JP2023016618A - Spark plug for internal combustion engine and internal combustion engine having the same - Google Patents

Abstract

To provide a spark plug for an internal combustion engine capable of improving ignitability, and an internal combustion engine having the same.SOLUTION: In a spark plug 1, a discharge gap G is formed such that a center-facing side surface 41 and a ground-facing side surface 63 face each other in the radial direction of a plug. An injection hole 51 formed in the plug cover 5 is formed so as to generate a swirl flow in a sub-combustion chamber 50. Some of the plurality of injection holes 51 are projection side injection holes 510 formed on the projecting side of a projecting end portion 62 of a ground electrode 6. A protruding edge 631 of the ground-facing side surface 63 is arranged downstream of the discharge gap G in the swirl flow passing through the discharge gap G when viewed in the axial direction of the plug. The distance from the edge tip 632, which is the tip of the protruding edge 631 to the projection side injection hole 510 is less than or equal to the distance from the edge tip 632 to the adjacent injection hole 512.SELECTED DRAWING: Figure 2

Description

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

For example, as disclosed in Japanese Unexamined Patent Application Publication No. 2002-100001, a spark plug is known that includes a sub-combustion chamber in which a discharge gap is arranged. The spark plug forms a discharge gap between the side of the ground electrode and the side of the center electrode.

DE 102017107679 A1

However, the spark plug described in Patent Document 1 does not consider the airflow formed in the sub-combustion chamber in the arrangement of the discharge gap, and there is room for improvement from the viewpoint of improving ignitability.

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 capable of improving ignitability, and an internal combustion engine having the same.

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 protruding 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) provided at the tip of the housing so as to cover the sub-combustion chamber (50) in which the discharge gap is arranged;
The plug cover is formed with a plurality of injection holes (51) for communicating the sub-combustion chamber with the outside, and an airflow is introduced into the sub-combustion chamber through the injection holes. is formed so that a swirl flow is generated in the sub-combustion chamber by
The ground electrode protrudes into the secondary combustion chamber from a fixed end (61) fixed to the housing or the plug cover,
The discharge gap is formed by the center-facing side surface (41) of the center electrode and the ground-facing side surface (63) of the ground electrode facing each other in the radial direction of the plug,
Some of the plurality of injection holes are projecting side injection holes (510) formed on the projecting side of the projecting end (62) of the ground electrode,
The edge tip (632), which is the tip of the projecting side edge (631) of the side facing the ground, is larger than the distance (D1) from the plug center axis (C) when viewed from the axial direction (Z) of the plug. arranged at a position where the distance (D2) to the center (511C) of the inner opening (511) of the projection side injection hole is short,
The protruding side edge is arranged at a position downstream of the swirl flow passing through the discharge gap from the discharge gap when viewed from the axial direction of the plug,
In a cross-sectional view along the axial direction of the plug including the central axis of the projection-side injection hole, the tip of the edge is located on the tip side of the extension region (510E) extending the projection-side injection hole in the opening direction. and
The injection hole other than the projection side injection hole is adjacent to the projection side injection hole in the plug circumferential direction and is formed on the upstream side of the swirl flow from the projection side injection hole when viewed from the axial direction of the plug. is the adjacent injection hole (512), the distance (D3) from the edge tip to the protrusion side injection hole is less than or equal to the distance (D4) from the edge tip to the adjacent injection hole in the spark plug (1) for

Another aspect of the present invention is an internal combustion engine (10) comprising the spark plug for the internal combustion engine,
a main combustion chamber (11);
the spark plug arranged such that the outer surface (52) of the plug cover faces the main combustion chamber;
an injector (12) for directly injecting fuel into the main combustion chamber;
The projection-side injection hole has a larger opening area than the other injection holes,
The spark plug is in an internal combustion engine, arranged such that an injection flow (F) containing the fuel injected from the injector is directed toward an outer opening (513) of the projecting side injection hole.

In the spark plug, the injection hole is formed so that a swirl flow is generated in the sub-combustion chamber by introducing an airflow into the sub-combustion chamber through the injection hole. Also, the ground electrode has a side facing the ground. Therefore, the swirl flow formed in the sub-combustion chamber is easily guided by the ground-facing side surface and passes through the discharge gap. Therefore, the discharge formed in the discharge gap tends to extend. As a result, ignitability can be improved.

Further, the spark plug has a protruding side injection hole. Also, the tip of the edge is arranged at the position described above. Therefore, the discharge formed in the discharge gap is likely to be extended toward the projection side injection hole by the airflow flowing out from the sub-combustion chamber through the projection side injection hole. As a result, ignitability can be improved.

