JP2003059620A - Spark plug - Google Patents
Spark plugInfo
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- JP2003059620A JP2003059620A JP2001244442A JP2001244442A JP2003059620A JP 2003059620 A JP2003059620 A JP 2003059620A JP 2001244442 A JP2001244442 A JP 2001244442A JP 2001244442 A JP2001244442 A JP 2001244442A JP 2003059620 A JP2003059620 A JP 2003059620A
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- ground electrode
- electrode
- metal shell
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- section
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Abstract
Description
【０００１】[0001]
【発明の属する技術分野】本発明はスパークプラグに関
する。TECHNICAL FIELD The present invention relates to a spark plug.
【０００２】[0002]
【従来の技術】自動車用エンジンなどの内燃機関に使用
されるスパークプラグのうち、レース用等の高出力エン
ジンに搭載されるものは、エンジンからの強い振動を受
けやすく、接地電極の折損や主体金具に対する溶接部の
剥離といった不具合が生じやすい問題がある。その原因
として、機関もしくは燃焼振動による共振と高加速度
（Ｇ）とが考えられる。一般のスパークプラグは、接地
電極が、先端側が中心電極側を向くようにアール状に曲
げ加工されていることから、主体金具への取り付け基端
側に曲げモーメントが作用しやすく、より折損等が生じ
やすいといえる。2. Description of the Related Art Among spark plugs used in internal combustion engines such as automobile engines, those installed in high-power engines for racing use are susceptible to strong vibrations from the engine and may damage the ground electrode or cause There is a problem that defects such as peeling of the welded part from the metal fitting are likely to occur. Resonance due to engine or combustion vibration and high acceleration (G) are considered as the causes. Since the ground electrode of a general spark plug is bent in a rounded shape so that the tip end side faces the center electrode side, a bending moment tends to act on the base end side attached to the metal shell, and breakage etc. is more likely to occur. It can easily occur.
【０００３】そこで、レース用に特化されたスパークプ
ラグの仕様として、接地電極を上記のようにアール状に
曲げ加工せず、主体金具との接合側端部から、主体金具
の中心軸線に近づく向きに直線的に延びる形態としたも
のが、例えば特開平５−７４５４９号や特開平２−３２
６９２号の各公報に開示されている。このような接地電
極形態とすることにより、接地電極の全長が短くなり、
振動が加わったときに電極の接合基端部に付加される片
振り曲げモーメントを小さくできるので、折損や剥離等
が生じにくくなる。Therefore, as a specification of a spark plug specialized for racing, the ground electrode is not bent into a round shape as described above, but is approached from the end portion on the side where the metal shell is joined to the center axis of the metal shell. For example, Japanese Patent Application Laid-Open No. 5-74549 and Japanese Patent Application Laid-Open No. 2-32 have a configuration that linearly extends in a direction.
No. 692 is disclosed. By adopting such a ground electrode form, the total length of the ground electrode is shortened,
When the vibration is applied, the oscillating bending moment applied to the joint base end portion of the electrode can be reduced, so that breakage or peeling is less likely to occur.
【０００４】[0004]
【発明が解決しようとする課題】しかしながら、近年、
レース用自動車やオートバイ用のエンジンはさらに高性
能・高出力化しており、より高温下にてスパークプラグ
に強い振動が加わるようになってきている。その結果、
上記従来のスパークプラグにおける接地電極の形態改良
だけでは、上記不具合の発生抑制を十分に図ることが困
難となっている。However, in recent years,
Engines for racing cars and motorcycles have become more sophisticated and have higher output, and strong vibrations are being applied to the spark plug at higher temperatures. as a result,
It is difficult to sufficiently suppress the above-mentioned problems only by improving the shape of the ground electrode in the conventional spark plug.
【０００５】本発明の課題は、レース用等の高出力エン
ジン用用途において、接地電極の折損や剥離を効果的に
防止ないし抑制できるスパークプラグを提供することに
ある。An object of the present invention is to provide a spark plug which can effectively prevent or suppress breakage or peeling of the ground electrode in high power engine applications such as racing.
【０００６】[0006]
【課題を解決するための手段及び作用・効果】上記の課
題を解決するために、本発明のスパークプラグは、中心
電極と、その中心電極の外側に設けられた絶縁体と、絶
縁体の外側に設けられるとともに内燃機関への取付ねじ
部が外周面に形成された主体金具と、一端側が主体金具
に結合され、他端側が中心電極の先端と対向するように
配置されて中心電極との間に火花放電ギャップを形成す
る接地電極とを備え、その特徴部が以下のように構成さ
れる（以下、理解の便宜を図るために図１、図２及び図
１０を援用して説明するが、本発明は該図面に開示され
たスパークプラグの形態に限定されるものでないことは
もちろんである）。In order to solve the above problems, a spark plug according to the present invention comprises a center electrode, an insulator provided outside the center electrode, and an outside of the insulator. Between the center electrode and the metal shell having a threaded portion for attachment to the internal combustion engine formed on the outer peripheral surface thereof, the one end side being coupled to the metal shell and the other end side being arranged so as to face the tip of the center electrode. And a ground electrode that forms a spark discharge gap, and the characteristic part thereof is configured as follows (hereinafter, for convenience of understanding, description will be given with reference to FIGS. 1, 2 and 10; Of course, the invention is not limited to the form of the spark plug disclosed in the drawing).
【０００７】すなわち、図１において、取付ねじ部６の
中心軸線Ｏと直交する第一投影面Ｐへの正射投影像（図
１（ｂ））において、該接地電極４は中心軸線Ｏに関す
る半径方向に直線的に延伸した外形形態を有する。ま
た、図１（ｂ）に示すように、中心軸線Ｏと、投影面Ｐ
上における接地電極４の正射投影像の延伸方向Ｌとのい
ずれとも平行な第二投影面Ｑを考えたとき、図２に示す
ように、接地電極４の火花放電ギャップｇに近い側の側
面（第一側面）Ｊが、該第二投影面Ｑへの正射投影像に
おいて、主体金具５との接合側の端Ａから先端Ｂに向け
て少なくともその途中区間まで、中心軸線Ｏに近づく向
きに直線的に延びる形態を有してなる。また、接地電極
４はＰｔを主成分とする合金にて構成される棒状素材の
一方の端部を、溶接区間Ｗにおいて主体金具５端面に溶
接接合して形成されたものである。なお、本発明におい
て「Ｐｔを主成分とする」とは、含有量の最も高い成分
がＰｔであることを意味する。That is, in FIG. 1, in the orthographic projection image (FIG. 1B) on the first projection plane P orthogonal to the central axis O of the mounting screw portion 6, the ground electrode 4 has a radius with respect to the central axis O. It has an external form linearly stretched in the direction. Further, as shown in FIG. 1B, the central axis O and the projection plane P
Assuming a second projection plane Q parallel to the extending direction L of the orthogonal projection image of the ground electrode 4 above, as shown in FIG. 2, the side surface of the ground electrode 4 on the side close to the spark discharge gap g. A direction in which the (first side surface) J approaches the central axis O from the end A on the side where the metal shell 5 is joined to the tip B in the orthographic projection image on the second projection plane Q, at least up to a midway section thereof. It has a linearly extending shape. The ground electrode 4 is formed by welding one end of a rod-shaped material made of an alloy containing Pt as a main component to the end surface of the metal shell 5 in the welding section W. In the present invention, “mainly containing Pt” means that the component with the highest content is Pt.
