JP3651467B2 - In-cylinder injection spark ignition internal combustion engine - Google Patents

In-cylinder injection spark ignition internal combustion engine Download PDF

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Publication number
JP3651467B2
JP3651467B2 JP2002339295A JP2002339295A JP3651467B2 JP 3651467 B2 JP3651467 B2 JP 3651467B2 JP 2002339295 A JP2002339295 A JP 2002339295A JP 2002339295 A JP2002339295 A JP 2002339295A JP 3651467 B2 JP3651467 B2 JP 3651467B2
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fuel
cavity
side wall
spark plug
injection valve
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JP2003148147A (en
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豊一 梅花
宗一 松下
静生 安部
孝志 羽島
辰夫 小林
伸幸 村松
泰人 堤
功吉 藤森
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Toyota Motor Corp
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02B—INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL
    • F02B23/00—Other engines characterised by special shape or construction of combustion chambers to improve operation
    • F02B23/08—Other engines characterised by special shape or construction of combustion chambers to improve operation with positive ignition
    • F02B23/10—Other engines characterised by special shape or construction of combustion chambers to improve operation with positive ignition with separate admission of air and fuel into cylinder
    • F02B23/104—Other engines characterised by special shape or construction of combustion chambers to improve operation with positive ignition with separate admission of air and fuel into cylinder the injector being placed on a side position of the cylinder
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02B—INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL
    • F02B75/00—Other engines
    • F02B75/12—Other methods of operation
    • F02B2075/125—Direct injection in the combustion chamber for spark ignition engines, i.e. not in pre-combustion chamber
