JP2023108870A - Spark plug for internal combustion engine - Google Patents

Abstract

To provide a spark plug for an internal combustion engine that can improve ignitability.SOLUTION: In a spark plug 1, a plug cover 5 is formed with a plurality of nozzle holes 51 for communicating a sub-combustion chamber 50 with the outside. A projecting end portion 62 of a ground electrode 6 and an inner wall surface 54 of a plug cover 5 are in contact with each other in the axial direction of a plug. Also, some nozzle holes 51 of the plurality of nozzle holes 51 are ground side nozzle holes 511 whose shortest distance to the projecting end 62 is equal to or less than the inner diameter of the nozzle hole 51. When viewed from the axial direction of the plug, at least a portion of the ground side injection hole 511 overlaps at least one of a ground extension area 6E and a gap extension area GE.SELECTED DRAWING: Figure 4

Description

The present invention relates to spark plugs for internal combustion engines.

For example, as disclosed in Japanese Unexamined Patent Application Publication No. 2002-100001, a spark plug having a sub-combustion chamber at its tip is known. In this spark plug, a plug cover that covers the auxiliary combustion chamber is formed with a plurality of injection holes. As a result, the flame is ejected from the sub-combustion chamber to the main combustion chamber through the injection holes, and the air-fuel mixture in the main combustion chamber is combusted.

JP 2020-009747 A

However, the spark plug described in Patent Literature 1 does not consider formation of the initial flame. In other words, no consideration is given to extending the discharge generated in the discharge gap to improve the ignitability. Further, in order to raise the catalyst temperature of the exhaust gas purification filter, etc., ignition by discharge may be performed in the expansion stroke of the internal combustion engine, but ignitability in the expansion stroke is not taken into consideration.

SUMMARY OF THE INVENTION The present invention has been made in view of such problems, and an object of the present invention is to provide a spark plug for an internal combustion engine that can improve ignitability.

One aspect of the present invention is a tubular insulator (3),
a center electrode (4) held on the inner peripheral side of the insulator and exposed from the insulator to the tip side;
a cylindrical housing (2) that holds the insulator on the inner peripheral side;
a ground electrode (6) forming a discharge gap (G) with the center electrode;
a plug cover (5) fixed to the tip of the housing so as to cover the sub-combustion chamber (50) in which the discharge gap is arranged;
The ground electrode protrudes into the secondary combustion chamber from a fixed end (61) fixed to the housing,
The plug cover is formed with a plurality of injection holes (51) for communicating the sub-combustion chamber with the outside,
The front end portion of the housing includes a housing fixing portion (21) facing the cover base end portion (52) of the plug cover in the plug radial direction, and a base end surface ( 53) and a facing surface (22) facing the axial direction (Z) of the plug,
The housing fixing portion and the cover base end portion are fixed to each other,
The base end surface of the plug cover is arranged at a position away from the opposing surface in the axial direction of the plug,
The projecting end (62) of the ground electrode and the inner wall surface (54) of the plug cover are in contact with each other in the axial direction of the plug,
Some of the plurality of nozzle holes are ground-side nozzle holes (511), the shortest distance (D1) to the projecting end being equal to or less than the inner diameter (D2) of the nozzle hole,
When viewed from the axial direction of the plug, at least part of the ground-side injection hole includes a ground extension region (6E) extending the ground electrode in the projecting direction, and a gap extending the discharge gap in the projecting direction of the ground electrode. In a spark plug (1) for an internal combustion engine, overlapping at least one of the extension zones (GE).

In the spark plug described above, the projecting end portion and the inner wall surface of the plug cover are in contact with each other in the axial direction of the plug. Further, when viewed from the axial direction of the plug, at least a portion of the ground-side injection hole overlaps at least one of the ground extension area and the gap extension area. Therefore, during the expansion stroke of the internal combustion engine, the discharge generated in the discharge gap tends to be extended by the airflow directed to the ground-side injection hole. As a result, ignitability can be improved.

As described above, according to the above aspect, it is possible to provide a spark plug for an internal combustion engine that can improve ignitability.
It should be noted that the symbols in parentheses described in the claims and the means for solving the problems indicate the corresponding relationship with the specific means described in the embodiments described later, and limit the technical scope of the present invention. not a thing

FIG. 3 is a cross-sectional view along the axial direction of the spark plug in the vicinity of the tip of the spark plug according to the first embodiment, taken along line I-I in FIG. 2; II-II arrow directional cross-sectional view of FIG. FIG. 4 is an explanatory diagram showing the inner diameter of an injection hole, etc., according to the first embodiment; FIG. 4 is an explanatory diagram showing a ground extension region and a gap extension region in Embodiment 1; FIG. 4 is a cross-sectional view for explaining the direction of a swirl flow formed in the sub-combustion chamber according to the first embodiment; FIG. 4 is an explanatory diagram showing an extended area of the ground-side injection hole, etc. in the first embodiment; FIG. 2 is a cross-sectional view showing a line segment L1 in Embodiment 1; FIG. 4 is a cross-sectional view showing how the ground electrode and the plug cover are brought into contact with each other according to the first embodiment; 1 is a cross-sectional view of an internal combustion engine in which a spark plug is installed according to Embodiment 1; FIG. FIG. 4 is a cross-sectional view of the vicinity of the tip portion of the spark plug before the discharge is extended during the expansion stroke in the first embodiment; FIG. 4 is a cross-sectional view of the vicinity of the tip of the spark plug when the discharge is extended during the expansion stroke in the first embodiment; FIG. 4 is a cross-sectional view of the vicinity of the tip of the spark plug when the discharge starting point on the side of the ground electrode moves to the ground side nozzle hole during the expansion stroke in the first embodiment; FIG. 4 is a cross-sectional view of the vicinity of the tip portion of the spark plug when the discharge extends to the main combustion chamber during the expansion stroke in the first embodiment; FIG. 6 is a cross-sectional view along the axial direction of the spark plug near the tip of the spark plug according to the second embodiment; FIG. 11 is a cross-sectional view along the plug axial direction near the tip of the spark plug in Embodiment 3; FIG. 12 is a cross-sectional view along the axial direction of the spark plug in the vicinity of the tip of the spark plug in the fourth embodiment; FIG. 5 is a cross-sectional view along the axial direction of the spark plug in the vicinity of the tip portion of the spark plug in Modified Mode 1; FIG. 11 is a cross-sectional view along the axial direction of the spark plug in the vicinity of the tip portion of the spark plug according to the fifth embodiment; FIG. 11 is a cross-sectional view along the axial direction of the spark plug near the tip of the spark plug according to the sixth embodiment; FIG. 12 is a cross-sectional view along the axial direction of the spark plug in the vicinity of the tip of the spark plug in Embodiment 7; FIG. 12 is a cross-sectional view along the axial direction of the spark plug near the tip of the spark plug according to the eighth embodiment; FIG. 20 is a cross-sectional view along the axial direction of the spark plug in the vicinity of the tip of the spark plug according to the ninth embodiment; FIG. 21 is a cross-sectional view along the axial direction of the spark plug in the vicinity of the tip of the spark plug in the tenth embodiment; FIG. 26 is a cross-sectional view along the axial direction of the spark plug in the vicinity of the tip portion of the spark plug in the eleventh embodiment, taken along line XXIV-XXIV of FIG. 25; XXV-XXV arrow directional cross-sectional view of FIG. FIG. 22 is a cross-sectional view along the axial direction of the spark plug in the vicinity of the tip portion of the spark plug according to the twelfth embodiment; FIG. 21 is a cross-sectional view orthogonal to the plug axial direction of the tip portion of the spark plug in Embodiment 13; FIG. 29 is a cross-sectional view along the axial direction of the spark plug in the vicinity of the tip portion of the spark plug in the fourteenth embodiment, taken along line XXVIII-XXVIII of FIG. 29; XXIX-XXIX arrow directional cross-sectional view of FIG. A cross-sectional view taken along line XXX-XXX in FIG. 29 . FIG. 21 is a cross-sectional view along the axial direction of the spark plug in the vicinity of the tip of the spark plug according to the fifteenth embodiment;

