JPS6258015A - Two-cycle engine - Google Patents

Two-cycle engine

Info

Publication number
JPS6258015A
JPS6258015A JP19489785A JP19489785A JPS6258015A JP S6258015 A JPS6258015 A JP S6258015A JP 19489785 A JP19489785 A JP 19489785A JP 19489785 A JP19489785 A JP 19489785A JP S6258015 A JPS6258015 A JP S6258015A
Authority
JP
Japan
Prior art keywords
exhaust
center line
exhaust port
cylinder
port
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.)
Granted
Application number
JP19489785A
Other languages
Japanese (ja)
Other versions
JPH0588366B2 (en
Inventor
Masaki Maeda
正樹 前田
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.)
Yamaha Motor Co Ltd
Original Assignee
Yamaha Motor Co 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 Yamaha Motor Co Ltd filed Critical Yamaha Motor Co Ltd
Priority to JP19489785A priority Critical patent/JPS6258015A/en
Publication of JPS6258015A publication Critical patent/JPS6258015A/en
Publication of JPH0588366B2 publication Critical patent/JPH0588366B2/ja
Granted 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
    • 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

  • Cylinder Crankcases Of Internal Combustion Engines (AREA)

Abstract

PURPOSE:To reduce the blow-bye of fresh air, without preventing an outflow of exhaust gas, by forming an exhaust route which extends from an exhaust port formed on the inner circumferential wall of a cylinder, diagonally downward, as the center line of this exhaust route bends, and the upper surface of the circumferential wall of this exhaust route slants along said center line. CONSTITUTION:An exhaust port 12 and others are opened on one-side surface of the inner circumferential wall of a cylinder of a cylinder head 6, and this exhaust port 12 leads to the outside through an exhaust route 14 which is extensionally formed diagonally downward. In this case, the exhaust route 14 is formed as its center line 20 bends gradually. That is, in the same way as the center line 20 of the exhaust port 12 side, slants in the axial direction of the cylinder, against the center line 20 on the lower stream side from the bending section A, the center line 20 is bent in the shape of 'chevron' at the bending section A following to the exhaust port 12. The upper surface 14a of the circumferential wall of the exhaust route 14, near the exhaust port 12, is also slanted along said center line 20, in the axial direction of the cylinder. That is, the upper surface 14a of the exhaust route 14 is gradually curved out, inwardly.

Description

【発明の詳細な説明】 〔産業上の利用分野〕 本発明は自動二輪車等を駆動する２サイクルエンジンに
関するものである。DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a two-stroke engine for driving motorcycles and the like.

〔従来の技術〕[Conventional technology]

自動二輪車等の２サイクルエンジンとしては、シリンダ
内周壁に排気口および掃気口を形成したものが一般的で
ある。Two-cycle engines for motorcycles and the like generally have an exhaust port and a scavenging port formed in the inner circumferential wall of the cylinder.

ところで、この種の２サイクルエンジンは、排気口を掃
気口よりも僅かに上方に設定することにより、掃気口か
ら噴出される新気によって残留ガスを押出すように構成
されているため、ピストンの上昇行程において掃気口が
閉じて排気口が閉じるまでの間に、新気の一部が排気口
から排出される吹抜けが発生する。その結果、排出され
た新気が大気汚染公害の原因になるという問題があり、
従来、特公昭５２−３７１３０号公報に開示されている
ように、排気通路の排気口に近接した部分に形成した水
平壁と隔壁とによって、新気の流出を妨げるようにして
いる。By the way, this type of two-stroke engine is configured so that the exhaust port is set slightly above the scavenging port so that residual gas is pushed out by the fresh air blown out from the scavenging port. During the upward stroke, between the closing of the scavenging port and the closing of the exhaust port, a blow-by occurs in which a portion of fresh air is discharged from the exhaust port. As a result, there is a problem that the fresh air discharged causes air pollution.
Conventionally, as disclosed in Japanese Patent Publication No. 52-37130, a horizontal wall and a partition wall formed in a portion of an exhaust passage close to an exhaust port are used to prevent fresh air from flowing out.

