JP2012009395A - Spark plug for spark ignition type internal combustion engine - Google Patents

Spark plug for spark ignition type internal combustion engine Download PDF

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JP2012009395A
JP2012009395A JP2010146601A JP2010146601A JP2012009395A JP 2012009395 A JP2012009395 A JP 2012009395A JP 2010146601 A JP2010146601 A JP 2010146601A JP 2010146601 A JP2010146601 A JP 2010146601A JP 2012009395 A JP2012009395 A JP 2012009395A
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spark
internal combustion
combustion engine
electric field
center electrode
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JP5495980B2 (en
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Takeshi Serizawa
毅 芹澤
Hiroo Oi
宏朗 尾井
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Daihatsu Motor Co Ltd
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Abstract

PROBLEM TO BE SOLVED: To suppress electrode deterioration due to plasma heat generated upon ignition using plasma without depending on the structure of spark ignition type internal combustion engine.SOLUTION: A spark plug for a spark ignition type internal combustion engine comprises: a center electrode which electrically connects an ignition coil for applying a high voltage to cause spark discharge and an electric field generation circuit for generating an electric field; and a ground electrode which is opposed to the center electrode. The spark ignition type internal combustion engine ignites an air-fuel mixture by plasma generated by the reaction of spark discharge and electric field. The ground electrode has at least two projections which project toward the center electrode.

Description

本発明は、燃焼室内に電界を生成させ、電界と点火プラグによる火花放電とによりプラズマを生成し混合気に着火する火花点火式内燃機関に取り付けられる点火プラグに関するものである。   The present invention relates to an ignition plug attached to a spark ignition type internal combustion engine that generates an electric field in a combustion chamber, generates plasma by the electric field and spark discharge by the ignition plug, and ignites an air-fuel mixture.

従来、着火性を改善するために、マイクロ波を利用して燃焼室内の混合気に点火するエンジンの点火装置が知られている。マイクロ波を利用することにより、着火性は改善されるものの、マイクロ波により生成されるプラズマの熱により、点火プラグの電極が劣化しやすいといった不具合が生じる。   Conventionally, in order to improve ignitability, an ignition device for an engine that ignites an air-fuel mixture in a combustion chamber using a microwave is known. Although the ignitability is improved by using the microwave, there is a problem that the electrode of the spark plug is likely to be deteriorated by the heat of the plasma generated by the microwave.

このような不具合を解消するために、例えば特許文献１に記載のものでは、点火プラグの放電部に対してマイクロ波を照射して、放電部に生成されたプラズマを放電部から離すように燃焼室内にガス流動を生起するガス流動生起手段を備えることを示している。この特許文献１のものでは、プラズマが拡大する過程において、ガス流動生起手段が生み出すガス流動によりプラズマを放電部から離して、プラズマの熱の影響が放電部に及ばないようにすることによって上記の不具合を解消している。   In order to solve such a problem, for example, in the device described in Patent Document 1, the discharge part of the spark plug is irradiated with microwaves and the plasma generated in the discharge part is burned away from the discharge part. It shows that a gas flow generating means for generating a gas flow is provided in the room. In this patent document 1, the plasma is separated from the discharge part by the gas flow generated by the gas flow generating means in the process of expanding the plasma, so that the influence of the heat of the plasma does not reach the discharge part. The bug has been resolved.

しかしながら、ガス流動を生起するために、シリンダ軸心と吸気ポートの中心線とのなす鋭角を９０°に近づくようにエンジンを構成するか、あるいは吸気ポート内に流動生起弁や吸入空気の指向性を改善するための隔壁を設ける必要があり、エンジンの構成を制約するものである。このような制約のために、製造コストの上昇を抑えることが困難である。   However, in order to generate the gas flow, the engine is configured so that the acute angle formed between the cylinder axis and the center line of the intake port approaches 90 °, or the directivity of the flow generation valve and intake air in the intake port. It is necessary to provide a partition wall for improving the engine, which restricts the configuration of the engine. Due to such restrictions, it is difficult to suppress an increase in manufacturing cost.

