JP2697100B2 - Engine piston - Google Patents

Engine piston

Info

Publication number
JP2697100B2
JP2697100B2 JP1067585A JP6758589A JP2697100B2 JP 2697100 B2 JP2697100 B2 JP 2697100B2 JP 1067585 A JP1067585 A JP 1067585A JP 6758589 A JP6758589 A JP 6758589A JP 2697100 B2 JP2697100 B2 JP 2697100B2
Authority
JP
Japan
Prior art keywords
cavity
lip
side wall
fuel
piston
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
JP1067585A
Other languages
Japanese (ja)
Other versions
JPH02248615A (en
Inventor
孝智 有福
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Isuzu Motors Ltd
Original Assignee
Isuzu Motors Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Isuzu Motors Ltd filed Critical Isuzu Motors Ltd
Priority to JP1067585A priority Critical patent/JP2697100B2/en
Publication of JPH02248615A publication Critical patent/JPH02248615A/en
Application granted granted Critical
Publication of JP2697100B2 publication Critical patent/JP2697100B2/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Classifications

    • 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
    • F02B23/02—Other engines characterised by special shape or construction of combustion chambers to improve operation with compression ignition
    • F02B23/06—Other engines characterised by special shape or construction of combustion chambers to improve operation with compression ignition the combustion space being arranged in working piston
    • F02B23/0645—Details related to the fuel injector or the fuel spray
    • F02B23/0669—Details related to the fuel injector or the fuel spray having multiple fuel spray jets per injector nozzle
    • 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
    • F02B23/02—Other engines characterised by special shape or construction of combustion chambers to improve operation with compression ignition
    • F02B23/06—Other engines characterised by special shape or construction of combustion chambers to improve operation with compression ignition the combustion space being arranged in working piston
    • F02B23/0672—Omega-piston bowl, i.e. the combustion space having a central projection pointing towards the cylinder head and the surrounding wall being inclined towards the cylinder center axis
    • 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
    • F02B23/02—Other engines characterised by special shape or construction of combustion chambers to improve operation with compression ignition
    • F02B23/06—Other engines characterised by special shape or construction of combustion chambers to improve operation with compression ignition the combustion space being arranged in working piston
    • F02B23/0618—Other engines characterised by special shape or construction of combustion chambers to improve operation with compression ignition the combustion space being arranged in working piston having in-cylinder means to influence the charge motion
    • F02B23/0624—Swirl flow
    • 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
    • F02B23/02—Other engines characterised by special shape or construction of combustion chambers to improve operation with compression ignition
    • F02B23/06—Other engines characterised by special shape or construction of combustion chambers to improve operation with compression ignition the combustion space being arranged in working piston
    • F02B23/0645—Details related to the fuel injector or the fuel spray
    • F02B23/0648—Means or methods to improve the spray dispersion, evaporation or ignition
    • F02B23/0651—Means or methods to improve the spray dispersion, evaporation or ignition the fuel spray impinging on reflecting surfaces or being specially guided throughout the combustion space
    • 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

【発明の詳細な説明】 ［産業上の利用分野］ この発明は、燃料噴霧を直接供給するキャビティをピ
ストン頂部に形成したエンジンのピストンに関する。Description: TECHNICAL FIELD The present invention relates to a piston of an engine in which a cavity for directly supplying fuel spray is formed at the top of the piston.

［従来の技術］ 通常、ターボ過給機付ディーゼルエンジンの高出力を
追及する場合は、エンジンの最大出力点、即ち燃料流量
最大の点で過給機圧力を最大に設定し、その最大出力点
で発生する燃焼圧力がエンジンの機械的強度以下になる
ように圧縮比を下げるのが一般であり、低い圧縮比にす
るほど低燃費を期待できる。[Prior Art] Normally, when pursuing a high output of a turbocharged diesel engine, the turbocharger pressure is set to the maximum at the maximum output point of the engine, that is, at the point of maximum fuel flow, and the maximum output point is set. In general, the compression ratio is reduced so that the combustion pressure generated by the engine becomes lower than the mechanical strength of the engine. The lower the compression ratio, the lower the fuel consumption.

