WO2012132628A1 - Two-stroke engine - Google Patents

Two-stroke engine Download PDF

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Publication number
WO2012132628A1
WO2012132628A1 PCT/JP2012/054009 JP2012054009W WO2012132628A1 WO 2012132628 A1 WO2012132628 A1 WO 2012132628A1 JP 2012054009 W JP2012054009 W JP 2012054009W WO 2012132628 A1 WO2012132628 A1 WO 2012132628A1
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WO
WIPO (PCT)
Prior art keywords
wall surface
cylinder
scavenging
opening
width
Prior art date
Application number
PCT/JP2012/054009
Other languages
French (fr)
Japanese (ja)
Inventor
健治 今福
Original Assignee
株式会社マキタ
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Filing date
Publication date
Application filed by 株式会社マキタ filed Critical 株式会社マキタ
Publication of WO2012132628A1 publication Critical patent/WO2012132628A1/en

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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
    • F02B25/00—Engines characterised by using fresh charge for scavenging cylinders
    • F02B25/20—Means for reducing the mixing of charge and combustion residues or for preventing escape of fresh charge through outlet ports not provided for in, or of interest apart from, subgroups F02B25/02 - F02B25/18
    • F02B25/22—Means for reducing the mixing of charge and combustion residues or for preventing escape of fresh charge through outlet ports not provided for in, or of interest apart from, subgroups F02B25/02 - F02B25/18 by forming air cushion between charge and combustion residues
    • 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
    • F02B25/00—Engines characterised by using fresh charge for scavenging cylinders
    • F02B25/14—Engines characterised by using fresh charge for scavenging cylinders using reverse-flow scavenging, e.g. with both outlet and inlet ports arranged near bottom of piston stroke
    • 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

