JP2001068251A - Spark plug for internal combustion engine - Google Patents
Spark plug for internal combustion engineInfo
- Publication number
- JP2001068251A JP2001068251A JP23886799A JP23886799A JP2001068251A JP 2001068251 A JP2001068251 A JP 2001068251A JP 23886799 A JP23886799 A JP 23886799A JP 23886799 A JP23886799 A JP 23886799A JP 2001068251 A JP2001068251 A JP 2001068251A
- Authority
- JP
- Japan
- Prior art keywords
- discharge gap
- center electrode
- insulator
- tip
- ground electrode
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
Classifications
-
- 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
- H01T13/52—Sparking plugs characterised by a discharge along a surface
-
- 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
- H01T13/02—Details
- H01T13/14—Means for self-cleaning
Landscapes
- Spark Plugs (AREA)
Abstract
Description
【０００１】[0001]
【発明の属する技術分野】本発明は、自己清浄作用を向
上させた内燃機関用スパークプラグに関し、特に、放電
ギャップにおける燃料ブリッジ形成の低減に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spark plug for an internal combustion engine having improved self-cleaning action, and more particularly to a reduction in the formation of a fuel bridge in a discharge gap.
【０００２】[0002]
【従来の技術】一般に、内燃機関用スパークプラグは、
中心電極の周囲を被覆保持する絶縁碍子を取付金具にて
保持するとともに、一端が取付金具に固定されるととも
に他端が中心電極の先端面とにより放電ギャップを形成
する接地電極を備えた構成を有し、該放電ギャップ間に
火花放電を起こし、燃焼室内の燃料混合気に着火させる
ものである。一方で、最近、環境に対する関心が高ま
り、内燃機関に対して層状燃焼を採用することにより、
低燃費でより環境に良い内燃機関が実現されている。2. Description of the Related Art Generally, a spark plug for an internal combustion engine is
A configuration is provided in which an insulator for covering and holding the periphery of the center electrode is held by a mounting bracket, and one end is fixed to the mounting bracket and the other end is provided with a ground electrode forming a discharge gap with the tip end surface of the center electrode. A spark discharge is generated between the discharge gaps to ignite the fuel mixture in the combustion chamber. On the other hand, recently, interest in the environment has increased, and by adopting stratified combustion for internal combustion engines,
A more environmentally friendly internal combustion engine with low fuel consumption has been realized.
【０００３】しかし、このような燃焼室内にて層状燃焼
を生じせしめる場合、過濃混合気がスパークプラグ近傍
に集まり、カーボン汚損し易い状態となってしまう。そ
して、このようなカーボン汚損によれば、中心電極を保
持する絶縁碍子の表面の絶縁性低下が生じ、ひいては中
心電極と接地電極との間の正規の放電ギャップ間での火
花放電ではなく、中心電極から碍子表面を伝って取付金
具奥への火花放電が生じ、着火性能が悪化するという問
題が発生する。[0003] However, when stratified combustion is caused in such a combustion chamber, an enriched air-fuel mixture collects near the spark plug, and carbon is easily contaminated. According to such carbon fouling, the insulation of the surface of the insulator holding the center electrode is deteriorated, and the spark is not generated between the center electrode and the ground electrode in the regular discharge gap, but the center discharge is caused. A spark discharge is generated from the electrode to the back of the mounting bracket along the surface of the insulator, causing a problem that ignition performance is deteriorated.
【０００４】このような不具合を解消するために、火花
清浄スパークプラグとして、例えば、実公昭５３−４１
６２９号公報や特開昭４７−１９２３６号公報に記載の
ものが知られている。これらのものは、上述した一般的
なプラグ構成における接地電極を第１接地電極（主接地
電極）、この第１接地電極により形成される放電ギャッ
プを第１放電ギャップとし、更に、第１接地電極とは別
部位に、一端が取付金具に固定されるとともに他端が中
心電極の側面とにより第２放電ギャップを形成する第２
接地電極（補助接地電極）を設けたものである（以下、
ダブル接地電極タイプという）。[0004] In order to solve such a problem, a spark-cleaning spark plug, for example, is disclosed in Japanese Utility Model Publication No. 53-41.
No. 629 and JP-A-47-19236 are known. In these devices, the ground electrode in the above-described general plug configuration is a first ground electrode (main ground electrode), a discharge gap formed by the first ground electrode is a first discharge gap, and a first ground electrode is further provided. And a second discharge gap having a second end fixed to the mounting bracket and the other end formed by the side surface of the center electrode.
A ground electrode (auxiliary ground electrode) is provided.
Double ground electrode type).
【０００５】ここで、該ダブル接地電極タイプにおいて
は、中心電極の側面と対向する第２接地電極の他端は絶
縁碍子の先端部外径よりも大きい径の外側に位置してい
る。そして、特に実公昭５３−４１６２９号公報では、
通常時の火花放電は、メインギャップとしての第１放電
ギャップにて発生させ、上述のような絶縁碍子のカーボ
ン汚損時には、サブギャップとしての第２放電ギャップ
にて火花放電させることにより、絶縁碍子を汚損してい
るカーボンを消失させて、放電の奥飛びを抑制し、着火
性の低減を抑制するようにしている。Here, in the double ground electrode type, the other end of the second ground electrode facing the side surface of the center electrode is located outside a diameter larger than the outer diameter of the tip of the insulator. And especially in Japanese Utility Model Publication No. 53-41629,
The spark discharge at the normal time is generated in the first discharge gap as the main gap, and when the insulator is carbon-contaminated as described above, the insulator is discharged by the spark discharge in the second discharge gap as the sub-gap. The carbon that has been contaminated is eliminated, thereby suppressing the depth of discharge and suppressing the decrease in ignitability.
【０００６】[0006]
【発明が解決しようとする課題】しかしながら、上記の
ダブル接地電極タイプの火花清浄スパークプラグにおい
ては、第１及び第２放電ギャップ間に内燃機関の燃料
（ガソリン等）が溜まって燃料ブリッジが形成され、こ
れら各ギャップにおいて火花放電が生じなくなる（失火
する）という問題がある。この燃料ブリッジが形成され
る様子を図１０に示す。ここで、図１０において、Ｊ１
は中心電極、Ｊ２は絶縁碍子、Ｊ３は取付金具、Ｊ４は
第１接地電極、Ｊ５及びＪ６はそれぞれ第２接地電極で
あり、燃料は片側斜線ハッチングにて示す。However, in the spark cleaning spark plug of the double ground electrode type described above, the fuel (gasoline or the like) of the internal combustion engine is accumulated between the first and second discharge gaps to form a fuel bridge. However, there is a problem that spark discharge does not occur (misfires) in each of these gaps. FIG. 10 shows how the fuel bridge is formed. Here, in FIG.
Is a center electrode, J2 is an insulator, J3 is a mounting bracket, J4 is a first ground electrode, J5 and J6 are each a second ground electrode, and fuel is indicated by hatching on one side.
【０００７】図１０（ａ）に示す様に、燃料ブリッジ
は、第１接地電極Ｊ４と中心電極Ｊ１との間の第１放電
ギャップ（メインギャップ）に形成される燃料ブリッジ
Ｊ７と、第２接地電極Ｊ５及びＪ６と中心電極Ｊ１との
間の第２放電ギャップ（サブギャップ）に形成される燃
料ブリッジＪ８とがある。ここで、両ギャップが十分に
広ければ、プラグに加わる振動（車両振動や燃焼室内の
圧力変動等）等によって、両ブリッジＪ７及びＪ８は切
れて、残らないが、第１放電ギャップを広げることは、
放電電圧の上昇を招き、第２放電ギャップを広くする
と、ギャップでの放電が行われれずに火花が碍子表面を
伝い、ハウジング奥に放電してしまう問題が起きてしま
うので、それほど広くすることはできない。As shown in FIG. 10A, a fuel bridge includes a fuel bridge J7 formed in a first discharge gap (main gap) between a first ground electrode J4 and a center electrode J1, and a second ground. There is a fuel bridge J8 formed in a second discharge gap (subgap) between the electrodes J5 and J6 and the center electrode J1. Here, if both gaps are sufficiently wide, both bridges J7 and J8 are cut off by vibrations applied to the plug (vehicle vibration, pressure fluctuation in the combustion chamber, etc.), but the first discharge gap cannot be widened. ,
If the second discharge gap is widened, which causes an increase in the discharge voltage, a problem occurs in that the spark does not take place in the gap and the spark travels on the surface of the insulator and discharges to the back of the housing. Can not.
