EP0202216B1 - Method of scavenging a two-stoke reverse-flow scavenged engine, and engine working according to this method - Google Patents

Method of scavenging a two-stoke reverse-flow scavenged engine, and engine working according to this method Download PDF

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Publication number
EP0202216B1
EP0202216B1 EP19860890118 EP86890118A EP0202216B1 EP 0202216 B1 EP0202216 B1 EP 0202216B1 EP 19860890118 EP19860890118 EP 19860890118 EP 86890118 A EP86890118 A EP 86890118A EP 0202216 B1 EP0202216 B1 EP 0202216B1
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EP
European Patent Office
Prior art keywords
crankcase
cylinder
primary
scavenge passages
piston
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Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
EP19860890118
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German (de)
French (fr)
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EP0202216A3 (en
EP0202216A2 (en
Inventor
Diethard Dipl.-Ing. Plohberger
Josef Dipl.-Ing. Greier
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AVL List GmbH
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AVL Gesellschaft fuer Verbrennungskraftmaschinen und Messtechnik mbH
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Publication of EP0202216A2 publication Critical patent/EP0202216A2/en
Publication of EP0202216A3 publication Critical patent/EP0202216A3/en
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    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02BINTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL
    • F02B25/00Engines characterised by using fresh charge for scavenging cylinders
    • F02B25/20Means 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

Definitions

  • the invention relates to a method for changing the charge in two-stroke internal combustion engines with reverse purging, with the piston-controlled outlet channel and at least two first and second overflow channels arranged on both sides of the outlet channel, via which the fresh charge is introduced into the cylinder by means of a crankcase pump, wherein at the start of flushing, a flow is generated by means of the first overflow channels immediately adjacent to the outlet channel on both sides, which prevents fresh charge from flowing over to the outlet channel, and to a two-stroke internal combustion engine for carrying out the method.
  • a two-stroke internal combustion engine in which the method mentioned at the outset is used, is known from US Pat. No. 4,253,433.
  • This internal combustion engine has two groups of overflow channels that connect the crankcase, which is designed as a crankcase pump, to the cylinder.
  • An inlet, through which the internal combustion engine is supplied with the fuel-air mixture, is connected directly to an overflow channel opposite the outlet channel, the opening of the inlet therein approximately in the middle between the inlet slot of the overflow channel into the cylinder and its opening into the Crankcase is done.
  • Another inlet, through which air is supplied to the internal combustion engine opens into the crankcase.
  • Two further overflow channels are located on both sides of a plane containing the cylinder axis and intersecting the first overflow channel and the outlet channel in the middle.
  • the piston in the downward movement compresses the air in the crankcase, as a result of which it enters the cylinder through all overflow channels and thereby entrains the mixture previously introduced from the first overflow channel.
  • the air emerging simultaneously from the further overflow channels separates the mixture from the outlet slot, thereby reducing the short-circuit loss of charge via the outlet channel. This should aim at lower fuel consumption and better combustion due to mixing with the air.
  • the disadvantage here is the relatively high design effort, given by the two inlet openings, which are provided with valves and two controlled throttle devices.
  • FR-PS 759 044 shows an embodiment very similar to that mentioned in US Pat. No.
  • Two groups of overflow channels are also present here, fresh charge being supplied via the channels opposite the outlet channel and air as a barrier against one via the overflow channels adjacent to the outlet channel direct overflow of fresh charge is introduced to the outlet duct.
  • a two-stroke internal combustion engine in which between the outlet channel and the inlet slots of overflow channels designed as storage spaces, which lead to a rich mixture, inlet slots of further overflow channels are arranged, which introduce a lean mixture, the lean mixture as Purge gas acts.
  • the piston moves down, as a result of which the lean fuel-air mixture is pre-compressed and enters the overflow channels and the storage spaces previously filled with a rich fuel-air mixture.
  • a lean fuel-air mixture flows from the overflow channels and a rich mixture flows into the cylinder from the storage spaces.
  • the lean mixture purges the residual gases from the cylinder, while the rich mixture from the storage spaces mixes with the lean mixture, so that an ignitable fuel-air mixture is formed. Because the inlet slots of the overflow channels lie between the inlet slots of the storage spaces and the outlet channel, a rich mixture cannot get into the outlet channel and be lost for combustion.
  • a disadvantage of this internal combustion engine is the considerable design effort, given by an additional auxiliary carburetor, or by at least one separate air inlet.
  • GB-A 2 083 550 discloses a process for changing the charge in two-stroke internal combustion engines, in which, during the downward movement of the piston, the inlet slots of two channels leading to pressure chambers are opened at a time when the actual overflow channels are still closed, so that compressed exhaust gas in flows into the pressure chambers. These compressed gases flow back into the cylinder chamber before the overflow channels are released, in order to establish the desired flushing flow before the fresh charge is admitted.
  • charge losses due to a direct overflow of fresh charge to the outlet channel cannot be avoided by the aforementioned method.
  • the object of the present invention is to provide a method for changing the charge in two-stroke internal combustion engines, which can be used with structurally simple, inexpensive precautions and guarantees good washing results, an improvement in terms of low-pollutant and more economical operation compared to conventional two-stroke internal combustion engines being achieved.
  • This object is achieved in that when the piston moves downward, the inlet slots of the at least two first overflow channels are opened at a time when the pressure in the cylinder is still higher than in the crankcase, so that exhaust gas flows into these overflow channels and forces the fresh charge back into them without penetrating into the crankcase itself, that when the pressure in the cylinder drops below the pressure in the crankcase, a connection is established between the first overflow channels and the crankcase and at the same time the inlet slots of the at least two second overflow channels are opened, whereby the cylinder is flushed and filled with fresh charge is, due to reversal of the pressure conditions from the first overflow channels, the previously introduced exhaust gas first emerges again and forms a barrier against the overflow of fresh charge to the outlet slot and then also fresh charge flows out through it.
  • an exhaust gas-fresh gas stratified flushing process is implemented which does not require any additional auxiliary carburetor or fresh air inlets, any additional inlet control elements which would have to be coordinated with one another being eliminated.
  • the method according to the invention requires considerably less design effort and also has good purge and charge properties, the exhaust gas barrier, which prevents a short-circuit loss of charge directly via the outlet, ensuring low-pollutant, economical operation of the internal combustion engine.
  • Another advantage is that the purge flow in the method according to the invention is maintained unchanged and only part of the fresh charge is replaced by an exhaust gas part in the period of impending charge losses.
  • the method according to the invention can be used particularly advantageously if, at the same time as the second overflow channels, at least one third overflow channel which opens at the wall of the cylinder opposite the outlet slot is opened or closed. This enables particularly good purging results to be achieved, in particular when using two or three channels, the gas kinetics being able to be influenced in a favorable manner in particular by freely selecting the inflow angles.
  • a two-stroke internal combustion engine for carrying out the method according to the invention, with reverse purging with an outlet channel controlled by the piston and at least two first and second overflow channels arranged on both sides of the outlet channel, the first overflow channels being arranged adjacent to both sides of the outlet channel, and with a crankcase pump for Introducing the fresh charge into the cylinder consists in the fact that the relative arrangement of the upper edge of the inlet slots of the first overflow channels to the control edge of the piston is determined such that when the piston moves downward, exhaust gas flows into the first overflow channels as long as the second overflow channels are still through the pistons are closed, that the first overflow channels have such dimensions and / or control devices that penetration of the exhaust gases into the crankcase is prevented, and that a connection when the pressure in the cylinder drops below the pressure in the crankcase is present between the first overflow channels and the crankcase.
  • a control device preventing the penetration of exhaust gases into the crankcase is formed by the crank web, which for this purpose has a recess which interacts with the confluence of each first overflow channel in the crankcase.
  • the purpose of this is to prevent the exhaust gases returning into the first channels from penetrating too quickly or too far in the direction of the crankcase and still to achieve an adequate filling of the channels with exhaust gas before the purging begins.
  • the control of overflow channels through the crank arm can also be seen in another context from DE-C 849 624.
  • the two-stroke internal combustion engine shown in FIGS. 1 to 12 has a cylinder 1 with a cylinder head 2 and a crankcase 3 with a crankshaft 4.
  • the piston 6, which is connected to the crankshaft 4 via the connecting rod 5, moves in the cylinder head 2.
  • a bore 7 is provided for the spark plug (not shown).
  • the cylinder 1 is connected to the crankcase 3 via a group of first overflow channels 8, a group of second overflow channels 9 and a group of third overflow channels 10, the group of first overflow channels 8 inlet slots 12, the group of second overflow channels 9 inlet slots 13 and the group of third overflow channels 10 has inlet slots 14 in the cylinder 1.
  • the group of the first and the second overflow channels 8 and 9 each comprise two channels on either side of a plane E containing the cylinder axis 15 and intersecting the outlet channel 16 in the middle. In the region 11 'of the first overflow channels 8, the control edge 11 of the piston 6 has a lowering.
  • the group of third overflow channels 10 also has two channels with inlet slots 14, which are diametrically opposite the outlet channel 16 with the outlet slot 17. However, this group can also have only one or more than two channels 10.
  • the first overflow channels 8 have a common opening 18 in the crankcase 3.
  • the opening of the second overflow channels 9 in the crankcase is designated by 19.
  • the charge change takes place according to the method described with reference to FIGS. 1 to 12.
  • the inlet slots 12, 13, 14 and the outlet slot 17 are not yet through the downwardly moving piston 6 or through its control edge 11, which has a lowering in the region 11 ' released and cylinder 1 is filled with exhaust gas.
  • the crankshaft 4 rotates according to the direction of rotation indicated by the arrow 28.
  • phase 2 of the process sequence (FIGS. 4 to 6) the piston 6 has moved further downward and now gives both the outlet slot 17 of the outlet channel 16 and the inlet slots 12 of the first overflow channels 8 through a control edge of the piston which is lowered in the region 11 ' 6 free.
  • These channels thus open earlier than the second overflow channels 9 and so early that the cylinder pressure is still higher than the purge pressure in the crankcase 3 and the channels 8, so that exhaust gas strikes back in the upper part 21 of these channels and the fresh charge in the lower part 22 repressed.
  • the overflow channels 8 are made so long that penetration of the exhaust gases into the crankcase 3 is avoided with certainty.
  • the expansion of the exhaust gases along the arrows 29 and 30 in FIGS. 4 and 5 can be clearly seen.
  • the upper parts 21 of the overflow channels 8 filled with exhaust gas can also be seen from FIG. 6.
  • phase 3 of the process sequence in which the piston 6 is at its bottom dead center, the overflow channels 9 and approximately at the same time the overflow channels 10 present here in order to achieve a better washing result and flush the cylinder 1 with them Fresh load.
  • the direction of flow reverses according to arrow 31 in FIG. 7 or 32 in FIG. 8 in channel 8 due to the pressure drop in cylinder 1, and the exhaust gas now emerging in the cylinder acts as a barrier (sealing gas) for the fresh charge flow from the channels 9 and 10. In this way the short-circuit loss of fresh charge is prevented directly into the outlet channel 16. Only towards the end of the rinsing phase does fresh charge emerge from the overflow channels 8.
  • the cylinder 1 At the end of the flushing in phase 4 of the process sequence (FIGS. 10 to 12), the cylinder 1 is ideally filled with fresh charge without part of it being lost in the outlet channel 16. As a result, the fresh charge with which the cylinder 1 is now completely filled (see FIGS. 11 and 12) is compressed by the piston 6 moving upward.
  • Different control times for the group of the first overflow channels 8 and the group of the second overflow channels 9 can also be achieved in that the upper edges 12 'of the inlet slots 12 of the channels 8 are higher than the upper edges 13' of the inlet slots 13 of the channels 9, the Control edge 11 of the piston 6 does not have a lowered area 11 ', or by a combination of different high top edges 12', 13 'with lowered areas 11'.
  • 13 to 17 is a variant of shown two-stroke internal combustion engine, which differs from the first-mentioned embodiment by the presence of a control device 20 for the first overflow channels 8.
  • This control device 20 consisting of separate openings 33 of the channels 8 in the crankcase 3 and a respective cooperating recess 27 on the circumference of each crank web 26, prevents the exhaust gases from penetrating into the crankcase 3.
  • phase 1 of the process sequence (FIGS. 13 and 14) all the inlet slots 12, 13, 14 and the outlet slot 17 and the opening 33 in the crankcase 3 are closed and the cylinder 1 is filled with the exhaust gas.
  • 15 to 17 show the phases 3 to 4 of the process sequence, which come about by rotating the crankshaft 4 according to arrow 28 and are identical to FIGS. 5, 8 and 11 of the first-mentioned example with regard to the piston position and the gas exchange.
  • the overflow channels 8 are still closed at the openings 33 in the crankcase 3 by the crank web 26, wherein, as indicated by the arrow 30, exhaust gas flows from the cylinder 1 into the latter, but not into the crankcase 3 can reach.
  • Phase 4 of the process sequence shows the internal combustion engine after the charge has been changed.
  • the control device 20 effectively prevents the exhaust gas front from penetrating into the crankcase 3, as a result of which there is more freedom in coordinating the dimensions of the overflow channels 8.
  • the overflow channels and the outlet channel are controlled in the following chronological sequence: the opening start ⁇ 0 of the outlet channel lies before the opening start ⁇ 1 of the upper flow channels 8, followed by the opening beginning ⁇ 2,3 of the overflow channels 9 and 10, which have the shortest opening duration D 2 , 3 and close first. Then close the channels 8, which have an average opening duration D i and finally the outlet channel with the opening duration D o .
  • the opening start a 4 of the control device 20 lies between the opening beginning ⁇ 0 of the outlet channel 16 and the bottom dead center (UT) of the piston, the opening end a 5 approximately between the bottom dead center of the piston and the outlet end.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Lubrication Details And Ventilation Of Internal Combustion Engines (AREA)
  • Combustion Methods Of Internal-Combustion Engines (AREA)
  • Cylinder Crankcases Of Internal Combustion Engines (AREA)
  • Electrical Control Of Air Or Fuel Supplied To Internal-Combustion Engine (AREA)
  • Exhaust-Gas Circulating Devices (AREA)