Definitions

  • the present invention relates to a two-stroke engine.
  • the two-stroke engine can be easily reduced in size and weight because of its simple structure. Therefore, it is often used for portable or small machines.
  • the portable or small machine means, for example, a brush cutter, a coffee harvester, an olive harvester, a hedge trimmer, a chain saw, a blower, a management machine, a cultivator, a generator, a compressor, a pump, a work machine, a pocket bike, a motor.
  • Leisure equipment such as paragliding.
  • Patent Document 1 discloses a technique of a two-stroke engine in which two exhaust passages are formed.
  • Patent Document 2 discloses a technique of a two-stroke engine in which a plurality of exhaust passages are formed.
  • Patent Document 1 it is possible to prevent the scavenging air (mixture) from blowing through the cylinder by colliding with the cylinder wall between the two exhaust passages.
  • the two exhaust passages are provided, the structure becomes complicated and the cost increases.
  • the technique disclosed in Patent Document 2 has a problem that the structure becomes complicated.
  • An object of the present invention is to provide a two-stroke engine with a simple structure and high thermal efficiency.
  • a two-stroke engine includes a cylinder, a piston capable of reciprocating in the cylinder, an exhaust passage provided in the cylinder, and a scavenging passage provided in the cylinder.
  • An exhaust opening portion of the exhaust passage portion and a cylinder side scavenging opening portion of the scavenging passage portion are formed on the inner peripheral surface, and the exhaust opening portion includes at least a part of a central portion in the width direction of the exhaust opening portion.
  • the width of the exhaust opening at the center position between the cylinder head side and the crank chamber side of the wall surface is larger than the total width of the exhaust opening at the cylinder head side of the wall surface.
  • the wall surface is formed such that the width of the wall surface at the center position between the cylinder head side and the crank chamber side is smaller than the width of the wall surface at the cylinder head side position.
  • the wall surface is formed such that the width of the wall surface at the center position between the cylinder head side and the crank chamber side is the same as the width of the wall surface at the crank chamber side position.
  • the wall surface is formed such that a width of the wall surface on the cylinder head side is larger than a width on the crank chamber side.
  • the exhaust passage part divided by the wall surface joins behind the wall surface.
  • the wall portion constituting the wall surface has a substantially triangular cross-sectional shape in the bore direction.
  • the wall surface is formed with the same width from the cylinder head side to the crank chamber side.
  • the width of the wall surface is approximately the same as the width of one of the exhaust openings divided by the wall surface.
  • the shape of the exhaust opening is substantially U-shaped.
  • the shape of the exhaust opening is substantially H-shaped.
  • the position of the wall surface end which is the end of the wall surface on the crank chamber side, coincides with the position of the scavenging opening end of the scavenging opening on the cylinder head side in the direction of the center axis of the cylinder. Yes.
  • FIG. 1 is a cross-sectional view of a two-stroke engine according to a first embodiment of the present invention. It is explanatory drawing in the cross section in II-II in FIG. It is explanatory drawing of the effect of a structure like FIG. It is explanatory drawing of A arrow in FIG. 1, and A arrow in FIG. It is explanatory drawing of a wall surface. It is explanatory drawing of 2nd Embodiment. It is explanatory drawing of 3rd Embodiment. It is explanatory drawing of 4th Embodiment. It is explanatory drawing of 5th Embodiment. It is explanatory drawing of 6th Embodiment. It is explanatory drawing of 7th Embodiment. It is explanatory drawing of 8th Embodiment. It is explanatory drawing of 9th Embodiment.
  • FIG. 1 is a cross-sectional view of a two-stroke engine 1 according to a first embodiment of the present invention.
  • the Schnurelet type two-stroke engine 1 includes a cylinder head 3, a cylinder 5, a crankcase 7, a piston 21, and a connecting rod 19.
  • the cylinder head 3 does not need to be separated from the cylinder 5 and may be formed integrally as shown in FIG.
  • a crank chamber 31 is formed by the cylinder 5, the crankcase 7 and the piston 21. That is, the crank chamber 31 is a space formed between the inner peripheral surface of the cylinder 5 and the piston 21 and the substantially cylindrical space on the crankcase 7 side, and the crankcase 7. The volume of the internal space of the crank chamber 31 changes as the piston 21 slides.
  • a cylinder inner space 29 is formed by the cylinder head 3, the cylinder 5, and the piston 21.
  • a crankshaft 9 is rotatably supported in the crank chamber 31.
  • the crankshaft 9 includes a crankpin 11, a crank journal 13, a counterweight 15, and a crank arm 17.
  • the connecting rod 19 supports the crank pin 11 in a rotatable manner.
  • the connecting rod 19 supports the piston 21 so as to be swingable.
  • the piston 21 slides inside the cylinder 5 via the piston pin 22.
  • An intake opening 23 a is formed in a portion of the cylinder 5 in the direction toward the crank chamber 31.
  • An intake passage portion 23 through which an air-fuel mixture that has passed through an air cleaner (not shown) and a carburetor (not shown) flows into the crank chamber 31 is provided through the intake opening portion 23a.
  • the crank chamber 31 has a crank chamber-side scavenging opening 25a.
  • the scavenging gas is sent to the scavenging passage 25 through the crank chamber side scavenging opening 25a.
  • the scavenging of the scavenging passage 25 flows into the cylinder 5 (cylinder inner space 29) through a cylinder-side scavenging opening 25b formed in the cylinder 5.
  • An exhaust opening 27 a is formed in the cylinder 5. Exhaust gas is discharged into the exhaust passage 27 through the exhaust opening 27a.
  • the two-stroke engine assumed in the present embodiment is small for carrying and is not necessarily operated in a certain direction because of its portability.
  • the direction is defined. In the normal use state, the upward direction in the vertical direction is referred to as the upper direction. Conversely, the ground side direction is defined as the lower direction. Further, the horizontal direction in the normal use state is defined as the horizontal direction.
  • the center axis of the cylinder 5 is formed to be horizontal or nearly horizontal, but it goes without saying that the cylinder 5 may be a vertical engine in which the center axis of the cylinder 5 is directed in the vertical direction. .
  • the central axis of the cylinder 5 is in a horizontal or nearly horizontal state. Needless to say, however, the vertical engine has a different positional relationship.
  • the cylinder head 3 is fitted with a spark plug 33 that penetrates the cylinder head 3 and exposes an ignition portion in the cylinder inner space 29.
  • a dome-shaped ignition space is also formed in the cylinder head 3 in the ignition portion of the ignition plug 33.
  • An intake opening 23 a is formed in a portion of the cylinder 5 in the direction toward the crank chamber 31.
  • the intake passage portion 23 that forms the intake opening portion 23 a communicates from the cylinder head 3 side toward the crank chamber 31 side and toward the center axis side of the cylinder 5.
  • a crank chamber side scavenging opening 25a is formed at the center of the cylinder 5 or in the upper direction (in the vertical engine, the direction of the inner circumferential surface in one direction).
  • the scavenging passage 25 forming the crank chamber side scavenging opening 25a is formed from the crank chamber 31 side toward the cylinder head 3 side. Further, the rotation direction of the crankshaft 9 rotates counterclockwise in FIG.
  • crankshaft 9 rotates in the direction in which the air-fuel mixture flowing in from the intake opening 23a enters.
  • the direction of the straight line coincides with the rotational direction of the crankshaft 9.
  • the air-fuel mixture can flow more smoothly from the intake opening 23a to the crank chamber 31 by the rotation of the crankshaft 9 (particularly the counterweight 15).
  • the cylinder 5 is formed with a cylinder-side scavenging opening 25b and an exhaust opening 27a.
  • the cylinder side scavenging opening 25b is formed at a position closer to the crank chamber 31 than the exhaust opening 27a.
  • the exhaust opening 27a is opened first, and the cylinder side scavenging opening 25b is then opened at the port timing.
  • the scavenging passage 25 extends in the axial direction of the center axis of the cylinder 5 (from the position in the crank chamber 31 side direction to the position in the cylinder head 3 side direction).
  • the scavenging passage 25 extends in the axial direction of the central axis of the cylinder 5 and opens into the cylinder 5 through a cylinder-side scavenging opening 25b. Therefore, the scavenging airflow (mixture) flowing in from the cylinder-side scavenging opening 25b has a component on the cylinder head 3 side (top dead center side). Further, in the Schnurelet-type two-stroke engine 1, scavenging air (air mixture) flows toward the side surface of the cylinder 5 at a position opposite to the exhaust opening 27a (see also FIG. 2 for the following explanation). .
  • the scavenging airflow (air mixture) flowing in from the cylinder-side scavenging opening 25b has a directional component in the lower direction than the central axis of the cylinder 5 in FIG.
  • the scavenging airflow (mixture) flowing from the cylinder-side scavenging opening 25 b flows toward the side surface on the lower side of the center axis of the cylinder 5 and the side surface on the cylinder head 3 side. Convection occurs by colliding with the side surface of the scavenging airflow (mixture) after flowing in from the side surface in the direction lower than the central axis of the cylinder 5 and the side surface on the cylinder head 3 side.
  • the convective scavenging air (air mixture) collides with the wall surface 27b and further convects. Then, before most of the scavenged airflow (air mixture) colliding with the wall surface 27 flows out from the exhaust opening 27a, the piston 21 moves to the cylinder head 3 side, and the cylinder side scavenging opening. 25b is closed.
  • the presence of the wall surface 27b makes it possible to prevent most of the scavenging air (air mixture) from flowing out of the exhaust opening 27a.
  • the fact that most of the scavenging air (air mixture) does not flow out means that the air is exhausted more efficiently. And since it becomes possible to discharge
  • FIG. 2 is an explanatory view in a section taken along line II-II in FIG.
  • FIG. 3 is an explanatory diagram of the effect of the configuration shown in FIG.
  • the scavenging passage 25 is composed of two passages.
  • a passage portion on the right side of the center axis of the cylinder 5 is the right scavenging passage portion 25R
  • a passage portion on the left side of the center axis of the cylinder 5 is the left scavenging passage portion 25L.
  • the right scavenging passage portion 25R and the left scavenging passage portion 25L are formed so as to extend from the back side to the front side in FIG. Note that the number of the scavenging passage portions 25 is not necessarily two as shown in FIG. 2, and may be more than that.
  • the opening part of the right scavenging passage 25R to the cylinder 5 is the right scavenging opening 25bR
  • the opening part of the left scavenging passage 25L to the cylinder 5 is the left scavenging opening 25bL.
  • a right scavenging opening 25bR and a left scavenging opening 25bL are formed at the right and left positions of the exhaust opening 27a, respectively.
  • the opening part to the cylinder 5 of the exhaust passage part 27 is the exhaust opening part 27a.
  • a wall surface 27b is formed in the exhaust opening 27a.
  • the exhaust gas is divided into the right side and the left side. That is, the left exhaust opening 27aL is formed by the wall surface 27b at the left side position of the wall surface 27b. Further, a right exhaust opening 27aR is formed by the wall surface 27b at a position on the right side of the wall surface 27b.
  • the wall portion 28 constituting the wall surface 27b has a substantially triangular cross-sectional shape in the bore direction as shown in FIG.
  • the wall surface 27 b forms the same surface as the inner peripheral surface of the cylinder 5. For this reason, the wall surface 27 b has a function of guiding the piston 21 that slides in the cylinder 5.
  • one of the other two sides of the wall portion 28 other than the wall surface 27b forms a part of the flow path from the left exhaust opening 27aL, and the last one of the flow path from the right exhaust opening 27aR. Forming part.
  • the other two sides other than the wall surface 27b have a shape that allows the exhaust to smoothly merge. Since it has such a shape, it becomes possible to join exhaust smoothly.
  • This wall surface 27b (exhaust passage) is positioned at the position of the inner peripheral surface of the cylinder 5 on the rotational direction side where the crankshaft 9 rotates and the position of the inner peripheral surface of the cylinder 5 forming the cylinder inner space 29 on the crank chamber 31 side. Part 27) is formed.
  • the position where the wall surface 27b is formed is a position where the pressure of the head of the piston 21 is applied when the piston 21 starts moving from the bottom dead center position toward the top dead center. Since the wall surface 27b capable of guiding the piston 21 is formed at such a position, the wall surface 27b can smoothly guide the piston 21. Since the wall surface 27b guides the piston 21 smoothly, it is possible to reduce vibration and wear loss.
  • the wall surface 27 b does not necessarily function as the inner peripheral surface of the cylinder 5.
  • the case may be a case where the wall surface 27b on the cylinder 5 side is at an outer position in the radial direction than the inner peripheral surface of the cylinder 5 (when it is in a retracted position).
  • the piston 21 and one side on the cylinder 5 side do not contact the piston 21, it is not necessary to increase the surface roughness accuracy on the one side of the cylinder 5 and can be manufactured at low cost. There is an effect of becoming.
  • the most important role of the wall surface 27b is that the scavenging air flowing out from the exhaust opening 27a collides with the wall surface 27b as shown in FIG. 29 for convection. That is, the wall surface 27b (exhaust passage portion 27) is formed in a portion that is about to flow out from the exhaust opening portion 27a. For this reason, it is possible to further convection a part of the scavenging air and prevent blow-through.
  • the scavenging air (mixed gas) that would otherwise flow out of the exhaust opening 27a can be further convected, the air supply efficiency and the charging efficiency are improved, the output is improved, and the exhaust gas performance is improved. Can be planned.
  • the scavenging airflow (air mixture) before colliding with the wall surface 27b flows as follows (see also FIG. 1). As shown in FIG. 2, the flow that has flowed out of the right scavenging opening 25bR and the left scavenging opening 25bL travels in the cylinder inner space 29, and then collides with a side surface at a position lower than the central axis of the cylinder 5. Further, the flow from the right scavenging opening 25bR and the flow from the left scavenging opening 25bL collide with each other and flow toward the wall surface 27b of the exhaust opening 27a.
  • a cross section in a direction perpendicular to the central axis of the cylinder 5 is called a bore cross section.
  • the direction away from the intersection of the bore cross section and the central axis of the cylinder 5 is referred to as the radial direction.
  • air-fuel mixture, liquid and particulate fuel components, oil, oil mist and the like flow into the cylinder internal space 29 in the cylinder 5 from the scavenging passage 25.
  • Most of the fuel components (liquid and particulate fuel, oil, oil mist, etc.) of the mass ride on the air-fuel mixture flow as indicated by arrows in FIG.
  • a part of the fuel component having a large mass does not get on the flow of the air-fuel mixture and propagates along the wall surface of the cylinder 5 between the cylinder-side scavenging opening 25b and the exhaust opening 27a (wall surface transmission) or along the wall surface. It flows and is directly discharged from the exhaust passage portion 27 (shortcut).
  • FIG. 4 is an explanatory view of the arrow A in FIG. 1 and the arrow A in FIG.
  • the right scavenging opening 25bR and the left scavenging opening 25bL are located closer to the crank chamber 31 than the exhaust opening 27a.
  • the exhaust passage portion 27 (exhaust opening 27a) first enters the cylinder inner space 29 as the piston 21 moves toward the crank chamber 31. You will communicate.
  • the exhaust in the cylinder inner space 29 is discharged out of the cylinder 5 from the portion of the exhaust opening 27a on the cylinder head 3 side.
  • the exhaust gas is discharged from the cylinder inner space 29 to some extent.
  • the right scavenging passage portion 25R (right scavenging opening portion 25bR) and the left scavenging passage portion 25L (left scavenging opening portion 25bL) communicate with the cylinder inner space 29 in a state where the pressure in the cylinder inner space 29 is reduced by the exhaust. To do. As a result, scavenging gas flows in with exhaust exhausted after the previous combustion cycle being exhausted, so exhaust can be exhausted more effectively. .
  • the wall surface 27 b has a Y shape when viewed from the center axis side of the cylinder 5.
  • the Y shape is formed so that the cylinder head 3 side is in an upward state.
  • FIG. 5 is an explanatory diagram of the wall surface 27b.
  • the exhaust opening 27a has a wall surface 27b at the center.
  • a right exhaust opening 27aR is formed on the right side of the wall surface 27b, and a left exhaust opening 27aL is formed on the left side.
  • the upper side of the drawing is the cylinder head 3 side
  • the lower side of the drawing is the crank chamber 31 side.
  • a right upper dead center inclined portion 27cR is formed on the cylinder head 3 side of the right exhaust opening 27aR
  • a left upper dead center inclined portion 27cL is formed on the cylinder head 3 side of the left exhaust opening 27aL.
  • the right upper dead center inclined portion 27cR and the left upper dead center inclined portion 27cL form a Y-shaped wall surface 27b.
  • the width of the right exhaust opening 27aR on the cylinder head 3 side is the right upper dead center length LUR
  • the width of the right exhaust opening 27aR on the crank chamber 31 side is the right lower dead center length LBR.
  • the width at the center position between the cylinder head 3 side and the crank chamber 31 side is defined as the right center length LMR.
  • the width of the left exhaust opening 27aL on the cylinder head 3 side is the left upper dead center length LUL
  • the width of the left exhaust opening 27aL on the crank chamber 31 side is the left lower dead center length LBL.
  • the width between the cylinder head 3 side and the crank chamber 31 side is the left central length LML.
  • the width on the cylinder head 3 side of the wall surface 27b is the wall top dead center length LUW
  • the width on the crank chamber 31 side of the wall surface 27b is the wall bottom dead center length LBW.
  • the width at the center position between the cylinder head 3 side and the crank chamber 31 side is the wall center length LMW.
  • LBW LMW and LMW ⁇ LUW
  • the Y-shaped wall surface 27b is formed.
  • a circular chamfer may be formed at the joint portion of each wall forming the pipe line of the right exhaust opening 27aR and the left exhaust opening 27aL.
  • the right upper dead center inclined portion 27cR and the left upper dead center inclined portion 27cL may be formed by a part of an arc (see also FIG. 7B described later).
  • the wall surface 27b is formed in this way, when the piston moves from the bottom dead center to the top dead center, the area of the exhaust opening 27a of the exhaust passage portion 27 is initially large. Accordingly, initially, the exhaust gas is discharged without any particular resistance into the exhaust passage portion 27 (see also FIG. 4 for the following description). However, when the piston 21 further rises and reaches the portion where the width of the wall surface 27b becomes large, the area of the rapid exhaust opening 27a decreases. At this time, since the right scavenging opening 25bR and the left scavenging opening 25bL are already closed by the piston 21, the internal pressure of the cylinder 5 increases as the piston 21 rises.
  • the wall surface 27b of the exhaust opening 27a is Y-shaped and has a small area, so that this blow-out can be suppressed. As a result, the air supply efficiency and the charging efficiency are improved, and the output and the exhaust gas performance can be improved.
  • FIG. 6 is an explanatory diagram of the second embodiment.
  • the wall surface 27b may have a shape as shown in FIGS. 6 (a) and 6 (b). That is, only the right upper dead center inclined portion 27cR and the left upper dead center inclined portion 27cL may form the wall surface 27b.
  • FIG. 7 is an explanatory diagram of the third embodiment.
  • the wall surface 27b may have a shape as shown in FIGS. 7A, 7B, and 7C.
  • the right bottom dead center inclined portion 27dR and the left bottom dead center inclined portion 27dL are formed so that the width on the crank chamber 31 side is also narrowed. The reason will be described below (see also FIG. 4 for the following description).
  • a fuel component oil mist, unvaporized fuel, etc.
  • the scavenging air air mixture
  • a fuel component having a large mass that has descended along the wall surface 27b reaches the top surface of the piston and is dispersed and discharged from the left exhaust opening 27aL and the right exhaust opening 27aR. Conceivable. Therefore, the right bottom dead center inclined portion 27dR and the left bottom dead center inclined portion 27dL are formed to reduce the width of the exhaust opening 27a on the crank chamber 31 side, thereby suppressing this blow-through as much as possible.
  • the wall surface 27b may be formed in an arc shape as shown in FIG.
  • FIG. 8 is an explanatory diagram of the fourth embodiment. That is, as shown in FIGS. 8A, 8B, and 8C, the shape of the wall surface 27b may be a straight shape.
  • FIG. 9 is an explanatory diagram of the fifth embodiment. That is, as shown in FIGS. 9A and 9B, the right exhaust opening 27aR and the left exhaust opening 27aL may be circular or arcuate.
  • FIG. 10 is an explanatory diagram of the sixth embodiment.
  • the left center length LML, the right center length LMR, and the wall center length LMW may have the same width.
  • FIG. 11 is an explanatory diagram of the seventh embodiment.
  • the right exhaust opening 27aR and the left exhaust opening 27aL may communicate with each other. This is because the effect of the present embodiment that it is possible to reverse a part of the flow of the scavenging air can be achieved even with such a shape.
  • the communication position is on the crank chamber 31 side in that it is possible to suppress the occurrence of blow-through.
  • the communicating portion may be formed relatively small in the vertical direction as shown in FIG. 11A, or may be formed relatively large in the vertical direction as shown in FIG. Good. 11 (a) and 11 (b), the wall surface 27b has a width at the center position between the cylinder head 3 side of the wall surface 27b and the crank chamber 31 side, and the width at the cylinder head 3 side position of the wall surface 27b. It is more preferable that it is formed so as to be smaller. It is because it can suppress that a blow-by arises more because it comprised in this way.
  • part of the wall surface 27b is interrupted, and the left exhaust opening 27aL and the right exhaust opening 27aR may be connected.
  • an effective size and shape that suppresses direct outflow of the scavenging airflow that is reversed and descends can be obtained.
  • the end face on the crank chamber side of the wall surface 27b is preferably formed at a position where the cylinder-side scavenging opening 25b is closed when the piston moves from the bottom dead center toward the top dead center.
  • scavenging air discharge (blow-through) can be suppressed at the time of blow-down or compression start.
  • FIG. 12 is an explanatory diagram of the eighth embodiment.
  • the communication between the right exhaust opening 27aR and the left exhaust opening 27aL may be provided at the center position.
  • FIG. 13 is an explanatory diagram of the ninth embodiment.
  • the position of the wall surface end 27c that is the end of the wall surface 27b on the crank chamber 31 side is the right scavenging opening end portion 25cR that is the end of the right scavenging opening 25bR on the cylinder head 3 side, and
  • the position of the left scavenging opening 25cL, which is the end of the left scavenging opening 25bL on the cylinder head 3 side, coincides with the direction of the central axis of the cylinder 5 (including substantially coincidence).
  • the position of the wall surface end portion 27c corresponds to the position of the wall surface end portion 27c. It can be said that it is located at With this configuration, when the cylinder-side scavenging opening 25b is opened and the scavenging air is flowing in, the exhaust opening 27a is largely opened, the cylinder-side scavenging opening 25b is closed, and the scavenging air flows. When the gas does not flow in, the opening area of the exhaust opening 27a can be configured to be rapidly reduced. And since it was set as such a structure, prevention of a blow-through can be performed more reliably.
  • the two-stroke engine 1 of the present embodiment includes a cylinder 5, a piston 21 that can reciprocate in the cylinder 5, an exhaust passage portion 27 provided in the cylinder 5, and a scavenging passage portion 25 provided in the cylinder 5. And an exhaust opening 27a of the exhaust passage 27 and a cylinder-side scavenging opening 25b of the scavenging passage 25 are formed on the inner peripheral surface of the cylinder 5.
  • the exhaust opening 27a has a width of the exhaust opening 27a.
  • a wall surface 27b is formed so as to block at least a part of the central portion in the direction, and the width of the exhaust opening 27a at the center position between the cylinder head 3 side and the crank chamber 31 side of the wall surface 27b is the cylinder head 3 side of the wall surface 27b.
  • the wall surface 27b is formed such that the width of the wall surface 27b at the center position between the cylinder head 3 side and the crank chamber 31 side is smaller than the width of the wall surface 27b at the cylinder head 3 side position. Since it has such a structure, it can suppress that a blow-through arises. As a result, the air supply efficiency and the charging efficiency are improved, and the output and the exhaust gas performance can be improved.
  • the wall surface 27b is formed so that the width of the wall surface 27b at the center position between the cylinder head 3 side and the crank chamber 31 side and the width of the wall surface 27b at the crank chamber 31 side position are the same. Since it has such a structure, it can suppress that a blow-through arises. As a result, the air supply efficiency and the charging efficiency are improved, and the output and the exhaust gas performance can be improved.
  • the wall surface 27b is formed such that the width of the wall surface 27b on the cylinder head 3 side is larger than the width on the crank chamber 31 side. Since it has such a structure, it can suppress that a blow-through arises. As a result, the air supply efficiency and the charging efficiency are improved, and the output and the exhaust gas performance can be improved.
  • the exhaust passage portion 27 divided by the wall surface 27b joins behind the wall surface 27b.
  • the structure can be simplified so that the two exhaust passage portions 27 are not required. It becomes.
  • the wall portion 28 constituting the wall surface 27b has a substantially triangular cross-sectional shape in the bore direction. Since it has such a structure, it becomes possible to join exhaust_gas
  • the wall surface 27b is formed with the same width from the cylinder head 3 side to the crank chamber 31 side. Since it has such a structure, it becomes possible to form the wall surface 27b easily.
  • the width of the wall surface 27b is approximately the same as the width of one exhaust opening portion 27a of the exhaust opening portion 27a divided by the wall surface 27b. Since it has such a configuration, it is possible to achieve both the exhaustion from the exhaust opening 27a while the wall surface 27b sufficiently convects the scavenging.
  • the shape of the exhaust opening 27a is formed in a substantially U shape. Since it has such a configuration, it is possible to suppress scavenging air discharge (blow-through) at the time of blow-down or compression start.
  • the shape of the exhaust opening 27a is formed in a substantially H shape. Since it has such a structure, it becomes possible to suppress blow-through more reliably.
  • the position of the wall surface end 27c that is the end of the wall surface 27b on the crank chamber 31 side is the right scavenging opening end 25cR that is the end of the right scavenging opening 25bR on the cylinder head 3 side, and the left scavenging opening 25bL.
  • the left scavenging opening end portion 25cL, which is the end portion on the cylinder head 3 side, coincides (including substantially coincident) in the direction of the central axis of the cylinder 5. Since it comprised in this way, it becomes possible to suppress that a blow-through arises more.
  • the present invention is not limited to the above embodiment, and various changed structures, configurations, and controls may be performed.
  • the direction of the central axis of the cylinder 5 may be the horizontal direction or the vertical direction. That is, the direction of the central axis of the one-stroke engine in the present invention may be any direction.
  • a cross section in a direction perpendicular to the central axis of the cylinder 5 is referred to as a bore cross section.
  • the inner peripheral surface direction of the cylinder 5 is referred to as a tangential direction.
  • the radiation direction from the intersection of the bore cross section and the central axis of the cylinder 5 is referred to as a radial direction.
  • the substantially inverted U shape of the present invention includes a substantially cap shape.
  • An example of the wall surface of the present invention is a wall surface 27b.
  • the shape of the wall surface can be changed variously. In other words, the wall surface of the present invention only needs to be formed so as to block at least a part of the central portion in the width direction of the exhaust opening. Further, the coincidence in the present invention may not be a complete coincidence.