In the internal combustion engine described above, the spark plug is arranged such that the injection flow injected from the injector is directed toward the outer opening of the projection-side injection hole having a larger opening area than the other injection holes. As a result, the air-fuel mixture having a high fuel density can be easily introduced into the sub-combustion chamber from the protruding side injection hole. As a result, the air-fuel mixture with a high fuel density can reach the discharge gap more easily, and 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, and an internal combustion engine having the same.
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 of the vicinity of the tip portion of the spark plug according to the first embodiment, taken along the axial direction of the plug, and is a view corresponding to the cross-sectional view taken along line I-I of FIG. 2 ; The figure of the II-II line arrow cross section equivalent of FIG. III arrow directional view of FIG. FIG. 7 is a view corresponding to a cross section taken along line IV-IV in FIG. 6 . FIG. 4 is a diagram viewed from the axial direction of the plug, showing an extension of the center axis of the injection hole in the first embodiment; FIG. 2 is a cross-sectional view showing distance D1 and distance D2 in Embodiment 1; FIG. 5 is a cross-sectional explanatory view for explaining the positional relationship between the extended region extending in the opening direction of the projection-side injection hole and the edge tip in the first embodiment; 4 is a cross-sectional view showing distance D3 and distance D4 in the first embodiment; FIG. FIG. 2 is a cross-sectional view showing a distance D9 in Embodiment 1; FIG. 4 is an explanatory diagram viewed from the axial direction of the plug, explaining the direction of the swirl flow formed in the sub-combustion chamber during the compression stroke in the first embodiment; FIG. 4 is a cross-sectional view of the tip portion of the spark plug before the discharge is extended during the compression stroke according to the first embodiment; FIG. 4 is a cross-sectional view of the tip portion of the spark plug when the discharge is extended during the compression stroke in the first embodiment; FIG. 4 is a cross-sectional view showing the direction of the airflow formed in the sub-combustion chamber in the expansion stroke according to the first embodiment; FIG. 4 is a cross-sectional view of the tip portion of the spark plug when the discharge starting point moves to the edge tip during the expansion stroke in the first embodiment; FIG. 4 is a cross-sectional view of the tip portion of the spark plug when the discharge starting point moves to the projection-side injection hole during the expansion stroke according to the first embodiment; FIG. 4 is a cross-sectional view 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; 1 is a cross-sectional view of an internal combustion engine according to Embodiment 1; FIG. FIG. 8 is a cross-sectional view orthogonal to the axial direction of the tip of the spark plug according to the second embodiment; FIG. 21 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 Embodiment 3, and is a cross-sectional view corresponding to the XIX-XIX line of FIG. 20; FIG. 19 is a view corresponding to the cross section taken along line XX-XX in FIG. 19 . FIG. 23 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 fourth embodiment, and is a cross-sectional view corresponding to the XXI-XXI arrow view in FIG. 22; A view corresponding to a cross section taken along the line XXII-XXII of FIG. 21 . FIG. 11 is a cross-sectional view along the axial direction of the spark plug near the tip of the spark plug in Embodiment 5; FIG. 26 is a cross-sectional view of the vicinity of the tip of the spark plug in Embodiment 6 along the axial direction of the spark plug, and is a view corresponding to the cross-sectional view taken along line XXIV-XXIV of FIG. 25; XXV-XXV A cross-sectional view corresponding to the arrow of FIG. 24 . FIG. 12 is a cross-sectional view along the axial direction of the spark plug near the tip of the spark plug in Embodiment 7; FIG. 11 is a view of a cross section along the axial direction of the spark plug in the vicinity of the tip of the spark plug according to the seventh embodiment, viewed from the projecting side of the ground electrode; Sectional drawing of the internal combustion engine in Embodiment 8. FIG.

(Embodiment 1)
An embodiment of a spark plug for an internal combustion engine and an internal combustion engine having the same will be described with reference to FIGS. 1 to 17. FIG.
As shown in FIGS. 1 to 4, a spark plug 1 for an internal combustion engine of this embodiment includes a tubular insulator 3, a center electrode 4, a tubular housing 2, a ground electrode 6, and a plug cover 5. , has The center electrode 4 is held on the inner peripheral side of the insulator 3 and protrudes from the insulator 3 toward 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 provided at the tip of the housing 2 so as to cover the auxiliary combustion chamber 50 in which the discharge gap G is arranged.

The plug cover 5 is formed with a plurality of injection holes 51 for communicating the sub-combustion chamber 50 with the outside. The injection hole 51 is formed so that a swirl flow is generated in the sub-combustion chamber 50 by introducing an airflow into the sub-combustion chamber 50 via the injection hole 51 .

The ground electrode 6 protrudes into the secondary combustion chamber 50 from a fixed end 61 fixed to the housing 2 or the plug cover 5 . The discharge gap G is formed by the center-facing side surface 41 of the center electrode 4 and the ground-facing side surface 63 of the ground electrode 6 facing each other in the radial direction of the plug.

Some of the plurality of injection holes 51 are projection side injection holes 510 formed on the projecting side of the projecting end portion 62 of the ground electrode 6 . As shown in FIG. 6, the end edge tip 632, which is the tip of the protruding side edge 631 of the ground facing side surface 63, is positioned closer to the protruding side nozzle hole than the distance D1 to the plug central axis C when viewed from the axial direction Z of the plug. The distance D2 from the center 511C of the inner opening 511 of 510 is short.

10, the protruding side edge 631 is arranged downstream of the discharge gap G in the swirl flow A2 passing through the discharge gap G when viewed from the axial direction Z of the plug.

Further, as shown in FIG. 7, in a cross-sectional view including the central axis of the projection side injection hole 510 and along the axial direction Z of the plug, the end edge tip 632 is an extension region 510E extending the projection side injection hole 510 in the opening direction. It is located on the tip side of the

As shown in FIG. 10, the projection side injection hole 510 is adjacent to the projection side injection hole 510 in the plug circumferential direction and is formed upstream of the projection side injection hole 510 in the swirl flow A1 when viewed from the axial direction Z of the plug. The injection holes 51 other than the hole 510 are called adjacent injection holes 512 . At this time, as shown in FIG. 8, the distance D3 from the edge tip 632 to the projecting side injection hole 510 is less than or equal to the distance D4 from the edge tip 632 to the adjacent injection hole 512 .

