mentioned spark plug 1 is shown in FIGS.
The internal combustion engine 10 has a main combustion chamber 101, an intake valve 72 and an exhaust valve 73 provided in the main combustion chamber 101, and a spark plug 1. The spark plug 1 is arranged so that the outer surface 53 of the plug cover 5 faces the main combustion chamber 101. As shown in Figure 6, the spark plug 1 is arranged so that an outer opening 511 of at least one large injection hole 51 faces the intake valve 72 side when viewed from the plug axial direction Z.

The internal combustion engine 10 of this embodiment includes a cylinder head 76, a cylinder block 75, and a piston 74 that reciprocates in the cylinder 70, as shown in FIG. 5. The cylinder head 76, the cylinder block 75, and the piston 74 form a main combustion chamber 101. The cylinder head 76 is formed with an intake port 721 and an exhaust port 731, each of which is provided with an intake valve 72 or an exhaust valve 73. A spark plug 1 is attached between the intake port 721 and the exhaust port 731 in the cylinder head 76. In detail, the spark plug 1 is disposed in a position surrounded by the two intake ports 721 and the two exhaust ports 731 in the cylinder head 76, as shown in FIG. 6.

As shown in FIG. 5, the intake port 721 and the exhaust port 731 are inclined with respect to the direction of movement of the piston 74 so that their opening direction faces the central axis of the main combustion chamber 101. In addition, the base end surface of the main combustion chamber 101 is inclined so that it faces the tip side as it moves away from the spark plug 1.

In the internal combustion engine 10, the intake stroke, compression stroke, expansion stroke, and exhaust stroke are repeated in sequence with the reciprocating motion of the piston 74. During the intake stroke of the internal combustion engine 10, gas is introduced into the main combustion chamber 101 from the two intake ports 721, and during the exhaust stroke, gas in the main combustion chamber 101 is exhausted from the two exhaust ports 731. Due to the way the airflow is introduced during the intake stroke, a certain airflow is formed in the main combustion chamber 101, and this airflow remains even during the compression stroke.

In the main combustion chamber 101, a tumble flow is formed, which is an airflow around an axis perpendicular to the sliding direction of the piston 74, as shown by the arrow AF1 in FIG. 5. This airflow AF1 is directed from the intake valve 72 side to the exhaust valve 73 side near the tip of the spark plug 1 in the main combustion chamber 101, as shown in FIG. 5 and FIG. 6. More specifically, as shown in FIG. 6, when viewed from the plug axial direction Z, the airflow AF1 along the direction from the midpoint between the two intake ports 721 to the midpoint between the two exhaust ports 731 is the main airflow near the tip of the spark plug 1.

The airflow in the main combustion chamber 101 is not always constant, but may vary between cycles or between different timings within one cycle. However, the direction of the main airflow, particularly the direction of the airflow at the ignition timing, is roughly fixed, and the above-mentioned airflow AF1 refers to the main airflow at the ignition timing. And when we say "airflow in the main combustion chamber 101," we mean the airflow AF1 near the tip of the spark plug 1 at the above-mentioned ignition timing, unless otherwise specified. And when we simply say "upstream side" and "downstream side," we mean the upstream side and downstream side of the above-mentioned "airflow in the main combustion chamber 101," unless otherwise specified.

In the internal combustion engine 10 configured as described above, during the compression stroke, gas from the main combustion chamber 101 is introduced into the auxiliary combustion chamber 50 through the nozzles 51 and 52. Here, the large nozzle 51 has a larger opening area than the small nozzle 52, and as shown in Figures 5 and 6, the outer opening 511 of the large nozzle 51 faces the upstream side of the air flow AF1 of the main combustion chamber 101. Therefore, more gas is introduced into the auxiliary combustion chamber 50 through the large nozzle 51 than through the small nozzle 52.

During the compression stroke, the main flow of gas introduced into the auxiliary combustion chamber 50 through the large nozzle hole 51, as shown by the arrow AF2 in FIG. 7, moves toward the inner wall surface 502 on the downstream side of the auxiliary combustion chamber 50, moves toward the base end side along the inner wall surface 502, and is introduced into the downstream pocket portion 501. The main flow of gas that has entered the downstream pocket portion 501 turns toward the upstream side in the pocket portion 501, and moves toward the tip side along the upstream pocket portion 501. In other words, an airflow (i.e., a tumble flow) around an axis in a direction perpendicular to the Z direction is formed. The airflow AF2 moving toward the tip side is guided by the base end surface 61 of the ground electrode 6 and moves toward the discharge gap G. Therefore, as shown in FIG. 7, the discharge S formed in the discharge gap G during the compression stroke is stretched by the airflow AF2 as shown in FIG. 8. The above airflow AF2 is merely the main flow, and not all gas necessarily flows in this way.

In other words, the gas flow AF2 introduced into the auxiliary combustion chamber 50 through the large nozzle hole 51 flows toward the inner wall surface 502 of the second plug portion 12 and is introduced into the pocket portion 501 of the second plug portion 12. The air flow AF2 introduced into the pocket portion 501 changes direction toward the first plug portion 11 and flows toward the base end surface 61 of the ground electrode 6, that is, toward the tip side. The air flow AF2 is then guided by the base end surface 61 of the ground electrode 6 toward the discharge gap G.

Next, the effects of this embodiment will be described.
In the above spark plug 1 for an internal combustion engine, when viewed from the plug axial direction Z, in the first plug portion 11, the fixed end portion 62 of the ground electrode 6 is disposed between extension lines 51L of the central axes of at least two large injection holes 51 in the plug circumferential direction. This makes it easier for the airflow formed in the auxiliary combustion chamber 50 to flow toward the discharge gap G by being guided by the base end surface 61 of the ground electrode 6. This makes it easier for the discharge formed in the discharge gap G to extend. As a result, it is possible to improve ignition performance.

That is, the opening area of the large injection hole 51 is larger than the opening area of the small injection hole 52. Therefore, during the compression stroke, the gas flow introduced into the auxiliary combustion chamber 50 through the large injection hole 51 tends to be stronger than the gas flow introduced into the auxiliary combustion chamber 50 through the small injection hole 52. In addition, the large injection hole 51 opens at an angle to the Z direction so that it moves toward the outside of the plug radial direction as it moves toward the tip side. Therefore, the strong air flow introduced into the auxiliary combustion chamber 50 through the large injection hole 51 tends to move toward the inner wall surface 502 of the auxiliary combustion chamber 50 of the second plug portion 12 and toward the base end side of the auxiliary combustion chamber 50. Then, the air flow toward the base end side of the auxiliary combustion chamber 50 changes direction and tends to move toward the tip side on the first plug portion 11 side. Therefore, the air flow is guided by the base end surface 61 of the ground electrode 6 of the first plug portion 11 and tends to move toward the discharge gap G. As a result, the discharge generated in the discharge gap G is extended, improving ignition performance.

