JP5508641B2

JP5508641B2 - Spark plug

Info

Publication number: JP5508641B2
Application number: JP2011022203A
Authority: JP
Inventors: 靖坂倉; 征信長谷川
Original assignee: NGK Spark Plug Co Ltd
Current assignee: NGK Spark Plug Co Ltd
Priority date: 2011-02-03
Filing date: 2011-02-03
Publication date: 2014-06-04
Anticipated expiration: 2031-02-03
Also published as: JP2012164445A

Description

本発明は、内燃機関やバーナー等の燃料に点火する点火プラグに関する。 The present invention relates to a spark plug that ignites fuel such as an internal combustion engine or a burner.

図９は、例えばガスタービンエンジンに使用する点火プラグ１００を示したものである。
この点火プラグ１００は、軸方向に軸孔を有し自身の一端に中心電極１０１を有する絶縁体１０２と、軸方向に貫通する貫通孔１０３を有してその貫通孔１０３内に前記絶縁体１０２が装着される主体金具１０４と、を備えており、前記中心電極１０１と、エンジン１０５側に設けられる接地電極（図示せず）との間で火花を発生させて燃料に点火するものである。 FIG. 9 shows a spark plug 100 used in, for example, a gas turbine engine.
This spark plug 100 has an insulator 102 having an axial hole in the axial direction and having a center electrode 101 at one end of the spark plug 100 and a through hole 103 penetrating in the axial direction. A metal fitting 104 is mounted, and a spark is generated between the center electrode 101 and a ground electrode (not shown) provided on the engine 105 side to ignite the fuel.

前記絶縁体１０２は、中心電極１０１が配置される端部側を先端側とし反対側を後端側としたとき、中間に位置する最大径部１０２ａの後端側にそれより小径の後軸部１０２ｂが形成され、一方、前記最大径部１０２ａの先端部側にもそれより小径の先軸部１０２ｃが形成され、さらに該先軸部１０２ｃの先端側にさらに小径の最先軸部１０２ｄが形成されている。 The insulator 102 has a rear shaft portion having a smaller diameter on the rear end side of the maximum diameter portion 102a located in the middle when the end portion side on which the center electrode 101 is disposed is the front end side and the opposite side is the rear end side. 102b is formed. On the other hand, a tip end portion 102c having a smaller diameter is also formed on the tip end side of the maximum diameter portion 102a, and a tip end shaft portion 102d having a smaller diameter is further formed on the tip end side of the tip shaft portion 102c. Has been.

前記主体金具１０４は、外周に、エンジン１０５側のプラグ取付孔１０６に形成された雌ネジ部に螺合する雄ネジ部１０７を有する。
また、主体金具１０４は、前記中心電極１０１が配置される端部側を先端側とし反対側を後端側としたとき、前記雄ネジ部１０７より後端側に拡径方向に突設されて前記プラグ取付孔１０６に向かう側の面を座面１０８とする締め止め部材１０９を有し、該締め止め部材１０９より後端側に六角ボルトの頭部形態である工具係合部１１０を有する。
また、主体金具１０４は、前記工具係合部１１０の後端側に突設されて前記絶縁体１０２の後端側を囲う筒状のシールド部１１１と、該シールド部１１１の後端を内向きに加締めて形成される加締め蓋１１２と、を備えている。
また、主体金具１０４の貫通孔１０３は、前記絶縁体１０２の最大径部１０２ａとほぼ同径の後孔部１０３ａと、絶縁体１０２の先軸部１０２ｃとほぼ同径の中孔部１０３ｂと、絶縁体１０２の最先軸部１０２ｄとほぼ同径の先孔部１０３ｃとを有する段付孔形態である。 The metal shell 104 has a male screw portion 107 that is screwed into a female screw portion formed in the plug mounting hole 106 on the engine 105 side on the outer periphery.
The metal shell 104 protrudes from the male screw portion 107 toward the rear end side in the diameter increasing direction when the end side where the center electrode 101 is disposed is the front end side and the opposite side is the rear end side. A fastening member 109 having a seating surface 108 as a surface facing the plug mounting hole 106 is provided, and a tool engaging portion 110 having a hexagonal bolt head shape is provided on the rear end side of the fastening member 109.
Further, the metal shell 104 protrudes from the rear end side of the tool engaging portion 110 so as to surround the rear end side of the insulator 102, and the rear end of the shield portion 111 faces inward. And a caulking lid 112 formed by caulking.
Further, the through hole 103 of the metal shell 104 has a rear hole portion 103a having substantially the same diameter as the maximum diameter portion 102a of the insulator 102, a middle hole portion 103b having substantially the same diameter as the front shaft portion 102c of the insulator 102, This is a stepped hole configuration having a foremost shaft portion 102d of the insulator 102 and a front hole portion 103c having substantially the same diameter.

そして点火プラグ１００は、前記主体金具１０４の貫通孔１０３に後孔部１０３ａ側から絶縁体１０２を挿通すると共に、その際、絶縁体１０２の先軸部１０２ｃと最先軸部１０２ｄとの境界に形成される境界段部１１３と、主体金具１０４の貫通孔１０３の中孔部１０３ｂと先孔部１０３ｃの境界に形成される棚段部１１４とを、両者の間に第１のパッキン１１５を介在させて係合させ、さらに前記主体金具１０４の貫通孔１０３の後孔部１０３ａの内周面と、前記絶縁体１０２の後軸部１０２の外周面とにより囲まれた円筒形状の空間１１６に、第２のパッキン１１７と、例えばタルクやカオリン等のセラミックで形成された粉末状の緩衝材１１８と、緩衝用のパッキン１１９を順に装填すると共に該空間１１６の後端側に絶縁碍管である押さえ管１２０を装填し、該押さえ管１２０の後端部（厳密には押さえ管１２０の後端部に載置したパッキン１２０ａ（アルミニウム製）を介して）を前記加締め蓋１１２で押さえるようにしている。従って、加締め蓋１１２により、主体金具１０４と絶縁体１０２の間の空間１１６に緩衝材１１８が加圧状態に封入され、その圧力で第１のパッキン１１５が主体金具１０４の棚段部１１４と絶縁体１０２の境界段部１１３の双方に密着して前記空間１１６の気密を保つ。 The spark plug 100 inserts the insulator 102 into the through hole 103 of the metal shell 104 from the rear hole portion 103a side, and at that time, at the boundary between the front shaft portion 102c and the frontmost shaft portion 102d of the insulator 102. The first step 115 is interposed between the boundary step 113 formed and the shelf step 114 formed at the boundary between the middle hole 103b and the front hole 103c of the through hole 103 of the metal shell 104. In the cylindrical space 116 surrounded by the inner peripheral surface of the rear hole portion 103a of the through hole 103 of the metal shell 104 and the outer peripheral surface of the rear shaft portion 102 of the insulator 102, A second packing 117, a powdery cushioning material 118 made of ceramic such as talc or kaolin, and a cushioning packing 119 are sequentially loaded, and an insulating soot pipe is provided on the rear end side of the space 116. The holding tube 120 is loaded, and the rear end portion of the holding tube 120 (strictly, the packing 120a (made of aluminum) placed on the rear end portion of the holding tube 120) is pressed by the crimping lid 112. ing. Therefore, the cushioning material 118 is sealed in the space 116 between the metal shell 104 and the insulator 102 by the crimping lid 112 in a pressurized state, and the first packing 115 is attached to the shelf step 114 of the metal shell 104 by the pressure. The space 116 is kept airtight by being in close contact with both the boundary step portions 113 of the insulator 102.

