JP2005330915A - Control device of internal combustion engine - Google Patents

Control device of internal combustion engine Download PDF

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JP2005330915A
JP2005330915A JP2004150892A JP2004150892A JP2005330915A JP 2005330915 A JP2005330915 A JP 2005330915A JP 2004150892 A JP2004150892 A JP 2004150892A JP 2004150892 A JP2004150892 A JP 2004150892A JP 2005330915 A JP2005330915 A JP 2005330915A
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ignition
internal combustion
combustion engine
nozzle hole
gaseous fuel
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JP4222256B2 (en
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Kenji Date
健治 伊達
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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
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/10—Internal combustion engine [ICE] based vehicles
    • Y02T10/30—Use of alternative fuels, e.g. biofuels

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control device of an internal combustion engine 1 capable of realizing stable combustion by increasing ignition stability without increasing the cost and volume of an ignition device. <P>SOLUTION: In this internal combustion engine 1, at least two ignition plugs 16 are installed at different positions so as to be able to cope with both compressive wave areas in cases where underexpansion flow occurs in a cylinder 3a and overexpansion flow occurs in the cylinder. Specifically, the internal combustion engine uses the first ignition plug 16 having an ignition position in the compressive wave area where the underexpansion flow occurs and the second ignition plug 16 having an ignition position in the compressive wave area where the overexpansion flow occurs. On the other hand, an ECU determines whether the underexpansion flow occurs or the overexpansion occurs based on the relation of the magnitudes of an injection pressure Pe at an injection outlet and a cylinder pressure Pa of the internal combustion engine 1. When the underexpansion flow occurs, the first ignition plug 16 is ignited, and when the overexpansion flow occurs, the second ignition plug 16 is ignited. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

本発明は、内燃機関の筒内に噴射された気体燃料と空気との混合気に点火して燃焼させる内燃機関の制御装置に関する。   The present invention relates to a control device for an internal combustion engine that ignites and burns a mixture of gaseous fuel and air injected into a cylinder of the internal combustion engine.

近年、自動車等に搭載される内燃機関の燃料として、水素や天然ガス等の気体燃料が注目されている。しかし、この気体燃料を内燃機関の筒内（燃焼室）に噴射して燃焼させる場合には、ａ）気体燃料の運動量が小さいために空気と混ざり難く、可燃混合気を形成しにくいため、良好な燃焼状態が得られ難いという問題がある。
また、ｂ）気体燃料は、ガソリン等の液体燃料を燃焼させた時に生じる液体から気体への蒸発過程がないことから、特に水素燃料では、燃焼が急速に行われて圧力上昇が急激であるため、高負荷側での運転が困難である。 In recent years, gaseous fuels such as hydrogen and natural gas have attracted attention as fuels for internal combustion engines mounted on automobiles and the like. However, when this gaseous fuel is injected into the cylinder (combustion chamber) of the internal combustion engine and burned, a) the momentum of the gaseous fuel is small, so it is difficult to mix with air and it is difficult to form a flammable mixture. There is a problem that it is difficult to obtain a proper combustion state.
In addition, b) gaseous fuel has no evaporation process from liquid to gas that occurs when liquid fuel such as gasoline is burned. In particular, hydrogen fuel burns rapidly and the pressure rises rapidly. Operation on the high load side is difficult.

上記ａ）の問題に対し、例えば、特許文献１では、シリンダの側方より燃料噴射弁を取り付けて、圧縮行程の途中で気体燃料を筒内（燃焼室）に噴射する（つまり、噴射タイミングを早くする）ことにより、時間をかけて空気との混合を促進させる技術が開示されている。
また、ｂ）の問題に対して、例えば、特許文献２では、比較的混ざり易い気体燃料の噴流外周部に点火源（点火プラグ）を配置している。これにより、噴射期間中での点火が行われ、気体燃料の噴流により、燃料と空気とが火炎中に供給されながら燃焼するため、燃焼期間中の圧力上昇が緩やかになって、急激な燃焼を抑制できる。
特開２０００−１６１０６６号公報 特開２００３−２５４０６８号公報 To solve the problem a), for example, in Patent Document 1, a fuel injection valve is attached from the side of the cylinder, and gaseous fuel is injected into the cylinder (combustion chamber) in the middle of the compression stroke (that is, the injection timing is set). A technique that promotes mixing with air over time.
Also, for the problem b), for example, in Patent Document 2, an ignition source (ignition plug) is disposed on the outer peripheral portion of a jet of gaseous fuel that is relatively easily mixed. As a result, ignition is performed during the injection period, and the fuel and air are combusted while being supplied into the flame by the jet of gaseous fuel, so the pressure rise during the combustion period is moderated and rapid combustion occurs. Can be suppressed.
JP 2000-161066 A JP 2003-254068 A

ところが、特許文献１に開示された公知技術では、早いタイミングで噴射を行うため、燃料噴射が略終了した時点で点火させることになる。その結果、急激な燃焼を生じるため、燃焼騒音が増大する、およびエンジン振動が増大する等の問題が生じる。
また、特許文献２に開示された公知技術では、低速低負荷域から高速高負荷域までの広い使用領域を必要とするエンジンにおいて、筒内の空気流動が大きく変動する場合には、安定した着火が出来ない恐れがある。これを回避するため、つまり安定した着火を得るためには、点火エネルギを増大させることも考えられるが、これでは、点火装置の大型化およびコストアップを生じてしまう。 However, in the known technique disclosed in Patent Document 1, since injection is performed at an early timing, ignition is performed when fuel injection is almost completed. As a result, rapid combustion occurs, which causes problems such as increased combustion noise and increased engine vibration.
Further, in the known technique disclosed in Patent Document 2, in an engine that requires a wide use range from a low speed and low load range to a high speed and high load range, stable ignition is achieved when the air flow in the cylinder fluctuates greatly. There is a risk of not being able to. In order to avoid this, that is, to obtain stable ignition, it is conceivable to increase the ignition energy. However, this increases the size and cost of the ignition device.

本発明は、上記事情に基づいて成されたもので、その目的は、点火装置のコストアップおよび体格の増大を招くことなく、点火安定性を高めることができ、それにより、安定した燃焼を実現できる内燃機関の制御装置を提供することにある。   The present invention has been made based on the above circumstances, and its purpose is to increase ignition stability without increasing the cost of the ignition device and increasing the physique, thereby realizing stable combustion. An object of the present invention is to provide a control device for an internal combustion engine.

（請求項１の発明）
本発明は、内燃機関の筒内に気体燃料を直接噴射する燃料噴射弁と、筒内に噴射された気体燃料と空気との混合気に点火するための点火装置とを有する内燃機関の制御装置であり、燃料噴射弁は、気体燃料を噴射するための噴孔の断面形状が、噴孔出口に向かってテーパ状に拡大する先広がり形状に設けられている。また、点火装置は、噴孔より超音速で放出された気体燃料の噴流境界に発生する圧力衝撃波が圧縮する領域（圧縮波となる領域）を圧縮波領域と呼ぶ時に、その圧縮波領域において点火を行うことを特徴とする。 (Invention of Claim 1)
The present invention relates to a control device for an internal combustion engine having a fuel injection valve for directly injecting gaseous fuel into a cylinder of the internal combustion engine and an ignition device for igniting a mixture of gaseous fuel and air injected into the cylinder. In the fuel injection valve, the cross-sectional shape of the injection hole for injecting the gaseous fuel is provided in a widening shape that expands in a tapered shape toward the injection hole outlet. Also, the ignition device ignites in the compression wave region when the region where the pressure shock wave generated at the jet boundary of the gaseous fuel discharged from the nozzle hole at the supersonic velocity is compressed (the region that becomes the compression wave) is called the compression wave region. It is characterized by performing.