In addition, each large nozzle hole 51 is formed so that the angle α2 (see FIG. 4) is equal to each other. This makes it easier to reliably form a tumble flow in the auxiliary combustion chamber 50. This makes it easier to reliably form an airflow that is guided to the base end surface 61 of the ground electrode 6. As a result, the discharge generated in the discharge gap G is easier to reliably extend.

Also, as shown in FIG. 7, during the compression stroke, the discharge S formed in the discharge gap G tends to extend in the Y direction opposite the side where the fixed end 62 is located, as shown in FIG. 8, due to the airflow AF2 guided by the base end surface 61 of the ground electrode 6. In other words, the discharge S tends to extend toward the second plug portion 12. The discharge S that extends toward the second plug portion 12 tends to extend toward the base end side due to the airflow AF2 toward the base end side of the second plug portion 12. Therefore, the combustion of the mixture grows from the base end side area in the auxiliary combustion chamber 50, and the pressure in the auxiliary combustion chamber 50 can be increased at the time when the flame reaches the nozzle holes 51 and 52. As a result, the flame jet to the main combustion chamber 101 can be strengthened.

The protruding side nozzle hole 521 is also inclined in the Z direction so that it opens radially outward in the plug direction toward the tip side. Therefore, as shown in FIG. 8, the discharge S that extends toward the second plug portion 12 during the compression stroke is also likely to extend toward the base end side by the airflow AF2 introduced into the auxiliary combustion chamber 50 through the protruding side nozzle hole 521. As a result, the combustion of the mixture can be developed starting from a region closer to the base end in the auxiliary combustion chamber 50.

The base end surface 61 of the ground electrode 6 is a flat surface. Therefore, the airflow AF2 in the auxiliary combustion chamber 50 is more easily guided by the base end surface 61. As a result, the discharge generated in the discharge gap G is more easily extended.

The base end surface 61 of the ground electrode 6 has an inclined surface 611. Therefore, the inflow angle of the airflow in the auxiliary combustion chamber 50 with respect to the base end surface 61 tends to be an obtuse angle. Therefore, the base end surface 61 makes it easier to guide the airflow toward the discharge gap G. Therefore, the discharge formed in the discharge gap G is easier to extend. As a result, ignition performance can be further improved.

The internal combustion engine 10 has the above-mentioned spark plug 1. The spark plug 1 is arranged so that the outer opening 511 of at least one large nozzle hole 51 faces the intake valve 72 side when viewed from the plug axial direction Z. This allows a large flame to be ejected from the auxiliary combustion chamber 50 to the intake valve 72 side of the main combustion chamber 101 through the large nozzle hole 51 when viewed from the plug axial direction Z. This improves the ignition ability of the mixture on the intake valve 72 side in the main combustion chamber 101 when viewed from the plug axial direction Z. This allows the mixture in the entire main combustion chamber 101 to be burned in a balanced manner. As a result, it is possible to suppress combustion abnormalities that cause knocking, etc.

That is, when viewed from the Z direction, the intake valve 72 side, which is provided with the intake port 721 that introduces relatively low-temperature gas into the main combustion chamber 101, tends to be at a low temperature compared to the exhaust valve 73 side, which is provided with the exhaust port 731 that discharges high-temperature gas. Therefore, when viewed from the Z direction, the combustion of the mixture on the intake valve 72 side in the main combustion chamber 101 is delayed compared to the mixture on the exhaust valve 73 side in the main combustion chamber 101, which may cause the balance of the combustion of the mixture in the main combustion chamber 101 to be poor. However, in this embodiment, as described above, when viewed from the Z direction, a large flame can be ejected from the auxiliary combustion chamber 50 to the intake valve 72 side of the main combustion chamber 101. Therefore, the mixture in the entire main combustion chamber 101 can be burned in a balanced manner, and the local residue of unburned fuel can be suppressed. As a result, it is possible to suppress combustion abnormalities that cause knocking, etc.

In addition, the outer opening 511 of the large nozzle hole 51 faces the intake valve 72 when viewed from the Z direction. Therefore, the outer opening 511 of the large nozzle hole 51 tends to face the upstream side of the airflow in the main combustion chamber 101. Therefore, gas is easily introduced into the auxiliary combustion chamber 50 through the large nozzle hole 51. Therefore, a strong airflow is easily generated in the auxiliary combustion chamber 50. As a result, the discharge S generated in the discharge gap G can be further extended.

As described above, this embodiment provides a spark plug 1 for an internal combustion engine that can improve ignition performance, and an internal combustion engine 10 equipped with the same.

(Embodiment 2)
As shown in FIG. 9, this embodiment is an embodiment in which the opening direction of the large injection hole 51 is changed from that of the first embodiment.
That is, the large injection hole 51 is formed so that an extension line 51L of the central axis of the large injection hole 51 does not pass through the tip protrusion 41. When viewed from the plug axial direction Z, the intersection point of the extension lines 51L of the central axes of at least two large injection holes 51 is defined as intersection point A. When viewed from the plug axial direction Z, intersection point A and the large injection hole 51 are located on opposite sides of each other in the Y direction, with the tip protrusion 41 in between.

In this embodiment, as shown in FIG. 9, when viewed from the Z direction, the intersection point A is located on an extension line 6L of the protruding direction of the ground electrode 6.
The rest is the same as in embodiment 1. Note that, among the reference symbols used in embodiment 2 and onwards, the reference symbols that are the same as those used in the above-mentioned embodiments represent the same components, etc. as those in the above-mentioned embodiments, unless otherwise specified.

The large nozzle hole 51 is formed so that an extension line 51L of the central axis of the large nozzle hole 51 does not pass through the tip protrusion 41. When viewed from the Z direction, the intersection point A and the large nozzle hole 51 are located on opposite sides of the tip protrusion 41 in the Y direction. Therefore, the airflow of gas introduced into the auxiliary combustion chamber 50 through the large nozzle hole 51 is less likely to be blocked by the tip protrusion 41, and a tumble flow is more likely to be formed. Therefore, the airflow guided to the base end surface 61 of the ground electrode 6 can be strengthened. As a result, the discharge formed in the discharge gap G can be further extended.
In addition, the second embodiment has the same effects as the first embodiment.

(Embodiment 3)
As shown in FIGS. 10 to 15, this embodiment is an embodiment in which the position of the protruding end portion 63 of the ground electrode 6 is changed from that of the second embodiment.

In this embodiment, as shown in FIG. 10, at least one small nozzle hole 52 is a protruding side nozzle hole 521 through which an extension line 6L of the protruding direction of the ground electrode 6 passes when viewed from the plug axial direction Z. When viewed from the plug axial direction Z, at least a part of the protruding end portion 63 of the ground electrode 6 is disposed between the tip protruding portion 41 and the protruding side nozzle hole 521.

In addition, at least a portion of the protruding end 63 is disposed between the tip protruding portion 41 and the inner wall surface 502 of the peripheral wall portion 54 of the plug cover 5 on the longitudinal extension line of the ground electrode 6 when viewed from the Z direction.

