JP2020087629A

JP2020087629A - Ignition plug

Info

Publication number: JP2020087629A
Application number: JP2018218337A
Authority: JP
Inventors: 山田　達範; Tatsunori Yamada; 達範山田; 馨 ▲高▼橋; Kaoru Takahashi; 俊介津荷; Shunsuke Tsuga
Original assignee: NGK Spark Plug Co Ltd
Current assignee: Niterra Co Ltd
Priority date: 2018-11-21
Filing date: 2018-11-21
Publication date: 2020-06-04
Anticipated expiration: 2038-11-21
Also published as: JP6942111B2

Abstract

To provide an ignition plug capable of suppressing energy loss that causes non-equilibrium plasma.SOLUTION: An ignition plug includes a conductor extending along an axis from the front end side to the rear end side, an insulator having a bottomed cylindrical tip that surrounds the periphery of the tip of the conductor, and in which the conductor is disposed inside with the rear end portion of the conductor protruding from the rear end side of the conductor, and a tubular metal fitting that holds the insulator from the outer periphery with the tip protruding from the tip of itself to the tip side, and a resistor is provided in at least a part of a region where the metal fitting and the conductor overlap in the axial direction between the conductor and the inner surface of the insulator.SELECTED DRAWING: Figure 1

Description

本発明は点火プラグに関し、特に非平衡プラズマを利用する点火プラグに関する。 The present invention relates to spark plugs, and more particularly to spark plugs that utilize non-equilibrium plasma.

非平衡プラズマを利用する点火プラグが知られている（例えば特許文献１）。このような点火プラグは、導電体の先端の周囲を取り囲む有底筒状の先端部を有する絶縁体が、主体金具に保持されている。点火プラグの導電体に交流電圧または複数回のパルス電圧を印加することにより、先端部の表面に非平衡プラズマが発生する。 A spark plug using non-equilibrium plasma is known (for example, Patent Document 1). In such a spark plug, an insulator having a bottomed cylindrical tip portion that surrounds the tip of a conductor is held by a metal shell. Non-equilibrium plasma is generated on the surface of the tip by applying an AC voltage or a pulse voltage multiple times to the conductor of the spark plug.

特開２０１８−１３９１７３号公報JP, 2018-139173, A

しかし上記従来の技術では、導電体に印加された交流電圧やパルス電圧による電流の一部が導電体と主体金具との間を流れると、先端部の表面に非平衡プラズマを生じさせるエネルギーの一部が失われるので、点火性能が低下するという問題点がある。 However, in the above-mentioned conventional technique, when a part of the current due to the AC voltage or the pulse voltage applied to the conductor flows between the conductor and the metal shell, the energy that causes non-equilibrium plasma is generated on the surface of the tip. Since the parts are lost, there is a problem that the ignition performance deteriorates.

本発明は上述した問題点を解決するためになされたものであり、非平衡プラズマを生じさせるエネルギーの損失を抑制できる点火プラグを提供することを目的としている。 The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide an ignition plug that can suppress energy loss that causes non-equilibrium plasma.

この目的を達成するために本発明の点火プラグは、先端側から後端側へと軸線に沿って延びる導電体と、導電体の先端の周囲を取り囲む有底筒状の先端部を有し、導電体の後端部が自身の後端側から突出する状態で導電体が内部に配置される絶縁体と、先端部が自身の先端から先端側に突出する状態で絶縁体を外周側から保持する筒状の主体金具と、を備え、導電体と絶縁体の内部表面との間の、主体金具と導電体とが軸線方向に重なる領域の少なくとも一部に配置される抵抗体を備える。 In order to achieve this object, the spark plug of the present invention has a conductor extending along the axis from the front end side to the rear end side, and a bottomed cylindrical tip end portion that surrounds the periphery of the tip end of the conductor, An insulator in which the conductor is arranged with the rear end portion of the conductor protruding from the rear end side of the conductor, and an insulator from the outer peripheral side with the tip portion protruding from the tip of itself to the tip side And a tubular metal shell, and a resistor disposed in at least a part of a region where the metal shell and the conductor overlap in the axial direction between the conductor and the inner surface of the insulator.

請求項１記載の点火プラグによれば、導電体と絶縁体の内部表面との間の、主体金具と導電体とが軸線方向に重なる領域の少なくとも一部に配置された抵抗体により、導電体に印加された交流電圧やパルス電圧による電流が、導電体と主体金具との間を流れ難くなる。よって、先端部に非平衡プラズマ（以下「プラズマ」と称す）を生じさせるエネルギーの損失を抑制できる。 According to the spark plug of claim 1, the resistor is disposed in at least a part of a region between the conductor and the inner surface of the insulator in which the metal shell and the conductor overlap in the axial direction. It becomes difficult for the current due to the AC voltage or the pulse voltage applied to the conductor to flow between the conductor and the metal shell. Therefore, it is possible to suppress energy loss that causes nonequilibrium plasma (hereinafter referred to as “plasma”) at the tip portion.

請求項２記載の点火プラグによれば、抵抗体は、軸線方向において、主体金具の内周面のうち内側に凸である部位の少なくとも一部に存在する。主体金具の内周面のうち内側に凸である部位は、電界が集中し易く不正な放電が生じ易いので、この部位の少なくとも一部に抵抗体が存在することにより、導電体と主体金具との間に電流をより流れ難くできる。よって、請求項１の効果に加え、先端部にプラズマを生じさせるエネルギーの損失をより抑制できる。 According to the ignition plug of the second aspect, the resistor is present in at least a part of a portion of the inner peripheral surface of the metal shell that is convex inward in the axial direction. Since the electric field is likely to be concentrated on the portion of the inner peripheral surface of the metal shell that is convex and an unauthorized electric discharge is likely to occur, the presence of the resistor in at least a part of this portion causes the conductor and the metal shell to be separated from each other. The current can be made more difficult to flow during the period. Therefore, in addition to the effect of the first aspect, it is possible to further suppress the loss of energy that causes plasma at the tip portion.

請求項３記載の点火プラグによれば、径方向の外側に張り出す絶縁体の係止部が、主体金具の棚部により、金属製のパッキンを介して先端側から係止される。抵抗体は、軸線方向において、パッキンの位置に少なくとも存在する。パッキンの位置は電界が集中し易く電流が流れやすいので、抵抗体が存在することにより、電流をより流れ難くできる。よって、請求項１又は２の効果に加え、先端部にプラズマを生じさせるエネルギーの損失をより抑制できる。 According to the ignition plug of the third aspect, the locking portion of the insulator protruding outward in the radial direction is locked by the shelf of the metal shell from the tip side through the metal packing. The resistor is present at least at the position of the packing in the axial direction. Since the electric field is likely to be concentrated and the current is likely to flow at the position of the packing, the presence of the resistor makes it more difficult for the current to flow. Therefore, in addition to the effect of claim 1 or 2, it is possible to further suppress the loss of energy that causes plasma at the tip portion.

請求項４記載の点火プラグによれば、一端部が主体金具に接続された接地電極の他端部は、絶縁体の先端部のうち導電体と軸線方向に重なる部位と放電ギャップを形成する。抵抗体の先端は、接地電極の他端部よりも後端側に位置する。よって、請求項１から３のいずれかの効果に加え、抵抗体に妨げられることなく絶縁体の先端部と接地電極との間にプラズマを発生できる。 According to the spark plug of the fourth aspect, the other end of the ground electrode, one end of which is connected to the metallic shell, forms a discharge gap with a portion of the tip of the insulator that axially overlaps with the conductor. The tip of the resistor is located on the rear end side of the other end of the ground electrode. Therefore, in addition to the effect of any one of claims 1 to 3, plasma can be generated between the tip of the insulator and the ground electrode without being blocked by the resistor.

請求項５記載の点火プラグによれば、抵抗体の先端は、主体金具の先端よりも後端側に位置する。よって、請求項１から４のいずれかの効果に加え、抵抗体に妨げられることなく絶縁体の先端部の表面にプラズマを発生できる。 According to the spark plug of the fifth aspect, the front end of the resistor is located on the rear end side of the front end of the metal shell. Therefore, in addition to the effect according to any one of claims 1 to 4, plasma can be generated on the surface of the tip of the insulator without being hindered by the resistor.

請求項６記載の点火プラグによれば、抵抗体の先端よりも先端側の絶縁体の内部に第１導体が充填され、第１導体は導電体に電気的に接続される。絶縁体の内部表面と導電体との隙間が第１導体に埋められると、請求項１から５のいずれかの効果に加え、第１導体により先端部の表面の広い範囲にプラズマを発生できる。 According to the spark plug of the sixth aspect, the first conductor is filled inside the insulator on the tip side of the resistor, and the first conductor is electrically connected to the conductor. When the gap between the inner surface of the insulator and the conductor is filled with the first conductor, in addition to the effect of any one of claims 1 to 5, plasma can be generated in a wide range of the surface of the tip portion by the first conductor.

請求項７記載の点火プラグによれば、先端部の内部表面の少なくとも一部に導電層が形成される。導電層は導電体に電気的に接続され、抵抗体の一部は先端部の内部に充填されているので、請求項１から４のいずれかの効果に加え、導電層により先端部の表面に部分的にプラズマを発生できる。 According to the ignition plug of the seventh aspect, the conductive layer is formed on at least a part of the inner surface of the tip portion. The conductive layer is electrically connected to the conductor, and part of the resistor is filled inside the tip portion. Therefore, in addition to the effect according to any one of claims 1 to 4, the conductive layer is formed on the surface of the tip portion. Plasma can be partially generated.