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. 17, the spark plug 1 is attached to the internal combustion engine 10 by screwing the threaded portion 21 of the housing 2 into the female threaded portion of the plug hole 130 of the cylinder head 13 .

The internal combustion engine 10 comprises a piston 17 reciprocating within a cylinder 16 . The volume of the main combustion chamber 11 changes due to the reciprocating motion of the piston 17 . An intake port 141 and an exhaust port 151 are formed in the internal combustion engine 10, and an intake valve 14 and an exhaust valve 15 are provided, respectively.

One end of the spark plug 1 in the axial direction Z is arranged in the main combustion chamber 11 of the internal combustion engine 10 . In the axial direction Z of the spark plug 1, the side exposed to the main combustion chamber 11 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.

In this embodiment, the plug cover 5 is joined to the front end portion of the housing 2 by welding or the like. With the spark plug 1 attached to the internal combustion engine 10 , the plug cover 5 separates the auxiliary combustion chamber 50 from the main combustion chamber 11 .

In this embodiment, the plug cover 5 has a peripheral wall portion 53, a bottom wall portion 54, and corner portions 55, as shown in FIG. The peripheral wall portion 53 is a substantially cylindrical portion that covers a portion of the auxiliary combustion chamber 50 on the outer peripheral side. The bottom wall portion 54 is a portion that covers the front end side of the auxiliary combustion chamber 50 . The corner portion 55 is a portion that connects the tip of the peripheral wall portion 53 and the outer periphery of the bottom wall portion 54 in a curved shape. A proximal end portion of the peripheral wall portion 53 is joined to a distal end portion of the housing 2 .

In the plug cover 5 , the injection holes 51 are formed at corners 55 . As shown in FIGS. 2, 5, 6, 8 and 9, the injection holes 51 are formed at regular intervals in the circumferential direction of the plug when viewed from the Z direction. As shown in FIGS. 1, 4 and 7, the injection hole 51 is opened 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.

In this embodiment, the plug cover 5 is formed with four injection holes 51 , one of which is a projecting side injection hole 510 . As shown in FIGS. 2, 5, 8 and 9, the adjacent injection hole 512 is formed at a position shifted by approximately 90.degree.

As shown in FIG. 17 , in the spark plug 1 installed in the internal combustion engine 10 , an injection hole 51 formed in the plug cover 5 allows the sub combustion chamber 50 and the main combustion chamber 11 to communicate with each other. During a compression stroke or the like of the internal combustion engine 10 , airflow is introduced from the main combustion chamber 11 to the sub-combustion chamber 50 through the nozzle holes 51 . A swirl flow (see dashed arrow A1 in FIG. 10) is formed in the sub-combustion chamber 50 by the airflow introduced into the sub-combustion chamber 50 through the nozzle holes 51 .

Specifically, as shown in FIG. 5, an extension line 51L of the central axis of the nozzle hole 51 is inclined with respect to the radial direction of the plug when viewed from the Z direction. That is, in this embodiment, when viewed from the Z direction, the injection hole 51 is an extension of the central axis of the injection hole 51 with respect to 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. Line 51L is slanted at an acute angle. In the injection holes 51, the inclination direction of the extension line 51L of the central axis of the injection hole 51 with respect to the imaginary straight line VL of each injection hole 51 is on the same side in the plug circumferential direction.

10, swirl flow A1 is formed in the sub-combustion chamber 50 by the air flow introduced into the sub-combustion chamber 50 through the injection hole 51. As shown in FIG. In the case of this embodiment, the swirl flow A1 is generated in a clockwise spiral shape in FIG. 10 around the central axis C of the plug.

Further, when viewed from the Z direction, the protruding end 62 of the ground electrode 6 protrudes so that its protruding direction is along the swirl flow A1. Further, the protruding end portion 62 is located upstream of the swirl flow A1 from the protruding side nozzle hole 510 when viewed in the Z direction. The protruding end portion 62 is located downstream of the adjacent injection hole 512 in the swirl flow A1 when viewed in the Z direction.

As shown in FIG. 2, when viewed from the Z direction, the projecting side injection hole 510 and the discharge gap G are located on opposite sides of the projecting end 62 in the projecting direction of the projecting end 62 . . Further, when viewed from the Z direction, the projecting side injection hole 510 and the fixed end portion 61 of the ground electrode 6 are located on opposite sides of each other with the projecting end 62 interposed therebetween in the projecting direction of the projecting end 62 . there is

Further, as shown in FIG. 5, the distance D5 from the protruding end 62 to the protruding side injection hole 510 is less than or equal to the distance D6 from the protruding end 62 to the adjacent injection hole 512 .

In addition, the projection side injection hole 510 has a larger opening area than the other injection holes 51 . That is, the inner diameter of the projection-side injection hole 510 is larger than the inner diameters of the other injection holes 51 . The inner diameter of the projection side injection hole 510 can be, for example, 1.2 to 1.4 times the inner diameter of the injection holes 51 other than the projection side injection hole 510 . Also, the opening area of the projection side injection hole 510 can be, for example, 1.4 to 2.0 times the opening area of the injection holes 51 other than the projection side injection hole 510 .