本発明の燃料噴射弁では、先広がり形状の噴孔を採用することで、噴孔より筒内へ噴出される気体燃料の噴流速度が超音速となるため、気体燃料と空気との混合を促進できる。また、圧力衝撃波が圧縮する圧縮波領域では、気体が圧縮されて高温となり、点火・着火が容易となる。一方、圧力衝撃波が膨張する膨張波領域では、気体が膨張して低温であるため、点火する際に大きな点火エネルギが必要となる。そこで、本発明では、気体温度が高温となる圧縮波領域において点火を行うことにより、低点火エネルギで安定した点火が可能であり、且つ、点火装置のコストアップおよび大型化を防止できる。
なお、本発明の燃料噴射弁に設けられる噴孔は、上記の様に、噴孔の断面形状が出口に向かってテーパ状に拡大する先広がり形状を有する、いわゆるラバールノズルと呼ばれるもので、気体燃料を超音速で噴出できる超音速ノズルを採用している。 In the fuel injection valve according to the present invention, by adopting the nozzle hole having a divergent shape, the jet velocity of the gaseous fuel ejected from the nozzle hole into the cylinder becomes supersonic, so that the mixing of the gaseous fuel and air is promoted. it can. In the compression wave region where the pressure shock wave is compressed, the gas is compressed to a high temperature, and ignition / ignition becomes easy. On the other hand, in the expansion wave region where the pressure shock wave expands, since the gas expands and is at a low temperature, a large ignition energy is required for ignition. Therefore, in the present invention, by performing ignition in the compression wave region where the gas temperature is high, stable ignition with low ignition energy is possible, and the cost and size of the ignition device can be prevented from increasing.
The injection hole provided in the fuel injection valve of the present invention is a so-called Laval nozzle, in which the cross-sectional shape of the injection hole expands in a tapered shape toward the outlet as described above. A supersonic nozzle that can eject at a supersonic speed.

（請求項２の発明） 請求項１に記載した内燃機関の制御装置において、点火装置は、噴孔より噴出する気体燃料の噴流が不足膨張流になる場合と、噴孔より噴出する気体燃料の噴流が過膨張流になる場合とに応じて、常に圧縮波領域で点火できる様に、点火位置を変化させることを特徴とする。   (Invention of Claim 2) In the control device for an internal combustion engine according to claim 1, the ignition device includes a case where the jet of the gaseous fuel ejected from the nozzle hole becomes an underexpanded flow, and a case of the gaseous fuel ejected from the nozzle hole. The ignition position is changed so that ignition can always be performed in the compression wave region in accordance with the case where the jet becomes an overexpanded flow.

噴孔より噴出する気体燃料は、例えば、噴孔出口の噴射圧と内燃機関の筒内圧との大小関係によって、気体燃料の噴流が不足膨張流になる場合と、過膨張流になる場合とがある。しかも、不足膨張流と過膨張流とでは、それぞれの圧縮波領域が異なる。つまり、不足膨張流に圧縮波が発生する位置（圧縮波領域）と、過膨張流に圧縮波が発生する位置（圧縮波領域）とが異なるため、点火装置の点火位置が１か所に固定されていると、圧縮波領域で点火できない場合が生じる。そこで、不足膨張流と過膨張流とに応じて、常に圧縮波領域で点火できる様に、点火装置の点火位置を変化させることで、低点火エネルギによる安定した点火が可能となる。   The gaseous fuel ejected from the nozzle hole may be, for example, a case where the jet of the gaseous fuel becomes an underexpanded flow or an overexpanded flow depending on the magnitude relationship between the injection pressure at the nozzle hole outlet and the in-cylinder pressure of the internal combustion engine. is there. In addition, the compression wave region is different between the underexpanded flow and the overexpanded flow. That is, the position where the compression wave is generated in the underexpanded flow (compression wave region) is different from the position where the compression wave is generated in the overexpanded flow (compression wave region), so the ignition position of the ignition device is fixed at one place. If this is the case, ignition may not occur in the compression wave region. Therefore, by changing the ignition position of the ignition device so that ignition can always be performed in the compression wave region according to the underexpanded flow and the overexpanded flow, stable ignition with low ignition energy becomes possible.

（請求項３の発明）
請求項２に記載した内燃機関の制御装置において、点火装置は、不足膨張流の圧縮波領域に点火位置を有する第１の点火装置と、過膨張流の圧縮波領域に点火位置を有する第２の点火装置とを備えていることを特徴とする。
この構成では、噴孔より噴出する気体燃料の噴流が不足膨張流の場合は、第１の点火装置を使用して、不足膨張流の圧縮波領域にて点火を行うことができる。一方、噴孔より噴出する気体燃料の噴流が過膨張流の場合は、第２の点火装置を使用して、過膨張流の圧縮波領域にて点火を行うことができる。この結果、噴孔より噴出する気体燃料の噴流が不足膨張流であるか過膨張流であるかに係わらず、常に圧縮波領域にて点火を行うことができる。 (Invention of Claim 3)
3. The control apparatus for an internal combustion engine according to claim 2, wherein the ignition device includes a first ignition device having an ignition position in a compression wave region of an underexpanded flow, and a second ignition device having an ignition position in a compression wave region of an overexpanded flow. The ignition device is provided.
In this configuration, when the gaseous fuel jet ejected from the nozzle hole is underexpanded, ignition can be performed in the compression wave region of the underexpanded flow using the first ignition device. On the other hand, when the jet of gaseous fuel ejected from the nozzle hole is an overexpanded flow, ignition can be performed in the compression wave region of the overexpanded flow using the second ignition device. As a result, ignition can always be performed in the compression wave region regardless of whether the jet of the gaseous fuel ejected from the nozzle hole is an underexpanded flow or an overexpanded flow.

（請求項４の発明）
請求項２に記載した内燃機関の制御装置において、点火装置は、圧縮波領域に点火位置を変更できる可変焦点レーザを採用していることを特徴とする。
この構成では、点火装置として可変焦点レーザを用いることにより、例えば、不足膨張流と過膨張流とで圧縮波領域の位置が異なる場合でも、その圧縮波領域に合わせて点火位置を変更できる。その結果、噴孔より噴出する気体燃料の噴流が不足膨張流であるか過膨張流であるかに係わらず、常に圧縮波領域にて点火を行うことができる。 (Invention of Claim 4)
In the control device for an internal combustion engine according to claim 2, the ignition device employs a variable focus laser capable of changing an ignition position in a compression wave region.
In this configuration, by using a variable focus laser as the ignition device, for example, even when the position of the compression wave region differs between the underexpanded flow and the overexpanded flow, the ignition position can be changed according to the compression wave region. As a result, ignition can always be performed in the compression wave region regardless of whether the jet of the gaseous fuel ejected from the nozzle hole is an underexpanded flow or an overexpanded flow.

（請求項５の発明）
請求項１に記載した内燃機関の制御装置において、点火装置の点火位置を基準として、圧縮波領域の位置を変化させることを特徴とする。
内燃機関に取り付けられる点火装置の位置が固定されていると、請求項２の発明でも記載した様に、噴孔より噴出する気体燃料の噴流が不足膨張流になる場合と、過膨張流になる場合とで、それぞれの圧縮波領域が異なるため、何方か一方の圧縮波領域に点火位置を合わせると、他方の圧縮波領域では点火できなくなる。 (Invention of Claim 5)
The control apparatus for an internal combustion engine according to claim 1 is characterized in that the position of the compression wave region is changed on the basis of the ignition position of the ignition device.
When the position of the ignition device attached to the internal combustion engine is fixed, as described in the second aspect of the invention, when the jet of gaseous fuel ejected from the nozzle hole becomes an underexpanded flow, it becomes an overexpanded flow. Since the respective compression wave regions are different from each other, if the ignition position is set to one of the compression wave regions, ignition cannot be performed in the other compression wave region.

