JP4843076B2 - 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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JP4843076B2
JP4843076B2 JP2009161483A JP2009161483A JP4843076B2 JP 4843076 B2 JP4843076 B2 JP 4843076B2 JP 2009161483 A JP2009161483 A JP 2009161483A JP 2009161483 A JP2009161483 A JP 2009161483A JP 4843076 B2 JP4843076 B2 JP 4843076B2
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insulator
tip
electrode
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base material
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JP2009224344A5 (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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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01T—SPARK GAPS; OVERVOLTAGE ARRESTERS USING SPARK GAPS; SPARKING PLUGS; CORONA DEVICES; GENERATING IONS TO BE INTRODUCED INTO NON-ENCLOSED GASES
    • H01T13/00—Sparking plugs
    • H01T13/50—Sparking plugs having means for ionisation of gap
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01T—SPARK GAPS; OVERVOLTAGE ARRESTERS USING SPARK GAPS; SPARKING PLUGS; CORONA DEVICES; GENERATING IONS TO BE INTRODUCED INTO NON-ENCLOSED GASES
    • H01T13/00—Sparking plugs
    • H01T13/54—Sparking plugs having electrodes arranged in a partly-enclosed ignition chamber
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01T—SPARK GAPS; OVERVOLTAGE ARRESTERS USING SPARK GAPS; SPARKING PLUGS; CORONA DEVICES; GENERATING IONS TO BE INTRODUCED INTO NON-ENCLOSED GASES
    • H01T21/00—Apparatus or processes specially adapted for the manufacture or maintenance of spark gaps or sparking plugs
    • H01T21/02—Apparatus or processes specially adapted for the manufacture or maintenance of spark gaps or sparking plugs of sparking plugs

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  • Engineering & Computer Science (AREA)
  • 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、更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. Then, a high voltage is applied to the spark discharge gap to cause a spark discharge, and a 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、その間隙や、その間隙と連通する主体金具と絶縁碍子との間の間隙内にプラズマの持つエネルギーが漏出してしまう場合がある。このような場合、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（ハウジング）が接地電極（外部電極）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。）。特許文献１のプラズマジェット点火プラグでは、接地電極と主体金具とを一体に成形しており、主体金具に対し、接地電極（接地電極に相当する部分）が正確に位置決めされている。従って絶縁碍子の寸法管理を行えばよく、主体金具に絶縁碍子を保持させた際に、絶縁碍子の先端部が接地電極に当接した状態となっている。   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 plasma has in the gap or between the metal shell and the insulator communicating with the gap. Energy may leak out. In such a case, there is a possibility that the amount of plasma energy ejected from the orifice is reduced and the ignitability is lowered. Therefore, a plasma jet ignition plug is proposed in which an insulator (housing) is provided in close contact with a ground electrode (external electrode), and there is no gap between the insulator and the ground electrode (for example, Patent Document 1). reference.). In the plasma jet ignition plug of Patent Document 1, the ground electrode and the metal shell are integrally formed, and the ground electrode (portion corresponding to the ground electrode) is accurately positioned with respect to the metal shell. Therefore, the size of the insulator may be controlled, and when the insulator is held by the metal shell, the tip of the insulator is in contact with the ground electrode.

特開２００６−２９４２５７号公報JP 2006-294257 A

しかしながら、プラズマジェット点火プラグの製造過程において、絶縁碍子は主体金具に加締められて保持されるため位置ずれが生じ得るが、その位置ずれを厳密に管理することは難しく、位置ずれの状態によっては絶縁碍子の先端部が接地電極に強く押し当てられるように負荷がかかってしまう場合があり、絶縁碍子が破損してしまう虞があった。   However, in the manufacturing process of the plasma jet spark plug, the insulator is crimped and held by the metal shell, so that it may be displaced. However, it is difficult to strictly manage the displacement, and depending on the state of the displacement, A load may be applied so that the tip of the insulator is strongly pressed against the ground electrode, and the insulator may be damaged.

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、絶縁碍子とその先端側に配置される接地電極との間の間隙や、その間隙と連通する主体金具と絶縁碍子との間の間隙に漏出するプラズマの持つエネルギーを低減させる一方で、絶縁碍子が接地電極に対し強く当接した状態となることを防止することができるプラズマジェット点火プラグおよびその製造方法を提供することを目的とする。   The present invention has been made in order to solve the above-described problems, and includes a gap between an insulator and a ground electrode disposed on the tip side thereof, and a gap between a metal shell communicating with the gap and the insulator. An object of the present invention is to provide a plasma jet ignition plug and a method of manufacturing the same that can reduce the energy of plasma leaking to the earth while preventing the insulator from being in strong contact with the ground electrode. .

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面を前記軸孔内先端側に収容すると共に、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、前記絶縁碍子の前記軸線方向に垂直な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に配置されると共に、前記絶縁碍子の前記先端部と環状に接触し、前記軸線方向から見たときに前記キャビティの開口部が自身の内側にある接触部と、前記キャビティの内部を外気と連通させる連通部とを有する接地電極とを備え、前記接地電極は、前記連通部を有し、前記軸線方向には前記絶縁碍子と非接触である一方、前記主体金具とは接触すると共に、自身の外縁部が前記主体金具と接合されて前記主体金具と電気的に接続されている電極母材と、前記連通部の一部、および前記接触部を有する接触部材とが接合された複合部材からなる電極であり、前記接地電極の前記電極母材は、前記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接触部材は、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、前記接地電極は、前記外突部と前記内突部とを前記軸線方向に重ねつつ、前記外突部を前記内突部よりも前記軸線方向先端側に配置させていることを特徴とする。 In order to achieve the above object, a plasma jet ignition plug according to a first aspect of the present invention has a center electrode and an axial hole extending in the axial direction, and the distal end surface of the central electrode is accommodated on the distal end side in the axial hole. And an insulator that holds the center electrode, and 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 tip of the insulator, A metal shell that surrounds and holds the periphery of the insulator perpendicular to the axial direction in the radial direction, and is disposed closer to the distal end side in the axial direction than the distal end portion of the insulator, and is annular with the distal end portion of the insulator And a ground electrode having a contact portion in which the opening of the cavity is inside itself when viewed from the axial direction, and a communication portion for communicating the inside of the cavity with outside air, the ground electrode Is While having the communication part and being in non-contact with the insulator in the axial direction, the outer metal is in contact with the metal shell, and its outer edge is joined to the metal shell to electrically connect with the metal shell. It is an electrode composed of a composite member in which a connected electrode base material, a part of the communication portion, and a contact member having the contact portion are joined, and the electrode base material of the ground electrode is in the radial direction And the contact member of the ground electrode has an outer protrusion located on the outer side in the radial direction than the inner protrusion, and the ground electrode is The outer projecting portion and the inner projecting portion are overlapped in the axial direction, and the outer projecting portion is arranged closer to the distal end side in the axial direction than the inner projecting portion .

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、前記接地電極が有する前記連通部の内周壁の少なくとも一部は、貴金属からなる貴金属部材で形成されていることを特徴とする。 According to a second aspect of the present invention, in addition to the configuration of the first aspect of the invention, at least a part of the inner peripheral wall of the communication portion of the ground electrode is a noble metal member made of a noble metal. It is formed.

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又は２に記載の発明の構成に加え、前記絶縁碍子の前記先端部には、前記接触部が係合する係合部が設けられていることを特徴とする。 The plasma jet spark plug according to claim 3, in addition to the configuration of the invention according to claim 1 or 2, wherein the said tip portion of the insulator, the engagement portion into which the contact portion is engaged is It is provided.

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面を前記軸孔内先端側に収容すると共に、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、前記絶縁碍子の前記軸線方向に垂直な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に配置されると共に、前記絶縁碍子の前記先端部と環状に接触し、前記軸線方向から見たときに前記キャビティの開口部が自身の内側にある接触部と、前記キャビティの内部を外気と連通させる連通部とを有する接地電極とを備え、前記接地電極は、前記径方向において最も内側に位置する部位である内突部および前記連通部を有し、前記軸線方向には前記絶縁碍子と非接触である一方、前記主体金具とは接触する電極母材と、前記内突部よりも前記径方向の外側に位置する外突部、前記連通部の一部、および前記接触部を有する接触部材とが接合された複合部材からなる電極である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、前記碍子保持工程後、前記電極母材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電極母材配置工程と、前記接地電極を構成する前記電極母材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、前記接触部材を前記電極母材の前記連通部に配置しつつ前記軸線方向に移動させ、前記内突部よりも前記外突部が前記軸線方向先端側に配置されるように、前記軸線方向に、前記電極母材の前記内突部を前記接触部材の前記外突部に重ねつつ、前記接触部を前記絶縁碍子の先端部に接触させて配置する接触部材配置工程と、前記接触部材を前記絶縁碍子の先端部に接触させたまま、前記電極母材に前記接触部材を接合する接触部材接合工程とを有する。 According to a fourth aspect of the present invention, there is provided a plasma jet spark plug manufacturing method including a center electrode and an axial hole extending in an axial direction, and the front end surface of the central electrode is accommodated on the front end side 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 metal shell that surrounds and holds a radial periphery perpendicular to the axial direction, and is disposed closer to the distal end side in the axial direction than the distal end portion of the insulator, and annularly contacts the distal end portion of the insulator. a contact portion where the opening of the cavity is inside its own when viewed from the axial direction, and a ground electrode having a communicating portion which communicate ambient air communicating the interior of the cavity, the ground electrode, the Diameter Innermost has a projection and the communicating portion in a portion located, while the in the axial direction is the insulator and non-contact, and the electrode base material to be contact with the metal shell, wherein the butt in A method of manufacturing a plasma jet ignition plug, which is an electrode composed of a composite member in which an outer protrusion located on the outer side in the radial direction than a portion, a part of the communication portion, and a contact member having the contact portion are joined together And an insulator holding step for holding the insulator holding the center electrode on the metal shell, and after the insulator holding step, the electrode base material is positioned closer to the tip in the axial direction than the tip of the insulator. An electrode base material placement step for placement, a ground electrode joining step for joining an outer edge portion of the electrode base material constituting the ground electrode to the metal shell, and the contact member disposed at the communication portion of the electrode base material. While said Is moved in the linear direction, so that the outer projection is disposed on the tip end side in the axial direction than the inner projection, in the axial direction, the outer of said contact member to said protruding portion of the electrode base material A contact member disposing step of placing the contact portion in contact with the tip of the insulator while overlapping the protrusion, and the electrode base material with the contact member in contact with the tip of the insulator A contact member joining step for joining the contact members.