When viewed from the plug axial direction Z, the protruding end 63 is positioned closer to the protruding side nozzle hole 521 than the tip protruding portion 41.

In other words, as shown in FIG. 11, when viewed from the Z direction, the shortest distance D1 from the protruding end 63 to the protruding side nozzle hole 521 is shorter than the shortest distance D2 from the protruding end 63 to the tip protruding portion 41.

When viewed from the Z direction, the shortest distance D3 from the protruding end 63 to the inner wall surface 502 of the peripheral wall portion 54 of the plug cover 5 on the longitudinal extension line of the ground electrode 6 is shorter than the shortest distance D2 from the protruding end 63 to the tip protruding portion 41.

As shown in FIG. 12, the ground electrode 6 has a portion closer to the protruding end 63 than the fixed end 62 in the longitudinal direction of the ground electrode 6, and the width in the Z direction becomes smaller as it approaches the protruding end 63. The surface on the tip side of the tapered portion of the ground electrode 6 is formed along the inner wall surface 502 of the bottom wall portion 55 of the plug cover 5.

As shown in FIG. 13, the straight line connecting the base end of the outer opening 522 of the projection side nozzle 521 and the tip end of the tip projection 41 at the shortest distance is defined as line L1. The projection end 63 is disposed on the tip side of line L1.

The straight line connecting the center of the outer opening 522 of the projection-side nozzle hole 521 and the tip of the tip projection 41 at the shortest distance is defined as line L2. As shown in FIG. 13, the projection end 63 is positioned on the tip side of line L2.

The straight line connecting the tip of the inner opening 523 of the projection side nozzle hole 521 and the tip of the tip projection portion 41 at the shortest distance is defined as line L3. As shown in FIG. 13, the projection end portion 63 is positioned on the tip side of line L3.

The discharge gap G is formed on the tip side of the tip of the housing 2. That is, the tip protruding portion 41 of the center electrode 4 protrudes on the tip side of the tip of the housing 2.
The rest is the same as in the second embodiment.

In this embodiment of the spark plug 1, when viewed from the plug axial direction Z, at least a portion of the protruding end 63 of the ground electrode 6 is disposed between the tip protruding portion 41 and the protruding side nozzle hole 521. Therefore, during the expansion stroke, the airflow discharged from the auxiliary combustion chamber 50 via the protruding side nozzle hole 521 is guided to the base end surface 61 of the ground electrode 6 and easily passes through the discharge gap G.

In this regard, let us consider the expansion stroke of an internal combustion engine (not shown) equipped with the spark plug 1 of this embodiment. During the expansion stroke, the piston moves toward the tip end, causing the main combustion chamber to become negative pressure relative to the auxiliary combustion chamber 50. This causes gas to be discharged from the auxiliary combustion chamber 50 to the main combustion chamber through the nozzle holes 51 and 52. The airflow AF2 formed in the auxiliary combustion chamber 50 as the gas is discharged through the protruding side nozzle hole 521 is guided to the base end surface 61 of the ground electrode 6 and heads toward the protruding side nozzle hole 521, as shown in Figures 14 and 15. The airflow AF2 guided to the base end surface 61 of the ground electrode 6 then passes through the discharge gap G.

Therefore, as shown in FIG. 14, during the expansion stroke, the discharge S generated in the discharge gap G is easily extended toward the protruding side nozzle hole 521 by the airflow AF2 as shown in FIG. 15, improving ignition in the auxiliary combustion chamber 50. In addition, since the ignition position can be easily brought closer to the protruding side nozzle hole 521, for example, under operating conditions where the temperature of the auxiliary combustion chamber 50 is low, cold loss is suppressed and the flame jet to the main combustion chamber can be strengthened. Furthermore, since the discharge S or discharge plasma or initial flame generated in the discharge gap G is easily ejected from the protruding side nozzle hole 521, ignition in the main combustion chamber can be improved.

Also, as shown in FIG. 14, during the expansion stroke, the starting point SP on the ground electrode 6 side of the discharge S generated in the discharge gap G tends to move toward the protrusion side nozzle hole 521 due to the airflow AF2 that is guided through the protrusion side nozzle hole 521, as shown in FIG. 15. Therefore, the discharge S tends to extend toward the protrusion side nozzle hole 521. As a result, ignition performance can be improved.

When viewed from the Z direction, the protruding end 63 is positioned closer to the protruding side nozzle hole 521 than the tip protruding portion 41. Therefore, during the expansion stroke, the airflow discharged from the auxiliary combustion chamber 50 through the protruding side nozzle hole 521 is more easily guided by the base end surface 61 of the ground electrode 6. Therefore, the discharge S generated in the discharge gap G is more easily extended toward the protruding side nozzle hole 521. As a result, ignition performance can be further improved.

The protruding end 63 is positioned further forward than the straight line L1. Therefore, during the expansion stroke, the discharge generated in the discharge gap G is not short-circuited by the protruding end 63, and is likely to reliably extend toward the protruding side nozzle hole 521 and the main combustion chamber. As a result, ignition performance can be reliably improved.

In other words, let us assume that the protruding end 63 is located closer to the base end than the straight line L1. In this case, the discharge extending toward the protruding side nozzle hole 521 is likely to be short-circuited by the protruding end 63 when it tries to extend further toward the protruding side nozzle hole 521 than the protruding end 63. On the other hand, in this embodiment, the protruding end 63 is disposed in the above-mentioned position. Therefore, as shown in FIG. 14, the discharge S generated in the discharge gap G during the expansion stroke is unlikely to be short-circuited by the protruding end 63 even if it extends further toward the protruding side nozzle hole 521 than the protruding end 63, as shown in FIG. 15. As a result, ignition performance can be improved.

In addition, because the protruding end 63 is positioned as described above, the starting point SP of the discharge S on the ground electrode 6 side is likely to move to the inner surface of the protruding side nozzle hole 521, as shown in FIG. 15. Furthermore, the starting point SP is likely to move toward the outer opening 522 of the protruding side nozzle hole 521. This makes it easier to extend the discharge S toward the main combustion chamber. As a result, the ignition ability of the main combustion chamber can be further improved.

In addition, the protruding end 63 is positioned further forward than the straight line L2. Therefore, the discharge generated in the discharge gap G is not short-circuited by the protruding end 63, and is more likely to extend toward the protruding side nozzle hole 521 and the main combustion chamber.

In addition, the protruding end 63 is positioned further forward than the straight line L3. Therefore, the discharge generated in the discharge gap G is not short-circuited by the protruding end 63, and is more likely to extend toward the protruding side nozzle hole 521 and the main combustion chamber.

The discharge gap G is formed closer to the tip of the housing 2 than the tip. Therefore, it is easy to check the discharge gap G formed between the ground electrode 6 and center electrode 4 fixed to the housing 2 before fixing the plug cover 5 to the housing 2. This makes it easy to adjust the discharge gap G. As a result, the spark plug 1 can be easily manufactured.

