EP0021170B1 - Two-stroke internal combustion engine - Google Patents

Two-stroke internal combustion engine Download PDF

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Publication number
EP0021170B1
EP0021170B1 EP80103129A EP80103129A EP0021170B1 EP 0021170 B1 EP0021170 B1 EP 0021170B1 EP 80103129 A EP80103129 A EP 80103129A EP 80103129 A EP80103129 A EP 80103129A EP 0021170 B1 EP0021170 B1 EP 0021170B1
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EP
European Patent Office
Prior art keywords
piston
internal combustion
combustion engine
combustion chamber
stroke internal
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EP80103129A
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German (de)
French (fr)
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EP0021170A1 (en
Inventor
Bernhard Dipl.-Ing. Büchner
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Individual
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Individual
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Priority to AT80103129T priority Critical patent/ATE1253T1/en
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    • 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
    • F02B75/16—Engines characterised by number of cylinders, e.g. single-cylinder engines
    • F02B75/18—Multi-cylinder engines
    • F02B75/22—Multi-cylinder engines with cylinders in V, fan, or star arrangement
    • F02B75/228—Multi-cylinder engines with cylinders in V, fan, or star arrangement with cylinders arranged in parallel banks
    • 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
    • F02B25/02—Engines characterised by using fresh charge for scavenging cylinders using unidirectional scavenging
    • F02B25/12—Engines with U-shaped cylinders, having ports in each arm
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02F—CYLINDERS, PISTONS OR CASINGS, FOR COMBUSTION ENGINES; ARRANGEMENTS OF SEALINGS IN COMBUSTION ENGINES
    • F02F7/00—Casings, e.g. crankcases or frames
    • F02F7/0002—Cylinder arrangements
    • F02F7/0019—Cylinders and crankshaft not in one plane (deaxation)
    • 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
    • F02B1/00—Engines characterised by fuel-air mixture compression
    • F02B1/02—Engines characterised by fuel-air mixture compression with positive ignition
    • F02B1/04—Engines characterised by fuel-air mixture compression with positive ignition with fuel-air mixture admission into cylinder
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02B—INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL
    • F02B75/00—Other engines
    • F02B75/02—Engines characterised by their cycles, e.g. six-stroke
    • F02B2075/022—Engines characterised by their cycles, e.g. six-stroke having less than six strokes per cycle
    • F02B2075/025—Engines characterised by their cycles, e.g. six-stroke having less than six strokes per cycle two
    • 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
    • F02B3/00—Engines characterised by air compression and subsequent fuel addition
    • F02B3/06—Engines characterised by air compression and subsequent fuel addition with compression ignition