また、請求項５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、請求項４に記載の発明の構成に加え、前記絶縁碍子の前記先端部には、前記接地電極の前記接触部が係合する係合部が設けられおり、前記接触部は前記係合部に係合されることを特徴とする。 According to a fifth aspect of the present invention, there is provided a method of manufacturing a plasma jet spark plug according to the fourth aspect of the invention, in addition to the structure of the fourth aspect of the invention, the contact portion of the ground electrode is engaged with the tip portion of the insulator. An engaging portion is provided, and the contact portion is engaged with the engaging portion.

なお、本発明に係るプラズマジェット点火プラグでは、絶縁碍子の先端部に対し接地電極が接触しているが、ここでいう「接触」とは、互いが触れている状態だけでなく、比較的弱い押圧力で両者が当接する状態を含むものである。「比較的弱い押圧力で両者が当接する状態」とは、接地電極と絶縁碍子の先端部とが互いに当接しつつも、両者間に生ずる抗力が、絶縁碍子に破損を生じさせない程度の抗力であることを意味する。つまり、接地電極に対し絶縁碍子の先端部が強く当接した状態にはならず、接地電極に対する絶縁碍子の応力が高まることはない。抗力の程度についてより具体的に説明すると、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のに必要な程度の押圧力で両者が接した状態が維持されれば足りるものであり、燃焼室から受ける燃焼圧の漏出までをも防止するものではない。   In the plasma jet ignition plug according to the present invention, the ground electrode is in contact with the tip of the insulator, but the term “contact” here is not only in a state of being in contact with each other but also relatively weak. This includes a state in which both abut against each other with a pressing force. "A state where both are in contact with each other with relatively weak pressing force" means a drag that does not cause damage to the insulator while the ground electrode and the tip of the insulator are in contact with each other. It means that there is. That is, the tip of the insulator does not come into strong contact with the ground electrode, and the stress of the insulator with respect to the ground electrode does not increase. The degree of drag will be described more specifically. It is only necessary to maintain the contact state with the pressing force necessary to prevent leakage of the plasma energy ejected from the cavity. It does not prevent even the leakage of the combustion pressure received from.

また、請求項１に係る発明のプラズマジェット点火プラグでは、接地電極の接触部が絶縁碍子の先端部に接触した状態で主体金具に接合されており、接地電極と絶縁碍子の先端部との間や絶縁碍子と主体金具との間に生じ得る間隙が塞がれた状態となっている。このため、キャビティ内で形成されるプラズマが噴出される際に、上記間隙が塞がれていない場合であればその間隙内にプラズマのエネルギーが漏出してしまうことが生じ得るが、本発明ではこうしたエネルギーの漏出が防止されるので、着火性の低下を防止することができる。また、接地電極は電極母材と接触部材とが接合された複合部材である。このため、製造時において、電極母材の外縁部を主体金具に接合させる工程と、接触部材を絶縁碍子の先端部とさせつつ、電極母材に接合させる工程とを分けることができる。軸線方向における電極母材と絶縁碍子の先端部との間の間隙は、絶縁碍子を主体金具に保持させる際に生じ得る軸線方向の組み付け公差を吸収する役割を果たす。このため、接地電極の外縁部を主体金具と接合させる際に、接触部を絶縁碍子の先端部に強く当接させることを回避することができ、接触部を絶縁碍子の先端部に強く当接させることに起因して、応力が高まることによる絶縁碍子の破損は生じない。 In the plasma jet ignition plug according to the first aspect of the present invention, the contact portion of the ground electrode is joined to the metal shell while being in contact with the tip portion of the insulator, and between the ground electrode and the tip portion of the insulator. In addition, a gap that may occur between the insulator and the metal shell is closed. For this reason, when the plasma formed in the cavity is ejected, if the gap is not closed, the plasma energy may leak into the gap. Since such leakage of energy is prevented, it is possible to prevent a decrease in ignitability. The ground electrode is a composite member in which an electrode base material and a contact member are joined. For this reason, at the time of manufacture, the process of joining the outer edge part of an electrode base material to a metal shell, and the process of joining to an electrode base material, making a contact member the front-end | tip part of an insulator can be divided. The gap between the electrode base material in the axial direction and the tip of the insulator serves to absorb axial assembly tolerances that may occur when the insulator is held by the metal shell. For this reason, when joining the outer edge portion of the ground electrode to the metal shell, it is possible to avoid making the contact portion strongly contact the tip portion of the insulator, and strongly contact the contact portion to the tip portion of the insulator. As a result, the insulator does not break due to increased stress.

また、請求項１に係る発明のプラズマジェット点火プラグでは、接触部材の外突部を電極母材の内突部よりも軸線方向先端側に配置し、その外突部を用いた位置決めを行って接触部材と電極母材とを一体に接合しているので、接触部材の軸ずれを防止することができる。 In the plasma jet ignition plug according to the first aspect of the present invention, the outer protrusion of the contact member is disposed closer to the distal end side in the axial direction than the inner protrusion of the electrode base material, and positioning using the outer protrusion is performed. since joining together the contact member and the electrode base material, it is possible to prevent the axial displacement of the contact member.

また、接地電極と中心電極との間には、キャビティ内でプラズマを発生させるため高いエネルギーが供給されることとなるため、請求項２に係る発明のように、接地電極の連通部の内周壁の少なくとも一部を貴金属部材で構成すれば、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る。 In addition, since high energy is supplied between the ground electrode and the center electrode in order to generate plasma in the cavity, the inner peripheral wall of the communication portion of the ground electrode as in the invention according to claim 2 If at least a part of these is made of a noble metal member, the consumption of the ground electrode due to the high energy of plasma can be reduced.

また、請求項３に係る発明のように、絶縁碍子の先端部の係合部に接地電極の接触部を係合させれば、接地電極の軸ずれを防止することができる。また、接触部と係合部との合わせ面が密接し、その合わせ面よりも径方向外側に位置する接地電極と絶縁碍子の先端部との間の間隙や絶縁碍子と主体金具との間に生じ得る間隙が塞がれる。 Further, as in the invention according to claim 3 , if the contact portion of the ground electrode is engaged with the engagement portion of the tip portion of the insulator, the axial displacement of the ground electrode can be prevented. In addition, the mating surfaces of the contact portion and the engaging portion are in close contact, and the gap between the ground electrode located on the radially outer side of the mating surface and the tip of the insulator or between the insulator and the metal shell. Possible gaps are closed.

絶縁碍子の主体金具への保持は、通常、加締めにより行われるが、その際に組み付け公差が生じ得る。 Holding to insulation insulator of the metal shell is usually carried out by crimping, Ru result in tolerance assembled at that time.

また、請求項４に係る発明のように、先に電極母材を主体金具に接合し、接触部材を電極部材の連通部に配置する際に配置位置の調整を行い、接触部材を絶縁碍子の先端部に接触させ、この状態で両者を接合すれば、接地電極と絶縁碍子の先端部との間の間隙を、電極母材の配置位置によらず、確実に塞ぐことができる。また、主体金具への電極母材の接合前に主体金具に絶縁碍子が保持されるので、絶縁碍子の組み付け公差が吸収されて絶縁碍子の破損が防止されることは、上記と同様である。接触部材の外突部を電極母材の内突部と重ねて配置することで位置決めを行うことができ、接触部材の軸ずれを防止することができる。 Further, as in the invention according to claim 4 , the electrode base material is first joined to the metal shell, and the arrangement position is adjusted when the contact member is arranged in the communication portion of the electrode member, and the contact member is made of the insulator. If they are brought into contact with the tip and bonded together in this state, the gap between the ground electrode and the tip of the insulator can be reliably closed regardless of the position of the electrode base material. Further, since the insulator is held by the metal shell before the electrode base material is joined to the metal shell, the assembly tolerance of the insulator is absorbed and the insulator is prevented from being damaged in the same manner as described above. Positioning can be performed by arranging the outer protrusion of the contact member so as to overlap with the inner protrusion of the electrode base material, and the contact member can be prevented from being displaced.

更に、請求項５に係る発明のように、絶縁碍子の先端部に設けた係合部に接地電極の接触部が係合されるようにすれば、接地電極と絶縁碍子の先端との間の位置決めを確実に行うことができると共に、接地電極と絶縁碍子の先端部との間の間隙を、より確実に塞ぐことができる。 Further, as in the invention according to claim 5 , if the contact portion of the ground electrode is engaged with the engaging portion provided at the tip portion of the insulator, it is between the ground electrode and the tip of the insulator. Positioning can be performed reliably, and the gap between the ground electrode and the tip of the insulator can be more reliably closed.

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. 第３の実施の形態のプラズマジェット点火プラグ３００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 300 of 3rd Embodiment was expanded. 第３の実施の形態のプラズマジェット点火プラグ３００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 300 of 3rd Embodiment. 変形例としてのプラズマジェット点火プラグ３０１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 301 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. 第４の実施の形態のプラズマジェット点火プラグ４００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 400 of 4th Embodiment was expanded. 第４の実施の形態のプラズマジェット点火プラグ４００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 400 of 4th Embodiment. 変形例としてのプラズマジェット点火プラグ４０１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 401 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４０２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 402 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４０３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 403 as a modification was expanded.

［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よりも更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 creepage distance between the metallic shell 50 and the terminal fitting 40. Further, a distal end side body portion 17 having an outer diameter smaller than that of 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.

