JP5322407B2 - Engine combustion chamber structure - Google Patents

Engine combustion chamber structure Download PDF

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JP5322407B2
JP5322407B2 JP2007178060A JP2007178060A JP5322407B2 JP 5322407 B2 JP5322407 B2 JP 5322407B2 JP 2007178060 A JP2007178060 A JP 2007178060A JP 2007178060 A JP2007178060 A JP 2007178060A JP 5322407 B2 JP5322407 B2 JP 5322407B2
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combustion chamber
wall
axis
intake valve
cylinder head
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JP2009013915A (en
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和献 長谷川
豊誠 山内
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Subaru Corp
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Fuji Jukogyo KK
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    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/10—Internal combustion engine [ICE] based vehicles
    • Y02T10/12—Improving ICE efficiencies

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Description

本発明は、燃焼室全体にわたるタンブルの生成に加えて吸気バルブ直下にタンブル流と逆タンブル流との同時生成も可能なエンジンの燃焼室構造に関するものである。   The present invention relates to a combustion chamber structure of an engine capable of simultaneously generating a tumble flow and a reverse tumble flow directly under an intake valve in addition to generating a tumble over the entire combustion chamber.

従来の燃焼室構造として、例えば図８に示すような、充填効率の低下を阻止しつつタンブル流を発生させる、とされた構造のものがある（特許文献１）。
この構造のものにおいては、吸気弁１００の周縁部と弁座１０１間に形成される開口に対面配置されてこの開口からの吸入空気又は燃料を含んだ吸入空気の流入を抑制する流入抑制壁１０２がシリンダヘッド内壁１０３ａ上に形成され、この流入抑制壁１０２は、図８（Ａ）に示すように各吸気弁１００の周縁部に沿って両吸気弁１００の軸線を含む平面Ｋ−Ｋに対して排気弁１０４と反対側から平面Ｋ−Ｋより最も離れた吸気弁１００の周縁部まで角度ａに亘って延びて、両吸気弁１００の間で端部壁１０５により互いに連結され、この端部壁１０５は、平面Ｋ−Ｋに対して排気弁１０４と反対側に位置している。
そして、吸気弁１００が開弁すると当該吸気弁１００と流入抑制壁１０２間からは吸入空気又は燃料を含んだ吸入空気はあまり流入せず、大部分は流入抑制壁１０２が設けられていない吸気弁１００の開口部分から燃焼室１０６内に流入する。このとき平面Ｋ−Ｋに対して流入抑制壁１０２と反対側の吸気弁１００の開口部分から流入した吸入空気又は燃料を含んだ吸入空気は、図８（Ｂ）において矢印Ｓ１で示すように排気弁１０４の下方に向かい、次いで矢印Ｓ２で示すように向きを変えてピストン１０７の頂面に沿って流れる。このため燃焼室１０６内には水平軸線周りの旋回流、即ちタンブル流が発生する。 As a conventional combustion chamber structure, for example, there is a structure that generates a tumble flow while preventing a decrease in charging efficiency as shown in FIG. 8 (Patent Document 1).
In this structure, the inflow suppressing wall 102 is disposed facing the opening formed between the peripheral portion of the intake valve 100 and the valve seat 101 and suppresses inflow of intake air or intake air containing fuel from the opening. Is formed on the cylinder head inner wall 103a, and the inflow suppressing wall 102 is formed along a peripheral edge of each intake valve 100 with respect to a plane KK including the axis of both intake valves 100 as shown in FIG. Then, it extends over an angle a from the opposite side of the exhaust valve 104 to the peripheral edge of the intake valve 100 farthest from the plane KK, and is connected to each other by an end wall 105 between the intake valves 100. The wall 105 is located on the opposite side of the exhaust valve 104 with respect to the plane KK.
When the intake valve 100 is opened, intake air or intake air containing fuel does not flow so much between the intake valve 100 and the inflow suppression wall 102, and most of the intake valves are not provided with the inflow suppression wall 102. It flows into the combustion chamber 106 from the opening portion of 100. In this case the intake air containing the inflow suppressing wall 102 with respect to the plane K-K of the intake air or fuel has flowed from the opening portion on the opposite side of the intake valve 100, as indicated by the arrow S 1 in FIG. 8 (B) downwardly of the exhaust valve 104, and then flows along the top face of the piston 107 in different directions as indicated by the arrow S 2. Therefore, a swirling flow around the horizontal axis, that is, a tumble flow is generated in the combustion chamber 106.