The ground electrode 6 has a tapered shape at a portion closer to the protruding end 63 than the fixed end 62 in the longitudinal direction of the ground electrode 6. The surface of the ground electrode 6 on the bottom wall portion 55 side of the plug cover 5 is inclined with respect to the longitudinal direction of the ground electrode. This makes it easy to position the protruding end 63 on the tip side of the straight line L1. As a result, the spark plug 1 of this embodiment can be easily manufactured.
In addition, the second embodiment has the same effects as the second embodiment.

(Embodiment 4)
As shown in FIG. 16, this embodiment is an embodiment in which the shape of the ground electrode 6 is modified from that of the third embodiment.

As shown in Figure 16, a portion of the base end surface 61 of the ground electrode 6 that is closer to the protruding end 63 than the fixed end 62 in the longitudinal direction of the ground electrode 6 has a larger inclination angle with respect to a plane perpendicular to the Z direction than other portions of the base end surface 61.
The other configurations and effects are the same as those of the third embodiment.

(Embodiment 5)
As shown in FIG. 17, this embodiment is an embodiment in which the shape of the tip portion of the center electrode 4 is modified from that of the first embodiment.
That is, the tip surface 411 of the center electrode 4 is inclined along the inclined surface 611 of the ground electrode 6 .

In this embodiment, the tip surface 411 of the center electrode 4 and the inclined surface 611 of the ground electrode 6 are both flat surfaces. As shown in Fig. 17, the flat surfaces are arranged substantially parallel to each other and opposed to each other, thereby forming a discharge gap G.
The rest is the same as in the first embodiment.

The tip end surface 411 of the center electrode 4 is inclined along the inclined surface 611 of the ground electrode 6. Therefore, the tip end surface 411 of the center electrode 4 and the inclined surface 611 of the ground electrode 6 can be made substantially parallel to each other. This makes it easy to disperse the starting points of discharge on the center electrode 4 side. This makes it possible to suppress localized wear of the center electrode 4 and to suppress the increase in the distance of the discharge gap G. As a result, the life of the spark plug 1 can be extended.
In addition, the second embodiment has the same effects as the first embodiment.

(Embodiment 6)
As shown in FIG. 18, this embodiment is an embodiment in which the shape of the tip portion of the center electrode 4 is modified from that of the fifth embodiment.

In this embodiment, the tip of the center electrode 4 has a tapered shape with a diameter that decreases toward the tip side, as shown in FIG. 18. The tip of the center electrode 4 having a tapered shape has a substantially truncated cone shape. The tip of the center electrode 4 can be substantially conical, substantially square pyramidal, substantially square pyramidal, etc.

The tapered surface 412 at the tapered tip of the center electrode 4 is formed in an annular shape. A part of the tapered surface 412 is inclined along the inclined surface 611 of the ground electrode 6. A discharge gap G is formed between the tapered surface 412 and the inclined surface 611 of the ground electrode 6.
The rest is the same as in the fifth embodiment.

In this embodiment, a discharge gap G is formed between the tapered surface 412 and the inclined surface 611. Therefore, in this embodiment as well, local wear of the center electrode 4 can be suppressed, and the distance of the discharge gap G can be suppressed from increasing.
In addition, the second embodiment has the same effects as the fifth embodiment.

(Embodiment 7)
In this embodiment, as shown in FIG. 19, a base end surface 61 of a ground electrode 6 has a concave surface recessed toward the tip side.

As shown in FIG. 19, the base end surface 61 of the ground electrode 6 has a concave surface that is recessed toward the tip side when viewed from the protruding direction of the ground electrode 6.

The base end surface 61 of the ground electrode 6 has a concave surface at least in a portion facing the tip end of the center electrode in the Z direction and extending from that portion to a part on the fixed end 62 side. In this embodiment, the entire base end surface 61 is concave.
The rest is the same as in the first embodiment.

In this embodiment, the base end surface 61 of the ground electrode 6, which has a concave shape, can easily guide the airflow along the longitudinal direction. Therefore, the airflow can be more easily guided to the discharge gap G.
In addition, the second embodiment has the same effects as the first embodiment.

(Embodiment 8)
As shown in FIG. 20, this embodiment has three large nozzle holes 51.

In this embodiment, the plug cover 5 has three large nozzle holes 51 and three small nozzle holes 52, as shown in FIG. 20.

In this embodiment, the multiple large injection holes 51 are formed so that the extension line 51L of the central axis of each large injection hole 51 passes through the small injection hole 52 when viewed from the Z direction. In other words, each large injection hole 51 is formed so as to face the small injection hole 52 in the plug radial direction when viewed from the Z direction. Each injection hole 51, 52 is arranged at equal intervals in the plug circumferential direction when viewed from the Z direction.

The three large nozzle holes 51 are formed in the first plug portion 11. The three small nozzle holes 52 are formed in the second plug portion 12.

The width of the ground electrode 6 is approximately the same as the diameter of the tip of the tip projection 41 .
The other configurations and effects are the same as those of the first embodiment.

(Embodiment 9)
In this embodiment, as shown in FIG. 21, the injection holes 51 and 52 are formed biased toward the first plug portion 11 side.

21 , the plug cover 5 is formed with three large injection holes 51 and three small injection holes 52. The three large injection holes 51 are formed in the first plug portion 11. The two small injection holes 52 are each formed in both the first plug portion 11 and the second plug portion 12. In addition, the projection side injection hole 521, which is one of the small injection holes 52, is formed in the second plug portion 12.
The other configurations and effects are the same as those of the eighth embodiment.

(Embodiment 10)
As shown in FIG. 22, this embodiment is an embodiment in which the number of small injection holes 52 is changed from that of the third embodiment.

In this embodiment, the plug cover 5 is formed with two large injection holes 51 and one small injection hole 52, as shown in FIG.
The other configurations and effects are the same as those of the third embodiment.

The position where the small injection hole 52 is formed is not necessarily limited to the second plug portion 12, but may be the first plug portion 11. It is also possible to configure the second plug portion 12 so that the small injection hole 52 does not exist.

(Embodiment 11)
In this embodiment, as shown in FIGS. 23 to 27, the number of injection holes 57 formed in the first plug portion 13 is made greater than the number of injection holes 57 formed in the second plug portion 14.

In this embodiment of the spark plug 1, the plug cover 5 has multiple injection holes 57 that connect the auxiliary combustion chamber 50 to the outside, as shown in Figures 23 to 26. The ground electrode 6 protrudes into the auxiliary combustion chamber 50 from a fixed end 62 that is fixed to the housing 2 or the plug cover 5.

The spark plug 1 is divided into two parts, a first plug part 13 including a fixed end 62, and a second plug part 14, by a plane P2 that includes the plug center axis C and is perpendicular to the protruding direction of the ground electrode 6 when viewed from the plug axial direction Z. At this time, injection holes 57 are formed in both the plug cover 5 of the first plug part 13 and the plug cover 5 of the second plug part 14.