(Embodiment 1)
An embodiment of a spark plug for an internal combustion engine will be described with reference to FIGS. 1 to 13. FIG.
In this embodiment, a spark plug 1 for an internal combustion engine comprises a cylindrical insulator 3, a center electrode 4, a cylindrical housing 2, a ground electrode 6 and a plug cover 5, as shown in FIGS. and have The center electrode 4 is held on the inner peripheral side of the insulator 3 and is exposed from the insulator 3 to the tip side. The housing 2 holds the insulator 3 on the inner peripheral side. The ground electrode 6 forms a discharge gap G with the center electrode 4 . The plug cover 5 is fixed to the tip of the housing 2 so as to cover the auxiliary combustion chamber 50 in which the discharge gap G is arranged.

The ground electrode 6 protrudes into the auxiliary combustion chamber 50 from a fixed end 61 fixed to the housing 2 . Further, the plug cover 5 is formed with a plurality of injection holes 51 for communicating the sub-combustion chamber 50 with the outside.

The distal end of the housing 2 has a housing fixing portion 21 and a facing surface 22 as shown in FIG. The housing fixing portion 21 faces the cover base end portion 52 of the plug cover 5 in the plug radial direction. The facing surface 22 faces the base end surface 53 of the plug cover 5 in the plug axial direction Z on the base end side of the housing fixing portion 21 . The housing fixing portion 21 and the cover base end portion 52 are fixed to each other. The base end surface 53 of the plug cover 5 is arranged at a position away from the facing surface 22 in the axial direction Z of the plug.

The projecting end portion 62 of the ground electrode 6 and the inner wall surface 54 of the plug cover 5 are in contact with each other in the axial direction Z of the plug.

Moreover, as shown in FIG. 3, some of the plurality of nozzle holes 51 have a shortest distance D1 to the protruding end 62 which is equal to or smaller than the inner diameter D2 of the nozzle hole 51. is. As shown in FIG. 4, when viewed from the axial direction Z of the plug, at least a portion of the ground-side injection hole 511 overlaps at least one of the ground extension region 6E and the gap extension region GE. The ground extension region 6E is a region obtained by extending the ground electrode 6 in the projecting direction. The gap extension region GE is a region obtained by extending the discharge gap G in the projecting direction of the ground electrode 6 .

The spark plug 1 of this embodiment can be used, for example, as ignition means in internal combustion engines such as automobiles. As shown in FIG. 9, the spark plug 1 is attached to the internal combustion engine 10 by screwing the threaded portion 23 of the housing 2 into the female threaded portion of the plug hole 711 of the cylinder head 71 .

Internal combustion engine 10 includes a piston 74 that reciprocates within cylinder 70 . The volume of the main combustion chamber 101 changes due to the reciprocating motion of the piston 74 . An intake port 721 and an exhaust port 731 are formed in the internal combustion engine 10, and an intake valve 72 and an exhaust valve 73 are provided, respectively.

One end of the spark plug 1 in the axial direction Z is arranged in the main combustion chamber 101 of the internal combustion engine 10 . In the axial direction Z of the spark plug 1, the side exposed to the main combustion chamber 101 is called the tip side, and the opposite side is called the base end side. Further, the axial direction Z of the spark plug 1 is also referred to as the plug axial direction Z or simply the Z direction as appropriate. It should be noted that the plug central axis C means the central axis C of the spark plug 1 . Further, the plug radial direction means the radial direction of a circle centered on the plug center axis C on a plane perpendicular to the plug center axis C. As shown in FIG. The circumferential direction of the plug is the direction along the circumference centered on the central axis C of the plug. The plug center axis C is also the center axis of the center electrode 4 in this embodiment.

When the spark plug 1 is attached to the internal combustion engine 10 , the plug cover 5 faces the main combustion chamber 101 and separates the auxiliary combustion chamber 50 from the main combustion chamber 101 . Further, the injection hole 51 allows the sub-combustion chamber 50 and the main combustion chamber 101 to communicate with each other.

In this embodiment, the plug cover 5 has a peripheral wall portion 56, a bottom wall portion 57 and corner portions 58 as shown in FIG. The peripheral wall portion 56 is a substantially cylindrical portion that covers a portion of the auxiliary combustion chamber 50 on the outer peripheral side. The bottom wall portion 57 is a portion that covers the tip side of the sub-combustion chamber 50 . The corner portion 58 is a portion that connects the tip of the peripheral wall portion 56 and the outer periphery of the bottom wall portion 57 in a curved shape.

The peripheral wall portion 56 has a cover base end portion 52 and a base end surface 53 . An inner wall surface 54 of the peripheral wall portion 56 is formed along the Z direction.

A plurality of nozzle holes 51 are formed in the corner portion 58 . As shown in FIG. 2, when viewed from the Z direction, the injection hole 51 formed in the corner portion 58 has an imaginary straight line VL passing through the injection hole 51 and the plug central axis C and extending in the radial direction of the plug. The tilted nozzle hole 512 is formed such that the nozzle hole axis 512L is inclined at an acute angle. In the plurality of inclined injection holes 512, the inclination direction of the injection hole axis 512L with respect to the imaginary straight line VL in each inclined injection hole 512 is on the same side in the plug circumferential direction. In addition, the inclined injection hole 512 is opened so as to be inclined with respect to the Z direction so as to extend outward in the radial direction of the plug toward the distal end side.