特開２００９‐１０３０３９号公報JP 2009-103039 A

本発明は、火花点火式内燃機関の構造に依存することなく、プラズマを利用した点火の際のプラズマの熱による電極の劣化を抑制することを目的とする。   An object of the present invention is to suppress electrode deterioration due to the heat of plasma during ignition using plasma without depending on the structure of a spark ignition internal combustion engine.

すなわち、本発明の火花点火式内燃機関用プラグは、火花放電させるための高電圧を印加する点火コイルと電界を生成する電界生成回路とを電気的に接続する中心電極と中心電極に対向する接地電極とを備えた火花点火式内燃機関用点火プラグであって、火花点火式内燃機関は、火花放電と電界とを反応させることにより生成されるプラズマで混合気に着火するものであり、接地電極が、中心電極に対して中心電極の方向に突出する少なくとも二つの突出部を備えることを特徴とする。   That is, the spark ignition type internal combustion engine plug according to the present invention has a center electrode that electrically connects an ignition coil that applies a high voltage for spark discharge and an electric field generation circuit that generates an electric field, and a ground that faces the center electrode. An ignition plug for a spark ignition internal combustion engine comprising an electrode, wherein the spark ignition internal combustion engine ignites an air-fuel mixture by plasma generated by reacting a spark discharge with an electric field, and a ground electrode Is provided with at least two protrusions protruding in the direction of the center electrode with respect to the center electrode.

このような構成によれば、火花放電と電界とで生成されたプラズマは、中心電極と接地電極の突出部とを直線で結んだ際に形成される三角形状の領域内に保持されることになる。このため、プラズマが接地電極の突出部に接触することが抑制され、高耐熱性物質により接地電極を構成せずとも接地電極の熱耐久性を確保することが可能になる。   According to such a configuration, the plasma generated by the spark discharge and the electric field is held in a triangular region formed when the central electrode and the protruding portion of the ground electrode are connected by a straight line. Become. For this reason, it is possible to prevent the plasma from coming into contact with the protruding portion of the ground electrode, and it is possible to ensure the thermal durability of the ground electrode without configuring the ground electrode with a high heat resistant material.

プラズマの移動を効果的に抑制するためには、突出部が、三つであり、ほぼ等間隔をあけて配置されるものが好ましい。   In order to effectively suppress the movement of the plasma, it is preferable that the number of the projecting portions is three and they are arranged at almost equal intervals.

本発明は、以上説明したような構成であり、プラズマが生成される領域を中心電極と接地電極の突出部とで囲まれる領域に限定することにより、プラズマが接地電極の突出部に接触することが抑制され、高耐熱性物質により接地電極を構成せずとも接地電極の熱耐久性を確保することができる。   The present invention is configured as described above, and the plasma is in contact with the projecting portion of the ground electrode by limiting the region where the plasma is generated to the region surrounded by the center electrode and the projecting portion of the ground electrode. Therefore, the thermal durability of the ground electrode can be ensured without forming the ground electrode with a high heat resistant material.

本発明の実施形態を適用するエンジンの構成を示す断面図。A sectional view showing composition of an engine to which an embodiment of the present invention is applied. 同実施形態の正面図。The front view of the embodiment. 同実施形態の要部拡大断面図。The principal part expanded sectional view of the embodiment. 同実施形態の要部拡大底面図。The principal part enlarged bottom view of the embodiment. 同実施形態の点火コイル、点火プラグ及び電界生成回路の接続を示すブロック図。The block diagram which shows the connection of the ignition coil of the same embodiment, a spark plug, and an electric field generation circuit. 同実施形態の電界生成回路を示すブロック図。The block diagram which shows the electric field generation circuit of the embodiment. 図６におけるＨブリッジ回路の一例を示す回路図。FIG. 7 is a circuit diagram showing an example of an H bridge circuit in FIG. 6. 同実施形態の変形例を示す図３相当図。FIG. 3 is a view corresponding to FIG. 3 showing a modification of the embodiment. 同実施形態の変形例を示す図４相当図。FIG. 4 is a view corresponding to FIG. 4 showing a modification of the embodiment.