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02F—CYLINDERS, PISTONS OR CASINGS, FOR COMBUSTION ENGINES; ARRANGEMENTS OF SEALINGS IN COMBUSTION ENGINES
    • F02F1/00—Cylinders; Cylinder heads 
    • F02F1/24—Cylinder heads
    • F02F2001/244—Arrangement of valve stems in cylinder heads
    • F02F2001/245—Arrangement of valve stems in cylinder heads the valve stems being orientated at an angle with the cylinder axis
    • 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
    • Y02T10/12—Improving ICE efficiencies

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Combustion Methods Of Internal-Combustion Engines (AREA)
  • Fuel-Injection Apparatus (AREA)

Description

【０００１】
【発明の属する技術分野】
本発明は、筒内噴射式火花点火内燃機関に関する。
【０００２】
【従来の技術】
気筒内へ直接的に燃料を噴射することにより、点火時点において点火プラグ近傍だけに着火性の良好な混合気（以下、可燃混合気）を形成し、気筒内全体としては希薄な混合気の燃焼を可能にする成層燃焼が公知である。成層燃焼を実施する際には、一般的に、燃料噴射弁は、圧縮行程後半に燃料を噴射する。こうして噴射された燃料は、ピストン頂面に形成された凹状の燃焼室内へ進入し、燃焼室壁面から熱を奪って気化しながら燃焼室形状によって点火プラグ方向へ偏向され、点火プラグ近傍に可燃混合気を形成することが意図されている。
【０００３】
一般的な燃料噴射弁は、燃料を円錐状に集中して噴射するものである。それにより、燃料噴射末期に噴射された燃料が燃焼室壁面からの熱によって可燃混合気となるのに必要な時間が比較的長くなり、この時間を確保するために、燃料噴射終了時期を早めなければならない。それにより、圧縮行程後半において噴射可能な燃料量は必然的に少なくなり、必要燃料量が比較的多くなる高負荷時には成層燃焼を断念せざるを得なかった。燃料消費率の低減に有効である成層燃焼を、より広い機関運転状態で実施することが望まれている。
【０００４】
スリット形状の噴孔を有する燃料噴射弁を使用して、燃料を比較的厚さの薄い平らな扇状に噴射することが提案されている（例えば、特許文献１参照）。こうして噴射された燃料は広範囲の燃焼室壁面から熱を奪えるために、短時間で可燃混合気とすることができ、燃料噴射終了時期を遅らせることが可能となるために、圧縮行程後半において噴射可能な燃料量を増加することができ、成層燃焼領域を高負荷側に拡大することができるとされている。
【０００５】
【特許文献１】
特開平９−１５８７３６号公報
【０００６】
【発明が解決しようとする課題】
前述の従来技術において、扇状に噴射された燃料は、燃焼室底面で幅方向に広がりながら進行するが、燃焼室側面が平面視において円弧形状を有しているために、この燃焼室側面に沿って上昇する際には中央方向に収束し、点火プラグ近傍に可燃混合気を形成できるとしている。確かに、燃焼室側面を円弧形状とすれば、幅方向に広がった燃料各部に中央方向の速度成分を付加することはできる。しかしながら、これらの燃料各部は同一位置へ向かう訳ではないので、必ずしも点火プラグ近傍に集中した可燃混合気を形成できずに失火が発生する可能性がある。
【０００７】
従って、本発明の目的は、燃料を比較的厚さの薄い平らな扇状に噴射する筒内噴射式火花点火内燃機関において、成層燃焼時における失火を確実に防止することである。
【０００８】
【課題を解決するための手段】