Due to the formation of the inclined injection holes 512 in this manner, the air flow introduced into the sub-combustion chamber 50 through the inclined injection holes 512 forms a swirl flow (see the dashed arrow SF in FIG. 5) in the sub-combustion chamber 50. . In the case of this embodiment, the swirl flow SF is generated in a counterclockwise spiral shape in FIG. 5 around the central axis C of the plug.

A ground-side injection hole 511 is formed in the bottom wall portion 57 . As shown in FIG. 3, the inner diameter D2 of the ground-side injection hole 511 is 1.2 to 1.4 times the inner diameter D3 of the other injection holes 51. As shown in FIG. That is, the ground-side injection hole 511 has a larger opening area than the inclined injection hole 512 . The opening area of the ground-side injection hole 511 can be, for example, 1.4 to 2.0 times the opening area of the other injection holes 51 .

In this embodiment, the ground-side injection hole 511 opens along the Z direction. That is, as shown in FIG. 6, the ground-side injection hole 511 is opened so that the injection hole axis 511L extends along the Z direction. The injection hole axis 511L is eccentric from the plug center axis C to the outside in the plug radial direction. In this embodiment, the injection hole axis 511L does not pass through the ground electrode 6 and the discharge gap G. Further, the extension region 511E in the opening direction of the ground-side injection hole 511 does not overlap with both the discharge gap G and the ground electrode 6. As shown in FIG.

As shown in FIG. 7, the line segment that connects the outermost outer end 514 of the outer opening 513 of the ground-side injection hole 511 in the radial direction of the plug and the tip of the center electrode 4 at the shortest distance is a line segment L1. . At this time, line segment L1 does not pass through both ground electrode 6 and plug cover 5 .

2 to 5, the ground-side injection hole 511 is formed on the projecting side of the ground electrode 6 when viewed from the axial direction Z of the plug. Further, as shown in FIG. 1, a projecting end surface 621 is formed on the projecting side of the projecting end portion 62 . The projecting end surface 621 is substantially parallel to the axial direction Z of the plug, or is inclined toward the projecting side of the ground electrode 6 toward the tip side. In this embodiment, the projecting end surface 621 is substantially parallel to the axial direction Z of the plug.

In this embodiment, as shown in FIG. 3, at least part of the projecting end face 621 is arranged between the tip of the center electrode 4 and the ground-side injection hole 511 when viewed in the Z direction. At least part of the projecting end face 621 is arranged between the discharge gap G and the ground-side injection hole 511 when viewed in the Z direction.

Further, as shown in FIG. 6, the distance D4 from the ground-side injection hole 511 to the projecting end 62 in the radial direction of the plug is greater than the distance D5 from the ground-side injection hole 511 to the inner wall surface 54 of the peripheral wall 56 in the radial direction of the plug. is also short. Also, the distance D4 is shorter than the inner diameter D2 (see FIG. 3). Also, the distance D6 from the ground-side injection hole 511 to the discharge gap G in the radial direction of the plug is shorter than the distance D5.

As shown in FIG. 4, when viewed from the Z direction, the radially innermost inner end 516 of the inner opening 515 of the ground-side injection hole 511 does not overlap the ground electrode 6, but overlaps the ground extension region 6E. ing. In this embodiment, the shortest distance from inner end 516 to projecting end 62 is distance D1 (see FIG. 3). Also, the shortest distance from the inner end 516 to the projecting end portion 62 is shorter than the shortest distance from the inner end 516 to the inner wall surface 54 of the peripheral wall portion 56 in the radial direction of the plug.

In addition, in this embodiment, when viewed from the Z direction, the entire contact hole 511 overlaps the contact extension area 6E. When viewed from the Z direction, the ground-side injection hole 511 also overlaps with the gap extension region GE.

Moreover, in this embodiment, the ground electrode 6 is joined to the front end surface of the housing 2 by welding or the like. When viewed from the Z direction, the ground electrode 6 is provided along the radial direction of the plug and protrudes toward the center axis C of the plug.

In this embodiment, the ground electrode 6 has a standing portion 64, a bent portion 65, and an extending portion 66, as shown in FIG. The erected portion 64 has a fixed end portion 61 and is erected from the distal end portion of the housing 2 toward the distal end side along the axial direction Z of the plug. The bent portion 65 is bent inward in the radial direction of the plug from the tip of the erected portion 64 . The extending portion 66 extends from the bent portion 65 toward the central axis C of the plug. The extended portion 66 forms a discharge gap G with the center electrode 4 .

The extending portion 66 is inclined with respect to the Z direction so as to move toward the distal end side as it approaches the projecting end portion 62 . A tip side surface 661 of the extended portion 66 is also inclined with respect to the Z direction so as to move toward the tip side as it approaches the projecting end portion 62 . Moreover, in this embodiment, the projecting end portion 62 is the tip of the ground electrode 6 . The projecting end portion 62 and the inner wall surface 54 of the bottom wall portion 57 are in contact with each other in the Z direction. An inner wall surface 54 of the bottom wall portion 57 is formed substantially orthogonal to the Z direction.

Further, the discharge gap G is formed by the front end portion of the center electrode 4 and the base end side surface 63 of the ground electrode 6 facing each other. The base end side surface 63 has a gap forming surface 631 that forms a discharge gap G with the center electrode 4 . The base end side surface 63 extends from at least the position of the gap forming surface 631 to the projecting end portion 62 in the projecting direction of the ground electrode 6 when viewed from the axial direction Z of the plug, and extends toward the distal side as it approaches the ground-side injection hole 511. It is slanted so that

In this embodiment, the discharge gap G is formed by the gap forming surface 631 and the tip surface 41 of the center electrode 4 facing each other. A distal end surface 41 of the center electrode 4 is positioned closer to the distal end than the distal end of the housing 2 . In other words, the discharge gap G is formed closer to the tip than the tip of the housing 2 .

The discharge gap G is, for example, a region obtained by projecting the front end surface 41 of the center electrode 4 in the Z direction and a region obtained by projecting the front end surface 41 in a direction orthogonal to the base end side surface 63 of the extended portion 66. It is the region between the distal end surface 41 and the proximal end surface 63 .

Moreover, in this embodiment, the plug cover 5 is fixed to the housing 2 by welding. Specifically, the cover base end portion 52 is fixed to the housing fixing portion 21 by welding.

