JP2017147086A - Internal combustion - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an internal combustion capable of achieving suppression of abrasion of a ground electrode, and improvement of ignition and stability of burning even under the condition that a high airflow flows by a low ignition energy.SOLUTION: An ignition plug included in an internal combustion, includes a center electrode and a ground electrode, and is constructed so that a spark discharge path between the center electrode and the ground electrode is generated by discharging. The ignition plug includes a vortex generation part generating a rear flow vortex in a down stream side by peeling an airflow near from the ground electrode. The vortex generation part is formed by the triangle ground electrode of which a cross sectional shape is an almost triangle. When the center electrode is arranged on the upper side of the ground electrode, and the airflow flows between the center electrode and the ground electrode from the left side to the right side, a side of the upper side of the ground electrode is almost horizontal or is inclined downward to the right, and the side of the down side of the ground electrode is inclined downward to the right. The vortex generation part includes a first projection part formed by an abrasion proof material on the upper side of the ground electrode and the upper stream side of the airflow from a center axis.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an internal combustion engine including an ignition plug protruding into a combustion chamber, the ignition plug including a center electrode and a ground electrode, and configured to generate a spark discharge path between the center electrode and the ground electrode by discharge. .

  Conventionally, an internal combustion engine in which the shape of the spark plug is devised has been proposed. For example, in the configuration described in Patent Document 1, the extension portion of the ground electrode of the spark plug extends into the combustion chamber, and the extension portion is bent so that the tip portion of the extension portion faces the tip portion of the center electrode. . In this configuration, a through hole that opens toward the gap between the distal end of the center electrode and the distal end of the ground electrode is formed on the wall surface of the housing distal end near the base end of the ground electrode. It inclines toward the clearance gap between electrodes with respect to the central-axis direction.

  Patent Document 2 describes a configuration in which a center electrode is provided at the tip of a ceramic insulator of a spark plug, and a ground electrode extends from a housing into a combustion chamber. The direction A of the airflow generated around the center electrode and the ground electrode when the spark plug is ignited intersects the direction B of the connection portion of the ground electrode with respect to the housing as viewed from the center electrode. At the tip of the ground electrode, on the side opposite to the center electrode, an inclined surface is formed that is inclined toward the downstream side in the airflow direction A and opposite to the ceiling surface of the combustion chamber. The ground electrode is opposed to the center electrode so that the tip of the center electrode coincides with the center axis.

  In the configurations described in Patent Document 1 and Patent Document 2, the spark formed by the discharge of the spark plug is burned by bending the airflow that has passed between the electrodes diagonally downward away from the upper wall surface of the combustion chamber. It is intended to suppress contact with the upper wall surface of the chamber.

  Patent Document 3 describes a configuration in which a noble metal block is installed on each of a center electrode and a ground electrode, and the cross-sectional area thereof is reduced. Patent Document 3 aims to improve the ignitability by reducing the volume of the electrode and preventing the thermal energy of the flame generated in the spark gap from being absorbed by the electrode.

  Patent Document 4 describes a configuration in which plasma as a high-temperature gas is injected into a combustion chamber of an internal combustion engine and a mixture of fuel and air in the combustion chamber is ignited. In addition, a protrusion that protrudes into the combustion chamber is provided on the downstream side of the airflow of the air-fuel mixture from the injection port of the high-temperature gas injection unit. This configuration is intended to improve the ignitability of the air-fuel mixture by retaining hot gas downstream of the protrusions.

Japanese Patent Laying-Open No. 2015-76193 Japanese Patent Laying-Open No. 2015-124673 JP-A 61-45583 JP 2010-482219 A

  In any of Patent Document 1 to Patent Document 4, a vortex is generated downstream of the ground electrode of the spark plug with respect to the airflow direction, and flame holding is performed to stably hold the flame by igniting the vortex. However, there is no disclosure of a configuration that can be used to promote and stabilize combustion. For example, the techniques described in Patent Document 1 and Patent Document 2 are intended to suppress contact of the spark discharge path or the flame with the upper wall surface of the combustion chamber. In any of the techniques described in Patent Document 1 and Patent Document 2, the spark discharge path and the flame are merely caused to flow downstream by the airflow, and the vortex behind the electrode is not used for flame holding.