Description

Die Erfindung bezieht sich auf ein Verfahren zum Ladungswechsel bei Zweitakt-Brennkraftmaschinen mit Umkehrspülung, mit vom Kolben gesteuerten Auslaßkanal und mindestens je zwei auf beiden Seiten des Auslaßkanals angeordneten ersten und zweiten Überströmkanälen, über welche die Frischladung mittels einer Kurbelgehäusepumpe in den Zylinder eingebracht wird, wobei zu Spülbeginn mittels der dem Auslaßkanal zu beiden Seiten unmittelbar benachbarten, ersten Überströmkanäle eine Strömung erzeugt wird, welche ein Überströmen von Frischladung zum Auslaßkanal verhindert, und auf eine Zweitakt-Brennkraftmaschine zur Ausübung des Verfahrens.The invention relates to a method for changing the charge in two-stroke internal combustion engines with reverse purging, with the piston-controlled outlet channel and at least two first and second overflow channels arranged on both sides of the outlet channel, via which the fresh charge is introduced into the cylinder by means of a crankcase pump, wherein at the start of flushing, a flow is generated by means of the first overflow channels immediately adjacent to the outlet channel on both sides, which prevents fresh charge from flowing over to the outlet channel, and to a two-stroke internal combustion engine for carrying out the method.