このように最大出力点で最適マッチングさせたエンジ
ンは、低速・軽負荷域、即ち過給機圧力が低い範囲で圧
縮圧力、温度そして燃焼室（キャビティ）温度が低くな
る傾向を示す。一般に、インジェクションノズルから噴
射された燃料は、通常、ピストン側壁に衝突して跳返り
火炎中で完全燃焼し、側壁に付着した燃料もその火炎に
よって完全に蒸発または炭化してしまう。しかし、上述
のようにターボ過給機エンジン用にマッチングさせた低
圧縮比エンジンでは、側壁に衝突して反射した燃料が未
着火であったり、側壁に付着した燃料の蒸発の遅れよ
り、より低温度の燃焼室底部に達して液化し、火炎に晒
されてキャビティ内に未燃燃料として浮遊し、これが排
気行程で排出されて青白煙（HC）、排気刺激臭を生む。The engine optimally matched at the maximum output point in this manner tends to have a lower compression pressure, temperature, and combustion chamber (cavity) temperature in a low speed / light load range, that is, in a range in which the supercharger pressure is low. Generally, the fuel injected from the injection nozzle collides with the piston side wall and is completely burned in the rebound flame, and the fuel attached to the side wall is completely evaporated or carbonized by the flame. However, in the low compression ratio engine matched for the turbocharger engine as described above, the fuel that has collided with the side wall and has not been ignited or has a lower evaporation rate than the evaporation delay of the fuel attached to the side wall. When the temperature reaches the bottom of the combustion chamber, it liquefies, is exposed to the flame, and floats as unburned fuel in the cavity, which is discharged in the exhaust stroke to produce blue-white smoke (HC) and exhaust irritating odor.

この理由からディーゼルエンジンの低圧縮化は、フリ
クション低減、過給率アップによる高出力化が可能であ
るにもかかわらず採用に至っていない。For this reason, low compression of diesel engines has not been adopted, although high output can be achieved by reducing friction and increasing the supercharging rate.

そこで、低圧縮比過給エンジンを得るためには、キャ
ビティに供給する燃料の状態（蒸発、分散、分布）を良
好な状態に制御し、正確な着火を生じさせて火炎伝播を
図らねばならない。Therefore, in order to obtain a low compression ratio supercharged engine, it is necessary to control the state (evaporation, dispersion, distribution) of the fuel supplied to the cavity to a favorable state, to cause accurate ignition, and to propagate the flame.

この種の課題を前提とした提案には、本出願人提案の
「直接噴射式ディーゼル機関の燃焼室」（実開昭58−10
2720号公報）がある。Proposals based on this type of problem include a “combustion chamber of a direct injection diesel engine” proposed by the present applicant (see Japanese Utility Model Application Laid-open No.
No. 2720).

提案は、ピストン頂面にキャビティを凹設しそのキャ
ビティの入り口を形成する開口周縁に半径方向内方へ突
出されたリップを形成し、キャビティの側壁を燃料噴射
ノズルの燃料噴霧線に対して直角となるように形成し、
キャビティ底中央にトロイダル方向の撹拌流を生成する
円錘形状の突出部を形成して構成したもので、側壁に燃
料を直角に衝突させることによって、噴射燃料の一部分
の燃料の粒子をさらに細かく砕きつつ、側壁に対する燃
料の残部分がその側壁に薄膜状に付着して拡散するよう
にし、そして上記リップが、側壁で粉砕した燃料，蒸発
した燃料そして薄膜状に付着させる燃料をキャビティ内
に閉込めようとしている。The proposal is to form a cavity on the piston top surface and form a lip protruding radially inward on the periphery of the opening forming the entrance of the cavity, and make the side wall of the cavity perpendicular to the fuel spray line of the fuel injection nozzle. Formed so that
It is formed by forming a protruding part in the shape of a cone that generates a stirring flow in the toroidal direction at the center of the bottom of the cavity.By colliding the fuel at right angles with the side wall, the fuel particles in a part of the injected fuel are further finely crushed. While allowing the remainder of the fuel to the sidewall to adhere and diffuse to the sidewall in a thin film, and the lip traps the pulverized fuel, the evaporated fuel and the fuel to be deposited in the thin film in the cavity in the sidewall. I am trying to do.

つまり、提案は、燃料噴霧の微粒子化を促進して、着
火および火炎伝播に必要な混合気を生成する一方で、撹
拌流の強度に依存させて薄膜状の燃料及び側壁付近に存
在する蒸気を側壁側から剥離させ、これをキャビティの
中心側に運んで火炎を伝播させ、燃焼を良好にするよう
にしている。In other words, the proposal promotes atomization of the fuel spray to generate the air-fuel mixture required for ignition and flame propagation, while reducing the strength of the agitated flow to remove the thin-film fuel and the vapor present near the side walls. It is peeled off from the side wall side and is carried to the center side of the cavity to propagate the flame so as to improve the combustion.

［発明が解決しようとする課題］ しかし、上述の提案を上述の低圧縮比高過給エンジン
に採用するためには、次の課題を解決する必要がある。[Problems to be Solved by the Invention] However, in order to adopt the above proposal to the above-described low compression ratio and high supercharged engine, it is necessary to solve the following problem.