これに対し、本発明では、不足膨張流と過膨張流とに応じて点火装置の点火位置を変更するのではなく、点火装置の点火位置を固定した状態で、その点火位置に圧縮波領域の位置を合わせるものである。これにより、点火装置の点火位置が１か所に固定されている場合でも、その点火位置に圧縮波の発生位置を変化させることにより、常に圧縮波領域にて点火を行うことができるので、低点火エネルギによる安定した点火が可能である。   In contrast, in the present invention, the ignition position of the ignition device is not changed according to the underexpanded flow and the overexpanded flow, but the ignition position of the ignition device is fixed in the state where the ignition position of the ignition device is fixed. The position is adjusted. Thus, even when the ignition position of the ignition device is fixed at one place, by changing the generation position of the compression wave to the ignition position, ignition can always be performed in the compression wave region. Stable ignition with ignition energy is possible.

（請求項６の発明）
請求項５に記載した内燃機関の制御装置において、噴孔より噴出する気体燃料の噴流が常に不足膨張流となる時に、点火装置は、不足膨張流の圧縮波領域に点火位置を有し、且つ噴孔より噴出する気体燃料の噴流が常に不足膨張流となる様に、燃料噴射弁の噴射圧力を規定圧以上で供給することを特徴とする。
噴孔より噴出する気体燃料の噴流が常に不足膨張流であれば、圧縮波の位置（圧縮波領域）も略特定できる（圧縮波の位置が大きくずれることがない）ため、その圧縮波領域に点火装置の点火位置を設けることで、常に圧縮波領域での点火が可能となる。 (Invention of Claim 6)
6. The control device for an internal combustion engine according to claim 5, wherein the ignition device has an ignition position in a compression wave region of the underexpanded flow when the jet of the gaseous fuel ejected from the nozzle hole always becomes an underexpanded flow, and It is characterized in that the injection pressure of the fuel injection valve is supplied at a specified pressure or higher so that the jet of gaseous fuel ejected from the nozzle hole is always underexpanded.
If the jet of gaseous fuel ejected from the nozzle hole is always underexpanded, the position of the compression wave (compression wave region) can also be substantially specified (the position of the compression wave does not deviate greatly). By providing the ignition position of the ignition device, ignition in the compression wave region is always possible.

（請求項７の発明）
請求項５に記載した内燃機関の制御装置において、噴孔より噴出する気体燃料の噴流が常に過膨張流となる時に、点火装置は、過膨張流の圧縮波領域に点火位置を有し、且つ噴孔より噴出する気体燃料の噴流が常に過膨張流となる様に、燃料噴射弁の噴射圧力を規定圧未満で供給することを特徴とする。
噴孔より噴出する気体燃料の噴流が常に過膨張流であれば、圧縮波の位置（圧縮波領域）も略特定できる（圧縮波の位置が大きくずれることがない）ため、その圧縮波領域に点火装置の点火位置を設けることで、常に圧縮波領域での点火が可能となる。 (Invention of Claim 7)
6. The control device for an internal combustion engine according to claim 5, wherein the ignition device has an ignition position in a compression wave region of the overexpanded flow when the jet of the gaseous fuel ejected from the nozzle hole always becomes an overexpanded flow, and It is characterized in that the injection pressure of the fuel injection valve is supplied below a specified pressure so that the jet of gaseous fuel ejected from the nozzle hole always becomes an overexpanded flow.
If the jet of gaseous fuel ejected from the nozzle hole is always an overexpanded flow, the position of the compression wave (compression wave region) can also be substantially specified (the position of the compression wave does not deviate greatly). By providing the ignition position of the ignition device, ignition in the compression wave region is always possible.

（請求項８の発明）
請求項２、３、４、６、７に記載した何れかの内燃機関の制御装置において、燃料噴射弁の噴孔出口の噴射圧Ｐｅと、内燃機関の筒内圧Ｐａ（噴射時の筒内圧）との大小関係において、
Ｐｅ＞Ｐａ…………（１）
Ｐｅ＜Ｐａ…………（２）
上記（１）の関係が成立する時に、噴孔より噴出する気体燃料の噴流が不足膨張流となり、上記（２）の関係が成立する時に、噴孔より噴出する気体燃料の噴流が過膨張流となることを特徴とする。なお、噴射圧Ｐｅは、燃料噴射弁に供給される燃料圧力（例えばコモンレール式燃料噴射装置のコモンレール圧）ではなく、噴孔の出口、つまり先広がり形状の噴孔内部の燃料圧力である。 (Invention of Claim 8)
8. The control apparatus for an internal combustion engine according to claim 2, 3, 4, 6, or 7, wherein the injection pressure Pe at the nozzle hole outlet of the fuel injection valve and the in-cylinder pressure Pa (in-cylinder pressure at the time of injection) of the internal combustion engine. In relation to
Pe> Pa ............ (1)
Pe <Pa ............ (2)
When the relationship (1) is established, the jet of gaseous fuel ejected from the nozzle hole becomes an underexpanded flow, and when the relationship (2) is established, the jet of gaseous fuel ejected from the nozzle hole is an overexpanded flow. It is characterized by becoming. The injection pressure Pe is not the fuel pressure supplied to the fuel injection valve (for example, the common rail pressure of the common rail type fuel injection device) but the fuel pressure inside the nozzle hole, that is, the inside of the nozzle hole having a widened shape.

上記（１）の関係が成立する時、つまり、内燃機関の筒内圧Ｐａに対して、噴孔出口の噴射圧Ｐｅが相対的に高い場合は、気体燃料の膨張エネルギが大きいため、先広がり形状の噴孔内で気体燃料が膨張しきれず、膨張エネルギを伴った気体燃料が、噴孔出口から膨張波となって筒内へ放出される。
一方、上記（２）の関係が成立する時、つまり、内燃機関の筒内圧Ｐａに対して、噴孔出口の噴射圧Ｐｅが相対的に低い場合は、気体燃料の膨張エネルギが小さいため、噴孔内で気体燃料の膨張が略収束する。その結果、膨張エネルギの小さい（あるいは膨張エネルギを使い切った）気体燃料が、噴孔出口から圧縮波となって筒内へ放出される。 When the relationship (1) is established, that is, when the injection pressure Pe at the nozzle hole outlet is relatively high with respect to the in-cylinder pressure Pa of the internal combustion engine, the expansion energy of the gaseous fuel is large, so The gas fuel cannot expand completely in the nozzle hole, and the gas fuel accompanied by the expansion energy is discharged into the cylinder as an expansion wave from the nozzle hole outlet.
On the other hand, when the relationship (2) is established, that is, when the injection pressure Pe at the nozzle hole outlet is relatively low with respect to the in-cylinder pressure Pa of the internal combustion engine, the expansion energy of the gaseous fuel is small. The expansion of the gaseous fuel substantially converges in the hole. As a result, the gaseous fuel with a small expansion energy (or the exhaustion energy is used up) is discharged into the cylinder as a compression wave from the nozzle hole outlet.

本発明を実施するための最良の形態を以下の実施例により詳細に説明する。   The best mode for carrying out the present invention will be described in detail with reference to the following examples.

