Spark plug for internal combustion engine and internal combustion engine

Abstract

To provide a spark plug for an internal combustion engine and an internal combustion engine capable of suppressing preignition.SOLUTION: A spark plug 1 for an internal combustion engine has an insulator 3, a center electrode 4, a housing 2, a ground electrode 6, and a plug cover 5. The ground electrode 6 is protruded from a fixed end part 61 to the inside of a sub combustion chamber 50. The plug cover 5 is formed with injection holes (51). When the spark plug 1 is divided into two of a first plug part 11 and a second plug part 12 by the following virtual plane P, at least one of the injection holes 51 is a first injection hole 511 formed on the first plug part 11 so that its injection hole axis 511L passes through the ground electrode 6. When seen from a plug axial direction Z, the virtual plane P is orthogonal to a virtual straight line Q connecting between a center of the fixed end part 61 and a plug central axis C, including a plug central axis C. The fixed end part 61 of the ground electrode 6 is arranged on the first plug part 11.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] A spark plug equipped with a sub-combustion chamber is disclosed, for example, in Patent Document 1. In the spark plug disclosed in Patent Document 1, the direction of the nozzle hole formed in the plug cover is specified in consideration of the direction of the flame jet. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2020-9747 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, the spark plug disclosed in Patent Document 1 does not take into consideration the airflow flowing into the auxiliary combustion chamber. On the other hand, there is a concern that if the ground electrode disposed in the auxiliary combustion chamber is overheated, pre-ignition may easily occur.

[0005] The present invention has been made in view of the above problems, and has an object to provide a spark plug for an internal combustion engine and an internal combustion engine capable of suppressing pre-ignition. [Means for solving the problem]

[0006] One aspect of the present invention comprises a cylindrical insulator (3); a center electrode (4) held on the inner circumferential side of the insulator and protruding from the insulator toward the tip side; a cylindrical housing (2) that holds the insulator on its inner periphery; a ground electrode (6) forming a discharge gap (G) between itself and the center electrode; a plug cover (5) provided at a tip end of the housing so as to cover a sub-combustion chamber (50) in which the discharge gap is disposed, The ground electrode protrudes into the auxiliary combustion chamber from a fixed end portion (61) fixed to the housing or the plug cover on the outer circumferential side of the auxiliary combustion chamber, The plug cover is formed with a nozzle hole (51) that communicates the auxiliary combustion chamber with the outside, When the above spark plug is divided into a first plug portion (11) and a second plug portion (12) by the following imaginary plane (P), At least one of the nozzle holes is a first nozzle hole (511) that is formed in the first plug portion and has a nozzle hole axis (511L) that passes through the ground electrode, The imaginary plane is a plane that is perpendicular to an imaginary line (Q) connecting the center of the fixed end and the plug central axis (C) as viewed from the plug axial direction (Z) and that includes the plug central axis, and the fixed end of the ground electrode is disposed in the first plug section. And, The nozzle hole includes a second nozzle hole (512) formed in the second plug portion, and the second nozzle hole is formed so that a second extension region (512E) extending from the second nozzle hole along a nozzle hole axis (512L) does not intersect with a first extension region (511E) extending from the first nozzle hole along the nozzle hole axis. , in spark plugs for internal combustion engines. Effect of the Invention

[0007] The spark plug for an internal combustion engine has at least one of the nozzle holes formed in the first plug portion and having a first nozzle hole axis passing through the ground electrode. Therefore, the airflow flowing from the first nozzle hole into the auxiliary combustion chamber is likely to collide with the ground electrode. This makes it possible to suppress overheating of the ground electrode and to suppress pre-ignition.