The nozzle holes 57 formed in the first plug portion 13 are referred to as first nozzle holes 571, and the nozzle holes 57 formed in the second plug portion 14 are referred to as second nozzle holes 572. In this case, the number of first nozzle holes 571 is greater than the number of second nozzle holes 572.

As shown in FIG. 24, the first injection hole 571 opens at an angle with respect to the plug axial direction Z so that it is closer to the tip side and is more outward in the plug radial direction. As shown in FIG. 23, when viewed from the plug axial direction Z, in the first plug part 13, the fixed end 62 is disposed between the extension lines 571L of the central axes of at least two first injection holes 571 in the plug circumferential direction.

In this embodiment, the plug cover 5 is formed with two first injection holes 571 and one second injection hole 572. In this embodiment, the inner diameter of the first injection hole 571 and the inner diameter of the second injection hole 572 are equal in size. In other words, the opening area of each of the first injection holes 571 and the opening area of the second injection hole 572 are equal in size. In addition, the total opening area of all the first injection holes 571 is greater than the total opening area of all the second injection holes 572.

In addition, in this embodiment, the first injection hole 571 is formed so that the extension line 571L of the central axis of the first injection hole 571 substantially intersects with the plug central axis C.

As shown in FIG. 26, when viewed from the Z direction, the inclination angles α3 of the extension lines 571L of the central axes of the first nozzle holes 571 relative to the straight line YL are equal to each other. In other words, when viewed from the Z direction, the inclination angles of the extension lines 571L relative to the protruding direction of the ground electrode 6 are equal to each other. The angle α3 can be, for example, 15° to 60°. When viewed from the Z direction, the angles between the extension lines 571L can be, for example, 30° to 120°.

In addition, in this embodiment, at least one second nozzle hole 572 is a protruding side nozzle hole 573 through which an extension line 6L of the protruding direction of the ground electrode 6 passes when viewed from the plug axial direction Z, as shown in FIG. 23. When viewed from the plug axial direction Z, at least a portion of the protruding end portion 63 is disposed between the tip protruding portion 41 and the protruding side nozzle hole 573. In addition, the protruding end portion 63 is disposed in the second plug portion 14.

As shown in FIG. 25, the protruding side nozzle hole 573 opens at an angle with respect to the Z direction so that it is closer to the tip side and is more outward in the plug radial direction. Also, as shown in FIG. 23 and FIG. 26, when viewed from the Z direction, the fixed end portion 62 of the ground electrode 6 and the protruding side nozzle hole 573 are arranged on opposite sides of the tip protruding portion 41 of the center electrode 4.

In addition, as shown in FIG. 25, the base end surface 61 of the ground electrode 6 has an inclined surface 611 that is inclined with respect to the plug axial direction Z so as to move toward the tip side as it approaches the protruding end portion 63 of the ground electrode 6.

Next, an internal combustion engine 10 equipped with the above-described spark plug 1 will be described.
27 , in the internal combustion engine 10, the spark plug 1 is arranged such that, when viewed from the plug axial direction Z, an outer opening 575 of at least one first nozzle hole 571 faces the intake valve 72. In this embodiment, the spark plug 1 is arranged such that, when viewed from the Z direction, the outer openings 575 of all the first nozzle holes 571 face the intake valve 72.
The rest is the same as in the first embodiment.

When viewed from the plug axial direction Z, the first plug portion 13 of the spark plug 1 has a fixed end 62 of the ground electrode 6 disposed between the extension lines 571L of the central axes of at least two first nozzle holes 571 in the plug circumferential direction. The number of first nozzle holes 571 is greater than the number of second nozzle holes 572. This makes it easier for the airflow formed in the auxiliary combustion chamber 50 to flow toward the discharge gap G by being guided by the base end surface 61 of the ground electrode 6. This makes it easier for the discharge formed in the discharge gap G to extend. As a result, ignition performance can be improved.

As described above, the number of first injection holes 571 is greater than the number of second injection holes 572. Therefore, during the compression stroke, the gas flow introduced into the auxiliary combustion chamber 50 from the first plug portion 13 side through the first injection hole 571 tends to be stronger than the gas flow introduced into the auxiliary combustion chamber 50 from the second plug portion 14 side through the second injection hole 572. In addition, the first injection hole 571 opens at an angle to the Z direction so as to move toward the outside of the plug radial direction as it moves toward the tip side. Therefore, the strong air flow introduced into the auxiliary combustion chamber 50 from the first plug portion 13 side through the first injection hole 571 tends to move toward the inner wall surface 502 of the auxiliary combustion chamber 50 of the second plug portion 14 and toward the base end side of the auxiliary combustion chamber 50. And the air flow toward the base end side of the auxiliary combustion chamber 50 changes direction and tends to move toward the tip side on the first plug portion 13 side. Therefore, the airflow is guided by the base end surface 61 of the ground electrode 6 of the first plug portion 13 and tends to flow toward the discharge gap G. As a result, the discharge generated in the discharge gap G is extended, improving ignition performance.

The first nozzle holes 571 are also formed so that the angle α3 (see FIG. 26) is equal to each other. This makes it easier to reliably form a tumble flow in the auxiliary combustion chamber 50. This makes it easier to reliably form an airflow that is guided to the base end surface 61 of the ground electrode 6. As a result, the discharge generated in the discharge gap G is easier to reliably extend.

The base end surface 61 of the ground electrode 6 has an inclined surface 611. Therefore, the base end surface 61 makes it easier to guide the airflow toward the discharge gap G. Therefore, the discharge formed in the discharge gap G is easier to extend. As a result, the ignition ability can be further improved.

At least one second nozzle hole 572 is a protruding side nozzle hole 573. When viewed from the plug axial direction Z, at least a part of the protruding end portion 63 is disposed between the tip protruding portion 41 and the protruding side nozzle hole 573. Therefore, during the expansion stroke, the starting point on the ground electrode 6 side of the discharge generated in the discharge gap G tends to move toward the protruding side nozzle hole 573 due to the airflow guided through the protruding side nozzle hole 573. Therefore, the discharge tends to extend toward the protruding side nozzle hole 573. As a result, ignition performance can be improved.

The internal combustion engine 10 has the spark plug 1. The spark plug 1 is arranged such that, when viewed from the plug axial direction Z, the outer opening 575 of at least one first nozzle hole 571 faces the intake valve 72. Therefore, the outer opening 575 of the first nozzle hole 571 tends to face the upstream side of the airflow formed in the main combustion chamber 101. This makes it easier for the airflow to be introduced from the main combustion chamber 101 to the auxiliary combustion chamber 50 through the first nozzle hole 571. Therefore, the discharge generated in the discharge gap G is easily extended by the airflow introduced into the auxiliary combustion chamber 50 through the first nozzle hole 571. As a result, ignition performance can be reliably improved.

