JP2019204586A - Spark plug - Google Patents

Abstract

To provide a spark plug capable of improving ignitability.SOLUTION: A spark plug includes a rod-like ground electrode having the other end connected with a main body metal fitting and one end forming a spark gap in the direction of a center electrode and an axis line. The ground electrode includes the inside having a discharge surface facing the apical surface of the center electrode via the spark gap, and first and second faces connected with the inside and extending from one end side to the other end side, an open hole leading from the first face to the second face is formed in the ground electrode, or a groove leading from the first face to the second face is formed in any face other than the discharge surface. At least the first opening, out of the first opening formed in the first face and the second opening formed in the second face, has at least a part located closer to the tip side than the tip of the center electrode, in the direction of the axis line.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a spark plug, and more particularly to a spark plug in which a spark gap is formed between a center electrode and a ground electrode.

  There is known a spark plug including a metal shell fixed to an engine, a center electrode insulated and held by the metal shell, and a ground electrode connected to the metal shell and facing the center electrode via a spark gap (patent) Reference 1). In this type of spark plug, when the insulation between the center electrode and the ground electrode is broken, a flame nucleus is generated in the spark gap, and the flame grows to ignite the combustible mixture.

JP 2014-41700 A

  There is a need for a technique that promotes flame growth and improves ignitability.

  The present invention has been made to meet this demand, and an object of the present invention is to provide a spark plug that can improve ignitability.

  In order to achieve this object, a spark plug according to the present invention includes an insulator having an axial hole extending from the front end side to the rear end side in the direction of the axis, a center electrode disposed on the front end side of the axial hole, and an insulator. And a rod-shaped ground electrode having one end connected to the metal shell and having one end connected to the center electrode and a spark gap in the direction of the axis. The ground electrode includes an inner surface having a discharge surface facing the front end surface of the center electrode via a spark gap, and a first surface and a second surface connected to the inner surface and extending from one end side to the other end side, The ground electrode is formed with a through hole that communicates from the first surface to the second surface, or a groove that communicates from the first surface to the second surface on any surface other than the discharge surface. At least the first opening of the first opening formed in the first surface and the second opening formed in the second surface has at least a part of the first opening closer to the tip side than the tip of the center electrode in the direction of the axis. To position.

  The spark plug of the present invention is provided with an insulator having an axial hole extending in the axial direction from the front end side to the rear end side, and disposed at the front end side of the shaft hole, and the front end of the spark plug is more advanced than the front end of the insulator. The center electrode located on the side, the cylindrical metal shell that holds the insulator inside, the other end of itself is connected to the metal shell, and one end forms a spark gap in the direction perpendicular to the axis A rod-shaped ground electrode. The ground electrode has a front end surface facing the side surface of the center electrode through the spark gap, an inner surface connected to the front end surface and facing the rear end side at least at one end portion, and connected to the front end surface and the inner surface and connected to the other end from the one end portion side. The ground electrode is provided with a through-hole extending from the first surface to the second surface, or the first surface on any surface other than the tip surface. To the second surface is formed. At least the first opening of the first opening formed on the first surface and the second opening formed on the second surface has at least a part of the first opening closer to the tip side than the tip of the insulator in the axial direction. To position.

  According to the spark plug according to claim 1, the spark plug is attached to the engine so that the first surface of the ground electrode faces the downstream side of the flow generated in the combustion chamber, so that the airflow flowing in from the second opening is the first opening. Since the flame comes out and blows out the flame, the growth of the flame is promoted and the ignitability can be improved.

  According to the spark plug of claim 2, when the ground electrode is viewed from a direction perpendicular to the first surface, at least a part of the first opening is positioned in a direction perpendicular to the axis. It exists in the range. In the spark gap, in the range where the tip surface of the center electrode is located, flame nuclei are likely to be generated. Therefore, by providing the first opening in the vicinity thereof, in addition to the effect of claim 1, it is possible to easily blow the flame.

  According to the spark plug of the third aspect, when the ground electrode is viewed from the direction perpendicular to the first surface, the entire first opening exists within the range in the direction orthogonal to the axis. In addition to the effect of item 2, the flame can be easily blown away.