[0008] As described above, according to the above-described aspects, it is possible to provide a spark plug for an internal combustion engine and an internal combustion engine capable of suppressing pre-ignition. In addition, the symbols in parentheses described in the claims and the means for solving the problems indicate a correspondence with the specific means described in the embodiments described below, and do not limit the technical scope of the present invention. [Brief description of the drawings]

[0009] [Figure 1] 2 is a cross-sectional view taken along line II in FIG. 2, showing a cross-sectional view taken along the central axis of the spark plug in the vicinity of the tip portion of the spark plug according to the first embodiment; [Diagram 2] FIG. 2 is a cross-sectional view taken along line II-II in FIG. [Diagram 3] FIG. 3 is a cross-sectional view taken along line III-III in FIG. 2 . [Figure 4] 4 is a cross-sectional view showing an extension region near the tip portion of the spark plug according to the first embodiment. FIG. [Diagram 5] FIG. 3 is a cross-sectional view of the vicinity of the tip of the spark plug, showing an inflow airflow, in the first embodiment. [Figure 6] FIG. 6 is an explanatory diagram equivalent to a cross section taken along line VI-VI in FIG. 5 . [Figure 7] FIG. 11 is a cross-sectional view taken along the central axis of a spark plug in the vicinity of a tip portion of the spark plug according to a second embodiment. [Figure 8] 8 is a cross-sectional view taken along the central axis of a spark plug in the vicinity of a tip portion of the spark plug according to a third embodiment, taken along the line VIII-VIII in FIG. [Figure 9] 9 is a cross-sectional view taken along line IX-IX in FIG. 8 . [Figure 10] 10 is a front view taken along the X arrow in FIG. 9, illustrating the airflow in the auxiliary combustion chamber. [Figure 11] FIG. 11 is a cross-sectional view of the vicinity of the tip portion of a spark plug according to a fourth embodiment, taken along a plane perpendicular to the plug axial direction. [Figure 12] FIG. 13 is a cross-sectional view of the vicinity of the tip portion of a spark plug according to a fifth embodiment, taken along a plane perpendicular to the plug axial direction. [Figure 13] FIG. 13 is a cross-sectional view of the vicinity of the tip portion of a spark plug according to a sixth embodiment, taken along a plane perpendicular to the axial direction of the plug. [Figure 14] FIG. 13 is a cross-sectional view of the vicinity of the tip portion of a spark plug according to a seventh embodiment, taken along a plane perpendicular to the axial direction of the plug. [Figure 15] FIG. 13 is a cross-sectional view of the vicinity of the tip portion of a spark plug according to an eighth embodiment, taken along a plane perpendicular to the axial direction of the plug. [Figure 16] FIG. 13 is a cross-sectional explanatory view of an internal combustion engine according to a ninth embodiment. [Figure 17] FIG. 13 is an explanatory diagram illustrating the direction of an airflow formed in a main combustion chamber in a ninth embodiment, as viewed from the front end side of the internal combustion engine. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] (Embodiment 1) An embodiment of a spark plug for an internal combustion engine will be described with reference to Figs. A spark plug 1 of this embodiment includes 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.

[0011] The center electrode 4 is held on the inner periphery of the insulator 3 and protrudes from the insulator 3 toward the tip side. The housing 2 holds the insulator 3 on the inner periphery. The ground electrode 6 forms a discharge gap G between the center electrode 4 and the ground electrode 6. The plug cover 5 is provided at the tip of the housing 2 to cover the auxiliary combustion chamber 50 in which the discharge gap G is located.

[0012] The ground electrode 6 is fixed to the housing 2 or the plug cover 5 on the outer periphery side of the auxiliary combustion chamber 50. The ground electrode 6 protrudes from its fixed end 61 into the auxiliary combustion chamber 50. The plug cover 5 is formed with an injection hole 51 that connects the auxiliary combustion chamber 50 to the outside.

[0013] 2, the spark plug is divided into two parts, a first plug portion 11 and a second plug portion 12, by the following imaginary plane P. At this time, at least one of the nozzle holes 51 is a first nozzle hole 511 that is formed in the first plug portion 11 and whose nozzle hole axis 511L passes through the ground electrode 6.

[0014] The imaginary plane P is a plane that is perpendicular to an imaginary line Q connecting the center of the fixed end 61 and the plug central axis C when viewed from the plug axial direction Z, and that includes the plug central axis C. The fixed end 61 of the ground electrode 6 is disposed in the first plug part 11. That is, of the first plug part 11 and the second plug part 12, the side on which the fixed end 61 is disposed is the first plug part 11.

