EP3519683B1 - Internal combustion engine with hydraulic variable valve drive - Google Patents

Internal combustion engine with hydraulic variable valve drive Download PDF

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Publication number
EP3519683B1
EP3519683B1 EP17787318.9A EP17787318A EP3519683B1 EP 3519683 B1 EP3519683 B1 EP 3519683B1 EP 17787318 A EP17787318 A EP 17787318A EP 3519683 B1 EP3519683 B1 EP 3519683B1
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EP
European Patent Office
Prior art keywords
hydraulic
housing
combustion engine
internal combustion
pressure chamber
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EP17787318.9A
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German (de)
French (fr)
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EP3519683A1 (en
Inventor
Steffen Pfeiffer
Philipp Galster
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Schaeffler Technologies AG and Co KG
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Schaeffler Technologies AG and Co KG
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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01L—CYCLICALLY OPERATING VALVES FOR MACHINES OR ENGINES
    • F01L9/00—Valve-gear or valve arrangements actuated non-mechanically
    • F01L9/10—Valve-gear or valve arrangements actuated non-mechanically by fluid means, e.g. hydraulic
    • F01L9/11—Valve-gear or valve arrangements actuated non-mechanically by fluid means, e.g. hydraulic in which the action of a cam is being transmitted to a valve by a liquid column
    • F01L9/12—Valve-gear or valve arrangements actuated non-mechanically by fluid means, e.g. hydraulic in which the action of a cam is being transmitted to a valve by a liquid column with a liquid chamber between a piston actuated by a cam and a piston acting on a valve stem
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01L—CYCLICALLY OPERATING VALVES FOR MACHINES OR ENGINES
    • F01L3/00—Lift-valve, i.e. cut-off apparatus with closure members having at least a component of their opening and closing motion perpendicular to the closing faces; Parts or accessories thereof
    • F01L3/06—Valve members or valve-seats with means for guiding or deflecting the medium controlled thereby, e.g. producing a rotary motion of the drawn-in cylinder charge
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01L—CYCLICALLY OPERATING VALVES FOR MACHINES OR ENGINES
    • F01L9/00—Valve-gear or valve arrangements actuated non-mechanically
    • F01L9/10—Valve-gear or valve arrangements actuated non-mechanically by fluid means, e.g. hydraulic
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01L—CYCLICALLY OPERATING VALVES FOR MACHINES OR ENGINES
    • F01L9/00—Valve-gear or valve arrangements actuated non-mechanically
    • F01L9/10—Valve-gear or valve arrangements actuated non-mechanically by fluid means, e.g. hydraulic
    • F01L9/11—Valve-gear or valve arrangements actuated non-mechanically by fluid means, e.g. hydraulic in which the action of a cam is being transmitted to a valve by a liquid column
    • F01L9/12—Valve-gear or valve arrangements actuated non-mechanically by fluid means, e.g. hydraulic in which the action of a cam is being transmitted to a valve by a liquid column with a liquid chamber between a piston actuated by a cam and a piston acting on a valve stem
    • F01L9/14—Valve-gear or valve arrangements actuated non-mechanically by fluid means, e.g. hydraulic in which the action of a cam is being transmitted to a valve by a liquid column with a liquid chamber between a piston actuated by a cam and a piston acting on a valve stem the volume of the chamber being variable, e.g. for varying the lift or the timing of a valve
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01L—CYCLICALLY OPERATING VALVES FOR MACHINES OR ENGINES
    • F01L1/00—Valve-gear or valve arrangements, e.g. lift-valve gear
    • F01L1/34—Valve-gear or valve arrangements, e.g. lift-valve gear characterised by the provision of means for changing the timing of the valves without changing the duration of opening and without affecting the magnitude of the valve lift
    • F01L1/344—Valve-gear or valve arrangements, e.g. lift-valve gear characterised by the provision of means for changing the timing of the valves without changing the duration of opening and without affecting the magnitude of the valve lift changing the angular relationship between crankshaft and camshaft, e.g. using helicoidal gear
    • F01L1/3442—Valve-gear or valve arrangements, e.g. lift-valve gear characterised by the provision of means for changing the timing of the valves without changing the duration of opening and without affecting the magnitude of the valve lift changing the angular relationship between crankshaft and camshaft, e.g. using helicoidal gear using hydraulic chambers with variable volume to transmit the rotating force
    • F01L2001/34423—Details relating to the hydraulic feeding circuit
    • F01L2001/34446—Fluid accumulators for the feeding circuit