【０００８】そして、本発明のスパークプラグの第一の
構成においては、図１０に示すように第一投影面Ｐへの
正射投影像において接地電極４が、延伸方向Ｌにおける
溶接区間Ｗの長さをｗ、該溶接区間Ｗよりも火花放電ギ
ャップｇ側に突出している部分（以下、電極突出部とも
いう）の長さをｄとしたとき、ｄ／（ｄ＋ｗ）が０．５
〜０．５８に調整されてなる。また、主体金具５は、取
付ねじ部６の形成部分にて内周面が円筒状面５ｅとされ
てなり、該円筒状面５ｅを火花放電ギャップｇの存在側
に延長したとき、接地電極４の該延長面５ｅよりも内側
に突出する部分が、主体金具５との接合側の端Ａから先
端Ｂに向けて、少なくともその途中区間までが中心軸線
が一定の直柱体状部とされ、該直柱体状部の軸断面積が
０．６４〜２ｍｍ２であることを特徴とする。In the first configuration of the spark plug of the present invention, as shown in FIG. 10, the ground electrode 4 is in the orthographic projection image on the first projection plane P and the length of the welding section W in the extending direction L is long. Where d is the length of the portion projecting to the spark discharge gap g side of the welding section W (hereinafter also referred to as the electrode projecting portion), d / (d + w) is 0.5.
It is adjusted to 0.58. Further, the metal shell 5 has a cylindrical surface 5e on the inner peripheral surface at the portion where the mounting screw portion 6 is formed. When the cylindrical surface 5e is extended to the side where the spark discharge gap g is present, the ground electrode 4 is formed. A portion projecting inward of the extension surface 5e from the end A on the joining side with the metal shell 5 toward the tip B is a straight column-shaped portion having a constant central axis at least in the intermediate section, An axial cross-sectional area of the straight columnar portion is 0.64 to 2 mm 2 .
【０００９】上記構成によると、接地電極４の電極突出
部の長さをｄ、同じく主体金具５に対する溶接区間Ｗの
長さをｗとして、ｄ／（ｄ＋ｗ）を０．５〜０．５８に
調整し、接地電極４の接合側の端Ａから延びる直柱体状
部の軸断面積を０．６４〜２ｍｍ２に設定することによ
り、接地電極４の折損や主体金具５からの剥離を効果的
に防止ないし抑制することができる。直柱体状部の軸断
面積が０．６４ｍｍ２未満になると、接地電極４の耐折
損性あるいは耐剥離性が不十分となる。また、ｄ／（ｄ
＋ｗ）が０．５未満になると、プレイグニッション発生
の観点から見たスパークプラグの耐熱性が不足すること
につながる。つまり、ｄ／（ｄ＋ｗ）が小さくなること
は、電極突出部の長さｄが短くなり、主体金具５の先端
開口径が小さくなることを意味する。本発明のスパーク
プラグでは、絶縁体３の先端が主体金具５の先端よりも
引っ込んで位置するため、主体金具５の先端開口径が小
さくなると絶縁体３の先端部の冷却が進みにくくなって
過度に温度上昇し、火花放電する点火進角よりも早く混
合気に着火してしまう、プレイグニッションが発生しや
すくなるのである。他方、直柱体状部の軸断面積が２ｍ
ｍ２を超えると着火性の低下につながる。他方、ｄ／
（ｄ＋ｗ）が０．５８以上になることは、電極突出部長
さが過大化して耐折損性の低下を招くことにつながる。According to the above construction, the length of the electrode protrusion of the ground electrode 4 is d and the length of the welding section W to the metal shell 5 is w, and d / (d + w) is 0.5 to 0.58. By adjusting and setting the axial cross-sectional area of the straight columnar portion extending from the end A on the joining side of the ground electrode 4 to 0.64 to 2 mm 2 , breakage of the ground electrode 4 and separation from the metal shell 5 are effective. Can be prevented or suppressed. When the axial cross-sectional area of the straight columnar portion is less than 0.64 mm 2 , the ground electrode 4 has insufficient breakage resistance or peeling resistance. Also, d / (d
If + w) is less than 0.5, the heat resistance of the spark plug will be insufficient from the viewpoint of preignition. That is, decreasing d / (d + w) means decreasing the length d of the electrode protrusion and decreasing the tip opening diameter of the metal shell 5. In the spark plug of the present invention, the tip end of the insulator 3 is located more retracted than the tip end of the metal shell 5, so that when the tip opening diameter of the metal shell 5 becomes smaller, cooling of the tip portion of the insulator 3 becomes difficult to proceed and becomes excessive. As a result, preignition easily occurs because the temperature rises and the mixture is ignited earlier than the ignition advance angle of spark discharge. On the other hand, the axial cross-sectional area of the columnar body is 2m.
If it exceeds m 2 , the ignitability will be reduced. On the other hand, d /
When (d + w) is 0.58 or more, the length of the electrode protruding portion becomes excessively large, which leads to a decrease in breakage resistance.
【００１０】他方、本発明のスパークプラグの第二の構
成においては、前記ｄ／ｄ＋ｗが０．５〜０．７に調整
されてなり、前記直柱体状部の軸断面積が０．８〜２ｍ
ｍ２とされる。それ以外は、第一の構成と同様であり、
各数値範囲は、上限値及び下限値の数値が異なるのみ
で、第一の構成と同様の臨界的意味を有する。On the other hand, in the second structure of the spark plug of the present invention, the d / d + w is adjusted to 0.5 to 0.7, and the axial sectional area of the straight columnar portion is 0.8. ~ 2m
m 2 . Other than that, it is the same as the first configuration,
Each numerical range has the same critical meaning as in the first configuration, only the numerical values of the upper limit and the lower limit differ.
【００１１】[0011]
【発明の実施の形態】以下、本発明のいくつかの実施の
形態を、図面を用いて説明する。図１（ａ）及び（ｂ）
に示す本発明の一例たるスパークプラグ１は、筒状の主
体金具５、その主体金具５の内側嵌め込まれた絶縁体
３、その絶縁体３の内側に設けられた中心電極２、一端
側が主体金具５に結合され、他端側が中心電極２の先端
と対向するように配置されて中心電極２との間に火花放
電ギャップｇを形成する接地電極４等を備えている。DESCRIPTION OF THE PREFERRED EMBODIMENTS Some embodiments of the present invention will be described below with reference to the drawings. 1 (a) and (b)
The spark plug 1 as an example of the present invention shown in FIG. 1 includes a tubular metal shell 5, an insulator 3 fitted inside the metal shell 5, a center electrode 2 provided inside the insulator 3, and a metal shell on one end side. A ground electrode 4 and the like, which are connected to the center electrode 5 and are arranged so that the other end side faces the tip of the center electrode 2 and form a spark discharge gap g between the center electrode 2 and the like.