特開平１１−２４２９８２号公報Japanese Patent Application Laid-Open No. 11-242982

従来より、長寿命の点火プラグ１００を得るために、主体金具１０４と絶縁体１０２の間の気密性を向上させる手段が有効であることが知られている（特許文献１：段落［０００４］参照）。
ところがシールド部１１１を有する従来の点火プラグ１００は、高温時に第１のパッキン１１５による主体金具１０４と絶縁体１０２の間の気密性が低下するおそれがあった。
すなわち従来の点火プラグ１００は、シールド部１１１後端の加締め蓋１１２で押さえ管１２０を押さえ、その押さえ管１２０で加締め荷重を伝達して最終的に前記第１のパッキン１１５を加圧し、そうして主体金具１０４と絶縁体１０２の間の気密を保つようにしていたが、金属製の主体金具１０４と、絶縁碍管である押さえ管１２０の線膨張率が異なり、主体金具１０４の線膨張が押さえ管１２０の熱膨張を上回るため、押さえ管１２０によって伝達される第１のパッキン１１５への加圧力が減少するのである。
特に、シールド部１１１を有する点火プラグ１００は、固定的な基点となる主体金具１０４の締め止め部材１０９の座面１０８から、加締め蓋１１２までの距離Ｌが長いため、線膨張の影響を受けやすい。
また、高温環境下での使用となるガスタービンエンジン用の点火プラグ１００は、耐熱性に優れたオーステナイト系ステンレス鋼（例えばＳＵＳ３０４、ＳＵＳ３１０Ｓ等）を用いることが一般的であり、かかる材料は炭素鋼やフェライト系ステンレス鋼に比べて線膨張率が大きいため、前記した気密性の低下が起きやすい。 Conventionally, it is known that means for improving the airtightness between the metal shell 104 and the insulator 102 is effective for obtaining a long-life spark plug 100 (see Patent Document 1: Paragraph [0004]). ).
However, in the conventional spark plug 100 having the shield portion 111, the airtightness between the metal shell 104 and the insulator 102 by the first packing 115 may be lowered at a high temperature.
That is, the conventional spark plug 100 presses the holding tube 120 with the caulking lid 112 at the rear end of the shield part 111, transmits the caulking load with the holding tube 120, and finally pressurizes the first packing 115, Thus, the airtightness between the metal shell 104 and the insulator 102 was maintained, but the linear expansion coefficient of the metal metal shell 104 and the presser tube 120 that is an insulating soot tube are different, and the linear expansion of the metal shell 104 is made. Since this exceeds the thermal expansion of the presser tube 120, the pressure applied to the first packing 115 transmitted by the presser tube 120 is reduced.
In particular, the spark plug 100 having the shield portion 111 is affected by linear expansion because the distance L from the seating surface 108 of the fastening member 109 of the metal shell 104 serving as a fixed base point to the caulking lid 112 is long. Cheap.
Further, the spark plug 100 for a gas turbine engine to be used in a high temperature environment is generally made of austenitic stainless steel (for example, SUS304, SUS310S, etc.) having excellent heat resistance, and such material is carbon steel. Further, since the linear expansion coefficient is larger than that of ferritic stainless steel, the aforementioned airtightness is likely to be lowered.

本発明は上記に鑑みなされたもので、その目的は、気密性に優れた長寿命の点火プラグを提供することにある。 The present invention has been made in view of the above, and an object thereof is to provide a long-life spark plug having excellent airtightness.

上記の目的を達成するため本発明は、
軸方向に軸孔を有し、自身の一端に中心電極を有する絶縁体と、
軸方向に貫通する貫通孔を有してその貫通孔内に前記絶縁体が装着される主体金具と、を備えており、
前記主体金具は、
外周にエンジン側のプラグ取付孔に形成された雌ネジ部に螺合する雄ネジ部を有すると共に、前記中心電極が配置される端部側を先端側とし反対側を後端側としたとき前記雄ネジ部より後端側に拡径方向に突設されて前記プラグ取付孔に向かう側の面を座面とする締め止め部材を有し、
さらに後端側には前記絶縁体の後端側を囲うシールド部と、該シールド部の後端を内向きに加締めて形成される加締め蓋と、を備えており、
この主体金具の内周面と前記絶縁体の外周面とにより囲まれた円筒形状の空間に緩衝材が充填されると共に該空間の後端側に前記加締め蓋で押さえられる押さえ管が装填されている点火プラグであって、
前記緩衝材と前記押さえ管との間に該押さえ管とは別体にした環状の押さえ部材を介装し、
一方、前記主体金具には、外部から前記押さえ部材に向けてピン用貫通孔を形成し、
前記主体金具の外部から前記ピン用貫通孔に固定ピンを挿通して、前記押さえ部材を主体金具の前記シールド部内面に固定するようにした点火プラグを提供する。 In order to achieve the above object, the present invention
An insulator having an axial hole in the axial direction and having a central electrode at one end thereof;
A metal shell having a through-hole penetrating in the axial direction and having the insulator mounted in the through-hole,
The metallic shell is
When the outer side has a male screw part screwed into a female screw part formed in the plug mounting hole on the engine side, the end side where the center electrode is disposed is the front end side, and the opposite side is the rear end side. A fastening member having a seating surface on the side facing the plug mounting hole that protrudes in the diameter increasing direction on the rear end side from the male screw portion,
Furthermore, the rear end side includes a shield part surrounding the rear end side of the insulator, and a crimping lid formed by caulking the rear end of the shield part inward,
A cylindrical space surrounded by the inner peripheral surface of the metal shell and the outer peripheral surface of the insulator is filled with a buffer material, and a holding tube pressed by the crimping lid is loaded on the rear end side of the space. Spark plug,
An annular pressing member separated from the pressing tube is interposed between the cushioning material and the pressing tube,
On the other hand, in the metal shell, a pin through hole is formed from the outside toward the pressing member,
The metal shell from outside by inserting the fixing pin in the pin hole of, providing a spark plug was so that to secure the retainer member to the shield interior surface of the metal shell.