[0015] The spark plug 1 of this embodiment can be used as an ignition means in an internal combustion engine of an automobile, a cogeneration system, or the like. One end of the spark plug 1 in the plug axial direction Z is disposed in the main combustion chamber of the internal combustion engine. In the plug axial direction Z, the side exposed to the main combustion chamber is referred to as the tip side, and the opposite side is referred to as the base side. Also, the direction perpendicular to the central axis of the spark plug 1 (i.e., the plug central axis C) is referred to as the plug radial direction. Also, the direction along the circumference centered on the plug central axis C is referred to as the plug circumferential direction.

[0016] In this embodiment, four injection holes 51 are formed. As shown in FIG. 2, the four injection holes 51 are arranged at equal intervals in the plug circumferential direction. It is also possible to arrange the injection holes 51 at non-equidistant intervals. Two of the four injection holes 51 are formed in the first plug portion 11. In this embodiment, both of the two injection holes 51 formed in the first plug portion 11 are first injection holes 511. That is, both of the injection hole axes 511L of the two first injection holes 511 pass through the ground electrode 6. In this embodiment, the injection hole axes 511L of the two first injection holes 511 are aligned along the plug radial direction as viewed from the plug axial direction Z. That is, the injection hole axis 511L of the first injection hole 511 substantially intersects with the plug central axis C.

[0017] As described above, the spark plug 1 has a plurality of first injection holes 511. When viewed from the plug axial direction Z, the first injection holes 511 are disposed on both sides of the fixed end portion 61 of the ground electrode 6. In this embodiment, the two first injection holes 511 are provided at positions and oriented line-symmetrically with respect to the imaginary straight line Q when viewed from the plug axial direction Z.

[0018] The other two of the four nozzle holes 51 are second nozzle holes 512 formed in the second plug portion 12. The spark plug 1 has the second nozzle hole 512 formed in the second plug portion 12 as the nozzle hole 51. As shown in Fig. 4, the second nozzle hole 512 is formed so that a second extension region 512E in which the second nozzle hole 512 is extended along a nozzle hole axis 512L does not intersect with a first extension region 511E in which the first nozzle hole 511 is extended along a nozzle hole axis 511L. In other words, the nozzle hole axis 511L of the first nozzle hole 511 and the nozzle hole axis 512L of the second nozzle hole 512 are configured not to pass near each other.

[0019] 2, when viewed from the plug axial direction Z, an intersection Q1 between the nozzle hole axis 511L of the first nozzle hole 511 and the imaginary line Q is located closer to the fixed end portion 61 of the ground electrode 6 than an intersection Q2 between the nozzle hole axis 512L of the second nozzle hole 512 and the imaginary line Q. In this embodiment, the intersection Q1 is on the plug central axis C. The intersection Q2 is located in the second plug portion 12. In this embodiment, the nozzle hole axes 511L of the two first nozzle holes 511 intersect with the imaginary line Q at the same position. In addition, the nozzle hole axes 512L of the two second nozzle holes 512 intersect with the imaginary line Q at the same position.

[0020] 1, the nozzle hole axis 511L of the first nozzle hole 511 and the nozzle hole axis 512L of the second nozzle hole 512 are inclined toward the base end as they approach the auxiliary combustion chamber 50. In this embodiment, the inclination angle θ1 of the nozzle hole axis 511L of the first nozzle hole 511 with respect to the plug axis direction Z and the inclination angle θ2 of the nozzle hole axis 512L of the second nozzle hole 512 with respect to the plug axis direction Z are approximately equal.

[0021] 3, the ground electrode 6 protrudes into the auxiliary 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 tip end of the center electrode 4 and the ground electrode 6 facing each other in the plug axial direction Z. The fixed end 61 is disposed in the first plug portion 11.

[0022] In this embodiment, the fixed end 61 is joined to the tip end of the housing 2 by welding or the like. The ground electrode 6 has a bent portion 611 at the fixed end 61. The ground electrode 6 extends in the plug radial direction from the bent portion 611 toward the plug central axis C. A portion of the ground electrode 6 near the protruding end faces the tip of the center electrode 4 in the plug axial direction Z, with a discharge gap G between them.