【００１２】絶縁体３は、例えばアルミナあるいは窒化
アルミニウム等のセラミック焼結体により構成され、図
１（ｃ）に示すように、その内部には自身の軸方向に沿
って中心電極２を嵌め込むための孔部（貫通孔）３ｄを
有している。また、主体金具５は、低炭素鋼等の金属に
より円筒状に形成されており、スパークプラグ１のハウ
ジングを構成するとともに、その外周面には、図１
（ａ）に示すように、スパークプラグ１を図示しないシ
リンダヘッドに取り付けるためのねじ部６が形成されて
いる。The insulator 3 is made of, for example, a ceramic sintered body such as alumina or aluminum nitride. As shown in FIG. 1 (c), the center electrode 2 is fitted inside the insulator 3 along its own axial direction. It has a hole portion (through hole) 3d for. Further, the metal shell 5 is formed of a metal such as low carbon steel into a cylindrical shape, constitutes a housing of the spark plug 1, and has an outer peripheral surface thereof as shown in FIG.
As shown in (a), a screw portion 6 for attaching the spark plug 1 to a cylinder head (not shown) is formed.
【００１３】他方、図１（ｃ）に示すように、絶縁体３
の孔部３ｄには、その一方の端部側に端子金具１３が挿
入・固定され、同じく他方の端部側に中心電極２が挿入
・固定されている。また、該貫通孔３ｄ内において端子
金具１３と中心電極２との間に抵抗体１５が配置されて
いる。この抵抗体１５の両端部は、導電性ガラスシール
層１６，１７を介して中心電極２と端子金具１３とにそ
れぞれ電気的に接続されている。また、中心電極２は、
電極の表層部分を構成する母材がＮｉ合金にて構成さ
れ、必要に応じてその内部に熱引き改善のための、図示
しない放熱促進用芯材部（例えばＣｕあるいはＣｕ合金
にて構成される）が埋設される。また、火花放電ギャッ
プｇに面する先端位置に、Ｉｒ合金あるいはＰｔ合金か
らなる貴金属発火部３２が溶接接合されている。On the other hand, as shown in FIG.
The terminal fitting 13 is inserted and fixed to one end of the hole 3d, and the center electrode 2 is inserted and fixed to the other end of the hole 3d. A resistor 15 is arranged between the terminal fitting 13 and the center electrode 2 in the through hole 3d. Both ends of the resistor 15 are electrically connected to the center electrode 2 and the terminal fitting 13 via conductive glass seal layers 16 and 17, respectively. The center electrode 2 is
The base material forming the surface layer of the electrode is made of a Ni alloy, and if necessary, a heat-dissipation promoting core material (not shown) (for example, Cu or Cu alloy) is provided inside the electrode for improving heat transfer. ) Is buried. Further, a noble metal igniting portion 32 made of an Ir alloy or a Pt alloy is welded and joined to a tip position facing the spark discharge gap g.
【００１４】図１（ｂ）に示すように、取付ねじ部６の
中心軸線Ｏと直交する第一投影面Ｐへの正射投影像にお
いて、該接地電極４は中心軸線Ｏに関する半径方向に直
線的に延伸した外形形態を有する。そして、図２に示す
ように、中心軸線Ｏと、投影面Ｐ上における接地電極４
の正射投影像の延伸方向Ｌとのいずれとも平行な第二投
影面Ｑを考えたとき、接地電極４の火花放電ギャップｇ
に近い側の側面（第一側面）Ｊが、該第二投影面Ｑへの
正射投影像において、主体金具５との接合側の端Ａから
先端Ｂに向けて少なくともその途中区間まで、本実施形
態においてはその全区間が、中心軸線Ｏに近づく向きに
直線的に延びる形態を有してなる。そして、接地電極４
は、その全体が、Ｐｔ−Ｉｒ合金等のＰｔ合金（Ｐｔを
主成分とする合金（Ｐｔの質量含有率が最も高い合
金））にて構成されてなる。As shown in FIG. 1B, in the orthographic projection image on the first projection plane P orthogonal to the central axis O of the mounting screw portion 6, the ground electrode 4 is linear in the radial direction with respect to the central axis O. Has an externally stretched external form. Then, as shown in FIG. 2, the central axis O and the ground electrode 4 on the projection plane P are arranged.
Considering the second projection plane Q parallel to the stretching direction L of the orthographic projection image of, the spark discharge gap g of the ground electrode 4
The side surface (first side surface) J closer to the main surface of the second projection plane Q is at least halfway from the end A on the side where the metal shell 5 is joined to the front end B in the orthographic projection image. In the embodiment, the entire section has a form that linearly extends in a direction approaching the central axis O. And the ground electrode 4
Is entirely composed of a Pt alloy such as a Pt-Ir alloy (alloy containing Pt as a main component (alloy having the highest Pt mass content)).
【００１５】接地電極４は、具体的には上記合金からな
る棒状素材の一方の端部を溶接区間Ｗにおいて溶接接合
して形成されたものである。この溶接は、公知の抵抗溶
接法あるいはレーザー溶接法により行われるものであ
る。また、主体金具５は、取付ねじ部６の形成部分にて
内周面が円筒状面５ｅとされてなり、該円筒状面５ｅを
火花放電ギャップｇの存在側に延長したとき、接地電極
４の該延長面５ｅよりも内側に突出する部分、つまり電
極突出部が、主体金具５との接合側の端Ａから先端Ｂに
向けて、少なくともその途中区間まで、本実施形態では
その全体が、正方形状又は長方形状の軸断面を有し、か
つ中心軸線が一定の直柱体状部とされている。Specifically, the ground electrode 4 is formed by welding and joining one end of a rod-shaped material made of the above alloy in a welding section W. This welding is performed by a known resistance welding method or laser welding method. Further, the metal shell 5 has a cylindrical surface 5e on the inner peripheral surface at the portion where the mounting screw portion 6 is formed. When the cylindrical surface 5e is extended to the side where the spark discharge gap g is present, the ground electrode 4 is formed. The portion of the electrode projecting inward of the extension surface 5e, that is, the electrode projecting portion, extends from the end A on the joining side with the metal shell 5 to the tip B, at least up to the intermediate section thereof, in the present embodiment, the entire It has a square-shaped or rectangular-shaped axial cross section, and is a right columnar portion having a constant central axis.
