JP2017157451A - Ignition plug - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve a pre-ignition performance in an ignition plug.SOLUTION: An ignition plug comprises: an insulator that includes a center electrode extended to an axial line direction and an axial hole penetrated along the axial line direction, and holds the center electrode in the axial hole; a main metal fitting that is arranged in the circumference of a radial direction of the insulator, and holds the insulator; and a ground electrode that is electrically connected to the main metal fitting, and forms a gap between the center electrodes. The main metal fitting includes a tip tube part that is exposed into a combustion chamber of an internal combustion when the main metal fitting is attached to the internal combustion. In the ignition plug, the tip tube part is penetrated from an outer peripheral surface to an inner peripheral surface, and includes a penetration hole in which a gas sucked to the combustion chamber passes. When viewing from a first opening of the outer peripheral surface side of the penetration hole to a second opening of an inner peripheral surface side of the penetration hole, a tip edge of the insulator can be visually confirmed.SELECTED DRAWING: Figure 2

Description

  The present specification relates to a spark plug for igniting a fuel gas in an internal combustion engine or the like.

  In Patent Document 1, in a spark plug used in an internal combustion engine, when the tip of an insulator protrudes toward the combustion chamber of the internal combustion engine, the tip of the metal shell disposed on the outer periphery of the insulator is burned. A technique is disclosed in which a vent hole is provided in the distal end portion while projecting to the chamber side. According to this technique, by providing the vent hole, it is possible to obtain a cooling effect of the insulator and to improve the pre-ignition resistance.

International Publication No. 2008/102842

  Here, due to the recent increase in output of internal combustion engines and the like, spark plugs tend to be used in higher temperature environments where pre-ignition is likely to occur. For this reason, the spark plug is required to further improve pre-ignition resistance.

  The present specification discloses a technique for improving pre-ignition resistance performance in a spark plug used in an internal combustion engine.

  The technology disclosed in this specification can be implemented as the following application examples.

Application Example 1 A center electrode extending in the direction of the axis,
An insulator having a shaft hole penetrating along the direction of the axis, and holding the center electrode in the shaft hole;
A metal shell that is disposed around a radial direction of the insulator and holds the insulator;
A ground electrode electrically connected to the metal shell and forming a gap with the center electrode;
With
The metal shell includes a tip tube portion that is exposed to a combustion chamber of the internal combustion engine when attached to the internal combustion engine,
The tip tube portion is an ignition plug that penetrates from the outer peripheral surface to the inner peripheral surface and has a through hole through which the gas sucked into the combustion chamber passes.
The front edge of the insulator is visible when viewed from the first opening on the outer peripheral surface side of the through hole toward the second opening on the inner peripheral surface side of the through hole. plug.

  According to the above configuration, the gas sucked into the combustion chamber passes through the through hole of the tip tube portion from the outer peripheral surface side and is blown toward the tip of the insulator. As a result, the tip of the insulator can be efficiently cooled using the gas sucked into the combustion chamber. Therefore, the occurrence of pre-ignition due to excessive heating of the tip of the insulator can be suppressed, so that the anti-pre-ignition performance of the spark plug can be improved.

[Application Example 2] The spark plug according to Application Example 1,
The spark plug according to claim 1, wherein an area of the first opening is larger than an area of the second opening.

  According to the said structure, the increase in the flow volume and flow velocity of the gas which pass a through-hole can be aimed at.

[Application Example 3] The spark plug according to Application Example 1 or 2,
The tip plug portion has four or more through holes having different circumferential positions from each other.

  According to the above configuration, the tip of the insulator can be efficiently cooled by the four or more through holes regardless of the circumferential position where the spark plug is attached to the internal combustion engine.

[Application Example 4] The spark plug according to any one of Application Examples 1 to 3,
The through-hole is formed so that the insulator cannot be seen from the first opening when the first opening is viewed from a direction perpendicular to the axis.

  According to the said structure, it can suppress that the pressure which generate | occur | produced by the abnormal combustion of an internal combustion engine hits an insulator through a through-hole. As a result, damage to the insulator due to abnormal combustion of the internal combustion engine can be prevented.

Application Example 5 The spark plug according to any one of Application Examples 1 to 3,
The through-hole is formed so that only the inner wall of the through-hole can be seen from the first opening when the first opening is viewed from a direction perpendicular to the axis.

  According to the said structure, it can suppress that the pressure which generate | occur | produced by the abnormal combustion of an internal combustion engine hits an insulator through a through-hole. As a result, damage to the insulator due to abnormal combustion of the internal combustion engine can be prevented.