  According to the spark plug of claim 4, the center of the first opening is the distance to the first edge of the first surface connected to the inner surface and the second of the first surface located on the opposite side of the first edge. The distance to the edge is closer to the first edge than the imaginary line that is a set of points on the first surface having the same distance. Since the air flow can be easily guided near the discharge surface, in addition to the effect of any one of claims 1 to 3, it is possible to easily blow the flame.

  The spark plug according to claim 5 has the same effect as that of claim 1.

It is a half sectional view of the spark plug in a 1st embodiment. It is a side view of a spark plug. It is a perspective view of a spark plug. It is sectional drawing of the spark plug in the IV-IV line of FIG. It is a side view of the spark plug in 2nd Embodiment. It is a side view of the spark plug in 3rd Embodiment.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a half sectional view with an axis O of a spark plug 10 according to the first embodiment as a boundary. In FIG. 1, the lower side of the drawing is referred to as the front end side of the spark plug 10, and the upper side of the drawing is referred to as the rear end side of the spark plug 10 (the same applies to FIGS. 2 to 6). As shown in FIG. 1, the spark plug 10 includes an insulator 11, a center electrode 20, a metal shell 30, and a ground electrode 40.

  The insulator 11 is a substantially cylindrical member in which a shaft hole 12 along the axis O is formed, and is formed of ceramics such as alumina that is excellent in mechanical properties and insulation at high temperatures. In the insulator 11, a rear end facing surface 13, which is an annular surface facing the rear end side, is formed on the front end side of the inner peripheral surface formed by the shaft hole 12. The rear end facing surface 13 is reduced in diameter toward the front end side.

  The center electrode 20 is a rod-like member whose head 21 is locked to the rear end-facing surface 13, and the shaft portion 22 is disposed in the shaft hole 12 on the front end side of the rear end-facing surface 13. In the center electrode 20, a bottomed cylindrical electrode base material mainly containing Ni covers a core material mainly containing copper. It is possible to omit the core material. The center electrode 20 is electrically connected to the terminal fitting 25 in the shaft hole 12.

  The terminal fitting 25 is a rod-like member to which a high voltage cable (not shown) is connected, and is formed of a conductive metal material (for example, low carbon steel). The terminal fitting 25 is fixed to the rear end of the insulator 11 with the tip end inserted into the shaft hole 12.

  The metal shell 30 is a substantially cylindrical member formed of a conductive metal material (for example, low carbon steel). The metal shell 30 surrounds the distal end side of the insulator 11 and holds the insulator 11 inside. The metal shell 30 has a screw 32 formed on the outer peripheral surface of the body portion 31 on the front end side of the metal shell 30. The male screw 32 is a part that is screwed into a screw hole of an engine (not shown). The metal shell 30 includes a seat portion 33 connected to the rear end side of the body portion 31 and a tool engaging portion 34 connected to the rear end side of the seat portion 33.

  The seat portion 33 is a portion for closing a gap between a screw hole of an engine (not shown) and the external screw 32, and has an outer diameter larger than the outer diameter of the body portion 31. The tool engaging portion 34 is a portion that engages a tool such as a wrench when the screw 32 is tightened in the screw hole of the engine. In the metal shell 30, the ground electrode 40 is connected to the body portion 31.

  The ground electrode 40 is a rod-like member formed of a conductive metal material (for example, a Ni-based alloy). The ground electrode 40 has one end 41 facing the center electrode 20 and the other end 42 connected to the metal shell 30.

  FIG. 2 is a side view of the spark plug 10, and FIG. 3 is a perspective view of the spark plug 10. 2 and 3, illustration of the rear end side of the spark plug 10 is omitted. 2 indicates the direction of the axis O (see FIG. 1), and the arrow P direction indicates the direction orthogonal to the axis O (the same applies to FIGS. 4 to 6). As shown in FIG. 2, a spark gap G is formed in the axial direction (arrow A direction) between the discharge surface 43 of the one end 41 of the ground electrode 40 and the tip surface 23 of the center electrode 20.