本発明による請求項１に記載の筒内噴射式火花点火内燃機関は、点火プラグと、ピストン頂面に形成されたキャビティと、前記キャビティ内に燃料を比較的厚さの薄い略扇状に噴射する燃料噴射弁とを具備し、前記キャビティは、底壁と、前記燃料噴射弁に対向する対向側壁と、前記対向側壁に設けられて前記対向側壁上を進行する前記燃料を前記キャビティの内側方向へ偏向させる返し部とを有し、前記対向側壁は、平面視において、前記燃料噴射弁の噴孔位置を一方の焦点とし点火プラグ近傍位置を他方の焦点とする楕円形状の一部から成る部分を有しており、前記他方の焦点とした前記点火プラグ近傍位置は、前記点火プラグの中心線から前記燃料噴射弁側に離間しており、前記燃料噴射弁から前記キャビティ内へ噴射された前記燃料が、前記底壁上を幅方向に扇状に広がりながら進行して前記対向側壁の前記返し部によって前記キャビティの内側方向に偏向される時に、前記燃料は、前記対向側壁の楕円形状を利用して、前記点火プラグ近傍位置に可燃混合気として集中することを特徴とする。
【０００９】
また、本発明による請求項２に記載の筒内噴射式火花点火内燃機関は、請求項１に記載の筒内噴射式火花点火内燃機関において、前記返し部は、前記燃料を前記キャビティの内側方向に偏向させるために前記底壁に対して鋭角な角度を形成し、平面視において前記点火プラグ近傍位置の前記焦点に近い前記対向側壁の中央部分に設けられた前記返し部の前記角度は、平面視において前記点火プラグ近傍位置の前記焦点から遠い前記対向側壁の両端部分に設けられた前記返し部の前記角度に比較して大きいことを特徴とする。
【００１０】
【発明の実施の形態】
図１は本発明による筒内噴射式火花点火内燃機関の実施形態を示す概略縦断面図であり、図２は図１におけるピストンの平面図である。これらの図において、１は吸気ポート、２は排気ポートである。吸気ポート１は吸気弁３を介して、排気ポート２は排気弁４を介して、それぞれ気筒内へ通じている。５はピストンであり、６は気筒略中心上部に配置された点火プラグである。燃料噴射弁７は、燃料を比較的厚さの薄い平らな扇状に噴射するものである。
【００１１】
燃料噴射弁７は、例えば、高い機関出力が必要な均一燃焼領域において、吸気行程で必要燃料量を噴射し、点火時点で気筒内に均一混合気を形成するようになっている。一方、成層燃焼領域においては、圧縮行程後半に必要燃料量を噴射するようになっている。圧縮行程後半で噴射された燃料は、図１に示すように、ピストン５の頂面に形成された凹状のキャビティ８内へ進入し、キャビティ８の底壁８ａに衝突した後に、底壁８ａに沿って幅方向に広がって徐々に気化しながら燃料噴射弁７に対向するキャビティ８の対向側壁８ｂの方向に進行する。
【００１２】
キャビティ８の対向側壁８ｂは、平面視において、燃料噴射弁７の噴孔位置と点火プラグ近傍位置とを焦点とする楕円形状の一部から成る部分を有している。すなわち、対向側壁８ｂは、特定水平面における断面形状が、燃料噴射弁７の噴孔位置を通る第１垂直線ＨＣと特定水平面との交点ＨＣ’と、点火プラグ中心線ＰＣの近傍位置を通る第２垂直線ＭＣと特定水平面との交点ＭＣ’とを焦点とする図３に示すような楕円の一部から成っている。さらに、対向側壁８ｂには燃料をキャビティ８内側方向に偏向させる返し部８ｃが設けられている。
【００１３】
楕円は、図３に示すように、一方の焦点からの放射線が全て楕円上で反射して他方の焦点に集中すると言う幾何学的な特徴を有している。それにより、対向側壁８ｂを前述のような楕円形状とし、返し部８ｃによって燃料を最終的にキャビティ８内側方向へ向けるようにすれば、一方の焦点を通る第１垂直線ＨＣ上から噴射された燃料は、キャビティ８の底壁８ａ上で幅方向に広がっても、対向側壁８ｂ及び返し部８ｃによって、最終的には他方の焦点を通る第２垂直線ＭＣ上に集中させられる。燃料は、第２垂直線ＭＣ上に集中する時点では、キャビティ８の底壁８ａ及び対向側壁８ｂから十分に熱を吸収して可燃混合気となっている。
【００１４】
もっとも、対向側壁８ｂから第２垂直線ＭＣまでの距離は、対向側壁８ｂの中央部分において短く、両端部分において長くなる。このように、各燃料部分において、対向側壁８ｂを離れてから第２垂直線ＭＣに到達するまでの移動距離が異なるために、返し部８ｃによって各燃料部分を同じ角度でキャビティ８内側方向へ偏向させる場合には、各燃料部分は第２垂直線ＭＣ上において高さ方向には異なる位置へ到達することとなる。こうして、この場合には、点火時点において、略円柱状の可燃混合気が、点火プラグ中心線ＰＣの近傍の第２垂直線ＭＣ回りに形成され、点火プラグ６の点火ギャップと確実に接触するために、失火を発生させることなく良好な成層燃焼を実現することができる。
【００１５】
燃料を集中させる第２垂直線ＭＣを、点火プラグ中心線ＰＣと一致させて、形成された可燃混合気と点火プラグ６の点火ギャップとの接触をさらに確実にすることも可能である。この場合には、略円柱状の可燃混合気の中央部から燃焼が開始することとなる。このような燃焼においては、可燃混合気の中央部が急激に膨張することによって可燃混合気の周囲部が分散し易く、可燃混合気の濃度が比較的希薄な場合では、周囲部への燃焼伝播が不良となって燃焼が悪化する可能性がある。
