JP4721237B2 - Plasma jet ignition plug and method for manufacturing the same - Google Patents

Plasma jet ignition plug and method for manufacturing the same Download PDF

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JP4721237B2
JP4721237B2 JP2008088295A JP2008088295A JP4721237B2 JP 4721237 B2 JP4721237 B2 JP 4721237B2 JP 2008088295 A JP2008088295 A JP 2008088295A JP 2008088295 A JP2008088295 A JP 2008088295A JP 4721237 B2 JP4721237 B2 JP 4721237B2
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tip
insulator
electrode
noble metal
base material
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JP2008277284A (en
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通 中村
友聡 加藤
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NGK Spark Plug Co Ltd
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NGK Spark Plug Co Ltd
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    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01TSPARK GAPS; OVERVOLTAGE ARRESTERS USING SPARK GAPS; SPARKING PLUGS; CORONA DEVICES; GENERATING IONS TO BE INTRODUCED INTO NON-ENCLOSED GASES
    • H01T13/00Sparking plugs
    • H01T13/50Sparking plugs having means for ionisation of gap
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01TSPARK GAPS; OVERVOLTAGE ARRESTERS USING SPARK GAPS; SPARKING PLUGS; CORONA DEVICES; GENERATING IONS TO BE INTRODUCED INTO NON-ENCLOSED GASES
    • H01T13/00Sparking plugs
    • H01T13/54Sparking plugs having electrodes arranged in a partly-enclosed ignition chamber
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01TSPARK GAPS; OVERVOLTAGE ARRESTERS USING SPARK GAPS; SPARKING PLUGS; CORONA DEVICES; GENERATING IONS TO BE INTRODUCED INTO NON-ENCLOSED GASES
    • H01T21/00Apparatus or processes specially adapted for the manufacture or maintenance of spark gaps or sparking plugs
    • H01T21/02Apparatus or processes specially adapted for the manufacture or maintenance of spark gaps or sparking plugs of sparking plugs

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  • Manufacturing & Machinery (AREA)
  • Spark Plugs (AREA)

Description

本発明は、プラズマを形成して混合気への点火を行う内燃機関用のプラズマジェット点火プラグおよびその製造方法に関するものである。   The present invention relates to a plasma jet ignition plug for an internal combustion engine that forms plasma and ignites an air-fuel mixture, and a method for manufacturing the same.

従来、例えば自動車用の内燃機関であるエンジンの点火プラグには、火花放電により混合気への着火を行うスパークプラグが使用されている。近年、内燃機関の高出力化や低燃費化が求められており、燃焼の広がりが速く、着火限界空燃比のより高い希薄混合気に対しても確実に着火できる着火性の高い点火プラグとして、プラズマジェット点火プラグが知られている。   2. Description of the Related Art Conventionally, spark plugs that ignite an air-fuel mixture by spark discharge are used as ignition plugs of engines that are internal combustion engines for automobiles, for example. In recent years, there has been a demand for higher output and lower fuel consumption of internal combustion engines, as a spark plug with high ignitability that can be ignited reliably even for a lean mixture with a fast combustion spread and a higher ignition limit air-fuel ratio, Plasma jet spark plugs are known.

このようなプラズマジェット点火プラグは、中心電極と、主体金具と一体になった接地電極との間の火花放電間隙の周囲をセラミックス等からなる絶縁碍子で包囲して、キャビティと称する小さな容積の放電空間を形成した構造を有している。そして、火花放電間隙に高電圧を印加して火花放電を行い、このときに生じた絶縁破壊によって比較的低電圧で電流を流すことができるようになるため、さらにエネルギーを供給することで放電状態を遷移させて、キャビティ内でプラズマを生じさせる。キャビティが形成された絶縁碍子よりも先端側には接地電極が配置されるため接地電極にはオリフィスと呼ばれる孔が設けられており、そしてこのオリフィスを介し、プラズマが外方へ噴出されて、混合気への着火が行われる。   Such a plasma jet ignition plug has a small volume discharge called a cavity in which a spark discharge gap between a center electrode and a ground electrode integrated with a metal shell is surrounded by an insulator made of ceramics or the like. It has a structure that forms a space. The spark discharge is performed by applying a high voltage to the spark discharge gap, and the current can flow at a relatively low voltage due to the dielectric breakdown that occurs at this time. To generate a plasma in the cavity. Since a ground electrode is arranged on the tip side of the insulator in which the cavity is formed, a hole called an orifice is provided in the ground electrode, and plasma is ejected to the outside through this orifice and mixed. Qi is ignited.

ところで、プラズマがオリフィスから噴出される過程において、接地電極と絶縁碍子との間に間隙を有するとその間隙内にプラズマの持つエネルギーが漏出してしまい、オリフィスから噴出されるプラズマのエネルギー量が減少して着火性の低下を招く虞がある。そこで、絶縁碍子が接地電極に対し密着した状態で設けられ、絶縁碍子と接地電極との間に間隙のないプラズマジェット点火プラグが提案されている(例えば、特許文献1参照)。
また、本出願人は接地電極の連通孔の内壁に貴金属部材を溶接することで、接地電極の耐火花消耗性を高めることができるということを見出している。
特開2006−294257号公報
By the way, in the process in which plasma is ejected from the orifice, if there is a gap between the ground electrode and the insulator, the energy of the plasma leaks into the gap, and the amount of plasma energy ejected from the orifice decreases. As a result, the ignitability may be reduced. Therefore, a plasma jet ignition plug has been proposed in which an insulator is provided in close contact with a ground electrode and there is no gap between the insulator and the ground electrode (see, for example, Patent Document 1).
Further, the present applicant has found that the spark wear resistance of the ground electrode can be improved by welding a noble metal member to the inner wall of the communication hole of the ground electrode.
JP 2006-294257 A

しかしながら、貴金属部材を接地電極に溶接した際に形成される溶融部が、接地電極の燃焼室側の面にない場合、熱膨張率の違いから貴金属部材および電極母材と溶融部との境界部に熱サイクルによる熱応力が作用し、境界部から発生するクラックが進展しやすくなるというおそれがあった。   However, if the melted portion formed when the noble metal member is welded to the ground electrode is not on the surface of the ground electrode on the combustion chamber side, the boundary between the noble metal member and the electrode base material and the melted portion due to the difference in thermal expansion coefficient There is a risk that the thermal stress due to the thermal cycle acts on the cracks, and cracks generated from the boundary portion are likely to progress.

本発明は、上記課題を解決するためになされたものであり、接地電極の電極母材と貴金属部材との溶融部の配置を規定することで、接地電極の耐久性を向上することができるプラズマジェット点火プラグおよびプラズマジェット点火プラグの製造方法を提供することを目的とする。   The present invention has been made to solve the above-described problem, and plasma that can improve the durability of the ground electrode by defining the arrangement of the melted portion of the electrode base material and the noble metal member of the ground electrode. It is an object of the present invention to provide a method for manufacturing a jet spark plug and a plasma jet spark plug.

上記目的を達成するために、請求項1に係る発明のプラズマジェット点火プラグは、中心電極と、軸線方向に延びる軸孔を有し、前記中心電極の先端を前記軸孔内に収容すると共に、前記中心電極を保持する絶縁碍子と、当該絶縁碍子の先端部において、前記軸孔の内周面と前記中心電極の先端面とを壁面とする凹部状に形成されたキャビティと、前記絶縁碍子の径方向周囲を取り囲んで保持する主体金具と、前記絶縁碍子の前記先端部よりも前記軸線方向先端側で前記主体金具に接合され、外気と前記キャビティの内部とを連通する連通部を有する接地電極とを備えたプラズマジェット点火プラグであって、前記接地電極は、前記連通部を有する電極母材に、前記連通部の一部をなす貴金属部材がレーザ溶接により接合された複合部材からなり、自身の外縁部に前記主体金具との接合部を有し、自身の前記軸線方向先端側に前記電極母材と前記貴金属部材との溶融部を有することを特徴とする。   In order to achieve the above object, a plasma jet ignition plug according to claim 1 has a center electrode and an axial hole extending in the axial direction, and the tip of the central electrode is accommodated in the axial hole. An insulator that holds the center electrode, a cavity formed in a concave shape with the inner peripheral surface of the shaft hole and the tip surface of the center electrode at the front end of the insulator, and the insulator A grounding electrode having a metal shell that surrounds and holds the periphery in the radial direction, and a communication portion that is joined to the metal shell on the front end side in the axial direction with respect to the front end portion of the insulator and that communicates the outside air with the inside of the cavity. The ground electrode is made of a composite member in which a noble metal member forming a part of the communication portion is joined to the electrode base material having the communication portion by laser welding. Ri has a joint between the metal shell to the outer edge of itself, and having a melting portion of the electrode base material and the noble metal member in the axial direction distal end side of itself.

また、請求項2に係る発明のプラズマジェット点火プラグは、請求項1に記載の発明の構成に加え、前記接地電極は、前記貴金属部材を前記絶縁碍子の前記先端部に接触させた状態で、前記外縁部が前記主体金具に接合されていることを特徴とする。   Further, in the plasma jet ignition plug of the invention according to claim 2, in addition to the configuration of the invention of claim 1, the ground electrode is in a state where the noble metal member is in contact with the tip of the insulator, The outer edge is joined to the metallic shell.

また、請求項3に係る発明のプラズマジェット点火プラグは、請求項1または2に記載の発明の構成に加え、前記接地電極の前記電極母材は、前記軸線方向と直交する径方向において最も内側に位置する部位である内突部を有すると共に、前記接地電極の前記貴金属部材は、前記内突部よりも前記径方向の外側に位置する外突部を有し、前記外突部は、前記軸線方向において前記内突部と重ねられつつ、その内突部よりも前記軸線方向後端側に配置されていることを特徴とする。   According to a third aspect of the present invention, in the plasma jet ignition plug according to the first or second aspect, in addition to the configuration of the first or second aspect, the electrode base material of the ground electrode is the innermost in the radial direction perpendicular to the axial direction. The noble metal member of the ground electrode has an outer protrusion located on the outer side in the radial direction than the inner protrusion, and the outer protrusion is While being overlapped with the inner protrusion in the axial direction, it is arranged on the rear end side in the axial direction from the inner protrusion.