〔発明″が解決しようとする問題点〕[Problem that the invention seeks to solve]

しかし、この種従来の２サイクルエンジンにおいては、
排気通路に水平壁と隔壁とを形成する構造であるため、
排気通路の形状が複雑になり、製造が困難になるという
不具合があった。また、高速時においては、排気通路中
に突出した隔壁が渦を発生させるため、渦によって流体
抵抗が大きくなる。その結果、排気の排出が妨げられる
ので高速性能が低下するという不都合もあった。However, in this kind of conventional two-stroke engine,
Since the exhaust passage has a horizontal wall and a partition wall,
There was a problem in that the shape of the exhaust passage became complicated, making manufacturing difficult. Furthermore, at high speeds, the partition wall protruding into the exhaust passage generates a vortex, which increases fluid resistance. As a result, the exhaust gas is obstructed, resulting in a disadvantage that high-speed performance is degraded.

〔問題点を解決するだめの手段〕[Failure to solve the problem]

本発明はこのような事情に鑑みなされたもので、節華な
構造でしかも高速性能を低下させることなく新気の吹１
友けを低減できる２サイクルエンジンを提供するもので
ある。本発明に係る２サイクルエンジンは、排気通路の
中心線を、排気口側において下流側に対してシリンダ軸
線方向に傾斜するように途中で屈曲させ、この中心線に
沿って排気通路周壁の排気口側近の上面をシリンダ軸線
方向に（頃斜させたものである。The present invention was developed in view of these circumstances, and has a compact structure that allows fresh air to flow without reducing high-speed performance.
The purpose of the present invention is to provide a two-stroke engine that can reduce the amount of noise. In the two-stroke engine according to the present invention, the center line of the exhaust passage is bent in the middle so as to be inclined in the cylinder axis direction with respect to the downstream side on the exhaust port side, and the exhaust port of the exhaust passage peripheral wall is bent along the center line. The upper surface of the aide is slanted in the direction of the cylinder axis.

〔作用〕[Effect]

本発明においては、排気口に対向して傾斜した排気通路
周壁の北面で、シリンダ内から略水平方向に向かう新気
のみの流れ方向を変化させることにより、排気を流出を
妨げることなく新気の流出を妨げる。In the present invention, by changing the flow direction of only fresh air from inside the cylinder toward a substantially horizontal direction on the north face of the exhaust passage circumferential wall that is inclined opposite to the exhaust port, fresh air can flow without obstructing the outflow of the exhaust gas. Prevent spills.

〔実施例〕〔Example〕

以下、本発明の一実施例を図により詳細に説明する。第
１図は本発明に係る２サイクルエンジンを示す縦断面図
で、同図において符号１で示すものは空冷式の２サイク
ルエンジンを示し、クランクケース２と、このクランク
ケース２の上方に取付けられピストン３を保持したシリ
ンダブロック４と、このシリンダブロック４の上方を被
覆して燃焼室５を形成するシリンダヘッド６とを備えて
いる。クランクケース２にはクランク室７が形成され、
クランク軸８が収容されている。９はクランク軸８と前
記ピストン３とを連結するコンロッド、１０はシリンダ
ヘッド６に取付けられ先端の電極を燃焼室５内に臨ませ
た点火プラグである。Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a longitudinal cross-sectional view showing a two-stroke engine according to the present invention. In the same figure, the reference numeral 1 indicates an air-cooled two-stroke engine, which includes a crankcase 2 and a crankcase installed above the crankcase 2. It includes a cylinder block 4 that holds a piston 3, and a cylinder head 6 that covers the upper part of the cylinder block 4 and forms a combustion chamber 5. A crank chamber 7 is formed in the crank case 2,
A crankshaft 8 is housed therein. 9 is a connecting rod that connects the crankshaft 8 and the piston 3; 10 is a spark plug that is attached to the cylinder head 6 and has an electrode at its tip facing into the combustion chamber 5;