A front end portion of the housing 2 is stepped by forming a housing fixing portion 21 and a facing surface 22 . A cover base end portion 52 is fixed to the outer peripheral side of the housing fixing portion 21 .

Also, the base end surface 53 of the plug cover 5 is positioned on the distal end side of the facing surface 22 . The facing surface 22 and the base end surface 53 face each other in the Z direction without contacting each other. That is, a gap g1 is formed between the facing surface 22 and the base end surface 53. As shown in FIG.

As shown in FIG. 8, the distance D7 from the opposing surface 22 to the tip of the ground electrode 6 in the Z direction is greater than the distance D8 from the base end surface 53 of the plug cover 5 to the inner wall surface 54 of the bottom wall portion 57 in the Z direction. . Since the distance D7 is larger than the distance D8, when the projecting end portion 62 is brought into contact with the inner wall surface 54 of the bottom wall portion 57 as shown in FIG. A gap g1 is formed between the base end face 53 of 5 and the base end face 53 of the base end face 53 . Further, in this embodiment, the distance from the base end face 53 of the plug cover 5 to the tip of the auxiliary combustion chamber 50 in the Z direction is substantially the same distance as the distance D8.

Next, a method for manufacturing the spark plug 1 of this embodiment will be described.
In manufacturing the spark plug 1, a preparation process, a contact process, and a joining process are performed. In the preparatory step, the housing 2 in which the ground electrode 6, the insulator 3 and the center electrode 4 are assembled, and the plug cover 5 in which the injection hole 51 is formed are produced. In the abutting step, after the preparatory step, the plug cover 5 is moved toward the base end side with respect to the housing 2 as indicated by an arrow M in FIG. The inner wall surface 54 of 57 is brought into contact with each other in the Z direction. In the abutment step, the housing fixing portion 21 and the cover base end portion 52 are overlapped in the radial direction of the plug, and the projecting end portion 62 and the inner wall surface 54 of the bottom wall portion 57 are brought into contact with each other in the Z direction. In this embodiment, the projecting end portion 62 and the inner wall surface 54 of the bottom wall portion 57 are brought into contact with each other in the Z direction while the plug cover 5 is fitted to the housing 2 . Further, in the joining step, the housing fixing portion 21 and the cover base end portion 52 are joined to each other after the contacting step. More specifically, in the joining step, the cover base is attached to the outer peripheral side of the housing fixing portion 21 while maintaining a state in which the projecting end portion 62 and the inner wall surface 54 of the bottom wall portion 57 are in contact with each other in the Z direction. The ends 52 are joined by welding. Thereby, as shown in FIGS. 1 and 2, the spark plug 1 of this embodiment can be produced.

Further, the outer peripheral surface of the housing fixing portion 21 and the inner wall surface 54 of the cover base end portion 52 are formed along the Z direction. In the abutting step, when the projecting end portion 62 and the inner wall surface 54 of the bottom wall portion 57 are brought into contact with each other in the Z direction, the outer peripheral surface of the housing fixing portion 21 and the inner wall surface 54 of the cover base end portion 52 are separated from each other. , are brought into contact with each other in the radial direction of the plug. However, a slight clearance may be provided between the outer peripheral surface of the housing fixing portion 21 and the inner wall surface 54 of the cover base end portion 52 to allow smooth sliding therebetween.

Next, the effects of this embodiment will be described.
In the spark plug 1 described above, the projecting end portion 62 and the inner wall surface 54 of the plug cover 5 are in contact with each other in the axial direction Z of the plug. Further, when viewed from the axial direction Z of the plug, at least a portion of the ground-side injection hole 511 overlaps at least one of the ground extension region 6E and the gap extension region GE. Therefore, during the expansion stroke of the internal combustion engine, the discharge generated in the discharge gap G is likely to be extended by the airflow directed toward the ground-side injection hole 511 . As a result, ignitability can be improved.

In the expansion stroke, the main combustion chamber becomes negative pressure with respect to the sub-combustion chamber 50 by moving the piston toward the tip side. As a result, the gas is led out from the sub-combustion chamber 50 to the main combustion chamber via the injection holes 51 . Further, an airflow directed toward the ground-side injection hole 511 is formed in the auxiliary combustion chamber 50 by discharging the gas through the ground-side injection hole 511 . Therefore, as shown in FIG. 10, in the expansion stroke, the starting point S1 of the discharge S generated in the discharge gap G on the side of the ground electrode 6 is moved to the base end by the airflow A directed to the ground side injection hole 511 as shown in FIG. It is easy to move along the side surface 63 and the projecting end surface 621 so as to approach the ground-side injection hole 511 . Therefore, the discharge S tends to extend toward the ground-side injection hole 511 . As a result, ignitability can be improved. The projecting end portion 62 and the inner wall surface 54 of the plug cover 5 are in contact with each other in the axial direction Z of the plug. Therefore, the starting point S1 of the discharge S is likely to move from the ground electrode 6 to the inner peripheral surface of the ground-side injection hole 511 via the inner wall surface 54 of the plug cover 5, as shown in FIG. As a result, the discharge S is further extended, and as shown in FIG. 13, a part of the discharge S can be expected to fly out from the ground-side injection hole 511 toward the main combustion chamber. Therefore, combustion in the main combustion chamber can be stabilized during the expansion stroke. As a result, the catalyst temperature of the exhaust gas purifying filter can be raised in a short period of time. As a result, improved fuel efficiency and reduced emissions can be expected.

The ground-side injection hole 511 is formed on the projecting side of the ground electrode 6 when viewed from the axial direction Z of the plug. Moreover, the projecting end surface 621 is substantially parallel to the axial direction Z of the plug. Therefore, the airflow A is likely to be sufficiently formed in the vicinity of the projecting end face 621 in the sub-combustion chamber 50 . Therefore, the starting point S1 is likely to move along the projecting end face 621 toward the ground-side injection hole 511 . As a result, the discharge can be extended further.

The inner diameter D2 (see FIG. 3) is 1.2 to 1.4 times the inner diameter D3 (see FIG. 3). Therefore, the airflow A directed to the ground-side injection hole 511 can be strengthened. Therefore, the discharge S is more likely to expand and more likely to fly out from the ground-side injection hole 511 toward the main combustion chamber. As a result, ignitability can be further improved.

A discharge gap G is formed by the front end portion of the center electrode 4 and the base end side surface 63 of the ground electrode 6 facing each other. The base end side surface 63 extends from at least the position of the gap forming surface 631 to the projecting end portion 62 in the projecting direction of the ground electrode 6 when viewed from the axial direction Z of the plug, and extends toward the distal side as it approaches the ground-side injection hole 511. It is slanted so that Therefore, the airflow A directed from the discharge gap G to the ground-side injection hole 511 can be strengthened. As a result, the discharge S can be extended further.