図１は内燃機関１の断面図である。
実施例１に記載する内燃機関１は、図１に示す様に、シリンダブロック２に形成されたシリンダ３内を往復動するピストン４と、このピストン４の上部に形成される筒内３ａ（燃焼室）に気体燃料を直接噴射するインジェクタ５と、筒内３ａに噴射された気体燃料と空気との混合気に点火させる点火装置（後述する）等を備え、図示しない電子制御ユニット（以下、ＥＣＵと呼ぶ）により内燃機関１の運転状態が電子制御される。 FIG. 1 is a cross-sectional view of the internal combustion engine 1.
As shown in FIG. 1, the internal combustion engine 1 described in the first embodiment includes a piston 4 that reciprocates in a cylinder 3 formed in a cylinder block 2, and an in-cylinder 3 a (combustion) formed on the top of the piston 4. The chamber 5 is provided with an injector 5 for directly injecting gaseous fuel, an ignition device (to be described later) for igniting a mixture of gaseous fuel and air injected into the cylinder 3a and the like, and an electronic control unit (hereinafter referred to as ECU). The operation state of the internal combustion engine 1 is electronically controlled.

ピストン４は、内燃機関１のクランク軸（図示せず）にコンロッド６を介して連結され、シリンダ３内を往復動するピストン４の往復運動が、コンロッド６を介してクランク軸に回転運動として伝達される。
インジェクタ５は、ＥＣＵによって電子制御される電磁弁（図示せず）、この電磁弁の開弁動作によって気体燃料を噴射するノズル７（図２参照）とを有し、図１に示す様に、ノズル７の先端部が内燃機関１の筒内３ａに突き出た状態でシリンダヘッド８に取り付けられている。シリンダヘッド８は、シリンダブロック２の上端面に配置されて、ピストン４の上端面との間に燃焼室を形成すると共に、その燃焼室に連通する吸気ポート９と排気ポート１０とが形成されている。 The piston 4 is connected to a crankshaft (not shown) of the internal combustion engine 1 via a connecting rod 6, and the reciprocating motion of the piston 4 reciprocating in the cylinder 3 is transmitted to the crankshaft as rotating motion via the connecting rod 6. Is done.
The injector 5 has a solenoid valve (not shown) electronically controlled by the ECU, and a nozzle 7 (see FIG. 2) that injects gaseous fuel by opening the solenoid valve. As shown in FIG. The tip of the nozzle 7 is attached to the cylinder head 8 in a state where the nozzle 7 protrudes into the cylinder 3 a of the internal combustion engine 1. The cylinder head 8 is disposed on the upper end surface of the cylinder block 2 to form a combustion chamber between the upper end surface of the piston 4 and an intake port 9 and an exhaust port 10 communicating with the combustion chamber. Yes.

吸気ポート９と排気ポート１０は、それぞれカム（図示せず）によって駆動される吸気弁１１と排気弁１２とにより開閉される。吸気弁１１は、ピストン４がシリンダ３内を降下（図示下方へ移動）する吸入行程の際に駆動されて吸気ポート９を開くことにより、新気（外気）をシリンダ３内へ吸入させる。排気弁１２は、ピストン４がシリンダ３内を上昇（図示上方へ移動）する排気行程の際に駆動されて排気ポート１０を開くことにより、シリンダ３内から燃焼ガスを排気させる。   The intake port 9 and the exhaust port 10 are opened and closed by an intake valve 11 and an exhaust valve 12 driven by cams (not shown), respectively. The intake valve 11 is driven during an intake stroke in which the piston 4 descends (moves downward in the drawing) within the cylinder 3 to open the intake port 9, thereby sucking fresh air (outside air) into the cylinder 3. The exhaust valve 12 is driven during an exhaust stroke in which the piston 4 moves up (moves upward in the drawing) in the cylinder 3 to open the exhaust port 10, thereby exhausting combustion gas from the cylinder 3.

ノズル７は、図２に示す様に、ノズルボディ１３とニードル１４とで構成される。
ノズルボディ１３は、ニードル１４を収容するガイド孔１３ａと、このガイド孔１３ａに気体燃料を導く燃料通路１３ｂと、ニードル１４がガイド孔１３ａをリフト（図示上方へ移動）した時に、気体燃料を噴射する噴孔１３ｃ等が形成されている。
ガイド孔１３ａは、ノズルボディ１３の軸芯部（径方向中央部）を長手方向に穿設されて、その下端部に円錐状のシート面１３ｄ（図３参照）が形成され、更に、シート面１３ｄの円錐中心部に袋状のサック室１３ｅが凹設されている。また、ガイド孔１３ａの途中には、孔径が拡大して設けられた燃料溜め室１３ｆを有し、この燃料溜め室１３ｆに燃料通路１３ｂが連通している。 As shown in FIG. 2, the nozzle 7 includes a nozzle body 13 and a needle 14.
The nozzle body 13 injects the gaseous fuel when the guide hole 13a for accommodating the needle 14, the fuel passage 13b for guiding the gaseous fuel to the guide hole 13a, and the needle 14 lifts (moves upward in the figure) the guide hole 13a. A nozzle hole 13c or the like is formed.
The guide hole 13a is formed by drilling the axial center portion (radially central portion) of the nozzle body 13 in the longitudinal direction, and a conical seat surface 13d (see FIG. 3) is formed at the lower end thereof. A bag-shaped sack chamber 13e is recessed in the center of the cone 13d. Further, in the middle of the guide hole 13a, there is a fuel reservoir chamber 13f provided with an enlarged hole diameter, and a fuel passage 13b communicates with the fuel reservoir chamber 13f.

ニードル１４は、ガイド孔１３ａに数μｍのクリアランスで挿入される摺動軸部１４ａと、燃料溜め室１３ｆの燃料圧力を受けるテーパ状の受圧面１４ｂと、この受圧面１４ｂより図示下方へ延びるニードル軸部１４ｃとで構成され、このニードル軸部１４ｃの外径が摺動軸部１４ａの外径より細く設けられて、ガイド孔１３ａとの間に環状の空間が形成されている。この環状の空間は、燃料溜め室１３ｆからノズルボディ１３のシート面１３ｄまで燃料を導く燃料通路１５として形成されている。また、ニードル軸部１４ｃの先端部は、先細り形状となる段付き円錐状に設けられ、その上段側円錐面と下段側円錐面との境界線（稜線）が、ノズルボディ１３のシート面１３ｄに着座するシート部１４ｄとして設けられている。   The needle 14 includes a sliding shaft portion 14a inserted into the guide hole 13a with a clearance of several μm, a tapered pressure receiving surface 14b that receives the fuel pressure in the fuel reservoir chamber 13f, and a needle that extends downward from the pressure receiving surface 14b in the drawing. The needle shaft portion 14c is formed so that the outer diameter of the needle shaft portion 14c is narrower than the outer diameter of the sliding shaft portion 14a, and an annular space is formed between the guide hole 13a. This annular space is formed as a fuel passage 15 that guides fuel from the fuel reservoir chamber 13 f to the seat surface 13 d of the nozzle body 13. The tip of the needle shaft portion 14 c is provided in a stepped conical shape having a tapered shape, and a boundary line (ridge line) between the upper-side conical surface and the lower-side conical surface is formed on the seat surface 13 d of the nozzle body 13. It is provided as a seat part 14d to be seated.

上記のノズル７は、ガソリン機関あるいはディーゼル機関等に使用されるインジェクタと比較した場合に、基本的な構造は略同一であるが、噴孔１３ｃの形状に特徴を有している。すなわち、本実施例のノズル７に設けられる噴孔１３ｃは、サック室１３ｅに開口する噴孔入口から、ノズルボディ１３の外面に開口する噴孔出口までの孔径が同一ではなく、図３に示す様に、噴孔入口の下流側（出口側）に孔径が小さくなるスロート部１３ｃ１が設けられ、このスロート部１３ｃ１から噴孔出口に向かって、噴孔１３ｃの断面形状がテーパ状に拡大する先広がり形状を有している。   The nozzle 7 is substantially the same in basic structure as compared with an injector used in a gasoline engine or a diesel engine, but is characterized by the shape of the injection hole 13c. That is, the nozzle hole 13c provided in the nozzle 7 of this embodiment has the same hole diameter from the nozzle hole inlet opening in the sack chamber 13e to the nozzle hole outlet opening in the outer surface of the nozzle body 13, and is shown in FIG. Similarly, a throat portion 13c1 having a small hole diameter is provided on the downstream side (outlet side) of the nozzle hole inlet, and the cross-sectional shape of the nozzle hole 13c expands in a tapered shape from the throat portion 13c1 toward the nozzle hole outlet. Has a spreading shape.

