JP5321431B2 - In-cylinder internal combustion engine - Google Patents

In-cylinder internal combustion engine Download PDF

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JP5321431B2
JP5321431B2 JP2009275107A JP2009275107A JP5321431B2 JP 5321431 B2 JP5321431 B2 JP 5321431B2 JP 2009275107 A JP2009275107 A JP 2009275107A JP 2009275107 A JP2009275107 A JP 2009275107A JP 5321431 B2 JP5321431 B2 JP 5321431B2
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electrode
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ground electrode
discharge gap
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JP2011117356A (en
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則夫 山本
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Denso Corp
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    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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    • Y02T10/10—Internal combustion engine [ICE] based vehicles
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Description

本発明は、筒内噴射式内燃機関に関するもので、特に極希薄な混合気の着火性向上に好適なものである。   The present invention relates to a direct injection internal combustion engine, and is particularly suitable for improving the ignitability of an extremely lean air-fuel mixture.

近年、燃焼室内の点火プラグ近傍に直接燃料を噴射して、成層燃焼を行うことにより排ガス特性と燃焼安定性との両立を図ろうとする、いわゆるスプレーガイド式の内燃機関について種々提案されている。   In recent years, various types of so-called spray guide type internal combustion engines have been proposed in which fuel is directly injected into the vicinity of an ignition plug in a combustion chamber and stratified combustion is performed to achieve both exhaust gas characteristics and combustion stability.

例えば、特許文献１には、３つの吸気弁と２つの排気弁を備えた５弁構造の燃焼室城壁の中央部に、インジェクタの噴射口と点火プラグの電極部とを、電極部が噴射口よりも燃焼室内方かつ燃料噴霧稜線の中に位置するように配置した筒内噴射型火花点火式内燃機関が開示されている。   For example, Patent Document 1 discloses that an injector injection port and a spark plug electrode portion are provided at the center of a five-valve combustion chamber wall having three intake valves and two exhaust valves. An in-cylinder injection type spark ignition type internal combustion engine arranged to be located in the combustion chamber and in the fuel spray ridge is disclosed.

特許文献２には、成層燃焼法を行う場合であっても、確実に混合気を着火させるべく、中心電極と中心電極との間に所定の着火領域を形成する接地電極とを備え、燃料噴射弁から直接噴射された燃料を含む混合気を着火する点火プラグが、着火領域より混合気の着火直前における混合気の気流の上流側であって、少なくとも対抗する２面の壁面に挟まれて形成されるガス流速減衰流路を備えることによって、混合気の流速を減速して混合気の着火を行う筒内噴射式内燃機関が開示されている。   Patent Document 2 includes a ground electrode that forms a predetermined ignition region between the center electrode and the center electrode in order to reliably ignite the air-fuel mixture even when the stratified combustion method is performed. A spark plug for igniting an air-fuel mixture containing fuel directly injected from a valve is formed on the upstream side of the air-flow of the air-fuel mixture immediately before the air-fuel mixture is ignited and sandwiched between at least two opposing wall surfaces An in-cylinder injection internal combustion engine is disclosed that includes a gas flow rate attenuation flow path that reduces the flow rate of the air-fuel mixture and ignites the air-fuel mixture.

ところが、特許文献１にあるような従来の燃焼制御装置では、点火プラグの電極部が燃料噴霧の稜線の中に位置するように配置してあるため、燃料噴霧の流速が極めて速い場合には、中心電極と接地電極と間に発生した放電火花が吹き飛ばされて、着火できなくなる虞がある。
また、噴射された燃料を含む混合気の空燃比が可燃領域よりも低い層が直接的に点火プラグの着火領域に達する場合には、着火が困難となったり、電極に未燃燃料が堆積したりする虞もある。 However, in the conventional combustion control device as disclosed in Patent Document 1, since the electrode portion of the spark plug is disposed in the ridge line of the fuel spray, when the flow rate of the fuel spray is extremely high, There is a possibility that the discharge spark generated between the center electrode and the ground electrode is blown off, and ignition is impossible.
In addition, when a layer whose air-fuel ratio of the air-fuel mixture including the injected fuel is lower than the combustible region directly reaches the ignition region of the spark plug, ignition becomes difficult or unburned fuel accumulates on the electrode. There is also a risk that.

筒内噴射式内燃機関では、燃料噴射弁から噴射された燃料が速い流速で燃料点火プラグ近傍を通過するため、放電アークが引き延ばされたり、吹き飛ばされたりすることがある。放電アークが引き延ばされた場合には、放電アークの表面積が増加し、可燃性の混合気に接触する確率が高くなり、着火性が改善される場合もある。
しかし、従来の筒内噴射式内燃機関においては、放電アークの引き延ばし形状や引き延ばし方向が安定せず、出力変動の要因となり、放電アークが吹き飛ばされた場合には、失火の虞もある。 In a direct injection internal combustion engine, the fuel injected from the fuel injection valve passes through the vicinity of the fuel spark plug at a high flow rate, so that the discharge arc may be extended or blown away. When the discharge arc is extended, the surface area of the discharge arc is increased, the probability of contact with the combustible air-fuel mixture is increased, and the ignitability may be improved.
However, in the conventional direct injection internal combustion engine, the extension shape and the extension direction of the discharge arc are not stable, which causes output fluctuations, and there is a risk of misfire if the discharge arc is blown away.

一般に、燃料噴射弁から燃焼室内に噴射された燃料噴霧は、中心部の燃料濃度が最も高く、外周方向に向かって、燃焼室内の空気との混合が進み、燃料濃度が徐々に低くなる。混合気中の燃料濃度が一定範囲を超え過剰に高濃度である場合や、過剰に希薄な場合には着火が不安定となる。
また、燃料噴霧の流速は、中心部が最も速く、外周方向に向かって徐々に遅くなる。混合気の流速が速すぎると、放電アークが吹き消され、混合気の流速が遅すぎると、放電アークの引き延ばしによる着火性向上効果は生まれない。
このため、点火プラグの近傍には、着火に適した混合比及び流速の混合気を配設する必要がある。
しかし、燃料噴射弁から噴射される燃料の流速や噴射方向は、内燃機関の運転状況によって変動し、着火に適した混合気の配置も燃焼サイクル間で変動するため、従来の筒内噴射式内燃機関では、着火が不安定となる虞がある。 In general, the fuel spray injected from the fuel injection valve into the combustion chamber has the highest fuel concentration in the center, and the mixing with the air in the combustion chamber proceeds toward the outer periphery, and the fuel concentration gradually decreases. When the fuel concentration in the air-fuel mixture exceeds a certain range and is excessively high or excessively lean, ignition becomes unstable.
Further, the flow rate of the fuel spray is fastest at the center and gradually slows toward the outer periphery. When the flow rate of the air-fuel mixture is too high, the discharge arc is blown out, and when the flow rate of the air-fuel mixture is too slow, the effect of improving the ignitability by extending the discharge arc is not produced.
For this reason, it is necessary to arrange an air-fuel mixture with a mixing ratio and flow rate suitable for ignition near the spark plug.
However, the flow rate and direction of fuel injected from the fuel injection valve vary depending on the operating conditions of the internal combustion engine, and the arrangement of the air-fuel mixture suitable for ignition also varies between combustion cycles. In an engine, ignition may become unstable.

また、従来の筒内噴射式内燃機関では、限界空燃比Ａ／Ｆは３０程度が限界とされ、より一層の希薄化が望まれている。   Further, in the conventional cylinder injection internal combustion engine, the limit air-fuel ratio A / F is limited to about 30, and further dilution is desired.

そこで、本発明はかかる実情に鑑み、燃焼室内に直接燃料が噴射される筒内噴射式内燃機関において、着火性に優れ信頼性の高い筒内噴射式内燃機関を提供することを目的とする。   Accordingly, an object of the present invention is to provide an in-cylinder injection internal combustion engine having excellent ignitability and high reliability in a direct injection internal combustion engine in which fuel is directly injected into a combustion chamber.