しかしながら、この燃焼室構造のように、流入抑制壁１０２が上述のように吸気弁１００の周縁部まで角度ａに亘って延びて、両吸気弁１００の間で端部壁１０５により互いに連結されるように形成されたものでは、タンブル流を強化させる場合には効果的かもしれないが、単一方向の流速の増加によるタンブル流の強化は、乱流生成の不均一性が高いためか、サイクル間での燃焼が安定せず燃焼変動の改善に繋がらない場合もある。したがって、燃焼室全体にわたるタンブル流の強化は、言い換えれば単一方向の吸入空気の流速の増加に繋がり、燃焼室内の吸入空気又は燃料を含んだ吸入空気の流速を上げずにその乱れを助長して燃焼速度を速め、良好な燃焼を得るには適していない構造となっている。
特開平８−２０００７５号公報（第３〜４頁、図１，２） However, like this combustion chamber structure, the inflow suppressing wall 102 extends over the angle a to the peripheral edge of the intake valve 100 as described above, and is connected to each other by the end wall 105 between the intake valves 100. It may be effective when strengthening the tumble flow, but the enhancement of the tumble flow by increasing the unidirectional flow velocity is due to the high non-uniformity of turbulent flow generation. Combustion may not be stable and may not improve combustion fluctuation. Therefore, the strengthening of the tumble flow throughout the combustion chamber, in other words, increases the flow velocity of the intake air in a single direction, and promotes the turbulence without increasing the flow velocity of the intake air or the intake air containing fuel in the combustion chamber. Therefore, the structure is not suitable for increasing the combustion speed and obtaining good combustion.
JP-A-8-200075 (pages 3 to 4, FIGS. 1 and 2)

解決しようとする課題は、燃焼室内の吸入空気又は燃料を含んだ吸入空気の流速を大きく上げることなくその乱れを助長して燃焼速度を速め、良好な燃焼を得るようにする点である。   The problem to be solved is that the intake air in the combustion chamber or the intake air containing fuel does not greatly increase the flow velocity of the combustion chamber to promote the turbulence, thereby increasing the combustion speed and obtaining good combustion.

本発明の請求項１に係るエンジンの燃焼室構造は、燃焼室を形成するシリンダヘッドにカムシャフトにより往復動される２つの吸気バルブと１つ又は２つの排気バルブとが配されるエンジンの燃焼室構造において、前記カムシャフトの軸線に垂直な軸線の方向には前記吸気バルブに近接する前記シリンダヘッドの内壁の所定範囲に延在し、且つ、前記カムシャフトの軸線の方向には前記シリンダヘッドの内壁から前記吸気バルブの傘部の外周縁近傍まで突設する突条壁を形成し、該突条壁は前記カムシャフトの軸線に対して垂直に交わる前記燃焼室の中心軸に対して互いに対称をなすようにしたもので、このような構造をなす突条壁は、排気ポート開口部側に流れを誘起するように作用し、吸気バルブ外周のうち、突条壁を避けて、燃焼室略中央側と、外周縁との間の所定隙間からそれぞれ流入した吸入空気の流れが、吸気バルブの傘部の中央に向かって巻き戻り、強く小径のタンブル、逆ダンブル状の循環流を生成することができ、その強く小径のタンブル、逆ダンブル状の循環流は渦径が小さく比較的強いために圧縮行程中も維持残存する結果、燃焼室内の吸入空気又は燃料を含んだ吸入空気の流速を大きく上げることなく、燃焼室内に安定的に適度な乱れを生成させることによりサイクル間の安定性を高め、複数サイクル間にわたる平均した燃焼速度の高い、すなわち一般的に言われる燃焼速度の高い、より良好な燃焼を得ることができる。 The combustion chamber structure of an engine according to claim 1 of the present invention is a combustion of an engine in which two intake valves and one or two exhaust valves reciprocated by a camshaft are arranged on a cylinder head forming the combustion chamber. In the chamber structure, the cylinder head extends in a predetermined range of the inner wall of the cylinder head close to the intake valve in the direction of the axis perpendicular to the axis of the cam shaft , and the cylinder head in the direction of the axis of the cam shaft A rib wall projecting from the inner wall of the intake valve to the vicinity of the outer peripheral edge of the umbrella portion of the intake valve, the rib walls being mutually perpendicular to the central axis of the combustion chamber perpendicular to the axis of the camshaft The rib wall having such a structure acts to induce a flow on the exhaust port opening side, avoids the rib wall on the outer periphery of the intake valve, and avoids the rib wall. Abbreviation The flow of intake air that has flowed in through a predetermined gap between the central side and the outer peripheral edge rewinds toward the center of the umbrella portion of the intake valve to generate a strong, small-diameter tumble and reverse dumble-like circulation flow The strong and small-diameter tumble and reverse dumble-shaped circulation flows have a small vortex diameter and are relatively strong, so that they remain and maintain during the compression stroke. As a result, the flow velocity of the intake air or the intake air containing fuel is increased. Increases the stability between cycles by stably generating moderate turbulence in the combustion chamber without increasing, and the average burning rate over multiple cycles is high, that is, the burning rate generally said is better Can be obtained.

本発明のエンジンの燃焼室構造は、シリンダヘッドの内壁の適宜位置に突条壁を設けることにより、燃焼室内にタンブル流に加えて吸気バルブ直下に小径のタンブル流と逆タンブル流とを生成させ、燃焼室内に安定的に適度な乱れを生成させることによりサイクル間の安定性を高め、複数サイクル間にわたる平均した燃焼速度の高い、より良好な燃焼を得ることができる利点がある。   In the combustion chamber structure of the engine of the present invention, a rib wall is provided at an appropriate position on the inner wall of the cylinder head to generate a tumble flow and a reverse tumble flow directly below the intake valve in addition to the tumble flow in the combustion chamber. There is an advantage that it is possible to improve the stability between cycles by stably generating appropriate turbulence in the combustion chamber, and to obtain better combustion with a high average combustion speed over a plurality of cycles.

