Spark plug for internal combustion engine and internal combustion engine equipped with same

Abstract

To provide a spark plug for internal combustion engine which can improve the ignitability and an internal combustion engine having the same.SOLUTION: A spark plug 1 comprises: a cylindrical insulator 3; a center electrode 4; a cylindrical housing 2; a ground electrode 6; and a plug cover 5. The plug cover 5 is provided on the tip of the housing 2 so as to cover a sub combustion chamber 50 where a discharge gap G is arranged. The ground electrode 6 protrudes into the sub combustion chamber 50 from a fixed end 62 fixed to the housing 2 or the plug cover 5. The discharge gap G is formed by making the tip of the center electrode 4 and a base end surface 61 of the ground electrode 6 face each other in a plug axis direction Z. The plug cover 5 is formed with a large injection hole 51 and a small injection hole 52 having the smaller opening area than the large injection hole 51. The large injection hole 51 and the small injection hole 52 make the sub combustion chamber 50 communicate to the outside. An extension line L1 of the center axis of the large injection hole 51 passes through the discharge gap G.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a spark plug for an internal combustion engine and an internal combustion engine equipped with the same. [Background technology]

[0002] For example, as disclosed in Patent Document 1, a spark plug with an auxiliary combustion chamber at its tip is known. In this spark plug, a cover portion covering the auxiliary combustion chamber is formed with a plurality of nozzle holes. This allows a flame to be ejected from the auxiliary combustion chamber through the nozzle holes into the main combustion chamber, thereby combusting the air-fuel mixture in the main combustion chamber. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2020-009747 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, the spark plug described in Patent Document 1 does not take into consideration the ignition of the mixture in the pre-combustion chamber, i.e., the formation of an initial flame itself. In other words, no consideration is given to improving ignition by extending the discharge in the pre-combustion chamber.

[0005] The present invention has been made in view of the above problems, and has an object to provide a spark plug for an internal combustion engine that can improve ignition performance, and an internal combustion engine equipped with the same. [Means for solving the problem]

[0006] The first aspect of the present invention is a cylindrical insulator (3), a center electrode (4) held on the inner circumferential side of the insulator and protruding from the insulator toward the tip side; 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 the tip of the housing so as to cover a sub-combustion chamber (50) in which the discharge gap is disposed, The ground electrode protrudes into the auxiliary combustion chamber from a fixed end (62) fixed to the housing or the plug cover, The discharge gap is formed by a tip 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 large nozzle hole (51) and a small nozzle hole (52) having an opening area smaller than that of the large nozzle hole, The large injection hole and the small injection hole each communicate the auxiliary combustion chamber with the outside, The extension line (L1) of the central axis of the large nozzle passes through the discharge gap. death , when viewed from the plug axial direction, at least a part of a protruding end portion (63) of the ground electrode is located between the tip portion of the center electrode and the large injection hole in the protruding direction of the ground electrode. In a spark plug (1) for an internal combustion engine. 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 protruding from the insulator toward the tip side; 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 the tip of the housing so as to cover a sub-combustion chamber (50) in which the discharge gap is disposed, The ground electrode protrudes into the auxiliary combustion chamber from a fixed end (62) fixed to the housing or the plug cover, The discharge gap is formed by a tip 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 large nozzle hole (51) and a small nozzle hole (52) having an opening area smaller than that of the large nozzle hole, The large injection hole and the small injection hole each communicate the auxiliary combustion chamber with the outside, An extension line (L1) of the central axis of the large nozzle hole passes through the discharge gap, The ground electrode protruding end (63) is located in a spark plug (1) for an internal combustion engine, where the distance (D2) to the large nozzle hole is shorter than the distance (D1) to the tip of the center electrode.

[0007] The present invention Third The embodiment of the present invention includes a cylindrical insulator (3), a center electrode (4) held on the inner circumferential side of the insulator and protruding from the insulator toward the tip side; 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 the tip of the housing so as to cover a sub-combustion chamber (50) in which the discharge gap is disposed, The ground electrode protrudes into the auxiliary combustion chamber from a fixed end (62) fixed to the housing or the plug cover, the discharge gap is formed by a center-facing side surface (43) of the center electrode and a ground-facing side surface (66) of the ground electrode facing each other in a plug radial direction, The plug cover is formed with a large nozzle hole (51) and a small nozzle hole (52) having an opening area smaller than that of the large nozzle hole, The large injection hole and the small injection hole each communicate the auxiliary combustion chamber with the outside, in a cross-sectional view including an extension line (L1) of the central axis of the large injection hole and taken along the plug axial direction (Z), the extension line and the discharge gap overlap each other, The above extension line is along the plug radial direction when viewed from the plug axial direction. Cage , The ground electrode has a ground tip surface (67) which is a surface on the tip side, and the ground tip surface is inclined toward the tip side at least from the position of the discharge gap to the protruding end (63) of the ground electrode in a protruding direction of the protruding end of the ground electrode, as it approaches the protruding end. In a spark plug (1) for an internal combustion engine. 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 protruding from the insulator toward the tip side; 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 the tip of the housing so as to cover a sub-combustion chamber (50) in which the discharge gap is disposed, The ground electrode protrudes into the auxiliary combustion chamber from a fixed end (62) fixed to the housing or the plug cover, the discharge gap is formed by a center-facing side surface (43) of the center electrode and a ground-facing side surface (66) of the ground electrode facing each other in a plug radial direction, The plug cover is formed with a large nozzle hole (51) and a small nozzle hole (52) having an opening area smaller than that of the large nozzle hole, The large injection hole and the small injection hole each communicate the auxiliary combustion chamber with the outside, in a cross-sectional view including an extension line (L1) of the central axis of the large injection hole and taken along the plug axial direction (Z), the extension line and the discharge gap overlap each other, The above-mentioned extension line is aligned along the radial direction of the plug when viewed from the axial direction of the plug, When viewed from the plug axial direction, at least a part of the protruding end portion (63) of the ground electrode is located between the tip end portion of the center electrode and the large injection hole in the protruding direction of the ground electrode. 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 protruding from the insulator toward the tip side; 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 the tip of the housing so as to cover a sub-combustion chamber (50) in which the discharge gap is disposed, The ground electrode protrudes into the auxiliary combustion chamber from a fixed end (62) fixed to the housing or the plug cover, the discharge gap is formed by a center-facing side surface (43) of the center electrode and a ground-facing side surface (66) of the ground electrode facing each other in a plug radial direction, The plug cover is formed with a large nozzle hole (51) and a small nozzle hole (52) having an opening area smaller than that of the large nozzle hole, The large injection hole and the small injection hole each communicate the auxiliary combustion chamber with the outside, in a cross-sectional view including an extension line (L1) of the central axis of the large injection hole and taken along the plug axial direction (Z), the extension line and the discharge gap overlap each other, The above-mentioned extension line is aligned along the radial direction of the plug when viewed from the axial direction of the plug, The ground electrode protruding end (63) is located in a spark plug (1) for an internal combustion engine, where the distance (D2) to the large nozzle hole is shorter than the distance (D1) to the tip of the center electrode.

[0008] The present invention Sixth The present invention relates to an internal combustion engine (10) having the above-mentioned spark plug for an internal combustion engine, 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, when viewed in the plug axial direction, an outer opening (511) of at least one of the large injection holes faces the intake valve side.

[0009] The present invention Seventh The present invention relates to an internal combustion engine (10) having the above-mentioned spark plug for an internal combustion engine, A main combustion chamber (101); The spark plug is disposed so that an outer surface (53) of the plug cover faces the main combustion chamber; an injector (71) for injecting fuel directly into the main combustion chamber; The spark plug is located in an internal combustion engine and is positioned such that an injection flow (F) containing the fuel injected from the injector during the compression stroke of the internal combustion engine is directed toward the outer opening (511) of the large injection hole. Effect of the Invention

[0010] Above No. 1 and secondIn the spark plug for an internal combustion engine according to the above aspect, the large injection hole is formed so that an extension line of the central axis of the large injection hole passes through the discharge gap. Therefore, the discharge formed in the discharge gap is easily extended by the airflow introduced into the auxiliary combustion chamber through the large injection hole or the airflow flowing out from the auxiliary combustion chamber. As a result, the ignition performance can be improved.

[0011] the above 3rd~5th In the spark plug for an internal combustion engine according to the aspect, in a cross-sectional view including an extension line of the central axis of the large injection hole and taken along the plug axial direction, the extension line and the discharge gap overlap each other. Therefore, the discharge formed in the discharge gap is easily extended by the airflow introduced into the auxiliary combustion chamber via the large injection hole or the airflow flowing out from the auxiliary combustion chamber. As a result, ignition performance can be improved.

