JP2007273411A - Spark plug - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a spark plug capable of achieving stable stratified lean combustion even if an earth electrode is arranged on the opposite side to an injector with a center electrode placed in between. <P>SOLUTION: The spark plug 50 comprises a plug body 51, the center electrode 52 provided at the plug body 51, and the earth electrode 53 provided around the center electrode 52 at the plug body 51 to carry out spark discharge between itself and the center electrode 52. The earth electrode 53 comprises a body part 57 extending from the plug body 51 to the tip side of the center electrode 52, and an extended part 58. The extended part 58 extends from the tip of the body part 57 in an axis direction D of the plug body 51 into a position to cover the center electrode 52 along a direction E to cross the axis direction D of the plug body 51, and is formed with a tip face 59 at the tip in the extending direction E to lead a part F1 of fuel F injected from an injector 40, to the center electrode 52. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a spark plug used in, for example, a direct injection type spark ignition internal combustion engine.

2. Description of the Related Art Conventionally, as a structure of an ignition plug used in an automobile gasoline engine, there is a structure including one center electrode and one ground electrode that is disposed around the center electrode and that generates a spark discharge between the center electrode. (For example, patent document 1).
JP 60-198077 A

  In a direct-injection spark-ignition internal combustion engine that directly injects fuel into the combustion chamber using an injector, a spray-guided engine in which the injector directly injects fuel toward the spark plug is injected in the compression stroke. In addition to the fuel directly reaching and evaporating part of the fuel, diffusion / air mixing / vaporization is promoted by the remaining part of the fuel striking the hot ground electrode. It stays around and forms an air-fuel mixture. The mixture is ignited and burned. As a result, the vicinity of the spark plug is made near the stoichiometric air-fuel ratio, and combustion at a very lean air-fuel ratio in the entire combustion chamber, so-called stratified lean combustion, is realized.

  In the case of a spark plug having one ground electrode as disclosed in Patent Document 1, when the ground electrode is disposed on the opposite side of the injector with the center electrode interposed therebetween, most of the fuel injected from the injector is centered. Contact with the ground electrode after passing through the electrode and contact with the center electrode before passing through the center electrode is limited to only a part of the tip of the ground electrode.

  In other words, the fuel injected from the injector hardly diffuses by colliding with the ground electrode and is hardly promoted to be mixed / vaporized with air, and passes through the center electrode. Therefore, when the ground electrode is disposed on the opposite side of the injector with the center electrode interposed therebetween, the air-fuel mixture is less likely to stay near the center electrode.

  In order to realize stable stratified lean combustion, it is necessary to place an air-fuel mixture near the stoichiometric air-fuel ratio around the center electrode at the time of ignition, but because only the fuel that reaches the center electrode is insufficient, After the collision with the ground electrode, the fuel introduced to the center electrode becomes important. If it is too small, the fuel will be too thin and cannot be ignited. If it is too much, it will become too concentrated and the plug will smolder. In the case where the ground electrode is disposed on the opposite side of the injector with the center electrode interposed therebetween, the amount of fuel that collides with the ground electrode is small, and the air-fuel ratio around the center electrode becomes lean. As a result, the fuel cannot be stably burned.

  Accordingly, an object of the present invention is to provide a spark plug that realizes stable stratified lean combustion even when a ground electrode is disposed on the opposite side of an injector with a center electrode interposed therebetween.

  The spark plug of the present invention is installed in a combustion chamber provided with an injector for injecting fuel. The spark plug includes a plug body, a center electrode provided on the plug body, and a ground electrode provided around the center electrode in the plug body and causing a spark discharge between the center electrode. The ground electrode includes a main body portion extending from the plug main body to the distal end side of the center electrode, and an extension portion. The extending portion extends from the front end of the main body portion to the central axis side in a direction crossing the axial center line direction of the plug main body, and fuel injected from the injector at the front end in the extending direction is the central electrode. A guide surface that leads to is formed.

  According to this structure, when the spark plug is disposed in the combustion chamber, the spark plug is injected from the injector even when the main body is positioned opposite to the injector with the center electrode interposed therebetween. A part of the fuel that has been applied collides with the guide surface and is diffused and mixed with air to form an air-fuel mixture, and then almost the entire amount is effectively guided to the center electrode along the guide surface.

  In a preferred embodiment of the present invention, a second edge separated in the axial direction from the first edge located on the center electrode side in the axial direction of the plug body on the guide surface is the first edge. It is a plane which protrudes in the direction where the extension part extends rather than the edge.

