EP3523512B1 - Hydraulic unit for an internal combustion engine with variable hydraulic valve drive - Google Patents

Hydraulic unit for an internal combustion engine with variable hydraulic valve drive Download PDF

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Publication number
EP3523512B1
EP3523512B1 EP17784837.1A EP17784837A EP3523512B1 EP 3523512 B1 EP3523512 B1 EP 3523512B1 EP 17784837 A EP17784837 A EP 17784837A EP 3523512 B1 EP3523512 B1 EP 3523512B1
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EP
European Patent Office
Prior art keywords
hydraulic
housing
pressure chamber
pressure
chamber
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EP17784837.1A
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German (de)
French (fr)
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EP3523512A1 (en
Inventor
Lothar Von Schimonsky
Nicola Morelli
Steffen Pfeiffer
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Schaeffler Technologies AG and Co KG
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Schaeffler Technologies AG and Co KG
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    • 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
    • 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

Definitions

  • the DE 10 2013 213 695 A1 discloses a hydraulic unit of a fully variable hydraulic valve control.
  • the hydraulic unit is mounted on the cylinder head of an internal combustion engine, and its hydraulic chambers vent - in the direction of gravity - down into the cylinder head.
  • the operational venting of the hydraulic system causes the air bubbles carried along by the hydraulic medium to be separated from the inside into the surroundings of the hydraulic housing and thus prevents excessive amounts of air from entering the pressure chamber and remaining there, whereby the stiffness of the hydraulic medium required for the hydraulic gas exchange valve actuation is inadmissible would be affected.
  • the venting also promotes 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, generates negative pressure in the hydraulic chambers, which is caused by suction of Air is balanced 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 housing opening positioned high in relation to gravity, ie geodetically high, and with the pressure relief chamber via a throttle point positioned geodetically low 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 present invention is based on the object of developing a hydraulic unit of the type mentioned at the outset so 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 solution to this problem results from the features of claim 1.
  • the ventilation duct should have a siphon with a first duct section leading downwards with respect to the direction of gravity and the ventilation direction and a second duct section leading upwards. When the gas exchange valve is closed, the lowest section of the siphon runs below the delimitation of the pressure chamber from the slave piston.
  • the siphon has two functions: On the one hand, it forms a hydraulic reservoir with the second channel section leading upwards, which is filled with hydraulic fluid at the time the internal combustion engine is switched off and which then partially or partially causes the cooling-related shrinkage of the hydraulic fluid in the hydraulic chambers - depending on the volume of the reservoir fully compensated.
  • the falling level in the second channel section causes a corresponding shortening (via the communicating tubes) of the hydraulic or oil column loading on the slave piston, so that the low pressure in the pressure chamber ideally completely prevents its leakage.
  • the ventilation duct should have a third duct section adjoining the second duct section, which (also) leads down to the duct opening on the outside of the housing with regard to the direction of gravity and the venting direction.
  • This structural design with a drilled vent channel leading down into the cylinder head of the internal combustion engine and preferably opening into the underside of the hydraulic housing from a manufacturing point of view enables the top of the cylinder head to be completely closed off from the environment by the hydraulic unit.
  • a vent opening on the upper side of the hydraulic unit on the other hand, a final cylinder head cover and thus a further component is required.
  • the dimensioning of the ventilation channel which determines the volume of the hydraulic reservoir, can also be relevant for the state in which the level in the lowest section of the siphon drops so far that air can be sucked back through the first channel section. Only from a minimum size of the channel cross-section can air bubbles rise in it without pushing the oil column above it and displacing it into the pressure relief space. Since the back-sucked air bubbles rise through the oil column in the first duct section and this quasi closes again, the leakage-inhibiting vacuum is maintained in the hydraulic housing.
  • its inner diameter should be at least 6 mm. Particularly good and robust results were achieved with an inner diameter of approx. 8 mm.
  • FIG. 1 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.
  • an electromagnetic hydraulic valve 9 in this case a normally open 2-2-way valve, interrupts the connection between the pressure relief chamber 6 and the pressure chamber 5 in the closed state.
  • a piston pressure accumulator 10 for receiving the displaced hydraulic medium is connected to each pressure relief chamber 6.
  • the pressure relief spaces 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 separates the air bubbles which are operationally conveyed from the hydraulic circuit into the hydraulic housing 4 from the hydraulic chambers into the cylinder head.
  • the ventilation duct 11 is hydraulically connected to the respective pressure relief chamber 6 on the inside of the housing via throttles 12 and opens out on the outside of the housing into the interior of the cylinder head 1.
  • the ventilation duct 11 runs geodetically, i.e. with respect to the direction of gravity g symbolized by the arrow above the throttle points 12, the pressure relief chambers 6 and the pressure chambers 5, which are limited by the slave piston 8 at the level of the limitation 13 when these are completely retracted into the hydraulic housing 4 with the gas exchange valves 2 closed.
  • the ventilation duct 11 has a siphon with a first duct section 14 and a first duct section 14 leading downwards in the ventilation direction in each case geodetically upward leading second channel section 15, which terminates at the channel opening 16 on the outside of the housing with the upper side of the hydraulic housing 4.
  • the hydraulic housing 4 is in the vented state shortly after the internal combustion engine has been switched off, in which the vent channel 11 is completely filled with hydraulic medium up to the channel opening 16.
  • Figure 1 shows the fill level at a significantly later point in time when the hydraulic fluid has cooled down completely to ambient temperature and its volume has accordingly shrunk.
  • the volume compensation takes place by lowering the hydraulic medium in the second channel section 15 to the level shown at the lowest section 17 of the siphon. This lowermost section 17 runs geodetically below the delimitation 13, so that the oil column in the first channel section 14 generates a negative pressure in the pressure chambers 5 that inhibits leakage.
  • first and second channel sections can be drilled at an angle to one another, in which case the lowermost section of the siphon would be formed by the intersection of the two channel sections.
  • the illustrated embodiment differs from the previously explained embodiment only in the geodetically deep positioning of the channel mouth 16 'on the hydraulic housing 4.
  • the ventilation duct 11' has a third duct section 19, which adjoins the second duct section 15 and which - also with regard to the direction of gravity and the venting direction - leads geodetically downwards like the first duct section 14 and to its duct opening 16 'on the outside of the housing the underside of the hydraulic housing 4 lies and in the present case terminates with its underside.
  • the duct opening on the outside of the housing of the ventilation duct can open below the level of a hydraulic reservoir which is formed, for example, in the cylinder head outside the hydraulic housing. In this way - without impairing the ventilation of the hydraulic spaces in the hydraulic housing - when the internal combustion engine is not running, air is sucked back into the hydraulic spaces via the ventilation duct.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Valve Device For Special Equipments (AREA)