本発明の第１の実施の形態に係るエンジンの燃焼室構造を図１，２を参照して説明する。
本燃焼室構造は、図１，２に示すように、燃焼室１を構成するシリンダヘッド２に２つの吸気バルブ３と２つの排気バルブ（図示せず）とが配され、これらバルブで囲まれる上記シリンダヘッド２の上壁中央に点火プラグ（図示せず）が配される構造をなし、シリンダヘッド２に成形された吸気ポート４ａ，４ｂの一方端部で、燃焼室１に臨むシリンダヘッド２の開口口にバルブシート５ａ，５ｂがそれぞれ取着され、また、排気ポート６ａ，６ｂの一方端部で、燃焼室１に臨むシリンダヘッド２の開口口にバルブシート７ａ，７ｂがそれぞれ取着され、例えば図２に示すように、吸気ポート４ａに配される吸気バルブ３は同図中の矢印方向に上下動し、吸気バルブ３の閉成時には当該吸気バルブ３の傘部３ａがバルブシート５ａに当接する一方、吸気バルブ３の開成時（同図は最大開成時を示す）には、吸気バルブ３の傘部３ａとバルブシート５ａとの間に隙間（この隙間をカーテンエリアとも言う。）が生じて、かかる隙間を通過する吸入空気又は燃料を含んだ吸入空気が燃焼室１内に流入するようになっている。
そして、本燃焼室構造においては、各吸気バルブ３のそれぞれに近接するシリンダヘッド２の内壁に、図１に示すように、各吸気バルブ３の傘部３ａの外周縁（尚、図１において、この外周縁は、バルブシート５ａ，５ｂの外周縁とほぼ一致するとみなしてよい。）との間に所定隙間が形成されるように、本実施の形態ではこれら吸気バルブ３の対称軸をも兼ねる燃焼室１の垂直方向の中心軸Ｎに対し対称をなし、且つ、互いに独立をなして突条壁８ａ，８ｂがそれぞれ突設されている。ところで、燃焼室１の中心軸Ｎは、当該燃焼室１の水平方向の中心軸（＝吸気バルブを往復動させるカムシャフト軸に平行な方向軸）Ｍに垂直をなすものである。
尚、図２において、９はシリンダヘッド２とともに燃焼室１を構成するシリンダブロックであり、１０は、シリンダブロック９内を摺動するピストンである。 An engine combustion chamber structure according to a first embodiment of the present invention will be described with reference to FIGS.
In this combustion chamber structure, as shown in FIGS. 1 and 2, two intake valves 3 and two exhaust valves (not shown) are arranged in a cylinder head 2 constituting the combustion chamber 1 and are surrounded by these valves. The cylinder head 2 has a structure in which an ignition plug (not shown) is arranged at the center of the upper wall of the cylinder head 2, and the cylinder head 2 facing the combustion chamber 1 at one end of intake ports 4 a and 4 b formed in the cylinder head 2. The valve seats 5a and 5b are respectively attached to the opening of the cylinder head, and the valve seats 7a and 7b are attached to the opening of the cylinder head 2 facing the combustion chamber 1 at one end of the exhaust ports 6a and 6b. For example, as shown in FIG. 2, the intake valve 3 disposed in the intake port 4a moves up and down in the direction of the arrow in the figure, and when the intake valve 3 is closed, the umbrella portion 3a of the intake valve 3 is moved to the valve seat 5a. Abut On the other hand, when the intake valve 3 is opened (the figure shows the maximum opened state), a gap (this gap is also called a curtain area) is generated between the umbrella portion 3a of the intake valve 3 and the valve seat 5a. The intake air passing through the gap or the intake air containing fuel flows into the combustion chamber 1.
In this combustion chamber structure, as shown in FIG. 1, on the inner wall of the cylinder head 2 adjacent to each intake valve 3, the outer peripheral edge of the umbrella portion 3a of each intake valve 3 (in FIG. 1, In this embodiment, the outer peripheral edge also serves as the axis of symmetry of the intake valves 3 so that a predetermined gap is formed between the outer peripheral edge and the outer peripheral edge of the valve seats 5a and 5b. The rib walls 8a and 8b are provided so as to be symmetrical with respect to the central axis N in the vertical direction of the combustion chamber 1 and independent of each other. By the way, the central axis N of the combustion chamber 1 is perpendicular to the horizontal central axis (= direction axis parallel to the camshaft axis for reciprocating the intake valve) of the combustion chamber 1.
In FIG. 2, 9 is a cylinder block that constitutes the combustion chamber 1 together with the cylinder head 2, and 10 is a piston that slides in the cylinder block 9.

