JP3823607B2

JP3823607B2 - Direct-injection spark ignition internal combustion engine

Info

Publication number: JP3823607B2
Application number: JP14473299A
Authority: JP
Inventors: 祐一入矢; 孝伸杉山; 泰之伊藤
Original assignee: Nissan Motor Co Ltd
Current assignee: Nissan Motor Co Ltd
Priority date: 1999-05-25
Filing date: 1999-05-25
Publication date: 2006-09-20
Anticipated expiration: 2019-05-25
Also published as: JP2000337149A

Description

【０００１】
【発明の属する技術分野】
本発明は、直噴火花点火式内燃機関に関する。
【０００２】
【従来の技術】
従来の直噴火花点火式内燃機関として、シリンダヘッド燃焼室壁面の略中央より燃焼室に臨ませた点火プラグと、シリンダヘッド燃焼室壁面の側部で吸気ポート下側より燃焼室に直接斜め下向きに燃料を噴射するように臨ませた燃料噴射弁と、を備え、機関運転条件に応じて、圧縮行程にて燃料を噴射して成層燃焼を行わせる成層運転と吸気行程にて燃料を噴射して均質燃焼を行わせる均質運転とを切換えるようにしたものがある（特開平４−１１２９３１号公報、特開平７−１９０４６号公報参照）。
【０００３】
ここで、吸気ポートの設定により、燃焼室内に順タンブル流動（燃料噴射弁から直接点火プラグへ向かう方向のタンブル流）を生成することで、成層運転時に、燃料の拡散を防止しつつ燃料を点火プラグ近傍へ確実に輸送して、燃料の成層化を可能にし、超希薄空燃比で運転して燃費の向上を図ることができる。
【０００４】
【発明が解決しようとする課題】
しかしながら、このような従来の直噴火花点火式内燃機関にあっては、アイドル時のような低回転時に、吸気ポートで形成する通常の順タンブル流動が弱まり、成層運転時に燃料が点火プラグ方向へ届きづらくなる。
【０００５】
また、成層運転時の圧縮行程噴射時（背圧下）に、燃料を直接点火プラグ方向へ向かわせるため、燃料噴射弁の噴霧角を大きく設定し、噴霧の上端角が点火プラグ近傍に届くようにする方法があるが、この場合には、成層運転時には、噴霧が直接点火プラグ方向へ届くものの、噴霧角が広過ぎて分散しやすくなり（図１３(a) 参照）、また、均質運転時の吸気行程噴射時（大気圧下）には、噴霧角が更に広くなりすぎてシリンダヘッド燃焼室壁面に燃料が付着し（図１３(b) 参照）、成層・均質運転条件ともに性能が悪化することになる。
【０００６】
そこで、燃料噴射弁の取付角度を寝かせ、かつ成層運転時（背圧下）に燃料を直接点火プラグ方向へ向かわせるため、噴霧角を小さく設定し、成層運転時（背圧下）に噴霧の上端角が点火プラグ近傍に届くようにする方法があるが、この場合には、小噴霧角のため、成層運転時の噴霧分散は防止でき（図１４(a) 参照）、均質運転時（大気圧下）の噴霧角の広がり度合も小さいのでシリンダヘッド燃焼室壁面への燃料付着も少なくなるものの、逆に均質運転時に噴霧角が狭すぎて燃料混合気の混合度合いが悪化し（図１４(b) 参照）、均質運転性能が悪化するという問題点があった。
【０００７】
本発明は、このような従来の問題点に着目してなされたもので、成層運転時の圧縮行程噴射時（背圧下）に噴霧が直接点火プラグ方向に届き、かつ分散も防止できる一方、均質運転時の吸気行程噴射時（大気圧下）には噴霧角を点火プラグとは反対方向に広げて燃料混合気の混合度合いを改善できるようにすることを目的とする。
【０００８】
【課題を解決するための手段】
このため、請求項１に係る発明では、シリンダヘッド燃焼室壁面の略中央より燃焼室に臨ませた点火プラグと、シリンダヘッド燃焼室壁面の側部で吸気ポート下側より燃焼室に直接斜め下向きに燃料を噴射するように臨ませた燃料噴射弁と、を備え、機関運転条件に応じて、圧縮行程にて燃料を噴射して成層燃焼を行わせる成層運転と吸気行程にて燃料を噴射して均質燃焼を行わせる均質運転とを切換える直噴火花点火式内燃機関において、燃料噴射弁を、圧縮行程にて燃料を噴射する成層運転時の燃料噴霧の外形の一部が点火プラグ近傍に届くように設定し、燃料噴射弁の噴口部に対し点火プラグとは反対方向のシリンダヘッド燃焼室壁面に、吸気行程にて燃料を噴射する均質運転時の燃料噴霧の外形の一部が近接するように、湾曲面を有する突出部を設けたことを特徴とする。
【０００９】
すなわち、前記湾曲面を有する突出部を設けることで、均質運転時に燃料噴射弁の噴口部に対し点火プラグとは反対方向の燃料噴霧の側面（外形角度）をコアンダ効果で外側に広げるのである。
【００１０】