Application Example 6 The spark plug according to any one of Application Examples 1 to 5,
The spark plug according to claim 1, wherein a front end of the metal shell is located closer to a front end side than a front end of the insulator.

  According to the said structure, it can suppress effectively that the pressure which generate | occur | produced by the abnormal combustion of an internal combustion engine hits an insulator directly. As a result, the insulator can be effectively prevented from being damaged due to abnormal combustion of the internal combustion engine.

Application Example 7 The spark plug according to any one of Application Examples 1 to 6,
The spark plug is characterized in that the through hole is formed at least in a circumferential position where the ground electrode is connected to the metal shell.

  The gas from the circumferential position where the ground electrode is connected toward the insulator is likely to be blocked by the ground electrode. By providing a through-hole at a circumferential position where the ground electrode is connected, gas directed from the circumferential position to the insulator can be guided to the insulator, so that the pre-ignition resistance performance can be more effectively achieved. Can be improved.

  The present invention can be realized in various modes. For example, an ignition plug and an ignition device using the ignition plug, an internal combustion engine equipped with the ignition plug, and an ignition device using the ignition plug are provided. This can be realized in the form of an internal combustion engine or the like to be mounted.

It is sectional drawing of an example of the ignition plug of embodiment. 2 is an enlarged cross-sectional view of the vicinity of a tip of a spark plug 100. FIG. It is the figure which looked at the ignition plug 100 toward the rear end direction BD from the front end side. FIG. 5 is an enlarged view of the vicinity of a through hole 551 in FIG. 2. It is explanatory drawing of the metal shell 50b of a modification. It is explanatory drawing of the metal shell 50c of a modification. It is explanatory drawing of the metal shell 50d of this modification.

A. Embodiment:
A-1. Spark plug configuration:
Drawing 1 is a sectional view of an example of a spark plug of an embodiment. The illustrated one-dot dashed line indicates the axis CL of the spark plug 100. The illustrated cross section is a cross section including the axis CL. Hereinafter, a direction parallel to the axis CL is also referred to as an “axis direction”. Of the directions parallel to the axis CL, the lower direction in FIG. 1 is referred to as a front end direction LD, and the upper direction is also referred to as a rear end direction BD. The tip direction LD is a direction from the terminal fitting 40 described later toward the electrodes 20 and 30. In addition, the radial direction of a circle centered on the axis CL and positioned on a plane perpendicular to the axis CL is simply referred to as “radial direction”, and the circumferential direction of the circle is also simply referred to as “circumferential direction”. An end in the front end direction LD is also simply referred to as a front end, and an end in the rear end direction BD is also simply referred to as a rear end.

  The spark plug 100 includes an insulator 10, a center electrode 20, a ground electrode 30, a terminal fitting 40, a metal shell 50, a first conductive seal layer 60, a resistor 70, and a second conductive material. A seal layer 80, a first packing 8, a talc 9, a second packing 6, and a third packing 7 are provided.

  The insulator 10 is a substantially cylindrical member having an axial hole 12 extending along the axial direction and penetrating the insulator 10. The insulator 10 is formed by firing alumina (other insulating materials can also be used). The insulator 10 includes a leg portion 13, a reduced outer diameter portion 15, a first body portion 17, a flange portion 19, and a second body portion 18 that are arranged in order in the rear end direction BD. ing. The outer diameter of the reduced outer diameter portion 15 gradually decreases in the distal direction LD. In the vicinity of the reduced outer diameter portion 15 of the insulator 10 (in the example of FIG. 1, the first body portion 17), a reduced inner diameter portion 16 whose inner diameter gradually decreases toward the distal direction LD is formed. .

  The center electrode 20 is located on the tip side in the shaft hole 12 of the insulator 10. The center electrode 20 is a rod-like body extending along the axial direction. The center electrode 20 includes a center electrode tip 28 and a center electrode body 26.

  The center electrode main body 26 has a leg portion 25, a flange portion 24, and a head portion 23 that are arranged in order in the rear end direction BD. A portion on the distal end side of the leg portion 25 is exposed outside the shaft hole 12 on the distal end side of the insulator 10. The other part of the center electrode 20 is held in the shaft hole 12. The front end side surface of the flange portion 24 is supported by the reduced inner diameter portion 16 of the insulator 10.

  The center electrode body 26 is formed using, for example, nickel (Ni) or an alloy containing nickel as a main component (for example, NCF600, NCF601). The center electrode body 26 may include a core material embedded in the inside and formed of copper or a copper-based alloy that is superior in thermal conductivity to Ni or an alloy containing Ni as a main component.