Definitions

  • the generic DE 10 2013 213 695 A1 shows an internal combustion engine with a fully variable hydraulic valve control. This is formed by a structural unit that is mounted on the cylinder head of the internal combustion engine and the hydraulic chambers of which - in the direction of gravity - vent down into the cylinder head.
  • the operational venting of the hydraulic system causes the air bubbles carried along by the hydraulic fluid to be separated into the vicinity of the hydraulic housing and thus prevents excessive amounts of air from entering the pressure chamber and impairing the hydraulic fluid's stiffness to an impermissible level, which is necessary for the hydraulic gas exchange valve actuation.
  • the venting promotes the leakage of the hydraulic medium from the hydraulic housing when the internal combustion engine is switched off.
  • the hydraulic fluid which cools down and shrinks in volume, creates negative pressure in the hydraulic chambers, which is compensated by sucking in air via the ventilation duct. During this pressure equalization, gravity ensures that the hydraulic chambers are emptied in the vicinity of the leakage through the guide gap between the slave piston and the hydraulic housing.
  • a hydraulic unit with an additional low-pressure chamber which communicates with the interior of the cylinder head via a geodetically high-position housing opening and with the pressure relief chamber via a geodetically low-lying throttle point for the purpose of venting.
  • the low-pressure chamber represents an expanded hydraulic reservoir which supplies the pressure chamber with sufficiently air-free hydraulic medium during the starting process of the internal combustion engine.
  • the vent which is not of the generic type, ie opens against the direction of gravity on the upper side of the hydraulic housing, requires a cylinder head cover that seals the cylinder head with the hydraulic housing from the environment, and therefore an additional component.
  • the present invention is based on the object of developing an internal combustion engine of the type mentioned at the outset in such a way that the hydraulic leakage from the hydraulic housing is reduced to such an extent that the hydraulic medium in the pressure chamber does not fall below a level that is critical for its starting process even after the internal combustion engine has been idle for a long time .
  • the vent channel should open into a hydraulic reservoir, the channel mouth being below the normal level of the hydraulic reservoir with respect to the direction of gravity.
  • the term “normal level” is to be understood as the level that is in the steady state shortly after the internal combustion engine has been switched off sets in the hydraulic reservoir, the internal combustion engine not being inclined or at most inclined to an insignificant extent with respect to its installation position.
  • the duct opening "immersed" in the hydraulic medium prevents air from being sucked back into the pressure relief chamber via the ventilation duct when the internal combustion engine is at a standstill and the hydraulic medium volume shrinks due to cooling. This state extends over a sufficiently long period of time and at least until the level of the hydraulic reservoir has dropped below the channel opening as a result of the cooling-related volume shrinkage of the hydraulic medium from the hydraulic housing.
  • the hydraulic reservoir open to the surroundings of the hydraulic housing can be formed either on the hydraulic housing itself or by a local trough or trough shape of a component or section of the cylinder head or of the engine block of the internal combustion engine.
  • the channel mouth should run as deep as possible with respect to the direction of gravity and specifically below the delimitation of the pressure chamber from the slave piston.
  • the geodetic height difference between the slave piston (retracted in the hydraulic housing) and the duct opening directly influences the negative pressure that is created in relation to the surroundings of the hydraulic housing when the internal combustion engine is switched off and the hydraulic fluid is shrinking and which counteracts the gravity-induced leakage of the hydraulic fluid from the hydraulic housing.
  • the channel mouth with respect to the direction of gravity i.e. geodetically always below the level of the hydraulic reservoir. This state presupposes that the hydraulic reservoir can be made sufficiently voluminous in view of the hydraulic volume in the hydraulic housing, which decreases due to temperature and leakage.
  • the volume of the hydraulic reservoir is structurally limited in such a way that a drop in the reservoir level below the channel mouth and consequently the sucking back of air cannot be avoided.
  • the downtime of the internal combustion engine until the critical level in the pressure chamber is reached can be significantly extended by the fact that the ventilation duct has, at least locally, a cross-section dimensioned in such a way that air bubbles can rise in it without pushing the hydraulic or oil column above it in front of it and to be displaced into the pressure relief space.
  • the cross-section is to be dimensioned so that the back-sucked air rises in the standing oil column, so that the remaining oil column more or less closes the channel mouth again and maintains the leakage-inhibiting vacuum in the hydraulic housing.
  • the ventilation duct in the case of an oil with the viscosity index 0W20, and in the case of a circular first pipe section, the ventilation duct must have an inside diameter of at least 6 mm. Particularly good and robust results have been achieved with the pipe inside diameter of approx. 8 mm.
  • the circular shape of the ventilation channel can have manufacturing advantages. However, other cross-sectional shapes are possible as long as the air can rise without displacing the oil column above.
  • the channel mouth should be formed by a circular second pipe section, which adjoins the first pipe section with (abrupt or gradual) reduction in the outer diameter of the pipe.
  • This structural design of the ventilation channel with the tube sections stepped in diameter may be necessary if the surface of the hydraulic reservoir is too small to accommodate the relatively large diameter of the first tube section.
  • the ventilation channel is expediently formed by a ventilation pipe fastened and preferably screwed in in the hydraulic housing, the first and optionally the second pipe section being parts of the ventilation pipe.
  • FIG. 1a shows schematically the section of an internal combustion engine with a hydraulically variable gas exchange valve drive which is essential for understanding the invention.
  • a cylinder head 1 is shown with two similar gas exchange valves 2 per cylinder, which are spring-loaded in the closing direction, and associated cams 3 of a camshaft.
  • the variability of the gas exchange valve drive is generated in a known manner by means of a hydraulic unit arranged between the cams 3 and the gas exchange valves 2.
  • This comprises a hydraulic housing 4 fastened in the cylinder head 1, in which a pressure chamber 5 and a pressure relief chamber 6 are formed for each cylinder and a master piston 7 is guided, which is driven by the cam 3 on the outside of the housing and delimits the pressure chamber 5 on the inside of the housing.
  • two slave pistons 8 per cylinder are guided in the hydraulic housing 4, which drive the gas exchange valves 2 on the outside of the housing and delimit the common pressure chamber 5 on the inside of the housing.
  • a piston pressure accumulator 10 for receiving the displaced hydraulic medium is connected to each pressure relief chamber 6.
  • the pressure relief chambers 6 are connected to the hydraulic circuit, ie the oil circuit of the internal combustion engine, via a hydraulic connection (not shown) on the hydraulic housing 4.
  • the functionality of the hydraulic gas exchange valve drive which is known per se, can be summarized in that the pressure chamber 5 between the master piston 7 and the slave piston 8 acts as a hydraulic linkage.
  • the hydraulic medium displaced by the master piston 7 - if leaks are neglected - proportionally to the stroke of the cam 3, depending on the opening time and the opening duration of the hydraulic valve 9, is transferred into a first partial volume that acts on the slave piston 8 and into a second partial volume, into the pressure relief chamber 6 including the piston pressure accumulator 10 outflowing partial volumes divided.
  • the transfer of the stroke of the master piston 7 to the slave piston 8 and consequently not only the control times but also the stroke height of the gas exchange valves 2 can be set in a fully variable manner.
  • the pressure relief chambers 6 are connected to a common ventilation duct 11 in the hydraulic housing 4, which is hydraulically connected to the respective pressure relief chamber 6 on the inside of the housing via throttling points 12 and opens on the outside of the housing in a hydraulic reservoir 13 inside the cylinder head 1.
  • the throttling points 12 are geodetically, ie above the pressure relief spaces 6 with respect to the direction of gravity g symbolized by the arrow, and the hydraulic reservoir 13 is geodetically below the pressure relief spaces 6 but also below the delimitation 16 of the pressure chamber 5 by the slave piston 8 when these are completely retracted into the hydraulic housing 4 with the gas exchange valves 2 closed.
  • the hydraulic reservoir 13, which is pressureless with respect to the internal pressure of the cylinder head 1, is formed by a trough which is closed in the direction of gravity 17 formed in cylinder head 1 (s. Figure 1b ), in which hydraulic fluid accumulates during operation of the internal combustion engine.
  • the ventilation duct 11 is formed on the outside of the housing by a ventilation tube 18 screwed tightly and sealingly into the hydraulic housing 4.
  • This has a circular first pipe section 19, the pipe inside diameter of which is between 8 mm and 9 mm.
  • the first pipe section 19 merges at a diameter step 20 into a circular second pipe section 21 with an inside diameter of approximately 4 mm.
  • the outer pipe diameter of the second pipe section 21 is correspondingly small and dimensioned in such a way that the second pipe section 21 can be inserted into the recess 17 without collision when the hydraulic unit is installed in the cylinder head 1.
  • Figure 1a shows the vented fill level of the hydraulic system shortly after the internal combustion engine has been switched off.
  • the level 15 of the hydraulic reservoir 13 is the normal level defined at the outset.
  • the particular according to Figure 1b shows the filling level of the hydraulic system at a significantly later point in time when the hydraulic medium has cooled down completely and its volume has accordingly shrunk.
  • the negative pressure that forms in the hydraulic chambers with the volume reduction causes hydraulic medium to be sucked in from the hydraulic reservoir 13 into the pressure relief chambers 6.
  • This air bubble-free sucking ends when the level 15 of the hydraulic reservoir 13 sinks geodetically below the channel mouth 14.
  • the pressure is then equalized between the pressure relief chambers 6 and the surroundings of the hydraulic housing 4 by sucking back air bubbles 22.
  • the in Figure 2 The second exemplary embodiment shown, the hydraulic reservoir 13 'is geodetically significantly lower than in the first exemplary embodiment.
  • the higher oil column between the delimitation 16 and the level 15 of the hydraulic reservoir 13 ' causes an increased negative pressure in the hydraulic system in favor of the further reduced leakage of the pressure chambers 5 through the guide gap around the slave piston 8.
  • the ventilation duct 11 is in this embodiment through a ventilation pipe 18' formed with a uniform diameter, wherein the pipe inner diameter is dimensioned so large in this case too that the air bubbles 22 rising therein can pass the oil column in the vent pipe 18 '.
  • the third embodiment according to Figure 3 has a hydraulic reservoir 13 ′′, the volume of which is so large that the channel mouth 14 is always geodetically below the level 15 of the hydraulic reservoir 13 ′′.