また、請求項4に係る発明のプラズマジェット点火プラグの製造方法は、中心電極と、軸線方向に延びる軸孔を有し、前記中心電極の先端を前記軸孔内に収容すると共に、前記中心電極を保持する絶縁碍子と、当該絶縁碍子の先端部において、前記軸孔の内周面と前記中心電極の先端面とを壁面とする凹部状に形成されたキャビティと、前記絶縁碍子の径方向周囲を取り囲んで保持する主体金具と、前記絶縁碍子の前記先端部よりも前記軸線方向先端側で前記主体金具に接合され、外気と前記キャビティの内部とを連通する連通部を有する接地電極とを備えたプラズマジェット点火プラグの製造方法であって、前記中心電極を保持した前記絶縁碍子を前記主体金具に保持させる碍子保持工程と、前記接地電極を前記絶縁碍子の前記先端部よりも前記軸線方向先端側に配置する配置工程と、前記接地電極の外縁部を前記主体金具に接合する接地電極接合工程と、前記軸線方向先端側からレーザを照射して、前記連通部を有する接地電極の電極母材と、前記連通部の一部をなす貴金属部材とをレーザ溶接する貴金属部材接合工程と、を有することを特徴とする。   According to a fourth aspect of the present invention, there is provided a plasma jet ignition plug manufacturing method comprising a center electrode and an axial hole extending in an axial direction, the tip of the central electrode being accommodated in the axial hole, and the central electrode An insulator that holds the inner periphery of the insulator, a cavity formed in a concave shape with the inner peripheral surface of the shaft hole and the front end surface of the center electrode at the front end portion of the insulator, and a radial periphery of the insulator And a grounding electrode having a communication part that is joined to the metal shell on the tip end side in the axial direction with respect to the tip end portion of the insulator and communicates the outside air with the inside of the cavity. A method of manufacturing a plasma jet ignition plug, wherein an insulator holding step of holding the insulator holding the center electrode on the metal shell, and the ground electrode from the tip of the insulator An arrangement step of disposing at the tip end side in the axial direction, a ground electrode joining step of joining an outer edge portion of the ground electrode to the metal shell, and a ground electrode having the communication portion by irradiating a laser from the tip end side in the axial direction A noble metal member joining step of laser welding the electrode base material and the noble metal member forming a part of the communication portion.

請求項1に係る発明のように、接地電極の電極母材の連通部に貴金属部材がレーザ溶接により接合され、接地電極の電極母材と貴金属部材との溶融部を接地電極の軸線方向先端側に有することで、プラズマの持つ高いエネルギーによる接地電極の消耗を低減することができ、かつ、接地電極の電極母材および貴金属部材と溶融部との境界部から発生するクラックの進展を防ぐことができる。   As in the invention according to claim 1, the noble metal member is joined to the communicating portion of the electrode base material of the ground electrode by laser welding, and the molten portion of the electrode base material of the ground electrode and the noble metal member is connected to the tip end side in the axial direction of the ground electrode. It is possible to reduce the consumption of the ground electrode due to the high energy of the plasma, and to prevent the progress of cracks generated from the electrode base material of the ground electrode and the boundary between the noble metal member and the melted portion. it can.

また、請求項2に係る発明のように、貴金属部材を絶縁碍子の先端部に接触させつつ接地電極の主体金具への接合を行えば、接地電極と絶縁碍子の先端部との間隙を貴金属部材で塞ぐことができ、キャビティから噴出されるプラズマのエネルギーの漏出を防止することができる。   Further, as in the invention according to claim 2, if the ground electrode is joined to the metal shell while the noble metal member is in contact with the tip portion of the insulator, the gap between the ground electrode and the tip portion of the insulator is set to the noble metal member. And the leakage of the energy of the plasma ejected from the cavity can be prevented.

更に、請求項3に係る発明のように、接地電極を構成する電極母材の内突部よりも貴金属部材の外突部を軸線方向後端側に配置させれば、貴金属部材の外突部を、絶縁碍子の先端部と電極母材の内突部との間に挟む構成とすることができる。つまり、電極母材によって貴金属部材の抜け落ちを防止することができる。   Further, as in the invention according to claim 3, if the outer protrusion of the noble metal member is arranged on the rear end side in the axial direction with respect to the inner protrusion of the electrode base material constituting the ground electrode, the outer protrusion of the noble metal member Can be sandwiched between the tip of the insulator and the inner protrusion of the electrode base material. That is, the electrode base material can prevent the noble metal member from falling off.

また、請求項4に係る発明のプラズマジェット点火プラグの製造方法では、軸線方向先端側からレーザを照射して、連通部を有する接地電極の電極母材と、連通部の一部をなす貴金属部材とをレーザ溶接するので、軸線方向先端側に電極母材と貴金属部材との溶融部を容易に形成することができる。   Further, in the method of manufacturing a plasma jet ignition plug according to the fourth aspect of the present invention, an electrode base material of a ground electrode having a communication portion by irradiating a laser from the axial front end side, and a noble metal member forming a part of the communication portion Are welded to each other, so that a melted portion of the electrode base material and the noble metal member can be easily formed on the tip end side in the axial direction.

[第1の実施の形態]
以下、本発明を具体化したプラズマジェット点火プラグの第1の実施の形態について、図面を参照して説明する。まず、図1,図2を参照して、一例としてのプラズマジェット点火プラグ100の構造について説明する。図1は、第1の実施の形態のプラズマジェット点火プラグ100の部分断面図である。図2は、第1の実施の形態のプラズマジェット点火プラグ100の先端部分を拡大した断面図である。なお、図1において、プラズマジェット点火プラグ100の軸線O方向を図面における上下方向とし、下側をプラズマジェット点火プラグ100の先端側(前方)、上側を後端側(後方)として説明する。
[First Embodiment]
Hereinafter, a first embodiment of a plasma jet ignition plug embodying the present invention will be described with reference to the drawings. First, with reference to FIG. 1 and FIG. 2, the structure of the plasma jet ignition plug 100 as an example is demonstrated. FIG. 1 is a partial cross-sectional view of a plasma jet ignition plug 100 according to the first embodiment. FIG. 2 is an enlarged cross-sectional view of the tip portion of the plasma jet ignition plug 100 according to the first embodiment. In FIG. 1, the axis O direction of the plasma jet ignition plug 100 is the vertical direction in the drawing, the lower side is the front end side (front), and the upper side is the rear end side (rear).

図1に示す、第1の実施の形態のプラズマジェット点火プラグ100は、概略、絶縁碍子10と、この絶縁碍子10を保持する主体金具50と、絶縁碍子10内に軸線O方向に保持された中心電極20と、主体金具50の先端部65に溶接された接地電極30と、絶縁碍子10の後端部に設けられた端子金具40とから構成されている。   The plasma jet spark plug 100 according to the first embodiment shown in FIG. 1 is generally held in the insulator 10, a metal shell 50 that holds the insulator 10, and the insulator 10 in the direction of the axis O. The center electrode 20, the ground electrode 30 welded to the front end portion 65 of the metal shell 50, and the terminal metal fitting 40 provided at the rear end portion of the insulator 10 are configured.

絶縁碍子10は、周知のようにアルミナ等を焼成して形成され、軸線O方向に軸孔12を有する筒状の絶縁部材である。軸線O方向の略中央には外径が最も大きな鍔部19が形成されており、これより後端側には後端側胴部18が形成されている。後端側胴部18の後端側外周面には、主体金具50と端子金具40との間の沿面距離を稼ぐためのコルゲーションとよばれる凹凸状の加工がなされている。また、鍔部19より先端側には後端側胴部18より外径の小さな先端側胴部17と、その先端側胴部17よりも先端側で先端側胴部17よりもさらに外径の小さな脚長部13とが形成されている。この脚長部13と先端側胴部17との間は段状をなす段部14として構成されている。   The insulator 10 is a cylindrical insulating member that is formed by firing alumina or the like and has an axial hole 12 in the direction of the axis O as is well known. A flange portion 19 having the largest outer diameter is formed substantially at the center in the direction of the axis O, and a rear end side body portion 18 is formed on the rear end side. The rear end side outer peripheral surface of the rear end side body portion 18 is subjected to uneven processing called corrugation for increasing the creeping distance between the metallic shell 50 and the terminal fitting 40. Further, a distal end side body portion 17 having a smaller outer diameter than the rear end side body portion 18 on the front end side from the flange portion 19, and a further outer diameter than the front end side body portion 17 on the front end side of the front end side body portion 17. A small leg length 13 is formed. A step portion 14 having a step shape is formed between the leg length portion 13 and the front end side body portion 17.

軸孔12の脚長部13の内周部分は、先端側胴部17、鍔部19および後端側胴部18の内周部分よりも縮径された電極収容部15として形成されている。この電極収容部15の内部には中心電極20が保持される。図2に示すように、軸孔12は、電極収容部15の先端側において内周が更に縮径されており、先端小径部61として形成されている。この先端小径部61は、絶縁碍子10の先端部16にて開口している。また、絶縁碍子10の先端部16には、先端小径部61の開口の周囲を取り巻く環状のチップ係合部62が凹部形成されており、後述する貴金属チップ36の外突部37が係合されている。   The inner peripheral portion of the leg long portion 13 of the shaft hole 12 is formed as an electrode housing portion 15 having a diameter smaller than the inner peripheral portions of the front end side body portion 17, the flange portion 19 and the rear end side body portion 18. A center electrode 20 is held inside the electrode housing portion 15. As shown in FIG. 2, the shaft hole 12 is formed as a tip small-diameter portion 61 with the inner circumference further reduced in diameter on the tip side of the electrode housing portion 15. The tip small diameter portion 61 opens at the tip portion 16 of the insulator 10. In addition, an annular tip engaging portion 62 surrounding the periphery of the opening of the tip small-diameter portion 61 is formed in the tip portion 16 of the insulator 10 as a recess, and an outer protrusion 37 of a noble metal tip 36 described later is engaged. ing.