低圧縮比高過給エンジンの燃料圧力に対してリップ
の機械的強度を向上させる必要がある。It is necessary to improve the mechanical strength of the lip with respect to the fuel pressure of a low compression ratio high supercharged engine.

エンジンの最大出力点は回転数が高く燃料噴射量も
多く噴射ポンプの角速度が大きいため動的な噴射タイミ
ングはかなり遅角する。このため最大出力点で最適タイ
ミングに設定すると低速回転では動的な噴射時期が進角
し、上死点前のかなり早い時期から上死点後の遅い時期
まで燃料が噴射されてピストン頂面（リップ上面）に付
着するため、過大量のHC（青白煙）が発生する。Since the maximum output point of the engine has a high rotational speed, a large fuel injection amount, and a large angular velocity of the injection pump, the dynamic injection timing is considerably delayed. Therefore, if the optimal timing is set at the maximum output point, the dynamic injection timing advances at low speed rotation, and fuel is injected from a considerably early time before the top dead center to a late time after the top dead center, and the piston top surface ( Large amount of HC (blue and white smoke) is generated because it adheres to the lip upper surface).

このため、付加装置として噴射時期を自動的に調節す
るオートタイマ等が必要になる。For this reason, an auto timer or the like for automatically adjusting the injection timing is required as an additional device.

［課題を解決するための手段］ 本発明は、ピストン頂面に凹設されたキャビティの側
壁に、キャビティ軸心側からの燃料噴霧に対してピスト
ン軸方向に切った断面でみて略直角に傾斜した傾斜面を
形成し、キャビティの開口縁に、突出端が断面円弧状で
且つ下面が直線状のリップを設けると共に、リップの下
面と側壁の傾斜面とを、その交角が90゜〜110゜になる
ように形成して曲面にて連続させたものであって、半径
方向に対向するリップの突出端間の間隔をD1、キャビテ
ィ底面に形成された円錐形状の突出部の底と側壁との接
続部分の半径方向の間隔をD2、リップの下面と側壁との
接続部の半径方向の間隔をD3、キャビティの最大深さを
Ｈとしたときに、D1＞D2、D3/H≒４としたものである。[Means for Solving the Problems] According to the present invention, a side wall of a cavity recessed on the top surface of a piston is inclined at a substantially right angle when viewed in a cross section cut in a piston axial direction with respect to fuel spray from a cavity axis side. A lip having an arc-shaped cross section and a straight lower surface is provided at the opening edge of the cavity, and an intersection angle between the lower surface of the lip and the inclined surface of the side wall is 90 ° to 110 °. The distance between the projecting ends of the lips facing in the radial direction is D 1 , and the bottom and side walls of the conical protrusion formed on the cavity bottom surface D 2 the radial spacing of the connecting portion of the radial spacing of the connecting portion between the lower surface and the side wall of the lip D 3, the maximum depth of the cavity is taken as H, D 1> D 2, D 3 / H ≒ 4.

［作用］ 上記構成によって、リップの強度が確保されると共
に、上死点付近で噴射された燃料噴射は、側壁の傾斜面
に衝突して適宜反転・拡散されると共に、上死点前後の
噴射始め及び噴射終わりの噴霧は、リップの突出端及び
下面に衝突して側壁の直線部へと円滑に導かれ、キャビ
ティ内方に流入する。[Operation] With the above configuration, the strength of the lip is ensured, and the fuel injection injected near the top dead center collides with the inclined surface of the side wall and is appropriately reversed and diffused, and the injection before and after the top dead center is performed. The spray at the beginning and at the end of the spray collides with the protruding end and the lower surface of the lip, is smoothly guided to the straight portion of the side wall, and flows into the cavity.

したがって、燃料噴霧及び混合気化した燃料の燃焼室
外への流出は未然に防止され、リップ下に着火性，火炎
の伝播性能の優れた混合気（予混合気）を分布させるよ
うになる。つまり、低速・軽負荷にあっても部分的にリ
ッチな混合気を分布させることができ、圧縮比を下げて
も迅速な着火と比較的急速な火炎伝播燃焼が可能にな
り、HCの排出量を大巾に減少できる。Therefore, the fuel spray and the mixture-vaporized fuel are prevented from flowing out of the combustion chamber, and a mixture (premixture) having excellent ignitability and flame propagation performance is distributed below the lip. In other words, even at low speeds and light loads, a rich mixture can be partially distributed, and even if the compression ratio is lowered, quick ignition and relatively rapid flame propagation combustion become possible, and HC emissions are reduced. Can be greatly reduced.

［実施例］ 以下、この発明の好適一実施例を添付図面に基づいて
説明する。Hereinafter, a preferred embodiment of the present invention will be described with reference to the accompanying drawings.

