JP4291423B2 - In-cylinder fuel injection internal combustion engine - Google Patents

In-cylinder fuel injection internal combustion engine Download PDF

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Publication number
JP4291423B2
JP4291423B2 JP14764497A JP14764497A JP4291423B2 JP 4291423 B2 JP4291423 B2 JP 4291423B2 JP 14764497 A JP14764497 A JP 14764497A JP 14764497 A JP14764497 A JP 14764497A JP 4291423 B2 JP4291423 B2 JP 4291423B2
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cavity
inclined surface
port side
fuel injection
exhaust port
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JPH10339142A (en
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雅司 的場
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Nissan Motor Co Ltd
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Nissan Motor Co Ltd
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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
    • F02F—CYLINDERS, PISTONS OR CASINGS, FOR COMBUSTION ENGINES; ARRANGEMENTS OF SEALINGS IN COMBUSTION ENGINES
    • F02F1/00—Cylinders; Cylinder heads 
    • F02F1/24—Cylinder heads
    • F02F1/42—Shape or arrangement of intake or exhaust channels in cylinder heads
    • F02F1/4214—Shape or arrangement of intake or exhaust channels in cylinder heads specially adapted for four or more valves per 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
    • 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)

Description

【０００１】
【発明の属する技術分野】
この発明は、筒内噴射式内燃機関にの改良に関する。
【０００２】
【従来の技術】
従来の筒内噴射式内燃機関としては、例えば特開平８−３５４２９号公報に記載されたものがある。これは、広い負荷範囲すなわち燃料噴射量の多寡に関わらず安定した成層燃焼を可能とすることを目的としたもので、ピストン上面に設けたキャビティ（キャビティ部）の形状として点火プラグに近接した壁面を略直線状するとともに、前記直線状壁面の後方にスワールにより燃料及び空気が拡散、混合する空間を構成している。このため、高負荷時すなわち燃料量の多い状態においても点火プラグ付近に過剰の燃料を停滞させることなく、可燃空燃比の混合気を形成できるというものである。
【０００３】
【発明が解決しようとする課題】
ところで、この筒内噴射式内燃機関のキャビティは、詳細にはスワールに対して上流側から円弧状の第１の壁面区間、直線状の第２の壁面区間、円弧状の第３の壁面区間を連続させた平面形状となっており、また縦断面としては深さ方向の中央付近が最も断面積が大きく、かつ第２の壁面区間はこれと対向する壁面区間よりも高さが大きくなるように形成されている。また、ピストンの上面には吸気ポートに面した傾斜面と排気ポートに面した傾斜面とからなる隆起形状が付与されている。
【０００４】
しかしながら、このようなキャビティ形状によると、噴射された燃料噴霧の多くはキャビティ内に保持されるため、ピストンが上死点近傍に到達するまで点火ができず、最適点火時期よりも遅れて十分な出力性能が得られなくなるおそれがある。
【０００５】
その一方、上述した各壁面区間はそれぞれピストン上面の隆起形状の頂部よりも排気側に広がる領域を有しているため、噴射された燃料がこれら壁面区間の排気側領域へ比較的拡散しやすくなり、この結果として点火プラグ付近の混合気が薄くなって着火性が悪化するおそれもある。
【０００６】
本発明は、このような従来の問題点を解消することを目的としている。
【０００７】
【課題を解決するための手段】