以下、本発明の一実施形態を、図１〜７を参照して説明する。   Hereinafter, an embodiment of the present invention will be described with reference to FIGS.

図１に点火プラグ１の取付部分を拡大して示す火花点火式内燃機関であるエンジン１００は、ダブルオーバーヘッドカムシャフト（ＤＯＨＣ）形式のもので、吸気ポート２の開口３及び排気ポート４の開口５が、燃焼室６の天井部分のほぼ中央に取り付けられる点火プラグ１を中心として対向配置されて、１気筒当たりそれぞれ２ヶ所に開口するものである。すなわち、このエンジン１００は、シリンダブロック７に取り付けられ、燃焼室６の天井部分を形成しているシリンダヘッド８には、吸気側と排気側とにそれぞれカムシャフト９、１０が取り付けてある。シリンダヘッド８の吸気ポート２は、カムシャフト９が回転することにより往復作動する吸気弁１１により、また排気ポート４は、カムシャフト１０が回転することにより往復作動する排気弁１２によりそれぞれ開閉されるものである。そして、燃焼室６の天井部分には、点火プラグ１が取り付けられてある。なお、点火プラグ１を除くエンジン１００それ自体は、この分野で知られている火花点火式のものを適用するものであってよい。   An engine 100, which is a spark ignition type internal combustion engine, showing an enlarged mounting portion of the spark plug 1 in FIG. 1, is of a double overhead camshaft (DOHC) type, and has an intake port 2 opening 3 and an exhaust port 4 opening 5. However, they are opposed to each other centering on a spark plug 1 attached to substantially the center of the ceiling portion of the combustion chamber 6 and open at two locations per cylinder. That is, the engine 100 is attached to the cylinder block 7, and the camshafts 9 and 10 are attached to the intake side and the exhaust side of the cylinder head 8 forming the ceiling portion of the combustion chamber 6, respectively. The intake port 2 of the cylinder head 8 is opened and closed by an intake valve 11 that reciprocates when the camshaft 9 rotates, and the exhaust port 4 is opened and closed by an exhaust valve 12 that reciprocates when the camshaft 10 rotates. Is. A spark plug 1 is attached to the ceiling portion of the combustion chamber 6. The engine 100 itself excluding the spark plug 1 may be a spark ignition type that is known in this field.

この実施例の点火プラグ１は、図２〜図４に示すように、導電材料からなるハウジング１３と、ハウジング１３内に絶縁されて取り付けられる中心電極１４と、中心電極１４から離れてハウジング１３の下端に設けられる接地電極１５とを備える。すなわち、点火プラグ１は、ハウジング１３がほぼ円柱形状の絶縁碍子１６を支持し、絶縁碍子１６の上端に取り付けられる接続端子１７が、ハウジング１３の下端から突出する中心電極１４と図示しない中軸により電気的に接続され、ハウジング１３下端から中心電極１４側面に対向する位置まで延びる位置に接地電極１５がハウジング１３に一体的に設けてある構造である。絶縁碍子１６は、中心電極１４とエンジン１００への取付部であるハウジング１３とを絶縁するとともに、中心電極１４と接続端子１７との接続部材である中軸も絶縁するもので、ほぼ円筒形状をしている。   As shown in FIGS. 2 to 4, the spark plug 1 of this embodiment includes a housing 13 made of a conductive material, a center electrode 14 that is insulated and attached in the housing 13, and a housing 13 that is separated from the center electrode 14. And a ground electrode 15 provided at the lower end. That is, in the spark plug 1, the housing 13 supports the substantially cylindrical insulator 16, and the connection terminal 17 attached to the upper end of the insulator 16 is electrically connected by the center electrode 14 protruding from the lower end of the housing 13 and the center shaft (not shown). The ground electrode 15 is integrally provided on the housing 13 at a position where the ground electrode 15 extends from the lower end of the housing 13 to a position facing the side surface of the center electrode 14. The insulator 16 insulates the center electrode 14 and the housing 13 that is an attachment portion to the engine 100, and also insulates the central shaft that is a connecting member between the center electrode 14 and the connection terminal 17, and has a substantially cylindrical shape. ing.

