JPS6065491A - Spark plug - Google Patents

Abstract

(57)【要約】本公報は電子出願前の出願データであるた
め要約のデータは記録されません。(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

【発明の詳細な説明】 この発明は背後電極効果をもったスパークプラグに関し
、特に該スパークプラグの耐汚損性を向上させたスパー
クプラグに関する。DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a spark plug having a back electrode effect, and more particularly to a spark plug with improved stain resistance.

近年、燃費の低減の面からスパークプラグの着火性の向
上が一層要望されており、かかる着火性向上に最も有効
な手段はスパークギャップの拡大であることがよく知ら
れているが、一般に気中で飛火する従来のスパークプラ
グは内燃機関の燃焼室内圧力が高いアイドリング加速時
には飛火要求電圧が高くなるため前記スパークギャップ
ヲ著シく広くすることはできず、満足すべき着火性が得
られない。In recent years, there has been a growing demand for improvements in the ignitability of spark plugs in order to reduce fuel consumption, and it is well known that the most effective means for improving ignition performance is to widen the spark gap. With conventional spark plugs, the spark gap cannot be significantly widened during idling and acceleration when the pressure in the combustion chamber of the internal combustion engine is high, so the spark gap cannot be significantly widened and satisfactory ignition performance cannot be obtained.

かかる不具合を解消するため、第１藺に示すように、中
心電極ｌの先端１”ｒ露出させて該中心電極を囲む磁器
絶縁体２の薄肉の発火部２ａｆ取付金具３の先端部３ａ
よＶ燃焼室側に突出させ、この発火部２ａの外周２ｂＶ
Ｃ対向して微小ギャップＧ１を隔て前記取付金具３の先
端面８ａＶＣ突役した接地１Ｅ極４を対設し、中・Ｕ雷
極ｌの先端１ａと接地電極４との間に中・し電極の背後
電極効果によって、発火部２ａの絶縁体表面に沿って沿
面放ｉＩＥしるスパークプラグが知られており、かくし
て背後７「極効果によＶ沿面放電の放電電圧が下り、そ
の分だけスパークギャップを広くし着火性を向上するも
のである。In order to solve this problem, as shown in the first step, the tip 1''r of the center electrode l is exposed and the thin firing part 2af of the porcelain insulator 2 surrounding the center electrode is exposed, and the tip 3a of the mounting bracket 3 is removed.
The outer circumference 2bV of this ignition part 2a is made to protrude toward the combustion chamber side.
The tip surface 8a of the mounting bracket 3 is provided with a protruding ground 1E electrode 4 facing each other with a small gap G1 therebetween, and a middle electrode is placed between the tip 1a of the middle U lightning pole l and the ground electrode 4. There is a known spark plug that emits creeping discharge along the insulator surface of the ignition part 2a due to the back electrode effect of the back electrode. This widens the gap and improves ignitability.

ところで、かかる背後電極効果をもったスパークプラグ
はスパークギャップの拡大および発火部を燃焼室内に突
出させることで石火性には有効であるが、前記の如く燃
焼室内に長く突出するため耐汚損性の而には不利となっ
て比較的くすぶり易い欠点を有していた。Incidentally, a spark plug with such a back electrode effect is effective in preventing ignition by expanding the spark gap and protruding the ignition part into the combustion chamber, but as mentioned above, the spark plug protrudes into the combustion chamber for a long time, so it has poor fouling resistance. However, it had the disadvantage of being relatively easy to smolder.

本発明は上述の問題全解決するためになされたもので、
背後？Ｄ：極効果をもったスパークプラグの耐汚損性を
督しく高めたスパークプラグの提供を目的とするもので
ある。その特徴は、中心電極の先端を露出させて該中心
電極を囲む磁器絶縁体の発火部を取付金具の先端面エリ
燃焼室側に突出させ、この発火部の外周と微小ギャップ
を隔てて取付金具の先端面に突設した接地電極と対向さ
せ、これによって背後電極効果金奏することを特徴とす
るスパークプラグにおいて、前記取付金具はそを設ける
と共に、この絞り部と前記発火部外周との間のギャップ
が前記微小ギャップよりも大きく設定したスパークプラ
グである。The present invention has been made to solve all of the above problems.
Behind? D: The purpose of the present invention is to provide a spark plug with extremely high antifouling properties. The feature is that the tip of the center electrode is exposed, and the firing part of the porcelain insulator surrounding the center electrode is made to protrude toward the combustion chamber side of the tip surface of the mounting bracket, and the outer periphery of this firing part and the mounting bracket are separated by a small gap. In the spark plug, the spark plug is arranged to face a ground electrode protruding from the distal end surface of the spark plug, thereby producing a rear electrode effect. This spark plug has a gap set larger than the minute gap.