また、請求項２に記載したように、軸方向に軸孔を有し、自身の一端に中心電極を有する絶縁体と、
軸方向に貫通する貫通孔を有してその貫通孔内に前記絶縁体が装着される主体金具と、を備えており、
前記主体金具は、
外周にエンジン側のプラグ取付孔に形成された雌ネジ部に螺合する雄ネジ部を有すると共に、前記中心電極が配置される端部側を先端側とし反対側を後端側としたとき前記雄ネジ部より後端側に拡径方向に突設されて前記プラグ取付孔に向かう側の面を座面とする締め止め部材を有し、
さらに後端側には前記絶縁体の後端側を囲うシールド部と、該シールド部の後端を内向きに加締めて形成される加締め蓋と、を備えており、
この主体金具の内周面と前記絶縁体の外周面とにより囲まれた円筒形状の空間に緩衝材が充填されると共に該空間の後端側に前記加締め蓋で押さえられる押さえ管が装填されている点火プラグであって、
前記緩衝材と前記押さえ管との間に該押さえ管とは別体にして軸方向の長さＫを３ｍｍ≦Ｋ≦１０ｍｍにした環状の押さえ部材を介装し、該押さえ部材が主体金具の前記シールド部内面に固定されるようにした点火プラグを提供する。 Further, as described in claim 2, an insulator having an axial hole in the axial direction and having a central electrode at one end thereof;
A metal shell having a through-hole penetrating in the axial direction and having the insulator mounted in the through-hole,
The metallic shell is
When the outer side has a male screw part screwed into a female screw part formed in the plug mounting hole on the engine side, the end side where the center electrode is disposed is the front end side, and the opposite side is the rear end side. A fastening member having a seating surface on the side facing the plug mounting hole that protrudes in the diameter increasing direction on the rear end side from the male screw portion,
Furthermore, the rear end side includes a shield part surrounding the rear end side of the insulator, and a crimping lid formed by caulking the rear end of the shield part inward,
A cylindrical space surrounded by the inner peripheral surface of the metal shell and the outer peripheral surface of the insulator is filled with a buffer material, and a holding tube pressed by the crimping lid is loaded on the rear end side of the space. Spark plug,
An annular pressing member having an axial length K of 3 mm ≦ K ≦ 10 mm is interposed between the cushioning material and the pressing tube separately from the pressing tube. A spark plug is provided which is fixed to the inner surface of the shield part.

また、請求項３に記載したように、前記押さえ部材の軸方向の長さＫが、３ｍｍ≦Ｋ≦１０ｍｍである請求項１記載の点火プラグを提供する。According to a third aspect of the present invention, there is provided the spark plug according to the first aspect, wherein a length K in the axial direction of the pressing member is 3 mm ≦ K ≦ 10 mm.

また、請求項４に記載したように、前記押さえ部材は、主体金具の外部から挿通した固定ピンにより固定されている請求項２記載の点火プラグを提供する。According to a fourth aspect of the present invention, there is provided the spark plug according to the second aspect, wherein the pressing member is fixed by a fixing pin inserted from the outside of the metal shell.

また、請求項５に記載したように、前記主体金具の前記座面から前記加締め蓋までの長さＬが３０ｍｍ以上である請求項１〜４の何れか１項に記載の点火プラグを提供する。 In addition, as described in claim 5 , the spark plug according to any one of claims 1 to 4, wherein a length L from the seating surface of the metal shell to the caulking lid is 30 mm or more. To do.

また、請求項６に記載したように、前記絶縁体は、先端部側の小径部と後端部側の大径部との間に境界段部が形成され、該境界段部が前記主体金具の前記貫通孔内に形成された棚段部に係合して固定されており、該棚段部と前記境界段部の係合位置が主体金具の前記座面より後端側に設けられている請求項１〜５の何れか１項に記載の点火プラグを提供する。 According to a sixth aspect of the present invention, in the insulator, a boundary step is formed between the small diameter portion on the front end side and the large diameter portion on the rear end portion side, and the boundary step portion is the metal shell. Is engaged with and fixed to a shelf step formed in the through hole, and the engagement position between the shelf step and the boundary step is provided on the rear end side of the seat surface of the metal shell. A spark plug according to any one of claims 1 to 5 is provided.

また、請求項７に記載したように、前記押さえ部材は、主体金具の前記シールド部内面に圧入されている請求項１〜６の何れか１項に記載の点火プラグを提供する。 Moreover, as described in claim 7 , the pressing member is provided with the spark plug according to any one of claims 1 to 6 , wherein the pressing member is press-fitted into the inner surface of the shield part of the metal shell.

また、請求項８に記載したように、前記主体金具の材質が、オーステナイト系ステンレス鋼である請求項１〜７の何れか１項に記載の点火プラグを提供する。 In addition, as described in claim 8 , the spark plug according to any one of claims 1 to 7 , wherein the metal shell is made of austenitic stainless steel.

請求項１に記載の点火プラグは、緩衝材と押さえ管との間に該押さえ管とは別体にした環状の押さえ部材を介装し、該押さえ部材が主体金具の前記シールド部内面に固定されるようにしたため、主体金具と押さえ管の線膨張の差により押さえ管から伝達される加締め荷重が減少しても、押さえ管とは別体の押さえ部材によって第１のパッキンへの加圧力がほぼ維持される。従って、高温下でも主体金具と絶縁体の間の気密性が殆ど低下しない。
また、請求項１、４に記載したように、前記押さえ部材を、主体金具の外部から挿通した固定ピンにより固定するようにすれば、押さえ部材の固定をより確実にすることができる。 The spark plug according to claim 1 includes an annular pressing member separated from the pressing tube between the buffer material and the pressing tube, and the pressing member is fixed to the inner surface of the shield part of the metal shell. Therefore, even if the caulking load transmitted from the presser tube decreases due to the difference in linear expansion between the metal shell and the presser tube, the pressurizing force applied to the first packing by the presser member separate from the presser tube Is almost maintained. Therefore, the airtightness between the metal shell and the insulator is hardly lowered even at high temperatures.
In addition, as described in claims 1 and 4, if the pressing member is fixed by a fixing pin inserted from the outside of the metal shell, the fixing of the pressing member can be made more reliable.

また、請求項２、３に記載したように、前記押さえ部材の軸方向の長さＫを３ｍｍ≦Ｋ≦１０ｍｍにすることにより、押さえ部材について十分な内部フラッシュバック（以下、「Ｆ／Ｏ」ともいう。）電圧を確保しながら十分な圧入摩擦力を得ることができる。 In addition, as described in claims 2 and 3 , by setting the axial length K of the pressing member to 3 mm ≦ K ≦ 10 mm, sufficient internal flashback (hereinafter referred to as “F / O”) for the pressing member. It is also possible to obtain a sufficient press-fitting friction force while securing a voltage.

