Spark plug for internal combustion engine and internal combustion engine

Abstract

To provide a spark plug for an internal combustion engine, the spark plug enabling stable combustibility to be obtained in an operation region of the internal combustion engine from low loading to high loading, and an internal combustion engine.SOLUTION: A spark plug 1 for an internal combustion engine is provided, including: an insulator; a center electrode 4; a housing; a ground electrode 6; and a plug cover 5. The ground electrode 6 projects from a fixed end portion 61 into a sub combustion chamber 50. Three or more injection holes 51 are formed in the plug cover 5. When the spark plug 1 is divided into a first plug portion 11 and a second plug portion 12 by a virtual flat surface P, and when a side in which the fixed end portion 61 is arranged is defined as the first plug portion 11, and when each injection hole 51 formed in the first plug portion 11 is defined as a first injection hole 511 and each injection hole 51 formed in the second plug portion 12 is defined as a second injection hole 512, the number of first injection holes 511 is larger than that of the second injection holes 512, and an inner diameter of the first injection hole 511 is smaller than that of the second injection hole 512.SELECTED DRAWING: Figure 2

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, in the spark plug described in Patent Document 1, no particular measures are taken in consideration of the combustibility in both the low load operating range and the high load operating range of the internal combustion engine.

[0005] The present invention has been made in view of the above-mentioned problems, and has an object to provide a spark plug for an internal combustion engine, and an internal combustion engine, which are capable of obtaining stable combustion characteristics over an operating range of the internal combustion engine from low load to high load. [Means for solving the problem]

[0006] One aspect of the present invention is a cylindrical insulator (3), a center electrode (4) held on the inner circumferential side of the insulator and protruding from the insulator toward the tip side; a cylindrical housing (2) that holds the insulator on its inner periphery; a ground electrode (6) forming a discharge gap (G) between itself and the center electrode; a plug cover (5) provided at 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 three or more nozzle holes (51) that communicate the auxiliary combustion chamber with the outside, The nozzle holes have nozzle holes whose axes (511L, 512L) are inclined with respect to the plug axis direction (Z) so as to be radially outward toward the tip side, When the spark plug is divided into two parts, a first plug portion (11) and a second plug portion (12), by a virtual plane (P) that includes the plug center axis (C) and is perpendicular to the extension direction of the ground electrode when viewed in the plug axial direction, the side on which the fixed end is arranged is defined as the first plug portion, the nozzle hole formed in the first plug portion is defined as a first nozzle hole (511), and the nozzle hole formed in the second plug portion is defined as a second nozzle hole (512), the number of the first nozzle holes is greater than the number of the second nozzle holes, The inner diameter of the first nozzle hole is smaller than the inner diameter of the second nozzle hole. Ku, At least one of the second nozzle holes is a projection-side nozzle hole (52) through which a central axis (C6) of the ground electrode passes when viewed in the plug axial direction, a projection end portion (63) of the ground electrode is disposed between the central electrode and the projection-side nozzle hole when viewed in the plug axial direction, the projection end portion is disposed at a position closer to the projection-side nozzle hole than to the central electrode when viewed in the plug axial direction, and the projection end portion is disposed on the tip side of a straight line (L1) that connects, at the shortest distance, a base end of an outer opening portion (522) of the projection-side nozzle hole and a tip end portion of the central electrode. , Found in spark plugs for internal combustion engines. Effect of the Invention

[0007] In the spark plug for an internal combustion engine, the number of the first injection holes is greater than the number of the second injection holes, and the inner diameter of the first injection holes is smaller than the inner diameter of the second injection holes. Thus, by appropriately mounting the spark plug to the internal combustion engine, stable combustibility can be obtained in an operating range of the internal combustion engine ranging from low load to high load.