Eine Zweitakt-Brennkraftmaschine, bei der das eingangs erwähnte Verfahren Anwendung findet, ist aus der US-PS 4 253 433 bekannt. Diese Brennkraftmaschine weist zwei Gruppen von Überströmkanälen auf, die das als Kurbelgehäusepumpe ausgebildete Kurbelgehäuse mit dem Zylinder verbinden. Ein Einlaß, durch welchen der Brennkraftmaschine das Kraftstoff-Luft-Gemisch zugeführt wird, ist direkt mit einem dem Auslaßkanal gegenüberliegenden Überströmkanal verbunden, wobei die Einmündung des Einlasses in diesen etwa in der Mitte zwischen dem Einlaßschlitz des Überströmkanals in den Zylinder und seiner Einmündung in das Kurbelgehäuse erfolgt. Ein weiterer Einlaß, durch welchen der Brennkraftmaschine Luft zugeführt wird, mündet in das Kurbelgehäuse. Je zwei weitere Überströmkanäle liegen zu beiden Seiten einer die Zylinderachse enthaltenden, sowohl den ersten Überströmkanal als auch den Auslaßkanal mittig schneidenden Ebene. Beim Betrieb der Brennkraftmaschine wird durch den sich nach unten bewegenden Kolben die Luft im Kurbelgehäuse komprimiert, wodurch diese durch alle Überströmkanäle in den Zylinder gelangt und dabei aus dem ersten Überströmkanal das zuvor eingebrachte Gemisch mitreißt. Die gleichzeitig aus den weiteren Überströmkanälen austretende Luft separiert das Gemisch vom Auslaßschlitz, wodurch der Kurzschlußverlust an Ladung über den Auslaßkanal verringert wird. Dadurch soll ein geringerer Kraftstoffverbrauch und infolge Vermischung mit der Luft eine bessere Verbrennung angestrebt werden. Nachteilig dabei ist der relativ hohe konstruktive Aufwand, gegeben durch die zwei Einlaßöffnungen, die mit Ventilen und zwei gesteuerten Drosseleinrichtungen versehen sind.A two-stroke internal combustion engine, in which the method mentioned at the outset is used, is known from US Pat. No. 4,253,433. This internal combustion engine has two groups of overflow channels that connect the crankcase, which is designed as a crankcase pump, to the cylinder. An inlet, through which the internal combustion engine is supplied with the fuel-air mixture, is connected directly to an overflow channel opposite the outlet channel, the opening of the inlet therein approximately in the middle between the inlet slot of the overflow channel into the cylinder and its opening into the Crankcase is done. Another inlet, through which air is supplied to the internal combustion engine, opens into the crankcase. Two further overflow channels are located on both sides of a plane containing the cylinder axis and intersecting the first overflow channel and the outlet channel in the middle. When the internal combustion engine is operating, the piston in the downward movement compresses the air in the crankcase, as a result of which it enters the cylinder through all overflow channels and thereby entrains the mixture previously introduced from the first overflow channel. The air emerging simultaneously from the further overflow channels separates the mixture from the outlet slot, thereby reducing the short-circuit loss of charge via the outlet channel. This should aim at lower fuel consumption and better combustion due to mixing with the air. The disadvantage here is the relatively high design effort, given by the two inlet openings, which are provided with valves and two controlled throttle devices.

Eine der genannten US-PS sehr ähnliche Ausführung zeigt die FR-PS 759 044. Auch hier sind im wesentlichen zwei Gruppen von Überströmkanälen vorhanden, wobei über die dem Auslaßkanal gegenüber liegenden Kanäle Frischladung zugeführt und über die dem Auslaßkanal benachbarten Überströmkanäle Luft als Barriere gegen ein direktes Überströmen von Frischladung zum Auslaßkanal eingebracht wird.FR-PS 759 044 shows an embodiment very similar to that mentioned in US Pat. No. Two groups of overflow channels are also present here, fresh charge being supplied via the channels opposite the outlet channel and air as a barrier against one via the overflow channels adjacent to the outlet channel direct overflow of fresh charge is introduced to the outlet duct.

Nach der DE-OS 26 50 834 ist eine Zweitakt-Brennkraftmaschine bekannt, bei der zwischen Auslaßkanal und den Einlaßschlitzen von als Speicherräume ausgebildeten Überströmkanälen, welche fettes Gemisch führen, Einlaßschlitze von weiteren Überströmkanälen angeordnet sind, welche mageres Gemisch einbringen, wobei das magere Gemisch als Sperrgas fungiert. Beim Verbrennungstakt bewegt sich der Kolben nach unten, wodurch das magere Kraftstoff-Luft-Gemisch vorkomprimiert und in die Überströmkanäle und die zuvor mit fettem Kraftstoff-Luft-Gemisch gefüllten Speicherräume eintritt. Sobald der Kolben die Einlaßschlitze freigibt, strömt aus den Überströmkanälen mageres Kraftstoff-Luft-Gemisch und aus den Speicherräumen fettes Gemisch in den Zylinder ein. Das magere Gemisch spült die Restgase aus dem Zylinder, während das fette Gemisch aus den Speicherräumen sich mit dem mageren Gemisch vermischt, sodaß ein zündfähiges Kraftstoff-Luft-Gemisch entsteht. Indem zwischen den Einlaßschlitzen der Speicherräume und dem Auslaßkanal die Einlaßschlitze der Überströmkanäle liegen, kann kein fettes Gemisch in den Auslaßkanal gelangen und für die Verbrennung verlorengehen. Nachteilig bei dieser Brennkraftmaschine ist der ebenfalls beträchtliche konstruktive Aufwand, gegeben durch einen zusätzlichen Hilfsvergaser, oder durch mindestens einen gesonderten Lufteinlaß.According to DE-OS 26 50 834 a two-stroke internal combustion engine is known, in which between the outlet channel and the inlet slots of overflow channels designed as storage spaces, which lead to a rich mixture, inlet slots of further overflow channels are arranged, which introduce a lean mixture, the lean mixture as Purge gas acts. During the combustion cycle, the piston moves down, as a result of which the lean fuel-air mixture is pre-compressed and enters the overflow channels and the storage spaces previously filled with a rich fuel-air mixture. As soon as the piston clears the inlet slots, a lean fuel-air mixture flows from the overflow channels and a rich mixture flows into the cylinder from the storage spaces. The lean mixture purges the residual gases from the cylinder, while the rich mixture from the storage spaces mixes with the lean mixture, so that an ignitable fuel-air mixture is formed. Because the inlet slots of the overflow channels lie between the inlet slots of the storage spaces and the outlet channel, a rich mixture cannot get into the outlet channel and be lost for combustion. A disadvantage of this internal combustion engine is the considerable design effort, given by an additional auxiliary carburetor, or by at least one separate air inlet.

Aus der AT-PS 138547 ist es bekannt, bei Zweitakt-Brennkraftmaschine mit Querspülung das während der Spülung unerwünschte Ausströmen von Frischgas über den Auslaßkanal dadurch zu verhindern, daß der Zylinder nacheinander mit Abgas und Frischgas gespült wird. Dies geschieht durch eine Kammer, die am Ende des Expansionshubes vor Erreichung der Totlage mit dem Zylinderraum in Verbindung gesetzt wird, so daß ein Teil der Verbrennungsgase in die Kammer eintritt. Darauf werden die Auslaßschlitze geöffnet, so daß ein Vorspülen des Zylinders durch die in der Kammer gespeicherten Verbrennungsgase erfolgt, wonach schließlich die Frischladung durch die Einlaßschlitze in den Zylinder eintritt. Die Auslaßkanaloberkante liegt hier tiefer als die Oberkante aller Spülkanäle. Dadurch sollen die während der Anfangsphase der Spülung auftretenden Spülverluste vermindert werden. Nachteilig ist jedoch, daß die während des weiteren Fortganges der Spülung auftretenden Gemischverluste durch diese Maßnahmen nicht beeinflußt werden können. Der bauliche Aufwand für diese Maschine liegt ebenfalls über dem vergleichbarer herkömmlicher Zweitakt-Brennkraftmaschinen.From AT-PS 138547 it is known to prevent the undesired outflow of fresh gas through the exhaust port during the purging in two-stroke internal combustion engines with cross-purging by the cylinder being purged with exhaust gas and fresh gas one after the other. This takes place through a chamber which is connected to the cylinder chamber at the end of the expansion stroke before reaching the dead position, so that part of the combustion gases enter the chamber. The outlet slots are then opened so that the cylinder is pre-rinsed by the combustion gases stored in the chamber, after which the fresh charge finally enters the cylinder through the inlet slots. The upper edge of the outlet channel is lower than the upper edge of all flushing channels. This is intended to reduce the flushing losses that occur during the initial phase of the flushing. However, it is disadvantageous that the mixture losses occurring during the further progress of the flushing cannot be influenced by these measures. The structural effort for this machine is also higher than that of comparable conventional two-stroke internal combustion engines.