Definitions

  • the invention relates to a two-stroke internal combustion engine with at least one double piston, the cylinders of which are connected to one another on the cylinder head side by a combustion chamber and are charged on the crank chamber side by a charging device with air or a fuel / air mixture, the leading piston of the double piston both overflowing in at least one of the cylinder chamber side of the crank chamber of the leading piston to the combustion chamber-side cylinder section of the trailing piston leading overflow channel as well as the exhaust process such that the exhaust process begins before the opening of the overflow channel.
  • the two-stroke internal combustion engine can work both on the gasoline principle and on the diesel principle, as well as in multi-fuel mode.
  • a two-stroke internal combustion engine of the above type is known from DE-C 2 523 712.
  • the overflow process is controlled exclusively by the leading piston and in such a way that the angle of rotation corresponding to the exhaust process and the overflow process have the same bisector and this is shifted in relation to the dead center of the crank against the direction of rotation.
  • the leading piston closes the overflow channel before the discharge process is completed.
  • the compression stroke of the double piston thus begins only after the overflow process has been completed, so that no pressure drop directed from the combustion chamber to the crank chamber can arise, which would lead part of the fresh charge of the combustion chamber back into the crank chamber when the overflow channel is open.
  • the overflow process determines the filling of the combustion chamber and thus the performance and the efficiency of the internal combustion engine.
  • the combustion chamber cannot be optimally filled when the crank chamber is charged, because the control time for the overflow is too short, since at the end there is still a pressure drop from the crank chamber into the combustion chamber.
  • An internal combustion engine with double pistons is also known from German Offenlegungsschrift 2,347,809, the cylinders of which are connected to one another on the cylinder head side by a combustion chamber.
  • the exhaust process is controlled by the leading piston, which also controls the intake process of the fuel-air mixture into the associated crank chamber sealed from the crank chamber of the trailing piston.
  • the trailing piston controls the intake process of purge air into the crank chamber space assigned to it.
  • the trailing piston also controls the overflow processes in two overflow channels, one of which leads from the crank chamber space of the leading piston to the combustion chamber side cylinder section of the trailing piston and the other from the crank chamber space of the trailing piston also to the combustion chamber side cylinder section of this piston.
  • a suitable choice of shape for the two overflow channels in the known internal combustion engine is intended to ensure that the combustion chamber is first purged exclusively with purge air from the crank chamber of the trailing piston, while the supply of the fuel-air mixture from the crank chamber of the leading piston is sufficient is delayed that it reaches the outlet controlled by the leading piston only after the completion of the exhaust process.
  • both overflow processes only start shortly before bottom dead center and thus too late for optimal charging.
  • the two overflow processes end long after the outlet closes at a point in time at which a reverse pressure drop from the cylinder chamber to the crank chamber is already present due to the increasing compression pressure in the cylinder. This pushes back a substantial part of the load just introduced to the crank chamber.
  • the object of the invention is to provide a two-stroke internal combustion engine with a double piston, in which, on the one hand, even when charging by means of a charging device, it is ensured that no combustion gases can flow back from the combustion chamber into the crank chamber and, on the other hand, optimum filling of the combustion chamber is nevertheless achieved.
  • This object is achieved in that the same overflow channel also leads from the crank chamber side cylinder section of the trailing piston to the combustion chamber side cylinder section of this piston and is controlled not only by the leading piston but also by the trailing piston, and in that the trailing piston at the earliest with the leading piston opens and closes later than the leading piston.
  • the leading piston still controls the exhaust process and the start of the overflow process.
  • the trailing piston then in turn opens the overflow channel, which increases the effective channel cross section.
  • the end of the overflow process is controlled exclusively by the lagging piston.
  • Both pistons control the same overflow channel, whereby its volume can be kept small and its harmful influence on the level of the crank chamber compression remains small.
  • the combined control of the overflow channel by both pistons allows the overflow process to be extended over a crank angle of approximately 2x90 ° around bottom dead center. This angle is only determined by the pressure drop between the crank chamber and the combustion chamber-side cylinder section of the trailing piston, depending on the degree of charging of the crank chamber.
  • the charger preferably generates a crank chamber compression ratio of at least 1.5.
  • the charging device can be a high-performance crank chamber pump, which expediently also controls the intake process on the crank chamber side. This can be done, for example, by circumferential surfaces of a connecting rod of the crankshaft-type rotary slide valve or rotary slide valve pair, the circumferential surface of which rotates contact-free or slightly touching and is therefore efficient in terms of efficiency.
  • devices for gas-dynamic vibrating charging for example resonance tubes, resonance volumes or the like, which are matched to a specific speed range of the internal combustion engine, are also suitable.
  • the lagging piston preferably closes the overflow channel at the same time as the outlet process controlled by the leading piston ends.
  • the combustion chamber can also be recharged if the trailing piston closes the overflow channel only after the exhaust process has ended, which is only made possible by the present invention.
  • the control of the overflow channel by the trailing piston must be dimensioned such that the boost pressure on the crankcase side is still sufficiently higher than the pressure of the beginning compression in the cylinders.
  • the boost pressure should be up to 0.5 atü higher than the beginning compression pressure in the cylinder.
  • the lagging piston and the leading piston open the overflow channel preferably at different times. In this way, a certain pre-charge or pre-discharge of the overflow channel can be achieved, coordinated with the desired speed level of the machine.
  • an overflow channel is arranged on both sides of a cylinder block wall separating the cylinders of the double piston. These overflow channels are controlled by windows in the shirt of the two pistons below the piston ring zones. The fresh gases cool this partition. If necessary, additional cooling water channels can be provided in the partition.
  • An embodiment offers significant advantages in which at least part of the wall of the combustion chamber opposite the pistons is formed by a counter-piston which is displaceably guided in the cylinder head and can be delivered to the pistons by means of a power device.
  • the power device can be a hydraulic cylinder which is actuated by a hydraulic control depending on the throttle position.
  • the counter-piston can also be adjusted via a cam, a spring assembly or the like. If a spark plug is required, it can remain in a central position in the counter-piston so that it is moved together with the counter-piston; but it can also be relocated to the periphery of the combustion chamber defined by the cylinder head.
  • an ignition electrode engaging in the combustion chamber is preferably provided, the counter electrode of which is provided on a surface facing the combustion chamber of a cylinder block wall extending between the two pistons.
  • the ignition electrode can be arranged on the cylinder head in the middle of the combustion chamber, so that a across the combustion chamber to the counter surface spark that reaches the cylinder block wall.
  • This cylinder block wall thus forms the ground electrode.
  • the high voltage required to generate such long ignition sparks can be easily achieved with the aid of a high-voltage capacitor ignition.
  • the ignition electrode and the counter electrode can also be arranged side by side on the surface of this cylinder block wall facing the combustion chamber. This arrangement has the advantage that it takes up relatively little space in the combustion chamber, which is then used to accommodate other elements such. B. injectors or the like is available.
  • Another aspect of the invention relates to the lubrication of connecting rods and base bearings of the double piston.
  • the connecting rod bearing and the base bearing are preferably encapsulated separately from the crank chamber in a lubricant-tight manner, lubricant lines of a central oil supply opening into the encapsulated bearing interior.
  • any remaining escape oil quantities from the bearings into the crank chamber can be taken into account in the total oil quantity required for the operation of the internal combustion engine.
  • H deducted from the amount of fresh oil that is introduced into the intake flow for piston lubrication.
  • the oil in the central oil supply can be supplied from an oil tank by means of an oil pump or a slope (drip lubrication), possibly supported by a slight overpressure in the oil tank.
  • FIG. 1 and 2 show a two-stroke internal combustion engine 10, the cylinder block 12 has two cylinders 14 and 16.
  • the cylinders 14 and 16 are closed by a cylinder head 20 which contains a combustion chamber 18 connecting the cylinders 14, 16.
  • a piston 22 or 24 is slidably guided in the cylinders 14, 16.
  • the pistons 22, 24 are articulated via a common connecting rod 26 by means of a crank pin 27 eccentrically on a lifting disk 30 mounted on a shaft pin 28.
  • the lifting disk 30 rotates in a crank chamber 34 closed by a trough 32.
  • the cylinders 14 and 16 are divided by piston heads 36 and 38 of the pistons 22, 24 into a cylinder section on the combustion chamber side and a cylinder section on the crank chamber side.
  • An overflow channel 44 is formed on both sides of an intermediate wall 42 of the cylinder block 12 that separates the cylinders 14, 16, so that the sucked-in mixture from the crank chamber 34 can get into the combustion chamber-side cylinder sections and the combustion chamber 18.
  • These overflow channels 44 each have an inlet slot 46 and 48 in the cylinder sections of the cylinders 14, 16 on the crankcase side and an outlet slot 50 in the cylinder section of the cylinder 16 on the combustion chamber side.
  • the inlet slots 46, 48 are opened by windows 52 and 54 in the piston skirt of the pistons 22 and 54 on the crankcase side, respectively 24 opened and closed.
  • the outlet slots 50 of the overflow channels 42 are controlled by the upper edge 56 of the trailing piston 24.
  • the upper edge 58 of the piston 22 controls an outlet slot 60 in the cylinder section of the cylinder 14 on the combustion chamber side.
  • the intake process is controlled by the lifting disk 30, the circumference 62 of which opens or closes the mouth of the intake manifold 40 in a contactless or slightly touching manner.
  • the internal combustion engine works as follows.
  • the lifting disc 30 rotates in the direction of arrow A, the piston 22 always leads the piston 24.
  • the lifting disc 30 closes the inlet port 40.
  • the mixture introduced into the crank chamber 34 is compressed by the pistons 22, 24 going downward.
  • the inlet slots 46, 48 of the overflow channels are closed.
  • the upper edge 58 of the leading piston 22 opens the outlet slot 60, so that the burned gases can flow out of the cylinder sections on the combustion chamber side and the combustion chamber 18.
  • the leading piston 22 then opens the inlet slots 46 of the overflow channels 44.
  • the upper edge 56 of the lagging piston 24 has opened the outlet slots 50 of the overflow channels 44. Due to the later opening, a large advance outlet with a long overflow control time is possible.
  • the compressed gases of the crank chamber 34 flow over the overflow channels 44 one after the other into the combustion chamber-side cylinder section of the trailing cylinder 16, then into the combustion chamber 18 and then into the combustion chamber-side cylinder section of the leading cylinder ders 14. They cool both the intermediate wall 42 and the two pistons through which the fresh air or fresh gas charge flows.
  • the intermediate wall can optionally be provided with additional cooling water channels 64.
  • the windows 54 of the lagging piston 24 only reach the inlet slots 48 of the two overflow channels 44 after the leading piston 22 has already opened the inlet slots 46.
  • the piston 22 closes the inlet slots 46 at a time when the outlet slot 60 is still open.
  • the entry slots 48 controlled by the piston 24 remain open beyond this point in time.
  • the inlet slots 48 are closed when the piston 22 closes the outlet slot 60.
  • the boost pressure on the crankcase side is sufficiently high, they can also remain open beyond the end of the exhaust process, so that the cylinder sections 14, 16 and the combustion chamber 18 on the combustion chamber side can still be reloaded via the overflow channels 44 even when the compression stroke is already beginning.
  • the overflow process can be extended by a crank angle of approximately 2 x 90 ° around bottom dead center. It is essentially only limited by the height of the pressure drop from the crank chamber 34 via the overflow channels 44 into the cylinder section of the cylinder 16 on the combustion chamber side.
  • the pressure difference between the boost pressure and the pressure of the commencement of compression in the cylinder section of the cylinder 16 on the combustion chamber side should be approximately between 0.5 and 1.5 atm.
  • the wall 66 of the combustion chamber 18 opposite the piston heads 36, 38 is formed by a counter-piston 68, which is guided and displaceably guided in a sealed manner in a hydraulic cylinder 70.
  • the hydraulic cylinder 70 is connected via a pressure medium supply line 72 to a control which moves the counter-piston 68 depending on the throttle position of the internal combustion engine.
  • the control increases the compression ratio into the partial load range; for example in a ratio of 1: 2. In this way, fuel consumption can be optimized and significantly reduced over the entire load range.
  • fuel injection nozzles 74 open into the overflow channels 44 and continuously inject fuel against the direction of flow in the overflow channels 44.
  • This injection method which is suitable for both gasoline and diesel engines, allows both a qualitative control of the operation, in which only the fuel supply is regulated while the air in the combustion chamber remains completely full, and a quantitative control, in which the charge is changed overall.
  • the combustion chamber 18 is essentially cylindrical and has two diametrically opposite regions in cross section, which widen from the end of the combustion chamber remote from the cylinder to the cylinders 14, 16.
  • the bulges 76 thus created are each delimited by a spherical triangular surface.
  • the bulges 76 that arise in the combustion chamber 18 need not be limited by a spherical triangular surface, they can also be formed by straight ramps that can extend beyond the centers of the cylinder axes 14 and 16 and in FIG. 1 and in FIG. 4 at 77 or 79 are indicated by dashed lines.
  • Fig. 3 shows schematically in a section through a cylinder head a further possibility of fuel injection, in which the very high swirl arising in the combustion chamber is used.
  • the swirl is indicated in FIG. 3 by arrows 78.
  • the fuel is injected by means of a nozzle 80 against the swirl direction either directly onto the wall 82 of the combustion chamber located between the cylinders 84, 86 or in an area immediately in front of the wall 82.
  • an ignition electrode 90 projecting into the combustion chamber is insulated, the counter electrode 92 of which is also integrated into the intermediate wall 88.
  • These ignition electrodes 90 and 92 can e.g. B. can also be integrated into the cylinder head gasket in another embodiment. In this way, the combustion chamber above remains free, so that there is space for accommodating other elements, for example the injection nozzle 80.
  • FIG. 4 shows a combustion chamber 94, in the middle of which an ignition electrode 96 is arranged.
  • the counter electrode of the ignition electrode 96 is formed by an intermediate wall 98 between the two cylinders 100 and 102.
  • a high-voltage capacitor ignition generates the high voltage required for the relatively large electrode spacing.
  • the two-stroke internal combustion engine is preferably supplied with oil for the piston lubrication via a central oil supply from a tank, not shown, via an oil pump, also not shown, or a slope.
  • the oil is introduced, for example, into the intake stream, the mixing ratio of oil to fuel-air mixture or air depending on the load state being between 1:80 and 1:200.
  • 5 shows details of a crankshaft bearing arrangement with two lifting disks 110, 112 which are axially spaced apart and are pressed on centrally on shaft journals 106, 108, between which there is an eccentric axis arranged crank pin 114 extends.
  • the shaft journals 106, 108 are mounted on roller bearings 116, 118 in the engine block 120.
  • a connecting rod 121 is mounted on the crank pin 114 between the lifting disks 110, 112 by means of roller rollers 122.
  • the connecting rod 121 has a connecting rod bearing outer ring 124 projecting axially over the bearing rollers 122, the axial end faces of which are sealed against the lifting disks 110, 112 by means of coaxial sealing rings 126, 128 and round cord rings 141, 142. If necessary, either the sealing rings 126, 128 or the round cord rings 141, 142 can be omitted.
  • the round cord rings are stored in standardized ring grooves.
  • a lubricant channel 130 opens into the sealed interior of the connecting rod bearing ring 124 and is connected to the central oil supply system via a supply bore 132.
  • the axially facing sides of the lifting disks 110, 112 each carry the circumferential half of a labyrinth seal 134 or 136, the fixed halves 143, 144 of which are provided on the cylinder block 120.
  • Some of the labyrinth seals 134, 136 are additionally sealed by sealing rings 138, 140 and piston rings 145, 146.
  • the labyrinth seal. gen 134 and 136 are self-contained components, the inner ring with the piston ring seal 145, 146 rotates with the shaft journal 106 and 108 (base bearing journal), while the outer rings 143, 144 as well as the bearing outer rings in the same outer diameter with in Housing is clamped.
  • the amount of fresh oil to be introduced into the intake flow for piston lubrication can be reduced by the amount of escape oil from these bearings, so that overall the oil consumption of the two-stroke internal combustion engine is reduced and can be set permanently for the overall running time of the machine. Unlike with oil sump-lubricated engines, it is independent of the machine's state of wear.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Output Control And Ontrol Of Special Type Engine (AREA)
  • Combustion Methods Of Internal-Combustion Engines (AREA)