[0008] As described above, according to the above aspects, it is possible to provide a spark plug for an internal combustion engine and an internal combustion engine that can obtain stable combustion characteristics in an operating range of the internal combustion engine ranging from low load to high load. 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] FIG. 3 is an explanatory sectional view of the spark plug according to the first embodiment, taken along line II in FIG. 2; [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] FIG. 2 is a cross-sectional explanatory view of an internal combustion engine according to the first embodiment. [Diagram 5] FIG. 5 is an explanatory diagram equivalent to a cross section taken along line VV in FIG. 4 . [Figure 6] FIG. 11 is a cross-sectional view illustrating the operation and effect of the first embodiment. [Figure 7] FIG. 11 is an explanatory diagram of a flame jet as viewed from the plug axial direction in the case of a relatively low load in the first embodiment. [Figure 8] FIG. 11 is an explanatory diagram of a flame jet as viewed from the plug axial direction in the case of a relatively high load in the first embodiment. [Figure 9] FIG. 11 is a cross-sectional explanatory view of an internal combustion engine according to a second embodiment. [Figure 10] FIG. 11 is a cross-sectional explanatory view of an internal combustion engine according to a third embodiment. [Figure 11] FIG. 11 is an explanatory cross-sectional view taken along the central axis of a spark plug according to a fourth embodiment of the present invention. [Figure 12] FIG. 13 is an explanatory cross-sectional view of a spark plug according to a fifth embodiment, taken along a line perpendicular to the central axis of the plug. [Figure 13] 13 is an explanatory sectional view of a spark plug according to a sixth embodiment, taken along line XIII-XIII in FIG. 14. [Figure 14] FIG. 14 is a cross-sectional view taken along line XIV-XIV in FIG. [Figure 15] FIG. 13 is a cross-sectional view illustrating the operation and effect of the sixth embodiment. [Figure 16]FIG. 13 is a cross-sectional view of a spark plug according to a seventh embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] ( Reference form 1 ) Spark plugs for internal combustion engines Reference form This 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 protrudes into the auxiliary combustion chamber 50 from a fixed end 61 that is fixed to the housing 2 or the plug cover 5 on the outer periphery of the auxiliary combustion chamber 50. Three or more nozzle holes 51 that communicate the auxiliary combustion chamber 50 with the outside are formed in the plug cover 5. The nozzle hole axes 511L, 512L of the nozzle holes 51 are inclined with respect to the plug axial direction Z so as to move outward in the plug radial direction toward the tip side.

[0013] An imaginary plane P is assumed which includes the plug center axis C and is perpendicular to the extension direction of the ground electrode 6 as viewed from the plug axial direction Z. The spark plug 1 is divided into two parts, a first plug portion 11 and a second plug portion 12, by this imaginary plane P. The side on which the fixed end portion 61 is arranged is defined as the first plug portion 11. The injection holes 51 formed in the first plug portion 11 are defined as first injection holes 511. The injection holes 51 formed in the second plug portion 12 are defined as second injection holes 512. In this case, the number of the first injection holes 511 is greater than the number of the second injection holes 512. The inner diameter of the first injection hole 511 is smaller than the inner diameter of the second injection hole 512.

[0014] The spark plug 1 of this embodiment can be used as an ignition means in an internal combustion engine of an automobile, a cogeneration system, or the like. As shown in Fig. 4, one end of the spark plug 1 in the plug axial direction Z is disposed in a main combustion chamber 101 of an internal combustion engine 10. In the plug axial direction Z, the side exposed to the main combustion chamber 101 is referred to as the tip side, and the opposite side is referred to as the base side. 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.

[0015] As shown in FIG. 2, in this embodiment, three injection holes 51 are formed. Two of the three injection holes 51 are first injection holes 511 formed in the first plug portion 11. 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. As 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 ground electrode 6 is joined to the tip portion of the housing 2 by welding or the like.

[0016] In this embodiment, the other of the three injection holes 51 is a second injection hole 512 formed in the second plug portion 12. The second injection hole 512 also extends along the plug radial direction when viewed from the plug axial direction Z. In other words, the injection hole axis 512L of the second injection hole 512 also substantially intersects with the plug central axis C.

[0017] When viewed from the plug axial direction Z, the multiple first injection holes 511 are arranged at positions that are symmetrical about the central axis C6 of the ground electrode 6. When viewed from the plug axial direction Z, the second injection hole 512 is arranged on the central axis C6 of the ground electrode 6. When viewed from the plug axial direction Z, the central axis C6 of the ground electrode 6 and the injection hole axis 512L of the second injection hole 512 overlap with each other.