第１図及び第２図に示すように、小型直接噴射デーゼ
ルエンジンに採用される一般のピストン１には、ピスト
ン頂面20に軸心方向に窪んだキャビティ２が形成され
る。実施例にあってキャビティ２は水平断面が四角形に
形成され、そのキャビティ２のほぼ軸心上に燃料噴射ノ
ズル３が配設される。この燃料噴射ノズル３の噴口部４
には円周方向に等間隔をおいて上記キャビティ２の角数
と同数の噴口が開口され、各噴口から対向する側壁また
は、コーナへ半径方向外方向でかつ斜め下方へ燃料噴霧
を噴射するように構成される。As shown in FIGS. 1 and 2, a general piston 1 employed in a small direct injection diesel engine has a cavity 2 which is recessed in the axial direction on a piston top surface 20. In the embodiment, the cavity 2 has a rectangular horizontal section, and the fuel injection nozzle 3 is disposed substantially on the axis of the cavity 2. The injection port 4 of the fuel injection nozzle 3
The same number of nozzles as the number of corners of the cavity 2 are opened at equal intervals in the circumferential direction, and the fuel spray is injected radially outward and obliquely downward from each nozzle to the opposing side wall or corner. It is composed of

さて、キャビティ２の各側壁５は、噴口からの燃料噴
霧線Ｆに対して一定角度範囲の傾斜角θを成して形成さ
れている。つまり、各側壁５は斜め上方を向く傾斜面を
成す。この側壁面の傾斜角θは、上記燃料噴射ノズル３
からの燃料噴霧線Ｆに対して略直角、具体的には90゜〜
110゜の範囲の傾斜角とし、かつ、その傾斜面の深さ方
向の間隔は、上記燃料噴霧Ｆの上下方向の拡散間隔l2と
同等かあるいはそれ以上とする。キャビティ２の底面11
はキャビティ２の中心軸O2上に水平面を基準として***
した円錘形状の突出部13によって形成する。ただし、そ
の突出部13の頂点は、キャビティの高さ方向の中間位置
近傍にあるようにし、キャビティ２内にトロイダル方向
の旋回流を生成するようにする。Now, each side wall 5 of the cavity 2 is formed to have an inclination angle θ within a certain angle range with respect to the fuel spray line F from the injection port. That is, each side wall 5 forms an inclined surface facing obliquely upward. The inclination angle θ of the side wall surface is
Approximately at right angles to the fuel spray line F from
An inclined angle of 110 DEG, and the depth direction of the spacing of the inclined surface is equal to or greater than the diffusion distance l 2 in the vertical direction of the fuel spray F. Bottom 11 of cavity 2
Is formed by the projecting portion 13 of the raised conical shape relative to the horizontal plane on the center axis O 2 of the cavity 2. However, the apex of the protruding portion 13 is located near an intermediate position in the height direction of the cavity, and a swirling flow in the toroidal direction is generated in the cavity 2.

一方、キャビティ２の入り口10を形成する開口周縁に
は、開口周縁に沿ってリップ６を形成する。リップ６
は、半径方向内方へ突出させて形成し、その突出端７
は、リップ６の半径方向外方に中心を置く円弧で丸く縁
どり、リップ６の下面と上記側壁との接続は、これらの
交角が上記傾斜角と同等範囲内となるように接続する。
すなわち交角βが90゜〜110゜となるように形成されて
いる。また、この接続部分の位置は上記ピストンが上死
点位置のとき燃料噴霧の到達点が上記側壁の上下方向の
中間にあるような位置に設定する。さらに、側壁５とリ
ップ下面９とは、圧縮行程終期にリップ６によって生成
されるスキッシュ流Ｖをリップ下面９側から剥離させて
キャビティ２の底面側に反転させることのできる曲率の
円弧で滑らかに接続し、底面と突出部13の底との接続部
分も円弧で滑らかに接続する。但し、リップ下面９と側
壁５とを接続する曲面と、リップ先端７を丸く縁どる円
弧との間に直線部分を形成する。On the other hand, a lip 6 is formed on the periphery of the opening forming the entrance 10 of the cavity 2 along the periphery of the opening. Lip 6
Are formed to protrude inward in the radial direction, and the protruding end 7
Are rounded by an arc centered radially outward of the lip 6, and the connection between the lower surface of the lip 6 and the side wall is made such that their intersection angle is within the same range as the above-mentioned inclination angle.
That is, the intersection angle β is formed to be 90 ° to 110 °. Further, the position of the connection portion is set at a position where the arrival point of the fuel spray is located in the middle of the side wall in the vertical direction when the piston is at the top dead center position. Further, the side wall 5 and the lip lower surface 9 are smoothly formed by an arc having a curvature capable of separating the squish flow V generated by the lip 6 at the end of the compression stroke from the lip lower surface 9 side and inverting to the bottom surface side of the cavity 2. The connection between the bottom surface and the bottom of the protruding portion 13 is also smoothly connected by an arc. However, a straight line portion is formed between the curved surface connecting the lower surface 9 of the lip and the side wall 5 and an arc that rounds the tip 7 of the lip.