Description

Die Erfindung betrifft eine Brennkraftmaschine mit hydraulisch variablem Gaswechselventiltrieb, der Folgendes umfasst:

  • ein Hydraulikgehäuse mit einem Druckraum, einem Druckentlastungsraum und einem Entlüftungskanal, wobei der Druckraum, der Druckentlastungsraum und der Entlüftungskanal hydraulisch miteinander verbunden sind,
  • einen im Hydraulikgehäuse geführten Geberkolben, der gehäuseaußenseitig von einem Nocken angetrieben ist und gehäuseinnenseitig den Druckraum begrenzt,
  • einen im Hydraulikgehäuse geführten Nehmerkolben, der gehäuseaußenseitig das Gaswechselventil antreibt und gehäuseinnenseitig den Druckraum begrenzt,
  • und ein Hydraulikventil, das in geschlossenem Zustand die Verbindung zwischen dem Druckentlastungsraum und dem Druckraum unterbricht,
    wobei der Entlüftungskanal gehäuseinnenseitig über eine Drosselstelle mit dem Druckentlastungsraum hydraulisch verbunden ist und gehäuseaußenseitig bezüglich der Schwerkraftrichtung unterhalb des Druckentlastungsraums mündet.
The invention relates to an internal combustion engine with a hydraulically variable gas exchange valve drive which comprises the following:
  • a hydraulic housing with a pressure chamber, a pressure relief chamber and a ventilation duct, the pressure chamber, the pressure relief chamber and the ventilation duct being hydraulically connected to one another,
  • a master piston guided in the hydraulic housing, which is driven by a cam on the outside of the housing and delimits the pressure chamber on the inside of the housing,
  • a slave piston guided in the hydraulic housing, which drives the gas exchange valve on the outside of the housing and delimits the pressure chamber on the inside of the housing,
  • and a hydraulic valve which, when closed, interrupts the connection between the pressure relief chamber and the pressure chamber,
    wherein the ventilation duct is hydraulically connected to the pressure relief space on the inside of the housing via a throttle point and opens out on the outside of the housing below the pressure relief space with respect to the direction of gravity.

Die gattungsgemäße DE 10 2013 213 695 A1 zeigt eine Brennkraftmaschine mit einer vollvariablen hydraulischen Ventilsteuerung. Diese ist durch eine Baueinheit gebildet, die auf dem Zylinderkopf der Brennkraftmaschine montiert ist und deren Hydraulikräume sich - in Schwerkraftrichtung - nach unten in den Zylinderkopf entlüften.The generic DE 10 2013 213 695 A1 shows an internal combustion engine with a fully variable hydraulic valve control. This is formed by a structural unit that is mounted on the cylinder head of the internal combustion engine and the hydraulic chambers of which - in the direction of gravity - vent down into the cylinder head.

Die betriebliche Entlüftung des Hydrauliksystems bewirkt das Abscheiden der vom Hydraulikmittel mitgeführten Luftblasen in die Umgebung des Hydraulikgehäuses und verhindert damit, dass Luft in übermäßiger Menge in den Druckraum gelangt und dort die für die hydraulische Gaswechselventilbetätigung erforderliche Steifigkeit des Hydraulikmittels in unzulässiger Höhe beeinträchtigt. Andererseits begünstigt die Entlüftung die Leckage des Hydraulikmittels aus dem Hydraulikgehäuse, wenn die Brennkraftmaschine abgestellt ist. Denn das abkühlende und dabei im Volumen schrumpfende Hydraulikmittel erzeugt Unterdruck in den Hydraulikräumen, der über Nachsaugen von Luft via Entlüftungskanal ausgeglichen wird. Während dieses Druckausgleichs sorgt die Schwerkraft dafür, dass sich die Hydraulikräume über die Leckage durch den Führungsspalt zwischen Nehmerkolben und Hydraulikgehäuse in dessen Umgebung entleeren. Somit besteht bei längerer Stillstandszeit der Brennkraftmaschine das erhöhte Risiko, dass sich die Hydraulikräume vollständig entleeren und die im Druckraum befindliche Luft infolge der hohen Kompressibilität den Druckaufbau im Druckraum so beeinträchtigt, dass das für den Startvorgang der Brennkraftmaschine erforderliche Öffnen des Gaswechselventils verhindert wird.The operational venting of the hydraulic system causes the air bubbles carried along by the hydraulic fluid to be separated into the vicinity of the hydraulic housing and thus prevents excessive amounts of air from entering the pressure chamber and impairing the hydraulic fluid's stiffness to an impermissible level, which is necessary for the hydraulic gas exchange valve actuation. On the other hand, the venting promotes the leakage of the hydraulic medium from the hydraulic housing when the internal combustion engine is switched off. The hydraulic fluid, which cools down and shrinks in volume, creates negative pressure in the hydraulic chambers, which is compensated by sucking in air via the ventilation duct. During this pressure equalization, gravity ensures that the hydraulic chambers are emptied in the vicinity of the leakage through the guide gap between the slave piston and the hydraulic housing. Thus, if the internal combustion engine is not used for a long time, there is an increased risk that the hydraulic chambers will empty completely and that the air in the pressure chamber will impair the pressure build-up in the pressure chamber due to the high compressibility so that the gas exchange valve that is required for starting the internal combustion engine is prevented from opening.