【００１６】そして、第一投影面Ｐへの正射投影像にお
いて接地電極４は、図１０に示すように、延伸方向Ｌに
おける溶接区間Ｗの長さをｗ、該溶接区間Ｗよりも火花
放電ギャップｇ側に突出している部分の長さをｄとした
とき、以下のいずれかの条件を満たすものとして構成さ
れている。
ｄ／（ｄ＋ｗ）が０．５〜０．５８に調整されてな
り、電極突出部をなす前記直柱体状部の軸断面積が０．
６４〜２ｍｍ２である。
ｄ／（ｄ＋ｗ）が０．５〜０．７に調整されてなり、
電極突出部をなす前記直柱体状部の軸断面積が０．８〜
２ｍｍ２である。
各数値範囲の臨界的意味は「課題を解決するための手段
及び作用・効果」の欄にて説明済みであるからここでは
繰り返さない。図１０（ａ）は、抵抗溶接により接合し
た例であり、（ｂ）はレーザー溶接により接合した例で
あるが、何れの場合も溶接区間Ｗの長さｗは、接地電極
４の溶接接合部位において、主体金具５との合金化の影
響を受けていない部分の長さとして定義する。In the orthographic projection image on the first projection plane P, the ground electrode 4 has a length w of the welding section W in the extending direction L as shown in FIG. When the length of the portion protruding toward the gap g side is d, it is configured to satisfy one of the following conditions. d / (d + w) is adjusted to 0.5 to 0.58, and the axial cross-sectional area of the straight columnar portion forming the electrode protrusion is 0.
It is 64 to 2 mm 2 . d / (d + w) is adjusted to 0.5 to 0.7,
The axial cross-sectional area of the straight columnar portion forming the electrode protrusion is 0.8 to
It is 2 mm 2 . The critical meaning of each numerical range has already been explained in the section of “Means and Actions / Effects for Solving Problems” and will not be repeated here. FIG. 10A shows an example of joining by resistance welding, and FIG. 10B shows an example of joining by laser welding. In any case, the length w of the welding section W is the welded joint portion of the ground electrode 4. In, the length is defined as the length of the portion that is not affected by alloying with the metal shell 5.
【００１７】図２に示す態様では、着火性を上げるため
に、中心電極２の先端部（あるいは貴金属発火部３２）
を主体金具１の先端面から突出配置している。そこで、
接地電極４は、第一側面Ｊが、主体金具５との接合側の
端Ａから先端Ｂに向けて、傾斜した形で中心軸線Ｏに近
づく向きに、全区間に渡り直線的に延びる形態とされ、
上記突出した中心電極２の先端面との間に火花放電ギャ
ップｇを形成している。このような接地電極形態を有す
るスパークプラグを、一般にスラント電極タイプと称し
ている。このように接地電極４を傾斜形態に接合するた
めには、図２に示すように、主体金具５の先端面５ｔを
内周側が突出する円錐面状に形成しておき、そこに角柱
形態（例えば軸断面が正方形状あるいは長方形状のも
の）の棒状素材の側面基端部を重ね合わせる形態で溶接
するとよい。In the embodiment shown in FIG. 2, the tip portion of the center electrode 2 (or the noble metal igniting portion 32) is provided in order to improve the ignitability.
Is arranged so as to project from the front end surface of the metal shell 1. Therefore,
The ground electrode 4 has a configuration in which the first side surface J extends linearly over the entire section in a direction in which the first side surface J is inclined from the end A on the joining side with the metal shell 5 toward the tip B and approaches the central axis O. Is
A spark discharge gap g is formed between the projecting center electrode 2 and the tip surface. A spark plug having such a ground electrode form is generally called a slant electrode type. In order to join the ground electrode 4 in the inclined shape in this way, as shown in FIG. 2, the tip surface 5t of the metal shell 5 is formed in a conical surface shape with the inner peripheral side protruding, and the prism shape ( For example, it is advisable to weld rod-shaped raw materials having axial cross-sections of square or rectangular shape in such a manner that the side base end portions are superposed.
【００１８】上記の形態の場合、着火性は大幅に向上す
るが、火花放電ギャップｇを形成する第一側面Ｊが、電
極先端に近づくほど中心電極２の先端面から離間してギ
ャップ長が大きくなるため、火花がギャップ間隔の短く
なる側に偏って発生しやすくなる。これが問題となる場
合は、図９に示すように、接地電極４の全長は若干長く
なるが、中心電極２の先端面と平行に対向する平行面部
Ｊ’を形成するようにしてもよい。この形態において
は、第一側面Ｊは、主体金具５との接合側の端Ａから先
端Ｂに向けて、途中区間までが、中心軸線Ｏに近づく向
きに直線的に延びることとなる。In the case of the above embodiment, the ignitability is greatly improved, but the first side surface J forming the spark discharge gap g is separated from the tip surface of the center electrode 2 as the tip of the electrode is approached, and the gap length is increased. Therefore, sparks are likely to be generated in a biased manner to the side where the gap interval becomes shorter. If this poses a problem, as shown in FIG. 9, the total length of the ground electrode 4 is slightly long, but a parallel surface portion J ′ facing in parallel with the tip end surface of the center electrode 2 may be formed. In this embodiment, the first side surface J extends linearly in a direction approaching the central axis O from the end A on the side where the metal shell 5 is joined to the tip B to a midway section.
【００１９】他方、図３に示すように、中心電極２の先
端部（あるいは貴金属発火部３２）を、主体金具１の先
端面より一定距離だけ引っ込んで位置させ、接地電極４
を中心軸線Ｏと略直交する向きに非傾斜に配置すること
もできる。この構成の場合、接地電極４が傾斜しない分
だけその全長を短くでき、ひいては耐折損性を一層高め
ることができる。また、接地電極４の第一側面Ｊを中心
電極２の先端面と平行に対向させることができるので、
図２の構成と比較して偏消耗が生じにくく、電極の長寿
命化を図ることができる。このような接地電極形態を有
するスパークプラグを、一般にサイド電極タイプと称し
ている。On the other hand, as shown in FIG. 3, the tip portion of the center electrode 2 (or the noble metal igniting portion 32) is positioned so as to be retracted from the tip surface of the metal shell 1 by a certain distance, and the ground electrode 4
Can also be arranged non-tilt in a direction substantially orthogonal to the central axis O. In the case of this structure, the total length of the ground electrode 4 can be shortened by the amount that the ground electrode 4 is not tilted, and the breakage resistance can be further enhanced. Moreover, since the first side surface J of the ground electrode 4 can be opposed to the tip surface of the center electrode 2 in parallel,
As compared with the configuration of FIG. 2, uneven wear is less likely to occur, and the life of the electrode can be extended. A spark plug having such a ground electrode form is generally called a side electrode type.