Aus der GB-A 2 083 550 ist schließlich ein Verfahren zum Ladungswechsel bei Zweitakt-Brennkraftmaschinen bekannt, bei welchem während der Abwärtsbewegung des Kolbens die Einlaßschlitze von zwei zu Druckkammem führenden Kanälen zu einem Zeitpunkt geöffnet werden, zu welchem die eigentlichen Überströmkanäle noch geschlossen sind, sodaß komprimiertes Abgas in die Druckkammern einströmt. Diese komprimierten Gase strömen noch vor Freigabe der Überströmkanäle in den Zylinderraum zurück, um bereits vor dem Einlaß der Frischladung die gewünschte Spülströmung zu etablieren. Durch das genannte Verfahren können jedoch Ladungsverluste bedingt durch ein direktes Überströmen von Frischladung zum Auslaßkanal nicht vermieden werden.Finally, GB-A 2 083 550 discloses a process for changing the charge in two-stroke internal combustion engines, in which, during the downward movement of the piston, the inlet slots of two channels leading to pressure chambers are opened at a time when the actual overflow channels are still closed, so that compressed exhaust gas in flows into the pressure chambers. These compressed gases flow back into the cylinder chamber before the overflow channels are released, in order to establish the desired flushing flow before the fresh charge is admitted. However, charge losses due to a direct overflow of fresh charge to the outlet channel cannot be avoided by the aforementioned method.

Aufgabe der vorliegenden Erfindung ist es, ein Verfahren zum Ladungswechsel bei Zweitakt-Brennkraftmaschinen anzugeben, das mit konstruktiv einfachen, kostengünstigen Vorkehrungen angewendet werden kann und einen guten Spülerfolg garantiert, wobei eine Verbesserung hinsichtlich schadstoffärmerem und sparsamerem Betrieb gegenüber herkömmlichen Zweitakt-Brennkraftmaschinen, erzielt wird.The object of the present invention is to provide a method for changing the charge in two-stroke internal combustion engines, which can be used with structurally simple, inexpensive precautions and guarantees good washing results, an improvement in terms of low-pollutant and more economical operation compared to conventional two-stroke internal combustion engines being achieved.

Diese Aufgabe wird erfindungsgemäß dadurch gelöst, daß bei der Abwärtsbewegung des Kolbens die Einlaßschlitze der mindestens zwei ersten Überströmkanäle zu einem Zeitpunkt geöffnet werden, wenn der Druck im Zylinder noch höher ist als im Kurbelgehäuse, so daß Abgas in diese Überströmkanäle einströmt und die Frischladung darin zurückdrängt ohne selbst in das Kurbelgehäuse einzudringen, daß bei Absinken des Druckes im Zylinder unter den Druck im Kurbelgehäuse eine Verbindung zwischen den ersten Überströmkanälen und dem Kurbelgehäuse hergestellt ist und gleichzeitig die Einlaßschlitze der mindestens zwei zweiten Überströmkanäle freigegeben werden, wodurch der Zylinder mit Frischladung gespült und gefüllt wird, wobei wegen Umkehr der Druckverhältnisse aus den ersten Überströmkanälen zunächst das zuvor eingebrachte Abgas wieder austritt und eine Barriere gegen das Überströmen von Frischladung zum Auslaßschlitz bildet und sodann ebenfalls Frischladung durch diese ausströmt. Dadurch ist ein Abgas-Frischgas-Schichtspülverfahren verwirklicht, das ohne zusätzliche Hilfsvergaser bzw. Frischlufteinlässe auskommt, wobei allfällige zusätzliche Einlaßsteuerelemente wegfallen, die überdies aufeinander abgestimmt sein müßten. Das erfindungsgemäße Verfahren setzt wesentlich weniger konstruktiven Aufwand voraus und weist zudem gute Spül- und Ladungseigenschaften auf, wobei die Abgasbarriere, die einen Kurzschlußverlust an Ladung direkt über den Auslaß verhindert, für einen schadstoffarmen, sparsamen Betrieb der Brennkraftmaschine sorgt. Ein weiterer Vorteil besteht darin, daß die Spülströmung beim Verfahren nach der Erfindung unverändert aufrechterhalten wird und lediglich in der Zeitspanne drohender Ladungsverluste ein Teil der Frischladung durch einen Abgasteil ersetzt wird.This object is achieved in that when the piston moves downward, the inlet slots of the at least two first overflow channels are opened at a time when the pressure in the cylinder is still higher than in the crankcase, so that exhaust gas flows into these overflow channels and forces the fresh charge back into them without penetrating into the crankcase itself, that when the pressure in the cylinder drops below the pressure in the crankcase, a connection is established between the first overflow channels and the crankcase and at the same time the inlet slots of the at least two second overflow channels are opened, whereby the cylinder is flushed and filled with fresh charge is, due to reversal of the pressure conditions from the first overflow channels, the previously introduced exhaust gas first emerges again and forms a barrier against the overflow of fresh charge to the outlet slot and then also fresh charge flows out through it. As a result, an exhaust gas-fresh gas stratified flushing process is implemented which does not require any additional auxiliary carburetor or fresh air inlets, any additional inlet control elements which would have to be coordinated with one another being eliminated. The method according to the invention requires considerably less design effort and also has good purge and charge properties, the exhaust gas barrier, which prevents a short-circuit loss of charge directly via the outlet, ensuring low-pollutant, economical operation of the internal combustion engine. Another advantage is that the purge flow in the method according to the invention is maintained unchanged and only part of the fresh charge is replaced by an exhaust gas part in the period of impending charge losses.

Besonders vorteilhaft kann das erfindungsgemäße Verfahren eingesetzt werden, wenn etwa gleichzeitig mit den zweiten Überströmkanälen mindestens ein dritter Überströmkanal, der an der dem Auslaßschlitz gegenüberliegenden Wand des Zylinders mündet, geöffnet bzw. geschlossen wird. Dadurch ist ein besonders guter Spülerfolg zu erzielen, insbesondere bei der Verwendung von zwei oder drei Kanälen, wobei insbesondere durch die freie Wahl der Einströmwinkel die Gaskinetik günstig beeinflußt werden kann.The method according to the invention can be used particularly advantageously if, at the same time as the second overflow channels, at least one third overflow channel which opens at the wall of the cylinder opposite the outlet slot is opened or closed. This enables particularly good purging results to be achieved, in particular when using two or three channels, the gas kinetics being able to be influenced in a favorable manner in particular by freely selecting the inflow angles.