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  • Chemical & Material Sciences (AREA)
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  • Cylinder Crankcases Of Internal Combustion Engines (AREA)

Abstract

Provided is a two-stroke engine having a simple structure and high thermal efficiency.　The two-stroke engine (1) comprises: a cylinder (5); a piston (21) capable of reciprocating in the cylinder (5); an exhaust passage (27) formed in the cylinder (5); and a scavenging passage (25) formed in the cylinder (5), wherein an exhaust opening part (27a) of the exhaust passage (27) and a cylinder-side scavenging opening part (25b) of the scavenging passage (25) are formed in the inner circumferential surface of the cylinder (5), a wall (27b) is formed in the exhaust opening part (27a) to block at least a portion of a widthwise center region of the exhaust opening part (27a), and the width of the exhaust opening part (27a) at a center position of the wall (27b) between a cylinder (3) side and a crank chamber (31) side is greater than the sum of widths of the exhaust opening part (27a) at the cylinder (3) side of the wall (27b).

Description

２ストロークエンジン2-stroke engine
　本発明は、２ストロークエンジンに関する。 The present invention relates to a two-stroke engine.
　２ストロークエンジンは、その構造の簡易性ゆえに、小型化・軽量化が容易である。
　そのため、携帯又は小型の機械には多く用いられている。
　ここで、携帯又は小型の機械とは、例えば、刈払機、コーヒーハーベスタ、オリーブハーベスタ、ヘッジトリマー、チェーンソー、ブロワ、管理機、耕耘機、発電機、コンプレッサ、ポンプ等の作業機やポケットバイク、モーターパラグライダー等のレジャー機器が挙げられる。
　これらの機械は、設置型又は大型の機械よりも、小型性、軽量性、さらに高い熱効率、低公害性等が求められている。 The two-stroke engine can be easily reduced in size and weight because of its simple structure.
Therefore, it is often used for portable or small machines.
Here, the portable or small machine means, for example, a brush cutter, a coffee harvester, an olive harvester, a hedge trimmer, a chain saw, a blower, a management machine, a cultivator, a generator, a compressor, a pump, a work machine, a pocket bike, a motor. Leisure equipment such as paragliding.
These machines are required to have smaller size, lighter weight, higher thermal efficiency, lower pollution, and the like than stationary or large machines.
　特許文献１には、２つの排気通路が形成された２ストロークエンジンの技術が開示されている。 Patent Document 1 discloses a technique of a two-stroke engine in which two exhaust passages are formed.
　特許文献２には、複数の排気通路が形成された２ストロークエンジンの技術が開示されている。 Patent Document 2 discloses a technique of a two-stroke engine in which a plurality of exhaust passages are formed.
特開２００５―２３３０６４号公報Japanese Patent Laid-Open No. 2005-233064 特開平９―２５６８５５号公報JP-A-9-256855
　特許文献１では、２つの排気通路の間のシリンダの壁面に、掃気流（混合気）が衝突することによって、シリンダ内での掃気流（混合気）が吹き抜けてしまうことを防止することができるが、２つの排気通路を有するため構造が複雑化し、コストの増加が生じてしまう。
　また、特許文献２に開示された技術においては、構造が複雑化してしまうという問題点があった。 In Patent Document 1, it is possible to prevent the scavenging air (mixture) from blowing through the cylinder by colliding with the cylinder wall between the two exhaust passages. However, since the two exhaust passages are provided, the structure becomes complicated and the cost increases.
In addition, the technique disclosed in Patent Document 2 has a problem that the structure becomes complicated.
　本発明の目的は、簡易な構造で高い熱効率の２ストロークエンジンを提供することである。 An object of the present invention is to provide a two-stroke engine with a simple structure and high thermal efficiency.
　本発明の２ストロークエンジンは、シリンダと、前記シリンダ内を往復可能なピストンと、前記シリンダに設けられた排気通路部と、前記シリンダに設けられた掃気通路部と、を有し、前記シリンダの内周面には、前記排気通路部の排気開口部および前記掃気通路部のシリンダ側掃気開口部が形成され、前記排気開口部には、前記排気開口部の幅方向における中央部の少なくとも一部を塞ぐように壁面が形成され、前記壁面のシリンダヘッド側とクランク室側との中央位置における排気開口部の幅は、前記壁面のシリンダヘッド側における排気開口部の幅の合計よりも大きく形成されている。 A two-stroke engine according to the present invention includes a cylinder, a piston capable of reciprocating in the cylinder, an exhaust passage provided in the cylinder, and a scavenging passage provided in the cylinder. An exhaust opening portion of the exhaust passage portion and a cylinder side scavenging opening portion of the scavenging passage portion are formed on the inner peripheral surface, and the exhaust opening portion includes at least a part of a central portion in the width direction of the exhaust opening portion. And the width of the exhaust opening at the center position between the cylinder head side and the crank chamber side of the wall surface is larger than the total width of the exhaust opening at the cylinder head side of the wall surface. ing.
　好適には、前記壁面は、前記壁面のシリンダヘッド側とクランク室側との中央位置における幅が前記壁面のシリンダヘッド側位置の幅よりも小さくなるように形成されている。 Preferably, the wall surface is formed such that the width of the wall surface at the center position between the cylinder head side and the crank chamber side is smaller than the width of the wall surface at the cylinder head side position.
　好適には、前記壁面は、前記壁面のシリンダヘッド側とクランク室側との中央位置における幅と前記壁面のクランク室側位置の幅とは同一となるように形成されている。 Preferably, the wall surface is formed such that the width of the wall surface at the center position between the cylinder head side and the crank chamber side is the same as the width of the wall surface at the crank chamber side position.
　好適には、前記壁面は、前記壁面のシリンダヘッド側の幅は、前記クランク室側の幅よりも大きく形成されている。 Preferably, the wall surface is formed such that a width of the wall surface on the cylinder head side is larger than a width on the crank chamber side.
　好適には、前記壁面によって分断された排気通路部は、前記壁面の後方において合流する。 Preferably, the exhaust passage part divided by the wall surface joins behind the wall surface.
　好適には、前記壁面を構成する壁部は、ボア方向の断面形状が略三角形状を有している。 Preferably, the wall portion constituting the wall surface has a substantially triangular cross-sectional shape in the bore direction.
　好適には、前記壁面は、シリンダヘッド側からクランク室側まで同一の幅で形成されている。 Preferably, the wall surface is formed with the same width from the cylinder head side to the crank chamber side.
　好適には、前記壁面の幅は、前記壁面によって分断された排気開口部の一方の排気開口部の幅と同程度である。 Preferably, the width of the wall surface is approximately the same as the width of one of the exhaust openings divided by the wall surface.
　好適には、前記排気開口部の形状が略Ｕ字状に形成されている。 Preferably, the shape of the exhaust opening is substantially U-shaped.
　好適には、前記排気開口部の形状が略Ｈ字状に形成されている。 Preferably, the shape of the exhaust opening is substantially H-shaped.
　好適には、前記壁面の前記クランク室側の端部である壁面端部の位置が、前記掃気開口部のシリンダヘッド側の掃気開口部端部の位置とシリンダの中心軸の方向において一致している。 Preferably, the position of the wall surface end, which is the end of the wall surface on the crank chamber side, coincides with the position of the scavenging opening end of the scavenging opening on the cylinder head side in the direction of the center axis of the cylinder. Yes.
　本発明によって、排気開口部からの掃気流（混合気）の吹き抜けを抑制し、簡易な構造で高い熱効率の２ストロークエンジンを提供することが可能となる。 According to the present invention, it is possible to provide a two-stroke engine having a simple structure and high thermal efficiency by suppressing the scavenging air (air mixture) through the exhaust opening.
本発明の第１の実施形態に係る２ストロークエンジンの断面図である。1 is a cross-sectional view of a two-stroke engine according to a first embodiment of the present invention. 図１におけるＩＩ―ＩＩでの断面での説明図である。It is explanatory drawing in the cross section in II-II in FIG. 図１のような構成の効果の説明図である。It is explanatory drawing of the effect of a structure like FIG. 図１におけるＡ矢視、及び、図２におけるＡ矢視の説明図である。It is explanatory drawing of A arrow in FIG. 1, and A arrow in FIG. 壁面の説明図である。It is explanatory drawing of a wall surface. 第２の実施形態の説明図である。It is explanatory drawing of 2nd Embodiment. 第３の実施形態の説明図である。It is explanatory drawing of 3rd Embodiment. 第４の実施形態の説明図である。It is explanatory drawing of 4th Embodiment. 第５の実施形態の説明図である。It is explanatory drawing of 5th Embodiment. 第６の実施形態の説明図である。It is explanatory drawing of 6th Embodiment. 第７の実施形態の説明図である。It is explanatory drawing of 7th Embodiment. 第８の実施形態の説明図である。It is explanatory drawing of 8th Embodiment. 第９の実施形態の説明図である。It is explanatory drawing of 9th Embodiment.
＜第１の実施形態＞
　図１は、本発明の第１の実施形態に係る２ストロークエンジン１の断面図である。 <First Embodiment>
FIG. 1 is a cross-sectional view of a two-stroke engine 1 according to a first embodiment of the present invention.
　以下、本発明の第１の実施形態を、図１を用いて詳細に説明する。
　図１のように、シュニューレ型の２ストロークエンジン１は、シリンダヘッド３、シリンダ５、クランクケース７、ピストン２１及びコネクティングロッド１９を有している。
　なお、シリンダヘッド３は、シリンダ５と分離されている必要はなく、図１のように、一体に形成されていてもよい。 Hereinafter, the first embodiment of the present invention will be described in detail with reference to FIG.
As shown in FIG. 1, the Schnurelet type two-stroke engine 1 includes a cylinder head 3, a cylinder 5, a crankcase 7, a piston 21, and a connecting rod 19.
The cylinder head 3 does not need to be separated from the cylinder 5 and may be formed integrally as shown in FIG.
　シリンダ５とクランクケース７及びピストン２１によってクランク室３１が形成されている。つまり、シリンダ５の内周面とピストン２１で形成されるクランクケース７側の略円柱状空間と、クランクケース７との空間がクランク室３１である。
　このクランク室３１は、ピストン２１が摺動移動するに従いその内部空間の容積が変化する。
　また、シリンダヘッド３、シリンダ５及びピストン２１によってシリンダ内空間２９が形成される。 A crank chamber 31 is formed by the cylinder 5, the crankcase 7 and the piston 21. That is, the crank chamber 31 is a space formed between the inner peripheral surface of the cylinder 5 and the piston 21 and the substantially cylindrical space on the crankcase 7 side, and the crankcase 7.
The volume of the internal space of the crank chamber 31 changes as the piston 21 slides.
A cylinder inner space 29 is formed by the cylinder head 3, the cylinder 5, and the piston 21.
　クランク室３１には、クランクシャフト９が回転自在に支持されている。
　クランクシャフト９は、クランクピン１１、クランクジャーナル１３、カウンタウエイト１５、クランクアーム１７を有する。
　コネクティングロッド１９のクランク室３１側において、コネクティングロッド１９は、クランクピン１１を回転自在に支持している。
　また、コネクティングロッド１９のシリンダヘッド３側において、コネクティングロッド１９は、ピストン２１を揺動自在に支持している。
　ピストン２１は、ピストンピン２２を介してシリンダ５内部を摺動する。 A crankshaft 9 is rotatably supported in the crank chamber 31.
The crankshaft 9 includes a crankpin 11, a crank journal 13, a counterweight 15, and a crank arm 17.
On the side of the connecting rod 19 on the crank chamber 31 side, the connecting rod 19 supports the crank pin 11 in a rotatable manner.
In addition, on the cylinder head 3 side of the connecting rod 19, the connecting rod 19 supports the piston 21 so as to be swingable.
The piston 21 slides inside the cylinder 5 via the piston pin 22.
　シリンダ５のクランク室３１側方向の部分に吸気開口部２３ａが形成されている。
　この吸気開口部２３ａを通じて、エアクリーナ（図示せず）及びキャブレタ（図示せず）を経由した混合気がクランク室３１に流入する吸気通路部２３が設けられている。
　また、クランク室３１には、クランク室側掃気開口部２５ａが開口している。
　このクランク室側掃気開口部２５ａを通じて、掃気が掃気通路部２５に送出される。
　掃気通路部２５の掃気は、シリンダ５に形成されたシリンダ側掃気開口部２５ｂを通じて、シリンダ５（シリンダ内空間２９）に流入する。
　シリンダ５には、排気開口部２７ａが形成されている。
　この排気開口部２７ａを通じて、排気が排気通路部２７に排出される。 An intake opening 23 a is formed in a portion of the cylinder 5 in the direction toward the crank chamber 31.