また、線膨張による気密性の低下は、主体金具の締め止め部材の座面から加締め蓋までの長さＬが３０ｍｍ以上である場合に起きやすい。従って、請求項５のように前記長さＬを３０ｍｍ以上とした場合に本発明の有用性が顕著になる。 Further, a decrease in airtightness due to linear expansion is likely to occur when the length L from the seating surface of the fastening member of the metal shell to the crimping lid is 30 mm or more. Therefore, when the length L is 30 mm or more as in claim 5 , the usefulness of the present invention becomes remarkable.

一方、前記した第１のパッキンによる気密性の低下は、線膨張による場合のほか、エンジンのプラグ取付孔に取り付ける際の過トルクによっても生じ得る。すなわち、点火プラグの取り付けは、プラグ取付孔の雌ネジ部と主体金具の雄ネジ部の螺合によって行われ、主体金具の締め止め部材がエンジンに当たってから所定のトルクで締め付けるのであるが、そのトルクが大きすぎた場合、座面と雄ネジ部の間に引張り応力が作用して伸びるため、相対的に絶縁体が縮んだ格好になって第１のパッキンへの加圧力が減少する。
これに対して請求項６のように、前記絶縁体の境界段部と、主体金具の棚段部の係合位置を主体金具の座面より後端側に設定しておけば、たとえ過トルクによって座面と雄ネジ部の間に過大な引張り応力が作用しても第１パッキンへの加圧力に影響が及ばない。従って、点火プラグ取り付け時の過トルクによる気密性の低下が防止できる。 On the other hand, the deterioration of the airtightness due to the first packing described above can be caused not only by linear expansion but also by excessive torque at the time of attachment to the plug attachment hole of the engine. That is, the spark plug is attached by screwing the female threaded portion of the plug mounting hole and the male threaded portion of the metal shell, and is tightened with a predetermined torque after the fastening member of the metal shell hits the engine. If is too large, a tensile stress acts between the seat surface and the male screw portion to extend, so that the insulator is relatively shrunk and the pressure applied to the first packing is reduced.
On the other hand, as in claim 6 , if the engagement position of the boundary step portion of the insulator and the shelf step portion of the metal shell is set to the rear end side from the seat surface of the metal shell, overtorque Therefore, even if an excessive tensile stress acts between the seating surface and the male screw portion, the pressure applied to the first packing is not affected. Accordingly, it is possible to prevent a decrease in airtightness due to excessive torque when the spark plug is attached.

また、請求項７に記載したように、前記押さえ部材を主体金具の前記シールド部内面に圧入しておけば、シールド部の後端を加締める工程に移行するときに一旦押さえ管の加圧を解除しても、押さえ部材の摩擦力で第１のパッキンへの加圧が継続されるから、加締め工程への移行を契機とする気密低下が防止できる。 In addition, as described in claim 7 , if the pressing member is press-fitted into the inner surface of the shield part of the metal shell, the pressure of the pressing pipe is temporarily increased when the process proceeds to the step of crimping the rear end of the shield part. Even if it cancels | releases, since the pressurization to the 1st packing is continued by the frictional force of a pressing member, the airtight fall triggered by transfer to a caulking process can be prevented.

また、主体金具の材質がオーステナイト系ステンレス鋼であると、線膨張率の高さから線膨張に起因する気密性の低下が起きやすくなる。従って請求項８のように主体金具の材質をオーステナイト系ステンレス鋼にした場合には、本発明の有効性が顕著になる。 Further, if the material of the metal shell is austenitic stainless steel, the airtightness due to the linear expansion is likely to occur due to the high linear expansion coefficient. Therefore, when the metal shell is made of austenitic stainless steel as in claim 8 , the effectiveness of the present invention becomes remarkable.

一部を断面にした点火プラグの斜視図である。It is a perspective view of the spark plug which made a part the cross section. 点火プラグの縦断面図である。It is a longitudinal cross-sectional view of a spark plug. （ａ）〜（ｅ）は、製造工程を説明する縦断面図である。(A)-(e) is a longitudinal cross-sectional view explaining a manufacturing process. 高温気密性評価試験の試験方法を説明する断面図である。It is sectional drawing explaining the test method of a high temperature airtightness evaluation test. 他の形態を示す点火プラグの縦断面図である。It is a longitudinal cross-sectional view of the spark plug which shows another form. 押さえ部材の長さと内部Ｆ／Ｏ開始電圧の関係を示すグラフである。It is a graph which shows the relationship between the length of a pressing member, and internal F / O start voltage. 押さえ部材の長さとプッシュバック荷重の関係を示すグラフである。It is a graph which shows the relationship between the length of a pressing member, and a pushback load. 高温気密性評価試験の結果を示すグラフである。It is a graph which shows the result of a high temperature airtightness evaluation test. 従来の点火プラグを示す縦断面図である。It is a longitudinal cross-sectional view which shows the conventional spark plug.

以下に本発明の実施の形態を図面を参照しつつ説明する。
点火プラグ１は、軸方向に軸孔を有し自身の一端に中心電極２を有する絶縁体３と、軸方向に貫通する貫通孔４を有してその貫通孔４内に前記絶縁体３が装着される主体金具５と、を備えており、前記中心電極２と、エンジン６側に設けられる接地電極（図示せず）との間で火花を発生させて燃料に点火するものである。 Embodiments of the present invention will be described below with reference to the drawings.
The spark plug 1 has an insulator 3 having an axial hole in the axial direction and having a center electrode 2 at one end thereof, and a through hole 4 penetrating in the axial direction, and the insulator 3 is disposed in the through hole 4. A metal shell 5 to be mounted is provided, and a spark is generated between the center electrode 2 and a ground electrode (not shown) provided on the engine 6 side to ignite the fuel.

前記絶縁体３は、中心電極２が配置される端部側を先端側とし反対側を後端側としたとき、中間に位置する最大径部３ａの後端側にそれより小径の後軸部３ｂが形成され、一方、前記最大径部３ａの先端部側にもそれより小径の先軸部３ｃが形成され、さらに該先軸部３ｃの先端側にさらに小径の最先軸部３ｄが形成されている。 The insulator 3 has a rear shaft portion having a smaller diameter on the rear end side of the maximum diameter portion 3a located in the middle when the end portion side on which the center electrode 2 is disposed is the front end side and the opposite side is the rear end side. 3b is formed. On the other hand, a tip shaft portion 3c having a smaller diameter is formed also on the tip end portion side of the maximum diameter portion 3a, and a tip shaft portion 3d having a smaller diameter is further formed on the tip end side of the tip shaft portion 3c. Has been.