請求項１の発明は、対向的に配置された吸気ポートと排気ポートとの間の燃焼室略中央部に点火プラグを位置させるとともに、上面に平面上略円形のキャビティを形成したピストンと、吸気ポート側から前記キャビティに向けて燃料を噴射供給する燃料噴射弁と、シリンダ内にスワールを発生させる手段とを備えた内燃機関において、ピストン上面を、吸気ポートに面した傾斜面と排気ポートに面した傾斜面とからなり、各傾斜面の境界を稜線とする隆起形状とするとともに、前記キャビティの主要部が前記各傾斜面の境界部分に近接して吸気ポート側傾斜面内に開口し、かつ前記スワールの下流域となるキャビティの一部が排気ポート側傾斜面であって、スワールに対して点火プラグをとおり前記稜線と直交する線の上流側となる領域のみに開口するように形成した。
【０００８】
請求項２の発明は、上記請求項１の発明において、吸気ポート側傾斜面と排気ポート側傾斜面の境界を燃焼室中央部よりも吸気ポート側に偏った位置に設定した。
【０００９】
請求項３の発明は、上記請求項１の発明において、吸気ポート側傾斜面と排気ポート側傾斜面の境界を燃焼室中央部よりも排気ポート側に偏った位置に設定した。
【００１０】
請求項４の発明は、上記各発明のキャビティを、その主要部の平面形状が円形であり、かつ排気ポート側傾斜面内に開口する部分が前記円形状から膨出した態様で形成したものとする。
【００１１】
請求項５の発明は、上記請求項１から請求項３の発明のキャビティを、その平面形状が、長軸が燃料噴射弁付近からスワール下流方向に沿うように形成した楕円形状とする。
【００１２】
請求項６の発明は、上記請求項１から請求項３の発明のキャビティを、その平面形状が、部分的に排気ポート側傾斜面に突出した円形状とする。
【００１３】
請求項７の発明は、上記各発明の燃料噴射弁を、その噴霧中心が、排気ポート側傾斜面に形成されたキャビティを指向するように設けたものとする。
【００１４】
【作用・効果】
上記各発明において、吸気ポート側に位置する燃料噴射弁から噴射された燃料噴霧の一部は対向するキャビティ内壁面に衝突する。キャビティの主要部は隆起形状の境界部分に近接して吸気ポート側傾斜面に位置しているため、前記燃料噴霧が衝突する内壁面はピストン上面までの高さが最も高く、かつ燃焼室の中央部に近い。このため、前記キャビティの対向壁面に衝突してキャビティ外へと上昇した燃料噴霧が点火プラグ付近へと集中し、点火プラグの近傍に濃混合気層を形成する。これにより、ピストンが上死点に達するよりも早期に着火可能となるため良好な出力性能が発揮される。
【００１５】
一方、燃料噴霧の一部はスワールにより該スワールの下流方向へと輸送されるが、このときキャビティがスワール下流方向について排気ポート側傾斜面に突出した形状となっているため、スワールに対して点火プラグの上流側のキャビティ内に多くの燃料を確保しておくことができ、これにより濃混合気層を維持しつつキャビティ内の吸気流動を活用して良好な燃焼性能が得られる。
【００１６】
請求項２の発明によれば、燃焼室内でのキャビティ容量が比較的小となるので、ボア・ストローク比の比較的大きい機関において、キャビティ内での燃料の分散を規制し、層状化を維持して良好な燃費性能を確保することができる。
【００１７】
請求項３の発明によれば、燃料噴射弁からキャビティの対向壁面までの距離が大きくなるので燃料気化時間が長期化して未燃ＨＣやスモークが低減する。また、ボア・ストローク比の比較的小さい機関において燃料噴霧を保持しうるだけのキャビティ容量を確保できるという利点もある。
【００１８】
請求項４の発明では、キャビティ主要部の平面形状が円形であり、かつ排気ポート側傾斜面内に開口する部分が前記円形状から膨出した態様で形成してあるので、円形形状によりキャビティ内へのスワールの導入及び維持を容易にしつつ、スワール下流域にキャビティ容積を確保して多くの燃料を保持させておくことができ、成層燃焼の改善効果が向上する。
【００１９】
請求項５の発明では、キャビティの平面形状を、長軸が燃料噴射弁付近からスワール下流方向に沿うように形成した楕円形状としてあるので、シリンダ内に生じるスワール全体の流れがキャビティ内に導入されやすく、これにより点火プラグ付近への燃料噴霧の集中を促して着火性をより向上させることができる。
【００２０】
請求項６の発明では、キャビティの平面形状を、部分的に排気ポート側傾斜面に突出した円形状としてあるので、キャビティ内のスワールが減衰しにくく、それだけ点火プラグ近傍への燃料輸送機会が増大して着火性が良好になるとともに活発な燃焼が得られる。またピストンの加工も容易である。
【００２１】
請求項７の発明では、燃料噴射弁を、その噴霧中心が、キャビティの排気ポート側傾斜面への突出部を指向するように設けたものとしたことより、キャビティ主要部に衝突して点火プラグ方向に案内すべき燃料噴霧の割合を調整しつつ噴射燃料の多くを確実にキャビティ内に確保しておくことが可能となる。
【００２２】
【発明の実施の形態】
以下、本発明のいくつかの実施の形態につき図面に基づいて説明する。
【００２３】
図１、図２はこの発明の一実施形態を示している。まず構成を説明すると、１はピストン、２はシリンダ内に直接燃料を噴射する噴射弁、３は点火プラグ、４はシリンダ、５はシリンダヘッド、６はピストン上面に形成されたキャビティを示す。また７は吸気弁、８は排気弁であり本実施形態では吸気弁７、排気弁８はそれぞれ２本づつ備えられた４弁形式である。点火プラグ３は前記吸排気弁間の燃焼室１２の略中央部に位置している。９ａ，９ｂは吸気ポート、１０ａ，１０ｂは前記各ポート９ａ，９ｂに接続された吸気マニホールド、１１は一方の吸気マニホールド１０ｂに介装されたスワール発生手段としての吸気制御弁、１２は燃焼室、１３ａ，１３ｂは排気ポートを示している。