An intake passage portion 23 through which an air-fuel mixture that has passed through an air cleaner (not shown) and a carburetor (not shown) flows into the crank chamber 31 is provided through the intake opening portion 23a.
The crank chamber 31 has a crank chamber-side scavenging opening 25a.
The scavenging gas is sent to the scavenging passage 25 through the crank chamber side scavenging opening 25a.
The scavenging of the scavenging passage 25 flows into the cylinder 5 (cylinder inner space 29) through a cylinder-side scavenging opening 25b formed in the cylinder 5.
An exhaust opening 27 a is formed in the cylinder 5.
Exhaust gas is discharged into the exhaust passage 27 through the exhaust opening 27a.
　本実施形態で想定する２ストロークエンジンは、携帯するために小型なものであり、その携帯性ゆえに、必ずしも一定の方向において作業されるものではない。
　しかし、通常用途であれば、もっとも一般的な作業状態というのが想定されているのが通常である。つまり、一時的には、天地を逆にして使用する、大きく傾けて使用する等の事態が想定されるが、総合的にみると多くの時間ある一定の状態における使用が想定されて設計される。そして、ユーザは一時的には異なった状態で使用しても、通常はその設計された状態において使用している。
　したがって、本実施形態において、図１等に記載の状態は通常の使用状態におけるものを記載している。
　ここで、方向を定義する。
　通常の使用状態における、鉛直方向の上方向を上側方向という。逆に、地面側方向を下側方向と定義する。
　また、通常の使用状態における水平方向を水平方向と定義する。 The two-stroke engine assumed in the present embodiment is small for carrying and is not necessarily operated in a certain direction because of its portability.
However, for normal use, it is usually assumed that the most common work state. In other words, it is temporarily assumed that the top and bottom are used upside down, or that they are used with a large inclination, but when viewed comprehensively, they are designed for use in a certain state for many hours. . Even if the user temporarily uses the device in a different state, the user usually uses the device in the designed state.
Therefore, in the present embodiment, the state described in FIG. 1 and the like is that in the normal use state.
Here, the direction is defined.
In the normal use state, the upward direction in the vertical direction is referred to as the upper direction. Conversely, the ground side direction is defined as the lower direction.
Further, the horizontal direction in the normal use state is defined as the horizontal direction.
　シリンダ５の中心軸は、図１では、水平又は水平に近い状態となるように形成されているが、シリンダ５の中心軸が鉛直方向に向いた縦型エンジンであってもよいことは言うまでもない。以下、水平または水平に近い状態にシリンダ５の中心軸がある実施形態について説明するが、縦型エンジンンの場合には、異なった位置関係となることは言うまでもない。 In FIG. 1, the center axis of the cylinder 5 is formed to be horizontal or nearly horizontal, but it goes without saying that the cylinder 5 may be a vertical engine in which the center axis of the cylinder 5 is directed in the vertical direction. . Hereinafter, an embodiment in which the central axis of the cylinder 5 is in a horizontal or nearly horizontal state will be described. Needless to say, however, the vertical engine has a different positional relationship.
　また、シリンダヘッド３には、シリンダヘッド３を貫通して、シリンダ内空間２９に点火部分が露出する点火プラグ３３が装着されている。
　この点火プラグ３３の点火部分には、ドーム状の点火空間もシリンダヘッド３に形成されている。 The cylinder head 3 is fitted with a spark plug 33 that penetrates the cylinder head 3 and exposes an ignition portion in the cylinder inner space 29.
A dome-shaped ignition space is also formed in the cylinder head 3 in the ignition portion of the ignition plug 33.
　シリンダ５のクランク室３１側方向の部分に吸気開口部２３ａが形成されている。
　吸気開口部２３ａを形成する吸気通路部２３は、シリンダヘッド３側からクランク室３１側、かつシリンダ５の中心軸側に向かって連通されている。
　シリンダ５の中央部又は上側方向（縦型エンジンにおいては、内周面の一方向側の方向）の部分にクランク室側掃気開口部２５ａが形成されている。
　この、クランク室側掃気開口部２５ａを形成する掃気通路部２５は、クランク室３１側からシリンダヘッド３側に向かって形成されている。
　また、クランクシャフト９の回転方向は、図１中、反時計回りに回転している。つまり、吸気開口部２３ａから流入した混合気が入って行く方向にクランクシャフト９は回転している。
　換言すると、図１の状態において、吸気開口部２３ａからクランクシャフト９のカウンタウエイト１５に直線を引いた場合に、この直線の向きと、クランクシャフト９の回転方向が一致する。
　このように形成されていることから、クランクシャフト９（特に、カウンタウエイト１５）の回転によって、吸気開口部２３ａからクランク室３１へと、よりスムーズに混合気が流れることが可能となっている。 An intake opening 23 a is formed in a portion of the cylinder 5 in the direction toward the crank chamber 31.
The intake passage portion 23 that forms the intake opening portion 23 a communicates from the cylinder head 3 side toward the crank chamber 31 side and toward the center axis side of the cylinder 5.
A crank chamber side scavenging opening 25a is formed at the center of the cylinder 5 or in the upper direction (in the vertical engine, the direction of the inner circumferential surface in one direction).
The scavenging passage 25 forming the crank chamber side scavenging opening 25a is formed from the crank chamber 31 side toward the cylinder head 3 side.
Further, the rotation direction of the crankshaft 9 rotates counterclockwise in FIG. That is, the crankshaft 9 rotates in the direction in which the air-fuel mixture flowing in from the intake opening 23a enters.
In other words, when a straight line is drawn from the intake opening 23 a to the counterweight 15 of the crankshaft 9 in the state of FIG. 1, the direction of the straight line coincides with the rotational direction of the crankshaft 9.
Thus, the air-fuel mixture can flow more smoothly from the intake opening 23a to the crank chamber 31 by the rotation of the crankshaft 9 (particularly the counterweight 15).
　シリンダ５には、シリンダ側掃気開口部２５ｂ及び排気開口部２７ａが形成されている。
　また、シリンダ側掃気開口部２５ｂは、排気開口部２７ａよりもクランク室３１側の位置に形成される。
　このことによって、排気開口部２７ａが先に開口され、その次に、シリンダ側掃気開口部２５ｂが開口するポートタイミングとなるように形成されている。
　さらに、掃気通路部２５は、シリンダ５の中心軸の軸方向（クランク室３１側方向位置からシリンダヘッド３側方向位置）に延びている。 The cylinder 5 is formed with a cylinder-side scavenging opening 25b and an exhaust opening 27a.
The cylinder side scavenging opening 25b is formed at a position closer to the crank chamber 31 than the exhaust opening 27a.
As a result, the exhaust opening 27a is opened first, and the cylinder side scavenging opening 25b is then opened at the port timing.
Further, the scavenging passage 25 extends in the axial direction of the center axis of the cylinder 5 (from the position in the crank chamber 31 side direction to the position in the cylinder head 3 side direction).
　掃気通路部２５は、シリンダ５の中心軸の軸方向に延び、シリンダ側掃気開口部２５ｂによってシリンダ５に開口している。
　そのため、シリンダ側掃気開口部２５ｂから流入した掃気流（混合気）は、シリンダヘッド３側の方向（上死点側）成分を有している。
　また、シュニューレ型の２ストロークエンジン１では、掃気流（混合気）が排気開口部２７ａとは反対位置のシリンダ５の側面側に向けて流入する（以下の説明について、図２も参照のこと）。
　そのため、シリンダ側掃気開口部２５ｂから流入した掃気流（混合気）は、図３においてはシリンダ５の中心軸よりも下側方向への方向成分を有している。
　以上より、シリンダ側掃気開口部２５ｂから流入した掃気流（混合気）は、シリンダ５の中心軸よりも下側方向の側面、かつ、シリンダヘッド３側の側面に向けて流入する。
　流入した後の掃気流（混合気）のシリンダ５の中心軸よりも下側方向の側面、かつ、シリンダヘッド３側の側面に衝突することによって対流する。
　さらに、この対流した掃気流（混合気）の少なくとも一部は、壁面２７ｂに衝突してさらに対流する。
　そして、この壁面２７に衝突し対流した掃気流（混合気）の大部分が、排気開口部２７ａから流出してしまう前に、ピストン２１がシリンダヘッド３側に移動して、シリンダ側掃気開口部２５ｂを閉塞する。
　このように、壁面２７ｂが存在することによって、掃気流（混合気）の大部分が排気開口部２７ａから流出することを防ぐことが可能となる。
　さらに、掃気流（混合気）の大部分が流出しないということは、より効率的に排気されることを意味する。
　そして、このように排気を効率的に排出することが可能となることから、給気比、給気効率及び充填効率を上げることが可能となっている。 The scavenging passage 25 extends in the axial direction of the central axis of the cylinder 5 and opens into the cylinder 5 through a cylinder-side scavenging opening 25b.
Therefore, the scavenging airflow (mixture) flowing in from the cylinder-side scavenging opening 25b has a component on the cylinder head 3 side (top dead center side).
Further, in the Schnurelet-type two-stroke engine 1, scavenging air (air mixture) flows toward the side surface of the cylinder 5 at a position opposite to the exhaust opening 27a (see also FIG. 2 for the following explanation). .
Therefore, the scavenging airflow (air mixture) flowing in from the cylinder-side scavenging opening 25b has a directional component in the lower direction than the central axis of the cylinder 5 in FIG.
As described above, the scavenging airflow (mixture) flowing from the cylinder-side scavenging opening 25 b flows toward the side surface on the lower side of the center axis of the cylinder 5 and the side surface on the cylinder head 3 side.
Convection occurs by colliding with the side surface of the scavenging airflow (mixture) after flowing in from the side surface in the direction lower than the central axis of the cylinder 5 and the side surface on the cylinder head 3 side.
Furthermore, at least a part of the convective scavenging air (air mixture) collides with the wall surface 27b and further convects.
Then, before most of the scavenged airflow (air mixture) colliding with the wall surface 27 flows out from the exhaust opening 27a, the piston 21 moves to the cylinder head 3 side, and the cylinder side scavenging opening. 25b is closed.
Thus, the presence of the wall surface 27b makes it possible to prevent most of the scavenging air (air mixture) from flowing out of the exhaust opening 27a.
Furthermore, the fact that most of the scavenging air (air mixture) does not flow out means that the air is exhausted more efficiently.
And since it becomes possible to discharge | emit exhaust efficiently in this way, it is possible to raise supply ratio, supply efficiency, and filling efficiency.
　図２は、図１におけるＩＩ―ＩＩでの断面での説明図である。
　図３は、図１のような構成の効果の説明図である。 FIG. 2 is an explanatory view in a section taken along line II-II in FIG.
FIG. 3 is an explanatory diagram of the effect of the configuration shown in FIG.
　図２のように、掃気通路部２５は、２本の通路部から構成されている。シリンダ５の中心軸よりも右側の通路部が右側掃気通路部２５Ｒであり、シリンダ５の中心軸よりも左側の通路部が左側掃気通路部２５Ｌである。
　右側掃気通路部２５Ｒ及び左側掃気通路部２５Ｌは、図２の紙面奥側から手前側に向かって延びるように形成されている。
　なお、掃気通路部２５の数は図２のように２本である必要はなく、それ以上であってもよい。
　右側掃気通路部２５Ｒのシリンダ５への開口部分が右側掃気開口部２５ｂＲであり、左側掃気通路部２５Ｌのシリンダ５への開口部分が左側掃気開口部２５ｂＬである。
　図２のように、排気開口部２７ａの右側方向位置及び左側方向位置にそれぞれ、右側掃気開口部２５ｂＲ及び左側掃気開口部２５ｂＬが形成されている。
　また、排気通路部２７のシリンダ５への開口部分が排気開口部２７ａである。 As shown in FIG. 2, the scavenging passage 25 is composed of two passages. A passage portion on the right side of the center axis of the cylinder 5 is the right scavenging passage portion 25R, and a passage portion on the left side of the center axis of the cylinder 5 is the left scavenging passage portion 25L.
The right scavenging passage portion 25R and the left scavenging passage portion 25L are formed so as to extend from the back side to the front side in FIG.
Note that the number of the scavenging passage portions 25 is not necessarily two as shown in FIG. 2, and may be more than that.
The opening part of the right scavenging passage 25R to the cylinder 5 is the right scavenging opening 25bR, and the opening part of the left scavenging passage 25L to the cylinder 5 is the left scavenging opening 25bL.
As shown in FIG. 2, a right scavenging opening 25bR and a left scavenging opening 25bL are formed at the right and left positions of the exhaust opening 27a, respectively.
Moreover, the opening part to the cylinder 5 of the exhaust passage part 27 is the exhaust opening part 27a.
　排気開口部２７ａ部分には、壁面２７ｂが形成されている。
　この壁面２７ｂによって、排気が右側及び左側に分断される。つまり、この壁面２７ｂによって、壁面２７ｂの左側方向位置に左側排気開口部２７ａＬが形成されている。また、この壁面２７ｂによって、壁面２７ｂ右側方向位置に右側排気開口部２７ａＲが形成されている。
