JPH0571352A - Combustion chamber structure for two-cycle internal combustion engine - Google Patents
Combustion chamber structure for two-cycle internal combustion engineInfo
- Publication number
- JPH0571352A JPH0571352A JP22796091A JP22796091A JPH0571352A JP H0571352 A JPH0571352 A JP H0571352A JP 22796091 A JP22796091 A JP 22796091A JP 22796091 A JP22796091 A JP 22796091A JP H0571352 A JPH0571352 A JP H0571352A
- Authority
- JP
- Japan
- Prior art keywords
- air supply
- wall surface
- valve
- recess
- valves
- 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.)
- Pending
Links
Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02F—CYLINDERS, PISTONS OR CASINGS, FOR COMBUSTION ENGINES; ARRANGEMENTS OF SEALINGS IN COMBUSTION ENGINES
- F02F1/00—Cylinders; Cylinder heads
- F02F1/24—Cylinder heads
- F02F1/42—Shape or arrangement of intake or exhaust channels in cylinder heads
- F02F1/4214—Shape or arrangement of intake or exhaust channels in cylinder heads specially adapted for four or more valves per cylinder
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02B—INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL
- F02B75/00—Other engines
- F02B75/02—Engines characterised by their cycles, e.g. six-stroke
- F02B2075/022—Engines characterised by their cycles, e.g. six-stroke having less than six strokes per cycle
- F02B2075/025—Engines characterised by their cycles, e.g. six-stroke having less than six strokes per cycle two
Landscapes
- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Combustion & Propulsion (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Valve-Gear Or Valve Arrangements (AREA)
- Combustion Methods Of Internal-Combustion Engines (AREA)
Abstract
Description
【０００１】[0001]
【産業上の利用分野】本発明は２サイクル内燃機関の燃
焼室構造に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combustion chamber structure for a two-cycle internal combustion engine.
【０００２】[0002]
【従来の技術】シリンダヘッド内壁面上に一対の排気弁
を配置し、一対の排気弁と反対側に位置するシリンダヘ
ッド内壁面上に凹部を形成してこの凹部内に一対の給気
弁を配置し、排気弁側に形成される各給気弁の開口を凹
部の周壁面により形成されるマスク壁によって覆うよう
にした２サイクル内燃機関の燃焼室構造が公知である
（特開平２−１５３２２２号公報参照）。この２サイク
ル内燃機関では排気弁側に形成される各給気弁の開口が
マスク壁によって覆われているので、吸入空気はマスク
壁と反対側の給気弁の開口から燃焼室内に流入する。こ
の吸入空気がシリンダボア内壁面に沿ってピストン頂面
に向かい、次いでピストン頂面上において向きを変えて
シリンダボア内壁面に沿い排気ポートに向けて流れるの
でループ掃気を行うことができる。2. Description of the Related Art A pair of exhaust valves are arranged on an inner wall surface of a cylinder head, a recess is formed on an inner wall surface of the cylinder head opposite to the pair of exhaust valves, and a pair of air supply valves are provided in the recess. A combustion chamber structure of a two-cycle internal combustion engine is known in which the openings of the intake valves arranged on the exhaust valve side are covered with a mask wall formed by a peripheral wall surface of a recess (Japanese Patent Laid-Open No. 2-153222). (See the official gazette). In this two-cycle internal combustion engine, the opening of each air supply valve formed on the exhaust valve side is covered by the mask wall, so the intake air flows into the combustion chamber through the opening of the air supply valve on the side opposite to the mask wall. This intake air flows toward the piston top surface along the inner wall surface of the cylinder bore, then changes its direction on the top surface of the piston and flows along the inner wall surface of the cylinder bore toward the exhaust port, so that loop scavenging can be performed.
【０００３】[0003]
【発明が解決しようとする課題】ところで、給気効率を
高めようとすると更に多くの給気弁、例えば３個の給気
弁を設けることが必要となる。この場合、上述の２サイ
クル内燃機関において３個の給気弁を配置しようとする
と３番目の給気弁は一対の給気弁の間のシリンダヘッド
内壁面周辺部上に配置せざるを得なくなる。この場合、
一対の給気弁と同様に、排気弁側に形成される３番目の
給気弁の開口を凹部周壁面により覆おうとすると、凹部
周壁面を一対の給気弁の周りに沿って３番目の給気弁ま
で延設せざるを得ない。しかしながらこのように凹部周
壁面を一対の給気弁の周りに沿って延設すると、凹部周
壁面によって覆われる一対の給気弁の開口領域が必然的
にかなり増大し、その結果、却って給気効率が低下して
しまうという問題を生ずる。By the way, in order to improve the air supply efficiency, it is necessary to provide more air supply valves, for example, three air supply valves. In this case, if three air supply valves are to be arranged in the above-described two-cycle internal combustion engine, the third air supply valve must be arranged on the peripheral portion of the inner wall surface of the cylinder head between the pair of air supply valves. .. in this case,
Similar to the pair of air supply valves, when the opening of the third air supply valve formed on the exhaust valve side is covered with the peripheral wall surface of the recess, the peripheral wall surface of the recess is located along the circumference of the pair of air supply valves. There is no choice but to extend to the air supply valve. However, when the peripheral wall surfaces of the recess are extended along the pair of air supply valves in this manner, the opening areas of the pair of air supply valves covered by the peripheral wall surfaces of the recess inevitably increase considerably. There is a problem that efficiency is reduced.