第１の発明では、燃焼室に燃料を直接噴射する燃料噴射弁と点火プラグとを備えた筒内噴射式内燃機関において、上記点火プラグが、少なくとも、プラグの中心に設けた中心電極と、絶縁碍子を介して所定の放電ギャップを設けて上記中心電極の先端に対向する接地電極と、上記中心電極に導通し上記中心電極の中心軸に対して上記燃料噴射弁から噴射される燃料噴霧に近づく側に延設した偏心電極と、上記接地電極の先端を上記偏心電極の上記燃料噴霧側に近い端縁に対向するように伸ばした接地電極延設部とを具備し、上記燃料噴射弁から燃料が噴射されたときに発生する引込み気流を上記放電ギャップに作用させる筒内噴射式内燃機関であって、上記中心電極の先端面とこれに対向する上記接地電極の上面までの最短距離を第１の放電ギャップとし、上記偏心電極の先端面とこれに対向する上記接地電極延設部の上面までの最短距離を第２の放電ギャップとしたとき、上記第１の放電ギャップを、上記第２の放電ギャップよりも短く設定すると共に、上記第２の放電ギャップを上記中心電極の先端から上記接地電極延設部の端縁までの距離よりも短く設定する(請求項１）。 In a first invention, in a direct injection internal combustion engine including a fuel injection valve for directly injecting fuel into a combustion chamber and an ignition plug, the ignition plug is insulated from at least a center electrode provided at the center of the plug. A grounding electrode facing the tip of the center electrode by providing a predetermined discharge gap via an insulator, and conducting to the center electrode and approaching the fuel spray injected from the fuel injection valve with respect to the center axis of the center electrode An eccentric electrode extending to the side, and a ground electrode extending portion that extends the tip of the ground electrode so as to face the edge of the eccentric electrode close to the fuel spraying side. In a cylinder injection internal combustion engine that causes a drawn air flow generated when a gas is injected to act on the discharge gap, the shortest distance between the front end surface of the center electrode and the upper surface of the ground electrode facing the first surface is a first distance. Discharge When the shortest distance between the tip surface of the eccentric electrode and the upper surface of the extended portion of the ground electrode facing this is the second discharge gap, the first discharge gap is the second discharge gap. And the second discharge gap is set to be shorter than the distance from the tip of the center electrode to the edge of the ground electrode extension (claim 1).

第１の発明によれば、上記中心電極の先端とその対向する位置における上記接地電極の端縁との間に発生した放電アークは、上記燃料噴射時に発生する引込み気流によって吹き消されることなく、該放電アークの一端が上記中心電極から上記偏心電極に移動し、より噴霧に近い位置に移動しながら放電アークが維持される。
このとき、中心電極と接地電極との最短距離で放電が開始されるため、一定の条件で放電が開始され、機関の運転状況によって変化する引込み気流の流速に応じて、放電アークが上記偏心電極と上記接地電極延設部との間に移動する。
放電アークを引き延ばす引込み気流の流速が遅い場合には、上記第１の放電ギャップにおいて放電が維持され、要求される放電電圧が低く、それだけ長く放電を維持でき、着火性の向上を図ることができる。
一方、放電アークを引き延ばす引込み気流の流速が速い場合には、放電アークが吹き飛ばされることなく、上記第１の放電ギャップから上記第２の放電ギャップへ放電アークが移動し、より燃料噴霧に近い位置で放電アークが形成されるので、着火性の向上を図ることができる。
さらに、上記中心電極の先端と上記接地電極延設部の端縁との間の絶縁耐圧よりも上記第２の放電ギャップの絶縁耐圧の方が低いので、中心電極と接地電極との間に形成された放電アークに引込み気流が作用したときに、上記中心電極の先端と上記接地電極延設部先端との間で放電アークを形成するのではなく、速やかに上記偏心電極の先端と接地電極延設部の先端との間へ移動し、燃料噴霧の着火性の良い可燃層に近づく。
したがって、所定の放電エネルギに対して放電時間を実質的に長くすることができるので、着火性が向上し、成層燃焼における更なる希薄化が可能となり、より安定した着火が実現できる。 According to the first invention, the discharge arc generated between the tip of the center electrode and the edge of the ground electrode at the opposite position is not blown out by the drawn air flow generated during the fuel injection, One end of the discharge arc moves from the center electrode to the eccentric electrode, and the discharge arc is maintained while moving to a position closer to spraying.
At this time, since the discharge is started at the shortest distance between the center electrode and the ground electrode, the discharge is started under a certain condition, and the discharge arc is changed to the eccentric electrode according to the flow velocity of the drawn airflow that changes depending on the engine operating condition. And the ground electrode extending portion.
When the flow velocity of the drawn-in air flow that extends the discharge arc is slow, the discharge is maintained in the first discharge gap, the required discharge voltage is low, the discharge can be maintained for that long, and the ignitability can be improved. .
On the other hand, when the flow velocity of the entrained air flow that extends the discharge arc is high, the discharge arc moves from the first discharge gap to the second discharge gap without being blown away, and is closer to the fuel spray. Since a discharge arc is formed, ignitability can be improved.
Further, since the withstand voltage of the second discharge gap is lower than the withstand voltage between the tip of the center electrode and the edge of the extended portion of the ground electrode, it is formed between the center electrode and the ground electrode. Instead of forming a discharge arc between the tip of the center electrode and the tip of the ground electrode extension portion when a drawn air current acts on the discharged arc, the tip of the eccentric electrode and the extension of the ground electrode are quickly formed. It moves to the tip of the installation part and approaches a combustible layer with good ignitability of fuel spray.
Accordingly, since the discharge time can be substantially increased with respect to the predetermined discharge energy, the ignitability is improved, further dilution in the stratified combustion is possible, and more stable ignition can be realized.

第２の発明では、上記点火プラグの放電ギャップを上記燃焼室内の所定位置に固定すべく上記接地電極に延設して設けたハウジングの先端と上記偏心電極の先端との最短距離を第３の放電ギャップとしたとき、該第３の放電ギャップを上記第２の放電ギャップよりも長く設定する（請求項２）。 In the second invention, the shortest distance between the tip of the housing and the tip of the eccentric electrode provided to extend to the ground electrode to fix the discharge gap of the spark plug at a predetermined position in the combustion chamber is the third distance. when the discharge gap, the discharge gap of the third set longer than the second discharge gap (claim 2).

第２の発明によれば、上記偏心電極と上記ハウジングの先端との間で放電するいわゆる横飛び現象を抑制し、確実に第２の放電ギャップに放電アークを発生させることができるので、着火が不安定となる虞がない。 According to the second invention, since a so-called side jump phenomenon that discharges between the eccentric electrode and the tip of the housing can be suppressed and a discharge arc can be generated in the second discharge gap with certainty, ignition can be prevented. There is no risk of instability.

第３の発明では、上記点火プラグを上記接地電極延設部の先端が上記燃料噴射弁の位置する側に向かうように配設しつつ、上記点火プラグの中心軸と上記燃料噴射弁の中心軸とを結ぶ直線を含む平面に対する、上記接地電極及び上記接地電極延設部のなす角度をプラグ搭載角としたとき、該プラグ搭載角を０°より大きく９０°より小さい範囲に設定する（請求項３）。 In a third aspect of the invention, the spark plug is disposed such that the tip of the ground electrode extending portion faces the side where the fuel injection valve is located, and the center axis of the ignition plug and the center axis of the fuel injection valve When the angle formed by the ground electrode and the ground electrode extension portion with respect to a plane including a straight line connecting the two is defined as a plug mounting angle, the plug mounting angle is set in a range larger than 0 ° and smaller than 90 °. 3 ).

第３の発明によれば、上記燃料噴射弁から燃焼室内に燃料が噴射されたときに周囲の空気の持ち去りによって発生する燃料の噴射方向とは略逆向きの引込み気流が上記点火プラグに発生する放電アークに作用すると、該放電アークが上記中心電極から上記偏心電極の先端に向かって移動しつつ、上記燃料噴射弁から噴射された燃料噴霧に近づき、安定した着火を実現できる。なお、本発明者等の鋭意試験により、本発明の範囲を外れ、上記プラグ搭載角度を９０°以上に設定した場合、即ち、上記接地電極延設部の先端を上記燃料噴射弁の載置位置から離れる方向に向けた場合、上記放電アークは燃料の噴射方向に対して下流側に伸び、着火が不安定となり、数％程度の確率で失火の虞があることが判明した。 According to the third invention, when the fuel is injected from the fuel injection valve into the combustion chamber, a drawn air flow is generated in the spark plug in a direction substantially opposite to the fuel injection direction generated by the removal of surrounding air. When acting on the discharge arc, the discharge arc moves toward the tip of the eccentric electrode from the center electrode, approaches the fuel spray injected from the fuel injection valve, and realizes stable ignition. It should be noted that when the plug mounting angle is set to 90 ° or more by the inventors' diligent test and the plug mounting angle is set to 90 ° or more, that is, the tip of the ground electrode extending portion is placed at the mounting position of the fuel injection valve. When the discharge arc is directed away from the fuel, it has been found that the discharge arc extends downstream with respect to the fuel injection direction, the ignition becomes unstable, and there is a possibility of misfire with a probability of several percent.

