WO2018181654A1 - Spark plug for internal combustion engine - Google Patents

Spark plug for internal combustion engine Download PDF

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Publication number
WO2018181654A1
WO2018181654A1 PCT/JP2018/013102 JP2018013102W WO2018181654A1 WO 2018181654 A1 WO2018181654 A1 WO 2018181654A1 JP 2018013102 W JP2018013102 W JP 2018013102W WO 2018181654 A1 WO2018181654 A1 WO 2018181654A1
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WO
WIPO (PCT)
Prior art keywords
plug
insulator
tip
axial direction
spark plug
Prior art date
Application number
PCT/JP2018/013102
Other languages
French (fr)
Japanese (ja)
Inventor
晋太郎 伊藤
田中　大介
明光 杉浦
亮太 若杉
香 土井
文明 青木
金千代 寺田
三輪　哲也
Original Assignee
株式会社デンソー
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from JP2018052539A external-priority patent/JP7022628B2/en
Application filed by 株式会社デンソー filed Critical 株式会社デンソー
Priority to CN201880021380.3A priority Critical patent/CN110462947B/en
Publication of WO2018181654A1 publication Critical patent/WO2018181654A1/en
Priority to US16/584,998 priority patent/US10886708B2/en

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01T—SPARK GAPS; OVERVOLTAGE ARRESTERS USING SPARK GAPS; SPARKING PLUGS; CORONA DEVICES; GENERATING IONS TO BE INTRODUCED INTO NON-ENCLOSED GASES
    • H01T13/00—Sparking plugs
    • H01T13/20—Sparking plugs characterised by features of the electrodes or insulation
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01T—SPARK GAPS; OVERVOLTAGE ARRESTERS USING SPARK GAPS; SPARKING PLUGS; CORONA DEVICES; GENERATING IONS TO BE INTRODUCED INTO NON-ENCLOSED GASES
    • H01T13/00—Sparking plugs
    • H01T13/20—Sparking plugs characterised by features of the electrodes or insulation
    • H01T13/32—Sparking plugs characterised by features of the electrodes or insulation characterised by features of the earthed electrode
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01T—SPARK GAPS; OVERVOLTAGE ARRESTERS USING SPARK GAPS; SPARKING PLUGS; CORONA DEVICES; GENERATING IONS TO BE INTRODUCED INTO NON-ENCLOSED GASES
    • H01T13/00—Sparking plugs
    • H01T13/52—Sparking plugs characterised by a discharge along a surface