Description

Die Erfindung betrifft eine Hydraulikeinheit für eine Brennkraftmaschine mit hydraulisch variablem Gaswechselventiltrieb. Die Hydraulikeinheit 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.
Der Entlüftungskanal ist gehäuseinnenseitig über eine Drosselstelle mit dem Druckentlastungsraum verbunden und mündet gehäuseaußenseitig.The invention relates to a hydraulic unit for an internal combustion engine with a hydraulically variable gas exchange valve drive. The hydraulic unit includes:
  • 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, in the closed state, interrupts the connection between the pressure relief space and the pressure space.
The ventilation duct is connected to the pressure relief chamber on the inside of the housing via a throttle point and opens out on the outside of the housing.

Die DE 10 2013 213 695 A1 offenbart eine Hydraulikeinheit einer vollvariablen hydraulischen Ventilsteuerung. Die Hydraulikeinheit ist auf dem Zylinderkopf einer Brennkraftmaschine montiert, und deren Hydraulikräume entlüften sich - in Schwerkraftrichtung - nach unten in den Zylinderkopf.The DE 10 2013 213 695 A1 discloses a hydraulic unit of a fully variable hydraulic valve control. The hydraulic unit is mounted on the cylinder head of an internal combustion engine, and its hydraulic chambers vent - in the direction of gravity - down into the cylinder head.