本発明の第１の実施形態における筒内噴射式内燃機関に用いられる点火プラグの要部を示し、（ａ）は、下面図、（ｂ）は、本図（ａ）中Ｘ−Ｘに沿った矢視断面図、（ｃ）は、図（ａ）中Ｙ−Ｙに沿った矢視断面図。The principal part of the ignition plug used for the direct injection internal combustion engine in the 1st Embodiment of this invention is shown, (a) is a bottom view, (b) is along XX in this figure (a). The arrow sectional drawing, (c) is arrow sectional drawing along YY in figure (a). 本発明の第１の実施形態における筒内噴射式内燃機関の概要を示す構成図。The block diagram which shows the outline | summary of the direct injection internal combustion engine in the 1st Embodiment of this invention. 本発明の第１の実施形態における筒内噴射式内燃機関に用いられる点火プラグの詳細を示す半断面図。1 is a half sectional view showing details of a spark plug used in a direct injection internal combustion engine according to a first embodiment of the present invention. 本発明の第１の実施形態における筒内噴射式内燃機関の効果を模式的に示し、（ａ）は、下面図、（ｂ）は、本図（ａ）中Ｂ−Ｂに沿った矢視断面図、（ｃ）は、図（ａ）中Ａ−Ａに沿った矢視断面図。The effect of the direct injection internal combustion engine in the 1st embodiment of the present invention is typically shown, (a) is a bottom view and (b) is an arrow view along BB in this figure (a). Sectional drawing and (c) are arrow sectional views along AA in figure (a). 本発明の第１の実施形態における筒内噴射式内燃機関の効果を模式的に示す要部斜視図。The principal part perspective view which shows typically the effect of the cylinder injection type internal combustion engine in the 1st Embodiment of this invention. 本発明の第１の実施形態における筒内噴射式内燃機関に用いられる燃料噴射弁から噴射された燃料噴霧の中心と点火プラグの放電ギャップ中心との距離に対する燃料噴霧の特性を示し、（ａ）は、燃料と空気との当量比分布を示す特性図、（ｂ）は、燃料噴霧の速度分布を示す特性図。The characteristics of the fuel spray with respect to the distance between the center of the fuel spray injected from the fuel injection valve used in the direct injection internal combustion engine in the first embodiment of the present invention and the center of the discharge gap of the spark plug are shown in FIG. Is a characteristic diagram showing an equivalence ratio distribution between fuel and air, and (b) is a characteristic diagram showing a velocity distribution of fuel spray. 本発明の第２の実施形態における筒内噴射式内燃機関の効果を模式的に示す下面図。The bottom view which shows typically the effect of the cylinder injection type internal combustion engine in the 2nd Embodiment of this invention. 本発明の第３の実施形態における筒内噴射式内燃機関に用いられる点火プラグの要部を示し、（ａ）は、下面図、（ｂ）は、本図（ａ）中Ｘ−Ｘに沿った矢視断面図、（ｃ）は、図（ａ）中Ｙ−Ｙに沿った矢視断面図。The principal part of the spark plug used for the cylinder injection type internal combustion engine in the 3rd Embodiment of this invention is shown, (a) is a bottom view, (b) is along XX in this figure (a). The arrow sectional drawing, (c) is arrow sectional drawing along YY in figure (a). （ａ）から（ｃ）は、本発明の第３の実施形態における筒内噴射式内燃機関における点火プラグの搭載角に対する効果を示す要部下面図。(A) to (c) is a bottom view of the main part showing the effect on the mounting angle of the spark plug in the direct injection internal combustion engine according to the third embodiment of the present invention. 本発明の第４の実施形態における筒内噴射式内燃機関の概要を示す構成図。The block diagram which shows the outline | summary of the direct injection internal combustion engine in the 4th Embodiment of this invention.

図１から図３を参照して、本発明の第１の実施形態における筒内噴射式内燃機関１及び本実施形態に用いられる点火プラグ１０について説明する。
図１（ａ）から（ｃ）に示すように、点火プラグ１０には、少なくとも、プラグの中心に設けた中心電極１１と、略筒状の絶縁碍子１２を介して所定の放電ギャップを設けて中心電極放電部１１０の先端面に対向する接地電極１３０と、中心電極１１に導通し中心電極１１の中心軸に対してプラグの外径方向に伸びるように延設した偏心電極２０と、接地電極１３０の先端を偏心電極２０の端縁に対向するように、プラグの外径方向に伸ばした接地電極延設部２１とが設けられている。
また、中心電極放電部１１０の先端面とこれに対向する接地電極１３０の上面までの最短距離を第１の放電ギャップＡＧ１とし、偏心電極２０の先端面とこれに対向する接地電極延設部２１の上面までの最短距離を第２の放電ギャップＡＧ２としたとき、第１の放電ギャップＡＧ１は、第２の放電ギャップＡＧ２よりも短く設定されている。
接地電極１３０に延設して設けられたハウジング１３の先端のシュラウド１３２と偏心電極２０の先端との最短距離を第３の放電ギャップＡＧ３としたとき、ハウジング１３の外径φＤに応じて、第３の放電ギャップＡＧ３が第２の放電ギャップＡＧ２よりも長くなるように絶縁碍子先端部１２０がシュラウド１３２から露出する部分の長さを適宜設定する。
中心電極放電部１１０の先端縁と接地電極延設部２１の外周方向先端縁までの対角距離ＡＧ４は、第２の放電ギャップＡＧ２よりも長くなっている。
放電部１１０の先端縁と接地電極１３０の側端縁との対角方向の距離ＡＧ５は、第２の放電ギャップＡＧ２と等しいかそれ以下とするのが望ましい。
偏心電極２０の幅Ｅは、中心電極放電部１１０の外径φｄと同等か、又は、接地電極延設部２１の幅Ｆと同等となるように設定されている。 With reference to FIGS. 1 to 3, a direct injection internal combustion engine 1 according to a first embodiment of the present invention and a spark plug 10 used in the present embodiment will be described.
As shown in FIGS. 1A to 1C, the spark plug 10 is provided with a predetermined discharge gap via at least a center electrode 11 provided at the center of the plug and a substantially cylindrical insulator 12. A ground electrode 130 facing the tip surface of the center electrode discharge section 110; an eccentric electrode 20 that is connected to the center electrode 11 and extends in the outer diameter direction of the plug with respect to the center axis of the center electrode 11; A ground electrode extending portion 21 extending in the outer diameter direction of the plug is provided so that the tip of 130 faces the edge of the eccentric electrode 20.
Further, the shortest distance to the upper surface of the distal end surface and the ground electrode 130 opposed thereto of the center electrode discharge portion 110 as a first discharge gap AG 1, the ground electrode extending portion of the distal end surface opposed to the eccentric electrode 20 when the shortest distance to the upper surface 21 and a second discharge gap AG 2, the first discharge gap AG 1 is set to be shorter than the second discharge gap AG 2.
When the shortest distance a third discharge gap AG 3 with the shroud 132 of the tip of the housing 13 which is provided to extend to the ground electrode 130 and the distal end of the eccentric electrode 20, depending on the outer diameter φD of the housing 13, third discharge gap AG 3 is the insulator tip 120 to be longer than the second discharge gap AG 2 sets the length of the portion exposed from the shroud 132 as appropriate.
Diagonal distance AG 4 to the outer peripheral direction leading edge of the leading edge of the center electrode discharge portion 110 and the ground electrode extending portion 21 is longer than the second discharge gap AG 2.
Distance AG 5 diagonal direction between the side edges of the leading edge and the ground electrode 130 of the discharge part 110, it is desirable to do it less equal to the second discharge gap AG 2.
The width E of the eccentric electrode 20 is set to be equal to the outer diameter φd of the center electrode discharge portion 110 or equal to the width F of the ground electrode extension portion 21.