請求項８記載の点火プラグによれば、先端部のうち導電層が形成された部位に少なくとも第２導体が充填される。第２導体は導電体と接続されるので、請求項７の効果に加え、第２導体により抵抗体の先端の位置を定めることができる。 According to the spark plug of the eighth aspect, at least the second conductor is filled in the portion of the tip portion where the conductive layer is formed. Since the second conductor is connected to the conductor, in addition to the effect of the seventh aspect, the position of the tip of the resistor can be determined by the second conductor.

第１実施の形態における点火プラグの片側断面図である。It is one side sectional drawing of the ignition plug in 1st Embodiment. （ａ）は図１のＩＩａで示す部分を拡大した部分拡大図であり、（ｂ）は図１のＩＩｂで示す部分を拡大した部分拡大図である。(A) is a partially enlarged view of a portion indicated by IIa in FIG. 1 and (b) is a partially enlarged view of a portion indicated by IIb in FIG. 1. 第２実施の形態における点火プラグの片側断面図である。It is one side sectional drawing of the ignition plug in 2nd Embodiment. 第３実施の形態における点火プラグの片側断面図である。It is one side sectional drawing of the ignition plug in 3rd Embodiment. 先端部の断面図である。It is sectional drawing of a front-end|tip part. 第４実施の形態における点火プラグの先端部の断面図である。It is sectional drawing of the front-end|tip part of the ignition plug in 4th Embodiment.

以下、本発明の好ましい実施形態について添付図面を参照して説明する。図１は第１実施の形態における点火プラグ１０の軸線Ｏを境にした片側断面図である。図２（ａ）は図１のＩＩａで示す部分を拡大した部分拡大図であり、図２（ｂ）は図１のＩＩｂで示す部分を拡大した部分拡大図である。図１では、紙面下側を点火プラグ１０の先端側、紙面上側を点火プラグ１０の後端側という（図２から図６においても同じ）。 Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a one-sided sectional view taken along the axis O of the spark plug 10 in the first embodiment. 2A is a partially enlarged view of a portion indicated by IIa in FIG. 1 and FIG. 2B is a partially enlarged view of a portion indicated by IIb in FIG. In FIG. 1, the lower side of the drawing is referred to as the front end side of the ignition plug 10, and the upper side of the drawing is referred to as the rear end side of the ignition plug 10 (the same applies to FIGS. 2 to 6).

図１に示すように点火プラグ１０は、絶縁体１１と、導電体２０と、絶縁体１１を介して導電体２０を絶縁保持する主体金具３０と、導電体２０と絶縁体１１との間に配置された抵抗体５０と、を備えている。 As shown in FIG. 1, the spark plug 10 includes an insulator 11, a conductor 20, a metal shell 30 for insulatingly holding the conductor 20 via the insulator 11, and a gap between the conductor 20 and the insulator 11. And the arranged resistor 50.

絶縁体１１は、高温下の絶縁性や機械的特性に優れるアルミナ等により形成された有底円筒状の部材である。絶縁体１１の内部表面１２は、絶縁体１１の後端に開口し先端が閉じている。絶縁体１１の内部表面１２は軸線Ｏに沿って形成されており、軸線Ｏに垂直な断面は円形である。内部表面１２の先端側には、先端側へ向かって縮径する環状の後端向き面１３が形成されている。 The insulator 11 is a bottomed cylindrical member made of alumina or the like, which has excellent insulating properties and mechanical properties at high temperatures. The inner surface 12 of the insulator 11 is open at the rear end of the insulator 11 and closed at the front end. The inner surface 12 of the insulator 11 is formed along the axis O, and the cross section perpendicular to the axis O is circular. On the tip side of the inner surface 12, there is formed an annular rear end facing surface 13 whose diameter decreases toward the tip side.

絶縁体１１は、径方向の外側へ張り出す第１係止部１４が、外周面に形成されている。絶縁体１１は、第１係止部１４よりも後端側の絶縁体１１の外周面に、第２係止部１５が形成されている。第１係止部１４の先端の外径は、第２係止部１５の先端の外径よりも小さい。本実施形態では、第１係止部１４は絶縁体１１の後端向き面１３よりも後端側に位置する。 The insulator 11 is provided with a first locking portion 14 that projects outward in the radial direction on the outer peripheral surface. The insulator 11 has a second engaging portion 15 formed on the outer peripheral surface of the insulator 11 on the rear end side of the first engaging portion 14. The outer diameter of the tip of the first locking portion 14 is smaller than the outer diameter of the tip of the second locking portion 15. In the present embodiment, the first locking portion 14 is located on the rear end side of the rear end facing surface 13 of the insulator 11.

導電体２０は複数の部位からなり、軸線Ｏに沿って先端側から後端側へと延び、絶縁体１１の内部表面１２の内側に配置されている。導電体２０は、本実施形態では中心電極２１、端子金具２５及び接続部２８を備えている。 The conductor 20 is composed of a plurality of parts, extends from the front end side to the rear end side along the axis O, and is arranged inside the inner surface 12 of the insulator 11. The electric conductor 20 includes a center electrode 21, a terminal fitting 25, and a connecting portion 28 in the present embodiment.

中心電極２１は導電性を有する金属材料（例えばニッケル基合金等）によって形成された棒状の部材である。中心電極２１は軸線Ｏに沿って絶縁体１１の内部表面１２の先端側に配置されている。中心電極２１は、絶縁体１１の後端向き面１３に係止され、軸線Ｏに沿って後端向き面１３よりも先端側に第１軸部２２が延び、後端向き面１３よりも後端側に第２軸部２３が延びている。絶縁体１１の後端向き面１３は、主体金具３０の先端４０よりも後端側に位置する。第２軸部２３の後端は、主体金具３０の後端４１よりも後端側に位置する。 The center electrode 21 is a rod-shaped member formed of a conductive metal material (for example, a nickel-based alloy). The center electrode 21 is arranged along the axis O on the tip side of the inner surface 12 of the insulator 11. The center electrode 21 is locked to the rear end facing surface 13 of the insulator 11, the first shaft portion 22 extends along the axis O toward the front end side of the rear end facing surface 13, and is located rearward of the rear end facing surface 13. The second shaft portion 23 extends on the end side. The rear end facing surface 13 of the insulator 11 is located on the rear end side with respect to the front end 40 of the metal shell 30. The rear end of the second shaft portion 23 is located on the rear end side of the rear end 41 of the metal shell 30.

端子金具２５は、交流電圧やパルス電圧が入力される棒状の部材であり、導電性を有する金属材料（例えば低炭素鋼等）によって形成されている。端子金具２５は、先端部２６が絶縁体１１の内側に挿入され、後端部２７が絶縁体１１から後端側へ突出している。端子金具２５は、先端部２６が、導電性ガラス等の接続部２８により中心電極２１の第２軸部２３に電気的に接続されている。 The terminal fitting 25 is a rod-shaped member to which an AC voltage or a pulse voltage is input, and is made of a conductive metal material (for example, low carbon steel). In the terminal fitting 25, the front end portion 26 is inserted inside the insulator 11, and the rear end portion 27 projects from the insulator 11 toward the rear end side. The tip portion 26 of the terminal fitting 25 is electrically connected to the second shaft portion 23 of the center electrode 21 by a connecting portion 28 made of conductive glass or the like.

主体金具３０は、導電性を有する金属材料（例えば低炭素鋼等）によって形成された略円筒状の部材である。主体金具３０は、外周面の少なくとも一部におねじ３１が形成された胴部３２と、胴部３２の後端側に隣接する座部３３と、座部３３の後端側に隣接する連結部３４と、連結部３４の後端側に隣接する拡径部３５と、拡径部３５の後端側に隣接する後端部３６と、を備えている。 The metal shell 30 is a substantially cylindrical member formed of a conductive metal material (for example, low carbon steel or the like). The metal shell 30 includes a body portion 32 having a screw 31 formed on at least a part of an outer peripheral surface thereof, a seat portion 33 adjacent to a rear end side of the body portion 32, and a connection portion adjacent to a rear end side of the seat portion 33. A portion 34, an enlarged diameter portion 35 adjacent to the rear end side of the connecting portion 34, and a rear end portion 36 adjacent to the rear end side of the enlarged diameter portion 35 are provided.

胴部３２に形成されたおねじ３１は、エンジン（図示せず）のねじ穴に螺合する。座部３３は、エンジン（図示せず）のねじ穴とおねじ３１との隙間を塞ぐための部位である。連結部３４は、主体金具３０を絶縁体１１に組み付けるときに湾曲状に塑性変形した部位である。拡径部３５は、エンジンのねじ穴におねじ３１を締め付けるときに、レンチ等の工具が係合する工具係合部である。後端部３６は径方向の内側へ向けて屈曲した部位であり、絶縁体１１の第２係止部１５よりも後端側に位置する。 The male screw 31 formed on the body portion 32 is screwed into a screw hole of an engine (not shown). The seat portion 33 is a portion for closing the gap between the screw hole of the engine (not shown) and the male screw 31. The connecting portion 34 is a portion that is plastically deformed into a curved shape when the metal shell 30 is assembled to the insulator 11. The expanded diameter portion 35 is a tool engagement portion with which a tool such as a wrench engages when the screw 31 is tightened in the screw hole of the engine. The rear end portion 36 is a portion that is bent inward in the radial direction, and is located on the rear end side of the second locking portion 15 of the insulator 11.

胴部３２の内周面に、パッキン３７（図２（ｂ）参照）を介して、絶縁体１１の第１係止部１４を先端側から係止する棚部３８が形成されている。パッキン３７は、主体金具３０を構成する金属材料よりも軟質の軟鋼板等の金属製の円環状の板材である。 A shelf portion 38 that locks the first locking portion 14 of the insulator 11 from the tip end side is formed on the inner peripheral surface of the body portion 32 via a packing 37 (see FIG. 2B). The packing 37 is a metal annular plate material such as a mild steel plate that is softer than the metal material forming the metal shell 30.