[0018] 1, the ground electrode 6 is inclined with respect to the plug axial direction Z so as to move toward the tip side from the fixed end 61 toward the plug central axis C. In other words, the ground electrode 6 is inclined toward the tip side in the plug axial direction Z from the fixed end 61 toward the protruding end.

[0019] Further, the discharge gap G is disposed further forward than the front end 21 of the housing 2. The front end face of the center electrode 4 is disposed further forward than the front end 21 of the housing 2 in the plug axial direction Z.

[0020] In this embodiment, the inner diameter of the second nozzle hole 512 is about 1.4 times the inner diameter of the first nozzle hole 511. The opening area of ​​the second nozzle hole 512 is about twice the opening area of ​​the first nozzle hole 511. As a result, the sum of the opening areas of the two first nozzle holes 511 and the opening area of ​​one second nozzle hole 512 are approximately equal to each other.

[0021] Note that the numbers of the first injection holes 511 are not particularly limited as long as they are greater than the number of the second injection holes 512. For example, the number of the first injection holes 511 may be three, and the number of the second injection holes 512 may be one or two. Alternatively, the number of the first injection holes 511 may be four, and the number of the second injection holes 512 may be one, two, or three. In any case, it is considered that the sum of the opening areas of all the first injection holes 511 and the opening areas of all the second injection holes 512 are approximately equal.

[0022] An internal combustion engine 10 equipped with the spark plug 1 of this embodiment 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. When viewed from the plug axial direction Z, the first plug portion 11 faces the intake valve 72 side.

[0023] That is, the spark plug 1 is attached to the internal combustion engine 10 so that the first plug portion 11 faces the intake valve 72 side.

[0024] As shown in Fig. 4, the internal combustion engine 10 includes a cylinder head 76, a cylinder block 75, and a piston 74 that reciprocates in the cylinder 70. The cylinder head 76, the cylinder block 75, and the piston 74 form a main combustion chamber 101. The cylinder head 76 is formed with an intake port 721 and an exhaust port 731, and each of the intake port 72 and the exhaust valve 73 is provided. The 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. 4 and 5, 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.

[0025] 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.

[0026] 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.

[0027] In the main combustion chamber 101, a tumble flow, i.e., an airflow AF1 around an axis perpendicular to the sliding direction of the piston 74, is mainly formed as shown in Fig. 4. In the vicinity of the tip of the spark plug 1 in the main combustion chamber 101, this airflow AF1 is directed from the intake valve 72 side to the exhaust valve 73 side as shown in Fig. 4 and Fig. 5. More specifically, as shown in Fig. 5, when viewed from the plug axial direction Z, the airflow AF1 along the direction from the intermediate position between the two intake ports 721 to the intermediate position between the two exhaust ports 731 becomes the main airflow in the vicinity of the tip of the spark plug 1.

[0028] 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 AF1 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 AF1 near the tip of the spark plug 1 at the ignition timing, unless otherwise specified.

[0029] Next, the effects of this embodiment will be described. In the spark plug 1 for an internal combustion engine, the number of the first nozzle holes 511 is greater than the number of the second nozzle holes 512, and the inner diameter of the first nozzle holes 511 is smaller than the inner diameter of the second nozzle holes 512. Thus, by appropriately mounting the spark plug 1 to the internal combustion engine 10, stable combustibility can be obtained in an operating range of the internal combustion engine ranging from low load to high load.

[0030] In other words, by mounting the spark plug 1 in the internal combustion engine 10 so that the first plug portion 11 faces the intake valve 72, the following phenomena can be expected in both a relatively low load operating range and a relatively high load operating range.

[0031] In a relatively low load operating range, as shown in Figures 4 and 5, an airflow AF1 is formed in the main combustion chamber 101 near the tip of the spark plug 1, flowing from the intake valve 72 side to the exhaust valve 73 side. This causes an airflow AF2 to flow from the first nozzle hole 511 into the auxiliary combustion chamber 50, as shown in Figure 6.