  In the technique described in Patent Document 4, ignition is performed using plasma, but ignition by plasma requires a larger amount of energy than spark ignition. In addition, since the distance from the plasma injection port to the back surface of the protrusion on the downstream side is large and diffusion or extinguishing proceeds before the high temperature gas enters, the effect of promoting the growth of the flame is low.

  An object of the present invention is to provide a structure capable of suppressing ground electrode wear in an internal combustion engine and improving ignitability and stabilization of combustion with low ignition energy even under conditions of high airflow. is there.

  An internal combustion engine according to the present invention includes a spark plug protruding into a combustion chamber, the spark plug including a center electrode and a ground electrode, and configured to generate a spark discharge path between the center electrode and the ground electrode by discharge. The spark plug has a vortex generating portion that peels off an air flow in the vicinity of the ground electrode and generates a wake vortex downstream, and the vortex generating portion is formed by the ground electrode having a substantially triangular cross-sectional shape. The center electrode is disposed on the upper side of the ground electrode, and when the airflow flows from the left to the right between the center electrode and the ground electrode, the upper side of the ground electrode is substantially horizontal, or A first lower portion made of a wear-resistant material on the upper side of the ground electrode and on the upstream side of the airflow from the central axis of the center electrode. Including protrusions. In the above description, the meaning of “substantially triangular” includes a shape in which a depression is formed on the downstream side of the triangle.

  According to the internal combustion engine according to the present invention, wear of the ground electrode can be suppressed, and improvement in ignitability and stabilization of combustion can be realized with low ignition energy even under conditions where a high airflow flows.

In the internal combustion engine of the embodiment according to the present invention, it is a perspective view showing a portion of the spark plug disposed in the combustion chamber. It is A arrow directional view of FIG. In FIG. 2, it is a figure which shows the time change from a discharge start to a spark discharge path approaching into a wake vortex. It is a figure which shows the simulation result performed in order to confirm the effect of embodiment. It is a figure corresponding to FIG. 2 which shows the other example of the internal combustion engine of embodiment which concerns on this invention. It is a figure corresponding to FIG. 2 which shows the other example of the internal combustion engine of embodiment which concerns on this invention. It is a figure corresponding to FIG. 1 which shows the other example of the internal combustion engine of embodiment which concerns on this invention. It is a B arrow line view of FIG. It is a figure corresponding to FIG. 1 which shows the other example of the internal combustion engine of embodiment which concerns on this invention. It is C arrow line view of FIG.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The shapes, materials, and mounting positions described below are illustrative examples and can be changed as appropriate according to the specifications of the internal combustion engine. In the following, when a plurality of embodiments and modified examples are included, they can be implemented by appropriately combining them. In the following description, identical elements are denoted by the same reference symbols in all drawings. In the description in the text, the symbols described before are used as necessary. Moreover, although the case where an ignition plug is attached to the upper part of a cylinder head is demonstrated below, the direction and attachment position in which an ignition plug faces in an actual use condition are not limited. For example, when the cylinder is obliquely up and down, the spark plug may be attached to the cylinder head in the obliquely up and down direction accordingly.

  FIG. 1 is a perspective view showing a portion of an ignition plug 14 disposed in a combustion chamber 50 in the internal combustion engine 10 of the embodiment. FIG. 2 is a view taken in the direction of arrow A in FIG.

  The internal combustion engine 10 includes a cylinder head 12 (FIG. 2), a cylinder member, and a piston (not shown). The cylinder head 12 is combined with a cylinder member to form a combustion chamber 50 inside. The piston is disposed so as to be reciprocally movable in the axial direction inside a cylinder hole formed in the cylinder member.

  The internal combustion engine 10 is, for example, a gasoline engine. In such an internal combustion engine 10, a mixture of fuel and air is introduced from an intake port (not shown) into a combustion chamber, compressed, ignited and burned, and then as an exhaust gas from an exhaust port (not shown). Discharged.

  The internal combustion engine 10 is configured such that when an air-fuel mixture is introduced into the combustion chamber 50, an intake air flow caused by the air-fuel mixture in the combustion chamber 50 forms a vertical vortex called a tumble flow. Then, even when the ignition timing is reached through the compression process after the intake process, the vertical vortex component remains in the combustion chamber 50.