[0023] Next, the effects of this embodiment will be described. The spark plug 1 for an internal combustion engine has, as at least one of the nozzle holes 51, a first nozzle hole 511 formed in the first plug portion 11 and formed so that a nozzle hole axis 511L passes through the ground electrode 6. Therefore, as shown in Figures 5 and 6, the airflow A1 flowing from the first nozzle hole 511 into the auxiliary combustion chamber 50 is likely to collide with the ground electrode 6. This makes it possible to suppress overheating of the ground electrode 6 and to suppress pre-ignition.

[0024] That is, the ground electrode 6 is likely to be heated by the discharge generated in the discharge gap G and the ignited flame. Moreover, since the ground electrode 6 is disposed inside the auxiliary combustion chamber 50, it is relatively difficult to dissipate heat. Therefore, as in this embodiment, the airflow A1 flowing in from the first nozzle hole 511 collides with the ground electrode 6, and the airflow A1 can dissipate heat from the ground electrode 6. In addition, the airflow A1 that collides with the ground electrode 6 flows along the periphery of the ground electrode 6. Therefore, it is easy to prevent the initial flame from staying in the vicinity of the ground electrode 6. Furthermore, the airflow At that passes near the ground electrode 6 can transfer the heat of the ground electrode 6 toward the base end side of the auxiliary combustion chamber 50. Therefore, the heat can be dissipated from the housing 2.

[0025] Furthermore, the airflow toward the base end forms a tumble flow At and returns to the vicinity of the ground electrode 6 again. The airflow At returning from the vicinity of the base end of the auxiliary combustion chamber 50 to the vicinity of the ground electrode 6 is cooled by the housing 2 and is therefore at a relatively low temperature. Therefore, when this airflow At returns to the vicinity of the ground electrode 6, it can contribute to cooling the ground electrode 6. In this way, the heat of the ground electrode 6 can be effectively dissipated. As a result, overheating of the ground electrode 6 can be suppressed, and pre-ignition can be suppressed.

[0026] Furthermore, when viewed from the plug axial direction Z, the first injection holes 501 are disposed on both sides of the fixed end 61 of the ground electrode 6. Therefore, as shown in Fig. 6, the airflow A1 can be made to impinge on the ground electrode 6 from both sides in the circumferential direction of the plug. This makes it possible to more effectively prevent the ground electrode 6 from overheating.

[0027] The second nozzle hole 512 is formed so that the second extension region 512E does not intersect with the first extension region 511E. This makes it possible to prevent the airflow A1 flowing in from the first nozzle hole 511 from being blocked by the airflow A2 flowing in from the second nozzle hole 512. Therefore, the airflow A1 can be effectively directed to the ground electrode 6, and overheating of the ground electrode 6 can be effectively suppressed.

[0028] When viewed from the plug axial direction Z, an intersection Q1 between the nozzle hole axis 511L of the first nozzle hole 511 and the imaginary line Q is disposed closer to the fixed end portion 61 of the ground electrode 6 than an intersection Q2 between the nozzle hole axis 512L of the second nozzle hole 512 and the imaginary line Q. This allows the airflow A1 flowing in from the first nozzle hole 511 to collide with the ground electrode 6 without being obstructed by the airflow A2 flowing in from the second nozzle hole 512.

[0029] As described above, according to this embodiment, it is possible to provide a spark plug for an internal combustion engine that is capable of suppressing pre-ignition.

[0030] (Embodiment 2) In this embodiment, as shown in FIG. 7, an inclination angle θ1 of a nozzle hole axis 511L of a first nozzle hole 511 relative to the plug axial direction Z and an inclination angle θ2 of a nozzle hole axis 512L of a second nozzle hole 512 relative to the plug axial direction Z are different from each other.

[0031] In this embodiment, the inclination angle θ1 of the nozzle hole axis 511L of the first nozzle hole 511 is larger than the inclination angle θ2 of the nozzle hole axis 512L of the second nozzle hole 512. Note that FIG. 7 shows a cross section parallel to both the nozzle hole axis 511L of the first nozzle hole 511 and the plug central axis C. Therefore, θ1 shown in the figure essentially represents the inclination angle θ1 itself. However, FIG. 7 shows a cross section non-parallel to the nozzle hole axis 512L of the second nozzle hole 512. θ2 shown in the figure appears as an angle smaller than the inclination angle θ2. θ2 shown in the figure is for convenience.