In der EP 2 060 754 A2 ist eine Hydraulikeinheit mit einem zusätzlichen Niederdruckraum vorgeschlagen, der zwecks Entlüftung über eine geodätisch hoch positionierte Gehäuseöffnung mit dem Inneren des Zylinderkopfs und über eine geodätisch tief positionierte Drosselstelle mit dem Druckentlastungsraum kommuniziert. Der Niederdruckraum stellt ein erweitertes Hydraulikreservoir dar, das den Druckraum während des Startvorgangs der Brennkraftmaschine mit hinreichend luftfreiem Hydraulikmittel versorgt. Die nicht gattungsgemäße, d.h. entgegen der Schwerkraftrichtung auf der Oberseite des Hydraulikgehäuses mündende Entlüftung erfordert jedoch einen Zylinderkopfdeckel, der den Zylinderkopf mit dem Hydraulikgehäuse zur Umgebung hin abdichtet, und mithin ein zusätzliches Bauteil.In the EP 2 060 754 A2 a hydraulic unit with an additional low-pressure chamber is proposed, which communicates with the interior of the cylinder head via a geodetically high-position housing opening and with the pressure relief chamber via a geodetically low-lying throttle point for the purpose of venting. The low-pressure chamber represents an expanded hydraulic reservoir which supplies the pressure chamber with sufficiently air-free hydraulic medium during the starting process of the internal combustion engine. However, the vent, which is not of the generic type, ie opens against the direction of gravity on the upper side of the hydraulic housing, requires a cylinder head cover that seals the cylinder head with the hydraulic housing from the environment, and therefore an additional component.

Der vorliegenden Erfindung liegt die Aufgabe zugrunde, eine Brennkraftmaschine der eingangs genannten Art dahingehend fortzubilden, dass die Hydraulikleckage aus dem Hydraulikgehäuse auf ein solches Maß reduziert wird, dass das im Druckraum befindliche Hydraulikmittel auch nach längerer Stillstandszeit der Brennkraftmaschine einen für deren Startvorgang kritischen Füllstand nicht unterschreitet.The present invention is based on the object of developing an internal combustion engine of the type mentioned at the outset in such a way that the hydraulic leakage from the hydraulic housing is reduced to such an extent that the hydraulic medium in the pressure chamber does not fall below a level that is critical for its starting process even after the internal combustion engine has been idle for a long time .

Die Lösung dieser Aufgabe ergibt sich aus den Merkmalen des Anspruchs 1. Demnach soll der Entlüftungskanal in einem Hydraulikreservoir münden, wobei die Kanalmündung bezüglich der Schwerkraftrichtung unterhalb des Normalpegels des Hydraulikreservoirs liegt. Unter dem Begriff 'Normalpegel' ist der Füllstand zu verstehen, der sich im stationären Zustand kurz nach dem Abstellen der Brennkraftmaschine im Hydraulikreservoir einstellt, wobei die Brennkraftmaschine gegenüber ihrer Einbauposition nicht oder allenfalls unwesentlich geneigt ist. Die im Hydraulikmittel "eintauchende" Kanalmündung verhindert es, dass bei stillstehender Brennkraftmaschine und infolge der Abkühlung schrumpfendem Hydraulikmittelvolumen Luft über den Entlüftungskanal in den Druckentlastungsraum zurückgesaugt wird. Dieser Zustand erstreckt sich über einen ausreichend langen Zeitraum und zumindest so lange, bis gegebenenfalls der Pegel des Hydraulikreservoirs infolge der abkühlbedingten Volumenschrumpfung des Hydraulikmittels aus dem Hydraulikgehäuse unter die Kanalmündung gesunken ist.The solution to this problem results from the features of claim 1. Accordingly, the vent channel should open into a hydraulic reservoir, the channel mouth being below the normal level of the hydraulic reservoir with respect to the direction of gravity. The term “normal level” is to be understood as the level that is in the steady state shortly after the internal combustion engine has been switched off sets in the hydraulic reservoir, the internal combustion engine not being inclined or at most inclined to an insignificant extent with respect to its installation position. The duct opening "immersed" in the hydraulic medium prevents air from being sucked back into the pressure relief chamber via the ventilation duct when the internal combustion engine is at a standstill and the hydraulic medium volume shrinks due to cooling. This state extends over a sufficiently long period of time and at least until the level of the hydraulic reservoir has dropped below the channel opening as a result of the cooling-related volume shrinkage of the hydraulic medium from the hydraulic housing.

Das zur Umgebung des Hydraulikgehäuses hin offene Hydraulikreservoir kann entweder am Hydraulikgehäuse selbst oder durch eine lokale Mulden- oder Wannenform eines Bauteils oder Abschnitts des Zylinderkopfs oder des Motorblocks der Brennkraftmaschine gebildet sein.The hydraulic reservoir open to the surroundings of the hydraulic housing can be formed either on the hydraulic housing itself or by a local trough or trough shape of a component or section of the cylinder head or of the engine block of the internal combustion engine.