ハウジング１３は、絶縁碍子１６を収容するのに十分な内部空間を備える円筒形状のもので、導電材料である、例えばステンレス製のものである。ハウジング１３は、その上端部分が、絶縁碍子１６を密着し気密性を維持するために内側に絞り込まれている。また、その長手方向の中央部から下側部分の外周には、シリンダヘッド８への取付のための雄ねじ部１８が形成してある。加えて、雄ねじ部１８と上端部分との間には、取り付ける場合に取付台座部となる主体金具１９が、雄ねじ部１８より大きな外径で形成してある。   The housing 13 has a cylindrical shape with an internal space sufficient to accommodate the insulator 16, and is made of, for example, stainless steel, which is a conductive material. The upper end portion of the housing 13 is squeezed inward in order to keep the insulator 16 in tight contact and maintain airtightness. Further, a male screw portion 18 for attachment to the cylinder head 8 is formed on the outer periphery of the lower portion from the central portion in the longitudinal direction. In addition, between the male screw part 18 and the upper end part, a metal shell 19 serving as a mounting base part when attached is formed with a larger outer diameter than the male screw part 18.

中心電極１４は、例えば円柱状のニッケル合金からなる金属材料にて形成されており、その下端が絶縁碍子１６から露出するとともに、ハウジング１３の下端から露出する。中心電極１４の先端面１４ａは、接地電極１５の下面とほぼ面一になる位置まで延びている。   The center electrode 14 is formed of a metal material made of, for example, a cylindrical nickel alloy, and the lower end thereof is exposed from the insulator 16 and is exposed from the lower end of the housing 13. The front end surface 14 a of the center electrode 14 extends to a position that is substantially flush with the lower surface of the ground electrode 15.

このような中心電極１４に対して、接地電極１５は、ハウジング１３下端面に一体的に形成される側面視ほぼＬ字状のもので、その先端面１５ａは、間隙をあけて中心電極１４の下端部の側面１４ｂに対向している。接地電極１５は、その先端面１５ａに、中心電極１４の方向に突出する２つの突出部１５ｂを備えている。この実施形態における突出部１５ｂは、端面形状がほぼ矩形の先端面１５ａの両端部分に、ほぼ同一高さ位置で配置される。突出部１５ｂは高耐熱性物質であるイリジウムで形成してあり、それ以外の接地電極１５の部分はニッケルで形成してある。突出部１５ｂの形状は、直方体又は立方体である。なお、高耐熱性物質としては、イリジウム合金や白金などであってもよい。又、突出部１５ａは、それらの高耐熱性物質で形成するもの以外に、例えばニッケルで形成されてその表面を高耐熱性物質でコーティングするものであってもよい。   With respect to the center electrode 14, the ground electrode 15 is substantially L-shaped in a side view formed integrally with the lower end surface of the housing 13, and the tip end surface 15 a is spaced from the center electrode 14. It faces the side surface 14b of the lower end. The ground electrode 15 is provided with two projecting portions 15b projecting in the direction of the center electrode 14 on the tip surface 15a. In this embodiment, the protruding portion 15b is disposed at substantially the same height position at both end portions of the end surface 15a having a substantially rectangular end surface shape. The protruding portion 15b is made of iridium, which is a highly heat resistant material, and the other portions of the ground electrode 15 are made of nickel. The shape of the protrusion 15b is a rectangular parallelepiped or a cube. The high heat resistant material may be an iridium alloy or platinum. Further, the protrusion 15a may be formed of nickel, for example, and the surface thereof may be coated with the high heat resistant material, in addition to those formed of the high heat resistant material.