Die betriebliche Entlüftung des Hydrauliksystems bewirkt das Abscheiden der vom Hydraulikmittel mitgeführten Luftblasen vom Inneren in die Umgebung des Hydraulikgehäuses und verhindert damit, dass Luft in übermäßiger Menge in den Druckraum gelangt und dort verbleibt, wobei die für die hydraulische Gaswechselventilbetätigung erforderliche Steifigkeit des Hydraulikmittels in unzulässiger Höhe beeinträchtigt wäre. Andererseits begünstigt die Entlüftung aber auch 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 medium to be separated from the inside into the surroundings of the hydraulic housing and thus prevents excessive amounts of air from entering the pressure chamber and remaining there, whereby the stiffness of the hydraulic medium required for the hydraulic gas exchange valve actuation is inadmissible would be affected. On the other hand, the venting also promotes 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, generates negative pressure in the hydraulic chambers, which is caused by suction of Air is balanced 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 und in der EP 2 653 703 A1 ist eine Hydraulikeinheit mit einem zusätzlichen Niederdruckraum vorgeschlagen, der zwecks Entlüftung über eine bezüglich der Schwerkraftrichtung, d.h. 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 zuvor erläuterte Problematik wird hierdurch jedoch nicht beseitigt, sondern nur entschärft, da die Zeitdauer der Druckraumentleerung lediglich etwas verlängert wird.In the EP 2 060 754 A2 and in the EP 2 653 703 A1 a hydraulic unit with an additional low pressure chamber is proposed, which communicates with the interior of the cylinder head via a housing opening positioned high in relation to gravity, ie geodetically high, and with the pressure relief chamber via a throttle point positioned geodetically low 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 problem explained above is not eliminated by this, but only mitigated, since the duration of the pressure chamber evacuation is only slightly increased.

Der vorliegenden Erfindung liegt die Aufgabe zugrunde, eine Hydraulikeinheit 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 Stillstandzeit der Brennkraftmaschine einen für deren Startvorgang kritischen Füllstand nicht unterschreitet. Die Lösung dieser Aufgabe ergibt sich aus den Merkmalen des Anspruchs 1. Demnach soll der Entlüftungskanal einen Siphon mit einem jeweils bezüglich der Schwerkraft- und der Entlüftungsrichtung herunter führenden ersten Kanalabschnitt und einem herauf führenden zweiten Kanalabschnitt haben. Der unterste Abschnitt des Siphons verläuft bei geschlossenem Gaswechselventil unterhalb der Begrenzung des Druckraums vom Nehmerkolben.The present invention is based on the object of developing a hydraulic unit of the type mentioned at the outset so 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 solution to this problem results from the features of claim 1. Accordingly, the ventilation duct should have a siphon with a first duct section leading downwards with respect to the direction of gravity and the ventilation direction and a second duct section leading upwards. When the gas exchange valve is closed, the lowest section of the siphon runs below the delimitation of the pressure chamber from the slave piston.

Der Siphon hat zwei Funktionen: Zum einen bildet er mit dem herauf führenden zweiten Kanalabschnitt ein Hydraulikreservoir, das zum Zeitpunkt des Abstellens der Brennkraftmaschine mit Hydraulikmittel befüllt ist und das anschließend die abkühlbedingte Schrumpfung des Hydraulikmittels in den Hydraulikräumen - je nach Volumen des Reservoirs - teilweise oder vollständig kompensiert. Zum anderen bewirkt der dabei fallende Pegel im zweiten Kanalabschnitt eine (über die kommunizierenden Röhren) entsprechende Verkürzung der auf dem Nehmerkolben lastenden Hydraulik- oder Ölsäule, so dass der niedrige Druck im Druckraum dessen Leckage idealerweise vollständig verhindert.The siphon has two functions: On the one hand, it forms a hydraulic reservoir with the second channel section leading upwards, which is filled with hydraulic fluid at the time the internal combustion engine is switched off and which then partially or partially causes the cooling-related shrinkage of the hydraulic fluid in the hydraulic chambers - depending on the volume of the reservoir fully compensated. On the other hand, the falling level in the second channel section causes a corresponding shortening (via the communicating tubes) of the hydraulic or oil column loading on the slave piston, so that the low pressure in the pressure chamber ideally completely prevents its leakage.