【００１６】
本実施形態においては、燃料を集中させる第２垂直線ＭＣを点火プラグ中心線ＰＣから離間させ、略円柱状の可燃混合気の周囲部から開始させた燃焼を略円柱状の可燃混合気の略直径方向へ伝播させるようになっており、それにより、燃焼した可燃混合気は、未燃焼の可燃混合気とは反対側へ膨張することができ、未燃焼の可燃混合気を分散させることがないために、可燃混合気の濃度が比較的希薄でも良好な燃焼伝播を実現することができる。これは燃料消費率をさらに低減することを可能とする。特に、本実施形態のように、燃料を集中させる第２垂直線ＭＣを点火プラグ中心線ＰＣから燃料噴射弁７側へ離間することによって、燃焼した可燃混合気は、キャビティ８内の燃料噴射弁７側の広い空間へ自由に膨張することができ、未燃焼の可燃混合気の分散を確実に防止することができる。
【００１７】
また、本実施形態において、図２のＡ−Ａ断面図である図４（Ａ）に示すように、対向側壁８ｂの中央部分に設けられた返し部８ｃは、水平面に対して第１鋭角度ＴＨ１を有しており、図２のＢ−Ｂ断面図である図４（Ｂ）に示すように、対向側壁８ｂの両端部分に設けられた返し部８ｃは、水平面に対して第１鋭角度ＴＨ１より小さな第２鋭角度ＴＨ２を有している。本実施形態において、キャビティ８の底壁８ａを水平面としたが、これは本発明を限定するものではなく、側壁８ａは特に水平面から構成されている必要はない。
【００１８】
このように返し部８ｃを構成することによって、各燃料部分が対向側壁８ｂを離れてから第２垂直線ＭＣに到達するまでの移動距離が異なっていても、各燃料部分を高さ方向に接近させて第２垂直線ＭＣ上へ到達させることができる。こうして、可燃混合気をさらに集中させることができるために、さらに少量の噴射燃料により形成される可燃混合気でも確実に着火燃焼させることができる。これは、例えば、アイドル時における燃料消費率を改善することを可能とする。
【００１９】
また、図４に示すように第１鋭角度ＴＨ１及び第２鋭角度ＴＨ２を第２垂直線ＭＣの位置及び対向側壁８ｂの形状を考慮して適当に決定すると共に、返し部８の各部分における水平面に対する鋭角度を徐々に変化させるようにすれば、可燃混合気を第２垂直線ＭＣ上においてほぼ同じ高さ位置（水平面からの高さＨ）へ集中させることができ、さらに噴射燃料を少量としても可燃混合気を確実に着火燃焼させることができる。
【００２０】
【発明の効果】
このように、本発明による筒内噴射式火花点火内燃機関によれば、点火プラグと、ピストン頂面に形成されたキャビティと、キャビティ内に燃料を比較的厚さの薄い略扇状に噴射する燃料噴射弁とを具備し、キャビティは、底壁と、燃料噴射弁に対向する対向側壁と、対向側壁に設けられて対向側壁上を進行する燃料をキャビティの内側方向へ偏向させる返し部とを有し、対向側壁は、平面視において、燃料噴射弁の噴孔位置を一方の焦点とし点火プラグ近傍位置を他方の焦点とする楕円形状の一部から成る部分を有しており、他方の焦点とした点火プラグ近傍位置は、点火プラグの中心線から燃料噴射弁側に離間しており、燃料噴射弁からキャビティ内へ噴射された燃料が、底壁上を幅方向に扇状に広がりながら進行して対向側壁の返し部によってキャビティの内側方向に偏向される時に、一方の焦点からの放射線は全て楕円上で反射して他方の焦点に集中すると言う楕円の幾何学的な特徴を利用して、燃料は対向側壁の楕円形状により点火プラグ位置近傍における点火プラグの中心線より燃料噴射弁側に可燃混合気として集中するために、可燃混合気の確実な着火性が保証されて成層燃焼時の失火を確実に防止することが可能となると共に、燃焼を開始した可燃混合気部分は、キャビティの燃料噴射弁側へ膨張するために、未燃焼の可燃混合気部分を分散させることがなく、全ての可燃混合気部分を良好に燃焼させることができる。
【図面の簡単な説明】
【図１】本発明による筒内噴射式火花点火内燃機関の実施形態を示す概略縦断面図である。
【図２】図１のピストンの平面図である。
【図３】楕円の幾何学的な特徴を説明する図である。
【図４】図２における各断面図であり、（Ａ）はＡ−Ａ断面図、（Ｂ）はＢ−Ｂ断面図である。
【符号の説明】
５…ピストン
６…点火プラグ
７…燃料噴射弁
８…キャビティ
８ｂ…対向側壁[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a direct injection spark ignition internal combustion engine.