この先広がり形状の噴孔１３ｃは、いわゆるラバールノズルと呼ばれるもので、気体燃料を超音速で噴出できる超音速ノズルである。なお、上記の噴孔１３ｃは、ノズル７の周方向に複数個、例えば等間隔あるいは不等間隔に設けることができる。また、ノズル７の上下方向に多段に設けることも可能であり、その両方を組み合わせる（つまり、周方向に複数個設けると共に、ノズル７の上下方向にも多段に配置する）ことも可能である。   This wide-spreading nozzle hole 13c is a so-called Laval nozzle, and is a supersonic nozzle that can eject gaseous fuel at supersonic speed. Note that a plurality of the nozzle holes 13c may be provided in the circumferential direction of the nozzle 7, for example, at regular intervals or at irregular intervals. It is also possible to provide the nozzle 7 in multiple stages in the vertical direction, and to combine both (that is, a plurality of nozzles 7 are arranged in the circumferential direction and arranged in multiple stages in the vertical direction of the nozzle 7).

点火装置は、気体燃料と空気との混合気に着火する点火プラグ１６（図１参照）と、こ点火プラグ１６に高電圧を供給する点火コイル（図示せず）、および点火コイルに発生する高電圧を制御するイグナイタ（図示せず）等より構成され、イグナイタの通電時間および点火タイミングなどがＥＣＵにより電子制御される。なお、図１では点火装置における点火プラグ１６のみが図示されている。
点火プラグ１６は、ガソリン機関に使用される一般的な点火プラグを使用することが可能であり、例えば、図４に示す様に、中心電極１６ａと外側電極１６ｂから成る一対の電極を有し、電極間に生じる火花放電によって混合気に点火する。なお、本発明の「点火位置」は、火花放電が発生する中心電極１６ａと外側電極１６ｂとの略中間点（図中Ａ点）とする。 The ignition device includes an ignition plug 16 (see FIG. 1) that ignites a mixture of gaseous fuel and air, an ignition coil (not shown) that supplies a high voltage to the ignition plug 16, and a high voltage generated in the ignition coil. An igniter (not shown) for controlling the voltage is used, and the energization time and ignition timing of the igniter are electronically controlled by the ECU. In FIG. 1, only the spark plug 16 in the ignition device is shown.
The spark plug 16 can be a general spark plug used in a gasoline engine. For example, as shown in FIG. 4, the spark plug 16 has a pair of electrodes including a center electrode 16a and an outer electrode 16b. The air-fuel mixture is ignited by a spark discharge generated between the electrodes. Note that the “ignition position” of the present invention is a substantially intermediate point (point A in the figure) between the center electrode 16a and the outer electrode 16b where spark discharge occurs.

ところで、インジェクタ５のノズル７の噴孔１３ｃを先広がり形状（超音速ノズル）とした場合、図５に示す様に、噴孔出口の噴射圧Ｐｅと、噴孔１３ｃから気体燃料が噴射される時（噴射タイミング）の内燃機関１の筒内圧Ｐａとの大小関係に応じて、筒内３ａに噴出される気体燃料の噴流状態が異なる。
つまり、
Ｐｅ＞Ｐａ…………（１）
Ｐｅ＜Ｐａ…………（２）
上記（１）の関係が成立する時には、噴孔１３ｃより噴出する気体燃料の噴流が不足膨張流となり、上記（２）の関係が成立する時には、噴孔１３ｃより噴出する気体燃料の噴流が過膨張流となる。 By the way, when the nozzle hole 13c of the nozzle 7 of the injector 5 is made to have a divergent shape (supersonic nozzle), as shown in FIG. 5, gaseous fuel is injected from the injection pressure Pe at the nozzle hole outlet and the nozzle hole 13c. Depending on the magnitude relationship with the in-cylinder pressure Pa of the internal combustion engine 1 at the time (injection timing), the jet state of the gaseous fuel injected into the in-cylinder 3a differs.
That means
Pe> Pa ............ (1)
Pe <Pa ............ (2)
When the relationship (1) is established, the gaseous fuel jet ejected from the nozzle hole 13c becomes an underexpanded flow, and when the relationship (2) is established, the gaseous fuel jet ejected from the nozzle hole 13c is excessive. It becomes an expansion flow.

詳述すると、上記（１）の関係が成立する時、つまり、内燃機関１の筒内圧Ｐａに対して、噴孔出口の噴射圧Ｐｅが相対的に高い場合は、気体燃料の膨張エネルギが大きいため、先広がり形状の噴孔１３ｃ内で気体燃料が膨張しきれず、図５（ａ）に示す様に、膨張エネルギを伴った気体燃料が、噴孔出口から膨張波となって筒内３ａへ放出されるため、不足膨張流となる。
一方、上記（２）の関係が成立する時、つまり、内燃機関１の筒内圧Ｐａに対して、噴孔出口の噴射圧Ｐｅが相対的に低い場合は、気体燃料の膨張エネルギが小さいため、噴孔１３ｃ内で気体燃料の膨張が略収束する。その結果、図５（ｂ）に示す様に、膨張エネルギの小さい（あるいは膨張エネルギを使い切った）気体燃料が、噴孔出口から圧縮波となって筒内３ａへ放出されるため、過膨張流となる。 More specifically, when the relationship (1) is established, that is, when the injection pressure Pe at the nozzle hole outlet is relatively higher than the in-cylinder pressure Pa of the internal combustion engine 1, the expansion energy of the gaseous fuel is large. For this reason, the gaseous fuel cannot expand completely in the nozzle hole 13c having a widened shape, and as shown in FIG. 5A, the gaseous fuel accompanied by the expansion energy becomes an expansion wave from the nozzle hole outlet to the cylinder 3a. Since it is discharged, it becomes an underexpanded flow.
On the other hand, when the relationship (2) is established, that is, when the injection pressure Pe at the nozzle hole outlet is relatively low with respect to the in-cylinder pressure Pa of the internal combustion engine 1, the expansion energy of the gaseous fuel is small. The expansion of the gaseous fuel substantially converges in the nozzle hole 13c. As a result, as shown in FIG. 5B, the gaseous fuel having a small expansion energy (or the exhaustion of the expansion energy) is discharged as a compression wave from the outlet of the nozzle hole into the cylinder 3a. It becomes.

ここで、噴孔１３ｃより超音速で放出された気体燃料の噴流境界に発生する圧力衝撃波が圧縮する圧縮波領域（図５の圧縮波が発生する領域）では、気体が圧縮されて高温となり、点火・着火が容易となる。一方、圧力衝撃波が膨張する膨張波領域（図５の膨張波が発生する領域）では、気体が膨張して低温であるため、点火する際に大きな点火エネルギが必要となる。そこで、実施例１では、少なくとも２本の点火プラグ１６を使用することにより、気体温度が高温となる圧縮波領域において常に点火を行うことを特徴とする。   Here, in the compression wave region where the pressure shock wave generated at the jet boundary of the gaseous fuel discharged at supersonic speed from the nozzle hole 13c is compressed (region where the compression wave of FIG. 5 is generated), the gas is compressed and becomes high temperature, Ignition and ignition are easy. On the other hand, in the expansion wave region in which the pressure shock wave expands (the region in which the expansion wave in FIG. 5 is generated), the gas expands and the temperature is low, so that a large ignition energy is required for ignition. Therefore, the first embodiment is characterized in that ignition is always performed in the compression wave region where the gas temperature becomes high by using at least two spark plugs 16.