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。   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. 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の開口部６６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 plasma is formed in this cavity 60 during spark discharge, and is ejected forward from the opening 66 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る。主体金具５０は、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において、軸線Ｏ方向に垂直な径方向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 an engine head (not shown) of the internal combustion engine. The metal shell 50 surrounds the periphery of the insulator 10 in the radial direction perpendicular to the direction of the axis O in a portion extending from the long leg portion 13 of the insulator 10 to the front end side of the rear end side body portion 18. The insulator 10 is held. 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に配設された接地電極３０について説明する。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複合部材からなる電極である。接地電極３０は、円盤状の形状を有し、その径方向中央には連通孔（連通部３１）が形成されている。貴金属チップ３６は、径方向内周側に配置され、電極母材３３と接合されている。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、電極母材３３と貴金属チップ３６とにより構成され、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の内部を外気と連通させるための開口を備える。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」に相当する。もっとも、接地電極３０が円盤状ではない場合でも、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 disposed at the distal end portion 65 of the metal shell 50 will be described. The ground electrode 30 shown in FIG. 2 is an electrode made of a composite member 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. The ground electrode 30 has a disk shape, and a communication hole (communication portion 31) is formed in the center in the radial direction. The noble metal tip 36 is disposed on the radially inner peripheral side and joined to the electrode base material 33. 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 communication portion 31 of the ground electrode 30 is constituted by the electrode base material 33 and the noble metal tip 36, and is used for communicating the inside of the cavity 60 with the outside air via the ground electrode 30 disposed on the tip side of the insulator 10. With an opening. 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、連通部３１の一部として連通部３１の内周壁７０を形成する。貴金属チップ３６は、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を備える。電極母材３３は円盤状をなし、径方向中央には連通部３１を構成する孔を有する。電極母材３３は、貴金属チップ３６と同様に、自身の孔の内周面を径方向内側に向けて鍔状に突出させた内突部３４が、軸線Ｏ方向の先端側に設けられている。そして、接地電極を構成する電極母材３３の内突部３４よりも貴金属チップ３６の外突部３７を軸線Ｏ方向後端側に配置させている。このような構成により、電極母材３３と貴金属チップ３６との接合に不具合が生じた場合でも、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ことができる。   The noble metal tip 36 of the first embodiment has a cylindrical shape, and an inner peripheral wall 70 of the communication part 31 is formed as a part of the communication part 31. The noble metal tip 36 includes an outer protrusion 37 that protrudes in a bowl shape with its outer peripheral surface facing radially outward on the rear end side in the axis O direction. The electrode base material 33 has a disk shape, and has a hole constituting the communication portion 31 at the center in the radial direction. Similarly to the noble metal tip 36, the electrode base material 33 is provided with an inner protrusion 34 that protrudes in a bowl shape with the inner peripheral surface of its own hole directed radially inward, on the tip side in the axis O direction. . The outer protrusion 37 of the noble metal tip 36 is arranged on the rear end side in the axis O direction with respect to the inner protrusion 34 of the electrode base material 33 constituting the ground electrode. With such a configuration, it is possible to prevent the noble metal tip 36 from slipping forward in the direction of the axis O even when a failure occurs in the joining between the electrode base material 33 and the noble metal tip 36.

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、キャビティ６０の開口部６６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の外突部３７は、このチップ係合部６２に係合して、絶縁碍子１０の先端部１６と環状に接触している。外突部３７のうち、チップ係合部６２に係合して、絶縁碍子１０の先端部１６と環状に接触している部分は、接触部３８である。軸線Ｏ方向から見たときに、キャビティ６０の開口部６６は、接触部３８の内側にある。一方、電極母材３３の後方に設けられ、絶縁碍子１０の先端部１６と対向する非接触部３９は、絶縁碍子１０の先端部１６と接触していない。貴金属チップ３６は、接地電極３０と絶縁碍子１０の先端部１６との間の間隙や、その間隙と連通する主体金具５０と絶縁碍子１０の先端部１６との間の間隙を塞いでおり、キャビティ６０の内部を外気と連通させている。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との間や絶縁碍子１０と主体金具５０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「接触部材」および「貴金属部材」に相当する。   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. The tip engaging portion 62 is formed in an annular shape surrounding the periphery of the opening 66 of the cavity 60. The outer projecting portion 37 of the noble metal tip 36 is engaged with the tip engaging portion 62 and is in annular contact with the distal end portion 16 of the insulator 10. A portion of the outer protrusion 37 that is engaged with the tip engaging portion 62 and is in annular contact with the tip 16 of the insulator 10 is a contact portion 38. When viewed from the direction of the axis O, the opening 66 of the cavity 60 is inside the contact portion 38. On the other hand, the non-contact portion 39 provided behind the electrode base material 33 and facing the tip portion 16 of the insulator 10 is not in contact with the tip portion 16 of the insulator 10. The noble metal tip 36 closes a gap between the ground electrode 30 and the tip 16 of the insulator 10 and a gap between the metal shell 50 communicating with the gap and the tip 16 of the insulator 10. The interior of 60 is in communication with outside air. With this configuration, when the plasma formed in the cavity 60 is ejected outward, the energy of the plasma is between the ground electrode 30 and the tip 16 of the insulator 10 or between the insulator 10 and the metal shell 50. Leakage into the gap between them is prevented. The noble metal tip 36 corresponds to the “contact member” and 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との間や絶縁碍子１０と主体金具５０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. 16, the insulator 10 is held before the ground electrode 30 is joined to the metal shell 50 in order to close the gap between the insulator 10 and 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（配置工程における接触部材配置工程）。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が形成された孔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の非接触部３９は、絶縁碍子１０の先端部１６と非接触の状態に維持される。貴金属チップ３６は、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との間に挟まれ、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. (Contact 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 disc-shaped electrode base material 33 having a hole 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 facing forward in the direction of the axis O. 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 non-contact portion 39 of the electrode base material 33 is maintained in a non-contact state with the tip portion 16 of the insulator 10. As for the noble metal tip 36, the outer projection 37 is sandwiched between the inner projection 34 of the electrode base material 33 and the tip engaging portion 62 of the insulator 10, and the arrangement position is regulated.

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周方向に一周して照射され、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が軸線Ｏ方向先端側に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（接触）状態となり、貴金属チップ３６と絶縁碍子１０の先端部１６との間の間隙、および接地電極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（接触部材接合工程）。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。   The laser beam is irradiated around the circumferential direction aiming at the mating surface between the outer edge portion 35 of the electrode base material 33 and the engagement step portion 57 of the metal shell 50, and the electrode base material of the metal shell 50 and the ground electrode 30 is irradiated. 33 is welded (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. Furthermore, when the noble metal tip 36 is pressed toward the tip end side in the axis O direction, the noble metal tip 36 and the tip engaging portion 62 are brought into a close (contact) state, and the noble metal tip 36 and the tip portion 16 of the insulator 10 are in contact with each other. The gap and the gap between the electrode base material 33 constituting the ground electrode 30 and the tip 16 of the insulator 10 are closed. 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 (contact 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に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。また製造時において、主体金具５０への加締めの際に絶縁碍子１０の先端部１６の位置に軸線Ｏ方向にずれが生じる場合、すなわち組み付け公差が大きくなる場合がある。このような場合でも、主体金具５０への電極母材３３の接合時に電極母材３３と絶縁碍子１０の先端部１６との間の軸線Ｏ方向の間隙により、公差を吸収することができる。   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 there is nothing that abuts the tip 16 of the insulator 10 during caulking. The tip 16 of the insulator 10 does not receive a strong pressing force from the outside. Further, at the time of manufacturing, when the metal fitting 50 is caulked, the position of the tip portion 16 of the insulator 10 may be displaced in the direction of the axis O, that is, the assembly tolerance may be increased. Even in such a case, the tolerance can be absorbed by the gap in the direction of the axis O between the electrode base material 33 and the tip 16 of the insulator 10 when the electrode base material 33 is joined to the metal shell 50.

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の一部および接触部３８を有する貴金属チップ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。   Further, a gap that may be generated between the electrode base material 33 of the ground electrode 30 and the tip end portion 16 of the insulator 10 causes the noble metal tip 36 having a part of the communication portion 31 and the contact portion 38 to be connected to the tip end portion 16 of the insulator 10. It can be blocked by bringing it into contact. 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.

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、貴金属チップ１９１の接触部１２０を絶縁碍子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, it is pressed to the rear end side in the direction of the axis O, and laser welding is performed while the contact portion 120 of the noble metal tip 191 is in contact with the tip portion 116 of the insulator 110. The gap between the electrode 171 (electrode base material 33) 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Ｏ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の接触部１２１，１２２を絶縁碍子１１０の先端部１１６に接触させつつ、貴金属チップ１９２，１９３と電極母材３３とレーザ溶接する時に、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 length of the noble metal tips 192 and 193 in the direction of the axis O is increased or decreased. Also 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, when the noble metal tips 192 and 193 and the electrode base material 33 are laser-welded while the contact portions 121 and 122 of the noble metal tips 192 and 193 are brought into contact with the tip portion 116 of the insulator 110, the axis line with respect to the mating surfaces of the two It becomes easy to irradiate laser light from an angle that intersects O with an acute angle. 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、貴金属チップ１９４の接触部１２３を絶縁碍子１１０の先端部１１６に接触させてもよい。この場合、電極母材１８４の孔に、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。   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 is tapered so that the diameter increases toward the rear end side in the axis O direction, and the noble metal tip 194 contacts. The portion 123 may be brought into contact with the distal end portion 116 of the insulator 110. In this case, by providing a tapered portion 132 that overlaps the outer protrusion 131 and the axis O direction in the hole 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.

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、貴金属チップ１９５，１９６の接触部１２４，１２５を絶縁碍子１１０の先端部１１６に接触させつつ、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. That is, if the joining portion of the noble metal tips 195 and 196 and the electrode base material 184 is stepped, the contact portions 124 and 125 of the noble metal tips 195 and 196 are brought into contact with the tip portion 116 of the insulator 110, It is possible to easily irradiate the laser beam from the angle that intersects the axis O with an acute angle with respect to the mating surface that is irradiated with the laser beam at the time of welding, so that more reliable bonding 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て、貴金属チップ１９７の接触部１２６を絶縁碍子１１０の先端部１１６に接触させながら、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。   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, after the electrode base material 33 is joined to the metal shell 150, the noble metal tip 197 is pressed toward the rear end side in the axis O direction, and the contact portion 126 of the noble metal tip 197 is insulated. The electrode base material 33 and the noble metal tip 197 may be joined while being brought into contact with the tip portion 116 of the metal. 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.