Vorteilhafte Weiterbildungen und Ausgestaltungen der Erfindung sind den Unteransprüchen entnehmbar. Demnach soll bei geschlossenem Gaswechselventil die Kanalmündung bezüglich der Schwerkraftrichtung möglichst tief und konkret unterhalb der Begrenzung des Druckraums vom Nehmerkolben verlaufen. Die geodätische Höhendifferenz zwischen dem (im Hydraulikgehäuse eingefahrenen) Nehmerkolben und der Kanalmündung beeinflusst unmittelbar den Unterdruck, der sich bei abgestellter Brennkraftmaschine und schrumpfendem Hydraulikmittel gegenüber der Umgebung des Hydraulikgehäuses bildet und der schwerkraftbedingten Leckage des Hydraulikmittels aus dem Hydraulikgehäuse entgegenwirkt.Advantageous further developments and refinements of the invention can be found in the subclaims. Accordingly, when the gas exchange valve is closed, the channel mouth should run as deep as possible with respect to the direction of gravity and specifically below the delimitation of the pressure chamber from the slave piston. The geodetic height difference between the slave piston (retracted in the hydraulic housing) and the duct opening directly influences the negative pressure that is created in relation to the surroundings of the hydraulic housing when the internal combustion engine is switched off and the hydraulic fluid is shrinking and which counteracts the gravity-induced leakage of the hydraulic fluid from the hydraulic housing.

Aus den zuvor erläuterten Gründen ist es besonders vorteilhaft, wenn die Kanalmündung bezüglich der Schwerkraftrichtung, d.h. geodätisch stets unterhalb des Pegels des Hydraulikreservoirs liegt. Dieser Zustand setzt voraus, dass das Hydraulikreservoir im Hinblick auf das temperatur- und leckagebedingt abnehmende Hydraulikvolumen im Hydraulikgehäuse hinreichend voluminös ausgeführt werden kann.For the reasons explained above, it is particularly advantageous if the channel mouth with respect to the direction of gravity, i.e. geodetically always below the level of the hydraulic reservoir. This state presupposes that the hydraulic reservoir can be made sufficiently voluminous in view of the hydraulic volume in the hydraulic housing, which decreases due to temperature and leakage.

Demgegenüber ist es eher wahrscheinlich, dass das Volumen des Hydraulikreservoirs konstruktiv derart beschränkt ist, dass ein Absinken des Reservoirpegels unter die Kanalmündung und folglich das Rücksaugen von Luft nicht vermeidbar sind. Dennoch kann die Stillstandszeit der Brennkraftmaschine bis zum Erreichen des kritischen Füllstands im Druckraum signifikant dadurch verlängert werden, dass der Entlüftungskanal zumindest lokal einen so dimensionierten Querschnitt hat, dass darin Luftblasen aufsteigen können, ohne die darüber liegende Hydraulik- oder Ölsäule vor sich her zu schieben und in den Druckentlastungsraum zu verdrängen. Vielmehr ist der Querschnitt so zu bemessen, dass die rückgesaugte Luft in der stehenden Ölsäule aufsteigt, so dass die verbleibende Ölsäule die Kanalmündung quasi wieder verschließt und den Leckage hemmenden Unterdruck im Hydraulikgehäuse aufrecht erhält. Diesbezügliche Versuche der Anmelderin haben gezeigt, dass der Entlüftungskanal im Falle eines Öls mit dem Viskositätsindex 0W20 und im Falle eines kreisförmigen ersten Rohrabschnitts einen Rohr-Innendurchmesser von wenigstens 6 mm haben muss. Besonders gute und robuste Ergebnisse wurden mit dem Rohr-Innendurchmesser von ca. 8 mm erzielt. Die Kreisform des Entlüftungskanals kann fertigungstechnische Vorteile haben. Dennoch sind andere Querschnittsformen möglich, solange das Aufsteigen der Luft ohne Verdrängen der darüber liegenden Ölsäule möglich ist.In contrast, it is more likely that the volume of the hydraulic reservoir is structurally limited in such a way that a drop in the reservoir level below the channel mouth and consequently the sucking back of air cannot be avoided. Nevertheless, the downtime of the internal combustion engine until the critical level in the pressure chamber is reached can be significantly extended by the fact that the ventilation duct has, at least locally, a cross-section dimensioned in such a way that air bubbles can rise in it without pushing the hydraulic or oil column above it in front of it and to be displaced into the pressure relief space. Rather, the cross-section is to be dimensioned so that the back-sucked air rises in the standing oil column, so that the remaining oil column more or less closes the channel mouth again and maintains the leakage-inhibiting vacuum in the hydraulic housing. Tests carried out by the applicant in this regard have shown that, in the case of an oil with the viscosity index 0W20, and in the case of a circular first pipe section, the ventilation duct must have an inside diameter of at least 6 mm. Particularly good and robust results have been achieved with the pipe inside diameter of approx. 8 mm. The circular shape of the ventilation channel can have manufacturing advantages. However, other cross-sectional shapes are possible as long as the air can rise without displacing the oil column above.

Weiterhin soll die Kanalmündung durch einen kreisförmigen zweiten Rohrabschnitt gebildet sein, der sich unter (abrupter oder allmählicher) Verkleinerung des Rohr-Außendurchmessers an den ersten Rohrabschnitt anschließt. Diese konstruktive Ausgestaltung des Entlüftungskanals mit den im Durchmesser gestuften Rohrabschnitten kann erforderlich sein, falls die Oberfläche des Hydraulikreservoirs zu klein ist, um den relativ großen Durchmesser des ersten Rohrabschnitts aufzunehmen.Furthermore, the channel mouth should be formed by a circular second pipe section, which adjoins the first pipe section with (abrupt or gradual) reduction in the outer diameter of the pipe. This structural design of the ventilation channel with the tube sections stepped in diameter may be necessary if the surface of the hydraulic reservoir is too small to accommodate the relatively large diameter of the first tube section.

Der Entlüftungskanal ist zweckmäßigerweise durch ein im Hydraulikgehäuse befestigtes und vorzugsweise eingeschraubtes Entlüftungsrohr gebildet, wobei der erste und gegebenenfalls der zweite Rohrabschnitt Teile des Entlüftungsrohrs sind.The ventilation channel is expediently formed by a ventilation pipe fastened and preferably screwed in in the hydraulic housing, the first and optionally the second pipe section being parts of the ventilation pipe.