  As shown in FIG. 3, the ground electrode 40 includes an inner surface 44 having a discharge surface 43 at one end 41, a first surface 45 connected to the inner surface 44, and a surface opposite to the first surface 45. A second surface 48 connected to 44, an outer surface 49 connected to the first surface 45 and the second surface 48 and located opposite to the inner surface 44, and the inner surface 44, the first surface 45, the second surface 48 and the outer surface 49. And a tip surface 50 connected to the. The first surface 45 is sandwiched between a first edge 46 connected to the inner surface 44 and a second edge 47 connected to the outer surface 49. The inner surface 44, the first surface 45, the second surface 48, and the outer surface 49 extend from the one end 41 side where the distal end surface 50 is located to the other end 42 side.

  The ground electrode 40 is formed with a through hole 51 that communicates from the first surface 45 to the second surface 48. The through hole 51 forms a first opening 52 on the first surface 45 and forms a second opening 53 on the second surface 48. In the present embodiment, the first opening 52 and the second opening 53 are circular.

  As shown in FIG. 2, when the ground electrode 40 is viewed from a direction perpendicular to the first surface 45 (a direction perpendicular to the paper surface of FIG. 2), at least a part of the first opening 52 is a direction orthogonal to the axis O. In the direction of arrow P, it exists in a range 56 where the tip surface 23 of the center electrode 20 exists. In the present embodiment, the entire first opening 52 exists within the range 56. Similar to the first opening 52, the entire second opening 53 exists within the range 56.

  At least a part of the first opening 52 is located in a range 57 on the tip side of the tip surface 23 (tip) of the center electrode 20 in the axial direction (arrow A direction). In the present embodiment, the entire first opening 52 is located within the range 57. Further, the center 54 of the first opening 52 is more than the virtual line 55 on the first surface 45 where the distance to the first edge 46 (see FIG. 3) is equal to the distance to the second edge 47 (see FIG. 3). Located near the first edge 46.

  4 is a cross-sectional view of the spark plug 10 taken along line IV-IV in FIG. The spark plug 10 is attached to an engine (not shown) so that the second surface 48 of the ground electrode 40 faces the upstream side of the air flow (mixture flow) generated in the combustion chamber and the first surface 45 faces the downstream side. It is done. The airflow that has entered the through hole 51 from the second opening 53 exits from the first opening 52.

  Since at least a part of the first opening 52 is located on the distal end side in the axial direction (arrow A direction) with respect to the distal end surface 23 (front end) of the center electrode 20, the distal end surface 23 of the center electrode 20 and the ground electrode 40. A flame 58 in which flame nuclei generated between the discharge surface 43 and the discharge surface 43 grow is blown downstream by an air flow coming out of the first opening 52. Thereby, since the airflow can be prevented from being disturbed by the ground electrode 40, the growth of the flame 58 is promoted by the airflow coming out of the first opening 52, and the ignitability can be improved. Further, since the airflow coming out of the first opening 52 keeps the flame 58 away from the ground electrode 40 and suppresses the extinguishing action by the ground electrode 40, the flame 58 can be grown greatly. In particular, in the present embodiment, since the entire first opening 52 is located within the range 57, the flame 58 is more easily affected by the flow, and the ignitability can be improved.

  Since the first opening 52 is circular, excessive stress concentration generated in the first opening 52 can be suppressed. Therefore, the generation of cracks starting from the first opening 52 can be suppressed, and a decrease in durability of the ground electrode 40 can be suppressed. Further, since the second opening 53 is circular, stress concentration can be suppressed similarly to the first opening 52, and a decrease in durability of the ground electrode 40 can be suppressed.

  Since the first opening 52 and the second opening 53 are formed by the through hole 51 formed in the ground electrode 40, the airflow collected in the through hole 51 can be discharged from the first opening 52. As a result, the velocity of the airflow flowing out from the first opening 52 can be increased compared to the case where the first opening and the second opening are formed by the groove. Therefore, it is possible to easily blow the spark between the spark gaps G.

  In the spark gap G, a range 56 where the tip surface 23 of the center electrode 20 is located is likely to generate a flame kernel. Therefore, when the ground electrode 40 is viewed from the direction perpendicular to the first surface 45, at least a part of the first opening 52 exists in the range 56 in the direction orthogonal to the axis O (the direction of the arrow P). In the spark gap G, it is possible to easily blow the flame in which the flame core has grown. Therefore, ignitability can be improved.