　壁面２７ｂを構成する壁部２８は、ボア方向の断面形状が図２のように略三角形状を有している。
　壁面２７ｂは、シリンダ５の内周面と同一の面を形成している。
　このため、この壁面２７ｂは、シリンダ５内を摺動するピストン２１をガイドする機能を有している。
　また、壁部２８の壁面２７ｂ以外の他の２辺の１つは左側排気開口部２７ａＬからの流路の一部を形成し、さらに最後の１つは右側排気開口部２７ａＲからの流路の一部を形成している。そして、壁面２７ｂ以外の他の２辺は、排気がスムーズに合流するような形状を有している。このような形状を有することから、排気をスムーズに合流させることが可能となる。 A wall surface 27b is formed in the exhaust opening 27a.
By this wall surface 27b, the exhaust gas is divided into the right side and the left side. That is, the left exhaust opening 27aL is formed by the wall surface 27b at the left side position of the wall surface 27b. Further, a right exhaust opening 27aR is formed by the wall surface 27b at a position on the right side of the wall surface 27b.
The wall portion 28 constituting the wall surface 27b has a substantially triangular cross-sectional shape in the bore direction as shown in FIG.
The wall surface 27 b forms the same surface as the inner peripheral surface of the cylinder 5.
For this reason, the wall surface 27 b has a function of guiding the piston 21 that slides in the cylinder 5.
Further, one of the other two sides of the wall portion 28 other than the wall surface 27b forms a part of the flow path from the left exhaust opening 27aL, and the last one of the flow path from the right exhaust opening 27aR. Forming part. The other two sides other than the wall surface 27b have a shape that allows the exhaust to smoothly merge. Since it has such a shape, it becomes possible to join exhaust smoothly.
　クランクシャフト９が回転する回転方向側のシリンダ５の内周面の位置、かつ、シリンダ内空間２９を形成するシリンダ５の内周面のうちクランク室３１側の位置、にこの壁面２７ｂ（排気通路部２７）が形成されている。
　そしてこの壁面２７ｂが形成されている位置は、ピストン２１が下死点位置から上死点方向に移動を開始する際に、ピストン２１の頭部の圧力が加わる位置である。
　このような位置に、ピストン２１をガイドすることも可能な、壁面２７ｂが形成されていることから、壁面２７ｂがピストン２１をスムーズにガイドすることが可能となる。
　この壁面２７ｂがピストン２１をスムーズにガイドすることから、振動の低減、磨耗損失の低減等が図られる。 This wall surface 27b (exhaust passage) is positioned at the position of the inner peripheral surface of the cylinder 5 on the rotational direction side where the crankshaft 9 rotates and the position of the inner peripheral surface of the cylinder 5 forming the cylinder inner space 29 on the crank chamber 31 side. Part 27) is formed.
The position where the wall surface 27b is formed is a position where the pressure of the head of the piston 21 is applied when the piston 21 starts moving from the bottom dead center position toward the top dead center.
Since the wall surface 27b capable of guiding the piston 21 is formed at such a position, the wall surface 27b can smoothly guide the piston 21.
Since the wall surface 27b guides the piston 21 smoothly, it is possible to reduce vibration and wear loss.
　なお、必ずしも、壁面２７ｂはシリンダ５の内周面として機能させる必然性はない。
　具体的にはシリンダ５側の壁面２７ｂがシリンダ５の内周面よりも半径方向の外側位置にある場合（後退した位置にある場合）であってもよい。
　そして、この場合には、ピストン２１とこのシリンダ５側の一辺は、ピストン２１と接触しないことから、このシリンダ５側の一辺の表面粗さ精度を高くする必要がなくなり、低コストで製造可能となるという効果がある。 Note that the wall surface 27 b does not necessarily function as the inner peripheral surface of the cylinder 5.
Specifically, the case may be a case where the wall surface 27b on the cylinder 5 side is at an outer position in the radial direction than the inner peripheral surface of the cylinder 5 (when it is in a retracted position).
In this case, since the piston 21 and one side on the cylinder 5 side do not contact the piston 21, it is not necessary to increase the surface roughness accuracy on the one side of the cylinder 5 and can be manufactured at low cost. There is an effect of becoming.
　本実施形態において、この壁面２７ｂのもっとも重要な役割は、壁面２７ｂによって、図２のように、排気開口部２７ａから流出しようとする掃気流がこの壁面２７ｂに衝突することによって、さらにシリンダ内空間２９で対流させることである。
　つまり、排気開口部２７ａから流出しようとする部分にこの壁面２７ｂ（排気通路部２７）が形成されている。
　このため、掃気流の一部をさらに対流させ、吹き抜けを防止することが可能となる。
　このように、本来ならば排気開口部２７ａから流出してしまう掃気流（混合気）をさらに対流させることができることから、給気効率、充填効率の向上が生じ、出力の向上、排ガス性能の向上が図れる。 In the present embodiment, the most important role of the wall surface 27b is that the scavenging air flowing out from the exhaust opening 27a collides with the wall surface 27b as shown in FIG. 29 for convection.
That is, the wall surface 27b (exhaust passage portion 27) is formed in a portion that is about to flow out from the exhaust opening portion 27a.
For this reason, it is possible to further convection a part of the scavenging air and prevent blow-through.
Thus, since the scavenging air (mixed gas) that would otherwise flow out of the exhaust opening 27a can be further convected, the air supply efficiency and the charging efficiency are improved, the output is improved, and the exhaust gas performance is improved. Can be planned.
　なお、壁面２７ｂに衝突する前の掃気流（混合気）は以下のように流れる（図１も参照のこと）。
　図２のように、右側掃気開口部２５ｂＲ及び左側掃気開口部２５ｂＬから流出した流れは、シリンダ内空間２９内を進み、次いで、シリンダ５の中心軸よりも下側の位置の側面に衝突する。
　さらに、右側掃気開口部２５ｂＲからの流れ及び左側掃気開口部２５ｂＬからの流れは、互いに衝突して一体となって排気開口部２７ａの壁面２７ｂに向かって流れる。 Note that the scavenging airflow (air mixture) before colliding with the wall surface 27b flows as follows (see also FIG. 1).
As shown in FIG. 2, the flow that has flowed out of the right scavenging opening 25bR and the left scavenging opening 25bL travels in the cylinder inner space 29, and then collides with a side surface at a position lower than the central axis of the cylinder 5.
Further, the flow from the right scavenging opening 25bR and the flow from the left scavenging opening 25bL collide with each other and flow toward the wall surface 27b of the exhaust opening 27a.
　図２のように、シリンダ５の中心軸に対して垂直な方向の断面をボア断面という。
　また、このボア断面において、ボア断面とシリンダ５の中心軸との交点から離れる方向を半径方向という。 As shown in FIG. 2, a cross section in a direction perpendicular to the central axis of the cylinder 5 is called a bore cross section.
In this bore cross section, the direction away from the intersection of the bore cross section and the central axis of the cylinder 5 is referred to as the radial direction.
　ここで、掃気通路部２５からは、混合気、液体状及び粒子状の燃料成分、オイル、オイルミスト等がシリンダ５内のシリンダ内空間２９に流入する。
　そのうちの質量の大きな燃料成分（液体状及び粒子状の燃料、オイル、オイルミスト等）は、その大部分が図２の矢印のような混合気の流れに乗ってシリンダ内空間２９に流入する。
　しかし、この質量の大きな燃料成分の一部は、この混合気の流れに乗らずシリンダ側掃気開口部２５ｂと排気開口部２７ａの間のシリンダ５の壁面を伝ったり（壁面伝達）、壁面沿いに流れて直接に排気通路部２７から排出されてしまう（ショートカット）。
　つまり、この質量の大きな燃料成分の一部は、未燃焼のまま排気通路部２７から排出されてしまうことになる。
　このように、未燃焼で排気通路部２７に侵入した燃料成分、オイル及びオイルミストが生じることは、給気効率と充填効率の低下を生じさせる。
　さらに、未燃焼での燃料成分、オイル及びオイルミストは、２ストロークエンジン１の排気を汚染し、２ストロークエンジン１の環境性能を悪化させる。 Here, air-fuel mixture, liquid and particulate fuel components, oil, oil mist and the like flow into the cylinder internal space 29 in the cylinder 5 from the scavenging passage 25.
Most of the fuel components (liquid and particulate fuel, oil, oil mist, etc.) of the mass ride on the air-fuel mixture flow as indicated by arrows in FIG.
However, a part of the fuel component having a large mass does not get on the flow of the air-fuel mixture and propagates along the wall surface of the cylinder 5 between the cylinder-side scavenging opening 25b and the exhaust opening 27a (wall surface transmission) or along the wall surface. It flows and is directly discharged from the exhaust passage portion 27 (shortcut).
That is, a part of the fuel component having a large mass is discharged from the exhaust passage portion 27 without being burned.
Thus, the generation of fuel components, oil, and oil mist that have entered the exhaust passage portion 27 unburned causes a reduction in air supply efficiency and charging efficiency.
Further, unburned fuel components, oil, and oil mist contaminate the exhaust of the 2-stroke engine 1 and deteriorate the environmental performance of the 2-stroke engine 1.
　図４は、図１におけるＡ矢視、及び、図２におけるＡ矢視の説明図である。 FIG. 4 is an explanatory view of the arrow A in FIG. 1 and the arrow A in FIG.
　図４のように、右側掃気開口部２５ｂＲ及び左側掃気開口部２５ｂＬは、排気開口部２７ａよりもクランク室３１側に位置している。
　このように、排気開口部２７ａがシリンダヘッド３側に位置することから、ピストン２１がクランク室３１側に移動するに従い、最初に、排気通路部２７（排気開口部２７ａ）がシリンダ内空間２９に連通することになる。
　その結果、シリンダ内空間２９内の排気は、排気開口部２７ａのシリンダヘッド３側の部分からシリンダ５外に排出される。
　そして、ピストン２１がクランク室３１側に移動する間に、ある程度シリンダ内空間２９から排気が排出される。
　その排気の排出によってシリンダ内空間２９の圧力が下がった状態で、右側掃気通路部２５Ｒ（右側掃気開口部２５ｂＲ）及び左側掃気通路部２５Ｌ（左側掃気開口部２５ｂＬ）が、シリンダ内空間２９に連通する。
　この様になっていることによって、前回の燃焼サイクルにおいて燃焼が終わった排気が排出された状態にて、掃気が流入することになるのでより効果的に排気を排出することが可能となっている。 As shown in FIG. 4, the right scavenging opening 25bR and the left scavenging opening 25bL are located closer to the crank chamber 31 than the exhaust opening 27a.
Thus, since the exhaust opening 27a is located on the cylinder head 3 side, the exhaust passage portion 27 (exhaust opening 27a) first enters the cylinder inner space 29 as the piston 21 moves toward the crank chamber 31. You will communicate.
As a result, the exhaust in the cylinder inner space 29 is discharged out of the cylinder 5 from the portion of the exhaust opening 27a on the cylinder head 3 side.
Then, while the piston 21 moves to the crank chamber 31 side, the exhaust gas is discharged from the cylinder inner space 29 to some extent.
The right scavenging passage portion 25R (right scavenging opening portion 25bR) and the left scavenging passage portion 25L (left scavenging opening portion 25bL) communicate with the cylinder inner space 29 in a state where the pressure in the cylinder inner space 29 is reduced by the exhaust. To do.
As a result, scavenging gas flows in with exhaust exhausted after the previous combustion cycle being exhausted, so exhaust can be exhausted more effectively. .
　図４のように、シリンダ５の中心軸側から見ると壁面２７ｂはＹ字形状を有する。
　Ｙ字形状は、シリンダヘッド３側を上にした状態となるように形成される。 As shown in FIG. 4, the wall surface 27 b has a Y shape when viewed from the center axis side of the cylinder 5.
The Y shape is formed so that the cylinder head 3 side is in an upward state.
　図５は、壁面２７ｂの説明図である。 FIG. 5 is an explanatory diagram of the wall surface 27b.
　排気開口部２７ａは、図５のように中央に壁面２７ｂが形成されている。そして、この壁面２７ｂの右側に右側排気開口部２７ａＲ、左側に左側排気開口部２７ａＬが形成されている。
　そして、図５において、紙面上側がシリンダヘッド３側であり、紙面下側がクランク室３１側である。
　右側排気開口部２７ａＲのシリンダヘッド３側には右側上死点傾斜部２７ｃＲが形成され、左側排気開口部２７ａＬのシリンダヘッド３側には左側上死点傾斜部２７ｃＬが形成されている。
　この右側上死点傾斜部２７ｃＲ及び左側上死点傾斜部２７ｃＬによってＹ字型の壁面２７ｂが形成されている。
　ここで、右側排気開口部２７ａＲのシリンダヘッド３側の幅を右側上死点長ＬＵＲとし、右側排気開口部２７ａＲのクランク室３１側の幅を右側下死点長ＬＢＲとする。そして、シリンダヘッド３側とクランク室３１側との中央位置における幅を右側中央長ＬＭＲとする。
　同様に、左側排気開口部２７ａＬのシリンダヘッド３側の幅を左側上死点長ＬＵＬとし、左側排気開口部２７ａＬのクランク室３１側の幅を左側下死点長ＬＢＬとする。そして、シリンダヘッド３側とクランク室３１側との間における幅を左側中央長ＬＭＬとする。
　さらに、壁面２７ｂのシリンダヘッド３側の幅を壁上死点長ＬＵＷとし、壁面２７ｂのクランク室３１側の幅を壁下死点長ＬＢＷとする。そして、シリンダヘッド３側とクランク室３１側との中央位置における幅を壁中央長ＬＭＷとする
　そして、ＬＢＷ＝ＬＭＷとし、ＬＭＷ＜ＬＵＷとしたことによって、Ｙ字型の壁面２７ｂが形成される。
　なお、右側排気開口部２７ａＲと左側排気開口部２７ａＬの管路を形成する各壁の接合部に円形状の面取がなされていてもよいことは言うまでもない。
　なお、右側上死点傾斜部２７ｃＲ及び左側上死点傾斜部２７ｃＬは、円弧の一部によって形成してもよい（後述する図７（ｂ）も参照のこと）。 As shown in FIG. 5, the exhaust opening 27a has a wall surface 27b at the center. A right exhaust opening 27aR is formed on the right side of the wall surface 27b, and a left exhaust opening 27aL is formed on the left side.