このような突条壁８ａ，８ｂは、吸気バルブ外周から燃焼室１に流入する吸入空気が、排気ポート開口部側に流れを誘起させるべく設けられたこれら突条壁８ａ，８ｂを避けて燃焼室１の略中央側に向かう流れと燃焼室１の外周側に向かう流れに別れて流入し、それぞれ吸気バルブの傘部の中央に向かって巻き戻って、強く小径のタンブル、逆タンブル状の循環流を生成するために、以下の条件を満たす範囲に突設させることが必要になる。尚、突条壁８ａ，８ｂは、上述のように中心軸Ｎについて対称となる形状をなしており、ここでは突条壁８ａについて説明する。
今、吸気バルブ３が配される吸気ポート４ａの中心軸をＹ軸とし、このＹ軸に垂直でシリンダヘッド３の内壁に向かう方向軸をＸ軸とし、吸気バルブ３のバルブリフトの方向軸をＺ軸（図２参照）とし、更に、上述のように吸気バルブを往復動させるカムシャフト軸に平行な方向軸、即ち、燃焼室１の水平方向の中心軸をＭ軸とすると、
まず、突条壁８ａが、シリンダヘッド２の内壁に沿って、吸気バルブ３の傘部３ａとシリンダヘッド２の内壁との隙間が最短となる当該内壁の位置（図１ではＡで示す）と、Ｚ軸上の点を始点としＸ軸に対し反時計回り方向に６０゜をなす半直線が交わる当該内壁の位置（図１ではＢで示す）とのうちでＹ軸により近い方の当該内壁の位置から、Ｚ軸上の点を始点としＭ軸に対し時計回り方向に４５゜をなす半直線が交わる当該内壁の位置（図１ではＣで示す）と、Ｚ軸上の点を始点としＸ軸に対し時計回り方向に４５゜をなす半直線が交わる当該内壁の位置（図１ではＤで示す）とのうちでＸ軸により遠い方の当該内壁の位置までの範囲内にあること、そして、Ｚ軸上の点と当該突条壁８ａの両端部とをそれぞれ結んで形成される挟角Ｋが１０゜以上をなし、少なくとも一方の上記端部の高さ長がＺ軸方向に平行な長さＬに換算して吸気バルブ３のバルブ径Ｄの０．１倍以上となるようにすることである（図２参照）。
尚、突条壁８ｂについては説明を割愛するが、突条壁８ｂについても突条壁８ａに準ずることはもちろんである。 Such ridge walls 8a and 8b avoid the ridge walls 8a and 8b provided so that the intake air flowing from the outer periphery of the intake valve into the combustion chamber 1 induces a flow on the exhaust port opening side. It flows separately into a flow toward the substantially central side of the chamber 1 and a flow toward the outer peripheral side of the combustion chamber 1, rewinds toward the center of the umbrella portion of the intake valve, and circulates in a strongly small-diameter tumble and reverse tumble shape. In order to generate a flow, it is necessary to project it in a range that satisfies the following conditions. Note that the ridge walls 8a and 8b have a symmetrical shape with respect to the central axis N as described above, and the ridge wall 8a will be described here.
Now, the central axis of the intake port 4a where the intake valve 3 is arranged is the Y axis, the direction axis perpendicular to the Y axis and directed to the inner wall of the cylinder head 3 is the X axis, and the direction axis of the valve lift of the intake valve 3 is Assuming that the Z axis (see FIG. 2) and the direction axis parallel to the camshaft axis for reciprocating the intake valve as described above, that is, the horizontal central axis of the combustion chamber 1 is the M axis,
First, the protruding wall 8a is positioned along the inner wall of the cylinder head 2 so that the gap between the umbrella portion 3a of the intake valve 3 and the inner wall of the cylinder head 2 is the shortest (indicated by A in FIG. 1). The inner wall that is closer to the Y axis among the positions of the inner wall (indicated by B in FIG. 1) where the half line that forms a 60 ° counterclockwise direction with respect to the X axis starts from a point on the Z axis. The position of the inner wall where the half line that makes a 45 ° clockwise rotation with respect to the M axis intersects with the point on the Z axis (indicated by C in FIG. 1), and the point on the Z axis. It is within the range to the position of the inner wall farther from the X axis among the positions of the inner wall (indicated by D in FIG. 1) where the half line forming 45 ° in the clockwise direction with respect to the X axis intersects. And there is an included angle K formed by connecting a point on the Z axis and both ends of the protruding wall 8a. By making it at least 0 °, the height length of at least one of the end portions is converted to a length L parallel to the Z-axis direction so that it is at least 0.1 times the valve diameter D of the intake valve 3. Yes (see FIG. 2).
Note that the description of the ridge wall 8b is omitted, but the ridge wall 8b is of course similar to the ridge wall 8a.