[0012] the above Sixth The internal combustion engine according to the aspect has the above-mentioned spark plug. The spark plug is arranged so that an outer opening of at least one large injection hole faces the intake valve side when viewed from the plug axial direction. This makes it possible to eject a large flame from the auxiliary combustion chamber to the intake valve side of the main combustion chamber through the large injection hole when viewed from the plug axial direction. This makes it possible to improve the ignition ability 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 and the like.

[0013] the above Seventh In the internal combustion engine according to the aspect, the spark plug is arranged so that the injection flow from the injector is directed toward the outer opening of the large injection hole. This makes it easier for a high-fuel-density mixture to be introduced from the large injection hole into the auxiliary combustion chamber. As a result, the high-fuel-density mixture can easily reach the discharge gap, improving ignition performance.

[0014] 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. [Brief description of the drawings]

[0015] [Figure 1] 2. FIG. 3 is a cross-sectional view of the spark plug in the axial direction in the vicinity of the tip portion of the spark plug according to the first embodiment, which corresponds to a cross-sectional view taken along line II in FIG. [Diagram 2] FIG. 2 is a cross-sectional view taken along line II-II in FIG. [Diagram 3] FIG. 4 is an explanatory cross-sectional view perpendicular to the plug axial direction, illustrating the position where an injection hole is formed in the first embodiment. [Figure 4] FIG. 1 is a cross-sectional explanatory view of an internal combustion engine according to a first embodiment. [Diagram 5] FIG. 4 is a cross-sectional view illustrating the direction of an injection flow relative to the spark plug in the first embodiment. [Figure 6] 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. [Figure 7] 4 is a cross-sectional view of the vicinity of the tip of the spark plug when the discharge is extended during the compression stroke in the first embodiment. FIG. [Figure 8] 4 is a cross-sectional view of the vicinity of the tip of the spark plug in the first embodiment during the expansion stroke and before the discharge is extended. [Figure 9] 4 is a cross-sectional view of the vicinity of the tip of the spark plug according to the first embodiment when the discharge is extended during the expansion stroke. [Figure 10] FIG. 11 is a cross-sectional explanatory view of an internal combustion engine according to a second embodiment. [Figure 11] FIG. 11 is an explanatory diagram illustrating the direction of an airflow formed in a main combustion chamber in a second embodiment, as viewed from the front end side of the internal combustion engine. [Figure 12]FIG. 11 is a cross-sectional view of the vicinity of the tip of a spark plug according to a second embodiment, during the compression stroke and before the discharge extends. [Figure 13] FIG. 11 is a cross-sectional view of the vicinity of the tip of a spark plug according to a second embodiment when a discharge is extended during a compression stroke. [Figure 14] 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 third embodiment. [Figure 15] FIG. 11 is an explanatory cross-sectional view of the vicinity of the tip portion of a spark plug in a third embodiment, illustrating the angle between an extension of the central axis of the large nozzle hole and the inclined surface of the ground electrode, etc. [Figure 16] FIG. 11 is a cross-sectional explanatory diagram of the vicinity of the tip portion of the spark plug, illustrating the relationship between the line segment L3 and the ground electrode in the third embodiment. [Figure 17] FIG. 11 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 fourth embodiment. [Figure 18] 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. [Figure 19] 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 sixth embodiment. [Figure 20] 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 seventh embodiment. [Figure 21] FIG. 13 is a cross-sectional view taken along the axial direction of a spark plug in an eighth embodiment, showing the vicinity of a tip portion of the spark plug. [Figure 22] 13 is a cross-sectional view of the tip portion of a spark plug according to a ninth embodiment, taken along a line perpendicular to the axial direction of the plug. FIG. [Figure 23] FIG. 13 is an explanatory cross-sectional view perpendicular to the plug axial direction, illustrating the position where an injection hole is formed in a ninth embodiment. [Figure 24] FIG. 23 is a cross-sectional view of the tip portion of a spark plug according to a tenth embodiment, taken perpendicular to the plug axial direction. [Diagram 25] FIG. 23 is a plan view of the ground electrode in the eleventh embodiment, as viewed from the protruding direction of the ground electrode. [Figure 26] FIG. 23 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 twelfth embodiment. [Figure 27] FIG. 23 is a cross-sectional view showing distances D1 and D2 in the twelfth embodiment. [Figure 28] FIG. 23 is a cross-sectional view of the vicinity of the tip of a spark plug according to a twelfth embodiment when the discharge is extended during the expansion stroke. [Figure 29] 30. FIG. 31 is a cross-sectional view taken along line XXIX-XXIX of FIG. 30, showing a portion of a spark plug in the axial direction of the plug in a thirteenth embodiment. [Diagram 30] FIG. 30 is a cross-sectional view taken along line XXX-XXX in FIG. 29. [Diagram 31] FIG. 31 is a cross-sectional view taken along line XXXI-XXXI in FIG. 30. [Diagram 32] FIG. 23 is a cross-sectional view of the tip of a spark plug according to a thirteenth embodiment during the compression stroke and before the discharge extends. [Diagram 33] FIG. 23 is a cross-sectional view of the tip of a spark plug according to a thirteenth embodiment when the discharge is extended during the compression stroke. [Diagram 34] FIG. 23 is a cross-sectional view of the tip of a spark plug according to a thirteenth embodiment when the discharge is extended during the expansion stroke. [Diagram 35] FIG. 23 is a cross-sectional view of the vicinity of the tip of a spark plug in a thirteenth embodiment when the discharge extends to the main combustion chamber during the expansion stroke. [Diagram 36] FIG. 23 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. [Figure 37] FIG. 23 is a cross-sectional view taken along the axial direction of a spark plug in a region near a tip end of the spark plug according to a fifteenth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] (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. 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, as shown in Fig. 1 and Fig. 2. The center electrode 4 is held on the inner periphery of the insulator 3 and protrudes from the insulator 3 toward the tip side. 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.

[0017] The ground electrode 6 protrudes into the auxiliary combustion chamber 50 from a fixed end 62 fixed to the housing 2 or the plug cover 5. A discharge gap G is formed by the tip end of the central electrode 4 and the base end face 61 of the ground electrode 6 facing each other in the plug axial direction Z. The plug cover 5 is formed with a large injection hole 51 and a small injection hole 52 having a smaller opening area than the large injection hole 51. The large injection hole 51 and the small injection hole 52 each communicate between the auxiliary combustion chamber 50 and the outside. An extension line L1 of the central axis of the large injection hole 51 passes through the discharge gap G.

[0018] The spark plug 1 of this embodiment can be used as an ignition means in an internal combustion engine of an automobile, a cogeneration system, or the like. As shown in FIG. 4, the mounting screw portion 23 formed on the outer circumferential surface of the housing 2 is screwed into a female screw portion of a plug hole 761 of a cylinder head 76, so that the spark plug 1 is mounted on the internal combustion engine 10. One end of the spark plug 1 in the axial direction Z is disposed 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 referred to as the tip side, and the opposite side is referred to as the base side. The axial direction Z of the spark plug 1 is also referred to as the plug axial direction Z or simply as the Z direction, as appropriate. The plug central axis C is referred to as the central axis C of the spark plug 1.

[0019] 1, the plug cover 5 is joined by welding or the like to the tip of the housing 2. When the spark plug 1 is attached to an internal combustion engine, the plug cover 5 separates the auxiliary combustion chamber 50 from the main combustion chamber.

[0020] In this embodiment, as shown in Fig. 2, the plug cover 5 is formed with one large injection hole 51 and three small injection holes 52. The injection holes 51, 52 are formed in a substantially cylindrical shape. The inner diameter of the large injection hole 51 may 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 may be, for example, 1.4 to 2.0 times the opening area of ​​the small injection hole 52.

[0021] As shown in Fig. 1, each of the nozzle holes 51, 52 opens at an incline with respect to the Z direction so as to be more outward as it approaches the tip side. As shown in Figs. 1 and 2, the nozzle holes 51, 52 open radially.

[0022] 2 and 3, the injection holes 51, 52 are formed at equal intervals in the plug circumferential direction when the spark plug 1 is viewed from the Z direction. As shown in Fig. 3, a straight line passing through the plug central axis C and the center of each injection hole 51, 52 when viewed from the Z direction is defined as a straight line L2. The injection holes 51, 52 are formed such that an angle α1 formed by each of the straight lines L2 passing through the injection holes 51, 52 adjacent to each other in the plug circumferential direction when viewed from the Z direction is 90°. The plug circumferential direction is a direction along a circumference centered on the plug central axis C.