  On the other hand, a spark plug 14 is attached to the top of the cylinder head 12. The spark plug 14 is disposed in the combustion chamber 50 so as to protrude downward from the cylinder head 12.

  The spark plug 14 includes a metal housing (not shown) formed in an outer cylindrical shape and an insulator 15 held inside the metal housing, and the tip of the insulator 15 protrudes into the combustion chamber 50. ing. A center electrode 16 is provided at the tip of the protruding insulator 15. The center axis CL of the center electrode 16 coincides with the center axis of the insulator 15.

  The spark plug 14 is attached to the cylinder head 12 by screw connection by a male screw portion (not shown) formed on the outer peripheral surface of the metal housing.

  The spark plug 14 includes a ground electrode 18 that extends from the lower end of the metal housing into the combustion chamber 50. The spark plug 14 is configured to generate a spark discharge path between the center electrode 16 and the ground electrode 18 by discharge, and is used to ignite the air-fuel mixture. Below, the case where the ignition plug 14 is arrange | positioned in the center part vicinity of the upper wall surface 51 (FIG. 2) of the combustion chamber 50 is demonstrated.

  The ground electrode 18 includes an extension portion 19 extending from the metal housing into the combustion chamber 50, an L-shape bent from the tip of the extension portion 19, and the tip of the insulator 15 (lower end in FIGS. 1 and 2). And an arm 20 extending to the facing side. A columnar first protrusion 21 is formed on a portion facing the tip of the insulator 15 above the tip of the arm 20.

  The ground electrode 18 is disposed at a position different from the central axis CL so that the first protrusion 21 does not face the tip of the central electrode 16 in the direction of the central axis CL. Between the first protrusion 21 of the ground electrode 18 and the tip of the center electrode 16, a discharge gap is formed in which a spark discharge path 62 is generated during discharge.

  As described above, in the internal combustion engine 10, the longitudinal vortex component remains in the combustion chamber 50 at the ignition timing, and therefore, is located slightly above the center of the longitudinal vortex near the electrode of the ignition plug 14 and has a relatively high flow velocity. High airflow, which is a high lateral airflow, is generated. In the combustion cycle of the internal combustion engine 10, when the air flow cycle fluctuation is averaged, the center electrode 16 and the ground electrode 18 of the spark plug 14 are exposed to a high air flow from the intake port side toward the exhaust port side. In FIG. 1 and FIG. 2, the flow direction of this high air current is indicated by an arrow α.

  The first protrusion 21 which is the tip of the ground electrode 18 is upstream of the airflow around the spark plug 14 with respect to the center axis CL of the center electrode 16 where the tip of the center electrode 16 is located (FIG. 1, FIG. 2 on the right). Thus, a wake vortex 60 as shown in FIGS. 1 and 2 is formed in the vicinity of the ground electrode 18 on the downstream side of the ground electrode 18 due to the airflow around the electrode.

  Specifically, the tip of the ground electrode 18 has a substantially triangular cross-sectional shape. When the center electrode 16 is disposed on the upper side of the ground electrode and the airflow flows between the center electrode 16 and the ground electrode 18 from the left to the right, the upper side of the ground electrode 18 is substantially horizontal or right It is going down. 1 and 2 show a case in which the upper side of the ground electrode 18 is downwardly inclined. At this time, the lower side of the ground electrode 18 is inclined downward. As a result, a flow along the side surface of the ground electrode 18 is generated on the upper side and the lower side of the arm portion 20 of the ground electrode 18, and a wake vortex 60 is generated at the rear end of the ground electrode 18. The wake vortex 60 makes it easy to stably hold a flame behind the ground electrode 18 on the downstream side of the airflow as will be described later.

  In addition, as shown in FIG. 2, in the substantially triangular shape that is the cross-sectional shape of the ground electrode 18, the right side has a shape having a recess 22 in the middle. In other words, as shown in FIG. 1, a groove 23 including a recess 22 is formed on the side surface facing the downstream side of the airflow at the tip of the ground electrode 18. The groove portion 23 is formed over substantially the entire length of the arm portion 20. The groove portion 23 formed by the depression 22 enhances the effect of generating the wake vortex 60 on the downstream side of the tip portion of the ground electrode 18 as will be described later.