In this embodiment, as shown in FIG. 9, when viewed from the Z direction, the extension region 6E extending the ground electrode 6 in the projecting direction and the projecting side injection hole 510 overlap each other.

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 63 . Also, the ground electrode 6 is fixed to the housing 2 .

A width D7 of the side surface 63 facing the ground shown in FIG. 1 in a direction orthogonal to the longitudinal direction of the ground electrode 6 is larger than a thickness D8 of the ground electrode 6 when viewed from the Z direction shown in FIG.

As shown in FIGS. 1 and 2, the side surface 63 facing the ground is formed in a continuous planar shape from the fixed end portion 61 to the projecting end portion 62 .

Is the tip end edge 633 of the side surface 63 facing the ground slanted toward the tip side as it approaches the protruding end 62 from the position of the discharge gap G to the projecting end 62 in the longitudinal direction of the ground electrode 6? , or perpendicular to the axial direction Z of the plug. In this embodiment, as shown in FIG. 1, the tip end edge 633 extends from the position of the discharge gap G to the protruding end 62 in the longitudinal direction of the ground electrode 6, and the closer the protruding end 62 is, the more toward the tip side. inclined to

As shown in FIGS. 1 and 3, the ground electrode 6 is inclined toward the distal end side as it approaches the projecting end portion 62 . In this embodiment, the tip end edge 633 is inclined from the fixed end portion 61 to the protruding end portion 62 toward the tip side as the protruding end portion 62 is approached.

Further, as shown in FIG. 7, the tip end 632 of the protruding side edge 631 is located on the tip side relative to the base end of the protruding side injection hole 510 . Further, the edge tip 632 is located on the tip side of the center 511C of the inner opening 511 of the projection-side injection hole 510 .

As shown in FIG. 9, the distance D9 from the edge tip 632 in the radial direction of the plug to the inner wall surface 56 of the peripheral wall portion 53 of the plug cover 5 is shorter than the distance D1 (see FIG. 6).

Further, as shown in FIG. 7, the distance D10 from the end edge tip 632 to the inner wall surface 56 of the bottom wall portion 54 of the plug cover 5 in the Z direction is equal to or less than the thickness D11 of the plug cover 5 .

Further, as shown in FIGS. 1 to 4, the center-facing side surface 41 of the center electrode 4 is formed flat. A discharge gap G is formed by arranging the planar ground-facing side surface 63 and the planar center-facing side surface 41 to face each other in the thickness direction of the ground electrode 6 . The center-facing side surface 41 is formed along the ground-facing side surface 63 .

The discharge gap G is formed by the ground-facing side surface 63 and the center-facing side surface 41 facing substantially parallel to each other. The discharge gap G is, for example, a region between the ground facing side 63 and the center facing side 41 facing each other in the thickness direction of the ground electrode 6 .

Further, in this embodiment, the center electrode 4 has a base diameter portion 42 and a gap forming portion 43 on the distal end side of the insulator 3, as shown in FIGS. The base diameter portion 42 has a substantially cylindrical shape. The gap forming portion 43 is formed on the distal end side of the base diameter portion 42 and forms a discharge gap G between the ground electrode 6 and the gap forming portion 43 . That is, the gap forming portion 43 is formed with a flat center-facing side surface 41 .

In this embodiment, the gap forming portion 43 has a substantially semi-cylindrical shape. That is, the gap forming portion 43 has a substantially semicircular cross-sectional shape perpendicular to the longitudinal direction of the center electrode 4 .

Next, an internal combustion engine 10 provided with the spark plug 1 will be described.
The internal combustion engine 10 has a main combustion chamber 11, a spark plug 1, and an injector 12, as shown in FIG. The spark plug 1 is arranged such that the outer surface 52 of the plug cover 5 faces the main combustion chamber 11 . The injector 12 injects fuel directly into the main combustion chamber 11 . Spark plug 1 is arranged such that injection flow F containing fuel injected from injector 12 is directed toward outer opening 513 of projection-side injection hole 510 . The arrow F shown in FIG. 17 indicates the direction of the injection flow immediately after fuel injection, which does not necessarily match the airflow in the main combustion chamber 11 during the compression stroke or expansion stroke. In addition, when the injection flow F is directed toward the outer opening 513 of the projection side injection hole 510, the outer opening 513 of the projection side injection hole 510 can be seen from the direction of the injection flow F in the vicinity of the plug cover 5 shown in FIG. It is in such a state.

In the internal combustion engine 10, the spark plug 1 is arranged such that the outer opening 513 of the projection-side injection hole 510 faces the exhaust valve 15 side when viewed in the Z direction (not shown).

Also, the injector 12 is provided at a position adjacent to the intake port 141 . The injector 12 is mounted in such a posture as to inject fuel toward the central axis of the main combustion chamber 11 .

In the compression stroke, the atmosphere inside the main combustion chamber 11 is compressed, and the airflow flows into the sub-combustion chamber 50 via the injection holes 51 . As a result, a swirl flow is formed within the sub-combustion chamber 50 and the pressure within the sub-combustion chamber 50 is also increased. Then, for example, in the compression stroke, the injector 12 injects fuel directly into the main combustion chamber 11 .