Vorteilhafte Weiterbildungen und Ausgestaltungen der Erfindung sind den Unteransprüchen entnehmbar. Demnach soll der Entlüftungskanal einen sich an den zweiten Kanalabschnitt anschließenden dritten Kanalabschnitt haben, der (ebenfalls) bezüglich der Schwerkraft- und der Entlüftungsrichtung bis zur gehäuseaußenseitigen Kanalmündung herunter führt. Diese konstruktive Ausgestaltung mit einem nach unten in den Zylinderkopf der Brennkraftmaschine führenden und fertigungstechnisch bevorzugt an der Unterseite des Hydraulikgehäuses mündenden, gebohrten Entlüftungskanal ermöglicht es, die Oberseite des Zylinderkopfs vollständig durch die Hydraulikeinheit gegenüber der Umgebung abzuschließen. Im Falle einer auf der Oberseite der Hydraulikeinheit mündenden Entlüftung ist demgegenüber ein abschließender Zylinderkopfdeckel und damit ein weiteres Bauteil erforderlich.Advantageous further developments and refinements of the invention can be found in the subclaims. Accordingly, the ventilation duct should have a third duct section adjoining the second duct section, which (also) leads down to the duct opening on the outside of the housing with regard to the direction of gravity and the venting direction. This structural design with a drilled vent channel leading down into the cylinder head of the internal combustion engine and preferably opening into the underside of the hydraulic housing from a manufacturing point of view enables the top of the cylinder head to be completely closed off from the environment by the hydraulic unit. In the case of a vent opening on the upper side of the hydraulic unit, on the other hand, a final cylinder head cover and thus a further component is required.

Die das Volumen des Hydraulikreservoirs bestimmende Dimensionierung des Entlüftungskanals kann auch für den Zustand relevant sein, in dem der Pegel im untersten Abschnitt des Siphons so weit absinkt, dass ein Rücksaugen von Luft über den ersten Kanalabschnitt nicht vermeidbar ist. Erst ab einer Mindestgröße des Kanalquerschnitts können darin Luftblasen aufsteigen, ohne die darüber liegende Ölsäule vor sich her zu schieben und in den Druckentlastungsraum zu verdrängen. Da die rückgesaugten Luftblasen durch die im ersten Kanalabschnitt stehende Ölsäule hindurch aufsteigen und sich diese quasi wieder verschließt, wird der Leckage hemmende Unterdruck im Hydraulikgehäuse aufrecht erhalten. Im Falle eines Öls mit dem Viskositätsindex 0W20 und im Falle des ersten Kanalabschnitts mit fertigungstechnisch günstigem, kreisförmigem Querschnitt soll dessen Innendurchmesser mindestens 6 mm betragen. Besonders gute und robuste Ergebnisse wurden mit einem Innendurchmesser von ca. 8 mm erzielt.The dimensioning of the ventilation channel, which determines the volume of the hydraulic reservoir, can also be relevant for the state in which the level in the lowest section of the siphon drops so far that air can be sucked back through the first channel section. Only from a minimum size of the channel cross-section can air bubbles rise in it without pushing the oil column above it and displacing it into the pressure relief space. Since the back-sucked air bubbles rise through the oil column in the first duct section and this quasi closes again, the leakage-inhibiting vacuum is maintained in the hydraulic housing. In the case of an oil with the viscosity index 0W20 and in the case of the first channel section With a circular cross-section that is favorable in terms of production technology, its inner diameter should be at least 6 mm. Particularly good and robust results were achieved with an inner diameter of approx. 8 mm.