Eine Zweitakt-Brennkraftmaschine zur Ausübung des erfindungsgemäßen Verfahrens, mit Umkehrspülung mit vom Kolben gesteuerten Auslaßkanal und mindestens je zwei auf beiden Seiten des Auslaßkanals angeordneten ersten und zweiten Überströmkanälen, wobei die ersten Überströmkanäle zu beiden Seiten des Auslaßkanals benachbart angeordnet sind, sowie mit einer Kurbelgehäusepumpe zum Einbringen der Frischladung in den Zylinder, besteht darin, daß die relative Anordnung der Oberkante der Einlaßschlitze der ersten Überströmkanäle zur Steuerkante des Kolbens so festgelegt ist, daß bei Abwärtsbewegung des Kolbens ein Einströmen von Abgas in die ersten Überströmkanäle erfolgt, solange die zweiten Überströmkanäle noch durch den Kolben verschlossen sind, daß die ersten Überströmkanäle solche Abmessungen und/oder Steuereinrichtungen aufweisen, daß ein Vordringen der Abgase in das Kurbelgehäuse unterbunden ist, sowie daß bei Absinken des Druckes im Zylinder unter den Druck im Kurbelgehäuse eine Verbindung zwischen den ersten Überströmkanälen und dem Kurbelgehäuse vorhanden ist. Dadurch sind zwei Möglichkeiten gegeben, die ersten Überströmkanäle mit Abgas zu füllen. In beiden Ausführungsvarianten muß, entweder durch bestimmte Abmessungen, wobei die Länge und der Querschnitt der ersten Überströmkanäle auf die Abmessungen des Zylinders abgestimmt sein müssen, oder durch Steuereinrichtungen in diesen Kanälen, ein Überströmen der Abgase in das Kurbelgehäuse verhindert werden.A two-stroke internal combustion engine for carrying out the method according to the invention, with reverse purging with an outlet channel controlled by the piston and at least two first and second overflow channels arranged on both sides of the outlet channel, the first overflow channels being arranged adjacent to both sides of the outlet channel, and with a crankcase pump for Introducing the fresh charge into the cylinder consists in the fact that the relative arrangement of the upper edge of the inlet slots of the first overflow channels to the control edge of the piston is determined such that when the piston moves downward, exhaust gas flows into the first overflow channels as long as the second overflow channels are still through the pistons are closed, that the first overflow channels have such dimensions and / or control devices that penetration of the exhaust gases into the crankcase is prevented, and that a connection when the pressure in the cylinder drops below the pressure in the crankcase is present between the first overflow channels and the crankcase. This gives two options for filling the first overflow channels with exhaust gas. In both design variants, overflow of the exhaust gases into the crankcase must be prevented, either by certain dimensions, the length and the cross section of the first overflow channels having to be matched to the dimensions of the cylinder, or by control devices in these channels.

Nach einer Ausgestaltung der Erfindung ist vorgesehen, daß eine das Vordringen von Abgasen in das Kurbelgehäuse verhindernde Steuereinrichtung durch die Kurbelwange gebildet ist, die zu diesem Zweck eine mit der Einmündung jedes ersten Überströmkanals in das Kurbelgehäuse zusammenwirkende Ausnehmung aufweist. Dies dient dazu, ein eventuell zu rasches oder zu weites Vordringen der in die ersten Kanäle rückschlagenden Abgase in Richtung Kurbelgehäuse zu verhindern und trotzdem eine ausreichende Füllung der Kanäle mit Abgas vor Beginn der Spülung zu erzielen. Die Steuerung von Überströmkanälen durch die Kurbelwange ist in einem anderen Zusammenhang auch aus der DE-C 849 624 ersichtlich.According to one embodiment of the invention, it is provided that a control device preventing the penetration of exhaust gases into the crankcase is formed by the crank web, which for this purpose has a recess which interacts with the confluence of each first overflow channel in the crankcase. The purpose of this is to prevent the exhaust gases returning into the first channels from penetrating too quickly or too far in the direction of the crankcase and still to achieve an adequate filling of the channels with exhaust gas before the purging begins. The control of overflow channels through the crank arm can also be seen in another context from DE-C 849 624.

Die Erfindung wird anhand der Zeichnungen näher erläutert. Es zeigen :

  • Figur 1 eine erfindungsgemäße Zweitakt-Brennkraftmaschine teilweise schematisch in der Phase 1 des erfindungsgemäßen Verfahrensablaufes teilweise geschnitten nach der Linie I-I in Fig. 3,
  • Figur 2 einen Schnitt nach der Linie 11-11 in Fig. 1 und
  • Figur 3 einen Schnitt nach der Linie 111-111 in Fig. 1, sowie in gleicher Schnittführung bei der selben Brennkraftmaschine, die
  • Figuren 4, 5 und 6 die Phase 2 des Verfahrensablaufes, die
  • Figuren 7, 8 und 9 die Phase 3 des Verfahrensablaufes, die
  • Figuren 10, 11 und 12 die Phase 4 des Verfahrensablaufes, weiters die
  • Figuren 13 und 14 eine andere Zweitakt-Brennkraftmaschine in der Phase 1 in einer Schnittführung entsprechend Fig. 1 und 2, die
  • Figuren 15, 16 und 17 die Phasen 2, 3 und 4 des Verfahrensablaufes entsprechend Fig. 5, 8 und 11 und
  • Figur 18 ein Kurbelwinkeldiagramm.
The invention is explained in more detail with reference to the drawings. Show it :
  • FIG. 1 shows a two-stroke internal combustion engine according to the invention, partially schematically in phase 1 of the process sequence according to the invention, partially cut along line II in FIG. 3,
  • Figure 2 is a section along the line 11-11 in Fig. 1 and
  • Figure 3 shows a section along the line 111-111 in Fig. 1, and in the same cut in the same internal combustion engine, the
  • Figures 4, 5 and 6 phase 2 of the process blaufes, the
  • Figures 7, 8 and 9, phase 3 of the process, the
  • Figures 10, 11 and 12, phase 4 of the process, further the
  • Figures 13 and 14 another two-stroke internal combustion engine in phase 1 in a sectional view corresponding to FIGS. 1 and 2, the
  • Figures 15, 16 and 17, phases 2, 3 and 4 of the process sequence corresponding to Fig. 5, 8 and 11 and
  • Figure 18 is a crank angle diagram.

Gleiche Teile sind mit den selben Bezugszeichen versehen.The same parts are provided with the same reference numerals.