【０００４】[0004]
【課題を解決するための手段】上記問題点を解決するた
めに本発明によれば、シリンダヘッド内壁面上に排気弁
を配置し、排気弁と反対側に位置するシリンダヘッド内
壁面上に凹部を形成して凹部内に給気弁を配置し、排気
弁側に形成される給気弁の開口を凹部の周壁面により形
成されるマスク壁によって覆うようにした２サイクル内
燃機関の燃焼室構造において、凹部の底壁面上に凹部の
周壁面から間隔を隔てて第２の凹部を形成し、第２の凹
部内に第２の給気弁を配置すると共に排気弁側に形成さ
れる第２の給気弁の開口を第２の凹部の周壁面により形
成されるマスク壁によって覆うようにしている。In order to solve the above problems, according to the present invention, an exhaust valve is arranged on the inner wall surface of a cylinder head, and a recess is formed on the inner wall surface of the cylinder head opposite to the exhaust valve. The structure of the combustion chamber of the two-cycle internal combustion engine in which the intake valve is formed in the recess, and the opening of the intake valve formed on the exhaust valve side is covered by the mask wall formed by the peripheral wall surface of the recess. A second concave portion is formed on the bottom wall surface of the concave portion at a distance from the peripheral wall surface of the concave portion, the second air supply valve is arranged in the second concave portion, and the second concave portion is formed on the exhaust valve side. The opening of the air supply valve is covered with a mask wall formed by the peripheral wall surface of the second recess.
【０００５】[0005]
【作用】排気弁側に形成される給気弁の開口が凹部の周
壁面により形成されるマスク壁によって覆われているの
で、吸入空気はマスク壁と反対側の給気弁の開口から燃
焼室内に流入する。また、排気弁側に形成される第２の
給気弁の開口が第２の凹部の周壁面により形成されるマ
スク壁によって覆われているので、吸入空気はマスク壁
と反対側の第２給気弁の開口から燃焼室内に流入する。
これらの吸入空気によって、排気弁と反対側に位置する
給気弁および第２給気弁の下方のシリンダボア内壁面に
沿ってピストン頂面に向かう掃気流が形成される。Since the opening of the intake valve formed on the exhaust valve side is covered by the mask wall formed by the peripheral wall surface of the recess, the intake air flows from the opening of the intake valve on the opposite side of the mask wall to the combustion chamber. Flow into. Further, since the opening of the second air supply valve formed on the exhaust valve side is covered by the mask wall formed by the peripheral wall surface of the second recess, the intake air is supplied to the second air supply side opposite to the mask wall. It flows into the combustion chamber through the opening of the air valve.
These intake air forms a scavenging air flow toward the top surface of the piston along the inner wall surface of the cylinder bore below the air supply valve and the second air supply valve located on the side opposite to the exhaust valve.
【０００６】[0006]
【実施例】図１から図３を参照すると、１はシリンダブ
ロック、２はシリンダブロック１内に固定されたシリン
ダライナ、４はシリンダライナ２内で往復動するピスト
ン、６はシリンダブロック１上に固定されたシリンダヘ
ッド、８はシリンダヘッド６の内壁面６ａとピストン４
の頂面間に形成された燃焼室を夫々示す。シリンダヘッ
ド内壁面６ａ上には第１の凹部１０が形成され、この第
１凹部１０の底壁面をなすシリンダヘッド内壁面部分６
ｂ上に一対の第１給気弁１２ａが配置される。一方、第
１凹部１０を除くシリンダヘッド内壁面部分６ｃは傾斜
したほぼ平坦をなし、このシリンダヘッド内壁面部分６
ｃ上に一対の第１排気弁１４ａと１個の第２排気弁１４
ｂとが配置される。図１に示されるように第２排気弁１
４ｂは一対の第１排気弁１４ａの間であって第１給気弁
１２ａと反対側のシリンダヘッド内壁面６ａの周辺部に
設けられており、従って第２排気弁１４ｂは第１排気弁
１４ａに比べて第１給気弁１２ａから離れた位置に配置
されている。1 to 3, reference numeral 1 is a cylinder block, 2 is a cylinder liner fixed in the cylinder block 1, 4 is a piston reciprocating in the cylinder liner 2, and 6 is on the cylinder block 1. The fixed cylinder head, 8 is the inner wall surface 6a of the cylinder head 6 and the piston 4
3A and 3B respectively show combustion chambers formed between the top surfaces of the. A first recess 10 is formed on the cylinder head inner wall surface 6a, and the cylinder head inner wall surface portion 6 forming the bottom wall surface of the first recess 10 is formed.