  According to this structure, the guide surface can be easily formed by making the guide surface a flat surface that is inclined with respect to the axial direction.

  In a preferred embodiment of the present invention, the ground electrode is formed with a through hole penetrating the ground electrode in a direction from the center electrode toward the ground electrode.

  According to this structure, when the spark plug is disposed in the combustion chamber, even if the attitude of the ignition plug is an attitude in which the ground electrode is positioned between the injector and the center electrode, the fuel injected from the injector A part of the ground collides with the ground electrode and diffuses to become an air-fuel mixture, and then is guided around the center electrode through the through hole. In addition, even if the spark plug is positioned so that the ground electrode is located on the opposite side of the injector with the center electrode in between, the fuel that has passed around the center electrode collides with the ground electrode and becomes an air-fuel mixture. Suppresses excessive concentration by staying around.

  In a preferred embodiment of the present invention, the main body portion is inclined such that the front end of the main body portion is located on the side of the center electrode with respect to the base portion connected to the plug main body in the main body portion.

  According to this structure, when the spark plug is disposed in the combustion chamber, the spark plug is positioned from the position where the main body portion is located on the opposite side of the injector with the center electrode interposed therebetween. Even in a posture rotated about 90 degrees around the core line, the amount of fuel injected from the injector hits the extension, and the surroundings of the center electrode are prevented from becoming excessively concentrated.

  Or in the preferable form of this invention, the both side surfaces which cross the circumferential direction of the said center electrode in the said main-body part incline to the said other side surface side, respectively as it leaves | separates from the said center electrode.

  According to this structure, when the spark plug is disposed in the combustion chamber, the spark plug is positioned from the position where the main body portion is located on the opposite side of the injector with the center electrode interposed therebetween. Even in a posture rotated approximately 90 degrees around the core line, the fuel injected from the injector hits the inclined side surface and is guided in a direction away from the center electrode along the side surface. Suppresses darkening.

  In a further preferred form of the above aspect, the through hole has a size through which an imaginary line connecting the injection port of the injector and the tip of the center electrode passes.

  According to this structure, the air-fuel mixture is effectively guided to the center electrode.

  According to the present invention, stable stratified lean combustion can be realized even when the ground electrode is disposed on the opposite side of the injector with the center electrode interposed therebetween.

  A spark plug according to a first embodiment of the present invention will be described with reference to FIGS. The spark plug 50 of this embodiment is used for, for example, a reciprocating gasoline engine 20 of an automobile. The engine 20 is a multi-cylinder engine. The engine 20 is an in-cylinder direct injection spark ignition internal combustion engine.

  FIG. 1 shows a cross-sectional view of the vicinity of one combustion chamber 30 of the engine 20. As shown in FIG. 1, the engine 20 includes a cylinder block 21, a cylinder head 22, and the like.

  A plurality of cylinders 23 are formed in the cylinder block 21. A piston 24 is accommodated in the cylinder 23. The piston 24 is connected to the crankshaft via a connecting rod (not shown). The piston 24 receives the pressure energy of the combustion gas and reciprocates in the cylinder 23. The crankshaft is rotated by the reciprocating motion of the piston 24. In the cylinder block 21, a water jacket 25 is formed in the vicinity of the cylinder 23. Cooling water flows in the water jacket 25.

  The cylinder head 22 is fixed to the upper end surface 21 a of the cylinder block 21. In the cylinder head 22, a combustion recess 22 b is formed at a portion overlapping the cylinder 23. The combustion recess 22b is, for example, a roof type. The combustion recess 22b covers the opening of the cylinder 23 that opens to the upper end surface 21a.

  A space defined by the combustion recess 22 b, the outer surface of the piston 24, and the inner surface of the cylinder 23 is a combustion chamber 30.

  An intake passage 26 and an exhaust passage 27 are formed in the cylinder head 22. One end of the intake passage 26 opens into the combustion recess 22b. In the intake passage 26, the opening end on the combustion recess 22b side is an intake port 26a. An intake valve 28 is provided at the intake port 26a.

  One end of the exhaust passage 27 opens into the combustion recess 22b. In the exhaust passage 27, the opening end on the combustion recess 22b side is an exhaust port 27a. An exhaust valve 29 is provided at the exhaust port 27a.

  The cylinder head 22 is provided with an injector 40 for injecting fuel F and a spark plug 50.