Abstract

A two stroke internal combustion engine with at least one dual piston, the cylinders of which are connected to each other by a combustion chamber on the cylinder head side. The engine can be charged on the crank chamber side with an air or air/fuel mixture by a turbo or supercharger. Both the leading and trailing pistons of the dual piston construction control the process of transfer of the air or air/fuel mixture through a transfer port from the crank chamber side of the cylinders to the combustion chamber side of the cylinder for the trailing piston as well as the exhaust process such that the exhaust process begins before the initiation of the transfer process. The engine can operate on either the Otto or Diesel cycles and use multiple fuels.

Description

Die Erfindung betrifft eine Zweitaktbrennkraftmaschine mit wenigstens einem Doppelkolben, dessen Zylinder zylinderkopfseitig durch einen Brennraum miteinander verbunden sind und kurbelkammerseitig von einer Aufladeeinrichtung mit Luft oder Brennstoff-Luft-Gemisch aufgeladen werden, wobei der voreilende Kolben des Doppelkolbens sowohl den Überströmvorgang in zumindest einem vom kurbelkammerseitigen Zylinderabschnitt des voreilenden Kolbens zum brennraumseitigen Zylinderabschnitt des nacheilenden Kolbens führenden Überströmkanal als auch den Auslaßvorgang derart steuert, daß der Auslaßvorgang vor dem Öffnen des Überströmkanals beginnt. Die Zweitaktbrennkraftmaschine kann sowohl nach dem Ottoprinzip wie nach dem Dieselprinzip, als auch in Vielstoffbetriebsweise arbeiten.The invention relates to a two-stroke internal combustion engine with at least one double piston, the cylinders of which are connected to one another on the cylinder head side by a combustion chamber and are charged on the crank chamber side by a charging device with air or a fuel / air mixture, the leading piston of the double piston both overflowing in at least one of the cylinder chamber side of the crank chamber of the leading piston to the combustion chamber-side cylinder section of the trailing piston leading overflow channel as well as the exhaust process such that the exhaust process begins before the opening of the overflow channel. The two-stroke internal combustion engine can work both on the gasoline principle and on the diesel principle, as well as in multi-fuel mode.

Eine Zweitaktbrennkraftmaschine der vorstehenden Art ist aus der DE-C 2 523 712 bekannt. Bei dieser Brennkraftmaschine wird der Überströmvorgang ausschließlich durch den voreilenden Kolben gesteuert und zwar so, daß der dem Auslaßvorgang und der dem Überströmvorgang entsprechende Drehwinkel dieselbe Winkelhalbierende haben und diese gegenüber dem Kurbelkammertotpunkt entgegen der Drehrichtung verschoben ist. Der voreilende Kolben schließt den Überströmkanal vor Beendigung des Auslaßvorgangs. Der Kompressionshub des Doppelkolbens beginnt damit erst nach Abschluß des Überströmvorgangs, so daß kein vom Brennraum zur Kurbelkammer gerichtetes Druckgefälle entstehen kann, welches bei geöffnetem Überströmkanal einen Teil der frischen Ladung des Brennraums wieder in die Kurbelkammer zurückführen würde.A two-stroke internal combustion engine of the above type is known from DE-C 2 523 712. In this internal combustion engine, the overflow process is controlled exclusively by the leading piston and in such a way that the angle of rotation corresponding to the exhaust process and the overflow process have the same bisector and this is shifted in relation to the dead center of the crank against the direction of rotation. The leading piston closes the overflow channel before the discharge process is completed. The compression stroke of the double piston thus begins only after the overflow process has been completed, so that no pressure drop directed from the combustion chamber to the crank chamber can arise, which would lead part of the fresh charge of the combustion chamber back into the crank chamber when the overflow channel is open.

Der Überströmvorgang bestimmt die Füllung des Brennraums und damit die Leistung und den Wirkungsgrad der Brennkraftmaschine. Bei der bekannten Brennkraftmaschine hat es sich herausgestellt, daß bei aufgeladener Kurbelkammer der Brennraum nicht optimal gefüllt werden kann, weil die Steuerzeit für das Überströmen zu kurz ist, da an dessen Ende immer noch ein Druckgefälle von der Kurbelkammer in den Brennraum vorhanden ist.The overflow process determines the filling of the combustion chamber and thus the performance and the efficiency of the internal combustion engine. In the known internal combustion engine, it has been found that the combustion chamber cannot be optimally filled when the crank chamber is charged, because the control time for the overflow is too short, since at the end there is still a pressure drop from the crank chamber into the combustion chamber.

Aus der deutschen Offenlegungsschrift 2 347 809 ist weiterhin eine Brennkraftmaschine mit Doppelkolben bekannt, deren Zylinder zylinderkopfseitig durch einen Brennraum miteinander verbunden sind. Der Auslaßvorgang wird vom voreilenden Kolben gesteuert, der auch den Einlaßvorgang des Brennstoff-Luft-Gemisches in den zugeordneten, vom Kurbelkammerraum des nacheilenden Kolbens abgedichteten Kurbelkammerraum steuert. Der nacheilende Kolben steuert den Einlaßvorgang von Spülluft in den ihm zugeordneten Kurbelkammerraum. Der nacheilende Kolben steuert ferner die Überströmvorgänge in zwei Überströmkanälen, von denen der eine vom Kurbelkammerraum des voreilenden Kolbens zum brennkammerseitigen Zylinderabschnitt des nacheilenden Kolbens und der andere vom Kurbelkammerraum des nacheilenden Kolbens ebenfalls zum brennkammerseitigen Zylinderabschnitt dieses Kolbens führt. Durch geeignete Formwahl der beiden Überströmkanäle soll bei der bekannten Brennkraftmaschine erreicht werden, daß die B:ennkam- mer zunächst ausschließlich mit Spülluft aus dem Kurbelkammerraum des nacheilenden Kolbens gespült wird, während die Zufuhr des Brennstoff-Luft-Gemisches aus dem Kurbelkammerraum des voreilenden Kolbens soweit verzögert wird, daß sie den vom voreilenden Kolben gesteuerten Auslaß erst nach Abschluß des Auslaßvorgangs erreicht.An internal combustion engine with double pistons is also known from German Offenlegungsschrift 2,347,809, the cylinders of which are connected to one another on the cylinder head side by a combustion chamber. The exhaust process is controlled by the leading piston, which also controls the intake process of the fuel-air mixture into the associated crank chamber sealed from the crank chamber of the trailing piston. The trailing piston controls the intake process of purge air into the crank chamber space assigned to it. The trailing piston also controls the overflow processes in two overflow channels, one of which leads from the crank chamber space of the leading piston to the combustion chamber side cylinder section of the trailing piston and the other from the crank chamber space of the trailing piston also to the combustion chamber side cylinder section of this piston. A suitable choice of shape for the two overflow channels in the known internal combustion engine is intended to ensure that the combustion chamber is first purged exclusively with purge air from the crank chamber of the trailing piston, while the supply of the fuel-air mixture from the crank chamber of the leading piston is sufficient is delayed that it reaches the outlet controlled by the leading piston only after the completion of the exhaust process.

Bei der aus der DE-A-2 347 809 bekannten Brennkraftmaschine werden beide Überströmvorgänge ausschließlich durch den nacheilenden Kolben gesteuert. Bei einer derartigen Steuerung beginnt jedoch der Einlaßvorgang zu spät und endet zu spät, und zwar ersteres zu einem Zeitpunkt, zu welchem in der Kurbelkammer längst Überdruck vorhanden ist. Dies führt dazu, daß ein wesentlicher Teil der gerade angesaugten Ladung zum Spüllufteinlaß zurückgedrückt wird. Hierbei wird nicht nur Luft zurückgedrückt, sondern auch Brennstoff-Luft-Gemisch, da die Aufteilung der Kurbelkammer in zwei getrennte Kurbelkammerräume für Luft bzw. Brennstoff-Luft-Gemisch in der Praxis nicht oder nur mit außerordentlich großem Aufwand möglich ist.In the internal combustion engine known from DE-A-2 347 809, both overflow processes are controlled exclusively by the lagging piston. With such a control, however, the intake process begins too late and ends too late, namely at a point in time at which there is long overpressure in the crank chamber. This means that a substantial part of the charge just sucked in is pushed back to the purge air inlet. Here, not only air is pushed back, but also the fuel-air mixture, since the division of the crank chamber into two separate crank chamber spaces for air or fuel-air mixture is not possible in practice or only with an extremely great effort.