[0023] In this embodiment, an extension line L1 of the central axis of the large injection hole 51 passes through the plug central axis C, as shown in Figures 1 and 2. However, the extension line L1 does not necessarily have to pass through the plug central axis C, but may pass through the discharge gap G. The extension line L1 passes through, for example, a part of the region between the center electrode 4 and the base end surface 61 of the ground electrode 6, which is a region obtained by projecting the center electrode 4 in the Z direction.

[0024] Moreover, the extension line L1 passes through the discharge gap G without passing through the ground electrode 6. As shown in Fig. 2, when viewed from the Z direction, the extension line L1 passes through the inner circumferential surface 21 of the housing 2 that faces the large injection hole 51 in the plug radial direction, across the tip end of the center electrode 4. As shown in Fig. 1, in a cross section including the extension line L1, the angle at which the extension line L1 intersects with the inner circumferential surface 21 is an obtuse angle on the base end side of the extension line L1. Note that the plug radial direction means the radial direction of a circle centered on the plug central axis C on a plane perpendicular to the plug central axis C.

[0025] In addition, in the opening direction of the large nozzle hole 51, at least a portion of the inner opening 512 of the large nozzle hole 51 and the discharge gap G directly face each other.

[0026] As shown in FIG. 2, when viewed from the plug axial direction Z, at least one large injection hole 51 and the fixed end portion 62 face each other in the plug radial direction.

[0027] In this embodiment, the fixed end 62 of the ground electrode 6 is fixed to the housing 2. Then, after the ground electrode 6 is fixed to the housing 2, the plug cover 5 is fixed to the housing 2, whereby the spark plug 1 of this embodiment can be manufactured.

[0028] 2, the ground electrode 6 is fixed to the housing 2 along the plug radial direction when viewed from the Z direction. When viewed from the Z direction, the fixed end 62 and the protruding end 63 of the ground electrode 6 are disposed on opposite sides of the center electrode 4.

[0029] In this embodiment, the ground electrode 6 has a substantially rectangular prism shape. That is, the ground electrode 6 has four flat side surfaces, one of which is a base end surface 61. As shown in FIG. 1, the base end surface 61 faces the tip surface 41 of the center electrode 4 in the Z direction.

[0030] 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 from at least a gap forming surface 612 that forms the discharge gap G to the protruding end 63 of the ground electrode 6 so as to move toward the tip side as it approaches the protruding end 63. In this embodiment, the entire base end surface 61 is the inclined surface 611.

[0031] Also, a tip can be joined to each of the tip end of the center electrode 4 and the inclined surface 611 of the ground electrode 6, which face each other in the Z direction (not shown). That is, a discharge gap G can be formed between the tip joined to the center electrode 4 and the tip joined to the ground electrode 6. The tip can be made of, for example, a precious metal such as iridium or platinum, or an alloy containing these as a main component.

[0032] As shown in FIG. 2, when viewed in the plug axial direction Z, at least a part of the projecting end portion 63 of the ground electrode 6 is located between the tip end portion of the center electrode 4 and the large injection hole 51.

[0033] Next, an internal combustion engine 10 equipped with the above-mentioned spark plug 1 is shown in FIG. The internal combustion engine 10 has a main combustion chamber 101, a spark plug 1 arranged so that an outer surface 53 of a plug cover 5 faces the main combustion chamber 101, and an injector 71 that injects fuel directly into the main combustion chamber 101. The spark plug 1 is arranged so that an injection flow F including fuel injected from the injector 71 during the compression stroke of the internal combustion engine 10 is directed toward an outer opening 511 of the large injection hole 51. Note that the arrow F shown in FIG. 4 indicates the direction of the injection flow immediately after fuel injection, and does not necessarily coincide with the air flow in the main combustion chamber 101 during the compression stroke or the expansion stroke. Also, the state in which the injection flow F is directed toward the outer opening 511 of the large injection hole 51 is a state in which the outer opening 511 of the large injection hole 51 is visible from the direction of the injection flow F near the plug cover 5 shown in FIG. 5.

[0034] 4, 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. A main combustion chamber 101 is formed by the cylinder head 76, the cylinder block 75, and the piston 74. An intake port 721 and an exhaust port 731 are formed in the cylinder head 76, and an intake valve 72 or an exhaust valve 73 is provided therein. A spark plug 1 is attached between the intake port 721 and the exhaust port 731 in the cylinder head 76. In this embodiment, the spark plug 1 is arranged such that the outer opening 511 of the large nozzle hole 51 faces the exhaust valve 73 when viewed from the Z direction (not shown).

[0035] The intake port 721 and the exhaust port 731 are inclined with respect to the forward and backward movement direction of the piston 74 so that the opening direction of the intake port 721 and the exhaust port 731 is directed toward the central axis of the main combustion chamber 101. In addition, the base end surface of the main combustion chamber 101 is inclined so as to be directed toward the tip side as it moves away from the spark plug 1.

[0036] An injector 71 is provided at a position adjacent to the intake port 721. The injector 71 is attached in such a position that it injects fuel toward the central axis of the main combustion chamber 101.

[0037] In the internal combustion engine 10, an intake stroke, a compression stroke, an expansion stroke, and an exhaust stroke are repeated in sequence in accordance with the reciprocating motion of the piston 74. During the intake stroke, gas (mainly air) is introduced into the main combustion chamber 101 from the intake port 721, and during the exhaust stroke, the gas in the main combustion chamber 101 is exhausted from the exhaust port 731. Due to the way in which the airflow is introduced during the intake stroke, a predetermined airflow is formed in the main combustion chamber 101, and this airflow remains even during the compression stroke.

[0038] During the compression stroke, the atmosphere in the main combustion chamber 101 is compressed, and air flows into the auxiliary combustion chamber 50 through the nozzle holes 51 and 52. This causes the pressure in the auxiliary combustion chamber 50 to increase. Then, for example, during the compression stroke, the injector 71 injects fuel directly into the main combustion chamber 101.

[0039] As shown in FIG. 4, the fuel injected into the main combustion chamber 101 forms an injection flow F together with the air in the main combustion chamber 101 and impinges on the base end surface of the piston 74. In this embodiment, the base end surface of the piston 74 has a concave surface. The injection flow F that impinges on the base end surface of the piston 74 changes its trajectory and travels toward the base end side, i.e., toward the spark plug 1. At this time, the injection flow F reaches the vicinity of the outer opening 511 of the large injection hole 51 in the spark plug 1, as shown in FIG.

[0040] The injection flow F is a mixture with a relatively high fuel ratio. Therefore, the vicinity of the outer opening 511 of the large injection hole 51 where the injection flow F reaches becomes a mixture containing a large amount of fuel. This mixture is then introduced into the auxiliary combustion chamber 50 via the large injection hole 51. Then, the airflow AF1 of the mixture with high fuel density drawn from the large injection hole 51 flows toward the discharge gap G.

[0041] Then, near the top dead center of the compression stroke, a discharge is generated in the discharge gap G of the spark plug 1. This efficiently ignites the air-fuel mixture. Note that the above-mentioned fuel injection timing and the discharge ignition timing of the spark plug 1 can be changed in various ways depending on the situation, purpose, etc., as described later.

[0042] During the expansion stroke, the piston 74 moves toward the tip end, causing the main combustion chamber 101 to become negative pressure relative to the auxiliary combustion chamber 50. Then, airflow flows from the auxiliary combustion chamber 50 to the main combustion chamber 101 through the large nozzle hole 51. As a result, as shown in Figs. 8 and 9, the airflow AF1 is guided by the base end surface 61 of the ground electrode 6 toward the large nozzle hole 51. The airflow AF1 guided by the base end surface 61 of the ground electrode 6 passes through the discharge gap G. As a result, the discharge S generated in the discharge gap G during the expansion stroke as shown in Fig. 8 is stretched toward the large nozzle hole 51 by the airflow AF1 as shown in Fig. 9.

[0043] Next, the effects of this embodiment will be described. In the above spark plug 1 for an internal combustion engine, the large injection hole 51 is formed so that an extension line L1 of the central axis of the large injection hole 51 passes through the discharge gap G. Therefore, the discharge formed in the discharge gap G is easily extended by the airflow introduced into the auxiliary combustion chamber 50 through the large injection hole 51 or the airflow flowing out from the auxiliary combustion chamber 50. As a result, the ignition performance can be improved.