Definitions

  • the present invention relates to a spark plug for an internal combustion engine.
  • Patent Document 1 there is a spark plug for an internal combustion engine that generates a discharge between a ground electrode and a center electrode by applying a high frequency voltage to the center electrode. Such a spark plug generates a creeping spark discharge that hits the surface of the insulator between the center electrode and the ground electrode.
  • an insulator is disposed inside a cylindrical ground electrode, and a center electrode is disposed further inside the insulator.
  • the insulator is arranged so that its tip protrudes toward the tip of the ground electrode.
  • the center electrode is arrange
  • the present invention has been made in view of such problems, and an object of the present invention is to provide a spark plug for an internal combustion engine that can improve the ignitability of an air-fuel mixture.
  • a first aspect of the present invention is a cylindrical ground electrode, and a cylindrical shape that is disposed inside the ground electrode and has an insulator protrusion that protrudes toward the tip end side in the plug axial direction from the tip end of the ground electrode. And a center electrode that is held inside the insulator and has an exposed portion exposed from a tip of the insulator protrusion, and the exposed portion of the center electrode includes the insulator protrusion.
  • a first part covering from the distal end side in the plug axial direction, and extending from the first part to the proximal end side in the plug axial direction, and the entire circumference of the outer peripheral surface of the lever projecting portion from the outer peripheral side in the plug radial direction A spark plug for an internal combustion engine having a second portion to cover.
  • the second aspect of the present invention includes a cylindrical ground electrode, and an insulator projecting portion that is disposed on the inner side of the ground electrode and projects further toward the distal end side in the plug axial direction than the distal end of the ground electrode.
  • the exposed portion of the center electrode has the first part and the second part. That is, the corner
  • the entire area between the exposed portion of the center electrode covering the entire periphery of the tip of the insulator protrusion and the ground electrode covering the entire periphery of the insulator protrusion is an area where discharge can be formed. For this reason, creeping discharge is repeatedly formed in a specific path on the surface of the insulator protrusion, so that so-called channeling in which the insulator surface is cut into a groove shape can be prevented from being concentrated in the specific path.
  • a part of the corner of the tip of the insulator protrusion is covered with the first part and the second part of the center electrode. Therefore, in this embodiment as well, discharge does not occur on the corner of the tip of the insulator protrusion, and is formed between the second portion of the center electrode and the ground electrode. As a result, the discharge is easily peeled off from the surface of the insulator projecting portion by the air flow or the electric repulsion of the air-fuel mixture in the combustion chamber, and is easily stretched downstream. Thereby, the ignitability to the air-fuel mixture can be improved.
  • the region where at least the second portion in the plug circumferential direction of the insulator projecting portion is formed is directed toward the distal end side in the plug shaft direction in the entire plug shaft direction.
  • the outer shape has a stepped shape that gradually decreases in outer diameter. Therefore, the path along the surface of the insulator protrusion from the second part to the ground electrode can be lengthened. Thereby, the distance of creeping discharge can be ensured without extending the insulator protrusion in the plug axis direction, and the ignitability can be improved.
  • FIG. 3 is an enlarged cross-sectional view around the tip of the spark plug according to the first embodiment.
  • FIG. 3 is an enlarged side view of the periphery of the spark plug in the first embodiment.
  • FIG. 5 is a diagram showing only the center electrode in the cross-sectional view taken along the line VV in FIG. 3.
  • FIG. 3 is an explanatory diagram showing an initial discharge spark in the enlarged cross-sectional view around the tip of the spark plug according to the first embodiment.
  • FIG. 3 is an explanatory view showing a state in which the discharge spark is pushed by the airflow and separated from the surface of the insulator exposure portion in the enlarged cross-sectional view around the tip portion of the spark plug in the first embodiment.
  • FIG. 3 is an explanatory view showing a state in which an electric discharge spark is pushed and stretched greatly in an enlarged cross-sectional view around the tip of a spark plug in the first embodiment.
  • Explanatory drawing which shows the state by which the discharge spark was pushed by the airflow in the expanded sectional view of the front-end
  • FIG. 4 is an enlarged cross-sectional view around the tip of a spark plug in Embodiment 2.
  • FIG. 5 is an enlarged cross-sectional view around the tip of a spark plug in Embodiment 3.
  • FIG. 6 is an enlarged cross-sectional view around the tip of a spark plug in Embodiment 4.
  • FIG. FIG. 9 is an explanatory diagram showing an initial discharge spark in an enlarged cross-sectional view around the tip of a spark plug according to a fourth embodiment.
  • FIG. 9 is an explanatory view showing a state in which an electric discharge spark is pushed and stretched greatly by an air current in an enlarged cross-sectional view around the tip of a spark plug in Embodiment 4.
  • FIG. 6 is an enlarged cross-sectional view around the tip of a spark plug in Embodiment 5.
  • FIG. 6 is an enlarged side view of the vicinity of a tip portion of a spark plug in Embodiment 5.
  • FIG. 9 is an explanatory diagram showing an initial discharge spark in an enlarged cross-sectional view around the tip of a spark plug in Embodiment 5.
  • FIG. 9 is an explanatory view showing a state in which an electric discharge spark is greatly stretched by being pushed by an air flow in an enlarged cross-sectional view around the tip of a spark plug in Embodiment 5.
  • FIG. 7 is an enlarged cross-sectional view around the tip of a spark plug in Embodiment 6.
  • FIG. 9 is an enlarged cross-sectional view of the vicinity of a tip portion of a spark plug in Embodiment 7.
  • FIG. 9 is an enlarged cross-sectional view of the vicinity of a tip portion of a spark plug in Embodiment 8.
  • FIG. 10 is an enlarged side view of the vicinity of a tip portion of a spark plug in Embodiment 8.
  • FIG. 10 is an explanatory diagram showing an initial discharge spark in an enlarged cross-sectional view around the tip of a spark plug in Embodiment 8.
  • FIG. 10 is an enlarged cross-sectional view around the tip of a spark plug in Embodiment 9.
  • FIG. 11 is an enlarged cross-sectional view around the tip of a spark plug in Embodiment 10.
  • FIG. 12 is an enlarged cross-sectional view of the periphery of a spark plug tip according to an eleventh embodiment.
  • FIG. 14 is an enlarged cross-sectional view around the tip of a spark plug according to a twelfth embodiment.
  • FIG. 14 is an enlarged cross-sectional view around the tip of a spark plug in Embodiment 13.
  • FIG. The expanded front view of the front-end
  • FIG. The figure which looked at the center electrode, the insulator, and the ground electrode in Embodiment 13 from the front end side of the plug axial direction.
  • FIG. 16 is an enlarged cross-sectional view around the tip of a spark plug in Embodiment 14.
  • FIG. 16 is an enlarged cross-sectional view around the distal end portion of a spark plug, showing a modification of the fourteenth embodiment.
  • FIG. 16 is an enlarged cross-sectional view around the tip of a spark plug in Embodiment 15.
  • FIG. 18 is an enlarged cross-sectional view around the tip of a spark plug in Embodiment 16.
  • FIG. 17 is an enlarged front view of the vicinity of a tip portion of a spark plug in Embodiment 16. The figure which looked at the center electrode, the insulator, and the ground electrode in Embodiment 16 from the front end side of the plug axial direction.
  • FIG. 18 is an enlarged cross-sectional view around the distal end portion of a spark plug in Embodiment 17.
  • a spark plug 1 for an internal combustion engine includes a cylindrical ground electrode 2, a cylindrical insulator 3 disposed inside the ground electrode 2, and an inner side of the insulator 3. And a held center electrode 4.
  • the insulator 3 has an insulator protrusion 31 that protrudes toward the tip end side in the plug axial direction Z from the ground electrode 2.
  • the center electrode 4 has an exposed portion 41 exposed from the tip of the insulator protruding portion 31.
  • the plug axis direction Z means the direction in which the central axis of the spark plug 1 extends. Further, in FIG. 1, a part of the center electrode 4 is shown in a sectional view and the other part in a front view.
  • the exposed portion 41 of the center electrode 4 has a first part 411 and a second part 412.
  • the first part 411 covers the insulator protrusion 31 from the distal end side in the plug axial direction Z.
  • the second part 412 extends from the first part 411 to the proximal end side in the plug axial direction Z and covers the entire outer periphery 31b of the lever protrusion 31 from the outer peripheral side in the plug radial direction.
  • the plug radial direction means the radial direction of the spark plug 1.
  • the term “plug circumferential direction” refers to the circumferential direction of the spark plug 1
  • the term “plug central axis” refers to the central axis of the spark plug 1.
  • the spark plug 1 of the present embodiment can be used as ignition means in an internal combustion engine for a vehicle such as an automobile.
  • the spark plug 1 for an internal combustion engine is configured to generate a discharge between the ground electrode 2 and the center electrode 4 by applying a high voltage to the center electrode 4.
  • the spark plug 1 is connected to a high-voltage power supply unit (not shown) on one end side in the plug axial direction Z, and is disposed on the other end side in the combustion chamber of the internal combustion engine.
  • the high voltage power supply unit can be, for example, a general ignition coil, a power supply for an ignition device capable of continuously controlling discharge, or a high frequency power supply capable of applying a high frequency voltage of 200 kHz to 5 MHz to the center electrode 4. .
  • the side on which the spark plug 1 is inserted into the combustion chamber is referred to as the distal end side, and the opposite side is referred to as the proximal end side.
  • the ground electrode 2 has a cylindrical shape.
  • the ground electrode 2 is formed so as to surround the insulator 3 from the entire circumference.
  • the front end surface 21 of the ground electrode 2 has an annular shape.
  • the tip surface 21 is orthogonal to the plug axial direction Z.
  • the tip surface 21 of the ground electrode 2 is entirely formed on a plane perpendicular to the plug axis direction Z.
  • the angle between the front end surface 21 of the ground electrode 2 and the inner peripheral surface is a right angle.
  • the insulator 3 has a through hole 30 penetrating in the plug axial direction Z.
  • the insulator 3 has an annular shape in cross section perpendicular to the plug axial direction Z.
  • the insulator 3 protrudes from the distal end surface 21 of the ground electrode 2 toward the distal end side while part of the insulator 3 is disposed inside the ground electrode 2.
  • the outer peripheral surface of the insulator 3 is opposed to the inner peripheral surface of the ground electrode 2 in the plug radial direction through a minute gap. Note that the minute gap may not be formed. That is, the outer peripheral surface of the insulator 3 and the inner peripheral surface of the ground electrode 2 may be in contact with each other.
  • the outer peripheral surface 31b of the insulator protrusion 31 is inclined so as to go to the inner peripheral side in the plug radial direction as it goes to the tip end side in the plug axial direction Z.
  • the outer peripheral surface 31 b of the insulator protrusion 31 has a linear shape in which the cross-sectional shape parallel to the plug axis direction Z is inclined toward the inner peripheral side in the plug radial direction toward the distal end side. Accordingly, the outer peripheral surface of the insulator exposed portion 310 exposed from both the center electrode 4 and the ground electrode 2 in the insulator protruding portion 31 is also directed toward the inner peripheral side in the plug radial direction toward the tip end side in the plug axial direction Z.
  • the outer peripheral surface of the insulator exposed portion 310 also has a linear shape in which a cross-sectional shape parallel to the plug axial direction Z is inclined toward the inner peripheral side in the plug radial direction toward the distal end side.
  • the insulator exposed portion 310 is located on the distal end surface 21 of the ground electrode 2 in the plug axial direction Z in the insulator protruding portion 31 and on the proximal end side in the plug axial direction Z in the second portion 412 of the center electrode 4. It is a site
  • the tip surface 31a of the insulator protrusion 31 is formed so as to be orthogonal to the plug axis direction Z.
  • the angle of the corner between the distal end surface 31a and the outer peripheral surface 31b of the insulator protrusion 31 is an obtuse angle.
  • the corner between the distal end surface 31 a and the outer peripheral surface 31 b of the lever protrusion 31 is located on the distal end side in the plug axial direction Z with respect to the end surface 412 a of the second portion 412.
  • the corner between the tip surface 31 a and the outer peripheral surface 31 b of the insulator protrusion 31 is not a part of the insulator exposure part 310. That is, the corner between the distal end surface 31 a and the outer peripheral surface 31 b of the insulator protrusion 31 is covered with the first portion 411 and the second portion 412 of the center electrode 4 and is not exposed from the center electrode 4.
  • the center electrode 4 is inserted and held at the tip of the through hole 30 of the insulator 3.
  • the center electrode 4 has a substantially cylindrical shape as a whole.
  • the exposed portion 41 of the center electrode 4 has a cup shape that opens toward the base end side in the plug axial direction Z as a whole.
  • the exposed portion 41 has a first portion 411 formed in a disc shape, and as shown in FIG. 2, the exposed portion 41 extends from the outer edge portion of the first portion 411 toward the proximal end side, and is cylindrical as a whole.
  • a second portion 412 formed in a shape.
  • the first portion 411 is opposed to the entire distal end surface 31 a of the lever protrusion 31 in the plug axial direction Z.
  • the second part 412 covers the entire circumference of the outer peripheral surface 31 b of the insulator protrusion 31 from the outer periphery side of the insulator protrusion 31.
  • the exposed portion 41 covers the entire corner portion of the distal end portion of the insulator protruding portion 31.
  • a radial gap rc is formed between the outer peripheral surface 31b of the insulator protrusion 31 and the inner peripheral surface 412b of the second portion 412. That is, the inner peripheral surface 412b of the second portion 412 is formed at a position away from the outer peripheral surface 31b of the insulator protrusion 31 toward the outer peripheral side in the plug radial direction.
  • the radial gap rc is open toward the base end side in the plug axial direction Z.
  • the radial gap rc may not be formed. That is, the inner peripheral surface 412 b of the second part 412 may be in contact with the outer peripheral surface 31 b of the lever protrusion 31.
  • the end surface 412a on the proximal end side in the plug axial direction Z in the second portion 412 has an annular shape. Further, the end surface 412 a on the proximal end side in the plug axial direction Z in the second portion 412 is orthogonal to the plug axial direction Z. As shown in FIG. 2, the spatial distance between the second portion 412 of the center electrode 4 and the ground electrode 2 is constant over the entire circumference. That is, the spatial distance between the center electrode 4 and the ground electrode 2 is substantially constant in any cross section that passes through both the center electrode 4 and the ground electrode 2 and is parallel to the plug axis direction Z. Further, the end surface 412a of the second part 412 and the tip surface 21 of the ground electrode 2 are directly opposed to each other, and the insulator 3 is not interposed therebetween.
  • the diameter of the distal end surface 31a of the insulator protrusion 31 is the diameter A [mm]
  • the inner diameter of the end surface 412a on the proximal end side of the second portion 412 is the inner diameter B [mm]
  • the outer diameter of the end surface 412a is the outer diameter.
  • the shortest spatial distance between the diameter C [mm] and the ground electrode 2 and the center electrode 4 is defined as a spatial distance D [mm].
  • the diameter A, the inner diameter B, and the outer diameter C satisfy the relationship of A ⁇ B ⁇ C.
  • the diameter A and the inner diameter B preferably satisfy A + 0.25 mm ⁇ B.
  • the inner diameter B and outer diameter C preferably satisfy B + 1.0 mm ⁇ C.
  • the spatial distance D preferably satisfies 3.0 mm ⁇ D ⁇ 5.0 mm.
  • the diameter A is 4.55 mm
  • the inner diameter B is 5.55 mm
  • the outer diameter C is 6.5 mm
  • the spatial distance D is 5.0 mm.
  • the length of the second portion 412 in the plug axial direction Z is 1.0 mm.
  • the exposed portion 41 may be formed separately from the inner portion of the insulator protrusion 31 in the center electrode 4 or may be formed integrally.
  • the ground electrode 2 extends from the tip of the housing 11 toward the tip.
  • the housing 11 has a cylindrical shape and holds the insulator 3 inside.
  • a mounting screw portion 111 is formed on the outer peripheral surface of the housing 11 to be screwed into the internal combustion engine.
  • the ground electrode 2 is joined to the tip of the portion of the housing 11 where the mounting screw portion 111 is provided.
  • a resistor 13 is disposed on the proximal end side of the center electrode 4 in the through hole 30 of the insulator 3 through a glass seal 12 having conductivity.
  • the resistor 13 can be formed by heat sealing a resistor composition including a resistor material such as carbon or ceramic powder and glass powder, or by inserting a cartridge type resistor.
  • the glass seal 12 is made of copper glass obtained by mixing copper powder into glass.
  • a stem 15 is disposed on the proximal end side of the resistor 13 via a glass seal 14 made of copper glass.
  • the stem 15 is made of, for example, an iron alloy.
  • the base end portion of the stem 15 protrudes from the insulator 3.
  • the spark plug 1 is connected to the high voltage power source at the protruding portion of the stem 15.
  • the exposed portion 41 of the center electrode 4 has a first part 411 and a second part 412. That is, the corner of the tip of the insulator protrusion 31 is covered with the first part 411 and the second part 412 of the center electrode 4. Therefore, it is possible to prevent the discharge from being generated, maintained and fixed on the corner of the tip of the insulator protrusion 31. As a result, the discharge is easily peeled off from the surface of the insulator projecting portion by the air flow or the electric repulsion of the air-fuel mixture in the combustion chamber, and is easily stretched downstream. Thereby, the ignitability to the air-fuel mixture can be improved.
  • channeling can be prevented from occurring at the corner of the tip of the insulator protrusion 31.
  • the entire area between the exposed portion of the center electrode covering the entire periphery of the tip of the insulator protrusion and the ground electrode covering the entire periphery of the insulator protrusion is an area where discharge can be formed. For this reason, creeping discharge is repeatedly formed in a specific path on the surface of the insulator protrusion, so that so-called channeling in which the insulator surface is cut into a groove shape can be prevented from being concentrated in the specific path.
  • the end face 412a on the proximal end side in the plug axis direction Z in the second portion 412 is orthogonal to the plug axis direction Z.
  • the front end surface 21 of the ground electrode 2 is also orthogonal to the plug axial direction Z. Therefore, the discharge generated between the center electrode 4 and the ground electrode 2 due to the airflow in the combustion chamber of the internal combustion engine to which the spark plug 1 is attached is separated from the surface of the insulator exposed portion 310 and on the downstream side of the airflow. Easy to stretch greatly. This will be described later.
  • the discharge starts from the inner peripheral end of the end surface 412 a on the proximal end side in the plug axis direction Z in the second portion 412 and the inner peripheral end of the distal end surface 21 of the ground electrode 2.
  • both starting points of the discharge spark S are pushed by the air flow F flowing in the direction orthogonal to the plug axis direction Z in the combustion chamber of the internal combustion engine to which the spark plug 1 is attached. It moves on the end surface 412a of the two parts 412 and the tip surface 21 of the ground electrode 2 toward the outer peripheral side in the plug radial direction. That is, the starting point S1 of the discharge spark S on the center electrode 4 side moves from the inner peripheral end of the end surface 412a of the second part 412 toward the outer peripheral end, and the starting point S2 of the discharge spark S on the ground electrode 2 side is The ground electrode 2 moves from the inner peripheral end of the front end surface 21 toward the outer peripheral end. Thereby, both starting points of the discharge spark S move in a direction away from the insulator exposure part 310 in the plug radial direction.
  • the portion between the both starting points of the discharge spark S is also exposed to the insulator exposing portion as shown in FIGS. It leaves
  • separated from the outer peripheral surface of the insulator exposure part 310 to the outer peripheral side is largely extended toward the downstream of the said air flow F by the air flow F in a combustion chamber. It is.
  • the contact area of the discharge spark S and the air-fuel mixture is gained, and it is easy to ensure the ignitability of the air-fuel mixture. Further, since the ignition point of the air-fuel mixture moves away from the spark plug 1, it is possible to suppress a cooling loss due to the heat of the initially formed flame, the so-called initial flame being taken away by the spark plug 1.
  • the spark plug 9 has a cylindrical center electrode protrusion 941 that protrudes toward the distal end side of the insulator protrusion 31.
  • the center electrode protrusion 941 has a cylindrical shape. When viewed from the plug axial direction Z, the center electrode protrusion 941 is accommodated inside the through hole 30 of the insulator 3.
  • the outer peripheral surface 941 b of the center electrode protruding portion 941 is formed in the plug axis direction Z.
  • tip of the insulator protrusion part 31 of the insulator 3 is formed in the gentle curved surface shape.
  • the starting point S2 of the discharge spark S on the ground electrode 2 side is an air flow F flowing in a direction orthogonal to the plug axial direction Z in the combustion chamber of the internal combustion engine to which the spark plug 9 is attached.
  • the starting point S1 of the discharge spark S on the center electrode 4 side hardly moves from the initial position. That is, the starting point S ⁇ b> 1 on the side of the center electrode 4 of the discharge spark S does not move in a direction away from the surface of the insulator protrusion 31. This is because the outer peripheral surface 941b of the center electrode projecting portion 941 is formed in the plug axis direction Z, so that the starting point S1 of the discharge spark S on the side of the center electrode 4 is on the outer peripheral surface 941b of the center electrode projecting portion 941. This is because it cannot move to the outer peripheral side in the direction.
  • the portion between the two starting points of the discharge spark S is difficult to be separated from the top corner 319 of the insulator protrusion 31. Accordingly, even if the discharge spark S is pushed by the airflow F, the portion between the two starting points is not easily stretched to the downstream side. For this reason, the spark plug 9 is less ignitable to the air-fuel mixture in the combustion chamber than the spark plug 1 of the present embodiment.
  • the spatial distance between the second portion 412 of the center electrode 4 of the spark plug 1 and the ground electrode 2 is constant over the entire circumference. Therefore, it is possible to prevent the discharge generated between the second portion 412 of the center electrode 4 and the ground electrode 2 from being concentrated at a position biased in the plug circumferential direction. Therefore, in the insulator 3, it is possible to prevent the consumption of the insulator 3 from being promoted due to channeling being concentrated at positions offset in the plug circumferential direction.
  • a radial gap rc is formed between the outer peripheral surface 31b of the insulator protrusion 31 and the inner peripheral surface 412b of the second portion 412 of the center electrode 4 in the plug radial direction. Therefore, the airflow in the combustion chamber also flows into the radial gap rc. Then, the airflow that has flowed into the radial gap rc flows out between the center electrode 4 and the ground electrode 2 toward the outside in the plug radial direction, that is, toward the side away from the insulator exposed portion 310. . Therefore, it is easy to stretch the discharge spark away from the insulator exposed portion 310.
  • the present embodiment is an embodiment in which an axial gap ac is formed between the first portion 411 in the plug axial direction Z and the insulator protrusion 31.
  • the distal end surface 31 a of the lever protrusion 31 is formed at a position away from the proximal end surface 411 a in the plug axial direction Z in the first portion 411 toward the proximal end side.
  • the distal end surface 31 a of the lever protrusion 31 is located on the distal end side in the plug axial direction Z with respect to the end surface 412 a on the proximal end side in the plug axial direction Z in the second portion 412.
  • FIG. The axial gap ac communicates with the radial gap rc.
  • the diameter A is 4.55 mm
  • the inner diameter B is 4.85 mm
  • the outer diameter C is 5.85 mm
  • the spatial distance D is 5.0 mm.
  • the airflow in the combustion chamber also flows into the axial gap ac and the radial gap rc.
  • the airflow that has flowed into the axial gap ac and the radial gap rc is directed outward in the radial direction of the plug between the center electrode 4 and the ground electrode 2, that is, toward the side away from the insulator exposed portion 310. It will be leaked. Therefore, it is easy to stretch the discharge spark away from the insulator exposed portion 310.
  • the thermal stress generated in the insulator 3 and the center electrode 4 due to the difference between the linear expansion coefficient of the insulator 3 and the linear expansion coefficient of the center electrode 4 can be reduced.
  • the same effects as those of the first embodiment are obtained.
  • the shapes of the end surface 411a on the proximal end side in the plug axial direction Z in the first portion 411 and the inner peripheral surface 412b of the second portion 412 are changed with respect to the second embodiment.
  • the radius of curvature of the curved surface between the end surface 411a of the first part 411 and the inner peripheral surface 412b of the second part 412 is 0.5 mm. Others are the same as in the second embodiment.
  • the airflow flowing into the axial gap ac and the radial gap rc can be smoothly sent out between the center electrode 4 and the ground electrode 2. Therefore, the airflow flowing out from the axial gap ac and the radial gap rc is less likely to be disturbed, and the discharge spark is more easily stretched. In addition, the same effects as those of the second embodiment are obtained.
  • the present embodiment is an embodiment in which the shape of the exposed portion 41 is changed with respect to the first embodiment.
  • the outer peripheral surface 41b of the exposed portion 41 has a portion that is inclined toward the outer peripheral side in the plug radial direction toward the distal end side in the plug axial direction Z.
  • the entire outer peripheral surface 41b of the exposed portion 41 is inclined toward the outer peripheral side in the plug radial direction toward the tip end side in the plug axial direction Z. That is, the outer shape of the exposed portion 41 is reduced in diameter toward the proximal end side in the plug axial direction Z.
  • FIG. 13 it is the angle of the corner
  • FIG. 13 the length of the outer peripheral surface 41b of the exposed portion 41 in the plug axial direction Z is 2.0 mm.
  • the lengths of the diameter A, the inner diameter B, the outer diameter C, and the spatial distance D are the same as those in the second embodiment. Others are the same as in the first embodiment.
  • the discharge generated between the center electrode 4 and the ground electrode 2 due to the airflow in the combustion chamber of the internal combustion engine to which the spark plug 1 is attached is separated from the surface of the insulator exposed portion 310, and the airflow It is easy to stretch greatly downstream. This will be described later with reference to FIGS.
  • the starting point S ⁇ b> 1 of the discharge spark S on the side of the central electrode 4 is generated at the corner of the end portion on the proximal end side in the plug axis direction Z in the second portion 412. 16 and 17, the starting point S1 of the discharge spark S on the central electrode 4 side is pushed by the air flow F flowing in the direction perpendicular to the plug axis direction Z in the combustion chamber, and the outer peripheral surface 41b of the exposed portion 41 It moves upward toward the tip end side in the plug axial direction Z and the outer peripheral side in the plug radial direction.
  • the starting point S2 on the ground electrode 2 side of the discharge spark S moves on the distal end surface 21 of the ground electrode 2 toward the outer peripheral side in the plug radial direction, as in the first embodiment.
  • both starting points of the discharge spark S move in a direction away from the insulator exposed portion 310 in the plug radial direction, and the distance between both starting points of the discharge spark S moves in the plug axis direction Z.
  • both starting points of the discharge spark S move in the direction away from the insulator exposed portion 310 in the plug radial direction, the portion between both starting points of the discharge spark S also moves away from the outer peripheral surface of the insulator exposed portion 310 to the outer peripheral side.
  • separated from the outer peripheral surface of the insulator exposure part 310 to the outer peripheral side is largely extended toward the downstream of the said air flow F by the air flow F in a combustion chamber.
  • the region between both starting points of the discharge spark S is: Easier to stretch. Thereby, it is easier to earn a contact area between the discharge spark S and the air-fuel mixture, and it is easier to ensure the ignitability of the air-fuel mixture.
  • the same effects as those of the first embodiment are obtained.
  • the present embodiment is an embodiment in which the shape of the ground electrode 2 is changed with respect to the first embodiment.
  • the distal end surface 21 of the ground electrode 2 has a portion that is inclined toward the proximal end side in the plug axial direction Z toward the outer peripheral side in the plug radial direction.
  • the entire distal end surface 21 of the ground electrode 2 is inclined so as to be directed toward the base end side in the plug axial direction Z toward the outer peripheral side in the plug radial direction.
  • the angle of the corner between the tip surface 21 of the ground electrode 2 and the inner peripheral surface is an acute angle.
  • the lengths of the diameter A, the inner diameter B, the outer diameter C, and the spatial distance D are the same as those in the second embodiment. Others are the same as in the first embodiment.
  • the discharge generated between the center electrode 4 and the ground electrode 2 due to the airflow in the combustion chamber of the internal combustion engine to which the spark plug 1 is attached is separated from the surface of the insulator exposed portion 310, and the airflow It is easy to stretch greatly downstream. This will be described later with reference to FIGS.
  • the starting point S2 of the discharge spark S on the ground electrode 2 side is generated starting from the corner of the inner peripheral end of the tip surface 21 of the ground electrode 2.
  • the starting point S ⁇ b> 2 of the discharge spark S on the ground electrode 2 side is pushed by the air flow F flowing in the direction perpendicular to the plug axis direction Z in the combustion chamber, and the tip surface 21 of the ground electrode 2. It moves upward toward the base end side in the plug axial direction Z and the outer peripheral side in the plug radial direction.
  • the starting point S1 of the discharge spark S on the side of the center electrode 4 is the same as in the first embodiment, on the end surface 412a on the proximal end side in the plug axial direction Z in the second portion 412 on the outer peripheral side in the plug radial direction. Move towards. Thereby, both starting points of the discharge spark S move in a direction away from the insulator exposed portion 310 in the plug radial direction, and the distance between the both starting points of the discharge spark S moves in the plug axial direction Z.
  • both starting points of the discharge spark S move in the direction away from the insulator exposed portion 310 in the plug radial direction, the portion between both starting points of the discharge spark S also moves away from the outer peripheral surface of the insulator exposed portion to the outer peripheral side.
  • separated from the outer peripheral surface of the insulator exposure part 310 to the outer peripheral side is largely extended toward the downstream of the said airflow by the airflow in a combustion chamber.
  • the region between both starting points of the discharge spark S is: Easier to stretch. Thereby, it is easier to earn a contact area between the discharge spark S and the air-fuel mixture, and it is easier to ensure the ignitability of the air-fuel mixture.
  • the same effects as those of the first embodiment are obtained.
  • the present embodiment is an embodiment in which a vent hole 40 penetrating the inside and outside of the exposed portion 41 is formed in the exposed portion 41.
  • One end of the vent hole 40 opens toward the radial gap rc.
  • the vent hole 40 is formed in the second portion 412 of the center electrode 4.
  • the vent hole 40 is formed so as to penetrate the second portion 412 in the plug radial direction.
  • the other end of the vent hole 40 opens toward the outer peripheral side of the outer peripheral surface 41 b of the exposed portion 41.
  • a plurality of, specifically four, air holes 40 are formed.
  • the four vent holes 40 are arranged at equal intervals in the plug circumferential direction. That is, the four vent holes 40 are formed at four intervals in the circumferential direction of the plug at 90 ° intervals.
  • the outer position of the vent hole 40 when viewed from the plug axial direction Z is indicated by a broken line.
  • the outer peripheral surface 41b of the exposed portion 41 has a shape that is recessed toward the inner peripheral side. Specifically, the outer peripheral surface 41b of the exposed portion 41 is recessed toward the outer peripheral side in the plug radial direction as the distance from the vent hole 40 in the plug axial direction Z increases. That is, the outer peripheral surface 41b of the exposed portion 41 has the smallest diameter at the portion where the vent hole 40 is formed.
  • the lengths of the diameter A, the inner diameter B, the outer diameter C, and the spatial distance D are the same as those in the second embodiment. Others are the same as in the first embodiment.
  • an air flow is easily generated between the center electrode 4 and the ground electrode 2 toward the outside in the plug radial direction, that is, the side away from the surface of the insulator exposed portion 310. That is, in the present embodiment, a part of the airflow in the combustion chamber is first introduced into the radial gap rc from the outside of the spark plug 1 through the vent hole 40. Then, the airflow flowing into the radial gap rc flows out between the center electrode 4 and the ground electrode 2 toward the outer peripheral side in the plug radial direction, that is, toward the side away from the insulator exposed portion 310. . Therefore, it is easier to extend the discharge spark. In addition, the same effects as those of the first embodiment are obtained.
  • the vent hole 40 is formed in the first portion 411 of the center electrode 4. As shown in FIG. 26, the vent hole 40 is formed so as to penetrate the first portion 411 in the plug axial direction Z. One end of the vent hole 40 opens toward a space between the outer peripheral surface 31 b of the insulator protrusion 31 and the inner peripheral surface 412 b of the second portion 412 of the exposed portion 41 of the center electrode 4. The other end of the vent hole 40 opens toward the tip side in the plug axial direction Z at the first portion 411.
  • a plurality of, specifically four, air holes 40 are formed.
  • the four vent holes 40 are arranged at equal intervals in the plug circumferential direction. That is, the four vent holes 40 are formed at four intervals in the circumferential direction of the plug at 90 ° intervals.
  • the end surface 41a on the distal end side in the plug axis direction Z of the exposed portion 41 is formed in an uneven shape.
  • the end surface 41a of the exposed portion 41 is formed in a concavo-convex shape so as to protrude toward the distal end side in the plug axial direction Z as the distance from the vent hole 40 increases in the plug radial direction.
  • the end surface 41a of the exposed portion 41 is recessed so that the portion where the vent hole 40 is formed is located closest to the base end side in the plug axial direction Z. Others are the same as in the sixth embodiment.
  • This embodiment also has the same function and effect as the sixth embodiment.
  • the present embodiment is an embodiment in which the shape of the insulator protrusion 31 is changed from that of the first embodiment.
  • the insulator protrusion 31 has an insulator step 312 whose tip end side in the plug axial direction Z has a smaller diameter than the base end side. Further, the insulator projecting portion 31 as a whole has a step shape in which the outer diameter gradually decreases toward the tip end side in the plug axial direction Z. Along with this, the insulator exposed portion 310 also has a stepped shape whose outer diameter gradually decreases toward the tip end side in the plug axial direction Z as a whole.
  • the insulator protrusion 31 has an insulator large-diameter portion 311 formed on the proximal end side in the plug axial direction Z, an insulator small-diameter portion 313 formed on the distal end side thereof, and an insulator step portion 312 connecting them.
  • the outer diameter of the insulator small diameter portion 313 is smaller than the outer diameter of the insulator large diameter portion 311.
  • the insulator step portion 312 is formed at the center of the insulator exposure portion 310 in the insulator protrusion 31 in the plug axial direction Z.
  • the insulator small diameter portion 313, the insulator step portion 312 and the insulator large diameter portion 311 are connected in a smooth curved shape. That is, the boundary between the small insulator diameter portion 313 and the insulator step portion 312 and the boundary between the insulator step portion 312 and the insulator large diameter portion 311 on the outer peripheral surface of the insulator exposed portion 310 are not sharp corners.
  • the insulator step portion 312 is formed at one place in the plug axial direction Z. That is, the insulator protrusion 31 in the present embodiment has a single step shape.
  • the insulator step portion 312 is located farther from the base end side than the end surface 412a on the base end side in the plug axis direction Z in the second portion 412 of the center electrode 4.
  • the second portion 412 is formed along the outer peripheral surface of the insulator small diameter portion 313.
  • the exposed portion 41 of the center electrode 4 is formed so as to fit inside the ground electrode 2 when viewed from the plug axial direction Z. That is, the maximum outer diameter of the exposed portion 41 of the center electrode 4 is smaller than the minimum inner diameter of the ground electrode 2.
  • the external position of the exposed part 41 when the sectional view of FIG. 28 is viewed from the plug axis direction Z is indicated by a one-dot chain line. Also in FIG. 28, it can be seen that the outer position of the exposed portion 41 is within the ground electrode 2.
  • the exposed portion 41 of the center electrode 4 fits inside the housing (see reference numeral 11 in FIG. 1) in addition to the ground electrode 2 when viewed from the plug axial direction Z. Is formed. Further, the exposed portion 41 of the center electrode 4 is formed so as to fit inside the outer shape of the insulator step portion 312 when viewed from the plug axial direction Z. In FIG. 30, the insulator step portion 312 is hatched for convenience. Others are the same as in the first embodiment.
  • the insulator protrusion 31 as a whole has a step shape in which the outer diameter decreases stepwise toward the distal end side in the plug axial direction Z. Therefore, the path along the surface of the insulator exposed portion 310 from the second portion 412 to the ground electrode 2 can be lengthened. Accordingly, the distance of creeping discharge can be ensured without extending the insulator exposed portion 310 in the plug axial direction Z, and the ignitability can be improved. That is, as shown in FIG.
  • the discharge is generated starting from the inner peripheral end of the end surface 412a on the proximal end side in the plug axis direction Z in the second portion 412 and the inner peripheral end of the distal end surface 21 of the ground electrode 2, A portion between both starting points of the discharge spark S generated by the discharge is formed in a step shape so as to crawl the outer peripheral surface of the insulator exposed portion 310 of the insulator protrusion 31.
  • the creeping distance can be secured by generating the discharge stepwise as compared with the case where the discharging is generated linearly.
  • the cooling loss due to the heat of the flame generated by the discharge of the spark plug 1 being taken away by the insulator protrusion 31 is reduced. can do. This can also improve the ignitability of the air-fuel mixture.
  • the exposed portion 41 of the center electrode 4 is formed so as to fit inside the ground electrode 2 when viewed from the plug axial direction Z. Therefore, it is easy to improve the productivity of the spark plug 1. That is, a structure in which components other than the housing 11 and the ground electrode 2 are assembled to the insulator 3 in advance is formed, and the structure is inserted into the housing 11 and the ground electrode 2 from the base end side of the housing 11 and the ground electrode 2. By making it, the spark plug 1 can be manufactured easily. Conversely, when the exposed portion 41 of the center electrode 4 is formed to have a larger diameter than the ground electrode 2, the exposed portion 41 of the center electrode 4 cannot be inserted inside the ground electrode 2.
  • the basic structure is the same as that of the eighth embodiment, and the outer peripheral surface 31b of the lever protrusion 31 and the inner peripheral surface 412b of the second portion 412 in the plug radial direction are
  • the radial gap rc described in the first embodiment is formed. That is, the inner peripheral surface 412b of the second portion 412 is formed at a position away from the outer peripheral surface 31b of the insulator protrusion 31 toward the outer peripheral side in the plug radial direction.
  • the radial gap rc is formed in an annular shape around the entire circumference in the plug circumferential direction.
  • the radial gap rc is open toward the base end side in the plug axial direction Z.
  • the position of the outer peripheral surface 41 b of the exposed portion 41 of the center electrode 4 in the plug radial direction is formed to be equal to the position of the inner peripheral surface of the ground electrode 2.
  • Others are the same as in the eighth embodiment.
  • the airflow in the combustion chamber also flows into the radial gap rc. Then, the airflow that has flowed into the radial gap rc flows out between the center electrode 4 and the ground electrode 2 toward the outside in the plug radial direction, that is, toward the side away from the insulator exposed portion 310. . Therefore, it is easy to stretch the discharge spark away from the insulator exposed portion 310. In addition, the same effects as those of the eighth embodiment are obtained.
  • the present embodiment is an embodiment in which the through hole 20 is formed in the second portion 412 of the center electrode 4 while the basic structure is the same as that of the ninth embodiment.
  • the configuration, formation position, and the like of the through hole 20 are the same as those of the through hole 20 shown in the sixth embodiment. Others are the same as in the ninth embodiment.
  • the present embodiment is an embodiment in which the through hole 20 is formed in the first portion 411 of the center electrode 4 while the basic structure is the same as that of the ninth embodiment.
  • the configuration, formation position, and the like of the through hole 20 are the same as those in the seventh embodiment.
  • Embodiment 12 As shown in FIG. 35, the present embodiment is an embodiment in which the shape of the center electrode 4 is changed with respect to the eighth embodiment.
  • the portion of the center electrode 4 that is disposed inside the insulator protrusion 31 has an electrode large diameter portion 42 that protrudes toward the outer peripheral side in the plug radial direction. That is, the electrode large-diameter portion 42 is formed at the distal end portion of the center electrode 4 at the portion inside the insulator protrusion 31.
  • the electrode large-diameter portion 42 is located on the tip side of the insulator step portion 312. That is, the electrode large diameter portion 42 is formed inside the insulator small diameter portion 313 of the insulator protrusion portion 31.
  • the distal end side of the electrode large-diameter portion 42 is connected to the exposed portion 41.
  • the electrode large-diameter portion 42 has a rotationally symmetric shape about the plug central axis.
  • the electrode large diameter portion 42 is formed with an electrode enlarged diameter portion 421, an electrode same diameter portion 422, and an electrode reduced diameter portion 423 from the proximal end side to the distal end side in the plug axial direction Z.
  • the electrode diameter-enlarged portion 421 increases in diameter toward the distal end side in the plug axial direction Z.
  • the electrode same-diameter portion 422 has a cylindrical shape that is straightly formed in the plug axial direction Z so as to extend from the electrode enlarged diameter portion 421 to the distal end side in the plug axial direction Z.
  • the electrode diameter-reduced portion 423 decreases in diameter toward the distal end side in the plug axial direction Z from the electrode same-diameter portion 422.
  • the change in diameter with respect to the change in the plug axis direction Z is larger in the electrode reduced diameter portion 423 than in the electrode enlarged diameter portion 421.
  • Others are the same as in the eighth embodiment.
  • the electrode large-diameter portion 42 is formed at a portion disposed inside the insulator protrusion 31, it is easy to prevent the occurrence of pre-ignition. This will be described later.
  • the insulator protrusion 31 as a whole has a step shape in which the outer diameter decreases stepwise toward the tip end in the plug axis direction Z, the heat capacity of the tip of the insulator protrusion 31 is increased. Becomes smaller and the temperature rises more easily. As a result, the temperature of the tip of the center electrode 4 located around the tip of the insulator protrusion 31 is also likely to rise.
  • the electrode large-diameter portion 42 is formed in a portion disposed inside the insulator protrusion portion 31 to ensure the heat capacity of the center electrode 4 tip, so that the tip of the center electrode 4 is sharply It is possible to prevent the temperature from rising.
  • the same effects as those of the eighth embodiment are obtained.
  • the present embodiment is an embodiment in which the shape of the exposed portion 41 of the center electrode 4 is changed with respect to the eighth embodiment.
  • the exposed portion 41 includes an extended exposed portion 413 extending from the inner side of the insulator 3 in the center electrode 4 to the distal end side, and an attachment attached to the extended exposed portion 413. And an exposed portion 414.
  • the extension exposure part 413 and the attachment exposure part 414 are separate bodies.
  • the extended exposed portion 413 has a cylindrical shape.
  • the attachment exposed portion 414 is formed with an attachment hole 410 that penetrates in the plug axial direction Z and has substantially the same diameter as the extended exposed portion 413.
  • the attachment exposure part 414 is joined to the extension exposure part 413 by inserting the extension exposure part 413 into the attachment hole 410.
  • the mounting exposed portion 414 has a first part 411 and a second part 412.
  • the first part 411 covers the insulator protrusion 31 from the distal end side in the plug axial direction Z.
  • the second part 412 extends from the first part 411 to the proximal end side in the plug axial direction Z and covers a part of the outer peripheral surface 31b of the lever protrusion 31 in the plug peripheral direction from the outer peripheral side in the plug radial direction. .
  • the first portion 411 has a rounded rectangular shape elongated in the lateral direction X perpendicular to the plug axis direction Z and is formed in a plate shape having a thickness in the plug axis direction Z.
  • the first portion 411 is formed with the mounting hole 410 described above.
  • one portion of the first portion 411 in the lateral direction X is formed so as to protrude beyond the outer peripheral end of the distal end surface 31 a of the lever protrusion 31.
  • part 412 is extended from the one end part of the horizontal direction X in the 1st site
  • the second portion 412 is formed in a plate shape having a thickness in the lateral direction X. Further, as shown in FIG. 38, the second portion 412 has a short rounded square shape in the plug axial direction Z.
  • part 412 have covered a part of plug peripheral direction of the corner
  • FIG. The second portion 412 is formed along the outer peripheral surface of the insulator small diameter portion 313. Also in the present embodiment, the proximal end surface 412a of the second part 412 is formed at a position away from the insulator step 312 toward the distal end side.
  • the airflow of the air-fuel mixture passing through the tip of the spark plug 1 is orthogonal to the direction in which the second portion 412 and the plug central axis are aligned (that is, the lateral direction X). It is configured to flow in the direction.
  • the airflow here is the airflow of the air-fuel mixture passing through the tip of the spark plug 1 at the engine ignition timing.
  • the mounting posture of the spark plug 1 in the internal combustion engine is determined by taking into consideration the flow of airflow around the tip of the spark plug 1 in the combustion chamber (see reference numeral 11 in FIG. 1). It can be adjusted by adjusting how to cut the screw. Others are the same as in the eighth embodiment.
  • a part of the corner at the tip of the insulator protrusion 31 is covered with the first part 411 and the second part 412 of the center electrode 4. Therefore, discharge does not occur on the corner of the tip of the insulator protrusion 31 and is formed between the second portion 412 of the center electrode 4 and the ground electrode 2. As a result, the discharge is easily peeled off from the surface of the insulator protrusion 31 by the air flow of the air-fuel mixture in the combustion chamber or the electric repulsive action, and is easily stretched downstream. Thereby, the ignitability to the air-fuel mixture can be improved.
  • At least the region where the second portion 412 in the plug circumferential direction of the lever protrusion 31 is formed is a step in which the outer diameter gradually decreases toward the tip end side in the plug axial direction Z in the entire plug axial direction Z. Has a shape. Therefore, the path along the surface of the insulator exposed portion 310 from the second portion 412 to the ground electrode 2 can be lengthened. Accordingly, the distance of creeping discharge can be ensured without extending the insulator exposed portion 310 in the plug axial direction Z, and the ignitability can be improved.
  • the cooling loss due to the heat of the flame generated by the discharge of the spark plug 1 being taken away by the insulator protrusion 31 is reduced. can do. This can also improve the ignitability of the air-fuel mixture.
  • the airflow of the air-fuel mixture passing through the tip of the spark plug 1 flows in a direction perpendicular to the direction in which the second portion 412 and the plug center axis are aligned (that is, the lateral direction X). It is configured. Therefore, the air flow in the combustion chamber passes directly between the second portion 412 and the ground electrode 2. Thereby, the airflow passing between the second part 412 and the ground electrode 2 can be prevented from being disturbed, and the discharge spark generated between the second part 412 and the ground electrode 2 can be more easily extended. In addition, the same effects as those of the eighth embodiment are obtained.
  • the present embodiment is an embodiment in which the shape of the insulator protrusion 31 is changed with respect to the thirteenth embodiment.
  • the insulator protrusion 31 has a plurality of insulator steps 312. Specifically, the insulator protrusion 31 has two insulator steps 312.
  • the two lever step portions 312 are arranged in a position that divides the lever exposure portion 310 into three equal parts in the plug axial direction Z.
  • the end surface 412a on the proximal end side of the second part 412, the two insulator step portions 312, and the distal end surface 21 of the ground electrode 2 are arranged at equal intervals in the plug axial direction Z. Others are the same as in the thirteenth embodiment.
  • the insulator protrusion 31 has a plurality of insulator steps 312, even if the length of the insulator exposure part 310 in the plug axial direction Z is shortened, the second along the surface of the insulator exposure part 310. A creepage distance from the portion 412 to the ground electrode 2 can be secured. Therefore, it is possible to reduce the size of the spark plug 1 without affecting the ignitability. In addition, the same effects as those of the thirteenth embodiment are obtained.
  • the insulator protrusion 31 has the two insulator steps 312 .
  • the present invention is not limited to this.
  • As shown in FIG. It is also possible to form three or more insulator steps.
  • the present embodiment is an embodiment in which the shape of the lever protrusion 31 is changed with respect to the thirteenth embodiment.
  • the outer circumferential surface of the insulator small-diameter portion 313 has a wave shape (uneven shape) in a cross section parallel to the plug axis direction Z.
  • the small-diameter portion 313 of the present embodiment has an outer diameter that varies in the plug axis direction Z when viewed microscopically, but has a constant outer diameter in the plug axis direction Z when viewed macroscopically.
  • the insulator projecting portion 31 has a step shape in which the entire outer diameter in the plug axis direction Z gradually decreases toward the distal end side in the plug axis direction Z. Others are the same as in the thirteenth embodiment.
  • the outer peripheral surface of the insulator small-diameter portion 313 has a wave shape, even if the length of the insulator exposed portion 310 in the plug axial direction Z is shortened, the first portion along the surface of the insulator exposed portion 310 is reduced. A creepage distance from the two parts 412 to the ground electrode 2 can be secured. Therefore, it is possible to reduce the size of the spark plug 1 without affecting the ignitability. In addition, the same effects as those of the thirteenth embodiment are obtained.
  • the present invention is not limited thereto, and only the outer peripheral surface of the insulator large-diameter portion 311 is corrugated, or the outer peripheral surface of the insulator small-diameter portion 313 is used. It is also possible to make both the outer peripheral surface of the insulator large-diameter portion 311 corrugated.
  • the present embodiment is an embodiment in which the shape of the lever protrusion 31 is changed with respect to the thirteenth embodiment.
  • most of the outer peripheral surface of the insulator protrusion 31 has a shape that is slightly reduced in diameter toward the distal end side.
  • the step shape of the insulator protrusion 31 is formed only in the region where the second portion 412 is arranged in the plug circumferential direction.
  • the step shape is formed by a step forming recess 314 described later.
  • the step forming recess 314 is formed such that a region where the second portion 412 in the plug circumferential direction on the outer peripheral surface 31b of the insulator protruding portion 31 is recessed is recessed toward the inner peripheral side.
  • the step forming recess 314 is formed so as to be connected from the center in the plug axial direction Z of the lever protrusion 31 to the tip surface 31 a of the lever protrusion 31.
  • the base end side end surface in the plug axial direction Z of the step forming recess 314 is an insulator step 312 facing the distal end side in the plug axial direction Z.
  • both end walls 315 in the plug circumferential direction of the step forming recess 314 are formed in a taper shape so as to be farther from each other in the plug circumferential direction toward the outer peripheral side in the plug radial direction.
  • the second portion 412 is formed so as to be accommodated in the step forming recess 314 in both the plug circumferential direction and the plug radial direction. Others are the same as in the thirteenth embodiment.
  • the stepped shape of the insulator protrusion 31 is formed only in the region where the second portion 412 is arranged in the plug circumferential direction. In this way, by forming the step shape only at a location necessary to ensure the creepage distance, it is possible to prevent the volume of the insulator 3 from becoming excessively small and the heat capacity from excessively decreasing. Therefore, it is easy to prevent the occurrence of pre-ignition. In addition, the same effects as those of the thirteenth embodiment are obtained.
  • the present embodiment is an embodiment in which the shape of the center electrode 4 is changed with respect to the thirteenth embodiment.
  • a portion of the center electrode 4 that is disposed inside the insulator protrusion 31 has an electrode large diameter portion 42 that protrudes to the outer peripheral side in the plug radial direction. That is, the electrode large-diameter portion 42 is formed at the distal end portion of the center electrode 4 at the portion inside the insulator protrusion 31.
  • the electrode large-diameter portion 42 is located on the tip side of the insulator step portion 312. That is, the electrode large diameter portion 42 is formed inside the insulator small diameter portion 313 of the insulator protrusion portion 31.
  • the distal end side of the electrode large-diameter portion 42 is connected to the exposed portion 41.
  • the shape of the electrode large-diameter portion 42 is the same as that of the electrode large-diameter portion 42 of the twelfth embodiment. Others are the same as in the thirteenth embodiment.
  • the electrode large-diameter portion 42 is formed at a portion disposed inside the insulator protrusion portion 31, it is easy to prevent the occurrence of pre-ignition as in the twelfth embodiment. In addition, the same effects as those of the thirteenth embodiment are obtained.
  • Embodiment 4 and Embodiment 5 can be combined, the shape of the center electrode can be as shown in Embodiment 4, and the shape of the ground electrode can be as shown in Embodiment 5.
  • the exposed part was formed integrally with the part inside the insulator protrusion part in the center electrode, the present invention is not limited to this, and the exposed part and the part inside the insulator protrusion part in the center electrode are separated. Is also possible.
  • the housing and the ground electrode may be integrally formed. That is, a part of the housing can be used as a ground electrode.
  • the number of the ventilation holes in an exposed part may be one, and may be two or more. good.