  The center electrode tip 28 is joined to the tip portion of the leg portion 25 of the center electrode body 26 by, for example, laser welding. The center electrode tip 28 is made of a material mainly composed of a high melting point noble metal. As the material of the center electrode tip 28, for example, iridium (Ir) or platinum (Pt), or an alloy mainly containing Ir or Pt is used.

  The terminal fitting 40 is located on the rear end side in the shaft hole 12 of the insulator 10. The terminal fitting 40 is a rod-like body extending along the axial direction, and is formed using a conductive material (for example, a metal such as low carbon steel). The terminal fitting 40 includes a cap mounting portion 41, a flange portion 42, and a leg portion 43 that are arranged in order in the distal direction LD. The cap mounting portion 41 is exposed outside the shaft hole 12 on the rear end side of the insulator 10. The leg portion 43 is inserted into the shaft hole 12 of the insulator 10.

  The columnar resistor 70 is disposed between the terminal fitting 40 and the center electrode 20 in the shaft hole 12 of the insulator 10. The resistor 70 has a function of reducing radio noise when a spark is generated. The resistor 70 is formed of, for example, a composition including glass particles that are main components, ceramic particles other than glass, and a conductive material.

The first conductive seal layer 60 is disposed between the center electrode 20 and the resistor 70, and the second conductive seal layer 80 is disposed between the terminal fitting 40 and the resistor 70. As a result, the center electrode 20 and the terminal fitting 40 are electrically connected via the resistor 70 and the conductive seal layers 60 and 80. The conductive seal layers 60 and 80 are formed of a composition containing glass particles such as B ₂ O ₃ —SiO ₂ and metal particles (Cu, Fe, etc.), for example.

  The metal shell 50 is a substantially cylindrical member having an insertion hole 59 extending along the axis CL and penetrating through the metal shell 50. The metal shell 50 is formed using a low carbon steel material (other conductive materials (for example, metal materials) can also be used). The insulator 10 is inserted into the insertion hole 59 of the metal shell 50. The metal shell 50 holds the insulator 10 in a state of being arranged around the insulator 10 in the radial direction. At the distal end side of the metal shell 50, the end portion on the distal end side of the insulator 10 (in this embodiment, the portion on the distal end side of the leg portion 13) is exposed outside the insertion hole 59. On the rear end side of the metal shell 50, the end portion on the rear end side of the insulator 10 (in this embodiment, the portion on the rear end side of the second body portion 18) is exposed outside the insertion hole 59.

  The metal shell 50 is arranged in order in the rear end direction BD, the distal end cylinder part 55, the screw part 52, the seat part 54, the deformation part 58, the tool engagement part 51, the caulking part 53, have. An annular gasket 5 formed by bending a metal plate is fitted between the seat portion 54 and the screw portion 52.

  The seat part 54 is a bowl-shaped part. The screw portion 52 is a substantially cylindrical portion in which a screw for screwing into a mounting hole of an internal combustion engine (for example, a gasoline engine) is formed on the outer peripheral surface. The distal end cylindrical portion 55 is a substantially cylindrical portion that is disposed on the distal end side of the screw portion 52 and has no screw formed on the outer peripheral surface thereof. The length in the axial direction of the distal end cylindrical portion 55 is preferably 1.5 mm or more, for example. The distal end cylindrical portion 55 has a plurality of through holes 551 that penetrate from the outer peripheral surface to the inner peripheral surface. A detailed configuration of the distal end cylindrical portion 55 will be described later.

  The metal shell 50 has a reduced inner diameter portion 56 disposed on the distal end side with respect to the deformable portion 58. The inner diameter of the reduced inner diameter portion 56 gradually decreases from the rear end side toward the front end direction LD. The first packing 8 is sandwiched between the reduced inner diameter portion 56 of the metal shell 50 and the reduced outer diameter portion 15 of the insulator 10. The first packing 8 is an iron O-ring (other materials (for example, metal materials such as copper) can also be used).

  The shape of the tool engaging portion 51 is a shape (for example, a hexagonal column) with which the spark plug wrench is engaged. A caulking portion 53 is provided on the rear end side of the tool engaging portion 51. The caulking portion 53 is disposed on the rear end side of the flange portion 19 of the insulator 10 and forms an end on the rear end side of the metal shell 50. The caulking portion 53 is bent toward the inner side in the radial direction.