絶縁体１１の第２係止部１５よりも後端側の外周面の全周に亘って、第２係止部１５と後端部３６との間に、タルク等の粉末が充填されたシール部３９が設けられている。主体金具３０の棚部３８から後端部３６までの部位は、絶縁体１１の第１係止部１４から第２係止部１５までの部位に、パッキン３７及びシール部３９を介して軸線方向の圧縮荷重を加える。これにより主体金具３０は第１係止部１４及び第２係止部１５を係止し、絶縁体１１を保持する。 A seal in which powder such as talc is filled between the second locking portion 15 and the rear end portion 36 over the entire circumference of the outer peripheral surface of the insulator 11 on the rear end side of the second locking portion 15. A section 39 is provided. A portion of the metal shell 30 from the shelf portion 38 to the rear end portion 36 is located at a portion from the first locking portion 14 to the second locking portion 15 of the insulator 11 via the packing 37 and the seal portion 39 in the axial direction. Apply the compressive load of. Thereby, the metal shell 30 locks the first locking portion 14 and the second locking portion 15 and holds the insulator 11.

絶縁体１１の先端部１６は、主体金具３０に保持された絶縁体１１のうち主体金具３０の先端４０から先端側に突出する有底筒状の部位である。先端部１６は、中心電極２１の第１軸部２２の先端２４の周囲を取り囲む。先端部１６は、先端側に位置する第１部１６ａと、第１部１６ａの後端に隣接する第２部１６ｂと、からなる。第１部１６ａは、肉厚（径方向の厚さ）が、第２部１６ｂの肉厚よりも薄い部位である。本実施形態では、第１部１６ａの肉厚は、先端の近傍を除き、軸線方向の全長に亘って同一である。 The tip portion 16 of the insulator 11 is a bottomed tubular portion of the insulator 11 held by the metal shell 30 that protrudes from the tip 40 of the metal shell 30 toward the tip side. The tip portion 16 surrounds the tip 24 of the first shaft portion 22 of the center electrode 21. The tip portion 16 includes a first portion 16a located on the tip side and a second portion 16b adjacent to the rear end of the first portion 16a. The first portion 16a is a portion having a wall thickness (thickness in the radial direction) smaller than that of the second portion 16b. In the present embodiment, the thickness of the first portion 16a is the same over the entire length in the axial direction except for the vicinity of the tip.

抵抗体５０は、導電体２０に印加された交流電圧やパルス電圧による電流が、導電体２０と主体金具３０との間に流れるのを抑制する部材である。抵抗体５０は、絶縁体１１の内部表面１２と中心電極２１の第２軸部２３との間に配置されている。 The resistor 50 is a member that suppresses a current caused by an AC voltage or a pulse voltage applied to the conductor 20 from flowing between the conductor 20 and the metal shell 30. The resistor 50 is arranged between the inner surface 12 of the insulator 11 and the second shaft portion 23 of the center electrode 21.

抵抗体５０は、骨材と導電性粉末とを混合したものが用いられる。抵抗体５０の骨材としては、例えばガラス粉末、無機化合物粉末が挙げられる。ガラス粉末としては、例えばＢ_２Ｏ_３−ＳｉＯ_２系、ＢａＯ−Ｂ_２Ｏ_３系、ＳｉＯ_２−Ｂ_２Ｏ_３−ＣａＯ−ＢａＯ系、ＳｉＯ_２−ＺｎＯ−Ｂ_２Ｏ_３系、ＳｉＯ_２−Ｂ_２Ｏ_３−Ｌｉ_２Ｏ系およびＳｉＯ_２−Ｂ_２Ｏ_３−Ｌｉ_２Ｏ−ＢａＯ系等の粉末が挙げられる。無機化合物粉末としては、例えばアルミナ、窒化ケイ素、ムライト及びステアタイト等の粉末が挙げられる。これらの骨材は１種のみを用いても良いし、２種以上を併用しても良い。 As the resistor 50, a mixture of aggregate and conductive powder is used. Examples of the aggregate of the resistor 50 include glass powder and inorganic compound powder. As the glass powder, for example, B ₂ O ₃ —SiO ₂ system, BaO—B ₂ O ₃ system, SiO ₂ —B ₂ O ₃ —CaO—BaO system, SiO ₂ —ZnO—B ₂ O ₃ system, SiO ₂ —. B ₂ O ₃ -Li powders such as ₂ O system and _{_{_{_{SiO 2 -B 2 O 3 -Li 2}}}} O-BaO systems. Examples of the inorganic compound powder include powders of alumina, silicon nitride, mullite, steatite, and the like. These aggregates may be used alone or in combination of two or more.

抵抗体５０の導電性粉末としては、例えば半導性酸化物、金属および非金属導電性材料等からなる粉末が挙げられる。半導性酸化物としては、例えばＳｎＯ_２が挙げられる。金属としては、例えばＺｎ，Ｓｂ，Ｓｎ，Ａｇ及びＮｉ等が挙げられる。非金属導電性材料としては、例えば無定形カーボン（カーボンブラック）、グラファイト、炭化ケイ素、炭化チタン、窒化チタン、炭化タングステン及び炭化ジルコニウム等が挙げられる。これらの導電性粉末は、１種のみを用いても良いし、２種以上を併用しても良い。 As the conductive powder of the resistor 50, for example, a powder made of a semiconductive oxide, a metal, a non-metal conductive material, or the like can be used. Examples of the semiconductive oxide include SnO ₂ . Examples of the metal include Zn, Sb, Sn, Ag and Ni. Examples of the non-metal conductive material include amorphous carbon (carbon black), graphite, silicon carbide, titanium carbide, titanium nitride, tungsten carbide and zirconium carbide. These conductive powders may be used alone or in combination of two or more.

抵抗体５０は、主体金具３０と導電体２０とが軸線方向に重なる領域４２の少なくとも一部に配置される。本実施形態では、抵抗体５０の先端は絶縁体１１の後端向き面１３に位置し、抵抗体５０の後端は主体金具３０の後端４１よりも後端側に位置する。絶縁体１１の後端向き面１３は、主体金具３０の先端４０よりも後端側に位置するので、抵抗体５０の先端は主体金具３０の先端４０よりも後端側に位置する。抵抗体５０は、自身の先端から後端まで連続する円筒状に形成されている。 The resistor 50 is arranged in at least a part of a region 42 where the metal shell 30 and the conductor 20 overlap each other in the axial direction. In the present embodiment, the front end of the resistor 50 is located on the rear end facing surface 13 of the insulator 11, and the rear end of the resistor 50 is located rearward of the rear end 41 of the metal shell 30. Since the rear end facing surface 13 of the insulator 11 is located rearward of the tip 40 of the metal shell 30, the tip of the resistor 50 is located rearward of the tip 40 of the metal shell 30. The resistor 50 is formed in a cylindrical shape that is continuous from its front end to its rear end.

抵抗体５０は、軸線方向において、主体金具３０の内周面のうち内側に凸である部位の少なくとも一部に存在する。図２（ａ）及び図２（ｂ）に示すように、主体金具３０の内周面のうち内側に凸である部位としては、後端部３６の内側の縁４３、連結部３４の内側の縁４４，４５、座部３３の内側の縁４６、棚部３８の内側の縁４９が挙げられる。 The resistor 50 is present in at least a part of a portion of the inner peripheral surface of the metal shell 30 that is convex inward in the axial direction. As shown in FIGS. 2A and 2B, the inner convex portion of the inner peripheral surface of the metal shell 30 includes the inner edge 43 of the rear end portion 36 and the inner portion of the connecting portion 34. The edges 44 and 45, the inner edge 46 of the seat portion 33, and the inner edge 49 of the shelf portion 38 are included.

絶縁体１１の第１係止部１４に接触するパッキン３７の角４７，４８も、内側に凸である。パッキン３７の角４７，４８及び棚部３８の縁４９と導電体２０との間の各々の距離は、縁４３，４４，４５，４６と導電体２０との間の各々の距離よりも短い。本実施形態では、主体金具３０の内周面のうち内側に凸である部位の全て、及び、パッキン３７の径方向の内側に抵抗体５０が配置されている。 The corners 47 and 48 of the packing 37 that come into contact with the first locking portion 14 of the insulator 11 are also convex inward. The distances between the conductors 20 and the corners 47, 48 of the packing 37 and the edge 49 of the shelf 38 are shorter than the distances between the edges 43, 44, 45, 46 and the conductor 20. In the present embodiment, the resistor 50 is arranged on all of the inner peripheral surfaces of the metal shell 30 that are convex inward, and on the inside in the radial direction of the packing 37.

点火プラグ１０は、例えば以下のような方法によって製造される。まず、絶縁体１１に中心電極２１を挿入し、中心電極２１を後端向き面１３に係止する。次いで、抵抗体５０の原料粉末を絶縁体１１の内部表面１２と中心電極２１の第２軸部２３との間に充填する。圧縮用棒材（図示せず）を用いて、絶縁体１１の内部に充填した原料粉末を予備圧縮する。次に、接続部２８の原料粉末を、抵抗体５０の原料粉末の後端側に充填する。圧縮用棒材を用いて、絶縁体１１の内部に充填した原料粉末を予備圧縮する。 The spark plug 10 is manufactured by the following method, for example. First, the center electrode 21 is inserted into the insulator 11, and the center electrode 21 is locked to the rear end facing surface 13. Then, the raw material powder of the resistor 50 is filled between the inner surface 12 of the insulator 11 and the second shaft portion 23 of the center electrode 21. The raw material powder filled in the insulator 11 is pre-compressed using a compression rod (not shown). Next, the raw material powder of the connecting portion 28 is filled in the rear end side of the raw material powder of the resistor 50. The raw material powder with which the inside of the insulator 11 is filled is pre-compressed using a compression rod.