  In the present embodiment, since all of the first openings 52 are present in the range 56, the flame can be easily blown downstream and the ignitability can be further improved. Furthermore, since the entire second opening 53 is present in the range 56, the loss due to the inner wall of the through hole 51 can be reduced as compared with the case where the second opening 53 is not present in the range 56. As a result, the speed of the airflow flowing out from the first opening 52 can be increased, so that the spark between the spark gaps G can be easily blown out.

  Since the center 54 of the first opening 52 is located closer to the first edge 46 than the imaginary line 55, it is possible to easily guide the airflow from the first opening 52 near the discharge surface 43 where flame nuclei are likely to occur. Therefore, it is possible to promote the flow of flame and improve the ignitability.

  A second embodiment will be described with reference to FIG. In the first embodiment, the case where the through hole 51 is formed in the ground electrode 40 has been described. In contrast, in the second embodiment, a case where the groove 61 is formed in the ground electrode 40 will be described. In addition, about the part same as the part demonstrated in 1st Embodiment, the same code | symbol is attached | subjected and the following description is abbreviate | omitted. FIG. 5 is a side view of the spark plug 60 in the second embodiment.

  As shown in FIG. 5, a groove 61 that extends from the first surface 45 to the second surface 48 is formed on the distal end surface 50 of the ground electrode 40. The groove 61 forms a first opening 62 in the first surface 45 and forms a second opening 63 in the second surface 48. At least a part of the first opening 62 is located on the tip side (in the range 57) of the tip surface 23 (tip) of the center electrode 20 in the axial direction (arrow A direction). In the present embodiment, the entire first opening 62 is located within the range 57.

  A spark plug 60 is attached to an engine (not shown) so that the second surface 48 of the ground electrode 40 faces the upstream side of the airflow (mixture flow) generated in the combustion chamber and the first surface 45 faces the downstream side. When the airflow enters the groove 61, the airflow exits the first opening 62. A flame (not shown) in which a flame nucleus formed between the front end surface 23 of the center electrode 20 and the discharge surface 43 of the ground electrode 40 grows is blown downstream by an air flow coming out of the first opening 62. . Thereby, the growth of flame can be promoted and the ignitability can be improved.

  At least a part of the first opening 62 is in a direction (arrow P direction) perpendicular to the axis O when the ground electrode 40 is viewed from a direction perpendicular to the first surface 45 (direction perpendicular to the paper surface of FIG. 5). It exists in the range 56 where the front end surface 23 of the center electrode 20 exists. Therefore, it is possible to easily blow the flame in which the flame kernel generated in the spark gap G has grown. Therefore, ignitability can be improved.

  Since the center 64 of the first opening 62 is located closer to the first edge 46 (see FIG. 3) than the imaginary line 55, airflow is guided from the first opening 62 near the discharge surface 43 where flame nuclei are likely to occur. Easy to do. Therefore, it is possible to promote the flow of flame and improve the ignitability. The center 64 of the first opening 62 coincides with the center of gravity of the figure when the first opening 62 is regarded as a figure (a semicircular fan shape in the present embodiment).

  A third embodiment will be described with reference to FIG. In the first and second embodiments, the case where the ground electrode 40 is separated from the center electrode 20 in the direction of the axis O and the spark gap G is formed therebetween has been described. In contrast, in the third embodiment, a case will be described in which the ground electrode 80 is separated from the center electrode 20 in a direction perpendicular to the axis O, and a spark gap G is formed therebetween. In addition, about the part same as the part demonstrated in 1st Embodiment, the same code | symbol is attached | subjected and the following description is abbreviate | omitted. FIG. 6 is a side view of the spark plug 70 according to the third embodiment. FIG. 6 shows the spark plug 70 as viewed from the first surface 85 side of the ground electrode 80.

  As shown in FIG. 6, the spark plug 70 has a plurality of ground electrodes 80 connected to the metal shell 30. In the present embodiment, two ground electrodes 80 are disposed with the center electrode 20 interposed therebetween. The ground electrode 80 is a rod-like member formed of a conductive metal material (for example, a Ni-based alloy). The ground electrode 80 has a front end surface 83 of one end 81 facing the side surface 24 of the center electrode 20 and a second end 82 connected to the metal shell 30. A spark gap G is formed between the front end surface 83 of the ground electrode 80 and the side surface 24 of the center electrode 20 in a direction (arrow P direction) orthogonal to the axis.