ところで突出部13の底と側壁５との接続部分の半径方
向の間隔D2と半径方向に対向する上記リップの突出端間
の間隔D1との関係は、D1＞D2とし、また、半径方向に対
向するリップ６の下面と上記側壁との接続部間の間隔D3
と上記キャビティの最大深さＨとの関係は、D3/H≒４と
する。尚、上記キャビティ２の角コーナ14,15,16,17は
隣接する側壁５相互をそれぞれ円周方向の曲面19,20,2
1,22で滑らかに接続して形成するが、この曲面19〜22も
燃料噴霧線に対しては90゜〜110゜範囲の傾斜面で形成
する。Meanwhile relation between the distance D 1 of the inter-protruding end of the lip facing the radial distance D 2 and the radial connecting portion between the bottom and the side wall 5 of the projecting portion 13, and D 1> D 2, also, The distance D 3 between the connection between the lower surface of the lip 6 facing in the radial direction and the side wall.
And the maximum depth H of the cavity is D 3 / H ≒ 4. The corners 14, 15, 16, 17 of the cavity 2 are formed by connecting the adjacent side walls 5 to each other in the circumferentially curved surfaces 19, 20, 2, 2 respectively.
The curved surfaces 19 to 22 are also formed as inclined surfaces in the range of 90 ° to 110 ° with respect to the fuel spray line.

以上のように構成すると、上記リップ下面9,上記側壁
５下部そして突出部13によってリップ下面９下には、キ
ャビティ２内に供給される燃焼用の空気の旋回流S1をト
ロイダル方向の撹拌流S2としつつ、上下方向には、圧縮
行程終期のスキッシュ流Ｖを導入する空間24（以下スワ
ール旋回部という）を形成する。With the configuration described above, the lip lower surface 9, the lower lip lower surface 9 by the side wall 5 lower and protrusions 13, stirred flow of the toroidal direction swirl S 1 of the air for combustion supplied to the cavity 2 while the S 2, in the vertical direction, introducing a squish flow V of the compression stroke end to form a space 24 (hereinafter referred to as swirl turning unit).

次に作用を説明する。 Next, the operation will be described.

ピストン頂面に凹設するキャビティ２の側壁５を、キ
ャビティ軸心側からの燃料噴霧線Ｆに対して90゜〜110
゜範囲の傾斜角θで形成し、キャビティ２の開口縁に、
リップ６の下面９と側壁５との交角βがその傾斜角θと
同等範囲でリップ６を形成し、そのリップ６の突出端７
を円弧状に縁どると、側壁５とリップ下面９との接続部
分は、側壁５と突出部13との接続部分に対して半径方向
外方に位置するようになり、さらに、底面と突出部13と
底との接続部分とが決定する半径方向の間隔D2と半径方
向に対向する上記リップ６の突出端７間の間隔D1との関
係をD1＞D2とすると、ピストン１の上死点前近傍で噴射
を開始し上死点後の近傍で噴射が終了する燃料噴霧Ｆ
は、その飛翔途上で飛翔を阻害されることなくキャビテ
ィ２内に供給されるようになる。この結果、低速・軽負
荷時にあっても燃料噴霧Ｆがリップ６の上面に付着する
ことがない。The side wall 5 of the cavity 2 recessed on the piston top surface is set at 90 ° to 110 ° with respect to the fuel spray line F from the cavity axis side.
゜ formed at an inclination angle θ in the range,
The lip 6 is formed in a range where the intersection angle β between the lower surface 9 of the lip 6 and the side wall 5 is equal to the inclination angle θ, and the projecting end 7 of the lip 6
Is arcuately shaped, the connecting portion between the side wall 5 and the lip lower surface 9 is located radially outward with respect to the connecting portion between the side wall 5 and the projecting portion 13, and furthermore, the bottom surface and the projecting portion Assuming that D 1 > D 2 , the relationship between the radial interval D 2 determined by the connection portion 13 and the bottom and the interval D 1 between the protruding ends 7 of the lip 6 opposed in the radial direction is D 1 > D 2 . Fuel spray F that starts injection near the top dead center and finishes injection near the top dead center
Is supplied into the cavity 2 without being hindered during the flight. As a result, the fuel spray F does not adhere to the upper surface of the lip 6 even at low speed and light load.