Weitere Merkmale der Erfindung ergeben sich aus der nachfolgenden Beschreibung und aus den Zeichnungen, in denen drei Ausführungsbeispiele der Erfindung schematisch dargestellt sind. Soweit nicht anders erwähnt, sind dabei gleiche oder funktionsgleiche Merkmale oder Bauteile mit gleichen Bezugszahlen versehen. Es zeigen:

Figur 1a
das erste Ausführungsbeispiel mit einem im Durchmesser gestuften Entlüftungskanal;
Figur 1b
in vergrößerter Einzelheit die Kanalmündung und das Hydraulikreservoir des ersten Ausführungsbeispiels;
Figur 2
das zweite Ausführungsbeispiel mit einem vergleichsweise tief liegenden Hydraulikreservoir;
Figur 3
das dritte Ausführungsbeispiel mit einer permanent im Hydraulikreservoir eintauchenden Kanalmündung.
Further features of the invention emerge from the following description and from the drawings, in which three exemplary embodiments of the invention are shown schematically. Unless otherwise stated, features or components that are the same or functionally the same are provided with the same reference numbers. Show it:
Figure 1a
the first embodiment with a vent channel stepped in diameter;
Figure 1b
in enlarged detail the channel mouth and the hydraulic reservoir of the first embodiment;
Figure 2
the second embodiment with a comparatively deep hydraulic reservoir;
Figure 3
the third embodiment with a channel mouth that is permanently immersed in the hydraulic reservoir.

Figur 1a zeigt schematisch den für das Verständnis der Erfindung wesentlichen Ausschnitt einer Brennkraftmaschine mit hydraulisch variablem Gaswechselventiltrieb. Dargestellt ist ein Zylinderkopf 1 mit zwei gleichartigen und in Schließrichtung federkraftbeaufschlagten Gaswechselventilen 2 pro Zylinder und zugehörigen Nocken 3 einer Nockenwelle. Die Variabilität des Gaswechselventiltriebs wird auf bekannte Weise mittels einer zwischen den Nocken 3 und den Gaswechselventilen 2 angeordneten Hydraulikeinheit erzeugt. Diese umfasst ein im Zylinderkopf 1 befestigtes Hydraulikgehäuse 4, in dem je Zylinder ein Druckraum 5 und ein Druckentlastungsraum 6 ausgebildet sowie ein Geberkolben 7 geführt sind, der gehäuseaußenseitig vom Nocken 3 angetrieben ist und gehäuseinnenseitig den Druckraum 5 begrenzt. Weiterhin sind im Hydraulikgehäuse 4 zwei Nehmerkolben 8 je Zylinder geführt, die gehäuseaußenseitig die Gaswechselventile 2 antreiben und gehäuseinnenseitig den gemeinsamen Druckraum 5 begrenzen. Ein elektromagnetisches Hydraulikventil 9, vorliegend ein stromlos geöffnetes 2-2-Wegeventil unterbricht in geschlossenem Zustand die hydraulische Verbindung zwischen dem Druckentlastungsraum 6 und dem Druckraum 5. Im geöffneten Zustand des Hydraulikventils 9 kann ein Teil des vom Geberkolben 7 verdrängten Hydraulikmittels in den Druckentlastungsraum 6 abströmen, ohne an der Betätigung des Nehmerkolbens 8 und des zugehörigen Gaswechselventils 2 teilzunehmen. An jedem Druckentlastungsraum 6 ist ein Kolbendruckspeicher 10 zur Aufnahme des verdrängten Hydraulikmittels angeschlossen. Die Druckentlastungsräume 6 sind über einen nicht dargestellten Hydraulikanschluss am Hydraulikgehäuse 4 mit dem Hydraulikkreislauf, d.h. dem Ölkreislauf der Brennkraftmaschine verbunden. Figure 1a shows schematically the section of an internal combustion engine with a hydraulically variable gas exchange valve drive which is essential for understanding the invention. A cylinder head 1 is shown with two similar gas exchange valves 2 per cylinder, which are spring-loaded in the closing direction, and associated cams 3 of a camshaft. The variability of the gas exchange valve drive is generated in a known manner by means of a hydraulic unit arranged between the cams 3 and the gas exchange valves 2. This comprises a hydraulic housing 4 fastened in the cylinder head 1, in which a pressure chamber 5 and a pressure relief chamber 6 are formed for each cylinder and a master piston 7 is guided, which is driven by the cam 3 on the outside of the housing and delimits the pressure chamber 5 on the inside of the housing. Furthermore, two slave pistons 8 per cylinder are guided in the hydraulic housing 4, which drive the gas exchange valves 2 on the outside of the housing and delimit the common pressure chamber 5 on the inside of the housing. An electromagnetic hydraulic valve 9, in the present case a normally open 2-2-way valve, interrupts the hydraulic connection between the pressure relief chamber 6 and the pressure chamber 5 in the closed state. In the open state of the hydraulic valve 9, part of the hydraulic medium displaced by the master piston 7 can flow off into the pressure relief space 6 without participating in the actuation of the slave piston 8 and the associated gas exchange valve 2. A piston pressure accumulator 10 for receiving the displaced hydraulic medium is connected to each pressure relief chamber 6. The pressure relief chambers 6 are connected to the hydraulic circuit, ie the oil circuit of the internal combustion engine, via a hydraulic connection (not shown) on the hydraulic housing 4.

Die an sich bekannte Funktionsweise des hydraulischen Gaswechselventiltriebs lässt sich dahingehend zusammenfassen, dass der Druckraum 5 zwischen dem Geberkolben 7 und den Nehmerkolben 8 als hydraulisches Gestänge wirkt. Dabei wird das - bei Vernachlässigung von Leckagen - proportional zum Hub des Nockens 3 vom Geberkolben 7 verdrängte Hydraulikmittel in Abhängigkeit des Öffnungszeitpunkts und der Öffnungsdauer des Hydraulikventils 9 in ein erstes, die Nehmerkolben 8 beaufschlagendes Teilvolumen und in ein zweites, in den Druckentlastungsraum 6 einschließlich Kolbendruckspeicher 10 abströmendes Teilvolumen aufgeteilt. Hierdurch sind die Hubübertragung des Geberkolbens 7 auf die Nehmerkolben 8 und mithin nicht nur die Steuerzeiten, sondern auch die Hubhöhe der Gaswechselventile 2 vollvariabel einstellbar.The functionality of the hydraulic gas exchange valve drive, which is known per se, can be summarized in that the pressure chamber 5 between the master piston 7 and the slave piston 8 acts as a hydraulic linkage. The hydraulic medium displaced by the master piston 7 - if leaks are neglected - proportionally to the stroke of the cam 3, depending on the opening time and the opening duration of the hydraulic valve 9, is transferred into a first partial volume that acts on the slave piston 8 and into a second partial volume, into the pressure relief chamber 6 including the piston pressure accumulator 10 outflowing partial volumes divided. As a result, the transfer of the stroke of the master piston 7 to the slave piston 8 and consequently not only the control times but also the stroke height of the gas exchange valves 2 can be set in a fully variable manner.