  Further, the first protrusion 21 of the ground electrode 18 is formed of a wear-resistant material such as platinum. Thereby, the wear of the ground electrode 18 during discharge is suppressed. Further, in the ground electrode 18, portions other than the first protrusion 21 are formed of an iron-based material that has lower wear resistance than the first protrusion 21.

  The tip of the ground electrode 18 is a vortex generator. More specifically, in the airflow direction α, the airflow flowing through the discharge gap G enters the side of the center electrode 16 behind the ground electrode 18 to form a wake vortex 60. At this time, on the upper side surface of the arm portion 20 of the ground electrode 18, the downstream end of the airflow peels off the airflow in the vicinity of the arm portion 20 on the rear side of the arm portion 20, that is, on the downstream side of the airflow, The wake vortex 60 is generated.

  The wake vortex 60 is a circulating flow generated on the downstream side of the electrode when the flow along the electrode is separated on the downstream side of the electrode. When the air-fuel mixture is ignited inside the wake vortex 60, as will be described later, a part of the flame is taken into the circulation region of the wake vortex 60 and the high-temperature combustion gas is stabilized in the vicinity of the downstream side of the electrode. Can be retained.

  Then, the spark discharge path 62 or the flame deformed by the airflow flowing between the electrodes 16 and 18, or the spark discharge path 62 and the flame enter the wake vortex 60 on the downstream side of the arm portion 20. Specifically, the ground electrode 18 and the center electrode 16 are disposed between the electrodes, that is, on the side where the airflow passing through the discharge gap is away from the upper wall surface 51 of the combustion chamber 50 as indicated by an arrow β in FIGS. It is bent in a certain diagonal downward direction. Since the airflow is bent obliquely downward while passing between the electrodes, the airflow is easily caught in the wake vortex 60. Further, the lower side surface of the arm portion 20 of the ground electrode 18 is inclined with respect to the vertical direction in the direction away from the upper wall surface 51 toward the downstream side of the airflow. Thereby, the airflow flowing under the arm portion 20 can be bent downward, and accordingly, the airflow passing through the discharge gap on the upper side can be bent more strongly downward. Further, the wake vortex 60 can be generated behind the arm portion 20 by the airflow flowing under the arm portion 20.

  Further, if there is a wake vortex 60 in the vicinity of the spark discharge path 62 generated between the center electrode 16 and the ground electrode 18, the spark discharge path 62 and an initial flame that is an initial flame generated around the spark discharge path 62. A nucleus (broken line γ in FIG. 3) enters the wake vortex 60 and enters. In addition, when the airflow passing between the electrodes is bent obliquely downward as described above, the spark discharge path 62 and the initial flame nucleus are also inclined in the obliquely downward direction along with the airflow as shown in FIGS. Bend. Then, the spark discharge path 62 and the initial flame core are entrained in the wake vortex 60 and entered and held. As will be described later, the spark discharge path 62 is formed so as to connect the first projecting portion 21 of the ground electrode 18 and the front end surface of the center electrode 16 immediately after the start of discharge. One end of 62 moves from the first protrusion 21 to the downstream end of the arm 20. 1 and 2, the broken line U1 shows the spark discharge path 62 immediately after the start of discharge, and the broken line U2 shows the spark discharge path 62 after moving downstream. Hereinafter, the spark discharge path 62 is referred to as a spark 62.

  FIG. 3 is a diagram showing a temporal change from the start of discharge until the spark 62 enters the wake vortex 60 in FIG. As shown in FIG. 3A, immediately after the start of discharge, the spark 62 includes the end of the center electrode 16 on the side of the ground electrode 18 (the left end of FIG. 3A) and the first protrusion of the ground electrode 18. 21 may be a substantially straight line connecting the end on the side of the center electrode 16 (the right end in FIG. 3A) on the tip surface of the line 21 with the shortest path. This happens probabilistically.