[0032] An injection hole axis 512L of the second injection hole 512 does not pass through the ground electrode 6. When viewed from a direction perpendicular to both the plug axial direction Z and the injection hole axis 512L, the injection hole axis 512L of the second injection hole 512 passes further base end side than the discharge gap G.

[0033] The rest is the same as in embodiment 1. Note that, among the symbols used in embodiment 2 and onwards, the same symbols used in the previous embodiments represent the same components, etc. as in the previous embodiments, unless otherwise specified.

[0034] In this embodiment, it is easy to configure the nozzle hole axis 511L of the first nozzle hole 511 and the nozzle hole axis 512L of the second nozzle hole 512 so that they do not pass near each other. Therefore, it is easier to prevent the airflow flowing in from the first nozzle hole 511 and the airflow flowing in from the second nozzle hole 512 from colliding with each other. Therefore, the airflow flowing in from the first nozzle hole 511 can be effectively caused to collide with the ground electrode 6, and overheating of the ground electrode 6 can be prevented. In addition, the same effects as those of the first embodiment are achieved.

[0035] (Embodiment 3) As shown in Figs. 8 to 10, this embodiment has, as the nozzle hole 51, a large nozzle hole 52 having a larger opening area than the other nozzle holes 51. The large nozzle hole 52 is a first nozzle hole 511 .

[0036] In this embodiment, both of the two first nozzle holes 511 are large nozzle holes 52. That is, the two first nozzle holes 511 have the same opening area and are larger than the opening area of ​​the second nozzle holes 512. Note that only a portion of the multiple first nozzle holes 511 may be large nozzle holes 52.

[0037] The opening area of ​​the large nozzle hole 52 is about 1.4 to 2 times the opening area of ​​each of the other two nozzle holes 51, i.e., the two second nozzle holes 512. The opening diameter of the large nozzle hole 52 is about 1.2 to 1.4 times the opening diameter of each of the second nozzle holes 512. The opening area is the area of ​​a cross section perpendicular to the nozzle hole axis of each nozzle hole 51. The rest is the same as in the first embodiment.

[0038] 10, the airflow A1 flowing in from the first nozzle hole 511, which is the large nozzle hole 52, is easily strengthened in this embodiment. Therefore, heat dissipation from the ground electrode 6 can be performed more effectively.

[0039] Furthermore, the airflow A1 flowing in from the large nozzle hole 52 flows toward the base end side in the auxiliary combustion chamber 50 of the second plug portion 12. As a result, a tumble flow At is formed, and a part of the tumble flow At is easily guided again to the ground electrode 6. This further improves the heat dissipation performance of the ground electrode 6. In addition, the same effects as those of the first embodiment are achieved.

[0040] (Embodiment 4) In this embodiment, as shown in FIG. 11, the orientation of the first injection hole 511 when viewed from the plug axial direction Z is changed. That is, the angles α1 and α2 of the nozzle hole axis 511L of the first nozzle hole 511 with respect to the imaginary line Q when viewed from the plug axial direction Z are set to be greater than 45°. In the first embodiment, the angles α1 and α2 are 45°.

[0041] Accordingly, an intersection Q1 between the nozzle hole axis 511L of the first nozzle hole 511 and the imaginary straight line Q is disposed in the first plug portion 11. In this embodiment, the angles α1 and α2 are smaller than 90°. The angles α1 and α2 are equal to each other. That is, the nozzle holes 511L of the two first nozzle holes 511 are provided in positions and orientations that are line-symmetrical with respect to the imaginary straight line Q.

[0042] In addition, the angles β1 and β2 of the nozzle hole axis 512L of the second nozzle hole 512 with respect to the imaginary line Q when viewed from the plug axial direction Z are also larger than 45°. This is the same as in the first embodiment. The rest is the same as in the first embodiment.