[0032] This airflow AF2 forms a tumble flow, which is an airflow AF3 that first flows toward the base end side of the second plug portion 12 and then flows toward the tip end side of the first plug portion 11 in the auxiliary combustion chamber 50. The airflow AF3 then passes through the discharge gap G along the base end side surface of the ground electrode 6 and flows toward the second nozzle hole 512. This causes the discharge S in the discharge gap G to be elongated.

[0033] Therefore, the combustion in the auxiliary combustion chamber 50 diffuses from a position close to the second nozzle hole 512. Here, since the inner diameter of the second nozzle hole 512 is large, the flame jet injected from the second nozzle hole 512 is less susceptible to cooling loss from the plug cover 5. Therefore, as shown in Fig. 7, the flame jet J2 from the second nozzle hole 512 is more easily injected, and ignition performance can be improved. For example, ignition performance can be more easily ensured even in an EGR (i.e., exhaust gas recirculation) environment.

[0034] In a relatively high load operating range, the fuel concentration is high and the temperature is also high. Therefore, the combustion diffusion in the auxiliary combustion chamber 50 is fast, and the difference in the arrival time of the flame to the multiple nozzle holes 51 is unlikely to occur. In other words, there is no large difference in the arrival time of the flame between the first nozzle hole 511 and the second nozzle hole 512. In addition, the flame is prevented from suffering cooling loss. Therefore, the flame jets J1 and J2 are sufficiently injected from both the first nozzle hole 511 and the second nozzle hole 512.

[0035] And because the first nozzle holes 511 have a small inner diameter, the penetration force of the flame jet J1 is high, and the flame jet J1 is injected from the first nozzle holes 511 with great force. Also, because there are a large number of first nozzle holes 511, the flame jet J1 injected from the first nozzle holes 511 tends to diffuse widely in the area on the intake valve 72 side in the main combustion chamber 101. That is, combustion can be promoted on the intake valve 72 side in the main combustion chamber 101, where the temperature is relatively low. This can improve the combustion balance in the main combustion chamber 101, and can suppress knocking and the like in the internal combustion engine.

[0036] 2, the first nozzle holes 511 are arranged in line symmetry with respect to the central axis C6 of the ground electrode 6 when viewed from the plug axial direction Z. This allows the air flows flowing in from the first nozzle holes 511 to join together and flow toward the second plug portion 12. This makes it possible to strengthen the tumble flow (see arrow AF3 in FIG. 6) in the auxiliary combustion chamber 50, thereby further improving combustibility in a relatively low load operating range.

[0037] 6, the ground electrode 6 is inclined with respect to the plug axial direction Z so as to move from the fixed end 61 toward the tip side as it approaches the plug central axis C. This allows the airflow AF3 in the auxiliary combustion chamber 50 to be guided to the discharge gap G more smoothly.

[0038] In addition, the discharge gap G is disposed closer to the tip side than the tip 21 of the housing 2. This makes it possible to suppress the cooling loss of the initial flame. Also, the discharge S is more likely to extend toward the second nozzle hole 512. As a result, it is possible to further improve the combustibility in the relatively low load operating range.

[0039] As described above, according to the present embodiment, it is possible to provide a spark plug for an internal combustion engine and an internal combustion engine that can obtain stable combustion characteristics in an operating range of the internal combustion engine ranging from low load to high load.

[0040] ( Reference form 2 ) As shown in FIG. 9, this embodiment is an internal combustion engine 10 having an injector 71 that directly injects fuel into a main combustion chamber 101. The spark plug 1 is disposed so that an injection flow F containing fuel injected from the injector 71 is directed toward the second nozzle hole 512.

[0041] At any timing from the intake stroke to the compression stroke of the internal combustion engine 10, fuel is injected from the injector 71 into the main combustion chamber 101. An injection flow F containing this fuel is formed in the main combustion chamber 101 and directed toward the outer opening of the second nozzle hole 512.

[0042] 9 indicates the direction of the injection flow immediately after fuel injection, and does not necessarily coincide with the airflow in the main combustion chamber 101 during the intake stroke, compression stroke, or expansion stroke. Also, the state in which the injection flow F is directed toward the second injection hole 512 is a state in which the outer opening of the second injection hole 512 is visible from the direction of the injection flow F near the plug cover 5.