[0002]
[Prior art]
By directly injecting fuel into the cylinder, an air-fuel mixture with good ignitability (hereinafter referred to as a combustible air-fuel mixture) is formed only near the spark plug at the time of ignition. Stratified combustion that makes it possible is known. When performing stratified combustion, generally, a fuel injection valve injects fuel in the latter half of a compression stroke. The injected fuel enters the concave combustion chamber formed on the top surface of the piston and is deflected in the direction of the spark plug by the shape of the combustion chamber while removing heat from the wall surface of the combustion chamber and vaporizing. It is intended to form a mind.
[0003]
A general fuel injection valve is one in which fuel is concentrated and injected in a conical shape. As a result, the time required for the fuel injected at the end of fuel injection to become a combustible mixture by the heat from the wall of the combustion chamber becomes relatively long, and in order to ensure this time, the fuel injection end time must be advanced. I must. As a result, the amount of fuel that can be injected in the latter half of the compression stroke inevitably decreases, and stratified combustion has to be abandoned at high loads when the required amount of fuel is relatively large. It is desired to perform stratified combustion, which is effective for reducing the fuel consumption rate, in a wider engine operating state.
[0004]
It has been proposed to use a fuel injection valve having a slit-shaped injection hole to inject fuel into a flat fan having a relatively thin thickness (see, for example, Patent Document 1). The fuel injected in this way can take heat from a wide range of combustion chamber walls, so that it can be made into a combustible air-fuel mixture in a short time and the fuel injection end time can be delayed so that it can be injected in the latter half of the compression stroke The amount of fuel can be increased and the stratified combustion region can be expanded to the high load side.
[0005]
[Patent Document 1]
JP-A-9-158736 [0006]
[Problems to be solved by the invention]
In the above-described prior art, the fan-injected fuel travels while spreading in the width direction on the bottom surface of the combustion chamber, but the side surface of the combustion chamber has an arc shape in plan view. When it rises, it converges in the central direction, and a combustible air-fuel mixture can be formed in the vicinity of the spark plug. Certainly, if the side surface of the combustion chamber has an arc shape, a velocity component in the center direction can be added to each part of the fuel spread in the width direction. However, since these fuel portions do not go to the same position, there is a possibility that a misfire may occur without necessarily forming a combustible mixture concentrated in the vicinity of the spark plug.
[0007]
Accordingly, an object of the present invention is to reliably prevent misfire during stratified combustion in a direct injection spark ignition internal combustion engine that injects fuel in a flat fan shape having a relatively thin thickness.
[0008]
[Means for Solving the Problems]
According to a first aspect of the present invention, the in-cylinder injection spark ignition internal combustion engine injects fuel into a relatively thin fan in a relatively thin thickness, a spark plug, a cavity formed in a piston top surface, and the cavity. A fuel injection valve, wherein the cavity has a bottom wall, an opposite side wall facing the fuel injection valve, and the fuel that is provided on the opposite side wall and travels on the opposite side wall in an inward direction of the cavity. And the opposed side wall has a portion made of an elliptical shape with the position of the injection hole of the fuel injection valve as one focal point and the position near the ignition plug as the other focal point in plan view. The spark plug adjacent position as the other focal point is spaced from the center line of the spark plug toward the fuel injection valve, and the fuel injected from the fuel injection valve into the cavity When the fuel is spread in a fan shape in the width direction on the bottom wall and deflected toward the inside of the cavity by the return portion of the opposing side wall, the fuel utilizes the elliptical shape of the opposing side wall, It is characterized by being concentrated as a combustible air-fuel mixture at a position near the spark plug.