A pair of first air supply valves 12a is arranged on b. On the other hand, the cylinder head inner wall surface portion 6c excluding the first recess 10 is inclined and substantially flat.
a pair of first exhaust valves 14a and one second exhaust valve 14 on c
b and are arranged. As shown in FIG. 1, the second exhaust valve 1
4b is provided between the pair of first exhaust valves 14a and around the cylinder head inner wall surface 6a opposite to the first air supply valve 12a. Therefore, the second exhaust valve 14b is the first exhaust valve 14a. It is arranged at a position distant from the first air supply valve 12a as compared with the above.
【０００７】図１に示されるようにシリンダヘッド内壁
面部分６ｂとシリンダヘッド内壁面部分６ｃは第１凹部
１０の周壁面１６を介して互いに接続されており、この
第１凹部周壁面１６は一対の第１給気弁１２ａと第１排
気弁１４ａ、第２排気弁１４ｂとの間においてシリンダ
ヘッド内壁面６ａの一方の周縁部から他方の周縁部まで
延びている。この第１凹部周壁面１６は第１給気弁１２
ａの周縁部に極めて近接配置されかつ第１給気弁１２ａ
の周縁部に沿って円弧状に延びる一対のマスク壁１６ａ
と、第１給気弁１２ａ間に位置する新気ガイド壁１６ｂ
と、シリンダヘッド内壁面６ａの周壁と第１給気弁１２
ａ間に位置する一対の新気ガイド壁１６ｃとにより構成
される。各マスク壁１６ａは最大リフト位置にある第１
給気弁１２ａよりも下方まで燃焼室８に向けて延びてお
り、従って排気弁１４ａ，１４ｂ側に位置する第１給気
弁１２ａ周縁部と弁座１８間の開口は第１給気弁１２ａ
の開弁期間全体に亘ってマスク壁１６ａにより閉鎖され
ることになる。また、各新気ガイド壁１６ｂ，１６ｃは
ほぼ同一平面内に位置しており、更にこれらの新気ガイ
ド壁１６ｂ，１６ｃは両第１給気弁１２ａの中心を結ぶ
線に対してほぼ平行に延びている。点火栓２０はシリン
ダヘッド内壁面６ａの中心に位置するようにシリンダヘ
ッド内壁面部分６ｃ上に位置されている。一方、第１排
気弁１４ａおよび第２排気弁１４ｂに対しては排気弁１
４ａ，１４ｂと弁座２２間の開口を覆うマスク壁が設け
られておらず、従って排気弁１４ａ，１４ｂが開弁する
と排気弁１４ａ，１４ｂと弁座２２間に形成される開口
はその全体が燃焼室８内に開口することになる。As shown in FIG. 1, the cylinder head inner wall surface portion 6b and the cylinder head inner wall surface portion 6c are connected to each other through a peripheral wall surface 16 of the first recess 10, and the first recess peripheral wall surface 16 is a pair. The first air supply valve 12a and the first exhaust valve 14a and the second exhaust valve 14b extend from one peripheral edge of the cylinder head inner wall surface 6a to the other peripheral edge. The peripheral wall surface 16 of the first recess is the first air supply valve 12
the first air supply valve 12a, which is arranged very close to the peripheral portion of a.
Of a pair of mask walls 16a extending in an arc shape along the peripheral edge of the
And the fresh air guide wall 16b located between the first air supply valve 12a
And the peripheral wall of the cylinder head inner wall surface 6a and the first air supply valve 12
It is constituted by a pair of fresh air guide walls 16c located between a. Each mask wall 16a has a first lift position at the maximum lift position.
It extends toward the combustion chamber 8 below the air supply valve 12a, and therefore the opening between the peripheral edge of the first air supply valve 12a located on the side of the exhaust valves 14a, 14b and the valve seat 18 is the first air supply valve 12a.