一方、リップ下面９と上記側壁５とを連続する曲面で
接続すると、圧縮行程終期においてキャビティ２内に導
入し側壁５に沿って上昇するスキッシュ流Ｖをその曲面
の終端で剥離させ、再度キャビティ２の底側へ反転させ
るようになる。この結果、側壁５に付着した燃料膜は次
第に側壁５から剥離されつつ蒸気化し、衝突によって微
粒子化し蒸気化した燃料と共に、そのスキッシュ流Ｖ中
に巻込まれ上下方向に旋回する。したがって、底側に液
として滞留することがなくHCの排出量が減少する。On the other hand, when the lip lower surface 9 and the side wall 5 are connected by a continuous curved surface, the squish flow V introduced into the cavity 2 at the end of the compression stroke and rising along the side wall 5 is separated at the end of the curved surface, and the cavity 2 Will be turned to the bottom. As a result, the fuel film attached to the side wall 5 is gradually vaporized while being separated from the side wall 5, and is taken up in the squish flow V together with the fuel atomized and vaporized by the collision and swirls up and down. Therefore, the discharge amount of HC is reduced without staying as a liquid on the bottom side.

このように、燃料噴霧Ｆ及び混合気化した燃料のキャ
ビティ２外への流出は未然に防止され、リップ下に着火
性，火炎の伝播性能の優れた混合気（予混合気）を分布
させるようになる。つまり、低速・軽負荷にあっても部
分的にリッチな混合気を分布させて、迅速な着火と比較
的急速な火炎伝播燃焼が可能になり、第３図に示すよう
に低速・軽負荷時の燃料流量（Ｑ）においてHCを200ppm
以上低減できるようになる。In this way, the fuel spray F and the vaporized fuel are prevented from flowing out of the cavity 2, and a mixture (premixture) having excellent ignitability and flame propagation performance is distributed under the lip. Become. In other words, even at low speeds and light loads, a partially rich mixture is distributed, enabling rapid ignition and relatively rapid flame propagation combustion. As shown in FIG. 200ppm HC at fuel flow rate (Q)
The above can be reduced.

ところでキャビィ２を五角形の水平断面に形成し、各
コーナへ燃料噴霧を供給するように構成すると、HCをさ
らに減少できるようになる。By the way, if the cab 2 is formed in a pentagonal horizontal cross section to supply fuel spray to each corner, HC can be further reduced.

つまり、旋回流S1として導入される旋回流の強度を角
数の増加に応じピストン頂面で減衰して燃料噴霧Ｆの貫
徹力を相対的に増加させ、各コーナに対する燃料の到達
率を増加させることができる一方で、燃料噴霧Ｆの噴霧
飛翔距離l1を、リップ先端７間距離Ｄを同一とし、か
つ、従来例のようにキャビティ２の辺となる側壁５に円
周方向に対してほぼ直角に供給するように構成した四角
形キャビティ２の場合と比較すると、l1＝0.323Dからl1
＝0.353Dに増加させて空気に対する混合時間を増加さ
せ、突出部13周りに火炎伝播に必要な拡散混合気が生成
されるようになる。またこれは、拡散混合気の生成量の
増加に反比例して、側壁５への燃料の到達量を減少させ
るようにも機能する。この結果、低速・軽負荷にあって
噴射時期を実質的に遅角調節することになり、ピストン
１の実圧縮比を増加させた場合と同等の結果を得ること
ができるから、側壁５の燃料膜厚を薄くして側壁５の過
度の冷却を防止する。つまり、壁面の蒸発能力は低速・
軽負荷時にあっても一定以上に維持されるようになる。That is, attenuated by the piston top surface according to the intensity of the swirling flow that is introduced as swirling flow S 1 to an increase in the angular speed relatively increase the penetration of fuel spray F and increase the arrival rate of fuel to each corner On the other hand, the spray distance l 1 of the fuel spray F is set to be equal to the distance D between the lip tips 7 and, as in the conventional example, to the side wall 5 which is the side of the cavity 2 in the circumferential direction. Compared to the case of a square cavity 2 configured to supply at almost right angles, l 1 = 0.323D to l 1
= 0.353D to increase the mixing time for air, so that a diffusion mixture necessary for flame propagation is generated around the protrusion 13. It also functions to reduce the amount of fuel that reaches the side walls 5 in inverse proportion to the increase in the amount of diffusion mixture produced. As a result, the injection timing is substantially retarded at low speed and light load, and the same result as when the actual compression ratio of the piston 1 is increased can be obtained. The film thickness is reduced to prevent excessive cooling of the side wall 5. In other words, the evaporation capacity of the wall is low
Even when the load is light, it is maintained at a certain level or more.