[0043] In this embodiment, the intersection Q1 between the nozzle hole axis 511L of the first nozzle hole 511 and the virtual line Q is located in the first plug portion 11, and the intersection Q2 between the nozzle hole axis 512L of the second nozzle hole 512 and the virtual line Q is located in the second plug portion 12. Therefore, it is easy to configure the nozzle hole axis 511L of the first nozzle hole 511 and the nozzle hole axis 512L of the second nozzle hole 512 so that they do not pass near each other. Therefore, it is possible to more easily prevent the airflow A1 flowing in from the first nozzle hole 511 from being obstructed by the airflow A2 flowing in from the second nozzle hole 512 until it collides with the ground electrode 6. In addition, the same effects as those of the first embodiment are achieved.

[0044] (Embodiment 5) In this embodiment, as shown in FIG. 12, angles β1, β2 of the nozzle hole axis 512L of the second nozzle hole 512 with respect to an imaginary line Q when viewed from the plug axial direction Z are set to be smaller than 45°. In this case, an intersection Q2 between the nozzle hole axis 512L of the second nozzle hole 512 and the imaginary line Q is disposed in the second plug portion 12. In this embodiment, the intersection Q2 is disposed closer to the fixed end portion 61 of the ground electrode 6 than an intersection Q1 between the nozzle hole axis 511L of the first nozzle hole 511 and the imaginary line Q. The rest is the same as in the first embodiment.

[0045] In this embodiment, it is also possible to configure the nozzle hole axis 511L of the first nozzle hole 511 and the nozzle hole axis 512L of the second nozzle hole 512 so that they do not pass near each other. By forming the first nozzle hole 511 and the second nozzle hole 512 in this manner, the airflow A1 flowing in from the first nozzle hole 511 can be made to collide with the ground electrode 6 effectively. In addition, the same effects as those of the first embodiment are achieved.

[0046] (Embodiment 6) In this embodiment, as shown in FIG. 13, angles α1, α2 of the nozzle hole axes 511L of the two first nozzle holes 511 with respect to a virtual straight line Q when viewed from the plug axial direction Z are made different from each other. For example, as shown in FIG. 13, the angle α1 can be greater than 45° and the angle α2 can be less than 45°. The rest is the same as in the first embodiment.

[0047] In this embodiment, it is also possible to configure the nozzle hole axis 511L of the first nozzle hole 511 and the nozzle hole axis 512L of the second nozzle hole 512 so that they do not pass near each other. By forming the first nozzle hole 511 and the second nozzle hole 512 in this manner, the airflow A1 flowing in from the first nozzle hole 511 can be made to collide with the ground electrode 6 effectively. In addition, the same effects as those of the first embodiment are achieved.

[0048] (Embodiment 7) In this embodiment, as shown in FIG. 14, angles β1, β2 of the nozzle hole axes 512L of the two second nozzle holes 512 with respect to an imaginary line Q when viewed from the plug axial direction Z are made different from each other. For example, as shown in FIG. 14, angle β1 can be greater than 45° and angle β2 can be less than 45°. The rest is the same as in the first embodiment.

[0049] In this embodiment, it is also possible to configure the nozzle hole axis 511L of the first nozzle hole 511 and the nozzle hole axis 512L of the second nozzle hole 512 so that they do not pass near each other. By forming the first nozzle hole 511 and the second nozzle hole 512 in this manner, the airflow A1 flowing in from the first nozzle hole 511 can be made to collide with the ground electrode 6 effectively. In addition, the same effects as those of the first embodiment are achieved.

[0050] (Embodiment 8) As shown in FIG. 15, this embodiment is an embodiment in which the number of first injection holes 511 and the number of second injection holes 512 are made different from each other. In this embodiment, there are two first injection holes 511 and one second injection hole 512. When viewed from the plug axial direction Z, the second injection hole 512 is disposed on an extension line of the ground electrode 6 in the protruding direction. The rest is the same as in embodiment 1. In this embodiment as well, the same effects as in embodiment 1 can be achieved.

[0051] The numbers of the first injection holes 511 and the second injection holes 512 are not particularly limited. The numbers of the first injection holes 511 and the second injection holes 512 may be the same as in the first embodiment, or may be different as in the eighth embodiment. The number of the second injection holes 512 may be greater than the number of the first injection holes 511.