[0009]
In addition, the direct injection spark ignition internal combustion engine according to claim 2 according to the present invention is the direct injection spark ignition internal combustion engine according to claim 1, wherein the return portion sends the fuel to the inside of the cavity. An acute angle with respect to the bottom wall in order to be deflected, and the angle of the return portion provided in the central portion of the opposing side wall near the focal point in the vicinity of the spark plug in a plan view is a plane The angle is larger than the angle of the return portion provided at both ends of the opposite side wall far from the focal point in the vicinity of the spark plug.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a schematic longitudinal sectional view showing an embodiment of a direct injection spark ignition internal combustion engine according to the present invention, and FIG. 2 is a plan view of a piston in FIG. In these figures, 1 is an intake port and 2 is an exhaust port. The intake port 1 communicates with the cylinder via the intake valve 3, and the exhaust port 2 communicates with the cylinder via the exhaust valve 4. Reference numeral 5 denotes a piston, and reference numeral 6 denotes a spark plug disposed substantially at the upper center of the cylinder. The fuel injection valve 7 injects fuel in a flat fan shape having a relatively small thickness.
[0011]
For example, the fuel injection valve 7 injects a required amount of fuel in the intake stroke in a uniform combustion region where high engine output is required, and forms a uniform mixture in the cylinder at the time of ignition. On the other hand, in the stratified combustion region, the required amount of fuel is injected in the latter half of the compression stroke. As shown in FIG. 1, the fuel injected in the latter half of the compression stroke enters into a concave cavity 8 formed on the top surface of the piston 5, collides with the bottom wall 8 a of the cavity 8, and then enters the bottom wall 8 a. It progresses in the direction of the opposite side wall 8b of the cavity 8 facing the fuel injection valve 7 while gradually evaporating along the width direction.
[0012]
The opposed side wall 8b of the cavity 8 has a portion formed of a part of an elliptical shape that focuses on the position of the injection hole of the fuel injection valve 7 and the position near the ignition plug in plan view. That is, the opposing side wall 8b has a cross-sectional shape in a specific horizontal plane that passes through an intersection HC ′ between the first vertical line HC passing through the nozzle hole position of the fuel injection valve 7 and the specific horizontal plane, and a position in the vicinity of the spark plug center line PC. It consists of a part of an ellipse as shown in FIG. 3 with the focal point at the intersection MC ′ of two vertical lines MC and a specific horizontal plane. Further, the opposed side wall 8b is provided with a return portion 8c for deflecting the fuel toward the inside of the cavity 8.
[0013]
As shown in FIG. 3, the ellipse has a geometric feature that all radiation from one focus is reflected on the ellipse and concentrated on the other focus. As a result, if the opposing side wall 8b has an elliptical shape as described above and the fuel is finally directed to the inside of the cavity 8 by the return portion 8c, the fuel is injected from the first vertical line HC passing through one focal point. Even if the fuel spreads in the width direction on the bottom wall 8a of the cavity 8, the fuel is finally concentrated on the second vertical line MC passing through the other focal point by the opposing side wall 8b and the return portion 8c. When the fuel is concentrated on the second vertical line MC, the fuel sufficiently absorbs heat from the bottom wall 8a and the opposite side wall 8b of the cavity 8 to become a combustible mixture.
[0014]
However, the distance from the opposing side wall 8b to the second vertical line MC is short at the central portion of the opposing side wall 8b and long at both end portions. As described above, since each fuel portion has a different moving distance from the opposite side wall 8b until it reaches the second vertical line MC, the return portion 8c deflects each fuel portion toward the inside of the cavity 8 at the same angle. In this case, each fuel portion reaches a different position in the height direction on the second vertical line MC. Thus, in this case, at the time of ignition, a substantially cylindrical combustible mixture is formed around the second vertical line MC in the vicinity of the spark plug center line PC and reliably contacts the ignition gap of the spark plug 6. In addition, good stratified combustion can be realized without causing misfire.
[0015]
It is also possible to make the second vertical line MC for concentrating the fuel coincide with the spark plug center line PC to further ensure the contact between the formed combustible mixture and the spark gap of the spark plug 6. In this case, combustion starts from the center of the substantially cylindrical combustible mixture. In such combustion, when the central portion of the combustible mixture expands rapidly, the surrounding portion of the combustible mixture tends to disperse, and when the concentration of the combustible mixture is relatively lean, the combustion propagation to the surrounding portion May become worse and combustion may worsen.