[0044] That is, the opening area of ​​the large injection hole 51 is larger than the opening area of ​​the small injection hole 52. Therefore, the airflow introduced into the auxiliary combustion chamber 50 through the large injection hole 51 or the airflow flowing out from the auxiliary combustion chamber 50 through the large injection hole 51 is likely to be stronger than the airflow introduced into the auxiliary combustion chamber 50 through the small injection hole 52 or the airflow flowing out from the auxiliary combustion chamber 50 through the small injection hole 52. In addition, the large injection hole 51 is formed so that the extension line L1 passes through the discharge gap G. That is, the discharge gap G is located on the extension line of the opening direction of the large injection hole 51. Therefore, as shown in FIG. 6 and FIG. 7, in the compression stroke, the airflow AF1 introduced through the large injection hole 51 is likely to flow toward the discharge gap G. Therefore, as shown in FIG. 6, the discharge S generated in the discharge gap G is likely to be extended by the airflow AF1 as shown in FIG. 7. As a result, the ignition performance can be improved.

[0045] In addition, during the expansion stroke, the airflow AF1 flowing out from the auxiliary combustion chamber 50 through the large nozzle hole 51 is guided to the base end surface 61 of the ground electrode 6, and thus easily passes through the discharge gap G. Therefore, as shown in FIG. 8, the discharge S generated in the discharge gap G is easily extended toward the large nozzle hole 51 by the airflow AF1 as shown in FIG. 9, and ignition performance in the auxiliary combustion chamber 50 can be improved. In addition, since the ignition position can be easily brought close to the large nozzle hole 51, for example, under operating conditions in which the temperature of the auxiliary combustion chamber 50 is low, cold loss can be suppressed and the flame jet to the main combustion chamber can be strengthened. Furthermore, the discharge S or discharge plasma or initial flame generated in the discharge gap G is easily ejected from the large nozzle hole 51, and therefore ignition performance in the main combustion chamber can be improved.

[0046] Furthermore, the large injection hole 51, which introduces a larger amount of gas into the auxiliary combustion chamber 50 and discharges a larger amount of gas from the auxiliary combustion chamber 50 than the small injection hole 52, opens toward the discharge gap. This makes it possible to generate a strong airflow around the discharge gap G. As a result, the discharge generated in the discharge gap G can be stably extended.

[0047] In addition, the base end surface 61 of the ground electrode 6 is a flat surface. Therefore, during the expansion stroke, the airflow flowing out from the auxiliary combustion chamber 50 through the large injection hole 51 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.

[0048] When viewed from the Z direction, at least one large injection hole 51 and the fixed end portion 62 face each other in the plug radial direction. Therefore, during the expansion stroke, the airflow flowing from the auxiliary combustion chamber 50 to the main combustion chamber through the large injection hole 51 can be more easily guided by the base end surface 61 of the ground electrode 6. As a result, during the expansion stroke, the discharge generated in the discharge gap G can be more easily extended.

[0049] When viewed from the Z direction, at least a part of the protruding end 63 of the ground electrode 6 is located between the tip of the center electrode 4 and the large nozzle hole 51. Therefore, as shown in FIG. 8, in the expansion stroke, the starting point SP on the ground electrode 6 side of the discharge S generated in the discharge gap G is easily moved toward the large nozzle hole 51 along the base end surface 61 of the ground electrode 6 by the airflow AF1 as shown in FIG. 9. Therefore, the discharge S is easily extended toward the large nozzle hole 51, and the ignition ability in the auxiliary combustion chamber 50 can be improved. In addition, since the ignition position can be brought closer to the large nozzle hole 51, the cold loss is suppressed, and the flame jet to the main combustion chamber 101 can be further strengthened. Furthermore, the discharge or discharge plasma, or the initial flame generated in the discharge gap G is more easily ejected from the large nozzle hole 51.

[0050] The base end surface 61 of the ground electrode 6 has an inclined surface 611 at least from the gap forming surface 612 to the protruding end 63. Therefore, during the expansion stroke, the airflow flowing out of the auxiliary combustion chamber 50 through the large nozzle hole 51 is easily guided by the inclined surface 611. As a result, the discharge generated in the discharge gap G is easily extended toward the large nozzle hole 51.

[0051] Moreover, the large nozzle hole 51 opens at an incline with respect to the Z direction so that it is more outward toward the tip side. Therefore, during the compression stroke, the airflow introduced into the auxiliary combustion chamber 50 through the large nozzle hole 51 tends to flow toward the base end side. Therefore, the discharge S generated in the discharge gap G tends to extend toward the base end side of the auxiliary combustion chamber 50. As a result, the combustion of the mixture grows from a region closer to the base end side in the auxiliary combustion chamber 50, and the pressure in the auxiliary combustion chamber 50 increases when the flame reaches the nozzle holes 51 and 52. Therefore, the flame jet to the main combustion chamber 101 can be strengthened.

[0052] In the above internal combustion engine 10, the spark plug 1 is disposed so that the injection flow F injected from the injector 71 is directed toward the outer opening 511 of the large injection hole 51. This makes it easier for a high-fuel-density mixture to be introduced from the large injection hole 51 into the auxiliary combustion chamber 50. As a result, the high-fuel-density mixture can more easily reach the discharge gap G, improving ignition performance.

[0053] Also, for example, in high load operation of an internal combustion engine, retarded injection and retarded ignition may be performed to suppress pre-ignition. Retarded injection and retarded ignition are fuel injection and ignition performed at a timing later than the timing of general fuel injection and ignition. That is, the fuel injection timing from the injector 71 is set to, for example, the timing immediately before the piston 74 reaches the top dead center during the compression stroke. Specifically, fuel is injected at, for example, a timing of 30° BTDC. BTDC is an abbreviation for Before Top Dead Center, and indicates how far in the crank angle the compression top dead center is. The ignition of the spark plug 1 is set to a timing substantially at the compression top dead center.

[0054] By injecting fuel and igniting at such timing, it is possible to suppress ignition earlier than the desired timing, i.e., early ignition, and to suppress pre-ignition. On the other hand, when retarded injection is performed, when fuel is supplied to the main combustion chamber 101, a certain amount of air has already filled the auxiliary combustion chamber 50, and the airflow in the main combustion chamber 101 is also weakened. This leads to a situation in which the amount of fuel introduced into the auxiliary combustion chamber 50 from the injection hole formed in the plug cover 5 is likely to be relatively small.

[0055] However, the spark plug 1 of this embodiment has the above-mentioned large injection hole 51. Therefore, when a mixture containing fuel is introduced into the auxiliary combustion chamber 50 from the large injection hole 51, the mixture with a high fuel density is likely to reach the discharge gap G. Therefore, even if the total amount of fuel introduced into the auxiliary combustion chamber 50 is reduced, the proportion of fuel supplied to the discharge gap G can be increased. As a result, as described above, the ignition performance in the auxiliary combustion chamber 50 is improved, and the ignition performance in the main combustion chamber 101 can be improved.

[0056] Even when the fuel injection timing is the intake stroke, the same effect as described above can be achieved in this embodiment in that the discharge in the discharge gap G can be easily extended. That is, for example, when EGR combustion (i.e., exhaust gas recirculation combustion) is used, fuel is injected in the intake stroke and ignited in the compression stroke. In this case, too, the spark plug 1 of this embodiment can easily extend the discharge, improving ignition performance. Furthermore, the improved ignition performance can increase the upper limit of the EGR amount, improving fuel economy.

[0057] As described above, according to the present embodiment, it is possible to provide the spark plug 1 for an internal combustion engine, which is capable of improving ignition performance, and the internal combustion engine 10 including the spark plug 1.

[0058] (Embodiment 2) In this embodiment, as shown in FIG. 11, the outer opening 511 of the large injection hole 51 faces the intake valve 72 side when viewed from the Z direction.

[0059] 10 and 11, the internal combustion engine 10 has an intake valve 72 and an exhaust valve 73 provided in the main combustion chamber 101. The spark plug 1 is arranged such 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, as shown in FIG.

[0060] The spark plug 1 is disposed in a position in the cylinder head 76 surrounded by two intake ports 721 and two exhaust ports 731. 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.

[0061] 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 an arrow AF2 in Fig. 10. In the vicinity of the tip of the spark plug 1 in the main combustion chamber 101, this airflow AF2 is directed from the intake valve 72 side to the exhaust valve 73 side, as shown in Fig. 10 and Fig. 11. More specifically, as shown in Fig. 11, when viewed from the plug axial direction Z, the airflow AF2 along the direction from the intermediate position between the two intake ports 721 to the intermediate position between the two exhaust ports 731 is the main airflow in the vicinity of the tip of the spark plug 1.