The spark plug 1 is arranged so that the outer openings 575 of all the first nozzle holes 571 face the intake valve 72 side when viewed from the Z direction. In addition, the total opening area of all the first nozzle holes 571 is larger than the total opening area of all the second nozzle holes 572. As a result, when viewed from the Z direction, it is possible to eject a large amount of flame from the auxiliary combustion chamber 50 to the intake valve 72 side of the main combustion chamber 101 through the first nozzle hole 571. In other words, when viewed from the Z direction, it is possible to eject a large amount of flame to the intake valve 72 side of the main combustion chamber 101 compared to the exhaust valve 73 side of the main combustion chamber 101. Therefore, it is possible to improve the ignition property of the mixture on the intake valve 72 side in the main combustion chamber 101 when viewed from the Z direction. Therefore, it is possible to burn the mixture in the entire main combustion chamber 101 in a balanced manner. As a result, it is possible to suppress combustion abnormalities that cause knocking and the like.
In addition, the second embodiment has the same effects as the first embodiment.

(Embodiment 12)
As shown in FIG. 28, this embodiment is an embodiment in which the number of injection holes 57 is changed from that of the eleventh embodiment.

In this embodiment, as shown in FIG. 28, three first injection holes 571 and two second injection holes 572 are formed in the plug cover 5. Of the three first injection holes 571, one first injection hole 571 is a tip injection hole 576 formed on the tip side of the ground electrode 6. When viewed from the Z direction, the ground electrode 6 and the tip injection hole 576 overlap each other.

When viewed from the Z direction, the tip nozzle hole 576 is formed so that the extension line 571L is aligned with the plug radial direction. Also, when viewed from the Z direction, the extension line 571L of the central axis of the tip nozzle hole 576 is aligned with the protruding direction of the ground electrode 6.

Further, two first injection holes 571 other than the tip side injection hole 576 are formed. That is, the number of the first injection holes 571 is an odd number, and the number of the first injection holes 571 other than the tip side injection hole 576 is an even number. When viewed from the Z direction, the first injection holes 571 other than the tip side injection hole 576 are formed in positions and orientations that are symmetrical to each other with the ground electrode 6 in between. Specifically, when viewed from the Z direction, the two first injection holes 571 are formed in positions and orientations that are symmetrical to each other with the ground electrode 6 in between.
The rest is the same as in embodiment 11.

The spark plug 1 of this embodiment has a tip side injection hole 576. Moreover, when viewed from the Z direction, the first injection holes 571 other than the tip side injection hole 576 are formed in positions and orientations that are symmetrical to each other with the ground electrode 6 in between. Therefore, the air flows flowing in from the respective first injection holes 571 tend to merge and flow from the first plug portion 13 to the second plug portion 14. Therefore, the tumble flow formed in the auxiliary combustion chamber 50 can be strengthened. As a result, the discharge generated in the discharge gap G tends to extend further.
In addition, it has the same effects as in the eleventh embodiment.

(Embodiment 13)
As shown in FIG. 29, this embodiment is an embodiment in which the opening direction of a first injection hole 571 is changed from that of the eleventh embodiment.

The first injection hole 571 is formed so that an extension line 571L of the central axis of the first injection hole 571 does not pass through the tip protrusion 41. As shown in FIG. 29, when viewed from the plug axial direction Z, the intersection point of the extension lines 571L of the central axes of at least two first injection holes 571 is defined as an intersection point A2. When viewed from the plug axial direction Z, the intersection point A2 and the first injection hole 571 are located on opposite sides of the tip protrusion 41 in the Y direction.

In this embodiment, when viewed from the Z direction, the intersection A2 is located between the tip projection 41 and the projection-side nozzle hole 573. Also, when viewed from the Z direction, the intersection A2 is located between the projection end 63 and the projection-side nozzle hole 573.
The rest is the same as in embodiment 11.

The first nozzle hole 571 is formed so that the extension line 571L does not pass through the tip protruding portion 41. In addition, when viewed from the Z direction, the intersection point A2 and the first nozzle hole 571 are located on opposite sides of the tip protruding portion 41 in the Y direction. Therefore, the airflow of the gas introduced into the auxiliary combustion chamber 50 through the first nozzle hole 571 is less likely to be blocked by the tip protruding portion 41, and a tumble flow is more likely to be formed. Therefore, the airflow guided to the base end surface 61 of the ground electrode 6 can be strengthened. As a result, the discharge formed in the discharge gap G can be further extended.
In addition, it has the same effects as in the eleventh embodiment.

(Embodiment 14)
As shown in Figs. 30 and 31, this embodiment is an embodiment in which the position of the protruding end portion 63 of the ground electrode 6 is changed from that of the thirteenth embodiment.

As shown in FIG. 30, when viewed from the plug axial direction Z, the protruding end portion 63 is positioned closer to the protruding side nozzle hole 573 than the tip protruding portion 41.

In other words, when viewed from the Z direction, the shortest distance D4 from the protruding end 63 to the protruding side nozzle hole 573 is shorter than the shortest distance D5 from the protruding end 63 to the tip protruding portion 41.

As shown in FIG. 31, the protruding end 63 is positioned distal to a straight line L4 that connects the base end of the outer opening 574 of the protruding side nozzle 573 and the tip end of the tip protruding portion 41 at the shortest distance.

The protruding end 63 is disposed on the tip side of a straight line L5 that connects the center of the outer opening 574 of the protruding side nozzle 573 and the tip of the tip protruding portion 41 at the shortest distance. The protruding end 63 is disposed on the tip side of a straight line L6 that connects the tip of the inner opening 577 of the protruding side nozzle 573 and the tip of the tip protruding portion 41 at the shortest distance.

As shown in FIG. 30, when viewed from the Z direction, the protruding side nozzle hole 573 is opened so that the extension line 573L of the central axis of the protruding side nozzle hole 573 overlaps with the protruding end portion 63. When viewed from the Z direction, the protruding side nozzle hole 573 is opened so that the extension line 573L is aligned with the protruding direction of the ground electrode 6.

As shown in FIG. 31, the discharge gap G is formed on the tip side of the housing 2 .
The rest is the same as in embodiment 13.

When viewed from the plug axial direction Z, the protruding end 63 is positioned closer to the protruding side nozzle hole 573 than the tip protruding portion 41. Therefore, during the expansion stroke, the starting point of the discharge on the ground electrode 6 side is more likely to move toward the protruding side nozzle hole 573 due to the airflow that is drawn out from the auxiliary combustion chamber 50 through the protruding side nozzle hole 573. Therefore, the discharge is more likely to extend toward the protruding side nozzle hole 573. As a result, ignition performance can be further improved.

The protruding end 63 is positioned further forward than the straight line L4. Therefore, during the expansion stroke, the discharge generated in the discharge gap G is not short-circuited by the protruding end 63, and is likely to reliably extend toward the protruding side nozzle hole 573 and the main combustion chamber. As a result, ignition performance can be reliably improved.