次に、中心電極20は、インコネル(商標名)600または601等のニッケル系合金等で形成された円柱状の電極棒で、内部に熱伝導性に優れる銅等からなる金属芯23を有している。中心電極20の先端部21には、貴金属やW(タングステン)を主成分とする合金からなる円盤状の電極チップ25が、中心電極20と一体となるように溶接されている。なお、第1の実施の形態では、中心電極20と一体になった電極チップ25も含め「中心電極」と称する。   Next, the center electrode 20 is a cylindrical electrode rod formed of a nickel-based alloy such as Inconel (trade name) 600 or 601, and has a metal core 23 made of copper or the like having excellent thermal conductivity. ing. A disc-shaped electrode tip 25 made of an alloy containing precious metal or W (tungsten) as a main component is welded to the tip 21 of the center electrode 20 so as to be integrated with the center electrode 20. In the first embodiment, the electrode chip 25 integrated with the center electrode 20 is also referred to as “center electrode”.

また、図1に示すように、中心電極20の後端側は鍔状に拡径され、この鍔状の部分が軸孔12内において電極収容部15のうちの段状の部位に当接されており、電極収容部15内で中心電極20が位置決めされている。そして図2に示すように、中心電極20の先端部21の先端面26(より具体的には中心電極20の先端部21にて中心電極20と一体に接合された電極チップ25の先端面26)の周縁が、径の異なる電極収容部15と先端小径部61との間の段部に当接された状態となっている。この構成により、軸孔12の先端小径部61の内周面と、中心電極20の先端面26とで包囲された有底円筒状をなす容積の小さな放電空間が形成されている。プラズマジェット点火プラグ100では、接地電極30と中心電極20との間にて形成される火花放電間隙にて火花放電が行われるが、その火花放電の経路はこの放電空間内を通過することとなる。この放電空間はキャビティ60と称され、火花放電の際にはこのキャビティ60でプラズマが形成され、先端部16の開口より前方へ噴出される。なお、キャビティ60は、先端小径部61よりも後端側の先端小径部61の内径よりも拡径した電極収容部15の一部を含むように構成してもよい。   Further, as shown in FIG. 1, the rear end side of the center electrode 20 is enlarged in a bowl shape, and this bowl-shaped portion is brought into contact with a stepped portion of the electrode housing portion 15 in the shaft hole 12. The center electrode 20 is positioned in the electrode housing portion 15. As shown in FIG. 2, the distal end surface 26 of the distal end portion 21 of the center electrode 20 (more specifically, the distal end surface 26 of the electrode tip 25 joined integrally with the central electrode 20 at the distal end portion 21 of the central electrode 20). ) Is in contact with a step portion between the electrode housing portion 15 and the tip small-diameter portion 61 having different diameters. With this configuration, a small discharge space having a bottomed cylindrical shape surrounded by the inner peripheral surface of the tip small diameter portion 61 of the shaft hole 12 and the tip surface 26 of the center electrode 20 is formed. In the plasma jet spark plug 100, spark discharge is performed in the spark discharge gap formed between the ground electrode 30 and the center electrode 20, and the path of the spark discharge passes through this discharge space. . This discharge space is referred to as a cavity 60, and during spark discharge, plasma is formed in the cavity 60 and is ejected forward from the opening of the tip end portion 16. The cavity 60 may be configured to include a part of the electrode housing portion 15 whose diameter is larger than the inner diameter of the tip small diameter portion 61 on the rear end side with respect to the tip small diameter portion 61.

また図1に示すように、中心電極20は、軸孔12の内部に設けられた金属とガラスの混合物からなる導電性のシール体4を経由して、先端側胴部17内で端子金具40と電気的に接続されている。中心電極20と端子金具40は、このシール体4によって軸孔12内で導通されつつ軸孔12内に固定される。端子金具40は軸孔12内を後方へ延び、後端部41が絶縁碍子10の後端より外部に突出されている。この後端部41には、プラグキャップ(図示外)を介して高圧ケーブル(図示外)が接続され、点火装置(図示外)から高電圧が印加されるようになっている。   Further, as shown in FIG. 1, the center electrode 20 is connected to the terminal fitting 40 in the distal end side body portion 17 via the conductive seal body 4 made of a mixture of metal and glass provided in the shaft hole 12. And are electrically connected. The center electrode 20 and the terminal fitting 40 are fixed in the shaft hole 12 while being conducted in the shaft hole 12 by the seal body 4. The terminal fitting 40 extends rearward in the shaft hole 12, and the rear end portion 41 projects outward from the rear end of the insulator 10. A high voltage cable (not shown) is connected to the rear end portion 41 via a plug cap (not shown), and a high voltage is applied from an ignition device (not shown).

次に、主体金具50について説明する。主体金具50は、内燃機関のエンジンヘッド(図示外)にプラズマジェット点火プラグ100を固定するための筒状の金具であり、絶縁碍子10の脚長部13から後端側胴部18の先端側にかけての部位の周囲を取り囲むようにして、自身の筒孔59内に絶縁碍子10を保持している。主体金具50は低炭素鋼材より形成されており、略中央から先端側にかけて取付部52が形成されている。取付部52の外周面には雄ねじ状のねじ山が形成されており、エンジンヘッドの取付孔(図示外)に形成された雌ねじに螺合する。なお、主体金具50は耐熱性を重視し、ステンレスやインコネル(商標名)等を用いてもよい。   Next, the metal shell 50 will be described. The metal shell 50 is a cylindrical metal fitting for fixing the plasma jet ignition plug 100 to the engine head (not shown) of the internal combustion engine, and extends from the leg long part 13 of the insulator 10 to the front end side of the rear end side body part 18. The insulator 10 is held in its own cylindrical hole 59 so as to surround the periphery of this part. The metal shell 50 is made of a low carbon steel material, and a mounting portion 52 is formed from approximately the center to the tip side. A male screw thread is formed on the outer peripheral surface of the mounting portion 52, and is screwed into a female screw formed in a mounting hole (not shown) of the engine head. The metal shell 50 places importance on heat resistance and may use stainless steel, Inconel (trade name), or the like.

また、取付部52の後端側には鍔状のシール部54が形成されている。そしてシール部54と取付部52との間の部位には、板体を折り曲げて形成した環状のガスケット5が嵌挿されている。ガスケット5は、プラズマジェット点火プラグ100をエンジンヘッドの取付孔(図示外)に取り付けた際に、シール部54の先端向きの面である座面55と、取付孔の開口の周縁部位との間に挟まれ変形し、両者間を封止することで、取付孔を介した燃焼ガスの流出を防止するものである。   A hook-shaped seal portion 54 is formed on the rear end side of the attachment portion 52. An annular gasket 5 formed by bending a plate is inserted into a portion between the seal portion 54 and the attachment portion 52. When the plasma jet ignition plug 100 is attached to the engine head mounting hole (not shown), the gasket 5 is formed between the seat surface 55 which is the surface facing the tip of the seal portion 54 and the peripheral portion of the opening of the mounting hole. By being sandwiched and deformed and sealed between the two, the outflow of combustion gas through the mounting hole is prevented.

シール部54の後端側には、図示外のプラグレンチが嵌合する工具係合部51が形成されている。工具係合部51より後端側には薄肉の加締部53が設けられており、工具係合部51とシール部54との間にも薄肉の座屈部58が設けられている。そして、工具係合部51から加締部53にかけての内周面と絶縁碍子10の後端側胴部18の外周面との間には円環状のリング部材6,7が介在されており、更に両リング部材6,7間にタルク(滑石)9の粉末が充填されている。   A tool engaging portion 51 into which a plug wrench (not shown) is fitted is formed on the rear end side of the seal portion 54. A thin caulking portion 53 is provided on the rear end side from the tool engagement portion 51, and a thin buckling portion 58 is also provided between the tool engagement portion 51 and the seal portion 54. And annular ring members 6, 7 are interposed between the inner peripheral surface from the tool engaging portion 51 to the caulking portion 53 and the outer peripheral surface of the rear end side body portion 18 of the insulator 10, Further, a powder of talc (talc) 9 is filled between the ring members 6 and 7.

また図2に示すように、取付部52の内周面には段状の段部56が形成されており、この段部56に環状のパッキン80を介して絶縁碍子10の段部14が支持されている。そして図1に示すように、加締部53の端部を内側に折り曲げるようにして加締めることにより、リング部材6,7およびタルク9を介し、絶縁碍子10が先端側に向け押圧される。この加締めの際に座屈部58は加熱され、圧縮力の付加に伴い膨らむように変形されることで、加締部53の圧縮ストロークを稼ぐ。これにより、主体金具50の加締部53と段部56との間に、絶縁碍子10の段部14と鍔部19との間の部位が挟まれ、主体金具50に絶縁碍子10が一体に保持される。そしてパッキン80により主体金具50と絶縁碍子10との間の気密性は保持され、筒孔59を介した燃焼ガスの流出が防止される。   As shown in FIG. 2, a stepped step portion 56 is formed on the inner peripheral surface of the mounting portion 52, and the step portion 14 of the insulator 10 is supported on the step portion 56 via an annular packing 80. Has been. As shown in FIG. 1, the insulator 10 is pressed toward the distal end side via the ring members 6, 7 and the talc 9 by crimping the end of the crimping portion 53 inwardly. The buckling portion 58 is heated during the caulking, and is deformed so as to swell with the addition of the compressive force, thereby earning a compression stroke of the caulking portion 53. As a result, a portion between the stepped portion 14 and the flange portion 19 of the insulator 10 is sandwiched between the crimped portion 53 and the stepped portion 56 of the metal shell 50, and the insulator 10 is integrated with the metal shell 50. Retained. And the gas tightness between the metal shell 50 and the insulator 10 is maintained by the packing 80, and the outflow of combustion gas through the cylindrical hole 59 is prevented.