At least part of the projecting end face 621 is arranged between the discharge gap G and the ground-side injection hole 511 when viewed in the Z direction. Therefore, the starting point S1 is more likely to move toward the ground-side injection hole 511 along the projecting end surface 621 . Therefore, the discharge S is more likely to expand and more likely to fly out from the ground-side injection hole 511 toward the main combustion chamber.

Also, the distance D6 (see FIG. 6) is shorter than the distance D5 (see FIG. 6). Therefore, it is easy to reliably and sufficiently form the airflow A in the discharge gap G, and it is easy to shorten the length from the fixed end portion 61 to the projecting end portion 62 of the ground electrode 6 . Therefore, it is easy to reliably extend the discharge S, and it is easy to shorten the heat radiation path of the ground electrode 6 . As a result, ignitability can be reliably improved, and overheating of the ground electrode 6 can be suppressed.

Line segment L1 (see FIG. 7) does not pass through both ground electrode 6 and plug cover 5 . Therefore, when the discharge S is extended toward the main combustion chamber by the airflow A, it is less likely to be short-circuited by the ground electrode 6 and the plug cover 5 . Therefore, the discharge tends to reliably extend towards the main combustion chamber. As a result, the ignitability of the main combustion chamber can be reliably improved.

Further, the extension region 511E does not overlap the discharge gap G. Therefore, in the compression stroke, it is possible to suppress blow-out and short-circuiting of the discharge generated in the discharge gap G due to the airflow flowing into the sub-combustion chamber 50 through the ground-side injection hole 511 . As a result, ignitability in the compression stroke can be reliably ensured.

A cover base end portion 52 is fixed to the outer peripheral side of the housing fixing portion 21 . Therefore, the volume of the sub-combustion chamber 50 tends to increase. Therefore, the momentum of the flame ejected from the auxiliary combustion chamber 50 to the main combustion chamber through the injection hole 51 can be increased. As a result, ignitability can be improved.

The spark plug 1 of this embodiment can be manufactured by performing a preparation process, a contact process, and a joining process. Therefore, the spark plug 1 can be manufactured efficiently. As a result, productivity of the spark plug 1 can be improved.

Moreover, the projecting end portion 62 is the tip of the ground electrode 6 . Therefore, it is easy to reliably bring the projecting end 62 into contact with the inner wall surface 54 of the plug cover. Therefore, the spark plug 1 can be manufactured more efficiently. As a result, the productivity of the spark plug 1 can be further improved.

Also, the distance D7 is greater than the distance D8 (see FIG. 8). Therefore, in the contact step, the projecting end portion 62 can be brought into contact with the inner wall surface 54 of the bottom wall portion 57 reliably. That is, the projecting end portion 62 can be brought into contact with the inner wall surface 54 of the bottom wall portion 57 without causing the base end surface 53 of the plug cover 5 to come into contact with the facing surface 22 . As a result, the spark plug 1 can be reliably and efficiently manufactured.

The inclined injection holes 512 are formed so that the swirl flow SF is generated in the sub-combustion chamber 50 by the airflow introduced into the sub-combustion chamber 50 via the oblique injection holes 512 . Therefore, the initial flame formed by the discharge generated in the discharge gap G is likely to spread within the sub-combustion chamber 50 by the swirl flow SF. Therefore, combustion in the sub-combustion chamber 50 is likely to be promoted. As a result, the ignitability of the auxiliary combustion chamber 50 can be improved.

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

The ground electrode 6 has a standing portion 64 , a bent portion 65 and an extended portion 66 . A discharge gap G is formed by the base end side surface 63 of the extended portion 66 and the tip end portion of the center electrode 4 facing each other. Therefore, when the spark plug 1 is manufactured, the length of the discharge gap G can be easily adjusted by slightly deforming the ground electrode 6 as necessary. As a result, the spark plug 1 can be manufactured efficiently.

As described above, according to the present embodiment, it is possible to provide the spark plug 1 for an internal combustion engine that can improve ignitability.

(Embodiment 2)
As shown in FIG. 14, this embodiment is a form in which the shape of the plug cover 5 is changed with respect to the first embodiment.

As shown in FIG. 14, the plug cover 5 has a projection 55 formed by a part of the inner wall surface 54 protruding toward the base end. The convex portion 55 and the projecting end portion 62 are in contact with each other in the axial direction Z of the plug.

The convex portion 55 is formed on the bottom wall portion 57 . Further, the center axis 55L of the projection 55 is eccentric to the plug center axis C outward in the plug radial direction. That is, the base end of the convex portion 55 is located outside the plug center axis C in the plug radial direction. When viewed from the Z direction (not shown), the central axis 55L is on the opposite side of the fixed end portion 61 across the central axis C of the plug in the projecting direction of the ground electrode 6 . When viewed from the Z direction, the center axis 55L is between the plug center axis C and the ground-side injection hole 511 in the direction in which the ground electrode 6 projects. In this embodiment, the convex portion 55 is formed integrally with other portions of the plug cover 5 .

The ground-side injection hole 511 is formed outside the projection 55 in the radial direction of the plug. Further, the ground-side injection hole 511 is formed on the tip side of the projecting end portion 62 .

Further, the extension portion 66 is inclined toward the base end side as it approaches the projecting end portion 62 . The inclination angle θ1 of the extending portion 66 with respect to the Z direction is less than 90°.
Others are the same as those of the first embodiment. Note that, of the reference numerals used in the second and subsequent embodiments, the same reference numerals as those used in the previous embodiments represent the same constituent elements as those in the previous embodiments, unless otherwise specified.

The convex portion 55 and the projecting end portion 62 are in contact with each other in the axial direction Z of the plug. Therefore, when manufacturing the spark plug 1, even if the inclination angle θ1 is less than 90°, the projecting end portion 62 and the plug cover 5 can be brought into contact with each other reliably in the Z direction. As a result, even if the inclination angle θ1 is less than 90°, the discharge can be reliably extended.

A center axis 55L of the projection 55 is eccentric to the plug center axis C outward in the plug radial direction. Therefore, when manufacturing the spark plug 1, even if the inclination angle θ1 is less than 90°, the projecting end portion 62 can be brought into contact with the plug cover 5 more reliably.

When viewed from the Z direction, the central axis 55L is on the opposite side of the fixed end portion 61 across the plug central axis C in the direction in which the ground electrode 6 protrudes. Therefore, when manufacturing the spark plug 1, even if the inclination angle θ1 is less than 90°, the protruding end portion 62 can be brought into contact with the plug cover 5 more reliably.
In addition, it has the same effects as those of the first embodiment.