Abstract

A spark plug 1 has: a cylindrical earthed electrode 2; an insulator 3; and a center electrode 4. The insulator 3 has an insulator projected part 31 that projects to a tip side in a plug axial direction Z more than the earthed electrode 2. The center electrode 4 has an exposed part 41 that is exposed from the tip of the insulator projected part 31. The exposed part 41 of the center electrode 4 has a first section 411 that covers the insulator projected part 31 from the tip side in the plug axial direction Z, and a second section 412 that extends from the first section 411 to the base end side in the plug axial direction Z and covers the entire circumference of the outer circumferential surface 31b of the insulator projected part 31 from the outer circumferential side in the plug diameter direction.

Description

内燃機関用のスパークプラグSpark plug for internal combustion engine
　本発明は、内燃機関用のスパークプラグに関する。 The present invention relates to a spark plug for an internal combustion engine.
　例えば特許文献１に開示されているように、内燃機関用のスパークプラグとして、中心電極に高周波電圧を印加することによって、接地電極と中心電極との間に放電を生じさせるものがある。かかるスパークプラグは、絶縁碍子の表面を這うような沿面火花放電を、中心電極と接地電極との間に生じさせる。 For example, as disclosed in Patent Document 1, there is a spark plug for an internal combustion engine that generates a discharge between a ground electrode and a center electrode by applying a high frequency voltage to the center electrode. Such a spark plug generates a creeping spark discharge that hits the surface of the insulator between the center electrode and the ground electrode.
　ここで、特許文献１に開示されたスパークプラグは、筒状の接地電極の内側に絶縁碍子が配置されており、絶縁碍子の更に内側に中心電極が配置されている。絶縁碍子は、その先端が接地電極の先端側に突出するように配置されている。そして、中心電極は、その先端が絶縁碍子の先端側に突出するように配置されている。 Here, in the spark plug disclosed in Patent Document 1, an insulator is disposed inside a cylindrical ground electrode, and a center electrode is disposed further inside the insulator. The insulator is arranged so that its tip protrudes toward the tip of the ground electrode. And the center electrode is arrange | positioned so that the front-end | tip may protrude to the front-end | tip side of an insulator.
特開昭６１－２９２８７５号公報Japanese Patent Laid-Open No. 61-292875
　しかしながら、特許文献１に記載のスパークプラグにおいては、絶縁碍子の先端部の角部（すなわち絶縁碍子の先端面と外周面との間の角）が露出している。それゆえ、中心電極と接地電極との間において、絶縁碍子の前記角部の表面を這うような沿面火花放電が形成される。これにより、中心電極と接地電極との間に生じた放電が、絶縁碍子の表面、特に前記角部の表面から剥離しにくい。それゆえ、前記スパークプラグは、中心電極と接地電極との間に生じる放電が、燃焼室内の気流によって大きく引き伸ばされにくく、混合気への着火性を確保し難い。 However, in the spark plug described in Patent Document 1, the corner of the tip of the insulator (that is, the corner between the tip of the insulator and the outer peripheral surface) is exposed. Therefore, a creeping spark discharge is formed between the center electrode and the ground electrode so as to crawl the surface of the corner of the insulator. As a result, the discharge generated between the center electrode and the ground electrode is unlikely to peel off from the surface of the insulator, particularly from the surface of the corner. Therefore, in the spark plug, the discharge generated between the center electrode and the ground electrode is not easily stretched by the air flow in the combustion chamber, and it is difficult to ensure the ignitability of the air-fuel mixture.
　本発明は、かかる課題に鑑みてなされたものであり、混合気への着火性の向上を図ることができる内燃機関用のスパークプラグを提供しようとするものである。 The present invention has been made in view of such problems, and an object of the present invention is to provide a spark plug for an internal combustion engine that can improve the ignitability of an air-fuel mixture.
　本発明の第一の態様は、筒状の接地電極と、前記接地電極の内側に配されると共に、前記接地電極の先端よりもプラグ軸方向の先端側へ突出した碍子突出部を有する筒状の絶縁碍子と、前記絶縁碍子の内側に保持されると共に、前記碍子突出部の先端から露出した露出部を有する中心電極と、を備え、前記中心電極の前記露出部は、前記碍子突出部をプラグ軸方向の先端側から覆う第一部位と、前記第一部位からプラグ軸方向の基端側に延設されると共に前記碍子突出部の外周面の全周を、プラグ径方向の外周側から覆う第二部位とを有する、内燃機関用のスパークプラグにある。 A first aspect of the present invention is a cylindrical ground electrode, and a cylindrical shape that is disposed inside the ground electrode and has an insulator protrusion that protrudes toward the tip end side in the plug axial direction from the tip end of the ground electrode. And a center electrode that is held inside the insulator and has an exposed portion exposed from a tip of the insulator protrusion, and the exposed portion of the center electrode includes the insulator protrusion. A first part covering from the distal end side in the plug axial direction, and extending from the first part to the proximal end side in the plug axial direction, and the entire circumference of the outer peripheral surface of the lever projecting portion from the outer peripheral side in the plug radial direction A spark plug for an internal combustion engine having a second portion to cover.
　また、本発明の第二の態様は、筒状の接地電極と、前記接地電極の内側に配されると共に、前記接地電極の先端よりもプラグ軸方向の先端側へ突出した碍子突出部を有する筒状の絶縁碍子と、前記絶縁碍子の内側に保持されると共に、前記碍子突出部の先端から露出した露出部を有する中心電極と、を備え、前記中心電極の前記露出部は、前記碍子突出部をプラグ軸方向の先端側から覆う第一部位と、前記第一部位からプラグ軸方向の基端側に延設されると共に前記碍子突出部の外周面のプラグ周方向の一部を、プラグ径方向の外周側から覆う第二部位とを有し、前記碍子突出部の少なくともプラグ周方向の前記第二部位が形成された領域は、プラグ軸方向の全体において、プラグ軸方向の先端側に向かうほど段階的に外径が小さくなる段形状を有する、内燃機関用のスパークプラグにある。 The second aspect of the present invention includes a cylindrical ground electrode, and an insulator projecting portion that is disposed on the inner side of the ground electrode and projects further toward the distal end side in the plug axial direction than the distal end of the ground electrode. A cylindrical insulator, and a center electrode that is held inside the insulator and has an exposed portion that is exposed from the tip of the insulator protrusion, and the exposed portion of the center electrode protrudes from the insulator protrusion. A first portion that covers the plug portion from the distal end side in the plug axial direction, and a portion of the outer circumferential surface of the lever protruding portion that extends from the first portion to the proximal end side in the plug axial direction, And a region where at least the second portion in the plug circumferential direction of the lever protrusion is formed is on the tip end side in the plug shaft direction in the entire plug shaft direction. A stage where the outer diameter decreases step by step With a Jo, in the spark plug for an internal combustion engine.
　前記第一の態様の内燃機関用のスパークプラグにおいて、中心電極の露出部は、前記第一部位と前記第二部位と、を有する。つまり、碍子突出部の先端部の角部は、中心電極の第一部位及び第二部位に覆われている。それゆえ、放電は、碍子突出部の先端部の角部上に生じることなく、中心電極の第二部位と接地電極との間で形成されることになる。これにより、燃焼室内の混合気の気流或いは電気的な反発作用により、放電を碍子突出部の表面から剥がして、下流側に引き伸ばしやすい。これにより、混合気への着火性の向上を図ることができる。また、碍子突出部の先端部全周を覆う中心電極の露出部と、碍子突出部の全周を覆う接地電極との間の全体が、放電形成可能な領域となる。そのため、碍子突出部の表面の特定の経路で沿面放電が繰り返し形成されることにより、碍子表面が溝状に削られるいわゆるチャネリングが特定の経路において集中して形成されることを防止できる。 In the spark plug for the internal combustion engine according to the first aspect, the exposed portion of the center electrode has the first part and the second part. That is, the corner | angular part of the front-end | tip part of an insulator protrusion part is covered with the 1st site | part and 2nd site | part of a center electrode. Therefore, the discharge is generated between the second portion of the center electrode and the ground electrode without being generated on the corner of the tip of the insulator protrusion. As a result, the discharge is easily peeled off from the surface of the insulator projecting portion by the air flow or the electric repulsion of the air-fuel mixture in the combustion chamber, and is easily stretched downstream. Thereby, the ignitability to the air-fuel mixture can be improved. Further, the entire area between the exposed portion of the center electrode covering the entire periphery of the tip of the insulator protrusion and the ground electrode covering the entire periphery of the insulator protrusion is an area where discharge can be formed. For this reason, creeping discharge is repeatedly formed in a specific path on the surface of the insulator protrusion, so that so-called channeling in which the insulator surface is cut into a groove shape can be prevented from being concentrated in the specific path.
　前記第二の態様の内燃機関用のスパークプラグにおいて、碍子突出部の先端部の角部の一部は、中心電極の第一部位および第二部位に覆われている。それゆえ、本態様においても、放電が碍子突出部の先端部の角部上に生じることがなく、中心電極の第二部位と接地電極との間で形成される。これにより燃焼室内の混合気の気流或いは電気的な反発作用により、放電を碍子突出部の表面から剥がして、下流側に引き伸ばしやすい。これにより、混合気への着火性の向上を図ることができる。 In the spark plug for the internal combustion engine according to the second aspect, a part of the corner of the tip of the insulator protrusion is covered with the first part and the second part of the center electrode. Therefore, in this embodiment as well, discharge does not occur on the corner of the tip of the insulator protrusion, and is formed between the second portion of the center electrode and the ground electrode. As a result, the discharge is easily peeled off from the surface of the insulator projecting portion by the air flow or the electric repulsion of the air-fuel mixture in the combustion chamber, and is easily stretched downstream. Thereby, the ignitability to the air-fuel mixture can be improved.
　さらに、第二の態様の内燃機関用のスパークプラグにおいては、碍子突出部の少なくともプラグ周方向の第二部位が形成された領域は、プラグ軸方向の全体において、プラグ軸方向の先端側に向かうほど段階的に外径が小さくなる段形状を有する。それゆえ、第二部位から接地電極までの、碍子突出部の表面に沿った経路を長くすることができる。これにより、碍子突出部をプラグ軸方向に伸ばすことなく、沿面放電の距離を確保することができ、着火性を高めることができる。さらに、碍子突出部の先端部のプラグ軸方向に直交する断面の面積が小さくなるため、スパークプラグの放電によって生じた火炎の熱が碍子突出部に奪われることによる冷損を低減することができる。これによっても、混合気への着火性の向上を図ることができる。 Further, in the spark plug for the internal combustion engine according to the second aspect, the region where at least the second portion in the plug circumferential direction of the insulator projecting portion is formed is directed toward the distal end side in the plug shaft direction in the entire plug shaft direction. The outer shape has a stepped shape that gradually decreases in outer diameter. Therefore, the path along the surface of the insulator protrusion from the second part to the ground electrode can be lengthened. Thereby, the distance of creeping discharge can be ensured without extending the insulator protrusion in the plug axis direction, and the ignitability can be improved. Furthermore, since the area of the cross section perpendicular to the plug axis direction of the tip portion of the insulator protrusion is reduced, it is possible to reduce the cooling loss due to the heat of the flame generated by the discharge of the spark plug being taken away by the insulator protrusion. . This can also improve the ignitability of the air-fuel mixture.
　以上のごとく、前記各態様によれば、混合気への着火性の向上を図ることができる内燃機関用のスパークプラグを提供することができる。
　なお、特許請求の範囲に記載した括弧内の符号は、後述する実施形態に記載の具体的手段との対応関係を示すものであり、本発明の技術的範囲を限定するものではない。 As described above, according to each aspect, it is possible to provide a spark plug for an internal combustion engine that can improve the ignitability of an air-fuel mixture.
In addition, the code | symbol in the parenthesis described in the claim shows the correspondence with the specific means as described in embodiment mentioned later, and does not limit the technical scope of this invention.
実施形態１における、内燃機関用のスパークプラグの一部を正面図で表し、他の部位を断面図で表した図。The figure which represented a part of spark plug for internal combustion engines in Embodiment 1 with the front view, and represented the other site | part with sectional drawing. 実施形態１における、スパークプラグの先端部周辺の拡大断面図。FIG. 3 is an enlarged cross-sectional view around the tip of the spark plug according to the first embodiment. 実施形態１における、スパークプラグの先端部周辺の拡大側面図。FIG. 3 is an enlarged side view of the periphery of the spark plug in the first embodiment. 実施形態１における、中心電極及び接地電極を、プラグ軸方向の先端側からみた図。The figure which looked at the center electrode and the ground electrode in Embodiment 1 from the front end side of the plug axial direction. 図３の、Ｖ－Ｖ線矢視断面図において、中心電極のみを表した図。FIG. 5 is a diagram showing only the center electrode in the cross-sectional view taken along the line VV in FIG. 3. 実施形態１における、スパークプラグの先端部周辺の拡大断面図において、初期の放電火花を表した説明図。FIG. 3 is an explanatory diagram showing an initial discharge spark in the enlarged cross-sectional view around the tip of the spark plug according to the first embodiment. 実施形態１における、スパークプラグの先端部周辺の拡大断面図において、放電火花が気流に押されて碍子露出部の表面から離れた様子を示す説明図。FIG. 3 is an explanatory view showing a state in which the discharge spark is pushed by the airflow and separated from the surface of the insulator exposure portion in the enlarged cross-sectional view around the tip portion of the spark plug in the first embodiment. 実施形態１における、スパークプラグの先端部周辺の拡大断面図において、放電火花が気流に押されて大きく引き伸ばされている様子を示す説明図。FIG. 3 is an explanatory view showing a state in which an electric discharge spark is pushed and stretched greatly in an enlarged cross-sectional view around the tip of a spark plug in the first embodiment. 比較形態における、スパークプラグの先端部周辺の拡大断面図において、初期の放電火花を表した説明図。The explanatory view showing the early discharge spark in the expanded sectional view near the tip part of a spark plug in a comparative form. 比較形態における、スパークプラグの先端部周辺の拡大断面図において、放電火花が、気流に押された状態を示す説明図。Explanatory drawing which shows the state by which the discharge spark was pushed by the airflow in the expanded sectional view of the front-end | tip part periphery of a spark plug in a comparison form. 実施形態２における、スパークプラグの先端部周辺の拡大断面図。FIG. 4 is an enlarged cross-sectional view around the tip of a spark plug in Embodiment 2. 実施形態３における、スパークプラグの先端部周辺の拡大断面図。FIG. 5 is an enlarged cross-sectional view around the tip of a spark plug in Embodiment 3. 実施形態４における、スパークプラグの先端部周辺の拡大断面図。FIG. 6 is an enlarged cross-sectional view around the tip of a spark plug in Embodiment 4. 実施形態４における、スパークプラグの先端部周辺の拡大側面図。The expanded side view of the front-end | tip part periphery of a spark plug in Embodiment 4. FIG. 実施形態４における、スパークプラグの先端部周辺の拡大断面図において、初期の放電火花を表した説明図。FIG. 9 is an explanatory diagram showing an initial discharge spark in an enlarged cross-sectional view around the tip of a spark plug according to a fourth embodiment. 実施形態４における、スパークプラグの先端部周辺の拡大断面図において、放電火花が気流に押されて碍子露出部の表面から離れた様子を示す説明図。In expanded sectional drawing of the tip part periphery of a spark plug in Embodiment 4, it is explanatory drawing which shows a mode that the discharge spark was pushed by the airflow and was separated from the surface of the insulator exposure part. 実施形態４における、スパークプラグの先端部周辺の拡大断面図において、放電火花が気流に押されて大きく引き伸ばされている様子を示す説明図。FIG. 9 is an explanatory view showing a state in which an electric discharge spark is pushed and stretched greatly by an air current in an enlarged cross-sectional view around the tip of a spark plug in Embodiment 4. 実施形態５における、スパークプラグの先端部周辺の拡大断面図。FIG. 6 is an enlarged cross-sectional view around the tip of a spark plug in Embodiment 5. 実施形態５における、スパークプラグの先端部周辺の拡大側面図。FIG. 6 is an enlarged side view of the vicinity of a tip portion of a spark plug in Embodiment 5. 実施形態５における、スパークプラグの先端部周辺の拡大断面図において、初期の放電火花を表した説明図。FIG. 9 is an explanatory diagram showing an initial discharge spark in an enlarged cross-sectional view around the tip of a spark plug in Embodiment 5. 実施形態５における、スパークプラグの先端部周辺の拡大断面図において、放電火花が気流に押されて碍子露出部の表面から離れた様子を示す説明図。In expanded sectional drawing of the tip part periphery of a spark plug in Embodiment 5, it is explanatory drawing which shows a mode that the discharge spark was pushed by the airflow and was separated from the surface of the insulator exposure part. 実施形態５における、スパークプラグの先端部周辺の拡大断面図において、放電火花が気流に押されて大きく引き伸ばされている様子を示す説明図。FIG. 9 is an explanatory view showing a state in which an electric discharge spark is greatly stretched by being pushed by an air flow in an enlarged cross-sectional view around the tip of a spark plug in Embodiment 5. 実施形態６における、スパークプラグの先端部周辺の拡大断面図。FIG. 7 is an enlarged cross-sectional view around the tip of a spark plug in Embodiment 6. 実施形態６における、スパークプラグの先端部周辺の拡大側面図。The expanded side view of the front-end | tip part periphery of a spark plug in Embodiment 6. FIG. 実施形態６における、中心電極及び接地電極を、プラグ軸方向の先端側からみた図。The figure which looked at the center electrode and the ground electrode in Embodiment 6 from the front end side of the plug axial direction. 実施形態７における、スパークプラグの先端部周辺の拡大断面図。FIG. 9 is an enlarged cross-sectional view of the vicinity of a tip portion of a spark plug in Embodiment 7. 実施形態７における、中心電極及び接地電極を、プラグ軸方向の先端側からみた図。The figure which looked at the center electrode and the ground electrode in Embodiment 7 from the front end side of the plug axial direction. 実施形態８における、スパークプラグの先端部周辺の拡大断面図。FIG. 9 is an enlarged cross-sectional view of the vicinity of a tip portion of a spark plug in Embodiment 8. 実施形態８における、スパークプラグの先端部周辺の拡大側面図。FIG. 10 is an enlarged side view of the vicinity of a tip portion of a spark plug in Embodiment 8. 実施形態８における、中心電極、絶縁碍子、及び接地電極を、プラグ軸方向の先端側からみた図。The figure which looked at the center electrode, the insulator, and the ground electrode in Embodiment 8 from the front end side of the plug axial direction. 実施形態８における、スパークプラグの先端部周辺の拡大断面図において、初期の放電火花を表した説明図。FIG. 10 is an explanatory diagram showing an initial discharge spark in an enlarged cross-sectional view around the tip of a spark plug in Embodiment 8. 実施形態９における、スパークプラグの先端部周辺の拡大断面図。FIG. 10 is an enlarged cross-sectional view around the tip of a spark plug in Embodiment 9. 実施形態１０における、スパークプラグの先端部周辺の拡大断面図。FIG. 11 is an enlarged cross-sectional view around the tip of a spark plug in Embodiment 10. 実施形態１１における、スパークプラグの先端部周辺の拡大断面図。FIG. 12 is an enlarged cross-sectional view of the periphery of a spark plug tip according to an eleventh embodiment. 実施形態１２における、スパークプラグの先端部周辺の拡大断面図。FIG. 14 is an enlarged cross-sectional view around the tip of a spark plug according to a twelfth embodiment. 実施形態１３における、スパークプラグの先端部周辺の拡大断面図。FIG. 14 is an enlarged cross-sectional view around the tip of a spark plug in Embodiment 13. 実施形態１３における、スパークプラグの先端部周辺の拡大側面図。The expanded side view of the front-end | tip part periphery of a spark plug in Embodiment 13. FIG. 実施形態１３における、スパークプラグの先端部周辺の拡大正面図。The expanded front view of the front-end | tip part periphery of a spark plug in Embodiment 13. FIG. 実施形態１３における、中心電極、絶縁碍子、及び接地電極を、プラグ軸方向の先端側からみた図。The figure which looked at the center electrode, the insulator, and the ground electrode in Embodiment 13 from the front end side of the plug axial direction. 実施形態１４における、スパークプラグの先端部周辺の拡大断面図。FIG. 16 is an enlarged cross-sectional view around the tip of a spark plug in Embodiment 14. 実施形態１４の変形形態を示す、スパークプラグの先端部周辺の拡大断面図。FIG. 16 is an enlarged cross-sectional view around the distal end portion of a spark plug, showing a modification of the fourteenth embodiment. 実施形態１５における、スパークプラグの先端部周辺の拡大断面図。FIG. 16 is an enlarged cross-sectional view around the tip of a spark plug in Embodiment 15. 実施形態１６における、スパークプラグの先端部周辺の拡大断面図。FIG. 18 is an enlarged cross-sectional view around the tip of a spark plug in Embodiment 16. 実施形態１６における、スパークプラグの先端部周辺の拡大正面図。FIG. 17 is an enlarged front view of the vicinity of a tip portion of a spark plug in Embodiment 16. 実施形態１６における、中心電極、絶縁碍子、及び接地電極を、プラグ軸方向の先端側からみた図。The figure which looked at the center electrode, the insulator, and the ground electrode in Embodiment 16 from the front end side of the plug axial direction. 実施形態１７における、スパークプラグの先端部周辺の拡大断面図。FIG. 18 is an enlarged cross-sectional view around the distal end portion of a spark plug in Embodiment 17.
（実施形態１）
　内燃機関用のスパークプラグの実施形態につき、図１～図８を用いて説明する。
　本実施形態の内燃機関用のスパークプラグ１は、図１に示すごとく、筒状の接地電極２と、接地電極２の内側に配された筒状の絶縁碍子３と、絶縁碍子３の内側に保持された中心電極４と、を有する。絶縁碍子３は、接地電極２よりもプラグ軸方向Ｚの先端側へ突出した碍子突出部３１を有する。中心電極４は、碍子突出部３１の先端から露出した露出部４１を有する。なお、プラグ軸方向Ｚとは、スパークプラグ１の中心軸が延びる方向を意味する。また、図１において、中心電極４は、一部を断面図、他の一部を正面図で表している。 (Embodiment 1)
An embodiment of a spark plug for an internal combustion engine will be described with reference to FIGS.
As shown in FIG. 1, a spark plug 1 for an internal combustion engine according to this embodiment includes a cylindrical ground electrode 2, a cylindrical insulator 3 disposed inside the ground electrode 2, and an inner side of the insulator 3. And a held center electrode 4. The insulator 3 has an insulator protrusion 31 that protrudes toward the tip end side in the plug axial direction Z from the ground electrode 2. The center electrode 4 has an exposed portion 41 exposed from the tip of the insulator protruding portion 31. The plug axis direction Z means the direction in which the central axis of the spark plug 1 extends. Further, in FIG. 1, a part of the center electrode 4 is shown in a sectional view and the other part in a front view.
　図１、図２に示すごとく、中心電極４の露出部４１は、第一部位４１１と第二部位４１２とを有する。第一部位４１１は、碍子突出部３１をプラグ軸方向Ｚの先端側から覆っている。第二部位４１２は、第一部位４１１からプラグ軸方向Ｚの基端側に延設されると共に碍子突出部３１の外周面３１ｂの全周を、プラグ径方向の外周側から覆っている。なお、プラグ径方向とは、スパークプラグ１の径方向を意味するものとする。また、プラグ周方向といったときは、スパークプラグ１の周方向を意味するものとし、プラグ中心軸といったときは、スパークプラグ１の中心軸を意味するものとする。 As shown in FIGS. 1 and 2, the exposed portion 41 of the center electrode 4 has a first part 411 and a second part 412. The first part 411 covers the insulator protrusion 31 from the distal end side in the plug axial direction Z. The second part 412 extends from the first part 411 to the proximal end side in the plug axial direction Z and covers the entire outer periphery 31b of the lever protrusion 31 from the outer peripheral side in the plug radial direction. The plug radial direction means the radial direction of the spark plug 1. The term “plug circumferential direction” refers to the circumferential direction of the spark plug 1, and the term “plug central axis” refers to the central axis of the spark plug 1.
　本実施形態のスパークプラグ１は、例えば、自動車等の車両用の内燃機関における着火手段として用いることができる。内燃機関用のスパークプラグ１は、中心電極４に高電圧を印加することによって、接地電極２と中心電極４との間に放電を生じさせるよう構成されている。スパークプラグ１は、プラグ軸方向Ｚの一端側において図示しない高電圧電源部と接続され、他端側において内燃機関の燃焼室内に配される。高電圧電源部は、例えば、一般的な点火コイル、放電を持続制御可能な点火装置の電源、或いは中心電極４に２００ｋＨｚ～５ＭＨｚの高周波電圧を印加することができる高周波電源等とすることができる。 The spark plug 1 of the present embodiment can be used as ignition means in an internal combustion engine for a vehicle such as an automobile. The spark plug 1 for an internal combustion engine is configured to generate a discharge between the ground electrode 2 and the center electrode 4 by applying a high voltage to the center electrode 4. The spark plug 1 is connected to a high-voltage power supply unit (not shown) on one end side in the plug axial direction Z, and is disposed on the other end side in the combustion chamber of the internal combustion engine. The high voltage power supply unit can be, for example, a general ignition coil, a power supply for an ignition device capable of continuously controlling discharge, or a high frequency power supply capable of applying a high frequency voltage of 200 kHz to 5 MHz to the center electrode 4. .
　本明細書において、プラグ軸方向Ｚにおいて、スパークプラグ１が燃焼室に挿入される側を先端側、その反対側を基端側という。 In this specification, in the plug axial direction Z, the side on which the spark plug 1 is inserted into the combustion chamber is referred to as the distal end side, and the opposite side is referred to as the proximal end side.
　接地電極２は、筒状を呈している。接地電極２は、絶縁碍子３を全周から囲むように形成されている。図４に示すごとく、接地電極２の先端面２１は、円環状を呈している。先端面２１は、プラグ軸方向Ｚに直交する。接地電極２の先端面２１は、その全体が、プラグ軸方向Ｚに直交する面上において面一に形成されている。図２に示すごとく、接地電極２の先端面２１と内周面との間の角度は、直角である。 The ground electrode 2 has a cylindrical shape. The ground electrode 2 is formed so as to surround the insulator 3 from the entire circumference. As shown in FIG. 4, the front end surface 21 of the ground electrode 2 has an annular shape. The tip surface 21 is orthogonal to the plug axial direction Z. The tip surface 21 of the ground electrode 2 is entirely formed on a plane perpendicular to the plug axis direction Z. As shown in FIG. 2, the angle between the front end surface 21 of the ground electrode 2 and the inner peripheral surface is a right angle.
　図１、図２に示すごとく、絶縁碍子３は、プラグ軸方向Ｚに貫通する貫通孔３０を有する。絶縁碍子３は、プラグ軸方向Ｚに直交する断面形状が円環状を呈している。絶縁碍子３は、その一部を接地電極２の内側に配しつつ、碍子突出部３１を接地電極２の先端面２１よりも先端側へ突出させている。絶縁碍子３の外周面は、接地電極２の内周面と微小隙間を介してプラグ径方向に対向している。なお、当該微小隙間は、形成されていなくてもよい。つまり、絶縁碍子３の外周面と接地電極２の内周面とは、接していてもよい。 As shown in FIGS. 1 and 2, the insulator 3 has a through hole 30 penetrating in the plug axial direction Z. The insulator 3 has an annular shape in cross section perpendicular to the plug axial direction Z. The insulator 3 protrudes from the distal end surface 21 of the ground electrode 2 toward the distal end side while part of the insulator 3 is disposed inside the ground electrode 2. The outer peripheral surface of the insulator 3 is opposed to the inner peripheral surface of the ground electrode 2 in the plug radial direction through a minute gap. Note that the minute gap may not be formed. That is, the outer peripheral surface of the insulator 3 and the inner peripheral surface of the ground electrode 2 may be in contact with each other.
　図２、図３に示すごとく、碍子突出部３１の外周面３１ｂは、プラグ軸方向Ｚの先端側へ向かうほどプラグ径方向の内周側へ向かうよう傾斜している。図２に示すごとく、碍子突出部３１の外周面３１ｂは、プラグ軸方向Ｚに平行な断面形状が、先端側へ向かうほどプラグ径方向の内周側へ向かうよう傾斜した直線形状を有する。これに伴い、碍子突出部３１における中心電極４及び接地電極２の双方から露出した碍子露出部３１０の外周面も、プラグ軸方向Ｚの先端側へ向かうほどプラグ径方向の内周側へ向かうよう傾斜している。そして、碍子露出部３１０の外周面も、プラグ軸方向Ｚに平行な断面形状が、先端側へ向かうほどプラグ径方向の内周側へ向かうよう傾斜した直線形状を有する。本実施形態において、碍子露出部３１０は、碍子突出部３１における、プラグ軸方向Ｚの、接地電極２の先端面２１と、中心電極４の第二部位４１２におけるプラグ軸方向Ｚの基端側の端面４１２ａとの間の部位である。 As shown in FIGS. 2 and 3, the outer peripheral surface 31b of the insulator protrusion 31 is inclined so as to go to the inner peripheral side in the plug radial direction as it goes to the tip end side in the plug axial direction Z. As shown in FIG. 2, the outer peripheral surface 31 b of the insulator protrusion 31 has a linear shape in which the cross-sectional shape parallel to the plug axis direction Z is inclined toward the inner peripheral side in the plug radial direction toward the distal end side. Accordingly, the outer peripheral surface of the insulator exposed portion 310 exposed from both the center electrode 4 and the ground electrode 2 in the insulator protruding portion 31 is also directed toward the inner peripheral side in the plug radial direction toward the tip end side in the plug axial direction Z. Inclined. The outer peripheral surface of the insulator exposed portion 310 also has a linear shape in which a cross-sectional shape parallel to the plug axial direction Z is inclined toward the inner peripheral side in the plug radial direction toward the distal end side. In the present embodiment, the insulator exposed portion 310 is located on the distal end surface 21 of the ground electrode 2 in the plug axial direction Z in the insulator protruding portion 31 and on the proximal end side in the plug axial direction Z in the second portion 412 of the center electrode 4. It is a site | part between the end surfaces 412a.