Will be closed by the mask wall 16a over the entire valve opening period. The fresh air guide walls 16b and 16c are located substantially in the same plane, and the fresh air guide walls 16b and 16c are substantially parallel to the line connecting the centers of both the first air supply valves 12a. It is extended. The spark plug 20 is located on the cylinder head inner wall surface portion 6c so as to be located at the center of the cylinder head inner wall surface 6a. On the other hand, the exhaust valve 1 is attached to the first exhaust valve 14a and the second exhaust valve 14b.
No mask wall is provided to cover the opening between the valve seats 4a, 14b and the valve seat 22. Therefore, when the exhaust valves 14a, 14b are opened, the opening formed between the exhaust valves 14a, 14b and the valve seat 22 is entirely covered. It will open into the combustion chamber 8.
【０００８】図１および図２に示されるように第１凹部
１０の底壁面上には第１凹部１０の周壁面１６から間隔
を隔てて第２の凹部２６が形成される。この第２凹部２
６の底壁面をなすシリンダヘッド内壁面部分６ｄ上に１
個の第２給気弁１２ｂが配置される。図１に示されるよ
うに第２給気弁１２ｂは一対の第１給気弁１２ａの間で
あって排気弁１４ａ，１４ｂと反対側のシリンダヘッド
内壁面６ａの周辺部に設けられており、従って第２給気
弁１２ｂは第１給気弁１２ａに比べて排気弁１４ａ，１
４ｂから離れた位置に配置されている。As shown in FIGS. 1 and 2, a second recess 26 is formed on the bottom wall surface of the first recess 10 at a distance from the peripheral wall surface 16 of the first recess 10. This second recess 2
1 on the cylinder head inner wall surface portion 6d forming the bottom wall surface of 6
The individual second air supply valves 12b are arranged. As shown in FIG. 1, the second air supply valve 12b is provided between the pair of first air supply valves 12a and in the peripheral portion of the cylinder head inner wall surface 6a opposite to the exhaust valves 14a and 14b. Therefore, the second air supply valve 12b is more exhaustive than the first air supply valve 12a.
It is arranged at a position away from 4b.
【０００９】図１に示されるようにシリンダヘッド内壁
面部分６ｄとシリンダヘッド内壁面部分６ｂは第２凹部
２６の周壁面２８を介して互いに接続されており、この
第２凹部周壁面２８は第２給気弁１２ｂと一対の第１給
気弁１２ａとの間においてシリンダヘッド内壁面６ａの
周縁部間に延びている。この第２凹部周壁面２８は第２
給気弁１２ｂの周縁部に極めて近接配置されかつ第２給
気弁１２ｂの周縁部に沿って円弧状に延びるマスク壁２
８ａと、シリンダヘッド内壁面６ａの周壁と第２給気弁
１２ｂ間に位置する一対の新気ガイド壁２８ｂとにより
構成される。マスク壁２８ａは最大リフト位置にある第
２給気弁１２ｂよりも下方まで燃焼室８に向けて延びて
おり、従って排気弁１４ａ，１４ｂ側に位置する第２給
気弁１２ｂ周縁部と弁座１８間の開口は第２給気弁１２
ｂの開弁期間全体に亘ってマスク壁２８ａにより閉鎖さ
れることになる。As shown in FIG. 1, the cylinder head inner wall surface portion 6d and the cylinder head inner wall surface portion 6b are connected to each other via a peripheral wall surface 28 of the second recess 26, and the second recess peripheral wall surface 28 is The second air supply valve 12b and the pair of first air supply valves 12a extend between the peripheral portions of the cylinder head inner wall surface 6a. This second recess peripheral wall surface 28 is the second
The mask wall 2 which is arranged very close to the peripheral edge of the air supply valve 12b and extends in an arc shape along the peripheral edge of the second air supply valve 12b.
8a and a pair of fresh air guide walls 28b located between the peripheral wall of the cylinder head inner wall surface 6a and the second air supply valve 12b. The mask wall 28a extends toward the combustion chamber 8 below the second intake valve 12b at the maximum lift position, and therefore the peripheral edge of the second intake valve 12b located on the exhaust valve 14a, 14b side and the valve seat. The opening between 18 is the second air supply valve 12
It will be closed by the mask wall 28a over the entire valve opening period of b.