ここで、コアンダ効果とは、湾曲面を有する突出部により、該湾曲面に近接した燃料噴霧が、該湾曲面に沿って流れる作用のことで、この効果が発揮されることにより該湾曲面に近接した噴霧の噴霧角は拡大されることになる。
【００１１】
請求項２に係る発明では、前記燃料噴射弁として、燃料噴霧の方向及び密度が偏るキャスティング型燃料噴射弁を用いて、燃料噴霧が点火プラグ側に偏るように取付け、圧縮行程にて燃料を噴射する成層運転時の燃料噴霧の外形の一部が点火プラグ近傍に届くように設定したことを特徴とする。
【００１２】
請求項３に係る発明では、前記湾曲面を有する突出部は、シリンダヘッド燃焼室壁面の周方向に沿って、燃料噴射弁の噴口部に対し左右方向に延長し、均質運転時の燃料噴霧の左右側面が近接するようにしたことを特徴とする。
【００１３】
【発明の効果】
請求項１に係る発明によれば、燃料噴射弁を、圧縮行程にて燃料を噴射する成層運転時の燃料噴霧の外形の一部が点火プラグ近傍に届くように設定したので、成層運転時の燃焼性能を確保でき、このときは、燃料噴射弁の噴口部に対し点火プラグとは反対方向のシリンダヘッド燃焼室壁面に設けられた湾曲面を有する突出部に燃料噴霧が接近しないため、コアンダ効果による噴霧外形角のさらなる拡大もないので、噴霧外形角度が広くなり過ぎず、分散も少ないため、安定して運転できる。
【００１４】
一方、吸気行程にて燃料を噴射する均質運転時は、大気圧下にて燃料噴射するため、成層運転時に対し噴霧外形角は広がり、燃料噴射弁の噴口部に対し点火プラグとは反対方向のシリンダヘッド燃焼室壁面に設けられた湾曲面を有する突出部に近接するようになるため、コアンダ効果が発生し、噴霧外形角はさらに下端側に拡大する。従って、噴霧外形角が下端側に広がることで、混合気の均質度合いが向上し、性能向上が図れる。
【００１５】
請求項２に係る発明によれば、燃料噴霧の方向及び密度が偏るキャスティング型燃料噴射弁を用いて、燃料噴霧が点火プラグ側に偏るように取付けることで、成層運転時の燃料噴霧をより確実に点火プラグ近傍へ輸送することができる。
【００１６】
請求項３に係る発明によれば、湾曲面を有する突出部を、シリンダヘッド燃焼室壁面の周方向に沿って延長して、均質運転時の燃料噴霧の左右側面を近接させることで、コアンダ効果をより一層発揮させることができる。
【００１７】
【発明の実施の形態】
以下に本発明の実施の形態を図面に基づいて説明する。
図１は本発明の第１実施形態を示している。
【００１８】
シリンダヘッド１とピストン２との間に燃焼室３が形成され、また、ピストン２の頂面には凹部４が形成されている。５は吸気ポート、６は排気ポート、７は吸気弁、８は排気弁である。
【００１９】
そして、シリンダヘッド１燃焼室壁面の略中央より燃焼室３に臨ませた点火プラグ９と、シリンダヘッド１燃焼室壁面の側部で吸気ポート５下側（かつ２本の吸気ポート５，５間）より燃焼室３に直接斜め下向きに燃料を噴射するように臨ませた燃料噴射弁１０と、を備えている。
【００２０】
コントロールユニット１１には、アクセル開度センサ１２により検出される機関負荷、クランク角センサ１３により検出される機関回転数、水温センサ１４により検出される水温等が入力されている。そして、コントロールユニット１１は、これらにより検出される機関運転条件に応じて、燃料噴射弁１０の噴射時期、噴射量、図示しないプレッシャレギュレータにより調圧される燃料噴射弁１０への燃圧、及び、点火プラグ９の点火時期を制御して、圧縮行程にて燃料を噴射して成層燃焼を行わせる成層運転と、吸気行程にて燃料を噴射して均質燃焼を行わせる均質運転と、を切換える。
【００２１】
ここにおいて、燃料噴射弁１０の取付角度を寝かせ、かつ噴霧外形角を小さくして、圧縮行程（背圧下）にて燃料を噴射する成層運転時の燃料噴霧の外形の一部（噴霧外形上端）が点火プラグ９近傍に届くように設定してある。
【００２２】
また、燃料噴射弁１０の噴口部に対し点火プラグ９とは反対方向のシリンダヘッド１燃焼室壁面に、吸気行程（大気圧下）にて燃料を噴射する均質運転時の燃料噴霧の外形の一部（噴霧外形下端）が近接するように、湾曲面１５ａを有する突出部１５を設けてある。
【００２３】
次に第１実施形態の作用を説明する。
図２〜図５は第１の実施形態の作用を説明する図である。
一般に燃料噴霧特性として、図２に大気圧下、背圧下での噴霧外形の変化を示すように、大気圧下の噴霧外形角に対し、背圧下では噴霧外形角が狭くなる。また、図３に噴霧外形角による大気圧下、背圧下での噴霧外形角の変化度合いを示すように、大気気圧下と背圧下との噴霧外形角差は、噴霧外形角が小さいほど小さくなる。
【００２４】