Weitere Merkmale der Erfindung ergeben sich aus der nachfolgenden Beschreibung und aus den Zeichnungen, in denen zwei 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 1
das erste Ausführungsbeispiel mit einem oben mündenden Entlüftungskanal;
Figur 2
das zweite Ausführungsbeispiel mit einem unten mündenden Entlüftungskanal.
Further features of the invention emerge from the following description and from the drawings, in which two exemplary embodiments of the invention are shown schematically. Unless otherwise mentioned, features or components that are the same or functionally the same are provided with the same reference numbers. Show it:
Figure 1
the first embodiment with a vent channel opening at the top;
Figure 2
the second embodiment with a vent channel opening at the bottom.

Figur 1 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. Jeweils ein elektromagnetisches Hydraulikventil 9, vorliegend ein stromlos geöffnetes 2-2-Wegeventil unterbricht in geschlossenem Zustand die 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 1 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. In each case an electromagnetic hydraulic valve 9, in this case a normally open 2-2-way valve, interrupts the 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 into the pressure relief chamber 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 spaces 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 einem gemeinsamen Entlüftungskanal 11 im Hydraulikgehäuse 4 angeschlossen, der die betrieblich aus dem Hydraulikkreislauf in das Hydraulikgehäuse 4 geförderten Luftblasen aus den Hydraulikräumen in den Zylinderkopf abscheidet. Der Entlüftungskanal 11 ist gehäuseinnenseitig über Drosselstellen 12 mit dem jeweiligen Druckentlastungsraum 6 hydraulisch verbunden und mündet gehäuseaußenseitig in das Innere des Zylinderkopfs 1. Der Entlüftungskanal 11 verläuft geodätisch, d.h. bezüglich der durch den Pfeil symbolisierten Richtung der Schwerkraft g oberhalb der Drosselstellen 12, der Druckentlastungsräume 6 und der Druckräume 5, die von den Nehmerkolben 8 in Höhe der Begrenzung 13 begrenzt werden, wenn diese bei geschlossenen Gaswechselventilen 2 vollständig im Hydraulikgehäuse 4 eingefahren sind.The pressure relief chambers 6 are connected to a common ventilation duct 11 in the hydraulic housing 4, which separates the air bubbles which are operationally conveyed from the hydraulic circuit into the hydraulic housing 4 from the hydraulic chambers into the cylinder head. The ventilation duct 11 is hydraulically connected to the respective pressure relief chamber 6 on the inside of the housing via throttles 12 and opens out on the outside of the housing into the interior of the cylinder head 1. The ventilation duct 11 runs geodetically, i.e. with respect to the direction of gravity g symbolized by the arrow above the throttle points 12, the pressure relief chambers 6 and the pressure chambers 5, which are limited by the slave piston 8 at the level of the limitation 13 when these are completely retracted into the hydraulic housing 4 with the gas exchange valves 2 closed.

Der Entlüftungskanal 11 hat einen Siphon mit einem stromabwärts in Entlüftungsrichtung jeweils geodätisch herunter führenden ersten Kanalabschnitt 14 und einem herauf führenden zweiten Kanalabschnitt 15, der an der gehäuseaußenseitigen Kanalmündung 16 mit der Oberseite des Hydraulikgehäuses 4 abschließt.The ventilation duct 11 has a siphon with a first duct section 14 and a first duct section 14 leading downwards in the ventilation direction in each case geodetically upward leading second channel section 15, which terminates at the channel opening 16 on the outside of the housing with the upper side of the hydraulic housing 4.