[0043] An injector 71 is provided at a position adjacent to the intake port 721. The injector 71 is attached in such a position that it injects fuel toward the central axis of the main combustion chamber 101.

[0044] The fuel injected into the main combustion chamber 101 forms an injection flow F together with the air in the main combustion chamber 101 and hits the base end surface of the piston 74, for example, as shown in FIG. 9. In this embodiment, the base end surface of the piston 74 has a concave surface. The injection flow F that hits the base end surface of the piston 74 changes its trajectory and travels toward the base end side, i.e., the spark plug 1 side. At this time, the injection flow F reaches the vicinity of the second nozzle hole 512 of the spark plug 1.

[0045] The injection flow F is a mixture with a relatively large fuel ratio. Therefore, the vicinity of the second injection hole 512 where the injection flow F reaches becomes a mixture containing a large amount of fuel. This mixture is introduced into the auxiliary combustion chamber 50 through the second injection hole 512. And, since the second injection hole 512 has an inner diameter larger than that of the first injection hole 511, the mixture is more easily introduced into the auxiliary combustion chamber 50 through the second injection hole 512.

[0046] Others: Reference form 1 It is the same as: Reference form 2 Among the symbols used below, form The same symbols as those used in form It represents the same components as those in.

[0047] In the internal combustion engine 10 of this embodiment, the spark plug 1 is disposed so that the injection flow F injected from the injector 71 is directed toward the second nozzle hole 512. This makes it easier for a mixture with high fuel density to be introduced from the second nozzle hole 512 into the auxiliary combustion chamber 50. As a result, the ignition performance in the auxiliary combustion chamber 50 is improved, and the ignition performance in the main combustion chamber 101 can be improved.

[0048] For example, the effect of improving ignition when retard injection and retard ignition are performed during high load operation of the internal combustion engine can be expected. During the compression stroke in which retard injection is performed, the atmosphere in the main combustion chamber 101 is compressed, and air flows into the auxiliary combustion chamber 50 through the nozzle hole 51. This causes the pressure in the auxiliary combustion chamber 50 to increase. Therefore, while it is relatively difficult for the mixture to flow into the auxiliary combustion chamber 50 at the timing of retard ignition, according to this embodiment, it is easy to introduce a high concentration mixture into the auxiliary combustion chamber 50 via the second nozzle hole 512. Alternatively, it can be said to be particularly effective in improving ignition when starting the internal combustion engine, where the air flow is relatively weak and the fuel concentration is likely to be uneven. others, Reference form 1 It has the same effect as above.

[0049] ( Reference form 3 ) As shown in FIG. 10, Reference form 2 In contrast, the orientation of the spark plug 1 installed in the internal combustion engine 10 is changed.

[0050] The internal combustion engine 10 of this embodiment is configured so that a part of the injection flow F injected from the injector 71 heads directly toward the spark plug 1. Therefore, in this embodiment, the spark plug 1 is disposed in an orientation such that a part of the injection flow F heads directly toward the second nozzle hole 512. In other words, the injector 71 injects fuel into the main combustion chamber 101 so that the injection flow F containing fuel heads directly toward the outer opening of the second nozzle hole 512.

[0051] In this embodiment, the spark plug 1 is disposed so that, when viewed from the Z direction, the outer opening of the second nozzle hole 512 faces the intake valve 72 side (not shown). Others: Reference form 2 is the same as:

[0052] The spark plug 1 is disposed so that the injection flow F injected from the injector 71 is directed directly toward the second nozzle hole 512. This ensures that a mixture with high fuel density is easily introduced into the auxiliary combustion chamber 50 from the second nozzle hole 512. In addition, since the second nozzle hole 512 has a larger inner diameter than the first nozzle hole 511, the mixture is more easily introduced into the auxiliary combustion chamber 50 through the second nozzle hole 512. others, Reference form 2 It has the same effect as above.

[0053] ( Reference form 4 ) In this embodiment, the first injection hole 511 and the second injection hole 512 are formed so that the extension region 511E and the extension region 512E do not overlap the discharge gap G, as shown in FIG.