前記主体金具５は、外周に、エンジン６側のプラグ取付孔７に形成された雌ネジ部に螺合する雄ネジ部８を有する。
また、主体金具５は、中心電極２が配置される端部側を先端側とし反対側を後端側としたとき、雄ネジ部８より後端側に拡径方向に突設されて前記プラグ取付孔７（エンジン６側）に向かう側の面を座面９とするフランジ状の締め止め部材１０を有し、該締め止め部材１０より後端側に六角ボルトの頭部形態である工具係合部１１を有する。
また、主体金具５は、前記工具係合部１１の後端側に突設されて前記絶縁体３の後端側を囲う筒状のシールド部１２と、該シールド部１２の後端に形成されたコネクタ固定用の外ネジ部１３と、該シールド部１２の前記外ネジ部１３より後端を内向きに加締めて形成される加締め蓋１４と、を備えている。
また、主体金具５の貫通孔４は、前記絶縁体３の最大径部３ａとほぼ同径の後孔部４ａと、絶縁体３の先軸部３ｃとほぼ同径（若干大径）の中孔部４ｂと、絶縁体３の最先軸部３ｄとほぼ同径（若干大径）の先孔部４ｃとを有する段付孔形態である。 The metal shell 5 has a male screw portion 8 that is screwed into a female screw portion formed in the plug mounting hole 7 on the engine 6 side on the outer periphery.
The metal shell 5 is projected in the diameter-expanding direction from the male screw portion 8 to the rear end side when the end side where the center electrode 2 is disposed is the front end side and the opposite side is the rear end side. A tool member having a flange-like fastening member 10 having a seating surface 9 on the side facing the mounting hole 7 (engine 6 side) and having a hexagonal bolt head on the rear end side of the fastening member 10 It has a joint part 11.
The metal shell 5 is formed on the rear end side of the tool engaging portion 11 so as to protrude from the cylindrical shield portion 12 surrounding the rear end side of the insulator 3 and on the rear end of the shield portion 12. And an outer screw portion 13 for fixing the connector, and a crimping lid 14 formed by crimping the rear end of the shield portion 12 inward from the outer screw portion 13.
Further, the through hole 4 of the metal shell 5 has a medium diameter (slightly larger) than that of the rear hole portion 4a having the same diameter as the maximum diameter portion 3a of the insulator 3 and the front shaft portion 3c of the insulator 3. This is a stepped hole configuration having a hole portion 4b and a tip hole portion 4c having substantially the same diameter (slightly larger diameter) as the most distal shaft portion 3d of the insulator 3.

この主体金具５の貫通孔４の内部に前記絶縁体３が装着されているが、この装着状態で、絶縁体３の最大径部３ａ（後端部側の大径部）と先軸部３ｃ（先端部側の小径部）との境界に形成される境界段部１５と、主体金具５の貫通孔４の後孔部４ａと中孔部４ｂの境界に形成される棚段部１６との間に第１のパッキン１７が介装されていて主体金具５と絶縁体３の間の隙間から燃焼ガスが外部に漏れないように気密が保たれている。なお、実施形態では、絶縁体３の最大径部３ａと先軸部３ｃとの境界に形成される境界段部１５と、主体金具５の貫通孔４の後孔部４ａと中孔部４ｂの境界に形成される棚段部１６とが係合するようになっており、従って主体金具５と絶縁体３の係合位置が、主体金具５の座面９より後端側にある。 The insulator 3 is mounted inside the through hole 4 of the metal shell 5, and in this mounted state, the maximum diameter portion 3a (large diameter portion on the rear end side) of the insulator 3 and the front shaft portion 3c. A boundary step portion 15 formed at the boundary with the small diameter portion on the front end portion, and a shelf step portion 16 formed at the boundary between the rear hole portion 4a and the middle hole portion 4b of the through hole 4 of the metal shell 5 A first packing 17 is interposed therebetween, and the airtightness is maintained so that the combustion gas does not leak outside through the gap between the metal shell 5 and the insulator 3. In the embodiment, the boundary step portion 15 formed at the boundary between the maximum diameter portion 3a of the insulator 3 and the front shaft portion 3c, and the rear hole portion 4a and the middle hole portion 4b of the through hole 4 of the metal shell 5 are provided. The shelf step portion 16 formed at the boundary is engaged, so that the engagement position of the metal shell 5 and the insulator 3 is on the rear end side from the seating surface 9 of the metal shell 5.

また、主体金具５の貫通孔４の後孔部４ａの内周面と、絶縁体３の後軸部３の外周面とにより囲まれた円筒形状の空間１８に、絶縁体３の最大径部３ａの後面に接する第２のパッキン１９と、例えばタルクやカオリン等のセラミックで形成された粉末状の緩衝材２０と、マイカ等の無機材繊維製のパッキン２１と、金属製（好ましくは主体金具５と同材（例えば、ＳＵＳ３０４やＳＵＳ３１０Ｓ））で筒状の押さえ部材２２と、マイカ等の無機材繊維製のパッキン２３と、絶縁碍管である押さえ管２４と、アルミニウム製のパッキン２５が順に装填され、該パッキン２５を介して押さえ管２４の後端が前記加締め蓋１４で押さえられている。 Further, the largest diameter portion of the insulator 3 is formed in a cylindrical space 18 surrounded by the inner peripheral surface of the rear hole portion 4 a of the through hole 4 of the metal shell 5 and the outer peripheral surface of the rear shaft portion 3 of the insulator 3. A second packing 19 in contact with the rear surface of 3a; a powdery cushioning material 20 made of ceramic such as talc or kaolin; a packing 21 made of inorganic material fibers such as mica; and a metal (preferably metal shell) 5 in the same material (for example, SUS304 or SUS310S), a packing 23 made of inorganic material fibers such as mica, a pressing tube 24 which is an insulating soot tube, and an aluminum packing 25 are sequentially loaded. The rear end of the pressing tube 24 is pressed by the caulking lid 14 through the packing 25.

次に、前記点火プラグ１の製造方法を図３（ａ）〜（ｅ）により説明する。
先ず、図３（ａ）に示した主体金具５の貫通孔４に後孔部４ａ側から絶縁体３を挿入する。その際、図３（ｂ）に示したように、絶縁体３の最大径部３ａと先軸部３ｃとの境界に形成される境界段部１５と、主体金具５の貫通孔４の後孔部４ａと中孔部４ｂの境界に形成される棚段部１６との間に第１のパッキン１７を介在させて両段部１５，１６を係合させる。 Next, a method for manufacturing the spark plug 1 will be described with reference to FIGS.
First, the insulator 3 is inserted into the through-hole 4 of the metal shell 5 shown in FIG. At that time, as shown in FIG. 3B, a boundary step portion 15 formed at the boundary between the maximum diameter portion 3a of the insulator 3 and the front shaft portion 3c, and the rear hole 4 of the through hole 4 of the metal shell 5 The step portions 15 and 16 are engaged with each other by interposing a first packing 17 between the shelf step portion 16 formed at the boundary between the portion 4a and the middle hole portion 4b.