  The injector 40 has an injection port 41 through which fuel F is injected. The injector 40 is attached in the vicinity of the apex portion 22c of the cylinder head 22 so that the injection port 41 faces the inside of the combustion recess 22b from the vicinity of the apex portion 22c of the combustion recess 22b.

  The spark plug 50 is attached at a position avoiding the injector 40 in the vicinity of the apex portion 22c of the combustion recess 22b. Specifically, the spark plug 50 is attached to the injector 40 so as to face the combustion chamber 30 from an inclined portion 22e shifted to the right in the drawing.

  The spark plug 50 includes a plug body 51, one center electrode 52 (shown by a dotted line in the figure), and one ground electrode 53.

  The plug body 51 is a concept of a portion of the spark plug 50 that is supported by a counterpart member to which the spark plug 50 is fixed, such as the cylinder head 22. The plug body 51 is substantially cylindrical. The plug body 51 includes, for example, a plug housing 54, a middle shaft (not shown), a lever 55 (shown by a dotted line), and the like. The middle shaft is accommodated in the plug housing 54. The middle shaft conducts current in the plug housing 54. The insulator 55 is accommodated in the plug housing 54 and a part thereof protrudes from one end of the plug housing 54.

  A threaded portion 56 is formed on the peripheral surface on the distal end side of the plug body 51. The screw portion 56 is formed with a male screw. A female screw portion 22 d is formed at a portion of the cylinder head 22 where the ignition plug 50 is fixed so as to be screwed with the screw portion 56. A female screw is formed in the female screw portion 22d. The spark plug 50 is fixed to the cylinder head 22 by the screw portion 56 being screwed into the female screw portion 22d.

  FIG. 2 is an enlarged cross-sectional view showing the periphery of the plug body 51 at the front end side of the combustion recess 22b. As shown in FIG. 2, the center electrode 52 is accommodated in the plug body 51. The center electrode 52 is disposed on the axis C of the plug body 51 and is surrounded by the insulator 55.

  As described above, the center electrode 52 is connected to the injection port 41 of the injector 40 as the spark plug 50 is attached at a position (inclined portion 22e) that avoids the apex portion 22c of the combustion recess 22b that is a roof type. Is also located inside the combustion chamber 30.

  The ground electrode 53 is disposed around the center electrode 52 at the tip of the plug body 51. The ground electrode 53 has a main body portion 57 and an extension portion 58.

  A base portion 57 a of the main body portion 57 is fixed to the plug main body 51. The main body 57 extends, for example, to a position advanced from the tip of the center electrode 52 along the axial direction D of the plug main body 51. The main body 57 is substantially parallel to the axial direction D, for example. Note that the axial center line direction D is a direction in which the axial center line C extends and also the axial center line direction of the center electrode 52.

  The extending portion 58 is located at a position facing the center electrode 52 in the axial direction D along a direction crossing the axial direction D from the front end 57b of the main body 57, for example, a direction E substantially perpendicular to the axial direction D. It extends to exceed. Therefore, the ground electrode 53 is substantially L-shaped when viewed from the side.

  FIG. 3 is a perspective view showing a state where the injector 40 and the spark plug 50 are viewed from the cylinder 23 side. In FIG. 3, components such as the intake valve 28 and the exhaust valve 29 are omitted. FIG. 3 shows the posture of the ground electrode 53 with respect to the center electrode 52. As shown in FIG. 3, the main body 57 of the ground electrode 53 is located on the opposite side of the injection port 41 of the injector 40 with the center electrode 52 interposed therebetween. Therefore, the extending part 58 extends to the injection port 41 side of the injector 40.

  As shown in FIG. 2, the distal end surface 59 of the extending portion 58 in the extending direction of the extending portion 58 (same as the direction E, and hence the extending direction is hereinafter referred to as E) is the distal end surface 59. It functions as a guide for guiding the received fuel F to the center electrode 52. The front end surface 59 is located inside the combustion chamber 30 with respect to the injection port 41 of the injector 40. The tip surface 59 is a guide surface as referred to in the present invention.

  The distal end surface 59 is farther from the central electrode 52 at the distal end surface 59 than the first edge 59a on the side of the central electrode 52 in the axial center line direction D at the distal end surface 59 so that the central electrode 52 is positioned on the extension. The second edge 59 b of the position protrudes toward the injector 40 along the extending direction E of the extending portion 58. Furthermore, the tip surface 59 is a substantially flat surface. Therefore, the tip surface 59 is inclined with respect to the axial direction D of the plug body 51.