以下本発明を図面の実施例に基づいて説明する。The present invention will be explained below based on embodiments shown in the drawings.

８ｇ２図は本発明の一実施例を示すスパークプラグの要
部拡大断面図であり、第１図に示す従来のものと同一部
分については同一符号で示す。■は中心電極、２は磁器
絶縁体、３は取付金具、４は接地電極である。中・ｕ正
極ｌの先端１ａを磁器絶縁体２の薄肉の発火部２ａの先
端よｔ）露出させ、該発火部２ａけ取付金具３の先端面
３ａよジ燃焼室側に突出さねでいる。この発火部２ａの
外周２ｂに面しＯｉＪ記取付金具３の先端面８８に溶接
された接地電極４が曲折されてｍＪ記外周２ｂとの間に
微小ギャップ０１を形成し、中・Ｕ電極１の先端と磁器
絶縁体の発火部表面に沿ってｔ＜ｉＪ記接地電極４との
間に沿面ギャップＧ２が設けられている。こ　（の場合
の接地電極は１個又は複数が設けられる。FIG. 8g2 is an enlarged sectional view of a main part of a spark plug showing an embodiment of the present invention, and the same parts as those of the conventional spark plug shown in FIG. 1 are designated by the same reference numerals. 2 is a center electrode, 2 is a porcelain insulator, 3 is a mounting bracket, and 4 is a ground electrode. The tip 1a of the middle/u positive electrode l is exposed from the tip of the thin firing part 2a of the porcelain insulator 2, and the tip 1a of the mounting bracket 3 for the firing part 2a protrudes toward the combustion chamber side. . The ground electrode 4 facing the outer periphery 2b of the firing part 2a and welded to the tip surface 88 of the OiJ mounting bracket 3 is bent to form a minute gap 01 between it and the mJ outer periphery 2b, and the middle/U electrode 1 A creeping gap G2 is provided between the tip of the ground electrode 4 and the ground electrode 4 with t<iJ along the surface of the firing part of the ceramic insulator. In this case, one or more ground electrodes are provided.

又、前記磁器絶縁体２の薄肉の発火部２ａは奸才しくは
段部２Ｃを設けて先端を径小としたテーパー状に形成さ
れている。この発火部２ａに面し、前記取付金具３の先
端部には内方に突設した環状の絞り部３ｂが形成されて
いる。この絞り部３ｂと発火部２ａの外周２ｂとの間の
ギャップＧ８は接地電極４と発火部外周２ｂとの間の微
小ギャップＧ１工９も大きく形成されているスパークプ
ラグである。Further, the thin firing portion 2a of the ceramic insulator 2 is formed into a tapered shape with a stepped portion 2C and a tip having a smaller diameter. An annular constricted part 3b that projects inward is formed at the tip of the mounting bracket 3 facing the firing part 2a. The spark plug is a spark plug in which the gap G8 between the throttle part 3b and the outer periphery 2b of the firing part 2a is also made larger than the minute gap G1 gap 9 between the ground electrode 4 and the firing part outer periphery 2b.

本発明のスパークプラグは上記紋り部を設けることによ
って、発火部２ａの基部と取付金具３の内壁３ｅとの間
のガス空間５内に、燃焼によって生成されたカーボン粒
子を含むガス尭填量全抑制して耐汚損性を著しく向上す
るものである。In the spark plug of the present invention, by providing the above-mentioned crest, the amount of gas containing carbon particles generated by combustion can be filled in the gas space 5 between the base of the ignition part 2a and the inner wall 3e of the mounting bracket 3. It completely suppresses staining and significantly improves stain resistance.