【００２０】また、接地電極４は、図４〜図８に示すよ
うに、火花放電ギャップｇから遠い側の側面を第二側面
Ｋとして、棒状素材の先端部を第二側面Ｋ側において一
部切り欠く切欠部４ａ，４ｂ，４ｃを形成することによ
り、該先端部にて体積が減じられた形態をなすものとし
て構成することができる。振動が加わったときに接地電
極４が受ける曲げモーメントは、接地電極４の長手方向
の質量分布において、拘束端（つまり主体金具１への接
合端）からの距離が長い位置に質量集中していると大き
くなる。そこで、接合端からの距離が長い電極先端部に
上記のような切欠部４ａ，４ｂ，４ｃを形成しておけ
ば、同じレベルの振動が加わった場合でも、接地電極４
が受ける曲げモーメントを小さくでき、ひいては耐折損
性を高めることができる。この場合、図４のように切欠
部４ａが形成されると、その区間において電極突出部は
直柱体状でなくなる。また、図５あるいは図６のように
切欠部４ｂあるいは４ｃが形成されると、その区間の軸
断面の重心位置が切欠部非形成の区間の重心位置からず
れるため、「中心軸線が一定」の条件を満たさなくな
る。いずれにしろ、電極突出部は、前記した端Ａから先
端Ｂに向けて途中区間までのみが、中心軸線が一定の直
柱体状部となる。Further, as shown in FIGS. 4 to 8, the ground electrode 4 has a side surface far from the spark discharge gap g as a second side surface K, and a tip portion of the rod-shaped material partially on the second side surface K side. By forming the cutout portions 4a, 4b, and 4c that are cut out, the tip portion can be configured to have a reduced volume. The bending moment that the ground electrode 4 receives when vibration is applied is concentrated at a position where the distance from the restraining end (that is, the joining end to the metal shell 1) is long in the mass distribution of the ground electrode 4 in the longitudinal direction. And grows. Therefore, if the notches 4a, 4b, 4c as described above are formed at the electrode tip portion having a long distance from the joining end, the ground electrode 4 can be formed even when the same level of vibration is applied.
It is possible to reduce the bending moment that is received by, and to enhance the breakage resistance. In this case, when the notch 4a is formed as shown in FIG. 4, the electrode protrusion does not have a right columnar shape in that section. Further, when the notch 4b or 4c is formed as shown in FIG. 5 or FIG. 6, the center of gravity of the axial cross section of that section deviates from the center of gravity of the section in which the notch is not formed, so that the “center axis is constant”. The condition will not be met. In any case, the electrode protruding portion becomes a straight columnar portion having a constant central axis only from the end A toward the tip B to an intermediate section.
【００２１】図４〜図６は、図２のスラント電極タイプ
のものに切欠部４ａ，４ｂ，４ｃを形成した例である。
図４では、第二側面Ｋの先端に向かうほど、接地電極４
の厚みを長手方向に連続的に減少させる平面状の切欠部
４ａを形成している。なお、接地電極４の厚みを段階的
に減少させる階段状の切欠部４ａを形成してもよい。図
５では、接地電極４の先端部に、基端側よりも薄肉とな
る一様な厚さの薄肉部を形成する切欠部４ｂが形成され
ている。さらに、図６においては、接地電極４の先端部
において、幅方向両側に傾斜面状の切欠部４ｃを形成す
ることにより、当該幅方向両側部分が中央部よりも薄肉
となる形態とされている。図７及び図８は、図３のサイ
ド電極タイプのものに、図４及び図５と同様の切欠部４
ａ，４ｂを形成した例である。4 to 6 show an example in which the notches 4a, 4b and 4c are formed in the slant electrode type of FIG.
In FIG. 4, the ground electrode 4 is moved toward the tip of the second side surface K.
Has a planar notch 4a that continuously reduces the thickness in the longitudinal direction. In addition, you may form the stepped notch 4a which reduces the thickness of the ground electrode 4 in steps. In FIG. 5, a notch 4b is formed at the tip of the ground electrode 4 to form a thin portion having a uniform thickness that is thinner than the base end side. Further, in FIG. 6, by forming the inclined surface-shaped notches 4c at both ends in the width direction at the tip end portion of the ground electrode 4, both side portions in the width direction are made thinner than the central portion. . FIG. 7 and FIG. 8 are the same as the side electrode type of FIG.
This is an example in which a and 4b are formed.
【００２２】上記切欠部の形成長さが過度に大きくなる
と、薄肉化する区間が長くなりすぎ、耐折損性向上効果
が帰って損なわれることにもつながる。この観点におい
て、例えば図４、図５、図７あるいは図８に示すよう
に、切欠部４ａ，４ｂは、接地電極４の先端から長手方
向に２ｍｍまでの区間Ｌに収まるように形成することが
望ましい。If the formation length of the notch is excessively large, the thinned section becomes too long, and the effect of improving the breakage resistance may be impaired. From this viewpoint, as shown in, for example, FIG. 4, FIG. 5, FIG. 7, or FIG. 8, the notches 4a and 4b may be formed so as to fit within a section L from the tip of the ground electrode 4 to 2 mm in the longitudinal direction. desirable.
【００２３】また、図４、図５、図７あるいは図８にお
いて、主体金具５は、取付ねじ部６の形成部分にて内周
面が円筒状面５ｅとされている。ここで、該円筒状面５
ｅを火花放電ギャップｇの存在側に延長し、接地電極４
の該延長面５ｅよりも内側に突出する部分（以下、電極
突出部という）の体積をＶ、切欠部４ａ，４ｂの形成に
より棒状素材から減じられる体積をＶ’としたとき、
Ｖ’／（Ｖ＋Ｖ’）の値は０．２以上０．５以下とする
ことが望ましい。Ｖ’／（Ｖ＋Ｖ’）の値が０．２未満
では接地電極４の耐折損性向上効果に乏しく、０．５を
超えると電極先端温度が上昇しやすくなり、電極の異常
消耗や溶損といった不具合を招きやすい。In addition, in FIG. 4, FIG. 5, FIG. 7 or FIG. 8, the metal shell 5 has a cylindrical surface 5e on the inner peripheral surface at the portion where the mounting screw portion 6 is formed. Here, the cylindrical surface 5
e is extended to the side where the spark discharge gap g exists, and the ground electrode 4
When the volume of a portion (hereinafter, referred to as an electrode protruding portion) projecting inward from the extension surface 5e is V, and the volume reduced from the rod-shaped material by forming the cutout portions 4a and 4b is V ′,
The value of V '/ (V + V') is preferably 0.2 or more and 0.5 or less. If the value of V '/ (V + V') is less than 0.2, the effect of improving the breakage resistance of the ground electrode 4 is poor, and if it exceeds 0.5, the temperature of the electrode tip tends to rise, resulting in abnormal wear and melting of the electrode. It is easy to cause defects.
【００２４】切欠部４ａ，４ｂの非形成区間において
は、電極突出部が直柱体状に形成されているので、その
直柱体状部と同一の軸断面形状及び寸法を有し、かつ電
極突出部と同一長さの直柱体の体積をＶ0として求めれ
ば、実際の電極突出部の体積Ｖを求めることにより、
Ｖ’は、Ｖ0とＶとの差分Ｖ0−Ｖとして算出することが
できる。各体積パラメータの値は、公知の３次元形状測
定器を用いて測定した、電極突出部の３次元形状プロフ
ァイルから計算することが可能である。In the section where the notches 4a and 4b are not formed, since the electrode protrusion is formed in the shape of a straight column, it has the same axial cross-sectional shape and dimensions as the straight column and the electrode is formed. If the volume of the right columnar body having the same length as the protrusion is obtained as V0, the volume V of the actual electrode protrusion is obtained.