  Next, the operation of the spark plug 50 will be described. The injector 40 is of a spray guide type and injects the fuel F in a cone shape, and is adjusted so that a part of the fuel F is directed to the center electrode 52. As shown by hatching in the figure, a part F1 (portion where hatching is marked) of the fuel F injected from the injection port 41 of the injector 40 hits the front end surface 59.

  A part F1 of the fuel F is diffused by hitting the front end surface 59, and mixing with air is promoted to become an air-fuel mixture M. Further, as described above, since the front end surface 59 extends toward the center electrode 52, the air-fuel mixture M is conveyed along the front end surface 59 to the center electrode 52 as indicated by an arrow A in the figure, It stays around the center electrode 52.

  Next, a spark discharge is performed between the center electrode 52 and the extended portion 58 of the ground electrode 53, whereby the air-fuel mixture M is combusted and the fuel F is combusted.

  In the spark plug 50 configured as described above, even if the ground electrode 53 is disposed on the opposite side of the injection port 41 of the injector 40 with the center electrode 52 interposed therebetween, a part F1 of the fuel F is It is diffused by hitting the front end surface 59 and becomes an air-fuel mixture M and stays around the center electrode 52.

  Therefore, even when the ground electrode 53 is disposed on the opposite side of the injection port 41 of the injector 40 with the center electrode 52 interposed therebetween, stable stratified lean combustion can be realized.

  Further, the tip surface 59 is inclined with respect to the axial direction D of the plug body 51 as a shape for guiding a part F1 of the fuel F to the center electrode 52 of the spark plug 50. That is, since it is only necessary to incline the front end surface 59, the front end surface 59 can be formed relatively easily. Furthermore, since the tip surface 59 is a flat surface, the tip surface 59 can be formed relatively easily.

  As shown in FIG. 4, the ignition plug 50 is positioned on the opposite side of the injection port 41 of the injector 40 with the center electrode 52 interposed therebetween (hereinafter, the ignition plug 50 is in the first attitude P1). For example, when rotating approximately 35 degrees around the axis C toward the injector 40 (that is, rotating approximately 35 degrees clockwise in the figure and rotating approximately 35 degrees counterclockwise in the figure). Even in this case, a part of the fuel F injected from the injector 40 hits the front end surface 59. FIG. 4 is a perspective view showing a state in which the injector 40 and the spark plug 50 are viewed from the cylinder 23 side. FIG. 4 shows a state where the spark plug 50 is rotated approximately 35 degrees clockwise from the first posture P1. In FIG. 4, components such as the intake valve 28 and the exhaust valve 29 are omitted.

  Therefore, a part of the fuel F that collides with the front end surface 59 stays around the center electrode 52, so that even if the spark plug 50 rotates approximately 35 degrees from the first posture P1, the fuel F is stable. Stratified lean combustion can be realized. Although not shown, the same applies to the case where the spark plug 50 is rotated approximately 35 degrees clockwise from the first posture.

  The above effect is not limited to the case where the spark plug 50 is rotated 35 degrees from the first posture P1 toward the injector 40. In this way, the same effect can be obtained as long as the attitude of the spark plug 50 is within a range in which the fuel F injected from the injector 40 hits the front end surface 59.

  Next, a spark plug 50 according to a second embodiment of the present invention will be described with reference to FIGS. In addition, the structure which has a function similar to 1st Embodiment attaches | subjects the same code | symbol, and abbreviate | omits description. This embodiment is different from the first embodiment in the structure of the main body 57 of the ground electrode 53. Other points may be the same as in the first embodiment. The different points will be specifically described.

  FIG. 5 is a side view of the spark plug 50 of the present embodiment. As shown in FIG. 5, the main body 57 of the ground electrode 53 of this embodiment is linear, and the base 57a and the tip 57b are positioned so that the tip 57b is located closer to the center electrode 52 than the base 57a. Is inclined toward the center electrode 52 side.

  Therefore, as shown by a two-dot chain line in the figure, when the main body portion 57 is not inclined, for example, compared with a case where the main body portion 57 extends substantially parallel to the axial center line C of the plug main body 51. The length of the protruding portion 58 is shortened.