　図２に示すごとく、碍子突出部３１の先端面３１ａは、プラグ軸方向Ｚに直交するよう形成されている。碍子突出部３１の先端面３１ａと外周面３１ｂとの間の角部の角度は、鈍角に形成されている。碍子突出部３１の先端面３１ａと外周面３１ｂとの間の角部は、第二部位４１２の端面４１２ａよりも、プラグ軸方向Ｚにおける先端側に位置している。碍子突出部３１の先端面３１ａと外周面３１ｂとの間の角部は、碍子露出部３１０の一部ではない。すなわち、碍子突出部３１の先端面３１ａと外周面３１ｂとの間の角部は、中心電極４の第一部位４１１及び第二部位４１２に覆われており、中心電極４から露出していない。 As shown in FIG. 2, the tip surface 31a of the insulator protrusion 31 is formed so as to be orthogonal to the plug axis direction Z. The angle of the corner between the distal end surface 31a and the outer peripheral surface 31b of the insulator protrusion 31 is an obtuse angle. The corner between the distal end surface 31 a and the outer peripheral surface 31 b of the lever protrusion 31 is located on the distal end side in the plug axial direction Z with respect to the end surface 412 a of the second portion 412. The corner between the tip surface 31 a and the outer peripheral surface 31 b of the insulator protrusion 31 is not a part of the insulator exposure part 310. That is, the corner between the distal end surface 31 a and the outer peripheral surface 31 b of the insulator protrusion 31 is covered with the first portion 411 and the second portion 412 of the center electrode 4 and is not exposed from the center electrode 4.
　絶縁碍子３の貫通孔３０における先端部に、中心電極４が挿通保持されている。中心電極４は、全体として略円柱形状を呈している。 The center electrode 4 is inserted and held at the tip of the through hole 30 of the insulator 3. The center electrode 4 has a substantially cylindrical shape as a whole.
　中心電極４の露出部４１は、全体として、プラグ軸方向Ｚの基端側に向かって開口するカップ形状を呈している。露出部４１は、図４に示すごとく、円盤状に形成された第一部位４１１と、図２に示すごとく、第一部位４１１の外縁部から基端側に向かって延設され、全体として円筒状に形成された第二部位４１２とを有する。図２に示すごとく、第一部位４１１は、碍子突出部３１の先端面３１ａの全体と、プラグ軸方向Ｚに対向している。第二部位４１２は、碍子突出部３１の外周面３１ｂの全周を、碍子突出部３１の外周側から覆っている。これにより、露出部４１は、碍子突出部３１の先端部の角部全体を覆っている。なお、プラグ径方向において、碍子突出部３１の外周面３１ｂと第二部位４１２の内周面４１２ｂとの間には、径方向空隙ｒｃが形成されている。すなわち、第二部位４１２の内周面４１２ｂは、碍子突出部３１の外周面３１ｂからプラグ径方向の外周側に離れた位置に形成されている。径方向空隙ｒｃは、プラグ軸方向Ｚの基端側に向かって開口している。なお、径方向空隙ｒｃは、形成されていなくてもよい。つまり、第二部位４１２の内周面４１２ｂが碍子突出部３１の外周面３１ｂに接触していてもよい。 The exposed portion 41 of the center electrode 4 has a cup shape that opens toward the base end side in the plug axial direction Z as a whole. As shown in FIG. 4, the exposed portion 41 has a first portion 411 formed in a disc shape, and as shown in FIG. 2, the exposed portion 41 extends from the outer edge portion of the first portion 411 toward the proximal end side, and is cylindrical as a whole. And a second portion 412 formed in a shape. As shown in FIG. 2, the first portion 411 is opposed to the entire distal end surface 31 a of the lever protrusion 31 in the plug axial direction Z. The second part 412 covers the entire circumference of the outer peripheral surface 31 b of the insulator protrusion 31 from the outer periphery side of the insulator protrusion 31. As a result, the exposed portion 41 covers the entire corner portion of the distal end portion of the insulator protruding portion 31. In the plug radial direction, a radial gap rc is formed between the outer peripheral surface 31b of the insulator protrusion 31 and the inner peripheral surface 412b of the second portion 412. That is, the inner peripheral surface 412b of the second portion 412 is formed at a position away from the outer peripheral surface 31b of the insulator protrusion 31 toward the outer peripheral side in the plug radial direction. The radial gap rc is open toward the base end side in the plug axial direction Z. The radial gap rc may not be formed. That is, the inner peripheral surface 412 b of the second part 412 may be in contact with the outer peripheral surface 31 b of the lever protrusion 31.
　図５に示すごとく、第二部位４１２におけるプラグ軸方向Ｚの基端側の端面４１２ａは、円環状を呈している。また、第二部位４１２におけるプラグ軸方向Ｚの基端側の端面４１２ａは、プラグ軸方向Ｚに直交する。図２に示すごとく、中心電極４の第二部位４１２と接地電極２との間の空間距離は、全周において一定である。つまり、中心電極４及び接地電極２の双方を通る断面であって、プラグ軸方向Ｚに平行なあらゆる断面において、中心電極４と接地電極２との間の空間距離は、略一定である。また、第二部位４１２の端面４１２ａと接地電極２の先端面２１とは、直接対向しており、これらの間に絶縁碍子３は介在していない。 As shown in FIG. 5, the end surface 412a on the proximal end side in the plug axial direction Z in the second portion 412 has an annular shape. Further, the end surface 412 a on the proximal end side in the plug axial direction Z in the second portion 412 is orthogonal to the plug axial direction Z. As shown in FIG. 2, the spatial distance between the second portion 412 of the center electrode 4 and the ground electrode 2 is constant over the entire circumference. That is, the spatial distance between the center electrode 4 and the ground electrode 2 is substantially constant in any cross section that passes through both the center electrode 4 and the ground electrode 2 and is parallel to the plug axis direction Z. Further, the end surface 412a of the second part 412 and the tip surface 21 of the ground electrode 2 are directly opposed to each other, and the insulator 3 is not interposed therebetween.
　図２に示すごとく、碍子突出部３１の先端面３１ａの直径を直径Ａ［ｍｍ］、第二部位４１２の基端側の端面４１２ａの内径を内径Ｂ［ｍｍ］、端面４１２ａの外径を外径Ｃ［ｍｍ］、接地電極２と中心電極４との間の最短の空間距離を空間距離Ｄ［ｍｍ］、と定義する。このとき、直径Ａ、内径Ｂ、及び外径Ｃは、Ａ＜Ｂ＜Ｃ、の関係を満たしている。また、直径Ａ及び内径Ｂは、Ａ＋０．２５ｍｍ≦Ｂを満たすことが好ましい。また、内径Ｂ及び外径Ｃは、Ｂ＋１．０ｍｍ≦Ｃを満たすことが好ましい。また、空間距離Ｄは、３．０ｍｍ≦Ｄ≦５．０ｍｍを満たすことが好ましい。本実施形態において、直径Ａは４．５５ｍｍであり、内径Ｂは５．５５ｍｍであり、外径Ｃは６．５ｍｍであり、空間距離Ｄは５．０ｍｍである。また、本実施形態において、第二部位４１２のプラグ軸方向Ｚの長さは、１．０ｍｍである。 As shown in FIG. 2, the diameter of the distal end surface 31a of the insulator protrusion 31 is the diameter A [mm], the inner diameter of the end surface 412a on the proximal end side of the second portion 412 is the inner diameter B [mm], and the outer diameter of the end surface 412a is the outer diameter. The shortest spatial distance between the diameter C [mm] and the ground electrode 2 and the center electrode 4 is defined as a spatial distance D [mm]. At this time, the diameter A, the inner diameter B, and the outer diameter C satisfy the relationship of A <B <C. The diameter A and the inner diameter B preferably satisfy A + 0.25 mm ≦ B. The inner diameter B and outer diameter C preferably satisfy B + 1.0 mm ≦ C. The spatial distance D preferably satisfies 3.0 mm ≦ D ≦ 5.0 mm. In this embodiment, the diameter A is 4.55 mm, the inner diameter B is 5.55 mm, the outer diameter C is 6.5 mm, and the spatial distance D is 5.0 mm. In the present embodiment, the length of the second portion 412 in the plug axial direction Z is 1.0 mm.
　露出部４１は、中心電極４における碍子突出部３１の内側の部位と別体で形成されていてもよいし、一体的に形成されていてもよい。 The exposed portion 41 may be formed separately from the inner portion of the insulator protrusion 31 in the center electrode 4 or may be formed integrally.
　図１に示すごとく、接地電極２は、ハウジング１１の先端から、先端側に向かって延設されている。ハウジング１１は、筒状を呈しており、絶縁碍子３を内側に保持している。ハウジング１１の外周面には、内燃機関に螺合するための取付ネジ部１１１が形成されている。ハウジング１１における、取付ネジ部１１１が設けられた部位の先端部に、接地電極２が接合されている。 As shown in FIG. 1, the ground electrode 2 extends from the tip of the housing 11 toward the tip. The housing 11 has a cylindrical shape and holds the insulator 3 inside. A mounting screw portion 111 is formed on the outer peripheral surface of the housing 11 to be screwed into the internal combustion engine. The ground electrode 2 is joined to the tip of the portion of the housing 11 where the mounting screw portion 111 is provided.
　絶縁碍子３の貫通孔３０における中心電極４の基端側には、導電性を有するガラスシール１２を介して抵抗体１３が配置されている。抵抗体１３は、カーボン又はセラミック粉末等の抵抗材及びガラス粉末を含むレジスタ組成物を加熱封着することにより形成する、或いはカートリッジ型抵抗体を挿入することによって構成することができる。ガラスシール１２は、ガラスに銅粉を混入させてなる銅ガラスからなる。また、抵抗体１３の基端側には、銅ガラスからなるガラスシール１４を介してステム１５が配されている。ステム１５は、例えば鉄合金からなる。ステム１５は、その基端部が絶縁碍子３から突出している。そして、スパークプラグ１は、ステム１５の突出部において、高電圧電源部に接続される。 A resistor 13 is disposed on the proximal end side of the center electrode 4 in the through hole 30 of the insulator 3 through a glass seal 12 having conductivity. The resistor 13 can be formed by heat sealing a resistor composition including a resistor material such as carbon or ceramic powder and glass powder, or by inserting a cartridge type resistor. The glass seal 12 is made of copper glass obtained by mixing copper powder into glass. A stem 15 is disposed on the proximal end side of the resistor 13 via a glass seal 14 made of copper glass. The stem 15 is made of, for example, an iron alloy. The base end portion of the stem 15 protrudes from the insulator 3. The spark plug 1 is connected to the high voltage power source at the protruding portion of the stem 15.
　次に、本実施形態の作用効果につき、説明する。
　本実施形態の内燃機関用のスパークプラグ１において、中心電極４の露出部４１は、第一部位４１１と第二部位４１２と、を有する。つまり、碍子突出部３１の先端部の角部は、中心電極４の第一部位４１１及び第二部位４１２に覆われている。それゆえ、碍子突出部３１の先端部の角部上に、放電が生じ、維持、固定されることを防止することができる。これにより、燃焼室内の混合気の気流或いは電気的な反発作用により、放電を碍子突出部の表面から剥がして、下流側に引き伸ばしやすい。これにより、混合気への着火性の向上を図ることができる。さらに、碍子突出部３１の先端部の角部に、チャネリングが生じることを防止することができる。また、碍子突出部の先端部全周を覆う中心電極の露出部と、碍子突出部の全周を覆う接地電極との間の全体が、放電形成可能な領域となる。そのため、碍子突出部の表面の特定の経路で沿面放電が繰り返し形成されることにより、碍子表面が溝状に削られるいわゆるチャネリングが特定の経路において集中して形成されることを防止できる。 Next, the effect of this embodiment will be described.
In the spark plug 1 for the internal combustion engine of the present embodiment, the exposed portion 41 of the center electrode 4 has a first part 411 and a second part 412. That is, the corner of the tip of the insulator protrusion 31 is covered with the first part 411 and the second part 412 of the center electrode 4. Therefore, it is possible to prevent the discharge from being generated, maintained and fixed on the corner of the tip of the insulator protrusion 31. As a result, the discharge is easily peeled off from the surface of the insulator projecting portion by the air flow or the electric repulsion of the air-fuel mixture in the combustion chamber, and is easily stretched downstream. Thereby, the ignitability to the air-fuel mixture can be improved. Furthermore, channeling can be prevented from occurring at the corner of the tip of the insulator protrusion 31. Further, the entire area between the exposed portion of the center electrode covering the entire periphery of the tip of the insulator protrusion and the ground electrode covering the entire periphery of the insulator protrusion is an area where discharge can be formed. For this reason, creeping discharge is repeatedly formed in a specific path on the surface of the insulator protrusion, so that so-called channeling in which the insulator surface is cut into a groove shape can be prevented from being concentrated in the specific path.
　また、第二部位４１２におけるプラグ軸方向Ｚの基端側の端面４１２ａは、プラグ軸方向Ｚに直交する。さらに、接地電極２の先端面２１も、プラグ軸方向Ｚに直交する。それゆえ、スパークプラグ１が取り付けられた内燃機関の燃焼室内の気流によって、中心電極４と接地電極２との間に生じる放電を、碍子露出部３１０の表面から引き離し、かつ、気流の下流側に大きく引き伸ばしやすい。このことにつき、以後説明する。 Further, the end face 412a on the proximal end side in the plug axis direction Z in the second portion 412 is orthogonal to the plug axis direction Z. Furthermore, the front end surface 21 of the ground electrode 2 is also orthogonal to the plug axial direction Z. Therefore, the discharge generated between the center electrode 4 and the ground electrode 2 due to the airflow in the combustion chamber of the internal combustion engine to which the spark plug 1 is attached is separated from the surface of the insulator exposed portion 310 and on the downstream side of the airflow. Easy to stretch greatly. This will be described later.
　図６に示すごとく、本実施形態において、放電は、第二部位４１２におけるプラグ軸方向Ｚの基端側の端面４１２ａにおける内周端と、接地電極２の先端面２１における内周端とを起点として生じる。そして、当該放電により発生する放電火花Ｓの両起点間の部位は、碍子突出部３１の碍子露出部３１０の外周面を這うように生じる。 As shown in FIG. 6, in the present embodiment, the discharge starts from the inner peripheral end of the end surface 412 a on the proximal end side in the plug axis direction Z in the second portion 412 and the inner peripheral end of the distal end surface 21 of the ground electrode 2. Arises as And the site | part between the both starting points of the discharge spark S which generate | occur | produces by the said discharge arises so that the outer peripheral surface of the insulator exposure part 310 of the insulator protrusion part 31 may be crawled.
　そして、図６～図８に示すごとく、放電火花Ｓの両起点は、スパークプラグ１が取り付けられた内燃機関の燃焼室内において、プラグ軸方向Ｚに直交する方向に流れる気流Ｆに押され、第二部位４１２の端面４１２ａ上及び接地電極２の先端面２１上を、プラグ径方向の外周側に向かって移動する。すなわち、放電火花Ｓの中心電極４側の起点Ｓ１は、第二部位４１２の端面４１２ａの内周端部から外周端部に向かって移動し、放電火花Ｓの接地電極２側の起点Ｓ２は、接地電極２の先端面２１の内周端部から外周端部に向かって移動する。これにより、放電火花Ｓの両起点が、プラグ径方向において、碍子露出部３１０から離れる方向に移動する。 As shown in FIGS. 6 to 8, both starting points of the discharge spark S are pushed by the air flow F flowing in the direction orthogonal to the plug axis direction Z in the combustion chamber of the internal combustion engine to which the spark plug 1 is attached. It moves on the end surface 412a of the two parts 412 and the tip surface 21 of the ground electrode 2 toward the outer peripheral side in the plug radial direction. That is, the starting point S1 of the discharge spark S on the center electrode 4 side moves from the inner peripheral end of the end surface 412a of the second part 412 toward the outer peripheral end, and the starting point S2 of the discharge spark S on the ground electrode 2 side is The ground electrode 2 moves from the inner peripheral end of the front end surface 21 toward the outer peripheral end. Thereby, both starting points of the discharge spark S move in a direction away from the insulator exposure part 310 in the plug radial direction.
　放電火花Ｓの両起点が、プラグ径方向において、碍子露出部３１０から離れる方向に移動することに伴い、放電火花Ｓの両起点間の部位も、図６～図８に示すごとく、碍子露出部３１０の外周面から外周側に離れる。そして、図８に示すごとく、碍子露出部３１０の外周面から外周側に離れた放電火花Ｓの両起点間の部位は、燃焼室内の気流Ｆにより、当該気流Ｆの下流側に向かって大きく引き伸ばされる。これにより、本実施形態においては、放電火花Ｓと混合気との接触面積を稼ぎ、混合気への着火性を確保しやすい。また、混合気の着火点がスパークプラグ１から遠ざかるため、初期に形成される火炎、いわゆる初期火炎の熱が、スパークプラグ１に奪われることによる冷却損失を抑制できる。 As the both starting points of the discharge spark S move in the direction away from the insulator exposing portion 310 in the plug radial direction, the portion between the both starting points of the discharge spark S is also exposed to the insulator exposing portion as shown in FIGS. It leaves | separates from the outer peripheral surface of 310 to an outer peripheral side. And as shown in FIG. 8, the site | part between both starting points of the discharge spark S which left | separated from the outer peripheral surface of the insulator exposure part 310 to the outer peripheral side is largely extended toward the downstream of the said air flow F by the air flow F in a combustion chamber. It is. Thereby, in this embodiment, the contact area of the discharge spark S and the air-fuel mixture is gained, and it is easy to ensure the ignitability of the air-fuel mixture. Further, since the ignition point of the air-fuel mixture moves away from the spark plug 1, it is possible to suppress a cooling loss due to the heat of the initially formed flame, the so-called initial flame being taken away by the spark plug 1.
　次に、図９、図１０に示すように、中心電極４が第一部位及び第二部位の双方を有していないスパークプラグ９につき、まずその構造を説明し、次いで放電の様子につき説明する。 Next, as shown in FIGS. 9 and 10, the structure of the spark plug 9 in which the center electrode 4 does not have both the first part and the second part will be described first, and then the state of discharge will be described. .
　スパークプラグ９は、碍子突出部３１の先端側に突出する円柱状の中心電極突出部９４１を有する。中心電極突出部９４１は円柱状を呈している。プラグ軸方向Ｚからみたとき、中心電極突出部９４１は、絶縁碍子３の貫通孔３０の内側に収まっている。中心電極突出部９４１の外周面９４１ｂは、プラグ軸方向Ｚに形成されている。また、絶縁碍子３の碍子突出部３１の先端の角部３１９は、緩やかな曲面状に形成されている。 The spark plug 9 has a cylindrical center electrode protrusion 941 that protrudes toward the distal end side of the insulator protrusion 31. The center electrode protrusion 941 has a cylindrical shape. When viewed from the plug axial direction Z, the center electrode protrusion 941 is accommodated inside the through hole 30 of the insulator 3. The outer peripheral surface 941 b of the center electrode protruding portion 941 is formed in the plug axis direction Z. Moreover, the corner | angular part 319 of the front-end | tip of the insulator protrusion part 31 of the insulator 3 is formed in the gentle curved surface shape.
　図９に示すごとく、スパークプラグ９において、放電は、接地電極２の先端面２１の内周端と、中心電極４の中心電極突出部９４１の外周面９４１ｂとを起点として生じる。そして、当該放電により発生する放電火花Ｓの両起点間の部位は、碍子突出部３１の表面を這うように生じる。このとき、放電火花Ｓの両起点間の部位は、少なくとも碍子突出部３１の先端の角部３１９上を這うように生じる。 As shown in FIG. 9, in the spark plug 9, discharge occurs from the inner peripheral end of the front end surface 21 of the ground electrode 2 and the outer peripheral surface 941 b of the center electrode protruding portion 941 of the center electrode 4. And the site | part between the both starting points of the discharge spark S which generate | occur | produces by the said discharge arises so that the surface of the insulator protrusion part 31 may be crawled. At this time, a portion between both starting points of the discharge spark S is generated so as to crawl on at least the corner 319 at the tip of the insulator protrusion 31.
　そして、図９、図１０に示すごとく、放電火花Ｓの接地電極２側の起点Ｓ２は、スパークプラグ９が取り付けられた内燃機関の燃焼室内において、プラグ軸方向Ｚに直交する方向に流れる気流Ｆに押され、接地電極２の先端面２１上を、プラグ径方向の外周側に向かって移動する。 9 and 10, the starting point S2 of the discharge spark S on the ground electrode 2 side is an air flow F flowing in a direction orthogonal to the plug axial direction Z in the combustion chamber of the internal combustion engine to which the spark plug 9 is attached. To move on the distal end surface 21 of the ground electrode 2 toward the outer peripheral side in the plug radial direction.
　一方、図９、図１０に示すごとく、放電火花Ｓの接地電極２側の起点Ｓ２が移動している間、放電火花Ｓの中心電極４側の起点Ｓ１は、初期の位置からほとんど動かない。すなわち、放電火花Ｓの中心電極４側の起点Ｓ１は、碍子突出部３１の表面から離れる方向に移動しない。これは、中心電極突出部９４１の外周面９４１ｂがプラグ軸方向Ｚに形成されているため、放電火花Ｓの中心電極４側の起点Ｓ１が、中心電極突出部９４１の外周面９４１ｂ上をプラグ径方向の外周側に移動することができないことに起因する。 On the other hand, as shown in FIGS. 9 and 10, while the starting point S2 of the discharge spark S on the ground electrode 2 side is moving, the starting point S1 of the discharge spark S on the center electrode 4 side hardly moves from the initial position. That is, the starting point S <b> 1 on the side of the center electrode 4 of the discharge spark S does not move in a direction away from the surface of the insulator protrusion 31. This is because the outer peripheral surface 941b of the center electrode projecting portion 941 is formed in the plug axis direction Z, so that the starting point S1 of the discharge spark S on the side of the center electrode 4 is on the outer peripheral surface 941b of the center electrode projecting portion 941. This is because it cannot move to the outer peripheral side in the direction.
　そのため、放電火花Ｓの両起点間の部位は、碍子突出部３１の先端の角部３１９上から離れ難い。これに伴い、放電火花Ｓは、気流Ｆに押されても、両起点間の部位が下流側に大きく引き伸ばされにくい。そのため、スパークプラグ９は、燃焼室内の混合気への着火性が本実施形態のスパークプラグ１と比べて悪くなる。 Therefore, the portion between the two starting points of the discharge spark S is difficult to be separated from the top corner 319 of the insulator protrusion 31. Accordingly, even if the discharge spark S is pushed by the airflow F, the portion between the two starting points is not easily stretched to the downstream side. For this reason, the spark plug 9 is less ignitable to the air-fuel mixture in the combustion chamber than the spark plug 1 of the present embodiment.
　また、スパークプラグ１の中心電極４の第二部位４１２と接地電極２との間の空間距離は、全周において一定である。それゆえ、中心電極４の第二部位４１２と、接地電極２との間に生じる放電が、プラグ周方向において偏った位置に集中して生じることを防止することができる。それゆえ、絶縁碍子３において、プラグ周方向において偏った位置にチャネリングが集中して生じることに起因して絶縁碍子３の消耗が促進されることを防止することができる。 Further, the spatial distance between the second portion 412 of the center electrode 4 of the spark plug 1 and the ground electrode 2 is constant over the entire circumference. Therefore, it is possible to prevent the discharge generated between the second portion 412 of the center electrode 4 and the ground electrode 2 from being concentrated at a position biased in the plug circumferential direction. Therefore, in the insulator 3, it is possible to prevent the consumption of the insulator 3 from being promoted due to channeling being concentrated at positions offset in the plug circumferential direction.
　また、プラグ径方向における碍子突出部３１の外周面３１ｂと中心電極４の第二部位４１２の内周面４１２ｂとの間には、径方向空隙ｒｃが形成されている。それゆえ、燃焼室内の気流が、径方向空隙ｒｃ内にも流入する。そして、径方向空隙ｒｃに流入された気流は、中心電極４と接地電極２との間において、プラグ径方向の外側に向かうよう、すなわち、碍子露出部３１０から遠ざかる側に向かうよう、流出される。それゆえ、放電火花を、碍子露出部３１０から遠ざけるように引き伸ばしやすい。 Further, a radial gap rc is formed between the outer peripheral surface 31b of the insulator protrusion 31 and the inner peripheral surface 412b of the second portion 412 of the center electrode 4 in the plug radial direction. Therefore, the airflow in the combustion chamber also flows into the radial gap rc. Then, the airflow that has flowed into the radial gap rc flows out between the center electrode 4 and the ground electrode 2 toward the outside in the plug radial direction, that is, toward the side away from the insulator exposed portion 310. . Therefore, it is easy to stretch the discharge spark away from the insulator exposed portion 310.
　以上のごとく、本実施形態によれば、混合気への着火性の向上を図ることができる内燃機関用のスパークプラグを提供することができる。 As described above, according to the present embodiment, it is possible to provide a spark plug for an internal combustion engine that can improve the ignitability of an air-fuel mixture.
（実施形態２）
　本実施形態は、図１１に示すごとく、プラグ軸方向Ｚにおける第一部位４１１と碍子突出部３１との間に軸方向空隙ａｃを形成した実施形態である。すなわち、碍子突出部３１の先端面３１ａは、第一部位４１１におけるプラグ軸方向Ｚの基端側の端面４１１ａから基端側に離れた位置に形成されている。一方、碍子突出部３１の先端面３１ａは、第二部位４１２におけるプラグ軸方向Ｚの基端側の端面４１２ａよりもプラグ軸方向Ｚの先端側に位置している。これにより、碍子突出部３１の角部は、中心電極４の第一部位４１１及び第二部位４１２によって覆われている。軸方向空隙ａｃは、径方向空隙ｒｃと連通している。 (Embodiment 2)
As shown in FIG. 11, the present embodiment is an embodiment in which an axial gap ac is formed between the first portion 411 in the plug axial direction Z and the insulator protrusion 31. In other words, the distal end surface 31 a of the lever protrusion 31 is formed at a position away from the proximal end surface 411 a in the plug axial direction Z in the first portion 411 toward the proximal end side. On the other hand, the distal end surface 31 a of the lever protrusion 31 is located on the distal end side in the plug axial direction Z with respect to the end surface 412 a on the proximal end side in the plug axial direction Z in the second portion 412. Thereby, the corner | angular part of the insulator protrusion part 31 is covered with the 1st site | part 411 and the 2nd site | part 412 of the center electrode 4. FIG. The axial gap ac communicates with the radial gap rc.
　なお、本実施形態において、直径Ａは４．５５ｍｍであり、内径Ｂは４．８５ｍｍであり、外径Ｃは５．８５ｍｍであり、空間距離Ｄは５．０ｍｍである。 In this embodiment, the diameter A is 4.55 mm, the inner diameter B is 4.85 mm, the outer diameter C is 5.85 mm, and the spatial distance D is 5.0 mm.
　その他は、実施形態１と同様である。
　なお、実施形態２以降において用いた符号のうち、既出の実施形態において用いた符号と同一のものは、特に示さない限り、既出の実施形態におけるものと同様の構成要素等を表す。 Others are the same as in the first embodiment.
Of the reference numerals used in the second and subsequent embodiments, the same reference numerals as those used in the above-described embodiments represent the same components as those in the above-described embodiments unless otherwise indicated.
　本実施形態においては、燃焼室内の気流が、軸方向空隙ａｃ内及び径方向空隙ｒｃ内にも流入する。そして、軸方向空隙ａｃ及び径方向空隙ｒｃに流入された気流は、中心電極４と接地電極２との間において、プラグ径方向の外側に向かうよう、すなわち、碍子露出部３１０から遠ざかる側に向かうよう、流出される。それゆえ、放電火花を、碍子露出部３１０から遠ざけるように引き伸ばしやすい。 In the present embodiment, the airflow in the combustion chamber also flows into the axial gap ac and the radial gap rc. The airflow that has flowed into the axial gap ac and the radial gap rc is directed outward in the radial direction of the plug between the center electrode 4 and the ground electrode 2, that is, toward the side away from the insulator exposed portion 310. It will be leaked. Therefore, it is easy to stretch the discharge spark away from the insulator exposed portion 310.
　また、絶縁碍子３の線膨張係数と中心電極４の線膨張係数との差に起因して、絶縁碍子３及び中心電極４に生じる熱応力を低減することができる。
　その他、実施形態１と同様の作用効果を有する。 Further, the thermal stress generated in the insulator 3 and the center electrode 4 due to the difference between the linear expansion coefficient of the insulator 3 and the linear expansion coefficient of the center electrode 4 can be reduced.
In addition, the same effects as those of the first embodiment are obtained.
（実施形態３）
　本実施形態は、図１２に示すごとく、実施形態２に対して、第一部位４１１におけるプラグ軸方向Ｚの基端側の端面４１１ａと、第二部位４１２の内周面４１２ｂとの形状を変更した実施形態である。すなわち、本実施形態において、第一部位４１１の端面４１１ａと第二部位４１２の内周面４１２ｂとは、曲面状に滑らかにつながっている。本実施形態において、第一部位４１１の端面４１１ａと第二部位４１２の内周面４１２ｂとの間の曲面の曲率半径は、０．５ｍｍである。
　その他は、実施形態２と同様である。 (Embodiment 3)
In the present embodiment, as shown in FIG. 12, the shapes of the end surface 411a on the proximal end side in the plug axial direction Z in the first portion 411 and the inner peripheral surface 412b of the second portion 412 are changed with respect to the second embodiment. Embodiment. That is, in the present embodiment, the end surface 411a of the first part 411 and the inner peripheral surface 412b of the second part 412 are smoothly connected in a curved shape. In the present embodiment, the radius of curvature of the curved surface between the end surface 411a of the first part 411 and the inner peripheral surface 412b of the second part 412 is 0.5 mm.
Others are the same as in the second embodiment.
　本実施形態においては、軸方向空隙ａｃ及び径方向空隙ｒｃに流入された気流を、中心電極４と接地電極２との間に向かって、滑らかに送り出すことができる。それゆえ、軸方向空隙ａｃ及び径方向空隙ｒｃから流出された気流に乱れが生じにくく、一層放電火花を引き伸ばしやすい。
　その他、実施形態２と同様の作用効果を有する。 In the present embodiment, the airflow flowing into the axial gap ac and the radial gap rc can be smoothly sent out between the center electrode 4 and the ground electrode 2. Therefore, the airflow flowing out from the axial gap ac and the radial gap rc is less likely to be disturbed, and the discharge spark is more easily stretched.
In addition, the same effects as those of the second embodiment are obtained.
（実施形態４）