次に、図３（ｂ）に示したように、主体金具５の後孔部４ａの内周面と、絶縁体３の後軸部３の外周面とにより囲まれた円筒形状の空間１８に第２のパッキン１９と、粉末状の緩衝材２０と、パッキン２１を充填する。なお、この状態で第２のパッキン１９が最大径部３ａの後側の面に密着して緩衝材２０の流出を止めている。 Next, as shown in FIG. 3 (b), in the cylindrical space 18 surrounded by the inner peripheral surface of the rear hole portion 4 a of the metal shell 5 and the outer peripheral surface of the rear shaft portion 3 of the insulator 3. The second packing 19, the powdery cushioning material 20, and the packing 21 are filled. In this state, the second packing 19 is in close contact with the rear surface of the maximum diameter portion 3a to stop the buffer material 20 from flowing out.

次に、図３（ｃ）に示したように、前記空間１８に前記押さえ管２４とは別体の押さえ部材２２を押圧工具（図示せず）で圧入し、該押さえ部材２２で緩衝材２０と第２のパッキン１９を加圧すると共に、その力で絶縁体３を押し込んで第１のパッキン１７を絶縁体３の境界段部１５と主体金具５の棚段部１６の間に密着させる。空間１８内に圧入された押さえ部材２２は、その摩擦力により該空間１８内に止まるため、空間１８から押圧工具を抜いても押さえ部材２２による第１のパッキン１７の加圧力は維持される。 Next, as shown in FIG. 3C, a pressing member 22 separate from the pressing tube 24 is press-fitted into the space 18 with a pressing tool (not shown), and the cushioning material 20 is pressed with the pressing member 22. The second packing 19 is pressurized and the insulator 3 is pushed in by the force to bring the first packing 17 into close contact between the boundary step portion 15 of the insulator 3 and the shelf step portion 16 of the metal shell 5. Since the pressing member 22 press-fitted into the space 18 stops in the space 18 due to the frictional force, the pressing force of the first packing 17 by the pressing member 22 is maintained even if the pressing tool is removed from the space 18.

次に、図３（ｄ）に示したように、空間１８にパッキン２３と押さえ管２４とパッキン２５を挿入した後、同図に想像線で示したような加締め治具２６をシールド部１２の後端に当てて内向きに加締める。これにより図３（ｅ）のようにシールド部１２の後端に加締め蓋１４が形成され、該加締め蓋１４で押さえ管２４が空間１８内に固定される。なお、実施形態の点火プラグ１は、図３（ｅ）に示した固定ピン２７を主体金具５の外部から挿通することにより、押さえ管２４の固定強度を高めるようにしてある。 Next, as shown in FIG. 3 (d), after inserting the packing 23, the holding tube 24 and the packing 25 into the space 18, the caulking jig 26 shown by the imaginary line in FIG. Clamp inward against the rear edge. As a result, as shown in FIG. 3E, a crimping lid 14 is formed at the rear end of the shield portion 12, and the presser tube 24 is fixed in the space 18 by the crimping lid 14. In the spark plug 1 of the embodiment, the fixing pin 27 shown in FIG. 3 (e) is inserted from the outside of the metal shell 5 to increase the fixing strength of the holding tube 24.

押さえ部材２２の好ましい長さＫを内部Ｆ／Ｏ耐性の面から確認するため、その長さＫを３ｍｍ、６ｍｍ、１０ｍｍ、１４ｍｍにしてそれぞれ実施形態の点火プラグ１を製造し、発火部を絶縁して各点火プラグ１ごとに内部Ｆ／Ｏ開始電圧を測定した。その結果を図６のグラフに示す。
この試験結果より、十分な内部Ｆ／Ｏ電圧を確保するために、押さえ部材２２の長さＫは１０ｍｍ以下であればよいことが確認できた。 In order to confirm the preferable length K of the holding member 22 from the aspect of internal F / O resistance, the length K is set to 3 mm, 6 mm, 10 mm, and 14 mm, and the ignition plug 1 of the embodiment is manufactured to insulate the ignition portion. Then, the internal F / O start voltage was measured for each spark plug 1. The result is shown in the graph of FIG.
From this test result, in order to ensure a sufficient internal F / O voltage, it was confirmed that the length K of the pressing member 22 should be 10 mm or less.

一方、押さえ部材２２の好ましい長さＫを強度面から確認するため、その長さＫを２ｍｍ、３ｍｍ、６ｍｍ、１０ｍｍにして図３（ｃ）の工程まで実行し、その中間品を固定して図３（ｃ）矢示の方向にプッシュバック荷重を加え、耐え得る荷重の大きさを測定した。その結果を図７のグラフに示す。
実際の燃焼圧力から想定される必要プッシュバック荷重を７５０ｋｇｆに設定すれば、十分な強度を確保するために、押さえ部材２２の長さＫは３ｍｍ以上であればよいことが確認できた。 On the other hand, in order to confirm the preferable length K of the pressing member 22 from the strength aspect, the length K is set to 2 mm, 3 mm, 6 mm, and 10 mm, and the process up to the step of FIG. A pushback load was applied in the direction of the arrow in FIG. The result is shown in the graph of FIG.
It has been confirmed that if the required pushback load assumed from the actual combustion pressure is set to 750 kgf, the length K of the pressing member 22 may be 3 mm or more in order to ensure sufficient strength.

以上、押さえ部材２２の長さに関する２つの試験結果より、押さえ部材２２の好ましい軸方向の長さＫは、３ｍｍ≦Ｋ≦１０ｍｍであることが確認できた。 As described above, it was confirmed from the two test results regarding the length of the pressing member 22 that the preferable axial length K of the pressing member 22 is 3 mm ≦ K ≦ 10 mm.

次に、主体金具５の材質の相違と、押さえ部材２２の固定手段の相違と、主体金具５と絶縁体３の係合位置の相違のそれぞれと、高温時の気密性との関係を確認するため、次のようなサンプル１〜４と、図９により説明した従来構造の比較例１〜３を製造して高温気密性評価試験を行った。 Next, the relationship between the difference in the material of the metal shell 5, the difference in the fixing means of the pressing member 22, the difference in the engagement position between the metal shell 5 and the insulator 3, and the airtightness at a high temperature will be confirmed. Therefore, the following samples 1 to 4 and comparative examples 1 to 3 having the conventional structure described with reference to FIG. 9 were manufactured and subjected to a high temperature hermeticity evaluation test.