【００１０】シリンダヘッド６内には各給気弁１２ａ，
１２ｂに対して夫々給気ポート３２が形成され、各排気
弁１４ａ，１４ｂに対して夫々排気ポート３３が形成さ
れる。各給気ポート３２は給気枝管（図示しない）を介
してサージタンク（図示しない）に連結される。また、
各第１給気弁１２ａの近傍のシリンダヘッド内壁面６ａ
の周縁部には一対の燃料噴射弁、即ち第１燃料噴射弁３
５ａと第２燃料噴射弁３５ｂとが配置され、これらの燃
料噴射弁３５ａ，３５ｂから燃料が燃焼室８内に向けて
噴射される。一方、図２および図３に示されるようにピ
ストン４の頂面上には点火栓２０の下方から燃料噴射弁
３５ａ，３５ｂの先端部の下方まで延びるキャビティ３
７が形成されている。また、図２および図３に示される
ように各給気弁１２ａ，１２ｂは給気弁駆動カム３９に
よって駆動され、各排気弁１４ａ，１４ｂは排気弁駆動
カム４１によって駆動される。In the cylinder head 6, each air supply valve 12a,
An air supply port 32 is formed for 12b, and an exhaust port 33 is formed for each exhaust valve 14a, 14b. Each air supply port 32 is connected to a surge tank (not shown) via an air supply branch pipe (not shown). Also,
Cylinder head inner wall surface 6a near each first air supply valve 12a
A pair of fuel injection valves, that is, the first fuel injection valve 3
5a and the second fuel injection valve 35b are arranged, and the fuel is injected into the combustion chamber 8 from these fuel injection valves 35a and 35b. On the other hand, as shown in FIGS. 2 and 3, on the top surface of the piston 4, a cavity 3 extending from below the spark plug 20 to below the tip of the fuel injection valves 35a and 35b.
7 are formed. Further, as shown in FIGS. 2 and 3, the air supply valves 12a and 12b are driven by the air supply valve drive cam 39, and the exhaust valves 14a and 14b are driven by the exhaust valve drive cam 41.
【００１１】図４に示されるように本実施例では排気弁
１４ａ，１４ｂが給気弁１２ａ，１２ｂよりも先に開弁
し、排気弁１４ａ，１４ｂが給気弁１２ａ，１２ｂより
も先に閉弁する。また、図４においてＩｒは機関低負荷
運転時における燃料噴射時期を示しており、Ｉｍ1 およ
びＩｍ2 は機関中負荷運転時における燃料噴射時期を示
しており、Ｉｈ1 およびＩｈ2 は機関高負荷運転時にお
ける燃料噴射時期を示している。なお、機関低負荷運転
時における燃料噴射Ｉｒおよび機関中負荷運転時におけ
る第２回目の燃料噴射Ｉｍ2 は第１燃料噴射弁３５ａに
より行われ、機関中負荷運転時における第１回目の燃料
噴射Ｉｍ1 は第２燃料噴射弁３５ｂにより行われ、機関
高負荷運転時における燃料噴射Ｉｈ1 およびＩｈ2は第
１燃料噴射弁３５ａおよび第２燃料噴射弁３５ｂの双方
により行われる。As shown in FIG. 4, in this embodiment, the exhaust valves 14a and 14b are opened before the intake valves 12a and 12b, and the exhaust valves 14a and 14b are opened before the intake valves 12a and 12b. Close the valve. Further, in FIG. 4, Ir indicates the fuel injection timing during engine low load operation, Im 1 and Im 2 indicate fuel injection timing during engine medium load operation, and Ih 1 and Ih 2 indicate engine high load. The fuel injection timing during operation is shown. It should be noted that the fuel injection Ir during the engine low load operation and the second fuel injection Im 2 during the engine medium load operation are performed by the first fuel injection valve 35a, and the first fuel injection Im during the engine medium load operation. 1 is performed by the second fuel injection valve 35b, and fuel injections Ih 1 and Ih 2 during engine high load operation are performed by both the first fuel injection valve 35a and the second fuel injection valve 35b.
【００１２】次に、排気弁１４ａ，１４ｂが開弁したと
きのブローダウン作用、および給気弁１２ａ，１２ｂが
開弁したときの掃気作用について説明する。排気弁１４
ａ，１４ｂが開弁すると燃焼室８内の既燃ガスが急激に
排気ポート３３内に流出し、所謂ブローダウンを生ず
る。その結果、図６に示されるように燃焼室８内の圧力
が急激に低下する。本実施例では３個の排気弁１４ａ，
１４ｂが設けられているので２個あるいは１個の排気弁
が設けられている場合に比べて排気弁の開口面積が増大
し、その結果燃焼室８内の既燃ガスの排出が促進され、
斯くして燃焼室８内の圧力がより急激に低下する。な
お、このブローダウンが生ずるブローダウン期間は排気
弁１４ａ，１４ｂの開弁開始時期から給気弁１２ａ，１
２ｂの開弁開始時期までの期間にほぼ対応する。Next, the blowdown action when the exhaust valves 14a and 14b are opened and the scavenging action when the air supply valves 12a and 12b are opened will be described. Exhaust valve 14
When the valves a and 14b are opened, the burnt gas in the combustion chamber 8 suddenly flows into the exhaust port 33, causing so-called blowdown. As a result, the pressure in the combustion chamber 8 drops sharply as shown in FIG. In this embodiment, three exhaust valves 14a,
Since 14b is provided, the opening area of the exhaust valve is increased as compared with the case where two or one exhaust valve is provided, and as a result, discharge of burnt gas in the combustion chamber 8 is promoted.