　本実施形態は、図１３、図１４に示すごとく、実施形態１に対して、露出部４１の形状を変更した実施形態である。露出部４１の外周面４１ｂは、プラグ軸方向Ｚの先端側に向かうほどプラグ径方向の外周側に向かうよう傾斜した部位を有する。本実施形態において、露出部４１の外周面４１ｂの全体は、プラグ軸方向Ｚの先端側に向かうほどプラグ径方向の外周側に向かうよう傾斜している。すなわち、露出部４１の外形は、プラグ軸方向Ｚの基端側に向かうほど縮径している。そして、図１３に示すごとく、露出部４１の外周面４１ｂと、第二部位４１２の内周面４１２ｂとの間の角部の角度である。なお、本実施形態において、プラグ軸方向Ｚにおける露出部４１の外周面４１ｂの長さは、２．０ｍｍである。また、直径Ａ、内径Ｂ、外径Ｃ、空間距離Ｄのそれぞれの長さは、実施形態２と同様である。
　その他は、実施形態１と同様である。 (Embodiment 4)
As shown in FIGS. 13 and 14, the present embodiment is an embodiment in which the shape of the exposed portion 41 is changed with respect to the first embodiment. The outer peripheral surface 41b of the exposed portion 41 has a portion that is inclined toward the outer peripheral side in the plug radial direction toward the distal end side in the plug axial direction Z. In the present embodiment, the entire outer peripheral surface 41b of the exposed portion 41 is inclined toward the outer peripheral side in the plug radial direction toward the tip end side in the plug axial direction Z. That is, the outer shape of the exposed portion 41 is reduced in diameter toward the proximal end side in the plug axial direction Z. And as shown in FIG. 13, it is the angle of the corner | angular part between the outer peripheral surface 41b of the exposed part 41, and the inner peripheral surface 412b of the 2nd site | part 412. FIG. In the present embodiment, the length of the outer peripheral surface 41b of the exposed portion 41 in the plug axial direction Z is 2.0 mm. The lengths of the diameter A, the inner diameter B, the outer diameter C, and the spatial distance D are the same as those in the second embodiment.
Others are the same as in the first embodiment.
　本実施形態においては、スパークプラグ１が取り付けられた内燃機関の燃焼室内の気流によって、中心電極４と接地電極２との間に生じる放電を、碍子露出部３１０の表面から引き離し、かつ、気流の下流側に大きく引き伸ばしやすい。このことにつき、図１５～１６を用いて以後説明する。 In the present embodiment, the discharge generated between the center electrode 4 and the ground electrode 2 due to the airflow in the combustion chamber of the internal combustion engine to which the spark plug 1 is attached is separated from the surface of the insulator exposed portion 310, and the airflow It is easy to stretch greatly downstream. This will be described later with reference to FIGS.
　図１５に示すごとく、本実施形態において、放電火花Ｓの中心電極４側の起点Ｓ１は、第二部位４１２におけるプラグ軸方向Ｚの基端側の端部の角に生じる。そして、図１６、図１７に示すごとく、放電火花Ｓの中心電極４側の起点Ｓ１は、燃焼室内においてプラグ軸方向Ｚに直交する方向に流れる気流Ｆに押され、露出部４１の外周面４１ｂ上を、プラグ軸方向Ｚの先端側及びプラグ径方向の外周側に向かって移動する。なお、このとき、放電火花Ｓの接地電極２側の起点Ｓ２は、実施形態１と同様、接地電極２の先端面２１をプラグ径方向の外周側に向かって移動する。これにより、放電火花Ｓの両起点が、プラグ径方向において碍子露出部３１０から離れる方向に移動するとともに、放電火花Ｓの両起点間の距離を、プラグ軸方向Ｚに拡大させるように移動する。 As shown in FIG. 15, in the present embodiment, the starting point S <b> 1 of the discharge spark S on the side of the central electrode 4 is generated at the corner of the end portion on the proximal end side in the plug axis direction Z in the second portion 412. 16 and 17, the starting point S1 of the discharge spark S on the central electrode 4 side is pushed by the air flow F flowing in the direction perpendicular to the plug axis direction Z in the combustion chamber, and the outer peripheral surface 41b of the exposed portion 41 It moves upward toward the tip end side in the plug axial direction Z and the outer peripheral side in the plug radial direction. At this time, the starting point S2 on the ground electrode 2 side of the discharge spark S moves on the distal end surface 21 of the ground electrode 2 toward the outer peripheral side in the plug radial direction, as in the first embodiment. Thereby, both starting points of the discharge spark S move in a direction away from the insulator exposed portion 310 in the plug radial direction, and the distance between both starting points of the discharge spark S moves in the plug axis direction Z.
　放電火花Ｓの両起点が、プラグ径方向において碍子露出部３１０から離れる方向に移動することに伴い、放電火花Ｓの両起点間の部位も、碍子露出部３１０の外周面から外周側に離れる。そして、碍子露出部３１０の外周面から外周側に離れた放電火花Ｓの両起点間の部位は、燃焼室内の気流Ｆにより、当該気流Ｆの下流側に向かって大きく引き伸ばされる。特に、本実施形態においては、放電火花Ｓの両起点間のプラグ軸方向Ｚの距離を拡大させるように、放電火花Ｓの両起点が移動するため、放電火花Ｓの両起点間の部位は、一層大きく引き伸ばされやすい。これにより、放電火花Ｓと混合気との接触面積を一層稼ぎやすく、混合気への着火性を一層確保しやすい。
　その他、実施形態１と同様の作用効果を有する。 As both starting points of the discharge spark S move in the direction away from the insulator exposed portion 310 in the plug radial direction, the portion between both starting points of the discharge spark S also moves away from the outer peripheral surface of the insulator exposed portion 310 to the outer peripheral side. And the site | part between both starting points of the discharge spark S which left | separated from the outer peripheral surface of the insulator exposure part 310 to the outer peripheral side is largely extended toward the downstream of the said air flow F by the air flow F in a combustion chamber. In particular, in the present embodiment, since the both starting points of the discharge spark S move so as to increase the distance in the plug axis direction Z between both starting points of the discharge spark S, the region between both starting points of the discharge spark S is: Easier to stretch. Thereby, it is easier to earn a contact area between the discharge spark S and the air-fuel mixture, and it is easier to ensure the ignitability of the air-fuel mixture.
In addition, the same effects as those of the first embodiment are obtained.
（実施形態５）
　本実施形態は、図１８、図１９に示すごとく、実施形態１に対して、接地電極２の形状を変更した実施形態である。接地電極２の先端面２１は、プラグ径方向の外周側に向かうほどプラグ軸方向Ｚの基端側に向かうよう傾斜した部位を有する。本実施形態において、接地電極２の先端面２１の全体は、プラグ径方向の外周側に向かうほどプラグ軸方向Ｚの基端側に向かうよう傾斜している。接地電極２の先端面２１と内周面との間の角部の角度は、鋭角である。なお、直径Ａ、内径Ｂ、外径Ｃ、空間距離Ｄのそれぞれの長さは、実施形態２と同様である。
　その他は、実施形態１と同様である。 (Embodiment 5)
As shown in FIGS. 18 and 19, the present embodiment is an embodiment in which the shape of the ground electrode 2 is changed with respect to the first embodiment. The distal end surface 21 of the ground electrode 2 has a portion that is inclined toward the proximal end side in the plug axial direction Z toward the outer peripheral side in the plug radial direction. In the present embodiment, the entire distal end surface 21 of the ground electrode 2 is inclined so as to be directed toward the base end side in the plug axial direction Z toward the outer peripheral side in the plug radial direction. The angle of the corner between the tip surface 21 of the ground electrode 2 and the inner peripheral surface is an acute angle. The lengths of the diameter A, the inner diameter B, the outer diameter C, and the spatial distance D are the same as those in the second embodiment.
Others are the same as in the first embodiment.
　本実施形態においては、スパークプラグ１が取り付けられた内燃機関の燃焼室内の気流によって、中心電極４と接地電極２との間に生じる放電を、碍子露出部３１０の表面から引き離し、かつ、気流の下流側に大きく引き伸ばしやすい。このことにつき、図２０～図２２を用いて以後説明する。 In the present embodiment, the discharge generated between the center electrode 4 and the ground electrode 2 due to the airflow in the combustion chamber of the internal combustion engine to which the spark plug 1 is attached is separated from the surface of the insulator exposed portion 310, and the airflow It is easy to stretch greatly downstream. This will be described later with reference to FIGS.
　図２０に示すごとく、本実施形態において、放電火花Ｓの接地電極２側の起点Ｓ２は、接地電極２の先端面２１における内周端の角を起点として生じる。そして、図２１、図２２に示すごとく、放電火花Ｓの接地電極２側の起点Ｓ２は、燃焼室内においてプラグ軸方向Ｚに直交する方向に流れる気流Ｆに押され、接地電極２の先端面２１上を、プラグ軸方向Ｚの基端側及びプラグ径方向の外周側に向かって移動する。なお、このとき、放電火花Ｓの中心電極４側の起点Ｓ１は、実施形態１と同様、第二部位４１２におけるプラグ軸方向Ｚの基端側の端面４１２ａ上を、プラグ径方向の外周側に向かって移動する。これにより、放電火花Ｓの両起点が、プラグ径方向において碍子露出部３１０から離れる方向に移動するとともに、放電火花Ｓの両起点間の距離をプラグ軸方向Ｚに拡大されるように移動する。 As shown in FIG. 20, in the present embodiment, the starting point S2 of the discharge spark S on the ground electrode 2 side is generated starting from the corner of the inner peripheral end of the tip surface 21 of the ground electrode 2. As shown in FIGS. 21 and 22, the starting point S <b> 2 of the discharge spark S on the ground electrode 2 side is pushed by the air flow F flowing in the direction perpendicular to the plug axis direction Z in the combustion chamber, and the tip surface 21 of the ground electrode 2. It moves upward toward the base end side in the plug axial direction Z and the outer peripheral side in the plug radial direction. At this time, the starting point S1 of the discharge spark S on the side of the center electrode 4 is the same as in the first embodiment, on the end surface 412a on the proximal end side in the plug axial direction Z in the second portion 412 on the outer peripheral side in the plug radial direction. Move towards. Thereby, both starting points of the discharge spark S move in a direction away from the insulator exposed portion 310 in the plug radial direction, and the distance between the both starting points of the discharge spark S moves in the plug axial direction Z.
　放電火花Ｓの両起点が、プラグ径方向において碍子露出部３１０から離れる方向に移動することに伴い、放電火花Ｓの両起点間の部位も、碍子露出部の外周面から外周側に離れる。そして、碍子露出部３１０の外周面から外周側に離れた放電火花Ｓの両起点間の部位は、燃焼室内の気流により、当該気流の下流側に向かって大きく引き伸ばされる。特に、本実施形態においては、放電火花Ｓの両起点間のプラグ軸方向Ｚの距離を拡大させるように、放電火花Ｓの両起点が移動するため、放電火花Ｓの両起点間の部位は、一層大きく引き伸ばされやすい。これにより、放電火花Ｓと混合気との接触面積を一層稼ぎやすく、混合気への着火性を一層確保しやすい。
　その他、実施形態１と同様の作用効果を有する。 As both starting points of the discharge spark S move in the direction away from the insulator exposed portion 310 in the plug radial direction, the portion between both starting points of the discharge spark S also moves away from the outer peripheral surface of the insulator exposed portion to the outer peripheral side. And the site | part between both starting points of the discharge spark S which left | separated from the outer peripheral surface of the insulator exposure part 310 to the outer peripheral side is largely extended toward the downstream of the said airflow by the airflow in a combustion chamber. In particular, in the present embodiment, since the both starting points of the discharge spark S move so as to increase the distance in the plug axis direction Z between both starting points of the discharge spark S, the region between both starting points of the discharge spark S is: Easier to stretch. Thereby, it is easier to earn a contact area between the discharge spark S and the air-fuel mixture, and it is easier to ensure the ignitability of the air-fuel mixture.
In addition, the same effects as those of the first embodiment are obtained.
（実施形態６）
　本実施形態は、図２３～図２５に示すごとく、露出部４１に、露出部４１の内外を貫通する通気孔４０を形成した実施形態である。通気孔４０は、一端が径方向空隙ｒｃに向かって開口している。本実施形態において、通気孔４０は、中心電極４の第二部位４１２に形成されている。図２３に示すごとく、通気孔４０は、第二部位４１２をプラグ径方向に貫通するよう形成されている。通気孔４０の他端は、露出部４１の外周面４１ｂの外周側に向かって開口している。 (Embodiment 6)
As shown in FIGS. 23 to 25, the present embodiment is an embodiment in which a vent hole 40 penetrating the inside and outside of the exposed portion 41 is formed in the exposed portion 41. One end of the vent hole 40 opens toward the radial gap rc. In the present embodiment, the vent hole 40 is formed in the second portion 412 of the center electrode 4. As shown in FIG. 23, the vent hole 40 is formed so as to penetrate the second portion 412 in the plug radial direction. The other end of the vent hole 40 opens toward the outer peripheral side of the outer peripheral surface 41 b of the exposed portion 41.
　図２５に示すごとく、本実施形態において、通気孔４０は複数、具体的には４つ形成されている。４つの通気孔４０は、プラグ周方向において等間隔に配されている。すなわち、４つの通気孔４０は、プラグ周方向の４箇所に、９０°の間隔で形成されている。なお、図２５においては、プラグ軸方向Ｚからみたときの通気孔４０の外形位置を、破線にて表している。 As shown in FIG. 25, in the present embodiment, a plurality of, specifically four, air holes 40 are formed. The four vent holes 40 are arranged at equal intervals in the plug circumferential direction. That is, the four vent holes 40 are formed at four intervals in the circumferential direction of the plug at 90 ° intervals. In FIG. 25, the outer position of the vent hole 40 when viewed from the plug axial direction Z is indicated by a broken line.
　図２３、図２４に示すごとく、露出部４１の外周面４１ｂは、内周側に向かって凹む形状を有する。具体的には、露出部４１の外周面４１ｂは、プラグ軸方向Ｚにおいて通気孔４０から遠ざかるほど、プラグ径方向の外周側に向かうよう凹んでいる。すなわち、露出部４１の外周面４１ｂは、通気孔４０が形成された部位が、最も小さい径を有する。なお、直径Ａ、内径Ｂ、外径Ｃ、空間距離Ｄのそれぞれの長さは、実施形態２と同様である。
　その他は、実施形態１と同様である。 As shown in FIGS. 23 and 24, the outer peripheral surface 41b of the exposed portion 41 has a shape that is recessed toward the inner peripheral side. Specifically, the outer peripheral surface 41b of the exposed portion 41 is recessed toward the outer peripheral side in the plug radial direction as the distance from the vent hole 40 in the plug axial direction Z increases. That is, the outer peripheral surface 41b of the exposed portion 41 has the smallest diameter at the portion where the vent hole 40 is formed. The lengths of the diameter A, the inner diameter B, the outer diameter C, and the spatial distance D are the same as those in the second embodiment.
Others are the same as in the first embodiment.
　本実施形態においては、中心電極４と接地電極２との間において、プラグ径方向の外側、すなわち碍子露出部３１０の表面から離れる側、に向かって気流を生じさせやすい。すなわち、本実施形態において、燃焼室内の気流の一部は、まず、通気孔４０を介して、スパークプラグ１の外側から、径方向空隙ｒｃに燃焼室内の気流を流入される。そして、径方向空隙ｒｃに流入した気流は、中心電極４と接地電極２との間において、プラグ径方向の外周側に向かうよう、すなわち、碍子露出部３１０から遠ざかる側に向かうよう、流出される。それゆえ、放電火花を一層引き伸ばしやすい。
　その他、実施形態１と同様の作用効果を有する。 In the present embodiment, an air flow is easily generated between the center electrode 4 and the ground electrode 2 toward the outside in the plug radial direction, that is, the side away from the surface of the insulator exposed portion 310. That is, in the present embodiment, a part of the airflow in the combustion chamber is first introduced into the radial gap rc from the outside of the spark plug 1 through the vent hole 40. Then, the airflow flowing into the radial gap rc flows out between the center electrode 4 and the ground electrode 2 toward the outer peripheral side in the plug radial direction, that is, toward the side away from the insulator exposed portion 310. . Therefore, it is easier to extend the discharge spark.
In addition, the same effects as those of the first embodiment are obtained.
（実施形態７）
　本実施形態は、図２６、図２７に示すごとく、通気孔４０を、中心電極４の第一部位４１１に形成した実施形態である。図２６に示すごとく、通気孔４０は、第一部位４１１をプラグ軸方向Ｚに貫通するよう形成されている。通気孔４０の一端は、碍子突出部３１の外周面３１ｂと中心電極４の露出部４１の第二部位４１２の内周面４１２ｂとの間の空間に向かって開口している。通気孔４０の他端は、第一部位４１１におけるプラグ軸方向Ｚの先端側に向かって開口している。 (Embodiment 7)
In the present embodiment, as shown in FIGS. 26 and 27, the vent hole 40 is formed in the first portion 411 of the center electrode 4. As shown in FIG. 26, the vent hole 40 is formed so as to penetrate the first portion 411 in the plug axial direction Z. One end of the vent hole 40 opens toward a space between the outer peripheral surface 31 b of the insulator protrusion 31 and the inner peripheral surface 412 b of the second portion 412 of the exposed portion 41 of the center electrode 4. The other end of the vent hole 40 opens toward the tip side in the plug axial direction Z at the first portion 411.
　図２７に示すごとく、本実施形態においても、通気孔４０は複数、具体的には４つ形成されている。４つの通気孔４０は、プラグ周方向において等間隔に配されている。すなわち、４つの通気孔４０は、プラグ周方向の４箇所に、９０°の間隔で形成されている。 As shown in FIG. 27, also in the present embodiment, a plurality of, specifically four, air holes 40 are formed. The four vent holes 40 are arranged at equal intervals in the plug circumferential direction. That is, the four vent holes 40 are formed at four intervals in the circumferential direction of the plug at 90 ° intervals.
　図２６に示すごとく、露出部４１におけるプラグ軸方向Ｚの先端側の端面４１ａは、凹凸状に形成されている。露出部４１の端面４１ａは、プラグ径方向において、通気孔４０から遠ざかるほど、プラグ軸方向Ｚの先端側に突出するような凹凸状に形成されている。すなわち、露出部４１の端面４１ａは、通気孔４０が形成された部位が、最もプラグ軸方向Ｚの基端側に位置するよう凹んでいる。
　その他は、実施形態６と同様である。 As shown in FIG. 26, the end surface 41a on the distal end side in the plug axis direction Z of the exposed portion 41 is formed in an uneven shape. The end surface 41a of the exposed portion 41 is formed in a concavo-convex shape so as to protrude toward the distal end side in the plug axial direction Z as the distance from the vent hole 40 increases in the plug radial direction. In other words, the end surface 41a of the exposed portion 41 is recessed so that the portion where the vent hole 40 is formed is located closest to the base end side in the plug axial direction Z.
Others are the same as in the sixth embodiment.
　本実施形態においても、実施形態６と同様の作用効果を有する。 This embodiment also has the same function and effect as the sixth embodiment.
（実施形態８）
　本実施形態は、図２８～図３０に示すごとく、実施形態１に対して、碍子突出部３１の形状を変更した実施形態である。 (Embodiment 8)
As shown in FIGS. 28 to 30, the present embodiment is an embodiment in which the shape of the insulator protrusion 31 is changed from that of the first embodiment.
　図２８、図２９に示すごとく、碍子突出部３１は、プラグ軸方向Ｚの先端側が、基端側よりも小径となる碍子段部３１２を有する。また、碍子突出部３１は、全体として、プラグ軸方向Ｚの先端側に向かうほど段階的に外径が小さくなる段形状を有する。これに伴い、碍子露出部３１０も、全体として、プラグ軸方向Ｚの先端側に向かうほど段階的に外径が小さくなる段形状を有する。 As shown in FIGS. 28 and 29, the insulator protrusion 31 has an insulator step 312 whose tip end side in the plug axial direction Z has a smaller diameter than the base end side. Further, the insulator projecting portion 31 as a whole has a step shape in which the outer diameter gradually decreases toward the tip end side in the plug axial direction Z. Along with this, the insulator exposed portion 310 also has a stepped shape whose outer diameter gradually decreases toward the tip end side in the plug axial direction Z as a whole.
　碍子突出部３１は、プラグ軸方向Ｚの基端側に形成された碍子大径部３１１と、その先端側に形成された碍子小径部３１３と、これらを連結する碍子段部３１２とを有する。碍子小径部３１３の外径は、碍子大径部３１１の外径よりも小さい。碍子段部３１２は、プラグ軸方向Ｚにおける碍子突出部３１のうちの碍子露出部３１０の中央に形成されている。碍子露出部３１０の外周面における、碍子小径部３１３と碍子段部３１２と碍子大径部３１１とは、滑らかな曲線状につながっている。すなわち、碍子露出部３１０の外周面における、碍子小径部３１３と碍子段部３１２との境界、碍子段部３１２と碍子大径部３１１との境界は、鋭利な角部になっていない。碍子突出部３１において、碍子段部３１２は、プラグ軸方向Ｚの一か所に形成されている。すなわち、本実施形態における碍子突出部３１は、一段の段形状である。碍子段部３１２は、中心電極４の第二部位４１２におけるプラグ軸方向Ｚの基端側の端面４１２ａよりも、基端側に離れた位置にある。 The insulator protrusion 31 has an insulator large-diameter portion 311 formed on the proximal end side in the plug axial direction Z, an insulator small-diameter portion 313 formed on the distal end side thereof, and an insulator step portion 312 connecting them. The outer diameter of the insulator small diameter portion 313 is smaller than the outer diameter of the insulator large diameter portion 311. The insulator step portion 312 is formed at the center of the insulator exposure portion 310 in the insulator protrusion 31 in the plug axial direction Z. On the outer peripheral surface of the insulator exposed portion 310, the insulator small diameter portion 313, the insulator step portion 312 and the insulator large diameter portion 311 are connected in a smooth curved shape. That is, the boundary between the small insulator diameter portion 313 and the insulator step portion 312 and the boundary between the insulator step portion 312 and the insulator large diameter portion 311 on the outer peripheral surface of the insulator exposed portion 310 are not sharp corners. In the insulator projecting portion 31, the insulator step portion 312 is formed at one place in the plug axial direction Z. That is, the insulator protrusion 31 in the present embodiment has a single step shape. The insulator step portion 312 is located farther from the base end side than the end surface 412a on the base end side in the plug axis direction Z in the second portion 412 of the center electrode 4.
　図２８に示すごとく、第二部位４１２は、碍子小径部３１３の外周面に沿うよう形成されている。また、図３０に示すごとく、中心電極４の露出部４１は、プラグ軸方向Ｚから見たとき、接地電極２の内側に収まるよう形成されている。すなわち、中心電極４の露出部４１の最大外径は、接地電極２の最小内径よりも小さい。なお、図２８の断面図をプラグ軸方向Ｚから見たときの露出部４１の外形位置を一点鎖線にて表している。図２８においても、露出部４１の外形位置は、接地電極２の内側に収まっていることが分かる。 As shown in FIG. 28, the second portion 412 is formed along the outer peripheral surface of the insulator small diameter portion 313. Further, as shown in FIG. 30, the exposed portion 41 of the center electrode 4 is formed so as to fit inside the ground electrode 2 when viewed from the plug axial direction Z. That is, the maximum outer diameter of the exposed portion 41 of the center electrode 4 is smaller than the minimum inner diameter of the ground electrode 2. In addition, the external position of the exposed part 41 when the sectional view of FIG. 28 is viewed from the plug axis direction Z is indicated by a one-dot chain line. Also in FIG. 28, it can be seen that the outer position of the exposed portion 41 is within the ground electrode 2.
　図３０に示すごとく、本実施形態において、中心電極４の露出部４１は、プラグ軸方向Ｚから見たとき、接地電極２に加え、ハウジング（図１の符号１１参照）の内側にも収まるよう形成されている。さらに、中心電極４の露出部４１は、プラグ軸方向Ｚから見たとき、碍子段部３１２の外形よりも内側に収まるよう形成されている。なお、図３０において、便宜上、碍子段部３１２にハッチングを施している。
　その他は、実施形態１と同様である。 As shown in FIG. 30, in this embodiment, the exposed portion 41 of the center electrode 4 fits inside the housing (see reference numeral 11 in FIG. 1) in addition to the ground electrode 2 when viewed from the plug axial direction Z. Is formed. Further, the exposed portion 41 of the center electrode 4 is formed so as to fit inside the outer shape of the insulator step portion 312 when viewed from the plug axial direction Z. In FIG. 30, the insulator step portion 312 is hatched for convenience.
Others are the same as in the first embodiment.
　本実施形態において、碍子突出部３１は、全体として、プラグ軸方向Ｚの先端側に向かうほど段階的に外径が小さくなる段形状を有する。それゆえ、第二部位４１２から接地電極２までの、碍子露出部３１０の表面に沿った経路を長くすることができる。これにより、碍子露出部３１０をプラグ軸方向Ｚに伸ばすことなく、沿面放電の距離を確保することができ、着火性を高めることができる。すなわち、図３１に示すごとく、放電は、第二部位４１２におけるプラグ軸方向Ｚの基端側の端面４１２ａにおける内周端と、接地電極２の先端面２１における内周端とを起点として生じ、当該放電により発生する放電火花Ｓの両起点間の部位は、碍子突出部３１の碍子露出部３１０の外周面を這うよう段状に生じる。このように、放電が段状に生じることにより、放電が直線状に生じる場合よりも、沿面距離を確保することができる。 In this embodiment, the insulator protrusion 31 as a whole has a step shape in which the outer diameter decreases stepwise toward the distal end side in the plug axial direction Z. Therefore, the path along the surface of the insulator exposed portion 310 from the second portion 412 to the ground electrode 2 can be lengthened. Accordingly, the distance of creeping discharge can be ensured without extending the insulator exposed portion 310 in the plug axial direction Z, and the ignitability can be improved. That is, as shown in FIG. 31, the discharge is generated starting from the inner peripheral end of the end surface 412a on the proximal end side in the plug axis direction Z in the second portion 412 and the inner peripheral end of the distal end surface 21 of the ground electrode 2, A portion between both starting points of the discharge spark S generated by the discharge is formed in a step shape so as to crawl the outer peripheral surface of the insulator exposed portion 310 of the insulator protrusion 31. Thus, the creeping distance can be secured by generating the discharge stepwise as compared with the case where the discharging is generated linearly.
　さらに、碍子突出部３１の先端部のプラグ軸方向Ｚに直交する断面の面積が小さくなるため、スパークプラグ１の放電によって生じた火炎の熱が碍子突出部３１に奪われることによる冷損を低減することができる。これによっても、混合気への着火性の向上を図ることができる。 Furthermore, since the area of the cross section orthogonal to the plug axial direction Z at the tip of the insulator protrusion 31 is reduced, the cooling loss due to the heat of the flame generated by the discharge of the spark plug 1 being taken away by the insulator protrusion 31 is reduced. can do. This can also improve the ignitability of the air-fuel mixture.
　また、中心電極４の露出部４１は、プラグ軸方向Ｚから見たとき、接地電極２の内側に収まるよう形成されている。それゆえ、スパークプラグ１の生産性を向上させやすい。すなわち、予めハウジング１１及び接地電極２以外の構成部品を絶縁碍子３に組み付けた構造体を形成し、その構造体をハウジング１１及び接地電極２に対しハウジング１１及び接地電極２の基端側から挿通させることにより、容易にスパークプラグ１を製造することができる。逆に、中心電極４の露出部４１が接地電極２よりも大径に形成されている場合、中心電極４の露出部４１を接地電極２の内側に挿通させることはできないため、まず中心電極４の露出部４１が組み付けられていない絶縁碍子３を接地電極２に挿通させ、その後中心電極４の露出部４１を絶縁碍子３に対して先端側から組み付ける等する必要があり、製造工程の増加につながる。
　その他、実施形態１と同様の作用効果を有する。 Further, the exposed portion 41 of the center electrode 4 is formed so as to fit inside the ground electrode 2 when viewed from the plug axial direction Z. Therefore, it is easy to improve the productivity of the spark plug 1. That is, a structure in which components other than the housing 11 and the ground electrode 2 are assembled to the insulator 3 in advance is formed, and the structure is inserted into the housing 11 and the ground electrode 2 from the base end side of the housing 11 and the ground electrode 2. By making it, the spark plug 1 can be manufactured easily. Conversely, when the exposed portion 41 of the center electrode 4 is formed to have a larger diameter than the ground electrode 2, the exposed portion 41 of the center electrode 4 cannot be inserted inside the ground electrode 2. It is necessary to insert the insulator 3 to which the exposed portion 41 is not assembled into the ground electrode 2 and then to assemble the exposed portion 41 of the center electrode 4 with respect to the insulator 3 from the front end side. Connected.
In addition, the same effects as those of the first embodiment are obtained.
（実施形態９）
　本実施形態は、図３２に示すごとく、基本構造を実施形態８と同様としつつ、プラグ径方向における、碍子突出部３１の外周面３１ｂと第二部位４１２の内周面４１２ｂとの間に、実施形態１で説明した径方向空隙ｒｃを形成した実施形態である。すなわち、第二部位４１２の内周面４１２ｂは、碍子突出部３１の外周面３１ｂからプラグ径方向の外周側に離れた位置に形成されている。径方向空隙ｒｃは、プラグ周方向の全周に環状に形成されている。径方向空隙ｒｃは、プラグ軸方向Ｚの基端側に向かって開口している。 (Embodiment 9)
In the present embodiment, as shown in FIG. 32, the basic structure is the same as that of the eighth embodiment, and the outer peripheral surface 31b of the lever protrusion 31 and the inner peripheral surface 412b of the second portion 412 in the plug radial direction are This is an embodiment in which the radial gap rc described in the first embodiment is formed. That is, the inner peripheral surface 412b of the second portion 412 is formed at a position away from the outer peripheral surface 31b of the insulator protrusion 31 toward the outer peripheral side in the plug radial direction. The radial gap rc is formed in an annular shape around the entire circumference in the plug circumferential direction. The radial gap rc is open toward the base end side in the plug axial direction Z.
　なお、本実施形態において、プラグ径方向における中心電極４の露出部４１の外周面４１ｂの位置は、接地電極２の内周面の位置と同等に形成されている。
　その他は、実施形態８と同様である。 In the present embodiment, the position of the outer peripheral surface 41 b of the exposed portion 41 of the center electrode 4 in the plug radial direction is formed to be equal to the position of the inner peripheral surface of the ground electrode 2.
Others are the same as in the eighth embodiment.
　本実施形態においては、燃焼室内の気流が、径方向空隙ｒｃ内にも流入する。そして、径方向空隙ｒｃに流入された気流は、中心電極４と接地電極２との間において、プラグ径方向の外側に向かうよう、すなわち、碍子露出部３１０から遠ざかる側に向かうよう、流出される。それゆえ、放電火花を、碍子露出部３１０から遠ざけるように引き伸ばしやすい。