この条件を満たす突条壁として、典型例を示したものが本実施の形態に係る図１，２に示した突条壁８ａ，８ｂである。
このうち突条壁８ａは、図１に示すように、吸気バルブ３の傘部３ａの外周縁に対向する側面８ａ１が円弧状に形成され、この側面８ａ１と上記外周縁との間に所定隙間が形成される構造をなし、この円弧の両端部（突条壁の両端部）を結ぶ当該円弧の弦線の二等分線が当該突条壁８ａの挟角Ｋの二等分線とほぼ一致するような構造とした場合のもので、当然のことながら、当該円弧状をなす突条壁８ａは上記範囲内に形成されていることは言うまでもない。そして、本実施の形態では、この突条壁８ａの上面８ａ２（図１参照）は、図２に示すように、シリンダヘッド２のシリンダブロック９との重ね合わせ面（以下、デッキ面という。）近傍にまで達しており、この突条壁８ａの上述した高さ長の、Ｚ軸方向に換算された長さＬは、上記条件下で、本実施の形態ではデッキ面から吸気バルブ３の最大開成時の下降量に略等しい長さとなっている。 A typical example of the projecting wall satisfying this condition is the projecting wall 8a, 8b shown in FIGS. 1 and 2 according to the present embodiment.
Among projection wall 8a, as shown in FIG. 1, a side 8a 1 facing the outer peripheral edge of the umbrella portion 3a of the intake valve 3 is formed in an arc shape, between the side surface 8a 1 and the outer peripheral edge A bisector of the chord line of the arc connecting the both ends of the arc (both ends of the ridge wall) is a bisector of the included angle K of the ridge wall 8a. Needless to say, the projecting wall 8a having the arc shape is formed within the above-mentioned range. In the present embodiment, the upper surface 8a 2 (see FIG. 1) of the ridge wall 8a is referred to as an overlapping surface (hereinafter referred to as a deck surface) with the cylinder block 9 of the cylinder head 2 as shown in FIG. ) The length L of the ridge wall 8a converted to the Z-axis direction of the ridge wall 8a is in the vicinity of the intake valve 3 from the deck surface in the present embodiment under the above conditions. The length is approximately equal to the amount of descent at maximum opening.

このような突条壁８ａ，８ｂが突設された燃焼室１内では、例えば吸気バルブ３の開成時に吸気ポート４ａから燃焼室１内に流入した吸入空気又は燃料を含んだ吸入空気の流れは、図１中の矢印で示すような流れとなって、吸気バルブ側及び排気バルブ側の両方に分かれて流入される。この流れの様子を燃焼室１の側断面方向から視ると、図２中の矢印で示すような流れを生じ、このうち符号イの流れは吸気バルブ側に生成される小径の逆タンブル流を、また、符号ロの流れは排気バルブ側に生成される小径のタンブル流を示し（以下、符号イと符号ロとを合わせて双子渦と称する。）、符号ハ及び符号ホの流れは燃焼室１内全体にわたり生成されるタンブル流を、符号ニの流れは燃焼室１内全体にわたり生成される逆タンブル流を示している。このような流れの生成により、燃焼室１内の吸入空気又は燃料を含んだ吸入空気の流速を大きく上げずにその乱れを助長して燃焼速度を速め、良好な燃焼を得ることができる。   In the combustion chamber 1 in which the protruding walls 8a and 8b are projected, for example, the flow of the intake air including the intake air or the fuel that flows into the combustion chamber 1 from the intake port 4a when the intake valve 3 is opened is The flow is as shown by the arrows in FIG. 1, and flows separately into both the intake valve side and the exhaust valve side. When the state of this flow is viewed from the side cross-sectional direction of the combustion chamber 1, a flow as indicated by an arrow in FIG. 2 is generated, and the flow of the symbol a is a small-diameter reverse tumble flow generated on the intake valve side. Further, the flow of the symbol B indicates a small-diameter tumble flow generated on the exhaust valve side (hereinafter, the symbols A and B are collectively referred to as a twin vortex), and the flows of the symbols C and E are the combustion chambers. The tumble flow generated over the entire combustion chamber 1 indicates the reverse tumble flow generated over the entire combustion chamber 1. By generating such a flow, the turbulence can be promoted without increasing the flow velocity of the intake air or the intake air containing fuel in the combustion chamber 1 to increase the combustion speed, and good combustion can be obtained.

ところで、本実施の形態に係る突条壁８ａ及び突条壁８ｂのうち、例えば突条壁８ａは、吸気バルブ３の傘部３ａの外周縁に対向する側面８ａ１が円弧状に形成されたものであったが、図３に示すように、突条壁８ａ，８ｂに代えて突条壁１５ａ，１５ｂとしてもよい。かかる突条壁１５ａ，１５ｂのうち、例えば突条壁１５ａは、突条壁８ａの円弧状側面８ａ１を直線状側面１５ａ１としたものであり、この側面１５ａ１の両端部（突条壁の両端部）の略中央で吸気バルブ３の傘部３ａの外周縁との間に所定隙間が形成されるような構造とした場合のものであり、このような場合のものにあっても、燃焼室１内にタンブル流に加えて吸気バルブ直下に双子渦を生成することができることはもちろんである。尚、図３において、図１，２の構成要素と同一のものには同一番号を付し、その説明は割愛する。 Meanwhile, among the ridges walls 8a and ridges wall 8b according to the present embodiment, for example, ridges wall 8a is a side 8a 1 facing the outer peripheral edge of the umbrella portion 3a of the intake valve 3 is formed in a circular arc shape However, as shown in FIG. 3, the rib walls 15a and 15b may be used instead of the rib walls 8a and 8b. Such protrusion walls 15a, of 15b, for example, protrusion walls 15a is in the arc-shaped side face 8a 1 of the projection wall 8a those straight sides 15a 1, both end portions (ridge wall of the side surface 15a 1 In the case where a predetermined gap is formed between the outer peripheral edge of the umbrella portion 3a of the intake valve 3 at substantially the center of both ends of the Of course, in addition to the tumble flow in the combustion chamber 1, a twin vortex can be generated directly under the intake valve. In FIG. 3, the same components as those in FIGS.