  On the rear end side of the metal shell 50, an annular space SP is formed between the inner peripheral surface of the metal shell 50 and the outer peripheral surface of the insulator 10. In the present embodiment, the space SP is a space surrounded by the crimping portion 53 and the tool engagement portion 51 of the metal shell 50, the rear end portion of the flange portion 19 of the insulator 10, and the second body portion 18. It is. A second packing 6 is disposed on the rear end side in the space SP. A third packing 7 is disposed on the front end side in the space SP. In this embodiment, these packings 6 and 7 are iron C-rings (other materials are also employable). Between the two packings 6 and 7 in the space SP, powder of talc (talc) 9 is filled.

  When the spark plug 100 is manufactured, the crimping portion 53 is crimped so as to be bent inward. And the crimping part 53 is pressed to the front end side. Thereby, the deformation | transformation part 58 deform | transforms and the insulator 10 is pressed toward the front end side in the metal shell 50 through the packings 6 and 7 and the talc 9. The first packing 8 is pressed between the reduced outer diameter portion 15 and the reduced inner diameter portion 56, and seals between the metal shell 50 and the insulator 10. As a result, the gas in the combustion chamber of the internal combustion engine is prevented from leaking outside through the metal shell 50 and the insulator 10. In addition, the metal shell 50 is fixed to the insulator 10.

  The ground electrode 30 has a ground electrode main body 33 and a ground electrode tip 38. The ground electrode body 33 is a rod-shaped member that is electrically connected to the metal shell 50. The ground electrode main body 33 is formed using, for example, Ni or an alloy containing Ni as a main component (for example, NCF600, NCF601). The ground electrode body 33 is formed of copper or an alloy containing copper as a main component, which is embedded in the interior and is superior in thermal conductivity to Ni or an alloy containing Ni as a main component, like the center electrode main body 26. A core material may be included. The ground electrode tip 38 is formed using, for example, Pt (platinum) or an alloy containing Pt as a main component, specifically, a Pt-20Ir alloy (a platinum alloy containing 20% by mass of iridium). .

A-2. Configuration near the tip of the spark plug The configuration near the tip of the spark plug 100 will be further described with reference to FIGS. FIG. 2 is an enlarged cross-sectional view of the vicinity of the tip of the spark plug 100. The enlarged cross-sectional view of FIG. 2 is a cross-sectional view in which the vicinity of the tip of the spark plug 100 in a state of being attached to the attachment hole PH of the head EH of the internal combustion engine is cut along a cross-section including the axis CL. FIG. 3 is a view of the spark plug 100 as viewed from the front end side toward the rear end direction BD. In FIG. 3, in order to avoid complication of the drawing, the distal end cylindrical portion 55 of the metal shell 50 and the distal end surface 13 s of the leg portion 13 of the insulator 10 are illustrated, and other components are not illustrated. .

  The tip tube portion 55 is exposed in the combustion chamber of the internal combustion engine when the spark plug 100 is attached to the internal combustion engine. More specifically, as shown in FIG. 2, when the spark plug 100 is attached to the attachment hole PH of the head EH of the internal combustion engine, the substantially entire tip cylinder portion 55 burns from the inner wall surface IS of the head EH. Projects into the room.

  The distal end of the insulator 10 (that is, the distal end of the leg portion 13) is located on the distal end side with respect to the distal end of the distal end cylindrical portion 55. The tip of the center electrode body 26 and the center electrode tip 28 are located on the tip side of the insulator 10.

  One end of the ground electrode body 33 is a connection end 31 connected to the tip of the metal shell 50 by, for example, resistance welding so that the ground electrode 30 and the metal shell 50 are electrically connected. The other end of the ground electrode body 33 is a free end 32. The ground electrode main body 33 extends from the connection end 31 connected to the metal shell 50 in the distal direction LD and is bent toward the axis CL. The ground electrode main body 33 extends in a direction perpendicular to the axis CL and reaches the free end 32.

  One side surface of the ground electrode body 33 on the side of the free end 32 extending in the direction perpendicular to the axis line CL is opposed to the center electrode chip 28 in the axial direction on the axis line CL. A ground electrode tip 38 is welded to the one side surface of the ground electrode main body 33 at a position facing the center electrode tip 28. The ground electrode tip 38 forms a spark gap with the center electrode tip 28.

  The above-described through hole 551 formed in the distal end cylindrical portion 55 is formed so that the gas taken in through the combustion chamber of the internal combustion engine passes. As shown in FIG. 3, the plurality of through-holes 551 have different circumferential positions so that the circumferential positions of the distal end cylindrical portion 55 are dispersed. Specifically, the plurality of through-holes 551 are arranged so that the circumferential angle θ between two through-holes 551 adjacent to each other in the circumferential direction is equal. In the example of FIG. 3, since the number of through holes 551 is four, θ = 90 degrees.