The fuel injected into the main combustion chamber 11 forms an injection flow F together with the air in the main combustion chamber 11 and hits the base end surface of the piston 17 . In this embodiment, the proximal end surface of piston 17 has a concave surface. The injection flow F that hits the base end face of the piston 17 changes its trajectory and heads toward the base end side, that is, the spark plug 1 side. At this time, the injection flow F reaches the vicinity of the outer opening 513 of the projection-side injection hole 510 in the spark plug 1, as shown in FIG.

The injection flow F is an air-fuel mixture having a relatively large fuel ratio. Therefore, the vicinity of the outer opening 513 of the projection-side injection hole 510 where the injection flow F reaches becomes an air-fuel mixture containing a large amount of fuel. Then, this air-fuel mixture is drawn into the sub-combustion chamber 50 in which the swirl flow is formed via the protruding side injection hole 510 . Then, the air-fuel mixture with high fuel density drawn from the protruding side injection hole 510 is directed toward the discharge gap G.

Then, a discharge is generated in the discharge gap G of the spark plug 1 near the compression top dead center. As a result, the air-fuel mixture is ignited efficiently. It should be noted that the fuel injection timing and the discharge ignition timing of the spark plug 1 described above can be changed in various ways depending on the situation, purpose, etc., as will be described later.

Next, the effect of this form is demonstrated.
In the spark plug 1 , the injection hole 51 is formed so that a swirl flow is generated in the sub-combustion chamber 50 by introducing an airflow into the sub-combustion chamber 50 through the injection hole 51 . Also, the ground electrode 6 has a side surface 63 facing the ground. Therefore, the swirl flow formed in the auxiliary combustion chamber 50 easily passes through the discharge gap G while being guided by the ground-facing side surface 63 . Therefore, the discharge formed in the discharge gap G tends to extend. As a result, ignitability can be improved.

In the compression stroke and the like, as shown in FIG. 10, an airflow is introduced into the sub-combustion chamber 50 through the nozzle hole 51, thereby generating a swirl flow A1 in the sub-combustion chamber 50. As shown in FIG. Further, when viewed from the Z direction, the protruding end portion 62 protrudes so that its protruding direction is along the swirl flow A1. Therefore, part of the swirl flow A1 easily passes through the discharge gap G by being guided by the side surface 63 facing the ground. Also, the swirl flow A2 passing through the discharge gap G tends to flow along the projecting direction of the projecting end portion 62 when viewed from the Z direction. Therefore, when viewed from the Z direction, the discharge S formed in the discharge gap G as shown in FIG. Cheap. As a result, ignitability can be improved in the compression stroke and the like.

Furthermore, the initial flame ignited by the discharge is likely to be carried more toward the base end side of the sub-combustion chamber 50 by the swirl flow A1. As a result, the flame spreads from a position sufficiently distant from the nozzle hole 51, and it can be expected that the flame jet is ejected from the nozzle hole 51 into the main combustion chamber 11 in a state of sufficiently high internal pressure. As a result, it can be expected to suppress knocking during high load of the internal combustion engine 10, improve the EGR rate (that is, exhaust gas recirculation rate) during low load or medium load, improve output and fuel efficiency, and reduce emissions.

Further, the spark plug 1 has a projecting side injection hole 510 . Also, the edge tip 632 is located at the position described above. Therefore, the discharge formed in the discharge gap G is easily extended toward the projection side injection hole 510 by the airflow flowing out of the sub combustion chamber 50 through the projection side injection hole 510 . As a result, ignitability can be improved.

In the expansion stroke, the pressure in the main combustion chamber 11 becomes negative with respect to the sub-combustion chamber 50 as the piston 17 moves toward the tip side. As a result, gas is led out from the sub-combustion chamber 50 to the main combustion chamber 11 via the injection holes 51 . As a result, as shown in FIG. 13 , an airflow A3 is formed in the sub-combustion chamber 50 toward the injection hole 51 from a position closer to the base end than the injection hole 51 . Also, during the expansion stroke, the swirl flow formed during the compression stroke remains. That is, even during the expansion stroke, a weak swirl flow remains in the same direction as the swirl flow during the compression stroke. As shown in FIGS. 14 and 15, part of this residual swirl flow A4 easily passes through the discharge gap G by being guided by the side surface 63 facing the ground. Also, the swirl flow A5 passing through the discharge gap G tends to flow along the projecting direction of the projecting end portion 62 when viewed from the Z direction. Therefore, when viewed from the Z direction, the discharge S formed in the discharge gap G tends to extend toward the protruding side of the protruding end 62 due to the swirl flow A5. Further, the discharge S extended by the swirl flow A5 is further likely to be extended toward the projection side injection hole 510 and the main combustion chamber by the airflow A3 flowing out from the sub combustion chamber 50 via the projection side injection hole 510 . As a result, ignitability during the expansion stroke can be improved.

Also, the edge tip 632 is arranged at a position that satisfies the above conditions. Therefore, the starting point of the discharge S on the side of the ground electrode 6 tends to shift from the ground electrode 6 to the inner peripheral surface of the projection side injection hole 510 . Specifically, as shown in FIG. 14, the starting point SP of the discharge S on the side of the ground electrode 6 is caused by the swirl flow A5 and the air flow A3 to move along the ground-facing side surface 63 toward the protruding side injection hole 510, Go to 632. Then, the starting point SP moves from the edge tip 632 to the inner wall surface 56 of the bottom wall portion 54 of the plug cover 5 by the airflow A3. After that, as shown in FIG. 15, the starting point SP of the discharge S moves along the inner wall surface 56 of the bottom wall portion 54 to the inner peripheral surface of the projecting side injection hole 510 . As a result, the discharge S is further extended, and as shown in FIG. 16, a part of the discharge S can be expected to fly out from the projection side injection hole 510 toward the main combustion chamber. As a result, the ignitability of the main combustion chamber during the expansion stroke can be improved.