【００２４】
上記吸気制御弁１１は予め定められた比較的負荷及び回転数の低い運転域で閉弁保持され、この場合図２で反時計方向のスワールを生起する。
【００２５】
ピストン１の上面は、点火プラグ３の直下部分を境界として吸気ポート９ａ，９ｂ側の傾斜面１Ａと排気ポート１３ａ，１３ｂ側の傾斜面１Ｂとからなる隆起形状となっている。
【００２６】
キャビティ６は、この場合図２に示したようにその主要部６Ａの平面形状は円形であり、該円形の中心はほぼ燃料噴霧の中心線上に位置している。ただし、このキャビティ６はスワール下流域となる一部が排気ポート側傾斜面１Ｂ内に膨出して開口する部分（以下「拡張部６Ｂ」という。）を有している。
【００２７】
成層燃焼時における新気は、吸気行程において、吸気マニホールド１０ｂに設けられた吸気制御弁１１が、吸気ポート９ｂからの新気導入を抑制するため、略直線形状に形成された吸気ポート９ａより選択的に流入し、吸気マニホールド１０ａおよび吸気ポート９ａでの流入抵抗が小さな状態で、シリンダ４内に旋回流を発生させる。キャビティ６内のスワールは前記シリンダ内旋回流が、吸気および圧縮行程にかけてキャビティ６内に導入されることにより発生する。また、成層燃焼時における燃料は、圧縮行程においてキャビティ６の底面を指向するように噴射弁２により噴射される。
【００２８】
次に作用を説明する。
【００２９】
図２に示したように、吸気ポート側に位置する燃料噴射弁２から噴射された燃料噴霧の一部は対向するキャビティ内壁面に衝突する。キャビティ主要部６Ａは隆起形状の境界部分（稜線Ｌ）に近接して吸気ポート側傾斜面１Ａに位置しているため、前記燃料噴霧が衝突する内壁面はピストン上面までの高さが最も高く、かつ燃焼室１２の中央部に近い。このため、前記キャビティ対向壁面に衝突してキャビティ外へと上昇した燃料噴霧が点火プラグ３付近へと集中し（図２のＦ部参照）、点火プラグ３の近傍に濃混合気層を形成する。これにより、ピストン１が上死点に達するよりも早期に着火可能となるため、適切な点火時期を設定して成層燃焼に特有の良好な燃費性能とともに高出力を発揮させることが可能となる。
【００３０】
一方、燃料噴霧の一部はスワールにより該スワールの下流方向へと輸送されるが、このときキャビティ６がスワール下流方向について排気ポート側傾斜面１Ｂに突出した拡張部６Ｂを有しているため、スワールに対して点火プラグ３の上流側のキャビティ６内に多くの燃料を確保しておくことができ、これにより濃混合気層を維持しつつキャビティ６内の吸気流動を活用して良好な燃焼性能が得られる。
【００３１】
図３と図４にそれぞれ本発明の第２、第３の実施の形態を示す。図３は、キャビティ６の平面形状を、長軸が燃料噴射弁２の付近からスワール下流方向に沿うように形成した楕円形状とし、その一部を拡張部６Ｂとして排気ポート側傾斜面１Ｂ内に突出させたもの、図４はキャビティ６の平面形状を、一部を拡張部６Ｂとして排気ポート側傾斜面１Ｂに突出させた円形状としたものである。
【００３２】
図３の実施形態によれば、燃料噴射弁２の直下からスワール下流方向に沿った楕円形状のキャビティ形状としてあるので、シリンダ内に生じるスワール全体の流れがキャビティ６内に導入されやすく、これにより点火プラグ３付近への燃料噴霧の集中を促して着火性をより向上させることができる。また、図４の実施形態によれば、キャビティ６の平面形状を、部分的に排気ポート側傾斜面１Ｂに突出した円形状としてあるので、キャビティ内のスワールが減衰しにくく、それだけ点火プラグ３近傍への燃料輸送機会が増大して着火性が良好になるとともに活発な燃焼が得られる。またピストン１の加工が容易であるという利点もある。
【００３３】
図５〜図７は本発明の第４〜第６の実施形態を示しており、それぞれキャビティ６の形状としては、図５は図２のものに、図６は図３のものに、図７は図４の物に、それぞれ対応している。ただし、これらの実施形態は、ピストン上面の稜線Ｌつまり吸気ポート側傾斜面１Ａと排気ポート側傾斜面１Ｂの境界を燃焼室１２中央部よりも吸気ポート９側に偏った位置に設定してある点で先の実施形態とは異なる。
【００３４】
これらの実施形態によれば、燃焼室１２内でのキャビティ６の容量が比較的小となるので、ボア・ストローク比の比較的大きい機関において、キャビティ６内での燃料の分散を規制し、混合気の層状化を維持して良好な燃費性能を確保することができる。
【００３５】
図８〜図１０は本発明の第７〜第９の実施形態を示しており、それぞれキャビティ６の形状としては、図８は図２のものに、図９は図３のものに、図１０は図４の物に、それぞれ対応している。ただし、これらの実施形態は、ピストン上面の稜線Ｌを燃焼室１２中央部よりも排気ポート１３側に偏った位置に設定してある点で先の実施例とは異なる。
【００３６】
これらの実施形態によれば、燃料噴射弁２からキャビティ６の対向壁面までの距離が大きくなるので噴射されてからキャビティ壁面に衝突するまでの燃料気化時間が長期化して未燃ＨＣやスモークがそれだけ低減する効果が期待できる。また、ボア・ストローク比の比較的小さい機関において燃料噴霧を保持しうるだけのキャビティ容量を確保できるという利点もある。
【００３７】