  In FIG. 3, a position where the connection end 31 of the ground electrode body 33 is connected is indicated by a dashed line. As can be seen, one of the four through holes 551 is formed at a circumferential position where the ground electrode 30 (ground electrode body 33) is connected to the metal shell 50.

  FIG. 4 is an enlarged view of the vicinity of the through hole 551 in FIG. The cross section of FIG. 4 can also be referred to as a cross section in which the through hole 551 is cut by a plane including the axis line CL and the center of the first opening OP1 on the outer peripheral surface side of the through hole 551. In the present embodiment, the cross section of FIG. 4 also includes the center of the second opening OP2. Each of the plurality of through holes 551 is a hole having a substantially cylindrical shape. The first opening OP1 on the outer peripheral surface side of the through hole 551 is shifted in the rear end direction BD with respect to the second opening OP2 on the inner peripheral surface side. For this reason, each of the plurality of through holes 551 is inclined with respect to both the direction of the axis line CL and the direction perpendicular to the axis line CL.

  When viewed from the first opening OP1 on the outer peripheral surface side of the through hole 551 toward the second opening OP2 on the inner peripheral surface side of the through hole 551, each of the plurality of through holes 551 is from the first opening OP1. It is formed so that the front end edge TP of the insulator 10 can be visually recognized. In the present embodiment, the tip edge TP is an outer edge of the tip surface 13 s of the leg portion 13 of the insulator 10.

  For example, in the cross section of FIG. 4, AR1 is a direction parallel to a line connecting the center of the first opening OP1 and the center of the second opening OP2. Among the straight line groups that are parallel to the direction AR1 and pass through the through hole 551 and do not pass through the wall portion of the front end cylindrical portion 55 where the through hole 551 is not formed, the straight line in the rear end direction BD is the most L11, A straight line on the tip direction LD side is L12. In the example of FIG. 4, the tip edge TP of the insulator 10 and the space TA on the tip side from the tip edge TP are included between the two straight lines L11 and L12. Therefore, in the example of FIG. 4, it can be seen that when the first opening OP1 of the through hole 551 is viewed along the direction AR1, the tip edge TP of the insulator 10 can be clearly recognized.

  Further, as shown in FIG. 4, each of the plurality of through holes 551 has the insulator 10 formed from the first opening OP1 when the first opening OP1 is viewed along the direction AR2 perpendicular to the axis CL. It is formed so that it cannot be seen.

  For example, in the cross section of FIG. 4, a straight line that is parallel to the direction AR2 and that passes through the rear end of the first opening OP1 is L21. A straight line that is parallel to the direction AR2 and passes through the tip of the first opening OP1 is defined as L22. In the example of FIG. 4, the straight line that is located between the two straight lines L21 and L22 and is parallel to the direction AR2 passes through the wall portion in which the through hole 551 is not formed in the distal end cylindrical portion 55. I understand that. Therefore, in the example of FIG. 4, it can be seen that when the first opening OP1 of the through hole 551 is viewed along the direction AR2, only the inner wall 551w of the through hole 551 is visible and the insulator 10 cannot be visually recognized.

  The spark plug 100 is provided with the tip tube portion 55 protruding into the combustion chamber, so that the ignition portion of the spark plug 100 (that is, the spark gap) can be obtained without excessively increasing the length of the ground electrode body 33. ) Can be projected into the combustion chamber. By projecting the ignition part into the combustion chamber and away from the inner wall surface IS of the head EH, it is possible to suppress the growth of the flame from being inhibited by the extinguishing action of the inner wall. Can be improved. If the length of the ground electrode main body 33 is excessively long, the length to the connection end 31 with the metal shell 50 that is the starting point of heat pulling of the ground electrode main body 33 becomes long, so that the heat pulling performance is deteriorated. Further, when the length of the ground electrode body 33 is excessively long, durability against vibration and impact is reduced. By providing the distal end cylindrical portion 55, such inconvenience can be suppressed.

  Also, a shock wave (pressure) higher than normal may be generated in the combustion chamber due to, for example, the occurrence of abnormal combustion. By providing the tip tube portion 55, it is possible to suppress such a shock wave during abnormal combustion from directly colliding with the leg portion 13 of the insulator 10, so that damage to the insulator 10 can be suppressed.

  On the other hand, the formation of the tip cylinder portion 55 makes it difficult for the intake gas sucked into the combustion chamber of the internal combustion engine to flow in the vicinity of the tip of the insulator 10 (tip of the leg portion 13). For example, the intake gas is suitable for cooling the insulator 10 because it has a lower temperature than the combustion gas. If the intake gas does not flow in the vicinity of the tip of the insulator 10, the heat generated in the igniting portion is accumulated, and the tip portion of the insulator 10 becomes excessively hot, which increases the possibility of causing so-called pre-ignition. The four through holes 551 formed in the distal end cylindrical portion 55 are provided to suppress such inconvenience and improve the pre-ignition resistance.