  That is, the position of the tip 57b when the main body 57 is tilted is positioned closer to the center electrode 52 along the extending direction E than the position of the tip 57b when the main body 57 is not tilted. become. Therefore, the length L1 of the extending portion 58 when the main body portion 57 is inclined is shorter than the length L2 of the extending portion 58 when the main body portion 57 is not inclined.

  As shown in FIG. 6, the extension plug 58 is shortened so that the spark plug 50 is stable even when the spark plug 50 is rotated by approximately 90 degrees from the first posture P1 toward the injector 40. Stratified lean combustion can be realized.

  FIG. 6 is a perspective view showing a state in which the injector 40 and the spark plug 50 are viewed from the cylinder 23 side. In FIG. 6, components such as the intake valve 28 and the exhaust valve 29 are omitted. The attitude of the ground electrode 53 is an attitude rotated approximately 90 degrees counterclockwise in the figure from the first attitude P1 or an attitude rotated approximately 90 degrees clockwise from the first attitude P1 to the second attitude P2. And FIG. 6 shows a case where the spark plug 50 is rotated 90 degrees counterclockwise from the first posture P1.

  This point will be specifically described. The extending portion 58 extends in the extending direction E so as to exceed a position facing the center electrode 52 in the axial center line direction D of the plug body 51. Therefore, the extending part 58 becomes longer in the extending direction E, and therefore the side surface 58a of the extending part 58 becomes relatively large. On the other hand, as shown in FIG. 5, when the ground electrode 53 is in the second posture P <b> 2, a part F <b> 1 of the fuel F injected from the injection port 41 of the injector 40 hits the side surface 58 a of the extension portion 58. In the drawing, a part F1 of the fuel F that collides with the extending portion 58 is hatched. Therefore, this hatching does not indicate a cross section of the extension portion 58.

  That is, if the extending portion 58 is long, the ratio of the portion F1 of the fuel F increases, so that a large amount of the air-fuel mixture M stays around the center electrode 52, and stable stratified lean combustion can be realized. However, when the spark plug 50 is in the second posture P2, the air-fuel mixture M tends to stay excessively around the center electrode 52. As a result, the spark plug 50 tends to smolder, and when smoldering occurs, ignition occurs. The insulation resistance of the plug decreases, and sufficient ignition energy cannot be supplied, leading to misfire.

  On the other hand, when the length of the extension portion 58 is shortened due to the inclination of the main body portion 57, the amount of the injected fuel F that strikes the extension portion 58 decreases, and therefore, around the center electrode 52. The amount of the air-fuel mixture M staying decreases. As a result, smoldering of the spark plug 50 is suppressed. Therefore, in this embodiment, in addition to the effects of the first embodiment, stable stratified lean combustion can be realized even when the spark plug 50 is in the second posture P2. The same applies to the case where the first posture P1 is rotated 90 degrees clockwise.

  This is not limited to the state where the ground electrode 53 is in the second posture P2. As shown in FIG. 7, the same effect can be obtained even when the ground electrode 53 is in a posture rotated, for example, by 45 degrees from the second posture P2 toward the injector 40. FIG. 7 shows a posture rotated 135 degrees counterclockwise from the first posture P1. Although not shown, the same effect can be obtained even with a posture rotated 135 degrees clockwise from the first posture P1.

  Thus, when a part F1 of the fuel F injected from the injector 40 hits the side surface 58a of the extension portion 58, the air-fuel mixture M is prevented from staying around the center electrode 52 excessively.

  Next, a spark plug according to a third embodiment of the present invention will be described with reference to FIGS. In addition, the structure which has the same function as 1st Embodiment attaches | subjects the same code | symbol, and abbreviate | omits description. In the present embodiment, the structure of the main body is different from that of the first embodiment. Other structures may be the same as those in the first embodiment. The different points will be specifically described.

  FIG. 8 is a side view showing the spark plug 50 of the present embodiment so that the side surface 58a of the extending portion 58 can be seen. FIG. 9 is a cross-sectional view of the main body 57 along the line F9-F9 shown in FIG. FIG. 9 shows a cross section of the main body 57 along the direction crossing the axial direction D of the plug main body 51. A cross section of the main body 57 that crosses the axial direction D in a substantially vertical direction is substantially trapezoidal.

  The main body 57 will be specifically described. The main body 57 has an inner surface 61, an outer surface 62, a first side surface 63, and a second side surface 64. The inner surface 61 is a surface facing the center electrode 52 in the main body 57 and is substantially flat. The outer surface 62 is a surface facing the opposite side of the center electrode 52 with the inner surface 61 interposed therebetween, and is a substantially flat surface. The inner surface 61 and the outer surface 62 are, for example, substantially parallel to each other.