In addition, because the protruding end 63 is positioned as described above, the starting point of the discharge generated in the discharge gap G on the ground electrode 6 side is likely to move to the inner surface of the protruding side nozzle hole 573. Furthermore, the starting point of the discharge on the ground electrode 6 side is likely to move toward the outer opening 574 of the protruding side nozzle hole 573. Therefore, the discharge is likely to extend from the protruding side nozzle hole 573 toward the main combustion chamber. As a result, the ignition ability of the main combustion chamber can be further improved.

In addition, the protruding end 63 is positioned further forward than the straight line L5. Therefore, the discharge is not short-circuited by the protruding end 63, and it is easier to extend more reliably toward the protruding side nozzle hole 573 and the main combustion chamber.

In addition, the protruding end 63 is positioned further forward than the straight line L6. Therefore, the discharge is not short-circuited by the protruding end 63, and it is easier to extend more reliably toward the protruding side nozzle hole 573 and the main combustion chamber.

The discharge gap G is formed on the tip side of the housing 2. This makes it easy to adjust the discharge gap G. As a result, the spark plug 1 can be manufactured easily.
In addition, it has the same effects as in the thirteenth embodiment.

(Embodiment 15)
As shown in FIG. 32, this embodiment is an embodiment in which the shape of the tip portion of the center electrode 4 is modified from that of the eleventh embodiment.
That is, the tip surface 411 of the center electrode 4 is inclined along the inclined surface 611 of the ground electrode 6 .
The rest is the same as in embodiment 11.

The tip surface 411 of the center electrode 4 is inclined along the inclined surface 611 of the ground electrode 6. Therefore, the tip surface 411 of the center electrode 4 and the inclined surface 611 of the ground electrode 6 can be made substantially parallel to each other. As a result, local wear of the center electrode 4 can be suppressed, and the distance of the discharge gap G can be suppressed from increasing.
In addition, it has the same effects as in the eleventh embodiment.

In the above embodiments 11 to 15, the ratio of the number of first injection holes 571 to the number of second injection holes 572 is 2:1 or 3:2. However, the ratio of the number of first injection holes 571 to the number of second injection holes 572 can be, for example, 3:1, 4:3, 4:2, etc.

The present invention is not limited to the above-described embodiments, and can be applied to various embodiments without departing from the spirit of the present invention.

1...spark plug, 11...first plug part, 12...second plug part, 2...housing, 3...insulator, 4...center electrode, 41...tip protrusion, 5...plug cover, 50...auxiliary combustion chamber, 51...large nozzle hole, 52...small nozzle hole, 6...ground electrode, 62...fixed end, 61...base end face, 51L...extension of the central axis of the large nozzle hole, G...discharge gap, Z...plug axial direction, C...plug central axis, P...predetermined plane including the plug central axis

Claims (18)