なお、紋り部３ｂと発火部外周２ｂとの間のギャップ０
３と該外周２ｂと接地電極との間の微小ギャップ０１の
（男係がＱ８）Ｑｌとする理由は、ギャップ（１８ｉＧ
１．ｌ：９小さくすると電位が分圧して沿面スパークギ
ャップＧ２で火花放電しなくなるためである。又接地電
極４を省略して絞り部３ｂによって接地電極の作用を代
行させ微小ギャップを形成する構成のスパークプラグの
場合は、発火部の燃焼室側の突出量が少なくなることか
ら着火性が劣る不利があり、又微小ギャップの寸法は小
さくなる程背後ＴＷＬ効果がよくて放電電圧が低くなる
。通常その寸法は０．７間以下である。従ってかかる値
だと絞り部でカーボンブリッジが容易に生じ全く実用的
でない。更に絞り部３ｂの形状としては取付金具の成形
、製作を容易にし、カーボン粒子等の未燃焼生成物が燃
焼室の壁面に沿って流れガス空間内へ侵入しブリッジ化
するのを防ぐため、絞り部３ｂの内方先端面３Ｃは軸方
向の厚みが小さく、特に燃焼室側ｋ　ＩＪｉＪ記内方先
端面に向ってデーパ−３ｄに形成″ｊ−る。例えば面取
り程度で十分に効果を有するものである。Note that the gap between the crest portion 3b and the firing portion outer periphery 2b is 0.
3 and the minute gap 01 between the outer periphery 2b and the ground electrode (Q8 for the male staff) is set to Ql because the gap (18iG
1. This is because if l:9 is made smaller, the potential will be divided and spark discharge will no longer occur in the creeping spark gap G2. In addition, in the case of a spark plug configured so that the ground electrode 4 is omitted and the constriction part 3b performs the function of the ground electrode to form a small gap, the ignition performance is poor because the amount of protrusion of the ignition part toward the combustion chamber is reduced. There are disadvantages, and the smaller the size of the minute gap, the better the rear TWL effect and the lower the discharge voltage. Usually its dimensions are 0.7 mm or less. Therefore, such a value would easily cause carbon bridges at the constriction portion, making it completely impractical. Furthermore, the shape of the throttle part 3b is designed to facilitate molding and manufacturing of the mounting fittings, and to prevent unburned products such as carbon particles from flowing along the wall surface of the combustion chamber and entering the gas space and forming a bridge. The inner tip surface 3C of the portion 3b has a small thickness in the axial direction, and is particularly tapered toward the combustion chamber side. It is.

又、本発明の磁器絶縁体２０煽大部２３は上記実施例に
訃いては径小の段部２Ｃ’ｉ１個設け、この段部の軸方
向の位置が取付金具３の絞り部３もの奥に配設したもの
であったが、第３図に示１−ように磁器絶縁体１２の発
火部１２ａには軸方向に絞り部３１）をはさんで段部１
２Ｃ，１２Ｃ’と２個形成し、こね、ら径小の発火部の
外周１２ａ、１２ａ′にはそれぞれ接地電極４、絞り部
３ｂ全対設することもできる。この構造のスパークプラ
グは磁器絶縁体の発火部の強度を高め、焼成歪が少なく
製作が容易である利点があり、又強度を高めることから
発火部１２Ｒの肉厚全よＶ薄くすることが可能で、背後
電極効果が裏ぐ放電電圧を低くすることができる効果が
ある。Further, the enlarged part 23 of the porcelain insulator 20 of the present invention is provided with one stepped part 2C'i having a smaller diameter than the above embodiment, and the position of this stepped part in the axial direction is deeper than the constricted part 3 of the mounting bracket 3. However, as shown in FIG.
2C and 12C' may be formed, and the ground electrode 4 and the constriction part 3b may be provided on the outer circumferences 12a and 12a' of the small-diameter firing parts, respectively. Spark plugs with this structure have the advantage of increasing the strength of the ignition part of the porcelain insulator, and are easy to manufacture with little firing distortion.Also, because of the increased strength, it is possible to make the entire wall thickness of the ignition part 12R thinner. This has the effect of lowering the discharge voltage due to the back electrode effect.

次に第２図に示し７た本発明のスパークプラグＡ１〜Ａ
８　（（）１＝Ｑ、４＃ｌｆｆ、Ｇ２＝１．５ｆｆＪＧ
８＝０．８開）と第１図に示した従来スパークプラグＢ
ｌ〜Ｉ３８　（Ｇ　ｌ　”　ｏ、　４　ｍｍ　＋　０２
””　ｔ、　５　ｍｍ　）　Ｙ用い、市販車全一１０°
Ｃの低温でア・イドリングと低速（１０〜２０７ｍ／Ｉ
Ｉ）の迎転パターンのサイクルを繰返した条件で耐汚損
性を比較テストした。その結果は第４図に承丁ように、
従来の背後電極効果をもったスパークプラグ１１１−１
３８はプラグの絶縁抵抗が約３サイクルから低下しはじ
め８〜１０サイクルで５ＫｎＷ下に低下するのに対し、
本発明の絞り部を設けたスパークプラグＡ１〜Ａ８は１
０サイクル経過後においても約５００にΩの低下するに
止まり耐汚損性を顕著に向上することができた。Next, spark plugs A1 to A of the present invention shown in FIG.
8 (()1=Q, 4#lff, G2=1.5ffJG
8=0.8 open) and conventional spark plug B shown in Figure 1.
l~I38 (G l” o, 4 mm + 02
""t, 5 mm) Y used, all commercially available cars 10°
Idling and low speed at low temperature of C (10~207m/I
A comparative test of stain resistance was conducted under the conditions of repeating the cycle of the transfer pattern of I). The results are shown in Figure 4.
Spark plug 111-1 with conventional back electrode effect
38, the insulation resistance of the plug starts to decrease from about 3 cycles and decreases to 5 KnW after 8 to 10 cycles.
The spark plugs A1 to A8 provided with the throttle part of the present invention are 1
Even after 0 cycles had elapsed, Ω only decreased to about 500, and the stain resistance was significantly improved.