  Thereafter, as shown in FIG. 3B, the spark 62 is deformed by flowing an intermediate portion downstream by the airflow, and extends downstream. When the spark 62 is further deformed by the airflow, a part of the spark 62 approaches the end on the side of the center electrode 16 on the upper surface of the arm portion 20 of the ground electrode 18. At this time, since the spark 62 is formed by selecting a path having a small electric resistance value, the position of one end which is the root of the spark 62 is downstream of the top surface of the arm portion 20 from the tip of the first protrusion 21 of the ground electrode 18. It moves to the side end (FIG. 3 (c)).

  Thereafter, as shown in FIG. 3 (d), the intermediate portion of the spark 62 is further deformed so as to be bent downstream by the air flow, and enters the wake vortex 60 behind the arm portion 20 of the ground electrode 18. Then get involved. At this time, the spark 62 passes through the wake vortex 60.

  During such discharge, the spark 62 supplies heat to the surroundings to ignite the air-fuel mixture. The initial flame kernel generated by the ignition is also caused to flow and deform by the air current in the same manner as the spark 62. 3B, 3C, and 3D, the initial flame kernel is indicated by a broken line γ surrounding the spark 62. FIG.

  When the wake vortex 60 is generated behind the arm portion 20 of the ground electrode 18, the initial flame kernel generated by the spark 62 passing through the wake vortex 60 is directly inside the circulation flow of the wake vortex 60. It is captured. As a result, the high-temperature combustion gas can be stably held in the immediate vicinity of the downstream side of the ground electrode 18. And by the heat | fever of the hold | maintained combustion gas, the unburned gas sent by the airflow can also be ignited continuously and a flame can be hold | maintained stably. Stable holding of the combustion gas and flame in the presence of such airflow is called “flame holding”. The spark 62 can supply energy directly to the inside of the flame-holding region indicated by the sandy P portion in FIG. 2 and promote the development of the flame. Thereby, even after the discharge of the spark 62 is completed, the unburned gas around the spark plug 14 can be continuously ignited, and combustion can be promoted and combustion can be stabilized. As a result, the energy required for stable ignition can be reduced as compared with the conventional ignition method.

  Further, since the initial flame core is also flowed by the air current, like the spark 62, the initial flame core is caused by the air current flowing diagonally downward through the electrodes, so that the initial flame core is behind the arm portion 20 of the ground electrode 18 in the wake vortex 60. Get involved in. Thereby, flame holding can be realized also by a part of the initial flame kernel ignited on the upstream side of the wake vortex 60.

  Further, as shown in FIG. 5 and FIG. 6 to be described later, a straight line L1 connecting the downstream end of the upper end surface of the first projection 21 of the ground electrode 18 and the upstream end of the lower end surface of the center electrode 16, and an ignition plug 14 is preferably in the range of −30 ° to + 45 °.

  At this time, as shown in FIG. 5, the direction from the upper end of the ground electrode 18 to the lower end of the center electrode 16 is lower than the airflow direction α, that is, on the side away from the upper wall surface 51 (for example, diagonally lower side in FIG. 5). In some cases, the angle between the straight line L1 and the airflow direction α is negative. On the other hand, when the direction from the upper end of the ground electrode 18 to the lower end of the center electrode 16 is upward from the airflow direction α, that is, the side closer to the upper wall surface 51 (obliquely upper side in FIG. 6) as shown in FIG. Means that the angle formed between the straight line L1 and the airflow direction α is positive.

  According to the internal combustion engine 10 described above, wear of the ground electrode 18 can be suppressed, and improvement in ignitability and stabilization of combustion can be achieved with low ignition energy even under conditions where a high airflow flows. And since combustion can be stabilized, combustion fluctuations and torque fluctuations can be suppressed. As a result, the ignition limit can be extended to a side where a leaner air with a higher airflow and a leaner air-fuel mixture occurs.

  FIG. 4 is a diagram illustrating a simulation result performed to confirm the effect of the embodiment. In the simulation, the same configuration as that of the embodiment shown in FIGS. 1 and 2 was used. In the simulation, a phenomenon from spark ignition to ignition of the air-fuel mixture was calculated using general-purpose fluid analysis software “STAR-CD” manufactured by CD-adapco. As understood from the simulation results shown in FIG. 4, flame holding is performed behind the ground electrode 18 (on the right side in FIG. 6) in the airflow direction α, and the flame 64 continuously spreads behind the ground electrode 18. . As a result, it was confirmed that the combustion could be stabilized.