【０００８】また、図１０（ｂ）及び（ｃ）に示す様
に、上記の振動等によって第２放電ギャップの燃料ブリ
ッジＪ８が切れても、その燃料が第１放電ギャップへ伝
わるため、第１放電ギャップの燃料ブリッジＪ７は切れ
にくく、残りやすい。このように、ダブル接地電極タイ
プにおいては、第２接地電極が無い構成である通常のプ
ラグ構成よりも、特に、燃料ブリッジの切れが悪くな
り、失火を生じやすい。Further, as shown in FIGS. 10 (b) and 10 (c), even if the fuel bridge J8 of the second discharge gap is cut by the above-mentioned vibration or the like, the fuel is transmitted to the first discharge gap. The fuel bridge J7 in the discharge gap is hard to break and easily remains. As described above, in the double ground electrode type, disconnection of the fuel bridge is particularly deteriorated and misfiring is more likely to occur than in a normal plug configuration having no second ground electrode.
【０００９】そして、このような燃料ブリッジは、特
に、寒冷地等にて使用される内燃機関（寒冷地仕様の自
動車エンジン等）の場合、低温始動時に燃料がリッチと
なり、形成されやすい。また、過濃混合気を燃焼させる
層状燃焼の場合にも、燃料ブリッジは形成されやすい。In the case of an internal combustion engine used in a cold region or the like (an automobile engine of a cold region specification or the like), the fuel becomes rich at the time of starting at a low temperature, and the fuel bridge is easily formed. Further, also in the case of stratified combustion for burning the rich mixture, the fuel bridge is easily formed.
【００１０】そこで、本発明は上記問題に鑑み、ダブル
接地電極タイプの内燃機関用スパークプラグにおいて、
着火性能を維持しつつ、第１放電ギャップ及び第２放電
ギャップにて燃料ブリッジが形成されるのを防止するこ
とを目的とする。In view of the above problems, the present invention provides a spark plug for an internal combustion engine of a double ground electrode type.
An object is to prevent a fuel bridge from being formed in the first discharge gap and the second discharge gap while maintaining the ignition performance.
【００１１】[0011]
【課題を解決するための手段】本発明は、第２接地電極
と中心電極との間の第２放電ギャップにおいては、上記
図１０に示す様に、第２接地電極Ｊ５、Ｊ６とこれに正
対する絶縁碍子Ｊ２の先端部側面との間に燃料が溜まり
やすいことから、第２放電ギャップにて第２接地電極と
絶縁碍子とが正対する部位における両者の各々の対向面
積の関係、及び、中心電極径と第１放電ギャップ（メイ
ンギャップ）との関係を特定することに着目してなされ
たものである。According to the present invention, in the second discharge gap between the second ground electrode and the center electrode, as shown in FIG. 10, the second ground electrodes J5, J6 and the positive Since the fuel easily accumulates between the insulator J2 and the tip side surface of the insulator J2, the relationship between the opposing areas of the second ground electrode and the insulator at the portion directly facing the insulator in the second discharge gap, and the center. This is done by paying attention to specifying the relationship between the electrode diameter and the first discharge gap (main gap).
【００１２】まず、請求項１記載の発明は、中心電極
（３）と、該中心電極の周囲を覆い該中心電極を保持す
る絶縁碍子（２）と、該絶縁碍子を保持する取付金具
（１）と、一端が該取付金具に固定されるとともに他端
が該中心電極の先端面と対向して第１放電ギャップを形
成する第１接地電極（４）と、一端が該取付金具に固定
されるとともに他端が該中心電極の側面と対向して第２
放電ギャップを形成する第２接地電極（５、６）とを備
え、該第２接地電極の他端が該絶縁碍子の先端部外径よ
りも大きい径の外側に位置しているスパークプラグ、即
ち、ダブル接地電極タイプの内燃機関用スパークプラグ
について、次のような構成としたことを特徴としてい
る。First, according to the first aspect of the present invention, there is provided a center electrode (3), an insulator (2) covering the periphery of the center electrode and holding the center electrode, and a mounting bracket (1) holding the insulator. ), A first ground electrode (4) having one end fixed to the mounting bracket and the other end facing the distal end surface of the center electrode to form a first discharge gap, and one end fixed to the mounting bracket. And the other end faces the side surface of the
A second ground electrode (5, 6) forming a discharge gap, wherein the other end of the second ground electrode is located outside a diameter larger than a tip outer diameter of the insulator, that is, a spark plug, The spark plug for a double ground electrode type internal combustion engine has the following configuration.
【００１３】即ち、第１放電ギャップをＡ、中心電極
（３）の先端部の径をＢとしたとき、これら寸法Ａ及び
Ｂを、Ｂ≦５Ａ−２．５（単位：ｍｍ）、の関係となる
ように設定し、更に、第２放電ギャップの幅方向と直交
する方向における第２接地電極（５、６）の他端の断面
積をＳ１、絶縁碍子（２）の先端部の側面に対して該第
２接地電極の他端面が正射影された投影面積をＳ２、第
２放電ギャップの幅方向における該第２接地電極の他端
から該絶縁碍子の先端部の側面への距離をＣとし、この
距離Ｃ（単位：ｍｍ）を横軸、上記面積Ｓ１と上記面積
Ｓ２との比Ｓ２／Ｓ１を縦軸とした直交座標を設定した
場合、 （Ｃ，Ｓ２／Ｓ１）＝（０．３，０） （Ｃ，Ｓ２／Ｓ１）＝（１．２，０） （Ｃ，Ｓ２／Ｓ１）＝（１．２，１．０） （Ｃ，Ｓ２／Ｓ１）＝（０．８，１．０） （Ｃ，Ｓ２／Ｓ１）＝（０．３，０．５） の各点を結ぶ線及びこれら線内の領域となるように、上
記距離Ｃ及び上記比Ｓ２／Ｓ１を設定したことを特徴と
している。That is, when the first discharge gap is A and the diameter of the tip of the center electrode (3) is B, the relation between these dimensions A and B is B ≦ 5A−2.5 (unit: mm). Further, the cross-sectional area of the other end of the second ground electrode (5, 6) in the direction orthogonal to the width direction of the second discharge gap is S1, and the cross-sectional area of the other end of the insulator (2) is On the other hand, the projected area of the other end surface of the second ground electrode is orthogonally projected, S2, and the distance from the other end of the second ground electrode to the side surface of the tip of the insulator in the width direction of the second discharge gap is C2. When orthogonal coordinates are set with the distance C (unit: mm) on the horizontal axis and the ratio S2 / S1 of the area S1 to the area S2 on the vertical axis, (C, S2 / S1) = (0. (3,0) (C, S2 / S1) = (1.2,0) (C, S2 / S1) = (1.2,1.0) (C , S2 / S1) = (0.8, 1.0) (C, S2 / S1) = (0.3, 0.5) It is characterized in that the distance C and the ratio S2 / S1 are set.
【００１４】これら、各寸法Ａ、Ｂ、Ｃ、Ｓ１及びＳ２
を規定する上記の範囲は、本発明者等が実験検討した結
果、即ち後述の図７及び図８に基づくものであり、本発
明によれば、プラグの着火性能を維持しつつ、第１放電
ギャップ及び第２放電ギャップにて燃料ブリッジが形成
されるのを防止することができる。These dimensions A, B, C, S1 and S2
Is based on the results of experiments and studies by the present inventors, that is, FIGS. 7 and 8 described below. According to the present invention, the first discharge is performed while maintaining the ignition performance of the plug. The formation of the fuel bridge in the gap and the second discharge gap can be prevented.
【００１５】なお、第２接地電極の他端と絶縁碍子の先
端部側面とが正対する部分（プラグの軸方向において重
なり合う部分）においては、両者の対向面は平面ではな
く多少湾曲しているため、本発明では、両者の対向面積
を、上記の各面積Ｓ１及びＳ２のように平面化した面積
で近似している。In the portion where the other end of the second ground electrode and the side surface of the tip of the insulator face each other (the portion overlapping in the axial direction of the plug), the opposing surfaces thereof are not plane but slightly curved. In the present invention, the opposing areas are approximated by flattened areas like the areas S1 and S2 described above.