なお、高温気密性評価試験は、図４に示したように点火プラグ１の先端側に１.５ＭＰａの圧力を加えると共に主体金具５の座面９の温度を上昇させつつ、後端側に連結して外ネジ部１３にナット締めした捕集チューブ２８で前記空間１８から１分間に漏れ出す気体の量を測定するものである。また、取り付け時の過トルクによる影響も同時に確認するため、４０Ｎｍの締め付けトルクで締め付けた場合と、５０Ｎｍの締め付けトルクで締め付けた場合のそれぞれについて前記試験を行った。 In the high temperature airtightness evaluation test, as shown in FIG. 4, a pressure of 1.5 MPa is applied to the front end side of the spark plug 1 and the temperature of the seating surface 9 of the metal shell 5 is increased, and connected to the rear end side. Then, the amount of gas leaking from the space 18 in one minute is measured by the collection tube 28 that is nut-tightened to the outer screw portion 13. Moreover, in order to confirm simultaneously the influence by the overtorque at the time of attachment, the said test was done about the case where it tightens with the tightening torque of 40 Nm, and the case where it tightens with the tightening torque of 50 Nm, respectively.

［サンプル１］
・主体金具５の材質…オーステナイト系ＳＵＳ（ＳＵＳ３１０Ｓ）
・押さえ部材２２の固定手段…圧入後に固定ピン２７使用
・主体金具５と絶縁体３の係合位置…座面９より後端側（図１参照）
［サンプル２］
・主体金具５の材質…オーステナイト系ＳＵＳ（ＳＵＳ３１０Ｓ）
・押さえ部材２２の固定手段…圧入のみ
・主体金具５と絶縁体３の係合位置…座面９より後端側（図１参照）
［サンプル３］
・主体金具５の材質…オーステナイト系ＳＵＳ（ＳＵＳ３１０Ｓ）
・押さえ部材２２の固定手段…圧入のみ
・主体金具５と絶縁体３の係合位置…座面９より先端側（図９参照）
［サンプル４］
・主体金具５の材質…フェライト系ＳＵＳ（ＳＵＳ４３０）
・押さえ部材２２の固定手段…圧入のみ
・主体金具５と絶縁体３の係合位置…座面９より後端側（図１参照）
［比較例１］
・主体金具１０４の材質…オーステナイト系ＳＵＳ（ＳＵＳ３１０Ｓ）
・押さえ部材…なし
・主体金具１０４と絶縁体１０２の係合位置…座面１０８より後端側（図１参照）
［比較例２］
・主体金具１０４の材質…オーステナイト系ＳＵＳ（ＳＵＳ３１０Ｓ）
・押さえ部材…なし
・主体金具１０４と絶縁体１０２の係合位置…座面１０８より先端側（図９参照）
［比較例３］
・主体金具１０４の材質…フェライト系ＳＵＳ（ＳＵＳ４３０）
・押さえ部材…なし
・主体金具１０４と絶縁体１０２の係合位置…座面１０８より後端側（図１参照）
［参考例］
比較のため、ノンシールドタイプの点火プラグについても同様の試験を行った。 [Sample 1]
-Material of metal shell 5: austenitic SUS (SUS310S)
-Fixing means for pressing member 22-Use of fixing pin 27 after press-fitting-Engagement position of metal shell 5 and insulator 3-Rear end side from seating surface 9 (see Fig. 1)
[Sample 2]
-Material of metal shell 5: austenitic SUS (SUS310S)
・ Fixing means for the pressing member 22: only press-fitting ・ Engagement position of the metal shell 5 and the insulator 3: the rear end side from the seating surface 9 (see FIG. 1)
[Sample 3]
-Material of metal shell 5: austenitic SUS (SUS310S)
・ Fixing means for the pressing member 22: only press-fitting ・ Engagement position of the metal shell 5 and the insulator 3...
[Sample 4]
・ Material of metal shell 5: Ferritic SUS (SUS430)
・ Fixing means for the pressing member 22: only press-fitting ・ Engagement position of the metal shell 5 and the insulator 3: the rear end side from the seating surface 9 (see FIG. 1)
[Comparative Example 1]
・ Material of metal shell 104: austenitic SUS (SUS310S)
-Holding member: None-Engagement position of metal shell 104 and insulator 102-Rear end side from seating surface 108 (see FIG. 1)
[Comparative Example 2]
・ Material of metal shell 104: austenitic SUS (SUS310S)
・ Pressing member: None ・ Engagement position of metal shell 104 and insulator 102: Front end side from seating surface 108 (see FIG. 9)
[Comparative Example 3]
-Material of the metal shell 104: Ferritic SUS (SUS430)
-Holding member: None-Engagement position of metal shell 104 and insulator 102-Rear end side from seating surface 108 (see FIG. 1)
[Reference example]
For comparison, a similar test was performed on a non-shielded type spark plug.

高温気密性評価試験の結果を図８のグラフに示す。この試験結果より次のことが確認できた。
（ｉ）サンプル１及びサンプル２と比較例１又はサンプル３と比較例２又はサンプル４と比較例３の比較より、押さえ部材２２を設けることで高温時の気密性に優れることが判る。
（ii）サンプル１とサンプル２の比較より、押さえ部材２２の固定手段として固定ピン２７を使用することで気密性に優れることが判る。
(iii) 主体金具５と絶縁体３の係合位置が座面９より先端側にあるサンプル３と比較例２について締め付けトルク間に漏洩温度差が生じている結果より、主体金具５と絶縁体３の係合位置が座面９より先端側にある場合、締め付けトルクが大きいと気密性が低下することが判る。そして、サンプル３の締め付けトルク間の漏洩温度差が比較例２の漏洩温度差の半分であることより、押さえ部材２２が有効に機能していることが判る。
（iv）サンプル２とサンプル４又は比較例１と比較例３の比較より、主体金具５の材質として線膨張率の大小が高温時の気密性に影響することが判り、且つ、サンプル２とサンプル４の気密性の差が比較例１と比較例３の気密性の差より小さいことより、押さえ部材２２を設けることで気密性の変動が効果的に抑制されることが判る。 The result of the high temperature airtightness evaluation test is shown in the graph of FIG. From the test results, the following could be confirmed.
(I) From the comparison of Sample 1 and Sample 2, Comparative Example 1 or Sample 3, Comparative Example 2 or Sample 4, and Comparative Example 3, it can be seen that providing the pressing member 22 is excellent in airtightness at high temperatures.
(Ii) From the comparison between Sample 1 and Sample 2, it can be seen that the use of the fixing pin 27 as a fixing means of the pressing member 22 provides excellent airtightness.
(iii) From the result of the leakage temperature difference between the tightening torques for the sample 3 and the comparative example 2 in which the engagement position of the metal shell 5 and the insulator 3 is on the tip side from the seating surface 9, the metal shell 5 and the insulator 3 is located on the tip side of the seating surface 9, it can be seen that the airtightness is lowered when the tightening torque is large. And since the leakage temperature difference between the tightening torques of the sample 3 is half of the leakage temperature difference of Comparative Example 2, it can be seen that the pressing member 22 functions effectively.
(Iv) From the comparison between Sample 2 and Sample 4 or Comparative Example 1 and Comparative Example 3, it can be seen that the size of the linear expansion coefficient as the material of the metal shell 5 affects the airtightness at high temperature, and Sample 2 and Sample 4 is smaller than the difference in airtightness between Comparative Example 1 and Comparative Example 3, it can be seen that the variation in the airtightness is effectively suppressed by providing the pressing member 22.