[0052] (Embodiment 9) In this embodiment, an internal combustion engine 10 equipped with a spark plug 1 will be described with reference to FIGS. The internal combustion engine 10 has a main combustion chamber 101, and an intake valve 72 and an exhaust valve 73 provided in the main combustion chamber 101. The first plug portion 11 of the spark plug 1 faces the intake valve 72. In other words, the first plug portion 11 in which the first nozzle hole 511 is formed faces the intake valve 72.

[0053] 17, when viewed from the plug axial direction Z, the first injection hole 511 is formed so as to face the intake valve 72. More specifically, the outer opening of the first injection hole 511 faces the intake valve 72. In this embodiment, two first injection holes 511 face the intake valve 72.

[0054] As shown in Fig. 16, the internal combustion engine 10 of this embodiment includes a cylinder head 76, a cylinder block 75, and a piston 74 that reciprocates in a cylinder 70. A main combustion chamber 101 is formed by being surrounded by the cylinder head 76, the cylinder block 75, and the piston 74. An intake port 721 and an exhaust port 731 are formed in the cylinder head 76, and an intake valve 72 or an exhaust valve 73 is provided therein. A spark plug 1 is attached between the intake port 721 and the exhaust port 731 in the cylinder head 76. That is, as shown in Figs. 16 and 17, the spark plug 1 is disposed in a position surrounded by the two intake ports 721 and the two exhaust ports 731 in the cylinder head 76.

[0055] The intake port 721 and the exhaust port 731 are inclined with respect to the forward and backward movement direction of the piston 74 so that the opening direction of the intake port 721 and the exhaust port 731 is directed toward the central axis of the main combustion chamber 101. In addition, the base end surface of the main combustion chamber 101 is inclined so as to be directed toward the tip side as it moves away from the spark plug 1.

[0056] In the internal combustion engine 10, an intake stroke, a compression stroke, an expansion stroke, and an exhaust stroke are repeated in sequence in accordance with the reciprocating motion of the piston 74. During the intake stroke, gas (mainly air) is introduced into the main combustion chamber 101 from the intake port 721, and during the exhaust stroke, the gas in the main combustion chamber 101 is exhausted from the exhaust port 731. Due to the way in which the airflow is introduced during the intake stroke, a predetermined airflow is formed in the main combustion chamber 101, and this airflow remains even during the compression stroke.

[0057] In the main combustion chamber 101, a tumble flow is formed, which is an airflow around an axis perpendicular to the sliding direction of the piston 74, as shown by an arrow AF2 in Fig. 16. In the vicinity of the tip of the spark plug 1 in the main combustion chamber 101, this airflow AF2 is directed from the intake valve 72 side to the exhaust valve 73 side, as shown in Fig. 16 and Fig. 17. More specifically, as shown in Fig. 17, when viewed from the plug axial direction Z, the airflow AF2 along the direction from the intermediate position between the two intake ports 721 to the intermediate position between the two exhaust ports 731 is the main airflow in the vicinity of the tip of the spark plug 1.

[0058] The airflow in the main combustion chamber 101 is not always constant, but may vary between cycles or between different timings in one cycle. However, the direction of the main airflow, particularly the direction of the airflow at the ignition timing, is roughly fixed, and the above-mentioned airflow AF2 means the main airflow at the ignition timing. And, when we say "airflow in the main combustion chamber 101," we mean the above-mentioned airflow AF2 near the tip of the spark plug 1 at the ignition timing, unless otherwise specified. The rest is the same as in the first embodiment.

[0059] In the internal combustion engine of this embodiment, when viewed from the plug axial direction Z, the first injection hole 511 is formed so that its outer opening faces the intake valve 72. As a result, the outer opening of the first injection hole 511 faces the upstream side of the airflow AF2 of the main combustion chamber 101. This makes it possible to further strengthen the inflow airflow (see arrow A1 in FIGS. 5 and 6) from the first injection hole 511, particularly during the compression stroke. As a result, the effect of suppressing overheating of the ground electrode 6 described in the above-mentioned first embodiment can be obtained more effectively.