　その他、実施形態８と同様の作用効果を有する。 In the present embodiment, the airflow in the combustion chamber also flows into the radial gap rc. Then, the airflow that has flowed into the radial gap rc flows out between the center electrode 4 and the ground electrode 2 toward the outside in the plug radial direction, that is, toward the side away from the insulator exposed portion 310. . Therefore, it is easy to stretch the discharge spark away from the insulator exposed portion 310.
In addition, the same effects as those of the eighth embodiment are obtained.
（実施形態１０）
　本実施形態は、図３３に示すごとく、基本構造を実施形態９と同様としつつ、中心電極４の第二部位４１２に貫通孔２０を形成した実施形態である。貫通孔２０の構成、形成位置等は、実施形態６で示した貫通孔２０と同様である。
　その他は、実施形態９と同様である。 (Embodiment 10)
As shown in FIG. 33, the present embodiment is an embodiment in which the through hole 20 is formed in the second portion 412 of the center electrode 4 while the basic structure is the same as that of the ninth embodiment. The configuration, formation position, and the like of the through hole 20 are the same as those of the through hole 20 shown in the sixth embodiment.
Others are the same as in the ninth embodiment.
　本実施形態においては、実施形態６、及び、実施形態９と同様の作用効果を有する。 In this embodiment, the same function and effect as those of the sixth and ninth embodiments are obtained.
（実施形態１１）
　本実施形態は、図３４に示すごとく、基本構造を実施形態９と同様としつつ、中心電極４の第一部位４１１に貫通孔２０を形成した実施形態である。貫通孔２０の構成、形成位置等は、実施形態７と同様である。 (Embodiment 11)
As shown in FIG. 34, the present embodiment is an embodiment in which the through hole 20 is formed in the first portion 411 of the center electrode 4 while the basic structure is the same as that of the ninth embodiment. The configuration, formation position, and the like of the through hole 20 are the same as those in the seventh embodiment.
　本実施形態においては、実施形態７、及び実施形態９と同様の作用効果を有する。 In the present embodiment, the same effects as those of the seventh and ninth embodiments are obtained.
（実施形態１２）
　本実施形態は、図３５に示すごとく、実施形態８に対し、中心電極４の形状を変更した実施形態である。 Embodiment 12
As shown in FIG. 35, the present embodiment is an embodiment in which the shape of the center electrode 4 is changed with respect to the eighth embodiment.
　本実施形態において、中心電極４における碍子突出部３１の内側に配された部位は、プラグ径方向の外周側に突出した電極大径部４２を有する。すなわち、電極大径部４２は、中心電極４における碍子突出部３１の内側の部位における先端部に形成されている。プラグ軸方向Ｚにおいて、電極大径部４２は、碍子段部３１２よりも先端側に位置している。すなわち、電極大径部４２は、碍子突出部３１の碍子小径部３１３の内側に形成されている。電極大径部４２の先端側は、露出部４１と接続している。 In the present embodiment, the portion of the center electrode 4 that is disposed inside the insulator protrusion 31 has an electrode large diameter portion 42 that protrudes toward the outer peripheral side in the plug radial direction. That is, the electrode large-diameter portion 42 is formed at the distal end portion of the center electrode 4 at the portion inside the insulator protrusion 31. In the plug axial direction Z, the electrode large-diameter portion 42 is located on the tip side of the insulator step portion 312. That is, the electrode large diameter portion 42 is formed inside the insulator small diameter portion 313 of the insulator protrusion portion 31. The distal end side of the electrode large-diameter portion 42 is connected to the exposed portion 41.
　電極大径部４２は、プラグ中心軸を中心として回転対称の形状を有する。電極大径部４２には、プラグ軸方向Ｚの基端側から先端側に向かって、電極拡径部４２１、電極同径部４２２、及び電極縮径部４２３が形成されている。電極拡径部４２１は、プラグ軸方向Ｚの先端側に向かうほど拡径する。電極同径部４２２は、電極拡径部４２１からプラグ軸方向Ｚの先端側に延設するようプラグ軸方向Ｚにまっすぐ形成された円柱状を呈している。電極縮径部４２３は、電極同径部４２２からプラグ軸方向Ｚの先端側に向かうほど縮径する。プラグ軸方向Ｚの変化に対する径の変化は、電極縮径部４２３の方が電極拡径部４２１よりも大きい。
　その他は、実施形態８と同様である。 The electrode large-diameter portion 42 has a rotationally symmetric shape about the plug central axis. The electrode large diameter portion 42 is formed with an electrode enlarged diameter portion 421, an electrode same diameter portion 422, and an electrode reduced diameter portion 423 from the proximal end side to the distal end side in the plug axial direction Z. The electrode diameter-enlarged portion 421 increases in diameter toward the distal end side in the plug axial direction Z. The electrode same-diameter portion 422 has a cylindrical shape that is straightly formed in the plug axial direction Z so as to extend from the electrode enlarged diameter portion 421 to the distal end side in the plug axial direction Z. The electrode diameter-reduced portion 423 decreases in diameter toward the distal end side in the plug axial direction Z from the electrode same-diameter portion 422. The change in diameter with respect to the change in the plug axis direction Z is larger in the electrode reduced diameter portion 423 than in the electrode enlarged diameter portion 421.
Others are the same as in the eighth embodiment.
　本実施形態においては、碍子突出部３１の内側に配された部位に電極大径部４２を形成しているため、プレイグニッションの発生を防止しやすい。このことにつき以後説明する。
　まず、本実施形態においては、碍子突出部３１が、全体として、プラグ軸方向Ｚの先端側に向かうほど段階的に外径が小さくなる段形状を有するため、碍子突出部３１の先端部の熱容量は小さくなり昇温しやすくなる。これに伴い、碍子突出部３１の先端部周辺に位置する中心電極４の先端部も昇温しやすくなる。そこで、本実施形態のように、碍子突出部３１の内側に配された部位に電極大径部４２を形成し、中心電極４先端部の熱容量を確保することにより、中心電極４先端部が急激に昇温することを防止することができる。
　その他、実施形態８と同様の作用効果を有する。 In the present embodiment, since the electrode large-diameter portion 42 is formed at a portion disposed inside the insulator protrusion 31, it is easy to prevent the occurrence of pre-ignition. This will be described later.
First, in this embodiment, since the insulator protrusion 31 as a whole has a step shape in which the outer diameter decreases stepwise toward the tip end in the plug axis direction Z, the heat capacity of the tip of the insulator protrusion 31 is increased. Becomes smaller and the temperature rises more easily. As a result, the temperature of the tip of the center electrode 4 located around the tip of the insulator protrusion 31 is also likely to rise. Therefore, as in the present embodiment, the electrode large-diameter portion 42 is formed in a portion disposed inside the insulator protrusion portion 31 to ensure the heat capacity of the center electrode 4 tip, so that the tip of the center electrode 4 is sharply It is possible to prevent the temperature from rising.
In addition, the same effects as those of the eighth embodiment are obtained.
（実施形態１３）
　本実施形態は、図３６～図３９に示すごとく、実施形態８に対して、中心電極４の露出部４１の形状を変更した実施形態である。 (Embodiment 13)
As shown in FIGS. 36 to 39, the present embodiment is an embodiment in which the shape of the exposed portion 41 of the center electrode 4 is changed with respect to the eighth embodiment.
　図３６、図３９に示すごとく、露出部４１は、中心電極４における絶縁碍子３の内側の部位から先端側に延設された延設露出部４１３と、延設露出部４１３に取り付けられた取付露出部４１４とを有する。延設露出部４１３と取付露出部４１４とは別体である。延設露出部４１３は、円柱状を呈している。取付露出部４１４は、プラグ軸方向Ｚに貫通するとともに延設露出部４１３と略同径の取付孔４１０が形成されている。そして、取付露出部４１４は、取付孔４１０に延設露出部４１３を挿入し、延設露出部４１３に接合されている。 As shown in FIGS. 36 and 39, the exposed portion 41 includes an extended exposed portion 413 extending from the inner side of the insulator 3 in the center electrode 4 to the distal end side, and an attachment attached to the extended exposed portion 413. And an exposed portion 414. The extension exposure part 413 and the attachment exposure part 414 are separate bodies. The extended exposed portion 413 has a cylindrical shape. The attachment exposed portion 414 is formed with an attachment hole 410 that penetrates in the plug axial direction Z and has substantially the same diameter as the extended exposed portion 413. The attachment exposure part 414 is joined to the extension exposure part 413 by inserting the extension exposure part 413 into the attachment hole 410.
　図３６に示すごとく、取付露出部４１４が第一部位４１１と第二部位４１２とを有する。第一部位４１１は、碍子突出部３１をプラグ軸方向Ｚの先端側から覆う。第二部位４１２は、第一部位４１１からプラグ軸方向Ｚの基端側に延設されると共に碍子突出部３１の外周面３１ｂのプラグ周方向の一部を、プラグ径方向の外周側から覆う。 As shown in FIG. 36, the mounting exposed portion 414 has a first part 411 and a second part 412. The first part 411 covers the insulator protrusion 31 from the distal end side in the plug axial direction Z. The second part 412 extends from the first part 411 to the proximal end side in the plug axial direction Z and covers a part of the outer peripheral surface 31b of the lever protrusion 31 in the plug peripheral direction from the outer peripheral side in the plug radial direction. .
　図３９に示すごとく、第一部位４１１は、プラグ軸方向Ｚに直交する横方向Ｘに長尺な角丸長方形状であり、かつプラグ軸方向Ｚに厚みを有する板状に形成されている。第一部位４１１には、前述の取付孔４１０が形成されている。図３６、図３７に示すごとく、第一部位４１１における横方向Ｘの一方の部分は、碍子突出部３１の先端面３１ａの外周端よりも外周側にはみ出るよう形成されている。 As shown in FIG. 39, the first portion 411 has a rounded rectangular shape elongated in the lateral direction X perpendicular to the plug axis direction Z and is formed in a plate shape having a thickness in the plug axis direction Z. The first portion 411 is formed with the mounting hole 410 described above. As shown in FIGS. 36 and 37, one portion of the first portion 411 in the lateral direction X is formed so as to protrude beyond the outer peripheral end of the distal end surface 31 a of the lever protrusion 31.
　そして、第二部位４１２は、第一部位４１１における横方向Ｘの一方の端部から基端側に延設されている。第二部位４１２は、横方向Ｘに厚みを有する板状に形成されている。また、図３８に示すごとく、第二部位４１２は、プラグ軸方向Ｚに短尺な角丸正方形状を呈している。 And the 2nd site | part 412 is extended from the one end part of the horizontal direction X in the 1st site | part 411 to the base end side. The second portion 412 is formed in a plate shape having a thickness in the lateral direction X. Further, as shown in FIG. 38, the second portion 412 has a short rounded square shape in the plug axial direction Z.
　第一部位４１１及び第二部位４１２は、碍子突出部３１の先端部の角部のプラグ周方向の一部を覆っている。第二部位４１２は、碍子小径部３１３の外周面に沿うよう形成されている。また、本実施形態においても、第二部位４１２の基端側の端面４１２ａは、碍子段部３１２から先端側に離れた位置に形成されている。 The 1st site | part 411 and the 2nd site | part 412 have covered a part of plug peripheral direction of the corner | angular part of the front-end | tip part of the insulator protrusion part 31. FIG. The second portion 412 is formed along the outer peripheral surface of the insulator small diameter portion 313. Also in the present embodiment, the proximal end surface 412a of the second part 412 is formed at a position away from the insulator step 312 toward the distal end side.
　図３９に示すごとく、プラグ軸方向Ｚから見たとき、スパークプラグ１の先端部を通る混合気の気流は、第二部位４１２とプラグ中心軸との並び方向（すなわち横方向Ｘ）に直交する方向に流れるよう構成されている。ここでいう気流は、エンジン点火時期においてスパークプラグ１の先端部を通す混合気の気流である。内燃機関におけるスパークプラグ１の取付姿勢は、燃焼室内におけるスパークプラグ１の先端部周辺の気流の流れを考慮してハウジング（図１の符号１１参照）の取付ネジ部（図１の符号１１１参照）のネジの切り方等を調整することにより、調整することができる。
　その他は、実施形態８と同様である。 As shown in FIG. 39, when viewed from the plug axial direction Z, the airflow of the air-fuel mixture passing through the tip of the spark plug 1 is orthogonal to the direction in which the second portion 412 and the plug central axis are aligned (that is, the lateral direction X). It is configured to flow in the direction. The airflow here is the airflow of the air-fuel mixture passing through the tip of the spark plug 1 at the engine ignition timing. The mounting posture of the spark plug 1 in the internal combustion engine is determined by taking into consideration the flow of airflow around the tip of the spark plug 1 in the combustion chamber (see reference numeral 11 in FIG. 1). It can be adjusted by adjusting how to cut the screw.
Others are the same as in the eighth embodiment.
　本実施形態においては、碍子突出部３１の先端部の角部の一部は、中心電極４の第一部位４１１および第二部位４１２に覆われている。それゆえ、放電が碍子突出部３１の先端部の角部上に生じることがなく、中心電極４の第二部位４１２と接地電極２との間で形成される。これにより燃焼室内の混合気の気流或いは電気的な反発作用により、放電を碍子突出部３１の表面から剥がして、下流側に引き伸ばしやすい。これにより、混合気への着火性の向上を図ることができる。 In this embodiment, a part of the corner at the tip of the insulator protrusion 31 is covered with the first part 411 and the second part 412 of the center electrode 4. Therefore, discharge does not occur on the corner of the tip of the insulator protrusion 31 and is formed between the second portion 412 of the center electrode 4 and the ground electrode 2. As a result, the discharge is easily peeled off from the surface of the insulator protrusion 31 by the air flow of the air-fuel mixture in the combustion chamber or the electric repulsive action, and is easily stretched downstream. Thereby, the ignitability to the air-fuel mixture can be improved.
　さらに、碍子突出部３１の少なくともプラグ周方向の第二部位４１２が形成された領域は、プラグ軸方向Ｚの全体において、プラグ軸方向Ｚの先端側に向かうほど段階的に外径が小さくなる段形状を有する。それゆえ、第二部位４１２から接地電極２までの、碍子露出部３１０の表面に沿った経路を長くすることができる。これにより、碍子露出部３１０をプラグ軸方向Ｚに伸ばすことなく、沿面放電の距離を確保することができ、着火性を高めることができる。さらに、碍子突出部３１の先端部のプラグ軸方向Ｚに直交する断面の面積が小さくなるため、スパークプラグ１の放電によって生じた火炎の熱が碍子突出部３１に奪われることによる冷損を低減することができる。これによっても、混合気への着火性の向上を図ることができる。 Further, at least the region where the second portion 412 in the plug circumferential direction of the lever protrusion 31 is formed is a step in which the outer diameter gradually decreases toward the tip end side in the plug axial direction Z in the entire plug axial direction Z. Has a shape. Therefore, the path along the surface of the insulator exposed portion 310 from the second portion 412 to the ground electrode 2 can be lengthened. Accordingly, the distance of creeping discharge can be ensured without extending the insulator exposed portion 310 in the plug axial direction Z, and the ignitability can be improved. Furthermore, since the area of the cross section orthogonal to the plug axial direction Z at the tip of the insulator protrusion 31 is reduced, the cooling loss due to the heat of the flame generated by the discharge of the spark plug 1 being taken away by the insulator protrusion 31 is reduced. can do. This can also improve the ignitability of the air-fuel mixture.
　また、プラグ軸方向Ｚから見たとき、スパークプラグ１の先端部を通る混合気の気流は、第二部位４１２とプラグ中心軸との並び方向（すなわち横方向Ｘ）に直交する向きに流れるよう構成されている。それゆえ、燃焼室内の気流は、直接的に第二部位４１２と接地電極２との間を通る。これにより、第二部位４１２と接地電極２との間を通る気流が、乱れることを防止することができ第二部位４１２と接地電極２との間に生じた放電火花を一層引き伸ばしやすい。
　その他、実施形態８と同様の作用効果を有する。 When viewed from the plug axis direction Z, the airflow of the air-fuel mixture passing through the tip of the spark plug 1 flows in a direction perpendicular to the direction in which the second portion 412 and the plug center axis are aligned (that is, the lateral direction X). It is configured. Therefore, the air flow in the combustion chamber passes directly between the second portion 412 and the ground electrode 2. Thereby, the airflow passing between the second part 412 and the ground electrode 2 can be prevented from being disturbed, and the discharge spark generated between the second part 412 and the ground electrode 2 can be more easily extended.
In addition, the same effects as those of the eighth embodiment are obtained.
（実施形態１４）
　本実施形態は、図４０に示すごとく、実施形態１３に対して、碍子突出部３１の形状を変更した実施形態である。 (Embodiment 14)
As shown in FIG. 40, the present embodiment is an embodiment in which the shape of the insulator protrusion 31 is changed with respect to the thirteenth embodiment.
　本実施形態において、碍子突出部３１は、複数の碍子段部３１２を有する。具体的には、碍子突出部３１は、２つの碍子段部３１２を有する。２つの碍子段部３１２は、プラグ軸方向Ｚにおいて、碍子露出部３１０を３等分するような位置に配されている。つまり、第二部位４１２の基端側の端面４１２ａと２つの碍子段部３１２と接地電極２の先端面２１とは、プラグ軸方向Ｚに等間隔に配されている。
　その他は、実施形態１３と同様である。 In this embodiment, the insulator protrusion 31 has a plurality of insulator steps 312. Specifically, the insulator protrusion 31 has two insulator steps 312. The two lever step portions 312 are arranged in a position that divides the lever exposure portion 310 into three equal parts in the plug axial direction Z. In other words, the end surface 412a on the proximal end side of the second part 412, the two insulator step portions 312, and the distal end surface 21 of the ground electrode 2 are arranged at equal intervals in the plug axial direction Z.
Others are the same as in the thirteenth embodiment.
　本実施形態においては、碍子突出部３１は複数の碍子段部３１２を有するため、碍子露出部３１０のプラグ軸方向Ｚの長さを短くしても、碍子露出部３１０の表面に沿った第二部位４１２から接地電極２までの沿面距離を確保できる。それゆえ、着火性に影響を及ぼすことなくスパークプラグ１の小型化を実現できる。
　その他、実施形態１３と同様の作用効果を有する。 In this embodiment, since the insulator protrusion 31 has a plurality of insulator steps 312, even if the length of the insulator exposure part 310 in the plug axial direction Z is shortened, the second along the surface of the insulator exposure part 310. A creepage distance from the portion 412 to the ground electrode 2 can be secured. Therefore, it is possible to reduce the size of the spark plug 1 without affecting the ignitability.
In addition, the same effects as those of the thirteenth embodiment are obtained.
　なお、本実施形態においては、碍子突出部３１が２つの碍子段部３１２を有する例を示したがこれに限られず、例えば図４１に示すごとく、３つの碍子段部３１２を形成したり、その他３つ以上の碍子段部を形成したりすることも可能である。 In the present embodiment, the example in which the insulator protrusion 31 has the two insulator steps 312 has been shown. However, the present invention is not limited to this. For example, as shown in FIG. It is also possible to form three or more insulator steps.
（実施形態１５）
　本実施形態は、図４２に示すごとく、実施形態１３に対して、碍子突出部３１の形状を変更した実施形態である。 (Embodiment 15)
As shown in FIG. 42, the present embodiment is an embodiment in which the shape of the lever protrusion 31 is changed with respect to the thirteenth embodiment.
　本実施形態において、碍子小径部３１３の外周面は、プラグ軸方向Ｚに平行な断面が波形状（凹凸形状）を呈している。本実施形態の碍子小径部３１３は、ミクロに見ればプラグ軸方向Ｚにおいて外径が変動しているが、マクロに見ればプラグ軸方向Ｚにおいて一定の外径を有する。そして、碍子突出部３１は、マクロに見た場合において、プラグ軸方向Ｚの全体が、プラグ軸方向Ｚの先端側に向かうほど段階的に外径が小さくなる段形状を有する。
　その他は、実施形態１３と同様である。 In the present embodiment, the outer circumferential surface of the insulator small-diameter portion 313 has a wave shape (uneven shape) in a cross section parallel to the plug axis direction Z. The small-diameter portion 313 of the present embodiment has an outer diameter that varies in the plug axis direction Z when viewed microscopically, but has a constant outer diameter in the plug axis direction Z when viewed macroscopically. Then, when viewed macroscopically, the insulator projecting portion 31 has a step shape in which the entire outer diameter in the plug axis direction Z gradually decreases toward the distal end side in the plug axis direction Z.
Others are the same as in the thirteenth embodiment.
　本実施形態においては、碍子小径部３１３の外周面が波形状となっているため、碍子露出部３１０のプラグ軸方向Ｚの長さを短くしても、碍子露出部３１０の表面に沿った第二部位４１２から接地電極２までの沿面距離を確保できる。それゆえ、着火性に影響を及ぼすことなくスパークプラグ１の小型化を実現できる。
　その他、実施形態１３と同様の作用効果を有する。 In the present embodiment, since the outer peripheral surface of the insulator small-diameter portion 313 has a wave shape, even if the length of the insulator exposed portion 310 in the plug axial direction Z is shortened, the first portion along the surface of the insulator exposed portion 310 is reduced. A creepage distance from the two parts 412 to the ground electrode 2 can be secured. Therefore, it is possible to reduce the size of the spark plug 1 without affecting the ignitability.
In addition, the same effects as those of the thirteenth embodiment are obtained.
　なお、本実施形態においては、碍子小径部３１３の外周面のみを波形状としたが、これに限られず、碍子大径部３１１の外周面のみを波形状にしたり、碍子小径部３１３の外周面と碍子大径部３１１の外周面との双方を波形状にしたりすることも可能である。 In the present embodiment, only the outer peripheral surface of the insulator small-diameter portion 313 is corrugated. However, the present invention is not limited thereto, and only the outer peripheral surface of the insulator large-diameter portion 311 is corrugated, or the outer peripheral surface of the insulator small-diameter portion 313 is used. It is also possible to make both the outer peripheral surface of the insulator large-diameter portion 311 corrugated.
（実施形態１６）
　本実施形態は、図４３～図４５に示すごとく、実施形態１３に対して、碍子突出部３１の形状を変更した実施形態である。 (Embodiment 16)
As shown in FIGS. 43 to 45, the present embodiment is an embodiment in which the shape of the lever protrusion 31 is changed with respect to the thirteenth embodiment.
　図４３、図４４に示すごとく、本実施形態において、碍子突出部３１の外周面の大部分は、先端側へ向かうほどやや縮径する形状を有する。そして、図４３～図４５に示すごとく、碍子突出部３１の段形状は、プラグ周方向における第二部位４１２が配された領域にのみ形成されている。当該段形状は、後述の段形成凹部３１４により形成されている。段形成凹部３１４は、碍子突出部３１の外周面３１ｂにおけるプラグ周方向の第二部位４１２が配された領域が、内周側に凹むよう形成されている。段形成凹部３１４は、碍子突出部３１におけるプラグ軸方向Ｚの中央から碍子突出部３１の先端面３１ａにつながるよう形成されている。段形成凹部３１４のプラグ軸方向Ｚの基端側端面が、プラグ軸方向Ｚの先端側を向く碍子段部３１２となっている。 43 and 44, in the present embodiment, most of the outer peripheral surface of the insulator protrusion 31 has a shape that is slightly reduced in diameter toward the distal end side. As shown in FIGS. 43 to 45, the step shape of the insulator protrusion 31 is formed only in the region where the second portion 412 is arranged in the plug circumferential direction. The step shape is formed by a step forming recess 314 described later. The step forming recess 314 is formed such that a region where the second portion 412 in the plug circumferential direction on the outer peripheral surface 31b of the insulator protruding portion 31 is recessed is recessed toward the inner peripheral side. The step forming recess 314 is formed so as to be connected from the center in the plug axial direction Z of the lever protrusion 31 to the tip surface 31 a of the lever protrusion 31. The base end side end surface in the plug axial direction Z of the step forming recess 314 is an insulator step 312 facing the distal end side in the plug axial direction Z.
　また、図４５に示すごとく、段形成凹部３１４のプラグ周方向の両端壁３１５は、プラグ径方向の外周側に向かうほど、互いにプラグ周方向に遠ざかるようテーパ状に形成されている。そして、図４３、図４４に示すごとく、第二部位４１２は、プラグ周方向、プラグ径方向のいずれにおいても、段形成凹部３１４内に収まるよう形成されている。
　その他は、実施形態１３と同様である。 As shown in FIG. 45, both end walls 315 in the plug circumferential direction of the step forming recess 314 are formed in a taper shape so as to be farther from each other in the plug circumferential direction toward the outer peripheral side in the plug radial direction. As shown in FIGS. 43 and 44, the second portion 412 is formed so as to be accommodated in the step forming recess 314 in both the plug circumferential direction and the plug radial direction.
Others are the same as in the thirteenth embodiment.
　本実施形態においては、プラグ周方向において、碍子突出部３１の段形状は、第二部位４１２が配された領域にのみ形成されている。このように、沿面距離を確保するために必要な箇所にのみ段形状を形成することにより、絶縁碍子３の体積が過度に小さくなり、熱容量が過度に小さくなることを防止することができる。それゆえ、プレイグニッションの発生を防止しやすい。
　その他、実施形態１３と同様の作用効果を有する。 In the present embodiment, the stepped shape of the insulator protrusion 31 is formed only in the region where the second portion 412 is arranged in the plug circumferential direction. In this way, by forming the step shape only at a location necessary to ensure the creepage distance, it is possible to prevent the volume of the insulator 3 from becoming excessively small and the heat capacity from excessively decreasing. Therefore, it is easy to prevent the occurrence of pre-ignition.
In addition, the same effects as those of the thirteenth embodiment are obtained.
（実施形態１７）
　本実施形態は、実施形態１３に対して、中心電極４の形状を変更した実施形態である。 (Embodiment 17)
The present embodiment is an embodiment in which the shape of the center electrode 4 is changed with respect to the thirteenth embodiment.
　図４６に示すごとく、本実施形態において、中心電極４における碍子突出部３１の内側に配された部位は、プラグ径方向の外周側に突出した電極大径部４２を有する。すなわち、電極大径部４２は、中心電極４における碍子突出部３１の内側の部位における先端部に形成されている。プラグ軸方向Ｚにおいて、電極大径部４２は、碍子段部３１２よりも先端側に位置している。すなわち、電極大径部４２は、碍子突出部３１の碍子小径部３１３の内側に形成されている。電極大径部４２の先端側は、露出部４１と接続している。電極大径部４２の形状は、実施形態１２の電極大径部４２と同様である。
　その他は、実施形態１３と同様である。 As shown in FIG. 46, in the present embodiment, a portion of the center electrode 4 that is disposed inside the insulator protrusion 31 has an electrode large diameter portion 42 that protrudes to the outer peripheral side in the plug radial direction. That is, the electrode large-diameter portion 42 is formed at the distal end portion of the center electrode 4 at the portion inside the insulator protrusion 31. In the plug axial direction Z, the electrode large-diameter portion 42 is located on the tip side of the insulator step portion 312. That is, the electrode large diameter portion 42 is formed inside the insulator small diameter portion 313 of the insulator protrusion portion 31. The distal end side of the electrode large-diameter portion 42 is connected to the exposed portion 41. The shape of the electrode large-diameter portion 42 is the same as that of the electrode large-diameter portion 42 of the twelfth embodiment.
Others are the same as in the thirteenth embodiment.
　本実施形態においては、碍子突出部３１の内側に配された部位に電極大径部４２を形成しているため、実施形態１２と同様、プレイグニッションの発生を防止しやすい。
　その他、実施形態１３と同様の作用効果を有する。 In the present embodiment, since the electrode large-diameter portion 42 is formed at a portion disposed inside the insulator protrusion portion 31, it is easy to prevent the occurrence of pre-ignition as in the twelfth embodiment.
In addition, the same effects as those of the thirteenth embodiment are obtained.
　本発明は、前記各実施形態に限定されるものではなく、その要旨を逸脱しない範囲において種々の実施形態に適用することが可能である。 The present invention is not limited to the above-described embodiments, and can be applied to various embodiments without departing from the scope of the invention.
　例えば、実施形態４と実施形態５とを組み合わせ、中心電極の形状を実施形態４で示したものとし、接地電極の形状を実施形態５で示したものとすることもできる。 For example, Embodiment 4 and Embodiment 5 can be combined, the shape of the center electrode can be as shown in Embodiment 4, and the shape of the ground electrode can be as shown in Embodiment 5.
　また、露出部を、中心電極における碍子突出部の内側の部位と一体的に形成したが、これに限られず、露出部と、中心電極における碍子突出部の内側の部位とを別体とすることも可能である。 Moreover, although the exposed part was formed integrally with the part inside the insulator protrusion part in the center electrode, the present invention is not limited to this, and the exposed part and the part inside the insulator protrusion part in the center electrode are separated. Is also possible.
　また、接地電極をハウジングの先端部に接合する形態を示したが、ハウジングと接地電極とを一体的に形成してもよい。すなわち、ハウジングの一部を接地電極とすることもできる。 In addition, although the configuration in which the ground electrode is joined to the tip of the housing has been shown, the housing and the ground electrode may be integrally formed. That is, a part of the housing can be used as a ground electrode.
　また、実施形態６、実施形態７において、中心電極の露出部に、４つの通気孔を形成した形態を示したが、露出部における通気孔の数は、１つでも良いし、２つ以上でも良い。 Moreover, in Embodiment 6 and Embodiment 7, although the form which formed the four ventilation holes in the exposed part of the center electrode was shown, the number of the ventilation holes in an exposed part may be one, and may be two or more. good.
　１　内燃機関用のスパークプラグ
　２　接地電極
　３　絶縁碍子
　３１　碍子突出部
　３１ｂ　碍子突出部の外周面
　４　中心電極
　４１　露出部
　４１１　第一部位
　４１２　第二部位
　Ｚ　プラグ軸方向 DESCRIPTION OF SYMBOLS 1 Spark plug for internal combustion engines 2 Ground electrode 3 Insulator 31 Insulator protrusion 31b Outer peripheral surface of insulator protrusion 4 Center electrode 41 Exposed part 411 First part 412 Second part Z Plug axial direction