【００１６】さらに、請求項２記載の発明のように、上
記距離Ｃと上記比Ｓ２／Ｓ１とを、上記直交座標におい
て、 （Ｃ，Ｓ２／Ｓ１）＝（０．３，０） （Ｃ，Ｓ２／Ｓ１）＝（１．２，０） （Ｃ，Ｓ２／Ｓ１）＝（１．２，１．０） （Ｃ，Ｓ２／Ｓ１）＝（１．０，１．０） （Ｃ，Ｓ２／Ｓ１）＝（０．３，０．３） の各点を結ぶ線及びこれら線内の領域となるように設定
すれば、より確実に第１及び第２放電ギャップにおける
燃料ブリッジの形成を防止することができる。Further, as in the second aspect of the present invention, the distance C and the ratio S2 / S1 are defined by the following formula: (C, S2 / S1) = (0.3, 0) (C, (S2 / S1) = (1.2,0) (C, S2 / S1) = (1.2,1.0) (C, S2 / S1) = (1.0,1.0) (C, S2 /S1)=(0.3, 0.3) If the line is set to be a line connecting the points and an area within these lines, the formation of the fuel bridge in the first and second discharge gaps can be more reliably prevented. can do.
【００１７】また、請求項３記載の発明では、ダブル接
地電極タイプの内燃機関用スパークプラグにおいて、−
２５℃の環境下において、内燃機関用の燃料中に浸漬し
た後、続いて、中心電極（３）の先端面を下方にして所
定の距離だけ自然落下させ空中で停止させるという、本
発明者等が独自に考案した試験方法に基づいてなされた
ものである。この試験方法によれば、実用上、プラグに
加わる振動等と同等の外力が発生する。According to a third aspect of the present invention, in the spark plug for an internal combustion engine of the double ground electrode type,
The inventors of the present invention immerse the fuel in a fuel for an internal combustion engine in an environment of 25 ° C., then drop the tip end face of the center electrode (3) downward naturally for a predetermined distance, and stop in the air. Was made based on the test method originally devised. According to this test method, practically, an external force equivalent to vibration or the like applied to the plug is generated.
【００１８】即ち、本発明によれば、上記試験におい
て、自然落下させて空中停止させた後、第１及び第２放
電ギャップが該燃料によってつながっていない状態とな
るように、上記請求項１記載の各寸法Ａ、Ｂ、Ｃ、Ｓ１
及びＳ２を規定したことを特徴としている。それによっ
て、実用上、プラグに加わる振動等によって第１及び第
２放電ギャップにて燃料ブリッジが切れて残らないよう
にできるため、燃料ブリッジが形成されるのを防止でき
る。ここで、実用レベルの振動等を鑑み、自然落下させ
る所定の距離は４ｃｍ以下であること（請求項４の発
明）が好ましい。That is, according to the present invention, in the above test, the first and second discharge gaps are not connected by the fuel after the natural fall and the suspension in the air. Each dimension A, B, C, S1
And S2 are defined. Thus, in practice, the fuel bridge can be prevented from being cut and remaining in the first and second discharge gaps due to vibration applied to the plug, and the formation of the fuel bridge can be prevented. Here, in consideration of a practical level of vibration and the like, it is preferable that the predetermined distance for the natural fall is 4 cm or less (the invention of claim 4).
【００１９】また、第２放電ギャップの幅方向における
第２接地電極（５、６）の他端から絶縁碍子（２）の先
端部の側面への距離Ｃは、０．３ｍｍ以上１．２ｍｍ以
下（請求項５の発明）が好ましく、第１放電ギャップＡ
は０．７ｍｍ以上１．３ｍｍ以下（請求項６の発明）が
好ましい。これは、それぞれの下限値未満であるとラフ
アイドルが生じやすく、一方、それぞれの上限値を超え
ると火花放電が起こりにくく失火しやすくなるためであ
る。また、中心電極の先端部の径Ｂは、実用面を考え
て、０．３ｍｍ以上２．８ｍｍ以下（請求項７の発明）
が好ましい。The distance C from the other end of the second ground electrode (5, 6) in the width direction of the second discharge gap to the side surface of the tip of the insulator (2) is 0.3 mm or more and 1.2 mm or less. (Invention of claim 5) is preferable, and the first discharge gap A
Is preferably 0.7 mm or more and 1.3 mm or less (the invention of claim 6). This is because rough idling is likely to occur when the value is less than each lower limit value, while spark discharge is unlikely to occur and misfiring tends to occur when the value exceeds each upper limit value. The diameter B of the tip of the center electrode is 0.3 mm or more and 2.8 mm or less in view of practical use (the invention of claim 7).
Is preferred.
【００２０】なお、上記各手段の括弧内の符号は、後述
する実施形態に記載の具体的手段との対応関係を示す一
例である。The reference numerals in parentheses of the above means are examples showing the correspondence with specific means described in the embodiments described later.
【００２１】[0021]
【発明の実施の形態】以下、本発明を図に示す実施形態
について説明する。図１は、本発明の実施形態に係るダ
ブル接地電極タイプのスパークプラグ１００の半断面
図、図２は、図１中のＸ矢視部分拡大図、図３は、図１
中のＹ矢視図である。なお、図２においては、絶縁碍子
内部の中心電極を示すために、絶縁碍子は断面形状を示
してある。また、図４において（ａ）は図２に対応した
部分の寸法説明図、（ｂ）は図３に対応した部分の寸法
説明図である。BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing a first embodiment of the present invention. FIG. 1 is a half cross-sectional view of a spark plug 100 of a double ground electrode type according to an embodiment of the present invention, FIG. 2 is a partially enlarged view taken along the arrow X in FIG. 1, and FIG.
It is a Y arrow view in the middle. In FIG. 2, the insulator has a cross-sectional shape in order to show the center electrode inside the insulator. 4A is a dimensional explanatory diagram of a portion corresponding to FIG. 2, and FIG. 4B is a dimensional explanatory diagram of a portion corresponding to FIG.
【００２２】スパークプラグ１００は、金属等よりなる
円筒形状の取付金具（ハウジング）１を有しており、こ
の取付金具１は、図示しないエンジンブロックに固定す
るための取付ネジ部１ａを備えている。取付金具１の内
部には、例えばアルミナセラミック（Ａｌ2 Ｏ3 ）等か
らなる絶縁碍子２が固定されており、この絶縁碍子２の
先端部２ａは、取付金具１から露出するように設けられ
ている。さらに、図２に示す様に、絶縁碍子２の先端部
２ａのさらなる先端には、この基部である先端部２ａよ
りも径小であるとともに、略同一径を有する細径部２ｂ
が設けられている。The spark plug 100 has a cylindrical mounting bracket (housing) 1 made of metal or the like, and the mounting bracket 1 has a mounting screw portion 1a for fixing to an engine block (not shown). . An insulator 2 made of, for example, alumina ceramic (Al 2 O 3 ) is fixed inside the mounting bracket 1, and a tip 2 a of the insulator 2 is provided so as to be exposed from the mounting bracket 1. I have. Further, as shown in FIG. 2, a further end of the tip 2a of the insulator 2 has a smaller diameter portion 2b having a diameter smaller than that of the base 2a and having substantially the same diameter.
Is provided.
【００２３】中心電極３は絶縁碍子２の軸孔２ｃに固定
され、絶縁碍子２を介して取付金具１に絶縁保持されて
いる。この中心電極３は、内材がＣｕ（銅）等の熱伝導
性に優れた金属材料、外材がＮｉ（ニッケル）基合金等
の耐熱性および耐食性に優れた金属材料により構成され
た円柱体で、中心電極３の先端が絶縁碍子２の先端部２
ａから露出するように設けられている。また、図２に示
す様に、中心電極３の基部３ａの先端には、基部３ａよ
りもさらに径小な有する径小部３ｂが形成されており、
径小部３ｂの外周は、絶縁碍子２の細径部２ｂの内周よ
りも内側に位置している。The center electrode 3 is fixed to a shaft hole 2 c of the insulator 2, and is insulated and held by the mounting bracket 1 via the insulator 2. The center electrode 3 is a cylindrical body whose inner material is made of a metal material having excellent thermal conductivity such as Cu (copper) and whose outer material is made of a metal material having excellent heat resistance and corrosion resistance such as a Ni (nickel) base alloy. The tip of the center electrode 3 is the tip 2 of the insulator 2
It is provided so as to be exposed from a. As shown in FIG. 2, a small-diameter portion 3b having a smaller diameter than the base 3a is formed at the tip of the base 3a of the center electrode 3,
The outer periphery of the small diameter portion 3b is located inside the inner periphery of the small diameter portion 2b of the insulator 2.
