EP0497194B1 - Method for actuating an exhaust valve tappet during braking of an internal combustion engine - Google Patents

Method for actuating an exhaust valve tappet during braking of an internal combustion engine Download PDF

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Publication number
EP0497194B1
EP0497194B1 EP92100960A EP92100960A EP0497194B1 EP 0497194 B1 EP0497194 B1 EP 0497194B1 EP 92100960 A EP92100960 A EP 92100960A EP 92100960 A EP92100960 A EP 92100960A EP 0497194 B1 EP0497194 B1 EP 0497194B1
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EP
European Patent Office
Prior art keywords
pressure
inner part
tappet
piston
pressure chamber
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
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EP92100960A
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German (de)
French (fr)
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EP0497194A1 (en
Inventor
Heribert Dipl.-Ing. Kubis
Dieter Wittmann
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MAN Truck and Bus SE
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MAN Nutzfahrzeuge AG
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Publication of EP0497194A1 publication Critical patent/EP0497194A1/en
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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
    • F01L13/00—Modifications of valve-gear to facilitate reversing, braking, starting, changing compression ratio, or other specific operations
    • F01L13/06—Modifications of valve-gear to facilitate reversing, braking, starting, changing compression ratio, or other specific operations for braking
    • 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
    • F01L1/20—Adjusting or compensating clearance
    • F01L1/22—Adjusting or compensating clearance automatically, e.g. mechanically
    • F01L1/24—Adjusting or compensating clearance automatically, e.g. mechanically by fluid means, e.g. hydraulically
    • F01L1/245—Hydraulic tappets