図２に示すように、筒内噴射式内燃機関１は、エンジン４０と、複数の噴孔３１から燃焼室４００内に燃料ＦＬを直接噴射する燃料噴射弁３０と、燃料噴射弁３０の直下で、点火プラグ１０の放電ギャップの中心点ＰＡＧと燃料噴射弁３０の先端ＰＺＮＬまでのプラグ−噴孔間距離が所定の範囲となるように配設された点火プラグ１０と、筒内噴射式内燃機関４０を制御する電子制御装置（ＥＣＵ）５０とによって構成されている。
筒内噴射式内燃機関４０は、エンジンヘッド４１と略筒状のシリンダ４２とシリンダ４２内に可動に収納されたピストン４３とによって構成され、エンジンヘッド４１の内壁とシリンダ４２の内周壁とピストン４３の頂面とによって燃焼室４００が区画されている。
エンジンヘッド４１には吸気バルブ４１１によって開閉される吸気筒４１０と、排気バルブ４２１によって開閉される排気筒４２０とが形成されている。 As shown in FIG. 2, the in-cylinder injection internal combustion engine 1 includes an engine 40, a fuel injection valve 30 that directly injects fuel FL into the combustion chamber 400 from the plurality of injection holes 31, and a position directly below the fuel injection valve 30. , the central point the plug to the tip P ZNL of P AG and the fuel injection valve 30 of the discharge gap of the spark plug 10 - the spark plug 10 injection hole distance is arranged to have a predetermined range, the in-cylinder injection type An electronic control unit (ECU) 50 that controls the internal combustion engine 40 is configured.
The in-cylinder injection internal combustion engine 40 includes an engine head 41, a substantially cylindrical cylinder 42, and a piston 43 movably housed in the cylinder 42, and the inner wall of the engine head 41, the inner peripheral wall of the cylinder 42, and the piston 43. Combustion chamber 400 is partitioned by the top surface of.
The engine head 41 is formed with an intake cylinder 410 that is opened and closed by an intake valve 411 and an exhaust cylinder 420 that is opened and closed by an exhaust valve 421.

燃料噴射弁３０から燃焼室４００内に、高圧の燃料ＦＬが噴射されると、その周囲の空気を持ち去り（エアエントレインメント）、低圧部が形成されるので、燃料ＦＬの噴射方向とは略逆向きの引込み気流ＡＲＥＮＴが発生する。
点火プラグ１０は、内燃機関４０のエンジンヘッド４１に先端部を燃焼室４００内に露出した状態で固定されており、点火プラグ１０には、点火プラグ１０の放電領域に発生する引込み気流ＡＲＥＮＴによって放電アークＡＲＣが吹き飛ばされるのを防ぐと共に、実質的な放電時間を延ばすべく、放電アークＡＲＣが燃焼室４００内に噴射された燃料噴霧ＦＬの可燃層ＬＳＴに近づくよう偏心電極２０及び接地電極延設部２１が設けられている。 When the high-pressure fuel FL is injected from the fuel injection valve 30 into the combustion chamber 400, the surrounding air is taken away (air entrainment), and a low-pressure portion is formed. A reverse airflow AR ENT is generated.
The spark plug 10 is fixed to the engine head 41 of the internal combustion engine 40 with its tip portion exposed in the combustion chamber 400, and the spark plug 10 is caused by a drawn air flow AR ENT generated in the discharge region of the spark plug 10. together prevent the discharge arc aRC is blown, to extend the substantial discharge time, discharge arc aRC is eccentric electrode 20 and the ground electrode extends to approach the combustible layer L ST of the fuel spray FL injected into the combustion chamber 400 An installation part 21 is provided.

本発明の筒内噴射式内燃機関１では、燃料噴射弁３０に対して点火プラグ１０を特定の距離に配設し、燃料噴射弁３０から燃料ＦＬが噴射されたときに燃料の噴射方向とは逆方向の引込み気流ＡＲＥＮＴを発生するエアエントレインメントを点火プラグ１０の第１の放電ギャップＡＧ１の中心点ＰＡＧ近傍に作用させるようにしている。
ＥＣＵ５０では、機関の運転状況に応じて燃料噴射弁の開弁開始時期及び開弁時間ｔ３を決定する燃料噴射信号ＩＮＪを発信し、燃料噴射弁３０への通電を開始し、燃料噴射弁３０の開弁の立ち上がりから所定の点火開始時間ｔ１経過後に、燃料噴射弁３０からの燃料噴射が継続中に、点火プラグ１０への２次電圧Ｖ２の印加が開始され、所定の点火エネルギ供給時間ｔ２の間、２次電流Ｉ２の放電を維持され、所定の燃料噴射時間ｔ３経過によって燃料噴射弁３０が閉弁される。
燃料噴射弁３０から燃料噴射が継続中に点火プラグ１０への高電圧の印加し、発生する初期放電アークＡＲＣＩＮＴをエアエントレインメントを利用して燃料噴霧ＦＬの可燃層ＬＳＴに近い位置に移動させつつ、引延ばされた放電アークＡＲＣＥＮＬを、噴射された燃料噴霧と周囲の空気とが適度な空燃比に混合された可燃層ＬＳＴにさらに近づけると共に延長放電アークＡＲＣＥＮＬの表面積の増加に伴う着火性の向上を利用することによって極めて希薄な混合気の点火を可能としたことを特徴としている。 In the in-cylinder internal combustion engine 1 of the present invention, the spark plug 10 is disposed at a specific distance from the fuel injection valve 30, and what is the fuel injection direction when the fuel FL is injected from the fuel injection valve 30? so that the action of air entrainment to occur in the reverse direction retraction airflow AR ENT to the first center point P AG vicinity of the discharge gap AG 1 of the spark plug 10.
In ECU 50, the fuel injection signal INJ for determining the valve opening start timing and valve opening time t 3 of the injector sent in accordance with the operating conditions of the engine, and starts energizing the fuel injection valve 30, fuel injection valve 30 After a predetermined ignition start time t 1 has elapsed from the rise of the valve opening, the application of the secondary voltage V 2 to the spark plug 10 is started while fuel injection from the fuel injection valve 30 is continuing, and a predetermined ignition energy is supplied. during the time t 2, is maintaining a discharge of the secondary current I 2, the fuel injection valve 30 by a predetermined fuel injection time t 3 has elapsed is closed.
High voltage is applied for to the fuel injection valve 30 ignition plug 10 the fuel injection for the duration of the movement the initial discharge arc ARC INT generated at a position close to the combustible layer L ST of the fuel spray FL by utilizing the air entrainment while the increase of the surface area of the extended discharge arc aRC ENL with the discharge arc aRC ENL which extended arguments, further closer to the mixed combustible layer L ST fuel spray injected and the surrounding air is moderate air It is characterized in that ignition of an extremely lean mixture is made possible by utilizing the improvement in ignitability associated with.

図３を参照して本実施形態における点火プラグ１０のより具体的な構成について詳述する。点火プラグ１０は、略筒状に形成された絶縁碍子１２と、絶縁碍子１２に設けた軸孔に挿入固定された略長軸状の中心電極１１と、絶縁碍子１２をその内部に収納しつつ内燃機関４０のシリンダヘッド４１に固定するハウジング１３と、ハウジング１３の先端に延設して設けられた接地電極１３０と、本発明の要部であり、中心電極１１に導通し中心電極１１の中心軸に対して燃料噴射弁３０から噴射される燃料噴霧ＦＬ近づく側に延設した偏心電極２０と、中心電極１１の先端部１１０に所定の放電ギャップＡＧ１を隔てて対向する接地電極１３０の先端を偏心電極２０の燃料噴霧側に近い端縁に対向するように伸ばした接地電極延設部２１とによって構成されている。 A more specific configuration of the spark plug 10 in the present embodiment will be described in detail with reference to FIG. The spark plug 10 accommodates an insulator 12 formed in a substantially cylindrical shape, a substantially long axis center electrode 11 inserted and fixed in a shaft hole provided in the insulator 12, and the insulator 12 therein. The housing 13 fixed to the cylinder head 41 of the internal combustion engine 40, the ground electrode 130 provided to extend at the tip of the housing 13, and the main part of the present invention, are electrically connected to the center electrode 11 and the center of the center electrode 11. distal end of the ground electrode 130 to the axis and eccentric electrode 20 that is extended to the side approaching fuel spray FL injected from the fuel injection valve 30, which face each other with a predetermined discharge gap AG 1 the distal end 110 of the center electrode 11 Is formed by a ground electrode extending portion 21 that extends so as to face the edge of the eccentric electrode 20 near the fuel spray side.

