WO2018181654A1 - Bougie d'allumage pour moteur à combustion interne - Google Patents

Bougie d'allumage pour moteur à combustion interne 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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WIPO (PCT)
Prior art keywords
plug
insulator
tip
axial direction
spark plug
Prior art date
Application number
PCT/JP2018/013102
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English (en)
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/ja
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/zh
Publication of WO2018181654A1 publication Critical patent/WO2018181654A1/fr
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.

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Abstract

L'invention concerne une bougie d'allumage 1 comprenant : une électrode cylindrique mise à la terre 2; un isolant 3; et une électrode centrale 4. L'isolant 3 a une partie saillante d'isolant 31 qui fait saillie vers un côté de pointe dans une direction axiale de fiche Z plus que l'électrode mise à la terre 2. L'électrode centrale 4 comprend une partie exposée 41 qui est exposée à partir de la pointe de la partie saillante d'isolant 31. La partie exposée 41 de l'électrode centrale 4 comprend une première section 411 qui recouvre la partie saillante d'isolant 31 depuis le côté de pointe dans la direction axiale de fiche Z, et une seconde section 412 qui s'étend à partir de la première section 411 vers le côté d'extrémité de base dans la direction axiale de fiche Z et recouvre toute la circonférence de la surface circonférentielle externe 31b de la partie saillante d'isolant 31 depuis le côté circonférentiel externe dans la direction du diamètre de la fiche.
PCT/JP2018/013102 2017-03-31 2018-03-29 Bougie d'allumage pour moteur à combustion interne WO2018181654A1 (fr)

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CN201880021380.3A CN110462947B (zh) 2017-03-31 2018-03-29 内燃机用的火花塞
US16/584,998 US10886708B2 (en) 2017-03-31 2019-09-27 Spark plug for internal combustion engine

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JP2017-069872 2017-03-31
JP2017069872 2017-03-31
JP2018-052539 2018-03-20
JP2018052539A JP7022628B2 (ja) 2017-03-31 2018-03-20 内燃機関用のスパークプラグ

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Cited By (1)

* 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

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS6132978A (ja) * 1984-07-25 1986-02-15 株式会社デンソー 小型点火プラグ
JP2014501432A (ja) * 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 形状化された絶縁体を有するコロナ点火器
JP2015129628A (ja) * 2013-12-26 2015-07-16 ジョン ジンク カンパニー，エルエルシー 改良された高エネルギー点火火花点火器
JP2016058196A (ja) * 2014-09-08 2016-04-21 株式会社日本自動車部品総合研究所 内燃機関用の点火プラグ

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS6132978A (ja) * 1984-07-25 1986-02-15 株式会社デンソー 小型点火プラグ
JP2014501432A (ja) * 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 形状化された絶縁体を有するコロナ点火器
JP2015129628A (ja) * 2013-12-26 2015-07-16 ジョン ジンク カンパニー，エルエルシー 改良された高エネルギー点火火花点火器
JP2016058196A (ja) * 2014-09-08 2016-04-21 株式会社日本自動車部品総合研究所 内燃機関用の点火プラグ

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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