(Embodiment 3)
In this embodiment, as shown in FIG. 15, the formation position of the convex portion 55 is changed from that of the second embodiment.

In this embodiment, as shown in FIG. 15, the convex portion 55 is formed so that the central axis 55L of the convex portion 55 substantially overlaps the central axis C of the plug. Moreover, the convex portion 55 has a flat base end surface. A base end surface of the convex portion 55 is formed so as to be substantially orthogonal to the Z direction.

Further, the extending portion 66 is formed along the radial direction of the plug. That is, the extended portion 66 protrudes in a direction substantially perpendicular to the Z direction. Further, a tip side surface 661 of the extended portion 66 is formed so as to be substantially perpendicular to the Z direction. The base end surface of the convex portion 55 is in surface contact with the tip side surface 661 .
Others are the same as those of the second embodiment.

The base end surface of the convex portion 55 is in surface contact with the tip side surface 661 . Therefore, the starting point of the discharge generated in the discharge gap G on the side of the ground electrode 6 is likely to move reliably from the ground electrode 6 to the plug cover 5 by the airflow toward the ground side injection hole 511 . As a result, the discharge can be reliably extended.
In addition, it has the same effects as those of the second embodiment.

(Embodiment 4)
In this embodiment, as shown in FIG. 16, the shape of the projecting end portion 62 is changed from that of the first embodiment.

In this embodiment, as shown in FIG. 16, the projecting end surface 621 is inclined toward the projecting side of the ground electrode 6 toward the tip side. That is, the protruding end face 621 is inclined outward in the radial direction of the plug toward the distal end side.
Others are the same as those of the first embodiment.

In this embodiment, the protruding end face 621 is inclined toward the protruding side of the ground electrode 6 toward the distal end side. Therefore, in the expansion stroke, the starting point of the discharge on the side of the ground electrode 6 is more likely to move toward the ground-side injection hole 511 on the projecting end surface 621 due to the airflow toward the ground-side injection hole 511 . As a result, the discharge can be extended further.

Here, as shown in FIG. 17, it is assumed that the protruding end face 621 is inclined so as to face the opposite side of the protruding side of the ground electrode 6 toward the distal end side. In this case, in the expansion stroke, a stagnation portion 501 with a relatively weak airflow is likely to be formed in the vicinity of the projecting end face 621 in the auxiliary combustion chamber 50 . Therefore, compared to this embodiment, the starting point of the discharge on the side of the ground electrode 6 is less likely to move along the protruding end surface 621 to the ground side injection hole 511 . On the other hand, in the case of this embodiment, as described above, the tip is inclined toward the protruding side of the ground electrode 6 toward the distal end side. Therefore, the airflow toward the ground-side injection hole 511 is likely to be sufficiently formed in the vicinity of the projecting end face 621 in the sub-combustion chamber 50 as well. Therefore, the starting point of the discharge on the side of the ground electrode 6 tends to move along the projecting end surface 621 to the ground side injection hole 511 . As a result, the discharge can be extended further.
In addition, it has the same effects as those of the first embodiment.

(Embodiment 5)
In this embodiment, as shown in FIG. 18, the formation position of the ground-side injection hole 511 is changed from that of the first embodiment.

In this embodiment, the ground-side injection hole 511 is formed at the corner portion 58 as shown in FIG. The ground-side injection hole 511 is inclined outward in the radial direction of the plug toward the tip side. Further, the ground-side injection hole 511 is also the inclined injection hole 512 .

Also, the shortest distance from the protruding end 62 to the inner wall surface 54 of the peripheral wall 56 is shorter than the shortest distance from the protruding end 62 to the central axis C of the plug.
Others are the same as those of the first embodiment.

The ground-side injection hole 511 is formed at the corner portion 58 . Further, the ground-side injection hole 511 is inclined outward in the radial direction of the plug toward the tip side. Therefore, the flame to be ejected from the sub-combustion chamber 50 to the main combustion chamber through the ground-side injection hole 511 can be ejected along the base end surface of the main combustion chamber. Therefore, the flame is less likely to collide with the base end surface of the main combustion chamber and the piston. Therefore, it is easy to improve the combustibility of the main combustion chamber. As a result, an improvement in knock suppression can be expected during medium load and high load conditions of the internal combustion engine.
In addition, it has the same effects as those of the first embodiment.

(Embodiment 6)
In this embodiment, as shown in FIG. 19, the shape of the ground electrode 6 is changed from that of the first embodiment.

In this embodiment, as shown in FIG. 19, the ground electrode 6 protrudes into the auxiliary combustion chamber 50 from the fixed end portion 61 without bending. That is, the ground electrode 6 is formed in a bar shape. Further, the ground electrode 6 is inclined toward the distal end side as it approaches the projecting end portion 62 .
Others are the same as those of the first embodiment.

The ground electrode 6 protrudes into the auxiliary combustion chamber 50 from the fixed end portion 61 without bending. Therefore, it is easy to shorten the length from the fixed end portion 61 to the projecting end portion 62 of the ground electrode 6 . Therefore, it is easy to shorten the heat radiation path to the housing 2 and the heat radiation path to the plug cover 5 in the ground electrode 6 . Therefore, the heat of the ground electrode 6 can be easily dissipated to the outside. As a result, overheating of the ground electrode 6 can be suppressed.
In addition, it has the same effects as those of the first embodiment.

(Embodiment 7)
In this embodiment, as shown in FIG. 20, the shape of the ground electrode 6 is changed from that of the sixth embodiment.

As shown in FIG. 20, a flat ground contact surface 67 is formed on the tip side of the projecting end portion 62 . The ground contact surface 67 is formed substantially orthogonal to the Z direction. Further, the ground contact surface 67 is formed along the inner wall surface 54 of the bottom wall portion 57 . The ground contact surface 67 is in surface contact with the inner wall surface 54 of the bottom wall portion 57 .
Others are the same as those of the sixth embodiment.

The ground contact surface 67 is in surface contact with the inner wall surface 54 of the bottom wall portion 57 . Therefore, the starting point of the discharge generated in the discharge gap G on the side of the ground electrode 6 is likely to move reliably from the ground electrode 6 to the plug cover 5 by the airflow toward the ground side injection hole 511 . As a result, the discharge can be reliably extended.
In addition, it has the same effects as those of the sixth embodiment.

(Embodiment 8)
In this embodiment, as shown in FIG. 21, the opening direction of the ground-side injection hole 511 is changed from that of the sixth embodiment.