中心電極１１は、例えば内材としてＣｕ等の熱伝導性に優れた金属材料が用いられ、外材としてＮｉ基合金等の耐熱性及び耐食性に優れた金属材料が用いられて長軸状に形成されている。
中心電極１１は、中心電極放電部１１０を絶縁碍子先端部１２０から燃焼室４００内に露出するように設けられている。
偏心電極２０は、中心電極放電部１１０に導通し、点火プラグ１０の外径方向に伸びるように、略平板状に形成されている。
中心電極放電部１１０及び偏心電極２０は、耐熱性の高いイリジウム合金や特殊なＮｉ合金によって形成されている。
中心電極１１の基端側には、絶縁碍子１２の軸孔内部において、中心電極中軸部１１１と導電性のガラスシール１１２を介して電気的に接続された長軸状のステム１１３が設けられている。さらにその基端側には、碍子頭部１２２から露出し、外部の図略の点火装置に接続される中心電極端子部１１４が形成されている。 The center electrode 11 is formed in a long axis shape using, for example, a metal material excellent in thermal conductivity such as Cu as an inner material, and using a metal material excellent in heat resistance and corrosion resistance such as a Ni-based alloy as an outer material. ing.
The center electrode 11 is provided so that the center electrode discharge part 110 is exposed from the insulator tip part 120 into the combustion chamber 400.
The eccentric electrode 20 is formed in a substantially flat plate shape so as to conduct to the center electrode discharge part 110 and extend in the outer diameter direction of the spark plug 10.
The center electrode discharge part 110 and the eccentric electrode 20 are made of an iridium alloy having high heat resistance or a special Ni alloy.
On the proximal end side of the center electrode 11, a long axis stem 113 is provided in the shaft hole of the insulator 12 and is electrically connected to the center electrode middle shaft portion 111 through a conductive glass seal 112. Yes. Further, a central electrode terminal portion 114 that is exposed from the insulator head portion 122 and connected to an external ignition device (not shown) is formed on the base end side.

絶縁碍子１２は、高純度アルミナ等の耐熱性、絶縁性に優れたセラミックス材料を用いて略筒状に形成されている。絶縁碍子１２の軸孔には略長軸状に形成された中心電極１１が挿入・固定されている。
絶縁碍子１２の中腹には径大となる係止部１２１が形成されており、ハウジング１３の内側に設けられたハウジング係止部１３５に係止されると共に、封止部材を介してハウジング加締め部１３７によって加締め固定されている。
絶縁碍子１２の碍子先端部１２０は燃焼室４００に露出しつつ、ハウジング１３の先端に設けられた略環状のシュラウド１３２によってその外側が取り囲まれている。
絶縁碍子１２の基端側は、ハウジング１３の加締め部１３７から露出する碍子頭部１２２が設けられている。碍子頭部１２２は、コルゲート状に形成され中心電極端子部１１２とハウジング１３との表面距離を長くして沿面リークを防止している。 The insulator 12 is formed in a substantially cylindrical shape using a ceramic material excellent in heat resistance and insulation, such as high-purity alumina. A central electrode 11 formed in a substantially long axis shape is inserted and fixed in the shaft hole of the insulator 12.
A locking portion 121 having a large diameter is formed in the middle of the insulator 12 and is locked to a housing locking portion 135 provided on the inner side of the housing 13, and the housing is tightened via a sealing member. It is fixed by caulking by a portion 137.
The insulator tip 120 of the insulator 12 is exposed to the combustion chamber 400 and is surrounded by a substantially annular shroud 132 provided at the tip of the housing 13.
On the base end side of the insulator 12, an insulator head 122 that is exposed from the crimped portion 137 of the housing 13 is provided. The insulator head 122 is formed in a corrugated shape, and the surface distance between the center electrode terminal portion 112 and the housing 13 is increased to prevent creeping leakage.

ハウジング１３は、例えば、導電性の低炭素鋼等の高耐熱性金属材料を用いて略筒状に形成されている。ハウジング１３の先端側は中心電極１１の側面に絶縁碍子１２を介して対向する側面電極１３４を形成している。側面電極１３４の外周面には、燃焼室４００内の所定位置に点火プラグ１０の先端を固定すべくエンジンヘッド４１に設けられたねじ穴に固定するためのネジ部１３３が設けられている。ネジ部１３３の先端側には略環状のシュラウド部１３２が設けられている。
ハウジング１３の中腹内周は先端側に向かって径小となる係止部１３５が形成され、内側に絶縁碍子１２の係止部１２１が係止され、基端側には加締め部１３７が形成され、封止部材を介して絶縁碍子１２の係止部１２１を覆うように加締め固定している。
ハウジング１３の基端側外周にはネジ部１３４を締めつけるためのナット部１３６が形成されている。ネジ部１３４は、エンジンヘッド４１に設けられたネジ穴にガスケットを介して螺結される。 The housing 13 is formed in a substantially cylindrical shape using a high heat resistant metal material such as conductive low carbon steel. A side electrode 134 is formed on the front end side of the housing 13 so as to face the side surface of the center electrode 11 with the insulator 12 interposed therebetween. On the outer peripheral surface of the side electrode 134, a screw portion 133 is provided for fixing to a screw hole provided in the engine head 41 so as to fix the tip of the spark plug 10 at a predetermined position in the combustion chamber 400. A substantially annular shroud portion 132 is provided on the distal end side of the screw portion 133.
A locking part 135 having a diameter that decreases toward the distal end is formed on the inner periphery of the housing 13, a locking part 121 of the insulator 12 is locked inside, and a crimping part 137 is formed on the proximal end side. Then, it is fixed by caulking so as to cover the locking portion 121 of the insulator 12 via the sealing member.
A nut portion 136 for tightening the screw portion 134 is formed on the outer periphery of the base end side of the housing 13. The screw part 134 is screwed into a screw hole provided in the engine head 41 via a gasket.

ハウジング１３のシュラウド部１３１に延設して、接地電極脚部１３１を介して略Ｌ字状に伸びる接地電極１３０が形成され、接地電極１３０は、所定の放電ギャップＡＧ１を設けて中心電極放電部１１０に対向している。
接地電極１３０の先端側に延設して、偏心電極２０に所定の放電ギャップＡＧ２を設けて対向する接地電極延設部２１が接地電極１３０と一体的に形成されている。
接地電極１３０及び接地電極延設部２１は、例えばＮｉを主成分とするＮｉ基合金等を用いて断面略角柱形状に形成されている。 And extended to the shroud portion 131 of the housing 13, the ground electrode 130 extending in a substantially L shape is formed through the ground electrode legs 131, ground electrode 130, the center electrode discharge with a predetermined discharge gap AG 1 It faces the part 110.
And extending the front end side of the ground electrode 130, the ground electrode extending portions 21 facing with a predetermined discharge gap AG 2 to the eccentric electrode 20 is integrally formed with the ground electrode 130.
The ground electrode 130 and the ground electrode extending portion 21 are formed in a substantially prismatic cross section using, for example, a Ni-based alloy containing Ni as a main component.