上記図７〜図１０に示す変形例では、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１７４，１７７（図８および図９において図示略）の接合を行えばよい。このようにすれば、電極母体１７４，１８４，１９８（非接触部１４０，１４１，１４２）と絶縁碍子１１０の先端部１１６との間の間隙により、絶縁碍子１１０を主体金具５０に保持させる際に生じ得る軸線Ｏ方向の組み付け公差を吸収する役割を果たす。このため、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、先端部１１６と接地電極１７４，１７７との間の間隙を、貴金属チップ１９４〜１９７で塞ぐことができる。なお、図４，図５，図７および図８に示すプラズマジェット点火プラグ１０１，１０２，１０４および１０５のように、貴金属チップ１９１，１９２，１９４，１９５の内周壁が連通部の内周壁７１，７２，７４，７５を構成してもよい。また、図６，図９および図１０に示すプラズマジェット点火プラグ１０３，１０６および１０７のように、貴金属チップ１９３，１９６，１９７の内周壁が連通部の内周壁７３，７６，７７の一部を構成してもよい。   In the modified examples shown in FIGS. 7 to 10, the ground electrodes 174 and 177 (not shown in FIGS. 8 and 9) may be joined to the metal shell 50 in the same process as in the first embodiment. In this way, when the insulator 110 is held by the metal shell 50 due to the gap between the electrode bases 174, 184, 198 (non-contact portions 140, 141, 142) and the tip portion 116 of the insulator 110. It serves to absorb the assembly tolerances in the direction of the axis O. Therefore, the gap between the tip portion 116 and the ground electrodes 174 and 177 can be closed with the noble metal tips 194 to 197 while preventing the tip portion 116 of the insulator 110 from receiving a strong pressing force from the outside. . 4, 5, 7, and 8, the inner peripheral walls of the noble metal tips 191, 192, 194, and 195 are the inner peripheral walls 71, 72, 74, 75 may be configured. Further, like the plasma jet ignition plugs 103, 106 and 107 shown in FIGS. 6, 9 and 10, the inner peripheral walls of the noble metal tips 193, 196 and 197 are part of the inner peripheral walls 73, 76 and 77 of the communicating portion. It may be configured.

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 of 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複合部材からなる電極ものである。接地電極２３０は、円盤状の形状を有し、その径方向中央には連通孔（連通部２３１）が形成されている。貴金属チップ２３６は円筒状をなす。一方、電極母材２３３は円盤状をなし、径方向中央に連通部２３１を構成する孔を有する。貴金属チップ２３６は、その外周面を電極母材２３３の孔の内周面に対向させた状態で、両面の合わせ部分において電極母材２３３とレーザ溶接されている。貴金属チップ２３６は、電極母材２３３の孔と共に、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よりも先端側において、連通部２３１の内周壁７８によって囲まれた連通孔を介し、キャビティ６０の内部を外気と連通させる。   As shown in FIG. 11, the ground electrode 230 disposed at the distal end portion 65 of the metal shell 50 is a composite in which an electrode base material 233 and a noble metal tip 236 are integrally joined, as in the first embodiment. The electrode is made of a member. The ground electrode 230 has a disk shape, and a communication hole (communication portion 231) is formed in the center in the radial direction. The noble metal tip 236 has a cylindrical shape. On the other hand, the electrode base material 233 has a disk shape and has a hole constituting the communication portion 231 at the center in the radial direction. The noble metal tip 236 is laser-welded to the electrode base material 233 at the joint portion of both surfaces with the outer peripheral surface facing the inner peripheral surface of the hole of the electrode base material 233. The noble metal tip 236 constitutes a communication portion 231 of the ground electrode 230 together with a hole in the electrode base material 233. The communication portion 231 communicates the inside of the cavity 60 with the outside air through a communication hole surrounded by the inner peripheral wall 78 of the communication portion 231 on the tip side of the insulator 10.

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の後端側に設けられた接触部１２７は、絶縁碍子２１０の先端部２１６に接触されており、軸線Ｏ方向から見たときに、キャビティ６０の開口部６６は、接触部１２７の内側にある。接触部および連通部の一部を有する貴金属チップ２３６は、絶縁碍子２１０の先端部２１６と、接地電極２３０との間の間隙を塞いでいる。一方、電極母材２３３の後方に設けられ、絶縁碍子２１０の先端部２１６と対向する非接触部１４３は、絶縁碍子２１０の先端部２１６と接触していない。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との間の間隙や、その間隙と連通する主体金具５０と絶縁碍子２１０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２３６が、本発明における「接触部材」および「貴金属部材」に相当する。   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 contact portion 127 provided on the rear end side of the noble metal tip 236 is in contact with the front end portion 216 of the insulator 210. When viewed from the direction of the axis O, the opening 66 of the cavity 60 is connected to the contact portion 127. Inside. The noble metal tip 236 having a contact portion and a part of the communication portion blocks a gap between the tip portion 216 of the insulator 210 and the ground electrode 230. On the other hand, the non-contact portion 143 provided behind the electrode base material 233 and facing the tip portion 216 of the insulator 210 is not in contact with the tip portion 216 of the insulator 210. 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. And the gap between the metal shell 50 communicating with the gap and the insulator 210 are prevented from leaking. The noble metal tip 236 corresponds to the “contact member” and the “noble metal member” in the present invention.

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、孔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と非接触の状態に維持される。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周方向に一周して照射され、主体金具５０と接地電極２３０の電極母材２３３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 a hole 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 is maintained in a non-contact state with the tip portion 216 of the insulator 210. In this state, laser light is emitted around the circumferential direction 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 the metal shell 50 and the ground electrode 230 are irradiated. Welding with the electrode base material 233 is performed (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の孔に挿入され、連通部２３１に配置される（接触部材配置工程）。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、貴金属チップ２３６と絶縁碍子２１０の先端部２１６との間の間隙、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、および絶縁碍子２１０の先端部２１６との間の間隙に連通する主体金具５０と絶縁碍子２１０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（接触部材接合工程）。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。   And the noble metal chip | tip 236 formed in the cylinder shape is inserted in the hole of the electrode base material 233, and is arrange | positioned at the communication part 231 (contact member arrangement | positioning process). 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 constitutes a gap between the noble metal tip 236 and the tip portion 216 of the insulator 210, and the ground electrode 230. The gap between the electrode base material 233 and the tip 216 of the insulator 210 and the gap between the metal shell 50 and the insulator 210 communicating with the gap between the tip 216 of the insulator 210 are 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 (contact 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や、その間隙と連通する主体金具５０と絶縁碍子２１０との間に生じ得る間隙を、接触部１２７および連通部２３１の一部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. A contact portion 127 is defined as a gap that may be generated between the electrode base material 233 of the ground electrode 230 and the tip 216 of the insulator 210 or a gap that may be generated between the metal shell 50 communicating with the gap and the insulator 210. And it can block with the noble metal chip | tip 236 which comprises a part of communication part 231, and can prevent a fall of ignitability.

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Ｏ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、貴金属チップ２９１，２９２の接触部１２８，１２９を絶縁碍子２１０の先端部２１６に接触させながら、レーザ溶接する際に、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が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. Alternatively, the mating portion with the electrode base material 33 may be stepped. In this way, when laser welding is performed while the contact portions 128 and 129 of the noble metal tips 291 and 292 are in contact with the tip portion 216 of the insulator 210, the mating surfaces of the noble metal tips 291 and 292 and the electrode base material 33 are used. Laser light is prevented from entering the gaps, and more reliable bonding 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、電極母材２８３の孔に、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ってもよい。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。なお、第１の実施の形態の変形例と同様に、図１４および図１５に示すプラズマジェット点火プラグ２０２，２０３のように、貴金属チップ２９２の内周壁が連通部の内周壁１６１，１６２を構成してもよい。また、図１３に示すプラズマジェット点火プラグ２０１のように、貴金属チップ２９１の内周壁が連通部の内周壁１６０の一部を構成してもよい。   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 tip mounting portion 244 whose diameter is increased on the tip side in the axis O direction may be provided in the hole of the electrode base material 283. 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 may also be performed. 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. As in the modified example of the first embodiment, the inner peripheral wall of the noble metal tip 292 constitutes the inner peripheral walls 161 and 162 of the communicating portion as in the plasma jet ignition plugs 202 and 203 shown in FIGS. May be. Further, like the plasma jet ignition plug 201 shown in FIG. 13, the inner peripheral wall of the noble metal tip 291 may constitute a part of the inner peripheral wall 160 of the communicating portion.

［第３の実施の形態］
次に、第３の実施の形態のプラズマジェット点火プラグ３００について、図面を参照して説明する。まず、図１６を参照して、プラズマジェット点火プラグ３００の構造について説明する。図１６は、第３の実施の形態のプラズマジェット点火プラグ３００の先端部分を拡大した断面図である。 [Third Embodiment]
Next, a plasma jet ignition plug 300 according to a third embodiment will be described with reference to the drawings. First, the structure of the plasma jet ignition plug 300 will be described with reference to FIG. FIG. 16 is an enlarged cross-sectional view of the tip portion of the plasma jet ignition plug 300 according to the third embodiment.

なお、第３の実施の形態のプラズマジェット点火プラグ３００も、第１の実施の形態のプラズマジェット点火プラグ１００とは、接地電極３３０の形状の点、および絶縁碍子３１０の先端部３１６にチップ係合部が形成されていない点で異なるものである。従って上記同様、ここではプラズマジェット点火プラグ３００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 300 according to the third embodiment is also different from the plasma jet ignition plug 100 according to the first embodiment in terms of the shape of the ground electrode 330 and the tip 316 of the insulator 310. This is different in that no joint is formed. Therefore, as described above, the structure of the tip portion of the plasma jet ignition plug 300 will be described here, and the other portions are the same, and the description thereof will be omitted or simplified.