Thus, the pressure in the combustion chamber 8 drops more rapidly. The blowdown period during which this blowdown occurs is from the opening start timing of the exhaust valves 14a, 14b to the air supply valves 12a, 1b.
It corresponds almost to the period up to the valve opening start timing of 2b.
【００１３】このように強力なブローダウン作用によっ
て燃焼室８内の圧力が急激に低下するので、次いで給気
弁１２ａ，１２ｂが開弁するとただちに新気が燃焼室８
内に流入を開始する。従って多量の新気を燃焼室８内に
送り込むことができる。このように給気弁１２ａ，１２
ｂが開弁すると新気が燃焼室８内に流入を開始するが排
気弁１４ａ，１４ｂ側の給気弁１２ａ，１２ｂの開口は
マスク壁１６ａ，２８ａによって夫々覆われているの
で、新気はマスク壁１６ａと反対側の第１給気弁１２ａ
の開口、およびマスク壁２８ａと反対側の第２給気弁１
２ｂの開口から燃焼室８内に流入する。この新気は図５
において矢印Ｗで示すように給気弁１２ａ，１２ｂ下方
のシリンダボア内壁面に沿い下降し、次いでピストン４
の頂面に沿い進んで排気弁１４ａ，１４ｂ下方のシリン
ダボア内壁面に沿い上昇し、斯くして新気は燃焼室８内
をループ状に流れることになる。このループ状に流れる
新気Ｗによって燃焼室８内の既燃ガスが排気弁１４ａ，
１４ｂを介して良好に排出される。斯くして良好な掃気
効率を確保することができる。Since the pressure in the combustion chamber 8 is drastically reduced by such a strong blowdown action, when the air supply valves 12a and 12b are subsequently opened, fresh air is immediately generated.
Inflow begins. Therefore, a large amount of fresh air can be sent into the combustion chamber 8. In this way, the air supply valves 12a, 12
When b is opened, fresh air begins to flow into the combustion chamber 8. However, since the openings of the air supply valves 12a and 12b on the side of the exhaust valves 14a and 14b are covered by the mask walls 16a and 28a, respectively, First air supply valve 12a opposite to the mask wall 16a
And the second air supply valve 1 on the side opposite to the mask wall 28a
It flows into the combustion chamber 8 through the opening of 2b. This new spirit is shown in Figure 5.
, The piston 4 moves downward along the inner wall surface of the cylinder bore below the air supply valves 12a and 12b, and then the piston 4
Along the inner wall surface of the cylinder bore below the exhaust valves 14a and 14b, and thus the fresh air flows in a loop in the combustion chamber 8. Burned gas in the combustion chamber 8 is exhausted by the exhaust air 14a,
Good discharge via 14b. Thus, good scavenging efficiency can be secured.
【００１４】ところで、図６に示されるように燃焼室８
内の圧力は上述のブローダウン作用により給気弁１２
ａ，１２ｂの開弁期間初期において最も低くなる。従っ
て、給気弁１２ａ，１２ｂの開弁期間初期において新気
が給気弁１２ａ，１２ｂを介して燃焼室８内にできるだ
け流入しやすくすることが給気効率および掃気効率の向
上につながる。この給気弁１２ａ，１２ｂの開弁期間初
期においては当然のことながら給気弁１２ａ，１２ｂの
リフト量が小さい。図７に代表的な例が示されているよ
うに、給気弁１２ａ，１２ｂのリフト量が小さいときに
給気弁１２ａ，１２ｂを介して燃焼室８内に流入する空
気量を増大させるためには、給気弁の開口面積、即ちカ
ーテン面積を大きくする方が給気ポート３２の断面積、
即ちスロート面積を大きくするよりも効果がある。図１
から図５に示す実施例では３個の給気弁１２ａ，１２ｂ
を設けているので、２個或いは１個の給気弁を設けた場
合に比べてカーテン面積が大きくなる。その結果、給気
弁１２ａ，１２ｂの開弁期間初期、即ち燃焼室８内の圧
力が低いときの新気の流入を更に促進させることができ
る。斯くして給気効率および掃気効率を高めることがで
きる。By the way, as shown in FIG. 6, the combustion chamber 8
The pressure in the air supply valve 12 is set by the above-mentioned blowdown action.