図４、図５を参照し、本発明の第１の実施形態における筒内噴射式内燃機関１の効果について説明する。
燃料噴射弁３０の複数の噴孔３１から燃料が噴射され、そのうち２つの燃料噴流ＦＬ１、ＦＬ２との間に挟まれるように点火プラグ１０が配設されている。
ＥＣＵ５０からの燃料噴射信号ＩＮＪにしたがって、燃料噴射弁３０から極めて高い圧力の燃料が噴射されると、燃料噴流ＦＬ１、ＦＬ２によって周囲の空気が持ち去られ、圧力の低い部分が形成され、燃焼室４００内の圧力の高い部分から低い部分に向かうように、燃料噴流ＦＬ１、ＦＬの噴射方向とは略逆向きの引込み気流ＡＲＥＮＴが発生する。
ＥＣＵ５０からの点火信号に従って、点火プラグ１０に高電圧が印加されると、中心電極放電部１１０の先端縁とこれに対向する接地電極１３０の側縁の最短距離、即ち第１の放電ギャップＡＧ１の近傍で、初期放電アークＡＲＣＩＮＴが発生する。
このとき、燃料噴射に伴うエアエントレインメントにより発生する引込み気流ＡＲＥＮＴによって、初期放電アークＡＲＣＩＮＴが燃料噴射弁３０の方向に引き寄せられる。
すると、中心電極放電部１１０と接地電極１３０との間で発生した初期放電アークは、偏心電極２０と接地電極１３０との間で放電するように移動し、さらに、偏心電極２０と接地電極延設部２１との間で放電するように移動し、偏心電極２０の先端縁と接地電極延設部２１の先端縁との間の放電に変わる。
さらに、両電極間の最短距離である第２の放電ギャップＡＧ２で放電が維持されるのに加え、偏心電極２０及び接地電極延設部２１の角部は電界集中により放電しやすくなっているので、要求電圧が低くなり、放電時間を長く継続できるようになる。
したがって、偏心電極２０の先端縁と接地電極延設部２１の先端縁との間に形成された放電アークは、燃料噴射弁３０の方向に向かう引込み気流ＡＲＥＮＴによって長く引き延ばされた延長放電アークＡＲＣＥＮＬとなる。
このとき、２つの燃料噴流ＦＬ１、ＦＬ２のうち、延長放電アークＡＲＣＥＮＬにより近い方の燃料噴流ＦＬ２の燃料と空気との混合比が安定して着火できる割合となった可燃層ＬＳＴに近づくため安定した着火が実現できる。 The effects of the direct injection internal combustion engine 1 according to the first embodiment of the present invention will be described with reference to FIGS.
The fuel is injected from the plurality of nozzle holes 31 of the fuel injection valve 30, and the spark plug 10 is disposed so as to be sandwiched between the two fuel jets FL 1 and FL 2 .
When extremely high pressure fuel is injected from the fuel injection valve 30 in accordance with the fuel injection signal INJ from the ECU 50, the surrounding air is taken away by the fuel jets FL 1 and FL 2 to form a low pressure portion and combustion An entrained airflow AR ENT is generated in a direction substantially opposite to the injection direction of the fuel jets FL 1 and FL so as to go from a high pressure portion to a low pressure portion in the chamber 400.
Accordance ignition signal from ECU 50, when a high voltage is applied to the spark plug 10, the shortest distance of the side edges of the leading edge and the ground electrode 130 opposed thereto of the center electrode discharge portion 110, i.e., the first discharge gap AG 1 , An initial discharge arc ARC INT is generated.
At this time, the initial discharge arc ARC INT is drawn toward the fuel injection valve 30 by the drawn air flow AR ENT generated by the air entrainment accompanying the fuel injection.
Then, the initial discharge arc generated between the center electrode discharge part 110 and the ground electrode 130 moves so as to discharge between the eccentric electrode 20 and the ground electrode 130, and further, the eccentric electrode 20 and the ground electrode are extended. It moves so as to discharge between the portions 21 and changes to discharge between the tip edge of the eccentric electrode 20 and the tip edge of the ground electrode extension portion 21.
Furthermore, in addition to the discharge being maintained at the second discharge gap AG2, which is the shortest distance between the two electrodes, the corners of the eccentric electrode 20 and the ground electrode extension portion 21 are liable to discharge due to electric field concentration. Therefore, the required voltage is lowered and the discharge time can be continued for a long time.
Therefore, the discharge arc formed between the front end edge of the eccentric electrode 20 and the front end edge of the ground electrode extending portion 21 is extended discharge that is extended by the drawn air flow AR ENT toward the fuel injection valve 30. Arc ARC ENL .
At this time, the combustible layer L ST in which the mixing ratio of the fuel and air of the fuel jet FL 2 closer to the extended discharge arc ARC ENL among the two fuel jets FL 1 and FL 2 can be stably ignited. Stable ignition can be realized because it approaches.

図５に模式的に示すように、初期放電アークＡＲＣＩＮＴに比べて延長放電アークＡＲＣＥＮＬは、長く引き延ばされ、かつ、燃料噴流ＦＬ２の可燃層ＬＳＴに近い位置に発生するので、極めて着火安定性に優れている。
従来のスパーク点火では、点火プラグの中心で放電アークが発生するため、消炎効果によって火炎核の成長速度が遅くなったり、燃料噴流の可燃層を点火プラグに近づける必要があるので、燃料が直接点火プラグに付着してデポジットを形成したりする虞がある。
一方、本発明によれば、延長放電アークＡＲＣＥＮＬが、点火プラグ１０の中心からはずれて偏心電極２０と接地電極延設部２１との間で形成されるため、消炎効果も小さくなり、火炎核の成長速度が速くなる。
加えて燃料噴流ＦＬを点火プラグ１０に近づけるのではなく、長く引き延ばされた延長放電アークＡＲＣＥＮＬが燃料噴流ＦＬの可燃層ＬＳＴに近づくのでデポジットも形成され難くなる。 As shown schematically in FIG. 5, the extension discharge arc ARC ENL in comparison to the initial discharge arc ARC INT is extended long and, therefore generated in a position close to the combustible layer L ST of the fuel jet FL 2, Excellent ignition stability.
In the conventional spark ignition, a discharge arc is generated at the center of the spark plug, so that the flame extinguishing effect slows the growth rate of the flame kernel, or the fuel jet combustible layer needs to be close to the spark plug, so the fuel is directly ignited. There is a risk of depositing on the plug.
On the other hand, according to the present invention, the extended discharge arc ARC ENL deviates from the center of the spark plug 10 and is formed between the eccentric electrode 20 and the ground electrode extension portion 21, so that the flame extinguishing effect is reduced and the flame core is reduced. The growth rate of will be faster.
In addition, instead of closer to the fuel jet FL to the spark plug 10, the deposit becomes difficult to form because extended discharge arc ARC ENL which stretched long approaches the combustible layer L ST of the fuel jet FL.

ここで、図６を参照して、燃料噴射弁３０から噴射された燃料噴流ＦＬの中心と点火プラグの放電ギャップの中心点ＰＡＧとの距離に対する、当量比分布の変化と、流速分布の変化について説明する。
図６（ａ）に示すように、燃料噴流の中心近傍では、当量比が１．５以上で、空気に対する燃料比率が高すぎて着火できない不燃層ＬＴＲを形成し、燃料噴流の外側に向かって徐々に燃料の混合比が低下し、安定して着火可能な当量比０．５〜１．５の可燃層ＬＳＴが形成され、さらにその外側には、燃料比率が低すぎて着火できない不燃層ＬＴＬが形成されている。
また、図６（ｂ）に示すように、燃料噴流の中心部分は流速ＶＡＲが極めて速く、外側に向かって徐々に流速が低下している。
流速ＶＡＲが２０ｍ／ｓより速いと、放電アークＡＲＣが吹き飛ばされてしまい着火が不安定となり、流速ＶＡＲが２０ｍ／ｓ以下であること、放電アークＡＲＣが安定して形成される。
本実施形態においては、燃料噴流ＦＬの中心から点火プラグ１０のギャップ中心ＰＡＧまでのプラグ−噴霧中心間距離ｄを１．１ｍｍ以上５．２ｍｍ以下の範囲となるように、点火プラグ１０と燃料噴射弁３０とを配設するのが望ましいことが判明した。
また、本実施形態における筒内噴射式内燃機関１の実機試験によって、限界空燃比Ａ／Ｆを４０程度まで向上させることができることが判明した。 Referring now to FIG. 6, with respect to the distance between the center point P AG discharge gap center and the ignition plug of the fuel jet FL injected from the fuel injection valve 30, the change in the equivalence ratio distribution, changes in the flow velocity distribution Will be described.
As shown in FIG. 6 (a), in the vicinity of the center of the fuel jet, in an equivalent ratio of 1.5 or more, to form a combustible layer L TR that can not be ignited fuel ratio is too high for the air, towards the outside of the fuel jet gradually decreases mixing ratio of the fuel, stably combustible layer L ST of ignitable equivalent ratio from 0.5 to 1.5 is formed, further the outside, non-combustible fuel ratio can not be ignited too low Te A layer LTL is formed.
Further, as shown in FIG. 6 (b), the flow velocity VAR is extremely high in the center portion of the fuel jet, and the flow velocity gradually decreases toward the outside.
When the flow velocity VAR is higher than 20 m / s, the discharge arc ARC is blown off, and the ignition becomes unstable, the flow velocity VAR is 20 m / s or less, and the discharge arc ARC is stably formed.
In the present embodiment, the plug from the center of the fuel jet FL to gap center P AG of the spark plug 10 - the spray center distance d such that 5.2mm or less in the range above 1.1 mm, the spark plug 10 and fuel It has been found desirable to provide the injection valve 30.
Further, it has been found that the limit air-fuel ratio A / F can be improved to about 40 by an actual machine test of the direct injection internal combustion engine 1 in the present embodiment.