図１６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３３０は、電極母材３３３と貴金属チップ３３６とが一体に接合された複合部材からなる電極である。接地電極３３０は、円盤状の形状を有し、径方向中央に連通孔（連通部３３１）を有する。貴金属チップ３３６および電極母材３３３はそれぞれ、円盤状（円環状）の形状を有し、径方向中央には孔が形成されている。貴金属チップ３３６の厚みは電極母材３３３より薄い。電極母材３３３は孔の内周側に、軸線Ｏ方向後端側が段状に拡径されたチップ取付部３３４を有する。このチップ取付部３３４に貴金属チップ３３６の外縁部３３７が係合され、電極母材３３３の盤面（円盤状（円環状）の厚み方向と直交する面をいう。）に自身の盤面を揃えるように、貴金属チップ３３６が配置される。そして貴金属チップ３３６の外縁部３３７は電極母材３３３にレーザ溶接されている。貴金属チップ３３６は、電極母材３３３の孔と共に、接地電極３３０の連通部３３１を構成している。   As shown in FIG. 16, the ground electrode 330 disposed at the distal end portion 65 of the metal shell 50 is an electrode made of a composite member in which an electrode base material 333 and a noble metal tip 336 are integrally joined. The ground electrode 330 has a disk shape and has a communication hole (communication portion 331) at the center in the radial direction. Each of the noble metal tip 336 and the electrode base material 333 has a disk shape (annular shape), and a hole is formed in the radial center. The noble metal tip 336 is thinner than the electrode base material 333. The electrode base material 333 has a tip mounting portion 334 whose rear end side in the axis O direction is enlarged in a step shape on the inner peripheral side of the hole. The outer edge portion 337 of the noble metal tip 336 is engaged with the tip attachment portion 334, and the surface of the electrode base material 333 is aligned with the surface of the electrode base material 333 (referred to as a surface orthogonal to the disk-shaped (annular) thickness direction). A noble metal tip 336 is arranged. The outer edge 337 of the noble metal tip 336 is laser welded to the electrode base material 333. The noble metal tip 336 constitutes a communication portion 331 of the ground electrode 330 together with a hole of the electrode base material 333.

また、接地電極３３０は、貴金属チップ３３６が接合された側の面を絶縁碍子３１０側に向け、外縁部３３５（すなわち電極母材３３３の外縁部３３５）が主体金具５０の先端部６５の係合段部５７に係合されている。更に接地電極３３０は、絶縁碍子３１０の先端部３１６と接触した状態で主体金具５０にレーザ溶接され、両者が一体に接合されている。つまり、接地電極３３０と絶縁碍子３１０の先端部３１６との間の間隙や、その間隙に連通する主体金具５０と絶縁碍子３１０との間の間隙は、両者が接触した状態となっていることで塞がれている。貴金属チップ３３６および電極母材３３３の絶縁碍子３１０の先端部３１６と対向する部分のうち、先端部３１６と接触する部分は、接触部３２０である。一方、軸線Ｏ方向において電極母材３３３の非接触部３４０と主体金具５０とは、接触していない。この構成により、第１，第２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３３０と絶縁碍子３１０の先端部３１６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３３６が、本発明における「貴金属部材」に相当する。   Further, the ground electrode 330 has the surface on which the noble metal tip 336 is bonded facing toward the insulator 310, and the outer edge portion 335 (that is, the outer edge portion 335 of the electrode base material 333) is engaged with the distal end portion 65 of the metal shell 50. The step 57 is engaged. Further, the ground electrode 330 is laser-welded to the metal shell 50 in contact with the tip 316 of the insulator 310, and both are integrally joined. That is, the gap between the ground electrode 330 and the tip 316 of the insulator 310 and the gap between the metal shell 50 communicating with the gap and the insulator 310 are in contact with each other. It is blocked. Of the portions of the noble metal tip 336 and the electrode base material 333 that face the tip portion 316 of the insulator 310, the portion that contacts the tip portion 316 is a contact portion 320. On the other hand, the non-contact part 340 of the electrode base material 333 and the metal shell 50 are not in contact with each other in the direction of the axis O. With this configuration, as in the first and second embodiments, when the plasma formed in the cavity 60 is ejected outward, the plasma energy is transferred to the ground electrode 330 and the tip 316 of the insulator 310. Leakage into the gap between the two is prevented. The noble metal tip 336 corresponds to the “noble metal member” in the present invention.

次に、第３の実施の形態のプラズマジェット点火プラグ３００の製造方法について、図１７を参照して説明する。図１７は、第３の実施の形態のプラズマジェット点火プラグ３００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 300 of 3rd Embodiment is demonstrated with reference to FIG. FIG. 17 is a diagram illustrating a part of the manufacturing process of the plasma jet ignition plug 300 according to the third embodiment.

図１７に示すように、第３の実施のプラズマジェット点火プラグ３００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３１０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. 17, also in the plasma jet ignition plug 300 of the third embodiment, the insulator 310, in which the center electrode 20 and the terminal fitting 40 (see FIG. 1), which are previously prepared in separate steps, are integrally assembled. Similarly, the metal shell 50 manufactured in a separate process is integrally held by crimping (insulator holding process).

次に、電極母材３３３のチップ取付部３３４に貴金属チップ３３６の外縁部３３７が係合される。このとき、電極母材３３３の盤面と貴金属チップ３３６の盤面とが揃えられる。この状態で、貴金属チップ３３６と電極母材３３３との合わせ面を狙ってレーザ光が照射され、貴金属チップ３３６が電極母材３３３と一体に接合された接地電極３３０が作製される（貴金属部材接合工程）。貴金属チップ３３６は電極母材３３３の孔と共に連通部３３１を構成する。   Next, the outer edge portion 337 of the noble metal tip 336 is engaged with the tip attachment portion 334 of the electrode base material 333. At this time, the surface of the electrode base material 333 and the surface of the noble metal tip 336 are aligned. In this state, laser light is irradiated toward the mating surface between the noble metal tip 336 and the electrode base material 333, and the ground electrode 330 in which the noble metal tip 336 is integrally joined with the electrode base material 333 is produced (noble metal member joining). Process). The noble metal tip 336 forms a communication portion 331 together with the hole of the electrode base material 333.

そしてこの接地電極３３０が、絶縁碍子３１０の先端部３１６より先端側に配置される（配置工程）。このとき、接地電極３３０は、貴金属チップ３３６が露出された側（電極母材３３３と盤面を揃えた側）を絶縁碍子３１０の先端部３１６側へ向け、厚み方向を軸線Ｏ方向に揃えて配置される。そして、接地電極３３０は軸線Ｏ方向後端側へ向けて押さえられ、接触部３２０と先端部３１６とを接触させて、接地電極３３０と、絶縁碍子３１０の先端部３１６との間の間隙が塞がれる。この状態のまま、接地電極３３０の外縁部３３５（すなわち電極母材３３３の外縁部３３５）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周方向に一周して照射され、両者の溶接が行われる（接地電極接合工程）。このようにして、主体金具５０の先端部６５に接地電極３３０が接合されて、第３の実施の形態のプラズマジェット点火プラグ３００が完成する。   And this ground electrode 330 is arrange | positioned in the front end side rather than the front-end | tip part 316 of the insulator 310 (arrangement | positioning process). At this time, the ground electrode 330 is disposed such that the side where the noble metal tip 336 is exposed (the side where the electrode base material 333 and the board surface are aligned) is directed to the tip 316 side of the insulator 310 and the thickness direction is aligned with the axis O direction. Is done. Then, the ground electrode 330 is pressed toward the rear end side in the axis O direction, and the contact portion 320 and the tip portion 316 are brought into contact with each other, so that the gap between the ground electrode 330 and the tip portion 316 of the insulator 310 is closed. Can be removed. In this state, the laser beam makes a round in the circumferential direction and irradiates the target surface of the outer edge portion 335 of the ground electrode 330 (that is, the outer edge portion 335 of the electrode base material 333) and the engagement step portion 57 of the metal shell 50. Then, the two are welded (ground electrode joining step). In this way, the ground electrode 330 is joined to the distal end portion 65 of the metal shell 50, and the plasma jet ignition plug 300 of the third embodiment is completed.

第３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３３０を接合しており、製造過程において絶縁碍子３１０の破損が生じにくい。接地電極３３０の主体金具５０への接合時に接地電極３３０を絶縁碍子３１０側に押さえながら行うので、接地電極３３０と絶縁碍子３１０の先端部３１６との間に間隙を生じないようにすることができる。このため。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３３０と絶縁碍子３１０の先端部３１６との間の間隙に漏出することが回避され、着火性の低下を防止することができる。   Also in the third embodiment, the insulator 10 is caulked and held on the metal shell 50, and then the ground electrode 330 is joined to the metal shell 50, so that the insulator 310 is not easily damaged during the manufacturing process. Since the ground electrode 330 is pressed against the insulator 310 when the ground electrode 330 is joined to the metal shell 50, no gap is generated between the ground electrode 330 and the tip 316 of the insulator 310. . For this reason. 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 330 and the tip portion 316 of the insulator 310, and the ignitability is reduced. Can be prevented.

なお、第３の実施の形態のプラズマジェット点火プラグ３００も各種の変形が可能である。例えば、図１８に示す、プラズマジェット点火プラグ３０１の主体金具３５０のように、係合段部３５７に接地電極３３０を係合させたときの係合段部３５７の軸線Ｏ方向先端側の面の位置を、接地電極３３０の軸線Ｏ方向先端側の面の位置よりも、軸線Ｏ方向後端側としてもよい。このようにすれば、上記同様、係合段部３５７と接地電極３３０の外縁部３３５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。また、図示しないが、係合段部３５７に接地電極３３０を係合させたときの係合段部３５７の軸線Ｏ方向先端側の面の位置を、接地電極３３０の軸線Ｏ方向先端側の面の位置よりも、軸線Ｏ方向先端側としてもよい。   The plasma jet ignition plug 300 according to the third embodiment can be variously modified. For example, like the metal shell 350 of the plasma jet ignition plug 301 shown in FIG. 18, the surface of the engagement step portion 357 on the front side in the axis O direction when the ground electrode 330 is engaged with the engagement step portion 357. The position may be the rear end side in the axis O direction with respect to the position of the surface of the ground electrode 330 on the front side in the axis O direction. In this way, similarly to the above, when joining the engaging step portion 357 and the outer edge portion 335 of the ground electrode 330, it is easy to irradiate the laser beam from an angle that intersects the axis O with an acute angle, and more reliable joining is achieved. It can be carried out. Further, although not shown, the position of the surface of the engagement step portion 357 on the tip side in the axis O direction when the ground electrode 330 is engaged with the engagement step portion 357 is the surface of the ground electrode 330 on the tip side in the axis O direction. It is good also as a front end side of an axis O direction rather than the position.