[0062] The airflow in the main combustion chamber 101 is not always constant, but may vary between cycles or between different timings in 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 AF2 means the main airflow at the ignition timing. And, when we say "airflow in the main combustion chamber 101," we mean the above-mentioned airflow AF2 near the tip of the spark plug 1 at the ignition timing, unless otherwise specified.

[0063] In this embodiment, an injector (not shown) is installed in the internal combustion engine 10 so as to inject fuel into the intake port 721. Note that, similarly to the first embodiment, the injector may also be installed in the internal combustion engine so as to inject fuel directly into the main combustion chamber. The rest is the same as in embodiment 1. Note that, among the symbols used in embodiment 2 and onwards, the same symbols used in the previous embodiments represent the same components, etc. as in the previous embodiments, unless otherwise specified.

[0064] The internal combustion engine 10 has the above-mentioned spark plug 1. The spark plug 1 is arranged such that, when viewed from the plug axial direction Z, the outer opening 511 of at least one large injection hole 51 faces the intake valve 72 side. 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 injection hole 51 when viewed from the plug axial direction Z. This makes it possible to improve 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 makes it possible to burn the mixture in the entire main combustion chamber 101 in a well-balanced manner. As a result, it is possible to suppress abnormal combustion that causes knocking and the like.

[0065] 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, is likely 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 localized residual unburned fuel can be suppressed. As a result, it is possible to suppress combustion abnormalities that cause knocking and the like.

[0066] Furthermore, when viewed from the Z direction, the spark plug 1 has the outer opening 511 of the large injection hole 51 facing the intake valve 72, so that the outer opening 511 of the large injection hole 51 is likely to face the upstream side of the airflow AF2 of the main combustion chamber 101. Therefore, the airflow is easily introduced from the main combustion chamber 101 to the auxiliary combustion chamber 50 through the large injection hole 51. Therefore, as shown in FIG. 12, the discharge S generated in the discharge gap G is easily extended by the airflow AF1 as shown in FIG. 13. As a result, the ignition ability in the auxiliary combustion chamber 50 can be reliably improved. In addition, the same effects as those of the first embodiment are achieved.

[0067] (Embodiment 3) In this embodiment, as shown in Figs. 14 to 16, an extension line L1 of the central axis of the large injection hole 51 and an inclined surface 611 intersect with each other.

[0068] 14, the large nozzle hole 51 is formed so that an extension line L1 of the central axis of the large nozzle hole 51 intersects with the inclined surface 611. The extension line L1 of the central axis of the large nozzle hole 51 passes through the base end side of the protruding end portion 63 of the ground electrode 6.

[0069] The ground electrode 6 has a flat protruding end surface 631 at the protruding end portion 63. An extension line L1 of the central axis of the large injection hole 51 passes through the base end side of the protruding end surface 631.

[0070] In this embodiment, an extension line L1 of the central axis of the large nozzle hole 51 passes through the ground electrode 6. The extension line L1 of the central axis of the large nozzle hole 51 and the inclined surface 611 intersect with each other at an intersection A on the inclined surface 611. As shown in FIG 16 , a line segment L3 that connects the large nozzle hole 51 and the intersection A, which is on the extension line L1 of the central axis of the large nozzle hole 51, does not pass through the ground electrode 6.

[0071] As shown in FIG. 15, the angle α2 at which an extension line L1 of the central axis of the large nozzle hole 51 and the inclined surface 611 intersect with each other is an obtuse angle on the base end side of the extension line L1.

[0072] In this embodiment, the plug central axis C passes through the extension line L1 and the inclined surface 611. As shown in FIG. 15, in a cross section including the plug central axis C and the extension line L1, the smaller angle α3 between the inclined surface 611 of the ground electrode 6 and the plug central axis C is smaller than the smaller angle α4 between the extension line L1 and the plug central axis C. In other words, the extension line L1 is inclined more with respect to the plug axial direction than the inclined surface 611 of the ground electrode 6. The angle α4 can be set to, for example, 45° to 75°. The angle α4 can be set to, for example, 5° or more larger than the angle α3. The rest is the same as in the first embodiment.

[0073] The large nozzle hole 51 is formed so that an extension line L1 of the central axis of the large nozzle hole 51 and the inclined surface 611 intersect with each other. In addition, the extension line L1 of the central axis of the large nozzle hole 51 passes through the base end side of the protruding end 63 of the ground electrode 6. Therefore, the airflow introduced into the auxiliary combustion chamber 50 via the large nozzle hole 51 is easily guided by the inclined surface 611 of the ground electrode 6 without being blocked by the protruding end 63 of the ground electrode 6. As a result, the discharge generated in the discharge gap G is easily and reliably extended.

[0074] In addition, the airflow introduced into the auxiliary combustion chamber 50 through the large nozzle hole 51 is easily guided toward the base end by the inclined surface 611 of the ground electrode 6. Therefore, the discharge generated in the discharge gap G is easily extended toward the base end of the auxiliary combustion chamber 50. Therefore, the combustion of the air-fuel mixture can be developed from the base end side or the center of the auxiliary combustion chamber 50. As a result, a flame jet can be strongly ejected into the main combustion chamber through the nozzle holes 51, 52. In addition, the same effects as those of the first embodiment are achieved.

[0075] (Embodiment 4) As shown in FIG. 17, this embodiment is an embodiment in which the shape of the ground electrode 6 is modified from that of the first embodiment. That is, the ground electrode 6 is fixed to the front end portion of the housing 2, and has a fixed side portion 64 including a fixed end portion 62, and an inclined portion 65 having an inclined surface 611. The fixed side portion 64 is formed along the plug radial direction. The inclined portion 65 is inclined with respect to the plug axial direction Z so as to move toward the front end side as it approaches the protruding end portion 63.

[0076] In this embodiment, the fixed end 62 of the ground electrode 6 is joined to the front end surface 22 of the housing 2 as shown in Fig. 17. The ground electrode 6 can be joined to the inner circumferential surface 21 of the front end of the housing 2. The rest is the same as in the first embodiment.

[0077] In this embodiment, the ground electrode 6 has the fixed side portion 64 and the inclined portion 65. Therefore, the ground electrode 6 can be easily and stably fixed to the tip portion of the housing 2 while the inclined surface 611 faces the center electrode 4. As a result, the productivity of the spark plug 1 can be easily improved. In addition, the same effects as those of the first embodiment are achieved.

[0078] (Embodiment 5) As shown in FIG. 18, this embodiment is an embodiment in which the shape of the ground electrode 6 is modified from that of the fourth embodiment.

[0079] In this embodiment, the ground electrode 6 is fixed to the front end surface 22 of the housing 2 along the plug radial direction, as shown in Fig. 18. The ground electrode 6 has a tapered shape in a part of the longitudinal direction of the ground electrode 6 that is closer to the protruding end 63 than the fixed end 62, such that the width in the Z direction decreases toward the protruding end 63. An inclined surface 611 is formed in the tapered portion. A discharge gap G is formed between the inclined surface 611 and the front end of the center electrode 4. The other configurations and effects are the same as those of the fourth embodiment.

[0080] (Embodiment 6) As shown in FIG. 19, this embodiment is an embodiment in which the position of the discharge gap G is changed from that of the first embodiment. In other words, the discharge gap G is formed on the tip side of the housing 2 relative to the tip of the housing 2 . The rest is the same as in the first embodiment.

[0081] The discharge gap G is formed on the tip side of the tip of the housing 2. Therefore, it is easy to check the discharge gap G formed between the ground electrode 6 and the 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 manufactured easily. In addition, the same effects as those of the first embodiment are achieved.

[0082] (Embodiment 7) As shown in FIG. 20, 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 41 of the center electrode 4 is inclined along the inclined surface 611 of the ground electrode 6 .

[0083] In this embodiment, the tip surface 41 of the center electrode 4 and the inclined surface 611 of the ground electrode 6 are both flat surfaces. As shown in Fig. 20, the flat surfaces are arranged substantially parallel to each other and face each other, thereby forming a discharge gap G. The rest is the same as in the first embodiment.

[0084] The tip surface 41 of the center electrode 4 is inclined along the inclined surface 611 of the ground electrode 6. This makes it possible to suppress the increase in the distance of the discharge gap G due to wear of the ground electrode 6 or the center electrode 4. As a result, the life of the spark plug 1 can be extended. In addition, the same effects as those of the first embodiment are achieved.

[0085] (Embodiment 8) As shown in FIG. 21, this embodiment is an embodiment in which the shape of the tip portion of the center electrode 4 is modified from that of the seventh embodiment.