Die in den Fig. 1 bis 12 dargestellte Zweitakt-Brennkraftmaschine weist einen Zylinder 1 mit einem Zylinderkopf 2 sowie ein Kurbelgehäuse 3 mit einer Kurbelwelle 4 auf. Im Zylinder 1 bewegt sich der über die Pleuelstange 5 mit der Kurbelwelle 4 antriebsverbundene Kolben 6. Im Zylinderkopf 2 ist eine Bohrung 7 für die nicht dargestellte Zündkerze vorgesehen. Der Zylinder 1 ist über eine Gruppe erster Überströmkanäle 8, eine Gruppe zweiter Überströmkanäle 9 und eine Gruppe dritter Überströmkanäle 10 mit dem Kurbelgehäuse 3 verbunden, wobei die Gruppe der ersten Überströmkanäle 8 Einlaßschlitze 12, die Gruppe der zweiten Überströmkanäle 9 Einlaßschlitze 13 und die Gruppe der dritten Überströmkanäle 10 Einlaßschlitze 14 in den Zylinder 1 aufweist. Die Gruppe der ersten und der zweiten Überströmkanäle 8 bzw. 9 umfassen je zwei Kanäle zu beiden Seiten einer die Zylinderachse 15 enthaltenden und den Auslaßkanal 16 mittig schneidenden Ebene E. Beide Gruppen können jedoch auch mehrere Kanäle auf beiden Seiten dieser Ebene E aufweisen. Im Bereich 11' der ersten Überströmkanäle 8 weist die Steuerkante 11 des Kolbens 6 eine Absenkung auf. Die Gruppe der dritten Überströmkanäle 10 weist ebenfalls zwei Kanäle mit Einlaßschlitzen 14 auf, die dem Auslaßkanal 16 mit dem Auslaßschlitz 17 diametral gegenüberliegen. Diese Gruppe kann jedoch auch über nur einen oder mehr als zwei Kanäle 10 verfügen. Die ersten Überströmkanäle 8 verfügen über eine gemeinsame Einmündung 18 in das Kurbelgehäuse 3. Die Einmündung der zweiten Überströmkanäle 9 in das Kurbelgehäuse ist mit 19 bezeichnet. Durch Abstimmung des Volumens der Überströmkanäle 8 auf jene des Zylinders 1 wird verhindert, daß beim Betrieb der Brennkraftmaschine Abgase aus dem Zylinder 1 in das Kurbelgehäuse 3 vordringen. Die gepunktet angedeutete Frischladung wird über den Vergaser 23, der über den Zuleitungskanal 24, welcher das Rückschlagventil 25 aufweist, mit dem Kurbelgehäuse 3 verbunden ist, zugeführt.The two-stroke internal combustion engine shown in FIGS. 1 to 12 has a cylinder 1 with a cylinder head 2 and a crankcase 3 with a crankshaft 4. In the cylinder 1, the piston 6, which is connected to the crankshaft 4 via the connecting rod 5, moves in the cylinder head 2. A bore 7 is provided for the spark plug (not shown). The cylinder 1 is connected to the crankcase 3 via a group of first overflow channels 8, a group of second overflow channels 9 and a group of third overflow channels 10, the group of first overflow channels 8 inlet slots 12, the group of second overflow channels 9 inlet slots 13 and the group of third overflow channels 10 has inlet slots 14 in the cylinder 1. The group of the first and the second overflow channels 8 and 9 each comprise two channels on either side of a plane E containing the cylinder axis 15 and intersecting the outlet channel 16 in the middle. In the region 11 'of the first overflow channels 8, the control edge 11 of the piston 6 has a lowering. The group of third overflow channels 10 also has two channels with inlet slots 14, which are diametrically opposite the outlet channel 16 with the outlet slot 17. However, this group can also have only one or more than two channels 10. The first overflow channels 8 have a common opening 18 in the crankcase 3. The opening of the second overflow channels 9 in the crankcase is designated by 19. By matching the volume of the overflow channels 8 to that of the cylinder 1, exhaust gases from the cylinder 1 are prevented from penetrating into the crankcase 3 during operation of the internal combustion engine. The fresh charge indicated by dots is supplied via the carburetor 23, which is connected to the crankcase 3 via the supply duct 24, which has the check valve 25.

Im Betrieb der Zweitakt-Brennkraftmaschine erfolgt der Ladungswechsel nach dem anhand der Fig. 1 bis 12 beschriebenen Verfahren. In der Phase 1 des Verfahrensablaufes (Fig. 1 bis 3) wird durch den sich abwärts bewegenden Kolben 6 bzw. durch seine Steuerkante 11, die im Bereich 11' eine Absenkung aufweist, die Einlaßschlitze 12, 13, 14 und der Auslaßschlitz 17 noch nicht freigegeben und der Zylinder 1 ist von Abgas erfüllt. Dabei dreht sich die Kurbelwelle 4 entsprechend der durch den Pfeil 28 angegebenen Drehrichtung.In the operation of the two-stroke internal combustion engine, the charge change takes place according to the method described with reference to FIGS. 1 to 12. In phase 1 of the process sequence (FIGS. 1 to 3), the inlet slots 12, 13, 14 and the outlet slot 17 are not yet through the downwardly moving piston 6 or through its control edge 11, which has a lowering in the region 11 ' released and cylinder 1 is filled with exhaust gas. The crankshaft 4 rotates according to the direction of rotation indicated by the arrow 28.

Gleichzeitig wird durch den Kolben 6 die sich im Kurbelgehäuse 3 befindliche Frischladung komprimiert, wobei die Überströmkanäle 8, 9, 10 durch den Kolben verschlossen sind. Im Zylinder 1 befindet sich zu diesem Zeitpunkt nur Abgas.At the same time, the fresh charge located in the crankcase 3 is compressed by the piston 6, the overflow channels 8, 9, 10 being closed by the piston. At this time there is only exhaust gas in cylinder 1.

In der Phase 2 des Verfahrensablaufes (Fig. 4 bis 6) ist der Kolben 6 weiter nach unten gewandert und gibt nun sowohl den Auslaßschlitz 17 des Auslaßkanals 16 als auch die Einlaßschlitze 12 der ersten Überströmkanäle 8 durch eine im Bereich 11' abgesenkte Steuerkante des Kolbens 6 frei. Diese Kanäle öffnen somit früher als die zweiten Überströmkanäle 9 und zwar so früh, daß der Zylinderdruck noch höher ist als der Spüldruck im Kurbelgehäuse 3 und den Kanälen 8, sodaß Abgas in den oberen Teil 21 dieser Kanäle zurückschlägt und die Frischladung in den unteren Teil 22 verdrängt. Die Überströmkanäle 8 sind, dabei so lang ausgeführt, daß ein Vordringen der Abgase bis ins Kurbelgehäuse 3 mit Sicherheit vermieden wird. Deutlich sieht man dabei die Ausbreitung der Abgase entlang der Pfeile 29 bzw. 30 in den Fig. 4 bzw. 5. Aus Fig. 6 sind ebenfalls die mit Abgas gefüllten oberen Teile 21 der Überströmkanäle 8 ersichtlich.In phase 2 of the process sequence (FIGS. 4 to 6), the piston 6 has moved further downward and now gives both the outlet slot 17 of the outlet channel 16 and the inlet slots 12 of the first overflow channels 8 through a control edge of the piston which is lowered in the region 11 ' 6 free. These channels thus open earlier than the second overflow channels 9 and so early that the cylinder pressure is still higher than the purge pressure in the crankcase 3 and the channels 8, so that exhaust gas strikes back in the upper part 21 of these channels and the fresh charge in the lower part 22 repressed. The overflow channels 8 are made so long that penetration of the exhaust gases into the crankcase 3 is avoided with certainty. The expansion of the exhaust gases along the arrows 29 and 30 in FIGS. 4 and 5 can be clearly seen. The upper parts 21 of the overflow channels 8 filled with exhaust gas can also be seen from FIG. 6.

In der Phase 3 des Verfahrensablaufes (Fig. 7 bis 9), in der sich der Kolben 6 an seinem unteren Totpunkt befindet, öffnen sich die Überströmkanäle 9 und etwa gleichzeitig die hier zur Erzielung eines besseren Spülergebnisses vorhandenen Überströmkanäle 10 und spülen den Zylinder 1 mit Frischladung. Gleichzeitig kehrt sich die Strömungsrichtung entsprechend Pfeil 31 in Fig. 7 bzw. 32 in Fig. 8 im Kanal 8 aufgrund des Druckabfalles im Zylinder 1 um, und das nunmehr in den Zylinder austretende Abgas wirkt als Barriere (Sperrgas) für den Frischladungsstrom aus den Kanälen 9 und 10. Solcherart wird der Kurzschlußverlust an Frischladung direkt in den Auslaßkanal 16 verhindert. Erst gegen Ende der Spülphase tritt auch aus den Überströmkanälen 8 Frischladung aus.In phase 3 of the process sequence (FIGS. 7 to 9), in which the piston 6 is at its bottom dead center, the overflow channels 9 and approximately at the same time the overflow channels 10 present here in order to achieve a better washing result and flush the cylinder 1 with them Fresh load. At the same time, the direction of flow reverses according to arrow 31 in FIG. 7 or 32 in FIG. 8 in channel 8 due to the pressure drop in cylinder 1, and the exhaust gas now emerging in the cylinder acts as a barrier (sealing gas) for the fresh charge flow from the channels 9 and 10. In this way the short-circuit loss of fresh charge is prevented directly into the outlet channel 16. Only towards the end of the rinsing phase does fresh charge emerge from the overflow channels 8.