  According to the embodiment, as described above, when viewed from the first opening OP1 on the outer peripheral surface side of the through hole 551 of the distal end cylindrical portion 55 toward the second opening OP2 on the inner peripheral surface side of the through hole 551. In addition, the tip edge TP of the insulator 10 can be visually recognized. Therefore, the intake gas that has passed through the through hole 551 from the first opening OP1 side is directed toward the tip of the tip tube portion 55. For this reason, the intake gas in the combustion chamber passes through the through hole 551 of the tip cylinder portion 55 from the outer peripheral surface side and is blown toward the tip of the insulator 10. As a result, the tip of the insulator 10 can be efficiently cooled using the intake gas in the combustion chamber. Therefore, since the occurrence of pre-ignition due to excessive heating of the tip of the insulator 10 can be suppressed, the pre-ignition resistance performance of the spark plug 100 can be improved.

  Furthermore, according to the spark plug 100 of the above-described embodiment, the distal end tubular portion 55 has four through holes 551 having different circumferential positions. As a result, the tip of the insulator 10 can be efficiently cooled regardless of the circumferential position where the spark plug 100 is attached to the internal combustion engine.

  More specifically, the flow direction AR of the intake gas in the combustion chamber (FIG. 2) is, for example, the direction from the intake port (not shown) of the internal combustion engine to the exhaust port (not shown). In the distal end cylinder portion 55, the through hole 551 is directed from the first opening OP1 toward the axis CL so that the intake gas flowing along the flow direction AR efficiently passes through the through hole 551 from the first opening OP1 side. However, it is preferably formed at a position in the circumferential direction so as to be parallel to the flow direction AR. However, due to the relationship between the internal thread formed in the mounting hole PH of the head EH and the external thread formed in the threaded portion 52 of the spark plug 100, the circumferential position of the through hole 551 in the combustion chamber is not always constant. It does not always become. If the distal end cylinder portion 55 has four or more through holes 551 having different circumferential positions, at least one through hole 551 is preferably disposed in the combustion chamber in the preferred circumferential direction described above, or The possibility of being arranged at a position close to a preferred circumferential position is increased. As a result, as described above, the tip of the insulator 10 can be efficiently cooled.

  Furthermore, as described above, the through hole 551 is formed so that the insulator 10 cannot be seen from the first opening OP1 when the first opening OP1 is viewed from the direction AR2 perpendicular to the axis CL. For example, the through hole 551 is formed so that only the inner wall 551w of the through hole 551 can be seen from the first opening OP1 when the first opening OP1 is viewed from the direction AR2. As a result, it is possible to suppress a shock wave (pressure) generated by abnormal combustion of the internal combustion engine from directly hitting the insulator 10 through the through hole 551. Therefore, it is possible to prevent damage to the insulator 10 due to abnormal combustion of the internal combustion engine, in particular, damage to the leg portion 13 having a relatively thin thickness.

  Furthermore, in the spark plug 100 of the above embodiment, one through hole 551 is formed at a circumferential position where the ground electrode 30 is connected to the metal shell (FIG. 3). Intake gas from the circumferential position where the ground electrode 30 is connected toward the insulator 10 is likely to be hindered by the ground electrode 30 (particularly the ground electrode body 33). By providing the through hole 551 at a circumferential position to which the ground electrode 30 is connected, intake gas directed from the circumferential position to the insulator 10 can be guided to the insulator 10. As a result, the pre-ignition resistance can be improved more effectively.

B. Modification (1) In the through hole 551 of the above embodiment, the hole diameter from the first opening OP1 to the second opening OP2 is constant, so the area of the first opening OP1 and the area of the second opening OP2 are: Equal to each other. Instead, the area of the first opening OP1 may be larger than the area of the second opening OP2.

  FIG. 5 is an explanatory diagram of a metal shell 50b according to a modification. The metal shell 50b shown in FIG. 5 includes a tip cylinder portion 55b having a through hole 551b. The through hole 551b includes an equal diameter hole 553 on the inner peripheral surface side and an enlarged diameter hole 552 on the outer peripheral surface side. The equal diameter hole 553 has a constant diameter regardless of the position of the hole in the axial direction. The diameter-enlarged hole 552 is increased in diameter from the inner peripheral surface side (equal diameter hole 553 side) toward the outer peripheral surface side. For this reason, in the through hole 551b of FIG. 5, the area of the first opening OP1 is larger than the area of the second opening OP2.