また、図１９に示す、プラズマジェット点火プラグ３０２や、図２０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、電極母材３８２の孔に、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、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. 19 and the plasma jet ignition plug 303 shown in FIG. 20, 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. Further, on the electrode base material 382 side, a stepped tip mounting portion 344 having a diameter enlarged at the front end side in the axis O direction is provided in the hole of the electrode base material 382. That is, the noble metal tip 392 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の盤面から軸線Ｏ方向後端側に突出する構成とし、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（接触部３２１）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 has a configuration in which a part of the noble metal tip 392 protrudes from the surface of the electrode base material 382 toward the rear end side in the axis O direction when the noble metal tip 382 is joined. At the time of joining 372, the protruding portion 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. The smoothness of the (contact portion 321) can be easily managed.

更に、図１９に示した主体金具３５１の係合段部３５８や、図２０に示した主体金具３５０の係合段部３５７のように、係合段部３５８，３５７に接地電極３７２を係合させたときの係合段部３５８，３５７の軸線Ｏ方向先端側の面の位置を、接地電極３３０の軸線Ｏ方向先端側の面の位置よりも、軸線Ｏ方向後端側となるように、あるいは軸線Ｏ方向先端側となるようにするとよい。こうすれば、上記同様、貴金属チップ３９２の接触部３２１を絶縁碍子３１０の先端部３１６に接触させながら、係合段部３５８，３５７と接地電極３７２の外縁部３４５とを接合させる際に、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 ground electrode 372 is engaged with the engagement step portions 358 and 357, such as the engagement step portion 358 of the metal shell 351 shown in FIG. 19 and the engagement step portion 357 of the metal shell 350 shown in FIG. The position of the engagement step portions 358 and 357 at the front end side in the axis O direction of the engagement step portions 358 and 357 is positioned on the rear end side in the axis O direction from the position of the surface on the front end side in the axis O direction of the ground electrode 330. Or it is good to make it be the front side of the axis O direction. In this way, as described above, the laser is used when joining the engaging step portions 358 and 357 and the outer edge portion 345 of the ground electrode 372 while the contact portion 321 of the noble metal tip 392 is in contact with the tip portion 316 of the insulator 310. Light can be easily irradiated from an angle that intersects the axis O with an acute angle, and more reliable bonding can be performed.

なお、第１の実施の形態の変形例と同様に、図１９および図２０に示すプラズマジェット点火プラグ３０２，３０３のように、貴金属チップ３９２の内周壁が連通部の内周壁１６４を構成してもよい。また、図１８に示すプラズマジェット点火プラグ３０１のように、貴金属チップ３３６の内周壁が連通部の内周壁１６３の一部を構成してもよい。更に、図１９および図２０に示すプラズマジェット点火プラグ３０２，３０３のように、貴金属チップ３９２のみが接触部３２１を備え、電極母材３８２の非接触部３４７は軸線Ｏ方向において主体金具３５１，３５０および絶縁碍子３１０の双方と接触しない構成としてもよい。また、図１８に示すプラズマジェット点火プラグ３０１のように、貴金属チップ３３６および電極母材３３３の双方が接触部３２０を備え、電極母材３３３の非接触部３４０は軸線Ｏ方向において主体金具３５０と接触しない構成としてもよい。   As in the modification of the first embodiment, the inner peripheral wall of the noble metal tip 392 constitutes the inner peripheral wall 164 of the communicating portion, as in the plasma jet ignition plugs 302 and 303 shown in FIGS. Also good. Further, like the plasma jet ignition plug 301 shown in FIG. 18, the inner peripheral wall of the noble metal tip 336 may constitute a part of the inner peripheral wall 163 of the communicating portion. Further, like the plasma jet ignition plugs 302 and 303 shown in FIGS. 19 and 20, only the noble metal tip 392 includes the contact portion 321, and the non-contact portion 347 of the electrode base material 382 is the metal shell 351, 350 in the axis O direction. In addition, it may be configured not to contact both the insulator 310 and the insulator 310. Further, like the plasma jet ignition plug 301 shown in FIG. 18, both the noble metal tip 336 and the electrode base material 333 are provided with a contact part 320, and the non-contact part 340 of the electrode base material 333 is connected to the metal shell 350 in the axis O direction. It is good also as a structure which does not contact.

［第４の実施の形態］
次に、第４の実施の形態のプラズマジェット点火プラグ４００について、図面を参照して説明する。まず、図２１を参照して、プラズマジェット点火プラグ４００の構造について説明する。図２１は、第４の実施の形態のプラズマジェット点火プラグ４００の先端部分を拡大した断面図である。 [Fourth Embodiment]
Next, a plasma jet ignition plug 400 according to a fourth embodiment will be described with reference to the drawings. First, the structure of the plasma jet ignition plug 400 will be described with reference to FIG. FIG. 21 is an enlarged cross-sectional view of the tip portion of the plasma jet ignition plug 400 according to the fourth embodiment.

上記同様、第４の実施の形態のプラズマジェット点火プラグ４００も、第１の実施の形態のプラズマジェット点火プラグ１００とは、接地電極４３０の形状の点、および絶縁碍子４１０の先端部４１６にチップ係合部が形成されていない点で異なるものである。従って、ここではプラズマジェット点火プラグ４００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。   Similar to the above, the plasma jet ignition plug 400 of the fourth embodiment is also different from the plasma jet ignition plug 100 of the first embodiment in that the ground electrode 430 has a shape and the tip of the insulator 410 has a tip. The difference is that the engaging portion is not formed. Therefore, the structure of the tip portion of the plasma jet ignition plug 400 will be described here, and the other portions are the same, and the description thereof will be omitted or simplified.

図２１に示すように、主体金具４５０の先端部４６５に配設された接地電極４３０は、電極母材４３３と貴金属チップ４３６とが一体に接合された複合部材からなる電極である。接地電極４３０は、円盤状の形状を有し、径方向中央に連通孔（連通部４３１）が形成されている。貴金属チップ４３６および電極母材４３３はそれぞれ、円盤状（円環状）に形成されており、径方向中央に孔を有する。貴金属チップ４３６の厚みは電極母材４３３より薄い。電極母材４３３は自身の孔の内周側に、軸線Ｏ方向先端側が段状に拡径されたチップ取付部４３４を有する。このチップ取付部４３４に貴金属チップ４３６の外縁部４３７が係合され、電極母材４３３の盤面に自身の盤面を揃えるように、貴金属チップ４３６が配置される。そして貴金属チップ４３６は外縁部４３７を電極母材４３３にレーザ溶接されており、電極母材４３３の孔と共に、接地電極４３０の連通部４３１を構成している。プラズマジェット点火プラグ４００では、電極母材４３３の内周壁の一部と、貴金属チップ４３６の内周壁とで、連通部４３１の内周壁１６６を構成する。   As shown in FIG. 21, the ground electrode 430 disposed at the tip 465 of the metal shell 450 is an electrode made of a composite member in which an electrode base material 433 and a noble metal tip 436 are integrally joined. The ground electrode 430 has a disk shape, and a communication hole (communication portion 431) is formed in the center in the radial direction. The noble metal tip 436 and the electrode base material 433 are each formed in a disc shape (annular shape) and have a hole in the center in the radial direction. The noble metal tip 436 is thinner than the electrode base material 433. The electrode base material 433 has a tip mounting portion 434 whose diameter is expanded stepwise on the tip side in the axis O direction on the inner peripheral side of its own hole. The noble metal tip 436 is disposed so that the outer edge portion 437 of the noble metal tip 436 is engaged with the tip attachment portion 434 and the board surface of the electrode base material 433 is aligned with its own board surface. The noble metal tip 436 is laser-welded at the outer edge portion 437 to the electrode base material 433, and constitutes a communication portion 431 of the ground electrode 430 together with a hole in the electrode base material 433. In the plasma jet ignition plug 400, a part of the inner peripheral wall of the electrode base material 433 and the inner peripheral wall of the noble metal tip 436 constitute the inner peripheral wall 166 of the communication portion 431.

また、接地電極４３０は、貴金属チップ４３６が接合された側の面を軸線Ｏ方向前方へ向け、外縁部４３５（すなわち電極母材４３３の外縁部４３５）が主体金具４５０の先端部４６５の係合段部４５７に係合されている。更に接地電極４３０は、絶縁碍子４１０の先端部４１６と接触した状態で主体金具４５０にレーザ溶接されている。つまり、接地電極４３０と絶縁碍子４１０の先端部４１６との間の間隙は、両者が接触した状態となっていることで塞がれている。電極母材４３３が絶縁碍子４１０の先端部４１６と接触する部分は、接触部４２０である。一方、電極母材４３３は、主体金具４５０と対向する面に非接触部４４０を有し、軸線Ｏ方向において主体金具４５０と接触しない。この構成により、第３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４３０と絶縁碍子４１０の先端部４１６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４３６が、本発明における「貴金属部材」に相当する。   In addition, the ground electrode 430 has the surface on which the noble metal tip 436 is bonded facing forward in the direction of the axis O, and the outer edge portion 435 (that is, the outer edge portion 435 of the electrode base material 433) is engaged with the tip portion 465 of the metal shell 450. The step 457 is engaged. Further, the ground electrode 430 is laser-welded to the metal shell 450 in a state where the ground electrode 430 is in contact with the tip 416 of the insulator 410. That is, the gap between the ground electrode 430 and the tip portion 416 of the insulator 410 is closed by being in contact with each other. A portion where the electrode base material 433 contacts the tip 416 of the insulator 410 is a contact portion 420. On the other hand, the electrode base material 433 has a non-contact portion 440 on the surface facing the metallic shell 450 and does not contact the metallic shell 450 in the axis O direction. With this configuration, as in the third embodiment, when the plasma formed in the cavity 60 is ejected outward, the plasma energy is transferred between the ground electrode 430 and the tip portion 416 of the insulator 410. Leakage into the gap is prevented. The noble metal tip 436 corresponds to the “noble metal member” in the present invention.