ところで、上記各実施形態において、その燃料噴射弁２の向きを、噴霧中心がキャビティ拡張部６Ｂを指向するよう設定することができる。これにより、キャビティ主要部６Ａの壁面に衝突して点火プラグ３方向に案内すべき燃料噴霧の割合を調整しつつ噴射燃料の多くを確実にキャビティ６内に確保して層状燃焼の効果を高めることができる。
【図面の簡単な説明】
【図１】 本発明による筒内噴射式機関の第１の実施形態を示す概略縦断面図。
【図２】 第１の実施形態のピストンの平面図。
【図３】 本発明の第２の実施形態のピストンの平面図。
【図４】 本発明の第３の実施形態のピストンの平面図。
【図５】 本発明の第４の実施形態のピストンの平面図。
【図６】 本発明の第５の実施形態のピストンの平面図。
【図７】 本発明の第６の実施形態のピストンの平面図。
【図８】 本発明の第７の実施形態のピストンの平面図。
【図９】 本発明の第８の実施形態のピストンの平面図。
【図１０】 本発明の第９の実施形態のピストンの平面図。
【符号の説明】
１ ピストン
１Ａ 吸気ポート側傾斜面
１Ｂ 排気ポート側傾斜面
２ 燃料噴射弁
３ 点火プラグ
４ シリンダ
５ シリンダヘッド
６ キャビティ
６Ａ キャビティ主要部
６Ｂ キャビティ拡張部
７ 吸気バルブ
８ 排気バルブ
９ａ，９ｂ 吸気ポート
１０ａ，１０ｂ 吸気マニホールド
１１ 吸気制御弁
１２ 燃焼室
１３ａ，１３ｂ 排気ポート
Ｌ 傾斜面の境界（稜線）[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an improvement in a direct injection internal combustion engine.
[0002]
[Prior art]
As a conventional in-cylinder injection internal combustion engine, for example, there is one described in JP-A-8-35429. The purpose of this is to enable stable stratified combustion regardless of the large load range, that is, the amount of fuel injection. The shape of the cavity (cavity part) provided on the upper surface of the piston is a wall surface close to the spark plug. And a space in which fuel and air are diffused and mixed by a swirl behind the straight wall surface. For this reason, even at a high load, that is, in a state where the amount of fuel is large, a combustible air-fuel ratio mixture can be formed without causing excess fuel to stagnate near the spark plug.
[0003]
[Problems to be solved by the invention]
By the way, in detail, the cavity of this direct injection internal combustion engine includes an arc-shaped first wall surface section, a linear second wall section, and an arc-shaped third wall section from the upstream side with respect to the swirl. It has a continuous planar shape, and the longitudinal section has the largest cross-sectional area near the center in the depth direction, and the second wall section is higher than the wall section facing it. Is formed. Further, the upper surface of the piston is provided with a raised shape composed of an inclined surface facing the intake port and an inclined surface facing the exhaust port.
[0004]
However, according to such a cavity shape, since most of the injected fuel spray is held in the cavity, ignition cannot be performed until the piston reaches the vicinity of the top dead center, which is sufficient after the optimal ignition timing. The output performance may not be obtained.