Das Hydraulikgehäuse 4 befindet sich kurz nach dem Abstellen der Brennkraftmaschine in entlüftetem Zustand, in dem der Entlüftungskanal 11 bis zur Kanalmündung 16 vollständig mit Hydraulikmittel befüllt ist. Figur 1 zeigt den Füllzustand zu einem deutlich späteren Zeitpunkt, an dem das Hydraulikmittel vollständig auf Umgebungstemperatur abgekühlt und dessen Volumen dementsprechend geschrumpft ist. Der Volumenausgleich erfolgt durch Absinken des Hydraulikmittels im zweiten Kanalabschnitt 15 bis zu dem dargestellten Pegel am untersten Abschnitt 17 des Siphons. Dieser unterste Abschnitt 17 verläuft geodätisch unterhalb der Begrenzung 13, so dass die im ersten Kanalabschnitt 14 stehende Ölsäule einen die Leckage hemmenden Unterdruck in den Druckräumen 5 erzeugt.The hydraulic housing 4 is in the vented state shortly after the internal combustion engine has been switched off, in which the vent channel 11 is completely filled with hydraulic medium up to the channel opening 16. Figure 1 shows the fill level at a significantly later point in time when the hydraulic fluid has cooled down completely to ambient temperature and its volume has accordingly shrunk. The volume compensation takes place by lowering the hydraulic medium in the second channel section 15 to the level shown at the lowest section 17 of the siphon. This lowermost section 17 runs geodetically below the delimitation 13, so that the oil column in the first channel section 14 generates a negative pressure in the pressure chambers 5 that inhibits leakage.

In einer nicht dargestellten Alternativausführung können der erste und der zweite Kanalabschnitt schräg zueinander gebohrt sein, wobei dann der unterste Abschnitt des Siphons durch die Verschneidung der beiden Kanalabschnitte gebildet wäre.In an alternative embodiment, not shown, the first and second channel sections can be drilled at an angle to one another, in which case the lowermost section of the siphon would be formed by the intersection of the two channel sections.

Für den Fall, dass der Volumenausgleich zu einem weiteren Absinken des dargestellten Pegels führt und der unterste Abschnitt 17 des Siphons belüftet wird, kann es infolge des Unterdrucks zum Nachsaugen von Luftblasen 18 in die Hydraulikräume kommen. Der zwischen 8 mm und 9 mm im Verhältnis zur Größe der Luftblasen 18 deutlich größere Innendurchmesser des ersten Kanalabschnitts 14 ermöglicht es, dass die Luftblasen 18 durch die darin stehende Ölsäule hindurch nach oben wandern können und sich die Ölsäule nach dem Passieren der Luftblasen 18 wieder schließt. Hierdurch wird der 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 zweiten Kanalabschnitt 15 - das kritische Entleeren der Druckräume 5 verzögert.In the event that the volume equalization leads to a further drop in the level shown and the lowest section 17 of the siphon is ventilated, air bubbles 18 can be sucked into the hydraulic chambers as a result of the negative pressure. The inner diameter of the first channel section 14, which is between 8 mm and 9 mm in relation to the size of the air bubbles 18, which is significantly larger, enables the air bubbles 18 to migrate upward through the oil column located therein and the oil column closes again after passing through the air bubbles 18 . This maintains the negative pressure 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 second channel section 15 - delays the critical emptying of the pressure chambers 5.

Das in Figur 2 dargestellte Ausführungsbeispiel unterscheidet sich von der zuvor erläuterten Ausführung lediglich durch die geodätisch tiefe Positionierung der Kanalmündung 16' am Hydraulikgehäuses 4. Dabei hat der Entlüftungskanal 11' einen sich an den zweiten Kanalabschnitt 15 anschließenden dritten Kanalabschnitt 19, der - ebenfalls bezüglich der Schwerkraft- und der Entlüftungsrichtung - wie der erste Kanalabschnitt 14 geodätisch herunter führt und dessen gehäuseaußenseitige Kanalmündung 16' an der Unterseite des Hydraulikgehäuses 4 liegt und vorliegend mit dessen Unterseite abschließt.This in Figure 2 The illustrated embodiment differs from the previously explained embodiment only in the geodetically deep positioning of the channel mouth 16 'on the hydraulic housing 4. The ventilation duct 11' has a third duct section 19, which adjoins the second duct section 15 and which - also with regard to the direction of gravity and the venting direction - leads geodetically downwards like the first duct section 14 and to its duct opening 16 'on the outside of the housing the underside of the hydraulic housing 4 lies and in the present case terminates with its underside.