前記シリンダへンド６のシリンダ内周壁の一側面には、
排気口１２および複数個の掃気口１３が開口されている
。これらの開口位置は排気口１゛２の方が掃気口１３に
よりも僅かに上方に設定されている。排気口１２は、こ
の排気口１２から斜め下方に向かって延設された排気通
路１４で外部に開放されており、掃気口１３は掃気通路
で前記クランク室７に連通されている。１５は排気口１
２の反対側のシリンダ周壁に開口された吸気口で、リー
ドバルブ１６が介装された吸気通路１７をクランク室７
に連通している。On one side of the cylinder inner peripheral wall of the cylinder head 6,
An exhaust port 12 and a plurality of scavenging ports 13 are opened. The positions of these openings are such that the exhaust ports 1 and 2 are slightly higher than the scavenging ports 13. The exhaust port 12 is open to the outside through an exhaust passage 14 extending diagonally downward from the exhaust port 12, and the scavenging port 13 is communicated with the crank chamber 7 through the scavenging passage. 15 is exhaust port 1
The intake passage 17 in which the reed valve 16 is inserted is connected to the crank chamber 7 through an intake port opened in the cylinder peripheral wall on the opposite side of the cylinder 2.
is connected to.

排気通路１４は、中心線２０が途中において比較的緩や
かに屈曲されるように形成されている。The exhaust passage 14 is formed such that the center line 20 is bent relatively gently in the middle.

すなわち、中心線２０は排気口１２よりの屈曲部Ａにお
いて、排気口１２例の中心線２０が屈曲部Ａよりも下流
側の中心線２０に対してシリンダ軸線方向に傾斜するよ
うにく字状に屈曲されている。That is, the center line 20 is formed in a dogleg shape at the bend A from the exhaust port 12 so that the center line 20 of the 12 exhaust ports is inclined in the cylinder axis direction with respect to the center line 20 on the downstream side of the bend A. It is bent to

そして、この中心線２０に沿って、排気通路周壁の排気
口１２付近の上面］、　４　ａはシリンダ軸線方向に傾
斜されている。換言すれば、排気通路１４は鎖線２１で
示した従来のものと異なり、上面１４ａが漸次内側方向
に膨出している。また、その膨出量は排気通路１４の断
面積に対して比較的小さく設定されている。一方、排気
通路１４の周壁の下面は途中で屈曲されるようなことが
なく円滑に形成されている。Along this center line 20, the upper surface of the peripheral wall of the exhaust passage in the vicinity of the exhaust port 12], 4a is inclined in the cylinder axis direction. In other words, the exhaust passage 14 differs from the conventional exhaust passage 14 shown by the chain line 21 in that the upper surface 14a gradually bulges inward. Further, the amount of bulge is set to be relatively small with respect to the cross-sectional area of the exhaust passage 14. On the other hand, the lower surface of the peripheral wall of the exhaust passage 14 is smoothly formed without being bent in the middle.

排気通路１４の断面形状について説明すると、第２図、
第３図、第４図に第１図のｎ−ｎ線断面図、ｎＩ　−Ｉ
ＩＩ線断面図、ＩＶ　−ＩＶ線断面図を示すように、排
気口１２付近では水平方向に長い矩形を呈しており、下
流に向かうにしたがって排気通路周壁の上面１４ａが漸
次下方に膨出している。上面１４ａの膨出量は第３図に
示す屈曲部Ａを含む断面において最大となっ、ている。The cross-sectional shape of the exhaust passage 14 will be explained as shown in FIG.
Figures 3 and 4 are cross-sectional views taken along the line n-n in Figure 1, and nI-I.
As shown in the sectional view taken along the line II and the sectional view taken along the line IV-IV, the vicinity of the exhaust port 12 has a horizontally long rectangular shape, and the upper surface 14a of the peripheral wall of the exhaust passage gradually bulges downward as it goes downstream. . The amount of bulge of the upper surface 14a is maximum in the cross section including the bent portion A shown in FIG.