  The ground electrode 80 is connected to the front end surface 83 and faces the rear end side (upper side in FIG. 6) at least at one end portion 81, a first surface 85 connected to the inner surface 84, and the opposite side of the first surface 85. A second surface 86 connected to the inner surface 84, and an outer surface 87 connected to the first surface 85 and the second surface 86 and positioned on the opposite side of the inner surface 84. The front end surface 83 is connected to the inner surface 84, the first surface 85, the second surface 86, and the outer surface 87. The inner surface 84, the first surface 85, the second surface 86, and the outer surface 87 extend from the one end portion 81 side where the distal end surface 83 is located to the other end portion 82 side.

  A groove 88 that communicates from the first surface 85 to the second surface 86 is formed on the outer surface 87 of the ground electrode 80 (left side in FIG. 6). The groove 88 forms a first opening 89 on the first surface 85 and a second opening 90 on the second surface 86. At least a part of the first opening 89 is located in a range 94 on the tip side (lower side in FIG. 6) of the insulator 11 in the axial direction (arrow A direction). In the present embodiment, the entire first opening 89 is located within the range 94.

  The ground electrode 80 (on the right side in FIG. 6) is formed with a through hole 91 that communicates from the first surface 85 to the second surface 86. The through hole 91 forms a first opening 92 in the first surface 85 and forms a second opening 93 in the second surface 86. At least a part of the first opening 92 is located in a range 94 on the distal end side (lower side in FIG. 6) with respect to the distal end 14 of the insulator 11 in the axial direction (arrow A direction). In the present embodiment, the entire first opening 92 is located within the range 94.

  A spark plug 70 is attached to the engine (not shown) so that the second surface 86 of the ground electrode 80 faces the upstream side of the airflow (mixture flow) generated in the combustion chamber and the first surface 85 faces the downstream side. Then, the airflows that have entered the groove 88 and the through hole 91 exit from the first openings 89 and 92, respectively. A flame (not shown) in which flame nuclei generated between the side surface 24 of the center electrode 20 and the front end surface 83 of the ground electrode 80 grows downstream (see FIG. 6) due to the air flow coming out of the first openings 89 and 92. It is blown away on the front side of the paper. Thereby, the growth of flame can be promoted and the ignitability can be improved.

  The present invention has been described above based on the embodiments. However, the present invention is not limited to the above embodiments, and various improvements and modifications can be made without departing from the spirit of the present invention. It can be easily guessed.

  In 1st Embodiment, the distance between the front end surface 50 and the 1st opening 52 and the distance between the front end surface 50 and the 2nd opening 53 were demonstrated. In the third embodiment, the case where the distance between the tip surface 83, the first openings 89, 92, the tip surface 83, and the second openings 90, 93 is the same has been described. However, it is not necessarily limited to this. The positions of the second openings 53, 90, and 93 can be appropriately set at positions where the combustible air-fuel mixture can enter when the spark plug is attached to the engine so that the second surfaces 48 and 86 face the upstream side. .

  In 1st Embodiment and 3rd Embodiment, although the case where the 1st opening 52,92 and the 2nd opening 53,93 which the through-holes 51 and 91 make was circular was demonstrated, it is not necessarily restricted to this. The shapes of the first openings 52 and 92 and the second openings 53 and 93 can be set as appropriate, such as a polygon such as a rectangle, or an ellipse.

  In the first and third embodiments, the entire circumference of the second openings 53 and 93 exists in the second surfaces 48 and 86, and the entire circumference of the first openings 52 and 92 exists in the first surfaces 45 and 85. Although the case has been described, the present invention is not necessarily limited to this. A part of the first opening 52 and the second opening 53 exists on the inner surface 44, the outer surface 49, and the tip surface 50, and a part of the first opening 92 and the second opening 93 exists on the inner surface 84 and the outer surface 87. Of course it is possible.

  In the second and third embodiments, the case where the first openings 62 and 89 and the second openings 63 and 90 formed by the grooves 61 and 88 are arc-shaped has been described, but the present invention is not necessarily limited thereto. The shapes of the first openings 62 and 89 and the second openings 63 and 90 may be angular.