次いで、絶縁体１１を炉内に移送し、例えば原料粉末に含まれるガラス成分の軟化点より高い温度まで加熱する。原料粉末を軟化させた後、絶縁体１１に挿入した端子金具２５によって、軟化した原料粉末を軸線方向へ圧縮する。この結果、原料粉末が圧縮・焼結され、絶縁体１１の内部に抵抗体５０及び接続部２８が形成される。次に、主体金具３０に絶縁体１１を挿入し、連結部３４及び後端部３６を屈曲して主体金具３０を絶縁体１１に組み付け、点火プラグ１０を得る。 Next, the insulator 11 is transferred into the furnace and heated to a temperature higher than the softening point of the glass component contained in the raw material powder, for example. After softening the raw material powder, the softened raw material powder is compressed in the axial direction by the terminal fitting 25 inserted into the insulator 11. As a result, the raw material powder is compressed and sintered, and the resistor 50 and the connecting portion 28 are formed inside the insulator 11. Next, the insulator 11 is inserted into the metal shell 30, the connecting portion 34 and the rear end portion 36 are bent, and the metal shell 30 is assembled to the insulator 11 to obtain the spark plug 10.

エンジン（図示せず）に取り付けられた点火プラグ１０の導電体２０と主体金具３０との間に交流電圧やパルス電圧が入力されると、絶縁体１１の先端部１６の表面に非平衡プラズマ（ストリーマ放電）が生じる。非平衡プラズマは熱エネルギーへの変換が少ないので、燃焼室（図示せず）内の可燃混合気の温度はあまり上がらないが、高いエネルギーをもつ電子が生成される。この高いエネルギーをもつ電子の衝突によりＯ，Ｎ，ＯＨ等のラジカルが大量に生成され、発熱反応による温度上昇およびラジカルによる連鎖反応が進行し点火に至る。 When an AC voltage or a pulse voltage is input between the conductor 20 of the spark plug 10 attached to the engine (not shown) and the metal shell 30, a non-equilibrium plasma ( Streamer discharge) occurs. Since the non-equilibrium plasma has little conversion to thermal energy, the temperature of the combustible mixture in the combustion chamber (not shown) does not rise very much, but electrons with high energy are generated. A large amount of radicals such as O, N, and OH are generated by the collision of the electrons having high energy, and the temperature rise due to the exothermic reaction and the chain reaction due to the radicals proceed to ignite.

しかし、導電体２０と主体金具３０との間にコロナ放電等の不正な放電が生じ、導電体２０に印加された交流電圧やパルス電圧による電流の一部が導電体２０と主体金具３０との間を流れると、導電体２０に入力されたエネルギーの一部が失われる。そうすると、その分だけ、プラズマが生成する高いエネルギーをもつ電子の量が減少する。発熱反応による温度上昇およびラジカルによる連鎖反応が進行し難くなるので、点火し難くなるおそれがある。 However, improper discharge such as corona discharge occurs between the conductor 20 and the metal shell 30, and a part of the current due to the AC voltage or the pulse voltage applied to the conductor 20 is generated between the conductor 20 and the metal shell 30. When flowing through, some of the energy input to the conductor 20 is lost. Then, the amount of electrons with high energy generated by the plasma is reduced accordingly. Since the temperature rise due to the exothermic reaction and the chain reaction due to radicals become difficult to proceed, there is a possibility that ignition may become difficult.

これを防ぐために点火プラグ１０は、導電体２０と絶縁体１１の内部表面１２との間の、主体金具３０と導電体２０とが軸線方向に重なる領域４２の少なくとも一部に抵抗体５０が配置される。これにより導電体２０に印加された交流電圧やパルス電圧による電流が導電体２０と主体金具３０との間を流れ難くなるので、先端部１６にプラズマを生じさせるエネルギーの損失を抑制できる。よって、点火プラグ１０の点火性能を向上できる。 In order to prevent this, in the spark plug 10, the resistor 50 is arranged in at least a part of a region 42 between the conductor 20 and the inner surface 12 of the insulator 11 where the metal shell 30 and the conductor 20 overlap in the axial direction. To be done. This makes it difficult for a current due to the AC voltage or the pulse voltage applied to the conductor 20 to flow between the conductor 20 and the metal shell 30, so that energy loss that causes plasma to be generated in the tip portion 16 can be suppressed. Therefore, the ignition performance of the spark plug 10 can be improved.

抵抗体５０の先端は主体金具３０の先端４０よりも後端側に位置するので、抵抗体５０に妨げられることなく先端部１６の表面にプラズマを発生できる。 Since the tip of the resistor 50 is located on the rear end side of the tip 40 of the metal shell 30, plasma can be generated on the surface of the tip 16 without being hindered by the resistor 50.

抵抗体５０は、軸線方向において、主体金具３０の内周面のうち内側に凸である部位（縁４３−４６，４９）の少なくとも一部に存在する。これらの各部位は電界が集中し易く不正な放電が生じ易いので、これらの少なくとも一部に抵抗体５０が存在することにより、これらの各部位と導電体２０との間に電流をより流れ難くできる。よって、先端部１６にプラズマを生じさせるエネルギーの損失をより抑制できる。 The resistor 50 is present in at least a part of a portion (rims 43-46, 49) that is convex inward on the inner peripheral surface of the metal shell 30 in the axial direction. Since an electric field is likely to be concentrated in each of these parts and an unauthorized discharge is likely to occur, the presence of the resistor 50 in at least a part of these parts makes it more difficult for current to flow between these parts and the conductor 20. it can. Therefore, it is possible to further suppress the loss of energy that causes plasma in the tip portion 16.

抵抗体５０は、軸線方向において、パッキン３７の位置に存在する。パッキン３７の位置（パッキン３７の角４７，４８及び棚部３８の縁４９）は電界が集中し易いだけでなく、導電体２０との間の距離が近く電流が流れやすい。軸線方向において、パッキン３７の位置に抵抗体５０を存在させることにより、先端部１６にプラズマを生じさせるエネルギーの損失をより抑制できる。 The resistor 50 exists at the position of the packing 37 in the axial direction. At the position of the packing 37 (the corners 47 and 48 of the packing 37 and the edge 49 of the shelf 38), the electric field is likely to be concentrated, and the distance between the packing 20 and the conductor 20 is short, and the current easily flows. By disposing the resistor 50 at the position of the packing 37 in the axial direction, it is possible to further suppress energy loss that causes plasma to be generated at the tip portion 16.

図３を参照して第２実施の形態について説明する。第１実施形態では、抵抗体５０の先端が主体金具３０の先端４０よりも後端側に位置する場合について説明した。これに対し第２実施形態では、抵抗体６８の先端６９が主体金具３０の先端４０よりも先端側に位置する場合について説明する。なお、第１実施形態で説明した部分と同一の部分については、同一の符号を付して以下の説明を省略する。図３は第２実施の形態における点火プラグ６０の片側断面図である。 A second embodiment will be described with reference to FIG. 1st Embodiment demonstrated the case where the front-end|tip of the resistor 50 was located in the rear end side rather than the front-end 40 of the metal shell 30. As shown in FIG. On the other hand, in the second embodiment, the case where the tip 69 of the resistor 68 is located closer to the tip side than the tip 40 of the metal shell 30 will be described. The same parts as those described in the first embodiment are designated by the same reference numerals, and the following description will be omitted. FIG. 3 is a one-sided sectional view of the spark plug 60 according to the second embodiment.

点火プラグ６０は、絶縁体１１の内部に配置された導電体６１と、絶縁体１１を保持する主体金具３０と、導電体６１と絶縁体１１との間に配置された抵抗体６８と、を備えている。導電体６１は複数の部位からなり、軸線Ｏに沿って先端側から後端側へと延びている。導電体６１は、本実施形態では中心電極６２及び端子金具６３を備えている。 The spark plug 60 includes a conductor 61 arranged inside the insulator 11, a metal shell 30 holding the insulator 11, and a resistor 68 arranged between the conductor 61 and the insulator 11. I have it. The conductor 61 is made up of a plurality of parts and extends along the axis O from the front end side to the rear end side. The conductor 61 includes a center electrode 62 and a terminal fitting 63 in this embodiment.

中心電極６２は導電性を有する金属材料（例えばニッケル基合金等）によって形成された棒状の部材である。中心電極６２は、絶縁体１１の内部表面１２の内側に、内部表面１２と隙間をあけて軸線Ｏに沿って配置されている。中心電極６２の後端は、絶縁体１１の後端向き面１３よりも後端側に位置する。 The center electrode 62 is a rod-shaped member made of a conductive metal material (for example, a nickel-based alloy). The center electrode 62 is arranged inside the inner surface 12 of the insulator 11 along the axis O with a gap from the inner surface 12. The rear end of the center electrode 62 is located on the rear end side of the rear end facing surface 13 of the insulator 11.

端子金具６３は、交流電圧やパルス電圧が入力される棒状の部材であり、導電性を有する金属材料（例えば低炭素鋼等）によって形成されている。端子金具６３は、先端部６４が絶縁体１１の内側に挿入され、後端部６５が絶縁体１１から後端側へ突出している。端子金具６３は、先端部６４が、導電性ガラス等の接続部６６により中心電極６２に接続されている。 The terminal fitting 63 is a rod-shaped member to which an AC voltage or a pulse voltage is input, and is made of a conductive metal material (for example, low carbon steel). In the terminal fitting 63, the front end 64 is inserted inside the insulator 11, and the rear end 65 projects from the insulator 11 toward the rear end. A tip 64 of the terminal fitting 63 is connected to the center electrode 62 by a connecting portion 66 made of conductive glass or the like.