[0086] In this embodiment, the tip of the center electrode 4 has a tapered shape with a diameter decreasing toward the tip side as shown in Fig. 21. The tip of the tapered center electrode 4 has a substantially truncated cone shape. The tip of the center electrode 4 may have a substantially conical shape, a substantially truncated square pyramid shape, a substantially square pyramid shape, or the like.

[0087] The tapered surface 42 at the tip of the center electrode 4 is formed in an annular shape. A part of the tapered surface 42 is inclined along the inclined surface 611 of the ground electrode 6. A discharge gap G is formed between the tapered surface 42 and the inclined surface 611 of the ground electrode 6. The rest is the same as in the seventh embodiment.

[0088] In this embodiment, a discharge gap G is formed between the tapered surface 42 and the inclined surface 611. Therefore, in this embodiment as well, it is possible to suppress the increase in the distance of the discharge gap G due to wear of the ground electrode 6 or the center electrode 4. In addition, the same effects as those of the seventh embodiment are obtained.

[0089] (Embodiment 9) This embodiment has two large nozzle holes 51, as shown in FIGS.

[0090] In this embodiment, the plug cover 5 has two large injection holes 51 and four small injection holes 52 formed therein, as shown in FIG.

[0091] 23, when viewed from the Z direction, a straight line L2 passing through the plug central axis C and the center of each of the injection holes 51, 52 passes through each of the two injection holes 51, 52. The injection holes 51, 52 are disposed at equal intervals in the circumferential direction of the plug such that an angle α5 formed between each of the straight lines L2 passing through adjacent injection holes 51, 52 in the circumferential direction of the plug is 60° when viewed from the Z direction.

[0092] 22, 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, the large injection hole 51 is formed in the first plug portion 11. In this embodiment, the two small injection holes 52 are formed in the second plug portion 12. The remaining two small injection holes 52 are formed in both the first plug portion 11 and the second plug portion 12.

[0093] Further, each of the two large nozzle holes 51 is formed so that an extension line L1 of the central axis of the large nozzle hole 51 passes through the discharge gap G. The other configurations and effects are the same as those of the first embodiment.

[0094] (Embodiment 10) In this embodiment, as shown in FIG. 24, the nozzle holes 51, 52 are formed biased toward the first plug portion 11 side.

[0095] In this embodiment, as shown in Fig. 24, three large injection holes 51 and two small injection holes 52 are formed in the plug cover 5. The three large injection holes 51 are formed in the first plug portion 11. The two small injection holes 52 are each formed throughout both the first plug portion 11 and the second plug portion 12.

[0096] In addition, each of the three large injection holes 51 is formed so that an extension line L1 of the central axis of the large injection hole 51 passes through the discharge gap G. The other configurations and effects are the same as those of the ninth embodiment.

[0097] (Embodiment 11) In this embodiment, as shown in FIG. 25, a base end surface 61 of a ground electrode 6 has a concave surface recessed toward the tip side.

[0098] 25, when the ground electrode 6 is viewed from the protruding direction of the ground electrode 6, the base end surface 61 is a concave surface recessed toward the tip side. In this embodiment, the entire base end surface 61 is a concave surface. The other configurations and effects are the same as those of the first embodiment.

[0099] (Embodiment 12) As shown in Figs. 26 to 28, this embodiment is an embodiment in which the position of the ground electrode 6 is changed from that of the sixth embodiment.

[0100] In this embodiment, the protruding end 63 of the ground electrode 6 is positioned further forward than a straight line L4 that connects the base end of the outer opening 511 of the large nozzle hole 51 and the tip end of the center electrode 4 at the shortest distance, as shown in FIG.

[0101] As shown in FIG. 27, the protruding end 63 is disposed at a position where the distance D2 to the large injection hole 51 is shorter than the distance D1 to the tip end of the center electrode 4. The rest is the same as in the sixth embodiment.

[0102] The protruding end 63 is disposed at a position where the distance D2 is shorter than the distance D1. Therefore, as shown in FIG. 28, during the expansion stroke, the starting point SP on the ground electrode 6 side of the discharge S generated in the discharge gap G is easily moved toward the large nozzle hole 51 by the airflow AF1 guided by the base end surface 61 of the ground electrode 6. Therefore, the discharge S is more likely to extend. As a result, the ignition performance can be further improved. In addition, the starting point SP is more likely to move to the inner surface of the large nozzle hole 51 by the airflow AF1. Therefore, the discharge S is more likely to extend, and it can be expected that a part of the discharge S will fly out of the large nozzle hole 51 toward the main combustion chamber. As a result, the ignition performance can be further improved.

[0103] The protruding end 63 is positioned further towards the tip side than the straight line L4. Therefore, during the expansion stroke, the discharge is less likely to be short-circuited by the protruding end 63 as it extends towards the large nozzle hole 51. Therefore, the discharge is more likely to extend. Also, the starting point of the discharge on the ground electrode 6 side is more likely to move to the inner surface of the large nozzle hole 51. Therefore, part of the discharge is more likely to fly out from the large nozzle hole 51 towards the main combustion chamber. As a result, ignition performance can be further improved. In addition, the same effects as those of the sixth embodiment are obtained.

[0104] (Embodiment 13) In this embodiment, as shown in Figs. 29 to 35, a center electrode 4 and a ground electrode 6 face each other in the plug radial direction, thereby forming a discharge gap G.

[0105] In the spark plug 1 of this embodiment, a discharge gap G is formed by the center-facing side surface 43 of the center electrode 4 and the ground-facing side surface 66 of the ground electrode 6 facing each other in the plug radial direction, as shown in FIGS.

[0106] As shown in Fig. 29, in a cross-sectional view that includes an extension line L1 of the central axis of the large injection hole 51 and is taken along the plug axial direction Z, the extension line L1 and the discharge gap G overlap each other. In addition, as shown in Fig. 30, the extension line L1 extends along the plug radial direction when viewed from the plug axial direction Z.

[0107] In this embodiment, as shown in Fig. 29, the ground electrode 6 is inclined toward the tip side as it approaches the protruding end 63. Also, as shown in Fig. 30, the ground electrode 6 is provided so that the protruding direction of the protruding end 63 is aligned with the arrangement direction of the large injection hole 51 and the tip end of the center electrode 4 when viewed from the Z direction.

[0108] When viewed from the plug axial direction Z, in the protruding direction of the ground electrode 6, the large injection hole 51 and the fixed end portion 62 are located on opposite sides to each other with the tip end portion of the center electrode 4 in between.

[0109] When viewed from the plug axial direction Z, at least a part of the protruding end 63 of the ground electrode 6 is located between the tip end of the center electrode 4 and the large injection hole 51 in the protruding direction of the ground electrode 6. In addition, when viewed from the Z direction, the large injection hole 51 and the discharge gap G are located on opposite sides of each other with the protruding end 63 sandwiched therebetween in the protruding direction of the ground electrode 6.

[0110] In this embodiment, the ground-facing side surface 66 is formed in a planar shape as shown in Fig. 29 and Fig. 30. Specifically, the ground-facing side surface 66 is formed in a continuous planar shape from the fixed end portion 62 to the protruding end portion 63. The ground-facing side surface 66 is formed along the protruding direction of the protruding end portion 63. The normal direction of the ground-facing side surface 66 is a surface that is perpendicular to the protruding direction of the ground electrode 6.

[0111] In this embodiment, the center facing side surface 43 which forms the discharge gap G together with the ground facing side surface 66 is curved.

[0112] In this embodiment, the discharge gap G is, for example, as shown in FIG. 29 , a region between the ground-facing side surface 66 overlapping with the tip end of the center electrode 4 and the center-facing side surface 43 overlapping with the ground electrode 6, when viewed from a facing direction in which the ground electrode 6 and the center electrode 4 face each other in the plug radial direction.

[0113] Moreover, the edge tip 662 is the tip of the protruding side edge 661 of the ground-facing side surface 66. In a cross-sectional view that includes an extension line L1 of the central axis of the large nozzle hole 51 and is along the plug axial direction Z, the edge tip 662 is located on the tip side of the extension line L1 of the central axis of the large nozzle hole 51. Moreover, the edge tip 662 is located on the tip side of the base end of the large nozzle hole 51.

[0114] 29 and 31, the ground electrode 6 has a ground tip surface 67 which is the surface on the tip side. The ground tip surface 67 is inclined at least from the position of the discharge gap G to the protruding end 63 in the protruding direction of the protruding end 63 of the ground electrode 6 so as to approach the tip side as it approaches the protruding end 63. In this embodiment, the ground tip surface 67 is inclined from the fixed end 62 to the protruding end 63 so as to approach the tip side as it approaches the protruding end 63.