[0005]
On the other hand, each of the wall sections described above has a region that extends to the exhaust side from the top of the raised shape on the upper surface of the piston, so that the injected fuel is relatively easily diffused to the exhaust side region of these wall sections. As a result, the air-fuel mixture in the vicinity of the spark plug may become thin and the ignitability may be deteriorated.
[0006]
The object of the present invention is to eliminate such conventional problems.
[0007]
[Means for Solving the Problems]
According to the first aspect of the present invention, there is provided a piston having an ignition plug positioned substantially in the center of the combustion chamber between the intake port and the exhaust port which are arranged opposite to each other, and a substantially circular cavity on the upper surface formed on the upper surface. In an internal combustion engine having a fuel injection valve that injects fuel from the port side toward the cavity and means for generating a swirl in the cylinder, the upper surface of the piston faces the inclined surface facing the intake port and the exhaust port was made as an inclined surface, with a raised shape to the ridge line of the boundary of the inclined surfaces, in major part of the cavity is close to the boundary portion of each inclined surface opened to the intake port side inclined plane, And a part of the cavity which becomes the downstream region of the swirl is an exhaust port side inclined surface, and only the region which is upstream of the line perpendicular to the ridge line passing through the spark plug with respect to the swirl It was formed so as to open.
[0008]
According to a second aspect of the present invention, in the first aspect of the present invention, the boundary between the intake port side inclined surface and the exhaust port side inclined surface is set at a position biased toward the intake port side from the center of the combustion chamber.
[0009]
According to a third aspect of the present invention, in the first aspect of the present invention, the boundary between the intake port side inclined surface and the exhaust port side inclined surface is set at a position biased toward the exhaust port side from the center of the combustion chamber.
[0010]
According to a fourth aspect of the present invention, the cavity of each of the above inventions is formed in such a manner that the planar shape of the main part is circular and the portion opened in the inclined surface on the exhaust port side bulges from the circular shape. To do.
[0011]
According to a fifth aspect of the present invention, the cavity of the first to third aspects of the present invention has an elliptical shape in which the long axis is formed so that the major axis is along the swirl downstream direction from the vicinity of the fuel injection valve.
[0012]
According to a sixth aspect of the invention, the cavity of the first to third aspects of the invention has a circular shape in which the planar shape partially protrudes from the inclined surface on the exhaust port side.
[0013]
In the invention of claim 7, the fuel injection valve of each of the above inventions is provided such that the spray center is directed to a cavity formed on the exhaust port side inclined surface .
[0014]
[Action / Effect]
In each of the above inventions, part of the fuel spray injected from the fuel injection valve located on the intake port side collides with the opposing cavity inner wall surface. Since the main part of the cavity is located on the inclined surface on the intake port side close to the boundary portion of the raised shape, the inner wall surface on which the fuel spray collides is the highest to the upper surface of the piston, and the center of the combustion chamber Close to the department. For this reason, the fuel spray that collides with the opposing wall surface of the cavity and rises out of the cavity concentrates in the vicinity of the spark plug and forms a rich mixture layer in the vicinity of the spark plug. Thereby, since the piston can be ignited at an earlier stage than reaching the top dead center, good output performance is exhibited.
[0015]
On the other hand, a part of the fuel spray is transported by the swirl in the downstream direction of the swirl. At this time, the cavity protrudes from the inclined surface on the exhaust port side in the swirl downstream direction, so that the swirl is ignited. A large amount of fuel can be secured in the cavity on the upstream side of the plug, and thereby, good combustion performance can be obtained by utilizing the intake air flow in the cavity while maintaining the rich mixture layer.
[0016]
According to the invention of claim 2, since the cavity capacity in the combustion chamber is relatively small, in an engine having a relatively large bore / stroke ratio, fuel dispersion in the cavity is restricted and stratification is maintained. And good fuel efficiency can be ensured.
[0017]
According to the invention of claim 3, since the distance from the fuel injection valve to the opposing wall surface of the cavity is increased, the fuel vaporization time is prolonged and unburned HC and smoke are reduced. Further, there is an advantage that a cavity capacity sufficient to hold fuel spray can be secured in an engine having a relatively small bore / stroke ratio.
[0018]
In the invention of claim 4, the planar shape of the cavity main part is circular, and the portion opened in the inclined surface on the exhaust port side is formed in a form bulging from the circular shape. While the swirl can be easily introduced and maintained, a cavity volume can be secured in the downstream area of the swirl to hold a large amount of fuel, thereby improving the effect of improving the stratified combustion.
[0019]
In the fifth aspect of the invention, the planar shape of the cavity is an elliptical shape with the long axis extending from the vicinity of the fuel injection valve to the swirl downstream direction, so that the entire swirl flow generated in the cylinder is introduced into the cavity. This facilitates the concentration of the fuel spray near the spark plug, thereby improving the ignitability.