絶縁体１１の内部表面１２と中心電極６２との間に第１導体６７が充填されている。本実施形態では、第１導体６７は先端部１６の内部表面１２と中心電極６２とに接触している。第１導体６７は少なくとも第１部１６ａに存在する。第１導体６７は導電性粉末やろう材等により形成される。ろう材としては、例えば金ろう、銀ろう、白金ろう、ニッケルろう、銅ろう、りん青銅ろう、黄銅ろう、りん銅ろう等が挙げられる。 The first conductor 67 is filled between the inner surface 12 of the insulator 11 and the center electrode 62. In the present embodiment, the first conductor 67 is in contact with the inner surface 12 of the tip portion 16 and the center electrode 62. The first conductor 67 exists at least in the first portion 16a. The first conductor 67 is formed of conductive powder, a brazing material, or the like. Examples of the brazing material include gold brazing, silver brazing, platinum brazing, nickel brazing, copper brazing, phosphor bronze brazing, brass brazing, phosphor copper brazing and the like.

第１導体６７の導電性粉末としては、例えば半導性酸化物、金属および非金属導電性材料等からなる粉末が挙げられる。半導性酸化物としては、例えばＳｎＯ_２が挙げられる。金属としては、例えばＡｕ，Ａｇ，Ｃｕ，Ｗ，Ｎｉ及びＰｔ等が挙げられる。金属は磁気モーメントによるエネルギー損失を抑制するため、Ｃｕ等の非磁性金属が好ましい。非金属導電性材料としては、例えば無定形カーボン（カーボンブラック）、グラファイト、炭化ケイ素、炭化チタン、窒化チタン、炭化タングステン及び炭化ジルコニウム等が挙げられる。 Examples of the conductive powder of the first conductor 67 include powder made of a semiconductive oxide, a metal and a non-metal conductive material, or the like. Examples of the semiconductive oxide include SnO ₂ . Examples of the metal include Au, Ag, Cu, W, Ni and Pt. Since the metal suppresses energy loss due to the magnetic moment, a nonmagnetic metal such as Cu is preferable. Examples of the non-metal conductive material include amorphous carbon (carbon black), graphite, silicon carbide, titanium carbide, titanium nitride, tungsten carbide and zirconium carbide.

抵抗体６８は第１導体６７の後端に隣接し、後端向き面１３よりも後端側まで軸線Ｏに沿って延びている。抵抗体６８は略円筒状に形成されている。抵抗体６８の材質は、第１実施形態の抵抗体５０の材質と同様なので、説明を省略する。抵抗体６８は、軸線方向において、パッキン３７（図２（ａ）参照）の位置に少なくとも存在する。抵抗体６８の先端６９は、主体金具３０の先端４０よりも先端側であって、第１部１６ａと第２部１６ｂとの境界に位置する。 The resistor 68 is adjacent to the rear end of the first conductor 67 and extends along the axis O to the rear end side of the rear end facing surface 13. The resistor 68 is formed in a substantially cylindrical shape. The material of the resistor 68 is the same as the material of the resistor 50 of the first embodiment, so the description thereof will be omitted. The resistor 68 exists at least at the position of the packing 37 (see FIG. 2A) in the axial direction. The tip 69 of the resistor 68 is located on the tip side of the tip 40 of the metal shell 30 and is located at the boundary between the first portion 16a and the second portion 16b.

点火プラグ６０は、例えば以下のような方法によって製造される。まず、絶縁体１１の内部表面１２の先端に、第１導体６７の粉末等の原料を少量供給する。第１導体６７にろう材を用いる場合、ろう材は箔、線材、箔、粉末、ペースト等の種々の状態で供給できる。絶縁体１１に中心電極６２を挿入し、第１導体６７の原料の後端側に中心電極６２を配置した後、第１導体６７の残りの原料を、中心電極６２と先端部１６の内部表面１２との間に充填する。 The spark plug 60 is manufactured by the following method, for example. First, a small amount of raw material such as powder of the first conductor 67 is supplied to the tip of the inner surface 12 of the insulator 11. When a brazing material is used for the first conductor 67, the brazing material can be supplied in various states such as foil, wire, foil, powder and paste. After inserting the center electrode 62 into the insulator 11 and disposing the center electrode 62 on the rear end side of the raw material of the first conductor 67, the remaining raw material of the first conductor 67 is fed to the center electrode 62 and the inner surface of the tip portion 16. Fill between 12 and.

次いで、抵抗体６８の原料粉末を絶縁体１１の内部表面１２と中心電極６２との間に充填する。圧縮用棒材（図示せず）を用いて、絶縁体１１の内部に充填した原料粉末を予備圧縮する。次に、接続部６６の原料粉末を、抵抗体６８の原料粉末の後端側に充填する。圧縮用棒材を用いて、絶縁体１１の内部に充填した原料粉末を予備圧縮する。その後、第１実施形態と同様に絶縁体１１を加熱し、絶縁体１１の内部に抵抗体６８及び接続部６６を形成した後、主体金具３０を絶縁体１１に組み付け、点火プラグ６０を得る。 Then, the raw material powder of the resistor 68 is filled between the inner surface 12 of the insulator 11 and the center electrode 62. The raw material powder filled in the insulator 11 is pre-compressed using a compression rod (not shown). Next, the raw material powder of the connecting portion 66 is filled in the rear end side of the raw material powder of the resistor 68. The raw material powder with which the inside of the insulator 11 is filled is pre-compressed using a compression rod. After that, the insulator 11 is heated in the same manner as in the first embodiment to form the resistor 68 and the connection portion 66 inside the insulator 11, and then the metal shell 30 is assembled to the insulator 11 to obtain the spark plug 60.

点火プラグ６０の導電体６１と絶縁体１１の内部表面１２との間に配置された抵抗体６８は、軸線方向において、少なくともパッキン３７の位置（パッキン３７の角４７，４８及び棚部３８の縁４９（図２（ｂ）参照））に存在する。これらの各部位は電界が集中し易く不正な放電が生じ易いので、抵抗体６８によって放電の発生を抑制することにより、先端部１６にプラズマを生じさせるエネルギーの損失を抑制できる。これにより抵抗体６８の体積を小さくできると共に、点火プラグ６０の点火性能を向上できる。 The resistor 68 arranged between the conductor 61 of the spark plug 60 and the inner surface 12 of the insulator 11 has at least the position of the packing 37 in the axial direction (corners 47 and 48 of the packing 37 and edges of the shelf portion 38). 49 (see FIG. 2B)). Since an electric field is likely to be concentrated in each of these parts and an unauthorized electric discharge is likely to occur, by suppressing the occurrence of the electric discharge by the resistor 68, it is possible to suppress the energy loss that causes the plasma in the tip portion 16. This makes it possible to reduce the volume of the resistor 68 and improve the ignition performance of the ignition plug 60.

点火プラグ６０は、抵抗体６８の先端６９よりも先端側の絶縁体１１（先端部１６）の内部に第１導体６７が充填されており、第１導体６７は導電体６１に電気的に接続されている。先端部１６の内部表面１２と導電体６１（中心電極６２）との隙間が第１導体６７に埋められるので、第１導体６７により先端部１６の表面の広い範囲にプラズマを発生できる。 In the spark plug 60, the first conductor 67 is filled inside the insulator 11 (the tip portion 16) on the tip side of the tip 69 of the resistor 68, and the first conductor 67 is electrically connected to the conductor 61. Has been done. Since the gap between the inner surface 12 of the tip portion 16 and the conductor 61 (center electrode 62) is filled with the first conductor 67, plasma can be generated in a wide range of the surface of the tip portion 16 by the first conductor 67.

第１導体６７により中心電極６２と絶縁体１１の内部表面１２との隙間（空気層）をなくすことができる。隙間（空気層）があると点火プラグの見かけの誘電率が低下するので、その分だけ絶縁体の表面に蓄えられる電荷が少なくなる。そのため、点火プラグに投入された電力に対して出力（プラズマの発生量）が低下する、即ちエネルギーの損失が生じるという問題点がある。これに対し点火プラグ６０によれば、中心電極６２と絶縁体１１の内部表面１２との隙間（空気層）が見かけの誘電率に与える影響を抑制できるので、エネルギーの損失を抑制できる。 The first conductor 67 can eliminate a gap (air layer) between the center electrode 62 and the inner surface 12 of the insulator 11. If there is a gap (air layer), the apparent permittivity of the spark plug lowers, and the amount of charge stored on the surface of the insulator decreases accordingly. Therefore, there is a problem that the output (amount of generated plasma) decreases with respect to the electric power supplied to the spark plug, that is, energy loss occurs. On the other hand, according to the spark plug 60, the influence of the gap (air layer) between the center electrode 62 and the inner surface 12 of the insulator 11 on the apparent dielectric constant can be suppressed, and thus the energy loss can be suppressed.

抵抗体６８の先端６９は、軸線方向において、主体金具３０の先端４０よりも先端側に位置するので、主体金具３０の先端４０と導電体６１との間に不正な放電を生じ難くできる。抵抗体６８の先端６９は、先端部１６の第１部１６ａと第２部１６ｂとの境界に位置し、第２部１６ｂよりも肉厚が薄くプラズマが生じ易い第１部１６ａに抵抗体６８は存在しないので、抵抗体６８に妨げられることなく第１部１６ａの表面にプラズマを発生できる。 Since the tip 69 of the resistor 68 is located closer to the tip side than the tip 40 of the metal shell 30 in the axial direction, it is possible to prevent illicit discharge from occurring between the tip 40 of the metal shell 30 and the conductor 61. The tip 69 of the resistor 68 is located at the boundary between the first portion 16a and the second portion 16b of the tip portion 16 and is thinner than the second portion 16b, and the resistor 68 is provided on the first portion 16a where plasma is easily generated. Therefore, plasma can be generated on the surface of the first portion 16a without being blocked by the resistor 68.