Bei der bekannten Brennkraftmaschine beginnen beide Überströmvorgänge erst kurz vor dem unteren Totpunkt und damit für eine optimale Aufladung zu spät. Darüber hinaus enden die beiden Überströmvorgänge weit nach Auslaßschluß zu einem Zeitpunkt, zu dem durch den ansteigenden Kompressionsdruck im Zylinder bereits ein umgekehrtes Druckgefälle aus dem Zylinderraum zur Kurbelkammer vorhanden ist. Damit wird ein wesentlicher Teil der gerade eingebrachten Ladung zur Kurbelkammer zurückgedrückt.In the known internal combustion engine, both overflow processes only start shortly before bottom dead center and thus too late for optimal charging. In addition, the two overflow processes end long after the outlet closes at a point in time at which a reverse pressure drop from the cylinder chamber to the crank chamber is already present due to the increasing compression pressure in the cylinder. This pushes back a substantial part of the load just introduced to the crank chamber.

Aufgabe der Erfindung ist es, eine Zweitaktbrennkraftmaschine mit Doppelkolben anzugeben, bei welcher auch bei Aufladung mittels einer Aufladeeinrichtung einerseits sichergestellt ist, daß keine Brenngase aus dem Brennraum in die Kurbelkammer zurückströmen können und andererseits trotzdem eine optimale Füllung des Brennraums erreicht wird.The object of the invention is to provide a two-stroke internal combustion engine with a double piston, in which, on the one hand, even when charging by means of a charging device, it is ensured that no combustion gases can flow back from the combustion chamber into the crank chamber and, on the other hand, optimum filling of the combustion chamber is nevertheless achieved.

Diese Aufgabe wird erfindungsgemäß dadurch gelöst, daß derselbe Überströmkanal auch vom kurbelkammerseitigen Zylinderabschnitt des nacheilenden Kolbens zum brennkammerseitigen Zylinderabschnitt dieses Kolbens führt und außer von dem voreilenden Kolben auch von dem nacheilenden Kolben gesteuert wird, und daß der nacheilende Kolben den Überströmkanal frühestens mit dem voreilenden Kolben öffnet und später als der voreilende Kolben schließt.This object is achieved in that the same overflow channel also leads from the crank chamber side cylinder section of the trailing piston to the combustion chamber side cylinder section of this piston and is controlled not only by the leading piston but also by the trailing piston, and in that the trailing piston at the earliest with the leading piston opens and closes later than the leading piston.

Der voreilende Kolben steuert nach wie vor den Auslaßvorgang und den Beginn des Überströmvorgangs. Der nacheilende Kolben öffnet nachfolgend seinerseits den Überströmkanal, wodurch der wirksame Kanalquerschnitt erhöht wird. Das Ende des Überströmvorgangs wird ausschließlich durch den nacheilenden Kolben gesteuert.The leading piston still controls the exhaust process and the start of the overflow process. The trailing piston then in turn opens the overflow channel, which increases the effective channel cross section. The end of the overflow process is controlled exclusively by the lagging piston.

Beide Kolben steuern denselben Überströmkanal, wodurch dessen Volumen klein gehalten werden kann, und sein schädlicher Einfluß auf die Höhe der Kurbelkammerverdichtung gering bleibt. Durch die kombinierte Steuerung des Überströmkanals durch beide Kolben kann der Überströmvorgang über einen Kurbelwinkel von etwa 2x90° um den unteren Totpunkt ausgedehnt werden. Dieser Winkel wird lediglich durch das Druckgefälle zwischen der Kurbelkammer und dem brennraumseitigen Zylinderabschnitt des nacheilenden Kolbens bestimmt, je nach dem Aufladegrad der Kurbelkammer.Both pistons control the same overflow channel, whereby its volume can be kept small and its harmful influence on the level of the crank chamber compression remains small. The combined control of the overflow channel by both pistons allows the overflow process to be extended over a crank angle of approximately 2x90 ° around bottom dead center. This angle is only determined by the pressure drop between the crank chamber and the combustion chamber-side cylinder section of the trailing piston, depending on the degree of charging of the crank chamber.

Die Aufladeeinrichtung erzeugt vorzugsweise ein Kurbelkammerverdichtungsverhältnis von wenigstens 1,5. Bei der Aufladeeinrichtung kann es sich um eine Kurbelkammerpumpe hoher Leistung handeln, die zweckmäßigerweise auch den kurbelkammerseitigen Einlaßvorgang steuert. Dies kann beispielsweise durch Umfangsflächen eines das Pleuel des Doppelkolbens tragenden Kurbelwangen-Drehschiebers oder Drehschieber-Paares erfolgen, dessen Umfangsfläche berührungsfrei oder leicht touchierend und damit wirkungsgradgünstig umläuft. Geeignet sind aber auch Einrichtungen zur gasdynamischen Schwingaufladung, beispielsweise Resonanzrohre, Resonanzvolumina oder dergleichen, die auf einen bestimmten Drehzahlbereich der Brennkraftmaschine abgestimmt sind.The charger preferably generates a crank chamber compression ratio of at least 1.5. The charging device can be a high-performance crank chamber pump, which expediently also controls the intake process on the crank chamber side. This can be done, for example, by circumferential surfaces of a connecting rod of the crankshaft-type rotary slide valve or rotary slide valve pair, the circumferential surface of which rotates contact-free or slightly touching and is therefore efficient in terms of efficiency. However, devices for gas-dynamic vibrating charging, for example resonance tubes, resonance volumes or the like, which are matched to a specific speed range of the internal combustion engine, are also suitable.

Der nacheilende Kolben schließt den Überströmkanal bevorzugt gleichzeitig mit Beendigung des vom voreilenden Kolben gesteuerten Auslaßvorgangs. In Verbindung mit einem hohen Kurbelkammerverdichtungsverhältnis ist jedoch auch eine Nachladung des Brennraums möglich, wenn der nacheilende Kolben den Überströmkanal erst nach Beendigung des Auslaßvorgangs schließt, was durch die vorliegende Erfindung erst ermöglicht wird. Die Absteuerung des Überströmkanals durch den nacheilenden Kolben muß so bemessen sein, daß der kurbelkammerseitige Ladedruck noch ausreichend höher als der Druck der beginnenden Verdichtung in den Zylindern ist. Der Ladedruck sollte noch bis zu 0,5 atü höher als der beginnende Verdichtungsdruck im Zylinder sein.The lagging piston preferably closes the overflow channel at the same time as the outlet process controlled by the leading piston ends. In connection with a high crank chamber compression ratio, however, the combustion chamber can also be recharged if the trailing piston closes the overflow channel only after the exhaust process has ended, which is only made possible by the present invention. The control of the overflow channel by the trailing piston must be dimensioned such that the boost pressure on the crankcase side is still sufficiently higher than the pressure of the beginning compression in the cylinders. The boost pressure should be up to 0.5 atü higher than the beginning compression pressure in the cylinder.

Der nacheilende Kolben und der voreilende Kolben öffnen den Überströmkanal bevorzugt zu unterschiedlichen Zeiten. Auf diese Weise kann eine gewisse Voraufladung oder auch Vorentladung des Überströmkanals, abgestimmt auf das gewünschte Drehzahlniveau der Maschine, erreicht werden.The lagging piston and the leading piston open the overflow channel preferably at different times. In this way, a certain pre-charge or pre-discharge of the overflow channel can be achieved, coordinated with the desired speed level of the machine.

Als günstig hat es sich erwiesen, wenn der Aufladevorgang der kurbelkammerseitigen Zylinderabschnitte schon beginnt, bevor der nacheilende Kolben den Überströmkanal schließt. Die frischen Gase werden kurz vor dem Schließen des Überströmkanals mit hohem Anfangsdruck zugeführt. Dies bewirkt eine sofortige kurbelkammerseitige Druckerhöhung, so daß der Überströmvorgang weiter verlängert werden kann. Darüber hinaus wird ein Zurücksaugen der gerade zuvor in den Brennraum eingebrachten Frischladung in die Kurbelkammer vermieden.It has proven to be advantageous if the charging process of the cylinder sections on the crank chamber side begins before the trailing piston closes the overflow channel. The fresh gases are supplied at high initial pressure shortly before the overflow channel is closed. This causes an immediate increase in pressure on the crank chamber side, so that the overflow process can be extended further. In addition, sucking back of the fresh charge that has just been introduced into the combustion chamber into the crank chamber is avoided.

In einer bevorzugten Ausführungsform ist je ein Überströmkanal zu beiden Seiten einer die Zylinder des Doppelkolbens trennenden Zylinderblockwand angeordnet. Diese Überströmkanäle werden durch Fenster im Hemd der beiden Kolben unterhalb der Kolbenringzonen gesteuert. Die Frischgase kühlen damit diese Trennwand. Gegebenenfalls können zusätzliche Kühlwasserkanäle in der Trennwand vorgesehen sein.In a preferred embodiment, an overflow channel is arranged on both sides of a cylinder block wall separating the cylinders of the double piston. These overflow channels are controlled by windows in the shirt of the two pistons below the piston ring zones. The fresh gases cool this partition. If necessary, additional cooling water channels can be provided in the partition.