【００２４】図２及び図３に示す様に、取付金具１の一
端には、第１接地電極４、第２接地電極５及び６が溶接
等により固定されている。これら第１及び第２接地電極
４〜６は、Ｎｉ基合金材料等から構成されている。第１
接地電極４においては、取付金具１に固定された一端と
は反対の他端が、中心電極３の径小部３ｂの先端面に対
向して配置され、該径小部３ｂの先端面との間に第１放
電ギャップＡを形成している。As shown in FIGS. 2 and 3, a first ground electrode 4 and second ground electrodes 5 and 6 are fixed to one end of the mounting bracket 1 by welding or the like. These first and second ground electrodes 4 to 6 are made of a Ni-based alloy material or the like. First
In the ground electrode 4, the other end opposite to the one end fixed to the mounting bracket 1 is disposed so as to face the distal end surface of the small diameter portion 3 b of the center electrode 3, and is in contact with the distal end surface of the small diameter portion 3 b. A first discharge gap A is formed therebetween.
【００２５】また、第２接地電極５及び６においては各
々、取付金具１に固定された一端とは反対の他端面（先
端面）が、中心電極３の径小部３ｂの側面に対向して配
置され、該径小部３ｂの側面との間に第２放電ギャップ
を形成している。ここで、第２接地電極５及び６の他端
面は、絶縁碍子２の細径部２ｂにおける外径よりも距離
Ｃ（図４参照）だけ大きい径の外側に位置している。In each of the second ground electrodes 5 and 6, the other end surface (tip surface) opposite to the one end fixed to the mounting bracket 1 faces the side surface of the small-diameter portion 3 b of the center electrode 3. And a second discharge gap is formed between the second discharge gap and the side surface of the small-diameter portion 3b. Here, the other end surfaces of the second ground electrodes 5 and 6 are located outside a diameter larger by the distance C (see FIG. 4) than the outer diameter of the small diameter portion 2b of the insulator 2.
【００２６】ところで、本実施形態においては、図４に
示す各寸法Ａ、Ｂ、Ｃ、Ｓ１及びＳ２を、次のように規
定した独自の構成としている。これら独自の構成につい
て、寸法規定の根拠とともに説明していく。ここで、第
１放電ギャップＡは当該ギャップの幅、寸法Ｂは中心電
極３の径小部３ｂの直径（本発明でいう中心電極の先端
部の径、以下、中心電極径という）である。また、上記
距離Ｃは、第２放電ギャップに幅方向（図４中の左右方
向）における第２接地電極５及び６の各他端面から絶縁
碍子２の細径部２ｂの側面への距離である。In this embodiment, each of the dimensions A, B, C, S1, and S2 shown in FIG. 4 has a unique configuration defined as follows. These unique configurations will be described together with the basis of the dimension regulations. Here, the first discharge gap A is the width of the gap, and the dimension B is the diameter of the small-diameter portion 3b of the center electrode 3 (the diameter of the tip of the center electrode in the present invention, hereinafter referred to as the center electrode diameter). The distance C is the distance from the other end surface of each of the second ground electrodes 5 and 6 in the width direction (the left-right direction in FIG. 4) to the side surface of the small-diameter portion 2b of the insulator 2 in the second discharge gap. .
【００２７】また、第２放電ギャップの幅方向と直交す
る方向における第２接地電極５及び６の各他端の断面積
をＳ１とする。この断面積Ｓ１は、図４中に一点鎖線に
て示す仮想平面（第２放電ギャップの幅方向と直交する
平面）９００内に位置する各第２接地電極５及び６の断
面の面積である。また、図示例では、第２接地電極５及
び６の各他端面と絶縁碍子２の細径部２ｂの側面とは、
軸方向において一部重なり合って正対した正対領域９０
１を有している。The sectional area of the other end of each of the second ground electrodes 5 and 6 in a direction orthogonal to the width direction of the second discharge gap is S1. This cross-sectional area S1 is the cross-sectional area of each of the second ground electrodes 5 and 6 located in a virtual plane (a plane orthogonal to the width direction of the second discharge gap) 900 indicated by a dashed line in FIG. In the illustrated example, the other end surfaces of the second ground electrodes 5 and 6 and the side surfaces of the small-diameter portion 2b of the insulator 2 are
Facing region 90 which is partially overlapped and facing in the axial direction.
One.
【００２８】この正対領域９０１において、絶縁碍子２
の細径部２ｂの側面に対して第２接地電極５及び６の各
他端面が正射影された投影面積をＳ２とする。よって、
これら各面積Ｓ１、Ｓ２は矩形状平面の面積となる。実
際には、図に示す様に、正対領域９０１においては、絶
縁碍子２及び第２接地電極５及び６の各対向面は平面で
はなく多少湾曲しているが、本実施形態では、両者の対
向面の面積を矩形状平面化した面積Ｓ１及びＳ２にて近
似している。In the facing area 901, the insulator 2
Let S2 be a projection area in which the other end surfaces of the second ground electrodes 5 and 6 are orthogonally projected on the side surface of the small-diameter portion 2b. Therefore,
These areas S1 and S2 are the areas of a rectangular plane. Actually, as shown in the figure, in the facing region 901, the facing surfaces of the insulator 2 and the second ground electrodes 5 and 6 are not planes but are slightly curved. The areas of the opposing surfaces are approximated by rectangular areas S1 and S2.
【００２９】そして、上記構成を有するスパークプラグ
１００について、次に述べるような燃料保持力試験を行
い、上記各寸法Ａ、Ｂ、Ｃ、Ｓ１及びＳ２の関係を検討
し、規定した。図５に、この試験方法の模式的説明図を
示す。まず、図５（ａ）に示す様に、−２５℃の低温室
内に、内燃機関に用いられる燃料（本例ではハイオクガ
ソリン）９１０を入れた容器（ビーカー等）９１１を用
意し、燃料９１０を約−２５℃の状態とする。これによ
り、燃料９１０は粘性が大きく燃料ブリッジを形成し易
い状態となる。The spark plug 100 having the above configuration was subjected to a fuel holding force test as described below, and the relationships among the dimensions A, B, C, S1, and S2 were examined and defined. FIG. 5 shows a schematic explanatory view of this test method. First, as shown in FIG. 5A, a container (a beaker or the like) 911 containing a fuel (high-octane gasoline in this example) 910 used for an internal combustion engine is prepared in a low temperature room at −25 ° C., and the fuel 910 is prepared. Keep the temperature at about -25 ° C. As a result, the fuel 910 has a large viscosity and is in a state in which a fuel bridge is easily formed.
【００３０】次に、この状態の低温室内にて、接地電極
４〜６側と反対側端部に固定されたひも９１２によっ
て、プラグ１００をつり下げ、その接地電極４〜６側に
て取付金具１の端面まで燃料９１０中に浸漬した後、燃
料９１０から取り出す。この浸漬によって本プラグ１０
０においても、上記図１０に示したのと同様に、第１接
地電極４と中心電極３との間の第１放電ギャップＡ、及
び、各第２接地電極５及び６と中心電極３との間の各第
２放電ギャップに、各々燃料ブリッジが形成され、これ
ら各放電ギャップが燃料９１０によってつながった状態
となる。Next, in the low-temperature room in this state, the plug 100 is suspended by the string 912 fixed to the end opposite to the ground electrodes 4 to 6 side, and the mounting bracket is mounted on the ground electrodes 4 to 6 side. After being immersed in the fuel 910 up to the end face of the fuel cell 910, the fuel cell 910 is taken out from the fuel 910. The plug 10
0, the first discharge gap A between the first ground electrode 4 and the center electrode 3 and the gap between the second ground electrodes 5 and 6 and the center electrode 3 as shown in FIG. A fuel bridge is formed in each of the second discharge gaps therebetween, and these discharge gaps are connected by the fuel 910.
【００３１】続いて、上記低温室内にて、図５（ｂ）に
示す様に、ひも９１２によりプラグ１００を空中で停止
させ、この状態から、ひも９１２でプラグ１００を支持
しながら、プラグ１００を中心電極３の先端面を下方に
して所定の距離（落下高さ）Ｈだけ自然落下させ、空中
で停止させる。この落下後の停止の際の衝撃によって、
各放電ギャップに形成された燃料ブリッジが切れようと
する。即ち、各放電ギャップにおいて燃料保持力が大き
ければ燃料ブリッジは残り、燃料保持力が弱ければ燃料
ブリッジは切れる。ここで、落下高さＨは０ｃｍ、１ｃ
ｍ、２ｃｍ、３ｃｍ、４ｃｍ、５ｃｍと変えて行った。Subsequently, as shown in FIG. 5B, the plug 100 is stopped in the air by the string 912 in the low-temperature room, and from this state, the plug 100 is supported while the plug 100 is supported by the string 912. The center electrode 3 is allowed to fall naturally by a predetermined distance (fall height) H with the tip end face facing downward, and is stopped in the air. By the impact at the time of stop after this fall,
The fuel bridge formed in each discharge gap is about to break. That is, if the fuel holding power is large in each discharge gap, the fuel bridge remains, and if the fuel holding power is weak, the fuel bridge is cut off. Here, the drop height H is 0 cm, 1 c
m, 2 cm, 3 cm, 4 cm, and 5 cm.