次に、主体金具50の先端部65には接地電極30が配設されている。図2に示す、接地電極30は、ニッケル系合金からなる電極母材33と貴金属からなる貴金属チップ36とが一体に接合された電極であり、中央に開口(連通部31)が形成された円盤状をなしている。接地電極30の外縁部35(すなわち電極母材33の外縁部35)は、主体金具50の先端部65の内周面を段状に形成した係合段部57に係合され、その状態で両者の合わせ面がレーザ溶接されており、接地電極30と主体金具50とが一体に接合されている。接地電極30の連通部31は、絶縁碍子10よりも先端側に配置される接地電極30を介し、キャビティ60内を外気と連通するために開口されたものであり、開口の内周側に貴金属チップ36が接合され、連通部31の一部を構成している。なお、ここでいう「外縁部」とは、接地電極30が主体金具50と接合される部位を指し、第1の実施の形態では接地電極30は円盤状をなすため、径方向の外周側の縁部分が「外縁部」相当する。もっとも、接地電極30が円盤状でない場合でも、径方向でみたときに外側の縁部分が主体金具50との接合部位となるものである。   Next, the ground electrode 30 is disposed at the distal end portion 65 of the metal shell 50. The ground electrode 30 shown in FIG. 2 is an electrode in which an electrode base material 33 made of a nickel-based alloy and a noble metal tip 36 made of a noble metal are integrally joined, and a disk having an opening (communication portion 31) formed in the center. It has a shape. The outer edge portion 35 of the ground electrode 30 (that is, the outer edge portion 35 of the electrode base material 33) is engaged with an engagement step portion 57 in which the inner peripheral surface of the distal end portion 65 of the metal shell 50 is formed in a step shape. The mating surfaces of the two are laser welded, and the ground electrode 30 and the metal shell 50 are joined together. The communicating portion 31 of the ground electrode 30 is opened to communicate with the outside air through the ground electrode 30 disposed on the tip side of the insulator 10, and a noble metal is provided on the inner peripheral side of the opening. The chip 36 is joined and constitutes a part of the communication portion 31. Here, the “outer edge portion” refers to a portion where the ground electrode 30 is joined to the metal shell 50, and in the first embodiment, the ground electrode 30 has a disk shape, so The edge portion corresponds to the “outer edge portion”. However, even when the ground electrode 30 is not in the shape of a disk, the outer edge portion becomes a joint portion with the metal shell 50 when viewed in the radial direction.

第1の実施の形態の貴金属チップ36は筒状をなしており、軸線O方向の後端側に、外周面を径方向外側に向けて鍔状に突出させた外突部37が形成されている。そして電極母材33にも同様に、開口の内周面を径方向内側に向けて突出させた内突部34が、軸線O方向の先端側に設けられている。そして、電極母材33の内突部34は、軸線O方向に貴金属チップ36の外突部37と重なる配置となっており、貴金属チップ36が軸線O方向前方へ抜けてしまうのを防止する抜け止めとして機能している。また、絶縁碍子10の先端部16には、貴金属チップ36の外突部37が係合するように先端面を凹部形成したチップ係合部62が設けられている。チップ係合部62は、貴金属チップ36の外突部37の形状にあわせ、キャビティ60の内周面を構成する絶縁碍子10の軸孔12の先端小径部61が絶縁碍子10の先端部16にて開口したその開口の周囲を取り巻く環状に形成されている。貴金属チップ36は、このチップ係合部62に係合しつつ接地電極30と絶縁碍子10の先端部16との間の間隙を塞いでおり、この状態で接地電極30の連通部31を構成し、キャビティ60の内部と外気とを連通している。この構成により、キャビティ60内で形成されたプラズマが外方に噴出される際に、プラズマのエネルギーが接地電極30と絶縁碍子10の先端部16との間の間隙に漏出してしまうことが防止されている。なお、貴金属チップ36が、本発明における「貴金属部材」に相当する。   The noble metal tip 36 of the first embodiment has a cylindrical shape, and an outer protrusion 37 is formed on the rear end side in the axis O direction so that the outer peripheral surface protrudes in a bowl shape with the outer side in the radial direction. Yes. Similarly, the electrode base material 33 is provided with an inner protrusion 34 that protrudes the inner peripheral surface of the opening inward in the radial direction on the distal end side in the axis O direction. The inner protrusion 34 of the electrode base material 33 is disposed so as to overlap the outer protrusion 37 of the noble metal tip 36 in the axis O direction, and prevents the noble metal tip 36 from slipping forward in the axis O direction. It functions as a stop. Further, a tip engaging portion 62 having a tip formed as a recess is provided at the tip 16 of the insulator 10 so that the outer protrusion 37 of the noble metal tip 36 is engaged. In the tip engaging portion 62, the tip small-diameter portion 61 of the shaft hole 12 of the insulator 10 constituting the inner peripheral surface of the cavity 60 corresponds to the shape of the outer protrusion 37 of the noble metal tip 36. It is formed in an annular shape surrounding the periphery of the opening. The noble metal tip 36 closes the gap between the ground electrode 30 and the distal end portion 16 of the insulator 10 while engaging with the tip engaging portion 62, and forms the communication portion 31 of the ground electrode 30 in this state. The interior of the cavity 60 communicates with the outside air. With this configuration, when the plasma formed in the cavity 60 is ejected outward, the plasma energy is prevented from leaking into the gap between the ground electrode 30 and the tip 16 of the insulator 10. Has been. The noble metal tip 36 corresponds to the “noble metal member” in the present invention.

このような構成の第1の実施の形態のプラズマジェット点火プラグ100を製造する過程では、上記のように、プラズマ噴出時のエネルギーの漏出を防止できるように接地電極30と絶縁碍子10の先端部16との間の間隙を塞ぐため、主体金具50に接地電極30を接合する前に絶縁碍子10を保持させている。以下、プラズマジェット点火プラグ100の製造方法について、図3を参照して説明する。図3は、第1の実施の形態のプラズマジェット点火プラグ100の製造過程の一部を示す図である。   In the process of manufacturing the plasma jet ignition plug 100 of the first embodiment having such a configuration, as described above, the tips of the ground electrode 30 and the insulator 10 are provided so as to prevent leakage of energy during plasma ejection. In order to close the gap between the insulator 16, the insulator 10 is held before the ground electrode 30 is joined to the metal shell 50. Hereinafter, a method for manufacturing the plasma jet ignition plug 100 will be described with reference to FIG. FIG. 3 is a diagram illustrating a part of the manufacturing process of the plasma jet ignition plug 100 according to the first embodiment.

プラズマジェット点火プラグ100の製造過程において、予め別の工程において作製された主体金具50の筒孔59内に、同様に別の工程において作製した中心電極20(電極チップ25が接合されている)および端子金具40を一体に組み付けた絶縁碍子10が挿入される。そして主体金具50の筒孔59の段部56上にパッキン80を介して絶縁碍子10の段部14が支持される。この状態で主体金具50の加締部53(図1参照)が加締められ、段部56との間に絶縁碍子10の段部14と鍔部19との間の部位を挟むことで、主体金具50に絶縁碍子10が一体に保持される(碍子保持工程)。   In the manufacturing process of the plasma jet ignition plug 100, the center electrode 20 (electrode tip 25 is joined) produced in the same process in the cylindrical hole 59 of the metal shell 50 produced in another process in advance. The insulator 10 in which the terminal fitting 40 is integrally assembled is inserted. The step portion 14 of the insulator 10 is supported on the step portion 56 of the cylindrical hole 59 of the metal shell 50 via the packing 80. In this state, the caulking portion 53 (see FIG. 1) of the metal shell 50 is caulked, and the portion between the step portion 14 and the flange portion 19 of the insulator 10 is sandwiched between the main portion 50 and the main portion 50, thereby The insulator 10 is integrally held by the metal fitting 50 (insulator holding step).

次に、外突部37を有する筒状に形成された貴金属チップ36が、外突部37側を絶縁碍子10側に向けつつ、絶縁碍子10の先端部16よりも軸線O方向先端側に配置される(配置工程における貴金属部材配置工程)。このとき、貴金属チップ36は、外突部37が絶縁碍子10の先端部16のチップ係合部62と向き合う位置に配置される。更に、内突部34が形成された開口を有する円盤状の電極母材33が、内突部34側を軸線O方向前方へ向け、内突部34と貴金属チップ36の外突部37とが軸線O方向に重なるように並べつつ、絶縁碍子10の先端部16より先端側に配置される(配置工程における電極母材配置工程)。そして、電極母材33の外縁部35を、段状をなす主体金具50の係合段部57に嵌め込むように係合させる。このとき、電極母材33は、絶縁碍子10の先端部16と接触した状態となってもよいし、非接触の状態に維持されてもよい。貴金属チップ36は電極母材33の開口とともに連通部31を構成し、外突部37が電極母材33の内突部34と絶縁碍子10のチップ係合部62との間に介在され、配置位置が規制される。   Next, the noble metal tip 36 formed in a cylindrical shape having the outer protrusion 37 is disposed closer to the distal end side in the axis O direction than the distal end portion 16 of the insulator 10 with the outer protrusion 37 side facing the insulator 10 side. (Noble metal member arranging step in the arranging step). At this time, the noble metal tip 36 is disposed at a position where the outer protrusion 37 faces the tip engaging portion 62 of the tip portion 16 of the insulator 10. Further, the disk-shaped electrode base material 33 having an opening in which the inner protrusion 34 is formed has the inner protrusion 34 and the outer protrusion 37 of the noble metal tip 36 with the inner protrusion 34 side facing forward in the axis O direction. It arrange | positions so that it may overlap with the axis line O direction, and it arrange | positions from the front-end | tip part 16 of the insulator 10 at the front end side (electrode base material arrangement | positioning process in an arrangement | positioning process). Then, the outer edge portion 35 of the electrode base material 33 is engaged so as to be fitted into the engagement step portion 57 of the metal shell 50 having a step shape. At this time, the electrode base material 33 may be in contact with the distal end portion 16 of the insulator 10 or may be maintained in a non-contact state. The noble metal tip 36 constitutes the communication portion 31 together with the opening of the electrode base material 33, and the outer protrusion 37 is interposed between the inner protrusion 34 of the electrode base material 33 and the tip engaging portion 62 of the insulator 10. The position is restricted.