[0115] Moreover, the tip side edge 663 of the ground facing side surface 66 is inclined at least in the protruding direction of the protruding end 63 from the position of the discharge gap G to the protruding end 63 so as to approach the tip side as it approaches the protruding end 63. In this embodiment, the tip side edge 663 is inclined from the fixed end 62 to the protruding end 63 so as to approach the tip side as it approaches the protruding end 63. The rest is the same as in the first embodiment.

[0116] In the spark plug 1 of this embodiment, in a cross-sectional view that includes an extension line L1 of the central axis of the large injection hole 51 and is taken along the plug axial direction Z, the extension line L1 and the discharge gap G overlap each other. Therefore, the discharge formed in the discharge gap G is easily extended by the airflow introduced into the auxiliary combustion chamber 50 via the large injection hole 51 or the airflow flowing out from the auxiliary combustion chamber 50. As a result, ignition performance can be improved.

[0117] When the positional relationship between the extension line L1 and the discharge gap G satisfies the above condition, the airflow introduced into the auxiliary combustion chamber 50 through the large injection hole 51 easily passes through the discharge gap G during the compression stroke, etc. That is, as shown in Figs. 32 and 33, the airflow AF1 introduced into the auxiliary combustion chamber 50 through the large injection hole 51 easily flows directly into the discharge gap G, or easily flows into the discharge gap G along the outer circumferential surface of the central electrode 4. Therefore, as shown in Fig. 32, the discharge S generated in the discharge gap G is easily extended by the airflow AF1, as shown in Fig. 33. As a result, the ignition performance during the compression stroke can be improved.

[0118] 34, in the discharge gap G, an airflow AF1 that flows out from the auxiliary combustion chamber 50 to the outside through the large nozzle hole 51 is likely to be formed. Therefore, the discharge S is likely to extend toward the large nozzle hole 51 by the airflow AF1. As a result, the ignition performance in the expansion stroke can be improved.

[0119] In addition, in a cross-sectional view including an extension line L1 of the central axis of the large nozzle hole 51 and taken along the plug axial direction Z, the edge tip 662 is located on the tip side of the extension line L1. Therefore, the starting point of the discharge on the ground electrode 6 side is likely to move from the ground electrode 6 to the inner peripheral surface of the large nozzle hole 51. Specifically, as shown in FIG. 34, during the expansion stroke, the starting point SP of the discharge S on the ground electrode 6 side moves toward the large nozzle hole 51 side to the edge tip 662 by the airflow AF1 flowing out of the auxiliary combustion chamber 50 via the large nozzle hole 51. After that, the starting point SP further moves from the edge tip 662 to the inner wall surface 54 of the plug cover 5 by the airflow AF1, and moves along the inner wall surface 54 to the inner peripheral surface of the large nozzle hole 51. Then, the discharge S is further extended, and it is expected that a part of the discharge S will fly out of the large nozzle hole 51 toward the main combustion chamber side, as shown in FIG. 35. This makes it possible to improve the ignition performance in the main combustion chamber during the expansion stroke.

[0120] The ground tip surface 67 is inclined toward the tip side at least from the position of the discharge gap G to the protruding end 63 in the protruding direction of the protruding end 63. Therefore, during the expansion stroke, the starting point on the ground electrode 6 side of the discharge generated in the discharge gap G is likely to move by the airflow along the ground tip surface 67 toward the large nozzle hole 51. Therefore, during the expansion stroke, the discharge is more likely to extend. As a result, the ignition performance during the expansion stroke can be further improved.

[0121] When viewed from the plug axial direction Z, the large injection hole 51 and the fixed end portion 62 are located on opposite sides of the tip portion of the center electrode 4 in the protruding direction of the ground electrode 6. Therefore, as shown in Fig. 33, during the compression stroke, the starting point SP of the discharge S on the ground electrode 6 side is likely to move in a direction away from the large injection hole 51 by the airflow AF1. In other words, during the compression stroke, the starting point SP is likely to move toward the fixed end portion 62 by the airflow AF1. As a result, the discharge S can be further extended.

[0122] When viewed from the plug axial direction Z, at least a part of the protruding end 63 is located between the tip end of the center electrode 4 and the large injection hole 51 in the protruding direction of the ground electrode 6. Therefore, during the expansion stroke, the starting point of the discharge on the ground electrode 6 side is likely to move toward the large injection hole 51 due to the airflow. Therefore, the discharge S is likely to be extended. As a result, the ignition performance can be improved.

[0123] The discharge gap G is formed by the center facing side surface 43 and the ground facing side surface 66 facing each other in the plug radial direction. Therefore, it is easy to position the ground electrode 6 so that the airflow introduced into the auxiliary combustion chamber 50 via the large injection hole 51 and the airflow discharged from the auxiliary combustion chamber 50 via the large injection hole 51 are not blocked by the ground electrode 6. Therefore, an airflow is easily formed in the discharge gap G. As a result, ignition performance can be improved.

[0124] Moreover, the extension line L1 is aligned along the plug radial direction when viewed from the plug axial direction Z. This makes it easy to open the large injection hole 51 in the plug cover 5. That is, the large injection hole 51 can be opened in a part of the outer surface of the plug cover 5 along the normal direction thereof by cutting using a drill or the like. As a result, the spark plug 1 with improved ignition performance can be efficiently manufactured. In addition, the same effects as those of the first embodiment are achieved.

[0125] (Embodiment 14) As shown in FIG. 36, this embodiment is an embodiment in which the shape of the center electrode 4 is modified from that of the thirteenth embodiment.

[0126] In this embodiment, as shown in FIG. 36, the tip portion of the center electrode 4 has a cross section perpendicular to the longitudinal direction of the center electrode 4 in the shape of a segmented circle.

[0127] In this embodiment, the center facing side surface 43 is formed in a planar shape. The planar center facing side surface 43 and the planar ground facing side surface 66 are opposed to each other in the plug radial direction, thereby forming a discharge gap G. The center facing side surface 43 is formed so as to extend along the ground facing side surface 66. In other words, the discharge gap G is formed by the center facing side surface 43 and the ground facing side surface 66 being opposed to each other substantially in parallel. The rest is the same as in the thirteenth embodiment.

[0128] The discharge gap G is formed by the planar center-facing side surface 43 and the planar ground-facing side surface 66 facing each other in approximately parallel relation. This makes it easy to disperse the starting positions of the discharge on the center electrode 4 side and the ground electrode 6 side. This makes it possible to suppress localized wear of the center electrode 4 and the ground electrode 6, 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, it has the same effects as the thirteenth embodiment.

[0129] (Embodiment 15) As shown in FIG. 37, this embodiment is an embodiment in which the shape of the ground electrode 6 is modified from that of the thirteenth embodiment.

[0130] The ground electrode 6 has a fixed portion 68 that includes a fixed end portion 62 and is formed along a direction perpendicular to the Z direction, and a protruding end portion 63 and a protruding inclined portion 69 that is inclined with respect to the Z direction. The protruding inclined portion 69 is inclined with respect to the Z direction so as to be more inclined toward the tip side as it approaches the protruding end portion 63. The other configurations and effects are the same as those of the thirteenth embodiment.

[0131] In the above-mentioned embodiments 13 to 15, the discharge gap G is formed by the center facing side surface 43 and the ground facing side surface 66 formed along the protruding direction of the protruding end portion 63 facing each other in the plug radial direction. However, the discharge gap can also be formed by the protruding end face on the protruding side of the ground electrode and the center facing side surface of the center electrode facing each other in the plug radial direction. In other words, the protruding end surface can be the ground facing side surface.

[0132] The present invention is not limited to the above-described embodiments, and can be applied to various embodiments without departing from the gist of the present invention. [Explanation of symbols]

[0133] 1...spark plug, 2...housing, 3...insulator, 4...center electrode, 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, L1...extension of central axis of large nozzle hole, G...discharge gap, Z...plug axial direction

Claims

1. A cylindrical insulator (3); a center electrode (4) held on the inner circumferential side of the insulator and protruding from the insulator toward the tip side; 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 the tip of the housing so as to cover a sub-combustion chamber (50) in which the discharge gap is disposed, The ground electrode protrudes into the auxiliary combustion chamber from a fixed end (62) fixed to the housing or the plug cover, The discharge gap is formed by a tip 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 large nozzle hole (51) and a small nozzle hole (52) having an opening area smaller than that of the large nozzle hole, The large injection hole and the small injection hole each communicate the auxiliary combustion chamber with the outside, An extension line (L1) of the central axis of the large nozzle hole passes through the discharge gap, a spark plug for an internal combustion engine, wherein at least a part of a protruding end portion of the ground electrode is located between the tip portion of the center electrode and the large injection hole in a protruding direction of the ground electrode, when viewed in a plug axial direction.