すなわち、不足膨張流が発生する時と、過膨張流が発生する時とで、どちらの圧縮波領域にも対応できる様に、少なくとも２本の点火プラグ１６を異なる位置に取り付けるものとする。具体的には、不足膨張流が発生する時の圧縮波領域に点火位置を有する第１の点火プラグ１６と、過膨張流が発生する時の圧縮波領域に点火位置を有する第２の点火プラグ１６とを使用する（なお、図１には１本の点火プラグ１６のみを示している）。
一方、ＥＣＵは、例えば、図６に示す方法に従って、噴射圧Ｐｅと筒内圧Ｐａとの大小関係を基に不足膨張流か過膨張流かを判定し、不足膨張流の時には、第１の点火プラグ１６に点火を行わせ、過膨張流の時には、第２の点火プラグ１６に点火を行わせる様に制御する。 That is, at least two spark plugs 16 are attached at different positions so that both compression wave regions can be handled when underexpanded flow occurs and when overexpanded flow occurs. Specifically, a first spark plug 16 having an ignition position in the compression wave region when the underexpanded flow occurs, and a second spark plug having an ignition position in the compression wave region when the overexpanded flow occurs. 16 (note that only one spark plug 16 is shown in FIG. 1).
On the other hand, for example, according to the method shown in FIG. 6, the ECU determines whether the underexpanded flow or the underexpanded flow based on the magnitude relationship between the injection pressure Pe and the in-cylinder pressure Pa. Control is performed so that the plug 16 is ignited and the second spark plug 16 is ignited in the case of an overexpanded flow.

図６は不足膨張流か過膨張流かを判定するための処理手順を示す方法（フローチャート）であり、先ず、ステップ１０、２０において、筒内圧Ｐａと噴射圧Ｐｅとを求めた後、ステップ３０にて両者の差（Ｐａ−Ｐｅ）を算出する。続いて、ステップ４０にて、両者の差が０以上か否かを判定し、判定結果がＮＯの場合、つまり、Ｐｅの方がＰａより高い時は、不足膨張流であると判断する。一方、判定結果がＹＥＳの場合、つまり、Ｐａの方がＰｅより高い時は、過膨張流であると判断する。   FIG. 6 is a method (flow chart) showing a processing procedure for determining whether the flow is an underexpanded flow or an overexpanded flow. First, in steps 10 and 20, after obtaining the in-cylinder pressure Pa and the injection pressure Pe, step 30. The difference between the two (Pa-Pe) is calculated. Subsequently, in step 40, it is determined whether or not the difference between the two is 0 or more. If the determination result is NO, that is, if Pe is higher than Pa, it is determined that the flow is insufficiently expanded. On the other hand, when the determination result is YES, that is, when Pa is higher than Pe, it is determined that the flow is an overexpanded flow.

筒内圧Ｐａは、図７に示す方法によって求めることができる。つまり、内燃機関１の筒内圧を検出できる筒内圧センサ１７を有している場合は、図７（ａ）に示す様に、噴射タイミング１８に同期して検出される筒内圧センサ１７の検出値（筒内圧）を入力することができる。また、筒内圧センサ１７を持たない場合でも、図７（ｂ）に示す様に、スロットル開度１９とサージタンク圧２０および筒内圧に関する諸元情報２１（例えば、ターボ回転数、ＥＧＲ率等）から、噴射タイミング１８に同期して筒内圧を演算することができる。   The in-cylinder pressure Pa can be obtained by the method shown in FIG. That is, when the cylinder pressure sensor 17 capable of detecting the cylinder pressure of the internal combustion engine 1 is provided, the detection value of the cylinder pressure sensor 17 detected in synchronization with the injection timing 18 as shown in FIG. (In-cylinder pressure) can be input. Even if the in-cylinder pressure sensor 17 is not provided, as shown in FIG. 7B, the throttle opening 19, the surge tank pressure 20, and specification information 21 about the in-cylinder pressure (for example, turbo rotation speed, EGR rate, etc.) Therefore, the in-cylinder pressure can be calculated in synchronization with the injection timing 18.

噴射圧Ｐｅは、図７（ｃ）に示す様に、噴射圧センサ２２（例えばコモンレール内の燃料圧力を検出する圧力センサ）あるいは噴射圧情報２３、機関負荷２４（例えばアクセル開度）、噴孔１３ｃに関する諸元情報２５（噴孔径、噴孔長さ、噴孔１３ｃの先広がり形状のテーパ角度等）、燃料情報２６等を基に演算可能である。   As shown in FIG. 7C, the injection pressure Pe includes an injection pressure sensor 22 (for example, a pressure sensor for detecting fuel pressure in the common rail) or injection pressure information 23, an engine load 24 (for example, accelerator opening), an injection hole. It can be calculated based on the specification information 25 (the nozzle hole diameter, the nozzle hole length, the taper angle of the tip of the nozzle hole 13c, etc.), the fuel information 26, etc.

（実施例１の効果）
実施例１に記載した内燃機関１では、インジェクタ５に超音速ノズルを採用しているので、筒内３ａへ噴出される気体燃料の噴流速度が超音速となり、空気との混合が促進されて、充分に混合された混合気を得ることができる。
また、不足膨張流が発生する時の圧縮波領域に点火位置を有する第１の点火プラグ１６と、過膨張流が発生する時の圧縮波領域に点火位置を有する第２の点火プラグ１６とを使用することにより、常に圧縮波領域にて点火することが可能である。 (Effect of Example 1)
In the internal combustion engine 1 described in the first embodiment, since the supersonic nozzle is adopted as the injector 5, the jet velocity of the gaseous fuel ejected into the cylinder 3a becomes supersonic, and the mixing with air is promoted. A sufficiently mixed gas mixture can be obtained.
Further, a first spark plug 16 having an ignition position in the compression wave region when the underexpanded flow is generated and a second spark plug 16 having an ignition position in the compression wave region when the overexpanded flow is generated are provided. By using it, it is possible to always ignite in the compression wave region.

つまり、不足膨張流が発生する時は、第１の点火プラグ１６を使用して、不足膨張流の圧縮波領域にて点火を行うことができる。また、過膨張流が発生する時は、第２の点火プラグ１６を使用して、過膨張流の圧縮波領域にて点火を行うことができる。これにより、噴孔１３ｃより噴出する気体燃料の噴流が不足膨張流であるか過膨張流であるかに係わらず、常に圧縮波領域にて点火を行うことができるので、低点火エネルギで安定した点火が可能であり、且つ、点火装置のコストアップおよび大型化を防止できる。   That is, when the underexpanded flow is generated, the first spark plug 16 can be used to perform ignition in the compression wave region of the underexpanded flow. When the overexpanded flow is generated, the second spark plug 16 can be used to perform ignition in the compression wave region of the overexpanded flow. Thereby, regardless of whether the jet of the gaseous fuel ejected from the nozzle hole 13c is an underexpanded flow or an overexpanded flow, the ignition can always be performed in the compression wave region, so that it is stable with low ignition energy. Ignition is possible, and an increase in cost and size of the ignition device can be prevented.