図７を参照して、本発明の第２の実施形態における筒内噴射式内燃機関１ａについて説明する。なお、上記実施形態と同様の構成については同じ符号を付したので説明を省略し、相違点についてのみ説明する（以下の実施形態において同様である。）。
本実施形態においては、上記実施形態と同様の構成を基本とし、点火プラグ１０ａとして、接地電極延設部２１の先端が燃料噴射弁３０の位置する側に向かうように配設しつつ、点火プラグ１０ａの中心軸と燃料噴射弁３０の中心軸とを結ぶ直線（ギャップ中心点ＰＡＧとノズル中心点ＰＮＺＬとを結ぶ直線）を含む平面に対する、接地電極１３０及び接地電極延設部２１のなす角度をプラグ搭載角θＰＬＧとしたとき、プラグ搭載角θＰＬＧを０°より大きく９０°より小さい範囲に設定した点が相違する。
このような角度で、点火プラグ１０ａを装着すると、燃料噴射弁３０から燃焼室４００内に燃料が噴射されたときに周囲の空気の持ち去りによって発生する燃料の噴射方向とは略逆向きの引込み気流ＡＲＥＮＴが点火プラグ１０ａに発生する初期放電アークＡＲＣＩＮＴに作用すると、初期放電アークＡＲＣＩＮＴが中心電極１１０から偏心電極２０の先端に向かって移動しつつ、燃料噴射弁３０から噴射された燃料噴霧ＦＬ２の可燃層ＬＳＴに近づき、安定した着火を実現できる。
なお、本発明者等の鋭意試験により、本発明の範囲を外れ、プラグ搭載角度θＰＬＧを９０°以上に設定した場合、即ち、接地電極延設部２１の先端を燃料噴射弁の載置位置から離れる方向に向けた場合、初期放電アークＡＲＣＩＮＴは燃料の噴射方向に対して下流側に伸び、着火が不安定となり、数％程度の確率で失火の虞があることが判明した。エアエントレインメントによる引込み気流ＡＲＥＮＴが燃料噴射弁３０に近づく方向に向かって発生するのに対し、接地電極延設部を燃料噴射弁３０から離れる方向に向けることにより、放電アークは、燃料噴射弁３０から離れる方向に引き寄せられるので、相反する力が作用し、放電が不安定となるためと推察される。 With reference to FIG. 7, the direct injection internal combustion engine 1a in the 2nd Embodiment of this invention is demonstrated. In addition, since the same code | symbol is attached | subjected about the structure similar to the said embodiment, description is abbreviate | omitted and only a difference is demonstrated (it is the same also in the following embodiment).
In the present embodiment, the spark plug 10a is basically configured in the same manner as the above embodiment, and the spark plug 10a is disposed so that the tip of the ground electrode extending portion 21 faces the side where the fuel injection valve 30 is located. for 10a central axis connecting the center axis of the fuel injection valve 30 straight plane containing the (straight line connecting the gap center point P AG and nozzle center point P NZL) the forms of the ground electrode 130 and the ground electrode extending portion 21 when the angle was a plug mounted angle theta PLG, in that the plug mounting angle theta PLG set to larger and smaller than 90 ° range from 0 ° is different.
When the spark plug 10a is mounted at such an angle, the fuel is drawn in in a direction substantially opposite to the fuel injection direction generated by the removal of surrounding air when the fuel is injected from the fuel injection valve 30 into the combustion chamber 400. When the air flow AR ENT acts on the initial discharge arc ARC INT generated in the spark plug 10a, the initial discharge arc ARC INT moves from the center electrode 110 toward the tip of the eccentric electrode 20 and fuel injected from the fuel injection valve 30. approaches the combustible layer L ST spraying FL 2, can realize stable ignition.
It should be noted that when the plug mounting angle θ PLG is set to 90 ° or more by an intensive test by the present inventors, the tip of the ground electrode extending portion 21 is placed at the mounting position of the fuel injection valve. When the direction is away from the initial discharge arc, the initial discharge arc ARC INT extends downstream with respect to the fuel injection direction, the ignition becomes unstable, and it has been found that there is a possibility of misfire with a probability of several percent. While the entrained air flow AR ENT due to air entrainment is generated in a direction approaching the fuel injection valve 30, the discharge arc is generated by directing the ground electrode extending portion in a direction away from the fuel injection valve 30. Since it is attracted in a direction away from 30, it is presumed that conflicting forces act and discharge becomes unstable.

図８を参照して、本発明の第３の実施形態における筒内噴射式内燃機関に用いられる点火プラグ１０ｂについて説明する。
本実施形態においては、上記実施形態と同様の構成を基本とし、接地電極延設部をさらに延設し、シュラウド１３２に繋ぐように、接地電極１３０ｂを略コ字形に形成し、偏心電極２０ｂを中心電極放電部１１０の両側に張り出すように形成した点が相違する。
本実施形態においては、燃料噴射弁３０から噴射される燃料噴流ＦＬ１、ＦＬ２に対して、均等の距離に偏心電極２０ｂの両側の端が位置するように点火プラグ１０ｂが配設した場合、燃料噴流ＦＬ１、ＦＬ２のいずれか一方に近い位置で延長放電アークＡＲＣＥＮＬが形成される。
また、初期放電アークＡＲＣＩＮＴにより強い引込み気流ＡＲＥＮＴが作用した場合に、上記実施形態のように接地電極を略Ｌ字形に形成したときには、延長放電アークＡＲＣＥＮＬをより長く引き伸ばすように作用するのに対して、本実施形態のようにコ字形に形成した場合には、放電経路がＬ字形の場合には放電アークが形成されない中心電極放電部１１０と接地電極脚部１３１ｂとの間の短い距離へ延長放電アークＡＲＣＥＮＬが移動するため、筒内流動が強く、放電アークの引き伸ばし長さが長くなる条件でも、放電維持に要するエネルギを低減することが可能となる。
なお、本実施形態において、シュラウド１３２と接地電極１３０ｂとを繋ぐ接地電極脚部１３１ｂが、偏心電極２０ｂの両端に近い位置に配置されるので、点火プラグ１０ｂの外径φＤによっては、偏心電極２０ｂと接地電極脚部１３１ｂとの間の距離を接地電極１３０の中心部までの最短距離以上に離すことができず、この間で初期放電ＡＲＣＩＮＴが起こる虞がある。
このような場合には、接地電極脚部１３１ｂの表面の一部を絶縁性耐熱部材でコーティングしたり、接地電極脚部１３１ｂを断面円形に形成して、電界集中し難くしたりする等によって、意図しない位置での初期放電ＡＲＣＩＮＴの発生を防止することも可能である。 With reference to FIG. 8, the ignition plug 10b used for the direct injection internal combustion engine in the 3rd Embodiment of this invention is demonstrated.
In the present embodiment, the ground electrode 130b is formed in a substantially U-shape so that the ground electrode extending portion is further extended and connected to the shroud 132, and the eccentric electrode 20b is formed based on the same configuration as the above embodiment. The difference is that the center electrode discharge part 110 is formed so as to protrude from both sides.
In the present embodiment, when the spark plug 10b is disposed so that the ends on both sides of the eccentric electrode 20b are located at an equal distance with respect to the fuel jets FL 1 and FL 2 injected from the fuel injection valve 30, An extended discharge arc ARC ENL is formed at a position close to one of the fuel jets FL 1 and FL 2 .
In addition, when a strong entrainment air flow AR ENT is acted on by the initial discharge arc ARC INT , when the ground electrode is formed in a substantially L shape as in the above embodiment, the extended discharge arc ARC ENL acts to extend longer. On the other hand, when it is formed in a U-shape as in this embodiment, when the discharge path is L-shaped, a short distance between the center electrode discharge portion 110 and the ground electrode leg portion 131b where no discharge arc is formed. Since the extended discharge arc ARC ENL moves to the center , the in-cylinder flow is strong, and the energy required for maintaining the discharge can be reduced even under the condition that the length of the discharge arc is increased.
In the present embodiment, the ground electrode legs 131b that connect the shroud 132 and the ground electrode 130b are disposed at positions close to both ends of the eccentric electrode 20b. Therefore, depending on the outer diameter φD of the spark plug 10b, the eccentric electrode 20b And the ground electrode leg 131b cannot be separated beyond the shortest distance to the center of the ground electrode 130, and there is a possibility that the initial discharge ARC INT may occur during this time.
In such a case, a part of the surface of the ground electrode leg 131b is coated with an insulating heat-resistant member, or the ground electrode leg 131b is formed in a circular cross section so that electric field concentration is difficult. It is also possible to prevent the occurrence of the initial discharge ARC INT at an unintended position.