このような構成において、点火プラグ１はエンジン１００のそれぞれの気筒に対して取り付けられ、火花放電を行う本来の機能とともに、後述するプラズマ生成のための電界を生成するための電極としても機能するものである。すなわちこのエンジン１００は、燃焼室６内の混合気に点火プラグ１を用いて着火する場合に、点火プラグ１の火花放電を燃焼室６内に生成する電界と反応させることにより、点火プラグ１の火花放電を電界と反応させない場合の火花放電に比較して、大きくしている。このために、点火プラグ１の中心電極１４には、図５に示すように、火花放電のための点火コイル２０がミキサ２１を介して接続されるとともに、電界を生成するための電界生成回路２２が接続されている。   In such a configuration, the spark plug 1 is attached to each cylinder of the engine 100 and functions as an electrode for generating an electric field for generating plasma, which will be described later, in addition to the original function of performing spark discharge. It is. That is, when the engine 100 ignites the air-fuel mixture in the combustion chamber 6 using the spark plug 1, the engine 100 reacts the spark discharge of the spark plug 1 with the electric field generated in the combustion chamber 6. The spark discharge is larger than the spark discharge in the case where the spark discharge does not react with the electric field. For this purpose, as shown in FIG. 5, an ignition coil 20 for spark discharge is connected to the center electrode 14 of the spark plug 1 via a mixer 21 and an electric field generating circuit 22 for generating an electric field. Is connected.

電界生成回路２２は例えば、図６に示すように、車両用のバッテリ２３の電圧例えば約１２Ｖ（ボルト）を昇圧回路であるＤＣ‐ＤＣコンバータ２４にて３００〜５００Ｖに昇圧し、昇圧された直流をＨブリッジ回路２５にて周波数が約２００ｋＨｚ〜６００ｋＨｚの交流に変化させ、さらに昇圧トランス２６により約４ｋＶｐ‐ｐ〜８ｋＶｐ‐ｐに昇圧した交流を出力する構成である。電界生成回路２２が出力する交流電圧を中心電極１４とシリンダヘッド８と間に交流電圧を印加することで、放電域である中心電極１４と接地電極１５との間隙に上記周波数帯であって極性が交互に入れ替わる電界が生成されるように構成してある。   For example, as shown in FIG. 6, the electric field generation circuit 22 boosts the voltage of the vehicle battery 23, for example, about 12 V (volts) to 300 to 500 V by a DC-DC converter 24 that is a booster circuit, and boosts the direct current. Is changed to an alternating current having a frequency of about 200 kHz to 600 kHz by the H bridge circuit 25, and an alternating current boosted to about 4 kVp-p to 8 kVp-p by the step-up transformer 26 is output. By applying the AC voltage output from the electric field generating circuit 22 between the center electrode 14 and the cylinder head 8, the polarity between the center electrode 14 and the ground electrode 15 serving as the discharge region is in the above frequency band and polarity. Is configured to generate an electric field that alternately alternates.

点火に際しては、点火プラグ１に点火コイル２０により火花放電を発生させて、火花放電とほぼ同時あるいはその直後に電界生成回路２２が出力する交流により電界を発生させてプラズマを生成させることにより、燃焼室６内の混合気を急速に燃焼させる構成である。   At the time of ignition, a spark discharge is generated in the spark plug 1 by the ignition coil 20, and an electric field is generated by an alternating current output from the electric field generation circuit 22 almost simultaneously with or immediately after the spark discharge to generate plasma. In this configuration, the air-fuel mixture in the chamber 6 is burned rapidly.

具体的には、中心電極１４と接地電極１５の突出部１５ｂとの間の最も距離が短い部分から火花放電が始まる。その後、点火プラグ１による火花放電が、電界中で振動され、増幅されてプラズマになり、火炎核を形成する。   Specifically, the spark discharge starts from the portion where the distance between the center electrode 14 and the protruding portion 15b of the ground electrode 15 is the shortest. Thereafter, the spark discharge generated by the spark plug 1 is vibrated in an electric field and amplified into plasma, forming a flame kernel.