Definitions

  • the invention relates to a method according to the preamble of claim 1.
  • GB-A 20 06 373 which is considered to be the subsequent state of the art, discloses a valve tappet which allows a valve clearance to be compensated for hydraulically.
  • the valve lifter has an inner part which is guided in an outer part so as to be axially movable. The movement of the inner part is limited by a stop.
  • the inner part interacts with a push rod of a valve.
  • a spring-loaded piston is provided in the inner part, which holds a check valve arranged at the base of the inner part in the open position via a mandrel connected to the piston. If pressure from an external pressure source is now applied to the pressure chamber under the piston, the inner part is first raised relative to the outer part until any valve play that may exist is equalized.
  • the inner part experiences a counterforce, so that the pressure under the piston rises and the piston and the mandrel are raised against the force of the spring and the check valve closes.
  • a reaction of the hydraulic pressure under the inner part on pressure-carrying parts of the periphery of the valve tappet is avoided.
  • the invention has for its object to further develop this method so that the stroke of the exhaust valve tappet during a compression stroke in engine braking mode takes place solely by application of an external pressure source and the amount of the stroke is limited to a predetermined value.
  • the valve stroke of the exhaust valve can be precisely regulated by the constant oil quantity supplied by the external pressure source. Damage caused by the reaction of excessive hydraulic pressure on the supply lines or the pressure source is reliably avoided.
  • the exhaust valve 4 In engine braking mode, the exhaust valve 4 should also be slightly raised during the compression stroke to blow off the compressed air, so that additional braking work is performed.
  • the outlet valve tappet 1 has an inner part 8 which is axially movable in a tappet outer part 7 and which is installed with a stroke 9.
  • pressure fluid is supplied from an external pressure source 11, which raises the inner part 8 together with the push rod 3 until the inner part 8 has performed a designated stroke 9 and between the inner part 8 and a stop 8a a game 9a remains ( Figure 2).
  • the outlet valve 4 thereby opens and the pre-compressed air is blown off.
  • the inner part 8 is subjected to a special design in order to prevent the reaction to excessive hydraulic pressure on the pressure-carrying parts.
  • the inner part 8 has an axially movable piston 12, which is held in the starting position by a compression spring 13 and keeps the valve seat 25 open.
  • the piston 12 has a stroke limiter 14 on the one hand and a mandrel 15 on the other hand.
  • the inner part has a ball socket 16 at its upper end, while the lower end is closed by a valve 17.
  • the push rod 3 shown in FIG. 1 is mounted in the ball socket 16.
  • a first pressure chamber 19 under the piston 12 can be connected to the external pressure source 11 (FIG. 1) via through bores 18.
  • the first pressure chamber 19 in turn communicates in the illustrated rest position of the piston 12 via first and second bores 20, 21 in the valve 17 with a second pressure chamber 22 below the inner part 8.
  • valve 17 there is a spring 23 with a ball 24 which is held in the starting position by means of the compression spring 13 via the mandrel 15.
  • the inner part 8 is limited with stroke 9 plus a game 9a by stop ring 8a in a tappet outer part 7 of the outlet valve tappet 1.
  • the first pressure chamber 19 can be connected via the bores 18 to the pressure source 11 shown in FIG. 1.
  • the compression spring 13 is first compressed by the piston 12 until the stroke limitation 14 on the inner part 8 comes to a stop.
  • the ball 24 is pressed into a seat 25 by the spring 23 and initially closes the first bore 20.
  • the force of the spring 23 is now designed so that the ball 24 can still open due to the pressure building up in the first pressure chamber 19 and opens the path of the pressure fluid via the first bore 20 and the second bore 21 to the second pressure chamber 22. Due to the force exerted by the second pressure chamber 22 on the inner part 8, the latter is lifted together with the push rod 3 (FIG. 1) mounted in the spherical cap 16 and moved until the stroke 9 (FIG. 2) is exhausted.
  • the stroke 9 results as a function of the amount of oil delivered by the pressure source 11. This represents a constant since the pressure source 11 (FIG. 1) is designed as a positive displacement pump.
  • the outlet valve 4 (FIG. 1) is opened in accordance with the distance of the stroke 9. Under normal operating conditions, a play 9a remains between the inner part 8 and the stop ring 8a.
  • first and second regulating bores 26, 27 are provided in the inner part 8, which are connected to one another via an overflow channel 28.
  • the hydraulic pressure supplied by the bore 18 can act on its side facing the first pressure chamber 19 and move it against the restoring force of the compression spring 13.
  • hydraulic fluid can flow into the space filled by the compression spring 13 via the overflow channel 28 and the second regulating bore 27.
  • This room is over a relief bore 30 is connected to the environment for pressure equalization, whereby a further movement of the piston 12 is stopped.
  • the functions of the other parts are similar to the embodiment according to FIGS. 2 and 3 and have been explained in detail there.
  • the advantage of this tappet design is that the pressure relief valve can be dispensed with.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Valve Device For Special Equipments (AREA)
  • Valve-Gear Or Valve Arrangements (AREA)

Description

Die Erfindung bezieht sich auf ein Verfahren gemäß dem Gattungsbegriff des Patentanspruches 1.The invention relates to a method according to the preamble of claim 1.