  In addition, although illustration is omitted, as a shape of the prior art, in the configuration in which the shape of the arm portion of the ground electrode is a rectangular parallelepiped shape, and the protrusion is formed on the upper side so as to face the direction of the central axis of the center electrode, It is conceivable that sparks are swept into the airflow under high airflow conditions. On the other hand, in this configuration, when the spark extends beyond a certain length, the spark is interrupted in the middle, and re-discharge occurs between the electrodes of the spark plug. This can lead to unstable combustion. In the above embodiment, such inconvenience is less likely to occur.

  FIGS. 5 and 6 are views corresponding to FIG. 2 showing two other examples of the internal combustion engine 10 according to the embodiment. In the example of FIG. 5, the upper end of the first protrusion 21 that is the tip of the ground electrode 18 is disposed above the lower end of the tip of the center electrode 16. Further, the angle formed by the straight line L1 and the airflow direction α in front of the spark plug 14 along the straight line L2 is −30 °.

  In the configuration shown in FIG. 5, the tip of the first protrusion 21 of the ground electrode 18 is very close to the tip of the insulator 15 (lower end of FIG. 5), so that the airflow passing between the electrodes is suddenly bent obliquely downward. It is done. With such a configuration, the vertical length of the portion of the spark plug 14 disposed inside the combustion chamber 50 can be reduced.

  On the other hand, in the example of FIG. 6, the upper end of the first protrusion 21 that is the tip of the ground electrode 18 is disposed below the lower end of the tip of the center electrode 16. Further, the angle formed by the straight line L1 and the airflow direction α in front of the spark plug 14 along the straight line L2 is + 45 °.

  In the configuration shown in FIG. 6, since the airflow flowing so as to collide with the center electrode 16 from the left side of FIG. 6 is bent obliquely downward as indicated by the arrow δ, the airflow passing between the electrodes on the lower side is also obliquely downward. Bent to the side.

  FIG. 7 is a view corresponding to FIG. 1 showing another example of the internal combustion engine of the embodiment. FIG. 8 is a view taken in the direction of arrow B in FIG.

  7 and 8, in the configuration shown in FIGS. 1 and 2, the second protrusion 24 having a substantially rectangular parallelepiped cross section is formed at the downstream end of the airflow on the upper side surface of the arm portion 20 of the ground electrode 18. It is formed. Accordingly, the second protrusion 24 is formed on the downstream side of the airflow with respect to the first protrusion 21. The second projecting portion 24 is formed at substantially the same position as the first projecting portion 21 in the longitudinal direction of the arm portion 20 (the front and back direction in FIG. 8). Similarly to the first protrusion 21, the second protrusion 24 is also formed of a wear-resistant material such as platinum. Furthermore, the upper end of the second protrusion 24 is lower than the upper end of the first protrusion 21.

  According to the above configuration, when the spark 62 formed between the first protrusion 21 and the center electrode 16 is caused to flow by the airflow, the spark 62 is formed in a path with low electrical resistance. One end can be moved from the first protrusion 21 to the second protrusion 24 on the downstream side. The second protrusion 24 is made of a wear resistant material. As a result, when the spark 62 is caused to flow by the air flow, one end of the spark 62 moves to the downstream end of the arm portion 20 of the material having lower wear resistance than the first protrusion 21 and the second protrusion 24. Can be suppressed. For this reason, wear of the ground electrode 18 can be further suppressed. Further, since the upper end of the second projecting portion 24 is lower than the upper end of the first projecting portion 21, the airflow is not excessively disturbed by the second projecting portion 24. Further, in the initial stage, no spark is formed between the second protrusion 24 and the center electrode 16 before the first protrusion 21. Other configurations and operations are the same as those in FIGS. 1 and 2.

  FIG. 9 is a view corresponding to FIG. 1 showing another example of the internal combustion engine of the embodiment. 10 is a view taken in the direction of arrow C in FIG.