Bei Beendigung der Spülung in der Phase 4 des Verfahrensablaufes (Fig. 10 bis 12) ist der Zylinder 1 im Idealfall mit Frischladung gefüllt, ohne daß ein Teil davon in den Auslaßkanal 16 verlorengeht. In der Folge wird die Frischladung, mit der der Zylinder 1 nun vollständig gefüllt ist (siehe Fig. 11 und 12), durch den sich aufwärts bewegenden Kolben 6 komprimiert.At the end of the flushing in phase 4 of the process sequence (FIGS. 10 to 12), the cylinder 1 is ideally filled with fresh charge without part of it being lost in the outlet channel 16. As a result, the fresh charge with which the cylinder 1 is now completely filled (see FIGS. 11 and 12) is compressed by the piston 6 moving upward.

Unterschiedliche Steuerzeiten für die Gruppe der ersten Überströmkanäle 8 und die Gruppe der zweiten Überströmkanäle 9 können auch dadurch erreicht werden, daß die Oberkanten 12' der Einlaßschlitze 12 der Kanäle 8 höher liegen, als die Oberkanten 13' der Einlaßschlitze 13 der Kanäle 9, wobei die Steuerkante 11 des Kolbens 6 keinen abgesenkten Bereich 11' aufweist, oder durch eine Kombination verschieden hoher Oberkanten 12', 13' mit abgesenkten Bereichen 11'.Different control times for the group of the first overflow channels 8 and the group of the second overflow channels 9 can also be achieved in that the upper edges 12 'of the inlet slots 12 of the channels 8 are higher than the upper edges 13' of the inlet slots 13 of the channels 9, the Control edge 11 of the piston 6 does not have a lowered area 11 ', or by a combination of different high top edges 12', 13 'with lowered areas 11'.

In den Fig. 13 bis 17 ist eine Variante der eingangs angegebenen Zweitakt-Brennkraftmaschine dargestellt, die sich von der erstgenannten Ausführung durch das Vorhandensein einer Steuereinrichtung 20 für die ersten Überströmkanäle 8 unterscheidet. Diese Steuereinrichtung 20, bestehend aus separaten Einmündungen 33 der Kanäle 8 in das Kurbelgehäuse 3 und je einer damit zusammenwirkenden Ausnehmung 27 am Umfang jeder Kurbelwange 26, verhindert ein Vordringen der Abgase in das Kurbelgehäuse 3.13 to 17 is a variant of shown two-stroke internal combustion engine, which differs from the first-mentioned embodiment by the presence of a control device 20 for the first overflow channels 8. This control device 20, consisting of separate openings 33 of the channels 8 in the crankcase 3 and a respective cooperating recess 27 on the circumference of each crank web 26, prevents the exhaust gases from penetrating into the crankcase 3.

In der Phase 1 des Verfahrensablaufes (Fig. 13 und 14) sind sämtliche Einlaßschlitze 12, 13, 14 und der Auslaßschlitz 17 sowie die Einmündung 33 in das Kurbelgehäuse 3 geschlossen und der Zylinder 1 ist vom Abgas erfüllt.In phase 1 of the process sequence (FIGS. 13 and 14), all the inlet slots 12, 13, 14 and the outlet slot 17 and the opening 33 in the crankcase 3 are closed and the cylinder 1 is filled with the exhaust gas.

Die Fig. 15 bis 17 zeigen die Phasen 3 bis 4 des Verfahrensablaufes, die durch Drehung der Kurbelwelle 4 entsprechend Pfeil 28 zustandekommen und bezüglich der Kolbenstellung und des Gaswechsels mit den Fig. 5, 8 und 11 des erstgenannten Beispiels ident sind.15 to 17 show the phases 3 to 4 of the process sequence, which come about by rotating the crankshaft 4 according to arrow 28 and are identical to FIGS. 5, 8 and 11 of the first-mentioned example with regard to the piston position and the gas exchange.

In der Fig. 15 sind die Überströmkanäle 8 an ihren Einmündungen 33 in das Kurbelgehäuse 3 noch immer von der Kurbelwange 26 verschlossen, wobei gleichzeitig, wie durch den Pfeil 30 angedeutet, Abgas aus dem Zylinder 1 in diese einströmt, aber nicht in das Kurbelgehäuse 3 gelangen kann.15, the overflow channels 8 are still closed at the openings 33 in the crankcase 3 by the crank web 26, wherein, as indicated by the arrow 30, exhaust gas flows from the cylinder 1 into the latter, but not into the crankcase 3 can reach.

Beim Weiterdrehen der Kurbelwelle 4 entsprechend dem Pfeil 28 zum unteren Totpunkt des Kolbens 6 (Fig. 16), werden auch die Oberströmkanäle 9 frei, sodaß durch diese Frischladung in den Zylinder 1 eindringt. Durch Umkehr der Druckverhältnisse und Freigabe der Einmündung 33 durch die Ausnehmung 27 tritt durch den Überströmkanal 8 als Sperrgas wirkendes Abgas entsprechend Pfeil 32 in den Zylinder 1 und verhindert ein Abströmen der Frischladung in den Auslaßkanal 16. Gegen Ende des Ladevorganges gelangt auch durch die Überströmkanäle 8 Frischladung in den Zylinder 1.When crankshaft 4 continues to rotate according to arrow 28 to the bottom dead center of piston 6 (FIG. 16), upper flow channels 9 are also cleared, so that fresh charge penetrates cylinder 1. By reversing the pressure conditions and releasing the opening 33 through the recess 27, exhaust gas acting as sealing gas passes through the overflow channel 8 according to arrow 32 into the cylinder 1 and prevents the fresh charge from flowing out into the outlet channel 16. Towards the end of the charging process, the overflow channels 8 also pass through Fresh charge in cylinder 1.

Die Phase 4 des Verfahrensablaufes (Fig. 17) zeigt die Brennkraftmaschine nach erfolgtem Ladungswechsel. Die Steuereinrichtung 20 verhindert, wie gezeigt, wirksam ein Vordringen der Abgasfront in das Kurbelgehäuse 3, wodurch bei der Abstimmung der Abmessungen der Überströmkanäle 8 mehr Freiheit besteht.Phase 4 of the process sequence (FIG. 17) shows the internal combustion engine after the charge has been changed. As shown, the control device 20 effectively prevents the exhaust gas front from penetrating into the crankcase 3, as a result of which there is more freedom in coordinating the dimensions of the overflow channels 8.

In der Fig. 18 ist zusammenfassend für beide Ausführungsvarianten ein Steuerdiagramm für die einzelnen Kanäle 8, 9, 10, 16, sowie für die Steuereinrichtung 20 dargestellt. Dabei ist der obere bzw. der untere Totpunkt mit OT bzw. UT bezeichnet. Der Winkelbereich, in dem die Steuereinrichtung 20 offenhält, ist mit SÖ bis SS bezeichnet. Die weiteren Abkürzungen im Kurbelwinkeldiagramm bedeuten :

  • α0.... Öffnungsbeginn des Auslaßkanals in °KW n.OT
  • α1.... Öffnungsbeginn der Gruppe der ersten Überströmkanäle 8 in °KW n.OT
  • α2,3.. Öffnungsbeginn der Gruppe der zweiten und der Gruppe der dritten Überströmkanäle 9, 10 in °KW n.OT
  • α4.... Öffnungsbeginn der Steuereinrichtung 20 in °KW n.OT
  • α5.... Öffnungsschluß der Steuereinrichtung 20 in °KW n.OT
  • Do.... Öffnungsdauer des Auslaßkanals in °KW
  • D1.... Öffnungsdauer der Gruppe der ersten Überströmkanäle 8 in °KW
  • D2,3.. Öffnungsdauer der Gruppe der zweiten und der Gruppe der dritten Überströmkanäle 9, 10 in °KW
A control diagram for the individual channels 8, 9, 10, 16 and for the control device 20 is shown in summary in FIG. 18 for both design variants. The top and bottom dead center is referred to as OT or UT. The angular range in which the control device 20 keeps open is designated SE to SS. The other abbreviations in the crank angle diagram mean:
  • α 0 .... start of opening of the exhaust duct in ° KW n.OT
  • α 1 .... opening of the group of the first overflow channels 8 in ° KW n.OT
  • α 2 , 3 .. opening of the group of the second and the group of the third overflow channels 9, 10 in ° KW n.OT
  • α 4 .... opening of the control device 20 in ° KW n.OT
  • α 5 .... Closing of the control device 20 in ° KW n.OT
  • D o .... opening time of the exhaust duct in ° KW
  • D 1 .... opening time of the group of the first overflow channels 8 in ° KW
  • D 2 , 3 .. opening time of the group of the second and the group of the third overflow channels 9, 10 in ° KW