Wesentliche Vorteile bietet eine Ausführungsform, bei der zumindest ein Teil der den Kolben gegenüberliegenden Wand des Brennraums durch einen im Zylinderkopf verschiebbar geführten und mittels eines Kraftgeräts auf die Kolben zustellbaren Gegenkolben gebildet ist. in dieser Ausführungsform kann das Verdichtungsverhältnis der Brennkraftmaschine auf konstruktiv einfache Weise während des Betriebs abhängig von der Drosselstellung der Brennkraftmaschine verändert werden. Im Teillastbetrieb kann die Verdichtung erhöht werden, so daß im gesamten Lastbereich ein geringerer Kraftstoffverbrauch erreicht wird, ohne daß das vom Dieselmotor bekannte, typische Nagelverhalten auftritt. Als ausreichend und praktikabel hat sich eine Veränderung des Verdichtungsverhältnisses etwa in den Grenzen 1 : 2 erwiesen. Beispielsweise kann eine Verdichtung von B = 8 bei Vollast im Teillastbetrieb bis aufs=16 erhöht werden. Bei dem Kraftgerät kann es sich um einen Hydraulikzylinder handeln, der von einer hydraulischen Steuerung abhängig von der Drosselstellung betätigt wird. Der Gegenkolben kann aber auch über einen Nocken, ein Federpaket oder dergleichen verstellt werden. Soweit eine Zündkerze erforderlich ist, kann sie in zentraler Lage in dem Gegenkolben verbleiben, so daß sie zusammen mit dem Gegenkolben bewegt wird; sie kann aber auch an die durch den Zylinderkopf festgelegte Peripherie des Brennraums verlegt sein.An embodiment offers significant advantages in which at least part of the wall of the combustion chamber opposite the pistons is formed by a counter-piston which is displaceably guided in the cylinder head and can be delivered to the pistons by means of a power device. In this embodiment, the compression ratio of the internal combustion engine can be changed in a structurally simple manner during operation depending on the throttle position of the internal combustion engine. In partial load operation, the compression can be increased so that lower fuel consumption is achieved in the entire load range without the typical nail behavior known from the diesel engine occurring. A change in the compression ratio within the limits of 1: 2 has proven to be sufficient and practical. For example, a compression of B = 8 at full load in partial load operation can be increased to = 16. The power device can be a hydraulic cylinder which is actuated by a hydraulic control depending on the throttle position. The counter-piston can also be adjusted via a cam, a spring assembly or the like. If a spark plug is required, it can remain in a central position in the counter-piston so that it is moved together with the counter-piston; but it can also be relocated to the periphery of the combustion chamber defined by the cylinder head.

Um das zündfähige Gemisch des Brennraums möglichst gleichzeitig zu zünden, ist vorzugsweise eine in den Brennraum eingreifende Zündelektrode vorgesehen, deren Gegenelektrode an einer zum Brennraum weisenden Fläche einer zwischen den beiden Kolben sich erstreckenden Zylinderblockwand vorgesehen ist. DieZündelektrode kann hierbei am Zylinderkopf in der Mitte des Brennraums angeordnet sein, so daß ein quer durch den Brennraum zur Gegenfläche an der Zylinderblockwand reichender Zündfunke entsteht. Diese Zylinderblockwand bildet also die Masseelektrode. Die zur Erzeugung derartiger langer Zündfunken erforderliche Hochspannung kann problemlos mit Hilfe einer Hochspan- nungskondensatorzündung erreicht werden. Die -ündelektrode und die Gegenelektrode können aber auch nebeneinander auf der zum Brennraum weisenden Fläche dieser Zylinderblockwand angeordnet sein. Diese Anordnungsweise hat den Vorteil, daß sie relativ wenig Platz im Brennraum beansprucht, der dann zur Unterbringung anderer Elemente, wie z. B. Einspritzdüsen oder dergleichen, zur Verfügung steht.In order to ignite the ignitable mixture of the combustion chamber as simultaneously as possible, an ignition electrode engaging in the combustion chamber is preferably provided, the counter electrode of which is provided on a surface facing the combustion chamber of a cylinder block wall extending between the two pistons. The ignition electrode can be arranged on the cylinder head in the middle of the combustion chamber, so that a across the combustion chamber to the counter surface spark that reaches the cylinder block wall. This cylinder block wall thus forms the ground electrode. The high voltage required to generate such long ignition sparks can be easily achieved with the aid of a high-voltage capacitor ignition. However, the ignition electrode and the counter electrode can also be arranged side by side on the surface of this cylinder block wall facing the combustion chamber. This arrangement has the advantage that it takes up relatively little space in the combustion chamber, which is then used to accommodate other elements such. B. injectors or the like is available.

Ein weiterer Gesichtspunkt der Erfindung betrifft die Schmierung von Pleuel und Grundlagern des Doppelkolbens. Vorzugsweise sind das Pleuellager als auch die Grundlager gesondert zur Kurbelkammer schmiermitteldicht gekapselt, wobei in die gekapselten Lagerinnenräume Schmiermittelleitungen einer zentralen Ölversorgung münden. Auf diese Weise können die etwa noch vorhandenen Fluchtölmengen aus den Lagern in die Kurbelkammer in der für den Betrieb der Brennkraftmaschine erforderlichen Gesamtölmenge berücksichtigt werden, d. h. von der Frischölmenge, die für die Kolbenschmierung in den Ansaugstrom eingebracht wird, abgezogen werden. Das Öl der zentralen Ölversorgung kann von einem Öltank her mittels Ölpumpe oder Gefälle (Tropfschmierung), eventuell unterstützt durch einen leichten Überdruck im Öltank, zugeführt werden.Another aspect of the invention relates to the lubrication of connecting rods and base bearings of the double piston. The connecting rod bearing and the base bearing are preferably encapsulated separately from the crank chamber in a lubricant-tight manner, lubricant lines of a central oil supply opening into the encapsulated bearing interior. In this way, any remaining escape oil quantities from the bearings into the crank chamber can be taken into account in the total oil quantity required for the operation of the internal combustion engine. H. deducted from the amount of fresh oil that is introduced into the intake flow for piston lubrication. The oil in the central oil supply can be supplied from an oil tank by means of an oil pump or a slope (drip lubrication), possibly supported by a slight overpressure in the oil tank.

Im folgenden sollen Ausführungsbeispiele der Erfindung anhand von Zeichnungen näher erläutert werden. Es zeigt

  • Fig. 1 einen die Zylinderachsen enthaltenden, schematischen Schnitt durch eine Zweitaktbrennkraftmaschine,
  • Fig. 2 einen Schnitt entlang der Linie 11-11 in Fig. 1,
  • Fig. 3 einen Schnitt normal zu den Zylinderachsen durch eine Variante eines Brennraums einer Zweitaktbrennkraftmaschine,
  • Fig.4 einen achsparallelen Schnitt durch eine weitere Variante eines Brennraums einer Zweitaktbrennkraftmaschine und
  • Fig. 5 einen die Drehachsen enthaltenden Schnitt durch eine Kurbelwelle mit Pleuel einer Zweitaktbrennkraftmaschine.
Exemplary embodiments of the invention are to be explained in more detail below with reference to drawings. It shows
  • 1 is a schematic section containing the cylinder axes through a two-stroke internal combustion engine,
  • 2 shows a section along the line 11-11 in FIG. 1,
  • 3 shows a section normal to the cylinder axes through a variant of a combustion chamber of a two-stroke internal combustion engine,
  • 4 shows an axially parallel section through a further variant of a combustion chamber of a two-stroke internal combustion engine and
  • 5 shows a section containing the axes of rotation through a crankshaft with a connecting rod of a two-stroke internal combustion engine.

Die Fig. 1 und 2 zeigen eine Zweitaktbrennkraftmaschine 10, deren Zylinderblock 12 zwei Zylinder 14 und 16 aufweist. Die Zylinder 14 und 16 sind durch einen Zylinderkopf 20 verschlossen, welcher einen die Zylinder 14, 16 verbindenden Brennraum 18 enthält. In den Zylindern 14,16 ist je ein Kolben 22 bzw. 24 verschiebbar geführt. Die Kolben 22, 24 sind über ein gemeinsames Pleuel 26 mittels eines Kurbelzapfens 27 exzentrisch an einer auf einem Wellenzapfen 28 gelagerten Hubscheibe 30 angelenkt. Die Hubscheibe 30 rotiert in einer von einer Wanne 32 geschlossenen Kurbelkammer 34.1 and 2 show a two-stroke internal combustion engine 10, the cylinder block 12 has two cylinders 14 and 16. The cylinders 14 and 16 are closed by a cylinder head 20 which contains a combustion chamber 18 connecting the cylinders 14, 16. A piston 22 or 24 is slidably guided in the cylinders 14, 16. The pistons 22, 24 are articulated via a common connecting rod 26 by means of a crank pin 27 eccentrically on a lifting disk 30 mounted on a shaft pin 28. The lifting disk 30 rotates in a crank chamber 34 closed by a trough 32.