この特性を考慮して、本発明においては、燃料噴射弁１０の取付角度を寝かせ、かつ、圧縮行程中（背圧下）に燃料噴射する成層運転時に燃料を直接点火プラグ９方向へ向かわせるために噴霧外形角を小さく設定し、成層運転時の噴霧外形上端角が点火プラグ９近傍に届くように設定してあるので、機関の運転条件が、成層運転領域では、図４に示すように、噴霧外形上端角が点火プラグ９を指向する。一方、噴霧外形下端角は、燃料噴射弁１０の取付角度が小さくかつ噴霧外形角が小さいため、燃料噴射弁１０の噴口部に対し点火プラグ９とは反対方向のシリンダヘッド１燃焼室壁面に設けられた湾曲面１５ａを有する突出部１５に接近しないため、コアンダ効果による噴霧外形下端角のさらなる拡大もないので、噴霧外形角が広くなり過ぎず、分散も少ないため、安定して運転できる。
【００２５】
また、機関の運転条件が、均質運転領域では、図５に示すように、吸気行程中（大気圧下）に燃料噴射するため、成層運転時に対し噴霧外形角は広がり、噴霧外形上端角・下端角共に広がる。このとき、噴霧外形角自体は小さいので、前述の噴霧特性より噴霧外形角の広がり代は少なく、噴霧外形上端側の燃料噴霧の点火プラグ９ヘのかぶり等は問題ない。一方、噴霧外形下端角は、広がることにより、燃料噴射弁１０の噴口部に対し点火プラグ９とは反対方向のシリンダヘッド１燃焼室壁面に設けられた湾曲面１５ａを有する突出部１５に近接するようになるため、コアンダ効果が発生することにより、噴霧外形下端角はさらに拡大する。従って、噴霧外形角が噴霧外形下端側に広がることで、混合気の均質度合いが向上し、性能向上が図れる。
【００２６】
図６は本発明の第２実施形態を示している。
この実施形態は、燃料噴射弁として、燃料噴霧の方向及び密度が偏るいわゆるキャスティング噴霧を生成するキャスティング型燃料噴射弁１０’を用いて、燃料噴霧が点火プラグ９側にキャスティングする（偏る）ように取付け、圧縮行程（背圧下）にて燃料を噴射する成層運転時の燃料噴霧の外形の一部（噴霧外形上端）が点火プラグ９近傍に届くようにしてある。そして、燃料噴射弁１０’の噴口部に対し点火プラグ９とは反対方向のシリンダヘッド１燃焼室壁面に、吸気行程（大気圧下）にて燃料を噴射する均質運転時の燃料噴霧の非キャスティング側（噴霧外形下端）が近接するように、湾曲面１５ａを有する突出部１５を設けてある。
【００２７】
尚、キャスティング型燃料噴射弁１０’は、例えば図７に示すように、燃料噴射弁の先端面を斜めにカットして、噴口までの距離を変えることにより、実現できる。
【００２８】
次に第２実施形態の作用を説明する。
図８〜図１０は第２実施形態の作用を説明する図である。
一般にキャスティング噴霧では、図８に示すように、大気圧下の噴霧外形角に対し、背圧下では噴霧外形角が狭くなる特性において、非キャスティング側の噴霧は狭くなるが、キャスティング側の噴霧は変わらないという特性がある。
【００２９】
この特性を考慮して、本発明においては、成層運転時の背圧下噴射のキャスティング側の噴霧（噴霧外形上端）が点火プラグ９近傍に届くように設定してあるので、機関の運転条件が、成層運転領域では、図９に示すように、キャスティング側の噴霧（噴霧外形上端）は点火プラグ９を指向する。一方、非キャスティング側の噴霧（噴霧外形下端）は、大気圧下の噴霧外形角に対しては狭く、燃料噴射弁１０’の噴口部に対し点火プラグ９とは反対方向のシリンダヘッド１燃焼室壁面に設けられた湾曲面１５ａを有する突出部１５に接近しないため、コアンダ効果による噴霧外形下端角のさらなる拡大もないので、噴霧外形角が広くなり過ぎず、分散も少ないため、安定して運転できる。
【００３０】
また、機関の運転条件が、均質運転領域では、図１０に示すように、吸気行程中（大気圧下）に燃料噴射するため、成層運転時に対し噴霧外形角は広がるものの、前述のキャスティング噴霧の特性により、キャスティング側の噴霧（噴霧外形上端）は広がらない（変化なし）のため、キャスティング側の噴霧の点火プラグ９ヘのかぶり等は問題ない。一方、非キャスティング側の噴霧（噴霧外形下端）は、成層運転時に対し広がることにより、燃料噴射弁１０’の噴口部に対し点火プラグ９とは反対方向のシリンダヘッド１燃焼室壁面に設けられた湾曲面１５ａを有する突出部１５に近接するようになるため、コアンダ効果が発生することにより、噴霧外形下端角はさらに拡大する。従って、噴霧外形角が噴霧外形下端側に広がることで、混合気の均質度合いが向上し、性能向上が図れる。
【００３１】
図１１及び図１２は本発明の第３実施形態を示している。
この実施形態は、第１及び第２実施形態において、燃料噴射弁１０（１０’）の噴口部に対し点火プラグ９とは反対方向のシリンダヘッド１燃焼室壁面に均質運転時の大気圧下噴射の噴霧（噴霧外形下端）が近接するように設けた湾曲面１５ａを有する突出部１５を、図１１(a) に示すような略円筒面形状から、図１１(b) に示すように、シリンダヘッド１燃焼室壁面の周方向に沿って、燃料噴射弁１０の噴口部に対し左右方向に延長して（延長部１６）、均質運転時の大気圧下噴射の噴露の左右側面が近接するようにしたものである。
【００３２】
こうすることにより、図１２に示すように、コアンダ効果をより一層発揮させて、均質運転時の噴霧をより広げることができる。
【図面の簡単な説明】
【図１】本発明の第１実施形態を示す図