Die Überströmkanäle und der Auslaßkanal werden in folgender zeitlicher Abfolge gesteuert: Der Öffnungsbeginn α0 des Auslaßkanals liegt vor dem Öffnungsbeginn α1 der Oberströmkanäle 8, danach folgt der Öffnungsbeginn α2,3 der Überströmkanäle 9 und 10, die die kürzeste Offnungsdauer D2,3 aufweisen und zuerst wieder schließen. Danach schließen die Kanäle 8, die eine mittlere Öffnungsdauer Di aufweisen und zuletzt der Auslaßkanal mit der Öffnungsdauer Do.The overflow channels and the outlet channel are controlled in the following chronological sequence: the opening start α 0 of the outlet channel lies before the opening start α 1 of the upper flow channels 8, followed by the opening beginning α 2,3 of the overflow channels 9 and 10, which have the shortest opening duration D 2 , 3 and close first. Then close the channels 8, which have an average opening duration D i and finally the outlet channel with the opening duration D o .

Der Öffnungsbeginn a4 der Steuereinrichtung 20 liegt dabei zwischen Öffnungsbeginn α0 des Auslaßkanals 16 und dem unteren Totpunkt (UT) des Kolbens, der Offnungsschluß a5 zirka zwischen dem unteren Totpunkt des Kolbens und Auslaßschluß.The opening start a 4 of the control device 20 lies between the opening beginning α 0 of the outlet channel 16 and the bottom dead center (UT) of the piston, the opening end a 5 approximately between the bottom dead center of the piston and the outlet end.

Claims (4)

1. A method of scavenging a two-stroke reverse-flow scavenged engine comprising a piston-controlled exhaust passage and two or more primary as well as secondary scavenge passages on either side of the said exhaust passage, through which the fresh charge is delivered to the cylinder by means of a crankcase pump, a flow being generated at the beginning of the scavenging process by the primary scavenge passages located on either side of the exhaust passage in the immediate vicinity of the latter, which will prevent the fresh charge from entering the exhaust passage, wherein during the downward stroke of the piston the intake ports of the two or more primary scavenge passages are uncovered at a time when the pressure in the cylinder still is higher than in the crankcase, inducing the exhaust gas to flow into said scavenge passages and to force back the fresh charge cnntained therein without entering the crankcase itself, and wherein upon a drop of the pressure in the cylinder below the pressure level in the crankcase a connection is established between the primary scavenge passages and the crankcase, the intake ports of the two or more secondary scavenge passages being uncovered at the same time, such that the cylinder is scavenged and filled with fresh charge, the exhaust gas admitted into the primary scavenge passages before being discharged again due to a reversal of pressures, forming a barrier against the escape of fresh charge through the exhaust port, upon which the fresh charge will be discharged through the said primary scavenge passages.
2. A method according to claim 1, wherein at least one tertiary scavenge passage opening into the wall of the cylinder opposite of the exhaust port is opened or closed approximately at the same time as the secondary scavenge passages.
3. A two-stroke reverse-flow scavenged engine working according to the method described in claim 1 or 2, comprising a piston-controlled exhaust passage and two or more primary as well as secondary scavenge passages on either side of the exhaust passage, the primary scavenge passages being located on either side of the exhaust passage in the immediate vicinity of the latter, and further comprising a crankcase pump for delivering the fresh charge to the cylinder, wherein the upper edges of the intake ports of the primary scavenge passages are positioned relative to the control edge of the piston such that upon the downward stroke of the piston exhaust gas is admitted into the primary scavenge passages as long as the secondary scavenge passages are still covered by the piston, and wherein the primary scavenge passages have dimensions and/or control devices which will prevent the exhaust gases from penetrating into the crankcase, and wherein a connection is established between the primary scavenge passages and the crankcase upon a pressure drop in the cylinder below the pressure level in the crankcase.
4. A two-stroke engine according to claim 3, wherein the control device preventing the exhaust gases from penetrating into the crankcase is formed by the crank cheek, which for this purpose is provided with a recess cooperating with the inlet of each primary scavenge passage into the crankcase.
EP19860890118 1985-05-10 1986-04-28 Method of scavenging a two-stoke reverse-flow scavenged engine, and engine working according to this method Expired EP0202216B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
AT1419/85 1985-05-10
AT141985A AT399913B (en) 1985-05-10 1985-05-10 TWO-STROKE INTERNAL COMBUSTION ENGINE WITH REVOLUTION

Publications (3)

Publication Number Publication Date
EP0202216A2 EP0202216A2 (en) 1986-11-20
EP0202216A3 EP0202216A3 (en) 1987-03-04
EP0202216B1 true EP0202216B1 (en) 1989-08-30

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Application Number Title Priority Date Filing Date
EP19860890118 Expired EP0202216B1 (en) 1985-05-10 1986-04-28 Method of scavenging a two-stoke reverse-flow scavenged engine, and engine working according to this method

Country Status (6)

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EP (1) EP0202216B1 (en)
JP (1) JPS6217315A (en)
CN (1) CN1007443B (en)
AT (1) AT399913B (en)
DE (1) DE3665349D1 (en)
IN (1) IN166656B (en)

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IT8912001A0 (en) * 1989-01-24 1989-01-24 Renzo Dellarosa PRESSURE COMPENSATION SYSTEM BETWEEN PUMP CASE AND EXHAUST AIR FOR TWO-STROKE CYCLE ENDothermic Engines
FR2693507B1 (en) * 1992-07-09 1994-08-26 Aura Method and device for feeding a two-stroke internal combustion engine cylinder.
US6729275B2 (en) 1999-02-05 2004-05-04 Avl List Gmbh Two-stroke internal combustion engine with crankcase scavenging
US6539900B2 (en) 1999-02-05 2003-04-01 Avl List Gmbh Two-stroke internal combustion engine with crankcase scavenging
DE10319216B4 (en) * 2003-04-29 2015-09-24 Andreas Stihl Ag & Co. Kg Two-stroke engine
CN103790690B (en) * 2014-02-21 2017-03-08 浙江天泰机械有限公司 A kind of gasoline engine
CN107366573A (en) * 2017-07-04 2017-11-21 贵州宝文电机科技有限公司 Revolving cylinder engine
CN107524514B (en) * 2017-07-25 2019-07-23 北京航空航天大学 The high power to weight ratio heavy oil piston engine air inlet buffer of two strokes of one kind and its design method
CN112696265A (en) * 2020-12-24 2021-04-23 南通理工学院 Two-stroke internal combustion engine capable of reducing environmental pollution

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Also Published As

Publication number Publication date
ATA141985A (en) 1994-12-15
EP0202216A3 (en) 1987-03-04
DE3665349D1 (en) 1989-10-05
CN86103240A (en) 1986-11-05
IN166656B (en) 1990-06-30
EP0202216A2 (en) 1986-11-20
CN1007443B (en) 1990-04-04
JPH0246772B2 (en) 1990-10-17
AT399913B (en) 1995-08-25
JPS6217315A (en) 1987-01-26

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