この実施例２は、実施例１に記載した点火プラグ１６の代わりに、点火位置を変更できる可変焦点レーザ（図示せず）を採用した場合の一例である。
可変焦点レーザを採用することにより、常に圧縮波領域に合わせて点火位置を変更できるので、実施例１の場合と同様に、低点火エネルギで安定した点火が可能であり、且つ、点火装置のコストアップおよび大型化を防止できる。 The second embodiment is an example in which a variable focus laser (not shown) capable of changing the ignition position is employed instead of the spark plug 16 described in the first embodiment.
By employing a variable focus laser, the ignition position can always be changed in accordance with the compression wave region, so that stable ignition with low ignition energy is possible and the cost of the ignition device is the same as in the first embodiment. Can prevent upsizing and upsizing.

なお、可変焦点レーザを採用する場合は、実施例１に記載した様に、噴射圧Ｐｅと筒内圧Ｐａとの大小関係から不足膨張流か過膨張流かを判定し、不足膨張流の時に発生する圧縮波領域と、過膨張流の時に発生する圧縮波領域とに合わせて点火位置を変更することができる。また、その他の方法として、図８に示す様に、噴出マッハ数２７、燃料物性値２８、噴孔形状の諸元情報２９などを基に、圧縮波の位置（圧縮波領域）を演算によって求めることも可能であり、その求められた圧縮波領域に合わせて点火位置を変更することにより、常に圧縮波領域での点火が可能となる。   When a variable focus laser is used, as described in the first embodiment, it is determined whether the flow is underexpanded or overexpanded based on the magnitude relationship between the injection pressure Pe and the in-cylinder pressure Pa. The ignition position can be changed according to the compression wave region that is generated and the compression wave region that is generated during the overexpanded flow. As another method, as shown in FIG. 8, the position (compression wave region) of the compression wave is obtained by calculation based on the ejection Mach number 27, the fuel property value 28, the specification information 29 of the nozzle hole shape, and the like. It is also possible to perform ignition in the compression wave region by changing the ignition position in accordance with the determined compression wave region.

この実施例３では、点火プラグ１６の点火位置に合わせて圧縮波領域を変化させる場合の一例を説明する。
点火プラグ１６の取付け位置が固定されていると、実施例１でも記載した様に、噴孔１３ｃより噴出する気体燃料の噴流が不足膨張流になる場合と、過膨張流になる場合とで、それぞれの圧縮波領域が異なるため、何方か一方の圧縮波領域に点火位置を合わせて点火プラグ１６を取り付けると、他方の圧縮波領域では点火できなくなる。 In the third embodiment, an example in which the compression wave region is changed in accordance with the ignition position of the spark plug 16 will be described.
When the mounting position of the spark plug 16 is fixed, as described in the first embodiment, the jet of the gaseous fuel ejected from the nozzle hole 13c becomes an underexpanded flow and an overexpanded flow. Since the respective compression wave regions are different, if the ignition plug 16 is attached with the ignition position aligned with one of the compression wave regions, ignition cannot be performed in the other compression wave region.

そこで、本実施例では、不足膨張流と過膨張流とに応じて点火プラグ１６の点火位置を変更するのではなく、点火プラグ１６の取付け位置を固定した状態で、その点火プラグ１６の点火位置に圧縮波領域の位置を合わせるものである。具体的には、噴孔１３ｃより噴出する気体燃料の噴流が常に不足膨張流となる様に、あるいは常に過膨張流となる様に、インジェクタ５の噴射圧力を調整する。   Therefore, in this embodiment, instead of changing the ignition position of the spark plug 16 according to the underexpanded flow and the overexpanded flow, the ignition position of the spark plug 16 is fixed in a state where the mounting position of the spark plug 16 is fixed. The position of the compression wave region is adjusted to the above. Specifically, the injection pressure of the injector 5 is adjusted so that the jet of gaseous fuel ejected from the nozzle hole 13c is always underexpanded or always overexpanded.

例えば、噴孔１３ｃより噴出する気体燃料の噴流が常に不足膨張流となる様に、インジェクタ５の噴射圧力を規定圧以上で供給することで、圧縮波領域の発生位置を点火プラグ１６の点火位置に合わせることが可能である。言い換えると、不足膨張流が発生する時の圧縮波領域に点火位置を合わせて点火プラグ１６を取り付けておくことで、常に不足膨張流の圧縮波領域にて点火を行うことができる。   For example, the generation position of the compression wave region is set to the ignition position of the spark plug 16 by supplying the injection pressure of the injector 5 at a specified pressure or higher so that the jet of gaseous fuel ejected from the nozzle hole 13c is always underexpanded. It is possible to match. In other words, it is possible to always perform ignition in the compression wave region of the underexpanded flow by attaching the ignition plug 16 with the ignition position aligned with the compression wave region when the underexpanded flow occurs.

あるいは、噴孔１３ｃより噴出する気体燃料の噴流が常に過膨張流となる様に、インジェクタ５の噴射圧力を規定圧未満で供給することで、圧縮波領域の発生位置を点火プラグ１６の点火位置に合わせることが可能である。言い換えると、過膨張流が発生する時の圧縮波領域に点火位置を合わせて点火プラグ１６を取り付けておくことで、常に過膨張流の圧縮波領域にて点火を行うことができる。
これにより、点火プラグ１６の点火位置が１か所に固定されている場合でも、その点火位置に合わせて圧縮波の発生位置を変化させることにより、常に圧縮波領域にて点火を行うことができるので、低点火エネルギによる安定した点火が可能である。 Alternatively, by supplying the injection pressure of the injector 5 below a specified pressure so that the jet of gaseous fuel ejected from the nozzle hole 13c is always overexpanded, the position where the compression wave region is generated is determined by the ignition position of the spark plug 16. It is possible to match. In other words, ignition can always be performed in the compression wave region of the overexpanded flow by attaching the ignition plug 16 with the ignition position aligned with the compression wave region when the overexpanded flow occurs.
Thereby, even when the ignition position of the spark plug 16 is fixed at one place, it is possible to always perform ignition in the compression wave region by changing the generation position of the compression wave in accordance with the ignition position. Therefore, stable ignition with low ignition energy is possible.

内燃機関の断面図である（実施例１）。1 is a sectional view of an internal combustion engine (Example 1). インジェクタのノズル断面図である。It is a nozzle sectional view of an injector. ノズル先端部の断面図である。It is sectional drawing of a nozzle front-end | tip part. 点火プラグの断面図である。It is sectional drawing of a spark plug. 不足膨張流（ａ）と過膨張流（ｂ）の説明図である。It is explanatory drawing of an underexpanded flow (a) and an overexpanded flow (b). ＥＣＵの処理手順を示すフローチャートである。It is a flowchart which shows the process sequence of ECU. 筒内圧Ｐａおよび噴射圧Ｐｅの算出方法を示すブロック図である（実施例２）。(Example 2) which is a block diagram which shows the calculation method of cylinder pressure Pa and injection pressure Pe. 圧縮波の位置を求めるためのブロック図である（実施例２）。(Example 2) which is a block diagram for calculating | requiring the position of a compression wave.