その下流側は、上面１４ａが角部を円滑にするように後
退し接続口２２においては図示しない排気管と接続する
ために円形とされている。On the downstream side, the upper surface 14a recedes to make the corners smooth, and the connection port 22 is circular in order to be connected to an exhaust pipe (not shown).

このように構成された２サイクルエンジンにおいては、
新気が燃焼してピストン３が下降すると、第５図に示す
ように先ず排気口１２が開いて排気２３が排出されるが
、このとき、排気２３は斜め下方の矢印Ｅ方向に向かい
排気通路周壁の上面１４ａの表面に沿って流れる。その
ため、上面１４ａは排気２３に対しては流出を妨げるこ
とがない。これは高速時であっても同様であり、排気２
３を円滑に案内するので、従来のように渦を発生させて
流体抵抗となることがない。In a two-stroke engine configured in this way,
When the fresh air is burned and the piston 3 descends, the exhaust port 12 first opens and the exhaust gas 23 is discharged, as shown in FIG. It flows along the surface of the upper surface 14a of the peripheral wall. Therefore, the upper surface 14a does not obstruct the outflow of the exhaust gas 23. This is the same even at high speeds, and the exhaust 2
3 is guided smoothly, so there is no need to generate vortices that create fluid resistance as in the conventional case.

ピストン３がさらに下降した第６図に示す状態では、ク
ランク室７内で予圧された新気２４が掃気口１３からシ
リンダ内に導入される。そのため、残された排気２３が
排気口１２から押出され、この状態で下死点に達する。In the state shown in FIG. 6 in which the piston 3 is further lowered, fresh air 24 pre-pressurized within the crank chamber 7 is introduced into the cylinder from the scavenging port 13. Therefore, the remaining exhaust gas 23 is pushed out from the exhaust port 12 and reaches the bottom dead center in this state.

その後、ピストン３は上昇行程に移り、第７図に示す掃
気口１３が閉じられる直前において排気２３の排出が終
了し、新気２４の一部が掃気口１３および排気口１２方
向に流れ始める。この新気２４の流れは第８図に示す排
気口１２が閉じられた状態まで続き排気口１２を吹抜け
ようとする。Thereafter, the piston 3 moves to an upward stroke, and exhaustion of the exhaust gas 23 ends just before the scavenging port 13 shown in FIG. 7 is closed, and a portion of fresh air 24 begins to flow toward the scavenging port 13 and the exhaust port 12. This flow of fresh air 24 continues until the exhaust port 12 is closed, as shown in FIG. 8, and attempts to blow through the exhaust port 12.

しかし、排気通路周壁の上面１４ａが排気口１２に対向
して傾斜しているので、新気２４の流出を妨げることが
できる。すなわち、新気２４は矢印Ｎで示す略水平方向
に向かうが、上面１４ａによってその流れの方向が変化
させられるからである。その結果、新気２４のエネルギ
が減衰され、上面１４ａより内側の圧力が高くなるため
、流出が妨げられて吹抜けが低減される。However, since the upper surface 14a of the circumferential wall of the exhaust passage is inclined to face the exhaust port 12, it is possible to prevent the fresh air 24 from flowing out. That is, although the fresh air 24 heads in the substantially horizontal direction indicated by the arrow N, the direction of the flow is changed by the upper surface 14a. As a result, the energy of the fresh air 24 is attenuated and the pressure inside the upper surface 14a becomes higher, which prevents outflow and reduces blow-through.