  In the second embodiment, the case where the groove 61 is formed on the tip surface 50 of the ground electrode 40 has been described, but the present invention is not necessarily limited thereto. The groove 61 can be formed on the inner surface 44 or the outer surface 49 other than the discharge surface 43 of the ground electrode 40.

  In the third embodiment, the case where the groove 88 is formed on the outer surface 87 of the ground electrode 80 has been described, but the present invention is not necessarily limited thereto. The groove 88 can be formed on the inner surface 84 except for the tip surface 83 of the ground electrode 80.

  In the third embodiment, the case where the groove 88 is formed on one side of the ground electrode 80 and the through hole 91 is formed on the other side of the ground electrode 80 has been described, but the present invention is not necessarily limited thereto. Of course, it is possible to form grooves or through holes in both of the ground electrodes 80.

  In the embodiment, the case where a chip containing noble metal or the like is not connected to the center electrode 20 and the ground electrode 40 has been described, but the present invention is not necessarily limited thereto. It is naturally possible to bond the chip to the center electrode 20 or the ground electrode 40. In the case of a spark plug having a center electrode 20 with the tip joined to the tip, the tip surface of the center electrode refers to the tip surface of the tip.

10, 60, 70 Spark plug 11 Insulator 12 Shaft hole 14 Tip of insulator 20 Center electrode 23 Tip surface (tip of center electrode)
24 side surface 30 metal shell 40, 80 ground electrode 41, 81 one end portion 42, 82 other end portion 43 discharge surface 44, 84 inner surface 45, 85 first surface 46 first edge 47 second edge 48, 86 second surface 51, 91 Through-hole 52,92 1st opening 53,93 2nd opening 55 Virtual line 56 Range 61,88 Groove 62,89 1st opening 63,90 2nd opening 83 Tip surface G Spark gap O Axis line

Claims (5)

An insulator having an axial hole extending in the direction of the axis from the front end side to the rear end side;
A center electrode disposed on the tip side of the shaft hole;
A cylindrical metal shell for holding the insulator inside;
A spark plug comprising: a rod-like ground electrode having one end connected to the metal shell and one end forming a spark gap in the direction of the axis;
The ground electrode includes an inner surface having a discharge surface facing the tip surface of the center electrode through the spark gap, and a first surface and a second surface connected to the inner surface and extending from the one end side to the other end side. A surface, and
The ground electrode is formed with a through hole that communicates from the first surface to the second surface, or a groove that communicates from the first surface to the second surface on any surface other than the discharge surface. ,
Of the first opening formed in the first surface and the second opening formed in the second surface, at least the first opening in the direction of the axis is at least part of itself from the tip of the center electrode. The spark plug is also located on the tip side.   When the ground electrode is viewed from a direction perpendicular to the first surface, at least a part of the first opening exists in a range where the tip surface of the center electrode is located in a direction orthogonal to the axis. The spark plug according to claim 1.   3. The spark plug according to claim 2, wherein when the ground electrode is viewed from a direction perpendicular to the first surface, the first opening is entirely within the range in a direction perpendicular to the axis.   The center of the first opening is a distance to the first edge of the first surface connected to the inner surface, a distance to the second edge of the first surface located on the opposite side of the first edge, 4. The spark plug according to claim 1, wherein the spark plug is located closer to the first edge than an imaginary line that is a set of points on the first surface with equal. An insulator having an axial hole extending in the direction of the axis from the front end side to the rear end side;
A central electrode disposed on the distal end side of the shaft hole, the distal end of which is located closer to the distal end side than the distal end of the insulator;
A cylindrical metal shell for holding the insulator inside;
A spark plug comprising a rod-shaped ground electrode that forms a spark gap with the center electrode in a direction orthogonal to the axis line, the other end portion of the metal shell being connected to the other end portion of the metal shell,
The ground electrode is connected to the front end surface facing the side surface of the center electrode through the spark gap, an inner surface connected to the front end surface and facing the rear end side at least at the one end, and connected to the front end surface and the inner surface And a first surface and a second surface extending from the one end side to the other end side,
The ground electrode is formed with a through hole that communicates from the first surface to the second surface, or a groove that communicates from the first surface to the second surface on any surface other than the tip surface. ,
Of the first opening formed in the first surface and the second opening formed in the second surface, at least the first opening in the direction of the axis is at least a part of the tip of the insulator. Spark plug located on the tip side.

Images