Durch GB-A 20 06 373, die als nachstliegender Stand der Technik angesehen wird, ist ein Ventilstößel bekannt, der es gestattet, ein Ventilspiel auf hydraulischem Wege auszugleichen. Zu diesem Zweck weist der Ventilstößel ein Innenteil auf, welches axial beweglich in einem Außenteil geführt ist. Die Bewegung des Innenteils wird durch einen Anschlag begrenzt. Das Innenteil wirkt mit einer Stößelstange eines Ventils zusammen. Im Innenteil ist ein federbelasteter Kolben vorgesehen, der über einen mit dem Kolben verbundenen Dorn ein am Grund des Innenteils angeordnetes Rückschlagventil in geöffneter Stellung hält. Wird nun der Druckraum unter dem Kolben mit Druck von einer externen Druckquelle beaufschlagt, so wird zunächst das Innenteil relativ zum Außenteil soweit angehoben, bis ein eventuell existierendes Ventilspiel ausgeglichen ist. Nach dem Ausgleich des Ventilspiels erfährt das Innenteil eine Gegenkraft, so daß der Druck unter dem Kolben ansteigt und der Kolben samt Dorn gegen die Kraft der Feder angehoben wird und das Rückschlagventil schließt. Durch das Schließen des Rückschlagventils wird eine Rückwirkung des Hydraulikdrucks unter dem Innenteil auf druckführende Teile der Peripherie des Ventilstößels vermieden. Mit einem derartigen Ventilstößel ist eine genau getaktete Öffnung eines Ventils unmöglich, da der bekannte Ventilstößel mit einer Konstantdruckquelle zusammenarbeitet.GB-A 20 06 373, which is considered to be the subsequent state of the art, discloses a valve tappet which allows a valve clearance to be compensated for hydraulically. For this purpose, the valve lifter has an inner part which is guided in an outer part so as to be axially movable. The movement of the inner part is limited by a stop. The inner part interacts with a push rod of a valve. A spring-loaded piston is provided in the inner part, which holds a check valve arranged at the base of the inner part in the open position via a mandrel connected to the piston. If pressure from an external pressure source is now applied to the pressure chamber under the piston, the inner part is first raised relative to the outer part until any valve play that may exist is equalized. After the valve clearance has been compensated, the inner part experiences a counterforce, so that the pressure under the piston rises and the piston and the mandrel are raised against the force of the spring and the check valve closes. By closing the check valve, a reaction of the hydraulic pressure under the inner part on pressure-carrying parts of the periphery of the valve tappet is avoided. With such a valve tappet, a precisely timed opening of a valve is impossible because the known valve tappet works together with a constant pressure source.

Ausgehend von einem Verfahren gemäß dem Gattungsbegriff liegt der Erfindung die Aufgabe zugrunde dieses Verfahren so weiterzubilden, daß der Hub des Auslaßventilstößels während eines Verdichtungstaktes im Motor-Bremsbetrieb allein durch Beaufschlagung mittels einer externen Druckquelle erfolgt und der Betrag des Hubes auf einen vorgegebenen Wert begrenzt ist.Starting from a method according to the generic term, the invention has for its object to further develop this method so that the stroke of the exhaust valve tappet during a compression stroke in engine braking mode takes place solely by application of an external pressure source and the amount of the stroke is limited to a predetermined value.

Erfindungsgemäß wird diese Aufgabe durch die Merkmale des Patentanspruches 1 gelöst.According to the invention, this object is achieved by the features of patent claim 1.

Durch die von der externen Druckquelle gelieferte, stets konstante Ölmenge, läßt sich der Ventilhub des Auslaßventils genau regeln. Schäden durch die Rückwirkung überhöhten Hydraulikdruckes auf die Zuleitungen, bzw. die Druckquelle, werden zuverlässig vermieden.The valve stroke of the exhaust valve can be precisely regulated by the constant oil quantity supplied by the external pressure source. Damage caused by the reaction of excessive hydraulic pressure on the supply lines or the pressure source is reliably avoided.

Vorteilhafte Weiterbildungen des erfindungsgemäßen Verfahrens lassen sich den Unteransprüchen 2 - 4 entnehmen.Advantageous developments of the method according to the invention can be found in subclaims 2-4.

Ausführungsbeispiele der Erfindung sind in Zeichnungen dargestellt. Es zeigt:

Figur 1
einen Auslaß-Ventilstößel zwischen Nockenwelle und Auslaßventil
Figur 2
einen Auslaß-Ventilstößel mit mechanisch wirkendem Anschlag in Ruhestellung
Figur 3
einen Auslaß-Ventilstößel mit mechanisch wirkendem Anschlag gemäß Figur 2, jedoch in Arbeitsstellung
Figur 4
einen Auslaß-Ventilstößel mit hydraulisch wirkender Hubbegrenzung in Ruhestellung
Figur 5
einen Auslaß-Ventilstößel mit hydraulisch wirkender Hubbegrenzung nach Figur 4, jedoch in Arbeitsstellung
Figur 1 zeigt einen Auslaß-Ventilstößel 1 welcher zwischen einer Nockenwelle 2 und einer Stößelstange 3 angeordnet ist. Die Stößelstange 3 betätigt ein Auslaßventil 4, welches gegen die Rückstellkraft einer Ventilfeder 5 geöffnet wird. Im normalen Motorbetrieb wird das Auslaßventil 4 durch einen Auslaßnocken 6 geöffnet, welcher den Auslaß-Ventilstößel 1 anhebt und dieser seine Bewegung nach Ausschöpfung eines Spieles über die Stößelstange 3 auf das Auslaßventil 4 weiterleitet.Embodiments of the invention are shown in drawings. It shows:
Figure 1
an exhaust valve lifter between the camshaft and exhaust valve
Figure 2
an exhaust valve tappet with a mechanical stop in the rest position
Figure 3
an outlet valve lifter with a mechanical stop according to Figure 2, but in the working position
Figure 4
an outlet valve lifter with hydraulically acting stroke limitation in the rest position
Figure 5
an outlet valve lifter with hydraulically acting stroke limitation according to Figure 4, but in the working position
Figure 1 shows an exhaust valve lifter 1 which is arranged between a camshaft 2 and a push rod 3. The push rod 3 actuates an outlet valve 4, which is opened against the restoring force of a valve spring 5. In normal engine operation, the exhaust valve 4 opened by an outlet cam 6, which lifts the outlet valve tappet 1 and, after exhausting a game, passes it on via the push rod 3 to the outlet valve 4.

Im Motorbremsbetrieb soll das Auslaßventil 4 zusätzlich während des Verdichtungstaktes leicht angehoben werden, um die verdichtete Luft abzublasen, so daß zusätzliche Bremsarbeit verrichtet wird.In engine braking mode, the exhaust valve 4 should also be slightly raised during the compression stroke to blow off the compressed air, so that additional braking work is performed.

Zu diesem Zweck weist der Auslaß-Ventilstößel 1 ein in einem Stößel-Außenteil 7 axial bewegliches Innenteil 8 auf, welches mit Hub 9 eingebaut ist. Während des Verdichtungstaktes, also wenn der Auslaß-Ventilstößel 1 auf einem Grundkreis 10 der Nockenwelle 2 aufsitzt wird von einer externen Druckquelle 11 Druckflüssigkeit zugeführt, welche den Innenteil 8 samt Stößelstange 3 anhebt, bis der Innenteil 8 einen vorgesehenen Hub 9 ausgeführt hat und zwischen Innenteil 8 und einem Anschlag 8a ein Spiel 9a verbleibt (Figur 2). Das Auslaßventil 4 öffnet dadurch und die vorverdichtete Luft wird abgeblasen. Da das Auslaßventil in dieser Phase nur geringfügig angehoben wird baut sich bis zum Ende des Verdichtungshubes ein beachtlicher Druck im Zylinder auf, der das Auslaßventil 4 in Richtung Schließstellung belastet. Das Auslaßventil 4 leitet diese Kraft über die Stößelstange 3 auf das Innenteil 8 des Auslaß-Ventilstößels 1 weiter. Durch diese Kraft baut sich in allen druckführenden Bauteilen ein hoher hydraulischer Druck auf, welcher zu Schäden führen kann.For this purpose, the outlet valve tappet 1 has an inner part 8 which is axially movable in a tappet outer part 7 and which is installed with a stroke 9. During the compression stroke, i.e. when the exhaust valve tappet 1 is seated on a base circle 10 of the camshaft 2, pressure fluid is supplied from an external pressure source 11, which raises the inner part 8 together with the push rod 3 until the inner part 8 has performed a designated stroke 9 and between the inner part 8 and a stop 8a a game 9a remains (Figure 2). The outlet valve 4 thereby opens and the pre-compressed air is blown off. Since the exhaust valve is only slightly raised in this phase, a considerable pressure builds up in the cylinder by the end of the compression stroke, which loads the exhaust valve 4 in the direction of the closed position. The exhaust valve 4 passes this force on the push rod 3 to the inner part 8 of the exhaust valve tappet 1. This force creates a high hydraulic pressure in all pressure-carrying components, which can lead to damage.