【００３２】まず、第２接地電極の断面積Ｓ１、投影面
積Ｓ２及び距離Ｃを種々変えたものについて上記燃料保
持力試験を行い、第２放電ギャップ間の燃料保持力につ
いて検討した例を示す。本例では、第２接地電極の断面
積Ｓ１を、１．４４ｍｍ2（サイズ０．８ｍｍ×１．８
ｍｍ）、２．６４ｍｍ2（サイズ１．２ｍｍ×２．２ｍ
ｍ）、４．１６ｍｍ2（サイズ１．６ｍｍ×２．６ｍ
ｍ）の３種類を用いた。First, an example is shown in which the above-mentioned fuel holding force test was carried out on variously changed cross-sectional areas S1, projected area S2 and distance C of the second ground electrode, and the fuel holding force between the second discharge gaps was examined. In this example, the cross-sectional area S1 of the second ground electrode is set to 1.44 mm 2 (0.8 mm × 1.8 in size).
mm), 2.64 mm 2 (size 1.2 mm x 2.2 m
m), 4.16 mm 2 (size 1.6 mm × 2.6 m)
m) were used.
【００３３】そして、図６に示す様に、各第２接地電極
５及び６の各他端面と絶縁碍子２の細径部２ｂの側面と
をプラグの軸方向にずらして上記投影面積Ｓ２を種々変
えていくことにより、上記断面積Ｓ１と投影面積Ｓ２と
の比Ｓ２／Ｓ１を、０〜１の間で種々変化させた。ちな
みに、図６（ａ）では比Ｓ２／Ｓ１が０、図６（ｂ）で
は比Ｓ２／Ｓ１が０より大きく１未満、図６（ｃ）では
比Ｓ２／Ｓ１が１の状態である。As shown in FIG. 6, the other end surfaces of the second ground electrodes 5 and 6 and the side surface of the small diameter portion 2b of the insulator 2 are shifted in the axial direction of the plug to change the projection area S2. By changing the ratio, the ratio S2 / S1 of the cross-sectional area S1 and the projected area S2 was variously changed between 0 and 1. 6A, the ratio S2 / S1 is 0, in FIG. 6B, the ratio S2 / S1 is greater than 0 and less than 1, and in FIG. 6C, the ratio S2 / S1 is 1.
【００３４】また、上記距離Ｃについては、第２放電ギ
ャップにおける着火性能を好適に維持するために、０．
３ｍｍ以上１．２ｍｍ以下の範囲で種々変えた。これ
は、距離Ｃが０．３ｍｍ未満であると、第１放電ギャッ
プ（メインギャップ）Ａよりも第２放電ギャップ（サブ
ギャップ）の方が優先的に火花放電を発生してラフアイ
ドルが生じやすく、一方、距離Ｃが１．２ｍｍを超える
と第２放電ギャップにて火花放電が起こりにくく、カー
ボン汚損時に沿面放電せず失火エンストしやすくなるた
めである。In addition, the distance C is set to 0. 0 to maintain the ignition performance in the second discharge gap suitably.
Various changes were made in the range of 3 mm or more and 1.2 mm or less. This is because if the distance C is less than 0.3 mm, spark discharge occurs preferentially in the second discharge gap (sub gap) over the first discharge gap (main gap) A, and rough idle is likely to occur. On the other hand, if the distance C exceeds 1.2 mm, spark discharge is unlikely to occur in the second discharge gap, and when carbon is contaminated, creepage discharge does not occur and misfire stalls easily.
【００３５】また、上記燃料保持力試験では、自然落下
後において、第２放電ギャップに燃料ブリッジが残って
いれば判定は否、第２放電ギャップに燃料ブリッジが残
っていなければ判定は良であるが、本発明者等の検討に
よれば、上記落下高さＨが４ｃｍ以下で良判定ならば、
実用上、燃料ブリッジが形成されないプラグとして使用
可能である。そのため、上記比Ｓ２／Ｓ１と距離Ｃを種
々変えた構成のプラグ１００を作製し、上記落下高さＨ
が４ｃｍ以下にて第２放電ギャップ間の燃料保持力試験
を行った。その結果を、上記距離Ｃと上記比Ｓ２／Ｓ１
との関係図として図７に示す。In the above-mentioned fuel holding force test, after the natural fall, the determination is no if the fuel bridge remains in the second discharge gap, and the determination is good if no fuel bridge remains in the second discharge gap. However, according to the study of the present inventors, if the drop height H is 4 cm or less and the determination is good,
Practically, it can be used as a plug in which a fuel bridge is not formed. Therefore, the plug 100 having a configuration in which the ratio S2 / S1 and the distance C are variously changed is manufactured, and the drop height H is set.
The fuel holding force test between the second discharge gaps was performed at a height of 4 cm or less. The result is expressed as the distance C and the ratio S2 / S1.
FIG.
【００３６】図７は、上記距離Ｃ（単位：ｍｍ）を横
軸、上記比Ｓ２／Ｓ１を縦軸とした直交座標を示すもの
ある。図７中、斜線ハッチングで示す五角形の領域Ｒ、
即ち、各点Ｐ１〜Ｐ５を結ぶ線内の領域（線も含む）Ｒ
が、上記落下高さＨが４ｃｍ以下で良判定となるよう
な、上記距離Ｃ及び各面積Ｓ１、Ｓ２の設定領域（以
下、第２放電ギャップの良判定領域という）である。こ
こで、各点Ｐ１〜Ｐ５の座標は、 （Ｃ，Ｓ２／Ｓ１）＝（０．３，０） （Ｃ，Ｓ２／Ｓ１）＝（１．２，０） （Ｃ，Ｓ２／Ｓ１）＝（１．２，１．０） （Ｃ，Ｓ２／Ｓ１）＝（０．８，１．０） （Ｃ，Ｓ２／Ｓ１）＝（０．３，０．５） である。FIG. 7 shows orthogonal coordinates with the distance C (unit: mm) on the horizontal axis and the ratio S2 / S1 on the vertical axis. In FIG. 7, a pentagonal region R indicated by oblique hatching,
That is, a region (including a line) R in a line connecting the points P1 to P5
Is a set area of the distance C and the areas S1 and S2 (hereinafter referred to as a good judgment area of the second discharge gap) such that a good judgment is made when the drop height H is 4 cm or less. Here, the coordinates of each point P1 to P5 are (C, S2 / S1) = (0.3, 0) (C, S2 / S1) = (1.2, 0) (C, S2 / S1) = (1.2, 1.0) (C, S2 / S1) = (0.8, 1.0) (C, S2 / S1) = (0.3, 0.5)
【００３７】なお、図７に示す結果は、ｎ数（試験の繰
り返し数）が３にて行った場合であるが、この第２放電
ギャップの良判定領域Ｒは、少なくとも３回のうち１回
は良判定となる領域である。さらに、３回とも全て良判
定となる領域（以下、第２放電ギャップの好ましい良判
定領域という）は、図７中の各点Ｐ１〜Ｐ３、Ｐ４’及
びＰ５’の各点を結ぶ線にて示される五角形内の領域
（線も含む）である。ここで、各点Ｐ４’及びＰ５’の
座標は、 （Ｃ，Ｓ２／Ｓ１）＝（１．０，１．０） （Ｃ，Ｓ２／Ｓ１）＝（０．３，０．３） である。The results shown in FIG. 7 are obtained when the number n (the number of repetitions of the test) is 3, and the good judgment region R of the second discharge gap is at least one out of three times. Is an area where a good judgment is made. Further, a region in which all three good determinations are made (hereinafter referred to as a preferable good determination region of the second discharge gap) is indicated by a line connecting the points P1 to P3, P4 ′, and P5 ′ in FIG. This is the area (including the line) within the pentagon shown. Here, the coordinates of each point P4 ′ and P5 ′ are (C, S2 / S1) = (1.0, 1.0) (C, S2 / S1) = (0.3, 0.3) .