【図２】燃料噴射弁の大気圧下及び背圧下での噴霧特性図
【図３】燃料噴射弁の噴霧外形角による噴霧特性図
【図４】第１実施形態の成層運転時の噴霧形状を示す図
【図５】第１実施形態の均質運転時の噴霧形状を示す図
【図６】本発明の第２実施形態を示す図
【図７】キャスティング型燃料噴射弁の構成例を示す図
【図８】キャスティング型燃料噴射弁の噴霧特性図
【図９】第２実施形態の成層運転時の噴霧形状を示す図
【図１０】第２実施形態の均質運転時の噴霧形状を示す図
【図１１】本発明の第３実施形態を示す図
【図１２】第３実施形態の均質運転時の噴霧形状を示す図
【図１３】従来例（１）の噴霧形状を示す図
【図１４】従来例（２）の噴霧形状を示す図
【符号の説明】
１シリンダヘッド
２ピストン
３燃焼室
４凹部
５吸気ポート
６排気ポート
９点火プラグ
１０燃料噴射弁
１０’ キャスティング型燃料噴射弁
１１コントロールユニット
１５突出部
１５ａ湾曲面
１６延長部[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a direct injection spark ignition internal combustion engine.
[0002]
[Prior art]
As a conventional direct-injection spark-ignition internal combustion engine, an ignition plug that faces the combustion chamber from the approximate center of the cylinder head combustion chamber wall surface, and obliquely downwards directly from the lower side of the intake port to the combustion chamber at the side of the cylinder head combustion chamber wall surface And a fuel injection valve that injects the fuel into the fuel, and injects fuel in the stratified operation and the intake stroke in which fuel is injected in the compression stroke and stratified combustion is performed according to engine operating conditions. In some cases, the operation is switched to a homogeneous operation for performing homogeneous combustion (see Japanese Patent Laid-Open Nos. 4-112931 and 7-19046).
[0003]
Here, by setting the intake port, a forward tumble flow (tumble flow in the direction from the fuel injection valve directly toward the ignition plug) is generated in the combustion chamber, thereby igniting the fuel while preventing fuel diffusion during stratified operation. The fuel can be stratified by reliably transporting to the vicinity of the plug, and the fuel consumption can be improved by operating at an ultra lean air-fuel ratio.
[0004]
[Problems to be solved by the invention]
However, in such a conventional direct-injection spark-ignition internal combustion engine, the normal tumble flow formed at the intake port is weakened at the time of low rotation, such as during idling, and the fuel moves toward the spark plug during stratified operation. It becomes difficult to reach.