In addition, when the internal combustion engine such as an automobile engine is operated in a cold state at the time of cold start, etc., the following merits can be obtained by generating discharge in the expansion stroke. During cold starting, the plug cover 5, the center electrode 4, the housing 2, the insulator 3, etc. may be at a low temperature. Moreover, the operation of the internal combustion engine 10 may be in the light load range and the fuel density may be low. Therefore, even if the air-fuel mixture in the sub-combustion chamber 50 is ignited by the discharge, the generated initial flame contacts the low-temperature plug cover 5, the center electrode 4, etc. and is cooled, so that the flame sufficiently reaches the main combustion chamber. It may not be ejected.

Therefore, especially during a cold start or the like, contact between the initial flame and the plug cover 5, the center electrode 4, etc. can be suppressed by extending the discharge toward the main combustion chamber. Thereby, it is easy to suppress the energy loss of the initial flame. It is also possible to directly ignite the air-fuel mixture in the main combustion chamber. As a result, it is possible to improve ignitability at the time of cold start or the like.

In other words, the spark plug 1 of this embodiment can improve ignitability regardless of whether the internal combustion engine 10 is operated in a high load range or a light load range.

In addition, the projection side injection hole 510 has a larger opening area than the other injection holes 51 . Therefore, in the expansion stroke, the airflow flowing out of the sub-combustion chamber 50 via the projection-side injection hole 510 tends to become stronger. Therefore, the discharge generated in the discharge gap G is more likely to extend toward the protrusion-side injection hole 510 and more likely to fly out toward the main combustion chamber. As a result, ignitability in the expansion stroke can be further improved.

Width D7 (see FIG. 1) is greater than thickness D8 (see FIG. 2). Therefore, the ground-facing side surface 63 can guide the swirl flow to the discharge gap G more easily. Therefore, the discharge generated in the discharge gap G is more likely to extend. As a result, ignitability can be further improved.

The tip-side edge 633 extends from the position of the discharge gap G to the protruding end 62 in the longitudinal direction of the ground electrode 6 and is inclined toward the tip side as the protruding end 62 is approached. Therefore, in the expansion stroke, the starting point of the discharge generated in the discharge gap G on the side of the ground electrode 6 tends to move to the edge tip 632 along the tip side edge 633 due to the airflow. Therefore, the discharge is more likely to extend in the expansion stroke. As a result, ignitability in the expansion stroke can be further improved.

The ground facing side surface 63 is formed in a continuous planar shape from the fixed end portion 61 to the projecting end portion 62 . Therefore, the ground-facing side surface 63 can guide the swirl flow to the discharge gap G more easily. As a result, the discharge generated in the discharge gap G is more likely to extend.

The discharge gap G is formed by a planar ground-facing side surface 63 and a planar center-facing side surface 41 facing each other substantially in parallel. Therefore, it is easy to disperse the starting point positions of the discharge on the ground electrode 6 side and the center electrode 4 side. Therefore, it is possible to suppress local wear of the ground electrode 6 and the center electrode 4, and suppress an increase in the distance of the discharge gap G. As a result, the life of the spark plug 1 can be extended.

In the internal combustion engine 10 described above, the spark plug 1 is arranged such that the injection flow F injected from the injector 12 is directed toward the outer opening 513 of the projecting side injection hole 510 having a larger opening area than the other injection holes 51 . ing. This makes it easier for the air-fuel mixture with high fuel density to be introduced into the sub-combustion chamber 50 from the protruding side injection hole 510 . As a result, the air-fuel mixture with a high fuel density can reach the discharge gap G more easily, and the ignitability can be improved.

Further, for example, in high-load operation of an internal combustion engine, retarded injection and retarded ignition may be performed for the purpose of suppressing pre-ignition. Retarded injection and retarded ignition are fuel injection and ignition performed at timings later than general fuel injection and ignition timings. In other words, the timing of fuel injection from the injector 12 is, for example, the timing just before the piston 17 reaches the top dead center in the compression stroke. Specifically, for example, the fuel is injected at a timing of 30° BTDC. BTDC is an abbreviation for Before Top Dead Center, and indicates how far ahead the crank angle timing is with respect to compression top dead center. Then, the ignition of the spark plug 1 is made substantially at the compression top dead center timing.

By performing fuel injection and ignition at such timing, it is possible to suppress ignition at timing earlier than desired timing, ie, early ignition, and to suppress pre-ignition. On the other hand, in the case of retarded injection, when the fuel is supplied to the main combustion chamber 11, the sub-combustion chamber 50 has already been filled with air to some extent, and the airflow in the main combustion chamber 11 has weakened. state. As a result, the amount of fuel introduced into the sub-combustion chamber 50 from the injection hole 51 formed in the plug cover 5 tends to become relatively small.