V'can be calculated as the difference V0-V between V0 and V. The value of each volume parameter can be calculated from the three-dimensional shape profile of the electrode protrusion, which is measured using a known three-dimensional shape measuring device.
【００２５】[0025]
【実施例】本発明の効果を確認するために、以下の実験
を行った。図１及び図２に示すスパークプラグの試験品
として、取付ねじ部６の呼びがＭ１４、中心電極２の主
体金具５からの出寸法が０．３ｍｍ、火花放電ギャップ
ｇの間隔（最小となる位置での値）が０．６ｍｍ、接地
電極４の断面形状が正方形状（一辺の長さが０．８〜
１．５６ｍｍ）であり、前記したｄ／（ｄ＋ｗ）が０．
４９〜０．７のものを種々に作製した。接地電極４の材
質として用いたのは、表１に示す種々の組成のＰｔ−Ｉ
ｒ二元合金であり、いずれも熱間伸線した線材を素材と
して用い、主体金具５に対して抵抗溶接により接合し
た。EXAMPLES In order to confirm the effects of the present invention, the following experiments were conducted. As test pieces of the spark plug shown in FIGS. 1 and 2, the nominal size of the mounting screw portion 6 is M14, the protruding size of the center electrode 2 from the metal shell 5 is 0.3 mm, and the interval of the spark discharge gap g (minimum position Value of 0.6 mm, and the ground electrode 4 has a square cross-sectional shape (the length of one side is 0.8 to
1.56 mm), and the above-mentioned d / (d + w) is 0.
Various products of 49 to 0.7 were prepared. As the material of the ground electrode 4, Pt-I having various compositions shown in Table 1 was used.
r Binary alloys, both of which were made of hot drawn wire rods as raw materials and joined to the metal shell 5 by resistance welding.
【００２６】上記の各スパークプラグを以下のようにし
て評価した。
（１）耐折損性評価：排気量２５０ｃｃの２サイクルエ
ンジンを搭載したオートバイに取り付け、テストコース
を、平均速度１６０ｋｍ／ｈにて３００ｋｍ走行した。
走行終了後、試験品を取り外し、接地電極と主体金具と
の溶接面及び電極母材にクラックが形成されているか否
かを目視により確認し、クラックが全く検出されなかっ
たものを良好（○）、０．５ｍｍ未満の微小なクラック
のみ認められたものを可（△）、０．５ｍｍ以上の顕著
なクラックが認められたものを不可（×）として判定し
た。
（２）着火性：上記（１）のテスト走行を３人のプロの
テストライダーにより実施させ、その加速フィーリング
についてのアンケートを行なうとともに、加速フィーリ
ングに好感触を示したライダーの数が、３人のものを着
火性良好（○）、２人のみのものを着火性普通（△）、
１人以下のものを着火性不良（×）として判定した。
（３）耐熱性試験：排気量５０ｃｃの２サイクルエンジ
ンに取り付け、点火進角を段階的に大きくしながら、ス
ロットル全開状態、エンジン回転数８５００ｒｐｍにて
運転を行い、プレイグニッションの発生が始まる臨界点
火進角を求めた（この臨界点火進角が小さいほどプレイ
グニッションが発生しやすく、耐熱性に劣ることを意味
する）。そして、該臨界点火進角が、エンジンの規定進
角と同等以上のものを良好（○）、規定進角未満であれ
ば不良（×）として評価した。以上の結果を表１に示
す。The above spark plugs were evaluated as follows. (1) Evaluation of breakage resistance: The test course was mounted on a motorcycle equipped with a two-cycle engine having a displacement of 250 cc, and the test course was run for 300 km at an average speed of 160 km / h.
After running, remove the test product and visually check whether or not cracks are formed on the welding surface between the ground electrode and the metal shell and on the electrode base metal. If no cracks are detected at all, it is good (○). It was judged that the case where only minute cracks of less than 0.5 mm were recognized (Δ) and the case where remarkable cracks of 0.5 mm or more were recognized (not acceptable). (2) Ignition: The test run in (1) above was conducted by three professional test riders, and a questionnaire about the acceleration feeling was conducted, and the number of riders who showed a favorable feeling in the acceleration feeling was Ignition is good for three people (○), normal for two people (△),
One or less was judged as poor ignitability (x). (3) Heat resistance test: Attached to a 2-cycle engine with a displacement of 50 cc, operating at engine speed 8500 rpm with throttle fully open while gradually increasing ignition advance angle, and critical ignition at which preignition begins to occur The advance angle was determined (the smaller the critical ignition advance angle, the easier preignition occurs and the poorer the heat resistance). When the critical ignition advance angle is equal to or more than the specified advance angle of the engine, it is evaluated as good (◯), and when it is less than the specified advance angle, it is evaluated as bad (x). The above results are shown in Table 1.
【００２７】[0027]
【表１】 [Table 1]
【００２８】これによると、接地電極４のｄ／（ｄ＋
ｗ）の値及び軸断面積の値を本発明の数値範囲内に設定
することにより、着火性や耐熱性を確保しつつ、接地電
極の耐折損性を良好なものとできることがわかる。According to this, d / (d + of the ground electrode 4
It can be seen that by setting the value of w) and the value of the axial cross-sectional area within the numerical range of the present invention, it is possible to ensure good puncture resistance of the ground electrode while ensuring ignitability and heat resistance.
【図１】本発明のスパークプラグの一例を示す正面図、
底面図及び部分縦断面図。FIG. 1 is a front view showing an example of a spark plug of the present invention,
A bottom view and a partial longitudinal section.
【図２】図１のスパークプラグの要部を拡大して示す半
断面図。FIG. 2 is a half sectional view showing an enlarged main part of the spark plug of FIG.
【図３】図１のスパークプラグの、第一変形例の要部を
拡大して示す半断面図。FIG. 3 is a half cross-sectional view showing enlarged main parts of a first modification of the spark plug of FIG.
【図４】図１のスパークプラグの、第二変形例の要部を
拡大して示す半断面図。FIG. 4 is a half cross-sectional view showing enlarged main parts of a second modification of the spark plug of FIG.
【図５】図１のスパークプラグの、第三変形例の要部を
拡大して示す半断面図。5 is a half cross-sectional view showing an enlarged main part of a third modified example of the spark plug of FIG. 1. FIG.
【図６】図１のスパークプラグの、第四変形例の要部を
拡大して示す半断面図。6 is a half cross-sectional view showing an enlarged main part of a fourth modified example of the spark plug of FIG. 1. FIG.
【図７】図１のスパークプラグの、第五変形例の要部を
拡大して示す半断面図。FIG. 7 is a half cross-sectional view showing enlarged main parts of a fifth modification of the spark plug of FIG.