  The first side surface 63 connects one side edge (the right side edge in the drawing) of the inner surface 61 and one side edge (the right side edge in the drawing) of the outer surface 62. The second side surface 64 connects the other side edge (the left side edge in the drawing) of the inner surface 61 and the other side edge (the left side edge in the drawing) of the outer surface 62. Therefore, the first and second side surfaces 63 and 64 are side surfaces crossing the circumferential direction Y in the axial direction D.

  The first side surface 63 is substantially flat, and the second side surface 64 side with respect to the direction X from the tip 52a of the center electrode 52 toward the center G of the cross section of the main body 57 as the distance from the center electrode 52 increases. It is inclined to. The second side surface 64 is a substantially flat surface and is inclined toward the first side surface 63 with respect to the direction X as the distance from the center electrode 52 increases. Therefore, as described above, the cross section of the main body 57 has a substantially trapezoidal shape from the base portion 57a to the tip 57b. The center G of the cross section of the main body 57 is a center along the circumferential direction Y in the cross section.

  FIG. 10 is a plan view of the spark plug 50 as viewed from the cylinder 23 side along the axial direction D of the plug body 51. As shown in FIGS. 8 and 10, the cross section of the main body 57 has a substantially trapezoidal shape from the base portion 57a to the tip 57b.

  Since the cross section of the main body 57 has a substantially trapezoidal shape, as described in the second embodiment, the spark plug 50 is stable even when the spark plug 50 is in the second posture P2. Stratified lean combustion can be realized.

  This point will be specifically described. As described in the second embodiment, when the spark plug 50 is in the second posture P2, the air-fuel mixture M tends to stay excessively around the center electrode 52. As a result, the center electrode 52 It tends to smolder.

  However, as shown in FIG. 10, a part F <b> 1 (shown by hatching in the drawing) of the fuel injected from the injector 40 that hits the main body portion 57 hits the second side face 64 of the main body portion 57. After that, the light is guided along the second side face 64 away from the center electrode 52. Therefore, the amount of the air-fuel mixture remaining around the center electrode 52 in the fuel F is reduced.

  In the present embodiment, the operation of the spark plug 50 in a state where the spark plug 50 is rotated 90 degrees counterclockwise from the first posture P1 is described, but the present invention is not limited to this. For example, when the spark plug 50 is rotated 90 degrees clockwise from the first posture P1, a part of the fuel injected from the injector 40 collides with the first side surface 63 and then the first side surface 63. Is guided away from the center electrode 52.

  According to this structure, the air-fuel mixture is restrained from remaining excessively around the center electrode 52, so that the fuel can be stably burned.

  In addition, since the first and second side surfaces 63 and 64 are inclined from the base portion 57a to the tip 57b, the fuel hitting the first and second side surfaces 63 and 64 is guided in a direction away from the center electrode. Further, it is possible to effectively suppress the air-fuel mixture from staying around the center electrode 52 effectively.

  Next, a spark plug according to a fourth embodiment of the present invention will be described with reference to FIGS. In addition, the structure which has a function similar to 1st Embodiment attaches | subjects the same code | symbol, and abbreviate | omits description. In the present embodiment, the structure of the ground electrode 53 is different from that of the first embodiment. Other structures may be the same as those in the first embodiment. The different points will be specifically described.

  FIG. 11 is a side view of the spark plug 50 shown so that the back surface 57c of the main body 57 of the ground electrode 53 can be seen. As shown in FIG. 11, a through hole 60 that penetrates the main body 57 is formed in the main body 57. The through hole 60 extends from the base portion 57 a of the main body portion 57 toward the distal end 57 b of the main body portion 57.

  By forming the through hole 60 in the main body portion 57, the spark plug 50 rotates 180 degrees around the axis C from the first posture P <b> 1 so that the main body portion 57 is interposed between the injector 40 and the center electrode 52. Even in the positioned position, stable stratified lean combustion can be realized. Note that a posture in which the main body 57 is positioned between the injector 40 and the center electrode 52 by rotating 180 degrees around the axis C from the first posture P1 is defined as a third posture P3.

  This point will be specifically described. FIG. 12 is an enlarged cross-sectional view showing the vicinity of the injector 40 of the combustion recess 22b in a state where the spark plug 50 is in the third posture P3. As shown in FIG. 12, when the spark plug 50 is in the third posture P3, the main body portion 57 of the ground electrode 53 is disposed between the injection port 41 of the injector 40 and the center electrode 52.