In FIG. 5, the upper side of the drawing is the cylinder head 3 side, and the lower side of the drawing is the crank chamber 31 side.
A right upper dead center inclined portion 27cR is formed on the cylinder head 3 side of the right exhaust opening 27aR, and a left upper dead center inclined portion 27cL is formed on the cylinder head 3 side of the left exhaust opening 27aL.
The right upper dead center inclined portion 27cR and the left upper dead center inclined portion 27cL form a Y-shaped wall surface 27b.
Here, the width of the right exhaust opening 27aR on the cylinder head 3 side is the right upper dead center length LUR, and the width of the right exhaust opening 27aR on the crank chamber 31 side is the right lower dead center length LBR. The width at the center position between the cylinder head 3 side and the crank chamber 31 side is defined as the right center length LMR.
Similarly, the width of the left exhaust opening 27aL on the cylinder head 3 side is the left upper dead center length LUL, and the width of the left exhaust opening 27aL on the crank chamber 31 side is the left lower dead center length LBL. The width between the cylinder head 3 side and the crank chamber 31 side is the left central length LML.
Furthermore, the width on the cylinder head 3 side of the wall surface 27b is the wall top dead center length LUW, and the width on the crank chamber 31 side of the wall surface 27b is the wall bottom dead center length LBW. Then, the width at the center position between the cylinder head 3 side and the crank chamber 31 side is the wall center length LMW. By setting LBW = LMW and LMW <LUW, the Y-shaped wall surface 27b is formed.
Needless to say, a circular chamfer may be formed at the joint portion of each wall forming the pipe line of the right exhaust opening 27aR and the left exhaust opening 27aL.
The right upper dead center inclined portion 27cR and the left upper dead center inclined portion 27cL may be formed by a part of an arc (see also FIG. 7B described later).
　このように壁面２７ｂを形成したことから、ピストンが下死点から上死点へ移動する際に、最初は排気通路部２７の排気開口部２７ａの面積は大きい状態となっている。したがって、最初は排気通路部２７に特に抵抗なく排気が排出される（以下の説明は図４も参照のこと）。
　しかし、ピストン２１がさらに上昇し、壁面２７ｂの幅が大きくなる部分に差し掛かると、急激排気開口部２７ａの面積が減少する。
　そして、この際には右側掃気開口部２５ｂＲ及び左側掃気開口部２５ｂＬはすでにピストン２１によって閉塞されていることから、ピストン２１の上昇に伴いシリンダ５の内圧が上昇する。
　その時、何ら対策を行わないと、排気開口部２７ａから掃気が吹き抜けてしまう。
　しかし、本実施形態では、前述のように排気開口部２７ａの壁面２７ｂはＹ字型をしておりその面積が小さくなっていることから、この吹き抜けが生ずることを抑制することができる。
　これによって給気効率の向上、充填効率の向上が生じ、出力の向上、排ガス性能の向上が図れる。 Since the wall surface 27b is formed in this way, when the piston moves from the bottom dead center to the top dead center, the area of the exhaust opening 27a of the exhaust passage portion 27 is initially large. Accordingly, initially, the exhaust gas is discharged without any particular resistance into the exhaust passage portion 27 (see also FIG. 4 for the following description).
However, when the piston 21 further rises and reaches the portion where the width of the wall surface 27b becomes large, the area of the rapid exhaust opening 27a decreases.
At this time, since the right scavenging opening 25bR and the left scavenging opening 25bL are already closed by the piston 21, the internal pressure of the cylinder 5 increases as the piston 21 rises.
At that time, if no countermeasure is taken, scavenging air will blow out from the exhaust opening 27a.
However, in the present embodiment, as described above, the wall surface 27b of the exhaust opening 27a is Y-shaped and has a small area, so that this blow-out can be suppressed.
As a result, the air supply efficiency and the charging efficiency are improved, and the output and the exhaust gas performance can be improved.
＜第２の実施形態＞
　図６は、第２の実施形態の説明図である。 <Second Embodiment>
FIG. 6 is an explanatory diagram of the second embodiment.
　壁面２７ｂは、図６（ａ）及び図６（ｂ）のような形状であってもよい。
　つまり、右側上死点傾斜部２７ｃＲ及び左側上死点傾斜部２７ｃＬのみが、壁面２７ｂを形成していてもよい。 The wall surface 27b may have a shape as shown in FIGS. 6 (a) and 6 (b).
That is, only the right upper dead center inclined portion 27cR and the left upper dead center inclined portion 27cL may form the wall surface 27b.
＜第３の実施形態＞
　図７は、第３の実施形態の説明図である。 <Third Embodiment>
FIG. 7 is an explanatory diagram of the third embodiment.
　壁面２７ｂは、図７（ａ）、図７（ｂ）及び図７（ｃ）のような形状であってもよい。
　このように、クランク室３１側の幅も狭くなるように、右側下死点傾斜部２７ｄＲ及び左側下死点傾斜部２７ｄＬを形成している。
　以下この理由を説明する（以下の説明について図４も参照のこと）。
　ピストン２１が下死点付近にある場合には、シリンダ側掃気開口部２５ｂも排気開口部２７ａも全開状態である。
　そのため、掃気流（混合気）の質量の大きな燃料成分（オイルミスト、気化していない燃料等）が、シリンダ内空間２９の下側位置を通過して、排気開口部２７ａに直接吹き抜けてしまうことが考えられる。
　特に、ピストン２１の下死点付近では、壁面２７ｂ沿いに降下した質量の大きな燃料成分がピストンの頂面に達して分散し、左側排気開口部２７ａＬ及び右側排気開口部２７ａＲから排出されることも考えられる。
　そこで、右側下死点傾斜部２７ｄＲ及び左側下死点傾斜部２７ｄＬを形成して、クランク室３１側の排気開口部２７ａの幅を小さくして、この吹き抜けをできるだけ抑制している。
　なお、図７（ｃ）のように、壁面２７ｂを円弧状に形成してもよい。 The wall surface 27b may have a shape as shown in FIGS. 7A, 7B, and 7C.
Thus, the right bottom dead center inclined portion 27dR and the left bottom dead center inclined portion 27dL are formed so that the width on the crank chamber 31 side is also narrowed.
The reason will be described below (see also FIG. 4 for the following description).
When the piston 21 is near the bottom dead center, the cylinder-side scavenging opening 25b and the exhaust opening 27a are fully open.
Therefore, a fuel component (oil mist, unvaporized fuel, etc.) having a large mass of the scavenging air (air mixture) passes through the lower position of the cylinder inner space 29 and blows directly into the exhaust opening 27a. Can be considered.
In particular, in the vicinity of the bottom dead center of the piston 21, a fuel component having a large mass that has descended along the wall surface 27b reaches the top surface of the piston and is dispersed and discharged from the left exhaust opening 27aL and the right exhaust opening 27aR. Conceivable.
Therefore, the right bottom dead center inclined portion 27dR and the left bottom dead center inclined portion 27dL are formed to reduce the width of the exhaust opening 27a on the crank chamber 31 side, thereby suppressing this blow-through as much as possible.
Note that the wall surface 27b may be formed in an arc shape as shown in FIG.
＜第４の実施形態＞
　図８は、第４の実施形態の説明図である。
　つまり、図８（ａ）、図８（ｂ）及び図８（ｃ）のように、壁面２７ｂの形状はストレート形状であってもよい。 <Fourth Embodiment>
FIG. 8 is an explanatory diagram of the fourth embodiment.
That is, as shown in FIGS. 8A, 8B, and 8C, the shape of the wall surface 27b may be a straight shape.
＜第５の実施形態＞
　図９は、第５の実施形態の説明図である。
　つまり、つまり、図９（ａ）及び図９（ｂ）のように、右側排気開口部２７ａＲ及び左側排気開口部２７ａＬは、円又は円弧であってもよい。 <Fifth Embodiment>
FIG. 9 is an explanatory diagram of the fifth embodiment.
That is, as shown in FIGS. 9A and 9B, the right exhaust opening 27aR and the left exhaust opening 27aL may be circular or arcuate.
＜第６の実施形態＞
　図１０は、第６の実施形態の説明図である。 <Sixth Embodiment>
FIG. 10 is an explanatory diagram of the sixth embodiment.
　図１０のように、左側中央長ＬＭＬ、右側中央長ＬＭＲ、壁中央長ＬＭＷが同一の幅を有するようにしてもよい。
　このようにしたことによって、壁面２７ｂが掃気を十分に対流させつつ、排気開口部２７ａから排気をすることの両立が可能となる。 As shown in FIG. 10, the left center length LML, the right center length LMR, and the wall center length LMW may have the same width.
By doing in this way, it becomes possible to coexist exhausting from the exhaust opening 27a while the wall surface 27b sufficiently convects the scavenging.
＜第７の実施形態＞
　図１１は、第７の実施形態の説明図である。 <Seventh Embodiment>
FIG. 11 is an explanatory diagram of the seventh embodiment.
　右側排気開口部２７ａＲと左側排気開口部２７ａＬとが、連通していてもよい。
　なぜなら、掃気流の流れの一部を反転させることが可能であるという本実施形態の効果等は、このような形状であっても達成することが可能であるからである。
　もっとも、その連通位置は、クランク室３１側であるほうが、吹き抜けが生ずることを抑制することが可能となるという点でより好適である。
　そして、連通する部分は、図１１（ａ）のように、縦方向に比較的小さく形成されていてもよいし、図１１（ｂ）のように、縦方向に比較的大きく形成されていてもよい。
　なお、図１１（ａ）及び図１１（ｂ）のように、壁面２７ｂは、壁面２７ｂのシリンダヘッド３側とクランク室３１側との中央位置における幅が壁面２７ｂのシリンダヘッド３側位置の幅よりも小さくなるように形成されているとより好適である。
　このように構成したことから、より吹き抜けが生ずることを抑制することができるからである。 The right exhaust opening 27aR and the left exhaust opening 27aL may communicate with each other.
This is because the effect of the present embodiment that it is possible to reverse a part of the flow of the scavenging air can be achieved even with such a shape.
However, it is more preferable that the communication position is on the crank chamber 31 side in that it is possible to suppress the occurrence of blow-through.
The communicating portion may be formed relatively small in the vertical direction as shown in FIG. 11A, or may be formed relatively large in the vertical direction as shown in FIG. Good.
11 (a) and 11 (b), the wall surface 27b has a width at the center position between the cylinder head 3 side of the wall surface 27b and the crank chamber 31 side, and the width at the cylinder head 3 side position of the wall surface 27b. It is more preferable that it is formed so as to be smaller.
It is because it can suppress that a blow-by arises more because it comprised in this way.
　この構成を換言すると、壁面２７ｂは、その一部が途切れていて、左側排気開口部２７ａＬと右側排気開口部２７ａＲが繋がっていても良い。
　このような構成として、さらに、反転して降下してくる掃気流が直接流出するのを抑制する有効な大きさ、形状にすることができる。
　特に、壁面２７ｂのクランク室側の端面は、ピストンが下死点から上死点に向かって移動するときのシリンダ側掃気開口部２５ｂが閉塞される位置に形成すると良い。
　このことにより、ブローダウンまたは圧縮開始の時期に掃気流の排出（吹き抜け）を抑制できる。
　以下、この繋がっている（連通している）構成の変形例について説明する。 In other words, part of the wall surface 27b is interrupted, and the left exhaust opening 27aL and the right exhaust opening 27aR may be connected.
As such a configuration, an effective size and shape that suppresses direct outflow of the scavenging airflow that is reversed and descends can be obtained.
In particular, the end face on the crank chamber side of the wall surface 27b is preferably formed at a position where the cylinder-side scavenging opening 25b is closed when the piston moves from the bottom dead center toward the top dead center.
As a result, scavenging air discharge (blow-through) can be suppressed at the time of blow-down or compression start.
Hereinafter, a modified example of the connected (connected) configuration will be described.
＜第８実施形態＞
　図１２は、第８の実施形態の説明図である。 <Eighth Embodiment>
FIG. 12 is an explanatory diagram of the eighth embodiment.
　図１２のように、右側排気開口部２７ａＲと左側排気開口部２７ａＬとの連通を中央位置に設けてもよい。
　このようにしたことによって、図７において示した実施形態とほぼ同様の効果もそうすることが可能となる。 As shown in FIG. 12, the communication between the right exhaust opening 27aR and the left exhaust opening 27aL may be provided at the center position.
By doing in this way, the effect almost the same as embodiment shown in FIG. 7 can also be done.
＜第９の実施形態＞
　図１３は、第９の実施形態の説明図である。 <Ninth Embodiment>