[0020]
In the invention of claim 6, the planar shape of the cavity is a circular shape that partially protrudes on the inclined surface on the exhaust port side, so that the swirl in the cavity is less likely to be attenuated, and the opportunity for transporting fuel to the vicinity of the spark plug is increased accordingly. As a result, ignitability is improved and active combustion is obtained. The piston can be easily processed.
[0021]
According to the seventh aspect of the invention, the fuel injection valve is provided so that the spray center thereof is directed to the protruding portion toward the exhaust port side inclined surface of the cavity. It is possible to ensure that most of the injected fuel is secured in the cavity while adjusting the ratio of the fuel spray to be guided in the direction.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, some embodiments of the present invention will be described with reference to the drawings.
[0023]
1 and 2 show an embodiment of the present invention. First, the structure will be described. 1 is a piston, 2 is an injection valve for directly injecting fuel into the cylinder, 3 is a spark plug, 4 is a cylinder, 5 is a cylinder head, and 6 is a cavity formed on the upper surface of the piston. Reference numeral 7 denotes an intake valve, and reference numeral 8 denotes an exhaust valve. In this embodiment, the intake valve 7 and the exhaust valve 8 are of a four-valve type in which two each are provided. The spark plug 3 is located at a substantially central portion of the combustion chamber 12 between the intake and exhaust valves. 9a, 9b are intake ports, 10a, 10b are intake manifolds connected to the respective ports 9a, 9b, 11 is an intake control valve as swirl generating means interposed in one intake manifold 10b, 12 is a combustion chamber, Reference numerals 13a and 13b denote exhaust ports.
[0024]
The intake control valve 11 is held closed in a predetermined operating range with a relatively low load and rotation speed, and in this case, a swirl in the counterclockwise direction is generated in FIG.
[0025]
The upper surface of the piston 1 has a raised shape composed of an inclined surface 1A on the intake port 9a, 9b side and an inclined surface 1B on the exhaust port 13a, 13b side with a portion immediately below the spark plug 3 as a boundary.
[0026]
In this case, as shown in FIG. 2, the cavity 6 has a main portion 6A having a circular planar shape, and the center of the circle is substantially located on the center line of the fuel spray. However, the cavity 6 has a portion (hereinafter referred to as “expansion portion 6B”) in which a part of the swirl downstream region bulges into the exhaust port side inclined surface 1B and opens.
[0027]
The fresh air during the stratified combustion is selected from the intake port 9a formed in a substantially linear shape so that the intake control valve 11 provided in the intake manifold 10b suppresses the introduction of fresh air from the intake port 9b during the intake stroke. Inflow, and a swirling flow is generated in the cylinder 4 with a small inflow resistance at the intake manifold 10a and the intake port 9a. The swirl in the cavity 6 is generated when the swirling flow in the cylinder is introduced into the cavity 6 through the intake and compression strokes. Further, the fuel during stratified combustion is injected by the injection valve 2 so as to be directed to the bottom surface of the cavity 6 in the compression stroke.
[0028]
Next, the operation will be described.
[0029]
As shown in FIG. 2, a part of the fuel spray injected from the fuel injection valve 2 located on the intake port side collides with the opposing inner wall surface of the cavity. Since the cavity main portion 6A is located on the intake port side inclined surface 1A in the vicinity of the raised boundary portion (ridge line L), the inner wall surface on which the fuel spray collides has the highest height to the upper surface of the piston, And it is near the center part of the combustion chamber 12. For this reason, the fuel spray that collides with the cavity-facing wall surface and rises out of the cavity is concentrated near the spark plug 3 (see section F in FIG. 2), and a rich mixture layer is formed in the vicinity of the spark plug 3. . As a result, the piston 1 can be ignited earlier than reaching the top dead center, so that it is possible to set an appropriate ignition timing and exhibit high output with good fuel efficiency performance unique to stratified combustion.
[0030]
On the other hand, a part of the fuel spray is transported by the swirl in the downstream direction of the swirl. At this time, since the cavity 6 has the extended portion 6B protruding to the exhaust port side inclined surface 1B in the swirl downstream direction, A large amount of fuel can be secured in the cavity 6 upstream of the spark plug 3 with respect to the swirl, so that good combustion is achieved by utilizing the intake air flow in the cavity 6 while maintaining the rich mixture layer Performance is obtained.