【図８】図１のスパークプラグの、第六変形例の要部を
拡大して示す半断面図。FIG. 8 is a half cross-sectional view showing an enlarged main part of a sixth modification of the spark plug of FIG.
【図９】図１のスパークプラグの、第七変形例の要部を
拡大して示す半断面図。9 is a half cross-sectional view showing an enlarged main part of a seventh modification of the spark plug of FIG.
【図１０】接地電極の溶接接合形態をいくつか例示して
示す拡大底面図。FIG. 10 is an enlarged bottom view showing some examples of welded joints of the ground electrode.
１ スパークプラグ ２ 中心電極 ３ 絶縁体 ４ 接地電極 ４ａ，４ｂ，４ｃ 切欠部 ５ 主体金具 Ｏ 中心軸線 ６ 取付ねじ部 ｇ 火花放電ギャップ Ｐ 第一投影面 Ｌ 延伸方向 Ｑ 第二投影面 Ｊ 第一側面 Ｋ 第二側面 Ｗ 溶接区間 1 spark plug 2 Center electrode 3 insulator 4 ground electrode 4a, 4b, 4c Notch 5 metal shell O central axis 6 Mounting thread g Spark discharge gap P First projection plane L stretching direction Q Second projection plane J First aspect K second side W welding section
───────────────────────────────────────────────────── フロントページの続き (72)発明者 近藤 清博 愛知県名古屋市瑞穂区高辻町14番18号 日 本特殊陶業株式会社内 Ｆターム(参考） 5G059 AA04 CC02 EE19 EE23 ─────────────────────────────────────────────────── ─── Continued front page (72) Inventor Kiyohiro Kondo 14-18 Takatsuji-cho, Mizuho-ku, Nagoya City, Aichi Prefecture Inside this special ceramics company F-term (reference) 5G059 AA04 CC02 EE19 EE23
Claims (2)
の外側に設けられた絶縁体（３）と、前記絶縁体（３）
の外側に設けられるとともに内燃機関への取付ねじ部
（６）が外周面に形成された主体金具（５）と、一端側
が前記主体金具（５）に結合され、他端側が前記中心電
極（２）の先端と対向するように配置されて前記中心電
極（２）との間に火花放電ギャップ（ｇ）を形成する接
地電極（４）とを備え、 前記取付ねじ部（６）の中心軸線（Ｏ）と直交する第一
投影面（Ｐ）への正射投影像において、該接地電極
（４）は前記中心軸線（Ｏ）に関する半径方向に直線的
に延伸した外形形態を有し、 前記中心軸線（Ｏ）と、前記投影面（Ｐ）上における前
記接地電極（４）の正射投影像の延伸方向（Ｌ）とのい
ずれとも平行な第二投影面（Ｑ）を考えたとき、前記接
地電極（４）の前記火花放電ギャップ（ｇ）に近い側の
側面（以下、第一側面という）（Ｊ）が、該第二投影面
（Ｑ）への正射投影像において、前記主体金具（５）と
の接合側の端（Ａ）から先端（Ｂ）に向けて、少なくと
もその途中区間まで、前記中心軸線（Ｏ）に近づく向き
に直線的に延びる形態を有してなり、 また、前記接地電極（４）はＰｔを主成分とする合金に
て構成される棒状素材の一方の端部を、溶接区間（Ｗ）
において前記主体金具（５）の端面に溶接接合して形成
されたものであり、かつ、前記第一投影面（Ｐ）への正
射投影像において前記接地電極（４）は、前記延伸方向
（Ｌ）における前記溶接区間（Ｗ）の長さをｗ、該溶接
区間（Ｗ）よりも前記火花放電ギャップ（ｇ）側に突出
している部分の長さをｄとしたとき、ｄ／（ｄ＋ｗ）が
０．５〜０．５８に調整されてなり、 また、前記主体金具（５）は、前記取付ねじ部（６）の
形成部分にて内周面が円筒状面（５ｅ）とされてなり、
該円筒状面（５ｅ）を前記火花放電ギャップ（ｇ）の存
在側に延長したとき、前記接地電極（４）の該延長面
（５ｅ）よりも内側に突出する部分は、前記主体金具
（５）との接合側の端（Ａ）から先端（Ｂ）に向けて、
少なくともその途中区間までが中心軸線が一定の直柱体
状部とされ、該直柱体状部の軸断面積が０．６４〜２ｍ
ｍ２であることを特徴とするスパークプラグ。1. A center electrode (2) and its center electrode (2)
(3) provided on the outer side of the insulator, and the insulator (3)
A metal shell (5) which is provided on the outer side of the metal shell and has a mounting screw part (6) for attachment to an internal combustion engine formed on the outer peripheral surface, one end side of which is connected to the metal shell (5) and the other end side of which is the central electrode (2 ) And a ground electrode (4) that is arranged so as to face the tip of the mounting electrode and forms a spark discharge gap (g) between the center electrode (2) and the center electrode (2). In an orthographic projection image onto the first projection plane (P) orthogonal to O), the ground electrode (4) has an outer shape linearly extended in the radial direction with respect to the central axis (O), When considering the second projection plane (Q) parallel to both the axis (O) and the extending direction (L) of the orthographic projection image of the ground electrode (4) on the projection plane (P), The side surface of the ground electrode (4) near the spark discharge gap (g) (hereinafter referred to as the first side surface). U) (J) is an orthographic projection image on the second projection surface (Q), from the end (A) on the joint side with the metal shell (5) to the tip (B), at least in the middle thereof. The ground electrode (4) has a shape extending linearly in a direction approaching the central axis (O) up to a section, and the ground electrode (4) is one of rod-shaped materials made of an alloy containing Pt as a main component. Weld the end (W)
In the orthographic projection image on the first projection plane (P), the ground electrode (4) is formed by welding to the end surface of the metal shell (5). When the length of the welding section (W) in L) is w and the length of the portion projecting to the spark discharge gap (g) side from the welding section (W) is d, d / (d + w) Is adjusted to 0.5 to 0.58, and the metal shell (5) has a cylindrical surface (5e) on the inner peripheral surface at the portion where the mounting screw portion (6) is formed. ,
When the cylindrical surface (5e) is extended to the side where the spark discharge gap (g) is present, the portion of the ground electrode (4) projecting inward from the extended surface (5e) is the metal shell (5). ) From the end (A) on the joining side to the tip (B),
A straight columnar portion having a constant central axis is formed at least in the middle of the section, and the axial cross-sectional area of the straight columnar portion is 0.64 to 2 m.
A spark plug characterized by being m 2 .