In this embodiment, as shown in FIG. 21, the ground-side injection hole 511 opens at an angle with respect to the Z direction so as to extend outward in the radial direction of the plug toward the tip side. That is, the injection hole axis 511L of the ground-side injection hole 511 is inclined with respect to the Z direction. The injection hole axis 511L passes through the center electrode 4 without passing through the discharge gap G.
Others are the same as those of the sixth embodiment.

The ground-side injection hole 511 opens at an angle with respect to the Z direction so as to extend outward in the radial direction of the plug toward the distal end side. Therefore, the discharge generated in the discharge gap G is less likely to be short-circuited by the ground electrode 6 and the plug cover 5 when extended toward the main combustion chamber by the airflow. Therefore, the discharge tends to reliably extend towards the main combustion chamber. As a result, ignitability in the main combustion chamber can be reliably improved.
In addition, it has the same effects as those of the sixth embodiment.

(Embodiment 9)
In this embodiment, as shown in FIG. 22, the shape of the ground electrode 6 is changed from that of the first embodiment.

In this embodiment, as shown in FIG. 22, the extended portion 66 of the ground electrode 6 is formed along the radial direction of the plug. A tip side surface 661 of the extended portion 66 is formed substantially orthogonal to the Z direction. A tip side surface 661 of the extended portion 66 is formed along the inner wall surface 54 of the bottom wall portion 57 . The tip side surface 661 is in surface contact with the inner wall surface 54 of the bottom wall portion 57 .
Others are the same as those of the first embodiment.

The tip side surface 661 is in surface contact with the inner wall surface 54 of the bottom wall portion 57 . Therefore, the starting point of the discharge generated in the discharge gap G on the side of the ground electrode 6 is likely to move reliably from the ground electrode 6 to the plug cover 5 by the airflow toward the ground side injection hole 511 . As a result, the discharge can be reliably extended.
In addition, it has the same effects as those of the first embodiment.

(Embodiment 10)
In this embodiment, as shown in FIG. 23, the base end portion 52 of the cover is fixed to the inner peripheral side of the fixing portion 21 of the housing.

In this embodiment, the contact step and the joining step are performed in a state in which the inner peripheral surface of the housing fixing portion 21 and the outer peripheral surface of the cover base end portion 52 are in contact with each other in the radial direction of the plug.

23, the ground electrode 6 protrudes into the auxiliary combustion chamber 50 from the inner peripheral surface 25 of the housing 2. As shown in FIG.
Other configurations and effects are the same as those of the first embodiment.

(Embodiment 11)
In this embodiment, as shown in FIGS. 24 and 25, a discharge gap G is formed by opposing the center electrode 4 and the ground electrode 6 in the radial direction of the plug.

As shown in FIGS. 24 and 25, the discharge gap G is formed by the center-facing side surface 42 of the center electrode 4 and the ground-facing side surface 68 of the ground electrode 6 facing each other in the radial direction of the plug.

Also, the ground electrode 6 is formed in a bar shape. Specifically, the ground electrode 6 has a substantially quadrangular prism shape. That is, the ground electrode 6 has four flat side surfaces, one of which is the ground facing side surface 68 . The ground-facing side surface 68 is formed in a continuous planar shape from the fixed end portion 61 to the projecting end portion 62 . Further, the ground electrode 6 is inclined toward the distal end side as it approaches the projecting end portion 62 .

Also, the discharge gap G is, for example, a region between the ground facing side 68 and the center facing side 42 facing each other in the thickness direction of the ground electrode 6 .

Further, as shown in FIG. 25, when viewed from the Z direction, the ground-side injection hole 511 does not overlap the ground extension area 6E, but overlaps the gap extension area GE.
Others are the same as those of the first embodiment.

The discharge gap G is formed by the center facing side 42 and the ground facing side 68 facing each other in the radial direction of the plug. Further, when viewed from the Z direction, the ground-side injection hole 511 overlaps the gap extension region GE. Therefore, in the expansion stroke, the airflow from the discharge gap G to the ground-side injection hole 511 is less likely to be blocked by the ground electrode 6 or the like. Therefore, the discharge is more likely to extend. Also, when the discharge is extended toward the main combustion chamber by the air current, the ground electrode 6 makes it difficult to short-circuit. Therefore, the discharge tends to extend more towards the main combustion chamber. As a result, ignitability can be further improved.

The ground electrode 6 has a ground facing side 68 . Therefore, the swirl flow formed in the sub-combustion chamber 50 easily passes through the discharge gap G by being guided by the ground-facing side surface 68 . Therefore, the discharge formed in the discharge gap G tends to extend. As a result, ignitability can be improved.
In addition, it has the same effects as those of the first embodiment.

(Embodiment 12)
In this embodiment, as shown in FIG. 26, the plug cover 5 is fixed to the housing 2 by screwing.

In this embodiment, as shown in FIG. 26, the housing fixing portion 21 and the cover base end portion 52 form a threaded portion that is fixed to each other by screwing the male screw portion 11 and the female screw portion 12 together. there is Specifically, the plug cover 5 is fixed to the housing 2 by screwing the female threaded portion 12 formed on the cover base end portion 52 and the male threaded portion 11 formed on the housing fixing portion 21 . In the case of this embodiment, the position of the ground-side injection hole 511 relative to the ground electrode 6 in the plug circumferential direction can be adjusted by adjusting the positions at which the threads of the male threaded portion 11 and the female threaded portion 12 start to be cut. can.

Next, a method for manufacturing the spark plug 1 of this embodiment will be described.
In the abutment step, the plug cover 5 is rotated in one direction in the plug circumferential direction with respect to the housing 2 while the male threaded portion 11 and the female threaded portion 12 are screwed together. As a result, as shown in FIG. 26, the plug cover 5 is moved proximally with respect to the housing 2 until the projecting end 62 and the inner wall surface 54 of the bottom wall portion 57 abut each other.
Other configurations and effects are the same as those of the first embodiment.

(Embodiment 13)
In this embodiment, as shown in FIG. 27, the formation position of the ground-side injection hole 511 is changed from that of the first embodiment.

In this embodiment, as shown in FIG. 27, when viewed from the Z direction, part of the ground-side injection hole 511 overlaps the ground extension area 6E.
Other configurations and effects are the same as those of the first embodiment.

(Embodiment 14)
In this embodiment, as shown in FIGS. 28 to 30, the base end portion 52 of the cover is provided with a protruding portion 521 on the base end side.