[0054] The extension region 511E is a region obtained by extending the first nozzle hole 511 along the nozzle hole axis 511L. The extension region 512E is a region obtained by extending the second nozzle hole 512 along the nozzle hole axis 512L. The first injection hole 511 and the second injection hole 512 are further formed such that the extension region 511E and the extension region 512E do not intersect with each other.

[0055] In this embodiment, the inclination angle of the nozzle hole axis 511L of the first nozzle hole 511 and the inclination angle of the nozzle hole axis 512L of the second nozzle hole 512 with respect to the plug axis direction Z are made different from each other, so that the extension regions 511E and 512E do not intersect with each other.

[0056] In this embodiment, the inclination angle of the nozzle hole axis 511L of the first nozzle hole 511 with respect to the plug axial direction Z is larger than the inclination angle of the nozzle hole axis 512L of the second nozzle hole 512 with respect to the plug axial direction Z. Others: Reference form 1 is the same as:

[0057] In this embodiment, the first injection hole 511 and the second injection hole 512 are formed so that the extension region 511E and the extension region 512E do not intersect with each other. As a result, the airflow flowing from the first injection hole 511 into the auxiliary combustion chamber 50 is not easily disturbed by the airflow flowing from the second injection hole 512. Therefore, a tumble flow (see arrow AF3 in FIG. 6) is easily formed in the auxiliary combustion chamber 50. As a result, the discharge S formed in the discharge gap G is easily extended toward the second plug portion 12.

[0058] In addition, the extension region 511E and the extension region 512E do not overlap with the discharge gap G. As a result, the airflow passing through the discharge gap G due to the above-mentioned tumble flow is less likely to be disturbed by the airflow flowing into the auxiliary combustion chamber 50 from the first nozzle hole 511 and the second nozzle hole 512. As a result, the discharge S formed in the discharge gap G can be easily extended toward the second plug portion 12. others, Reference form 1 It has the same effect as above.

[0059] ( Reference form 5 ) In this embodiment, the first injection hole 511 and the second injection hole 512 are formed so that the extension region 511E and the extension region 512E do not overlap the discharge gap G, as shown in FIG. Also in this embodiment, the first injection hole 511 and the second injection hole 512 are formed such that the extension region 511E and the extension region 512E do not intersect with each other.

[0060] In this embodiment, the inclination angle of the injection hole axis 511L of the first injection hole 511 and the inclination angle of the injection hole axis 512L of the second injection hole 512 with respect to the central axis C6 as viewed in the plug axial direction Z are made different.

[0061] In this embodiment, the number of first injection holes 511 is three, and the number of second injection holes 512 is two. One of the three first injection holes 511 is formed at a position overlapping with the fixed end portion 61 of the ground electrode 6 when viewed from the plug axial direction Z. The injection hole axis 511L of this first injection hole 511 is aligned along the plug radial direction when viewed from the plug axial direction Z.

[0062] On the other hand, the other two of the three first injection holes 511 are formed at positions opposite to each other across the ground electrode 6 when viewed from the plug axial direction Z. The injection hole axes 511L of these first injection holes 511 are shifted from the plug radial direction when viewed from the plug axial direction Z and intersect with the central axis C6 of the ground electrode 6 at the second plug portion 12.

[0063] In addition, the nozzle hole axes 512L of the two second nozzle holes 512 also intersect with the central axis C6 of the ground electrode 6 in the second plug portion 12 when viewed from the plug axial direction Z.

[0064] Others: Reference form 1 is the same as: In this embodiment, Reference form 2 The same effect can be obtained.

[0065] (Embodiment 6) In this embodiment, as shown in FIGS. 13 to 15, the ground electrode 6 protrudes significantly toward the second plug portion 12 side.

[0066] In this embodiment, at least one of the second injection holes 512 is a projection-side injection hole 52 through which the central axis C6 of the ground electrode 6 passes when viewed from the plug axial direction Z. When viewed from the plug axial direction Z, the projection end portion 63 of the ground electrode 6 is disposed between the center electrode 4 and the projection-side injection hole 52.