Die Druckentlastungsräume 6 sind an einen gemeinsamen Entlüftungskanal 11 im Hydraulikgehäuse 4 angeschlossen, der gehäuseinnenseitig über Drosselstellen 12 mit dem jeweiligen Druckentlastungsraum 6 hydraulisch verbunden ist und gehäuseaußenseitig in einem Hydraulikreservoir 13 im Inneren des Zylinderkopfs 1 mündet. Die Drosselstellen 12 liegen geodätisch, d.h. bezüglich der durch den Pfeil symbolisierten Richtung der Schwerkraft g oberhalb der Druckentlastungsräume 6, und das Hydraulikreservoir 13 liegt geodätisch unterhalb der Druckentlastungsräume 6. Die Kanalmündung 14 des Entlüftungskanals 11 liegt geodätisch nicht nur unterhalb des Pegels 15 des Hydraulikreservoirs 13 sondern auch unterhalb der Begrenzung 16 des Druckraums 5 durch die Nehmerkolben 8, wenn diese bei geschlossenen Gaswechselventilen 2 vollständig im Hydraulikgehäuse 4 eingefahren sind. Das gegenüber dem Innendruck des Zylinderkopfs 1 drucklose Hydraulikreservoir 13 ist durch eine in Schwerkraftrichtung geschlossene Mulde 17 im Zylinderkopf 1 gebildet (s. Figur 1b), in der sich während des Betriebs der Brennkraftmaschine Hydraulikmittel ansammelt.The pressure relief chambers 6 are connected to a common ventilation duct 11 in the hydraulic housing 4, which is hydraulically connected to the respective pressure relief chamber 6 on the inside of the housing via throttling points 12 and opens on the outside of the housing in a hydraulic reservoir 13 inside the cylinder head 1. The throttling points 12 are geodetically, ie above the pressure relief spaces 6 with respect to the direction of gravity g symbolized by the arrow, and the hydraulic reservoir 13 is geodetically below the pressure relief spaces 6 but also below the delimitation 16 of the pressure chamber 5 by the slave piston 8 when these are completely retracted into the hydraulic housing 4 with the gas exchange valves 2 closed. The hydraulic reservoir 13, which is pressureless with respect to the internal pressure of the cylinder head 1, is formed by a trough which is closed in the direction of gravity 17 formed in cylinder head 1 (s. Figure 1b ), in which hydraulic fluid accumulates during operation of the internal combustion engine.

Der Entlüftungskanal 11 ist gehäuseaußenseitig durch ein im Hydraulikgehäuse 4 fest und dichtend eingeschraubtes Entlüftungsrohr 18 gebildet. Dieses hat einen kreisförmigen ersten Rohrabschnitt 19, dessen Rohr-Innendurchmesser zwischen 8 mm und 9 mm beträgt. Der erste Rohrabschnitt 19 geht an einer Durchmesserstufe 20 in einen kreisförmigen zweiten Rohrabschnitt 21 mit einem Rohr-Innendurchmesser von ca. 4 mm über. Der Rohr-Außendurchmesser des zweiten Rohrabschnitts 21 ist dementsprechend klein und so dimensioniert, dass der zweite Rohrabschnitt 21 bei der Montage der Hydraulikeinheit in den Zylinderkopf 1 kollisionsfrei in die Mulde 17 einführbar ist.The ventilation duct 11 is formed on the outside of the housing by a ventilation tube 18 screwed tightly and sealingly into the hydraulic housing 4. This has a circular first pipe section 19, the pipe inside diameter of which is between 8 mm and 9 mm. The first pipe section 19 merges at a diameter step 20 into a circular second pipe section 21 with an inside diameter of approximately 4 mm. The outer pipe diameter of the second pipe section 21 is correspondingly small and dimensioned in such a way that the second pipe section 21 can be inserted into the recess 17 without collision when the hydraulic unit is installed in the cylinder head 1.

Figur 1a zeigt den entlüfteten Füllzustand des Hydrauliksystems kurz nach dem Abstellen der Brennkraftmaschine. Dabei ist der Pegel 15 des Hydraulikreservoirs 13 der eingangs definierte Normalpegel. Die Einzelheit gemäß Figur 1b zeigt den Füllzustand des Hydrauliksystems zu einem deutlich späteren Zeitpunkt, an dem das Hydraulikmittel vollständig abgekühlt und dessen Volumen dementsprechend geschrumpft ist. Der sich mit der Volumenverkleinerung in den Hydraulikräumen bildende Unterdruck bewirkt das Nachsaugen von Hydraulikmittel aus dem Hydraulikreservoir 13 in die Druckentlastungsräume 6. Dieses luftblasenfreie Nachsaugen endet dann, wenn der Pegel 15 des Hydraulikreservoirs 13 geodätisch unter die Kanalmündung 14 sinkt. Danach erfolgt der Druckausgleich zwischen den Druckentlastungsräumen 6 und der Umgebung des Hydraulikgehäuses 4 durch Rücksaugen von Luftblasen 22. Der im Verhältnis zur Luftblasengröße deutlich größere Rohr-Innendurchmesser des ersten Rohrabschnitts 19 ermöglicht es, dass die Luftblasen 22 durch die darin stehende Ölsäule hindurch nach oben wandern können, wobei sich die Ölsäule nach dem Passieren der Luftblasen 22 wieder schließt. Hierdurch wird ein Unterdruck aufrechterhalten, der die hydraulische Leckage durch den Führungsspalt zwischen den Nehmerkolben 8 und dem Hydraulikgehäuse 4 in den Zylinderkopf 1 hemmt und damit - zusätzlich zum Volumenausgleich aus dem Hydraulikreservoir 13 - das kritische Entleeren des Druckraums 5 verzögert. Figure 1a shows the vented fill level of the hydraulic system shortly after the internal combustion engine has been switched off. The level 15 of the hydraulic reservoir 13 is the normal level defined at the outset. The particular according to Figure 1b shows the filling level of the hydraulic system at a significantly later point in time when the hydraulic medium has cooled down completely and its volume has accordingly shrunk. The negative pressure that forms in the hydraulic chambers with the volume reduction causes hydraulic medium to be sucked in from the hydraulic reservoir 13 into the pressure relief chambers 6. This air bubble-free sucking ends when the level 15 of the hydraulic reservoir 13 sinks geodetically below the channel mouth 14. The pressure is then equalized between the pressure relief chambers 6 and the surroundings of the hydraulic housing 4 by sucking back air bubbles 22. The inside diameter of the pipe of the first pipe section 19, which is significantly larger in relation to the size of the air bubbles, enables the air bubbles 22 to migrate upwards through the oil column in it can, wherein the oil column closes again after passing through the air bubbles 22. This maintains a vacuum that inhibits the hydraulic leakage through the guide gap between the slave piston 8 and the hydraulic housing 4 in the cylinder head 1 and thus - in addition to the volume compensation from the hydraulic reservoir 13 - delays the critical emptying of the pressure chamber 5.