  In the configuration shown in FIGS. 9 and 10, in the configuration shown in FIGS. 7 and 8, the tip surface of the arm portion 20 (see FIGS. 9 and 10) The wall portion 26 is formed so as to protrude substantially parallel to the front side surface of the paper. The wall portion 26 is formed in a portion extending from the substantially upstream end (the left end in FIGS. 9 and 10) to the substantially downstream end (the right end in FIGS. 9 and 10) with respect to the airflow around the arm portion 20. The wall portion 26 is fixed to the upper side surface of the arm portion 20 by welding, for example. The wall portion 26 corresponds to a first protrusion. In such a configuration, the wall portion 26 has a function of combining the first protruding portion 21 and the second protruding portion 24 in the configurations of FIGS. The wall portion 26 is formed of a wear resistant material such as platinum. In the wall portion 26, the upper end of the downstream end is lower than the upper end of the upstream end.

  According to the above configuration, first, the spark 62 indicated by U1 is formed between the upper end of the upstream end of the wall portion 26 and the center electrode 16, and then the spark 62 is caused to flow by the air current and indicated by U2. Thus, one end of the spark 62 often moves from the upstream end of the wall portion 26 to the upper end of the downstream end. Thereby, even when the spark 62 is flowed by the airflow, it is possible to suppress the end of the spark 62 from moving to the downstream end of the arm portion 20 made of a material having low wear resistance. For this reason, wear of the ground electrode 18 can be suppressed. Furthermore, the number of times of welding when the wall portion 26 is fixed to the arm portion 20 by welding can be reduced as compared with the case where the projection portion separated into the upstream portion and the downstream portion of the arm portion 20 is fixed by welding. Other configurations and operations are the same as those in FIGS.

  In the configuration of each of the above examples, at the tip of the ground electrode 18 having a substantially triangular cross section, the right side serving as the downstream side may be a straight line and may have a shape that does not have a hollow in the middle part. Moreover, although the case where the 1st projection part 21 was cylindrical shape was demonstrated in the structure of said each example, the 1st projection part is a wall long in the longitudinal direction of the arm part 20 (for example, the front and back direction of the paper surface of FIG. 2). It is good also as a shape. Further, in the configurations of FIGS. 7 and 8, the second protrusions may be similarly wall-shaped.

  DESCRIPTION OF SYMBOLS 10 Internal combustion engine, 12 Cylinder head, 14 Spark plug, 15 Insulator, 16 Center electrode, 18 Ground electrode, 19 Extension part, 20 Arm part, 21 1st projection part, 22 Depression, 23 Groove part, 24 2nd projection part , 26 wall, 50 combustion chamber, 51 upper wall surface, 60 wake vortex, 62 spark discharge path (spark) 64 flame.

Claims (4)

With a spark plug protruding into the combustion chamber,
The spark plug includes a center electrode and a ground electrode, and is configured such that a spark discharge path is generated between the center electrode and the ground electrode by discharge,
The spark plug is
Having a vortex generating part for separating the airflow in the vicinity of the ground electrode and generating a wake vortex on the downstream side;
The vortex generator is formed by the ground electrode having a substantially triangular cross-sectional shape, the center electrode is disposed above the ground electrode, and an air current flows from the left to the right between the center electrode and the ground electrode. When flowing, the upper side of the ground electrode is substantially horizontal or lower right, and the lower side of the ground electrode is lower right,
An internal combustion engine including a first protrusion formed of a wear-resistant material on the upper side of the ground electrode and upstream of the central axis of the center electrode. The internal combustion engine according to claim 1,
When the center electrode is disposed on the upper side of the ground electrode and an airflow flows between the center electrode and the ground electrode from the left to the right, the right side of the ground electrode is linear or in the middle. An internal combustion engine having a shape with a depression. The internal combustion engine according to claim 1 or 2,
The angle formed by the straight line connecting the downstream end of the upper end surface of the ground electrode and the upstream end of the lower end surface of the center electrode and the direction of the airflow upstream of the spark plug is from the upper end of the ground electrode to the center. An internal combustion engine having a range of −30 ° to + 45 ° when the direction toward the lower end of the electrode is negative with respect to the air flow direction and negative when the direction is upward. The internal combustion engine according to any one of claims 1 to 3,
A second protrusion formed of an abrasion-resistant material on the upper side of the ground electrode and on the downstream side of the airflow from the first protrusion;
An internal combustion engine, wherein an upper end of the second protrusion is lower than an upper end of the first protrusion.

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