FIG. 13 is an explanatory diagram of the ninth embodiment.
　図１３のように、壁面２７ｂのクランク室３１側の端部である壁面端部２７ｃの位置が、右側掃気開口部２５ｂＲのシリンダヘッド３側の端部である右側掃気開口部端部２５ｃＲ、及び、左側掃気開口部２５ｂＬのシリンダヘッド３側の端部である左側掃気開口部端部２５ｃＬ、の位置とシリンダ５の中心軸の方向において一致（略一致を含む）している。
　この位置は、換言すると、壁面端部２７ｃの位置は、ピストン２１が右側掃気開口部端部２５ｃＲ及び左側掃気開口部端部２５ｃＬを完全に閉塞した場合に、ピストン２１の頂部が壁面端部２７ｃに位置する位置ということができる。
　このように構成したことから、シリンダ側掃気開口部２５ｂが開口して掃気流が流入している際には、排気開口部２７ａが大きく開口し、シリンダ側掃気開口部２５ｂが閉塞されて掃気流が流入しなくなった場合には、排気開口部２７ａの開口面積が急速に小さくなるように構成することが可能となる。
　そして、このような構成としたことから、吹き抜けの防止をより確実に行うことができる。 As shown in FIG. 13, the position of the wall surface end 27c that is the end of the wall surface 27b on the crank chamber 31 side is the right scavenging opening end portion 25cR that is the end of the right scavenging opening 25bR on the cylinder head 3 side, and The position of the left scavenging opening 25cL, which is the end of the left scavenging opening 25bL on the cylinder head 3 side, coincides with the direction of the central axis of the cylinder 5 (including substantially coincidence).
In other words, when the piston 21 completely closes the right scavenging opening end portion 25cR and the left scavenging opening end portion 25cL, the position of the wall surface end portion 27c corresponds to the position of the wall surface end portion 27c. It can be said that it is located at
With this configuration, when the cylinder-side scavenging opening 25b is opened and the scavenging air is flowing in, the exhaust opening 27a is largely opened, the cylinder-side scavenging opening 25b is closed, and the scavenging air flows. When the gas does not flow in, the opening area of the exhaust opening 27a can be configured to be rapidly reduced.
And since it was set as such a structure, prevention of a blow-through can be performed more reliably.
＜実施形態の構成及び効果＞
　本実施形態の２ストロークエンジン１は、シリンダ５と、シリンダ５内を往復可能なピストン２１と、シリンダ５に設けられた排気通路部２７と、シリンダ５に設けられた掃気通路部２５と、を有し、シリンダ５の内周面には、排気通路部２７の排気開口部２７ａおよび掃気通路部２５のシリンダ側掃気開口部２５ｂが形成され、排気開口部２７ａには、排気開口部２７ａの幅方向における中央部の少なくとも一部を塞ぐように壁面２７ｂが形成され、壁面２７ｂのシリンダヘッド３側とクランク室３１側との中央位置における排気開口部２７ａの幅は、壁面２７ｂのシリンダヘッド３側における排気開口部２７ａの幅の合計よりも大きく形成されている。
　このような構成を有することから、本来ならば排気開口部２７ａから流出してしまう掃気流（混合気）をさらに対流させることができることから、吹き抜けを抑制し、給気効率、充填効率の向上が生じ、出力の向上、排ガス性能の向上が図れる。 <Configuration and Effect of Embodiment>
The two-stroke engine 1 of the present embodiment includes a cylinder 5, a piston 21 that can reciprocate in the cylinder 5, an exhaust passage portion 27 provided in the cylinder 5, and a scavenging passage portion 25 provided in the cylinder 5. And an exhaust opening 27a of the exhaust passage 27 and a cylinder-side scavenging opening 25b of the scavenging passage 25 are formed on the inner peripheral surface of the cylinder 5. The exhaust opening 27a has a width of the exhaust opening 27a. A wall surface 27b is formed so as to block at least a part of the central portion in the direction, and the width of the exhaust opening 27a at the center position between the cylinder head 3 side and the crank chamber 31 side of the wall surface 27b is the cylinder head 3 side of the wall surface 27b. Are formed larger than the total width of the exhaust openings 27a.
Since it has such a configuration, it is possible to further convect the scavenging airflow (air mixture) that would otherwise flow out of the exhaust opening 27a, thereby suppressing blow-through and improving air supply efficiency and filling efficiency. As a result, output can be improved and exhaust gas performance can be improved.
　壁面２７ｂは、壁面２７ｂのシリンダヘッド３側とクランク室３１側との中央位置における幅が壁面２７ｂのシリンダヘッド３側位置の幅よりも小さくなるように形成されている。
　このような構成を有することから、吹き抜けが生ずることを抑制することができる。
　そして、これによって給気効率の向上、充填効率の向上が生じ、出力の向上、排ガス性能の向上が図れる。 The wall surface 27b is formed such that the width of the wall surface 27b at the center position between the cylinder head 3 side and the crank chamber 31 side is smaller than the width of the wall surface 27b at the cylinder head 3 side position.
Since it has such a structure, it can suppress that a blow-through arises.
As a result, the air supply efficiency and the charging efficiency are improved, and the output and the exhaust gas performance can be improved.
　壁面２７ｂは、壁面２７ｂのシリンダヘッド３側とクランク室３１側との中央位置における幅と壁面２７ｂのクランク室３１側位置の幅とは同一となるように形成されている。
　このような構成を有することから、吹き抜けが生ずることを抑制することができる。
　そして、これによって給気効率の向上、充填効率の向上が生じ、出力の向上、排ガス性能の向上が図れる。 The wall surface 27b is formed so that the width of the wall surface 27b at the center position between the cylinder head 3 side and the crank chamber 31 side and the width of the wall surface 27b at the crank chamber 31 side position are the same.
Since it has such a structure, it can suppress that a blow-through arises.
As a result, the air supply efficiency and the charging efficiency are improved, and the output and the exhaust gas performance can be improved.
　壁面２７ｂは、壁面２７ｂのシリンダヘッド３側の幅は、クランク室３１側の幅よりも大きく形成されている。
　このような構成を有することから、吹き抜けが生ずることを抑制することができる。
　そして、これによって給気効率の向上、充填効率の向上が生じ、出力の向上、排ガス性能の向上が図れる。 The wall surface 27b is formed such that the width of the wall surface 27b on the cylinder head 3 side is larger than the width on the crank chamber 31 side.
Since it has such a structure, it can suppress that a blow-through arises.
As a result, the air supply efficiency and the charging efficiency are improved, and the output and the exhaust gas performance can be improved.
　壁面２７ｂによって分断された排気通路部２７は、壁面２７ｂの後方において合流する
　このような構成を有することから、２本の排気通路部２７を必要としないという、構造の簡易化を図ることが可能となる。 The exhaust passage portion 27 divided by the wall surface 27b joins behind the wall surface 27b. Thus, the structure can be simplified so that the two exhaust passage portions 27 are not required. It becomes.
　壁面２７ｂを構成する壁部２８は、ボア方向の断面形状が略三角形状を有している。
　このような構成を有することから、排気をスムーズに合流させることが可能となる。 The wall portion 28 constituting the wall surface 27b has a substantially triangular cross-sectional shape in the bore direction.
Since it has such a structure, it becomes possible to join exhaust_gas | exhaustion smoothly.
　壁面２７ｂは、シリンダヘッド３側からクランク室３１側まで同一の幅で形成されている。
　このような構成を有することから、容易に壁面２７ｂを形成することが可能となる。 The wall surface 27b is formed with the same width from the cylinder head 3 side to the crank chamber 31 side.
Since it has such a structure, it becomes possible to form the wall surface 27b easily.
　壁面２７ｂの幅は、壁面２７ｂによって分断された排気開口部２７ａの一方の排気開口部２７ａの幅と同程度である。
　このような構成を有することから、壁面２７ｂが掃気を十分に対流させつつ、排気開口部２７ａから排気をすることの両立が可能となる。 The width of the wall surface 27b is approximately the same as the width of one exhaust opening portion 27a of the exhaust opening portion 27a divided by the wall surface 27b.
Since it has such a configuration, it is possible to achieve both the exhaustion from the exhaust opening 27a while the wall surface 27b sufficiently convects the scavenging.
　排気開口部２７ａの形状が略Ｕ字状に形成されている。
　このような構成を有することから、ブローダウンまたは圧縮開始の時期に掃気流の排出（吹き抜け）を抑制することができる。 The shape of the exhaust opening 27a is formed in a substantially U shape.
Since it has such a configuration, it is possible to suppress scavenging air discharge (blow-through) at the time of blow-down or compression start.
　排気開口部２７ａの形状が略Ｈ字状に形成されている。
　このような構成を有することから、吹き抜けをより確実に抑制することが可能となる。 The shape of the exhaust opening 27a is formed in a substantially H shape.
Since it has such a structure, it becomes possible to suppress blow-through more reliably.
　壁面２７ｂのクランク室３１側の端部である壁面端部２７ｃの位置が、右側掃気開口部２５ｂＲのシリンダヘッド３側の端部である右側掃気開口部端部２５ｃＲ、及び、左側掃気開口部２５ｂＬのシリンダヘッド３側の端部である左側掃気開口部端部２５ｃＬ、の位置とシリンダ５の中心軸の方向において一致（略一致を含む）している。
　このように構成したことから、より吹き抜けが生ずることを抑制することが可能となる。 The position of the wall surface end 27c that is the end of the wall surface 27b on the crank chamber 31 side is the right scavenging opening end 25cR that is the end of the right scavenging opening 25bR on the cylinder head 3 side, and the left scavenging opening 25bL. The left scavenging opening end portion 25cL, which is the end portion on the cylinder head 3 side, coincides (including substantially coincident) in the direction of the central axis of the cylinder 5.
Since it comprised in this way, it becomes possible to suppress that a blow-through arises more.
　また、本発明は以上の実施形態に限定されるものではなく、様々な変化した構造、構成、制御を行っていても良い。 Further, the present invention is not limited to the above embodiment, and various changed structures, configurations, and controls may be performed.
＜定義等＞
　本発明における２ストロークエンジンは、シリンダ５の中心軸の方向は、水平方向であってもよいし、鉛直方向であってもよい。つまり、本発明における１ストロークエンジンの中心軸の方向はどのような方向であってもよい。 <Definition etc.>
In the two-stroke engine in the present invention, the direction of the central axis of the cylinder 5 may be the horizontal direction or the vertical direction. That is, the direction of the central axis of the one-stroke engine in the present invention may be any direction.
　シリンダ５の中心軸に対して垂直な方向の断面をボア断面という。
　また、このボア断面においてシリンダ５の内周面方向を接線方向という。さらに、このボア断面において、ボア断面とシリンダ５の中心軸との交点からの放射線方向を半径方向という。
　本発明の略逆Ｕ字状には、略キャップ状も含まれている。
　本発明の壁面の一例が、壁面２７ｂである。壁面の形状は様々に変化させることが可能である。つまり、本発明の壁面は、前記排気開口部の幅方向における中央部の少なくとも一部を塞ぐように壁面が形成されていればよい。
　また、本発明における一致とは、完全な一致でなくともよい。 A cross section in a direction perpendicular to the central axis of the cylinder 5 is referred to as a bore cross section.
Further, in the bore cross section, the inner peripheral surface direction of the cylinder 5 is referred to as a tangential direction. Further, in this bore cross section, the radiation direction from the intersection of the bore cross section and the central axis of the cylinder 5 is referred to as a radial direction.
The substantially inverted U shape of the present invention includes a substantially cap shape.
An example of the wall surface of the present invention is a wall surface 27b. The shape of the wall surface can be changed variously. In other words, the wall surface of the present invention only needs to be formed so as to block at least a part of the central portion in the width direction of the exhaust opening.
Further, the coincidence in the present invention may not be a complete coincidence.
　１　　　　ストロークエンジン
　５　　　　シリンダ
　９　　　　クランクシャフト
　２１　　　ピストン
　２２　　　ピストンピン
　２３　　　吸気通路部
　２３ａ　　吸気開口部
　２５　　　掃気通路部
　２５ｂ　　シリンダ側掃気開口部
　２５ｂＬ　左側掃気開口部
　２５ｂＲ　右側掃気開口部
　２７　　　排気通路部
　２７ａ　　排気開口部
　２７ａＬ　左側排気開口部
　２７ａＲ　右側排気開口部
　２７ｂ　　壁面 DESCRIPTION OF SYMBOLS 1 Stroke engine 5 Cylinder 9 Crankshaft 21 Piston 22 Piston pin 23 Intake passage part 23a Intake opening part 25 Scavenging passage part 25b Cylinder side scavenging opening part 25bL Left scavenging opening part 25bR Right scavenging opening part 27 Exhaust passage part 27a Exhaust opening part 27aL Left exhaust opening 27aR Right exhaust opening 27b Wall surface