[0005]
Also, during the compression stroke injection during stratified operation (under back pressure), the fuel is directed directly toward the spark plug so that the spray angle of the fuel injection valve is set large so that the upper end angle of the spray reaches the vicinity of the spark plug. In this case, in stratified operation, the spray reaches directly to the spark plug, but the spray angle is too wide to disperse (see Fig. 13 (a)). During the intake stroke injection (under atmospheric pressure), the spray angle becomes too wide and the fuel adheres to the cylinder head combustion chamber wall (see Fig. 13 (b)), which degrades performance in both stratified and homogeneous operating conditions. become.
[0006]
Therefore, in order to lay down the fuel injection valve mounting angle and direct the fuel directly toward the spark plug during stratified operation (under back pressure), set the spray angle to a small value, and during the stratified operation (under back pressure), the upper spray angle However, in this case, because of the small spray angle, spray dispersion during stratification operation can be prevented (see Fig. 14 (a)), and during homogeneous operation (under atmospheric pressure) ) Has a small spread of the spray angle, so the amount of fuel adhering to the wall surface of the cylinder head combustion chamber is reduced, but conversely, the spray angle is too narrow during homogeneous operation and the degree of mixing of the fuel mixture deteriorates (FIG. 14 (b)). See), and there was a problem that the homogeneous operation performance deteriorated.
[0007]
The present invention has been made paying attention to such conventional problems, and spray can directly reach the spark plug direction during compression stroke injection (under back pressure) during stratification operation, and can prevent dispersion. It is an object of the present invention to improve the degree of mixing of the fuel mixture by expanding the spray angle in the direction opposite to the spark plug at the time of intake stroke injection (under atmospheric pressure) during operation.
[0008]
[Means for Solving the Problems]
For this reason, in the invention according to claim 1, the spark plug that faces the combustion chamber from the substantially center of the cylinder head combustion chamber wall surface, and the side of the cylinder head combustion chamber wall surface directly obliquely downwards from the lower side of the intake port to the combustion chamber. And a fuel injection valve that injects the fuel into the fuel, and injects fuel in the stratified operation and the intake stroke in which fuel is injected in the compression stroke and stratified combustion is performed according to engine operating conditions. In a direct-injection spark-ignition internal combustion engine that switches between homogeneous operation and homogeneous combustion, part of the outer shape of the fuel spray during stratified operation in which fuel is injected in the compression stroke of the fuel injection valve reaches the vicinity of the ignition plug In this way, a part of the outer shape of the fuel spray during homogeneous operation in which fuel is injected in the intake stroke is close to the cylinder head combustion chamber wall in the direction opposite to the spark plug with respect to the nozzle part of the fuel injection valve Have curved surfaces Characterized in that a that the projecting portion.
[0009]
That is, by providing the projecting portion having the curved surface, the side surface (outside angle) of the fuel spray in the direction opposite to the spark plug with respect to the injection port portion of the fuel injection valve during the homogeneous operation is expanded outward by the Coanda effect.
[0010]
Here, the Coanda effect is an action in which the fuel spray close to the curved surface flows along the curved surface by the projecting portion having the curved surface, and this effect is exerted on the curved surface. The spray angle of the close spray will be enlarged.
[0011]
In the invention according to claim 2, a casting type fuel injection valve in which the direction and density of fuel spray is biased as the fuel injection valve is mounted so that the fuel spray is biased toward the spark plug, and fuel is injected in the compression stroke. It is characterized in that a part of the outer shape of the fuel spray during the stratified operation is set to reach the vicinity of the spark plug.
[0012]
In the invention which concerns on Claim 3, the protrusion part which has the said curved surface is extended in the left-right direction with respect to the nozzle part of a fuel injection valve along the circumferential direction of a cylinder head combustion chamber wall surface, and the fuel spray at the time of homogeneous operation The left and right side surfaces are close to each other.
[0013]
【The invention's effect】
According to the first aspect of the present invention, the fuel injection valve is set so that a part of the outer shape of the fuel spray during the stratification operation in which fuel is injected in the compression stroke reaches the vicinity of the spark plug. Combustion performance can be ensured. At this time, the fuel spray does not approach the protruding portion having a curved surface provided on the wall surface of the cylinder head combustion chamber opposite to the spark plug with respect to the nozzle part of the fuel injection valve. Since there is no further expansion of the spray outer angle due to the spray, the spray outer angle does not become too wide and the dispersion is small, so that stable operation is possible.
[0014]
On the other hand, during homogeneous operation in which fuel is injected in the intake stroke, fuel is injected under atmospheric pressure, so the spray external angle is wider than in stratified operation, and the injection port is in the direction opposite to the spark plug. Since it comes close to the projecting portion having the curved surface provided on the wall surface of the cylinder head combustion chamber, the Coanda effect occurs, and the spray external angle is further expanded to the lower end side. Therefore, the spray outer shape angle spreads to the lower end side, so that the degree of homogeneity of the air-fuel mixture is improved and the performance can be improved.