In this embodiment, as shown in FIGS. 28 to 30, the cover base end portion 52 has a base end side projecting portion 521 formed by a part of the base end face 53 projecting to the base end side. In this embodiment, the plug cover 5 is formed with four base-end projections 521 . Note that the illustration of the ground electrode is omitted in FIG. 30 for the sake of convenience.

29 and 30, the distal end portion of the housing 2 has a concave portion 24 formed by partially retreating the facing surface 22 toward the proximal end side. Four recesses 24 are formed in the tip of the housing 2 . A proximal-side protrusion 521 is arranged inside the recess 24 . In other words, the base-end protruding portion 521 is fitted into the recess 24 .
Others are the same as those of the sixth embodiment.

In this embodiment, the base-end protruding portion 521 is arranged inside the recess 24 . Therefore, it is easy to determine the position of the plug cover 5 relative to the housing 2 and the ground electrode 6 in the plug circumferential direction. Therefore, during assembly, the ground-side injection hole 511 can be easily arranged at a desired position. As a result, the spark plug 1 can be manufactured more efficiently.
In addition, it has the same effects as those of the sixth embodiment.

(Embodiment 15)
As shown in FIG. 31, this embodiment is a form in which the shape of the ground electrode 6 is changed with respect to the first embodiment.

As shown in FIG. 31, the length of the standing portion 64 in the Z direction is substantially the same as the length of the extending portion 66 in the extending direction.

The housing 2 has an inner peripheral concave portion 26 formed by recessing a part of the inner peripheral surface 25 outward in the radial direction of the plug. The inner circumferential recess 26 opens toward the tip. Also, a standing portion 64 is fitted inside the inner circumferential recess 26 . The erected portion 64 is joined to the recessed portion forming surface that forms the inner circumferential recessed portion 26 .
Others are the same as those of the first embodiment.

The erected portion 64 is joined to the recessed portion forming surface that forms the inner circumferential recessed portion 26 . Therefore, it is easy to increase the bonding area of the ground electrode 6 with respect to the housing 2 . As a result, the ground electrode 6 can be firmly fixed to the housing 2 .
In addition, it has the same effects as those of the first embodiment.

In Embodiments 1 to 15 described above, the corner portion 58 of the plug cover 5 is formed with an inclined injection hole 512 . However, the injection holes formed at the corners can also be formed so that the injection hole axis extends along the radial direction of the plug when viewed from the Z direction.

Further, in Embodiments 1 to 4 and 6 to 15, the ground electrode 6 is provided so that the ground electrode 6 and the injection hole 51 do not overlap each other when viewed in the Z direction. However, as in the fifth embodiment, the ground electrode 6 can be provided so that the ground electrode 6 and the injection hole 51 overlap each other when viewed from the Z direction.

In Embodiments 2 and 3, the convex portion 55 is formed integrally with other portions of the plug cover 5 . However, the protrusion can also be formed by joining a separate member to the plug cover.

Also, the ground electrode can be arranged so that the innermost inner end in the plug radial direction of the inner opening of the ground-side injection hole and the projecting end surface of the projecting end overlap each other when viewed from the Z direction. .

Also, a tip can be joined to each of the tip of the center electrode forming the discharge gap and the ground electrode. That is, a discharge gap can be formed between the tip joined to the tip of the center electrode and the tip joined to the ground electrode. The tip can be made of, for example, noble metals such as iridium or platinum, or alloys based on these metals.

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

REFERENCE SIGNS LIST 1 spark plug 2 housing 21 housing fixing portion 22 facing surface 3 insulator 4 center electrode 5 plug cover 50 auxiliary combustion chamber 51 injection hole 511 ground side Injection hole 52 Base end of cover 53 Base end surface 54 Inner wall surface 6 Ground electrode 61 Fixed end 62 Protruding end 6E Ground extension area G Discharge gap GE Gap extension area, Z... plug axial direction, D1... shortest distance, D2... inner diameter

Claims (5)

a cylindrical insulator (3);
a center electrode (4) held on the inner peripheral side of the insulator and exposed from the insulator to the tip side;
a cylindrical housing (2) that holds the insulator on the inner peripheral side;
a ground electrode (6) forming a discharge gap (G) with the center electrode;
a plug cover (5) fixed to the tip of the housing so as to cover the sub-combustion chamber (50) in which the discharge gap is arranged;
The ground electrode protrudes into the secondary combustion chamber from a fixed end (61) fixed to the housing,
The plug cover is formed with a plurality of injection holes (51) for communicating the sub-combustion chamber with the outside,
The front end portion of the housing includes a housing fixing portion (21) facing the cover base end portion (52) of the plug cover in the plug radial direction, and a base end surface ( 53) and a facing surface (22) facing the axial direction (Z) of the plug,
The housing fixing portion and the cover base end portion are fixed to each other,
The base end surface of the plug cover is arranged at a position away from the opposing surface in the axial direction of the plug,
The projecting end (62) of the ground electrode and the inner wall surface (54) of the plug cover are in contact with each other in the axial direction of the plug,
Some of the plurality of nozzle holes are ground-side nozzle holes (511), the shortest distance (D1) to the projecting end being equal to or less than the inner diameter (D2) of the nozzle hole,
When viewed from the axial direction of the plug, at least part of the ground-side injection hole includes a ground extension region (6E) extending the ground electrode in the projecting direction, and a gap extending the discharge gap in the projecting direction of the ground electrode. A spark plug (1) for an internal combustion engine, overlapping at least one of the extension zones (GE). When viewed from the axial direction of the plug, the ground-side injection hole is formed on the projecting side of the ground electrode,
A protruding end face (621) is formed on the protruding side of the protruding end, and the protruding end face is substantially parallel to the axial direction of the plug, or the ground electrode protrudes toward the tip side. 2. A spark plug for an internal combustion engine as claimed in claim 1, which is slanted towards the side. The plug cover has a protrusion (55) formed by protruding a part of the inner wall surface toward the base end, and the protrusion and the protruding end abut each other in the axial direction of the plug. 3. A spark plug for an internal combustion engine according to claim 1 or 2, wherein The spark for an internal combustion engine according to any one of claims 1 to 3, wherein the inner diameter of the ground-side injection hole is 1.2 to 1.4 times the inner diameter (D3) of the other injection holes. plug. The discharge gap is formed by the tip portion of the center electrode and the base end side surface (63) of the ground electrode facing each other, and the base end side surface forms the discharge gap between the center electrode and the base end side surface. The proximal side surface extends from at least the position of the gap forming surface to the protruding end in the projecting direction of the ground electrode when viewed from the axial direction of the plug. The spark plug for an internal combustion engine according to any one of claims 1 to 4, which is inclined toward the tip side as it approaches the ground-side injection hole.

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