絶縁体１１の内部表面１２と中心電極６２との間に充填された第１導体６７の後端に隣接して抵抗体６８が配置される。第１導体６７によって、抵抗体６８の先端６９の位置を定めることができる。抵抗体６８の先端６９は主体金具３０の先端４０よりも先端側に位置するので、第１導体６７及び抵抗体６８により、プラズマが発生し易い部位と発生し難い部位とを先端部１６の表面に区画できる。 The resistor 68 is disposed adjacent to the rear end of the first conductor 67 filled between the inner surface 12 of the insulator 11 and the center electrode 62. The position of the tip 69 of the resistor 68 can be determined by the first conductor 67. Since the tip 69 of the resistor 68 is located closer to the tip side than the tip 40 of the metal shell 30, the first conductor 67 and the resistor 68 define a portion where plasma is easily generated and a portion where plasma is not easily generated on the surface of the tip 16. Can be divided into

図４及び図５を参照して第３実施の形態について説明する。第３実施形態では、主体金具３０に接地電極７１，７４が接続された点火プラグ７０について説明する。なお、第１実施形態および第２実施形態で説明した部分と同一の部分については、同一の符号を付して以下の説明を省略する。図４は第３実施の形態における点火プラグ７０の片側断面図であり、図５は先端部１６の軸線Ｏを含む断面図である。 A third embodiment will be described with reference to FIGS. 4 and 5. In the third embodiment, the spark plug 70 in which the ground electrodes 71 and 74 are connected to the metal shell 30 will be described. The same parts as those described in the first and second embodiments are designated by the same reference numerals, and the following description will be omitted. FIG. 4 is a one-sided sectional view of the spark plug 70 according to the third embodiment, and FIG. 5 is a sectional view including the axis O of the tip portion 16.

図４に示すように点火プラグ７０は、絶縁体１１の内部に配置された導電体６１と、絶縁体１１を保持する主体金具３０と、主体金具３０に接続された接地電極７１，７４と、導電体６１と絶縁体１１との間に配置された抵抗体６８と、を備えている。 As shown in FIG. 4, the spark plug 70 includes a conductor 61 arranged inside the insulator 11, a metal shell 30 holding the insulator 11, ground electrodes 71, 74 connected to the metal shell 30, And a resistor 68 disposed between the conductor 61 and the insulator 11.

接地電極７１，７４は、主体金具３０の胴部３２に接合された棒状の金属製（例えばニッケル基合金製）の部材である。本実施形態では、接地電極７１，７４は軸線Ｏに沿って配置されており、軸線Ｏに垂直な断面が矩形状である。接地電極７１の一端部７２及び接地電極７４の一端部７５は主体金具３０に接続されている。接地電極７４の他端部７６は、接地電極７１の他端部７３よりも先端側に位置する。接地電極７１の他端部７３及び接地電極７４の他端部７６は、軸線Ｏを中心にして互いに１８０°離れた位置に存在する。 The ground electrodes 71 and 74 are rod-shaped metal (for example, nickel-based alloy) members joined to the body 32 of the metal shell 30. In the present embodiment, the ground electrodes 71, 74 are arranged along the axis O, and the cross section perpendicular to the axis O has a rectangular shape. One end 72 of the ground electrode 71 and one end 75 of the ground electrode 74 are connected to the metal shell 30. The other end 76 of the ground electrode 74 is located closer to the tip side than the other end 73 of the ground electrode 71. The other end portion 73 of the ground electrode 71 and the other end portion 76 of the ground electrode 74 are located 180° apart from each other about the axis O.

図５に示すように、接地電極７１，７４は他端部７３，７６を除き、軸線Ｏに平行に配置されている。他端部７３，７６は絶縁体１１の先端部１６へ向かって屈曲しているので、接地電極７１，７４の中で他端部７３，７６は先端部１６との距離が最も短い。接地電極７１，７４の他端部７３，７６は、先端部１６のうち中心電極６２と軸線方向に重なる部位との間に、放電ギャップ７７，７８をそれぞれ形成する。 As shown in FIG. 5, the ground electrodes 71 and 74 are arranged parallel to the axis O except the other ends 73 and 76. Since the other ends 73 and 76 are bent toward the tip 16 of the insulator 11, the other ends 73 and 76 of the ground electrodes 71 and 74 have the shortest distance from the tip 16. The other end portions 73 and 76 of the ground electrodes 71 and 74 form discharge gaps 77 and 78 between the tip portion 16 and the portion overlapping the center electrode 62 in the axial direction.

絶縁体１１は、先端部１６の内部表面１２に導電層７９が形成されている。導電層７９は、化学的または物理的な力によって絶縁体１１の内部表面１２に結合した導電性を有する層である。本実施形態では、第１部１６ａの内部表面１２の先端から第１部１６ａと第２部１６ｂとの境界までの全面が導電層７９で覆われている。導電層７９は、例えばめっき、導電ペースト等の導電性樹脂材料の塗布、溶射、蒸着などにより形成される。本実施形態では、無電解ニッケルめっきにより導電層７９が形成されている。 In the insulator 11, a conductive layer 79 is formed on the inner surface 12 of the tip portion 16. The conductive layer 79 is a conductive layer bonded to the inner surface 12 of the insulator 11 by a chemical or physical force. In the present embodiment, the entire surface from the tip of the inner surface 12 of the first portion 16a to the boundary between the first portion 16a and the second portion 16b is covered with the conductive layer 79. The conductive layer 79 is formed by, for example, plating, applying a conductive resin material such as a conductive paste, spraying, vapor deposition, or the like. In this embodiment, the conductive layer 79 is formed by electroless nickel plating.

導電層７９と中心電極６２との間に第２導体８０が充填されている。第２導体８０は導電層７９と中心電極６２とに接触している。第２導体８０の材質は、第２実施形態の第１導体６７の材質と同様なので、説明を省略する。抵抗体６８は第２導体８０の後端に隣接する。抵抗体６８の先端６９は、導電層７９の後端よりも後端側に位置する。また、抵抗体６８の先端６９は、接地電極７１，７４の他端部７３，７６よりも後端側に位置する。 The second conductor 80 is filled between the conductive layer 79 and the center electrode 62. The second conductor 80 is in contact with the conductive layer 79 and the center electrode 62. The material of the second conductor 80 is the same as the material of the first conductor 67 of the second embodiment, so description thereof will be omitted. The resistor 68 is adjacent to the rear end of the second conductor 80. The tip 69 of the resistor 68 is located on the rear end side of the rear end of the conductive layer 79. The tip 69 of the resistor 68 is located on the rear end side of the other end 73, 76 of the ground electrode 71, 74.

点火プラグ７０は、例えば、以下のような方法によって製造される。まず、絶縁体１１の先端部１６の内部表面１２に導電層７９を形成する。次に、先端部１６の内部表面１２の先端に形成された導電層７９の上に、第２導体８０の粉末等の原料を少量供給する。第２導体８０にろう材を用いる場合、ろう材は箔、線材、箔、粉末、ペースト等の種々の状態で供給できる。絶縁体１１に中心電極６２を挿入し、第２導体８０の原料の後端側に中心電極６２を配置した後、第２導体８０の残りの原料を、中心電極６２と先端部１６の内部表面１２との間に充填する。その後、第１実施形態と同様に絶縁体１１を加熱し、絶縁体１１の内部に抵抗体６８及び接続部６６を形成した後、主体金具３０を絶縁体１１に組み付け、点火プラグ７０を得る。 The spark plug 70 is manufactured by the following method, for example. First, the conductive layer 79 is formed on the inner surface 12 of the tip portion 16 of the insulator 11. Next, a small amount of raw material such as powder of the second conductor 80 is supplied onto the conductive layer 79 formed on the tip of the inner surface 12 of the tip portion 16. When a brazing material is used for the second conductor 80, the brazing material can be supplied in various states such as foil, wire, foil, powder and paste. After inserting the center electrode 62 into the insulator 11 and disposing the center electrode 62 on the rear end side of the raw material of the second conductor 80, the remaining raw material of the second conductor 80 is fed to the inner surface of the center electrode 62 and the tip portion 16. Fill between 12 and. After that, the insulator 11 is heated in the same manner as in the first embodiment to form the resistor 68 and the connection portion 66 inside the insulator 11, and then the metal shell 30 is assembled to the insulator 11 to obtain the spark plug 70.

点火プラグ７０は、抵抗体６８の先端６９が、接地電極７１，７４の他端部７３，７６よりも後端側に位置する。接地電極７１，７４の他端部７３，７６に電界を集中させ易くできるので、他端部７３，７６と先端部１６との間に放電を生じさせ易くできる。その結果、抵抗体６８に妨げられることなく先端部１６と接地電極７１，７４との間にプラズマを発生できる。 In the spark plug 70, the tip 69 of the resistor 68 is located rearward of the other ends 73 and 76 of the ground electrodes 71 and 74. Since it is possible to easily concentrate the electric field on the other end portions 73 and 76 of the ground electrodes 71 and 74, it is possible to easily generate an electric discharge between the other end portions 73 and 76 and the tip end portion 16. As a result, plasma can be generated between the tip portion 16 and the ground electrodes 71, 74 without being blocked by the resistor 68.

先端部１６の内部表面１２の少なくとも一部に、化学的または物理的な力によって内部表面１２に結合する導電層７９が形成され、導電層７９は導電体６１に電気的に接続される。導電層７９により中心電極６２と絶縁体１１の内部表面１２との隙間（空気層）をなくすことができるので、隙間（空気層）が見かけの誘電率に与える影響を抑制できる。よって、先端部１６にプラズマを生じさせるエネルギーの損失を抑制できる。 A conductive layer 79 is formed on at least a part of the inner surface 12 of the tip portion 16 and is bonded to the inner surface 12 by a chemical or physical force, and the conductive layer 79 is electrically connected to the conductor 61. Since the gap (air layer) between the center electrode 62 and the inner surface 12 of the insulator 11 can be eliminated by the conductive layer 79, the influence of the gap (air layer) on the apparent dielectric constant can be suppressed. Therefore, it is possible to suppress the loss of energy that causes plasma in the tip portion 16.