Dieser Überdruck wird auf den Auslaßventilstößel begrenzt und kann sich nicht weiter in die druckführenden Organe fortpflanzen.This overpressure is limited to the outlet valve tappet and cannot propagate further into the pressure-carrying organs.

Nach Figur 2 wird dabei das Innenteil 8 einer besonderen Ausbildung unterzogen, um die Rückwirkung zu hohen Hydraulikdruckes auf die druckführenden Teile zu unterbinden. Zu diesem Zweck weist der innenteil 8 einen axial beweglichen Kolben 12 auf, welcher durch eine Druckfeder 13 in Ausgangslage gehalten wird und den Ventilsitz 25 geöffnet hält. Der Kolben 12 verfügt einerseits über eine Hubbegrenzung 14 und andererseits über einen Dorn 15. Das Innenteil weist an seinem oberen Ende eine Kugelpfanne 16 auf, während das untere Ende durch ein Ventil 17 abgeschlossen ist. In der Kugelpfanne 16 ist die aus Figur 1 zu ersehende Stößelstange 3 gelagert. Über durchgehende Bohrungen 18 kann ein erster Druckraum 19 unter dem Kolben 12 mit der externen Druckquelle 11 (Figur 1) verbunden werden.According to FIG. 2, the inner part 8 is subjected to a special design in order to prevent the reaction to excessive hydraulic pressure on the pressure-carrying parts. For this purpose, the inner part 8 has an axially movable piston 12, which is held in the starting position by a compression spring 13 and keeps the valve seat 25 open. The piston 12 has a stroke limiter 14 on the one hand and a mandrel 15 on the other hand. The inner part has a ball socket 16 at its upper end, while the lower end is closed by a valve 17. The push rod 3 shown in FIG. 1 is mounted in the ball socket 16. A first pressure chamber 19 under the piston 12 can be connected to the external pressure source 11 (FIG. 1) via through bores 18.

Der erste Druckraum 19 wiederum kommuniziert in der dargestellten Ruhelage des Kolbens 12 über erste und zweite Bohrungen 20, 21 im Ventil 17 mit einem zweiten Druckraum 22 unterhalb des Innenteils 8.The first pressure chamber 19 in turn communicates in the illustrated rest position of the piston 12 via first and second bores 20, 21 in the valve 17 with a second pressure chamber 22 below the inner part 8.

Im Ventil 17 befindet sich eine Feder 23 mit Kugel 24, welche über den Dorn 15 mittels der Druckfeder 13 in Ausgangslage gehalten wird.In the valve 17 there is a spring 23 with a ball 24 which is held in the starting position by means of the compression spring 13 via the mandrel 15.

Das Innenteil 8 ist mit Hub 9 plus einem Spiel 9a begrenzbar durch Anschlagring 8a in einem Stößel-Außenteil 7 des Auslaß-Ventilstößels 1 geführt.The inner part 8 is limited with stroke 9 plus a game 9a by stop ring 8a in a tappet outer part 7 of the outlet valve tappet 1.

Was die Funktion betrifft, wird auf Figur 3 verwiesen. Bei Betätigung der Motorbremse kann der erste Druckraum 19 über die Bohrungen 18 mit der in Figur 1 dargestellten Druck--quelle 11 verbunden werden. Beim Druckbeaufschlagen des Druckraumes 19 wird zunächst die Druckfeder 13 durch den Kolben 12 gestaucht, bis die Hubbegrenzung 14 am Innenteil 8 zum Anschlag kommt. Gleichzeitig wird die Kugel 24 nach Freigabe durch den Dorn 15 mittels der Feder 23 in einen Sitz 25 gedrückt und verschließt zunächst die erste Bohrung 20.With regard to the function, reference is made to FIG. 3. When the engine brake is actuated, the first pressure chamber 19 can be connected via the bores 18 to the pressure source 11 shown in FIG. 1. When pressurizing the Pressure chamber 19, the compression spring 13 is first compressed by the piston 12 until the stroke limitation 14 on the inner part 8 comes to a stop. At the same time, after being released by the mandrel 15, the ball 24 is pressed into a seat 25 by the spring 23 and initially closes the first bore 20.