[0067] As shown in Fig. 14, when viewed from the plug axial direction Z, the protruding end 63 is disposed at a position closer to the protruding side nozzle hole 52 than to the center electrode 4. As shown in Fig. 13, the protruding end 63 is disposed on the tip side of a straight line L1. The straight line L1 is a straight line connecting the base end of the outer opening 522 of the protruding side nozzle hole 52 and the tip end of the center electrode 4 at the shortest distance.

[0068] The ground electrode 6 has a thickness in the plug axial direction Z of a portion of the ground electrode 6 that is closer to the protruding end 63 than the fixed end 61 in the longitudinal direction of the ground electrode 6, the thickness decreasing toward the protruding end 63. The tip surface of the tapered portion of the ground electrode 6 is formed along the inner surface of the bottom wall of the plug cover 5. Others: Reference form 1 is the same as:

[0069] In the case of this embodiment, the airflow discharged from the auxiliary combustion chamber 50 through the projection side nozzle hole 52 is guided to the ground electrode 6 and easily passes through the discharge gap G, particularly during the expansion stroke.

[0070] In this regard, the expansion stroke of an internal combustion engine 10 (see FIG. 4) equipped with the spark plug 1 of this embodiment will be considered. During the expansion stroke, the piston 74 moves to the tip end side, causing the main combustion chamber 101 to have a negative pressure relative to the auxiliary combustion chamber 50. As a result, gas is discharged from the auxiliary combustion chamber 50 to the main combustion chamber 101 through the nozzle hole 51. An airflow AF4 formed in the auxiliary combustion chamber 50 as the gas is discharged through the projection side nozzle hole 52 is guided to the ground electrode 6 and moves toward the projection side nozzle hole 52, as shown in FIG. 15. The airflow AF4 guided to the ground electrode 6 passes through the discharge gap G.

[0071] Therefore, during the expansion stroke, the discharge S generated in the discharge gap G is easily extended toward the projection side nozzle hole 52 by the airflow AF4 as shown in Fig. 15, improving ignition performance in the auxiliary combustion chamber 50. In addition, since the ignition position can be easily brought close to the projection side nozzle hole 52, for example, under operating conditions in which the temperature of the auxiliary combustion chamber 50 is low, cold loss is suppressed and the flame jet to the main combustion chamber 101 can be strengthened. Furthermore, since the discharge S or discharge plasma or initial flame generated in the discharge gap G is easily ejected from the projection side nozzle hole 52, ignition performance in the main combustion chamber 101 can be improved.

[0072] Furthermore, during the expansion stroke, the starting point on the ground electrode 6 side of the discharge S generated in the discharge gap G tends to move toward the projection side nozzle hole 52 due to the airflow AF4 guided through the projection side nozzle hole 52. Therefore, the discharge S tends to extend toward the projection side nozzle hole 52. As a result, the ignition performance can be improved.

[0073] When viewed from the plug axial direction Z, the protruding end 63 is disposed at a position closer to the protruding side nozzle hole 52 than to the center electrode 4. Therefore, during the expansion stroke, the airflow AF4 guided by the ground electrode 6 is more likely to flow toward the protruding side nozzle hole 52. Therefore, the discharge S generated in the discharge gap G is more likely to extend toward the protruding side nozzle hole 52. As a result, the ignition performance can be further improved.

[0074] The protruding end 63 is disposed on the tip side of the straight line L1. Therefore, during the expansion stroke, the discharge S generated in the discharge gap G is not short-circuited by the protruding end 63 and easily extends toward the protruding side nozzle hole 52 and the main combustion chamber. As a result, the ignition performance can be reliably improved.

[0075] Let us assume that the protruding end 63 is located closer to the base end than the straight line L1. In this case, the discharge extending toward the protruding side nozzle hole 52 is likely to be short-circuited by the protruding end 63 when it tries to extend further toward the protruding side nozzle hole 52 than the protruding end 63. On the other hand, in this embodiment, the protruding end 63 is disposed at the above-mentioned position. Therefore, during the expansion stroke, the discharge S generated in the discharge gap G is unlikely to be short-circuited by the protruding end 63 even if it extends further toward the protruding side nozzle hole 52 than the protruding end 63, as shown in FIG. 15. As a result, ignition performance can be improved.