そして電極母材33の外縁部35と、主体金具50の係合段部57との合わせ面を狙ってレーザ光が照射され、周方向に一周して、主体金具50と接地電極30の電極母材33との溶接が行われる(接地電極接合工程)。このとき、貴金属チップ36は非固定の状態となっている。次の工程において、貴金属チップ36は軸線O方向後端側へ向けて押さえられ、外突部37が絶縁碍子10のチップ係合部62に係合されて位置決めされる。これにより、貴金属チップ36の軸ずれが防止される。更に、貴金属チップ36が押さえられることにより、貴金属チップ36とチップ係合部62とが密接状態となり、接地電極30を構成する電極母材33と、絶縁碍子10の先端部16との間の間隙が、塞がれる。そして貴金属チップ36が押さえられたまま、貴金属チップ36と電極母材33との合わせ面を狙ってレーザ光が照射され、周方向に一周して両者の溶接が行われる(貴金属部材接合工程)。貴金属チップ36は電極母材33と一体となって、連通部31を構成する。   Then, laser light is irradiated aiming at the mating surface between the outer edge portion 35 of the electrode base material 33 and the engaging step portion 57 of the metal shell 50, and makes a round in the circumferential direction, and the electrode base metal of the metal shell 50 and the ground electrode 30. Welding with the material 33 is performed (ground electrode joining step). At this time, the noble metal tip 36 is in an unfixed state. In the next step, the noble metal tip 36 is pressed toward the rear end side in the axis O direction, and the outer protrusion 37 is engaged with the tip engaging portion 62 of the insulator 10 to be positioned. Thereby, the axial shift of the noble metal tip 36 is prevented. Further, when the noble metal tip 36 is pressed, the noble metal tip 36 and the tip engaging portion 62 are brought into close contact with each other, and a gap between the electrode base material 33 constituting the ground electrode 30 and the tip portion 16 of the insulator 10 is obtained. But it is blocked. Then, with the noble metal tip 36 being held down, laser light is irradiated aiming at the mating surface between the noble metal tip 36 and the electrode base material 33, and the two are welded around the circumference (noble metal member joining step). The noble metal tip 36 is integrated with the electrode base material 33 to form the communication portion 31.

このようにして、主体金具50の先端部65に接地電極30が接合されて、図1に示すプラズマジェット点火プラグ100が完成する。上記のように、主体金具50に接地電極30を接合する前に、絶縁碍子10を主体金具50に加締め保持させるため、加締めの際に絶縁碍子10の先端部16が当接するものがなく、絶縁碍子10の先端部16が外部から強い押圧力を受けることがない。また、主体金具50への加締めの際に絶縁碍子10の先端部16の位置が軸線O方向にずれを生じても、すなわち組み付け公差が大きくても、主体金具50への電極母材33の接合時に電極母材33の配置位置を任意に調整し、公差を吸収することができる。更に、接地電極30の電極母材33と絶縁碍子10の先端部16との間に生じ得る間隙は、連通部31を構成する貴金属チップ36を絶縁碍子10の先端部16に、接触させることによって塞ぐことができる。従って、プラズマのエネルギーが上記間隙に漏出することがなく、着火性の低下を防止することができる。また、貴金属チップ36は、外突部37が電極母材33の内突部34と軸線O方向に重なる位置にあるため、製造過程において電極母材33が配置されてから貴金属チップ36が接合されるまで、貴金属チップ36が抜け落ちることがない。そしてプラズマジェット点火プラグ100が長期間使用され、貴金属チップ36と電極母材33との間の接合状態に劣化を生じた場合でも、貴金属チップ36の脱落は防止される。更に、貴金属チップ36と電極母材33との合わせ面を狙ってレーザ光が照射され、周方向に一周して両者の溶接を行うことによって、貴金属チップ36と電極母材33の溶融部32を軸線O方向先端側へ形成することができる。従って、接地電極の電極母材および貴金属部材と溶融部32との境界部から発生するクラックの進展を防ぐことができる。   In this way, the ground electrode 30 is joined to the distal end portion 65 of the metal shell 50, and the plasma jet ignition plug 100 shown in FIG. 1 is completed. As described above, before the ground electrode 30 is joined to the metal shell 50, the insulator 10 is caulked and held on the metal shell 50, so that the tip 16 of the insulator 10 does not come into contact during caulking. The tip 16 of the insulator 10 does not receive a strong pressing force from the outside. Even if the position of the tip 16 of the insulator 10 is shifted in the direction of the axis O during caulking to the metal shell 50, that is, even if the assembly tolerance is large, the electrode base material 33 to the metal shell 50 is The arrangement position of the electrode base material 33 can be arbitrarily adjusted at the time of joining, and a tolerance can be absorbed. Further, a gap that can be generated between the electrode base material 33 of the ground electrode 30 and the tip portion 16 of the insulator 10 is obtained by bringing the noble metal tip 36 constituting the communication portion 31 into contact with the tip portion 16 of the insulator 10. Can be closed. Therefore, the plasma energy does not leak into the gap, and the ignitability can be prevented from being lowered. Further, since the noble metal tip 36 is located at the position where the outer protrusion 37 overlaps the inner protrusion 34 of the electrode base material 33 in the axis O direction, the noble metal tip 36 is joined after the electrode base material 33 is arranged in the manufacturing process. Until the noble metal tip 36 is not dropped. Even when the plasma jet ignition plug 100 is used for a long period of time and the joining state between the noble metal tip 36 and the electrode base material 33 is deteriorated, the noble metal tip 36 is prevented from falling off. Furthermore, laser light is irradiated aiming at the mating surface between the noble metal tip 36 and the electrode base material 33, and the welded portion 32 of the noble metal tip 36 and the electrode base material 33 is welded by making a round in the circumferential direction. It can be formed on the tip side in the direction of the axis O. Accordingly, it is possible to prevent the development of cracks generated from the boundary between the electrode base material of the ground electrode and the noble metal member and the molten portion 32.

なお、第1の実施の形態のプラズマジェット点火プラグ100は各種の変形が可能である。例えば図4に示すプラズマジェット点火プラグ101のように、絶縁碍子110の先端部116にチップ係合部を形成しなくともよい。貴金属チップ191を電極母材33に接合する際に軸線O方向後端側へ押さえ、絶縁碍子110の先端部116に接触させつつレーザ溶接を行えば十分に、接地電極171(電極母材33)と絶縁碍子110の先端部116との間の間隙を塞ぐことができる。   The plasma jet ignition plug 100 according to the first embodiment can be variously modified. For example, as in the plasma jet ignition plug 101 shown in FIG. 4, the tip engaging portion may not be formed at the tip portion 116 of the insulator 110. When the noble metal tip 191 is joined to the electrode base material 33, the ground electrode 171 (electrode base material 33) can be sufficiently pressed by holding the noble metal tip 191 to the rear end side in the direction of the axis O and contacting the tip 116 of the insulator 110. And the tip 116 of the insulator 110 can be closed.

更に、図5に示す、プラズマジェット点火プラグ102や、図6に示す、プラズマジェット点火プラグ103のように、貴金属チップ192,193の軸線方向の長さを長くしたり、短くしたりしてもよい。このようにすれば、貴金属チップ192,193と電極母材33との合わせ部分が段状になる。すると貴金属チップ192,193と電極母材33とのレーザ溶接時に、両者の合わせ面に対し、軸線Oと鋭角に交差する角度からレーザ光を照射しやすくなる。このようにすれば、貴金属チップ192,193と電極母材33との合わせ面の隙間にレーザ光か入り込むことが防止され、より確実な接合を行うことができる。   Further, as in the plasma jet ignition plug 102 shown in FIG. 5 and the plasma jet ignition plug 103 shown in FIG. 6, the axial lengths of the noble metal tips 192 and 193 may be increased or decreased. Good. If it does in this way, the joint part of the noble metal tip 192,193 and the electrode base material 33 will become step shape. Then, at the time of laser welding of the noble metal tips 192 and 193 and the electrode base material 33, it becomes easy to irradiate the laser beam from the angle intersecting the axis O with an acute angle with respect to the mating surfaces of the two. In this way, laser light can be prevented from entering the gap between the mating surfaces of the noble metal tips 192 and 193 and the electrode base material 33, and more reliable joining can be performed.

また、図7に示す、プラズマジェット点火プラグ104のように、貴金属チップ194の外突部131の形状を、軸線O方向の後端側へ向けて拡径するテーパ状としてもよい。この場合、電極母材184の開口に、外突部131と軸線O方向に重なるテーパ部132を設けることで、製造過程において電極母材184が配置されてから貴金属チップ194が接合されるまで、貴金属チップ194が抜け落ちることがない。そして第1の実施の形態と同様の工程で主体金具50への接地電極174の接合を行えば、絶縁碍子110の先端部116が外部から強い押圧力を受けないようにしながらも、その先端部116と接地電極174との間の間隙を、貴金属チップ194で塞ぐことができる。   Further, like the plasma jet ignition plug 104 shown in FIG. 7, the shape of the outer protrusion 131 of the noble metal tip 194 may be a tapered shape whose diameter increases toward the rear end side in the axis O direction. In this case, by providing a taper portion 132 that overlaps the outer protrusion 131 and the axis O direction in the opening of the electrode base material 184, until the noble metal tip 194 is joined after the electrode base material 184 is disposed in the manufacturing process. The noble metal tip 194 will not fall out. If the ground electrode 174 is joined to the metal shell 50 in the same process as that of the first embodiment, the tip portion 116 of the insulator 110 is not subjected to strong pressing force from the outside, but the tip portion The gap between 116 and the ground electrode 174 can be closed with the noble metal tip 194.

このようなテーパ状の外突部を有する貴金属チップを用いた場合でも同様に、図8に示す、プラズマジェット点火プラグ105や、図9に示す、プラズマジェット点火プラグ106のように、貴金属チップ195,196の軸線方向の長さを長くしたり、短くしたりしてもよい。すなわち、貴金属チップ195,196と電極母材184との合わせ部分が段状となれば、両者それぞれの溶接時にレーザ光を照射する合わせ面に対し、軸線Oと鋭角に交差する角度からレーザ光を照射しやすくでき、より確実な接合を行うことができる。   Similarly, when a noble metal tip having such a tapered outer protrusion is used, a noble metal tip 195 such as a plasma jet ignition plug 105 shown in FIG. 8 or a plasma jet ignition plug 106 shown in FIG. 9 is used. , 196 may be lengthened or shortened in the axial direction. In other words, if the joining portions of the noble metal tips 195 and 196 and the electrode base material 184 are stepped, the laser light is emitted from an angle that intersects the axis O at an acute angle with respect to the mating surface to which the laser light is irradiated during welding of each of them. Irradiation can be facilitated, and more reliable joining can be performed.