[0031]
3 and 4 show the second and third embodiments of the present invention, respectively. 3 shows that the cavity 6 has an elliptical shape in which the long axis is formed along the swirl downstream direction from the vicinity of the fuel injection valve 2, and a part of the planar shape is formed as an expansion portion 6B in the inclined surface 1B on the exhaust port side. FIG. 4 shows a projecting shape of the cavity 6 having a circular shape in which a part of the cavity 6 is projected to the exhaust port side inclined surface 1B as an extended portion 6B.
[0032]
According to the embodiment of FIG. 3, since the cavity shape is elliptical along the downstream direction of the swirl from directly below the fuel injection valve 2, the entire swirl flow generated in the cylinder is easily introduced into the cavity 6, thereby It is possible to improve the ignitability by promoting the concentration of the fuel spray near the spark plug 3. Further, according to the embodiment of FIG. 4, the planar shape of the cavity 6 is a circular shape that partially protrudes from the inclined surface 1B on the exhaust port side, so that the swirl in the cavity is difficult to attenuate, and that much in the vicinity of the spark plug 3 The opportunities for transporting fuel to the fuel increase, the ignitability becomes better, and the active combustion is obtained. There is also an advantage that the processing of the piston 1 is easy.
[0033]
5 to 7 show the fourth to sixth embodiments of the present invention. The shape of the cavity 6 is as shown in FIG. 5, as shown in FIG. 2, as shown in FIG. Corresponds to the one in FIG. However, in these embodiments, the ridgeline L on the piston upper surface, that is, the boundary between the intake port side inclined surface 1A and the exhaust port side inclined surface 1B is set to a position that is biased toward the intake port 9 side from the center of the combustion chamber 12. This is different from the previous embodiment.
[0034]
According to these embodiments, since the capacity of the cavity 6 in the combustion chamber 12 is relatively small, fuel dispersion in the cavity 6 is regulated and mixed in an engine having a relatively large bore / stroke ratio. It is possible to maintain good mileage performance by maintaining the stratification.
[0035]
FIGS. 8 to 10 show the seventh to ninth embodiments of the present invention. The shape of the cavity 6 is that of FIG. 8, FIG. 9 is the same as that of FIG. Corresponds to the one in FIG. However, these embodiments differ from the previous examples in that the ridge line L on the upper surface of the piston is set at a position that is biased toward the exhaust port 13 side with respect to the central portion of the combustion chamber 12.
[0036]
According to these embodiments, since the distance from the fuel injection valve 2 to the opposite wall surface of the cavity 6 is increased, the fuel vaporization time from the injection to the collision with the wall surface of the cavity is prolonged, and unburned HC and smoke are reduced accordingly. A reduction effect can be expected. Further, there is an advantage that a cavity capacity sufficient to hold fuel spray can be secured in an engine having a relatively small bore / stroke ratio.
[0037]
By the way, in each said embodiment, the direction of the fuel injection valve 2 can be set so that a spray center may face the cavity expansion part 6B. Thereby, while adjusting the ratio of the fuel spray to collide with the wall surface of the cavity main part 6A and to be guided in the direction of the spark plug 3, a large amount of the injected fuel is surely secured in the cavity 6 to enhance the effect of the layered combustion. Can do.
[Brief description of the drawings]
FIG. 1 is a schematic longitudinal sectional view showing a first embodiment of an in-cylinder injection engine according to the present invention.
FIG. 2 is a plan view of the piston according to the first embodiment.
FIG. 3 is a plan view of a piston according to a second embodiment of the present invention.
FIG. 4 is a plan view of a piston according to a third embodiment of the present invention.
FIG. 5 is a plan view of a piston according to a fourth embodiment of the present invention.
FIG. 6 is a plan view of a piston according to a fifth embodiment of the present invention.
FIG. 7 is a plan view of a piston according to a sixth embodiment of the present invention.
FIG. 8 is a plan view of a piston according to a seventh embodiment of the present invention.
FIG. 9 is a plan view of a piston according to an eighth embodiment of the present invention.