Claims (16)

  1. 　筒状の接地電極（２）と、
    　前記接地電極の内側に配されると共に、前記接地電極の先端よりもプラグ軸方向（Ｚ）の先端側へ突出した碍子突出部（３１）を有する筒状の絶縁碍子（３）と、
    　前記絶縁碍子の内側に保持されると共に、前記碍子突出部の先端から露出した露出部（４１）を有する中心電極（４）と、を備え、
    　前記中心電極の前記露出部は、前記碍子突出部をプラグ軸方向の先端側から覆う第一部位（４１１）と、前記第一部位からプラグ軸方向の基端側に延設されると共に前記碍子突出部の外周面（３１ｂ）の全周を、プラグ径方向の外周側から覆う第二部位（４１２）とを有する、内燃機関用のスパークプラグ（１）。     A cylindrical ground electrode (2);
    A cylindrical insulator (3) which is arranged inside the ground electrode and has an insulator protrusion (31) which protrudes from the tip of the ground electrode to the tip side in the plug axial direction (Z);
    A center electrode (4) held inside the insulator and having an exposed portion (41) exposed from the tip of the insulator protrusion, and
    The exposed portion of the center electrode extends from the first portion to the proximal end side in the plug axis direction and extends from the first portion to the base end side in the plug axis direction, covering the insulator protrusion from the distal end side in the plug axis direction. A spark plug (1) for an internal combustion engine having a second portion (412) that covers the entire circumference of the outer peripheral surface (31b) of the protruding portion from the outer peripheral side in the plug radial direction.
  2. 　プラグ軸方向における、前記第一部位と前記碍子突出部との間には、軸方向空隙（ａｃ）が形成されている、請求項１に記載の内燃機関用のスパークプラグ。 The spark plug for an internal combustion engine according to claim 1, wherein an axial gap (ac) is formed between the first part and the insulator protrusion in the plug axial direction.
  3. 　前記第二部位におけるプラグ軸方向の基端側の端面（４１２ａ）は、プラグ軸方向に直交する、請求項１又は２に記載の内燃機関用のスパークプラグ。 The spark plug for an internal combustion engine according to claim 1 or 2, wherein an end surface (412a) on the proximal end side in the plug axial direction in the second part is orthogonal to the plug axial direction.
  4. 　前記露出部の外周面（４１ｂ）は、プラグ軸方向の先端側に向かうほどプラグ径方向の外周側に向かうよう傾斜した部位を有する、請求項１～３のいずれか一項に記載の内燃機関用のスパークプラグ。 The internal combustion engine according to any one of claims 1 to 3, wherein the outer peripheral surface (41b) of the exposed portion has a portion inclined toward the outer peripheral side in the plug radial direction toward the tip end side in the plug axial direction. Spark plug for use.
  5. 　前記接地電極の先端面（２１）は、プラグ径方向の外周側に向かうほどプラグ軸方向の基端側に向かうよう傾斜した部位を有する、請求項１～４のいずれか一項に記載の内燃機関用のスパークプラグ。 The internal combustion engine according to any one of claims 1 to 4, wherein the distal end surface (21) of the ground electrode has a portion that is inclined toward the proximal end side in the plug axial direction toward the outer peripheral side in the plug radial direction. Spark plug for engines.
  6. 　前記中心電極の前記第二部位と前記接地電極との間の空間距離は、全周において一定である、請求項１～５のいずれか一項に記載の内燃機関用のスパークプラグ。 The spark plug for an internal combustion engine according to any one of claims 1 to 5, wherein a spatial distance between the second portion of the center electrode and the ground electrode is constant over the entire circumference.
  7. 　プラグ径方向における、前記碍子突出部の前記外周面と前記中心電極の前記第二部位の内周面（４１２ｂ）との間には、径方向空隙（ｒｃ）が形成されている、請求項１～６のいずれか一項に記載の内燃機関用のスパークプラグ。 A radial gap (rc) is formed between the outer peripheral surface of the insulator protrusion and the inner peripheral surface (412b) of the second portion of the center electrode in the plug radial direction. A spark plug for an internal combustion engine according to any one of claims 1 to 6.
  8. 　前記露出部には、前記露出部の内外を貫通するとともに、一端が前記径方向空隙に向かって開口する通気孔（４０）が形成されている、請求項７に記載の内燃機関用のスパークプラグ。 The spark plug for an internal combustion engine according to claim 7, wherein the exposed portion is formed with a vent hole (40) penetrating the inside and outside of the exposed portion and having one end opening toward the radial gap. .
  9. 　前記碍子突出部は、全体として、プラグ軸方向の先端側に向かうほど段階的に外径が小さくなる段形状を有する、請求項１～８のいずれか一項に記載の内燃機関用のスパークプラグ。 The spark plug for an internal combustion engine according to any one of claims 1 to 8, wherein the insulator projecting portion as a whole has a step shape in which an outer diameter gradually decreases toward a tip end side in a plug axial direction. .
  10. 　前記中心電極における前記碍子突出部の内側に配された部位は、プラグ径方向の外周側に突出した電極大径部（４２）を有する、請求項９に記載の内燃機関用のスパークプラグ。 10. The spark plug for an internal combustion engine according to claim 9, wherein a portion of the center electrode disposed inside the insulator protrusion has an electrode large diameter portion (42) protruding toward the outer peripheral side in the plug radial direction.
  11. 　前記中心電極の前記露出部は、プラグ軸方向から見たとき、前記接地電極の内側に収まるよう形成されている、請求項１～１０のいずれか一項に記載の内燃機関用のスパークプラグ。 The spark plug for an internal combustion engine according to any one of claims 1 to 10, wherein the exposed portion of the center electrode is formed so as to fit inside the ground electrode when viewed from a plug axial direction.
  12. 　筒状の接地電極（２）と、
    　前記接地電極の内側に配されると共に、前記接地電極の先端よりもプラグ軸方向（Ｚ）の先端側へ突出した碍子突出部（３１）を有する筒状の絶縁碍子（３）と、
    　前記絶縁碍子の内側に保持されると共に、前記碍子突出部の先端から露出した露出部（４１）を有する中心電極（４）と、を備え、
    　前記中心電極の前記露出部は、前記碍子突出部をプラグ軸方向の先端側から覆う第一部位（４１１）と、前記第一部位からプラグ軸方向の基端側に延設されると共に前記碍子突出部の外周面（３１ｂ）のプラグ周方向の一部を、プラグ径方向の外周側から覆う第二部位（４１２）とを有し、
    　前記碍子突出部の少なくともプラグ周方向の前記第二部位が形成された領域は、プラグ軸方向の全体において、プラグ軸方向の先端側に向かうほど段階的に外径が小さくなる段形状を有する、内燃機関用のスパークプラグ（１）。     A cylindrical ground electrode (2);
    A cylindrical insulator (3) which is arranged inside the ground electrode and has an insulator protrusion (31) which protrudes from the tip of the ground electrode to the tip side in the plug axial direction (Z);
    A center electrode (4) held inside the insulator and having an exposed portion (41) exposed from the tip of the insulator protrusion, and
    The exposed portion of the center electrode extends from the first portion to the proximal end side in the plug axis direction and extends from the first portion to the base end side in the plug axis direction, covering the insulator protrusion from the distal end side in the plug axis direction. A second portion (412) that covers a part of the outer circumferential surface (31b) of the protruding portion in the plug circumferential direction from the outer circumferential side in the plug radial direction;
    The region in which at least the second portion in the plug circumferential direction of the lever projecting portion is formed has a step shape in which the outer diameter gradually decreases toward the distal end side in the plug axis direction in the entire plug axis direction. A spark plug (1) for an internal combustion engine.
  13. 　プラグ周方向において、前記碍子突出部の前記段形状は、前記第二部位が配された領域にのみ形成されている、請求項１２に記載の内燃機関用のスパークプラグ。 The spark plug for an internal combustion engine according to claim 12, wherein in the circumferential direction of the plug, the step shape of the insulator protrusion is formed only in a region where the second part is arranged.
  14. 　プラグ軸方向から見たとき、前記スパークプラグの先端部を通る混合気の気流は、前記第二部位とプラグ中心軸との並び方向に直交する向きに流れるよう構成されている、請求項１２又は１３に記載の内燃機関用のスパークプラグ。 The airflow of the air-fuel mixture passing through the tip end portion of the spark plug when viewed from the plug axis direction is configured to flow in a direction orthogonal to the arrangement direction of the second portion and the plug center axis. 13. A spark plug for an internal combustion engine according to 13.
  15. 　プラグ軸方向から見たとき、前記中心電極の前記露出部は、前記接地電極の内側に収まるよう形成されている、請求項１２～１４のいずれか一項に記載の内燃機関用のスパークプラグ。 The spark plug for an internal combustion engine according to any one of claims 12 to 14, wherein the exposed portion of the center electrode is formed to be inside the ground electrode when viewed from the plug axial direction.
  16. 　前記中心電極における前記碍子突出部の内側に配された部位は、プラグ径方向の外周側に突出した電極大径部（４２）を有する、請求項１２～１５のいずれか一項に記載の内燃機関用のスパークプラグ。 The internal combustion engine according to any one of claims 12 to 15, wherein a portion of the center electrode that is disposed inside the insulator protrusion has an electrode large-diameter portion (42) that protrudes to the outer peripheral side in the plug radial direction. Spark plug for engines.
PCT/JP2018/013102 2017-03-31 2018-03-29 Spark plug for internal combustion engine WO2018181654A1 (en)