【００３８】従って、この第２放電ギャップの良判定領
域Ｒとなるように、上記距離Ｃ及び各面積Ｓ１、Ｓ２を
設定すれば、第２放電ギャップにおける燃料ブリッジの
形成を防止できる。更に、第２放電ギャップの好ましい
良判定領域となるように、上記距離Ｃ及び各面積Ｓ１、
Ｓ２を設定すれば、より確実に第２放電ギャップにおけ
る燃料ブリッジの形成を防止することができる。また、
上記距離Ｃを０．３ｍｍ以上１．２ｍｍ以下としている
ため、第２放電ギャップにおける着火性能を好適に維持
できる。Therefore, if the distance C and the areas S1 and S2 are set so as to be in the good judgment region R of the second discharge gap, formation of a fuel bridge in the second discharge gap can be prevented. Further, the distance C and the respective areas S1,
By setting S2, it is possible to more reliably prevent the formation of the fuel bridge in the second discharge gap. Also,
Since the distance C is 0.3 mm or more and 1.2 mm or less, the ignition performance in the second discharge gap can be suitably maintained.
【００３９】また、上記比Ｓ２／Ｓ１が０でもよいた
め、本実施形態では上記正対領域９０１が無くても良
い。つまり、図６（ａ）に示す様に、第２接地電極５及
び６の各他端面と絶縁碍子２の細径部２ｂの側面とが、
軸方向において重なり合っていない（正対していない）
状態でも良い。ここまでが、第２放電ギャップ間の燃料
保持力の検討例である。Further, since the ratio S2 / S1 may be 0, the facing region 901 may not be provided in the present embodiment. That is, as shown in FIG. 6A, the other end surfaces of the second ground electrodes 5 and 6 and the side surface of the small-diameter portion 2b of the insulator 2 are in contact with each other.
Not overlapping in the axial direction (not facing)
It may be in a state. The above is an example of studying the fuel holding force between the second discharge gaps.
【００４０】次に、第１放電ギャップＡ及び中心電極径
（中心電極の先端部の径）Ｂを種々変えたものについて
上記燃料保持力試験を行い、第１放電ギャップ間の燃料
保持力について検討した例を示す。ここで、本検討で
は、上記第２放電ギャップ間の燃料保持力の検討におい
て、落下高さＨが３ｃｍ以下で良判定となるように、上
記距離Ｃ及び上記比Ｓ２／Ｓ１を設定したものについ
て、更に、第１放電ギャップＡ及び中心電極径Ｂを種々
変えた。Next, the above-mentioned fuel holding force test was performed on the first discharge gap A and the center electrode diameter (diameter of the tip of the center electrode) B which were variously changed, and the fuel holding force between the first discharge gaps was examined. An example is shown below. Here, in the present study, in the study of the fuel holding force between the second discharge gaps, the distance C and the ratio S2 / S1 are set so that a good determination is made when the drop height H is 3 cm or less. Further, the first discharge gap A and the center electrode diameter B were variously changed.
【００４１】本例では、第１接地電極４のサイズを１．
４ｍｍ×２．６ｍｍとした。なお、このサイズは上記図
４（ａ）に示す第１接地電極４の厚さＤを１．４ｍｍ、
その幅Ｅを２．６ｍｍとしたものに相当する。また、第
１放電ギャップＡは０．７ｍｍ以上１．３ｍｍ以下の範
囲で種々変えた。これは、第１放電ギャップＡが０．７
ｍｍ未満であるとラフアイドルが生じやすく、一方、第
１放電ギャップＡが１．３ｍｍを超えると失火エンスト
しやすくなるためである。また、中心電極径Ｂは実用面
を考えて最小０．３ｍｍ、最大２．８ｍｍまでとした。In this embodiment, the size of the first ground electrode 4 is set to 1.
It was 4 mm x 2.6 mm. Note that this size is such that the thickness D of the first ground electrode 4 shown in FIG.
This corresponds to a width E of 2.6 mm. Further, the first discharge gap A was variously changed in a range of 0.7 mm or more and 1.3 mm or less. This is because the first discharge gap A is 0.7
If it is less than 1 mm, rough idle is likely to occur, while if the first discharge gap A exceeds 1.3 mm, misfire stalling tends to occur. Further, the center electrode diameter B is set to a minimum of 0.3 mm and a maximum of 2.8 mm in consideration of practical use.
【００４２】本検討においても、上記落下高さＨが４ｃ
ｍ以下で良判定ならば、実用上、燃料ブリッジが形成さ
れないプラグに相当するため、プラグ１００において、
上記ギャップＡ及び中心電極径Ｂを種々変えた構成のも
のを作製し、上記落下高さＨが４ｃｍ以下にて第１放電
ギャップ間の燃料保持力試験を行った。その結果を、第
１放電ギャップＡと中心電極径Ｂとの関係図として図８
に示す。In this study, the drop height H was 4c.
m or less, the plug is practically equivalent to a plug in which a fuel bridge is not formed.
A fuel cell having a configuration in which the gap A and the center electrode diameter B were variously changed was manufactured, and a fuel holding force test between the first discharge gaps was performed at the drop height H of 4 cm or less. FIG. 8 is a graph showing the relationship between the first discharge gap A and the center electrode diameter B.
Shown in
【００４３】図８は、横軸に第１放電ギャップＡ（単
位：ｍｍ）、縦軸に中心電極径Ｂ（単位：ｍｍ）とし、
図中の実線Ｒ１を含みこの実線Ｒ１よりも右側が良判定
領域（以下、第１放電ギャップの良判定領域という）で
あり、この実線Ｒ１を含まずにこの実線Ｒ１よりも左側
が否判定領域であることを示す。従って、図８から、Ｂ
≦５Ａ−２．５（単位：ｍｍ）、となるように、第１放
電ギャップＡ及び中心電極径Ｂを設定すれば、第１放電
ギャップＡにおける燃料ブリッジの形成を防止できる。
また、第１放電ギャップＡを０．７ｍｍ以上１．３ｍｍ
以下としているため、第１放電ギャップＡにおける着火
性能を好適に維持できる。In FIG. 8, the horizontal axis represents the first discharge gap A (unit: mm), the vertical axis represents the center electrode diameter B (unit: mm),
The area including the solid line R1 in the figure and the right side of the solid line R1 is a good judgment area (hereinafter, referred to as a good judgment area of the first discharge gap), and the left side of the solid line R1 without including the solid line R1 is a negative judgment area. It is shown that. Therefore, from FIG.
If the first discharge gap A and the center electrode diameter B are set so as to satisfy ≦ 5A-2.5 (unit: mm), formation of a fuel bridge in the first discharge gap A can be prevented.
Further, the first discharge gap A is set to 0.7 mm or more and 1.3 mm.
Because of the following, the ignition performance in the first discharge gap A can be suitably maintained.
【００４４】なお、比較例として、第２接地電極の無い
通常のプラグ構成、即ち上記プラグ１００において第２
接地電極が無く第１接地電極のみ有る構成において上記
燃料保持力試験を行った。その結果を、図８中の破線Ｒ
２に示す。この結果から、通常プラグ構成では、ダブル
接地電極タイプよりも放電ギャップが狭い範囲まで燃料
ブリッジ形成の防止が可能であることがわかる。即ち、
本実施形態は、通常プラグ構成よりも燃料ブリッジが形
成されやすいダブル接地電極タイプにおいて、好適にブ
リッジ形成を防止するものである。As a comparative example, a normal plug structure without the second ground electrode, that is, the second plug in the plug 100 is used.
The above-mentioned fuel holding force test was performed in a configuration having no ground electrode and only the first ground electrode. The result is shown by the broken line R in FIG.
It is shown in FIG. From this result, it is understood that the formation of the fuel bridge can be prevented in the normal plug configuration to a range where the discharge gap is narrower than that of the double ground electrode type. That is,
The present embodiment suitably prevents the formation of a bridge in a double ground electrode type in which a fuel bridge is more easily formed than in a normal plug configuration.
【００４５】このように、本実施形態によれば、本発明
者等が独自に考案した上記の燃料保持力試験を用いて、
燃料保持力の良否判定を行い、その結果から、上記図７
及び図８に示す様な良判定領域を求めることができる。
そして、これら良判定領域に入るように上記の各寸法
Ａ、Ｂ、Ｃ、Ｓ１及びＳ２が設定されたスパークプラグ
１００によれば、プラグの着火性能を維持しつつ、第１
放電ギャップ及び第２放電ギャップにて燃料ブリッジが
形成されるのを防止することができる。As described above, according to the present embodiment, using the above-described fuel holding force test uniquely devised by the present inventors,
The quality of the fuel holding force is determined, and the result is shown in FIG.
And a good judgment area as shown in FIG.
According to the spark plug 100 in which the dimensions A, B, C, S1, and S2 are set so as to fall within these good determination regions, the first performance is maintained while maintaining the ignition performance of the plug.
A fuel bridge can be prevented from being formed in the discharge gap and the second discharge gap.