Die Zylinder 14 und 16 werden durch Kolbenböden 36 bzw. 38 der Kolben 22, 24 jeweils in einen brennraumseitigen Zylinderabschnitt und einen kurbelkammerseitigen Zylinderabschnitt unterteilt. Die kurbelkammerseitigen Zylinderabschnitte bilden zusammen mit der Kurbelkammer 34 und den hin- und hergleitenden Kolben 22, 24 eine Kurbelkammerpumpe, welche zum Ansaugen der über eine Aufladevorrichtung (nicht dargestellt) zugeführten Verbrennungsluft oder des Luft-BrennstoffGemisches durch einen in die Kurbelkammer 34 hineinreichenden Ansaugstutzen 40 dient.The cylinders 14 and 16 are divided by piston heads 36 and 38 of the pistons 22, 24 into a cylinder section on the combustion chamber side and a cylinder section on the crank chamber side. The cylinder sections on the crank chamber side, together with the crank chamber 34 and the reciprocating pistons 22, 24, form a crank chamber pump which serves to suck in the combustion air supplied via a charging device (not shown) or the air-fuel mixture through an intake port 40 which extends into the crank chamber 34 .

Damit das angesaugte Gemisch aus der Kurbelkammer 34 in die brennraumseitigen Zylinderabschnitte und den Brennraum 18 gelangen kann, ist beiderseits einer die Zylinder 14,16 voneinander trennenden Zwischenwand 42 des Zylinderblocks 12 je ein Überströmkanal 44 gebildet. Diese Überströmkanäle 44 haben je einen Eintrittsschlitz 46 bzw. 48 in den kurbelkammerseitigen Zylinderabschnitten der Zylinder 14, 16 und einen Austrittsschlitz 50 im brennraumseitigen Zylinderabschnitt des Zylinders 16. Die Eintrittsschlitze 46, 48 werden durch Fenster 52 bzw. 54 im kurbelkammerseitigen Kolbenhemd der Kolben 22 bzw. 24 geöffnet und geschlossen. Die Austrittsschlitze 50 der Überströmkanäle 42 werden von der Oberkante 56 des nacheilenden Kolbens 24 gesteuert. Die Oberkante 58 des Kolbens 22 steuert einen Auslaßschlitz 60 im brennraumseitigen Zylinderabschnitt des Zylinders 14. Der Einlaßvorgang wird von der Hubscheibe 30 gesteuert, deren Umfang 62 berührungsfrei oder leicht touchierend die Mündung desAnsaugstutzens 40 öffnet bzw. schließt.An overflow channel 44 is formed on both sides of an intermediate wall 42 of the cylinder block 12 that separates the cylinders 14, 16, so that the sucked-in mixture from the crank chamber 34 can get into the combustion chamber-side cylinder sections and the combustion chamber 18. These overflow channels 44 each have an inlet slot 46 and 48 in the cylinder sections of the cylinders 14, 16 on the crankcase side and an outlet slot 50 in the cylinder section of the cylinder 16 on the combustion chamber side. The inlet slots 46, 48 are opened by windows 52 and 54 in the piston skirt of the pistons 22 and 54 on the crankcase side, respectively 24 opened and closed. The outlet slots 50 of the overflow channels 42 are controlled by the upper edge 56 of the trailing piston 24. The upper edge 58 of the piston 22 controls an outlet slot 60 in the cylinder section of the cylinder 14 on the combustion chamber side. The intake process is controlled by the lifting disk 30, the circumference 62 of which opens or closes the mouth of the intake manifold 40 in a contactless or slightly touching manner.

Die Brennkraftmaschine arbeitet wie folgt. Wenn sich die Hubscheibe 30 in Richtung des Pfeils A dreht, eilt der Kolben 22 stets dem Kolben 24 voraus. In Fig. 1 ist der Einlaßvorgang bereits beendet; die Hubscheibe 30 verschließt den Einlaßstutzen 40. Das in die Kurbelkammer 34 eingeführte Gemisch wird durch die nach unten gehenden Kolben 22, 24 verdichtet. Die Eintrittsschlitze 46, 48 der Überströmkanäle sind geschlossen. Bevor die Fenster 52 des voreilenden Kolbens 22 die Eintrittsschlitze 46 der Überströmkanäle 44 erreichen, öffnet die Oberkante 58 des voreilenden Kolbens 22 den Auslaßschlitz 60, so daß die verbrannten Gase aus den brennraumseitigen Zylinderabschnitten und dem Brennraum 18 ausströmen können. Dann öffnet der voreilende Kolben 22 die Eintrittsschlitze 46 der Überströmkanäle 44. Kurz zuvor, gleichzeitig oder etwas später, hat die Oberkante 56 des nacheilenden Kolbens 24 die Austrittsschlitze 50 der Überströmkanäle 44 geöffnet. Durch die spätere Öffnung wird ein großer Vorauslaß mit einer trotzdem langen Uberströmsteuerzeit möglich. Die verdichteten Gase der Kurbelkammer 34 strömen über die Überströmkanäle 44 nacheinander zunächst in den brennraumseitigen Zylinderabschnitt des nacheilenden Zylinders 16, dann in den Brennraum 18 und anschließend in den brennraumseitigen Zylinderabschnitt des voreilenden Zylinders 14. Sie kühlen hierbei sowohl die Zwischenwand 42 als auch die beiden von der Frischluft- bzw. von der Frischgasladung durchströmten Kolben. Die Zwischenwand kann gegebenenfalls mit zusätzlichen Kühlwasserkanälen 64 versehen sein. Die Fenster 54 des nacheilenden Kolbens 24 erreichen die Eintrittsschlitze 48 der beiden Überströmkanäle 44 erst nachdem der voreilende Kolben 22 die Eintrittsschlitze 46 bereits geöffnet hat. Der Kolben 22 schließt die Eintrittsschlitze 46 zu einem Zeitpunkt, zu dem der Auslaßschlitz 60 noch geöffnet ist. Die vom Kolben 24 gesteuerten Eintrittsschlitze 48 bleiben über diesen Zeitpunkt hinaus geöffnet. Die Eintrittsschlitze 48 werden geschlossen, wenn der Kolben 22 den Auslaßschlitz 60 schließt. Sie können aber bei ausreichend hohem kurbelkammerseitigen Ladedruck auch über das Ende des Auslaßvorgangs hinaus geöffnet bleiben, so daß die brennraumseitigen Zylinderabschnitte 14, 16 und der Brennraum 18 auch bei bereits beginnendem Verdichtungshub noch über die Überströmkanäle 44 nachgeladen werden können.The internal combustion engine works as follows. When the lifting disc 30 rotates in the direction of arrow A, the piston 22 always leads the piston 24. In Fig. 1, the intake process has already ended; the lifting disc 30 closes the inlet port 40. The mixture introduced into the crank chamber 34 is compressed by the pistons 22, 24 going downward. The inlet slots 46, 48 of the overflow channels are closed. Before the windows 52 of the leading piston 22 reach the inlet slots 46 of the overflow channels 44, the upper edge 58 of the leading piston 22 opens the outlet slot 60, so that the burned gases can flow out of the cylinder sections on the combustion chamber side and the combustion chamber 18. The leading piston 22 then opens the inlet slots 46 of the overflow channels 44. Shortly before, simultaneously or somewhat later, the upper edge 56 of the lagging piston 24 has opened the outlet slots 50 of the overflow channels 44. Due to the later opening, a large advance outlet with a long overflow control time is possible. The compressed gases of the crank chamber 34 flow over the overflow channels 44 one after the other into the combustion chamber-side cylinder section of the trailing cylinder 16, then into the combustion chamber 18 and then into the combustion chamber-side cylinder section of the leading cylinder ders 14. They cool both the intermediate wall 42 and the two pistons through which the fresh air or fresh gas charge flows. The intermediate wall can optionally be provided with additional cooling water channels 64. The windows 54 of the lagging piston 24 only reach the inlet slots 48 of the two overflow channels 44 after the leading piston 22 has already opened the inlet slots 46. The piston 22 closes the inlet slots 46 at a time when the outlet slot 60 is still open. The entry slots 48 controlled by the piston 24 remain open beyond this point in time. The inlet slots 48 are closed when the piston 22 closes the outlet slot 60. However, if the boost pressure on the crankcase side is sufficiently high, they can also remain open beyond the end of the exhaust process, so that the cylinder sections 14, 16 and the combustion chamber 18 on the combustion chamber side can still be reloaded via the overflow channels 44 even when the compression stroke is already beginning.