これは、火花放電による電子の流れ及び火花放電によって生じたイオンやラジカルが、電界の影響を受け振動、蛇行することで行路長が長くなり、周囲の水分子や窒素分子と衝突する回数が飛躍的に増加することによるものである。イオンやラジカルの衝突を受けた水分子や窒素分子は、ＯＨラジカルやＮラジカルになると共に、イオンやラジカルの衝突を受けた周囲の気体は電離した状態、言換するとプラズマ状態となることで、火花放電のみの火炎核に比較して飛躍的に火炎核が大きくなるものである。   This is because the flow of electrons due to the spark discharge and the ions and radicals generated by the spark discharge are vibrated and meandered by the influence of the electric field, resulting in a longer path length and a dramatic increase in the number of collisions with surrounding water and nitrogen molecules. This is due to the increase. Water molecules and nitrogen molecules that have been struck by ions and radicals become OH radicals and N radicals, and the surrounding gas that has been struck by ions and radicals is ionized, in other words, a plasma state. Compared to a flame kernel with only spark discharge, the flame kernel is dramatically increased.

この結果、電界と反応することにより増大した火花放電つまりプラズマにより混合気に着火するため、着火領域が拡大し、点火プラグ１のみの二次元的な着火から三次元的な着火になる。したがって、初期燃焼が安定し、上述したラジカルの増加に伴って燃焼が燃焼室６内に急速に伝播し、高い燃焼速度で燃焼が拡大する。   As a result, the air-fuel mixture is ignited by spark discharge, that is, plasma increased by reacting with the electric field, so that the ignition region is expanded, and the two-dimensional ignition of only the spark plug 1 is changed to the three-dimensional ignition. Therefore, the initial combustion is stabilized, and the combustion rapidly propagates into the combustion chamber 6 as the radicals increase, and the combustion expands at a high combustion rate.

このようにして生じるプラズマは、接地電極１５が対をなす突出部１５ｂを備えているので、中心電極１４と２つの突出部１５ｂとを頂点とする三角形状の領域内に保持される。したがって、シリンダ内に混合気の気流つまり筒内流が生じていても、そのような筒内流に影響されて移動することがない。しかも突出部１５ｂは、ほぼ同じ高さに設けてあるので、上述の三角形状の領域がシリンダ内にほぼ水平に形成されることになり、燃焼室内に上述の筒内流が生じた場合であっても、その筒内流によりプラズマが流されることを抑制することができる。   The plasma generated in this manner is provided in the triangular region having the center electrode 14 and the two protruding portions 15b as apexes because the ground electrode 15 includes the protruding portions 15b that make a pair. Therefore, even if an air-fuel mixture, that is, an in-cylinder flow, is generated in the cylinder, it is not affected by the in-cylinder flow and moves. Moreover, since the projecting portions 15b are provided at substantially the same height, the above-described triangular region is formed almost horizontally in the cylinder, and this is the case where the above-described in-cylinder flow is generated in the combustion chamber. However, it is possible to suppress the plasma from flowing by the in-cylinder flow.

それゆえ、突出部１５ｂを含む接地電極１５がプラズマにさらされる状態が低減され、接地電極１５の劣化を抑えることができる。このことは、接地電極１５全体を高耐熱性物質により形成することなく、接地電極１５の熱耐久性を確保することができることを示すものである。   Therefore, the state in which the ground electrode 15 including the protrusion 15b is exposed to plasma is reduced, and deterioration of the ground electrode 15 can be suppressed. This indicates that the thermal durability of the ground electrode 15 can be ensured without forming the entire ground electrode 15 from a highly heat resistant material.

さらに、プラズマが移動しないために、混合気に対して定位置において着火することができ、燃焼を安定させることができる。   Furthermore, since the plasma does not move, the air-fuel mixture can be ignited at a fixed position, and combustion can be stabilized.