次に、本発明の第２の実施の形態に係る燃焼室構造を図４を参照して説明する。尚、これら図４において、図１〜３の構成部材と同一のものには同一番号を付し、その説明は割愛する。
本燃焼室構造においては、燃焼室２０に当該燃焼室２０の垂直方向の中心軸Ｎに対し対称をなし、且つ、互いに独立をなして突条壁２１ａ，２１ｂを突設させた構造をなすものである。尚、突条壁２１ａ，２１ｂは、上述のように中心軸Ｎについて対称となる形状をなしており、ここでは突条壁２１ａについて説明する。
この突条壁２１ａは、本燃焼室構造のように吸気バルブ３等のバルブと燃焼室２０の内壁との間隔が大きい場合に効果的である。
このような突条壁２１ａは、上記条件を満たす範囲内で、吸気バルブ３が配される近傍の、燃焼室２０の内壁の隅Ｒ部の一つに突設され、吸気バルブ３の傘部３ａの外周縁に対向する側面２１ａ１が円弧状に形成されてこの側面２１ａ１と上記外周縁との間に所定隙間が形成されるが、この突条壁２１ａの上面２１ａ２の面積が小さくなること等から突条壁２１ａのマスが小さくなる。このため、圧縮比をあまり上げたくないような場合に好適である。 Next, a combustion chamber structure according to a second embodiment of the present invention will be described with reference to FIG. 4, the same components as those in FIGS. 1 to 3 are denoted by the same reference numerals, and the description thereof is omitted.
In this combustion chamber structure, the combustion chamber 20 is symmetrical with respect to the central axis N in the vertical direction of the combustion chamber 20 and has a structure in which the projecting walls 21a and 21b project from each other independently of each other. It is. Note that the ridge walls 21a and 21b have a symmetric shape with respect to the central axis N as described above, and the ridge wall 21a will be described here.
The rib wall 21a is effective when the distance between the valve such as the intake valve 3 and the inner wall of the combustion chamber 20 is large as in the present combustion chamber structure.
Such a ridge wall 21a protrudes from one of the corners R of the inner wall of the combustion chamber 20 in the vicinity where the intake valve 3 is disposed within a range satisfying the above-described conditions. Although side 21a 1 opposite to the outer peripheral edge of 3a predetermined gap between the side surface 21a 1 and the outer peripheral edge is formed in an arc shape is formed, a small area of the upper surface 21a 2 of the ridge wall 21a As a result, the mass of the ridge wall 21a becomes smaller. For this reason, it is suitable when it is not desired to increase the compression ratio too much.

次に、本発明の第３の実施の形態に係る燃焼室構造を図５を参照して説明する。尚、これら図５において、図１〜４の構成部材と同一のものには同一番号を付し、その説明は割愛する。
本燃焼室構造においては、燃焼室３０に当該燃焼室３０の垂直方向の中心軸Ｎに対し対称をなし、且つ、互いに独立をなして突条壁３１ａ，３１ｂを突設させた構造をなすものである。尚、突条壁３１ａ，３１ｂは、上述のように中心軸Ｎについて対称となる形状をなしており、ここでは突条壁３１ａについて説明する。
この突条壁３１ａは、本燃焼室構造のように燃焼室３０の中心軸Ｍ付近の内壁（図中の矢印で示すところ）が大きくえぐられた形状をなすものの場合に効果的である。
このような突条壁３１ａは、上記条件を満たす範囲内で、燃焼室３０の中心軸Ｍ付近の内壁に突設され、吸気バルブ３の傘部３ａの外周縁に対向する側面３１ａ１が円弧状に形成されてこの側面３１ａ１と上記外周縁との間に所定隙間が形成されるが、この突条壁３１ａの上面３１ａ２の面積が大きくなること等から突条壁３１ａのマスが大きくなる。このため、圧縮比を大きく高めても問題がないような場合に好適である。 Next, a combustion chamber structure according to a third embodiment of the present invention will be described with reference to FIG. In FIG. 5, the same components as those in FIGS. 1 to 4 are denoted by the same reference numerals, and the description thereof is omitted.
In this combustion chamber structure, the combustion chamber 30 is symmetrical with respect to the central axis N in the vertical direction of the combustion chamber 30 and has a structure in which the projecting walls 31a and 31b project from each other independently. It is. Note that the ridge walls 31a and 31b have a symmetric shape with respect to the central axis N as described above, and the ridge wall 31a will be described here.
This rib wall 31a is effective in the case where the inner wall (indicated by the arrow in the figure) in the vicinity of the central axis M of the combustion chamber 30 has a large shape like the present combustion chamber structure.
Such a ridge wall 31a is provided on the inner wall in the vicinity of the central axis M of the combustion chamber 30 within a range satisfying the above conditions, and the side surface 31a 1 facing the outer peripheral edge of the umbrella portion 3a of the intake valve 3 is circular. Although formed in an arc shape predetermined gap between the side surface 31a 1 and the outer peripheral edge is formed, large mass ridges wall 31a since such area of the upper surface 31a 2 of the projection wall 31a becomes larger Become. For this reason, it is suitable when there is no problem even if the compression ratio is greatly increased.