  FIG. 6 is an explanatory view of a metal shell 50c according to a modification. The metal shell 50c shown in FIG. 6 includes a tip cylinder portion 55c having a through hole 551c. The through hole 551c includes a small equal diameter hole 555 on the inner peripheral surface side and a large equal diameter hole 554 on the outer peripheral surface side. The small-diameter hole 555 has a constant diameter regardless of the axial position of the hole. The large equal diameter hole 554 is constant regardless of the position of the hole in the axial direction, and has a diameter larger than the diameter of the small equal diameter hole 555. Therefore, in the through hole 551c of FIG. 6, the area of the first opening OP1 is larger than the area of the second opening OP2 as in the case of the through hole 551b of FIG.

  According to this modification, since the area of the first opening OP1 is larger than the area of the second opening OP2, the flow rate of the intake gas introduced from the first opening OP1 into the through holes 551b and 551c is increased. And the flow rate of the intake gas blown from the second opening OP2 to the tip of the insulator 10 can be increased. As a result, the tip of the insulator 10 can be cooled more efficiently.

  As can be seen from the straight lines L11 and L12 in FIGS. 5 and 6, the through holes 551b and 551c of the present modification are the first on the outer peripheral surface side of the through holes 551b and 551c, similarly to the through hole 551 of the embodiment. When viewed from the opening OP1 toward the second opening OP2 on the inner peripheral surface side of the through holes 551b and 551c, the tip edge TP of the insulator 10 is formed to be visible from the first opening OP1. Further, as can be seen from the straight lines L21 and L22 in FIGS. 5 and 6, the through holes 551b and 551c of the present modified example are arranged along the direction AR2 perpendicular to the axis CL in the same manner as the through hole 551 of the embodiment. When one opening OP1 is viewed, the insulator 10 is not visible from the first opening OP1, and only the inner walls 551wb and 551wc of the through holes 551b and 551c are visible.

(2) FIG. 7 is an explanatory view of the metallic shell 50d of this modification. The metal shell 50d in FIG. 7 includes a distal end cylinder portion 55d having a through hole 551c. Since the through-hole 551c in FIG. 7 is the same as the through-hole 551c in FIG. 6, the same reference numerals are given in FIG. The length in the axial direction of the tip tube portion 55d in FIG. 7 is longer than the tip tube portion 55c in FIG. For this reason, in the above embodiment and the modified examples of FIGS. 5 and 6, the distal ends 55s of the metal shells 50, 50b, and 50c are located on the rear end side (rear end direction BD side) from the front end 13s of the insulator 10. However, in this modification, the tip 55sd of the metal shell 50d in FIG. 7 is located on the tip side (tip direction LD side) from the tip 13s of the insulator 10. As a result, since the entire tip portion of the insulator 10 is surrounded by the tip tube portion 55d when viewed from the direction AR2 perpendicular to the axial direction, a shock wave (pressure) generated by abnormal combustion of the internal combustion engine is generated by the insulator 10. It is possible to effectively suppress direct hits. As a result, damage to the insulator 10 due to abnormal combustion of the internal combustion engine can be effectively prevented.

  7 has a through-hole 551c similar to that in FIG. 6, even though the entire distal end portion of the insulator 10 is surrounded by the front-end cylinder 55, the through-hole 551c. The tip of the insulator 10 can be effectively cooled by the intake gas passing through the. For this reason, pre-ignition resistance is not sacrificed.

(3) In the above embodiment, the number of through holes 551 is four, but is not limited thereto. The number of through holes 551 may be more than four, for example, five or six. Further, the number of through holes 551 may be less than four, for example, one, two, or three. When the number of the through holes 551 is plural, it is preferable that the circumferential positions are different from each other so that the circumferential positions of the distal end tubular portion 55 are dispersed as in the embodiment. . For example, when there are two, three, five, and six through holes 551, the circumferential angle θ between two through holes 551 that are adjacent to each other in the circumferential direction is 180 degrees. 120 degrees, 72 degrees, 60 degrees, or an angle close to these angles is preferable. Further, it is more preferable that at least one through hole 551 is formed at a circumferential position where the ground electrode 30 (ground electrode body 33) is connected.

(4) In the above embodiment, as shown in FIG. 4, when the first opening OP1 is viewed along the direction AR2 perpendicular to the axis CL, the through hole 551 can see the insulator 10 from the first opening OP1. However, the insulator 10 may be visible.