[0015]
According to the second aspect of the invention, by using the casting type fuel injection valve in which the direction and density of the fuel spray is biased, the fuel spray is more reliably biased toward the spark plug, so that the fuel spray during the stratified operation is more reliably performed. Can be transported to the vicinity of the spark plug.
[0016]
According to the invention of claim 3, the Coanda effect is achieved by extending the projecting portion having a curved surface along the circumferential direction of the cylinder head combustion chamber wall surface and bringing the left and right side surfaces of the fuel spray during homogeneous operation close to each other. Can be further exhibited.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 shows a first embodiment of the present invention.
[0018]
A combustion chamber 3 is formed between the cylinder head 1 and the piston 2, and a recess 4 is formed on the top surface of the piston 2. 5 is an intake port, 6 is an exhaust port, 7 is an intake valve, and 8 is an exhaust valve.
[0019]
A spark plug 9 facing the combustion chamber 3 from substantially the center of the combustion chamber wall surface of the cylinder head 1 and a lower side of the intake port 5 (and between the two intake ports 5 and 5 on the side of the combustion chamber wall surface of the cylinder head 1). ) And a fuel injection valve 10 facing the combustion chamber 3 so as to inject the fuel directly obliquely downward.
[0020]
The control unit 11 receives an engine load detected by the accelerator opening sensor 12, an engine speed detected by the crank angle sensor 13, a water temperature detected by the water temperature sensor 14, and the like. Then, the control unit 11 determines the injection timing and injection amount of the fuel injection valve 10, the fuel pressure to the fuel injection valve 10 regulated by a pressure regulator (not shown), and the ignition according to the engine operating conditions detected by these. The ignition timing of the plug 9 is controlled to switch between a stratified operation in which fuel is injected in the compression stroke to perform stratified combustion and a homogeneous operation in which fuel is injected in the intake stroke to perform homogeneous combustion.
[0021]
Here, a part of the outer shape of the fuel spray during the stratified operation in which fuel is injected in the compression stroke (under the back pressure) (the upper end of the spray outer shape) with the mounting angle of the fuel injection valve 10 laid down and the spray outer angle reduced. Is set to reach the vicinity of the spark plug 9.
[0022]
In addition, the fuel spray outer shape is one of the outer shapes of the fuel spray in the homogeneous operation in which fuel is injected into the combustion chamber wall surface of the cylinder head 1 in the direction opposite to the spark plug 9 with respect to the nozzle part of the fuel injection valve 10 in the intake stroke (under atmospheric pressure). The protruding portion 15 having the curved surface 15a is provided so that the portion (lower end of the spray outer shape) is close to the surface.
[0023]
Next, the operation of the first embodiment will be described.
2-5 is a figure explaining the effect | action of 1st Embodiment.
In general, as the fuel spray characteristics, as shown in FIG. 2, changes in the spray contour under atmospheric pressure and back pressure, the spray contour angle becomes narrower under back pressure than the spray contour angle under atmospheric pressure. Further, as shown in FIG. 3 showing the degree of change in the spray external angle under atmospheric pressure and back pressure depending on the spray external angle, the difference in spray external angle between the atmospheric pressure and the back pressure is smaller as the spray external angle is smaller. .
[0024]
In consideration of this characteristic, in the present invention, in order to direct the fuel toward the spark plug 9 during the stratified operation in which the mounting angle of the fuel injection valve 10 is laid down and the fuel is injected during the compression stroke (back pressure). Since the spray outer angle is set to be small and the upper end angle of the spray outer shape at the time of stratification operation is set so as to reach the vicinity of the spark plug 9, the engine operating conditions are as shown in FIG. The upper end angle of the outer shape is directed to the spark plug 9. On the other hand, the spray outer shape lower end angle is provided on the cylinder head 1 combustion chamber wall surface in the direction opposite to the spark plug 9 with respect to the nozzle part of the fuel injection valve 10 because the mounting angle of the fuel injection valve 10 is small and the spray outer angle is small. Since the protrusion 15 having the curved surface 15a is not approached, the spray contour lower end angle is not further expanded due to the Coanda effect. Therefore, the spray contour angle is not excessively wide and the dispersion is small, so that stable operation is possible.