〔発明の効果〕〔Effect of the invention〕

以上説明したように本発明によれば、排気通路の中心線
を、排気口側において下流側に対してシリンダ軸線方向
に傾斜するように途中で屈曲させ、この中心線に沿って
排気通路周壁の排気口付近の上面をシリンダ軸線方向に
傾斜させたから、排気口に対向して傾斜した排気通路周
壁の上面で、シリンダ内から略水平方向に向かう新気の
みの流れ方向を変化させることにより、排気を流出を妨
げることなく新気の流出を妨げることができる。As explained above, according to the present invention, the center line of the exhaust passage is bent in the middle on the exhaust port side so as to be inclined in the cylinder axis direction with respect to the downstream side, and the peripheral wall of the exhaust passage is bent along the center line. Since the upper surface near the exhaust port is inclined in the direction of the cylinder axis, the upper surface of the circumferential wall of the exhaust passage, which is inclined opposite to the exhaust port, changes the flow direction of fresh air from inside the cylinder in a substantially horizontal direction. It can prevent the outflow of fresh air without blocking the outflow.

したがって、従来のように排気通路の形状を複雑にした
り、排気の流出を妨げることがないから、簡単な構造で
しかも高速性能を低下させることなく新気の吹抜けが低
減できる。Therefore, unlike in the past, the shape of the exhaust passage is not complicated and the outflow of exhaust gas is not obstructed, so that blow-by of fresh air can be reduced with a simple structure and without deteriorating high-speed performance.

【図面の簡単な説明】[Brief explanation of the drawing]

第１図は本発明に係る２サイクルエンジンを示す縦断面
図、第２図は第１図のｎ−ｍ線断面図゛、第３図は同じ
＜ｍ−ｍ線断面図、第４図は同しくＩＶ−ＩＶ線断面図
、第５図〜第８図は動作状態を説明するための概略図で
ある。 ３・・・・ピストン、４・・・　・シリンダブロック、
１２・・・・排気口、１３・・・・掃気口、１４・・・
・排気通路、１４ａ・・・・上面、２０・・・・中心線
。 第１図 第２図　　　第３図　　　第４図 第５図　　　　　第６図FIG. 1 is a longitudinal cross-sectional view showing a two-stroke engine according to the present invention, FIG. Similarly, sectional views taken along the line IV-IV and FIGS. 5 to 8 are schematic diagrams for explaining the operating state. 3... Piston, 4... ・Cylinder block,
12...Exhaust port, 13...Scavenging port, 14...
- Exhaust passage, 14a...Top surface, 20...Center line. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6

Claims (1)

【特許請求の範囲】[Claims] シリンダ内周壁に排気口に有する２サイクルエンジンに
おいて、前記排気口から斜め下方に延びる排気通路の中
心線を、排気口側において下流側に対してシリンダ軸線
方向に傾斜するように途中で屈曲させ、この中心線に沿
って排気通路周壁の排気口付近の上面をシリンダ軸線方
向に傾斜させてなる２サイクルエンジン。In a two-stroke engine having an exhaust port on the inner circumferential wall of the cylinder, the center line of the exhaust passage extending diagonally downward from the exhaust port is bent midway on the exhaust port side so as to be inclined in the cylinder axis direction with respect to the downstream side, A two-stroke engine is constructed in which the upper surface of the peripheral wall of the exhaust passage near the exhaust port is inclined in the direction of the cylinder axis along this center line.
JP19489785A 1985-09-05 1985-09-05 Two-cycle engine Granted JPS6258015A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
JP19489785A JPS6258015A (en) 1985-09-05 1985-09-05 Two-cycle engine

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP19489785A JPS6258015A (en) 1985-09-05 1985-09-05 Two-cycle engine

Publications (2)

Publication Number Publication Date
JPS6258015A true JPS6258015A (en) 1987-03-13
JPH0588366B2 JPH0588366B2 (en) 1993-12-22

Family

ID=16332145

Family Applications (1)

Application Number Title Priority Date Filing Date
JP19489785A Granted JPS6258015A (en) 1985-09-05 1985-09-05 Two-cycle engine

Country Status (1)

Country Link
JP (1) JPS6258015A (en)

Also Published As

Publication number Publication date
JPH0588366B2 (en) 1993-12-22

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