  As shown in FIG. 11, a part F1 of the fuel F injected from the injection port 41 of the injector 40 collides with the back surface 57c of the main body 57 (the surface opposite to the center electrode 52 in the main body 57) and diffuses. As a result, the air-fuel mixture is mixed with air M (indicated by a two-dot chain line), passes through the through-hole 60 and stays around the center electrode 52.

  Part F1 is hatched. Therefore, this hatching does not indicate a cross section of the main body portion 57.

  As shown in FIG. 12, the through hole 60 has a size through which an imaginary line V connecting the injection port 41 of the injector 40 and the tip 52 a of the center electrode 52 passes, and therefore the tip 57 b of the through hole 60. The position of the side edge 60 a is considered so that the virtual line V passes through the through hole 60.

  On the other hand, when the through hole 60 is not formed in the main body portion 57 of the ground electrode 53 in a state where the spark plug 50 is in the third posture P3, the fuel F injected from the injector 40 collides with the main body portion 57. However, it is difficult to reach the center electrode 52 by being blocked by the main body 57.

  From this, in addition to the effect of the first embodiment, stable stratified lean combustion can be realized even when the spark plug 50 is in the third posture P3.

  Further, since the position of the edge 60a on the tip 57b side of the through hole 60 is determined so that the virtual line V passes through the through hole 60, the air-fuel mixture M is inhibited by the edge 60a of the through hole 60. Without being guided to the periphery of the tip 52a of the center electrode 52.

  Next, a spark plug according to a fifth embodiment of the present invention will be described with reference to FIG. In addition, the structure which has a function similar to 4th Embodiment attaches | subjects the same code | symbol, and abbreviate | omits description. In the present embodiment, the structure of the main body 57 of the ground electrode 53 is different from that of the third embodiment. Other points may be the same as in the third embodiment. The above different points will be specifically described.

  FIG. 13 is a side view showing the side surface 58a of the extending portion 58 in the vicinity of the ignition plug 50 in the combustion recess 22b in a state where the ignition plug 50 of the present embodiment is in the third posture P3. As shown in FIG. 13, in the present embodiment, the main body 57 of the ground electrode 53 is inclined as described in the second embodiment.

  Therefore, the Coanda effect is generated by the inclination of the main body portion 57, and a part of the air-fuel mixture M that has passed through the through hole 60 is formed between the inner surface 61 (the surface on the center electrode 52 side) of the main body portion 57 and the extending portion 58. It is guided to the center electrode 52 along the inner surface 61 (the surface on the center electrode 52 side).

  Therefore, the air-fuel mixture M is carried around the center electrode 52 without considering the position of the edge 60 a on the tip 57 b side of the through hole 60 so that the phantom line V passes through the through hole 60. Therefore, even if the position of the edge 60a on the tip 57b side of the through hole 60 is moved to the base portion 57a side, in other words, even if the through hole 60 is reduced, the fuel F can be sufficiently guided around the center electrode 52. It becomes like this.

  According to this structure, since the through hole 60 can be reduced, the surface area of the main body 57 can be reduced. By reducing the surface area of the main body 57, the temperature drop of the main body 57 is suppressed. A flame generated by the combustion of the air-fuel mixture M is in contact with the main body 57. Therefore, since the temperature drop of the main body portion 57 is suppressed, the flame grows efficiently. In addition to the effect of the third aspect, the fuel F is stably burned. Furthermore, since the main body 57 is inclined, the same effect as that of the second embodiment can be obtained.

  Further, in the engine 20 including the spark plug 50 of the present embodiment, stable stratified lean combustion can be realized without significant cost increase even in an engine having a plurality of cylinders. This point will be specifically described.

  The spark plug 50 is fixed to the cylinder head 22 by screwing the screw part 56 into the female screw part 22d. Therefore, the attitude of the ground electrode 53 with respect to the injector 40 varies depending on how the spark plug 50 is attached, that is, how the spark plug 50 rotates with respect to the cylinder head 22.

  Therefore, it is conceivable that the attitude of the spark plug 50 installed in each cylinder is different.