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US20200182132A1 (en) * 2018-12-06 2020-06-11 Federal-Mogul Ignition Gmbh Spark plug

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JPS6132978A (en) * 1984-07-25 1986-02-15 株式会社デンソー Small-sized spark plug
JP2014501432A (en) * 2010-12-14 2014-01-20 フェデラル−モーグル・イグニション・カンパニー Corona igniter with shaped insulator
JP2015129628A (en) * 2013-12-26 2015-07-16 ジョン ジンク カンパニー，エルエルシー Improved high energy ignition spark igniter
JP2016058196A (en) * 2014-09-08 2016-04-21 株式会社日本自動車部品総合研究所 Ignition plug for internal combustion engine

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS6132978A (en) * 1984-07-25 1986-02-15 株式会社デンソー Small-sized spark plug
JP2014501432A (en) * 2010-12-14 2014-01-20 フェデラル−モーグル・イグニション・カンパニー Corona igniter with shaped insulator
JP2015129628A (en) * 2013-12-26 2015-07-16 ジョン ジンク カンパニー，エルエルシー Improved high energy ignition spark igniter
JP2016058196A (en) * 2014-09-08 2016-04-21 株式会社日本自動車部品総合研究所 Ignition plug for internal combustion engine

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20200182132A1 (en) * 2018-12-06 2020-06-11 Federal-Mogul Ignition Gmbh Spark plug
US10892605B2 (en) * 2018-12-06 2021-01-12 Federal-Mogul Ignition Gmbh Spark plug

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