【００４６】なお、上記した図示例によれば、第２接地
電極５及び６の各他端面と絶縁碍子２の細径部２ｂの側
面とは、略平行になっているが、図９（図中、第１接地
電極４は省略）に変形例として示す様に、これら両面が
±３０°以内の角度（絶縁碍子２の細径部２ｂの側面と
第２接地電極５及び６の各他端面とのなす角度）θをも
って対向していれば良い。これは、当該角度θが±３０
°よりも大きくなると、第２接地電極５及び６の他端に
おけるエッジＫ１０が放電部分に突き出た形となり、消
耗が激しくなる可能性があるためである。また、一方の
第２接地電極５と他方の第２接地電極６とで、角度θが
異なっていても良い。According to the illustrated example, the other end surfaces of the second ground electrodes 5 and 6 and the side surface of the small-diameter portion 2b of the insulator 2 are substantially parallel. As shown in a modified example in FIG. 3, the first ground electrode 4 is omitted, and both surfaces have an angle of ± 30 ° or less (the side surface of the small-diameter portion 2b of the insulator 2 and the other end surfaces of the second ground electrodes 5 and 6). It is sufficient that they face each other with an angle θ). This is because the angle θ is ± 30.
If the angle is larger than 0 °, the edge K10 at the other ends of the second ground electrodes 5 and 6 becomes a shape protruding into the discharge portion, and there is a possibility that the exhaustion becomes severe. The angle θ may be different between one second ground electrode 5 and the other second ground electrode 6.
【００４７】以上述べてきたように、本実施形態は、ダ
ブル接地電極タイプのスパークプラグにおいて、燃料ブ
リッジの形成防止という目的からは従来為されていなか
った各部寸法の最適化を、本発明者等が独自に考案した
試験方法を用いて鋭意検討した結果、実現したものであ
る。As described above, in the present embodiment, in the spark plug of the double ground electrode type, optimization of the dimensions of each part, which has not been conventionally performed for the purpose of preventing the formation of the fuel bridge, has been achieved by the present inventors. Has been realized as a result of intensive studies using a test method originally devised.
【００４８】（他の実施形態）なお、上記実施形態にお
いて、中心電極の先端面及びこれに対向する第１接地電
極の部位に、ＰｔやＩｒ等の貴金属やＰｔやＩｒ等を主
成分とする貴金属チップ（貴金属部材）が設けられてい
ても良い。この場合、設置されたチップは各電極の一部
に相当するものである。また、絶縁碍子２の先端には細
径部２ｂが形成されてい無くても良い。(Other Embodiments) In the above embodiment, the tip surface of the center electrode and the portion of the first ground electrode opposed thereto are mainly composed of a noble metal such as Pt or Ir or Pt or Ir. A noble metal tip (noble metal member) may be provided. In this case, the installed chip corresponds to a part of each electrode. Also, the small diameter portion 2b may not be formed at the tip of the insulator 2.
【００４９】また、第２接地電極は上記実施形態のよう
に２本でなくとも、１本もしくは３本以上であってもよ
い。また、第２接地電極が複数個あり、それぞれに対応
して第２放電ギャップが形成されている場合、全ての第
２接地電極について上記距離Ｃ及び上記各面積Ｓ１、Ｓ
２が同一でなくとも良く、これら寸法Ｃ、Ｓ１、Ｓ２
は、上記良判定領域にあれば、個々の第２接地電極毎に
異なっていても良い。The number of the second ground electrodes is not limited to two as in the above embodiment, but may be one or three or more. When there are a plurality of second ground electrodes and a second discharge gap is formed corresponding to each of the second ground electrodes, the distance C and the respective areas S1, S
2 may not be the same, and these dimensions C, S1, S2
May be different for each individual second ground electrode as long as it is in the above-mentioned good judgment area.
【図１】本発明の実施形態に係るスパークプラグの半断
面図である。FIG. 1 is a half sectional view of a spark plug according to an embodiment of the present invention.
【図２】図１中のＸ矢視部分拡大図である。FIG. 2 is a partially enlarged view as viewed from an arrow X in FIG.
【図３】図１中のＹ矢視図である。FIG. 3 is a view as viewed in the direction of the arrow Y in FIG. 1;
【図４】図１に示すスパークプラグの部分寸法説明図で
ある。FIG. 4 is an explanatory diagram of a partial dimension of the spark plug shown in FIG. 1;
【図５】上記実施形態に係る燃料保持力試験の模式的説
明図である。FIG. 5 is a schematic explanatory diagram of a fuel holding force test according to the embodiment.
【図６】上記実施形態にて投影面積Ｓ２を変化させた状
態を示す説明図である。FIG. 6 is an explanatory diagram showing a state where a projection area S2 is changed in the embodiment.
【図７】第２放電ギャップ間の燃料保持力試験の結果を
示す図である。FIG. 7 is a diagram showing a result of a fuel holding force test between second discharge gaps.
【図８】第１放電ギャップ間の燃料保持力試験の結果を
示す図である。FIG. 8 is a diagram showing a result of a fuel holding force test between first discharge gaps.
【図９】上記実施形態の変形例を示す図である。FIG. 9 is a diagram showing a modification of the embodiment.
【図１０】燃料ブリッジが形成される様子を示す説明図
である。FIG. 10 is an explanatory diagram showing how a fuel bridge is formed.
１…取付金具、２…絶縁碍子、３…中心電極、４…第１
接地電極、５、６…第２接地電極。DESCRIPTION OF SYMBOLS 1 ... Mounting bracket, 2 ... Insulator, 3 ... Center electrode, 4 ... First
Ground electrodes, 5, 6,... Second ground electrodes.
Claims (7)
碍子（２）と、 前記絶縁碍子を保持する取付金具（１）と、 一端が前記取付金具に固定されるとともに、他端が前記
中心電極の先端面と対向配置されて前記中心電極の先端
面との間に第１放電ギャップを形成する第１接地電極
（４）と、 一端が前記取付金具に固定されるとともに、他端が前記
中心電極の側面と対向配置されて前記中心電極の側面と
の間に第２放電ギャップを形成する第２接地電極（５、
６）とを備え、 前記第２接地電極の他端は前記絶縁碍子の先端部外径よ
りも大きい径の外側に位置しており、 前記第１放電ギャップをＡ、前記中心電極の先端部の径
をＢとしたとき、これら寸法Ａ及びＢは、 Ｂ≦５Ａ−２．５（単位：ｍｍ）、の関係にあり、 前記第２放電ギャップの幅方向と直交する方向における
前記第２接地電極の他端の断面積をＳ１、前記絶縁碍子
の先端部の側面に対して前記第２接地電極の他端面が正
射影された投影面積をＳ２、前記第２放電ギャップの幅
方向における前記第２接地電極の他端から前記絶縁碍子
の先端部の側面への距離をＣとし、 前記距離Ｃ（単位：ｍｍ）を横軸、前記面積Ｓ１と前記
面積Ｓ２との比Ｓ２／Ｓ１を縦軸とした直交座標を設定
した場合、 （Ｃ，Ｓ２／Ｓ１）＝（０．３，０） （Ｃ，Ｓ２／Ｓ１）＝（１．２，０） （Ｃ，Ｓ２／Ｓ１）＝（１．２，１．０） （Ｃ，Ｓ２／Ｓ１）＝（０．８，１．０） （Ｃ，Ｓ２／Ｓ１）＝（０．３，０．５） の各点を結ぶ線及びこれら線内の領域となるように、前
記距離Ｃ及び前記比Ｓ２／Ｓ１は設定されていることを
特徴とする内燃機関用スパークプラグ。1. A center electrode (3), an insulator (2) that covers the periphery of the center electrode and holds the center electrode, a mounting bracket (1) that holds the insulator, and one end of the attachment. A first ground electrode (4) fixed to the metal fitting, the other end of the first ground electrode (4) being opposed to the tip end face of the center electrode to form a first discharge gap with the tip end face of the center electrode; A second ground electrode (5, 5) fixed to a mounting bracket and having the other end opposed to the side surface of the center electrode to form a second discharge gap between the side surface of the center electrode.