2. 2. A spark plug for an internal combustion engine as set forth in claim 1, wherein a distance (D2) between the projecting end (63) of the ground electrode and the large nozzle hole is shorter than a distance (D1) between the projecting end (63) and the tip end of the center electrode.

3. A cylindrical insulator (3); a center electrode (4) held on the inner circumferential side of the insulator and protruding from the insulator toward the tip side; 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 the tip of the housing so as to cover a sub-combustion chamber (50) in which the discharge gap is disposed, The ground electrode protrudes into the auxiliary combustion chamber from a fixed end (62) fixed to the housing or the plug cover, The discharge gap is formed by a tip 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 large nozzle hole (51) and a small nozzle hole (52) having an opening area smaller than that of the large nozzle hole, The large injection hole and the small injection hole each communicate the auxiliary combustion chamber with the outside, An extension line (L1) of the central axis of the large nozzle hole passes through the discharge gap, A spark plug (1) for an internal combustion engine, wherein a projecting end (63) of the ground electrode is disposed at a position where a distance (D2) to the large nozzle hole is shorter than a distance (D1) to the tip end of the center electrode.

4. 4. The spark plug for an internal combustion engine according to claim 1, wherein, when viewed in the plug axial direction, at least one of the large injection holes and the fixed end portion face each other in the plug radial direction.

5. 5. 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 located between a tip end portion of said center electrode and said large injection hole, when viewed in a plug axial direction.

6. 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) that is inclined with respect to the plug axial direction from at least a gap forming surface (612) that forms the discharge gap to a protruding end (63) of the ground electrode so as to move toward a tip side as the protruding end approaches the protruding end.

7. 7. A spark plug for an internal combustion engine according to claim 6, wherein the large injection hole is formed such that an extension line of a central axis of the large injection hole intersects with the inclined surface, and the extension line of the central axis of the large injection hole passes through a base end side of a projecting end portion of the ground electrode.

8. The ground electrode is fixed to the tip portion of the housing and has a fixed side portion (64) including the fixed end portion and an inclined portion (65) having the inclined surface, The fixed side portion is formed along a radial direction of the plug, 8. The spark plug for an internal combustion engine according to claim 6, wherein the inclined portion is inclined with respect to the plug axial direction so as to move toward a tip side as it approaches the protruding end portion.

9. 9. The spark plug for an internal combustion engine according to claim 6, wherein a tip surface (41) of said center electrode is inclined along said inclined surface of said ground electrode.

10. 10. A spark plug for an internal combustion engine according to claim 1, wherein the protruding end (63) of the ground electrode is located on the tip side of a straight line (L4) that connects, at the shortest distance, a base end of the outer opening (511) of the large nozzle hole and the tip end of the center electrode.

11. A cylindrical insulator (3); a center electrode (4) held on the inner circumferential side of the insulator and protruding from the insulator toward the tip side; 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 the tip of the housing so as to cover a sub-combustion chamber (50) in which the discharge gap is disposed, The ground electrode protrudes into the auxiliary combustion chamber from a fixed end (62) fixed to the housing or the plug cover, The discharge gap is formed by a center-facing side surface (43) of the center electrode and a ground-facing side surface (66) of the ground electrode facing each other in a plug radial direction, The plug cover is formed with a large nozzle hole (51) and a small nozzle hole (52) having an opening area smaller than that of the large nozzle hole, The large injection hole and the small injection hole each communicate the auxiliary combustion chamber with the outside, in a cross-sectional view including an extension line (L1) of the central axis of the large injection hole and taken along the plug axial direction (Z), the extension line and the discharge gap overlap each other, The above-mentioned extension line is aligned along the radial direction of the plug when viewed from the axial direction of the plug, the ground electrode has a ground tip surface (67) which is a surface on the tip side, and the ground tip surface is inclined at least in a protruding direction of a protruding end (63) of the ground electrode from a position of the discharge gap to the protruding end so as to approach the tip side the closer to the protruding end.

12. 12. A spark plug for an internal combustion engine according to claim 11, wherein at least a part of a protruding end portion (63) of said ground electrode is located between a tip end portion of said center electrode and said large injection hole in a protruding direction of said ground electrode, when viewed in a plug axial direction.

13. A cylindrical insulator (3); a center electrode (4) held on the inner circumferential side of the insulator and protruding from the insulator toward the tip side; 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 the tip of the housing so as to cover a sub-combustion chamber (50) in which the discharge gap is disposed, The ground electrode protrudes into the auxiliary combustion chamber from a fixed end (62) fixed to the housing or the plug cover, The discharge gap is formed by a center-facing side surface (43) of the center electrode and a ground-facing side surface (66) of the ground electrode facing each other in a plug radial direction, The plug cover is formed with a large nozzle hole (51) and a small nozzle hole (52) having an opening area smaller than that of the large nozzle hole, The large injection hole and the small injection hole each communicate the auxiliary combustion chamber with the outside, in a cross-sectional view including an extension line (L1) of the central axis of the large injection hole and taken along the plug axial direction (Z), the extension line and the discharge gap overlap each other, The above-mentioned extension line is aligned along the radial direction of the plug when viewed from the axial direction of the plug, a spark plug for an internal combustion engine, wherein at least a part of a protruding end portion of the ground electrode is located between the tip portion of the center electrode and the large injection hole in a protruding direction of the ground electrode, when viewed in a plug axial direction.

14. 14. A spark plug for an internal combustion engine according to claim 11, wherein a protruding end portion (63) of the ground electrode is disposed at a position where a distance (D2) to the large nozzle hole is shorter than a distance (D1) to the tip end portion of the center electrode.

15. A cylindrical insulator (3); a center electrode (4) held on the inner circumferential side of the insulator and protruding from the insulator toward the tip side; 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 the tip of the housing so as to cover a sub-combustion chamber (50) in which the discharge gap is disposed, The ground electrode protrudes into the auxiliary combustion chamber from a fixed end (62) fixed to the housing or the plug cover, The discharge gap is formed by a center-facing side surface (43) of the center electrode and a ground-facing side surface (66) of the ground electrode facing each other in a plug radial direction, The plug cover is formed with a large nozzle hole (51) and a small nozzle hole (52) having an opening area smaller than that of the large nozzle hole, The large injection hole and the small injection hole each communicate the auxiliary combustion chamber with the outside, in a cross-sectional view including an extension line (L1) of the central axis of the large injection hole and taken along the plug axial direction (Z), the extension line and the discharge gap overlap each other, The above-mentioned extension line is aligned along the radial direction of the plug when viewed from the axial direction of the plug, A spark plug (1) for an internal combustion engine, wherein a projecting end (63) of the ground electrode is disposed at a position where a distance (D2) to the large nozzle hole is shorter than a distance (D1) to the tip end of the center electrode.

16. 16. A spark plug for an internal combustion engine according to claim 11, wherein, in a cross-sectional view which includes an extension line of a central axis of the large injection hole and is taken along the plug axial direction, an edge tip (662) which is a tip of a protruding-side edge (661) of the ground-facing side surface is located on the tip side of the extension line of the central axis of the large injection hole.

17. 17. The spark plug for an internal combustion engine according to claim 1, wherein the discharge gap is formed on a tip side of the tip of the housing.

18. 18. A spark plug for an internal combustion engine according to claim 1, wherein, when viewed in a plug axial direction, in a protruding direction of the ground electrode, the large injection hole and the fixed end portion are located on opposite sides to each other with the tip end portion of the center electrode interposed therebetween.

19. An internal combustion engine (10) comprising a spark plug for an internal combustion engine according to any one of claims 1 to 18, 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.

20. An internal combustion engine (10) comprising a spark plug for an internal combustion engine according to any one of claims 1 to 18, A main combustion chamber (101); The spark plug is disposed so that an outer surface (53) of the plug cover faces the main combustion chamber; an injector (71) for injecting fuel directly into the main combustion chamber; The spark plug is positioned so that an injection flow (F) containing the fuel injected from the injector during a compression stroke of the internal combustion engine is directed toward an outer opening (511) of the large injection hole.

21. The main combustion chamber has an intake valve (72) and an exhaust valve (73), 21. The internal combustion engine according to claim 20, wherein 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 in the plug axial direction.

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