Claims (11)

  1. 　シリンダと、
    　前記シリンダ内を往復可能なピストンと、
    　前記シリンダに設けられた排気通路部と、
    　前記シリンダに設けられた掃気通路部と、を有し、
    　前記シリンダの内周面には、前記排気通路部の排気開口部および前記掃気通路部のシリンダ側掃気開口部が形成され、
    　前記排気開口部には、前記排気開口部の幅方向における中央部の少なくとも一部を塞ぐように壁面が形成され、
    　前記壁面のシリンダヘッド側とクランク室側との中央位置における排気開口部の幅は、前記壁面のシリンダヘッド側における排気開口部の幅の合計よりも大きく形成されている
    　２ストロークエンジン。     A cylinder,
    A piston capable of reciprocating in the cylinder;
    An exhaust passage provided in the cylinder;
    A scavenging passage portion provided in the cylinder,
    An exhaust opening of the exhaust passage and a cylinder-side scavenging opening of the scavenging passage are formed on the inner peripheral surface of the cylinder,
    In the exhaust opening, a wall surface is formed so as to block at least a part of a central portion in the width direction of the exhaust opening,
    A two-stroke engine, wherein the width of the exhaust opening at the center position between the cylinder head side and the crank chamber side of the wall surface is larger than the total width of the exhaust opening at the cylinder head side of the wall surface.
  2. 　前記壁面は、前記壁面のシリンダヘッド側とクランク室側との中央位置における幅が前記壁面のシリンダヘッド側位置の幅よりも小さくなるように形成されている
    　請求項１に記載の２ストロークエンジン。     The two-stroke engine according to claim 1, wherein the wall surface is formed such that a width of the wall surface at a center position between the cylinder head side and the crank chamber side is smaller than a width of the wall surface at a cylinder head side position.
  3. 　前記壁面は、前記壁面のシリンダヘッド側とクランク室側との中央位置における幅と前記壁面のクランク室側位置の幅とは同一となるように形成されている
    　請求項２に記載の２ストロークエンジン。     The two-stroke engine according to claim 2, wherein the wall surface is formed such that a width of the wall surface at a center position between the cylinder head side and the crank chamber side is the same as a width of the wall surface at a crank chamber side position. .
  4. 　前記壁面は、前記壁面のシリンダヘッド側の幅は、前記クランク室側の幅よりも大きく形成されている
    　請求項２に記載の２ストロークエンジン。     The two-stroke engine according to claim 2, wherein the wall surface is formed such that a width of the wall surface on the cylinder head side is larger than a width on the crank chamber side.
  5. 　前記壁面によって分断された排気通路部は、前記壁面の後方において合流する
    　請求項１に記載の２ストロークエンジン。     The two-stroke engine according to claim 1, wherein the exhaust passage part divided by the wall surface merges behind the wall surface.
  6. 　前記壁面を構成する壁部は、ボア方向の断面形状が略三角形状を有している
    　請求項５に記載の２ストロークエンジン。     The two-stroke engine according to claim 5, wherein the wall portion constituting the wall surface has a substantially triangular cross-sectional shape in the bore direction.
  7. 　前記壁面は、シリンダヘッド側からクランク室側まで同一の幅で形成されている
    　請求項１に記載の２ストロークエンジン。     The two-stroke engine according to claim 1, wherein the wall surface is formed with the same width from a cylinder head side to a crank chamber side.
  8. 　前記壁面の幅は、前記壁面によって分断された排気開口部の一方の排気開口部の幅と同程度である
    　請求項１に記載の２ストロークエンジン。     The two-stroke engine according to claim 1, wherein the width of the wall surface is approximately the same as the width of one exhaust opening of the exhaust opening divided by the wall surface.
  9. 　前記排気開口部の形状が略Ｕ字状に形成されている
    　請求項１に記載の２ストロークエンジン。     The two-stroke engine according to claim 1, wherein a shape of the exhaust opening is formed in a substantially U shape.
  10. 　前記排気開口部の形状が略Ｈ字状に形成されている
    　請求項１に記載の２ストロークエンジン。     The two-stroke engine according to claim 1, wherein a shape of the exhaust opening is substantially H-shaped.
  11. 　前記壁面の前記クランク室側の端部である壁面端部の位置が、前記掃気開口部のシリンダヘッド側の掃気開口部端部の位置とシリンダの中心軸の方向において一致している
    　請求項９または請求項１０に記載の２ストロークエンジン。     The position of the wall surface end portion, which is the end portion of the wall surface on the crank chamber side, coincides with the position of the scavenging opening portion end portion on the cylinder head side of the scavenging opening portion in the direction of the center axis of the cylinder. The two-stroke engine according to claim 10.
PCT/JP2012/054009 2011-03-31 2012-02-20 Two-stroke engine WO2012132628A1 (en)

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JP2011-080283 2011-03-31
JP2011080283A JP2014114699A (en) 2011-03-31 2011-03-31 Two-stroke engine

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Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS56151238A (en) * 1980-04-24 1981-11-24 Yamaha Motor Co Ltd Shape of exhaust port of two-cycle engine
JPH02207129A (en) * 1989-02-06 1990-08-16 Yamaha Motor Co Ltd Two-cycle engine

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS56151238A (en) * 1980-04-24 1981-11-24 Yamaha Motor Co Ltd Shape of exhaust port of two-cycle engine
JPH02207129A (en) * 1989-02-06 1990-08-16 Yamaha Motor Co Ltd Two-cycle engine

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