Bei dem in Figur 2 dargestellten zweiten Ausführungsbeispiel liegt das Hydraulikreservoir 13' geodätisch deutlich tiefer als beim ersten Ausführungsbeispiel. Die höhere Ölsäule zwischen der Begrenzung 16 und dem Pegel 15 des Hydraulikreservoirs 13' bewirkt einen erhöhten Unterdruck im Hydrauliksystem zugunsten der weiter verringerten Leckage der Druckräume 5 durch den Führungsspalt um die Nehmerkolben 8. Der Entlüftungskanal 11 ist bei dieser Ausführung durch ein Entlüftungsrohr 18' mit gleichmäßigem Durchmesser gebildet, wobei der Rohr-Innendurchmesser auch in diesem Fall so groß bemessen ist, dass die darin aufsteigenden Luftblasen 22 die im Entlüftungsrohr 18' stehende Ölsäule passieren können.The in Figure 2 The second exemplary embodiment shown, the hydraulic reservoir 13 'is geodetically significantly lower than in the first exemplary embodiment. The higher oil column between the delimitation 16 and the level 15 of the hydraulic reservoir 13 'causes an increased negative pressure in the hydraulic system in favor of the further reduced leakage of the pressure chambers 5 through the guide gap around the slave piston 8. The ventilation duct 11 is in this embodiment through a ventilation pipe 18' formed with a uniform diameter, wherein the pipe inner diameter is dimensioned so large in this case too that the air bubbles 22 rising therein can pass the oil column in the vent pipe 18 '.

Das dritte Ausführungsbeispiel gemäß Figur 3 hat ein Hydraulikreservoir 13", dessen Volumen so groß ist, dass die Kanalmündung 14 geodätisch stets unterhalb des Pegels 15 des Hydraulikreservoirs 13" liegt.The third embodiment according to Figure 3 has a hydraulic reservoir 13 ″, the volume of which is so large that the channel mouth 14 is always geodetically below the level 15 of the hydraulic reservoir 13 ″.

Liste der BezugszahlenList of reference numbers

11
ZylinderkopfCylinder head
22
GaswechselventilGas exchange valve
33
Nockencam
44th
HydraulikgehäuseHydraulic housing
55
DruckraumPrinting room
66th
DruckentlastungsraumPressure relief space
77th
GeberkolbenMaster piston
88th
NehmerkolbenSlave piston
99
HydraulikventilHydraulic valve
1010
KolbendruckspeicherPiston accumulator
1111
EntlüftungskanalVentilation duct
1212
DrosselstelleThrottling point
1313
HydraulikreservoirHydraulic reservoir
1414th
KanalmündungCanal mouth
1515th
Pegellevel
1616
BegrenzungLimitation
1717th
Muldetrough
1818th
EntlüftungsrohrVent pipe
1919th
erster Rohrabschnittfirst pipe section
2020th
DurchmesserstufeDiameter grade
2121st
zweiter Rohrabschnittsecond pipe section
2222nd
LuftblaseAir bubble

Claims (7)

  1. An internal combustion engine with a hydraulically variable gas exchange valve train, comprising:
    - a hydraulic housing (4) with a pressure chamber (5), a pressure relief chamber (6), and a ventilation channel (11), wherein the pressure chamber (5), the pressure relief chamber (6) and the ventilation channel (11) are hydraulically connected to one another,
    - a master piston (7) guided in the hydraulic housing (4), which is driven by a cam (3) on the outside of the housing and delimits the pressure chamber (5) on the inside of the housing,
    - a slave piston (8) guided in the hydraulic housing (4), which drives the gas exchange valve (2) on the outside of the housing and delimits the pressure chamber (5) on the inside,
    - and a hydraulic valve (9) which in the closed state interrupts the connection between the pressure relief chamber (6) and the pressure chamber (5),
    wherein the ventilation channel (11) is hydraulically connected on the inside of the housing to the pressure relief chamber (6) via a throttle point and opens on the outside of the housing with respect to the direction of gravity below the pressure relief chamber (6), characterized in that the ventilation channel (11) opens out into a hydraulic reservoir (13, 13', 13 "), wherein the channel opening (14) is below the normal level of the hydraulic reservoir (13, 13', 13") with respect to the direction of gravity.
  2. The internal combustion engine according to claim 1, characterized in that, when the gas exchange valve (2) is closed, the channel opening (14) extends from the slave piston (8) with respect to the direction of gravity below the boundary (16) of the pressure chamber (5).
  3. The internal combustion engine according to claim 1 or 2, characterized in that the channel mouth (14) with respect to the direction of gravity is always below the level (15) of the hydraulic reservoir (13").
  4. The internal combustion engine according to any one of the preceding claims, characterized in that the ventilation duct (11) has a circular first tube section (19), the tube inner diameter of which is at least 6 mm.
  5. The internal combustion engine according to claim 4, characterized in that the channel opening (14) is formed by a circular second pipe section (21) which adjoins the first pipe section (19) while reducing the outer pipe diameter.
  6. The internal combustion engine according to claim 4 or 5, characterized in that the first pipe section (19) is part of a ventilation pipe (18) fastened in the hydraulic housing (4).
  7. The internal combustion engine according to claim 6, characterized in that the ventilation pipe (18) is screwed into the hydraulic housing (4).
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DE102016218918.2A DE102016218918B4 (en) 2016-09-29 2016-09-29 Internal combustion engine with hydraulically variable gas exchange valve drive
PCT/DE2017/100828 WO2018059627A1 (en) 2016-09-29 2017-09-28 Internal combustion engine with a hydraulically variable gas exchange valve train

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EP3519683A1 (en) 2019-08-07
WO2018059627A1 (en) 2018-04-05
DE102016218918A1 (en) 2018-03-29
US10900389B2 (en) 2021-01-26
CN109715911A (en) 2019-05-03
CN109715911B (en) 2021-10-12
DE102016218918B4 (en) 2018-09-13

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