したがって各コーナ内には、スワール旋回部24内を部
分的にリッチ濃度の混合気を生成するゾーンとして活用
できるようになり、コーナの円周方向前後のスワール旋
回部24内には、火炎伝播に適した濃度の拡散混合気が存
在するようになる。つまり、低速・軽負荷運転時のキャ
ビティ２内の燃焼条件（混合気の濃度、キャビティ内雰
囲気温度等）が改善され、HCの排出量が減少する。Therefore, in each corner, the inside of the swirl swirl part 24 can be partially used as a zone for generating an air-fuel mixture of a rich concentration, and in the swirl swirl part 24 around the corner in the circumferential direction, the flame spreads. A suitable concentration of diffusion mixture will be present. That is, the combustion conditions (concentration of air-fuel mixture, atmosphere temperature in the cavity, etc.) in the cavity 2 during low-speed / light-load operation are improved, and the amount of HC emission is reduced.

着火が開始すると、火炎が円周方向に伝播され、比較
的急速に燃焼する。即ち燃焼温度が上昇して一定のエン
ジン出力が確保され、HCの排出量が減少する。When ignition begins, the flame propagates circumferentially and burns relatively quickly. That is, the combustion temperature rises, a constant engine output is secured, and the amount of HC emission decreases.

次に、上述のキャビティ２を備えたピストン１を、低
圧縮比過給エンジン用として採用した場合のHCの排出量
に関する四角形のキャビティ２と五角形のキャビティを
第４図乃至第７図に示すテストデータに基づいて比較す
る。Next, a square cavity 2 and a pentagonal cavity shown in FIGS. 4 to 7 are tested for the HC discharge amount when the piston 1 having the above-described cavity 2 is used for a low compression ratio supercharged engine. Compare based on data.

第４図は、回転数が変化しても四角形のキャビティ２
に対して五角形のキャビティの性能が優れていること、
また、回転数の大小を問わず四角形のキャビティ２に対
して五角形のキャビティの性能が優れていることを示
し、第５図は回転数、圧縮比を固定し、噴射時期を変化
させた場合において、噴射時期を上死点前約18゜とする
とHCの排出量が減少することを示している。FIG. 4 shows that even if the rotational speed changes,
That the performance of the pentagonal cavity is excellent,
In addition, it shows that the performance of the pentagonal cavity is superior to that of the rectangular cavity 2 regardless of the rotation speed, and FIG. 5 shows the case where the rotation speed and the compression ratio are fixed and the injection timing is changed. This indicates that when the injection timing is about 18 ° before the top dead center, the amount of HC emission decreases.

一方、第６図及び第７図は、回転数1000RPM,2200RPM
におけるHCの排出量と圧縮比εとの関係を調べたもので
ある。この結果、各回転数について圧縮比εを下げるこ
とによってHCの排出量が減少することが確認できた。On the other hand, FIGS. 6 and 7 show the rotation speeds of 1000 RPM and 2200 RPM.
The relationship between the amount of HC discharged and the compression ratio ε was examined. As a result, it was confirmed that the HC discharge amount was reduced by reducing the compression ratio ε for each rotation speed.

以上の結果から明らかなように、上述のような構成の
五角形のキャビティは、低圧縮比エンジンに好適であ
り、圧縮比εを約15.4、燃料の噴射時期を約18゜（BTD
C）とすると、着実な着火と火炎伝播燃焼が保障される
ようになる。As is clear from the above results, the pentagonal cavity having the above configuration is suitable for a low compression ratio engine, and has a compression ratio ε of about 15.4 and a fuel injection timing of about 18 ° (BTD
If C), steady ignition and flame spread combustion are guaranteed.

したがって、低圧縮比エンジンにおいて自動タイマを
用いて噴射時期の調整必要性がなく、低速・低負荷運転
にあっても青白煙（HC）、刺激臭を減少でき、燃費を向
上できる。Therefore, there is no need to adjust the injection timing using an automatic timer in a low compression ratio engine, and blue-white smoke (HC) and irritating odor can be reduced even in low-speed / low-load operation, and fuel efficiency can be improved.

尚、上記テストデータから明らかなように四角形のキ
ャビティ２を形成する場合には、四角形を対角線上に拡
大して各コーナ14〜17へ燃料噴霧を供給するようにすれ
ば、その燃焼性能（HC等）を向上できる。As is apparent from the above test data, when forming the rectangular cavity 2, if the square is expanded diagonally to supply the fuel spray to each of the corners 14 to 17, the combustion performance (HC Etc.) can be improved.