以上、本発明を実施の形態及び実施例について説明したが、もちろん本発明は上記実施形態及び実施例に限定されるものではない。例えば、実施形態では押さえ部材２２に固定ピン２７を通したが、図５に示したように押さえ部材２２を圧入のみで固定するようにしてもよい。その場合でも、前記高温気密性評価試験のサンプル２、３、４で実証したように十分な効果を発揮する。
また、実施形態では、主体金具５と絶縁体３の係合位置を座面９より後端側に設定したが、該係合位置を図９のように座面９より先端側に設定するようにしてもよい。その場合でも高温時の気密性についてはサンプル３で実証したように押さえ部材２２による利益を享受することができる。 Although the present invention has been described above with reference to the embodiments and examples, the present invention is of course not limited to the above embodiments and examples. For example, although the fixing pin 27 is passed through the pressing member 22 in the embodiment, the pressing member 22 may be fixed only by press-fitting as shown in FIG. Even in that case, as demonstrated in the samples 2, 3, and 4 of the high temperature airtightness evaluation test, sufficient effects are exhibited.
Further, in the embodiment, the engagement position between the metal shell 5 and the insulator 3 is set to the rear end side from the seat surface 9, but the engagement position is set to the front end side from the seat surface 9 as shown in FIG. It may be. Even in that case, as demonstrated in the sample 3, the airtightness at the time of high temperature can benefit from the pressing member 22.

１ …点火プラグ
２ …中心電極
３ …絶縁体
３ａ …絶縁体の最大径部（後端部側の大径部）
３ｃ …絶縁体の先軸部（先端部側の小径部）
４ …貫通孔
５ …主体金具
６ …エンジン
７ …プラグ取付孔
８ …雄ネジ部
９ …座面
１０ …締め止め部材
１２ …シールド部
１４ …加締め蓋
１５ …境界段部
１６ …棚段部
１８ …空間
２０ …緩衝材
２２ …押さえ部材
２４ …押さえ管
２７ …固定ピン DESCRIPTION OF SYMBOLS 1 ... Spark plug 2 ... Center electrode 3 ... Insulator 3a ... The largest diameter part (large diameter part by the side of a rear end) of an insulator
3c ... front shaft part of insulator (small diameter part on tip side)
DESCRIPTION OF SYMBOLS 4 ... Through-hole 5 ... Metal fitting 6 ... Engine 7 ... Plug mounting hole 8 ... Male screw part 9 ... Seat surface 10 ... Fastening member 12 ... Shield part 14 ... Clamping lid 15 ... Boundary step part 16 ... Shelf step part 18 ... Space 20 ... Buffer material 22 ... Holding member 24 ... Holding pipe 27 ... Fixing pin

Claims

An insulator having an axial hole in the axial direction and having a central electrode at one end thereof;
A metal shell having a through-hole penetrating in the axial direction and having the insulator mounted in the through-hole,
The metallic shell is
When the outer side has a male screw part screwed into a female screw part formed in the plug mounting hole on the engine side, the end side where the center electrode is disposed is the front end side, and the opposite side is the rear end side. A fastening member having a seating surface on the side facing the plug mounting hole that protrudes in the diameter increasing direction on the rear end side from the male screw portion,
Furthermore, the rear end side includes a shield part surrounding the rear end side of the insulator, and a crimping lid formed by caulking the rear end of the shield part inward,
A cylindrical space surrounded by the inner peripheral surface of the metal shell and the outer peripheral surface of the insulator is filled with a buffer material, and a holding tube pressed by the crimping lid is loaded on the rear end side of the space. Spark plug,
An annular pressing member separated from the pressing tube is interposed between the cushioning material and the pressing tube,
On the other hand, in the metal shell, a pin through hole is formed from the outside toward the pressing member,
The metal shell from outside by inserting the fixing pin in the pin hole of the spark plug, characterized in that the so that to secure the retainer member to the shield interior surface of the metal shell.

An insulator having an axial hole in the axial direction and having a central electrode at one end thereof;
A metal shell having a through-hole penetrating in the axial direction and having the insulator mounted in the through-hole,
The metallic shell is
When the outer side has a male screw part screwed into a female screw part formed in the plug mounting hole on the engine side, the end side where the center electrode is disposed is the front end side, and the opposite side is the rear end side. A fastening member having a seating surface on the side facing the plug mounting hole that protrudes in the diameter increasing direction on the rear end side from the male screw portion,
Furthermore, the rear end side includes a shield part surrounding the rear end side of the insulator, and a crimping lid formed by caulking the rear end of the shield part inward,
A cylindrical space surrounded by the inner peripheral surface of the metal shell and the outer peripheral surface of the insulator is filled with a buffer material, and a holding tube pressed by the crimping lid is loaded on the rear end side of the space. Spark plug,
An annular pressing member having an axial length K of 3 mm ≦ K ≦ 10 mm is interposed between the cushioning material and the pressing tube separately from the pressing tube. A spark plug characterized by being fixed to the inner surface of the shield part.

The pressing spark plug of claim 1 Symbol placement, wherein the axial length K of the member is 3 mm ≦ K ≦ 10 mm.

The spark plug according to claim 2 , wherein the pressing member is fixed by a fixing pin inserted from the outside of the metal shell.

The spark plug according to any one of claims 1 to 4, wherein a length L from the seat surface of the metal shell to the caulking lid is 30 mm or more.

The insulator has a shelf step formed between a small diameter portion on the front end side and a large diameter portion on the rear end side, and the boundary step portion is formed in the through hole of the metal shell. parts are engaged with fixed, claim 1-5, characterized in that the engagement position of the boundary stepped portion and the shelf stepped portion is provided on the rear side of the seat face of the metal shell The spark plug according to any one of the above.

The pressing member, the spark plug according to any one of claim 1 to 6, characterized by being press-fitted into the shield portion inner surface of the metal shell.

The spark plug according to any one of claims 1 to 7 , wherein a material of the metal shell is austenitic stainless steel.