また、図10に示す、プラズマジェット点火プラグ107のように、貴金属チップ197に外突部を形成しなくとも、その外周が、電極母材33の内突部34よりも径方向外側に突出した状態にあれば、第1の実施の形態と同様に、貴金属チップ197の脱落を防止することができる。もちろん、第1の実施の形態と同様に、電極母材33を主体金具150に接合してから貴金属チップ197を軸線O方向後端側へ押さえながら、電極母材33と貴金属チップ197との接合を行えばよい。あるいは、接地電極接合工程において、電極母材33を軸線O方向後端側に押さえ、貴金属チップ197を絶縁碍子110の先端部116に接触させつつ、電極母材33の外縁部35を主体金具150の係合段部157に接合してもよい。このようにすれば、電極母材33の配置位置をより絶縁碍子110側に近づけることができるので、主体金具150の係合段部157と電極母材33の外縁部35との合わせ部分を段状にすることができ、上記同様、より確実な接合を行うことができる。そして第1の実施の形態と同様の工程で主体金具50への接地電極177の接合を行えば、絶縁碍子110の先端部116が外部から強い押圧力を受けないようにしながらも、その先端部116と接地電極177との間の間隙を、貴金属チップ197で塞ぐことができる。     Further, as in the plasma jet ignition plug 107 shown in FIG. 10, the outer periphery of the noble metal tip 197 protrudes radially outward from the inner protrusion 34 of the electrode base material 33 without forming the outer protrusion. If it is in the state, it is possible to prevent the noble metal tip 197 from falling off as in the first embodiment. Of course, as in the first embodiment, the electrode base material 33 and the noble metal tip 197 are joined while the noble metal tip 197 is pressed toward the rear end side in the axis O direction after the electrode base material 33 is joined to the metal shell 150. Can be done. Alternatively, in the ground electrode joining step, the outer periphery 35 of the electrode base material 33 is attached to the metal shell 150 while the electrode base material 33 is pressed to the rear end side in the axis O direction and the noble metal tip 197 is brought into contact with the tip portion 116 of the insulator 110. The engagement step 157 may be joined. In this way, the arrangement position of the electrode base material 33 can be made closer to the insulator 110 side, so that the mating portion between the engagement step portion 157 of the metal shell 150 and the outer edge portion 35 of the electrode base material 33 is stepped. As described above, more reliable joining can be performed. If the ground electrode 177 is joined to the metal shell 50 in the same process as that of the first embodiment, the tip portion 116 of the insulator 110 is not subjected to strong pressing force from the outside, but the tip portion A gap between 116 and the ground electrode 177 can be closed with a noble metal tip 197.

なお、第1の実施の形態において、外突部37は筒状をなす貴金属チップ36に鍔状に設けたが、必ずしも鍔状に連続していなくともよく、突部形状であってもよい。電極母材33の内突部34についても同様であり、貴金属チップ36と電極母材33とが一体となったときに、外突部37と内突部34とが軸線O方向に重なる配置となるように位置決めされれば足りる。   In the first embodiment, the outer protrusion 37 is provided in a bowl shape on the cylindrical noble metal tip 36, but it does not necessarily have to be continuous in a bowl shape and may have a protrusion shape. The same applies to the inner protrusion 34 of the electrode base material 33. When the noble metal tip 36 and the electrode base material 33 are integrated, the outer protrusion 37 and the inner protrusion 34 overlap in the axis O direction. It is sufficient to be positioned so that

[第2の実施の形態]
次に、第2の実施の形態のプラズマジェット点火プラグ200について、図面を参照して説明する。まず、図11を参照して、プラズマジェット点火プラグ200の構造について説明する。図11は、第2の実施の形態のプラズマジェット点火プラグ200の先端部分を拡大した断面図である。
[Second Embodiment]
Next, a plasma jet ignition plug 200 according to a second embodiment will be described with reference to the drawings. First, the structure of the plasma jet ignition plug 200 will be described with reference to FIG. FIG. 11 is an enlarged cross-sectional view of the tip portion of the plasma jet ignition plug 200 according to the second embodiment.

なお、第2の実施の形態のプラズマジェット点火プラグ200と、第1の実施の形態のプラズマジェット点火プラグ100とが構造上で異なる点は、接地電極230の形状が異なる点、および絶縁碍子210の先端部216にチップ係合部が形成されていない点である。従って、ここではプラズマジェット点火プラグ200の先端部分の構造について説明し、その他の部分については同一であるため説明を省略または簡略化する。   The plasma jet ignition plug 200 of the second embodiment and the plasma jet ignition plug 100 of the first embodiment are structurally different in that the shape of the ground electrode 230 is different and the insulator 210 The tip engaging portion 216 is not formed with a tip engaging portion. Therefore, the structure of the tip portion of the plasma jet ignition plug 200 will be described here, and the other portions are the same, and the description thereof will be omitted or simplified.

図11に示すように、主体金具50の先端部65に配設された接地電極230は、第1の実施の形態と同様に、電極母材233と貴金属チップ236とが一体に接合されたものであり、中央に開口(連通部231)を有する円盤状に形成されている。貴金属チップ236は円筒状をなし、その外周面を電極母材233の開口の内周面に対向させた状態で、両面の合わせ部分がレーザ溶接されており、その開口と共に、接地電極230の連通部231を構成している。連通部231は、絶縁碍子10よりも先端側に配置される接地電極230を介し、キャビティ60内を外気と連通するために開口されたものである。また、接地電極230は、その外縁部235(すなわち電極母材233の外縁部235)が主体金具50の先端部65に設けられた係合段部57に係合され、その状態でレーザ溶接され、主体金具50と一体に接合されている。そして貴金属チップ236は、絶縁碍子210の先端部216に接触されており、その先端部216と、接地電極230との間の間隙を塞いでいる。この構成により、第1の実施の形態と同様に、キャビティ60内で形成されたプラズマが外方に噴出される際に、プラズマのエネルギーが接地電極230と絶縁碍子210の先端部216との間の間隙に漏出してしまうことが防止されている。   As shown in FIG. 11, the ground electrode 230 disposed at the distal end portion 65 of the metal shell 50 is obtained by integrally joining an electrode base material 233 and a noble metal tip 236, as in the first embodiment. It is formed in a disk shape having an opening (communication portion 231) in the center. The noble metal tip 236 has a cylindrical shape, and the joint portion of both surfaces is laser-welded with the outer peripheral surface thereof facing the inner peripheral surface of the opening of the electrode base material 233, and the ground electrode 230 communicates with the opening. Part 231 is configured. The communication portion 231 is opened to communicate the inside of the cavity 60 with the outside air via the ground electrode 230 disposed on the tip side of the insulator 10. Further, the outer edge portion 235 of the ground electrode 230 (that is, the outer edge portion 235 of the electrode base material 233) is engaged with the engagement step portion 57 provided at the distal end portion 65 of the metal shell 50, and laser welding is performed in this state. The metal shell 50 is integrally joined. The noble metal tip 236 is in contact with the tip 216 of the insulator 210 and closes the gap between the tip 216 and the ground electrode 230. With this configuration, as in the first embodiment, when the plasma formed in the cavity 60 is ejected outward, the plasma energy is transferred between the ground electrode 230 and the tip 216 of the insulator 210. Leakage into the gap is prevented.

次に、第2の実施の形態のプラズマジェット点火プラグ200の製造方法について、図12を参照して説明する。図12は、第2の実施の形態のプラズマジェット点火プラグ200の製造過程の一部を示す図である。   Next, the manufacturing method of the plasma jet ignition plug 200 of 2nd Embodiment is demonstrated with reference to FIG. FIG. 12 is a diagram illustrating a part of the manufacturing process of the plasma jet ignition plug 200 according to the second embodiment.

図12に示すように、第2の実施のプラズマジェット点火プラグ200においても、予め別の工程で作製された中心電極20および端子金具40(図1参照)が一体に組み付けられた絶縁碍子210が、同様に別の工程において作製された主体金具50に、加締めによって一体に保持される(碍子保持工程)。   As shown in FIG. 12, also in the plasma jet spark plug 200 of the second embodiment, the insulator 210 in which the center electrode 20 and the terminal fitting 40 (see FIG. 1), which have been previously prepared in separate steps, are assembled together. Similarly, the metal shell 50 manufactured in a separate process is integrally held by crimping (insulator holding process).

次に、開口を有する円盤状の電極母材233が、絶縁碍子210の先端部216より先端側に配置される(電極母材配置工程)。この工程では、電極母材233の外縁部235が、段状をなす主体金具50の係合段部57に嵌め込むように係合される。このとき、電極母材233は、絶縁碍子210の先端部216と接触した状態となってもよいし、非接触の状態に維持されてもよい。この状態で、電極母材233の外縁部235と、主体金具50の係合段部57との合わせ面を狙ってレーザ光が照射され、周方向に一周して、主体金具50と接地電極330の電極母材333との溶接が行われる(接地電極接合工程)。   Next, the disc-shaped electrode base material 233 having an opening is disposed on the front end side of the front end portion 216 of the insulator 210 (electrode base material disposing step). In this step, the outer edge portion 235 of the electrode base material 233 is engaged so as to be fitted into the engaging step portion 57 of the metal shell 50 having a step shape. At this time, the electrode base material 233 may be in contact with the tip 216 of the insulator 210 or may be maintained in a non-contact state. In this state, laser light is irradiated aiming at the mating surface between the outer edge portion 235 of the electrode base material 233 and the engagement step portion 57 of the metal shell 50, and makes a round in the circumferential direction, and the metal shell 50 and the ground electrode 330. The electrode base material 333 is welded (ground electrode joining step).