It becomes the lowest at the beginning of the valve opening period of a and 12b. Therefore, it is possible to improve the air supply efficiency and the scavenging efficiency by making it as easy as possible for fresh air to flow into the combustion chamber 8 via the air supply valves 12a and 12b in the early stage of the opening period of the air supply valves 12a and 12b. At the beginning of the opening period of the air supply valves 12a and 12b, the lift amounts of the air supply valves 12a and 12b are naturally small. As shown in a typical example in FIG. 7, in order to increase the amount of air flowing into the combustion chamber 8 via the intake valves 12a and 12b when the lift amount of the intake valves 12a and 12b is small. Is the cross-sectional area of the air supply port 32 when increasing the opening area of the air supply valve, that is, the curtain area.
That is, it is more effective than increasing the throat area. Figure 1
3 to the three air supply valves 12a and 12b in the embodiment shown in FIG.
As a result, the curtain area becomes larger than the case where two or one air supply valves are provided. As a result, the inflow of fresh air can be further promoted at the beginning of the opening period of the air supply valves 12a and 12b, that is, when the pressure in the combustion chamber 8 is low. Thus, the air supply efficiency and the scavenging efficiency can be improved.
【００１５】また、図１に示されるように第１給気弁１
２ａのマスク壁１６ａは第１凹部１０の周壁面１６によ
って形成され、一方第２給気弁１２ｂのマスク壁２８ａ
は第２凹部２６の周壁面２８によって形成される。即
ち、互いに隣接配置された第１給気弁１２ａと第２給気
弁１２ｂのマスク壁１６ａ，２８ａは接続されていな
い。従って一方の給気弁１２ｂのマスク壁２８ａの形状
が他方の給気弁１２ａのマスク壁１６ａの形状に影響を
与えることがない。斯くして各給気弁１２ａ，１２ｂに
対して、給気抵抗を低く抑えつつ良好なループ掃気流を
確保するために最適なマスク量を夫々与えることができ
る。Further, as shown in FIG. 1, the first air supply valve 1
The mask wall 16a of 2a is formed by the peripheral wall surface 16 of the first recess 10, while the mask wall 28a of the second air supply valve 12b.
Is formed by the peripheral wall surface 28 of the second recess 26. That is, the mask walls 16a and 28a of the first air supply valve 12a and the second air supply valve 12b arranged adjacent to each other are not connected. Therefore, the shape of the mask wall 28a of the one air supply valve 12b does not affect the shape of the mask wall 16a of the other air supply valve 12a. In this way, it is possible to give the respective air supply valves 12a and 12b an optimum mask amount for ensuring a good loop scavenging air while suppressing the air supply resistance.
【００１６】図４に示されるようにピストン４が下死点
ＢＤＣを過ぎて上昇を開始するとその後燃料噴射弁３５
ａ，３５ｂからの燃料噴射が開始される。図４に示され
る燃料噴射ＩｒおよびＩｍ2 では第１燃料噴射弁３５ａ
からピストン４頂面上に形成されたキャビティ３７内に
燃料が噴射され、点火栓２０周りに最適な濃度の混合気
が形成されるようにしている。一方、燃料噴射Ｉｍ1 ，
Ｉｈ1 およびＩｈ2 では噴射燃料がピストン４頂面の広
い領域に亘って衝突せしめられ、燃焼室８内に均一混合
気が形成されるようにしている。As shown in FIG. 4, when the piston 4 starts to rise past the bottom dead center BDC, the fuel injection valve 35
Fuel injection from a and 35b is started. In the fuel injections Ir and Im 2 shown in FIG. 4, the first fuel injection valve 35a
The fuel is injected into the cavity 37 formed on the top surface of the piston 4 so that the air-fuel mixture having the optimum concentration is formed around the spark plug 20. On the other hand, the fuel injection Im 1 ,
At Ih 1 and Ih 2 , the injected fuel is made to collide over a wide area of the top surface of the piston 4, so that a uniform mixture is formed in the combustion chamber 8.
【００１７】[0017]
【発明の効果】凹部内に配置された給気弁と第２の凹部
内に配置された第２の給気弁とがそれぞれ独立して最適
なマスク壁を有することができるので、良好な給気効率
を確保すると共に良好なループ掃気を得ることができ
る。As described above, the air supply valve arranged in the recess and the second air supply valve arranged in the second recess can independently have the optimum mask wall. It is possible to secure gas efficiency and obtain good loop scavenging.