Der Überströmvorgang kann über einen Kurbelwinkel von etwa 2 x 90° um den unteren Totpunkt ausgedehnt werden. Er ist im wesentlichen nur durch die Höhe des Druckgefälles von der Kurbelkammer 34 über die Überströmkanäle 44 in den brennraumseitigen Zylinderabschnitt des Zylinders 16 begrenzt. Der Druckunterschied zwischen dem Ladedruck und dem Druck der beginnenden Verdichtung in dem brennraumseitigen Zylinderabschnitt des Zylinders 16 sollte etwa zwischen 0,5 und 1,5 atü betragen.The overflow process can be extended by a crank angle of approximately 2 x 90 ° around bottom dead center. It is essentially only limited by the height of the pressure drop from the crank chamber 34 via the overflow channels 44 into the cylinder section of the cylinder 16 on the combustion chamber side. The pressure difference between the boost pressure and the pressure of the commencement of compression in the cylinder section of the cylinder 16 on the combustion chamber side should be approximately between 0.5 and 1.5 atm.

Die den Kolbenböden 36, 38 gegenüberliegende Wand 66 des Brennraums 18 ist durch einen Gegenkolben 68 gebildet, der in einem Hydraulikzylinder 70 abgedichtet verschiebbar geführt ist. Der Hydraulikzylinder 70 ist über eine Druckmittelzuleitung 72 an eine Steuerung angeschlossen, die den Gegenkolben 68 abhängig von der Drosselstellung der Brennkraftmaschine verschiebt. Durch Verschieben des Gegenkolbens 68 kann das Verdichtungsverhältnis der beiden Zylinder 14, 16 abhängig von der Drosselstellung verändert werden. Die Steuerung erhöht das Verdichtungsverhältnis in den Teillastbereich hinein; beispielsweise im Verhältnis 1 : 2. Auf diese Weise kann im gesamten Lastbereich der Brennstoffverbrauch optimiert und deutlich verringert werden.The wall 66 of the combustion chamber 18 opposite the piston heads 36, 38 is formed by a counter-piston 68, which is guided and displaceably guided in a sealed manner in a hydraulic cylinder 70. The hydraulic cylinder 70 is connected via a pressure medium supply line 72 to a control which moves the counter-piston 68 depending on the throttle position of the internal combustion engine. By moving the counter-piston 68, the compression ratio of the two cylinders 14, 16 can be changed depending on the throttle position. The control increases the compression ratio into the partial load range; for example in a ratio of 1: 2. In this way, fuel consumption can be optimized and significantly reduced over the entire load range.

Bei der Brennkraftmaschine der Fig. 1 und 2 münden in die Überströmkanäle 44 Brennstoffeinspritzdüsen 74, die entgegen der Strömungsrichtung in den Überströmkanälen 44 kontinuierlich Brennstoff einspritzen. Diese, sowohl für Otto- wie auch für Dieselmotoren geeignete Einspritzweise erlaubt sowohl eine qualitative Regelung des Betriebs, bei welcher lediglich die Brennstoffzufuhr bei gleichbleibend vollständiger Luftfüllung des Brennraums geregelt wird, als auch eine quantitative Regelung, bei welcher die Füllung insgesamt verändert wird.1 and 2, fuel injection nozzles 74 open into the overflow channels 44 and continuously inject fuel against the direction of flow in the overflow channels 44. This injection method, which is suitable for both gasoline and diesel engines, allows both a qualitative control of the operation, in which only the fuel supply is regulated while the air in the combustion chamber remains completely full, and a quantitative control, in which the charge is changed overall.

Der Brennraum 18 ist im wesentlichen zylinderförmig ausgebildet und weist im Querschnitt zwei einander diametral gegenüberliegende Bereiche auf, die sich vom zylinderfernen Brennraumende zu den Zylindern 14, 16 hin erweitern. Die dadurch entstehenden Ausbuchtungen 76 sind jeweils durch eine sphärische Dreiecksfläche begrenzt. Durch diese Ausbildung des Brennraums 18 strömt das Gemisch aus dem Zylinder 16 tangential in den Brennraum 18 ein und wird durch den dabei erzeugten, sehr hohen Drall sehr wirksam verwirbelt, zu einem Zeitpunkt also, wo die Erzeugung des Dralls keine Leistung mehr kostet.The combustion chamber 18 is essentially cylindrical and has two diametrically opposite regions in cross section, which widen from the end of the combustion chamber remote from the cylinder to the cylinders 14, 16. The bulges 76 thus created are each delimited by a spherical triangular surface. As a result of this design of the combustion chamber 18, the mixture flows from the cylinder 16 tangentially into the combustion chamber 18 and is swirled very effectively by the very high swirl that is generated, at a time when the generation of the swirl no longer costs any power.

Die im Brennraum 18 entstehenden Ausbuchtungen 76 müssen nicht durch eine sphärische Dreieckfläche begrenzt sein, sie können auch durch gerade Rampen gebildet werden, die über die Mitten der Zylinderachsen 14 und 16 hinausreichen können und in Fig. 1, als auch in Fig. 4 bei 77 bzw. 79 gestrichelt angedeutet sind.The bulges 76 that arise in the combustion chamber 18 need not be limited by a spherical triangular surface, they can also be formed by straight ramps that can extend beyond the centers of the cylinder axes 14 and 16 and in FIG. 1 and in FIG. 4 at 77 or 79 are indicated by dashed lines.

Fig. 3 zeigt schematisch in einem Schnitt durch einen Zylinderkopf eine weitere Möglichkeit der Brennstoffeinspritzung, bei welcher der im Brennraum entstehende, sehr hohe Drall ausgenutzt wird. Der Drall ist in Fig. 3 durch Pfeile 78 angedeutet. Der Brennstoff wird mittels einer Düse 80 entgegen der Drallrichtung entweder direkt auf die Wand 82 des zwischen den Zylindern 84, 86 gelegenen Brennraums oder in einem Bereich unmittelbar vor der Wand 82 eingespritzt. Auf der zum Brennraum weisenden Oberseite einer Zwischenwand 88 zwischen den beiden Zylindern 84, 86 ist isoliert eine in den Brennraum ragende Zündelektrode 90 angebracht, deren Gegenelektrode 92 ebenfalls in die Zwischenwand 88 integriert ist. Diese Zündelektroden 90 und 92 können z. B. in einer anderen Ausführung auch in die Zylinderkopfdichtung integriert sein. Auf diese Weise bleibt der darüber befindliche Brennraum frei, so daß Platz zur Unterbringung anderer Elemente, beispielsweise der Einspritzdüse 80, bleibt.Fig. 3 shows schematically in a section through a cylinder head a further possibility of fuel injection, in which the very high swirl arising in the combustion chamber is used. The swirl is indicated in FIG. 3 by arrows 78. The fuel is injected by means of a nozzle 80 against the swirl direction either directly onto the wall 82 of the combustion chamber located between the cylinders 84, 86 or in an area immediately in front of the wall 82. On the upper side of an intermediate wall 88 facing the combustion chamber between the two cylinders 84, 86, an ignition electrode 90 projecting into the combustion chamber is insulated, the counter electrode 92 of which is also integrated into the intermediate wall 88. These ignition electrodes 90 and 92 can e.g. B. can also be integrated into the cylinder head gasket in another embodiment. In this way, the combustion chamber above remains free, so that there is space for accommodating other elements, for example the injection nozzle 80.

Fig.4 zeigt einen Brennraum 94, in dessen Mitte eine Zündelektrode 96 angeordnet ist. Die Gegenelektrode der Zündelektrode 96 wird durch eine Zwischenwand 98 zwischen den beiden Zylindern 100 und 102 gebildet. Eine Hochspannungskondensatorzündung erzeugt die für den relativ großen Elektrodenabstand erforderlichen Hochspannung.4 shows a combustion chamber 94, in the middle of which an ignition electrode 96 is arranged. The counter electrode of the ignition electrode 96 is formed by an intermediate wall 98 between the two cylinders 100 and 102. A high-voltage capacitor ignition generates the high voltage required for the relatively large electrode spacing.