[0060] Furthermore, in the above-mentioned embodiment 9, the spark plug 1 of embodiment 1 is attached to an internal combustion engine. However, a configuration in which the spark plug 1 of embodiment 3 is attached to an internal combustion engine is also conceivable. In this case, the large injection hole 52, which is the first injection hole 511, faces the intake valve 72 side when viewed from the plug axial direction Z. This can further strengthen the inflow airflow A1 from the large injection hole 52. Therefore, the airflow colliding with the ground electrode 6 can be further strengthened. As a result, overheating of the ground electrode 6 can be further suppressed.

[0061] Various configurations are possible in addition to the above-described embodiment 1. Furthermore, the above-described embodiments may be appropriately combined with each other to form an embodiment.

[0062] The present invention is not limited to the above-described embodiments, and can be applied to various embodiments without departing from the gist of the present invention. [Explanation of symbols]

[0063] 1...spark plug, 10...internal combustion engine, 11...first plug portion, 12...second plug portion, 2...housing, 3...insulator, 4...center electrode, 5...plug cover, 50...auxiliary combustion chamber, 51...nozzle hole, 511...first nozzle hole, 511L...nozzle hole axis (of first nozzle hole), 6...ground electrode, C...plug center axis, G...discharge gap, P...imaginary plane, Q...imaginary line, Z...plug axial direction

Claims

1. A cylindrical insulator (3); a center electrode (4) held on the inner circumferential side of the insulator and protruding from the insulator toward the tip side; a cylindrical housing (2) that holds the insulator on its inner periphery; a ground electrode (6) forming a discharge gap (G) between itself and the center electrode; a plug cover (5) provided at a tip end of the housing so as to cover a sub-combustion chamber (50) in which the discharge gap is disposed, The ground electrode protrudes into the auxiliary combustion chamber from a fixed end portion (61) fixed to the housing or the plug cover on the outer circumferential side of the auxiliary combustion chamber, The plug cover is formed with a nozzle hole (51) that communicates the auxiliary combustion chamber with the outside, When the above spark plug is divided into a first plug portion (11) and a second plug portion (12) by the following imaginary plane (P), At least one of the nozzle holes is a first nozzle hole (511) that is formed in the first plug portion and has a nozzle hole axis (511L) that passes through the ground electrode, the imaginary plane is a plane that is perpendicular to an imaginary line (Q) connecting a center of the fixed end and a central axis (C) of the plug as viewed from the axial direction (Z) of the plug and that includes the central axis of the plug, the fixed end of the ground electrode is disposed in the first plug section, The spark plug for an internal combustion engine has a second nozzle hole (512) formed in the second plug portion as the nozzle hole, and the second nozzle hole is formed such that a second extension region (512E) extending from the second nozzle hole along a nozzle hole axis (512L) does not intersect with a first extension region (511E) extending from the first nozzle hole along the nozzle hole axis.

2. 2. The spark plug for an internal combustion engine according to claim 1, further comprising a plurality of the first injection holes, the first injection holes being disposed on both sides of the fixed end of the ground electrode as viewed in the plug axial direction.

3. 3. A spark plug for an internal combustion engine according to claim 1, wherein an intersection (Q1) between an axis of the first nozzle hole and the imaginary line is located closer to the fixed end of the ground electrode than an intersection (Q2) between an axis of the second nozzle hole and the imaginary line when viewed in a plug axial direction.

4. 4. The spark plug for an internal combustion engine according to claim 1, wherein an inclination angle (θ1) of a nozzle hole axis of the first nozzle hole with respect to a plug axial direction and an inclination angle (θ2) of a nozzle hole axis of the second nozzle hole with respect to the plug axial direction are different from each other.

5. 5. The spark plug for an internal combustion engine according to claim 1, wherein the nozzle hole includes a large nozzle hole (52) having an opening area larger than other nozzle holes, the large nozzle hole being the first nozzle hole.

6. An internal combustion engine (10) equipped with the spark plug for an internal combustion engine according to any one of claims 1 to 5, The invention comprises a main combustion chamber (101), and an intake valve (72) and an exhaust valve (73) provided in the main combustion chamber, the first plug portion faces the intake valve side when viewed from the plug axial direction.

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