次に、第４の実施の形態のプラズマジェット点火プラグ４００の製造方法について、図２２を参照して説明する。図２２は、第４の実施の形態のプラズマジェット点火プラグ４００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 400 of 4th Embodiment is demonstrated with reference to FIG. FIG. 22 is a diagram illustrating a part of the manufacturing process of the plasma jet ignition plug 400 according to the fourth embodiment.

図２２に示すように、第４の実施のプラズマジェット点火プラグ４００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４１０が、同様に別の工程において作製された主体金具４５０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. 22, also in the plasma jet ignition plug 400 of the fourth embodiment, the insulator 410, in which the center electrode 20 and the terminal fitting 40 (see FIG. 1) previously produced in separate steps are assembled together, is provided. Similarly, the metal shell 450 manufactured in another process is integrally held by crimping (insulator holding process).

次に、孔を有する円盤状の電極母材４３３が、絶縁碍子４１０の先端部４１６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４３３の外縁部４３５が、段状をなす主体金具４５０の係合段部４５７に嵌め込むように係合される。更に電極母材４３３が絶縁碍子４１０の先端部４１６へ向けて押さえられ、電極母材４３３と、絶縁碍子４１０の先端部４１６との間の間隙が塞がれる。そのまま電極母材４３３の外縁部４３５（図２１参照）と、主体金具４５０の係合段部４５７との合わせ面を狙ってレーザ光が周方向に一周して照射される。電極母材４３３の配置位置の調整を行いやすくするため、電極母材４３３が係合段部４５７に配置されたときの位置よりも係合段部４５７が軸線Ｏ方向先端側へ突出されるようになっており、レーザ光は軸線Ｏと鋭角に交差する角度から照射される。これにより、主体金具４５０と接地電極４３０の電極母材４３３とは、より確実に接合される（接地電極接合工程）。   Next, the disc-shaped electrode base material 433 having a hole is disposed on the distal end side from the distal end portion 416 of the insulator 410 (electrode base material disposing step). In this step, the outer edge portion 435 of the electrode base material 433 is engaged so as to be fitted into the engagement step portion 457 of the metal shell 450 having a step shape. Further, the electrode base material 433 is pressed toward the tip portion 416 of the insulator 410, and the gap between the electrode base material 433 and the tip portion 416 of the insulator 410 is closed. As it is, the laser beam is irradiated around the circumferential direction aiming at the mating surface between the outer edge portion 435 (see FIG. 21) of the electrode base material 433 and the engagement step portion 457 of the metal shell 450. In order to facilitate adjustment of the arrangement position of the electrode base material 433, the engagement step portion 457 protrudes toward the front end side in the axis O direction from the position when the electrode base material 433 is disposed in the engagement step portion 457. The laser beam is irradiated from an angle that intersects the axis O at an acute angle. Thereby, the metal shell 450 and the electrode base material 433 of the ground electrode 430 are more reliably joined (ground electrode joining step).

そして、筒状に形成された貴金属チップ４３６が電極母材４３３の孔に挿入され、連通部４３１に配置される（貴金属部材配置工程）。その状態で、貴金属チップ４３６と電極母材４３３との合わせ面を狙ってレーザ光が周方向に一周して照射され、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４３６は電極母材４３３と一体となって、連通部４３１を構成する。このようにして、主体金具４５０の先端部４６５に接地電極４３０が接合されて、第４の実施の形態のプラズマジェット点火プラグ４００が完成する。   Then, the noble metal tip 436 formed in a cylindrical shape is inserted into the hole of the electrode base material 433 and arranged in the communication portion 431 (noble metal member arranging step). In this state, the laser beam is irradiated around the circumferential direction aiming at the mating surface between the noble metal tip 436 and the electrode base material 433, and the two are welded (noble metal member joining step). The noble metal tip 436 is integrated with the electrode base material 433 to form a communication portion 431. In this way, the ground electrode 430 is joined to the distal end portion 465 of the metal shell 450, and the plasma jet ignition plug 400 of the fourth embodiment is completed.

この第４の実施の形態においても、主体金具４５０に絶縁碍子４１０を加締め保持させてから主体金具４５０に接地電極４３０を接合しており、製造過程において絶縁碍子４１０の破損が生じにくい。また、接地電極４３０の主体金具４５０への接合時に接地電極４３０を絶縁碍子４１０側に押さえながら行うので、接地電極４３０と絶縁碍子４１０の先端部４１６との間に間隙を生じないようにすることができ、着火性の低下を防止することができる。   Also in the fourth embodiment, the insulator 410 is caulked and held on the metal shell 450, and then the ground electrode 430 is joined to the metal shell 450, so that the insulator 410 is not easily damaged during the manufacturing process. Further, since the ground electrode 430 is pressed to the insulator 410 side when the ground electrode 430 is joined to the metal shell 450, a gap is not generated between the ground electrode 430 and the tip 416 of the insulator 410. It is possible to prevent ignitability from being lowered.

なお、第４の実施の形態のプラズマジェット点火プラグ４００も各種の変形が可能である。例えば、図２３に示す、プラズマジェット点火プラグ４０１の主体金具４５１のように、係合段部４５８に接地電極４３０を係合させたときの軸線Ｏ方向に係合段部４５８の先端側の面の位置を、接地電極４３０の先端側の面の位置よりも後端側にしてもよい。このようにすることで、上記同様、係合段部４５８と接地電極４３０の外縁部４３５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。   The plasma jet ignition plug 400 of the fourth embodiment can be variously modified. For example, like the metal shell 451 of the plasma jet ignition plug 401 shown in FIG. 23, the surface on the distal end side of the engagement step portion 458 in the axis O direction when the ground electrode 430 is engaged with the engagement step portion 458. This position may be on the rear end side of the position of the surface on the front end side of the ground electrode 430. By doing so, similarly to the above, when joining the engagement step portion 458 and the outer edge portion 435 of the ground electrode 430, it is possible to easily irradiate the laser beam from an angle intersecting the axis O with an acute angle, and more reliable joining. It can be performed.

また、図２４に示す、プラズマジェット点火プラグ４０２のように、接地電極４７２は、貴金属チップを備えないものであってもよい。更に、第３，第４の実施の形態のプラズマジェット点火プラグでは、主体金具が取付段部を備えていたが、図２５に示す、プラズマジェット点火プラグ４０３のように、主体金具４５３は、取付段部を備えないものであってもよい。これらの場合でも、接地電極４７２，４７３の接触部４２１，４２２を主体金具４５２，４５３に接合する際に、接地電極４７２を絶縁碍子４１０の先端部４１６側に押さえながら行えば、接地電極４７２，４７３と絶縁碍子４１０の先端部４１６との間に間隙が生じないようにすることができる。プラズマジェット点火プラグ４０２，４０３では、貴金属チップを備えない接地電極４７２，４７３の内周壁が、連通部の内周壁１６７，１６８を構成する。   Further, like the plasma jet ignition plug 402 shown in FIG. 24, the ground electrode 472 may not include a noble metal tip. Furthermore, in the plasma jet ignition plugs of the third and fourth embodiments, the metal shell is provided with a mounting step portion. However, like the plasma jet ignition plug 403 shown in FIG. You may not provide a step part. Even in these cases, when the contact portions 421 and 422 of the ground electrodes 472 and 473 are joined to the metal shells 452 and 453, if the ground electrode 472 is pressed against the tip portion 416 side of the insulator 410, the ground electrode 472 It is possible to prevent a gap from being generated between 473 and the tip portion 416 of the insulator 410. In the plasma jet ignition plugs 402 and 403, the inner peripheral walls of the ground electrodes 472 and 473 that do not include the noble metal tip constitute the inner peripheral walls 167 and 168 of the communication portion.

上記説明した第１〜第４の実施の形態のプラズマジェット点火プラグでは、貴金属チップとして、筒状あるいは円環状のものを例に説明を行った。そのうち、第３，第４の実施の形態のプラズマジェット点火プラグでは、電極母材あるいは電極母材に接合された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、必ずしも貴金属チップが筒状あるいは円環状である必要はない。すなわち、第３，第４の実施の形態では、少なくとも電極母材が円環状をなし、その電極母材が絶縁碍子の先端部に接触しつつ主体金具に接合されれば十分に、両者の間に生じ得る間隙を塞ぐことができる。従って、貴金属チップは連通部の一部として電極母材に接合され、その貴金属チップと中心電極との間で火花放電が行われる構成（すなわち、電極母材と中心電極との間の絶縁破壊抵抗値よりも貴金属チップと中心電極との間の絶縁破壊抵抗値が低い構成）となれば足りる。   In the plasma jet spark plugs of the first to fourth embodiments described above, the noble metal tip has been described as an example of a cylindrical or annular shape. Among them, in the plasma jet ignition plugs of the third and fourth embodiments, the gap between the ground electrode and the tip of the insulator is closed using the electrode base material or the noble metal tip joined to the electrode base material. For this reason, the noble metal tip is not necessarily cylindrical or annular. That is, in the third and fourth embodiments, at least the electrode base material has an annular shape, and it is sufficient that the electrode base material is joined to the metal shell while being in contact with the tip of the insulator. It is possible to close gaps that may occur. Therefore, the noble metal tip is joined to the electrode base material as a part of the communication portion, and a spark discharge is performed between the noble metal tip and the center electrode (that is, the dielectric breakdown resistance between the electrode base material and the center electrode). The dielectric breakdown resistance value between the noble metal tip and the center electrode is lower than the value).