以上の如く本発明のスパークプラグは背後゛厄極効果ヲ
もったスパークプラグにおいて、取付金具の先端部に微
小ギャップよりも大きい環状の絞り部を設けることによ
り背後電極効果を損うことなく耐汚損性を著しく向上さ
せることができる。As described above, the spark plug of the present invention is a spark plug that has a rear electrode effect, and by providing an annular constriction part larger than the minute gap at the tip of the mounting bracket, it is stain resistant without impairing the rear electrode effect. can significantly improve performance.

【図面の簡単な説明】[Brief explanation of the drawing]

第１図は従来の背後電極効果をもったスパークプラグの
要部断面図、第２図及び第３図は本発明の実ｈθ）例ン
：示すスパークプラグの一安部拡大断面図、第４図は耐
汚損性テスト結果を示すグラフである。 １・・・中・ｂ電極　１ａ・・・先端　２，１２・・・
磁器絶縁体　２ａ、１２３・・・発火部　２ｂｌ１２ｂ
・・・発火部外周　３−・・取付金具　３ａ・・・先端
面　３ｂ・・・紋り部　３Ｃ・・・内方先端面　３ｄ・
・・テーパー　４・・・接地電極　Ｇ１・・・微小ギャ
ップ　Ｇ３・・・ギャップ 第２図 第４図 竹うクル奪文−Fig. 1 is a sectional view of the main part of a conventional spark plug with a back electrode effect, Figs. 2 and 3 are an enlarged sectional view of the bottom part of the spark plug according to the present invention; is a graph showing the stain resistance test results. 1... Middle/b electrode 1a... Tip 2, 12...
Porcelain insulator 2a, 123...Ignition part 2bl12b
...Outer periphery of firing part 3-...Mounting bracket 3a...Tip surface 3b...Cutting portion 3C...Inner tip surface 3d.
...Taper 4...Ground electrode G1...Minute gap G3...Gap Figure 2 Figure 4 Bamboo Ukuru pattern -

Claims (2)

【特許請求の範囲】[Claims] （１）　中心電極の先端ヲ鎗出させて該中心電極を囲む
磁器絶縁体の発火部を取付金具の先端面より燃焼室側に
突出させ、この発火部の外周と対向して微小ギヤツブ金
隔てて取付金具の先端面に接地電極を突設した背後電極
効果を有するスパークプラグにおいて、前記取付金具は
その先端部に前記発火部外周に面して環状の絞り部を設
けると共に、この絞り部と前記発火部外周との間のギャ
ップが０１１記微小ギヤツプよりも大きく設定したこと
を特徴とするスパークプラグ。(1) The tip of the center electrode is protruded so that the ignition part of the porcelain insulator surrounding the center electrode protrudes toward the combustion chamber from the end surface of the mounting bracket, and a minute gear latch is placed opposite the outer periphery of this ignition part. In a spark plug having a back electrode effect in which a ground electrode is protruded from the distal end surface of the mounting bracket, the mounting bracket has an annular constriction part facing the outer periphery of the ignition part at the distal end thereof, and the constriction part and A spark plug characterized in that a gap between the ignition part and the outer periphery is set larger than the minute gap described in 011. （２）上記取付金具の絞り部は少なくとも燃焼室側が内
方先端部に向って厚みが小さくなるデーパに形成されて
いる特許請求の範囲第１項記載のスパークプラグ。(2) The spark plug according to claim 1, wherein the throttle portion of the mounting bracket is formed into a tapered shape whose thickness decreases toward the inner tip end at least on the combustion chamber side.