先端部１６のうち導電層７９が形成された部位に少なくとも第２導体８０が充填され、第２導体８０は導電体６１と接続されるので、第２導体８０により抵抗体６８の先端６９の位置を定めることができる。その結果、第２導体８０及び抵抗体６８により、プラズマが発生し易い部位と発生し難い部位とを先端部１６の表面に区画できる。 Since at least the second conductor 80 is filled in the portion of the tip portion 16 where the conductive layer 79 is formed, and the second conductor 80 is connected to the conductor 61, the position of the tip 69 of the resistor 68 by the second conductor 80. Can be determined. As a result, by the second conductor 80 and the resistor 68, a site where plasma is easily generated and a site where plasma is difficult to be generated can be partitioned on the surface of the tip portion 16.

図６を参照して第４実施の形態について説明する。第１実施形態から第３実施形態では、抵抗体５０，６８が軸線方向に連続する場合について説明した。これに対し第４実施形態では、第１抵抗体９２及び第２抵抗体９４（抵抗体）が軸線方向に離間する場合について説明する。なお、第１実施形態から第３実施形態で説明した部分と同一の部分については、同一の符号を付して以下の説明を省略する。図６は第４実施の形態における点火プラグ９０の先端部１６の軸線Ｏを含む断面図である。 A fourth embodiment will be described with reference to FIG. In the first to third embodiments, the case where the resistors 50 and 68 are continuous in the axial direction has been described. On the other hand, in the fourth embodiment, a case where the first resistor 92 and the second resistor 94 (resistors) are separated from each other in the axial direction will be described. The same parts as those described in the first to third embodiments are designated by the same reference numerals, and the following description will be omitted. FIG. 6 is a sectional view including the axis O of the tip portion 16 of the spark plug 90 according to the fourth embodiment.

図６に示すように点火プラグ９０は、絶縁体１１の内部に配置された導電体６１（中心電極６２）と、絶縁体１１を保持する主体金具３０と、主体金具３０に接続された接地電極７１，７４と、導電体６１と絶縁体１１との間に配置された第１抵抗体９２及び第２抵抗体９４と、を備えている。 As shown in FIG. 6, the spark plug 90 includes a conductor 61 (center electrode 62) arranged inside the insulator 11, a metal shell 30 holding the insulator 11, and a ground electrode connected to the metal shell 30. 71, 74, and a first resistor 92 and a second resistor 94 arranged between the conductor 61 and the insulator 11.

点火プラグ９０は、絶縁体１１の内部表面１２と中心電極６２との間に、先端側から後端側へ順に、第１導体９１、第１抵抗体９２、第１導体９３及び第２抵抗体９４が充填されている。第２抵抗体９４の後端の位置は、第２実施形態の抵抗体６８の後端と同じ位置である。第１導体９１，９３は、絶縁体１１の内部表面１２及び中心電極６２に接触している。第１導体９１，９３の材質は、第２実施形態の第１導体６７の材質と同様であり、第１抵抗体９２及び第２抵抗体９４の材質は、第１実施形態の抵抗体５０の材質と同様なので、いずれも説明を省略する。 The spark plug 90 includes a first conductor 91, a first resistor 92, a first conductor 93, and a second resistor between the inner surface 12 of the insulator 11 and the center electrode 62 in order from the front end side to the rear end side. 94 is filled. The position of the rear end of the second resistor 94 is the same as the position of the rear end of the resistor 68 of the second embodiment. The first conductors 91 and 93 are in contact with the inner surface 12 of the insulator 11 and the center electrode 62. The materials of the first conductors 91 and 93 are the same as those of the first conductor 67 of the second embodiment, and the materials of the first resistor 92 and the second resistor 94 are the same as those of the resistor 50 of the first embodiment. Since it is the same as the material, the description thereof is omitted.

軸線方向において、第１導体９１は先端部１６の内部表面１２の先端に位置し、第１抵抗体９２は第１導体９１の後端に隣接する。第１導体９３は第１抵抗体９２の後端に隣接し、第２抵抗体９４は第１導体９３の後端に隣接する。第２抵抗体９４の先端９４ａは、主体金具３０の先端よりも先端側であって、接地電極７１の他端部７３よりも後端側に位置する。第１導体９３の先端９３ａは、接地電極７１の他端部７３よりも先端側に位置し、第１抵抗体９２の先端９２ａは、接地電極７４の他端部７６よりも後端側に位置する。中心電極６２及び第１導体９１は、接地電極７４の他端部７６と重なる位置に配置されている。 In the axial direction, the first conductor 91 is located at the tip of the inner surface 12 of the tip portion 16, and the first resistor 92 is adjacent to the rear end of the first conductor 91. The first conductor 93 is adjacent to the rear end of the first resistor 92, and the second resistor 94 is adjacent to the rear end of the first conductor 93. The tip 94 a of the second resistor 94 is located on the tip side of the tip of the metal shell 30 and on the rear side of the other end 73 of the ground electrode 71. The tip 93a of the first conductor 93 is located on the tip side of the other end 73 of the ground electrode 71, and the tip 92a of the first resistor 92 is located on the rear side of the other end 76 of the ground electrode 74. To do. The center electrode 62 and the first conductor 91 are arranged at positions overlapping the other end portion 76 of the ground electrode 74.

点火プラグ９０は、例えば以下のような方法によって製造される。まず、絶縁体１１の内部表面１２の先端に、第１導体９１の粉末等の原料を供給する。絶縁体１１に中心電極６２を挿入し、第１導体９１の原料の後端側に中心電極６２を配置した後、第１抵抗体９２の原料を、中心電極６２と先端部１６の内部表面１２との間に充填する。次いで、第１導体９３の原料、第２抵抗体９４の原料を順に充填する。その後、第１実施形態と同様に絶縁体１１を加熱し、絶縁体１１の内部に接続部６６を形成した後、主体金具３０を絶縁体１１に組み付け、点火プラグ９０を得る。 The spark plug 90 is manufactured by the following method, for example. First, a raw material such as powder of the first conductor 91 is supplied to the tip of the inner surface 12 of the insulator 11. After inserting the center electrode 62 into the insulator 11 and disposing the center electrode 62 on the rear end side of the raw material of the first conductor 91, the raw material of the first resistor 92 is fed to the center electrode 62 and the inner surface 12 of the tip portion 16. Fill between and. Then, the raw material of the first conductor 93 and the raw material of the second resistor 94 are sequentially filled. After that, the insulator 11 is heated in the same manner as in the first embodiment to form the connection portion 66 inside the insulator 11, and then the metal shell 30 is assembled to the insulator 11 to obtain the spark plug 90.

点火プラグ９０は、第１抵抗体９２の先端９２ａが、接地電極７４の他端部７６よりも後端側に位置し、第１導体９１が、接地電極７４の他端部７６と重なる位置に配置されている。第１導体９１は中心電極６２に接続されているので、第１導体９１と接地電極７４との間にストリーマ放電を生じさせることができる。 In the spark plug 90, the tip 92a of the first resistor 92 is located rearward of the other end 76 of the ground electrode 74, and the first conductor 91 is located at a position overlapping the other end 76 of the ground electrode 74. It is arranged. Since the first conductor 91 is connected to the center electrode 62, streamer discharge can be generated between the first conductor 91 and the ground electrode 74.

また、第２抵抗体９４の先端９４ａが、接地電極７１の他端部７３よりも後端側に位置し、第１導体９３が、接地電極７１の他端部７３と重なる位置に配置されている。第１導体９３は中心電極６２に接続されているので、第１導体９３と接地電極７１との間にストリーマ放電を生じさせることができる。 The tip 94 a of the second resistor 94 is located rearward of the other end 73 of the ground electrode 71, and the first conductor 93 is arranged at a position overlapping the other end 73 of the ground electrode 71. There is. Since the first conductor 93 is connected to the center electrode 62, streamer discharge can be generated between the first conductor 93 and the ground electrode 71.

第２抵抗体９４の先端９４ａは主体金具３０の先端よりも先端側に位置するので、接地電極７１の他端部７３以外の部位と中心電極６２との間に放電を生じ難くできる。また、第１導体９３と第１導体９３との間に第１抵抗体９２が存在するので、接地電極７４の他端部７６以外の部位と中心電極６２との間に放電を生じ難くできる。これにより接地電極７１，７４の他端部７３，７６と絶縁体１１の先端部１６との間に、局所的にプラズマを生じさせ易くできる。 Since the tip 94a of the second resistor 94 is located closer to the tip side than the tip of the metal shell 30, it is possible to make it difficult for discharge to occur between the center electrode 62 and a portion other than the other end 73 of the ground electrode 71. Further, since the first resistor 92 is present between the first conductor 93 and the first conductor 93, it is possible to make it difficult for discharge to occur between the center electrode 62 and a portion of the ground electrode 74 other than the other end portion 76. This makes it easier to locally generate plasma between the other ends 73, 76 of the ground electrodes 71, 74 and the tip 16 of the insulator 11.

以上、実施の形態に基づき本発明を説明したが、本発明は上記実施の形態に何ら限定されるものではなく、本発明の趣旨を逸脱しない範囲内で種々の改良変形が可能であることは容易に推察できるものである。 Although the present invention has been described above based on the embodiments, the present invention is not limited to the above embodiments, and various improvements and modifications are possible without departing from the spirit of the present invention. It can be easily guessed.