  In other words, the multi-cylinder engine cannot operate normally unless the ignition plug 50 is in a state where stable stratified lean combustion is established in any posture. If there is even one spark plug posture that does not achieve stable combustion, it is necessary to position the cylinder so that the spark plug posture of each cylinder does not become that position. However, positioning is accompanied by a significant cost increase, making it difficult in practice. However, in the spark plug 50 of this embodiment, stable stratified lean combustion can be realized in any of the first to third postures P1 to P3 and the postures in the vicinity of the first to third postures P1 to P3. That is, with the spark plug 50 of the present embodiment, stable stratified lean combustion can be realized without the need for positioning of the spark plug even in an engine having a plurality of cylinders.

  This is the end of the description of the embodiment. However, the embodiment of the present invention is not limited to this embodiment. For example, in the above-described embodiment, the fuel is injected in a cone shape, but may not be in a cone shape.

Sectional drawing which shows the vicinity of a combustion chamber in an engine provided with the ignition plug of the 1st Embodiment of this invention. Sectional drawing which expands and shows the circumference | surroundings of the front end side of a plug main body in the combustion recessed part shown by FIG. The perspective view which shows the state which looked at the injector and the spark plug from the cylinder side shown by FIG. The perspective view which looked at the state which the ignition plug shown by FIG. 3 rotated about 35 degree | times to the injector side from the cylinder side. The side view which shows the ignition plug which concerns on the 2nd Embodiment of this invention. FIG. 6 is a perspective view showing a state where an injector and a spark plug are viewed from the cylinder side in an engine including the spark plug shown in FIG. 5. The perspective view which shows the state which the ignition plug shown in FIG. 6 rotated 45 degree | times to the injector side. The side view which shows the ignition plug which concerns on the 3rd Embodiment of this invention so that the side surface of a main-body part can be seen. Sectional drawing of the main-body part shown along F9-F9 line shown by FIG. The front view which shows the ignition plug shown in FIG. 8 attached in the combustion chamber so that it may become a 2nd attitude | position along an axial center line direction. The side view which shows the ignition plug which concerns on the 3rd Embodiment of this invention so that the back surface of the main-body part of a ground electrode can be seen. FIG. 12 is an enlarged cross-sectional view showing the vicinity of an injector in a combustion recess in a state where the ignition plug is in a third posture in the engine including the ignition plug shown in FIG. 11. Sectional drawing which expands and shows the injector vicinity of a combustion recessed part in the state provided with a spark plug in a 3rd attitude | position in an engine provided with the spark plug which concerns on the 4th Embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 30 ... Combustion chamber, 40 ... Injector, 50 ... Spark plug, 51 ... Plug body, 52 ... Center electrode, 52a ... Tip (tip of center electrode), 53 ... Ground electrode, 57 ... Body part, 57a ... Base part, 57b ... tip (tip of body part), 58 ... extension part, 59 ... tip end face (guide face), 59a ... first edge, 59b ... second edge, 60 ... through hole, 63 ... first side face ( Side surface), 64: Second side surface (side surface), V: Virtual line, X: Direction from the center electrode toward the main body, Y: Circumferential direction.

Claims (6)

A plug body;
A center electrode provided on the plug body;
An ignition plug installed in a combustion chamber provided with an injector for injecting fuel, comprising a ground electrode provided around the center electrode in the plug body and performing spark discharge with the center electrode. And
The ground electrode is
A main body extending from the plug main body to the distal end side of the central electrode;
A guide surface that extends from the front end of the main body portion toward the center electrode along a direction crossing the axial center direction of the plug main body and guides fuel injected from the injector to the center electrode at the front end in the extending direction. An ignition plug comprising: an extending portion formed.   The guide surface has a second edge that is further away from the first edge in the axial direction than the first edge located on the center electrode side in the axial direction of the plug body on the guide surface. The spark plug according to claim 1, wherein the spark plug is a flat surface protruding in a direction in which the extending portion extends.   The spark plug according to claim 1 or 2, wherein the ground electrode is formed with a through-hole penetrating the ground electrode in a direction from the center electrode toward the ground electrode.   The said main-body part inclines so that the front-end | tip of the said main-body part may be located in the said center electrode side rather than the base part connected to the said plug main body in the said main-body part. The spark plug of any one of them.   The both side surfaces crossing the circumferential direction of the central electrode in the main body portion are inclined to the other side surface side as they are separated from the central electrode, respectively. The spark plug described.   The through hole has a size through which an imaginary line connecting the injection port of the injector and the tip of the center electrode passes when the main body is disposed between the injector and the center electrode. The spark plug according to claim 3.

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