However, the spark plug 1 of this embodiment is arranged so that the injection flow injected from the injector 12 is directed toward the outer opening 513 of the projecting side injection hole 510 having a larger opening area than the other injection holes 51. . Therefore, an air-fuel mixture having a high fuel density is easily introduced into the sub-combustion chamber 50 from the protruding side injection hole 510 . As a result, the ignitability in the sub-combustion chamber 50 can be improved, and the ignitability of the main combustion chamber 11 can be improved.

As described above, according to the present embodiment, it is possible to provide the spark plug 1 for an internal combustion engine and the internal combustion engine 10 having the spark plug 1, which can improve ignitability.

(Embodiment 2)
In this embodiment, as shown in FIG. 18, the shape of the center electrode 4 is changed from that of the first embodiment.

In this embodiment, as shown in FIG. 18, the gap forming portion 43 of the center electrode 4 has a cross-sectional shape perpendicular to the longitudinal direction of the center electrode 4, which is a partial circular shape. When viewed from the Z direction, the distance from the center-facing side surface 41 to the ground-facing side surface 63 is shorter than the distance from the central axis of the center electrode 4 to the ground-facing side surface 63 .
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 components as those in the previous embodiments, unless otherwise specified.
This embodiment also has the same effect as the first embodiment.

(Embodiment 3)
As shown in FIGS. 19 and 20, this embodiment is a form in which the shape of the center electrode 4 is changed with respect to the first embodiment.

In this embodiment, as shown in FIGS. 19 and 20, the center electrode 4 has a substantially cylindrical shape on the tip side of the insulator 3 . The outer diameter of the gap forming portion 43 is the same size as the outer diameter of the base diameter portion 42 .

The center-facing side surface 41 forming the discharge gap G together with the ground-facing side surface 63 is curved.
Others are the same as those of the first embodiment.

The center electrode 4 has a substantially cylindrical shape on the distal end side of the insulator 3 . Therefore, the center electrode 4 can be easily formed. As a result, productivity of the spark plug 1 can be improved.

Moreover, the gap forming portion 43 has a substantially cylindrical shape. Therefore, when forming the discharge gap G at the time of assembly, the side surface 41 facing the center and the side surface 63 facing the ground can be easily made to face each other. Therefore, it is easy to form the discharge gap G easily. As a result, productivity of the spark plug 1 can be improved.
In addition, it has the same effects as those of the first embodiment.

(Embodiment 4)
As shown in FIGS. 21 and 22, this embodiment is a form in which the shape of the center electrode 4 is changed with respect to the third embodiment.

In this embodiment, the base portion 42 and the gap forming portion 43 of the center electrode 4 each have a substantially cylindrical shape. The outer diameter of the gap forming portion 43 is smaller than the outer diameter of the base diameter portion 42 .
Other configurations and effects are the same as those of the third embodiment.

(Embodiment 5)
As shown in FIG. 23, this embodiment is a form in which the shape of the ground electrode 6 is changed with respect to the first embodiment.

In this embodiment, the ground electrode 6 has a fixed side portion 64 including a fixed end portion 61 and an inclined portion 65 including a projecting end portion 62, as shown in FIG. The fixed side portion 64 is formed along a direction perpendicular to the Z direction. The inclined portion 65 is inclined with respect to the Z direction toward the distal end side as it approaches the projecting end portion 62 .

The side surface 63 facing the ground is formed in a continuous flat shape from the fixed end portion 61 of the fixed side portion 64 to the projecting end portion 62 of the inclined portion 65 .
Other configurations and effects are the same as those of the first embodiment.

(Embodiment 6)
In this embodiment, as shown in FIGS. 24 and 25, the shape of the ground electrode 6 is changed from that of the fifth embodiment.

As shown in FIG. 25, the ground electrode 6 has a substantially L shape when viewed from the Z direction. Specifically, when viewed from the Z direction, the ground electrode 6 is bent such that the longitudinal direction of the fixed side portion 64 and the longitudinal direction of the inclined portion 65 are perpendicular to each other.
Other configurations and effects are the same as those of the fifth embodiment.

(Embodiment 7)
As shown in FIGS. 26 and 27, 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 FIGS. 26 and 27, the ground electrode 6 has a narrow portion 66 and a wide portion 67 whose width in the Z direction is larger than that of the narrow portion 66 . The narrowed portion 66 has a fixed end 61 . The widened portion 67 has a protruding end 62 .

The ground electrode 6 has a wide portion 67 extending from the position of the discharge gap G in the longitudinal direction of the ground electrode 6 to the projecting end portion 62 .

A front end edge 633 of the ground-facing side surface 63 in the wide portion 67 is perpendicular to the Z direction from the position of the discharge gap G to the projecting end 62 in the longitudinal direction of the ground electrode 6 .
Others are the same as those of the first embodiment.

The tip-side edge 633 is perpendicular to the Z direction from the position of the discharge gap G to the projecting end 62 in the longitudinal direction of the ground electrode 6 . Therefore, in the expansion stroke, the starting point of the discharge generated in the discharge gap G on the side of the ground electrode 6 tends to move to the edge tip 632 along the tip side edge 633 due to the airflow. Therefore, the discharge is more likely to extend in the expansion stroke. As a result, ignitability in the expansion stroke can be further improved.
In addition, it has the same effects as those of the first embodiment.

(Embodiment 8)
As shown in FIG. 28, this embodiment is a form in which the arrangement of the spark plug 1 installed in the internal combustion engine 10 is changed from that of the first embodiment.