実施形態では、絶縁体１１の先端部１６のうち第１部１６ａの外径が、軸線方向の全長に亘って同一の場合について説明したが、必ずしもこれに限られるものではない。例えば、第１部１６ａの先端側の外径が後端側の外径よりも小さくなるように第１部１６ａの外周面を先端側へ向けて縮径させたり、第１部１６ａの先端側の外径が後端側の外径よりも大きくなるように第１部１６ａの外周面を先端側へ向けて拡径させたりすることは当然可能である。また、第１部１６ａの軸線方向の中央付近の外径が先端側の外径や後端側の外径よりも大きくなるように第１部１６ａの外周面を中央が膨らんだ円筒状にすることは当然可能である。先端部１６の外周面の形状を適宜変更することより、絶縁体１１の先端部１６の径方向の厚さ等との関係で、先端部１６の周囲の電界強度を適宜設定できる。 In the embodiment, the case where the outer diameter of the first portion 16a of the tip portion 16 of the insulator 11 is the same over the entire length in the axial direction has been described, but the present invention is not necessarily limited to this. For example, the outer diameter of the first portion 16a may be reduced toward the tip end so that the outer diameter of the first portion 16a on the front end side is smaller than the outer diameter on the rear end side of the first portion 16a. It is, of course, possible to expand the outer peripheral surface of the first portion 16a toward the tip side so that the outer diameter of is larger than the outer diameter of the rear end side. Further, the outer peripheral surface of the first portion 16a has a cylindrical shape with a bulged center so that the outer diameter near the center of the first portion 16a in the axial direction is larger than the outer diameter on the tip side or the outer diameter on the rear end side. Of course it is possible. By appropriately changing the shape of the outer peripheral surface of the tip portion 16, the electric field strength around the tip portion 16 can be appropriately set in relation to the radial thickness of the tip portion 16 of the insulator 11.

実施形態では、絶縁体１１の先端部１６の先端が平面状に形成される場合について説明したが、必ずしもこれに限られるものではない。例えば、先端部１６の先端を球冠状にすることは当然可能である。 In the embodiment, the case where the tip of the tip portion 16 of the insulator 11 is formed in a flat shape has been described, but the present invention is not limited to this. For example, it is naturally possible to make the tip of the tip 16 into a spherical crown shape.

実施形態では、抵抗体５０，６８、第１抵抗体９２及び第２抵抗体９４が、円筒状に形成される場合について説明したが、必ずしもこれに限られるものではない。軸線Ｏに垂直な断面が円弧状となるように抵抗体を形成することは当然可能である。この場合、絶縁体１１の内部表面１２と導電体２０との間に配置できる抵抗体を予め準備しておき、絶縁体１１の内部に導電体２０，６１を配置するときに、絶縁体１１の内部に抵抗体を挿入する。予め準備しておいた抵抗体を絶縁体１１の内部に配置するので、抵抗体を任意の形状にできる。この場合も抵抗体が配置された部位で不正放電の発生を抑制できるので、エネルギー損失を抑制できる。 In the embodiment, the case where the resistors 50 and 68, the first resistor 92, and the second resistor 94 are formed in a cylindrical shape has been described, but the present invention is not limited to this. It is naturally possible to form the resistor so that the cross section perpendicular to the axis O has an arc shape. In this case, a resistor that can be arranged between the inner surface 12 of the insulator 11 and the conductor 20 is prepared in advance, and when the conductors 20 and 61 are arranged inside the insulator 11, Insert the resistor inside. Since the resistor prepared in advance is arranged inside the insulator 11, the resistor can be formed into an arbitrary shape. Also in this case, it is possible to suppress the occurrence of unauthorized discharge at the portion where the resistor is arranged, and thus it is possible to suppress energy loss.

第３実施形態で説明した導電層７９を、第１実施形態、第２実施形態および第４実施形態の先端部１６の内部表面１２に形成することは当然可能である。第１実施形態、第２実施形態および第４実施形態の先端部１６に導電層７９を形成した場合、中心電極２１，６２を導電層７９に直接接触させても良いし、中心電極２１，６２と導電層７９との間に第２導体を充填し、第２導体を介して中心電極２１，６２を導電層７９に接続しても良い。 It is of course possible to form the conductive layer 79 described in the third embodiment on the inner surface 12 of the tip portion 16 of the first, second, and fourth embodiments. When the conductive layer 79 is formed on the tip portion 16 of the first embodiment, the second embodiment, and the fourth embodiment, the center electrodes 21 and 62 may directly contact the conductive layer 79, or the center electrodes 21 and 62. The second conductor may be filled between the conductive layer 79 and the conductive layer 79, and the center electrodes 21 and 62 may be connected to the conductive layer 79 via the second conductor.

第３実施形態および第４実施形態では、接地電極の数が２つの場合について説明したが、必ずしもこれに限られるものではない。接地電極の数は適宜設定できるので、接地電極の数を１つ、３つ又はそれ以上にすることは当然可能である。 In the third and fourth embodiments, the case where the number of ground electrodes is two has been described, but the number of ground electrodes is not limited to this. Since the number of ground electrodes can be appropriately set, it is naturally possible to set the number of ground electrodes to one, three or more.

第３実施形態および第４実施形態では、接地電極７１，７４が直線状に形成され、さらに各電極の他端部側の部位が軸線Ｏと平行に配置される場合について説明したが、必ずしもこれに限られるものではない。軸線Ｏを含む平面に接地電極が含まれるように各電極の端部側の部位を傾け、各電極の他端部と先端部１６との間に放電ギャップを形成することは当然可能である。また、軸線Ｏに対してねじれの位置に接地電極を配置したり、接地電極を曲線状にしたりすることは当然可能である。 In the third and fourth embodiments, the case where the ground electrodes 71 and 74 are linearly formed and the other end side portion of each electrode is arranged parallel to the axis O has been described, but this is not always the case. It is not limited to. It is naturally possible to incline the end portion side of each electrode so that the ground electrode is included in the plane including the axis O and form the discharge gap between the other end portion of each electrode and the tip portion 16. Further, it is naturally possible to dispose the ground electrode at a position twisted with respect to the axis O or to make the ground electrode curved.

第４実施形態では第１導体９１，９３間に第１抵抗体９２が配置される場合について説明したが、必ずしもこれに限られるものではない。第１抵抗体９２の代わりに導体を充填して、第１導体９１から第１導体９３まで連続させることは当然可能である。 Although the case where the first resistor 92 is arranged between the first conductors 91 and 93 has been described in the fourth embodiment, the present invention is not limited to this. It is naturally possible to fill the conductor in place of the first resistor 92 so that the first conductor 91 to the first conductor 93 are continuous.

１０，６０，７０，９０点火プラグ
１１絶縁体
１２内部表面
１４第１係止部（係止部）
１６先端部
２０，６１導電体
２４導電体の先端
２７，６５導電体の後端部
３０主体金具
３７パッキン
３８棚部
４０主体金具の先端
４２領域
４３，４４，４５，４６，４９縁（凸である部位）
５０，６８抵抗体
６７，９１，９３第１導体
６９抵抗体の先端
７１，７４接地電極
７２，７５一端部
７３，７６他端部
７７，７８放電ギャップ
７９導電層
８０第２導体
９２第１抵抗体（抵抗体）
９２ａ第１抵抗体の先端
９４第２抵抗体（抵抗体）
９４ａ第２抵抗体の先端
Ｏ軸線 10, 60, 70, 90 Spark plug 11 Insulator 12 Inner surface 14 First locking part (locking part)
16 tip part 20,61 conductor 24 tip of conductor 27,65 conductor rear end 30 metal shell 37 packing 38 shelf 40 tip of metal shell 42 region 43, 44, 45, 46, 49 edge (convex) (Some part)
50,68 resistor 67,91,93 first conductor 69 tip of resistor 71,74 ground electrode 72,75 one end 73,76 other end 77,78 discharge gap 79 conductive layer 80 second conductor 92 first resistance Body (resistor)
92a Tip of first resistor 94 Second resistor (resistor)
94a Tip O axis of second resistor

Claims

A conductor extending along the axis from the front end side to the rear end side,
An insulator having a bottomed cylindrical tip portion that surrounds the periphery of the tip of the conductor, the conductor being disposed inside in a state where the rear end of the conductor projects from the rear end side of the conductor; ,
A spark plug comprising: a tubular metal shell that holds the insulator from the outer peripheral side in a state where the tip portion projects from the tip of the tip to the tip side.
An ignition plug comprising a resistor disposed in at least a part of a region between the conductor and the inner surface of the insulator where the metal shell and the conductor overlap in the axial direction.

The spark plug according to claim 1, wherein the resistor is present in at least a part of a portion of the inner peripheral surface of the metal shell that is convex inward in the axial direction.

The insulator is provided on its outer peripheral surface with a locking portion protruding outward in the radial direction,
The metal shell includes a shelf portion that locks the locking portion from the tip end side through a metal packing on the inner peripheral surface of itself.
The spark plug according to claim 1, wherein the resistor is present at least at a position of the packing in the axial direction.

One end is connected to the metal shell, and the other end is provided with a ground electrode that forms a discharge gap with a portion of the tip that overlaps the conductor in the axial direction,
The spark plug according to any one of claims 1 to 3, wherein the tip of the resistor is located on the rear end side of the other end of the ground electrode.

The spark plug according to claim 1, wherein a front end of the resistor is located on a rear end side of the front end of the metal shell.

A first conductor filled in the inside of the insulator on the tip side of the tip of the resistor;
The spark plug according to claim 1, wherein the first conductor is electrically connected to the conductor.

A conductive layer formed on at least a part of the inner surface of the tip portion,
The conductive layer is electrically connected to the conductor,
The spark plug according to any one of claims 1 to 4, wherein a part of the resistor is filled inside the tip portion.

The spark plug according to claim 7, further comprising a second conductor that is filled in at least a portion of the tip portion where the conductive layer is formed and that is connected to the conductor.