[0076] In addition, by arranging the protruding end portion 63 in the above-mentioned position, the starting point of the discharge S on the ground electrode 6 side is likely to move to the inner surface of the protrusion-side nozzle hole 52, as shown in Fig. 15. Furthermore, the starting point is likely to move toward the outer opening 522 of the protrusion-side nozzle hole 52. Therefore, the discharge S is more likely to extend toward the main combustion chamber 101. As a result, the ignition ability of the main combustion chamber 101 can be further improved. others, Reference form 1 It has the same effect as above.

[0077] ( Reference form 7 ) In this embodiment, as shown in FIG. 16, the shape of the ground electrode 6 is modified. That is, in this embodiment, the ground electrode 6 has a portion along the plug axial direction Z on the fixed end 61 side, and is bent from that portion toward the plug central axis C. The surface of the ground electrode 6 facing the center electrode 4 is a surface that is approximately perpendicular to the plug axial direction Z. Others: Reference form 1 and has the same effect.

[0078] 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]

[0079] 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, 512...second nozzle hole, 511L, 512L...nozzle hole axis, 6...ground electrode, 61...fixed end, C...plug center axis, G...discharge gap, P...imaginary plane, 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 three or more nozzle holes (51) that communicate the auxiliary combustion chamber with the outside, The nozzle hole axes (511L, 512L) of the nozzle holes are inclined with respect to the plug axial direction (Z) so as to be outward in the plug radial direction toward the tip side, When the spark plug is divided into two parts, a first plug portion (11) and a second plug portion (12), by a virtual plane (P) which includes the plug center axis (C) and is perpendicular to the extending direction of the ground electrode as viewed in the plug axial direction, the side on which the fixed end is arranged is defined as the first plug portion, the injection hole formed in the first plug portion is defined as a first injection hole (511), and the injection hole formed in the second plug portion is defined as a second injection hole (512), the number of the first nozzle holes is greater than the number of the second nozzle holes, an inner diameter of the first nozzle hole is smaller than an inner diameter of the second nozzle hole, at least one of the second nozzle holes is a protruding side nozzle hole (52) through which a central axis (C6) of the ground electrode passes when viewed from the plug axial direction, a protruding end portion (63) of the ground electrode is disposed between the central electrode and the protruding side nozzle hole when viewed from the plug axial direction, the protruding end portion is disposed at a position closer to the protruding side nozzle hole than to the central electrode when viewed from the plug axial direction, and the protruding end portion is disposed on the tip side of a straight line (L1) connecting, at the shortest distance, a base end of an outer opening portion (522) of the protruding side nozzle hole and a tip end portion of the central electrode. Spark plugs for internal combustion engines.

2. 2. A spark plug for an internal combustion engine according to claim 1, wherein the first nozzle hole and the second nozzle hole are formed such that an extension region (511E) formed by extending the first nozzle hole along a nozzle hole axis and an extension region (512E) formed by extending the second nozzle hole along a nozzle hole axis do not overlap the discharge gap and do not intersect with each other.

3. 3. The spark plug for an internal combustion engine according to claim 1, wherein the first nozzle holes are arranged in line symmetry with respect to a central axis of the ground electrode when viewed in a plug axial direction.

4. 4. The spark plug for an internal combustion engine according to claim 1, wherein the ground electrode is inclined with respect to the axial direction of the plug so as to move from the fixed end toward a tip side as the plug approaches a central axis of the plug.

5. 5. The spark plug for an internal combustion engine according to claim 1, wherein the discharge gap is disposed on a tip side of the tip (21) of the housing.

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 present invention has 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.

7. An internal combustion engine (10) equipped with the spark plug for an internal combustion engine according to any one of claims 1 to 5, A main combustion chamber (101); an injector (71) for injecting fuel directly into the main combustion chamber; The spark plug is disposed so that an injection flow (F) containing the fuel injected from the injector is directed toward the second nozzle hole.

8. 8. The internal combustion engine according to claim 7, further comprising an intake valve (72) and an exhaust valve (73) provided in the main combustion chamber, and the first plug portion faces the intake valve side when viewed from a plug axial direction.

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