[0016]
In the present embodiment, the second vertical line MC for concentrating the fuel is separated from the spark plug center line PC, and the combustion started from the periphery of the substantially cylindrical combustible mixture is substantially the same as that of the substantially cylindrical combustible mixture. It is designed to propagate in the diametrical direction so that the combusted combustible mixture can expand to the opposite side of the unburned combustible mixture and does not disperse the unburned combustible mixture. Therefore, good combustion propagation can be realized even when the concentration of the combustible mixture is relatively lean. This makes it possible to further reduce the fuel consumption rate. In particular, as in the present embodiment, the burned combustible mixture is separated from the fuel injection valve in the cavity 8 by separating the second vertical line MC for concentrating the fuel from the spark plug center line PC toward the fuel injection valve 7 side. It can expand freely into a wide space on the 7 side and can reliably prevent dispersion of unburned combustible air-fuel mixture.
[0017]
Moreover, in this embodiment, as shown to FIG. 4 (A) which is AA sectional drawing of FIG. 2, the return part 8c provided in the center part of the opposing side wall 8b is a 1st acute angle with respect to a horizontal surface. As shown in FIG. 4B, which is a cross-sectional view taken along the line BB of FIG. 2, the return portions 8c provided at both end portions of the opposing side wall 8b have a first acute angle with respect to the horizontal plane. The second acute angle TH2 is smaller than TH1. In the present embodiment, the bottom wall 8a of the cavity 8 is a horizontal plane, but this is not a limitation of the present invention, and the side wall 8a does not have to be configured from a horizontal plane.
[0018]
By configuring the return portion 8c in this way, the fuel portions approach each other in the height direction even if the movement distances from when the fuel portions leave the opposing side wall 8b to reach the second vertical line MC are different. To reach the second vertical line MC. Thus, since the combustible air-fuel mixture can be further concentrated, even the combustible air-fuel mixture formed with a smaller amount of injected fuel can be reliably ignited and combusted. This makes it possible, for example, to improve the fuel consumption rate during idling.
[0019]
Further, as shown in FIG. 4, the first acute angle TH1 and the second acute angle TH2 are appropriately determined in consideration of the position of the second vertical line MC and the shape of the opposing side wall 8b, and at each portion of the return portion 8 If the acute angle with respect to the horizontal plane is gradually changed, the combustible air-fuel mixture can be concentrated at substantially the same height position (height H from the horizontal plane) on the second vertical line MC, and a small amount of fuel is injected. As a result, the combustible air-fuel mixture can be reliably ignited and combusted.
[0020]
【The invention's effect】
As described above, according to the in-cylinder injection spark ignition internal combustion engine according to the present invention, the spark plug, the cavity formed on the top surface of the piston, and the fuel that injects fuel into the cavity in a substantially thin fan shape. The cavity has a bottom wall, an opposite side wall facing the fuel injection valve, and a return portion provided on the opposite side wall and deflecting the fuel traveling on the opposite side wall toward the inside of the cavity. The opposing side wall has an elliptical part with the position of the injection hole of the fuel injection valve as one focal point and the vicinity of the spark plug as the other focal point in plan view. The position near the spark plug is separated from the center line of the spark plug toward the fuel injection valve, and the fuel injected from the fuel injection valve into the cavity advances while spreading in a fan shape in the width direction on the bottom wall. Return part of the opposite side wall Thus, when deflected inwardly into the cavity, fuel takes advantage of the geometrical feature of the ellipse that all radiation from one focal point is reflected on the ellipse and concentrated at the other focal point. Because the shape concentrates as a combustible air-fuel mixture on the fuel injection valve side from the center line of the spark plug near the spark plug position, it ensures reliable ignitability of the combustible air-fuel mixture and reliably prevents misfire during stratified combustion In addition, the combustible mixture portion that has started combustion expands toward the fuel injection valve side of the cavity, so that the unburned combustible mixture portion is not dispersed and all the combustible mixture portions are excellent. Can be burned.