【図１】シリンダヘッドの底面図である。FIG. 1 is a bottom view of a cylinder head.
【図２】図１のII−II線に沿ってみた２サイクル内燃機
関の断面図である。FIG. 2 is a sectional view of the two-cycle internal combustion engine taken along line II-II in FIG.
【図３】図１の III−III 線に沿ってみた断面図であ
る。FIG. 3 is a sectional view taken along line III-III in FIG.
【図４】給排気弁の開弁時期と燃焼噴射時期を示す線図
である。FIG. 4 is a diagram showing a valve opening timing of a supply / exhaust valve and a combustion injection timing.
【図５】ループ掃気流の流れを示す図２と同様の断面図
である。5 is a cross-sectional view similar to FIG. 2 showing the flow of loop scavenging air.
【図６】クランク角と筒内圧力の関係を示す線図であ
る。FIG. 6 is a diagram showing the relationship between crank angle and cylinder pressure.
【図７】給気弁のカーテン面積が大きい場合と給気ポー
トのスロート面積が大きい場合とで吸入空気流を比較し
た代表的な例を示す線図である。FIG. 7 is a diagram showing a typical example in which the intake air flow is compared when the curtain area of the air supply valve is large and when the throat area of the air supply port is large.
６ａ…シリンダヘッド内壁面 １０…凹部（第１の凹部） １２ａ…給気弁（第１の給気弁） １２ｂ…第２の給気弁 １４ａ…第１排気弁 １４ｂ…第２排気弁 １６…第１の凹部の周壁面 １６ａ…マスク壁 ２６…第２の凹部 ２８…第２の凹部の周壁面 ２８ａ…マスク壁 6a ... Cylinder head inner wall surface 10 ... Recessed portion (first recessed portion) 12a ... Air supply valve (first air supply valve) 12b ... Second air supply valve 14a ... First exhaust valve 14b ... Second exhaust valve 16 ... Peripheral wall surface of first concave portion 16a ... Mask wall 26 ... Second concave portion 28 ... Perimeter wall surface of second concave portion 28a ... Mask wall
Claims (1)
し、排気弁と反対側に位置するシリンダヘッド内壁面上
に凹部を形成して該凹部内に給気弁を配置し、排気弁側
に形成される給気弁の開口を該凹部の周壁面により形成
されるマスク壁によって覆うようにした２サイクル内燃
機関の燃焼室構造において、上記凹部の底壁面上に上記
凹部の周壁面から間隔を隔てて第２の凹部を形成し、該
第２の凹部内に第２の給気弁を配置すると共に排気弁側
に形成される第２の給気弁の開口を第２の凹部の周壁面
により形成されるマスク壁によって覆うようにした２サ
イクル内燃機関の燃焼室構造。1. An exhaust valve is arranged on an inner wall surface of a cylinder head, a recess is formed on an inner wall surface of the cylinder head located on the side opposite to the exhaust valve, and an air supply valve is arranged in the recess. In a combustion chamber structure of a two-cycle internal combustion engine in which an opening of an air supply valve formed in the recess is covered by a mask wall formed by a peripheral wall surface of the recess, a space is provided on a bottom wall surface of the recess from the peripheral wall surface of the recess. A second recess is formed with a space between the second recess and the second air supply valve is arranged in the second recess, and the opening of the second air supply valve formed on the exhaust valve side is formed around the second recess. A combustion chamber structure of a two-cycle internal combustion engine that is covered by a mask wall formed by wall surfaces.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP22796091A JPH0571352A (en) | 1991-09-09 | 1991-09-09 | Combustion chamber structure for two-cycle internal combustion engine |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP22796091A JPH0571352A (en) | 1991-09-09 | 1991-09-09 | Combustion chamber structure for two-cycle internal combustion engine |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH0571352A true JPH0571352A (en) | 1993-03-23 |
Family
ID=16868957
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP22796091A Pending JPH0571352A (en) | 1991-09-09 | 1991-09-09 | Combustion chamber structure for two-cycle internal combustion engine |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH0571352A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2017110957A1 (en) * | 2015-12-26 | 2017-06-29 | 康仁 矢尾板 | Engine with improved knocking resistance |
-
1991
- 1991-09-09 JP JP22796091A patent/JPH0571352A/en active Pending
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2017110957A1 (en) * | 2015-12-26 | 2017-06-29 | 康仁 矢尾板 | Engine with improved knocking resistance |
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