[0025]
In addition, when the engine operating conditions are in the homogeneous operation region, as shown in FIG. 5, fuel injection is performed during the intake stroke (under atmospheric pressure), so the spray external angle is widened during stratified operation, and the spray external upper end angle and lower end Both corners spread. At this time, since the spray outer angle itself is small, the spread margin of the spray outer angle is less than the spray characteristics described above, and there is no problem with the fogging of the fuel spray on the spark plug 9 on the upper end side of the spray outer shape. On the other hand, the spray outer shape lower end angle widens and approaches the protrusion 15 having the curved surface 15a provided on the wall surface of the cylinder head 1 combustion chamber in the direction opposite to the spark plug 9 with respect to the injection port of the fuel injection valve 10. Therefore, when the Coanda effect is generated, the lower end angle of the spray outer shape is further enlarged. Therefore, the spray outer shape angle spreads toward the lower end of the spray outer shape, whereby the degree of homogeneity of the air-fuel mixture is improved and the performance can be improved.
[0026]
FIG. 6 shows a second embodiment of the present invention.
This embodiment uses a casting type fuel injection valve 10 ′ that generates a so-called casting spray in which the direction and density of the fuel spray is biased as the fuel injection valve, so that the fuel spray is cast (biased) on the spark plug 9 side. A part of the outer shape of the fuel spray (the upper end of the spray outer shape) during the stratified operation in which fuel is injected in the mounting and compression stroke (under the back pressure) reaches the vicinity of the spark plug 9. Then, non-casting of fuel spray at the time of homogeneous operation in which fuel is injected into the cylinder head 1 combustion chamber wall surface in the direction opposite to the spark plug 9 with respect to the nozzle part of the fuel injection valve 10 'in the intake stroke (under atmospheric pressure) A protruding portion 15 having a curved surface 15a is provided so that the side (the lower end of the spray outer shape) is close.
[0027]
The casting type fuel injection valve 10 ′ can be realized by, for example, cutting the front end surface of the fuel injection valve obliquely and changing the distance to the injection port as shown in FIG.
[0028]
Next, the operation of the second embodiment will be described.
8-10 is a figure explaining the effect | action of 2nd Embodiment.
In general, as shown in FIG. 8, in the case of casting spray, the non-casting side spray becomes narrower while the spraying side spray becomes narrower in the characteristic that the spray outer angle becomes narrower under back pressure than the spray outer angle under atmospheric pressure. There is no characteristic.
[0029]
In consideration of this characteristic, in the present invention, since the spray on the casting side of the back pressure injection during the stratified operation (spray outer shape upper end) reaches the vicinity of the spark plug 9, the engine operating condition is In the stratification operation region, as shown in FIG. 9, the spray on the casting side (the upper end of the spray outer shape) is directed to the spark plug 9. On the other hand, the spray on the non-casting side (spray outer shape lower end) is narrower than the spray outer angle under atmospheric pressure, and the cylinder head 1 combustion chamber in the direction opposite to the spark plug 9 with respect to the nozzle part of the fuel injection valve 10 ′. Since it does not approach the protrusion 15 having the curved surface 15a provided on the wall surface, there is no further expansion of the lower end angle of the spray outer shape due to the Coanda effect. it can.
[0030]
In addition, when the engine operating conditions are in the homogeneous operation region, as shown in FIG. 10, fuel is injected during the intake stroke (under atmospheric pressure). Due to the characteristics, the spray on the casting side (the upper end of the outer shape of the spray) does not spread (no change), so there is no problem with fogging of the spray on the casting side to the spark plug 9. On the other hand, the spray on the non-casting side (spray outer shape lower end) is provided on the wall surface of the combustion chamber of the cylinder head 1 in the direction opposite to the spark plug 9 with respect to the nozzle part of the fuel injection valve 10 ′ by spreading over the stratified operation. Since it comes close to the protrusion part 15 which has the curved surface 15a, when the Coanda effect occurs, the spray outer shape lower end angle is further enlarged. Therefore, the spray outer shape angle spreads toward the lower end of the spray outer shape, whereby the degree of homogeneity of the air-fuel mixture is improved and the performance can be improved.
[0031]
11 and 12 show a third embodiment of the present invention.
In this embodiment, in the first and second embodiments, injection under atmospheric pressure during homogeneous operation is performed on the cylinder head 1 combustion chamber wall surface in the direction opposite to the spark plug 9 with respect to the injection port portion of the fuel injection valve 10 (10 ′). As shown in FIG. 11 (b), the protrusion 15 having the curved surface 15a provided so that the spray (the lower end of the spray outer shape) is close to the cylinder surface as shown in FIG. 11 (a). Along the circumferential direction of the wall surface of the head 1 combustion chamber, it extends in the left-right direction with respect to the nozzle part of the fuel injection valve 10 (extension part 16), and the right and left side surfaces of the spray of atmospheric pressure injection in the homogeneous operation approach each other. It is what I did.
[0032]
By doing so, as shown in FIG. 12, the Coanda effect can be further exhibited, and the spray during the homogeneous operation can be further expanded.