[Brief description of the drawings]
FIG. 1 is a schematic longitudinal sectional view showing an embodiment of a direct injection spark ignition internal combustion engine according to the present invention.
FIG. 2 is a plan view of the piston of FIG.
FIG. 3 is a diagram for explaining geometrical features of an ellipse.
4A and 4B are cross-sectional views in FIG. 2, in which FIG. 4A is a cross-sectional view taken along the line AA, and FIG. 4B is a cross-sectional view taken along the line BB.
[Explanation of symbols]
5 ... Piston 6 ... Spark plug 7 ... Fuel injection valve 8 ... Cavity 8b ... Opposite side wall

Claims (2)

点火プラグと、ピストン頂面に形成されたキャビティと、前記キャビティ内に燃料を比較的厚さの薄い略扇状に噴射する燃料噴射弁とを具備し、前記キャビティは、底壁と、前記燃料噴射弁に対向する対向側壁と、前記対向側壁に設けられて前記対向側壁上を進行する前記燃料を前記キャビティの内側方向へ偏向させる返し部とを有し、前記対向側壁は、平面視において、前記燃料噴射弁の噴孔位置を一方の焦点とし点火プラグ近傍位置を他方の焦点とする楕円形状の一部から成る部分を有しており、前記他方の焦点とした前記点火プラグ近傍位置は、前記点火プラグの中心線から前記燃料噴射弁側に離間しており、前記燃料噴射弁から前記キャビティ内へ噴射された前記燃料が、前記底壁上を幅方向に扇状に広がりながら進行して前記対向側壁の前記返し部によって前記キャビティの内側方向に偏向される時に、前記燃料は、前記対向側壁の楕円形状を利用して、前記点火プラグ近傍位置に可燃混合気として集中することを特徴とする筒内噴射式火花点火内燃機関。An ignition plug, a cavity formed on the top surface of the piston, and a fuel injection valve for injecting fuel into the cavity in a substantially fan shape, the cavity including a bottom wall, and the fuel injection An opposing side wall that faces the valve; and a return portion that is provided on the opposing side wall and deflects the fuel traveling on the opposing side wall toward the inner side of the cavity. The fuel injection valve has a portion formed of a part of an elliptical shape in which the injection hole position is one focal point and the vicinity of the ignition plug is the other focal point. The fuel is injected from the center line of the spark plug to the fuel injection valve side, and the fuel injected from the fuel injection valve into the cavity advances while spreading in a fan shape in the width direction on the bottom wall. The fuel is concentrated as a combustible air-fuel mixture in the vicinity of the spark plug by utilizing the elliptical shape of the opposing side wall when deflected inward of the cavity by the return portion of the wall. Internal injection spark ignition internal combustion engine. 前記返し部は、前記燃料を前記キャビティの内側方向に偏向させるために前記底壁に対して鋭角な角度を形成し、平面視において前記点火プラグ近傍位置の前記焦点に近い前記対向側壁の中央部分に設けられた前記返し部の前記角度は、平面視において前記点火プラグ近傍位置の前記焦点から遠い前記対向側壁の両端部分に設けられた前記返し部の前記角度に比較して大きいことを特徴とする請求項１に記載の筒内噴射式火花点火内燃機関。The return portion forms an acute angle with respect to the bottom wall in order to deflect the fuel in the direction toward the inside of the cavity, and a central portion of the opposite side wall close to the focal point in the vicinity of the spark plug in a plan view The angle of the return portion provided at the top is larger than the angle of the return portion provided at both ends of the opposite side wall far from the focal point in the vicinity of the spark plug in a plan view. The in-cylinder injection spark ignition internal combustion engine according to claim 1.
JP2002339295A 2002-11-22 2002-11-22 In-cylinder injection spark ignition internal combustion engine Expired - Fee Related JP3651467B2 (en)

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