Die Zweitaktbrennkraftmaschine wird bevorzugt über eine zentrale Ölversorgung aus einem nicht näher dargestellten Tank über eine ebenfalls nicht dargestellte Ölpumpe bzw. ein Gefälle mit Öl für die Kolbenschmierung versorgt. Das Öl wird beispielsweise in den Ansaugstrom eingebracht, wobei das Mischungsverhältnis Öl zu Brennstoff-Luft-Gemisch bzw. Luft abhängig vom Lastzustand zwischen 1 : 80 und 1 : 200 liegen kann. Fig. 5 zeigt Einzelheiten einer Kurbelwellenlagerung mit zwei in axialem Abstand voneinander angeordneten, zentrisch auf Wellenzapfen 106, 108 aufgepreßten Hubscheiben 110, 112, zwischen welchem sich achsparallel ein exzentrisch angeordneter Kurbelzapfen 114 erstreckt. Die Wellenzapfen 106, 108 sind an Wälzlagern 116, 118 im Motorblock 120 gelagert. Zwischen den Hubscheiben 110, 112 ist an dem Kurbelzapfen 114 ein Pleuel 121 mittels Wälziagerrollen 122 gelagert. Das Pleuel 121 hat einen über die Lagerrollen 122 axial vorstehenden Pleuellageraußenring 124, dessen axiale Stirnflächen über gleichachsige Dichtringe 126, 128 und Rundschnurringe 141,142 gegen die Hubscheiben 110, 112 abgedichtet sind. Gegebenenfalls können entweder die Dichtringe 126, 128 oder die Rundschnurringe 141, 142 entfallen. Die Rundschnurringe sind in genormten Ringnuten gelagert. In den abgedichteten innenraum des Pleuellagerrings 124 mündet ein Schmiermittelkanal 130, der über eine Zuleitungsbohrung 132 mit dem System der zentralen Ölversorgung in Verbindung steht. Die einander axial abgekehrten Seiten der Hubscheiben 110, 112 tragen die umlaufende Hälfte je einer Labyrinthdichtung 134 bzw. 136, deren feststehende Hälften 143, 144 am Zylinderblock 120 vorgesehen sind. Ein Teil der Labyrinthdichtungen 134, 136 wird zusätzlich durch Dichtringe 138, 140 und Kolbenringe 145, 146 abgedichtet. Die Labyrinthdichtun . gen 134 bzw. 136 sind in sich geschlossene Bauteile, wobei der innere Ring mit der Kolbenringabdichtung 145, 146 mit dem Wellenzapfen 106 bzw. 108 (Grundlagerzapfen) umläuft, während die äußeren Ringe 143, 144 ebenso wie die Lageraußenringe im selben Außendurchmesser mit in das Gehäuse eingespannt sind. Weitere, nicht dargestellte Dichtungen sind auf den von den Labyrinthdichtungen 134, 136 axial abgekehrten Seiten der Wälzlager 116, 118 vorgesehen, so daß auch die Wälzlager 116, 118 voll abgekapselt sind. Die Zuleitungsbohrung 132 ist so geführt, daß sie eine Öffnung zum Innenraum dieser Wälzlager 116, 118 hat. Ein Vorteil der in Fig.5 dargestellten Ausführungsform der Kurbelwellenlagerung ist, daß Fluchtölmengen, die an den Dichtringen 126, 128 bzw. den Labyrinthdichtungen 134, 136 mit den integrierten Dichtringen 138, 140, 145, 146 vorbei in die Kurbelkammer eintreten, bei der zur Kolbenschmierung benötigten Gesamtölmenge berücksichtigt werden können. Die in den Ansaugstrom zur Kolbenschmierung einzubringende Frischölmenge kann um die Fluchtölmenge dieser Lager verringert werden, so daß sich insgesamt der Ölverbrauch der Zweitaktbrennkraftmaschine verringert und für die Gesamtlaufzeit der Maschine fest eingestellt werden kann. Er ist - anders als bei ölsumpfgeschmierten Motoren - unabhängig vom Verschleißzustand der Maschine.The two-stroke internal combustion engine is preferably supplied with oil for the piston lubrication via a central oil supply from a tank, not shown, via an oil pump, also not shown, or a slope. The oil is introduced, for example, into the intake stream, the mixing ratio of oil to fuel-air mixture or air depending on the load state being between 1:80 and 1:200. 5 shows details of a crankshaft bearing arrangement with two lifting disks 110, 112 which are axially spaced apart and are pressed on centrally on shaft journals 106, 108, between which there is an eccentric axis arranged crank pin 114 extends. The shaft journals 106, 108 are mounted on roller bearings 116, 118 in the engine block 120. A connecting rod 121 is mounted on the crank pin 114 between the lifting disks 110, 112 by means of roller rollers 122. The connecting rod 121 has a connecting rod bearing outer ring 124 projecting axially over the bearing rollers 122, the axial end faces of which are sealed against the lifting disks 110, 112 by means of coaxial sealing rings 126, 128 and round cord rings 141, 142. If necessary, either the sealing rings 126, 128 or the round cord rings 141, 142 can be omitted. The round cord rings are stored in standardized ring grooves. A lubricant channel 130 opens into the sealed interior of the connecting rod bearing ring 124 and is connected to the central oil supply system via a supply bore 132. The axially facing sides of the lifting disks 110, 112 each carry the circumferential half of a labyrinth seal 134 or 136, the fixed halves 143, 144 of which are provided on the cylinder block 120. Some of the labyrinth seals 134, 136 are additionally sealed by sealing rings 138, 140 and piston rings 145, 146. The labyrinth seal. gen 134 and 136 are self-contained components, the inner ring with the piston ring seal 145, 146 rotates with the shaft journal 106 and 108 (base bearing journal), while the outer rings 143, 144 as well as the bearing outer rings in the same outer diameter with in Housing is clamped. Further seals, not shown, are provided on the sides of the roller bearings 116, 118 axially facing away from the labyrinth seals 134, 136, so that the roller bearings 116, 118 are also fully encapsulated. The feed hole 132 is guided so that it has an opening to the interior of these bearings 116, 118. An advantage of the embodiment of the crankshaft bearing arrangement shown in FIG. 5 is that quantities of escape oil that pass the sealing rings 126, 128 or the labyrinth seals 134, 136 with the integrated sealing rings 138, 140, 145, 146 enter the crank chamber, at which Piston lubrication required total amount of oil can be taken into account. The amount of fresh oil to be introduced into the intake flow for piston lubrication can be reduced by the amount of escape oil from these bearings, so that overall the oil consumption of the two-stroke internal combustion engine is reduced and can be set permanently for the overall running time of the machine. Unlike with oil sump-lubricated engines, it is independent of the machine's state of wear.

Claims (12)

1. Two-stroke internal combustion engine having at least one double piston the cylinders of which are connected with one another on the cylinder head side by a combustion chamber (18) and are charged with air or fuel-air mixture on the crank case side by a charging device, where the leading piston (22) of the double piston controls both the transfer process in at least one transfer passage (44) leading from the crank case side cylinder section of the leading piston (22) to the combustion chamber side cylinder section of the trailing piston (24) and the exhaust process in such a way that the exhaust process begins before the opening of the transfer passage, characterised in that the same transfer passage (44) also leads from the crank chamber side cylinder section of the trailing piston (24) to the combustion chamber side cylinder section of this piston (24) and on the crank case side is controlled, as well as by the leading piston (22), by the trailing piston (24) too, and in that the trailing piston (24) opens the transfer passage (44) at the earliest with the leading piston (22) and closes it later than the leading piston (22).
2. Two-stroke internal combustion engine according to claim 1, characterised in that the charging device (22, 24, 30) has a crank chamber compression ratio of at least 1.5.
3. Two-stroke internal combustion engine according to claim 1, characterised in that the trailing piston (24) closes the transfer passage (44) simultaneously with or after termination of the exhaust process controlled by the leading piston (22).
4. Two-stroke internal combustion engine according to claim 1, characterised in that the operation of charging of the cylinder sections on the crank case side begins before the trailing piston (24) closes the transfer passage.
5. Two-stroke internal combustion engine according to claim 1, characterised in that the admission process on the crank case side is controlled by circumferential faces (62) of a crank web rotary slide valve (30) carrying the connecting rod (26) of the double piston.
6. Two-stroke internal combustion engine according to claim 1, characterised in that a transfer passage (44) is arranged on each of the two sides of a cylinder block wall (42) separating the cylinders (14, 16) of the double piston.
7. Two-stroke internal combustion engine according to claim 1, characterised in that at least a part of the wall (66) of the combustion chamber (18) lying opposite to the pistons (22, 24) is formed by a counter-piston (68) which is guided displaceably in the cylinder head (20) and movable towards the pistons (22,24) by means of a power appliance (70, 72).
8. Two-stroke internal combustion engine according to claim 1, characterised in that into the combustion chamber (18) there extends an ignition electrode (90, 96) the counterelectrode (92, 98) of which is provided on a surface, pointing towards the combustion chamber (94), of a cylinder block wall (88, 98) extending between the two pistons (84,86,100,102).
9. Twostrike internal combustion engine according to claim 8, characterised in that the ignition electrode (96) is arranged on the cylinder head in the middle of the combustion chamber (94).
10. Two-stroke internal combustion engine according to claim 8, characterised in that the ignition electrode (90) and the counter-electrode (92) are arranged side by side on the surface of the cylinder block wall (88) pointing towards the combustion chamber.
11. Two-stroke internal combustion engine according to claim 1, characterised in that the connecting rod bearing (122) and the main bearings (116, 118) are separately enclosed in lubricant-tight manner from the crank case and in that lubricant conduits (130,132) of a central oil supply of the two-stroke internal combustion engine open into the enclosed internal spaces of the bearings.
12. Two-stroke internal combustion engine according to claim 1, characterised in that the fuel is injected continuously into the transfer passage (44) contrarily of the direction of flow.
EP80103129A 1979-06-13 1980-06-04 Two-stroke internal combustion engine Expired EP0021170B1 (en)

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AT80103129T ATE1253T1 (en) 1979-06-13 1980-06-04 TWO-STROKE ENGINE.

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DE2923941A DE2923941C2 (en) 1979-06-13 1979-06-13 Two-stroke internal combustion engine

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IT246813Y1 (en) * 1999-06-23 2002-04-10 Katia Marroffino SPONGE HOLDER STRUCTURE

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EP0021170A1 (en) 1981-01-07
ATE1253T1 (en) 1982-07-15
US4296714A (en) 1981-10-27
DE2923941C2 (en) 1982-12-30
DE2923941A1 (en) 1981-05-07

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