次に、本発明の第４の実施の形態に係る燃焼室構造を図６を参照して説明する。尚、これら図６において、図１〜５の構成部材と同一のものには同一番号を付し、その説明は割愛する。
本燃焼室構造においては、上記燃焼室１の内壁の、上記突条壁１５ａ，１５ｂが突設されたところとほぼ同一のところに当該燃焼室１の中心軸Ｎに対し対称をなし、且つ、互いに独立をなして突条壁４０ａ，４０ｂを突設させた構造をなすものであるが、突条壁４０ａ，４０ｂの形状が上記突条壁１５ａ，１５ｂのそれと一部異なっている。尚、突条壁４０ａ，４０ｂは、上述のように中心軸Ｎについて対称となる形状をなしており、ここでは突条壁４０ａについて説明する。
かかる突条壁４０ａは、突条壁１５ａと比較すると、この突条壁１５ａの上面１５ａ２がデッキ面近傍にまで達していたが、当該突条壁４０ａの上面４０ａ２はデッキ面より低くなるように形成され、また、当該突条壁４０ａの直線状側面４０ａ１の両端部からシリンダヘッド２の内壁にそれぞれ至る稜面４０ａ３は当該内壁に対し６０゜ぐらい傾斜する傾斜面で形成されており、そのため、当該突条壁４０ａに角張った部分が少なくなっている。このため、本燃焼室構造のものは、ノッキングが発生し易いエンジンに好適である。但し、燃焼室１内にタンブル流に加えて吸気バルブ直下に双子渦を生成させる能力は若干劣る。 Next, a combustion chamber structure according to a fourth embodiment of the present invention will be described with reference to FIG. In FIG. 6, the same components as those in FIGS. 1 to 5 are designated by the same reference numerals, and the description thereof is omitted.
In the present combustion chamber structure, the inner wall of the combustion chamber 1 is symmetric with respect to the central axis N of the combustion chamber 1 at substantially the same location as the protruding walls 15a and 15b. The ridge walls 40a and 40b are formed so as to be independent from each other, but the shape of the ridge walls 40a and 40b is partially different from that of the ridge walls 15a and 15b. Note that the ridge walls 40a and 40b are symmetrical with respect to the central axis N as described above, and the ridge wall 40a will be described here.
Such ridges wall 40a is different from the rib walls 15a, but the upper surface 15a 2 of the projection wall 15a has reached to the vicinity of the deck surface, the upper surface 40a 2 of the ridge wall 40a is lower than the deck surface It is formed as, also, crest surfaces 40a 3 extending respectively from both ends of the linear sides 40a 1 of the projection wall 40a to the inner wall of the cylinder head 2 is formed with inclined surface inclined about 60 ° with respect to the inner wall Therefore, there are few angular portions on the ridge wall 40a. For this reason, the combustion chamber structure is suitable for an engine in which knocking is likely to occur. However, the ability to generate a twin vortex directly under the intake valve in addition to the tumble flow in the combustion chamber 1 is slightly inferior.

ところで、上述した第１〜４の実施の形態に係る燃焼室構造において、例えば第１の実施の形態の突条壁８ａ，８ｂは、各吸気バルブ３のそれぞれに近接するシリンダヘッド２の内壁に、燃焼室１の中心軸Ｎに対し対称をなし、且つ、互いに独立をなしてそれぞれ突設されるものであったが、例えば図７に示すように、両吸気バルブ３に挟まれたところで、且つ、シリンダヘッド２の内壁寄りのところに一つの突条壁５０を設け、この突条壁５０の、両吸気バルブ３の傘部３ａの外周縁にそれぞれ対向する円弧状の側面５０ａ，５０ｂと当該外周縁との間に所定隙間が形成されるようにしたものであってもよく、吸気ポートの主流がシリンダ内側を向いているような場合に有効である。
尚、場合によっては、例えば突条壁８ａ，８ｂなどと突条壁５０とが組み合わせて設けられた燃焼室構造としてもよいことはもちろんである。 Incidentally, in the combustion chamber structures according to the first to fourth embodiments described above, for example, the protrusion walls 8a and 8b of the first embodiment are formed on the inner wall of the cylinder head 2 adjacent to each of the intake valves 3. , Which are symmetrical with respect to the central axis N of the combustion chamber 1 and are provided so as to be independent of each other. For example, as shown in FIG. In addition, one ridge wall 50 is provided near the inner wall of the cylinder head 2, and arc-shaped side surfaces 50a and 50b of the ridge wall 50 facing the outer peripheral edges of the umbrella portions 3a of the two intake valves 3, respectively. A predetermined gap may be formed between the outer peripheral edge and this is effective when the main flow of the intake port faces the inside of the cylinder.
In some cases, for example, a combustion chamber structure in which the ridge walls 8a and 8b and the ridge wall 50 are provided in combination may be used.