そして、筒状に形成された貴金属チップ236が電極母材233の開口に挿入され、連通部231に配置される(貴金属部材配置工程)。貴金属チップ236は非固定の状態であり、次の工程において軸線O方向後端側へ向けて押さえられ、接地電極230を構成する電極母材233と、絶縁碍子210の先端部216との間の間隙が塞がれる。そして貴金属チップ236が押さえられたまま、貴金属チップ236と電極母材233との合わせ面を狙ってレーザ光が照射され、周方向に一周して両者の溶接が行われる(貴金属部材接合工程)。貴金属チップ36は電極母材33と一体となって、連通部31を構成する。このようにして、主体金具50の先端部65に接地電極230が接合されて、第2の実施の形態のプラズマジェット点火プラグ200が完成する。   Then, the noble metal tip 236 formed in a cylindrical shape is inserted into the opening of the electrode base material 233 and arranged in the communication portion 231 (noble metal member arranging step). The noble metal tip 236 is in an unfixed state, and is pressed toward the rear end side in the axis O direction in the next step, and between the electrode base material 233 constituting the ground electrode 230 and the tip portion 216 of the insulator 210. The gap is closed. Then, with the noble metal tip 236 being held down, laser light is irradiated aiming at the mating surface between the noble metal tip 236 and the electrode base material 233, and the two are welded around the circumference (noble metal member joining step). The noble metal tip 36 is integrated with the electrode base material 33 to form the communication portion 31. Thus, the ground electrode 230 is joined to the front-end | tip part 65 of the metal shell 50, and the plasma jet ignition plug 200 of the second embodiment is completed.

第2の実施の形態においても、主体金具50に絶縁碍子10を加締め保持させてから主体金具50に接地電極230を接合しており、製造過程において絶縁碍子210の破損が生じにくい。そして接地電極230の電極母材233と絶縁碍子210の先端部216との間に生じ得る間隙を、連通部231を構成する貴金属チップ236で塞ぐことができ、着火性の低下を防止することができる。   Also in the second embodiment, since the insulator 10 is caulked and held on the metal shell 50, the ground electrode 230 is joined to the metal shell 50, and the insulator 210 is not easily damaged during the manufacturing process. The gap that can be generated between the electrode base material 233 of the ground electrode 230 and the tip 216 of the insulator 210 can be closed by the noble metal tip 236 that constitutes the communication portion 231, thereby preventing a decrease in ignitability. it can.

なお、第2の実施の形態のプラズマジェット点火プラグ200も各種の変形が可能である。例えば上記同様に、図13に示す、プラズマジェット点火プラグ201や、図14に示す、プラズマジェット点火プラグ202のように、貴金属チップ291,292の軸線方向の長さを長くしたり、短くしたりして、電極母材33との合わせ部分を段状にしてもよい。このようにすれば、レーザ溶接の際に、貴金属チップ291,292と電極母材33との合わせ面の隙間にレーザ光か入り込むことが防止され、より確実な接合を行うことができる。   The plasma jet ignition plug 200 of the second embodiment can be variously modified. For example, as in the case of the plasma jet ignition plug 201 shown in FIG. 13 and the plasma jet ignition plug 202 shown in FIG. 14, the lengths of the noble metal tips 291 and 292 in the axial direction are increased or decreased, for example. The mating portion with the electrode base material 33 may be stepped. In this way, laser light can be prevented from entering the gap between the mating surfaces of the noble metal tips 291 and 292 and the electrode base material 33 during laser welding, and more reliable joining can be performed.

また、図15に示す、プラズマジェット点火プラグ203のように、筒状の貴金属チップ293の軸線O方向先端側の外周に径方向外側へ突出する鍔状の外突部247を設け、電極母材283側にも、開口に、軸線O方向先端側を拡径した段状のチップ取付部244を設けてもよい。このようにすれば、上記同様に、軸線O方向に貴金属チップ293の配置位置を調整して電極母材283と絶縁碍子210の先端部216との間の間隙を塞ぎつつ、チップ取付部244によって軸ずれを防止することができる。また、このような外突部247を有する貴金属チップ293を用いた場合、貴金属チップ293による軸線O方向の配置位置の調整に制限を受ける(外突部247がチップ取付部244に当接するとそれより軸線O方向後端側へ移動できない。)ため、電極母材283による配置位置調整も行うとなおよい。すなわち、電極母材283を絶縁碍子210の先端部216に近接あるいは接触させた状態で主体金具250の係合段部257に接合すると共に、貴金属チップ293を絶縁碍子210の先端部216へ向けて押さえながら電極母材283に接合するとよい。また、主体金具250の係合段部257は、係合段部257に接地電極273を係合させたときの接地電極273の配置位置よりも軸線O方向先端側へ突出させるように設けるとよい。このようにすれば、係合段部257と電極母材283の外縁部245との接合の際に、レーザ光を軸線Oと鋭角に交差する角度から照射しやすくでき、より確実な接合を行うことができる。   Further, like a plasma jet ignition plug 203 shown in FIG. 15, a flange-like outer protrusion 247 that protrudes radially outward is provided on the outer periphery of the cylindrical noble metal tip 293 at the front end side in the axis O direction. Also on the 283 side, a stepped chip mounting portion 244 whose diameter is enlarged at the front end side in the axis O direction may be provided in the opening. In this way, as described above, the tip mounting portion 244 adjusts the arrangement position of the noble metal tip 293 in the direction of the axis O and closes the gap between the electrode base material 283 and the tip portion 216 of the insulator 210. Axis misalignment can be prevented. Further, when the noble metal tip 293 having such an outer protrusion 247 is used, the adjustment of the arrangement position of the noble metal tip 293 in the direction of the axis O is limited (when the outer protrusion 247 abuts the tip mounting portion 244, Therefore, the arrangement position adjustment by the electrode base material 283 is preferably performed. That is, the electrode base material 283 is joined to the engagement step portion 257 of the metal shell 250 in a state where the electrode base material 283 is close to or in contact with the tip portion 216 of the insulator 210 and the noble metal tip 293 is directed toward the tip portion 216 of the insulator 210. The electrode base material 283 may be joined while being pressed. In addition, the engagement step portion 257 of the metal shell 250 may be provided so as to protrude from the position where the ground electrode 273 is disposed when the ground electrode 273 is engaged with the engagement step portion 257 toward the front end side in the axis O direction. . In this way, when joining the engaging step portion 257 and the outer edge portion 245 of the electrode base material 283, it is easy to irradiate the laser beam from an angle that intersects the axis O with an acute angle, thereby performing more reliable joining. be able to.

また、図16に示す、プラズマジェット点火プラグ302や、図17に示す、プラズマジェット点火プラグ303のように、接地電極372の連通部341を構成する貴金属チップ392を筒状に形成し、軸線O方向先端側の外周に径方向外側へ突出する鍔状の外突部342を設けてもよい。そして電極母材382側にも、開口に、軸線O方向先端側を拡径した段状のチップ取付部344を設ける。つまり、電極母材382の開口と共に連通部341を構成する貴金属チップ392を電極母材382に対し位置決めできるようにする。このようにすれば、電極母材382と貴金属チップ392との接合を容易に行うことができる。   Further, like the plasma jet ignition plug 302 shown in FIG. 16 and the plasma jet ignition plug 303 shown in FIG. 17, a noble metal tip 392 constituting the communication portion 341 of the ground electrode 372 is formed in a cylindrical shape, and the axis O A hook-shaped outer protrusion 342 that protrudes radially outward may be provided on the outer periphery on the tip side in the direction. A stepped tip mounting portion 344 having an enlarged diameter at the front end side in the axis O direction is also provided in the opening on the electrode base material 382 side. That is, the noble metal tip 392 that forms the communication portion 341 together with the opening of the electrode base material 382 can be positioned with respect to the electrode base material 382. In this way, the electrode base material 382 and the noble metal tip 392 can be easily joined.

また、貴金属チップ392の構成を、電極母材382に接合された際に一部が電極母材382の盤面から突出する構成とし、主体金具351,350への接地電極372の接合時には、その突出部分を絶縁碍子310の先端部316と接触させるとよい。このようにすれば、接地電極372の盤面全面を絶縁碍子310の先端部316に接触させて両者の間隙を塞ぐ場合よりも両者の接触面積を小さくすることができ、間隙を塞ぐための接触面の平滑性の管理を容易とすることができる。   Further, the noble metal tip 392 is configured such that a part of the noble metal tip 392 protrudes from the surface of the electrode base material 382 when it is bonded to the electrode base material 382, and when the ground electrode 372 is bonded to the metal shell 351, 350 The part may be brought into contact with the tip 316 of the insulator 310. In this way, the contact area between the ground electrodes 372 can be made smaller than when the entire surface of the ground electrode 372 is brought into contact with the tip 316 of the insulator 310 to close the gap between the two, and the contact surface for closing the gap. It is possible to easily manage the smoothness.

更に、図16に示した主体金具351の係合段部358や、図17に示した主体金具350の係合段部357のように、軸線O方向への突出量が、係合段部358,357に接地電極372を係合させたときの接地電極372の配置位置よりも小さくなるように、あるいは大きくなるようにするとよい。こうすれば、上記同様、係合段部358,357と接地電極372の外縁部345との接合の際にレーザ光を軸線Oと鋭角に交差する角度から照射しやすくでき、より確実な接合を行うことができる。   Further, the amount of protrusion in the direction of the axis O is such that the engagement step 358 of the metal shell 351 shown in FIG. 16 and the engagement step 357 of the metal shell 350 shown in FIG. , 357 may be made smaller or larger than the arrangement position of the ground electrode 372 when the ground electrode 372 is engaged. If it carries out like this, when joining the engagement step part 358,357 and the outer edge part 345 of the ground electrode 372 like the above, it will become easy to irradiate a laser beam from the angle which cross | intersects the axis line O, and more reliable joining. It can be carried out.

第1,第2の実施の形態のプラズマジェット点火プラグでは、貴金属チップを用いて接地電極と絶縁碍子の先端部との間の間隙を塞ぐ構成であるため、必ずしも電極母材が円環状でなくともよく、貴金属チップが筒状あるいは円環状をなせば足りる。すなわち、電極母材は貴金属チップを絶縁碍子の先端部に接触させた状態が維持されるように支持する部材であればよい。   In the plasma jet ignition plugs of the first and second embodiments, the gap between the ground electrode and the tip of the insulator is closed using a noble metal tip, so the electrode base material is not necessarily annular. In any case, it is sufficient if the noble metal tip has a cylindrical shape or an annular shape. In other words, the electrode base material may be a member that supports the noble metal tip so that the noble metal tip is in contact with the tip of the insulator.