［発明の効果］ 以上要するに本発明によれば、リップの強度を確保で
きると共に、噴射期間が長い運転領域においても、上死
点の前後における燃料噴霧のピストン頂面及びキャビテ
ィ底への滞留を防止でき、HCの排出量低減が達成される
という優れた効果を発揮する。[Effects of the Invention] In summary, according to the present invention, the strength of the lip can be ensured, and the fuel spray can be prevented from remaining on the piston top surface and the cavity bottom before and after the top dead center even in the operation region where the injection period is long. And an excellent effect that reduction of HC emission is achieved.

【図面の簡単な説明】[Brief description of the drawings]

第１図はこの発明の好適一実施例を示す断面図、第２図
は第１図のII−II線矢視図、第３図はHC性能を示す性能
線図、第４図乃至第７図は四角形と五角形のHC性能を示
す性能線図である。 図中、１はピストン、２はキャビティ、５は側壁、６は
リップ、14〜18はコーナである。FIG. 1 is a sectional view showing a preferred embodiment of the present invention, FIG. 2 is a view taken along the line II-II of FIG. 1, FIG. 3 is a performance diagram showing HC performance, and FIGS. The figure is a performance diagram showing HC performance of a square and a pentagon. In the figure, 1 is a piston, 2 is a cavity, 5 is a side wall, 6 is a lip, and 14 to 18 are corners.

Claims (1)

(57)【特許請求の範囲】(57) [Claims] 【請求項１】ピストン頂面に凹設されたキャビティの側
壁に、キャビティ軸心側からの燃料噴霧に対して、ピス
トン軸方向に切った断面でみて略直角に傾斜した傾斜面
を形成し、上記キャビティの開口縁に、突出端が断面円
弧状で且つ下面が直線状のリップを設けると共に、該リ
ップの下面と上記側壁の傾斜面とを、その交角が90゜〜
110゜になるように形成して曲面にて連続させ、半径方
向に対向する上記リップの突出端間の間隔をD1、キャビ
ティ底面に形成された円錐形状の突出部の底と上記側壁
との接続部分の半径方向の間隔をD2、上記リップの下面
と側壁との接続部の半径方向の間隔をD3、上記キャビテ
ィの最大深さをＨとしたときに、D1＞D2、D3/H≒４とし
たことを特徴とするエンジンのピストン。1. A side wall of a cavity concavely formed on a top surface of a piston is formed with an inclined surface which is substantially perpendicular to fuel spray from a cavity axis side when viewed in a cross section cut in a piston axis direction. At the opening edge of the cavity, a protruding end is provided with a lip having an arc-shaped cross section and a lower surface is linear, and an intersection angle between the lower surface of the lip and the inclined surface of the side wall is 90 ° or more.
It is formed so as to be 110 ° and is continuous on a curved surface, the interval between the protruding ends of the lip facing in the radial direction is D 1 , and the bottom of the conical protruding portion formed on the bottom surface of the cavity and the side wall the radial spacing of the connecting portion D 2, the radial spacing of the connecting portion between the lower surface and the side walls of the lip D 3, the maximum depth of the cavity is taken as H, D 1> D 2, D An engine piston characterized by 3 / H ≒ 4.
JP1067585A 1989-03-22 1989-03-22 Engine piston Expired - Lifetime JP2697100B2 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
JP1067585A JP2697100B2 (en) 1989-03-22 1989-03-22 Engine piston

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP1067585A JP2697100B2 (en) 1989-03-22 1989-03-22 Engine piston

Publications (2)

Publication Number Publication Date
JPH02248615A JPH02248615A (en) 1990-10-04
JP2697100B2 true JP2697100B2 (en) 1998-01-14

Family

ID=13349140

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Application Number Title Priority Date Filing Date
JP1067585A Expired - Lifetime JP2697100B2 (en) 1989-03-22 1989-03-22 Engine piston

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Country Link
JP (1) JP2697100B2 (en)

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2861809A1 (en) * 2003-11-03 2005-05-06 Renault Sas PISTON FOR COMBUSTION CHAMBER FOR REDUCING SOOT EMISSIONS
FR2872855A1 (en) * 2004-07-09 2006-01-13 Renault Sas INTERNAL COMBUSTION ENGINE COMPRISING A PISTON HAVING A TRUNCONIC WALL CAVITY

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5474012A (en) * 1977-11-24 1979-06-13 Hino Motors Ltd Combustion chamber for diesel engine
JPS58102720A (en) * 1981-12-15 1983-06-18 Matsushita Electric Works Ltd Synthetic resin molded product
JPS58189321U (en) * 1982-06-10 1983-12-16 日産自動車株式会社 Direct injection diesel engine
JPS59150942U (en) * 1983-03-28 1984-10-09 日産自動車株式会社 Combustion chamber of direct injection diesel engine

Also Published As

Publication number Publication date
JPH02248615A (en) 1990-10-04

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