本発明のエンジンの燃焼室構造は、燃焼室を構成するシリンダヘッド内壁の適宜な位置に突条壁を設けるだけで、燃焼室内にタンブル流に加えて双子渦を吸気バルブ直下に生成することができるようになるので、広範囲での利用価値が高いと言える。   The combustion chamber structure of the engine according to the present invention can generate a twin vortex directly below the intake valve in addition to the tumble flow in the combustion chamber only by providing a protrusion wall at an appropriate position on the inner wall of the cylinder head constituting the combustion chamber. It can be said that the utility value in a wide range is high.

本発明の第１の実施の形態に係る燃焼室構造を構成するシリンダヘッドの底面図である。It is a bottom view of the cylinder head which comprises the combustion chamber structure which concerns on the 1st Embodiment of this invention. 本発明の第１の実施の形態に係る燃焼室内の吸入空気等の流れを示す側断面図である。It is a sectional side view which shows the flow of the intake air etc. in the combustion chamber which concerns on the 1st Embodiment of this invention. 図１のシリンダヘッド内壁の突条壁とは形状の異なる突条壁が突設されたシリンダヘッドの底面図である。FIG. 2 is a bottom view of a cylinder head in which a protruding wall having a shape different from the protruding wall of the inner wall of the cylinder head in FIG. 1 is provided. 本発明の第２の実施の形態に係る燃焼室構造を構成するシリンダヘッドの底面図である。It is a bottom view of the cylinder head which comprises the combustion chamber structure which concerns on the 2nd Embodiment of this invention. 本発明の第３の実施の形態に係る燃焼室構造を構成するシリンダヘッドの底面図である。It is a bottom view of the cylinder head which comprises the combustion chamber structure which concerns on the 3rd Embodiment of this invention. 本発明の第４の実施の形態に係る燃焼室構造を構成するシリンダヘッドの底面図である。It is a bottom view of a cylinder head which constitutes a combustion chamber structure concerning a 4th embodiment of the present invention. 本発明の第１〜４の実施の形態に係る突条壁とは異質の突条壁が突設されたシリンダヘッドの底面図である。It is a bottom view of the cylinder head by which the rib wall different from the rib wall which concerns on the 1st-4th embodiment of this invention was protrudingly provided. 従来の燃焼室の構造図である。It is a structural diagram of a conventional combustion chamber.

符号の説明Explanation of symbols

１，２０，３０ 燃焼室
２ シリンダヘッド
３ 吸気バルブ
３ａ 傘部
８ａ，８ｂ 突条壁
１５ａ，１５ｂ 突条壁
２１ａ，２１ｂ 突条壁
３１ａ，３１ｂ 突条壁
４０ａ，４０ｂ 突条壁
５０ 突条壁
Ｋ 挟角
Ｙ軸 吸気バルブが配される吸気ポートの中心軸
Ｘ軸 Ｙ軸に垂直でシリンダヘッドの内壁に向かう方向軸
Ｚ軸 吸気バルブのバルブリフトの方向軸
Ｍ軸 燃焼室の水平方向の中心軸（＝吸気バルブを往復動させるカムシャフト軸に平行な方向軸）
Ｎ軸 燃焼室の垂直方向の中心軸
1,20,30 Combustion chamber 2 Cylinder head 3 Intake valve 3a Umbrella 8a, 8b Rib wall 15a, 15b Rib wall 21a, 21b Rib wall 31a, 31b Rib wall 40a, 40b Rib wall 50 Rib wall K Narrowing angle Y axis Center axis of the intake port where the intake valve is arranged X axis Direction axis perpendicular to the Y axis toward the inner wall of the cylinder head Z axis Direction axis of the valve lift of the intake valve M axis Horizontal center of the combustion chamber Axis (= direction axis parallel to the camshaft axis for reciprocating the intake valve)
N axis Vertical axis of combustion chamber

Claims (1)

燃焼室を形成するシリンダヘッドにカムシャフトにより往復動される２つの吸気バルブと１つ又は２つの排気バルブとが配されるエンジンの燃焼室構造において、前記カムシャフトの軸線に垂直な軸線の方向には前記吸気バルブに近接する前記シリンダヘッドの内壁の所定範囲に延在し、且つ、前記カムシャフトの軸線の方向には前記シリンダヘッドの内壁から前記吸気バルブの傘部の外周縁近傍まで突設する突条壁を形成し、該突条壁は前記カムシャフトの軸線に対して垂直に交わる前記燃焼室の中心軸に対して互いに対称をなすことを特徴とするエンジンの燃焼室構造。 In a combustion chamber structure of an engine in which two intake valves reciprocated by a camshaft and one or two exhaust valves are arranged on a cylinder head forming a combustion chamber, the direction of the axis perpendicular to the axis of the camshaft Extends in a predetermined range of the inner wall of the cylinder head adjacent to the intake valve , and projects in the axial direction of the camshaft from the inner wall of the cylinder head to the vicinity of the outer peripheral edge of the umbrella portion of the intake valve. An engine combustion chamber structure characterized in that a projecting ridge wall is formed, and the ridge wall is symmetrical with respect to a central axis of the combustion chamber perpendicular to the axis of the camshaft.
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