符号の説明Explanation of symbols

１ 内燃機関
３ａ 筒内
５ インジェクタ（燃料噴射弁）
１６ 点火プラグ（点火装置）
１３ｃ 噴孔
Ｐｅ 噴孔出口の噴射圧
Ｐａ 内燃機関の筒内圧
1 Internal combustion engine 3a In-cylinder 5 Injector (fuel injection valve)
16 Spark plug (ignition device)
13c Injection hole Pe Injection pressure at injection hole Pa In-cylinder pressure of internal combustion engine

Claims (8)

内燃機関の筒内に気体燃料を直接噴射する燃料噴射弁と、
前記筒内に噴射された気体燃料と空気との混合気に点火するための点火装置とを有する内燃機関の制御装置であって、
前記燃料噴射弁は、気体燃料を噴射するための噴孔の断面形状が、噴孔出口に向かってテーパ状に拡大する先広がり形状に設けられ、
前記点火装置は、前記噴孔より超音速で放出された気体燃料の噴流境界に発生する圧力衝撃波が圧縮する領域（圧縮波となる領域）を圧縮波領域と呼ぶ時に、その圧縮波領域において点火を行うことを特徴とする内燃機関の制御装置。 A fuel injection valve for directly injecting gaseous fuel into the cylinder of the internal combustion engine;
An internal combustion engine control device having an ignition device for igniting a mixture of gaseous fuel and air injected into the cylinder;
The fuel injection valve is provided with a tip shape in which a cross-sectional shape of a nozzle hole for injecting gaseous fuel expands in a tapered shape toward the nozzle hole outlet,
The ignition device ignites in a compression wave region when a region where a pressure shock wave generated at a jet boundary of a gaseous fuel discharged from the nozzle hole at a supersonic speed is compressed (a region that becomes a compression wave) is called a compression wave region. A control device for an internal combustion engine, characterized in that 請求項１に記載した内燃機関の制御装置において、
前記点火装置は、前記噴孔より噴出する気体燃料の噴流が不足膨張流になる場合と、前記噴孔より噴出する気体燃料の噴流が過膨張流になる場合とに応じて、常に圧縮波領域で点火できる様に、点火位置を変化させることを特徴とする内燃機関の制御装置。 The control apparatus for an internal combustion engine according to claim 1,
The ignition device always has a compression wave region according to a case where the jet of gaseous fuel ejected from the nozzle hole becomes an underexpanded flow and a case where the jet of gaseous fuel ejected from the nozzle hole becomes an overexpanded flow. A control apparatus for an internal combustion engine, wherein the ignition position is changed so that ignition can be performed with the engine. 請求項２に記載した内燃機関の制御装置において、
前記点火装置は、前記不足膨張流の圧縮波領域に点火位置を有する第１の点火装置と、前記過膨張流の圧縮波領域に点火位置を有する第２の点火装置とを備えていることを特徴とする内燃機関の制御装置。 The control device for an internal combustion engine according to claim 2,
The ignition device includes: a first ignition device having an ignition position in a compression wave region of the underexpanded flow; and a second ignition device having an ignition position in a compression wave region of the overexpansion flow. A control device for an internal combustion engine characterized by the above. 請求項２に記載した内燃機関の制御装置において、
前記点火装置は、前記圧縮波領域に点火位置を変更できる可変焦点レーザを採用していることを特徴とする内燃機関の制御装置。 The control device for an internal combustion engine according to claim 2,
The ignition apparatus employs a variable focus laser capable of changing an ignition position in the compression wave region. 請求項１に記載した内燃機関の制御装置において、
前記点火装置の点火位置を基準として、前記圧縮波領域の位置を変化させることを特徴とする内燃機関の制御装置。 The control apparatus for an internal combustion engine according to claim 1,
A control device for an internal combustion engine, wherein the position of the compression wave region is changed with reference to an ignition position of the ignition device. 請求項５に記載した内燃機関の制御装置において、
前記噴孔より噴出する気体燃料の噴流が常に不足膨張流となる時に、前記点火装置は、前記不足膨張流の圧縮波領域に点火位置を有し、且つ前記噴孔より噴出する気体燃料の噴流が常に不足膨張流となる様に、前記燃料噴射弁の噴射圧力を規定圧以上で供給することを特徴とする内燃機関の制御装置。 The control apparatus for an internal combustion engine according to claim 5,
When the jet of gaseous fuel ejected from the nozzle hole is always underexpanded, the ignition device has an ignition position in the compression wave region of the underexpanded stream and the jet of gaseous fuel ejected from the nozzle hole A control device for an internal combustion engine, wherein the injection pressure of the fuel injection valve is supplied at a specified pressure or higher so that the fuel is always underexpanded. 請求項５に記載した内燃機関の制御装置において、
前記噴孔より噴出する気体燃料の噴流が常に過膨張流となる時に、前記点火装置は、前記過膨張流の圧縮波領域に点火位置を有し、且つ前記噴孔より噴出する気体燃料の噴流が常に過膨張流となる様に、前記燃料噴射弁の噴射圧力を規定圧未満で供給することを特徴とする内燃機関の制御装置。 The control apparatus for an internal combustion engine according to claim 5,
When the jet of gaseous fuel ejected from the nozzle hole always becomes an overexpanded flow, the ignition device has an ignition position in the compression wave region of the overexpanded flow, and the jet of gaseous fuel ejected from the nozzle hole A control device for an internal combustion engine, wherein the injection pressure of the fuel injection valve is supplied at a pressure lower than a specified pressure so that the flow is always overexpanded. 請求項２、３、４、６、７に記載した何れかの内燃機関の制御装置において、
前記燃料噴射弁の噴孔出口の噴射圧Ｐｅと、前記内燃機関の筒内圧Ｐａ（噴射時の筒内圧）との大小関係において、
Ｐｅ＞Ｐａ…………（１）
Ｐｅ＜Ｐａ…………（２）
上記（１）の関係が成立する時に、前記噴孔より噴出する気体燃料の噴流が不足膨張流となり、上記（２）の関係が成立する時に、前記噴孔より噴出する気体燃料の噴流が過膨張流となることを特徴とする内燃機関の制御装置。 The control device for an internal combustion engine according to any one of claims 2, 3, 4, 6, and 7,
In the magnitude relationship between the injection pressure Pe at the nozzle hole outlet of the fuel injection valve and the in-cylinder pressure Pa (in-cylinder pressure at the time of injection) of the internal combustion engine,
Pe> Pa ............ (1)
Pe <Pa ............ (2)
When the relationship (1) is established, the jet of gaseous fuel ejected from the nozzle hole becomes an underexpanded flow, and when the relationship (2) is established, the jet of gaseous fuel ejected from the nozzle hole is excessive. A control device for an internal combustion engine, characterized by being an expansion flow.
JP2004150892A 2004-05-20 2004-05-20 Control device for internal combustion engine Expired - Fee Related JP4222256B2 (en)

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JP2009008087A (en) * 2007-06-26 2009-01-15 Delphi Technologies Inc Spray hole profile
JP2013124617A (en) * 2011-12-15 2013-06-24 Nippon Soken Inc Ignition control device
JP2014152646A (en) * 2013-02-05 2014-08-25 Denso Corp Fuel injection nozzle
JP2021006708A (en) * 2019-06-28 2021-01-21 ロベルト・ボッシュ・ゲゼルシャフト・ミト・ベシュレンクテル・ハフツングＲｏｂｅｒｔ Ｂｏｓｃｈ Ｇｍｂｈ Fuel injection valve and internal combustion engine including the same

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2009008087A (en) * 2007-06-26 2009-01-15 Delphi Technologies Inc Spray hole profile
US8544770B2 (en) 2007-06-26 2013-10-01 Delphi Technologies Spray hole profile
JP2013124617A (en) * 2011-12-15 2013-06-24 Nippon Soken Inc Ignition control device
JP2014152646A (en) * 2013-02-05 2014-08-25 Denso Corp Fuel injection nozzle
US9556843B2 (en) 2013-02-05 2017-01-31 Denso Corporation Fuel injection nozzle
JP2021006708A (en) * 2019-06-28 2021-01-21 ロベルト・ボッシュ・ゲゼルシャフト・ミト・ベシュレンクテル・ハフツングＲｏｂｅｒｔ Ｂｏｓｃｈ Ｇｍｂｈ Fuel injection valve and internal combustion engine including the same
JP7350533B2 (en) 2019-06-28 2023-09-26 ロベルト・ボッシュ・ゲゼルシャフト・ミト・ベシュレンクテル・ハフツング Fuel injection valve and internal combustion engine equipped with the fuel injection valve

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