6), the other end of the second ground electrode is located outside a diameter larger than the outer diameter of the tip of the insulator, the first discharge gap is A, the tip of the center electrode is When the diameter is B, these dimensions A and B have a relationship of B ≦ 5A-2.5 (unit: mm), and the second ground electrode in a direction orthogonal to the width direction of the second discharge gap. Is the cross-sectional area of the other end of the insulator, S2 is the projected area of the other end surface of the second ground electrode orthogonally projected to the side surface of the tip of the insulator, and S2 is the second discharge electrode in the width direction of the second discharge gap. Let C be the distance from the other end of the ground electrode to the side surface of the tip of the insulator, the horizontal axis be the distance C (unit: mm), and the vertical axis be the ratio S2 / S1 of the area S1 to the area S2. (C, S2 / S1) = (0.3, 0) (C , S2 / S1) = (1.2, 0) (C, S2 / S1) = (1.2, 1.0) (C, S2 / S1) = (0.8, 1.0) (C, The distance C and the ratio S2 / S1 are set so that a line connecting the points of (S2 / S1) = (0.3, 0.5) and an area within these lines are set. Spark plug for internal combustion engines.
記直交座標において、 （Ｃ，Ｓ２／Ｓ１）＝（０．３，０） （Ｃ，Ｓ２／Ｓ１）＝（１．２，０） （Ｃ，Ｓ２／Ｓ１）＝（１．２，１．０） （Ｃ，Ｓ２／Ｓ１）＝（１．０，１．０） （Ｃ，Ｓ２／Ｓ１）＝（０．３，０．３） の各点を結ぶ線及びこれら線内の領域となるように設定
されていることを特徴とする請求項１に記載の内燃機関
用スパークプラグ。2. The distance C and the ratio S2 / S1 are represented by (C, S2 / S1) = (0.3, 0) (C, S2 / S1) = (1.2, 0) (C, S2 / S1) = (1.2,1.0) (C, S2 / S1) = (1.0,1.0) (C, S2 / S1) = (0.3,0 3. The spark plug for an internal combustion engine according to claim 1, wherein the spark plug is set so as to be a line connecting the respective points of (1) and (2) and an area within these lines.
碍子（２）と、 前記絶縁碍子を保持する取付金具（１）と、 一端が前記取付金具に固定されるとともに、他端が前記
中心電極の先端面と対向配置されて前記中心電極の先端
面との間に第１放電ギャップを形成する第１接地電極
（４）と、 一端が前記取付金具に固定されるとともに、他端が前記
中心電極の側面と対向配置されて前記中心電極の側面と
の間に第２放電ギャップを形成する第２接地電極（５、
６）とを備え、 前記第２接地電極の他端は前記絶縁碍子の先端部外径よ
りも大きい径の外側に位置しており、 −２５℃の環境下において、内燃機関用の燃料中に浸漬
した後、前記中心電極の先端面を下方にして所定の距離
だけ自然落下させ空中で停止させ、前記第１及び第２放
電ギャップが前記燃料によってつながっていない状態と
なるように、 前記第１放電ギャップＡ、前記中心電極の先端部の径
Ｂ、前記第２放電ギャップの幅方向と直交する方向にお
ける前記第２接地電極の他端の断面積Ｓ１、前記絶縁碍
子の先端部の側面に対して前記第２接地電極の他端面が
正射影された投影面積Ｓ２、及び、前記第２放電ギャッ
プの幅方向における前記第２接地電極の他端から前記絶
縁碍子の先端部の側面への距離Ｃ、が規定されているこ
とを特徴とする内燃機関用スパークプラグ。3. A center electrode (3); an insulator (2) that covers the periphery of the center electrode and holds the center electrode; a mounting bracket (1) that holds the insulator; A first ground electrode (4) fixed to the metal fitting, the other end of the first ground electrode (4) being opposed to the tip end face of the center electrode to form a first discharge gap with the tip end face of the center electrode; A second ground electrode (5, 5) fixed to a mounting bracket and having the other end opposed to the side surface of the center electrode to form a second discharge gap between the side surface of the center electrode.
6), wherein the other end of the second ground electrode is located outside a diameter larger than an outer diameter of a tip portion of the insulator, and in an environment of −25 ° C., in a fuel for an internal combustion engine. After the immersion, the center electrode is naturally dropped by a predetermined distance with the tip end face downward, and stopped in the air, and the first and second discharge gaps are not connected by the fuel. With respect to the discharge gap A, the diameter B of the tip of the center electrode, the cross-sectional area S1 of the other end of the second ground electrode in a direction orthogonal to the width direction of the second discharge gap, and the side surface of the tip of the insulator. The projected area S2 of the other end surface of the second ground electrode, and the distance C from the other end of the second ground electrode to the side surface of the tip of the insulator in the width direction of the second discharge gap. , It is specified that Spark plug for an internal combustion engine to be.
であることを特徴とする請求項３に記載の内燃機関用ス
パークプラグ。4. The spark plug for an internal combustion engine according to claim 3, wherein the predetermined distance for dropping is 4 cm or less.
前記第２接地電極（５、６）の他端から前記絶縁碍子
（２）の先端部の側面への距離Ｃは、０．３ｍｍ以上
１．２ｍｍ以下であることを特徴とする請求項３または
４に記載の内燃機関用スパークプラグ。5. The distance C from the other end of the second ground electrode (5, 6) in the width direction of the second discharge gap to the side surface of the tip of the insulator (2) is at least 0.3 mm. The spark plug for an internal combustion engine according to claim 3 or 4, wherein the spark plug is not more than 0.2 mm.
上１．３ｍｍ以下であることを特徴とする請求項１ない
し５のいずれか１つに記載の内燃機関用スパークプラ
グ。6. The spark plug for an internal combustion engine according to claim 1, wherein the first discharge gap A is not less than 0.7 mm and not more than 1.3 mm.
ｍｍ以上２．８ｍｍ以下であることを特徴とする請求項
１ないし６のいずれか１つに記載の内燃機関用スパーク
プラグ。7. The diameter B of the tip of the center electrode is 0.3
The spark plug for an internal combustion engine according to any one of claims 1 to 6, wherein the spark plug is not less than 2.8 mm and not more than 2.8 mm.
Priority Applications (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP23886799A JP3721877B2 (en) | 1999-08-25 | 1999-08-25 | Spark plug for internal combustion engine |
| EP20000118389 EP1079487B1 (en) | 1999-08-25 | 2000-08-24 | Spark plug for internal combustion engine |
| DE2000637955 DE60037955T2 (en) | 1999-08-25 | 2000-08-24 | Spark plug for internal combustion engines |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP23886799A JP3721877B2 (en) | 1999-08-25 | 1999-08-25 | Spark plug for internal combustion engine |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JP2001068251A true JP2001068251A (en) | 2001-03-16 |
| JP3721877B2 JP3721877B2 (en) | 2005-11-30 |
Family
ID=17036445
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP23886799A Expired - Lifetime JP3721877B2 (en) | 1999-08-25 | 1999-08-25 | Spark plug for internal combustion engine |
Country Status (3)
| Country | Link |
|---|---|
| EP (1) | EP1079487B1 (en) |
| JP (1) | JP3721877B2 (en) |
| DE (1) | DE60037955T2 (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7554253B2 (en) | 2004-09-14 | 2009-06-30 | Denso Corporation | Spark plug with increased durability and carbon fouling resistance |
| US20140299087A1 (en) * | 2011-11-02 | 2014-10-09 | Denso Corporation | Spark plug for internal combustion engines and mounting structure for the spark plug |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7663296B2 (en) | 2006-03-29 | 2010-02-16 | Ngk Spark Plug Co., Ltd. | Spark plug for internal combustion engine |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE2106893A1 (en) * | 1971-02-13 | 1972-08-31 | Bosch Gmbh Robert | Combined high voltage air and sliding spark spark plug |
| JP3140006B2 (en) * | 1998-06-11 | 2001-03-05 | 日本特殊陶業株式会社 | Spark plug |
-
1999
- 1999-08-25 JP JP23886799A patent/JP3721877B2/en not_active Expired - Lifetime
-
2000
- 2000-08-24 DE DE2000637955 patent/DE60037955T2/en not_active Revoked
- 2000-08-24 EP EP20000118389 patent/EP1079487B1/en not_active Revoked
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7554253B2 (en) | 2004-09-14 | 2009-06-30 | Denso Corporation | Spark plug with increased durability and carbon fouling resistance |
| US20140299087A1 (en) * | 2011-11-02 | 2014-10-09 | Denso Corporation | Spark plug for internal combustion engines and mounting structure for the spark plug |
| US9482203B2 (en) * | 2011-11-02 | 2016-11-01 | Denso Corporation | Spark plug for internal combustion engines and mounting structure for the spark plug |
Also Published As
| Publication number | Publication date |
|---|---|
| DE60037955D1 (en) | 2008-03-20 |
| JP3721877B2 (en) | 2005-11-30 |
| DE60037955T2 (en) | 2009-03-19 |
| EP1079487A1 (en) | 2001-02-28 |
| EP1079487B1 (en) | 2008-02-06 |
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