第1の実施の形態のプラズマジェット点火プラグ100の部分断面図である 。It is a fragmentary sectional view of plasma jet ignition plug 100 of a 1st embodiment. 第1の実施の形態のプラズマジェット点火プラグ100の先端部分を拡大した断面図である。It is sectional drawing to which the front-end | tip part of the plasma jet ignition plug 100 of 1st Embodiment was expanded. 第1の実施の形態のプラズマジェット点火プラグ100の製造過程の一部を示す図である。It is a figure which shows a part of manufacturing process of the plasma jet ignition plug 100 of 1st Embodiment. 変形例としてのプラズマジェット点火プラグ101の先端部分を拡大した断面図である。It is sectional drawing to which the front-end | tip part of the plasma jet ignition plug 101 as a modification was expanded. 変形例としてのプラズマジェット点火プラグ102の先端部分を拡大した断面図である。It is sectional drawing to which the front-end | tip part of the plasma jet ignition plug 102 as a modification was expanded. 変形例としてのプラズマジェット点火プラグ103の先端部分を拡大した断面図である。It is sectional drawing to which the front-end | tip part of the plasma jet ignition plug 103 as a modification was expanded. 変形例としてのプラズマジェット点火プラグ104の先端部分を拡大した断面図である。It is sectional drawing to which the front-end | tip part of the plasma jet ignition plug 104 as a modification was expanded. 変形例としてのプラズマジェット点火プラグ105の先端部分を拡大した断面図である。It is sectional drawing to which the front-end | tip part of the plasma jet ignition plug 105 as a modification was expanded. 変形例としてのプラズマジェット点火プラグ106の先端部分を拡大した断面図である。It is sectional drawing to which the front-end | tip part of the plasma jet ignition plug 106 as a modification was expanded. 変形例としてのプラズマジェット点火プラグ107の先端部分を拡大した断面図である。It is sectional drawing to which the front-end | tip part of the plasma jet ignition plug 107 as a modification was expanded. 第2の実施の形態のプラズマジェット点火プラグ200の先端部分を拡大した断面図である。It is sectional drawing to which the front-end | tip part of the plasma jet ignition plug 200 of 2nd Embodiment was expanded. 第2の実施の形態のプラズマジェット点火プラグ200の製造過程の一部を示す図である。It is a figure which shows a part of manufacturing process of the plasma jet ignition plug 200 of 2nd Embodiment. 変形例としてのプラズマジェット点火プラグ201の先端部分を拡大した断面図である。It is sectional drawing to which the front-end | tip part of the plasma jet ignition plug 201 as a modification was expanded. 変形例としてのプラズマジェット点火プラグ202の先端部分を拡大した断面図である。It is sectional drawing to which the front-end | tip part of the plasma jet ignition plug 202 as a modification was expanded. 変形例としてのプラズマジェット点火プラグ203の先端部分を拡大した断面図である。It is sectional drawing to which the front-end | tip part of the plasma jet ignition plug 203 as a modification was expanded. 変形例としてのプラズマジェット点火プラグ302の先端部分を拡大した断面図である。It is sectional drawing to which the front-end | tip part of the plasma jet ignition plug 302 as a modification was expanded. 変形例としてのプラズマジェット点火プラグ303の先端部分を拡大した断面図である。It is sectional drawing to which the front-end | tip part of the plasma jet ignition plug 303 as a modification was expanded.

符号の説明Explanation of symbols

10 絶縁碍子
12 軸孔
20 中心電極
26 先端面
30 接地電極
31 連通部
32 溶融部
33 電極母材
34 内突部
35 外縁部
36 貴金属チップ
37 外突部
50 主体金具
60 キャビティ
61 先端小径部
100 プラズマジェット点火プラグ
DESCRIPTION OF SYMBOLS 10 Insulator 12 Shaft hole 20 Center electrode 26 Tip surface 30 Ground electrode 31 Communication part 32 Melting part 33 Electrode base material 34 Inner protrusion 35 Outer edge part 36 Precious metal tip 37 Outer protrusion part 50 Metal fitting 60 Cavity 61 Tip small diameter part 100 Plasma Jet spark plug

Claims (4)

中心電極と、
軸線方向に延びる軸孔を有し、前記中心電極の先端を前記軸孔内に収容すると共に、前記中心電極を保持する絶縁碍子と、
当該絶縁碍子の先端部において、前記軸孔の内周面と前記中心電極の先端面とを壁面とする凹部状に形成されたキャビティと、
前記絶縁碍子の径方向周囲を取り囲んで保持する主体金具と、
前記絶縁碍子の前記先端部よりも前記軸線方向先端側で前記主体金具に接合され、外気と前記キャビティの内部とを連通する連通部を有する接地電極と
を備えたプラズマジェット点火プラグであって、
前記接地電極は、前記連通部を有する電極母材に、前記連通部の一部をなす貴金属部材がレーザ溶接により接合された複合部材からなり、
自身の外縁部に前記主体金具との接合部を有し、自身の前記軸線方向先端側に前記電極母材と前記貴金属部材との溶融部を有する
ことを特徴とするプラズマジェット点火プラグ。
A center electrode;
An insulator that has an axial hole extending in the axial direction, houses the tip of the central electrode in the axial hole, and holds the central electrode;
At the tip of the insulator, a cavity formed in a concave shape with the inner peripheral surface of the shaft hole and the tip surface of the center electrode as wall surfaces;
A metal shell that surrounds and holds the periphery of the insulator in the radial direction;
A plasma jet ignition plug comprising: a ground electrode that is joined to the metal shell on the distal end side in the axial direction with respect to the distal end portion of the insulator and has a communication portion that communicates outside air with the inside of the cavity;
The ground electrode is composed of a composite member in which a noble metal member forming a part of the communication portion is joined to the electrode base material having the communication portion by laser welding,
A plasma jet ignition plug having a joint portion with the metal shell at an outer edge portion thereof, and a melting portion of the electrode base material and the noble metal member at the tip end side in the axial direction of the plasma jet ignition plug.
前記接地電極は、前記貴金属部材を前記絶縁碍子の前記先端部に接触させた状態で、前記外縁部が前記主体金具に接合されていることを特徴とする請求項1に記載のプラズマジェット点火プラグ。   2. The plasma jet ignition plug according to claim 1, wherein the outer edge portion of the ground electrode is joined to the metal shell in a state where the noble metal member is in contact with the tip portion of the insulator. 3. . 前記接地電極の前記電極母材は、前記軸線方向と直交する径方向において最も内側に位置する部位である内突部を有すると共に、前記接地電極の前記貴金属部材は、前記内突部よりも前記径方向の外側に位置する外突部を有し、
前記外突部は、前記軸線方向において前記内突部と重ねられつつ、その内突部よりも前記軸線方向後端側に配置されていることを特徴とする請求項1または2に記載のプラズマジェット点火プラグ。
The electrode base material of the ground electrode has an inner protrusion that is an innermost portion in a radial direction orthogonal to the axial direction, and the noble metal member of the ground electrode is more than the inner protrusion. Having an outer protrusion located on the outside in the radial direction,
3. The plasma according to claim 1, wherein the outer protrusion is arranged on the rear end side in the axial direction with respect to the inner protrusion while being overlapped with the inner protrusion in the axial direction. Jet spark plug.
中心電極と、
軸線方向に延びる軸孔を有し、前記中心電極の先端を前記軸孔内に収容すると共に、前記中心電極を保持する絶縁碍子と、
当該絶縁碍子の先端部において、前記軸孔の内周面と前記中心電極の先端面とを壁面とする凹部状に形成されたキャビティと、
前記絶縁碍子の径方向周囲を取り囲んで保持する主体金具と、
前記絶縁碍子の前記先端部よりも前記軸線方向先端側で前記主体金具に接合され、外気と前記キャビティの内部とを連通する連通部を有する接地電極と
を備えたプラズマジェット点火プラグの製造方法であって、
前記中心電極を保持した前記絶縁碍子を前記主体金具に保持させる碍子保持工程と、
前記接地電極を前記絶縁碍子の前記先端部よりも前記軸線方向先端側に配置する配置工程と、
前記接地電極の外縁部を前記主体金具に接合する接地電極接合工程と、
前記軸線方向先端側からレーザを照射して、前記連通部を有する接地電極の電極母材と、前記連通部の一部をなす貴金属部材とをレーザ溶接する貴金属部材接合工程と、
を有することを特徴とするプラズマジェット点火プラグの製造方法。
A center electrode;
An insulator that has an axial hole extending in the axial direction, houses the tip of the central electrode in the axial hole, and holds the central electrode;
At the tip of the insulator, a cavity formed in a concave shape with the inner peripheral surface of the shaft hole and the tip surface of the center electrode as wall surfaces;
A metal shell that surrounds and holds the periphery of the insulator in the radial direction;
A method of manufacturing a plasma jet ignition plug comprising: a grounding electrode having a communication portion that is joined to the metal shell at the tip end in the axial direction with respect to the tip portion of the insulator and that communicates outside air with the inside of the cavity. There,
An insulator holding step of holding the insulator holding the center electrode on the metal shell;
An arrangement step of disposing the ground electrode closer to the front end side in the axial direction than the front end portion of the insulator;
A ground electrode joining step for joining an outer edge portion of the ground electrode to the metal shell;
A noble metal member joining step in which laser irradiation is performed on the electrode base material of the ground electrode having the communication portion and the noble metal member forming a part of the communication portion by irradiating a laser from the tip end side in the axial direction;
A method of manufacturing a plasma jet ignition plug, comprising:
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JP5303014B2 (en) * 2010-10-05 2013-10-02 日本特殊陶業株式会社 Plasma jet ignition plug and manufacturing method thereof
JP5140718B2 (en) * 2010-12-15 2013-02-13 日本特殊陶業株式会社 Plasma jet ignition plug
CN102155344B (en) * 2011-01-21 2012-07-04 电子科技大学 Slot coupling micro-wave plasma igniter for internal-combustion engine
JP6039436B2 (en) * 2013-01-17 2016-12-07 日本特殊陶業株式会社 Plasma jet ignition plug
JP6045464B2 (en) * 2013-09-11 2016-12-14 日本特殊陶業株式会社 Spark plug manufacturing method and spark plug
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