(5) In the above embodiment, as shown in FIG. 4, the through hole 551 is formed from the first opening OP1 along the direction AR1 parallel to the straight line between the center of the first opening OP1 and the center of the second opening OP2. When viewed toward the two openings OP2, the tip edge TP of the insulator 10 is formed so as to be visible from the first opening OP1. The through-hole 551 is not limited to the direction AR1, but when viewed along one of the arbitrary directions from the first opening OP1 to the second opening OP2, the tip of the insulator 10 from the first opening OP1. What is necessary is just to form so that the edge TP can be visually recognized.

(6) The shape of the through hole 551 in the above embodiment is not limited to this. For example, the through hole 551 may be, for example, a hole having a square tube shape with a triangular or quadrangular cross section.

(7) The specific configuration of the spark plug 100 of the above embodiment is an example, and other configurations may be employed. For example, various configurations can be adopted as the configuration of the ignition portion of the spark plug. For example, the spark plug may be a spark plug of a type in which the ground electrode and the center electrode 20 face each other in the direction perpendicular to the axis to form a gap. For example, the material of the insulator 10 and the material of the terminal fitting 40 are not limited to the above-described materials. For example, the insulator 10 is composed of other compounds (for example, AlN, ZrO ₂ , SiC, TiO ₂ , Y ₂ O _3, etc.) as the main component instead of ceramics whose main component is alumina (Al ₂ O ₃ ). It may be formed using ceramics.

As mentioned above, although embodiment and modification of this invention were described, this invention is not limited to these embodiment and modification at all, and implementation in a various aspect is possible within the range which does not deviate from the summary. It is.

  5 ... Gasket, 6 ... Packing, 6 ... Second packing, 7 ... Third packing, 8 ... First packing, 9 ... Talc, 10 ... Insulator, 12 ... shaft hole, 13 ... leg part, 13s ... tip surface, 15 ... reduced outer diameter part, 16 ... reduced inner diameter part, 17 ... first body part, 18 ... 2nd body part, 19 ... collar part, 20 ... center electrode, 23 ... head, 24 ... collar part, 25 ... leg part, 26 ... center electrode body, 28. ..Center electrode tip, 30 ... ground electrode, 31 ... connection end, 32 ... free end, 33 ... ground electrode body, 38 ... ground electrode tip, 40 ... terminal fitting, 41 ... Cap mounting part, 42 ... Bridge part, 43 ... Leg part, 50, 50b to 50d ... Metal fitting, 51 ... Tool engaging part, 52 ... Screw part, 53 ... caulking part, 54 ... seat part, 55, 55b to 55d ... tip tube part, 56 ... reduced inner diameter part, 58 ... deformation part, 59 ... insertion hole, 60. .. First conductive sealing layer, 70. .. Resistor, 80 ... second conductive sealing layer, 100 ... spark plug, 551, 551b, 551c ... through hole, OP1 ... first opening, OP2 ... second opening

Claims (7)

A central electrode extending in the direction of the axis;
An insulator having a shaft hole penetrating along the direction of the axis, and holding the center electrode in the shaft hole;
A metal shell that is disposed around a radial direction of the insulator and holds the insulator;
A ground electrode electrically connected to the metal shell and forming a gap with the center electrode;
With
The metal shell includes a tip tube portion that is exposed to a combustion chamber of the internal combustion engine when attached to the internal combustion engine,
The tip tube portion is an ignition plug that penetrates from the outer peripheral surface to the inner peripheral surface and has a through hole through which the gas sucked into the combustion chamber passes.
The front edge of the insulator is visible when viewed from the first opening on the outer peripheral surface side of the through hole toward the second opening on the inner peripheral surface side of the through hole. plug. The spark plug according to claim 1,
The spark plug according to claim 1, wherein an area of the first opening is larger than an area of the second opening. The spark plug according to claim 1 or 2,
The tip plug portion has four or more through holes having different circumferential positions from each other. The spark plug according to any one of claims 1 to 3,
The through-hole is formed so that the insulator cannot be seen from the first opening when the first opening is viewed along a direction perpendicular to the axis. The spark plug according to any one of claims 1 to 3,
The through-hole is formed so that only the inner wall of the through-hole can be seen from the first opening when the first opening is viewed from a direction perpendicular to the axis. The spark plug according to any one of claims 1 to 5,
The spark plug according to claim 1, wherein a front end of the metal shell is located closer to a front end side than a front end of the insulator. The spark plug according to any one of claims 1 to 6,
The spark plug is characterized in that the through hole is formed at least in a circumferential position where the ground electrode is connected to the metal shell.

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