In einer weiteren, nicht dargestellten Ausführung kann die gehäuseaußenseitige Kanalmündung des Entlüftungskanals unterhalb des Pegels eines Hydraulikreservoirs münden, das beispielsweise im Zylinderkopf außerhalb des Hydraulikgehäuses gebildet ist. Hierdurch wird - ohne die Entlüftung der Hydraulikräume im Hydraulikgehäuse zu beeinträchtigen - verhindert, dass bei stilstehender Brennkraftmaschine Luft über den Entlüftungskanal in die Hydraulikräume rückgesaugt wird.In a further embodiment, not shown, the duct opening on the outside of the housing of the ventilation duct can open below the level of a hydraulic reservoir which is formed, for example, in the cylinder head outside the hydraulic housing. In this way - without impairing the ventilation of the hydraulic spaces in the hydraulic housing - when the internal combustion engine is not running, air is sucked back into the hydraulic spaces via the ventilation duct.

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
BegrenzungLimitation
1414th
erster Kanalabschnittfirst channel section
1515th
zweiter Kanalabschnittsecond canal section
1616
KanalmündungCanal mouth
1717th
unterster Abschnitt des Siphonslowest section of the siphon
1818th
LuftblaseAir bubble
1919th
dritter Kanalabschnittthird channel section

Claims (4)

  1. Hydraulic unit for an internal combustion engine having a hydraulically variable gas exchange valve train, comprising:
    - a hydraulic housing (4) having a pressure chamber (5), a pressure relief chamber (6) and a venting duct (11, 11'), wherein the pressure chamber (5), the pressure relief chamber (6) and the venting duct (11, 11') are hydraulically connected to each other,
    - a master piston (7) which is guided in the hydraulic housing (4), 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) which is guided in the hydraulic housing (4), drives the gas exchange valve (2) on the outside of the housing and delimits the pressure chamber (5) on the inside of the housing,
    - and a hydraulic valve (9) which, when in the closed state, interrupts the connection between the pressure relief chamber (6) and the pressure chamber (5),
    wherein the venting duct (11, 11') is connected on the inside of the housing via a throttle point (12) to the pressure relief chamber (6) and opens on the outside of the housing, characterised in that the venting duct (11, 11') has a siphon having a first channel portion (14) leading downwards and a second channel portion (15) leading upwards in relation to the direction of gravity and the venting direction, wherein the lowest portion (17) of the siphon runs from the slave piston (8) below the boundary (13) of the pressure chamber (5) when the gas exchange valve (2) is closed.
  2. Hydraulic unit according to claim 1, characterised in that the venting duct (11') has a third channel portion (19) adjoining the second channel portion (15) and leading downwards in relation to the direction of gravity and the venting direction to the channel opening (16') on the outside of the housing.
  3. Hydraulic unit according to claim 2, characterised in that the channel opening (16') is located is located on the underside of the hydraulic housing (4) in relation to the direction of gravity.
  4. Hydraulic unit according to one of the preceding claims, characterised in that the first channel portion (14) has a circular cross section, the inside diameter of which is at least 6 mm.
EP17784837.1A 2016-10-05 2017-09-29 Hydraulic unit for an internal combustion engine with variable hydraulic valve drive Active EP3523512B1 (en)

Applications Claiming Priority (2)

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DE102016219297.3A DE102016219297B4 (en) 2016-10-05 2016-10-05 Hydraulic unit for an internal combustion engine with a hydraulically variable gas exchange valve drive
PCT/DE2017/100833 WO2018065010A1 (en) 2016-10-05 2017-09-29 Hydraulics unit for an internal combustion engine with hydraulically variable gas exchange valve gear

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EP3523512B1 true EP3523512B1 (en) 2020-11-11

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EP (1) EP3523512B1 (en)
CN (1) CN109790766B (en)
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CN111546119A (en) * 2020-04-28 2020-08-18 东莞市固达机械制造有限公司 Numerical control double-changing-table precision plane milling machine

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DE102016219297A1 (en) 2018-04-05
WO2018065010A1 (en) 2018-04-12
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DE102016219297B4 (en) 2021-12-30
CN109790766B (en) 2021-01-26
CN109790766A (en) 2019-05-21
US11187117B2 (en) 2021-11-30

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