As shown in FIG. 28, the internal combustion engine 10 of this embodiment is configured such that a portion of the injection flow F injected from the injector 12 is directly directed toward the spark plug 1. As shown in FIG. Therefore, in this embodiment, the spark plug 1 is arranged so that part of the injection flow F is directly directed to the outer opening 513 of the projection-side injection hole 510 . In other words, the injector 12 injects fuel into the main combustion chamber 11 so that part of the injection flow F containing fuel is directed directly toward the outer opening 513 of the projection-side injection hole 510 .

In this embodiment, the spark plug 1 is arranged such that the outer opening 513 of the projection-side injection hole 510 faces the intake valve 14 side when viewed in the Z direction (not shown).
Others are the same as those of the first embodiment.

The spark plug 1 is arranged such that the injection flow F injected from the injector 12 is directed directly toward the outer opening 513 of the projection-side injection hole 510 . As a result, the air-fuel mixture having a high fuel density can be reliably introduced into the sub-combustion chamber 50 from the projection-side injection hole 510 . As a result, the air-fuel mixture with a high fuel density can reliably reach the discharge gap G more easily, and ignitability can be reliably improved.
In addition, it has the same effects as those of the first embodiment.

In Embodiments 1 to 8 described above, the ground electrode 6 has a substantially quadrangular prism shape. However, the ground electrode 6 may have, for example, a substantially semi-cylindrical shape with a planar ground-facing side surface. At this time, the ground-facing side surface can be planar only in the portion extending from the position of the discharge gap to the projecting end in the longitudinal direction of the ground electrode.

In Embodiments 1 to 8 described above, the plug cover 5 is formed with four injection holes 51 . However, five or more injection holes may be formed in the plug cover. Also, the number of injection holes formed in the plug cover can be three or less.

Also, a tip can be joined to each of the tip of the center electrode forming the discharge gap and the ground electrode. In other words, a discharge gap can be formed between the chip bonded to the side facing the center and the chip bonded to the side facing the ground. The tip can be made of, for example, a noble metal such as iridium or platinum, or an alloy 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.

DESCRIPTION OF SYMBOLS 1... Spark plug 2... Housing 3... Insulator 4... Center electrode 41... Side facing center 5... Plug cover 50... Sub-combustion chamber 51... Injection hole 510... Protruding side injection hole 510E... Extension area 511 inner opening 511C center of inner opening 512 adjacent nozzle hole 6 ground electrode 61 fixed end 62 protruding end 63 side facing ground 631 protruding side edge, 632... edge tip, C... plug central axis, G... discharge gap, Z... plug axial direction

Claims (5)

a cylindrical insulator (3);
a center electrode (4) held on the inner peripheral side of the insulator and protruding 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) provided at the tip of the housing so as to cover the sub-combustion chamber (50) in which the discharge gap is arranged;
The plug cover is formed with a plurality of injection holes (51) for communicating the sub-combustion chamber with the outside, and an airflow is introduced into the sub-combustion chamber through the injection holes. is formed so that a swirl flow is generated in the sub-combustion chamber by
The ground electrode protrudes into the secondary combustion chamber from a fixed end (61) fixed to the housing or the plug cover,
The discharge gap is formed by the center-facing side surface (41) of the center electrode and the ground-facing side surface (63) of the ground electrode facing each other in the radial direction of the plug,
Some of the plurality of injection holes are projecting side injection holes (510) formed on the projecting side of the projecting end (62) of the ground electrode,
The edge tip (632), which is the tip of the projecting side edge (631) of the side facing the ground, is larger than the distance (D1) from the plug center axis (C) when viewed from the axial direction (Z) of the plug. arranged at a position where the distance (D2) to the center (511C) of the inner opening (511) of the projection side injection hole is short,
The protruding side edge is arranged at a position downstream of the swirl flow passing through the discharge gap from the discharge gap when viewed from the axial direction of the plug,
In a cross-sectional view along the axial direction of the plug including the central axis of the projection-side injection hole, the tip of the edge is located on the tip side of the extension region (510E) extending the projection-side injection hole in the opening direction. and
The injection hole other than the projection side injection hole is adjacent to the projection side injection hole in the plug circumferential direction and is formed on the upstream side of the swirl flow from the projection side injection hole when viewed from the axial direction of the plug. is the adjacent injection hole (512), the distance (D3) from the edge tip to the protrusion side injection hole is less than or equal to the distance (D4) from the edge tip to the adjacent injection hole spark plug (1) for The tip end edge (633) of the ground facing side surface is inclined toward the tip side as it approaches the protruding end in the longitudinal direction of the ground electrode from the position of the discharge gap to the protruding end. or perpendicular to the plug axis. 3. The spark plug for an internal combustion engine according to claim 1, wherein said ground facing side surface is formed in a continuous plane from said fixed end portion to said projecting end portion. The spark plug for an internal combustion engine according to any one of claims 1 to 3, wherein said projecting side injection hole has a larger opening area than other said injection holes. An internal combustion engine (10) comprising a spark plug for an internal combustion engine according to claim 4,
a main combustion chamber (11);
the spark plug arranged such that the outer surface (52) of the plug cover faces the main combustion chamber;
an injector (12) for directly injecting fuel into the main combustion chamber;
The internal combustion engine, wherein the spark plug is arranged such that an injection flow (F) containing the fuel injected from the injector is directed toward an outer opening (513) of the projecting side injection hole.

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