図９を参照して、本発明の第３の実施形態における筒内噴射式内燃機関１ｂにおける点火プラグ１０ｂの搭載角θＰＬＧを変化させた場合の効果について説明する。
図９（ａ）に示すように、搭載角θＰＬＧを０°に設定した場合、中心電極放電部１１０の両側に偏心電極２０ｂが伸びているので、放電アークＡＲＣが燃料噴射の状況に応じて任意の位置に移動できる。
図９（ｂ）に示すように、搭載角θＰＬＧを０°より大きく９０°より小さく設定した場合、上記第２の実施形態と同様の効果が期待できる。
図９（ｃ）に示すように、搭載角θＰＬＧを９０°に設定した場合、燃料噴射弁３０の位置する側の接地電極脚部１３１ｂによって、引込み気流ＡＲＥＮＴに乱れが生じ、火炎核の燃焼速度を向上させる効果が期待できる。
従って、本発明の第１の実施形態のように接地電極延設部２１を含む接地電極１３０を略Ｌ字形に形成した場合に比べて、本実施形態のように接地電極１３０ｂを略コ字形にすることによって点火プラグ１０ｂの搭載角θＰＬＧの自由度が増す。 With reference to FIG. 9, the effect when the mounting angle θ PLG of the spark plug 10b in the direct injection internal combustion engine 1b in the third embodiment of the present invention is changed will be described.
As shown in FIG. 9A, when the mounting angle θ PLG is set to 0 °, since the eccentric electrodes 20b extend on both sides of the center electrode discharge part 110, the discharge arc ARC depends on the state of fuel injection. Can move to any position.
As shown in FIG. 9B, when the mounting angle θ PLG is set larger than 0 ° and smaller than 90 °, the same effect as in the second embodiment can be expected.
As shown in FIG. 9 (c), when the mounting angle θ PLG is set to 90 °, the ground electrode leg 131b on the side where the fuel injection valve 30 is located causes a disturbance in the drawn air flow AR ENT , and the flame kernel The effect of improving the burning rate can be expected.
Therefore, compared to the case where the ground electrode 130 including the ground electrode extension portion 21 is formed in a substantially L shape as in the first embodiment of the present invention, the ground electrode 130b is formed in a substantially U shape as in the present embodiment. This increases the degree of freedom of the mounting angle θ PLG of the spark plug 10b.

図１０を参照して、本発明の第４の実施形態における筒内噴射式内燃機関１ｃについて説明する。上記実施形態においては、エンジン４０の中心に燃料噴射弁３０を載置し、その直下に位置するように点火プラグ１０を配設した例を示したが、本発明は上記実施形態に限定するものではなく、燃料噴射弁と点火プラグとを特定の距離で配置し、放電ギャップ中心から燃料噴射弁から噴射される２つの燃料噴流までの距離を所定の範囲に設定し、燃料噴射継続中に点火を行うことによって、燃料噴射時に発生するエアエントレインメントによる引込み気流を放電アークに作用させたときに、放電アークが偏心電極２０と接地電極延設部２１との間に移動し、噴射された燃料噴流の可燃層に近い位置で引き延ばされた放電アークを発生させて着火性向上させることができるものであれば、図１０に示すように、点火プラグ１０ｃを燃焼室４００ｃの中央に載置し、燃料噴射弁３０ｃを点火プラグ１０ｃの直下となる位置に載置しても良い。   With reference to FIG. 10, a direct injection internal combustion engine 1c according to a fourth embodiment of the present invention will be described. In the said embodiment, although the fuel injection valve 30 was mounted in the center of the engine 40 and the spark plug 10 was arrange | positioned so that it might be located in the direct bottom, the present invention is limited to the said embodiment. Instead, the fuel injection valve and the spark plug are arranged at a specific distance, the distance from the center of the discharge gap to the two fuel jets injected from the fuel injection valve is set within a predetermined range, and ignition is performed while fuel injection continues. As a result, the discharge arc moves between the eccentric electrode 20 and the ground electrode extension portion 21 when the air flow caused by the air entrainment generated during fuel injection is applied to the discharge arc, and the injected fuel As long as the discharge arc extended at a position close to the combustible layer of the jet can be generated to improve the ignitability, the spark plug 10c is connected to the combustion chamber 400 as shown in FIG. Of placing in the center, the fuel injection valve 30c may be placed in a position to be directly below the spark plug 10c.

１ 筒内噴射式内燃機関
１０ 点火プラグ
１１ 中心電極
１１０ 中心電極放電部
１２ 絶縁碍子
１２０ 絶縁碍子先端部
１３ ハウジング
１３０ 接地電極
１３１ 接地電極脚部
２０ 偏心電極
２１ 接地電極延設部
３０ 燃料噴射弁
４００ 燃焼室
ＡＲＥＮＴ エアエントレインメントによる引込み気流
ＡＲＣＩＮＴ 初期放電アーク
ＡＲＣＥＮＬ 延長放電アーク
ＡＧ１ 第１の放電ギャップ
ＡＧ２ 第２の放電ギャップ
ＦＬ 燃料噴流 DESCRIPTION OF SYMBOLS 1 In-cylinder injection type internal combustion engine 10 Spark plug 11 Center electrode 110 Center electrode discharge part 12 Insulator 120 Insulator tip part 13 Housing 130 Ground electrode 131 Ground electrode leg 20 Eccentric electrode 21 Ground electrode extension part 30 Fuel injection valve 400 Combustion chamber AR ENT Air entrainment induced airflow ARC INT initial discharge arc ARC ENL extended discharge arc AG 1 First discharge gap AG 2 Second discharge gap FL Fuel jet

特開２００５−２４８８５７号公報JP 2005-248857 A

Claims (3)

燃焼室に燃料を直接噴射する燃料噴射弁と点火プラグとを備えた筒内噴射式内燃機関において、
上記点火プラグが、少なくとも、プラグの中心に設けた中心電極と、絶縁碍子を介して所定の放電ギャップを設けて上記中心電極の先端に対向する接地電極と、上記中心電極に導通し上記中心電極の中心軸に対して上記燃料噴射弁から噴射される燃料噴霧に近づく側に延設した偏心電極と、上記接地電極の先端を上記偏心電極の上記燃料噴霧側に近い端縁に対向するように伸ばした接地電極延設部とを具備し、
上記燃料噴射弁から燃料が噴射されたときに発生する引込み気流を上記放電ギャップに作用させる筒内噴射式内燃機関であって、
上記中心電極の先端面とこれに対向する上記接地電極の上面までの最短距離を第１の放電ギャップとし、上記偏心電極の先端面とこれに対向する上記接地電極延設部の上面までの最短距離を第２の放電ギャップとしたとき、上記第１の放電ギャップを、上記第２の放電ギャップよりも短く設定すると共に、
上記第２の放電ギャップを上記中心電極の先端から上記接地電極延設部の端縁までの距離よりも短く設定したことを特徴とする筒内噴射式内燃機関 In a cylinder injection internal combustion engine including a fuel injection valve that directly injects fuel into a combustion chamber and an ignition plug,
The spark plug includes at least a center electrode provided at the center of the plug, a ground electrode facing a tip of the center electrode with a predetermined discharge gap provided through an insulator, and the center electrode connected to the center electrode. An eccentric electrode extending toward the fuel spray injected from the fuel injection valve with respect to the central axis of the central electrode, and a tip of the ground electrode facing an edge of the eccentric electrode near the fuel spray side. An extended ground electrode extending portion,
A direct injection internal combustion engine that causes a drawn airflow generated when fuel is injected from the fuel injection valve to act on the discharge gap ,
The shortest distance between the front end surface of the center electrode and the upper surface of the ground electrode facing the first discharge gap is the first discharge gap, and the shortest distance between the front end surface of the eccentric electrode and the upper surface of the ground electrode extending portion facing the first discharge gap. When the distance is the second discharge gap, the first discharge gap is set shorter than the second discharge gap,
The in-cylinder injection internal combustion engine, wherein the second discharge gap is set to be shorter than the distance from the tip of the center electrode to the edge of the ground electrode extension portion. 上記点火プラグの放電ギャップを上記燃焼室内の所定位置に固定すべく上記接地電極に延設して設けたハウジングの先端と上記偏心電極の先端との最短距離を第３の放電ギャップとしたとき、該第３の放電ギャップを上記第２の放電ギャップよりも長く設定した請求項１に記載の筒内噴射式内燃機関 When the discharge gap of the points fire plugs and a third discharge gap to the shortest distance between the tip of the tip and the eccentric electrode housing provided extending to the ground electrode to secure the predetermined position of the combustion chamber The in- cylinder injection internal combustion engine according to claim 1 , wherein the third discharge gap is set longer than the second discharge gap. 上記点火プラグを上記接地電極延設部の先端が上記燃料噴射弁の位置する側に向かうように配設しつつ、上記点火プラグの中心軸と上記燃料噴射弁の中心軸とを結ぶ直線を含む平面に対する、上記接地電極及び上記接地電極延設部のなす角度をプラグ搭載角としたとき、該プラグ搭載角を０°より大きく９０°より小さい範囲に設定した請求項１又は２に記載の筒内噴射式内燃機関 The ignition plug includes a straight line connecting the center axis of the ignition plug and the center axis of the fuel injection valve while being arranged such that the tip of the ground electrode extending portion faces the side where the fuel injection valve is located. The cylinder according to claim 1 or 2 , wherein when the angle formed by the ground electrode and the extended portion of the ground electrode with respect to a plane is a plug mounting angle, the plug mounting angle is set in a range larger than 0 ° and smaller than 90 °. Internal injection internal combustion engine
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