なお、本発明は、上述の実施形態に限定されるものではない。   In addition, this invention is not limited to the above-mentioned embodiment.

上述の実施形態にあっては、接地電極１５の先端部分の幅方向において突出部１５ｂを配置したものを説明したが、図８に示すように、同先端部分の厚み方向の同一直線上において突出部１５１ｂを配置するものであってもよい。この場合にあっては、中心電極１４の先端面が、突出部１５１ｂの中央高さ位置になるように、両突出部１５１ｂを形成する。中心電極１４の先端面１４ａの外周部の一部分と突出部１５１ｂとで形成する三角形状の領域は、シリンダの中心軸と平行に形成されるものとなる。この例にあっても、上述の実施形態同様に、その三角形状の領域にプラズマが保持されるものである。   In the above-described embodiment, the protrusion 15b is arranged in the width direction of the tip portion of the ground electrode 15. However, as shown in FIG. 8, the tip portion protrudes on the same straight line in the thickness direction. The part 151b may be arranged. In this case, both protrusions 151b are formed such that the tip surface of the center electrode 14 is at the center height position of the protrusion 151b. A triangular region formed by a part of the outer peripheral portion of the tip surface 14a of the center electrode 14 and the protruding portion 151b is formed in parallel to the central axis of the cylinder. Even in this example, plasma is held in the triangular region as in the above-described embodiment.

又、突出部２１５ｂは、図９に示すように、ほぼ等間隔をあけて配置される３つであってもよい。すなわち、突出部２１５ｂは、接地電極１５の先端部分の幅方向のほぼ中央と幅方向のほぼ両端とに形成する。このように突出部分を配置することにより、中心電極１４と中央の突出部２１５ｂと一方の端部の突出部２１５ｂとにより三角形状の領域が形成されるとともに、中心電極１４と中央の突出部２１５ｂと他方の端部の突出部２１５ｂとにより三角形状の領域が形成される。つまり、中心電極１４と中央の突出部２１５ｂとを結ぶ線分の両側に線対称となる形状の領域が形成されるものとなる。   Moreover, as shown in FIG. 9, the protrusion part 215b may be three arrange | positioned at substantially equal intervals. In other words, the protruding portion 215b is formed at substantially the center in the width direction and at almost both ends in the width direction of the tip portion of the ground electrode 15. By arranging the projecting portions in this manner, the center electrode 14, the center projecting portion 215b, and the projecting portion 215b at one end form a triangular region, and the center electrode 14 and the center projecting portion 215b. And a projection 215b at the other end form a triangular region. That is, regions having line symmetry are formed on both sides of a line segment connecting the center electrode 14 and the central protrusion 215b.

このように、三角形状の領域を二つ形成することで、そのいずれか一方の領域にプラズマが生成され保持される。したがって、プラズマ生成の開始時に筒内流が生じても、どちらかの領域にプラズマを保持することができる。このため、着火性を向上させることができる。   Thus, by forming two triangular regions, plasma is generated and held in one of the regions. Therefore, even if an in-cylinder flow occurs at the start of plasma generation, the plasma can be held in either region. For this reason, ignitability can be improved.

接地電極の突出部の形状は、上述の実施形態以外に、円錐や角錐であってもよい。この場合、頂点を中心電極の方向に向けて形成する。頂点は、針状の尖端以外に、球状や半球状であってよい。   The shape of the protruding portion of the ground electrode may be a cone or a pyramid other than the above-described embodiment. In this case, the apex is formed in the direction of the center electrode. The apex may be spherical or hemispherical other than the needle-like tip.

電界生成回路としては、上述した交流を発生させるもの以外に、交流を整流した脈流や、直流をオンオフするもの、さらには高周波発生回路などであってもよい。   As the electric field generation circuit, in addition to the above-described circuit that generates alternating current, a pulsating current obtained by rectifying alternating current, a circuit that turns on / off direct current, and a high-frequency generation circuit may be used.