Die Kraft der Feder 23 ist nun so ausgelegt, daß die Kugel 24 dennoch durch den sich im ersten Druckraum 19 aufbauenden Druck öffnen kann und den Weg der Druckflüssigkeit über die erste Bohrung 20 und die zweite Bohrung 21 zum zweiten Druckraum 22 freigibt. Durch die vom zweiten Druckraum 22 auf das Innenteil 8 ausgeübte Kraft wird dieses samt der in der Kugelkalotte 16 gelagerten Stößelstange 3 (Figur 1) angehoben und solange verschoben, bis der Hub 9 (Figur 2) ausgeschöpft ist. Der Hub 9 ergibt sich als eine Funktion der von der Durckquelle 11 geförderten Ölmenge. Diese stellt eine Konstante dar, da die Druckquelle 11 (Figur 1) als Verdrängerpumpe ausgeführt ist. Entsprechend der Wegstrecke des Hubes 9 wird das Auslaßventil 4 (Figur 1) geöffnet. Unter normalen Betriebsbedingungen verbleibt zwischen Innenteil 8 und Anschlagring 8a ein Spiel 9a.The force of the spring 23 is now designed so that the ball 24 can still open due to the pressure building up in the first pressure chamber 19 and opens the path of the pressure fluid via the first bore 20 and the second bore 21 to the second pressure chamber 22. Due to the force exerted by the second pressure chamber 22 on the inner part 8, the latter is lifted together with the push rod 3 (FIG. 1) mounted in the spherical cap 16 and moved until the stroke 9 (FIG. 2) is exhausted. The stroke 9 results as a function of the amount of oil delivered by the pressure source 11. This represents a constant since the pressure source 11 (FIG. 1) is designed as a positive displacement pump. The outlet valve 4 (FIG. 1) is opened in accordance with the distance of the stroke 9. Under normal operating conditions, a play 9a remains between the inner part 8 and the stop ring 8a.

Da die Öffnung des Auslaßventiles 4 während des Verdichtungstaktes erfolgt steigt mit zunehmendem verdichtungsdruck die in Schließrichtung wirkende Kraft auf das Auslaßventil. Diese Kraft wird über die Stößelstange 3 (Figur 1) auf das Innenteil 8 übertragen.Since the opening of the exhaust valve 4 takes place during the compression stroke, the force acting in the closing direction on the exhaust valve increases with increasing compression pressure. This force is transmitted to the inner part 8 via the push rod 3 (FIG. 1).

Um das Auslaßventil 4 gegen diese steigende Kraft im geöffneten Zustand zu halten müßte der von der Druckquelle 11 bereitzustellende Druck - resultierend aus der Kraft auf das Innenteil 8 und dessen Querschnittsfläche - ständig steigen. Dies fuhrt aber zu Schäden durch Kavitation und Undichtheiten in den druckführenden Organen.In order to keep the outlet valve 4 open against this increasing force, the pressure to be provided by the pressure source 11 would have to be constant - as a result of the force on the inner part 8 and its cross-sectional area climb. However, this leads to damage due to cavitation and leaks in the pressure-carrying organs.