[Brief description of the drawings]
FIG. 1 is a diagram showing a first embodiment of the present invention. FIG. 2 is a spray characteristic diagram under atmospheric pressure and back pressure of a fuel injection valve. FIG. 3 is a spray characteristic diagram according to a spray external angle of the fuel injection valve. FIG. 5 is a diagram showing a spray shape during a stratification operation according to the first embodiment. FIG. 5 is a diagram showing a spray shape during a homogeneous operation according to the first embodiment. FIG. 6 is a diagram showing a second embodiment of the present invention. 7] A diagram showing a configuration example of a casting type fuel injection valve. [Fig. 8] A spray characteristic diagram of a casting type fuel injection valve. [Fig. 9] A diagram showing a spray shape in a stratified operation of the second embodiment. The figure which shows the spray shape at the time of homogeneous operation of embodiment. FIG. 11 The figure which shows 3rd Embodiment of this invention. FIG. 12 The figure which shows the spray shape at the time of homogeneous operation of 3rd Embodiment. FIG. 14 is a diagram showing a spray shape of (1). FIG. 14 is a diagram showing a spray shape of a conventional example (2).
DESCRIPTION OF SYMBOLS 1 Cylinder head 2 Piston 3 Combustion chamber 4 Recessed part 5 Intake port 6 Exhaust port 9 Spark plug 10 Fuel injection valve 10 'Casting type fuel injection valve 11 Control unit 15 Protrusion part 15a Curved surface 16 Extension part

Claims

シリンダヘッド燃焼室壁面の略中央より燃焼室に臨ませた点火プラグと、シリンダヘッド燃焼室壁面の側部で吸気ポート下側より燃焼室に直接斜め下向きに燃料を噴射するように臨ませた燃料噴射弁と、を備え、機関運転条件に応じて、圧縮行程にて燃料を噴射して成層燃焼を行わせる成層運転と吸気行程にて燃料を噴射して均質燃焼を行わせる均質運転とを切換える直噴火花点火式内燃機関において、
燃料噴射弁を、圧縮行程にて燃料を噴射する成層運転時の燃料噴霧の外形の一部が点火プラグ近傍に届くように設定し、
燃料噴射弁の噴口部に対し点火プラグとは反対方向のシリンダヘッド燃焼室壁面に、吸気行程にて燃料を噴射する均質運転時の燃料噴霧の外形の一部が近接するように、湾曲面を有する突出部を設けたことを特徴とする直噴火花点火式内燃機関。A spark plug that faces the combustion chamber from the approximate center of the wall surface of the cylinder head combustion chamber, and a fuel that faces the cylinder head combustion chamber wall surface so that the fuel is injected obliquely downward from the lower side of the intake port directly into the combustion chamber And switching between a stratified operation in which fuel is injected in the compression stroke to perform stratified combustion and a homogeneous operation in which fuel is injected during the intake stroke to perform homogeneous combustion according to engine operating conditions In a direct injection spark ignition internal combustion engine,
Set the fuel injection valve so that part of the outer shape of the fuel spray during stratified operation that injects fuel in the compression stroke reaches the vicinity of the spark plug,
A curved surface is arranged so that a part of the outer shape of the fuel spray during homogeneous operation in which fuel is injected in the intake stroke is close to the cylinder head combustion chamber wall in the direction opposite to the spark plug with respect to the nozzle part of the fuel injection valve. A direct-injection spark-ignited internal combustion engine characterized in that a projecting portion is provided.

前記燃料噴射弁として、燃料噴霧の方向及び密度が偏るキャスティング型燃料噴射弁を用いて、燃料噴霧が点火プラグ側に偏るように取付け、圧縮行程にて燃料を噴射する成層運転時の燃料噴霧の外形の一部が点火プラグ近傍に届くように設定したことを特徴とする請求項１記載の直噴火花点火式内燃機関。As the fuel injection valve, a casting type fuel injection valve in which the direction and density of the fuel spray is biased is attached so that the fuel spray is biased toward the spark plug, and the fuel spray during stratified operation in which fuel is injected in the compression stroke is used. 2. The direct injection spark ignition type internal combustion engine according to claim 1, wherein a part of the outer shape is set so as to reach the vicinity of the spark plug.

前記湾曲面を有する突出部は、シリンダヘッド燃焼室壁面の周方向に沿って、燃料噴射弁の噴口部に対し左右方向に延長し、均質運転時の燃料噴霧の左右側面が近接するようにしたことを特徴とする請求項１又は請求項２記載の直噴火花点火式内燃機関。The projecting portion having the curved surface extends in the left-right direction along the circumferential direction of the wall surface of the cylinder head combustion chamber so that the left and right side surfaces of the fuel spray during homogeneous operation are close to each other. The direct-injection spark-ignition internal combustion engine according to claim 1 or 2.