の外側に設けられた絶縁体（３）と、前記絶縁体（３）
の外側に設けられるとともに内燃機関への取付ねじ部
（６）が外周面に形成された主体金具（５）と、一端側
が前記主体金具（５）に結合され、他端側が前記中心電
極（２）の先端と対向するように配置されて前記中心電
極（２）との間に火花放電ギャップ（ｇ）を形成する接
地電極（４）とを備え、 前記取付ねじ部（６）の中心軸線（Ｏ）と直交する第一
投影面（Ｐ）への正射投影像において、該接地電極
（４）は前記中心軸線（Ｏ）に関する半径方向に直線的
に延伸した外形形態を有し、 前記中心軸線（Ｏ）と、前記投影面（Ｐ）上における前
記接地電極（４）の正射投影像の延伸方向（Ｌ）とのい
ずれとも平行な第二投影面（Ｑ）を考えたとき、前記接
地電極（４）の前記火花放電ギャップ（ｇ）に近い側の
側面（以下、第一側面という）（Ｊ）が、該第二投影面
（Ｑ）への正射投影像において、前記主体金具（５）と
の接合側の端（Ａ）から先端（Ｂ）に向けて、少なくと
もその途中区間まで、前記中心軸線（Ｏ）に近づく向き
に直線的に延びる形態を有してなり、 また、前記接地電極（４）はＰｔを主成分とする合金に
て構成される棒状素材の一方の端部を、溶接区間（Ｗ）
において前記主体金具（５）の端面に溶接接合して形成
されたものであり、かつ、前記第一投影面（Ｐ）への正
射投影像において前記接地電極（４）は、前記延伸方向
（Ｌ）における前記溶接区間（Ｗ）の長さをｗ、該溶接
区間（Ｗ）よりも前記火花放電ギャップ（ｇ）側に突出
している部分の長さをｄとしたとき、ｄ／（ｄ＋ｗ）が
０．５〜０．７に調整されてなり、 また、前記主体金具（５）は、前記取付ねじ部（６）の
形成部分にて内周面が円筒状面（５ｅ）とされてなり、
該円筒状面（５ｅ）を前記火花放電ギャップ（ｇ）の存
在側に延長したとき、前記接地電極（４）の該延長面
（５ｅ）よりも内側に突出する部分は、前記主体金具
（５）との接合側の端（Ａ）から先端（Ｂ）に向けて、
少なくともその途中区間までが中心軸線が一定の直柱体
状部とされ、該直柱体状部の軸断面積が０．８〜２ｍｍ
２であることを特徴とするスパークプラグ。2. A center electrode (2) and the center electrode (2).
(3) provided on the outer side of the insulator, and the insulator (3)
A metal shell (5) which is provided on the outer side of the metal shell and has a mounting screw part (6) for attachment to an internal combustion engine formed on the outer peripheral surface, one end side of which is connected to the metal shell (5) and the other end side of which is the central electrode (2 ) And a ground electrode (4) that is arranged so as to face the tip of the mounting electrode and forms a spark discharge gap (g) between the center electrode (2) and the center electrode (2). In an orthographic projection image onto the first projection plane (P) orthogonal to O), the ground electrode (4) has an outer shape linearly extended in the radial direction with respect to the central axis (O), When considering the second projection plane (Q) parallel to both the axis (O) and the extending direction (L) of the orthographic projection image of the ground electrode (4) on the projection plane (P), The side surface of the ground electrode (4) near the spark discharge gap (g) (hereinafter referred to as the first side surface). U) (J) is an orthographic projection image on the second projection surface (Q), from the end (A) on the joint side with the metal shell (5) to the tip (B), at least in the middle thereof. The ground electrode (4) has a shape extending linearly in a direction approaching the central axis (O) up to a section, and the ground electrode (4) is one of rod-shaped materials made of an alloy containing Pt as a main component. Weld the end (W)
In the orthographic projection image on the first projection plane (P), the ground electrode (4) is formed by welding to the end surface of the metal shell (5). When the length of the welding section (W) in L) is w and the length of the portion projecting to the spark discharge gap (g) side from the welding section (W) is d, d / (d + w) Is adjusted to 0.5 to 0.7, and the metal shell (5) has a cylindrical surface (5e) on the inner peripheral surface at the portion where the mounting screw portion (6) is formed. ,
When the cylindrical surface (5e) is extended to the side where the spark discharge gap (g) is present, the portion of the ground electrode (4) projecting inward from the extended surface (5e) is the metal shell (5). ) From the end (A) on the joining side to the tip (B),
A straight columnar portion having a constant central axis is formed at least up to the middle section, and the axial cross-sectional area of the straight columnar portion is 0.8 to 2 mm.
A spark plug characterized by being 2 .
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2001244442A JP4638093B2 (en) | 2001-08-10 | 2001-08-10 | Spark plug |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2001244442A JP4638093B2 (en) | 2001-08-10 | 2001-08-10 | Spark plug |
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| Publication Number | Publication Date |
|---|---|
| JP2003059620A true JP2003059620A (en) | 2003-02-28 |
| JP4638093B2 JP4638093B2 (en) | 2011-02-23 |
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| JP2001244442A Expired - Fee Related JP4638093B2 (en) | 2001-08-10 | 2001-08-10 | Spark plug |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2008277272A (en) * | 2007-04-03 | 2008-11-13 | Ngk Spark Plug Co Ltd | Method of manufacturing spark plug |
Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5949180A (en) * | 1982-09-15 | 1984-03-21 | 日本特殊陶業株式会社 | Spark plug for high pressure compression internal combustionengine |
| JPH01172292U (en) * | 1988-05-25 | 1989-12-06 | ||
| JPH0574549A (en) * | 1991-09-12 | 1993-03-26 | Ngk Spark Plug Co Ltd | Spark plug |
| JPH06333664A (en) * | 1993-05-20 | 1994-12-02 | Ngk Spark Plug Co Ltd | Spark plug for internal combustion engine |
-
2001
- 2001-08-10 JP JP2001244442A patent/JP4638093B2/en not_active Expired - Fee Related
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5949180A (en) * | 1982-09-15 | 1984-03-21 | 日本特殊陶業株式会社 | Spark plug for high pressure compression internal combustionengine |
| JPH01172292U (en) * | 1988-05-25 | 1989-12-06 | ||
| JPH0574549A (en) * | 1991-09-12 | 1993-03-26 | Ngk Spark Plug Co Ltd | Spark plug |
| JPH06333664A (en) * | 1993-05-20 | 1994-12-02 | Ngk Spark Plug Co Ltd | Spark plug for internal combustion engine |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2008277272A (en) * | 2007-04-03 | 2008-11-13 | Ngk Spark Plug Co Ltd | Method of manufacturing spark plug |
| JP2011044440A (en) * | 2007-04-03 | 2011-03-03 | Ngk Spark Plug Co Ltd | Method of manufacturing spark plug |
| JP4674696B2 (en) * | 2007-04-03 | 2011-04-20 | 日本特殊陶業株式会社 | Manufacturing method of spark plug |
| US8399799B2 (en) | 2007-04-03 | 2013-03-19 | Ngk Spark Plug Co., Ltd. | Method for manufacturing spark plug |
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| Publication number | Publication date |
|---|---|
| JP4638093B2 (en) | 2011-02-23 |
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