Dies wird dadurch vermieden, daß der im zweiten Druckraum 22 sich aufbauende Druck die Kugel 24 zusätzlich zur Kraft der Feder 23 in den Sitz 25 preßt und dadurch der zweite Druckraum 22 hermetisch abgeriegelt wird und sich der ansteigende Druck nicht mehr über die erste Bohrung 20 und die Bohrungen 18 in die druckführenden Organe zurück fortpflanzen kann. Somit wird die Druckquelle 11 und die Verbindungsleitungen vor erhöhten Drücken und deren nachteiligen Wirkungen verschont. Wenn der von der Druckquelle 11 aufgebrachte Druck absinkt, entriegelt der, von der Druckfeder 13 in Ausgangsstellung zurückbewegte Kolben 12 die Kugel 24 des Ventils 17. Das Öl aus dem zweiten Druckraum 22 kann abströmen und der Hub 9 des Innenteils 8 und damit des Auslaßventils 4 werden beendet.This is avoided by the fact that the pressure building up in the second pressure chamber 22 presses the ball 24 into the seat 25 in addition to the force of the spring 23 and the second pressure chamber 22 is thereby hermetically sealed and the increasing pressure is no longer via the first bore 20 and the holes 18 can propagate back into the pressure-carrying organs. Thus, the pressure source 11 and the connecting lines are spared from increased pressures and their adverse effects. When the pressure applied by the pressure source 11 drops, the piston 12, moved back by the compression spring 13 in the initial position, unlocks the ball 24 of the valve 17. The oil from the second pressure chamber 22 can flow out and the stroke 9 of the inner part 8 and thus of the outlet valve 4 are ended.

Nach den Figuren 4 und 5 kann anstelle der mechanischen Hubbegrenzung 14 eine hydraulisch wirkende Hubbegrenzung verwendet werden. Aus diesem Grund werden nach Figur 4 im Innenteil 8 erste und zweite Abregelbohrungen 26, 27 vorgesehen, welche über einen Überströmkanal 28 untereinander verbunden sind. In Ruhestellung des Kolbens 12 kann der von der Bohrung 18 zugeführte Hydraulikdruck auf dessen, dem ersten Druckraum 19 zugewandte Seite einwirken und ihn gegen die Rückstellkraft der Druckfeder 13 verschieben. Wenn die Unterkante 29 des Kolbens 12 die erste Abregelbohrung 26 erreicht, wie es in Figur 5 dargestellt ist, kann über diese, den Überströmkanal 28 und die zweite Abregelbohrung 27 Hydraulikflüssigkeit in den von der Druckfeder 13 ausgefüllten Raum einströmen. Dieser Raum ist über eine Entlastungsbohrung 30 zum Druckausgleich mit der Umgebung verbunden, wodurch eine weitere Bewegung des Kolbens 12 gestoppt wird. Die Funktionen der übrigen Teile gleicht der Ausführung nach den Figuren 2 und 3 und wurde dort ausführlich erläutert. Vorteil dieser Stößelausführung ist, daß auf das Überdruckventil verzichtet werden kann.According to FIGS. 4 and 5, instead of the mechanical stroke limitation 14, a hydraulically acting stroke limitation can be used. For this reason, according to FIG. 4, first and second regulating bores 26, 27 are provided in the inner part 8, which are connected to one another via an overflow channel 28. In the rest position of the piston 12, the hydraulic pressure supplied by the bore 18 can act on its side facing the first pressure chamber 19 and move it against the restoring force of the compression spring 13. When the lower edge 29 of the piston 12 reaches the first regulating bore 26, as shown in FIG. 5, hydraulic fluid can flow into the space filled by the compression spring 13 via the overflow channel 28 and the second regulating bore 27. This room is over a relief bore 30 is connected to the environment for pressure equalization, whereby a further movement of the piston 12 is stopped. The functions of the other parts are similar to the embodiment according to FIGS. 2 and 3 and have been explained in detail there. The advantage of this tappet design is that the pressure relief valve can be dispensed with.