FIG. 10 is a plan view of a piston according to a ninth embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Piston 1A Intake port side inclined surface 1B Exhaust port side inclined surface 2 Fuel injection valve 3 Spark plug 4 Cylinder 5 Cylinder head 6 Cavity 6A Cavity main part 6B Cavity expansion part 7 Intake valve 8 Exhaust valves 9a, 9b Intake ports 10a, 10b Intake manifold 11 Intake control valve 12 Combustion chambers 13a, 13b Exhaust port L Boundary (ridgeline) of inclined surface

Claims (7)

対向的に配置された吸気ポートと排気ポートとの間の燃焼室略中央部に点火プラグを位置させるとともに、上面に平面上略円形のキャビティを形成したピストンと、吸気ポート側から前記キャビティに向けて燃料を噴射供給する燃料噴射弁と、シリンダ内にスワールを発生させる手段とを備えた内燃機関において、
ピストン上面を、吸気ポートに面した傾斜面と排気ポートに面した傾斜面とからなり、各傾斜面の境界を稜線とする隆起形状とするとともに、
前記キャビティの主要部が前記各傾斜面の境界部分に近接して吸気ポート側傾斜面内に開口し、かつ前記スワールの下流域となるキャビティの一部が排気ポート側傾斜面であって、スワールに対して点火プラグをとおり前記稜線と直交する線の上流側となる領域のみに開口するように形成したことを特徴とする筒内燃料噴射式内燃機関。A spark plug is positioned in the substantially central portion of the combustion chamber between the intake port and the exhaust port that are arranged opposite to each other, and a piston having a substantially circular cavity on the top surface is formed on the upper surface, and the cavity is directed from the intake port side toward the cavity. In an internal combustion engine comprising a fuel injection valve for injecting fuel and means for generating a swirl in the cylinder,
The upper surface of the piston is composed of an inclined surface facing the intake port and an inclined surface facing the exhaust port, and has a raised shape with the boundary of each inclined surface as a ridgeline ,
The major portion of the cavity is close to the boundary portion of each inclined surface opened to the intake port side inclined plane, and a portion of the cavity as the lower reaches of the swirl is an exhaust port side inclined surface, An in-cylinder fuel injection type internal combustion engine characterized in that it is formed so as to open only in a region upstream of a line perpendicular to the ridge line through a spark plug with respect to a swirl . 吸気ポート側傾斜面と排気ポート側傾斜面の境界を燃焼室中央部よりも吸気ポート側に偏った位置に設定したことを特徴とする請求項１に記載の筒内燃料噴射式内燃機関。 The in-cylinder fuel injection internal combustion engine according to claim 1, wherein the boundary between the intake port side inclined surface and the exhaust port side inclined surface is set at a position biased toward the intake port side with respect to the center of the combustion chamber. 吸気ポート側傾斜面と排気ポート側傾斜面の境界を燃焼室中央部よりも排気ポート側に偏った位置に設定したことを特徴とする請求項１に記載の筒内燃料噴射式内燃機関。 The in-cylinder fuel injection internal combustion engine according to claim 1, wherein a boundary between the intake port side inclined surface and the exhaust port side inclined surface is set at a position biased toward the exhaust port side from the center of the combustion chamber. キャビティは、その主要部の平面形状が円形であり、かつ排気ポート側傾斜面内に開口する部分が前記円形状から膨出した態様で形成されていることを特徴とする請求項１から請求項３の何れかに記載の筒内燃料噴射式内燃機関。 2. The cavity according to claim 1, wherein a planar shape of a main portion of the cavity is circular, and a portion opened in the inclined surface on the exhaust port side is formed so as to bulge from the circular shape. The in-cylinder fuel injection internal combustion engine according to any one of claims 3 to 4. キャビティは、その平面形状が、長軸が燃料噴射弁付近からスワール下流方向に沿うように形成された楕円形状であることを特徴とする請求項１から請求項３の何れかに記載の筒内燃料噴射式内燃機関。 The in-cylinder according to any one of claims 1 to 3, wherein a planar shape of the cavity is an ellipse formed so that a major axis thereof extends along the swirl downstream direction from the vicinity of the fuel injection valve. Fuel injection internal combustion engine. キャビティは、その平面形状が、部分的に排気ポート側傾斜面に突出した円形状であることを特徴とする請求項１から請求項３の何れかに記載の筒内燃料噴射式内燃機関。 The in-cylinder fuel injection internal combustion engine according to any one of claims 1 to 3, wherein a planar shape of the cavity is a circular shape partially protruding on the inclined surface on the exhaust port side. 燃料噴射弁は、その噴霧中心が、排気ポート側傾斜面に形成されたキャビティを指向するように設けられていることを特徴とする請求項１から請求項６の何れかに記載の筒内燃料噴射式内燃機関。The in-cylinder fuel according to any one of claims 1 to 6, wherein the fuel injection valve is provided such that a spray center thereof is directed to a cavity formed on the inclined surface on the exhaust port side. Injection-type internal combustion engine.
JP14764497A 1997-06-05 1997-06-05 In-cylinder fuel injection internal combustion engine Expired - Lifetime JP4291423B2 (en)

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US6286477B1 (en) * 1999-12-21 2001-09-11 Ford Global Technologies, Inc. Combustion chamber for direct-injected spark-ignited engines with swirl airflows

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