A cylindrical insulator (3);
a center electrode (4) held on the inner circumferential side of the insulator and having a tip protrusion (41) protruding toward the tip side of the insulator;
a cylindrical housing (2) that holds the insulator on its inner periphery;
a ground electrode (6) forming a discharge gap (G) between itself and the center electrode;
a plug cover (5) provided at a tip end of the housing so as to cover a sub-combustion chamber (50) in which the discharge gap is disposed,
The discharge gap is formed by a front end portion of the center electrode and a base end surface (61) of the ground electrode facing each other in an axial direction (Z),
The plug cover is formed with at least two large nozzle holes (51) and a small nozzle hole (52) having an opening area smaller than that of the large nozzle holes,
The large injection hole and the small injection hole each communicate the auxiliary combustion chamber with the outside,
The large nozzle hole opens at an angle with respect to the plug axial direction so as to extend radially outwardly toward the tip side of the plug,
when the spark plug is divided into a first plug portion (11) and a second plug portion (12) by a predetermined plane (P) including a plug center axis (C), both of the at least two large injection holes are formed in the first plug portion,
The ground electrode protrudes into the auxiliary combustion chamber from a fixed end (62) of the first plug portion that is fixed to the housing or the plug cover,
when viewed from the plug axial direction, in the first plug portion, the fixed end portion is disposed between extension lines (51L) of respective central axes of the at least two large injection holes in the plug circumferential direction,
a spark plug for an internal combustion engine, wherein the large injection hole is formed such that an extension line of a central axis of the large injection hole does not pass through the tip projection portion, and when viewed in the plug axial direction, an intersection (A) of extension lines of central axes of at least two of the large injection holes and the large injection hole are located on opposite sides of the tip projection portion in an arrangement direction (Y) of the fixed end and the tip projection portion when viewed in the plug axial direction . At least one of the small injection holes is a projection-side injection hole (521) through which an extension line (6L) of the projection direction of the ground electrode passes when viewed from the plug axial direction,
2. A spark plug for an internal combustion engine according to claim 1 , wherein at least a part of a protruding end portion (63) of said ground electrode is disposed between said tip protruding portion and said protruding side nozzle hole when viewed in a plug axial direction. A cylindrical insulator (3);
a center electrode (4) held on the inner circumferential side of the insulator and having a tip protrusion (41) protruding toward the tip side of the insulator;
a cylindrical housing (2) that holds the insulator on its inner periphery;
a ground electrode (6) forming a discharge gap (G) between itself and the center electrode;
a plug cover (5) provided at a tip end of the housing so as to cover a sub-combustion chamber (50) in which the discharge gap is disposed,
The discharge gap is formed by a front end portion of the center electrode and a base end surface (61) of the ground electrode facing each other in an axial direction (Z),
The plug cover is formed with at least two large nozzle holes (51) and a small nozzle hole (52) having an opening area smaller than that of the large nozzle holes,
The large injection hole and the small injection hole each communicate the auxiliary combustion chamber with the outside,
The large nozzle hole opens at an angle with respect to the plug axial direction so as to extend radially outwardly toward the tip side of the plug,
when the spark plug is divided into a first plug portion (11) and a second plug portion (12) by a predetermined plane (P) including a plug center axis (C), both of the at least two large injection holes are formed in the first plug portion,
The ground electrode protrudes into the auxiliary combustion chamber from a fixed end (62) of the first plug portion that is fixed to the housing or the plug cover,
when viewed from the plug axial direction, in the first plug portion, the fixed end portion is disposed between extension lines (51L) of respective central axes of the at least two large injection holes in the plug circumferential direction,
At least one of the small injection holes is a projection-side injection hole (521) through which an extension line (6L) of the projection direction of the ground electrode passes when viewed from the plug axial direction,
a spark plug for an internal combustion engine , wherein at least a part of a projecting end portion (63) of the ground electrode is disposed between the tip projecting portion and the projection side nozzle hole when viewed in the plug axial direction . 4. The spark plug for an internal combustion engine according to claim 2, wherein, when viewed in the plug axial direction, the protruding end portion is located closer to the protruding side nozzle hole than the tip protruding portion. 5. A spark plug for an internal combustion engine according to claim 2, wherein the protruding end portion is disposed on a tip side of a straight line (L1) that connects, at a shortest distance, a base end of an outer opening ( 522) of the protruding side nozzle hole and the tip end of the tip protruding portion. 6. A spark plug for an internal combustion engine according to claim 1, wherein a base end surface of the ground electrode has an inclined surface (611) inclined with respect to a plug axial direction so as to move toward a tip side as the base end surface approaches the protruding end (63) of the ground electrode. 7. The spark plug for an internal combustion engine according to claim 6 , wherein a tip surface (411) of said center electrode is inclined along said inclined surface of said ground electrode. A spark plug for an internal combustion engine according to any one of claims 1 to 7, wherein the discharge gap is formed on the tip side of the housing. An internal combustion engine (10) comprising a spark plug for an internal combustion engine according to any one of claims 1 to 8,
A main combustion chamber (101);
an intake valve (72) and an exhaust valve (73) provided in the main combustion chamber;
The spark plug is disposed so that an outer surface (53) of the plug cover faces the main combustion chamber,
The spark plug is arranged such that an outer opening (511) of at least one of the large nozzle holes faces the intake valve side when viewed from the plug axial direction. A cylindrical insulator (3);
a center electrode (4) held on the inner circumferential side of the insulator and having a tip protrusion (41) protruding toward the tip side of the insulator;
a cylindrical housing (2) that holds the insulator on its inner periphery;
a ground electrode (6) forming a discharge gap (G) between itself and the center electrode;
a plug cover (5) provided at a tip end of the housing so as to cover a sub-combustion chamber (50) in which the discharge gap is disposed,
The discharge gap is formed by a front end portion of the center electrode and a base end surface (61) of the ground electrode facing each other in an axial direction (Z),
The plug cover is formed with a plurality of nozzle holes (57) that communicate the auxiliary combustion chamber with the outside,
The ground electrode protrudes into the auxiliary combustion chamber from a fixed end (62) fixed to the housing or the plug cover,
when the spark plug is divided into two parts, a first plug part (13) including the fixed end part and a second plug part (14) by a plane (P2) which includes a plug center axis (C) and is perpendicular to a protruding direction of the ground electrode as viewed in the plug axial direction, the injection hole is formed in both the plug cover of the first plug part and the plug cover of the second plug part,
When the nozzle holes formed in the first plug portion are referred to as first nozzle holes (571) and the nozzle holes formed in the second plug portion are referred to as second nozzle holes (572), the number of the first nozzle holes is greater than the number of the second nozzle holes,
the first injection hole opens at an incline with respect to the plug axial direction so as to extend outward in the plug radial direction toward the tip side,
when viewed from the plug axial direction, in the first plug portion, the fixed end portion is disposed between extension lines (571L) of respective central axes of the at least two first injection holes in the plug circumferential direction,
a spark plug for an internal combustion engine, wherein the first injection hole is formed such that an extension line of a central axis of the first injection hole does not pass through the tip projection portion, and an intersection (A2) of extension lines of central axes of at least two of the first injection holes and the first injection hole are located on opposite sides of the tip projection portion in an arrangement direction (Y) of the fixed end and the tip projection portion as viewed in the plug axial direction . At least one of the second nozzle holes is a projection-side nozzle hole (573) through which an extension line (6L) of the projection direction of the ground electrode passes when viewed from the plug axial direction,
11. The spark plug for an internal combustion engine according to claim 10 , wherein at least a portion of the protruding end portion (63) of the ground electrode is disposed between the tip protruding portion and the protruding side nozzle hole when viewed in the plug axial direction. A cylindrical insulator (3);
a center electrode (4) held on the inner circumferential side of the insulator and having a tip protrusion (41) protruding toward the tip side of the insulator;
a cylindrical housing (2) that holds the insulator on its inner periphery;
a ground electrode (6) forming a discharge gap (G) between itself and the center electrode;
a plug cover (5) provided at a tip end of the housing so as to cover a sub-combustion chamber (50) in which the discharge gap is disposed,
The discharge gap is formed by a front end portion of the center electrode and a base end surface (61) of the ground electrode facing each other in an axial direction (Z),
The plug cover is formed with a plurality of nozzle holes (57) that communicate the auxiliary combustion chamber with the outside,
The ground electrode protrudes into the auxiliary combustion chamber from a fixed end (62) fixed to the housing or the plug cover,
when the spark plug is divided into two parts, a first plug part (13) including the fixed end part and a second plug part (14) by a plane (P2) which includes a plug center axis (C) and is perpendicular to a protruding direction of the ground electrode as viewed in the plug axial direction, the injection hole is formed in both the plug cover of the first plug part and the plug cover of the second plug part,
When the nozzle holes formed in the first plug portion are referred to as first nozzle holes (571) and the nozzle holes formed in the second plug portion are referred to as second nozzle holes (572), the number of the first nozzle holes is greater than the number of the second nozzle holes,
the first injection hole opens at an incline with respect to the plug axial direction so as to extend outward in the plug radial direction toward the tip side,
when viewed from the plug axial direction, in the first plug portion, the fixed end portion is disposed between extension lines (571L) of respective central axes of the at least two first injection holes in the plug circumferential direction,
At least one of the second nozzle holes is a projection-side nozzle hole (573) through which an extension line (6L) of the projection direction of the ground electrode passes when viewed from the plug axial direction,
a spark plug for an internal combustion engine , wherein at least a part of a projecting end portion (63) of the ground electrode is disposed between the tip projecting portion and the projection side nozzle hole when viewed in the plug axial direction . 13. The spark plug for an internal combustion engine according to claim 11, wherein, when viewed in the plug axial direction, the projecting end portion is located closer to the projection side nozzle hole than the tip projecting portion is. 14. A spark plug for an internal combustion engine according to claim 11, wherein the protruding end portion is disposed on a tip side of a straight line (L4) that connects, at a shortest distance, a base end of an outer opening ( 574) of the protruding side nozzle hole and the tip end of the tip protruding portion. 15. The spark plug for an internal combustion engine according to claim 10, wherein a base end surface of the ground electrode has an inclined surface (611) inclined with respect to the plug axial direction so as to move toward a tip side as the base end surface approaches the projecting end (63) of the ground electrode. 16. The spark plug for an internal combustion engine according to claim 15 , wherein a tip surface (411) of said center electrode is inclined along said inclined surface of said ground electrode. A spark plug for an internal combustion engine according to any one of claims 10 to 16, wherein the discharge gap is formed on the tip side of the housing. An internal combustion engine (10) comprising a spark plug for an internal combustion engine according to any one of claims 10 to 17,
A main combustion chamber (101);
an intake valve (72) and an exhaust valve (73) provided in the main combustion chamber;
The spark plug is disposed so that an outer surface (53) of the plug cover faces the main combustion chamber,
The spark plug is arranged such that an outer opening (575) of at least one of the first nozzle holes faces the intake valve side when viewed in a plug axial direction.

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