Claims (4)

  1. A method of operating an exhaust valve tappet during the braking operation of an internal-combustion engine, wherein the valve tappet (1) is inserted between an exhaust cam (6) and a tappet push rod (3) of an exhaust valve train, wherein the valve tappet (1) is substantially formed from a tappet outer part (7) and an inner part (8) axially movable therein and acted upon by an external pressure source, and the inner part (8) is axially movably guided with clearance in the tappet outer part (7), wherein the inner part (8) has a piston (12) held in the starting position by means of a compression spring (13), the axial movement of the said piston (12) towards the tappet push rod (3) being restrictable by a stroke limiter and, at the end facing away from the compression spring (13), by a pin (15), wherein the pin (15) presses on a ball (24) loadable by a spring (23) in the direction of the piston (12) in such a manner that firstly a second pressure chamber (22) between the tappet outer part (7) and inner part (8) is connectable to the external pressure source (11) via bores (18), first and second bores (20, 21) and a valve seat (25), and then the piston (12) is moved towards the compression spring (13) by means of increasing pressure in a first pressure chamber (19), produced by the external pressure source (11), releasing the ball (24) as a result, wherein the ball (24) shuts off the second pressure chamber (22) from the first pressure chamber (19) by means of the spring (23), and wherein the spring (23) is adjusted such that the pressure from the pressure source (11) is firstly sufficient to lift the ball (24) from the valve seat (25), the oil flowing into the second pressure chamber (22) raising the inner part (8) and the exhaust valve (4) being opened as a result, and that as the pressure from the force of the tappet push rod (3) on the inner part (8) increases due to the resultant rising pressure in the second pressure chamber (22), the ball (24) shuts off the pressure chamber (22) via the valve seat (25) and prevents backflow from the second pressure chamber (22) to the external pressure source (11) by closing the valve seat (25), and, after the pressure from the external pressure source has dropped, the compression spring (13) moves the piston (12) back towards the ball (24) into its starting position, as a result of which the valve seat (25) is opened, the oil flows out of the second pressure chamber (22) and the stroke of the inner part (8) and thereby of the exhaust valve (4) is terminated, characterised in that the pressure source (11), formed by a displacement pump, feeds a constant quantity of oil into the second pressure chamber (22) during the compression stroke of the internal-combustion engine, as a result of which the inner part (8) partially opens the exhaust valve (4) via the tappet push rod (3), and in that the pressure applied by the pressure source (11) drops towards the end of the compression stroke, and oil can flow back into the pressure source (11) from the second pressure chamber (22).
  2. A method according to claim 1, characterised in that the stroke of the piston (12) is limited by a stop (14) which is rigidly connected to the piston (12).
  3. A method according to claim 1, characterised in that the stroke (9) is limited by first and second regulating bores (26, 27), the first regulating bore (26) being located in the inner part (8) in such a manner that, when the piston (12) is in the desired end position, this piston opens the first regulating bore (26) so that it communicates with the atmosphere via an overflow duct (28), the second regulating bore (27) and a relief bore (30).
  4. A method according to claim 1, characterised in that the stroke (9) is set in such a manner that, during regular engine braking with a maximum additional stroke, which is triggered by the hydraulic pump unit of the pressure source (11), there is a clearance (9a) between the tappet inner part (8) and the stop ring (8a).
EP92100960A 1991-01-29 1992-01-22 Method for actuating an exhaust valve tappet during braking of an internal combustion engine Expired - Lifetime EP0497194B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE4102537 1991-01-29
DE4102537A DE4102537A1 (en) 1991-01-29 1991-01-29 EXHAUST VALVE TUNEL FOR AN INTERNAL COMBUSTION ENGINE

Publications (2)

Publication Number Publication Date
EP0497194A1 EP0497194A1 (en) 1992-08-05
EP0497194B1 true EP0497194B1 (en) 1995-04-05

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EP92100960A Expired - Lifetime EP0497194B1 (en) 1991-01-29 1992-01-22 Method for actuating an exhaust valve tappet during braking of an internal combustion engine

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US (1) US5161500A (en)
EP (1) EP0497194B1 (en)
JP (1) JPH04311615A (en)
DE (2) DE4102537A1 (en)
ZA (1) ZA92569B (en)

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Also Published As

Publication number Publication date
DE59201799D1 (en) 1995-05-11
DE4102537A1 (en) 1992-07-30
EP0497194A1 (en) 1992-08-05
JPH04311615A (en) 1992-11-04
US5161500A (en) 1992-11-10
ZA92569B (en) 1992-10-28

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