高周波発生回路は、例えば６００ｋＨｚの高周波を発生させる送信機と、送信機の出力端に同軸ケーブルで接続されるマッチングチューナ（又はアンテナチューナ）と、マッチングチューナの出力端に不平衡ケーブルで接続されるとともに点火コイルにも接続され送信機からの高周波と点火コイルからの放電高圧信号を混合するミキサとを備えている。なお、高周波の周波数としては、約２００ｋＨｚ〜６００ＭＨｚのものが使用できる。   The high frequency generation circuit is connected to a transmitter that generates a high frequency of, for example, 600 kHz, a matching tuner (or antenna tuner) connected to the output end of the transmitter with a coaxial cable, and an unbalanced cable to the output end of the matching tuner. And a mixer that is connected to the ignition coil and mixes the high frequency from the transmitter and the discharge high-voltage signal from the ignition coil. In addition, as a high frequency, the thing of about 200 kHz-600 MHz can be used.

その他、各部の具体的構成についても上記実施形態に限られるものではなく、本発明の趣旨を逸脱しない範囲で種々変形が可能である。   In addition, the specific configuration of each part is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention.

本発明の活用例として、ガソリンや液化天然ガスを燃料として点火プラグによる火花放電を着火に必要とする火花点火式内燃機関に活用することができる。   As an application example of the present invention, it can be used for a spark ignition type internal combustion engine that uses gasoline or liquefied natural gas as fuel and requires spark discharge by an ignition plug for ignition.

１…点火プラグ
６…燃焼室
１４…中心電極
１５…接地電極
１５ｂ…突出部 DESCRIPTION OF SYMBOLS 1 ... Spark plug 6 ... Combustion chamber 14 ... Center electrode 15 ... Ground electrode 15b ... Projection part

Claims (2)

火花放電させるための高電圧を印加する点火コイルと電界を生成する電界生成回路とを電気的に接続する中心電極と中心電極に対向する接地電極とを備えた火花点火式内燃機関用点火プラグであって、火花点火式内燃機関は、火花放電と電界とを反応させることにより生成されるプラズマで混合気に着火するものであり、
接地電極が、中心電極に対して中心電極の方向に突出する少なくとも二つの突出部を備える火花点火式内燃機関用プラグ。 A spark ignition internal combustion engine ignition plug comprising a center electrode for electrically connecting an ignition coil for applying a high voltage for spark discharge and an electric field generation circuit for generating an electric field, and a ground electrode facing the center electrode. The spark ignition internal combustion engine ignites an air-fuel mixture with plasma generated by reacting a spark discharge with an electric field.
A spark ignition type internal combustion engine plug, wherein the ground electrode includes at least two protrusions protruding in the direction of the center electrode with respect to the center electrode. 突出部が、三つであり、ほぼ等間隔をあけて配置される請求項１記載の火花点火式内燃機関用プラグ。   The spark-ignition internal combustion engine plug according to claim 1, wherein there are three protrusions, and the protrusions are arranged at substantially equal intervals.
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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103794987A (en) * 2014-01-20 2014-05-14 陈三明 Sparking plug of gasoline engine

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS6130989U (en) * 1984-07-30 1986-02-25 惠民 王 spark plug
JPH0992434A (en) * 1995-09-22 1997-04-04 Tamotsu Nakano Spark plug
JP2009103039A (en) * 2007-10-23 2009-05-14 Nissan Motor Co Ltd Engine ignition device

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS6130989U (en) * 1984-07-30 1986-02-25 惠民 王 spark plug
JPH0992434A (en) * 1995-09-22 1997-04-04 Tamotsu Nakano Spark plug
JP2009103039A (en) * 2007-10-23 2009-05-14 Nissan Motor Co Ltd Engine ignition device

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103794987A (en) * 2014-01-20 2014-05-14 陈三明 Sparking plug of gasoline engine

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