第１〜第４の実施の形態のプラズマジェット点火プラグでは、接触部が接地電極の径方向内周壁側に設けられていた。そして、第１，第２の実施の形態のプラズマジェット点火プラグのように、接地電極と絶縁碍子の先端部との間に間隙がある場合でも、その間隙はキャビティの内部と連通しておらず、着火性の低下を最大限防止する構成となっていた。しかし、接地電極の径方向における接触部の設置位置は、上記実施形態に限定されず、例えば、接触部が接地電極の径方向中央部に設けられてもよい。すなわち、接地電極と絶縁碍子の先端部との間に間隙がキャビティの内部と連通していてもよい。このような場合であっても、接触部が存在する部位の接地電極と絶縁碍子の先端部との間に間隙、およびその間隙に連通する主体金具と絶縁碍子との間に間隙を塞ぐことができる。ただし、着火性の低下を防止する観点から、接地電極と絶縁碍子の先端部との間にキャビティの内部と連通する間隙がある場合、その間隙の容積が小さいほど好ましい。   In the plasma jet ignition plugs of the first to fourth embodiments, the contact portion is provided on the radially inner wall side of the ground electrode. And even if there is a gap between the ground electrode and the tip of the insulator as in the plasma jet ignition plug of the first and second embodiments, the gap is not in communication with the inside of the cavity. Therefore, it was configured to prevent the decrease in ignitability as much as possible. However, the installation position of the contact portion in the radial direction of the ground electrode is not limited to the above embodiment, and for example, the contact portion may be provided in the central portion in the radial direction of the ground electrode. That is, the gap may be communicated with the inside of the cavity between the ground electrode and the tip of the insulator. Even in such a case, it is possible to close the gap between the ground electrode in the portion where the contact portion exists and the tip of the insulator, and between the metal shell and the insulator communicating with the gap. it can. However, from the viewpoint of preventing a decrease in ignitability, when there is a gap communicating with the inside of the cavity between the ground electrode and the tip of the insulator, it is preferable that the volume of the gap is smaller.

そして同様に、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。更に、接触部材として貴金属チップを用いていたが、接触部材として貴金属以外の導電性部材からなる金属チップを用いてもよい。   Similarly, in the plasma jet spark plugs of the first and second embodiments, the noble metal tip is used to close the gap between the ground electrode and the tip of the insulator, so that the electrode base material is not necessarily used. It is not necessary to have an annular shape, and it is sufficient that 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. Furthermore, although the noble metal tip is used as the contact member, a metal tip made of a conductive member other than the noble metal may be used as the contact member.

また、第１〜第４の実施の形態のプラズマジェット点火プラグの説明においては、絶縁碍子の主体金具による保持方法について所謂熱加締めによる構成を説明したが、この保持方法についてはなんら限定されることはない。例えば、加熱を行わず冷間加工にて加締めを行ってもよいし、タルクを用いず、直接またはパッキン等を介して間接的に加締部の端部が絶縁碍子を押圧して絶縁碍子を保持してもよい。更には、加締めによらずとも絶縁碍子を保持できればよく、その方法を限定するものではない。しかしながら、保持方法として加締め等により絶縁碍子が軸線Ｏ方向の先端側へ押圧される方法である場合には、本発明に係る製造過程のように、絶縁碍子の先端部に当接するものがない状態で主体金具による加締め保持を行えば、絶縁碍子の破損を防ぐ効果を有する面で好適である。   In the description of the plasma jet ignition plug according to the first to fourth embodiments, the structure by the so-called heat caulking has been described with respect to the method of holding the insulator by the metal shell, but this holding method is not limited at all. There is nothing. For example, it may be crimped by cold working without heating, or without using talc, either directly or indirectly through packing, etc., the end of the crimped portion presses the insulator, and the insulator May be held. Furthermore, the method is not limited as long as the insulator can be held regardless of caulking. However, when the insulator is pressed toward the tip end side in the direction of the axis O by caulking or the like as a holding method, there is nothing that comes into contact with the tip portion of the insulator as in the manufacturing process according to the present invention. If the caulking is held with the metal shell in the state, it is preferable in terms of the effect of preventing breakage of the insulator.

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
３３ 電極母材
３４ 内突部
３５ 外縁部
３６ 貴金属チップ
３７ 外突部
３８ 接触部
５０ 主体金具
６０ キャビティ
６１ 先端小径部
６６ 開口部
７０ 内周壁
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 33 Electrode base material 34 Inner protrusion 35 Outer edge part 36 Precious metal tip 37 Outer protrusion part 38 Contact part 50 Metallic fitting 60 Cavity 61 Tip small diameter part 66 Opening 70 inner wall 100 plasma jet spark plug

Claims (5)

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面を前記軸孔内先端側に収容すると共に、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、
前記絶縁碍子の前記軸線方向に垂直な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に配置されると共に、前記絶縁碍子の前記先端部と環状に接触し、前記軸線方向から見たときに前記キャビティの開口部が自身の内側にある接触部と、前記キャビティの内部を外気と連通させる連通部とを有する接地電極と
を備え、
前記接地電極は、
前記連通部を有し、前記軸線方向には前記絶縁碍子と非接触である一方、前記主体金具とは接触すると共に、自身の外縁部が前記主体金具と接合されて前記主体金具と電気的に接続されている電極母材と、
前記連通部の一部、および前記接触部を有する接触部材と
が接合された複合部材からなる電極であり、
前記接地電極の前記電極母材は、前記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接触部材は、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、
前記接地電極は、前記外突部と前記内突部とを前記軸線方向に重ねつつ、前記外突部を前記内突部よりも前記軸線方向先端側に配置させてい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;
Having an axial hole extending in the axial direction, accommodating the distal end surface of the central electrode on the distal end side in the axial hole, and an insulator for holding 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 a radial circumference perpendicular to the axial direction of the insulator;
The insulator is disposed closer to the distal end side in the axial direction than the distal end portion of the insulator, and is in annular contact with the distal end portion of the insulator, so that the opening of the cavity is located inside itself when viewed from the axial direction. A grounding electrode having a contact portion and a communication portion for communicating the inside of the cavity with the outside air,
The ground electrode is
While having the communication part and being in non-contact with the insulator in the axial direction, the outer metal is in contact with the metal shell, and its outer edge is joined to the metal shell to electrically connect with the metal shell. A connected electrode base material;
An electrode comprising a composite member in which a part of the communication portion and a contact member having the contact portion are joined together ,
The electrode base material of the ground electrode has an inner protrusion that is a part located on the innermost side in the radial direction, and the contact member of the ground electrode is located on the outer side in the radial direction than the inner protrusion. Having an outer protrusion located,
The plasma is characterized in that the ground electrode is arranged such that the outer protrusion and the inner protrusion overlap in the axial direction, and the outer protrusion is disposed closer to the distal end side in the axial direction than the inner protrusion. Jet spark plug. 前記接地電極が有する前記連通部の内周壁の少なくとも一部は、貴金属からなる貴金属部材で形成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。 The plasma jet ignition plug according to claim 1 , wherein at least a part of an inner peripheral wall of the communication portion of the ground electrode is formed of a noble metal member made of a noble metal. 前記絶縁碍子の前記先端部には、前記接触部が係合する係合部が設けられていることを特徴とする請求項１又は２に記載のプラズマジェット点火プラグ。 The plasma jet ignition plug according to claim 1 or 2 , wherein an engagement portion with which the contact portion engages is provided at the tip portion of the insulator. 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面を前記軸孔内先端側に収容すると共に、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、
前記絶縁碍子の前記軸線方向に垂直な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に配置されると共に、前記絶縁碍子の前記先端部と環状に接触し、前記軸線方向から見たときに前記キャビティの開口部が自身の内側にある接触部と、前記キャビティの内部を外気と連通させる連通部とを有する接地電極と
を備え、
前記接地電極は、前記径方向において最も内側に位置する部位である内突部および前記連通部を有し、前記軸線方向には前記絶縁碍子と非接触である一方、前記主体金具とは接触する電極母材と、
前記内突部よりも前記径方向の外側に位置する外突部、前記連通部の一部、および前記接触部を有する接触部材と
が接合された複合部材からなる電極である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、
前記碍子保持工程後、前記電極母材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電極母材配置工程と、
前記接地電極を構成する前記電極母材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、
前記接触部材を前記電極母材の前記連通部に配置しつつ前記軸線方向に移動させ、前記内突部よりも前記外突部が前記軸線方向先端側に配置されるように、前記軸線方向に、前記電極母材の前記内突部を前記接触部材の前記外突部に重ねつつ、前記接触部を前記絶縁碍子の先端部に接触させて配置する接触部材配置工程と、
前記接触部材を前記絶縁碍子の先端部に接触させたまま、前記電極母材に前記接触部材を接合する接触部材接合工程と
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;
Having an axial hole extending in the axial direction, accommodating the distal end surface of the central electrode on the distal end side in the axial hole, and an insulator for holding 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 a radial circumference perpendicular to the axial direction of the insulator;
The insulator is disposed closer to the distal end side in the axial direction than the distal end portion of the insulator, and is in annular contact with the distal end portion of the insulator, so that the opening of the cavity is located inside itself when viewed from the axial direction. A grounding electrode having a contact portion and a communication portion for communicating the inside of the cavity with the outside air,
The ground electrode has an inner protrusion and a communication portion that are the innermost portion in the radial direction, and is in non-contact with the insulator in the axial direction, while in contact with the metal shell. An electrode base material;
A plasma jet ignition plug that is an electrode composed of a composite member in which an outer protrusion located outside the inner protrusion in the radial direction, a part of the communication portion, and a contact member having the contact portion are joined. A manufacturing method comprising:
An insulator holding step for holding the insulator holding the center electrode on the metal shell;
After the insulator holding step, an electrode base material placement step of placing the electrode base material closer to the tip end side in the axial direction than the tip end portion of the insulator,
A ground electrode joining step of joining an outer edge of the electrode base material constituting the ground electrode to the metal shell;
The contact member is moved in the axial direction while being arranged in the communication portion of the electrode base material, and the outer projection is arranged in the axial direction so as to be arranged on the distal end side in the axial direction with respect to the inner projection. A contact member placement step of placing the contact portion in contact with the tip of the insulator while overlapping the inner protrusion of the electrode base material with the outer protrusion of the contact member;
And a contact member joining step of joining the contact member to the electrode base material while the contact member is in contact with the tip of the insulator. 前記絶縁碍子の前記先端部には、前記接地電極の前記接触部が係合する係合部が設けられおり、
前記接触部は前記係合部に係合されることを特徴とする請求項４に記載のプラズマジェット点火プラグの製造方法。 At the tip of the insulator, an engagement portion is provided to engage the contact portion of the ground electrode,
The method of manufacturing a plasma jet ignition plug according to claim 4 , wherein the contact portion is engaged with the engagement portion.
JP2009161483A 2007-03-30 2009-07-08 Plasma jet ignition plug and method for manufacturing the same Expired - Fee Related JP4843076B2 (en)

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